Patent Abstract:
the invention provides for nucleotide sequences encoding for a chimeric sulfatase , viral vectors expressing such sequences for gene therapy and pharmaceutical uses of the chimeric expressed protein . the invention is particularly applied in the therapy of mucopolysaccharidosis , preferably type iiia .

Detailed Description:
construction of chimeric sgsh cassettes , recombinant nucleic acid vectors and viral vectors the alternative signal peptides were produced by ligation of two fragments : a sequence from human sgsh cdna ( fragment i ) and the signal peptide sequence ( fragment ii ). fragment i was amplified from a hsgsh expressing plasmid and started at the 3 ′ terminus of hsgsh signal peptide sequence ( corresponding to the nucleotide in position 61 on the sgsh sequence ) and extended to a unique xbai site and contained the entire sgsh cdna ( oligos used : sgshfor 5 ′- cgt ccc cgg aac gca ctg ctg ctc ct - 3 ′ ( seq id no . 28 ) and sgshrev 5 ′- gcg gcc tct aga tga cag ctc att gtg gag ggg ctg - 3 ′ ( seq id no . 29 )). fragment ii was unique for each expression cassette . for haatsp - sgsh - cflag , fragment ii was synthesized by annealing two specific oligonucleotide sequences ( haatspfor 5 ′- ggc cgc atg ccg tct tct gtc tcg tgg ggc atc ctc ctg ctg gca ggc ctg tgc tgc ctg gtc cct gtc tcc ctg gct 3 ′ ( seq id no . 30 ) and haatsprev 5 ′- agc cag gga gac agg gac cag gca gca cag gcc tgc cag cag gag gat gcc ccacga gac aga aga cgg cat gc - 3 ′ ( seq id no . 31 )) containing the human α1 - antitrypsin signal peptide sequence [ human a1 - antitrypsin cdna : 72 bp ]. the fragment encoding for such signal peptide was : for idssp - sgsh - cflag expression cassette , fragment ii was synthesized by annealing two specific oligonucleotide sequences ( idsspfor 5 ′- ggc cgc atg ccc ccg ccc cgc acc ggc cgc ggc ctg ctg tgg ctg ggc ctg gtg ctg agc agc gtg tgc gtg gcc ctg ggc - 3 ′ ( seq id no . 32 ) and idssprev 5 ′- gcc cag ggc cac gca cac gct gct cag cac cag gcc cag cca cag cag gcc gcg gcc ggt gcg ggg cgg ggg cat gc - 3 ′ ( seq id no . 33 ) containing the human iduronate sulfatase signal peptide sequence [ homo sapiens iduronate 2 - sulfatase ( ids ) cdna : 75 bp ]. the fragment encoding for such signal peptide was : 5 ′- atgccgccaccccggaccggccgaggccttctctggctgggtctggttct gagctccgtctgcgtcgccctcgga - 3 ′ ( seq id no . 3 ) or an optimized sequence 5 ′- atgcccccgccccgcaccggccgcggcctgctgtggctgggcctggtg ctgagcagcgtgtgcgtggccctgggc - 3 ′ ( seq id no . 5 ). the two above sequences differ only for the codon usage and encode for the same signal peptide aa . sequence ( seq id no . 4 or 6 ). the oligonucleotide sequences of fragment 11 have 5 ′ noti site and 3 ′ blunt end site . the forward and reverse oligonucleotide sequences were incubated for three minutes at 100 ° c . after chilling at rt we added the pnk to oligos for 30 minutes at 37 ° c . the fragment i ( 5 ′ noti - 3 ′ blunt ) and fragment ii ( 5 ′ blunt - 3 ′ xba ) were ligated with p3xflag - cmv14 vector plasmid ( 5 ′ not - 3 ′ xba ). dh5α competent cells was transformed with the resulting ligation mix . to obtain the complete sgsh chimeric constructs , the amino acid sequence 3371 - 3409 of human apob ( 114 bp : 5 ′ tctgtcattgatgcactgcagtacaaattagaggg caccacaagattgacaagaaaaaggggattgaagttagccacagctctgtc tctgagcaacaaatttgtggagggtagt - 3 ′ ( seq id no . 9 ) was amplified by a human cdna library ( oligos : apobdfor 5 ′- aga tct ctg tca ttg atg cac tgc agt - 3 ′ ( seq id no . 34 ) and apobdrev 5 ′- aga tct act acc ctc cac aaa ttt gtt gc - 3 ′( seq id no . 35 )) and cloned into the bglii sites at 5 ′ terminus of 3xflag tag of either haatsp - sgsh - cflag or idssp - sgsh - cflag . the different expression cassettes containing either the partial chimeric constructs ( haatsp - sgsh - cflag and hidssp - sgsh - cflag ) or the complete chimeric constructs ( haatsp - sgsh - cflag - apob and hidssp - sgsh - cflag - apob ) were subcloned in the paav2 . 1 - tbg - gfp between noti ( 5 ′) and hindiii ( 3 ′) ( the gfp sequence was replaced with the expression cassettes ). the resulting plasmids ( fig1 ) were used to produce recombinant aav serotype 8 ( aav2 / 8 ) ( 19 ). the aav vectors were produced using a transient transfection of three plasmids in 293 cells : pad helper , paav rep - cap ( packaging plasmid containing the aav2 rep gene fused with cap genes of aav serotype 8 ), paav cis ( this plasmid is paav2 . 1 - tgb vector expressing the chimeric sulfamidase proteins ). the recombinant aav2 / 8 viral vectors were purified by two rounds of cscl , as described previously ( 19 ). vector titers , expressed as genome copies ( gc / ml ), were assessed by real - time pcr ( geneamp 7000 applied biosystem ). the aav vectors were produced by the tigem aav vector core facility ( http :// www . tigem . it / core - facilities / adeno - associated - virus - aav - vector - core ). hela and mpsiiia mef cells were maintained in dmem supplemented with 10 % fbs and penicillin / streptomycin ( normal culture medium ). sub - confluent cells were transfected using lipofectamine ™ 2000 ( invitrogen ) according to manufacturer &# 39 ; s protocols . one day after transfection the medium was replaced with dmem 0 . 5 % fbs . two days after transfection we collected the conditioned medium and the pellet for the enzyme assays and western blot analysis . 3xflag lysis buffer 1 × ( 50 mm tris - hcl ph8 , 200 mm nacl , 1 % triton x100 , 1 mm edta , 50 mm hepes ) was added to the cell pellets . the lysates were obtained by incubating the cell pellets with lysis buffer for 1 hour in ice . protein concentration was determined using the bio - rad ( bio - rad , hercules , calif ., usa ) colorimetric assay . the conditioned medium was concentrated in the vivaspin 500 ( sartorius ) by centrifugation of the medium at 13 , 000 rpm for 7 min . flagged sulfamidase proteins were revealed by western blot analysis using a anti - flag m2 monoclonal peroxidase - conjugate antibodies ( a8592 sigma - aldrich ) diluted 1 : 1000 in 5 % milk . cells were washed three times in cold pbs and then fixed in 4 % paraformaldehyde ( pfa ) for 15 min . fixed cells were washed four times in cold pbs , permeabilized with blocking solution ( 0 . 1 % saponin and 10 % fbs in pbs ) for 30 min and immunolabelled with appropriate primary antibody : rabbit anti h - sulfamidase ( 1 : 300 , sigma ). after four washes in pbs we incubated the cells with secondary antibody anti - rabbit alexa fluor - 488 conjugated ( 1 : 1000 ). cells were then washed four times in cold pbs and mounted in vectashield mounting medium . to determine degradation rates of sulfamidase enzyme , mpsiiia mefs transfected with different chimeric constructs were radiolabeled with 30 μci / 10 6 cells [ 35s ] methionine : cysteine mixture ( easytag ™ expre35s35s protein labeling mix , [ 3s ]; perkinelmer ) for 30 minutes in methionine : cysteine - free medium ( sigma ) supplemented with 1 % fetal calf serum . after extensive washing , cells were maintained in the presence of 5 % fetal calf serum and supplemented with methionine and cysteine . cells were recovered at different time points and lysed using 3xflag lysis buffer . lysates were cleared by centrifugation and supernatants were immunoprecipitated by using agarose - conjugated antibody against flag ( anti - flag m2 affinity gel , a2220 sigma - aldrich ). after extensive washing with lysis buffer , the immunoprecipitate was subjected to sds - page . dried gels were exposed to a phosphorimager screen and quantified with a phosphorimager system . homozygous mutant ( mps - iiia , −/−) and heterozygous ( phenotypically normal +/−) c57bl / 6 mice were utilized . consequently , the term ‘ normal mice ’ is used to refer to the mouse phenotype . experiments were conducted in accordance with the guidelines of the animal care and use committee of cardarelli hospital in naples and authorized by the italian ministry of health . newborn mps - iiia and normal mice at postnatal day 0 - 1 were cryo - anesthetized . the vectors were delivered in the systemic route via temporal vein ( 2 × 10 11 particles in 100 μl ). the adult mpsiiia mice ( 1 month ) were injected via caudal vein ( 2 × 10 11 particles in 100 μl ). the serum of animals were collected at different time points after injection for the enzyme assays . to evaluate liver and brain transduction the animals were sacrificed at different time points . some of them were perfused / fixed with 4 % ( w / v ) paraformaldehyde in pbs , the liver was then removed for gfp staining . the remaining mice were sacrificed and liver and brain removed to measure sgsh activity . sgsh activity was measured following protocols described in fraldi et al ., hum mol gen 2007 ). liver tissues were subjected to a saccharose gradient ( from 10 to 30 %) and incubated o / n in 30 % saccharose at 4 ° c . finally , tissues were embedded in oct embedding matrix ( kaltek ) and snap - frozen in a bath of dry ice and ethanol . tissue cryosections were cut at 10 j m of thickness , washed with pbs for 10 min , mounted in vectashield mounting medium and processed for gfp analysis . the aim of the project was to develop a low - invasive systemic gene therapy strategy based on the intravenous injection of aav serotype 8 . this serotype displays high tropism to the liver ( 18 - 20 ) and can be used to delivery of an engineered gene encoding a chimeric modified sulfamidase optimized ( i ) to be highly secreted from the liver thus reaching high levels of circulating enzyme in the blood stream . sulfamidase is poor secreted respect to other sulfatase enzymes such as the iduronate - 2 - sulfatase ( ids ). sulfamidase signal peptide was replaced with that of either ids or human α - antitrypsin ( aat ), a highly secreted enzyme ; ( ii ) to efficiently cross the bbb . the chimeric sulfamidase was further engineered with a specific brain - targeting protein domain , the ( ldlr )- binding domain of the apolipoprotein b ( apob ldlr - bd ). the efficacy of the new treatment is strictly dependent on the ability of the liver to be highly transduced by the transgene in order to efficiently secrete in the blood stream the sulfamidase that will then cross the bbb and transduce the brain by means of its brain - target sequence . therefore , the serum levels of the therapeutic enzyme may represent critical factor in determining the efficacy of the therapy . no previous studies have been done to analyze liver transduction and the systemic levels of sgsh upon systemic gene delivery of exogenous sgsh in mps - iiia mice . thus , we decided to investigate this issue in order to produce useful preliminary data for designing an effective therapeutic strategy . the delivery of therapeutic enzyme to neonatal mice is a useful tool to prevent pathology in mps - iiia mice . we then decided to test whether the aav2 / 8 - mediated systemic injection in newborn mpsiiia could be a feasible approach to develop our new therapeutic strategy . to this aim we injected mps - iiia newborn mice with aav2 / 8 containing the sulfamidase coding sequence under the control of a liver specific promoter ( thyroid hormone - globulin , tbg ) in order to specifically target the liver and make it like a factory organ of the therapeutic enzyme . mice were injected via temporal vein with 1 × 10 11 particles of virus . three experimental groups of mice were established : control mice ( heterozygous mice ; these mice display a normal phenotype ) treated with aav2 / 8 - tbg - gfp , mps - iiia mice treated with aav2 / 8 - tbg - gfp and mps - iiia mice treated with aav2 / 8 - tbg - sgsh . to test the efficiency of injection we analyzed the gfp fluorescence in the liver of gfp - injected mice ( normal and mps - iiia mice ). the gfp signal was present at either early or late time point after injection ; however , a significant decrease of gfp signal was observed in the liver of mice analyzed at later time point after injection ( fig1 ). the mps - iiia mice injected with aav2 / 8 - tbg - sgsh were checked for sgsh activity in plasma and in the liver at different time points after injection ( 5 , 8 , 10 , 14 days and at 3 , 4 , 5 , and 10 weeks ). the sgsh activity in plasma of aav2 / 8 - tbg - sgsh - treated mps - iiia mice increased during the first two weeks period after neonatal treatment , and then decreased through the time to reach the levels measured in control gfp - injected mps - iiia mice ( fig2 a ). the analysis of liver sgsh activity showed a trend similar to that observed in the plasma with higher levels of activity detected within the first week after injection ( fig2 b ). this preliminary study in newborn mice demonstrated that although the liver is efficiently transduced by aav2 / 8 - mediated neonatal delivery of sulfamidase , the enzyme is present at low levels ( comparable to control gfp - injected mps - iiia mice ) into both the liver and serum after 1 week post - injection making this approach unfeasible to treat the brain . to evaluate whether the proliferation of hepatocytes during the period after the treatment is responsible for the liver dilution of vector after neonatal injection we performed a new study based on the systemic ( caudal vein injection ) aav2 / 8 - mediated delivery of sgsh in adult mice ( 1 . 5 month of age ), in which the liver has completed its growth . also in this study we established three experimental groups of mice : normal mice treated with aav2 / 8 - tbg - gfp , mps - iiia mice treated with aav2 / 8 - tbg - gfp and mps - iiia mice treated with aav2 / 8 - tbg - sgsh . the analysis of gfp expression , at different time points after treatment ( 1 week and 5 weeks after injection ) underlined a high and stable expression of the transgene in the liver of adult treated mice ( fig3 ). mpsiiia treated mice were also checked for the sgsh activity in the liver and in the serum at different time points ( 1 week , 2 -, 3 -, 4 -, 5 - weeks ) after the treatment . in the liver of mpsiiia mice injected with aav2 / 8 - tbg - sgsh we observed a strong increase of sgsh activity compared with low enzyme activity in the animals injected with gfp vector , and this activity remained stable until 5 weeks after injection ( the later time point analyzed ) ( fig4 a ). also the analysis of sgsh activity in the serum of treated mice was very high and stable until during the entire post - injection period analyzed ( fig4 b ). importantly , this treatment did not result in any detectable sulfamidase activity into the brain of aav2 / 8 - injected mps - iiia mice ( not shown ). in conclusion these preliminary studies show that : ( i ) liver is highly transduced by aav2 / 8 - mediated systemic injection ( ii ) the decrease of sgsh activity in the newborn treated mice was due to the dilution of vector in the liver and allow us to consider the adult mice a good model to test the systemic treatment with aav2 / 8 containing the chimeric sulfamidase ( iii ) the secreted ( non modified ) sulfamidase did not result in a detectable enzymatic activity into the brain . the latter is an expected result and further justifies the rationale behind the aim of our project . in order to increase sulfamidase secretion from the liver and thus the amount of the enzyme in the blood stream available to specifically target the brain , we engineered the sulfamidase by replacing its own signal peptide ( sp ) with an alternative one . two signal peptides have been tested , the iduronate - 2 - sulfatase ( ids ) signal peptide and the human α - antitrypsin ( aat ) signal peptide ( fig5 ). the rationale behind the use of these two signal peptides is that ids is a lysosomal enzyme that was demonstrated to be secreted at high levels from the liver [ 21 ] while the aat is a highly secreted enzyme . the final goal of our project is to produce a modified sulfamidase capable to cross the bbb and target the cns via receptor - mediated transcytosis ( fig6 ). for this reason before starting the experiments aimed at evaluating the therapeutic efficacy of the substituting sp signal in sgsh , we further engineered the modified sgsh with a specific brain - targeting protein domain , the low density lipoprotein receptor ( ldlr )- binding domain of the apolipoprotein b ( apob ldlr - bd ). the binding domain of apob will allow the sulfamidase to reach the brain cells by binding ldl receptors , which are abundant on the endothelial cells of bbb ( fig6 ). the two finally engineered sulfamidase constructs contain at c - terminal the apob ldlr - bd and at n - terminal either an ids or an haat signal peptide ( idssp - sgshflag - apob and haatsp - sgshflag - apob ) ( fig5 ). to evaluate the functionality of chimeric sulfamidase proteins we transfected mpsiiia mef cells with either partial or final engineered sulfamidase proteins and compared the outcomes with those resulting from the transfections with not - engineered sulfamidase . surprisingly , we observed that sgsh activity in the pellet and in the conditioned medium was higher in the cells transfected with the final chimeric constructs compared with the activity measured in the cells transfected with the other constructs , indicating that finally engineered sulfamidase were efficiently secreted ( fig7 a ). indeed , these results were associated with a higher secretion efficiency of the finally engineered sulfamidase enzymes with respect to non - engineered sulfamidase ( fig7 b ). however , this secretion efficiency was similar to that measured after transfection of partially chimeric sulfamidase ( containing only the alternative signal peptide ) ( fig7 b ). remarkably , we observed that the modifications of the sulfamidase , in particular those present in the finally engineered sulfamidase , confer to the chimeric proteins a higher stability compared to the non - engineered sulfamidase ( fig8 a and b ). thus , we concluded that the increase in the sulfamidase protein levels in the medium of cells transfected with engineered sulfamidase proteins was due to both increased efficiency in secretion and increased stability of engineered sulfamidase . moreover , immunostaining with anti - sgsh antibodies showed a lysosomal - like localization for both partial and final engineered constructs ( fig8 c ). in conclusion these results demonstrate that : ( i ) the chimeric sulfamidase enzymes containing the alternative signal peptide are functional and active ; ( ii ) they are more stable with respect to non - modified sulfamidase ; ( iii ) they are secreted with increased efficiency compared to non - engineered sulfamidase enzyme ; ( iv ) the introduction of the apob ldlr - bd to produce the finally engineered sulfamidase did not affect either the functionality or the increased secretion efficiency observed in the cells transfected with the partially engineered sulfamidase . in addition , the finally engineered constructs appear to be more stable compared to partially engineered constructs . in vivo results in mps iiia mice injected with finally engineered sulfamidase we produced aav2 / 8 vectors containing one of the finally engineered sulfamidase ( haatsp - sgshflag - apob ) under the liver specific promoter tbg . we obtained very preliminary but extremely encouraging results in mps - iiia injected with this viral vector . adult mps - iiia mice were systemically injected with aav2 / 8 - tbg - haatsp - sgshflag - apob . a group of mps - iiia were also injected with aav2 / 8 - tbg - sgsh ( containing the not modified sulfamidase ) as control . the mice were sacrificed one month after injection . in the mice injected with the chimeric sulfamidase we observed higher liver sulfamidase activity and a very strong increase in the sulfamidase secretion respect to control mice ( fig9 ). moreover , we detected a significant increase in sgsh activity into the brain of mice injected with the chimeric sulfamidase ( fig9 ). we completed the production of the aav2 / 8 vectors containing all the engineered sulfamidase proteins ( partial and final ). specifically , besides the aav2 / 8 - tbg - haatsp - sgshflag - apob , we now produced aav2 / 8 - tbg - hidssp - sgshflag - apob ; aav2 / 8 - tbg - haatsp - sgshflag and aav2 / 8 - tbg - hidssp - sgshflag . these vectors may be used to perform a large in vivo study by the following procedure : mps - iiia mice ( 1 month of age ) are injected ( by a caudal vein route of administration ) with aav2 / 8 vectors containing the engineered constructs in order to test the clinical efficacy of the chimeric sulfamidase enzymes . results are useful to evaluate ( i ) the efficiency of cns transduction and ( ii ) the rescue of cns pathology in the treated mice . 1 . muenzer , j . 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