Patent Publication Number: US-2023158172-A1

Title: Codon optimized rep1 genes and uses thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/740,045, filed May 9, 2022, which is a continuation of U.S. patent application Ser. No. 17/463,262, filed Aug. 31, 2021, which claims the benefit of U.S. Provisional Patent Application Ser. No. 63/073,837, filed Sep. 2, 2020, the full disclosure of each of which is incorporated herein by reference. 
    
    
     SEQUENCE LISTING SUBMISSION VIA EFS-WEB 
     A computer readable XML file, entitled “090400-5011-US-02-Sequence-Listing” created on or about Nov. 4, 2022, with a file size of about 23,000 bytes, contains the sequence listing for this application and is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Choroideremia is a rare, X-linked recessive form of hereditary retinal degeneration that affects roughly 1 in 50,000 males. The disease causes a gradual loss of vision, starting with childhood night blindness, followed by peripheral vision loss and progressing to loss of central vision later in life. Progression continues throughout the individual&#39;s life, but both the rate of change and the degree of visual loss are variable among those affected, even within the same family. 
     Choroideremia is caused by a loss-of-function mutation in the CHM gene which encodes Rab escort protein-1 (REP1), a protein involved in lipid modification of Rab proteins. While the complete mechanism of disease is not fully understood, the lack of a functional protein in the retina results in cell death and the gradual deterioration of the retinal pigment epithelium (RPE), photoreceptors and the choroid. 
     Although there are currently no approved treatments for choroideremia, several preclinical studies support the use of wild type cDNA of CHM to rescue the choroideremia disease phenotype. However, suboptimal expression level of the wild type sequence in human photoreceptors and RPE are challenges to gene therapy approaches to treat choroideremia. 
     SUMMARY OF THE INVENTION 
     Disclosed are codon optimized nucleic acid molecules encoding a human Rab escort protein-1 (REP1) protein. In one aspect, the disclosure provides a nucleic acid comprising the nucleotide sequence of SEQ ID NO:1 or a nucleic acid comprising a nucleotide sequence at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the nucleotide sequence of SEQ ID NO:1 and which encodes a human REP1 polypeptide having the amino acid sequence of SEQ ID NO:2. In some embodiments, a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:1 is provided. In related embodiments, the nucleic acid is expressed at a higher level compared with the level of expression of a wild type CHM nucleic acid sequence (e.g. SEQ ID NO:3) in an otherwise identical cell. 
     In some aspects, a codon optimized nucleic acid molecule as herein described has a human codon adaptation index that is increased relative to that of the wild type CHM cDNA (GenBank Accession No. NM_000390.4; SEQ ID NO:3). In some embodiments, the codon optimized nucleic acid molecule has a human codon adaptation index of at least about 0.9, at least about 0.92, or at least about 0.94. 
     In certain embodiments, the nucleic acid contains a higher percentage of G/C nucleotides compared to the percentage of G/C nucleotides in SEQ ID NO:3. In other embodiments, the nucleic acid contains a percentage of G/C nucleotides that is at least about 55%, at least about 57.5%, at least about 60% or at least about 61%. In some aspects, the nucleic acid contains a percentage of G/C nucleotides that is from about 55% to about 70%, from about 57.5% to about 70% or from about 61% to about 70%. 
     In other embodiments, the nucleic acid comprises one or more optimized parameters relative to SEQ ID NO:3: frequency of optimal codons; reduction in maximum length of direct repeat sequences; removal of restriction enzymes, including without limitation, removal of Bglll(AGATCT); removal of CIS-acting elements, including without limitation, and removal of destabilizing (ATTTA) elements. 
     In another embodiment, the nucleic acid is operatively linked to at least one transcription control sequence, preferably a transcription control sequence that is heterologous to the nucleic acid. In some aspects, the transcription control sequence is a cell- or tissue-specific promoter that results in cell-specific expression of the nucleic acid e.g. in photoreceptor cells such as vitelliform macular dystrophy 2 promoter which is selectively expressed in the RPE. In other aspects, the transcription control sequence is a constitutive promoter that results in similar expression level of the nucleic acid in many cell types (e.g. a CAG, CBA (chicken beta actin), CMV, or PGK promoter). In preferred embodiments, the transcription control sequence comprises a CAG promoter comprising (i) the cytomegalovirus (CMV) early enhancer element, (ii) the promoter, first exon and first intron of chicken beta-actin gene and (iii) the splice acceptor of the rabbit beta-globin geneas described in Miyazaki et al., Gene 79(2):269-77 (1989). In a particularly preferred embodiment, the CAG promoter comprises the sequence of SEQ ID NO:4 or comprises a sequence at least 95%, at least 96%, at least 97%, at least 98% or at least 99% identical thereto: 
     
       
         
           
               
               
            
               
                 (SEQ ID NO: 4) 
                   
               
               
                 ACTAGTTATTAATAGTAATCAATTACGGGGTCATTAGTTCATAGCCCATATATGGA 
                   
               
               
                   
               
               
                 GTTCCGCGTTACATAACTTACGGTAAATGGCCCGCCTGGCTGACCGCCCAACGACC 
               
               
                   
               
               
                 CCCGCCCATTGACGTCAATAATGACGTATGTTCCCATAGTAACGCCAATAGGGACT 
               
               
                   
               
               
                 TTCCATTGACGTCAATGGGTGGAGTATTTACGGTAAACTGCCCACTTGGCAGTACA 
               
               
                   
               
               
                 TCAAGTGTATCATATGCCAAGTACGCCCCCTATTGACGTCAATGACGGTAAATGGC 
               
               
                   
               
               
                 CCGCCTGGCATTATGCCCAGTACATGACCTTATGGGACTTTCCTACTTGGCAGTAC 
               
               
                   
               
               
                 ATCTACGTATTAGTCATCGCTATTACCATOGTCGAGGTGAGCCCCACGTTCTGCTTC 
               
               
                   
               
               
                 ACTCTCCCCATCTCCCCCCCCTCCCCACCCCCAATTTTGTATTTATTTATTTTTTAAT 
               
               
                   
               
               
                 TATTTTGTGCAGCGATGGGGGCGGGGGGGGGGGGGGGGCGCGCGCCAGGCGGGGC 
               
               
                   
               
               
                 GGGGCGGGGCGAGGGGCGGGGCGGGGCGAGGCGGAGAGGTGCGGCGGCAGCCAA 
               
               
                   
               
               
                 TCAGAGCGGCGCGCTCCGAAAGTTTCCTTTTATGGCGAGGCGGCGGCGGCGGCGG 
               
               
                   
               
               
                 CCCTATAAAAAGCGAAGCGCGCGGCGGGCGGGGAGTCGCTGCGACGCTGCCTTCG 
               
               
                   
               
               
                 CCCCGTGCCCCGCTCCGCCGCCGCCTCGCGCCGCCCGCCCCGGCTCTGACTGACCG 
               
               
                   
               
               
                 CGTTACTCCCACAGGTGAGCGGGCGGGACGOCCCTTCTCCTCCGGGCTGTAATTAG 
               
               
                   
               
               
                 CGCTTGGTTTAATGACGGCTTGTTTCTTTTCTOTGGCTGCGTGAAAGCCTTGAGGGG 
               
               
                   
               
               
                 CTCCGGGAGGGCCCTTTGTGCGGGGGGAGCGGCTCGGGGGGTGCGTGCGTGTGTG 
               
               
                   
               
               
                 TGTGCGTGGGGAGCGCCGCGTGCGGCTCCGCGCTGCCCGGCGGCTGTGAGCGCTGC 
               
               
                   
               
               
                 GGGCGCGGCGCGGGGCTTTGTGCGCTCCGCAGTGTGCGCGAGGGGAGCGCGGCCG 
               
               
                   
               
               
                 GGGOCGGTGCCCCGCGGTGCGGGGGGGGCTGCGAGGGGAACAAAGGCTGCGTGC 
               
               
                   
               
               
                 GGGGTGTGTGCGTGGGGGGGTGAGCAGGGGGTGTGGGCGCGTCGGTCGGGCTGCA 
               
               
                   
               
               
                 ACCCCCCCTGCACCCCCCTCCCCGAGTTOCTGAGCACGGCCCGGCTTCGGGTGCGG 
               
               
                   
               
               
                 GGCTCCGTACGGGGCGTGGCGCGGGGCTCGCCGTGCCGGGCGGGGGGTGGCGGCA 
               
               
                   
               
               
                 GGTGGGGGTGCCGGGCGGGGCGGGGCCGCCTCGGGCCGGGGAGGGCTCGGGGGA 
               
               
                   
               
               
                 GGGGCGCGGCGGCCCCCGGAGCGCCGGCGGCTGTCGAGGCGCGGCGAGCCGCAGC 
               
               
                   
               
               
                 CATTGCCTTTTATGGTAATCGTGCGAGAGGGCGCAGGGACTTCCTTTGTCCCAAAT 
               
               
                   
               
               
                 CTGTGCGGAGCCGAAATCTGGGAGGCGCCGCCGCACCCCCTCTAGCGGGCGCGGG 
               
               
                   
               
               
                 GCGAAGCGGTGCGGCGCCGGCAGGAAGGAAATGGGCGGGGAGGGCCTTCGTGCGT 
               
               
                   
               
               
                 CGCCGCGCCGCCGTCCCCTTCTCCCTCTCCAGCCTCGGGGCTGTCCGCGGGGGGAC 
               
               
                   
               
               
                 GGCTGCCTTCGGGGGGGACGGGGCAGGGCGGGGTTCGGCTTCTGGCGTGTGACCG 
               
               
                   
               
               
                 GCGGCTCTAGAGCCTCTGCTAACCATGTTCATGCCTTCTTCTTTTTCCTACAG 
               
            
           
         
       
     
     The transcription control sequence may also comprise one or more elements downstream of the REP1 coding sequence such as a Woodchuck hepatitis virus posttranscriptional regulatory element (WPRE), which has been shown to enhance AAV transgene expression in the retina. In related embodiments, provided herein is an expression cassette comprising a nucleic acid comprising the nucleotide sequence of SEQ ID NO:1, or a nucleotide sequence at least 90% identical thereto, operably linked to an expression control sequence. 
     In related embodiments, provided herein is a vector comprising a nucleic acid comprising the nucleotide sequence of SEQ ID NO:1, or a nucleotide sequence at least 90% identical thereto. In preferred embodiments, the vector is a recombinant adeno-associated (rAAV) expression vector. In some embodiments, the rAAV vector comprises a native capsid (e.g. a capsid of AAV serotype 2, AAV serotype 4, AAV serotype 5 or AAV serotype 8). In other embodiments, the rAAV vector comprises a capsid that is modified (e.g. comprises one or more peptide insertions and/or one or more amino acid substitutions (e.g. tyrosine to phenylalanine) and/or amino acid insertions or amino acid deletions) relative to a native AAV capsid (e.g. comprising one or more modifications relative to an AAV capsid of serotype 2, 4, 5 or 8). 
     In another embodiment, provided herein is a host cell comprising a nucleic acid comprising the nucleotide sequence of SEQ ID NO:1, or a nucleotide sequence at least 90% identical thereto. In some aspects, the host cell is a mammalian cell, including without limitation, a CHO cell, an HEK293 cell, a HeLa cell, a BHK21 cell, a Vero cell or a V27 cell. In related aspects, the host cell is selected from a CHO cell, an HEK293 cell, an HEK293T cell, a HeLa cell, a BHK21 cell and a Vero cell. In other aspects, the host cell is a photoreceptor cell (e.g. rods; cones), a retinal ganglion cell (RGC), a glial cell (e.g. a Muller glial cell, a microglial cell), a bipolar cell, an amacrine cell, a horizontal cell, or a retinal pigmented epithelium (RPE) cell. In related embodiments, the disclosure provides a method of increasing expression of a polypeptide of SEQ ID NO: 2 comprising culturing the host cell under conditions whereby a polypeptide of SEQ ID NO: 2 is expressed by the nucleic acid molecule, wherein the expression of the polypeptide is increased relative to a host cell cultured under the same conditions comprising a reference nucleic acid comprising the nucleotide sequence of SEQ ID NO:3 (comparator sequence). 
     In another embodiment, the disclosure provides a method of increasing expression of a polypeptide of SEQ ID NO: 2 in a human subject comprising administering to the subject an isolated nucleic acid molecule comprising a nucleotide sequence at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% identical, or 100% identical to the nucleotide sequence of SEQ ID NO: 1 and which encodes a polypeptide having the amino acid sequence of SEQ ID NO:2 or a vector comprising such a nucleotide sequence, wherein the expression of the polypeptide is increased relative to a reference nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:3 (comparator sequence) or a vector comprising the reference nucleic acid molecule. 
     In some embodiments, the disclosure provides a method of treating an ocular disorder associated with insufficient REP1 activity in a human subject comprising administering to the subject a nucleic acid molecule or a vector disclosed herein. In some embodiments, the retinal disorder is choroideremia. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A-D   FIGS.  1 A and  1 B  illustrate immunocytochemical analysis of iPSCs derived from choroideremia patients CHM1 ( FIG.  1 A ) and CHM2 ( FIG.  1 B ) using antibodies against pluripotent transcription factors NANOG, OCT4 and SOX2.  FIGS.  1 C and  1 D  illustrate representative images of CHM1 ( FIG.  1 C ) and CHM2 ( FIG.  11   )) cultures randomly differentiated into ectodermal, mesodermal and endodermal cell lineages as indicted by expression of TUJ1, α-smooth muscle actin (ASMA) and Hepatocyte Nuclear Factor 4 Alpha (HNF4A). 
         FIG.  2 A-C   FIGS.  2 A and  2 B  illustrate immunocytochemical analysis of RPE cells derived from iPSCs derived from choroideremia patients CHM1 ( FIG.  2 A ) and CHM2 ( FIG.  2 B ). The RPE phenotype after 45 days of differentiation and maturation by ICC showed proper RPE transcriptional factor expression of Melanogenesis Associated Transcription Factor (MITF) and Orthodenticle Homeobox 2 (OTX2), expression of mature RPE cell marker RPE65, and expression of tight junction marker Zonula Occludens (ZO-1). The nuclei were counterstained with DAPI for CHM1 images. Scale bar:=50 μm.  FIG.  2 C  is a graph illustrating that CHM1 RPE and CHM2 RPE phagocytose at similar levels to wild type (WT) RPE. In addition, phagocytosis occurs through the known mechanism in vivo, aVi5 integrin binding, as seen by a decrease in phagocytosis following αVβ5 inhibition. n=3 for quantitative measurements; Error bars±S.D.; *p&lt;0.05, compared to the “No ROS” condition; two-tailed t-test. 
         FIGS.  3 A-B   FIG.  3 A : Western blot images are shown illustrating REP1 and housekeeping protein GADPH levels in CHM1 RPE or normal iPSC-derived RPE cells following transduction with recombinant AAV virions carrying the codon optimized REP1 gene or carrying the unmodified REP1 gene, in each case driven by a CAG promoter. The codon optimized REP1 showed significantly higher levels of protein expression.  FIG.  3 B : band intensity was quantified and graphed as a ratio over GAPDH. n=3 for quantitative measurements; Error bars±S.D.; *p&lt;0.05, compared to the WT-REP1; two-tailed t-test. 
         FIG.  4    Schematic illustration of the functional prenylation assay showing required components, including the biotinylated prenyl group serving as the readout of the biochemical assay. Normal RPE cells with functional REP1 protein successfully facilitate the prenylation of Rab27A GTPase, leading to the incorporation of the biotin groups. In CHM RPE, cells lack REP1 protein, causing accumulation of unprenylated Rab27a GTPase protein. 
         FIGS.  5 A- 5 D  Transduction of CHMJ and CHM2 RPE with rAAV virions comprising codon optimized REP1 of SEQ ID NO:1 under the control of a CAG promoter restored prenylation of Rab27a GTPase.  FIGS.  5 A and  5 B : Gel images illustrating the level of REP1 protein by Western blot analysis and incorporation of a biotinylated prenyl donor as a measure of prenylation in cell lysates, in transduced and untransduced CHM1 ( FIG.  5 A ) and CHM2 ( FIG.  5 B ) RPE cells (compared to normal iPSC-derived RPE cells).  FIGS.  5 C and  5 D : Band intensity was quantified and depicted in bar graphs as biotinylated Rab27a GTPase relative to the housekeeping protein GADPH, in CHM1 ( FIG.  5 C ) and CHM2 ( FIG.  5 D ) RPE cells. n=3 for quantitative measurements; Error bars±S.D.; *p&lt;0.05, compared to the untreated CHM RPE; two-tailed t-test. 
         FIGS.  6 A- 6 C   FIG.  6 A : Immunostaining of CHM1 RPE with anti-REP1 and anti-RAB27A antibodies illustrates that CHIMl RPE lacked proper membrane localization of Rab27a GTPase.  FIGS.  6 B and  6 C : Delivery of codon optimized REP1 of SEQ ID NO:1 by rAAV vector, corrected Rab27 GTPase membrane trafficking in CHM1 RPE ( FIG.  6 B ), and restored localization to a control RPE phenotype ( FIG.  6 C ). 
         FIG.  7   : DNA alignment of the optimized region of SEQ ID NO:1 with native REP1 of SEQ ID NO:3. 
         FIG.  8    is a schematic of the transgene cassette contained within the rAAV described in Example 2 below. The transgene cassette comprises a 5′AAV2 ITR, a CAG Promoter, a Codon Optimized Human CHM cDNA of SEQ ID NO:1, an SV40 Polyadenylation Signal, and a 3′ AAV2 ITR and has the nucleotide sequence of SEQ ID NO:5. 
         FIG.  9    illustrates safety of 4D-110 (comprising the transgene cassette shown in  FIG.  8    and a capsid protein of SEQ ID NO:9) following intravitreal administration to non-human primates through quantification of ocular inflammation, as assessed by aqueous flare, aqueous cells, and vitreous cells. Ophthalmoscopic signs of transient mild ocular inflammation were observed at the high dose. These changes responded to an increase in the systemic steroid treatment. There were no adverse findings considered related to 4D-110. IOP values were within normal limits for all animals at the different examination intervals. ERG values and OCT images including macular morphology were also within normal limits. 
         FIG.  10    illustrates vector genome biodistribution in selected retinal, ocular, and non-ocular tissues, as measured by qPCR at 3 necropsy timepoints in NHPs intravitreally administered 4D-110. LOD=lower limit of detection; all samples “BLOD” graphed at LOD value for visualization purposes. 
         FIG.  11    illustrates REP1 transgene mRNA expression in selected retinal, ocular, and non-ocular tissues, as measured by RT-qPCR at 3 necropsy timepoints in NHPs intravitreally administered 4D-110. LOD=lower limit of detection; all samples “BLOD” graphed at LOD value for visualization purposes. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Definitions 
     A “codon adaptation index,” as used herein, refers to a measure of codon usage bias. A codon adaptation index (CAI) measures the deviation of a given protein coding gene sequence with respect to a reference set of genes (Sharp P M and Li W H, Nucleic Acids Res. 15(3):1281-95 (1987)). CAI is calculated by determining the geometric mean of the weight associated to each codon over the length of the gene sequence (measured in codons): 
     
       
         
           
             
               
                 
                   
                     CAI 
                     = 
                     
                       exp 
                       ⁡ 
                       ( 
                       
                         1 
                         / 
                         L 
                         ⁢ 
                         
                           
                             ∑ 
                             
                               l 
                               = 
                               1 
                             
                             L 
                           
                           
                             ln 
                             ⁡ 
                             ( 
                             
                               
                                 w 
                                 1 
                               
                               ( 
                               l 
                               ) 
                             
                             ) 
                           
                         
                       
                       ) 
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   I 
                   ) 
                 
               
             
           
         
       
     
     For each amino acid, the weight of each of its codons, in CAI, is computed as the ratio between the observed frequency of the codon (fi) and the frequency of the synonymous codon (fj) for that amino acid: 
     
       
         
           
             
               
                 
                   
                     w 
                     i 
                   
                   = 
                   
                     
                       
                         
                           f 
                           i 
                         
                         
                           max 
                           ( 
                           
                             f 
                             
                               i 
                               ) 
                             
                           
                         
                       
                       ⁢ 
                           
                       ij 
                     
                     ∈ 
                     
                       [ 
                       
                         synonymous 
                         ⁢ 
                             
                         codons 
                         ⁢ 
                             
                         for 
                         ⁢ 
                             
                         amino 
                         ⁢ 
                             
                         acid 
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   II 
                   ) 
                 
               
             
           
         
       
     
     The term “isolated” designates a biological material (cell, nucleic acid or protein) that has been removed from its original environment (the environment in which it is naturally present). For example, a polynucleotide present in the natural state in a plant or an animal is not isolated, however the same polynucleotide separated from the adjacent nucleic acids in which it is naturally present, is considered “isolated.” 
     The term “4D-110” refers to a recombinant AAV particle comprising (i) a capsid protein comprising the amino acid sequence of SEQ ID NO:9 and a heterologous nucleic acid comprising the nucleotide sequence of SEQ ID NO:5. 
     The term “R100” refers to a variant AAV capsid protein comprising the amino acid sequence of SEQ ID NO:9. 
     The term “having” as used herein is equivalent to the term “comprising” and is intended to be open-ended allowing additional elements. 
     As used herein, a “coding region” or “coding sequence” is a portion of polynucleotide which consists of codons translatable into amino acids. Although a “stop codon” (TAG, TGA, or TAA) is typically not translated into an amino acid, it can be considered to be part of a coding region, but any flanking sequences, for example promoters, ribosome binding sites, transcriptional terminators, introns, and the like, are not part of a coding region. The boundaries of a coding region are typically determined by a start codon at the 5′ terminus, encoding the amino terminus of the resultant polypeptide, and a translation stop codon at the 3′ terminus, encoding the carboxyl terminus of the resulting polypeptide. Two or more coding regions can be present in a single polynucleotide construct, e.g., on a single vector, or in separate polynucleotide constructs, e.g., on separate (different) vectors. It follows, then that a single vector can contain just a single coding region, or comprise two or more coding regions. 
     As used herein, the term “regulatory region” refers to nucleotide sequences located upstream (5′ non-coding sequences), within, or downstream (3′ non-coding sequences) of a coding region, and which influence the transcription, RNA processing, stability, or translation of the associated coding region. Regulatory regions can include promoters, translation leader sequences, introns, polyadenylation recognition sequences, RNA processing sites, effector binding sites and stem-loop structures. If a coding region is intended for expression in a eukaryotic cell, a polyadenylation signal and transcription termination sequence will usually be located 3′ to the coding sequence. 
     As used herein, the term “nucleic acid” is interchangeable with “polynucleotide” or “nucleic acid molecule” and a polymer of nucleotides is intended. 
     A polynucleotide which encodes a gene product, e.g., a polypeptide, can include a promoter and/or other transcription or translation control elements operably associated with one or more coding regions. In an operable association a coding region for a gene product, e.g., a polypeptide, is associated with one or more regulatory regions in such a way as to place expression of the gene product under the influence or control of the regulatory region(s). For example, a coding region and a promoter are “operably associated” if induction of promoter function results in the transcription of mRNA encoding the gene product encoded by the coding region, and if the nature of the linkage between the promoter and the coding region does not interfere with the ability of the promoter to direct the expression of the gene product or interfere with the ability of the DNA template to be transcribed. Other transcription control elements, besides a promoter, for example enhancers, operators, repressors, and transcription termination signals, can also be operably associated with a coding region to direct gene product expression. 
     “Transcriptional control sequences” refer to DNA regulatory sequences, such as promoters, enhancers, terminators, and the like, that provide for the expression of a coding sequence in a host cell. A variety of transcription control regions are known to those skilled in the art. These include, without limitation, transcription control regions which function in vertebrate cells, such as, but not limited to, promoter and enhancer segments from cytomegaloviruses (the immediate early promoter, in conjunction with intron-A), simian virus 40 (the early promoter), and retroviruses (such as Rous sarcoma virus). Other transcription control regions include those derived from vertebrate genes such as actin, heat shock protein, bovine growth hormone and rabbit beta-globin, as well as other sequences capable of controlling gene expression in eukaryotic cells. Additional suitable transcription control regions include tissue-specific promoters and enhancers as well as lymphokine-inducible promoters (e.g., promoters inducible by interferons or interleukins). 
     Similarly, a variety of translation control elements are known to those of ordinary skill in the art. These include, but are not limited to ribosome binding sites, translation initiation and termination codons, and elements derived from picornaviruses (particularly an internal ribosome entry site, or IRES, also referred to as a CITE sequence). 
     The term “expression” as used herein refers to a process by which a polynucleotide produces a gene product, for example, an RNA or a polypeptide. It includes without limitation transcription of the polynucleotide into messenger RNA (mRNA), transfer RNA (tRNA), small hairpin RNA (shRNA), small interfering RNA (siRNA) or any other RNA product, and the translation of an mRNA into a polypeptide. Expression produces a “gene product.” As used herein, a gene product can be either a nucleic acid, e.g., a messenger RNA produced by transcription of a gene, or a polypeptide which is translated from a transcript. Gene products described herein further include nucleic acids with post transcriptional modifications, e.g., polyadenylation or splicing, or polypeptides with post translational modifications, e.g., methylation, glycosylation, the addition of lipids, association with other protein subunits, or proteolytic cleavage. 
     A “vector” refers to any vehicle for the cloning of and/or transfer of a nucleic acid into a host cell. A vector can be a replicon to which another nucleic acid segment can be attached so as to bring about the replication of the attached segment. The term “vector” includes both viral and nonviral vehicles for introducing the nucleic acid into a cell in vitro, ex vivo or in vivo. A large number of vectors are known and used in the art including, for example, plasmids, modified eukaryotic viruses, or modified bacterial viruses. Insertion, of a polynucleotide into a suitable vector can be accomplished by ligating the appropriate polynucleotide fragments into a chosen vector that has complementary cohesive termini. 
     Vectors can be engineered to encode selectable markers or reporters that provide for the selection or identification of cells that have incorporated the vector. Expression of selectable markers or reporters allows identification and/or selection of host cells that incorporate and express other coding regions contained on the vector. Examples of selectable marker genes known and used in the art include: genes providing resistance to ampicillin, streptomycin, gentamycin, kanamycin, hygromycin, bialaphos herbicide, sulfonamide, and the like; and genes that are used as phenotypic markers, i.e., anthocyanin regulatory genes, isopentanyl transferase gene, and the like. Examples of reporters known and used in the art include: luciferase (Luc), green fluorescent protein (GFP), chloramphenicol acetyltransferase (CAT), -galactosidase (LacZ), -glucuronidase (Gus), and the like. Selectable markers can also be considered to be reporters. 
     Eukaryotic viral vectors that can be used include, but are not limited to, adenovirus vectors, retrovirus vectors, adeno-associated virus vectors, poxvirus, e.g., vaccinia virus vectors, baculovirus vectors, or herpesvirus vectors. Non-viral vectors include plasmids, liposomes, electrically charged lipids (cytofectins), DNA-protein complexes, and biopolymers. 
     “Promoter” and “promoter sequence” are used interchangeably and refer to a DNA sequence capable of controlling the expression of a coding sequence or functional RNA. In general, a coding sequence is located 3′ to a promoter sequence. Promoters can be derived in their entirety from a native gene, or be composed of different elements derived from different promoters found in nature, or even comprise synthetic DNA segments. It is understood by those skilled in the art that different promoters can direct the expression of a gene in different tissues or cell types, or at different stages of development, or in response to different environmental or physiological conditions. Promoters that cause a gene to be expressed in most cell types at most times are commonly referred to as “constitutive promoters.” Promoters that cause a gene to be expressed in a specific cell type are commonly referred to as “cell-specific promoters” or “tissue-specific promoters.” Promoters that cause a gene to be expressed at a specific stage of development or cell differentiation are commonly referred to as “developmentally-specific promoters” or “cell differentiation-specific promoters.” Promoters that are induced and cause a gene to be expressed following exposure or treatment of the cell with an agent, biological molecule, chemical, ligand, light, or the like that induces the promoter are commonly referred to as “inducible promoters” or “regulatable promoters.” It is further recognized that since in most cases the exact boundaries of regulatory sequences have not been completely defined, DNA fragments of different lengths can have identical promoter activity. 
     The term “plasmid” refers to an extra-chromosomal element often carrying a gene that is not part of the central metabolism of the cell, and usually in the form of circular double-stranded DNA molecules. Such elements can be autonomously replicating sequences, genome integrating sequences, phage or nucleotide sequences, linear, circular, or supercoiled, of a single- or double-stranded DNA or RNA, derived from any source, in which a number of nucleotide sequences have been joined or recombined into a unique construction which is capable of introducing a promoter fragment and DNA sequence for a selected gene product along with appropriate 3′ untranslated sequence into a cell. 
     A polynucleotide or polypeptide has a certain percent “sequence identity” to another polynucleotide or polypeptide, meaning that, when aligned, that percentage of bases or amino acids are the same when comparing the two sequences. Sequence similarity can be determined in a number of different manners. To determine sequence identity, sequences can be aligned using the methods and computer programs, including BLAST, available over the world wide web at ncbi.nlm.nih.gov/BLAST/. Another alignment algorithm is FASTA, available in the Genetics Computing Group (GCG) package, from Madison, Wis., USA. Other techniques for alignment are described in Methods in Enzymology, vol. 266: Computer Methods for Macromolecular Sequence Analysis (1996), ed. Doolittle, Academic Press, Inc. Of particular interest are alignment programs that permit gaps in the sequence. The Smith-Waterman is one type of algorithm that permits gaps in sequence alignments. See Meth. Mol. Biol. 70: 173-187 (1997). Also, the GAP program using the Needleman and Wunsch alignment method can be utilized to align sequences. See J. Mol. Biol. 48: 443-453 (1970). 
     In one embodiment, the present invention provides a modified nucleic acid molecule comprising a nucleotide sequence that encodes a polypeptide of SEQ ID NO:2 (human REP1), wherein the nucleic acid sequence has been codon optimized. In another embodiment, the starting nucleic acid sequence that encodes a polypeptide of SEQ ID NO:2 and that is subject to codon optimization has the nucleotide sequence set forth as SEQ ID NO:3. In preferred embodiments, the sequence that encodes a polypeptide of SEQ ID NO:2 is codon optimized for human expression. SEQ ID NO:1 is a codon optimized version of SEQ ID NO:3, optimized for human expression: 
     
       
         
           
               
               
            
               
                 (SEQ ID NO: 1) 
                   
               
               
                 ATGGCTGATACACTGCCTTCTGAGTTTGATGTGATCGTGATTGGAACTGGACTGCC 
                   
               
               
                   
               
               
                 TOAGAGTATTATTGCTGCTGCTTGTAGTAGAAGCGGCCGGAGAGTGCTGCACGTGG 
               
               
                   
               
               
                 ACAGCAGATCCTACTATGGCGGCAACTGGGCCTCTTTCAGCTTTTCCGGCCTGCTG 
               
               
                   
               
               
                 AGCTGGCTGAAGGAGTACCAGGAGAACTCCGACATCGTGTCTGATAGCCCCGTGT 
               
               
                   
               
               
                 GOCAGGACCAGATCCTGGAGAATGAGGAGGCCATCGCCCTGTCCAGGAAGGATAA 
               
               
                   
               
               
                 GACCATCCAGCACGTGGAGGTGTTCTGCTATGCCAGCCAGGACCTGCACGAGGAT 
               
               
                   
               
               
                 GTGGAGGAGOCAGGCGCCCTGCAGAAGAACCACGCCCTGGTGACCTCCGCCAATT 
               
               
                   
               
               
                 CTACAGAGGCCGCCGACTCCGCCTTTCTGCCTACCGAGGATGAGTCCCTOTCTACA 
               
               
                   
               
               
                 ATGTCTTOTGAGATGCTOACCGAGCAGACACCTAGCTCCGATCCAGAGAACGCCCT 
               
               
                   
               
               
                 GGAGGICAATGGCGCCGAGGTGACCGGCGAGAAGGAGAACCACTGCGACGATAA 
               
               
                   
               
               
                 GACCTGCGTOCCAAGCACATCCGCCGAGGACATGTCCGAGAACGTGCCTATCGCC 
               
               
                   
               
               
                 GAGGATACCACAGAGCAGCCAAAGAAGAATCGCATCACATACAGCCAGATCATCA 
               
               
                   
               
               
                 AGGAGGGCAGGCGCTTCAATATCGACCTGGTGTCTAAGCTGCTGTACAGCCGGGG 
               
               
                   
               
               
                 CCTGCTGATCGATCTGCTGATCAAGAGCAACGTGTCCCGCTATGCCGAGTTCAAGA 
               
               
                   
               
               
                 ATATCACCAGAATCCTGGCCTTTCGGGAGGGAAGAGTGGAGCAGGTGCCCTGCAG 
               
               
                   
               
               
                 CAGAGCCGACGTGTTCAACTCCAAGCAGCTGACAATGGTGGAGAAGAGGATGCTG 
               
               
                   
               
               
                 ATGAAGTTCCTOACATTTTGTATGGAGTACGAGAAGTATCCAGATGAGTACAAGGG 
               
               
                   
               
               
                 CTATGAGGAGATCACCTTTTACGAGTATCTGAAGACCCAGAAGCTGACACCCAATC 
               
               
                   
               
               
                 TOCAGTACATCGTGATGCACTCCATCGCCATGACCTCTGAGACAGCCTCTAGCACC 
               
               
                   
               
               
                 ATCGACGGCCTGAAGGCCACAAAGAACTTCCTGCACTOCCTGGOCCGGTACGGCA 
               
               
                   
               
               
                 ATACACCCTTCCTGTTTCCTCTGTATGGCCAGGGCGAGCTGCCCCAGTGCTTCTGTA 
               
               
                   
               
               
                 GAATGTGCGCCGTGTTTGGCGGCATCTATTGCCTGAGGCACTCTGTGCAGTGTCTG 
               
               
                   
               
               
                 GTGGTOGACAAGGAGAGCCGCAAGTGTAAGGCCATCATCGATCAGTTTGGCCAGC 
               
               
                   
               
               
                 GGATCATCTCTGAGCACTTCCTGGTGGAGGACAGCTACTTTCCTGAGAACATGTGC 
               
               
                   
               
               
                 TCCAGGGTGCAGTATCGCCAGATCAGCCGGGCCGTGCTGATCACCGATAGATCCGT 
               
               
                   
               
               
                 GCTGAAGACAGACAGCGATCAGCAGATCAGCATCCTGACCGTGCCAGCAGAGGAG 
               
               
                   
               
               
                 CCAGGCACCTTCGCCGTGAGAGTGATCGAGCTGTGCTCCTCTACCATGACATGTAT 
               
               
                   
               
               
                 GAAOGGCACCTACCTGGTGCACCTGACCTGCACAAGCTCCAAGACAGCCCGCGAG 
               
               
                   
               
               
                 GACCTOGGAGAGCGTGGTGCAGAAGCTGTTCGTGCCCTACACCGAGATGGAGATCG 
               
               
                   
               
               
                 AGAACGAGCAGGTGGAGAAGCCTAGAATCCTGTGGGCCCTGTACTTCAACATGAG 
               
               
                   
               
               
                 AGACTCTAGCGATATCTCTAGGAGCTGTTACAACGATCTGCCCTCTAACGTGTACG 
               
               
                   
               
               
                 TGTGCAGCGGACCTGACTGTGGCCTGGGAAACGATAATGCCGTGAAGCAGGCCGA 
               
               
                   
               
               
                 GACACTGTTCCAGGAGATTTGCCCTAACGAGGACTTTTGTCCCCCTCCACCCAATC 
               
               
                   
               
               
                 CAGAGGATATCATCCTGGACGGCGATTCCCTGCAGCCAGAGGCCTCTGAGTCCTCT 
               
               
                   
               
               
                 GCCATCCCCGAGGCCAATAGCGAAACATTCAAAGAAAGCACAAATCTGGGAAACC 
               
               
                   
               
               
                 TGGAAGAAAGTAGTGAGTAA  
               
            
           
         
       
     
     In some embodiments, a codon-optimized sequence encoding human REP1 is provided lacking the TAA stop codon of SEQ ID NO:1 (i.e. consisting of nucleotides 1-1959 of SEQ ID NO:1). 
     In one aspect, the disclosure provides a polynucleotide comprising the nucleotide sequence of SEQ ID NO:1 or polynucleotide comprising a nucleotide sequence at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the nucleotide sequence of SEQ ID NO:1 and which encodes a human REP1 polypeptide having the amino acid sequence of SEQ ID NO:2: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 2) 
               
               
                 MADTLPSEFDVIVIGTGLPESIIAAACSRSGRRVLHVDSRSYYGGNWAS 
               
               
                   
               
               
                 FSFSGLLSWLKEYQENSDIVSDSPVWQDQILENEEAIALSRKDKTIQHV 
               
               
                   
               
               
                 EVFCYASQDLHEDVEEAGALQKNHALVTSANSTEAADSAFLPTEDESLS 
               
               
                   
               
               
                 TMSCEMLTEQTPSSDPENALEVNGAEVTGEKENHCDDKTCVPSTSAEDM 
               
               
                   
               
               
                 SENVPIAEDTTEQPKKNRITYSQIIKEGRRFNIDLVSKLLYSRGLLIDL 
               
               
                   
               
               
                 LIKSNVSRYAEFKNITRILAFREGRVEQVPCSRADVFNSKQLTMVEKRM 
               
               
                   
               
               
                 LMKFLTFCMEYEKYPDEYKGYEEITFYEYLKTQKLTPNLQYIVMHSIAM 
               
               
                   
               
               
                 TSETASSTIDGLKATKNFLHCLGRYGNTPFLFPLYGQGELPQCFCRMCA 
               
               
                   
               
               
                 VFGGIYCLRHSVQCLVVDKESRKCKAIIDQFGQRIISEHFLVEDSYFPE 
               
               
                   
               
               
                 NMCSRVQYRQISRAVLITDRSVLKTDSDQQISILTVPAEEPGTFAVRVI 
               
               
                   
               
               
                 ELCSSTMTCMKGTYLVHLTCTSSKTAREDLESVVQKLFVPYTEMEIENE 
               
               
                   
               
               
                 QVEKPRILWALYFNMRDSSDISRSCYNDIPSNVYVCSGPDCGLGNDNAV 
               
               
                   
               
               
                 KQAETLFQEICPNEDFCPPPPNPEDIILDGDSLQPEASESSAIPEANSE 
               
               
                   
               
               
                 TFKESTNLGNLEESSE  
               
            
           
         
       
     
     The term “codon-optimized” as it refers to genes or coding regions of nucleic acid molecules for transformation of various hosts, refers to the alteration of codons in the gene or coding regions of the nucleic acid molecules to reflect the typical codon usage of the host organism without altering the polypeptide encoded by the DNA. Such optimization includes replacing at least one, or more than one, or a significant number, of codons with one or more codons that are more frequently used in the genes of that organism. 
     Deviations in the nucleotide sequence that comprises the codons encoding the amino acids of, any polypeptide chain allow for variations in the sequence coding for the gene. Since each codon consists of three nucleotides, and the nucleotides comprising DNA are restricted to four specific bases, there are 64 possible combinations of nucleotides, 61 of which encode amino acids (the remaining three codons encode signals ending translation). The “genetic code” which shows which codons encode which amino acids is reproduced herein as Table 1. As a result, many amino acids are designated by more than one codon. For example, the amino acids alanine and proline are coded for by four triplets, serine and arginine by six, whereas tryptophan and methionine are coded by just one triplet. This degeneracy allows for DNA base composition to vary over a wide range without altering the amino acid sequence of the proteins encoded by the DNA. 
     
       
         
           
               
             
               
                 TABLE-US-00001 TABLE 1 
               
               
                   
               
               
                 The Standard Genetic Code 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 T C A G TTT TPhe (F) TCT Ser (S) TAT Tyr (Y) TGT  
               
               
                   
               
               
                 Cys (C) TTC Phe (F) TCC Ser (S) TAG Tyr (Y) TGC  
               
               
                   
               
               
                 TTA Leu (L) TCA Ser (S) TAA Stop TGA Stop TTG  
               
               
                   
               
               
                 Leu (L) TCG Ser (S) TAG Stop TGG Trp (W) C CTT  
               
               
                   
               
               
                 Leu (L) CCT Pro (P) CAT His (H) CGT Arg (R) CTC  
               
               
                   
               
               
                 Leu (L) CCC Pro (P) CAC His (H) CGC Arg (R) CTA  
               
               
                   
               
               
                 Leu (L) CCA Pro (P) CAA Gln (Q) CGA Arg (R) CTG  
               
               
                   
               
               
                 Leu (L) CCG Pro (P) CAG Gln (Q) CGG Arg (R) AAT  
               
               
                   
               
               
                 THe (I) ACT Thr (T) AAT Asn (N) AGT Ser (S) ATC  
               
               
                   
               
               
                 Ile (I) ACC Thr (T) AAC Asn (N) AGC Ser (S) ATA  
               
               
                   
               
               
                 Ile (I) ACA Thr (T) AAA Lys (K) AGA Arg (R) ATG  
               
               
                   
               
               
                 Met (M) ACG Thr (T) AAG Lys (K) AGG Arg (R) G  
               
               
                   
               
               
                 GTT Val (V) GCT Ala (A) GAT Asp (D) GGT Gly (G)  
               
               
                   
               
               
                 GTC Val (V) GCC Ala (A) GAC Asp (D) GGC Gly (G)  
               
               
                   
               
               
                 GTA Val (V) GCA Ala (A) GAA Glu (E) GGA Gly (G)  
               
               
                   
               
               
                 GTG Val (V) GCG Ala (A) GAG Glu (E) GGG Gly 
               
               
                   
               
            
           
         
       
     
     Many organisms display a bias for use of particular codons to code for insertion of a particular amino acid in a growing peptide chain. Codon preference, or codon bias, differences in codon usage between organisms, is afforded by degeneracy of the genetic code, and is well documented among many organisms. Codon bias often correlates with the efficiency of translation of messenger RNA (mRNA), which is in turn believed to be dependent on, inter alia, the properties of the codons being translated and the availability of particular transfer RNA (tRNA) molecules. The predominance of selected tRNAs in a cell is generally a reflection of the codons used most frequently in peptide synthesis. Accordingly, genes can be tailored for optimal gene expression in a given organism based on codon optimization. 
     Given the large number of gene sequences available for a wide variety of animal, plant and microbial species, the relative frequencies of codon usage have been calculated. Codon usage tables are available, for example, at the “Codon Usage Database” available on the world wide web at kazusa.or.jp/codon/ (visited Jun. 18, 2012). See Nakamura, Y., et al. Nucl. Acids Res. 28:292 (2000). 
     Randomly assigning codons at an optimized frequency to encode a given polypeptide sequence can be done manually by calculating codon frequencies for each amino acid, and then assigning the codons to the polypeptide sequence randomly. Additionally, various algorithms and computer software programs can be used to calculate an optimal sequence. 
     Non-Viral Vectors 
     In some embodiments, a non-viral vector (e.g. an expression plasmid) comprising a modified nucleic acid as herein described is provided. Preferably, the non-viral vector is a plasmid comprising a nucleic acid sequence of SEQ ID NO: 1, or a sequence at least 90% identical thereto. 
     Viral Vectors 
     In preferred embodiments, a viral vector comprising a modified (codon optimized) nucleic acid as herein described is provided. Preferably, the viral vector comprises a nucleic acid sequence of SEQ ID NO: 1, or a sequence at least 90% identical thereto, operably linked to an expression control sequence. Examples of suitable viral vectors include but are not limited to adenoviral, retroviral, lentiviral, herpesvirus and adeno-associated virus (AAV) vectors. 
     In a preferred embodiment, the viral vector includes a portion of a parvovirus genome, such as an AAV genome with the rep and cap genes deleted and/or replaced by the modified REP1 gene sequence and its associated expression control sequences. The modified human REP1 gene sequence is typically inserted adjacent to one or two (i.e., is flanked by) AAV TRs or TR elements adequate for viral replication (Xiao et al., 1997, J. Virol. 71(2): 941-948), in place of the nucleic acid encoding viral rep and cap proteins. Other regulatory sequences suitable for use in facilitating tissue-specific expression of the modified REP1 gene sequence in the target cell may also be included. 
     In some preferred embodiments, the AAV viral vector comprises a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) a codon optimized REP1 gene as herein described (d) a polyadenylation sequence and (e) an AAV2 terminal repeat. In a particularly preferred embodiment, the AAV viral vector comprises a nucleic acid (transgene cassette) comprising the sequence of SEQ ID NO:5 or a sequence at least 90%, at least 95%, at least 98% or at least 99% identical thereto: 
     
       
         
           
               
               
            
               
                 (SEQ ID NO: 5 
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 TTGGCCACTC 
                 CCTCTCTGCG 
                 CGCTCGCTCG 
                 CTCACTGAGG 
                 CCGGGCGACC 
                 AAAGGTCGCC 
                 60 
                   
               
               
                   
               
               
                 CGACGCCCGG 
                 GCTTTGCCCG 
                 GGCGGCCTCA 
                 GTGAGCGAGC 
                 GAGCGCGCAG 
                 AGAGGGAGTG 
                 120 
               
               
                   
               
               
                 GCCAACTCCA 
                 TCACTAGGGG 
                 TTCCTATCGA 
                 TTGAATTCCC 
                 CGGGGATCCA 
                 CTAGTTATTA 
                 180 
               
               
                   
               
               
                 ATAGTAATCA 
                 ATTACGGGGT 
                 CATTAGTTCA 
                 TAGCCCATAT 
                 ATCGAGTTCC 
                 GCGTTACATA 
                 240 
               
               
                   
               
               
                 ACTTACGGTA 
                 AATGGCCGGC 
                 CTGGCTGACC 
                 GCCCAACGAC 
                 CCCCGCCCAT 
                 TGACGTCAAT 
                 300 
               
               
                   
               
               
                 AATGACGTAT 
                 GTTCCCATAG 
                 TAACGCCAAT 
                 AGGGACTTTC 
                 CATTGAGGTC 
                 AATGGGTGGA 
                 360 
               
               
                   
               
               
                 GTATTTACGG 
                 TAAACTGCCC 
                 ACTTGGCAGT 
                 ACATCAAGTG 
                 TATCATATGC 
                 CAAGTACGCC 
                 420 
               
               
                   
               
               
                 CCCTATTGAC 
                 GTCAATGACG 
                 GTAAATGGCC 
                 CGCCTGGCAT 
                 TATGCCCAGT 
                 ACATGACCTT 
                 480 
               
               
                   
               
               
                 ATGGGACTTT 
                 CCTACTTGGC 
                 AGTACATCTA 
                 CGTATTAGTC 
                 ATCGCTATTA 
                 CCATGGTCGA 
                 540 
               
               
                   
               
               
                 GGTGAGCCCC 
                 ACGTTCTGCT 
                 TCACTCTCCC 
                 CATCTCCCCC 
                 CCCTCCCCAC 
                 CCCCAATTTT 
                 600 
               
               
                   
               
               
                 GTATTTATTT 
                 ATTTTTTAAT 
                 TATTTTGTGC 
                 AGCGATGGCG 
                 GCGGGGGGGG 
                 GGGGGGGGCG 
                 660 
               
               
                   
               
               
                 CGCGCCAGGC 
                 GGGGCGGGGC 
                 GGGGCGAGGG 
                 GCGGGGCGGG 
                 GCGAGGCGGA 
                 GAGGTGCGGC 
                 720 
               
               
                   
               
               
                 GGCAGCCAAT 
                 CAGAGCGGCG 
                 CGCTCCGAAA 
                 GTTTCCTTTT 
                 ATGGCGAGGC 
                 GGCGGCGGCG 
                 780 
               
               
                   
               
               
                 GCGGCCCTAT 
                 AAAAAGCGAA 
                 GCGCGCGGCE 
                 GGCGGGGAGT 
                 CGCTGCGACG 
                 CTGCCTTCGC 
                 840 
               
               
                   
               
               
                 CCCGTGCCCC 
                 GCTCCGCCGC 
                 CGCCTCGCGC 
                 CGCCCGCCCC 
                 GGCTCTGACT 
                 GACCGCGTTA 
                 900 
               
               
                   
               
               
                 CTCCCACAGG 
                 TGAGCGGGCG 
                 GGACGGCCCT 
                 TCTCCTCCGG 
                 GCTGTAATTA 
                 GCGCTTGGTT 
                 960 
               
               
                   
               
               
                 TAATGACGGC 
                 TTGTTTCTTT 
                 TCTGTGGCTG 
                 CGTGAAAGCC 
                 TTGAGGGGCT 
                 CCGGGAGGGC 
                 1020 
               
               
                   
               
               
                 CCTTTGTGCG 
                 GGGGGAGCGG 
                 CTCGGGGGGT 
                 GCGTGCGTGT 
                 GTGTGTGCGT 
                 GGGGAGCGCC 
                 1030 
               
               
                   
               
               
                 GCGTGCGGCT 
                 CCGCGCTGCC 
                 CGGCGGCTGT 
                 GAGCGCTGCG 
                 GGCGCGGCGG 
                 GGGGCTTTGT 
                 1140 
               
               
                   
               
               
                 GCGCTCCGCA 
                 GTGTGCGCGA 
                 GGGGAGCGCG 
                 GCCGGGGGCG 
                 GTGCCCCGCG 
                 GTGCGGGGGG 
                 1200 
               
               
                   
               
               
                 GGCTGCGAGG 
                 GGAACAAAGG 
                 CTGCGTGCGG 
                 GGTGTGTGCG 
                 TGGGGGGGTG 
                 AGCAGGGGGT 
                 1260 
               
               
                   
               
               
                 GTGGGCGCGT 
                 CGGTCGGGCT 
                 GCAACCCCCC 
                 CTGCACCCCC 
                 CTCCCCGAGT 
                 TGCTGAGCAC 
                 1320 
               
               
                   
               
               
                 GGCCCGGCTT 
                 CGGGTGCGGG 
                 GCTCCGTACG 
                 GGGCGTGGCG 
                 CGGGGCTCGC 
                 CGTGCCGGGC 
                 1380 
               
               
                   
               
               
                 GGGGGGTGGC 
                 GGCAGGTGCG 
                 GGTGCCGGGC 
                 GGGGCGGGGC 
                 CGCCTCGGGC 
                 CGGGGAGGGC 
                 1440 
               
               
                   
               
               
                 TCGGGGGAGG 
                 GGCGCGGCGG 
                 CCCCCGGAGC 
                 GCCGGCGGCT 
                 GTCGAGGCGC 
                 GGCGAGCCGC 
                 1500 
               
               
                   
               
               
                 AGCCATTGCC 
                 TTTTATGGTA 
                 ATCGTGCGAG 
                 AGGGCGCAGG 
                 GACTTCCTTT 
                 GTCCCAAATC 
                 1560 
               
               
                   
               
               
                 TGTGCGGAGC 
                 CGAAATCTGG 
                 GAGGCGCGGC 
                 CGCACCCCCT 
                 CTAGCGGGCG 
                 CGGGGCGAAG 
                 1620 
               
               
                   
               
               
                 CGGTGCGGCG 
                 CCGGCAGGAA 
                 GGAAATGGGC 
                 GGGGAGGGCC 
                 TTCGTGCGTC 
                 GGCGCGGCGG 
                 1680 
               
               
                   
               
               
                 CGTCCCCTTC 
                 TCCCTCTCCA 
                 GCCTCGGGGC 
                 TGTCCGCGGG 
                 GGGACGGCTG 
                 CCTTCGGGGG 
                 1740 
               
               
                   
               
               
                 GGACGGGGCA 
                 GGGCGGGGTT 
                 CGGCTTCTGG 
                 CGTGTGACCG 
                 GCGGCTCTAG 
                 AGCCTCTGCT 
                 1800 
               
               
                   
               
               
                 AACCATGTTC 
                 ATGCCTTCTT 
                 CTTTTTCCTA 
                 CAGTCTAGAG 
                 TCGACCTGCA 
                 GAAGCTTCCA 
                 1860 
               
               
                   
               
               
                 CCATGGCTGA 
                 TACACTGCCT 
                 TCTGAGTTTG 
                 ATGTGATCGT 
                 GATTGGAACT 
                 GGACTGCCTG 
                 1920 
               
               
                   
               
               
                 AGAGTATTAT 
                 TGCTGCTGCT 
                 TGTAGTAGAA 
                 GCGGCCGGAG 
                 AGTGCTGCAC 
                 GTGGACAGCA 
                 1980 
               
               
                   
               
               
                 GATCCTACTA 
                 TGGCGGCAAC 
                 TGGGCCTCTT 
                 TCAGCTTTTC 
                 CGGCCTGCTG 
                 AGCTGGCTGA 
                 2040 
               
               
                   
               
               
                 AGGAGTACCA 
                 GGAGAACTCC 
                 GACATCGTGT 
                 CTGATAGCCC 
                 CGTGTGGCAG 
                 GACCAGATCC 
                 2100 
               
               
                   
               
               
                 TGGAGAATGA 
                 GGAGGCCATC 
                 GCCCTGTCCA 
                 GGAAGGATAA 
                 GACCATCCAG 
                 CACGTGGAGG 
                 2160 
               
               
                   
               
               
                 TGTTCTGCTA 
                 TGCCAGCCAG 
                 GACCTGCACG 
                 AGGATGTGGA 
                 GGAGGCAGGC 
                 GCCCTGCAGA 
                 2220 
               
               
                   
               
               
                 AGAACCACGC 
                 CCTGGTGACC 
                 TCCGCCAATT 
                 CTACAGAGGC 
                 CGCCGACTCC 
                 GCCTTTCTGC 
                 2280 
               
               
                   
               
               
                 CTACCGAGGA 
                 TGAGTCCCTG 
                 TCTACAATGT 
                 CTTGTGAGAT 
                 GCTGACCGAG 
                 CAGACACCTA 
                 2340 
               
               
                   
               
               
                 GCTCCGATCG 
                 AGAGAACGCC 
                 CTGGAGGTCA 
                 ATGGCGCCGA 
                 GGTGACCGGC 
                 GAGAAGGAGA 
                 2400 
               
               
                   
               
               
                 ACCACTGCGA 
                 CGATAAGACC 
                 TGCGTGCCAA 
                 GCACATCCGC 
                 CGAGGACATG 
                 TCCGAGAACG 
                 2460 
               
               
                   
               
               
                 TGCCTATCGC 
                 CGAGGATACC 
                 ACAGAGCAGC 
                 CAAAGAAGAA 
                 TCGCATCACA 
                 TACAGCCAGA 
                 2520 
               
               
                   
               
               
                 TCATCAAGGA 
                 GGGCAGGCGC 
                 TTCAATATCG 
                 ACCTGGTGTC 
                 TAAGCTGCTG 
                 TACAGCCGGG 
                 2580 
               
               
                   
               
               
                 GCCTGCTGAT 
                 CGATCTGCTG 
                 ATCAAGAGCA 
                 ACGTGTCCCG 
                 CTATGCCGAG 
                 TTCAAGAATA 
                 2640 
               
               
                   
               
               
                 TCACCAGAAT 
                 CCTGGCCTTT 
                 CGGGAGGGAA 
                 GAGTGGAGCA 
                 GGTGCCCTGC 
                 AGCAGAGCCG 
                 2700 
               
               
                   
               
               
                 ACGTGTTCAA 
                 CTCCAAGCAG 
                 CTGACAATGG 
                 TGGAGAAGAG 
                 GATGCTGATG 
                 AAGTTCCTGA 
                 2760 
               
               
                   
               
               
                 CATTTTGTAT 
                 GGAGTACGAG 
                 AAGTATCCAG 
                 ATGAGTACAA 
                 GGGCTATGAG 
                 GAGATCACCT 
                 2820 
               
               
                   
               
               
                 TTTACGAGTA 
                 TCTGAAGACC 
                 CAGAAGCTGA 
                 CACCCAATCT 
                 GCAGTACATC 
                 GTGATGCACT 
                 2880 
               
               
                   
               
               
                 CCATCGCCAT 
                 GACCTCTGAG 
                 ACAGCCTCTA 
                 GCACCATCGA 
                 CGGCCTGAAG 
                 GCCACAAAGA 
                 2940 
               
               
                   
               
               
                 ACTTCCTGCA 
                 CTGCCTGGGC 
                 CGGTACGGCA 
                 ATACACCCTT 
                 CCTGTTTCCT 
                 CTGTATGGCC 
                 3000 
               
               
                   
               
               
                 AGGGCGAGCT 
                 GCCCCAGTGC 
                 TTCTGTAGAA 
                 TGTGGGCCGT 
                 GTTTGCCGGC 
                 ATCTATTGCC 
                 3060 
               
               
                   
               
               
                 TGAGGCACTC 
                 TGTGCAGTGT 
                 CTGGTGGTGG 
                 ACAAGGAGAG 
                 CCGCAAGTGT 
                 AAGGCCATCA 
                 3120 
               
               
                   
               
               
                 TCGATCAGTT 
                 TGGCCAGCGG 
                 ATCATCTCTG 
                 AGCACTTCCT 
                 GGTGGAGGAC 
                 AGCTACTTTC 
                 3180 
               
               
                   
               
               
                 CTGAGAACAT 
                 GTGCTCCAGG 
                 GTGCAGTATC 
                 GCCAGATCAG 
                 CCGGGCCGTG 
                 CTGATCACCG 
                 3240 
               
               
                   
               
               
                 ATAGATCCGT 
                 GCTGAAGACA 
                 GACAGCGATC 
                 AGCAGATCAG 
                 CATCCTGACC 
                 GTGCCAGCAG 
                 3300 
               
               
                   
               
               
                 AGGAGTCAGG 
                 CACCTTCGCC 
                 GTGAGAGTGA 
                 TCGAGCTGTG 
                 CTCCTCTACC 
                 ATGACATGTA 
                 3360 
               
               
                   
               
               
                 TGAAGGGCAC 
                 CTACCTGGTG 
                 CACCTGACCT 
                 GCACAAGCTC 
                 CAAGACAGCC 
                 CGCGAGGACC 
                 3420 
               
               
                   
               
               
                 TGGAGAGCGT 
                 GGTGCAGAAG 
                 CTGTTCGTGC 
                 CCTACACCGA 
                 GATGGAGATC 
                 GAGAACGAGC 
                 3480 
               
               
                   
               
               
                 AGGTGGACAA 
                 GCCTAGAATC 
                 CTGTGGGCCC 
                 TGTACTTCAA 
                 CATGAGAGAC 
                 TCTAGCGATA 
                 3540 
               
               
                   
               
               
                 TCTCTAGGAG 
                 CTGTTACAAC 
                 GATCTGCCCT 
                 CTAACGTGTA 
                 CGTGTGCAGC 
                 GGACCTGACT 
                 3600 
               
               
                   
               
               
                 GTGGCCTGGG 
                 AAACGATAAT 
                 GCCGTGAAGC 
                 AGGCCGAGAC 
                 ACTGTTCCAG 
                 GAGATTTGCC 
                 3660 
               
               
                   
               
               
                 CTAACGAGGA 
                 CTTTTGTCCC 
                 CCTCCACCCA 
                 ATCCAGAGGA 
                 TATCATCCTG 
                 GACGGCGATT 
                 3720 
               
               
                   
               
               
                 CCCTGCAGCC 
                 AGAGGCCTCT 
                 GAGTCCTCTG 
                 CCATCCCCGA 
                 GGCCAATAGC 
                 GAAACATTCA 
                 3780 
               
               
                   
               
               
                 AAGAAAGCAC 
                 AAATCTGCGA 
                 AACCTGGAAG 
                 AAAGTAGTGA 
                 GTAAGCCTCG 
                 AGCAGCGCTG 
                 3840 
               
               
                   
               
               
                 CTCGAGAGAT 
                 CTGCGGCCGC 
                 GAGCTCGGGG 
                 ATCCAGACAT 
                 GATAAGATAC 
                 ATTGATGAGT 
                 3900 
               
               
                   
               
               
                 TTGGACAAAC 
                 CACAACTAGA 
                 ATGCAGTGAA 
                 AAAAATGCTT 
                 TATTTGTGAA 
                 ATTTGTGATG 
                 3960 
               
               
                   
               
               
                 CTATTGCTTT 
                 ATTTGTAACC 
                 ATTATAAGCT 
                 GCAATAAACA 
                 AGTTAACAAC 
                 AACAATTGCA 
                 4020 
               
               
                   
               
               
                 TTCATTTTAT 
                 GTTTCAGGTT 
                 CAGGGGGAGG 
                 TGTGGGAGGT 
                 TTTTTAAAGC 
                 AAGTAAAACC 
                 4080 
               
               
                   
               
               
                 TCTACAAATG 
                 TGGTATGGCT 
                 GATTATGATC 
                 AATGCATCCT 
                 AGCCGGAGGA 
                 ACCCCTAGTG 
                 4140 
               
               
                   
               
               
                 ATGGAGTTGG 
                 CCACTCCCTC 
                 TCTGCGCGCT 
                 CGCTCGCTCA 
                 CTGAGGCCGC 
                 CCGGGCAAAG 
                 4200 
               
               
                   
               
               
                 CCCGGGCGTC 
                 GGGCGACCTT 
                 TGGTCGCCCG 
                 GCCTCAG1GA 
                 GCGAGCGAGC 
                 GCGCAGAGAG 
                 4260 
               
               
                   
               
               
                 GGAGTGGCCA 
                 A; 
                   
                   
                   
                   
                 4271 
               
            
           
         
       
     
     The components of the transgene cassette of SEQ ID NO:5 and their respective locations are identified in Table 2 below: 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Location (bp) 
                 Component 
                 Length (bp) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                  1-145 
                 5′ 1TR 
                 145 
               
               
                  170-1833 
                 CAG promoter 
                 1664 
               
               
                 1863-3824 
                 Codon-optimized hREP1 cDNA 
                 1962 
               
               
                 3867-4111 
                 SV40 PolyA 
                 245 
               
               
                 4127-4271 
                 3′ ITR 
                 145 
               
               
                   
               
            
           
         
       
     
     The 5′ ITR has the following sequence: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 6) 
               
               
                 TTGGCCACTCCCTCTCTGCGCGCTCGCTCGCTCACTGAGGCCGGGCGAC 
               
               
                   
               
               
                 CAAAGGTCGCCCGACGCCCGGGCTTTGCCCGGGCGGCCTCAGTGAGCGA 
               
               
                   
               
               
                 GCGAGCGCGCAGAGAGGGAGTGGCCAACTCCATCACTAGGGGTTCCT 
               
            
           
         
       
     
     The 3′ ITR has the following sequence: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 7) 
               
               
                 AGCCGGAGGAACCCCTAGTGATGGAGTTGGCCACTCCCTCTCTGCGCGC 
               
               
                   
               
               
                 TCGCTCGCTCACTGAGGCCGCCCGGGCAAAGCCCGGGCGTCGGGCGACC 
               
               
                   
               
               
                 TTTGGTCGCCCGGCCTCAGTGAGCGAGCGAGCGCGCAGAGAGGGAGTGG 
               
               
                   
               
               
                 CCAA 
               
            
           
         
       
     
     The SV40 polyadenylation sequence has the following sequence: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 8) 
               
               
                 GAGCTCGGGGATCCAGACATGATAAGATACATTGATGAGTTTGGACAAA 
               
               
                   
               
               
                 CCACAACTAGAATGCAGTGAAAAAAATGCTTTATTTGTGAAATTTGTGA 
               
               
                   
               
               
                 TGCTATTGCTTTATTTGTAACCATTATAAGCTGCAATAAACAAGTTAAC 
               
               
                   
               
               
                 AACAACAATTGCATTCATTTTATGTTTCAGGTTCAGGGGGAGGTGTGGG 
               
               
                   
               
               
                 AGGTTTTTTAAAGCAAGTAAAACCTCTACAAATGTGGTATGGCTGATTA 
               
               
                   
               
               
                 TGATCAATGCATCCT 
               
            
           
         
       
     
     Those skilled in the art will appreciate that an AAV vector comprising a transgene and lacking virus proteins needed for viral replication (e.g., cap and rep), cannot replicate since such proteins are necessary for virus replication and packaging. Helper viruses include, typically, adenovirus or herpes simplex virus. Alternatively, as discussed below, the helper functions (E1a, E1b, E2a, E4, and VA RNA) can be provided to a packaging cell including by transfecting the cell with one or more nucleic acids encoding the various helper elements and/or the cell can comprise the nucleic acid encoding the helper protein. For instance, HEK 293 were generated by transforming human cells with adenovirus 5 DNA and now express a number of adenoviral genes, including, but not limited to E1 and E3 (see, e.g., Graham et al., 1977, J. Gen. Virol. 36:59-72). Thus, those helper functions can be provided by the HEK 293 packaging cell without the need of supplying them to the cell by, e.g., a plasmid encoding them. 
     The viral vector may be any suitable nucleic acid construct, such as a DNA or RNA construct and may be single stranded, double stranded, or duplexed (i.e., self complementary as described in WO 2001/92551). 
     The viral capsid component of the packaged viral vectors may be a parvovirus capsid. AAV Cap and chimeric capsids are preferred. For example, the viral capsid may be an AAV capsid (e.g., AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7 AAV8, AAV9, AAV10, AAV11, AAV12, AAV1.1, AAV2.5, AAV6.1, AAV6.3.1, AAV9.45, AAVrb10, AAVrh74, RHM4-1, AAV2-TT, AAV2-TT-S312N, AAV3B-S312N, AAV-LK03, snake AAV, avian AAV, bovine AAV, canine AAV, equine AAV, ovine AAV, goat AAV, shrimp AAV, and any other AAV now known or later discovered, see, e.g., Fields et al., VIROLOGY, volume 2, chapter 69 (4.sup.th ed., Lippincott-Raven Publishers). 
     In some embodiments, the viral capsid component of the packaged viral vector is a variant of a native AAV capsid (i.e. comprises one or more modifications relative to a native AAV capsid). In some embodiments, the capsid is a variant of an AAV2, AAV5 or AAV8 capsid. In preferred embodiments, the capsid is a variant of an AAV2 capsid, such as those described in U.S. Patent Application Publication Number 2019/0255192A1 (e.g. comprising the amino acid sequence of any of SEQ ID NOs: 42-59). In a particularly preferred embodiment, the capsid comprises a capsid protein having the following amino acid sequence: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 9) 
               
               
                 MAADGYLPDWLEDTLSEGIRQWWKLKPGPPPPKAAERHKDDSRGLVLPG 
               
               
                   
               
               
                 YKYLGPFNGLDKGEPVNEADAAALEHDKAYDRQLDSGDNPYLKYNHADA 
               
               
                   
               
               
                 EFQERLKEDTSFGGNLGRAVFQAKKRVLEPLGLVEEPVKTAPGKKRPVE 
               
               
                   
               
               
                 HSPVEPDSSSGTGKAGQQPARKRLNFGQTGDADSVPDPQPLGQPPAAPS 
               
               
                   
               
               
                 GLGTNTMATGSGAPMADNNEGADGVGNSSGNWHCDSTWMGDRVITTSTR 
               
               
                   
               
               
                 TWALPTYNNHLYKQISSQSGASNDNHYFGYSTPWGYFDFNRFHCHFSPR 
               
               
                   
               
               
                 DWQRLINNNWGFRPKRLNFKLFNIQVKEVTQNDGTTTIANNLTSTVQVF 
               
               
                   
               
               
                 TDSEYQLPYVLGSAHQGCLPPFPADVFMVPQYGYLTLNNGSQAVGRSSF 
               
               
                   
               
               
                 YCLEYFPSQMLRTGNNFTFSYTFEDVPFHSSYAHSQSLDRLMNPLIDQY 
               
               
                   
               
               
                 LYYLSRTNTPSGTTTQSRLQFSQAGASDIRDQSRNWLPGPCYRQQRVSK 
               
               
                   
               
               
                 TSADNNNSEYSWTGATKYHLNGRDSLVNPGPAMASHKDDEEKFFPQSGV 
               
               
                   
               
               
                 LIFOKQGSEKTNVDIEKVMITDEEEIRTTNPVATEQYGSVSTNLQRGNL 
               
               
                   
               
               
                 AISDQTKHARQAATADVNTQGVLPGMVWQDRDVYLQGPIWAKIPHTDGH 
               
               
                   
               
               
                 FHPSPLMGGFGLKHPPPQILIKNTPVPANPSTTFSAAKFASFITQYSTG 
               
               
                   
               
               
                 QVSVEIEWELQKENSKRWNPEIQYTSNYNKSVNVDFTVDTNGVYSEPRP 
               
               
                   
               
               
                 IGTRYLTRNL  
               
            
           
         
       
     
     The variant AAV capsid protein of SEQ ID NO:9 contains the following modifications relative to native AAV2 capsid: (i) a proline (P) to alanine (A) mutation at amino acid position 34, which is located inside the assembled capsid (VP1 protein only), and (ii) an insertion of 10 amino acids (leucine-alanine-isoleucine-serine-aspartic acid-glutamine-threonine-lysine-histidine-alanine/LAISDQTKHA) at amino acid position 588, which is present in VP1, VP2, and VP3. 
     A full complement of AAV Cap proteins includes VP1, VP2, and VP3. The ORF comprising nucleotide sequences encoding AAV VP capsid proteins may comprise less than a full complement AAV Cap proteins or the full complement of AAV Cap proteins may be provided. 
     In yet another embodiment the present invention provides for the use of ancestral AAV vectors for use in therapeutic in vivo gene therapy. Specifically, in silico-derived sequences were synthesized de novo and characterized for biological activities. This effort led to the generation of nine functional putative ancestral AAVs and the identification of Anc80, the predicted ancestor of AAV serotypes 1, 2, 8 and 9 (Zinn et al., 2015, Cell Reports 12:1056-1068). Predicting and synthesis of such ancestral sequences in addition to assembling into a virus particle may be accomplished by using the methods described in WO 2015/054653, the contents of which are incorporated by reference herein. Notably, the use of the virus particles assembled from ancestral viral sequences may exhibit reduced susceptibility to pre-existing immunity in current day human population than do contemporary viruses or portions thereof. 
     The invention includes packaging cells, which are encompassed by “host cells,” which may be cultured to produce packaged viral vectors of the invention. The packaging cells of the invention generally include cells with heterologous (1) viral vector function(s), (2) packaging function(s), and (3) helper function(s). Each of these component functions is discussed in the ensuing sections. 
     Initially, the vectors can be made by several methods known to skilled artisans (see, e.g., WO 2013/063379). A preferred method is described in Grieger, et. al. 2015, Molecular Therapy 24(2):287-297, the contents of which are incorporated by reference herein for all purposes. Briefly, efficient transfection of HEK293 cells is used as a starting point, wherein an adherent HEK293 cell line from a qualified clinical master cell bank is used to grow in animal component-free suspension conditions in shaker flasks and WAVE bioreactors that allow for rapid and scalable rAAV production. Using the triple transfection method (e.g., WO 96/40240), the suspension HEK293 cell line generates greater than 10 5  vector genome containing particles (vg)/cell or greater than 10 14  vg/L of cell culture when harvested 48 hours post-transfection. More specifically, triple transfection refers to the fact that the packaging cell is transfected with three plasmids: one plasmid encodes the AAV rep and cap genes, another plasmid encodes various helper functions (e.g., adenovirus or HSV proteins such as E1a, E1b, E2a, E4, and VA RNA, and another plasmid encodes the transgene and its various control elements (e.g., modified REP1 gene and CAG promoter). 
     To achieve the desired yields, a number of variables are optimized such as selection of a compatible serum-free suspension media that supports both growth and transfection, selection of a transfection reagent, transfection conditions and cell density. A universal purification strategy, based on ion exchange chromatography methods, was also developed that resulted in high purity vector preps of AAV serotypes 1-6, 8, 9 and various chimeric capsids. This user-friendly process can be completed within one week, results in high full to empty particle ratios (&gt;90% full particles), provides post-purification yields (&gt;10 13  vg/L) and purity suitable for clinical applications and is universal with respect to all serotypes and chimeric particles. This scalable manufacturing technology has been utilized to manufacture GMP Phase I clinical AAV vectors for retinal neovascularization (AAV2), Hemophilia B (scAAV8), Giant Axonal Neuropathy (scAAV9) and Retinitis Pigmentosa (AAV2), which have been administered into patients. In addition, a minimum of a 5-fold increase in overall vector production by implementing a perfusion method that entails harvesting rAAV from the culture media at numerous time-points post-transfection. 
     The packaging cells include viral vector functions, along with packaging and vector functions. The viral vector functions typically include a portion of a parvovirus genome, such as an AAV genome, with rep and cap deleted and replaced by the modified REP1 sequence and its associated expression control sequences. The viral vector functions include sufficient expression control sequences to result in replication of the viral vector for packaging. Typically, the viral vector includes a portion of a parvovirus genome, such as an AAV genome with rep and cap deleted and replaced by the transgene and its associated expression control sequences. The transgene is typically flanked by two AAV TRs, in place of the deleted viral rep and cap ORFs. Appropriate expression control sequences are included, such as a tissue-specific promoter and other regulatory sequences suitable for use in facilitating tissue-specific expression of the transgene in the target cell. The transgene is typically a nucleic acid sequence that can be expressed to produce a therapeutic polypeptide or a marker polypeptide. 
     The terminal repeats (TR(s)) (resolvable and non-resolvable) selected for use in the viral vectors are preferably AAV sequences, with serotypes 1, 2, 3, 4, 5 and 6 being preferred. Resolvable AAV TRs need not have a wild-type TR sequence (e.g., a wild-type sequence may be altered by insertion, deletion, truncation or missense mutations), as long as the TR mediates the desired functions, e.g., virus packaging, integration, and/or provirus rescue, and the like. The TRs may be synthetic sequences that function as AAV inverted terminal repeats, such as the “double-D sequence” as described in U.S. Pat. No. 5,478,745 to Samulski et al., the entire disclosure of which is incorporated in its entirety herein by reference. Typically, but not necessarily, the TRs are from the same parvovirus, e.g., both TR sequences are from AAV2. 
     The packaging functions include capsid components. The capsid components are preferably from a parvoviral capsid, such as an AAV capsid or a chimeric AAV capsid function. Examples of suitable parvovirus viral capsid components are capsid components from the family Parvoviridae, such as an autonomous parvovirus or a Dependovirus. For example, the capsid components may be selected from AAV capsids, e.g., AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV10, AAV11, AAV12, AAVrh10, AAVrh74, RHM4-1, RHM15-1, RHM15-2, RHM15-3/RHM15-5, RHM15-4, RHM15-6, AAV Hu.26, AAV1.1, AAV2.5, AAV6.1, AAV6.3.1, AAV9.45, AAV2i8, AAV2G9, AAV2i8G9, AAV2-TT, AAV2-TT-S312N, AAV3B-S312N, and AAV-LK03, and other novel capsids as yet unidentified or from non-human primate sources. Capsid components may include components from two or more AAV capsids. 
     The packaged viral vector generally includes the modified REP1 gene sequence and expression control sequences flanked by TR elements, referred to herein as the “transgene” or “transgene expression cassette,” sufficient to result in packaging of the vector DNA and subsequent expression of the modified REP1 gene sequence in the transduced cell. The viral vector functions may, for example, be supplied to the cell as a component of a plasmid or an amplicon. The viral vector functions may exist extrachromosomally within the cell line and/or may be integrated into the cell&#39;s chromosomal DNA. 
     Any method of introducing the nucleotide sequence carrying the viral vector functions into a cellular host for replication and packaging may be employed, including but not limited to, electroporation, calcium phosphate precipitation, microinjection, cationic or anionic liposomes, and liposomes in combination with a nuclear localization signal. In embodiments wherein the viral vector functions are provided by transfection using a virus vector; standard methods for producing viral infection may be used. 
     The packaging functions include genes for viral vector replication and packaging. Thus, for example, the packaging functions may include, as needed, functions necessary for viral gene expression, viral vector replication, rescue of the viral vector from the integrated state, viral gene expression, and packaging of the viral vector into a viral particle. The packaging functions may be supplied together or separately to the packaging cell using a genetic construct such as a plasmid or an amplicon, a Baculovirus, or HSV helper construct. The packaging functions may exist extrachromosomally within the packaging cell, but are preferably integrated into the cell&#39;s chromosomal DNA. Examples include genes encoding AAV Rep and Cap proteins. 
     The helper functions include helper virus elements needed for establishing active infection of the packaging cell, which is required to initiate packaging of the viral vector. Examples include functions derived from adenovirus, baculovirus and/or herpes virus sufficient to result in packaging of the viral vector. For example, adenovirus helper functions will typically include adenovirus components E1a, E1b, E2a, E4, and VA RNA. The packaging functions may be supplied by infection of the packaging cell with the required virus. The packaging functions may be supplied together or separately to the packaging cell using a genetic construct such as a plasmid or an amplicon. See, e.g., pXR helper plasmids as described in Rabinowitz et al., 2002, J. Virol. 76:791, and pDG plasmids described in Grimm et al., 1998, Human Gene Therapy 9:2745-2760. The packaging functions may exist extrachromosomally within the packaging cell, but are preferably integrated into the cell&#39;s chromosomal DNA (e.g., E1 or E3 in HEK 293 cells). 
     Any suitable helper virus functions may be employed. For example, where the packaging cells are insect cells, baculovirus may serve as a helper virus. Herpes virus may also be used as a helper virus in AAV packaging methods. Hybrid herpes viruses encoding the AAV Rep protein(s) may advantageously facilitate for more scalable AAV vector production schemes. 
     Any method of introducing the nucleotide sequence carrying the helper functions into a cellular host for replication and packaging may be employed, including but not limited to, electroporation, calcium phosphate precipitation, microinjection, cationic or anionic liposomes, and liposomes in combination with a nuclear localization signal. In embodiments wherein the helper functions are provided by transfection using a virus vector or infection using a helper virus; standard methods for producing viral infection may be used. 
     Any suitable permissive or packaging cell known in the art may be employed in the production of the packaged viral vector. Mammalian cells or insect cells are preferred. Examples of cells useful for the production of packaging cells in the practice of the invention include, for example, human cell lines, such as VERO, WI38, MRC5, A549, HEK 293 cells (which express functional adenoviral E1 under the control of a constitutive promoter), B-50 or any other HeLa cells, HepG2, Saos-2, HuH7, and HT1080 cell lines. In one aspect, the packaging cell is capable of growing in suspension culture, more preferably, the cell is capable of growing in serum-free culture. In one embodiment, the packaging cell is a IHIEK293 that grows in suspension in serum free medium. In another embodiment, the packaging cell is the HEK293 cell described in U.S. Pat. No. 9,441,206 and deposited as ATCC No. PTA 13274. Numerous rAAV packaging cell lines are known in the art, including, but not limited to, those disclosed in WO 2002/46359. In another aspect, the packaging cell is cultured in the form of a cell stack (e.g. 10-layer cell stack seeded with HEK293 cells). 
     Cell lines for use as packaging cells include insect cell lines. Any insect cell which allows for replication of AAV and which can be maintained in culture can be used in accordance with the present invention. Examples include  Spodoptera frugiperda , such as the Sf9 or Sf21 cell lines,  Drosophila  spp. cell lines, or mosquito cell lines, e.g.,  Aedes albopictus  derived cell lines. A preferred cell line is the  Spodoptera frugiperda  Sf9 cell line. The following references are incorporated herein for their teachings concerning use of insect cells for expression of heterologous polypeptides, methods of introducing nucleic acids into such cells, and methods of maintaining such cells in culture: Methods in Molecular Biology, ed. Richard, Humana Press, N J (1995); O&#39;Reilly et al., Baculovirus Expression Vectors: A Laboratory Manual, Oxford Univ. Press (1994); Samulski et al., 1989, J. Virol. 63:3822-3828; Kajigaya et al., 1991, Proc. Nat&#39;l. Acad. Sci. USA 88: 4646-4650; Ruffing et al., 1992, J. Virol. 66:6922-6930; Kimbauer et al., 1996, Virol. 219:37-44; Zhao et al., 2000, Virol. 272:382-393; and Samulski et al., U.S. Pat. No. 6,204,059. 
     Virus capsids according to the invention can be produced using any method known in the art, e.g., by expression from a baculovirus (Brown et al., (1994) Virology 198:477-488). As a further alternative, the virus vectors of the invention can be produced in insect cells using baculovirus vectors to deliver the rep/cap genes and rAAV template as described, for example, by Urabe et al., 2002, Human Gene Therapy 13:1935-1943. 
     In another aspect, the present invention provides for a method of rAAV production in insect cells wherein a baculovirus packaging system or vectors may be constructed to carry the AAV Rep and Cap coding region by engineering these genes into the polyhedrin coding region of a baculovirus vector and producing viral recombinants by transfection into a host cell. Notably when using Baculavirus production for AAV, preferably the AAV DNA vector product is a self-complementary AAV like molecule without using mutation to the AAV1TR. This appears to be a by-product of inefficient AAV rep nicking in insect cells which results in a self-complementary DNA molecule by virtue of lack of functional Rep enzyme activity. The host cell is a baculovirus-infected cell or has introduced therein additional nucleic acid encoding baculovirus helper functions or includes these baculovirus helper functions therein. These baculovirus viruses can express the AAV components and subsequently facilitate the production of the capsids. 
     During production, the packaging cells generally include one or more viral vector functions along with helper functions and packaging functions sufficient to result in replication and packaging of the viral vector. These various functions may be supplied together or separately to the packaging cell using a genetic construct such as a plasmid or an amplicon, and they may exist extrachromosomally within the cell line or integrated into the cell&#39;s chromosomes. 
     The cells may be supplied with any one or more of the stated functions already incorporated, e.g., a cell line with one or more vector functions incorporated extrachromosomally or integrated into the cell&#39;s chromosomal DNA, a cell line with one or more packaging functions incorporated extrachromosomally or integrated into the cell&#39;s chromosomal DNA, or a cell line with helper functions incorporated extrachromosomally or integrated into the cell&#39;s chromosomal DNA. 
     The rAAV vector may be purified by methods standard in the art such as by column chromatography or cesium chloride gradients. Methods for purifying rAAV vectors are known in the art and include methods described in Clark et al., 1999, Human Gene Therapy 10(6):1031-1039; Schenpp and Clark, 2002, Methods Mol. Med. 69:427-443; U.S. Pat. No. 6,566,118 and WO 98/09657. 
     Treatment Methods 
     In certain embodiments, a method is provided for the treatment of choroideremia in a subject in need of such treatment by administering to the subject a therapeutically effective amount of a nucleic acid having a nucleotide sequence at least 90%, at least 95%, at least 98% identical, or 100% identical to the nucleotide sequence of SEQ ID NO:1 or a pharmaceutical composition comprising such a nucleic acid and at least one pharmaceutically acceptable excipient. 
     In related aspects, a nucleic acid comprising a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 for use in the treatment of choroideremia is provided. 
     In other related aspects, the use of a nucleic acid comprising a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 for the manufacture of a medicament is provided. 
     In other related aspects, the use of a nucleic acid comprising a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 for the manufacture of a medicament for the treatment of choroideremia is provided. 
     In some aspects, the nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 is operably linked to an expression control sequence. In some embodiments, the nucleotide sequence of SEQ ID NO:1 is operably linked to a CAG promoter. In some preferred embodiments, the CAG promoter has the sequence of SEQ ID NO:4. 
     In some embodiments, the nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 forms part of an expression cassette. In some aspects, the expression cassette comprises from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. In preferred embodiments, the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. In a particularly preferred embodiment, the expression cassette comprises a nucleic acid comprising the nucleotide sequence of SEQ ID NO:5 or a sequence at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% identical thereto. 
     In further embodiments, a method is provided for the treatment of choroideremia in a subject in need of such treatment by administering to the subject a therapeutically effective amount of a recombinant AAV (rAAV) virion, or a pharmaceutical composition comprising same, the rAAV virion comprising (i) a nucleic acid having a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 operably linked to an expression control sequence and (ii) an AAV capsid. 
     In related embodiments, provided is the use of a recombinant AAV (rAAV) virion comprising (i) a nucleic acid having a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 operably linked to an expression control sequence and (ii) an AAV capsid for the treatment of choroideremia. 
     In other related embodiments, provided is the use of a recombinant AAV (rAAV) virion comprising (i) a nucleic acid having a nucleotide sequence at least 90%, at least 95%, at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1 operably linked to an expression control sequence and (ii) an AAV capsid for the manufacture of a medicament for the treatment of choroideremia. 
     In some embodiments, the rAAV virion comprises a native AAV2, AAV4, AAV5 or AAV8 capsid. In other embodiments, the rAAV virion comprises a variant AAV capsid that comprises one or more modifications relative to AAV2, AAV4, AAV5 or AAV8. In a preferred embodiment, the AAV capsid comprises the sequence of SEQ ID NO:9. 
     In some embodiments, the rAAV virion comprises (i) a native AAV2 capsid or variant thereof and (ii) an expression cassette comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. In preferred embodiments, the rAAV comprises (i) a capsid comprising a capsid protein of SEQ ID NO:9 and (ii) a nucleic acid comprising a 5′ AAV2 terminal repeat of SEQ ID NO:6, a CAG promoter of SEQ ID NO:4, an SV40 polyadenylation sequence of SEQ ID NO:8 and a 3′ AAV2 terminal repeat of SEQ ID NO:7. In a particularly preferred embodiment, the rAAV comprises (i) a capsid comprising a capsid protein of SEQ ID NO:9 and (ii) an expression cassette comprising the nucleotide sequence of SEQ ID NO:5. 
     In particularly preferred embodiments, the use of an rAAV in the treatment of choroideremia or for the manufacture of a medicament for the treatment of choroideremia is provided, wherein the rAAV comprises (i) a nucleic acid comprising a nucleotide sequence of SEQ ID NO:5 and (ii) a capsid comprising a capsid protein having the amino acid sequence of SEQ ID NO:9. In some aspects, the rAAV is administered by intravitreal injection. 
     In other particularly preferred embodiments, a method for the treatment of choroideremia is provided comprising administering to the subject an effective amount of an rAAV comprising (i) a nucleic acid comprising a nucleotide sequence of SEQ ID NO:5 and (ii) a capsid comprising a capsid protein having the amino acid sequence of SEQ ID NO:9. In some aspects, the rAAV is administered to the subject by intravitreal injection. 
     In other aspects, a pharmaceutical composition is provided comprising a nucleic acid having a nucleotide sequence at least 90%, at least 95% at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:1, optionally operably linked to an expression control sequence, and at least one pharmaceutically acceptable excipient. 
     In some embodiments, the pharmaceutical composition comprises a nucleic acid comprising the nucleotide sequence of SEQ ID NO:1 operably linked to a constitutive promoter, preferably a CAG promoter having a sequence at least 90%, at least 95% at least 98% identical or 100% identical to the nucleotide sequence of SEQ ID NO:4. 
     In other aspects, a pharmaceutical composition is provided comprising at least one pharmaceutically acceptable excipient and an infectious rAAV comprising (i) an AAV capsid and (ii) a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. In related embodiments, the pharmaceutical composition comprises between 10 9  vg and 10 14  vg, preferably between 10 10  vg and 10 13  vg of the rAAV, more preferably comprises about 3×10 11  vg or about 1×10 12  vg of the rAAV. 
     In preferred embodiments, the pharmaceutical composition comprises an rAAV comprising (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising codon optimized REP1 gene of SEQ ID NO:1, wherein the nucleic acid further comprises a 5′ AAV2 terminal repeat of SEQ ID NO:6 and/or a CAG promoter of SEQ ID NO:4 and/or an SV40 polyadenylation sequence of SEQ ID NO:8 and/or an AAV2 terminal repeat of SEQ ID NO:7. In related embodiments, the pharmaceutical composition comprises between 10 9  vg and 10 14  vg, preferably between 10 10  vg and 10 13  vg of the rAAV, more preferably comprises about 3×10 11  vg or about 1×10 12  vg of the rAAV. 
     In some embodiments, a method for expressing REP1 in one or more retinal pigmented epithelial cells and one or more rod photoreceptor cells of a human subject is provided comprising administering to the human subject an effective amount of an infectious rAAV as herein described, wherein the REP1 is expressed in the one or more retinal pigmented epithelial cells and one or more rod photoreceptor cells. In some preferred embodiments, the effective amount of infectious rAAV is 10 9  vg/eye to 10 14  vg/eye and/or a single dose of the rAAV is intravitreally administered (bilaterally or unilaterally) to the human subject and/or the rAAV comprises a capsid of SEQ ID NO:9 and/or the rAAV comprises a heterologous nucleic acid comprising the nucleotide sequence of SEQ ID NO:5. 
     In a particularly preferred embodiment, a pharmaceutical composition is provided comprising at least one pharmaceutically acceptable excipient and an infectious rAAV comprising (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:5. In related embodiments, the pharmaceutical composition comprises 10 9  vg and 10 14  vg, preferably between 10 10  vg and 10 13  vg of the rAAV, more preferably comprises about 3×10 11  vg or about 1×10 12  vg of the rAAV. 
     In some embodiments, a nucleic acid or infectious rAAV as herein described is administered by periocular or intraocular (intravitreal, suprachoroidal or subretinal) injection to a human with choroideremia, whereby the choroideremia is treated in the subject. In other embodiments, a nucleic acid or infectious rAAV as herein described is administered subretinally or intravitreally to a human with choroideremia, whereby the choroideremia is treated in the subject. In preferred embodiments, a human subject with choroideremia is administered a single intravitreal injection (bilateral or unilateral) of an rAAV as herein described. 
     In related aspects, treatment of choroideremia in a treated subject comprises (i) an improvement (i.e. gain) in visual function or functional vision relative to a control (e.g. relative to a baseline measurement in the treated patient prior to treatment, relative to the untreated eye if the nucleic acid or rAAV is administered unilaterally, or relative to an untreated concurrent or historical control group of choroideremia patients) and/or (ii) a decrease in loss of visual function and/or retinal degeneration in a treated eye compared to a control (e.g. untreated eye in same patient or untreated control group) at e.g. 6 months, 12 months or 24 months after treatment. These improvements can be assessed by an appropriate ophthalmological test, including but not limited to visual acuity testing, microperimetry and other visual field testing, anatomical testing, such as optical coherence tomography scans and fundus autofluorescence imaging, retinal electrophysiology, and/or quality of life (QoL) assessments. 
     In some aspects, an effective amount of a nucleic acid or rAAV (or pharmaceutical composition comprising same) as herein described is an amount effective to treat choroideremia in a human patient. In related aspects, an effective amount of an rAAV as herein described is between 10 9  and 10 14  rAAV particles (or vector genomes (vg))/eye), preferably between 10 10  and 10 13  vg/eye, or between 1×10 11  vg/eye and 5×10 12  vg/eye, more preferably is about 3×10 11  vg/eye or about 1×10 12  vg/eye. In some preferred embodiments, a single dose of about 3×10 11  vg/eye or about 1×10 12  vg/eye is intravitreally administered to a human patient with choroideremia, whereby the choroideremia is treated. 
     Some embodiments of the invention are exemplified in the following items 1 to 41: 
     1. A nucleic acid encoding human Rab escort protein-1 (REP1) protein of SEQ ID NO:2 and codon optimized for expression in humans, the nucleic acid comprising the nucleotide sequence set forth as SEQ ID NO: 1 or comprising a nucleotide sequence at least 95% identical thereto, wherein the nucleic acid is expressed at a greater level compared with the level of expression of the wild type REP1 nucleotide sequence of SEQ ID NO: 3 in an otherwise identical cell. 
     2. The nucleic acid according to item 1, wherein the nucleotide sequence has a codon adaptation index of at least 0.94. 
     3. The nucleic acid according to item 1, comprising the nucleotide sequence set forth as SEQ ID NO: 1. 
     4. An expression cassette comprising the nucleic acid according to any one of items 1 to 3 and an expression control sequence operably linked and heterologous to the nucleic acid sequence. 
     5. The expression cassette of item 4, wherein the expression control sequence is a constitutive promoter, preferably a CAG promoter comprising the nucleotide sequence set forth as SEQ ID NO:4 or a sequence at least 90%, at least 95%, or at least 98% identical thereto. 
     6. The expression cassette of item 5, comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. 
     7. The expression cassette of item 6, wherein the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or wherein the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or wherein the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or wherein the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. 
     8. The expression cassette of item 7, comprising or consisting of the nucleotide sequence of SEQ ID NO:5 or a sequence at least 90%, at least 95%, at least 98% identical thereto. 
     9. The expression cassette of item 3, wherein the expression control sequence is a promoter that directs preferential expression of the nucleic acid in rods and cones. 
     10. A vector comprising the nucleic acid according to any one of items 1 to 3 or an expression cassette according to any one of items 4 to 9. 
     11. The vector of item 10, wherein the vector is a recombinant adeno-associated (rAAV) vector. 
     12. The vector of item 11, wherein the rAAV vector comprises an AAV capsid of serotype 2, 4, 5 or 8 or a variant thereof. 
     13. The vector of item 12, wherein the rAAV vector comprises an AAV2 capsid or variant thereof. 
     14. The vector of item 13, wherein the rAAV vector comprises an AAV2 capsid variant comprising a capsid protein comprising or consisting of the sequence of SEQ I D NO:9. 
     15. The vector of any one of items 11-14, wherein the rAAV vector comprises a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. 
     16. The vector of item 15, wherein the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or wherein the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or wherein the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or wherein the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. 
     17. The vector of item 16, wherein the rAAV comprises a nucleic acid comprising the nucleotide sequence of SEQ ID NO:5 or a sequence at least 90%, at least 95% or at least 98% identical thereto. 
     18. The vector of item 17, wherein the rAAV comprises (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:5. 
     19. A host cell comprising the nucleic acid according to any one of items 1 to 3 or an expression cassette according to any one of items 4 to 9. 
     20. The host cell according to item 19, wherein the host cell is a mammalian cell. 
     21. The host cell of item 19 or 20, wherein the host cell is a CHO cell, an HEK293 cell, an HEK293T cell, a HeLa cell, a BHK21 cell or a Vero cell and/or wherein the host cell is grown in a suspension or cell stack culture and/or wherein the host cell is a photoreceptor cell, a retinal ganglion cell, a glial cell, a bipolar cell, an amacrine cell, a horizontal cell, or a retinal pigmented epithelium cell. 
     22. A method for treating choroideremia in a subject in need thereof, comprising administering to the subject a therapeutically effective amount of a nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9 or a vector according to any one of items 10-18. 
     23. A method for treating choroideremia in a subject in need thereof, comprising administering to the subject an infectious rAAV comprising (i) an AAV capsid and (ii) a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. 
     24. The method according to item 23, wherein the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or wherein the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or wherein the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or wherein the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. 
     25. The method according to item 23 or 24, wherein the rAAV comprises (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:5. 
     26. The method according to any one of items 22-25, wherein the nucleic acid or vector is administered to the subject by intravitreal or subretinal injection and/or wherein the vector is administered to the subject at a dosage from about 10 10  vector genomes (vg)/eye to about 10 13  vg/eye, preferably from about 1×10 11  vg/eye to about 5×10 12  vg/eye, more preferably at a dosage of about 3×10 11  vg/eye or at a dosage of about 1×10 12  vg/eye. 
     27. A nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9, or a vector according to any one of items 10-18 for use in the treatment of choroideremia. 
     28. A nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9, or a vector according to any one of items 10-18 for use in the manufacture of a medicament for the treatment of choroideremia. 
     29. The nucleic acid, expression cassette or vector for use according to item 27 or 28, wherein the nucleic acid or vector is administered by intravitreal or subretinal injection and/or wherein the vector is for administration at a dosage from about 10 10  vector genomes (vg)/eye to about 10 13  vg/eye, preferably from about 1×10 11  vg/eye to about 5×10 12  vg/eye, more preferably is for administration at a dosage of about 3×10 11  vg/eye or at a dosage of about 1×10 12  vg/eye. 
     30. An infectious rAAV comprising (i) an AAV capsid and (ii) a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat, for use in the treatment of choroideremia. 
     31. An infectious rAAV comprising (i) an AAV capsid and (ii) a nucleic acid comprising from 5 to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat, for use in the manufacture of a medicament for the treatment of choroideremia. 
     32 The infectious rAAV according to item 30 or 31, wherein the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or wherein the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or wherein the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or wherein the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. 
     33. The infectious rAAV according to item 32, wherein the rAAV comprises (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:5. 
     34. The infectious rAAV for use according to any one of items 30-33, wherein the rAAV is administered by intravitreal injection and/or wherein the vector is administered at a dosage from about 10 10  vector genomes (vg)/eye to about 10 13  vg/eye, preferably from about 1×10 11  vg/eye to about 5×10 12  vg/eye, more preferably is administered at a dosage of about 3×10 11  vg/eye or at a dosage of about 1×10 12  vg/eye. 
     35. A method for treating a disease or condition mediated by a decreased level of REP1 in a mammal, the method comprising administering a therapeutically effective amount of a nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9, or a vector according to any one of items 10-18. 
     36. A method for increasing the level of REP1 in a mammal, the method comprising administering to the mammal a nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9, or a vector according to any one of items 10-18. 
     37. A pharmaceutical composition comprising a nucleic acid according to any one of items 1-3, an expression cassette according to any one of items 4-9, or a vector according to any one of items 10-18, and at least one pharmaceutically acceptable excipient. 
     38. A pharmaceutical composition comprising an infectious rAAV comprising (i) an AAV capsid and (ii) a nucleic acid comprising from 5′ to 3′: (a) an AAV2 terminal repeat (b) a CAG promoter (c) codon optimized REP1 gene of SEQ ID NO:1 (d) an SV40 polyadenylation sequence and (e) an AAV2 terminal repeat. 
     39. The pharmaceutical composition according to item 38, wherein the 5′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:6 and/or wherein the CAG promoter has the nucleotide sequence set forth as SEQ ID NO:4 and/or wherein the SV40 polyadenylation sequence has the nucleotide sequence set forth as SEQ ID NO:8 and/or wherein the 3′ AAV2 terminal repeat has the nucleotide sequence set forth as SEQ ID NO:7. 
     40. The pharmaceutical composition according to item 39, wherein the rAAV comprises (i) a capsid comprising a capsid protein comprising or consisting of the sequence of SEQ ID NO:9 and (ii) a nucleic acid comprising or consisting of the nucleotide sequence of SEQ ID NO:5. 
     41. The pharmaceutical composition according to any one of items 38-40, wherein the pharmaceutical composition comprises between 10 9  vg and 10 14  vg of the rAAV, preferably between 10 10  vg and 10 13  vg of the rAAV, more preferably comprises about 3×10 11  vg or about 1×10 12  vg of the rAAV. 
     EXAMPLES 
     The following examples illustrate preferred embodiments of the present invention and are not intended to limit the scope of the invention in any way. While this invention has been described in relation to its preferred embodiments, various modifications thereof will be apparent to one skilled in the art from reading this application. 
     Example 1—Codon Optimization of REP1 cDNA Sequence 
     The human REP1 open reading frame cDNA sequence (NCBI Reference Sequence NM_000390.4) was codon optimized for human expression. The optimization algorithm included parameters including, but not limited to, codon usage bias, GC content, CpG dinucleotides content, negative CpG islands, mRNA secondary structure, RNA instability motifs, cryptic splicing sites, premature polyadenylation sites, internal chi sites and ribosomal binding sites, and repeat sequences. 
     The native human REP1 gene employs tandem rare codons that can reduce the efficiency of translation or even disengage the translational machinery. The codon usage bias in humans was changed by upgrading the codon adaptation index (CAI) from 0.70 to 0.94. The average GC content was optimized from 54.24 in the native sequence to 61.22 in the optimized sequence to prolong the half-life of the mRNA. Stem-Loop structures, which impact ribosomal binding and stability of mRNA, were broken in the optimized sequence. In addition, negative cis-acting sites such as ATTTA (6 of which are deleted in the optimized sequence) were screened and deleted to optimize expression of the gene in human cells and several restriction enzyme sites were deleted (2 BglII(AGATCT), 1 EcoRI(GAATTC), 1 XhoI(CTCGAG) and 1 ARE sites were deleted). 
     The resulting codon optimized nucleotide sequence, set forth herein as SEQ ID NO:1, contains improved codon usage, altered GC content, better mRNA stability, and modification of negative cis acting elements relative to the native sequence of SEQ ID NO:3. 
     Example 2—Codon Optimized REP1 cDNA Sequence is Expressed at Higher Levels in RPE Cells from Patients with Choroideremia 
     A human in vitro model system was generated to evaluate expression of codon optimized human REP1 nucleic acid having the nucleotide sequence of SEQ ID NO:1 in diseased human RPE cells derived from human choroideremia patients and functional correction of the CHM disease phenotype. This model system was chosen for in vitro pharmacology because a suitable non-human primate model of choroideremia (CHM) is lacking for pre-clinical studies. Two CHM patient fibroblast samples were reprogrammed to iPSCs, then differentiated into functional mature RPE cells. Lack of Rep1 protein in CHM patients has been shown to correlate with cellular defects in Rab27a trafficking and prenylation (see e.g. Strunnikova, N. V. et al., PLoS Biol. 4, e8402 (2009); Sergeev, Y. V. el al., Mutat. Res. —Fundam. Mol. Mech. Mutagen, 665, 44-50 (2009); Rak, A. et al., Cell 117, 749-760 (2004)). 
     Materials and Methods 
     Generation of Induced Pluripotent Stem Cell Lines from Choroideremia Patient Cells 
     Cellular reprogramming of fibroblasts from two choroideremia patients (referred to herein as CHM1 and CHM2), was performed by Simplicon RNA reprogramming (EMD Millipore). At day 10, approximately 5×10 4 -1×10 5  reprogrammed cells were re-plated on growth factor reduced Matrigel (Corning) in mouse embryonic fibroblasts (MEF)-conditioned medium containing B18R protein (200 ng/mL) supplemented with human iPSC Reprogramming Boost Supplement II (EMI) Millipore). At day 20, reprogrammed cells, recognized by altered morphology and ability to form small colonies, were transitioned to mTeSR-1 media (Stem Cell Technologies). Colonies of approximately 200 cells or larger were isolated manually and plated on growth factor reduced Matrigel coated plates in mTeSR-1 medium. CHM-iPSC lines were expanded from a single colony. The CHM-iPSC lines were cultured on Vitronectin XF (Stem Cell Technologies) in mTeSR-1 maintenance medium and sub-cultured using Gentle Cell Dissociation Reagent (Stem Cell Technologies), every 4-5 days at 70-80% confluence. To ensure random differentiation into all three germ layers, iPSC embryoid bodies (EBs) were formed in suspension culture for one week and then differentiated in adherent conditions for an additional four weeks in mTeSR-1 basal medium, plus 20% Knockout Serum Replacement (Thermo Fisher Scientific). 
     Generation of Human Choroideremia Retinal Pigmented Epithelial (RPE) Cells 
     RPE cells were generated by a directed differentiation protocol as previously described (Leach et al.,  Investigative ophthalmology  &amp;  visual science  56(2):1002-13 (2015)). Briefly, iPSCs were passaged directly onto Matrigel (BD Biosciences) in DMEM/F12 with 1×B27, 1×N2, and 1×NEAA (Invitrogen). From days 0 to 2, 50 ng/ml Noggin, 10 ng/ml Dkk1, 10 ng/ml IGF1 (R&amp;D Systems Inc.), and 10 mM nicotinamide were added to the base medium. From days 2 to 4, 10 ng/ml Noggin, 10 ng/ml Dkk1, 10 ng/ml IGF1, and 5 ng/ml bFGF and 10 mM nicotinamide were added to the base medium. From days 4 to 6, 10 ng/ml Dkk1 and 10 ng/ml IGF1 and in 100 ng/ml Activin A (R&amp;D Systems) were added to the base medium. From days 6 to 14, 100 ng/ml Activin A, 10 μM SU5402 (EMD Millipore), and 1 mM VIP (Sigma-Aldrich) were added to the base medium. At day 14, the cells were mechanically enriched by scraping away cells with non-RPE morphology. Subsequently, the remaining RPE were digested using TrypLE Express (Invitrogen) for ˜5 minutes at 37° C. The cells were passed through a 30-μm single-cell strainer and seeded onto Matrigel-coated tissue culture plastic, transwell membranes (Corning Enterprises), or CC2-treated chambered slides in XVIVO-10 media (Lonza). 
     Functional Characterization of Human Choroideremia RPE Cells 
     CHM RPE cells were cultured using a formulated media to analyze rod outer segment (ROS) phagocytosis (Maminishkis, et al.,  Investigative Ophthalmology and Visual Science,  47(8):3612-24 (2006)). Cells were plated in quadruplicate at 1×10 5  cells per cm 2  on 0.1% gelatin-coated black-walled, clear bottom 96 well plates and cultured for 30 days. Photoreceptor ROSs were isolated from bovine eyes (Sierra for Medical Science) as previously described (Molday R S and Molday L L,  Journal of Cell Biology,  105(6 Pt 1):2589-601 (1987)) and fluorescently labeled with fluorescein isothiocyanate (FITC) protein (Thermo Fisher Scientific). In some conditions, cultured cells were treated with 62.5 μg/ml αVβ5 integrin function-blocking antibody (Abcam) or IgG isotype control (Abcam) for 30 minutes at 37° C. Following the initial antibody incubation, cells were challenged with 1×10 6  FITC-ROSs per well for five hours at 37° C. and 5% CO2 (Buchholz et al.,  STEM CELLS TRANSLATIONAL MEDICINE  2(5):384-93 (2013)) (Rowland et al.,  Journal of Tissue Engineering and Regenerative Medicine,  7(8):642-53 (2013)). After ROS incubation, the wells were washed six times with PBS and 0.4% trypan blue was then added for 20 minutes to quench fluorescence from extracellular ROS. Each well was imaged using epifluorescent microscopy, and integrated pixel density of photomicrographs was determined with Image J software using a rolling pixel radius of 50 (National Institutes of Health). 
     Immunocytochemistry 
     Cells were fixed with 4% paraformaldehyde (PFA) (Santa Cruz Biotechnologies) for 15 minutes at 4° C. All antibody staining was done in a blocking solution of PBS with 0.2% Triton-X100 (Sigma-Aldrich), 2% bovine serum albumin (Calbiochem), and 5% goat serum (Thermo Fisher). Primary antibody incubations were done overnight at 4° C. Cells were then incubated with secondary antibodies for one hour at room temperature and then counterstained with DAPI (Sigma Aldrich) in PBS for five minutes at room temperature. Cells were imaged using a Zeiss Axio Observer.D1. Image processing was performed using Zeiss Zen 2 software and FIJI. A list of primary and secondary antibodies is provided below at Table 3: 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Antibody 
                 Host 
                 Company-Catalog No. 
                 Dilution 
               
               
                   
               
             
            
               
                 Primary Antibodies 
                   
                   
                   
               
               
                 OCT4 
                 Mouse 
                 Millipore- MAB4401 
                 1:50 
               
               
                 Nanog 
                 Rabbit 
                 Abcam- ab21624 
                 1:50 
               
               
                 SOX2 
                 Rabbit 
                 Abcam- ab92494 
                 1:50 
               
               
                 BEST1 
                 Rabbit 
                 Abcam-ab14927 
                 1:100 
               
               
                 TUJ-1 
                 Mouse 
                 Promega-G7121 
                 1:200 
               
               
                 HNF4-A 
                 Rabbit 
                 Santa Cruz-SC-8987 
                 1:100 
               
               
                 ASMA 
                 Mouse 
                 Sigma Aldrich- A2547 
                 1:500 
               
               
                 GFP 
                 Chicken 
                 Abcam-ab13970 
                 1:200 
               
               
                 MITF 
                 Mouse 
                 Thermo Fisher-MA5- 
                 1:100 
               
               
                   
                   
                 14146 
               
               
                 OTX2 
                 Mouse 
                 R&amp;D Systems-MAB1979 
                 1:20 
               
               
                 RPE-65 
                 Rabbit 
                 Sant Cruz-sc32896 
                 1:10 
               
               
                 ZO-1 
                 Mouse 
                 Thermo Fisher-33-9100 
                 1:200 
               
               
                 Secondary Antibodies 
               
               
                 Alexa Fluor488 anti-rabbit 
                 Goat 
                 Invitrogen-A11078 
                 1:250 
               
               
                 Alexa Fluor555 anti-rabbit 
                 Goat 
                 Invitrogen-A21428 
                 1:250 
               
               
                 Alexa Fluor680 anti-rabbit 
                 Goat 
                 Invitrogen-A21109 
                 1:250 
               
               
                 Alexa Fluor488 anti-mouse 
                 Goat 
                 Invitrogen-A11029 
                 1:250 
               
               
                 Alexa Fluor555 anti-mouse 
                 Goat 
                 Invitrogen-A21422 
                 1:250 
               
               
                 Alexa Fluor680 anti-mouse 
                 Goat 
                 Invitrogen-35518 
                 1:250 
               
               
                   
               
            
           
         
       
     
     SDS-PAGE and Western Blot 
     CHM RPE cell lysates were harvested using a standard RIPA Buffer (Thermo Fisher) with a Complete Protease Inhibitor Tablet (Millipore Sigma) and incubated on ice for 15 minutes. Samples were then centrifuged at 21×g for 15 minutes. Supernatants were collected, and protein concentrations were determined using a BCA protein assay (Thermo Fisher Scientific) normalized and adjusted to 2 μM DTT. Biorad 4×Sample Buffer was added and samples were heated at 70° C. for 10 minutes. An XT Criterion gel was run followed by gel transfer to a membrane. The membrane was then blocked and probed with REP1 and GADPH antibodies. Membranes were incubated with secondary antibodies conjugated to HRP and bands were visualized with ECL. 
     Prenylation Assay 
     The prenylation assay was performed using RPE cell lysates as described in K5hnke et al.,  PLoS ONE  8(12):1-11 (2013). Following a wash with PBS, cell lysates were prepared in cold Prenylation Buffer (500 sM HEPES pH 7.0, 50 μM NaCl, 2 μM MgCl2, 0.1 μM GDP, 0.5% NP-40, and a Complete Protease Inhibitor Tablet) and incubated on ice for 10-15 minutes. Protein concentrations were determined using a BCA protein assay (Thermo Fisher Scientific). Protein concentrations were normalized, and lysates adjusted to 2 μM DTT. Prenylation reactions were performed using 20 μL of lysate corresponding to 50-200 sg protein. The reaction for the functional complex was composed of 2 μM RabGGTase, 4 μM Rab27a and 4 μM BiotinGeranyl-PPi (Jena Bioscience). Reactions were incubated at 25° C. for 5 hours and stopped by adding 4×Sample Buffer (Biorad), DTT to 40 mM and heating at 70° C. for 10 minutes. Western blotting was carried out on XT Criterion gels according to manufacturer&#39;s protocols. Prenylation reactions were analyzed using streptavidin-HRP (Abcam). 
     Rab27A Trafficking Assay 
     RPE cells were seeded onto vitronectin coated eight chambered slides at 25,000 cells per cm 2  in XVIVO-10 media. Two days after seeding, the CHM RPE cells were transduced with recombinant AAV virions comprising (i) a transgene expression cassette having the sequence of SEQ ID NO:5 and (ii) a modified AAV2 capsid protein having the amino acid sequence of SEQ ID NO:9, at a multiplicity of infection (MOI) of 5000 vg/cell. Fourteen days post infection, cells were fixed and stained as described above. 
     Experimental Data 
     Two CHM patient fibroblast samples were obtained and reprogrammed to iPSCs followed by differentiation to RPE cells as described above. More specifically, cellular reprogramming of fibroblast cells (CHM1 and CHM2) was performed by Simplicon RNA reprogramming using synthetic in vitro transcribed RNA expressing four reprogramming factors (Oct4, Klf4, Sox2 and Glisl) in a polycistronic transcript that self-replicates for a limited number of cell divisions. Inununocytochemical analysis of human PSC markers NANOG, SOX2 and OCT4 was performed to confirm the pluripotency of both choroideremia iPSC lines, CH:M11 and CHM2 ( FIGS.  1   a  and  1   b   ). To confirm pluripotency of the generated iPSC lines, cells were randomly differentiated in suspension culture as EBs and then differentiated in adherent conditions for four weeks and evaluated for the ability to differentiate into the ectodermal, mesodermal, and endodermal lineages. At that time, markers associated with neurons (TUJ1+), smooth muscle cells (ASMA+), and hepatocytes (HNF4A+) belonging to the ectoderm, mesoderm, and endoderm germ layers, respectively, were detected ( FIGS.  1   e  and  1   d   ). After confirmation of pluripotency, the iPSC lines generated from CHM1 and CHM2 patient cells were differentiated to RPE cells. RPE cells were allowed to mature for 30 days, followed by analysis for proper RPE cell marker expression and function. Protein expression and localization of Melanogenesis Associated Transcription Factor (MITF) and Orthodenticle Homeobox 2 (OTX2), RPE65 and zonula occludens (ZO-1) ( FIGS.  2   a  and  2   b   ) was normal. No changes in photoreceptor outer segment phagocytosis, a known function of RPE, ( FIG.  2   c   ) confirmed that CHM iPSC-derived RPE, cells exhibit key physiological characteristics similar to those of native RPE. 
     Expression levels of codon optimized REP1 transgene versus unmodified REP1 were assessed. To that end, recombinant AAV (rAAV) virions were isolated comprising (i) a modified AAV2 capsid protein having the amino acid sequence of SEQ ID NO:9 and (ii) a transgene expression cassette comprising either codon optimized REP1 of SEQ ID NO:1 or native REP1 of SEQ ID NO:3, each under the control of a CAG promoter of SEQ ID NO:4. Briefly, CHM RPE cells were transduced with the rAAV virions at two different MOIs, 500 or 5000 vg/cell. Cell lysates were collected 14 days post transduction and SDS-PAGE and Western blot analysis was carried out to evaluate REP1 expression levels. As illustrated in  FIGS.  3 A-B , codon optimized REP1 resulted in higher expression levels than unmodified REP1. Further, REP1 protein levels reached levels found in normal RPE at the lower dose (MOI 500 vg/cell). 
     A functional assay was developed to assess the ability of delivered REP1 protein to prenylate Rab27a GTPase ( FIG.  4   ). CHM RPE cells were transduced with rAAV comprising (i) a transgene expression cassette having the sequence of SEQ ID NO:5 and (ii) a modified AAV2 capsid protein having the amino acid sequence of SEQ ID NO:9. Cell lysates from transduced or control CHM1 and CHM2 RPE cells were collected 14 days post infection. Wild type RPE cells were used as a positive control. Prenylation of Rab27a GTPase will only occur in the presence of REP1 and, the prenyl donor, RabGGTase. To visualize the prenyl transfer from RabGGTase to Rab27a GTPase, the prenyl groups were labeled with biotin. The cell lysates, following transduction, were combined with Rab27a GTPase, RabGGTase and biotinylated prenyl groups. The in vitro reaction was incubated for 5 hours to optimize prenyl group transfer. Following the reaction, the lysates were subjected to SDS-PAGE and Western blotting analysis. A SA-HRP conjugate revealed the level of prenylation in each reaction ( FIGS.  5   a - d   ). RPE cells derived from a normal fibroblast cell-derived iPSC line were used as a positive control in this experiment. 
     A second functional experiment was done to confirm that prenylation of Rab27a GTPases, following delivery of the rAAV results in proper trafficking of Rab27a to the target membrane. CHM RPE cells were cultivated at low density (2.5×10 4  cells/cm 2 ) and then transduced with rAAV comprising (i) a transgene expression cassette having the sequence of SEQ ID NO:5 and (ii) a modified AAV2 capsid protein having the amino acid sequence of SEQ ID NO:9 at a MOI of 5000 vg/cell. After 14 days, cultures were immunostained with anti-REP1 and anti-RAB27A antibodies and imaged to visualize the subcellular localization of RAB27A in transduced versus untreated cultures. Treatment of CHM RPE cells ( FIG.  6   a   ) with the rAAV caused trafficking of RAB27A from the cytoplasmic regions to target membranes ( FIG.  6   b   ) analogous to normal FB-iPSC-derived RPE cells ( FIG.  6   c   ). These data demonstrate that two weeks after delivery of codon optimized REP1 of SEQ ID NO:1, RAB27A trafficking from the cytoplasmic regions to target membranes was normalized and this correction was associated with restitution of the normal cellular RPE phenotype. 
     CONCLUSION 
     The studies described above demonstrate that codon optimized REP1 of SEQ ID NO:1 is expressed at significantly higher levels in disease-relevant (REP1 deficient) human RPE cells compared to the native (unmodified) REP1 gene. The studies also demonstrate that REP1 expressed from codon optimized REP1 of SEQ ID NO:1 is functional, rescues the prenylation defect (Rab27) and corrects the intracellular trafficking defect in RAb proteins, thus restoring the normal cellular RPE phenotype in the diseased RPE cells. In vitro pharmacology indicates that cohREP1 shows superior correction of REP1 protein deficiency in Retinal Pigment Epithelial (RPE) cells derived from choroideremia patients when compared with the normal gene. 
     Example 3—Assessment of Safety and Biodistribution of Codon Optimized REP1 cDNA Sequence Delivered by R100 Via Intravitreal Administration in Non-Human Primates 
     Materials and Methods 
     GLP Toxicology and Biodistribution Studies 
     Male cynomolgus macaques (macacafawicularis) aged 2-14 years were dosed via two 50 μL intravitreal injections into each eye through the sclera for a total dose volume of 100 μL/eye. Doses of 1×10 11  vg/eye (unilateral administration), 3×10 11  vg/eye (bilateral administration only), and 1×100 12  vg/eye (unilateral &amp; bilateral administration) were evaluated. The animals were anesthetized with Ketamine IM and given topical ophthalmic solutions to eliminate pain. 20-80 mg of methylprednisolone was administered by IM injection weekly post-injection. Euthanasia was performed by trained veterinary staff at Week 3, Week 13, and Week 26 post-administration. 
     4D-110 (rAAV comprising a capsid protein of SEQ ID NO:9 and a heterologous nucleic acid comprising the nucleotide sequence of SEQ ID NO:5) genome biodistribution was assessed in all major ocular compartments (retina, optic nerve, ciliary body, iris, trabecular meshwork), and major systemic organs (including the testes) using validated, GLP-compliant qPCR assay. In tissues where genomes were detected, transgene expression was assessed by a qualified, GLP-compliant RT-qPCR assay. 
     Serial toxicology assessments performed in the study were: clinical ocular evaluations (complete ophthalmic examinations, including SD-OCT imaging and ERG), systemic evaluations, clinical pathology, gross pathology and microscopic pathology. Assays were validated to determine the anti-capsid and anti-transgene antibody responses. ELiSpot assays were validated to detect cellular responses to the R100 capsid (comprising a variant capsid protein of SEQ ID NO:9) and expressed proteins. 
     Neutralizing Antibody Assay 
     2v6.11 cells were plated at a density of 3×10 4  cells/well 24 hours prior to infection. rAAV vectors encoding firefly luciferase driven by the CAG promoter were incubated at 37° C. for 1 hour with individual serum samples prior to infection, and cells were then infected at a genomic MOI of 1,000. Luciferase activity was assessed 48 hours post infection using the Luc-Screen Extended-Glow Luciferase Reporter Gene Assay System (Invitrogen) or the ONE-Glo Luciferase Assay System (Promega) and quantified using the BioTek Cytation 3 Cell Imaging Multi-Mode Reader and Gen5 software. 
     Prior to enrollment in studies, non-human primates (NHP) serum was screened for the presence of neutralizing antibodies against R100. NHPs were enrolled in studies when samples resulted in less than 50% neutralization of AAV transduction at a 1:10 serum dilution. 
     AAV Manufacturing 
     Recombinant R100 viral vectors were produced by transient transfection in HEK293 cells. Cells were cultured in DMEM supplemented with FBS and were maintained at 37° C. in a 5% CO 2  environment. Cells were triply transfected (payload, capsid, and helper plasmids) using polyethylenimine (PEI). 48-96 hours post-transfection, viral particles were harvested from cells and/or supernatant and cells lysed via microfluidization. Cell lysate and/or supernatant was enzymatically treated to degrade plasmid and host-cell DNA, then clarified and concentrated by tangential flow filtration (TFF). The TFF retentate was then loaded onto an affinity resin column for purification. Following pH-gradient elution, post-affinity material was buffer exchanged, then further purified (if needed) by anion-exchange chromatography. Purified rAAV was then formulated into DPBS with 0.001% polysorbate-20, sterile filtered, and filled to yield rAAV Drug Product. 
     Results 
     4D-110 delivery is safe and results in expression of therapeutic transgene in NHP 
     4D-110 (R100.CAG-cohRep1) has been advanced into a Phase 1-2 clinical trial. Investigational New Drug (IND)-enabling data for this product includes evaluation in two separate 6-month Good Laboratory Practices (GLP) toxicology and biodistribution studies (Table 4). A total of 61 eyes of 44 NHPs were injected by intravitreal injection with either a single eye administration, sequential bilateral administration, or simultaneous bilateral administration. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Good Laboratory Practices (GLP) Toxicology and Biodistribution Studies 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 4DMT 
                   
                   
                   
                   
                   
                   
               
               
                 Study 
               
               
                 Number 
                 Lot Number 
                 Number 
                 Gender 
                 Eye(s) 
                 Dose 
                 In-Life 
               
               
                   
               
               
                 4D17-02 
                 N/A 
                 1 
                 Male 
                 OD 
                 vehicle 
                  3 weeks 
               
               
                   
                 4DEP000003.01 
                 4 
                 Male 
                 OD 
                 1E+11 vg/eye 
               
               
                   
                 4DEP000004.01 
                 5 
                 Male 
                 OD 
                 1E+12 vg/eye 
               
               
                   
                 N/A 
                 1 
                 Male 
                 OD 
                 vehicle 
                 13 weeks 
               
               
                   
                 4DEP000003.01 
                 4 
                 Male 
                 OD 
                 1E+11 vg/eye 
               
               
                   
                 4DEP000004.01 
                 5 
                 Male 
                 OD 
                 1E+12 vg/eye 
               
               
                   
                 N/A 
                 1 
                 Male 
                 OD 
                 vehicle 
                 26 weeks 
               
               
                   
                 4DEP000003.01 
                 4 
                 Male 
                 OD 
                 1E+11 vg/eye 
               
               
                   
                 4DEP000004.01 
                 5 
                 Male 
                 OD 
                 1E+12 vg/eye 
               
               
                 4D18-13 
                 N/A 
                 3 
                 Male 
                 OU 
                 vehicle 
                 26 weeks 
               
               
                   
                 4DEP000011.01 
                 3 
                 Male 
                 OU 
                 3E+11 vg/eye 
               
               
                   
                   
                 3 
                 Male 
                 OD + OS 
                 3E+11 vg/eye 
               
               
                   
                   
                 4 
                 Male 
                 OU 
                 1E+12 vg/eye 
               
               
                   
                   
                 4 
                 Male 
                 OD + OS 
                 1E+12 vg/eye 
               
               
                   
                   
                 3 
                 Male 
                 OU 
                 1E+12 vg/eye 
                 13 weeks 
               
               
                   
               
            
           
         
       
     
     No significant toxicities were observed with 4D-110 at either dose level, as determined by clinical observations, histopathology, OCT, or ERG. Administration of 4D-110 into a single eye resulted in only minimal to mild anterior uveitis that was restricted to the immediate post-administration period and resolved by Week 3 ( FIG.  9   ); in some cases systemic steroid doses were transiently increased. Bilateral administration of 4D-110 resulted in transient minimal to moderate anterior uveitis in both low and high dose groups; this finding resolved within two weeks generally, coincident with an increase in systemic steroid treatment. 
     Very high levels of vector genomes were present in the retina of the treated eye at all timepoints (week 3, left panel; week 13, middle panel; week 26, right panel) indicating persistence of the vector in ocular tissue ( FIG.  10   ). In addition to the retina, vector genomes were detected in the treated eye within samples from the aqueous humor, vitreous humor, iris/ciliary body, and the optic nerve at all timepoints. Non-ocular tissues generally had no detectable vector genomes with the exception of low levels in liver, spleen, and the lymph nodes ( FIG.  10   ). R100 vector-derived transgene expression was detected in the treated retina and iris/ciliary body from both low and high dose groups ( FIG.  11   ). Gene expression was dose-dependent and increased from Week 3 to Week 13 and remained stable at Week 26 ( FIG.  11   , left, middle and right panel respectively). No non-ocular vector expression was detected at Week 26 in any study ( FIG.  11   ). 
     Using an ELISpot assay to evaluate cellular immune responses, no animals developed significant responses to R100 capsid peptides or transgene peptides (data not shown). A majority of animals dosed with 4D-110 generated an anti-capsid antibody response post-administration (data not shown). 
     SUMMARY 
     4D-110 (R100.CAG-cohRep1) has recently been translated into a clinical trial for the inherited retinal disease choroideremia (NCT04483440). This therapeutic product has been evaluated in two separate GLP toxicology and biodistribution studies (Table 4). A total of 44 NHPs were injected with a single eye administration, sequential bilateral administration, or simultaneous bilateral administration; a total of 61 NHP eyes were injected. No significant test-article-related adverse events or T-cell responses were reported. Mild to moderate, transient corticosteroid-responsive anterior uveitis was observed. Transgene expression was localized to the retina, and expression was not detected in any of the systemic organs evaluated. Human clinical trials are underway in order to determine the safety, pharniacodynamics, and efficacy (including through serial visual field testing and optical coherence tomography scans) of this product by intravitreal injection. 
     Example 4—Assessment of Safety of Codon Optimized REP1 cDNA Sequence Delivered by R100 Via Intravitreal Administration in Human Choroideremia Patients 
     Initial Phase 1 Dose Escalation Safety and Tolerability Data Summary 
     Clinical Trial Designs and Enrollment 
     The clinical trial employed a standard “3+3” dose-escalation designed to assess the safety, tolerability and biologic activity of a single intravitreal injection of 4D-110 at two dose levels (3E11 or 1E12 vg/eye). A total of six patients were enrolled across dose escalation cohorts, with three at each dose level. Patients received a standard immunosuppression regimen with taper; adjustments were determined by investigators. The results described are based on data cut-offs between 1-9 months post-administration. 
     Initial Tolerability and Adverse Event Profile 
     4D-110 was well-tolerated throughout the assessment period as outlined in the treatment-emergent adverse event (AE) summary table (Table 5): 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Adverse Event Summary 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Patient # enrolled 
                 6 
               
               
                   
                 Doses 
                 3E11 or 1E12 vg/eye 
               
               
                   
                 Follow-up at data cut-off (months) 
                 1-9 months 
               
            
           
           
               
               
               
               
            
               
                   
                 Dose-Limiting Toxicities (DLTs) 
                 0 
                 (0%) 
               
               
                   
                 Serious AE 
                 0 
                 (0%) 
               
               
                   
                 Any CTCAE Grade ≥3 
                 0 
                 (0%) 
               
               
                   
                 Retinal AE (Any Grade) 
                 0 
                 (0%) 
               
               
                   
                 Uveitis CTCAE Grade 2 (moderate) 
                 1/6 
                 (17%) 
               
               
                   
                 Uveitis CTCAE Grade 1 (mild) 
                 4/6 
                 (67%) 
               
               
                   
                   
               
            
           
         
       
     
     Clinical Assessments 
     Patients&#39; ocular and systemic status is closely monitored including detailed ophthalmic evaluations and retinal imaging together with blood testing and systemic examinations, as necessary. A variety of visual function and anatomical assessments is performed to detect any preliminary efficacy signal. These assessments include, but are not limited to, measurements of ellipsoid zone (EZ) area, fundus autofluorescence, microperimetry, static automated perimetry, and best corrected visual acuity (BCVA). 
     While the materials and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention.