METHODS FOR INDUCTION OF TOLERANCE TO ADENOVIRAL VECTORS AND TRANSGENE PRODUCTS

Abstract: The invention relates to a method for inducing tolerance to an adenoviral vector and/or transgene product in a host, thereby allowing persistent transgene expression in the host and allowing repeated vector administration to the host while minimizing or eliminating the host immune response. The method comprises pretreating a host by administering to the host adenoviral vector-infected antigen presenting cells wherein said adenoviral vector comprises heterologous nucleic acids encoding an immunomodulatory molecule and a transgene and wherein said adenoviral vector-infected antigen presenting cells migrate to lymphoid organs and/or lymph nodes and induce tolerance. The method further provides for subsequentadministration to the host of an adenoviral vector comprising a heterologous nucleic acid encoding said transgene wherein the host immune response is reduced or eliminated to said adenoviral vector and said transgene even upon repeated administration of said adenoviral vector.

Description: METHODS FOR INDUCTION OF TOLERANCE TO ADENOVIRAL VECTORS AND TRANSGENE PRODUCTS FIELD OF THE INVENTION The present invention relates to the induction of tolerance to an adenoviral vector (and its adenovirus antigens) comprising a transgene and/or its transgene product in a host, thereby allowing persistent transgene expression in the host, and allowing repeated vector administration to the host while minimizing or eliminating the host immune response. The invention provides for pretreatment of the host with an intravenous administration of dendritic cells or other antigen presenting cells infected with an adenoviral vector comprising heterologous nucleic acids encoding a transgene and a heterologous nucleic acid encoding an immunomodulatory molecule. The adenoviral vector-infected dendritic cells of the invention migrate predominantly to the lymphoid organs, such as the spleen, where they interact with T cells resulting in high levels of expression of the transgene and immunomodulatory molecule therein. The present invention also provides for the infection of dendritic cells in vivo by intradermal injection of an adenoviral vector comprising a transgene and a heterologous nucleic acid encoding an immunomodulatory molecule. The dendritic cells thus infected will migrate to the regional lymph nodes where they would interact with T cells. Additionally, the present invention provides for the clonal deletion of T cells through fas/fasL mediated apoptosis of T cells. The method further provides for subsequent administration to the host of an adenoviral vector comprising said transgene wherein the host immune response is reduced or eliminated to said adenoviral vector and said transgene, even upon repeated administration of said adenoviral vector. BACKGROUND OF INVENTION The ability to deliver a transgene to a target cell or tissue and have it expressed therein to produce a desired phenotypic effect depends on the development of gene transfer vehicles that can safely and efficiently deliver an exogenous nucleic acid (transgene) to the recipient cell. To this end, most efforts have focused on the use of virus-derived vectors in order to exploit the natural ability of a virus to deliver its genetic content to a target cell. Early gene transfer strategies focused on retroviral vectors which have been the vectors of choice to deliver transgene coding for a biologically active molecules for gene therapy because of their ability to integrate into the cellular genome. However, the disadvantages of retroviral vectors have become evident, including their tropism for dividing cells only, the possibility of insertional mutagenesis in the host genome upon integration of the vector nucleic acid into the host cell genome, decreased expression of the transgene over time, rapid inactivation of retroviruses by the serum complement system, and the possibility of generating replication-competent retroviruses (Jolly, D., Cancer Gene Therapy 1:51-64, 1994; Hodgson, C.P., Bio/Technology 13:222-225, 1995). Adenovirus, a nuclear double-stranded DNA virus with a genome of about 36 kb, has been well-characterized through studies in classical genetics and molecular biology (Horwitz, M.S., "Adenoviridae and Their Replication," in Virology, 2nd edition, Fields et al., eds., Raven Press, New York, 1990). The adenovirus genome is classified into early (known as E1-E4) and late (known as L1-L5) transcriptional units, referring to the generation of two temporal classes of viral proteins. The demarcation between these events is viral DNA replication. The cloning capacity of an adenoviral vector is proportional to the size of the adenovirus genome present in the vector. For example, a cloning capacity of about 8 kb can be created from the deletion of certain regions of the virus genome dispensable for virus growth, e.g., E3, and the deletion of a genomic region such as El whose function may be restored in trans from 293 cells (Graham, F.L., J. Gen. Virol. 36:59-72, 1977) or A549 cells (Imler et al., Gene Therapy 3:75-84, 1996). Such El-deleted vectors are rendered replication-defective. The upper limit of vector DNA capacity for optimal carrying capacity is about 105 -108% of the length of the wild-type genome. Further adenovirus genomic modifications are possible in vector design using cell lines which supply other viral gene products in trans, e.g., complementation of E2a (Zhou et al., J. Virol. 70:7030-7038, 1996), complementation of E4 (Krougliak et al., Hum. Gene Ther. 6:1575-1586, 1995; Wang et al., Gene Ther. 2:775-783, 1995), or complementation of protein IX (Caravokyri et al., J. Virol. 69:6627-6633, 1995; Krougliak et al., Hum. Gene Ther. 6: 1575-1586, 1995). Adenovirus-derived vectors have several advantages, including tropism for both dividing and non-dividing cells, lessened pathogenic potential, ability to replicate to high titer for preparation of vector stocks, and the potential to carry large DNA inserts (Berkner, K.L., Curr. Top. Micro. Immunol. 158:39-66, 1992; Jolly, D., Cancer Gene Therapy 1:51-64, 1994). The cloning capacity of an adenoviral vector is a factor of the deletion of certain regions of the virus genome dispensable for virus growth (e.g., E3) or deletions of regions whose function is restored in trans from a packaging cell line (e.g., El, with complementation of El functions by 293 cells (Graham, F.L., J. Gen. Virol. 36:59-72, 1977). The upper limit for optimal packaging may be extended to about 105%-108 of wild-type adenoviral genome length for increased carrying capacity in the vector. Genes that have been expressed to date by adenoviral vectors include p53 (Wills et al., Human Gene Therapy 5:1079-188, 1994); dystrophin (Vincent et al., Nature Genetics 5:130- 134, 1993); erythropoietin (Descamps et al., Human Gene Therapy 5:979-985, 1994); oraithine transcarbamylase (Stratford-Perricaudet et al., Human Gene Therapy 1:241-256, 1990; We et al., J. Biol. Chem. 271:3639-3646, 1996); adenosine deaminase (Mitani et al., Human Gene Therapy 5:941-948, 1994); interleukin-2 (Haddada et al., Human Gene Therapy 4:703-711, 1993); al-antitrypsin (Jaffe et al., Nature Genetics 1:372-378, 1992); thrombopoietin (Ohwada et al., Blood 88:778-784, 1996); cytosine deaminase (Ohwada et al., Hum. Gene Ther. 7: 1567- 1576, 1996); human alpha-galactosidase A (PCT No. PCT/US98/22886), human beta- galactosidase (Arthur et al., Cancer Gene Therapy 4:17-25, 1997); interleukin-7 (Arthur et al, Cancer Gene Therapy 4:17-25, 1997); a Herpes Simplex Virus thymidine kinase gene (U.S. Patent No. 5,763,415) and cystic fibrosis transmembrane conductance regulator (CFTR) (U.S. Patent Nos. 5,670,488 and 5,882,877; Zabner et al., J. Clin. Invest. 97:1504-1511, 1996). The tropism of adenoviruses for cells of the respiratory tract has particular relevance to the use of adenoviral vectors in therapy for cystic fibrosis (CF), which is the most common autosomal recessive disease in Caucasians. Individuals with CF sustain pulmonary dysfunction resulting from mutations in the transmembrane conductance regulator (CFTR) gene that disturb the proper functioning of the cAMP-regulated Cl " channel in airway epithelia (Zabner, J. et al., Nature Genetics 6:75-83, 1994). Adenoviral vectors which carry the CFTR gene have been developed (Rich, D. et al., Human Gene Therapy 4:461-476, 1993) and studies have shown that these vectors can deliver CFTR to the airway epithelia of CF patients (Zabner, J. et al., Cell 75:207-216, 1993; Zabner, J. et al., J. Clin. Invest. 97:1504-1511, 1996), the airway epithelia of cotton rats and primates (Zabner, J. et al., Nature Genetics 6:75-83, 1994), and the respiratory epithelium of CF patients (Crystal, R.G. et al., Nature Genetics 8:42-51, 1994). Recent studies have shown that administering an adenoviral vector containing a DNA encoding CFTR to airway epithelial cells of CF patients can restore a functioning chloride ion channel in the treated epithelial cells (Zabner et al., J. Clin. Invest. 97:1504-1511, 1996). The preclinical studies and clinical trials so far conducted using adenoviral vectors for gene therapy, however, have suggested that administration of these vectors is associated with an antiviral host immune response that may limit positive results. The immune system functions to protect the body against infection by detecting the presence of macromolecules that are "foreign". These foreign molecules can be viral or other parasite proteins; these proteins can be present in the circulatory system of the body or present only within certain cells in the body. This form of immunity is based on the ability of the body to recognize foreign agents and to respond with the production of antibodies, so-called humoral immunity, or lymphocytes with killing activity, so-called cellular immunity. The effectors of humoral and cellular immunity have a high degree of specificity and immunological memory. In addition, more general defense mechanisms that do not depend on previous exposure of the body to the foreign agent also exist; this is referred to as innate immunity. The ability of macrophages to engulf particles, cytokine responses as part of the inflammatory response and the recognition of bacterial DNA methylation patterns are all examples of innate immunity. Viruses are examples of infectious agents to which the body responds with both innate and specific immunity. Viral structural proteins can stimulate antibody responses which can neutralize virus infectivity, and viral proteins synthesized within the cell can stimulate a cellular immune response which can target virus-infected cells for destruction. Moreover, viruses can provoke a non-specific inflammatory response as well. Vectors based on viruses can, in theory, be affected by specific and innate immune responses, depending on whether viral genes are retained within the vector and whether the viral genes are expressed at levels sufficient to provoke an immune response. The level at which viral genes are expressed is potentially very significant, since inflammatory and immune responses are proportional to dose. A low dose of antigen can escape detection by the body while a large dose is far more likely to be detected and to provoke a response. Some viral-based vectors are believed to present less of an immunological problem. AAV and retroviral vectors, for example, in most instances have had all viral genes deleted, thus eliminating the possibility that a cellular immune response will be generated against viral gene products. These vectors can, nonetheless, stimulate antibody responses to the virion coat proteins if sufficient amounts of vector are introduced into the body. As discussed above, El -deleted replication-defective adenoviral (Ad) vectors are attractive vehicles for gene transfer to host cells because of their ability to transduce a wide variety of dividing and non-dividing cells in vivo (Stratford-Perricaudet et al., Hum. Gene Ther. 1:241-256 (1990); Rosenfeld et al., CeU 68:143-155 (1992); Zabner et al., CeU 75:207- 216 (1993); Crystal et al.. Nat. Genetics 8:42-51 (1994); Zabner et al., Nat. Genetics 6:75-83 (1994)). Such vectors have been used for transfer of the gene encoding normal human cystic fibrosis transmembrane conductance regulator (CFTR) into airway epithelial cells of experimental animals (e.g. mice, cotton rats, monkeys) and to airway epithelium of individuals with cystic fibrosis (CF) (Rosenfeld et al., CeU 68:143-155 (1992); Zabner et al., CeU 75:207- 216 (1993); Crystal et al.. Nat. Genetics 8:42-51 (1994); Zabner et al.. Nat. Genetics 6:75-83 (1994)). Such vectors have transiently produced normal chloride ion channel function in CF patient airway epithelial cells. A number of studies, however, have suggested that administration of high doses of such first generation (El deleted) Ad vectors results in only transient CFTR gene expression in the lung due, at least in part, to destruction of vector-transduced cells by host cellular immune responses (predominantly CD8 + cytotoxic T cells) directed against Ad viral proteins and/or immunogenic transgene products (Yang et al., J. Virol. 69, 2004-2015 (1995); Kaplan et al., Gene Ther. 3:117-127 (1996); Tripathy et al.. Nat. Medicine 2:545-550 (1996); Yang et al., Gene Ther. 3: 137-144 (1996)). Reduction of this adverse immune response has been reported with the use of second generation vectors having decreased viral gene expression (Yang et al., Nature Genet. 7:362-369 (1994); Engelhardt et al., Proc. Natl. Acad. Sci. USA 9_l:6196-6200 (1994)) and with transgenes encoding self rather than foreign proteins (Tripathy et al., Nat. Medicine 2:545-550 (1996)). The treatment of chronic diseases such as CF with Ad vectors will likely require repeated administrations of Ad vectors containing the CFTR gene throughout the lifetime of the patient. However, as noted, the effectiveness of current Ad vectors is limited by the diffi- culty in obtaining successful readministration to an individual using a vector of the same Ad serotype, because of adverse immunologic responses. Various groups have demonstrated that a strong dose-dependent humoral immune response is induced by Ad vectors leading to the development of Ad-specific neutralizing antibodies, which leads to the inactivation by the host of readministered vector. (Yang et al., J. Virol. 69:2004-2015 (1995); Kaplan et al., Gene Ther. 3: 117-127 (1996); Smith et al., Gene Ther. 5:397-402 (1993); Yei et al., Gene Ther. 1:192-200 (1994); Van Ginkel et al.. Human Gene Ther. 6:895-903 (1995); Mastrangeli et al., Hum. Gene Ther. 7:79-87 (1996)). Studies using immunodeficient mice have shown that this process is dependent on MHC class II presentation of the input viral proteins and activation of CD4 + T (helper) cells and can be induced by inactive as well as active viral particles (Yang et al., J. Virol. 69:2004- 2015 (1995)). One solution to the immune response problem has been vectors, termed pseudoadenoviral vectors or PAV, which are adenoviral vectors derived from the genome of an adenovirus containing minimal cis-acting nucleotide sequences required for the replication and packaging of the vector genome and which can contain one or more transgenes (See, U.S. Patent No. 5,882,877 which covers PAV vectors and methods for producing PAV, incorporated herein by reference). Such PAV vectors, which can accommodate up to 36 kb of foreign nucleic acid, are advantageous because the carrying capacity of the vector is optimized, while the potential for host immune responses to the vector or the generation of replication- competent viruses is reduced. PAV vectors contain the 5' inverted terminal repeat (ITR) and the 3' ITR nucleotide sequences that contain the origin of replication, and the s-acting nucleotide sequence required for packaging of the PAV genome, and can accommodate one or more transgenes with appropriate regulatory elements. Another solution to overcome the immunologic problems associated with repeat administration of Ad vectors, is the use of broad immunosuppressants (Engelhardt et al., Proc. Natl. Acad. Sci. USA 91:6196-6200 (1994)) and cytoablative agents (Dai et al., Proc. Natl. Acad. Sci. USA 9.2:1401-1405 (1995)). Transient co-administration of an immunoglobulin, CTLA4-Ig, along with an intravenous injection of Ad vector expressing a nonimmunogenic transgene product (human α-1 anti-trypsin) has been shown to lead to persistent transgene expression from mouse liver (Kay et al., Nat. Genetics 11:191-197 (1995)). CTLA4-Ig blocks the B7-CD28 pathway of T cell co-stimulation, which is required for optional activation of T cells. (Jenkins et al., Immunity 1:443-446 (1994); Lenschow et al., Ann. Rev. Immunol. 14:233-258 (1996)). Although Ad-specific antibody levels were reduced in CTLA4-Ig treated mice, the inhibition was not sufficient to allow secondary gene transfer via repeat administration of the vector under the conditions tested (Kay et al., Nat. Genetics 11:191-197 (1995)). Co-administration of interferon-γ (INF-γ) or interleukin-12 (IL-12) with recombinant Ad vectors was shown to diminish the formation of Ad-specific neutralizing antibodies and allowed readministration of the vector to mouse airways (Yang et al., Nat. Medicine 1:890-893 (1995)). However, IL-12 is a potent mediator which affects T hl -type CD4 + T cell responses and is involved in stimulating natural killer (NK) cells and promoting the differentiation of cytotoxic T cells (CTLs) (Paul et al., CeU 76:241-251 (1994); Trinchieri, G., Blood 84:4008- 4027 (1994); Bliss et al., J. Immunol. 156:887-894 (1996)). INF-γ is known to upregulate MHC class I on antigen presenting cells (Yang et al., Proc. Natl. Acad. Sci. USA 22:7257- 7261 (1995)). Thus, both INF-γ and IL-12, while capable of inhibiting humoral immunity, might enhance the elimination of Ad vector transduced cells by CTLS (enhanced T hl response). The immunosuppressive properties of interleukin-10 (IL-10) also have been well documented. Several studies have shown that IL-10 can inhibit the function of both antigen presenting cells and T cells (Moore et al., Ann. Rev. Immunol. JJ,: 165-190, 1993; de Waal Malefyt et al, J. Exp. Med. 174:915, 1991; Enk et al., J. Immunol. 151:2390, 1993). Production of IL-10 by tumor cells may be a mechanism by which tumors escape a protective immune response. Viral IL-10 (vIL-10), a product of the Epstein Barr virus is homologous to both murine and human IL-10 and while vIL-10 shares many biological properties with murine IL-10 and human IL-10, it does not possess some of the immuno- stimulatory activities of cellular IL-10 (de Waal Malefyt et al, J. Exp. Med. 174:915). Additionally, transforming growth-factor- β (TGFβ) is also known as a very potent immunosuppressant acting on NK cells, T cells, B cells and macrophages (Fontana et al., J. Immunol. 143:3230, 1995; Bellone et al., J. Immunol. 158:136, 1997; Bright and Sriram, J. Immunol. 161:1772-1777, 1998; Pardoux et al., Blood 23 . : 1448-1445). TGFβ promotes a reversible phenotypic transformation of non-neoplastic fibroblasts and was originally described to inhibit generation of allogeneic CTL and T cell growth induced by interleukin 2 (IL2) (Fontana et al., J. Immunol. 132:1837, 1984). More recently, TGFβ has been shown to inhibit the generation of cytotoxic T cells in virus-infected mice (Fontana et al., J. Immunol. 143:3230, 1995). Still another strategy used to overcome the immune response to adenoviral vector proteins as well as transgene product is the induction of peripheral T-cell tolerance to both the adenoviral vector and the transgene products which, in many cases, may be a neoantigen in the patient. It is known that activation-induced cell death in T cells, in which apoptosis of the T cells is mediated by upregulation of fas and fas ligand (fasL) is responsible for down regulation of the T-cell response and T cell homeostasis (Watanabe-Fukunaga et al., Nature 314-317, 1992; Zhou et al., J. Exp. Med. 176:1063-1072, 1992; Nagata, Adv. Immunol. 57:129-144, 1994, and Dhein et al., Nature 373:438-441, 1995). Recently, it has been shown that adenovirus mediated fasL expression in balloon-injured rat carotid artery, even in animals pre-immunized with adenoviral vector, resulted in effective inhibition of neointima formation as well as protection of the Ad/fasL infected cells from immune destruction (Sata et al., Proc. Natl. Acad. USA 95:1213-1217, 1998). The mammalian fas/CD95 ligand (fasL) cell surface protein induces apoptosis of T cells responding to foreign antigens in transplantation (Griffith et al., Science 270:1189-1192. 1995). The p35 gene of baculovirus encodes a protein which blocks apoptosis of baculovirus-infected cells (Clem et al., Science 254:1388-1389, 1991; Hershberger et al., J. Virol. 68:3467-3477, 1994; Bump et al., Science 269:1885-1888, 1995; Xue et al., Nature 377: 248-251, 1995). One mechanism of tolerance is via the natural occurrence of immune privileged sites. Clonal deletion of antigen-specific T cells, mediated by apoptosis of T cells via the fas-fasL pathway has been shown to be an important mechanism in creating immune-privileged sites, as well as in the maintenance of peripheral tolerance, and in the prevention of graft rejection (Nagata, Adv. Immunol. 57:129-144, 1994; Dhein et al., Nature 373:438-441, 1995; Bellgrau et al., Nature 377:630-632, 1995; Griffith et al, Science 270:1189-1192, 1995 and Lau et al, Science 273: 109-112, 1996). Insertion of adenovirus at these sites results in tolerance to adenovirus and its transgene product. The injection of El deleted adenovirus into the sub- retinal space resulted in minimal cellular and humoral immune response (Bennet et al., Hum. Gene Therap. 8:1625-1634, 1996). Recently, it has been disclosed that pretreatment of mice with an antigen-presenting line expressing Ad/fasL can induce Ad-specific T cell tolerance (WO98/52615, WO98/51340 and Zhang et al., Nature BioTechnology 16:1045-1049). Upon subsequent intravenous administration of an Ad/lacZ vector, persistent expression of the lacZ gene was achieved in the liver for 50 days. However, there are two major drawbacks to this procedure. The first is that the method used for expression of the fasL gene in the antigen-presenting cell line involves coinfection with two different adenoviral vectors, AdLoxpfasL (Zhang et al., J. Virol. 72:2483- 2490, 1998) and AxCANCre (Kanegae et al, Nucl. Acids Res. 23:3816-3821, 1995). In this method, AxCANCre expresses the Cre recombinase and is required to turn on expression of the fasL gene from the AdLoxpfasL vector. Thus, an extra component besides the vector which contains the fas gene is required for its effective delivery. Ad vectors constitutively expressing fasL cannot be grown to high titers, because fasL induces apoptosis of the 293 cells used to propagate the Ad vectors (Larregina et al., Gene Ther. 5:563-568, 1998). Secondly, the antigen-presenting cell line used was derived from a fas-mutant B6-lpr lpr mouse, since fasL expression can kill normal cells expressing the fas receptor (Muruve et al., Hum. Gene Ther. 8:955-963, 1997; Kang et al., Nature. Med. 3:738-743, 1997 and Larregina et al., Gene Ther. 5:563-568, 1998). Therefore, the expression of fasL would be extremely difficult to accomplish in cells derived from normal individuals. It is known that antigen presenting cells (APCs) such as dendritic cells (DCs), macrophages and B cells are involved in the generation of an optimal immune response to pathogens, alloantigens and tumors. Dendritic cells are highly specialized APCs of the immune system (Steinman, Annu. Rev. Immunol. 2:271, 1991). The strategic positioning of DCs in nonlymphoid tissue and their ability to circulate via blood and lymph to lymphoid organs after antigen stimulation demonstrate their important role in the induction of immune responses against invading pathogens (Hoefsmit et al., Immunobiology 161:255. 1982; Austyn et al., J. Exp. Med. 166:646, 1988). During their migration, DCs such as Langerhans Cells (LCs) are thought to undergo characteristic modulations of function and phenotype (Larsen et al., J. Exp. Med. 172:1483, 1990; Schuler et al., . Exp. Med. 161:526, 1985). Locally produced inflammatory cytokines and the encounter with an antigen promote the maturation and migration of DCs to regional lymph nodes. During this process, DCs undergo a differentiation from a processing to a presenting functional cell type, characterized by the expression of co-stimulatory molecules, cytokine production, and a typical morphology ( Schuler et al., . Exp. Med. 161:526, 1985; Steinman et al., Curr. Opin. Immunol. 3:361, 1991; Young et al., J. Clin. Invest. 2Q:229, 1992). In contrast to other types of APCs, fully mature DCs are potent activators of naive T cells and are regarded as important initiators of primary specific immune responses ((Steinman, Annu. Rev. Immunol. 2:271, 1991). Recently it has been shown that IL-10 treated human dendritic cells can induce tumor- antigen specific anergy in CD8+ T cells (Suzuki et al., J. Exp. Med. 182:477-486, 1995; Steinbringk et al., Blood 23: 1634-1642). It has also been recently shown that IL-10-treated human DCs, generated from peripheral blood, induce a state of antigen specific anergy in various populations of CD4+ cells (Steinbrink, et al., J. Immunol. 159:4772. 1997). SUMMARY OF THE INVENTION The present invention is directed to reducing the immune response of a host to administered adenoviral (Ad) vectors carrying a transgene coding for a biologically active molecule, thereby allowing for repeat administration of such vectors to the host without (or with minimized) adverse immune responses. The present invention is also directed to reducing the immune response of a host to immunogenic polypeptides encoded by a transgene without (or with minimized) adverse immune responses to promote the efficacy of the therapeutic effect of the transgene within the host. The immune response to Ad vectors appears to be mediated through activation of CD4+ cells by viral antigens leading to CD8+ cytotoxic T lymphocyte (CTL) and humoral immune responses to the Ad vector. IL-10 treated human dendritic cells can induce tumor- antigen specific anergy in CD8+ T cells and in CD4+ T cells. Furthermore, TGFβ is also a potent immunosuppressant. The present invention provides for the pretreatment of a host with an intravenous administration of DCs or other antigen presenting cells which have been infected with an Ad vector comprising a transgene coding for a biologically active molecule and a heterologous nucleic acid encoding an immunosuppressant molecule such as IL-10, vIL-10 and/or TGFβ. The dendritic cells migrate predominantly to the lymphoid organs like the spleen where they interact with T cells resulting in the expression of IL-10, vIL-10 and/or TGFβ therein. IL-10 acts on the DCs making them tolerogenic and TGFβ acts on the splenic T cells, B cells and macrophages. A further method for inducing tolerance to an adenoviral vector and/or transgene product in a host entails clonal deletion of antigen specific T cells mediated by apoptosis of T cells via the fas-fasL pathway. Therefore, the present invention also provides for the pretreatment of a host with an intravenous administration of DCs or other antigen presenting cells which have been infected with an Ad vector comprising a nucleic acid encoding fasL, as well as an inhibitor of apoptosis, such as p35. When the dendritic cells migrate to the lymphoid organs such as the spleen where they interact with T cells, the expression of fasL on the surface of the dendritic cells induces apoptosis of the T cells through the fas/fasL apoptosis pathway, while the expression of the apoptosis inhibitor within the dendritic cells protects the dendritic cells from apoptosis. The present invention further provides for the infection of DCs in vivo by intradermal injection of an Ad vector comprising a transgene coding for a biologically active molecule and a heterologous nucleic acid encoding an immunosuppressant molecule such as IL-10, vIL-10 and/or TGFβ or alternatively encoding fasL as well as an inhibitor of apoptosis, such as p35. DCs thus infected will migrate to the regional lymph nodes where they would interact with T cells. BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be further understood with reference to the attached drawings, of which, Figure 1 shows an Ad2 vector encoding TGFβ. Figure 2 shows an Ad2 vector encoding TGFβ and CFTR. Figure 3 shows an Ad2 vector encoding TGFβ and vIL-10. Figure 4 shows an Ad2 vector encoding vIL-10. Figure 5 shows an Ad2 vector encoding vIL-10 and CFTR. Figure 6 shows an Ad2 vector encoding vIL-10 and βgal. Figure 7 shows an Ad2 vector encoding fasL and p35. Figure 8 shows the results of the LDH assay. Figure 9 shows a DeAd vector genome. Figure 10 shows a map of the plasmid pCMV. Figure 11 shows a map of the plasmid pAd/E4+/E3Δ2.9. Figure 12 shows an Ad2 vector encoding a transgene, fasL and p35. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to diminishing or inhibiting adverse immunological responses in a host individual to an administered Ad vector comprising a transgene coding for a biologically active molecule. The invention involves pretreatment of the host with an intravenous administration of dendritic cells or other antigen presenting cells infected with and Ad vector comprising heterologous nucleic acids encoding an immunosuppressant molecule or a molecule capable of mediating T cell apoptosis, and a transgene coding for a biologically active molecule. The administration of such Ad vector-infected dendritic cells allows for repeat administration of the Ad vector comprising the same transgene to the host with minimized adverse immunological consequences and persistent transgene expression in treated host cells. The nucleic acid encoding an immunosuppressant molecule or a molecule capable of mediating T cell apoptosis and a transgene may be cloned into any recombinant adenoviral vector suitable for the delivery of a desired nucleic acid to a recipient cell. In preferred aspects of the invention, the adenoviral (Ad) vector is derived from adenovirus serotype 2 (Ad 2) and has a substantially deleted El and E3 region. Other adenovirus serotypes can also be used as backbones for the adenoviral vector including, inter alia, Ad 5, Ad 6, Ad 9, Ad 12, Ad 15, Ad 17, Ad 19, Ad 20, Ad 22, Ad 26, Ad 27, Ad 28, Ad 30 and Ad 39. From these enumerated adenovirus serotypes, Ad 2, Ad 5, Ad 6 and Ad 17 are preferred. In one embodiment of the invention, the adenoviral vector comprises an adenovirus genome in which the El region and a 1.6 kb portion in the E3 region of the adenovirus genome from nucleotides 29292-30840 are deleted as disclosed in U.S. Application Ser. No. 08/839,553, incorporated herein by reference. In a specific embodiment of the invention, the adenoviral vector is Ad2/CMV/E3Δ1.6. In other aspects of the invention, the vector is a partially-deleted adenoviral (DeAd) vector in which a majority of the adenovirus early genes (E1-E4) required for virus replication have been deleted from the vector. The DeAd vector is described in co-pending provisional application Ser. Nos. 60/083,841 filed May 1, 1998 and 60/118,118 filed February 1, 1999 and their corresponding international application No. PCT/US99/09590 filed April 30, 1999, incorporated herein by reference. The deleted adenovirus genes, with the possible exception of E3, which is not required for replication, are inserted into a producer cell chromosome under the control of a conditional promoter in order to facilitate vector production. A preferred producer cell is the human 293 cell line which was established by transfecting human embryonic kidney cells with fragments of the Ad5 genome and selecting for a transformed phenotype (Graham, F.L. et al., J. Gen Virol. 36:59-72, 1997). In addition, the A549 cell line and the KB cell line may also be used (all of which are available from ATCC). In further aspects of the invention, the adenoviral vectors are pseudoadenoviral vectors (PAV) which are derived from the genome of an adenovirus which contain minimal c/s-acting nucleotide sequences required for the replication and packaging of the vector genome and which can contain one or more transgenes (See, U.S. Patent No. 5,882,877 which covers PAV vectors and methods for producing PAV, incorporated herein by reference). Such PAV vectors can accommodate up to 36 kb of foreign nucleic acid. Additionally, the heterologous nucleic acid encoding immunosuppressant molecules, e.g., IL-10, vIL-10 and TGFβ, the transgene coding for a biologically active molecules, and the nucleic acids encoding fas, fasL, and p35 may be operably linked to expression control sequences, e.g., a promoter that directs expression of the transgene or the immunomodulatory molecule. As used herein, the phrase "operably linked" refers to the functional relationship of a polynucleotide/transgene with regulatory and effector sequences of nucleotides, such as promoters, enhancers, transcriptional and translational stop sites, and other signal sequences. For example, operative linkage of a nucleic acid to a promoter refers to the physical and functional relationship between the polynucleotide and the promoter, such that transcription of DNA is initiated from the promoter by an RNA polymerase that specifically recognizes and binds to the promoter, and wherein the promoter directs the transcription of RNA from the polynucleotide. Promoter regions include specific sequences that are sufficient for RNA polymerase recognition, binding and transcription initiation. Additionally, promoter regions include sequences that modulate the recognition, binding and transcription initiation activity of RNA polymerase. Such sequences may be cis acting or may be responsive to trans acting factors. Depending upon the nature of the regulation, promoters may be constitutive or regulated. Examples of promoters are SP6, T4, T7, SV40 early promoter, cytomegalovirus (CMV) promoter and CMV-derived promoters, mouse mammary tumor virus (MMTV) steroid- inducible promoter, Moloney murine leukemia virus (MMLV) promoter, Rous sarcoma virus long terminal repeat (RSV-LTR) viral promoters, phosphoglycerate kinase (PGK) promoter and the like. Alternatively, the promoter may be an endogenous adenovirus promoter, for example the El a promoter or the Ad2 major late promoter (MLP). The promoter may also be capable of driving persistent transgene expression such as the CMV derived promoter element described by Armentano et al. in international patent application PCT/US99/00915 incorporated herein by reference. Similarly those of ordinary skill in the art can construct adenoviral vectors utilizing endogenous or heterologous polyA adenylation signals, e.g., the SV40, BGH, adenoviral or native polyA signal. Where the vector contains multiple heterologous nucleic acid molecules, the nucleic acid molecules may be expressed from different promoters in order to optimize specific expression of each type of gene. For example, the transgene bay be placed under the control of a constitutive promoter, and the immunosuppressant molecule may be placed under an inducible promoter. Alternatively the multiple copies of the same promoter may be used for the expression of multiple nucleic acids or a single promoter may be operatively linked to heterologous nucleic acids placed adjacently to achieve simultaneous expression. Polynucleotides/transgenes are inserted into Ad vectors using methods well known in the art. Transgenes are defined herein as nucleic acid molecules or structural genes that encode a particular polypeptide or protein or a ribozyme or an antisense RNA or the like. Transgenes encoding polypeptides or proteins include, inter alia, those coding for enzymes, e.g., human lysosomal enzymes, such as -galactosidase A and β-glucocerebrosidase, hormones, growth factors, cytokines, antigens, and such specific proteins such as CFTR, αl- antitrypsin, soluble CD4, adenosine deaminase, Herpes Simplex Virus thymidine kinase, the tumor antigens gplOO, MART-1 and TRP-2; and clotting factors, such as factor VIII, factor IX, factor VII and Von Willebrand factor. Representative human lysosomal enzymes in accordance with the present invention are provided in Table I. References relating to isolation and characterization of the lysosomal enzymes and nucleic acid molecules (transgenes) encoding said enzymes in Table I may be found in Scriver et al., The Metabolic Basis of Inherited Disease, 7 th Ed., vol. II, pp. 2427-2879, McGraw Hill, 1995, incorporated herein by reference. Table I. Lysosomal storage diseases and associated enzymatic defects *MPS = mucopolysaccaridosis Polynucleotides encoding immunosuppressant molecules include, inter alia, those coding for IL-10, vIL-10 and TGFβ. Other polynucleotides of the present invention include the p35 gene of baculovirus which encodes a protein that blocks apoptosis of baculovirus- infected cells (Clem et al., Science 254:1388-1389, 1991; Hershberger et al., J. Virol. 68:3467- 3477, 1994; Bump et al., Science 269:1885-1888, 1995; Xue et al., Nature 377: 248-251, 1995) and the mammalian fas/CD95 ligand (fasL) gene which encodes a cell surface protein that induces apoptosis of T cells responding to foreign antigens in transplantation (Griffith et al., Science 270:1189-1192, 1995). By way of example, in order to insert the polynucleotide/transgene into the vector, the polynucleotides/transgene and vector nucleic can be contacted, under suitable conditions, with a restriction enzyme to create complementary ends on each molecule that can pair with each other and be joined together with a ligase. Alternatively, synthetic nucleic acid linkers can be ligated to the termini of the restricted polynucleotide. These synthetic linkers contain nucleic acid sequences that correspond to a particular restriction site in the vector nucleic acid. Additionally, an oligonucleotide containing a termination codon and an appropriate restriction site can be ligated for insertion into a vector containing, for example, some or all of the following: a selectable marker gene, such as the neomycin gene for selection of stable or transient transfectants in mammalian cells; enhancer/promoter sequences from the immediate early gene of human CMV for high levels of transcription; transcription termination and RNA processing signals from SV40 for mRNA stability; SV40 polyoma origins of replication and ColEl for proper episomal replication; versatile multiple cloning sites; and T7 and SP6 RNA promoters for in vitro transcription of sense and antisense RNA. Other means are well known and available in the art. In a preferred embodiment of the present invention, (as illustrated in Example 1), a nucleic acid molecule encoding an immunosuppressant molecule is inserted into the E3- deleted region of the adenoviral vector (Fig. 1 and Fig 4). Alternatively, a nucleic acid encoding an immunosuppressant molecule is inserted into the E3-deleted region of the adenoviral vector and a nucleic acid encoding a second molecule (either another immunosuppressant molecule or a transgene) is inserted into the El -deleted region of the adenoviral vector (Fig. 2, Fig. 3, Fig. 5 and Fig. 6). In another alternative embodiment of the invention, a nucleic acid encoding p35 is inserted into the E3-deleted region of the adenoviral vector and a nucleic acid encoding a fasL is inserted into the El -deleted region of the adenoviral vector (Fig. 7) as described in a co-pending U.S. provisional patent application Ser. No. 60/130,415, filed April 21, 1999, incorporated herein by reference. The present invention includes a method of using the vectors of the present invention for inducing tolerance to adenovirus antigens and/or transgenes included in an adenoviral vector in antigen-presenting cells (APCs) of an individual to whom the vectors are administered comprising introducing into said APCs an amount of a vector comprising an adenovirus genome comprising nucleic acids encoding said adenoviral antigens, said adenovirus genome also comprising a deletion of the El region and a deletion in a second region, wherein a first nucleic acid molecule is inserted into one deleted region and a second nucleic acid molecule is inserted into the other deleted region and wherein the vector is taken up by the cells and wherein the first and second nucleic acids encode a protein which is expressed in the APCs. The first and second nucleic acids which encode a protein include, ter alia, vIL-10, TGFβ, fasL, p35 and a transgene. In a preferred embodiment, the first nucleic acid comprises a transgene and the second nucleic acid encodes TGFβ or IL-10 or vIL- 10. In another preferred embodiment of the invention, a first nucleic acid encodes a transgene, a second nucleic acid encodes fasL and a third nucleic acid encodes p35. Suitable sources of APCs include but are not limited to whole cells, such as dendritic cells or macrophages and foster antigen-presenting cells. The APCs, preferably dendritic cells (DCs), may be infected either in vitro or in vivo. DCs, which are the principle initiators of antigen-specific immune responses have several molecules on their surface that are critical for T-cell activation (reviewed in van Schooten et al., Mol. Medicine Today, pp 254-260, 1997). For infection in vitro, DCs may be purified from bone marrow by isolating bone marrow precursor cells (CD34+) from blood and stimulating them to differentiate into DCs. The individual must be treated with cytokines such as GM-CSF to boost the number of circulating CD34+ stem cells in the peripheral blood. Inaba et al., J. Exp. Med. 176:1693. A second approach for isolating DCs is to collect the relatively large numbers of precommitted DCs already circulating in the blood. Known procedures for preparing mature DCs from human peripheral blood have involved combinations of physical procedures such as metrisamide gradients and adherence/nonadherence steps (Freudenthal et al., Proc. Natl. Acad. Sci. U.S.A. 87:7698-7702, 1990); percoll gradient separations (Mehta-Damani et al., J. Immunol. 153:6840-6852, 1993). The preferred methods for isolation and culturing of DCs are described in Bender et al., J. Immunol. Meth. 196:121-135. 1996 and Romani et al, J. Immunol Meth. 196:137-151. 1996, incorporated herein by reference. Harvested DCs may then be infected in vitro with an Ad vector comprising either a nucleic acid encoding an immunosuppressant molecule (IL-10, vIL-10 and/or TGFβ) and a transgene, such as those described above, or the fasL gene and the p35 gene. Infected DCs may then used to pretreat a host by the multiple administration of the infected DCs into the host by intravenous injection. After administration of the infected DCs to the host, the DCs migrate to lymphoid organs, such as the spleen, and interact with T cells. Such interaction would either suppress the immunogenic response of the T cells where IL-10, vIL-10 and/or TGFβ are expressed, or induce apoptosis of the T cells where the fasL is expressed. The p35 will act to protect the DCs from being lysed through the fas/fasL mediated pathway. After pretreatment, an Ad vector comprising the same transgene as that introduced by the adenoviral vector-infected DCs, may be introduced to the host by any route of administration, e.g., intravenous, intranasal, intramuscular, etc. The transgene coding for a biologically active molecule can then be expressed in the absence of an immune response or with a minimized immune response. The absent or reduced immune response allows for repeated administration of the Ad vector and persistent expression of the transgene coding for a biologically active molecule with a minimized or eliminated host immune response. Alternatively, the Ad vector comprising either a nucleic acid encoding an immunosuppressant molecule (IL-10, vIL-10 and/or TGFβ ) and a transgene, such as those disclosed above, or the fasL gene and the p35 gene may be used to infect DCs in vivo by intradermal injection of the Ad vector or any other suitable route of administration known in the art. DCs thus transduced will migrate to the regional lymph nodes where they can interact with T cells. After administration of DCs to the host in vivo, an Ad vector comprising the same transgene coding for a biologically active molecule as that introduced by the adenoviral vector-infected DCs, may be introduced by any route of administration, e.g., intravenous, intranasal, intramuscular, etc. As stated above, the transgene coding for a biologically active molecule may then be expressed in the absence of an immune response or with a minimized immune response and may be repeatedly administered. Other routes of administration for the Ad vectors comprising the transgene coding for a biologically active molecule include conventional and physiologically acceptable routes such as direct delivery to target cells, organs or tissues, intranasal, intravenous, intramuscular, subcutaneous, intradermal, oral and other parenteral routes of administration. The Ad vectors may also be administered via inhalation of liquid or dry powder aerosols (e.g. as disclosed in U.S. provisional patent application Ser. No. 60/110,899, filed December 4, 1998, incorporated herein by reference). Dosage of an Ad vector which is to be administered to an individual is determined with reference to various parameters, including the condition to be treated, the age, weight and clinical status of the individual and particular molecular defect requiring the provision of a biologically active protein. The dosage is preferably chosen so that administration causes a specific phenotypic result, as measured by molecular assays or clinical markers described above. Dosages of an Ad vector of the invention which can be used for example in providing a transgene contained in a vector to an individual for persistent expression of a biologically active protein encoded by the transgene and to achieve a specific phenotypic result range from approximately 10 infectious units (I.U.) to 10 u I.U. for humans. It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. "Dosage unit form" as used herein refers to physically discrete units suited as unitary dosages for the subjects to be treated, each unit containing a predetermined quantity of active ingredient calculated to produce the specific phenotypic result in association with the required physiological carrier. The specification for the novel dosage unit forms of the invention are dictated by and directly depend on the unique characteristics of the adenoviral vector used in the formulation and the limitations inherent in the art of compounding. The principle active ingredient (the adenoviral vector) is compounded for convenient and effective administration with the physiologically acceptable carrier in dosage unit form as discussed above. The Ad vectors administered after pretreatment with Ad infected DCs to induce tolerance may be targeted to specific cells by linking a targeting molecule to the vector, e.g. as disclosed in international application No. PCT/US99/02680 filed February 8, 1999, incorporated herein by reference. A targeting molecule is any agent that is specific for a cell or tissue type of interest, including for example, a ligand, antibody, sugar, receptor, or other binding molecule. Targeted vectors are particularly useful in the treatment of lysosomal diseases. For example, including a targeting molecule, such as VEGF or an antibody to a VEGF receptor, can provide targeting to vascular endothelial cells in individuals with Fabry's disease. In addition, the Ad vectors administered after pretreatment with infected DCs, can be complexed with a cationic amphiphile, such as a cationic lipid, polyL-lysine (PLL), and diethylaminoethyldextran (DEAE-dextran) to provide increased efficiency of viral infection of target cells (See, e.g., W098/22144, incorporated herein by reference). Representative cationic lipids include those disclosed, for example, in U.S. Patent Nos. 5,238,185 and 5,767,099, with preferred lipids being GL-67 (N 4 -spermine cholesteryl carbamate), GL-53 (N 4 -spermine cholesteryl carbamate), and GL-89 (1-(N 4 - spermine)-2,3-dilaurylglycerol carbamate). Ad vectors complexed with DEAE dextran are particularly preferred. In addition, to further eliminate the immune response which occurs from repeat administration of viral vectors, adenovirus and other viral vectors may be polymer-modified, e.g., complexed with polyethylene glycol (PEG), to reduce viral immunogenicity and allow for repeat administration of the vector (See, e.g., WO/98/44143, incorporated herein by reference). Also, Ad vectors complexed with a cationic molecule, preferably DEAE, and a polyalkylene glycol polymer, e.g. PEG, as disclosed in U.S. provisional patent application Serial NO. 60/097,653, filed August 24, 1998, are contemplated herein. Transfer of the transgene to the target cells by the Ad vectors of the invention can be evaluated by measuring the level of the transgene product in the target cell and correlating a phenotypic alteration associated with transgene expression . For example, expression of a CFTR transgene in target cells from an individual with cystic fibrosis is correlated with production of a functional chloride ion channel in such cells that may be measured by techniques known in the art. The level of transgene product in the target cell directly correlates with the efficiency of transfer of the transgene by the Ad vectors. Any method known in the art can be used to measure transgene product levels, such as ELISA, radioimmunoassay, assays using an fluorescent and chemiluminescent enzyme substrates. Expression of the transgene can be monitored by a variety of methods known in the art including, inter alia, immunological, histochemical and activity assays. Immunological procedures useful for in vitro detection of the transgene product in a sample include immunoassays that employ a detectable antibody. Such immunoassays include, for example, ELISA, Pandex microfluorimetric assay, agglutination assays, flow cytometry, serum diagnostic assays and immunohistochemical staining procedures which are well known in the art. An antibody can be made detectable by various means well known in the art. For example, a detectable marker can be directly or indirectly attached to the antibody. Useful markers include, for example, radionuclides, enzymes, fluorogens, chromogens and chemiluminescent labels. For in vivo imaging methods, a detectable antibody can be administered to a subject and the binding of the antibody to the transgene product can be detected by imaging techniques well known in the art. Suitable imaging agents are known and include, for example, gamma- emitting radionuclides such as ι u ln, 99m Tc, 51 Cr and the like, as well as paramagnetic metal ions, which are described in U.S. Patent No. 4,647,447. The radionuclides permit the imaging of tissues by gamma scintillation photometry, positron emission tomography, single photon emission computed tomography and gamma camera whole body imaging, while paramagnetic metal ions permit visualization by magnetic resonance imaging. The method of present invention which induces tolerance to Ad vector gene products and transgene products, can be analyzed for the ability of the method to provide persistence of transgene expression in vivo. The method may be assessed in an animal model system where the DCs of the animal are harvested by methods known in the art, infected in vitro with an Ad vector comprising an immunosuppressant and a transgene and used to pretreat the animal to induce tolerance therein or DCs may alternatively be infected with adenoviral vectors in vivo via intradermal injection as described above. After pretreatment, an Ad vector encoding the same transgene may be repeatedly administered to the animal by acceptable routes. Such a model may be chosen with reference to such parameters as ease of delivery, identity of transgene, relevant molecular assays and assessment of clinical status. Where the transgene encodes a protein whose lack is associated with a particular disease state, an animal model which is representative of the disease state may optimally be used in order to assess a specific phenotypic result correlated with the presence of biologically active transgene product e.g., Fabry knockout mice (as disclosed in international No. PCT/US98/22886, filed October 29, 1998), may be used to assay the ability of Ad vectors comprising an α-galactosidase A transgene to reduce the levels of GL-3 in such mice. In such an animal model system, the immune response may also be analyzed. The ability to achieve persistent gene expression and to repeatedly administer the Ad vector comprising transgene coding for a biologically active molecule with a reduced or eliminated immune response may also be analyzed. Relevant animals in which the transgene expression system may be assayed include, but are not limited to, mice, rats, monkeys and rabbits. Suitable mouse strains in which the transgene expression system may be tested include, but are not limited to, C3H, C57B1/6 (wild-type and nude) and Balb/c (available from Taconic Farms, Germantown, New York). Where it is desirable to assess the host immune response to Ad vector administration, testing in immune-competent and immune-deficient animals may be compared in order to define specific adverse responses generated by the immune system. The use of immune- deficient animals, e.g., nude mice, may be used to characterize vector performance and persistence of transgene expression, independent of an acquired host response and to identify other determinants of transgene persistence. In order to determine the persistence of Ad vectors in the host, one skilled in the art can assay for the presence of these vectors by any means which identifies the transgene (and its expression), for example, by assaying for transgene or nucleic acid encoding the immunomodulatory molecule mRNA level by RT-PCR, Northern blot or SI analysis, or by assaying for transgene protein expression by Western blot, immunoprecipitation, or radioimmunoassay. Alternatively, the presence of the Ad vector or the desired transgene DNA sequences per se in a host can be determined by any technique that identifies DNA sequences, including Southern blot or slot blot analysis, or other methods 'known to those skilled in the art. Where the vector contains a marker gene, e.g., lacZ coding for E. coli, β-galactosidase, the presence of the vector may be determined by these same assays or a specific functional assay that screens for the marker protein (e.g., X-gal). The persistence of a vector of the invention in the host can also be determined from the continued observation of a phenotypic alteration conferred by the administration of the Ad vector containing the transgene, e.g., the improvement or stabilization of pulmonary function following administration of a vector containing the CFTR gene to an individual with cystic fibrosis or the reduction in stored GL3 lipid in an individual with Fabry's disease. Spirometry can be used for pulmonary function tests (PFT) in CF individuals. Demonstration of the restoration of chloride ion channel function in vector-treated cells of a CF patient can also be used to assess the persistence of the transgene CFTR (Zabner et al., J. Clin. Invest. 97:1504-1511, 1996). The practice of the invention employs, unless otherwise indicated, conventional techniques of recombinant DNA technology, protein chemistry, microbiology and virology which are within the skill of those in the art. Such techniques are explained fully in the literature. See, e.g., Current Protocols in Molecular Biology, Ausubel et al., eds., John Wiley & Sons, Inc., New York, 1995. The invention is further illustrated by reference to the following examples. EXAMPLES Example 1: E1/E3 deleted Ad vectors containing vIL-10. TGFβ. CFTR and βgal The Ad vectors are all El deleted (Ad2 nucleotides 358-3328 deleted) and E3 deleted (Ad2 nucleotides 27971-30937 deleted). The transgene (CFTR, β-galactosidase (βgal), α- galactosidase, etc.) is inserted in the El-deleted region and IL-10, vIL-10 and TGFβ are inserted in the E3-deleted region. Both genes are driven by the CMV promoter. See Fig. 1 through Fig. 6. All vectors contain wild- type E2 and E4 regions but may also have an E4 deletion. A transgene (e.g. CFTR or βgal) expression cassette containing a transgene operably linked to a promoter (e.g. CMV or CMV-derived promoters) followed by a polyA signal, is cloned into an Ad2 -based vector with most of the El region deleted and retains wild-type E2 and E3 regions with open reading frame 6 (ORF6) of E4. The transgene expression cassette replaces the El region of the Ad2 vector. This vector is termed Ad2/transgene. See e.g. Ad2/CFTR-2 and Ad2/CFTR-5 of Scaria et al, 1998, J. Virol. 72:7302-7309 and U.S. provisional patent application Ser. No. 60/130,415, incorporated herein by reference. The immunomodulatory gene (either IL-10, vIL-10 or TGFβ) is cloned by PCR and is inserted into an expression cassette plasmid pCMV (see Figure 10) using Xhol and Notl restriction sites, so that the immunomodulatory gene is cloned behind the CMV promoter and uses the SV40 polyA sequence. The entire expression cassette is then cut out using the unique Rsrll sites at either end of the cassette and cloned into the E3Δ2.9 deletion in an adenoviral plasmid, pAd/Ε4+/E3Δ2.9 (see Figure 11) which contains the right end of Ad2. This plasmid is then co-transfected with digested DNA from Ad2/transgene so that homologous recombination occurs between the plasmid and the vector to yield Ad/transgene/CMVimmunomodulatory gene which can express the transgene and also the immunomodulatory molecule from their respective promoters. Example 2: Ad vector containing FasL and p35 The mouse fas ligand (fasL) cDNA is cloned by PCR from a mouse testis quick-clone cDNA library (Clonetech Laboratories) and is inserted into the expression plasmid, pCMV using the Xhol and Notl restriction sites (Figure 7), so that the cDNA is cloned behind the CMV promoter and uses the SV40 polyA site. The entire expression cassette is then cut out using the unique Rsrll sites at either end of the cassette and cloned into the Rsrll site in the El deleted (Ad2 nucleotides 358 to 3328 deleted) pre-adenoviral plasmid called pAdEl-R which contains the left end of Ad2 including the protein IX gene and E2B sequences. This plasmid is then cotransfected with restricted DNA from an Ad2/CFTR p35 (such as the vector described above) vector so that homologous recombination occurs between the plasmid and the Ad vector to yield Ad/fasL/p35 which expresses fasL from the El region and p35 from the E3 region, both genes being driven by the CMV promoter (Fig. 7). Alternatively, the transgene is inserted, as described above in Example 1, into the El- deleted region and nucleic acids encoding fasL and p35 are inserted into the E3-deleted region as a single expression cassette (as described above in Example 1 for a single immunomodulatory molecule) such that all three, the transgene, fasL and p35, are contained within the same Ad vector (see Figure 12). The Ad/fasL/p35 or Ad/transgene/fasL/p35 vector is produced in high titers of 10" I.U./ml in regular 293 cells used to produce El deleted Ad vectors. To determine if the Ad/fasL/p35 or Ad/transgene/fasL/p35 vector kills infected cells, a cell killing assay is performed on CV-1 cells using an LDH kit purchased from Promega. The results are shown in Figure 8 and indicate that the Ad/fasL/p35 vector does not kill infected cells like the control Ad/fasL vector. Example 3: Inducing Host Tolerance to Ad Vectors For infection in vitro, DCs may be purified from bone marrow by isolating bone marrow precursor cells (CD34+) from blood and stimulating them to differentiate into DCs. DCs are isolated from an individual and cultured as described in Bender et al., J. Immunol. Meth. 126:121-135, 1996 and Romani et al, J. Immunol Meth. 126:137-151, 1996. Harvested DCs may then be infected in vitro with an Ad vector comprising either a nucleic acid encoding an immunosuppressant molecule (IL-10, vIL-10 and/or TGFβ) and a transgene, such as those described above in Example 1 (Fig. 1 through Fig. 6), or the fasL gene and the p35 gene as described in Example 2 (Fig. 7). To infect DCs in vitro with an Ad vector, the DCs are incubated with a multiplicity of infection (m.o.i.) of 500 for the Ad vector for 18 to 24 hours. Infected DCs may then used to pretreat a host by the multiple administration of the infected DCs into the host accomplished via intravenous injection. After administration of the infected DCs to the host, the DCs migrate to lymphoid organs like the spleen and interact with T cells. Such interaction will either suppress the immunogenic response of the T cells where IL-10, vIL-10 and/or TGFβ are expressed, or induce apoptosis of the T cells where the fasL is expressed. The p35 will act to protect the DCs from being lysed through the fas/fasL mediated pathway. After pretreatment, an Ad vector comprising the same transgene coding for a biologically active molecule is introduced to the host by any route of administration, e.g., intravenous, intranasal, intramuscular, etc. The transgene coding for a biologically active molecule is then expressed in the absence of an immune response or with a minimized immune response. The absent or reduced immune response allows for repeated administration of the Ad vector and persistent expression of the transgene coding for a biologically active molecule. Alternatively, the Ad vector comprising either a nucleic acid encoding an immunosuppressant molecule (IL-10, vIL-10 and/or TGFβ) and a transgene coding for a biologically active molecule, such as those described above, or the fasL gene and the p35 gene are used to infect DCs in vivo by intradermal injection of the Ad vector or any other suitable route of administration known in the art. DCs thus transduced migrate to the regional lymph nodes where they interact with T cells. Subsequent administration of an Ad vector encoding the same transgene is accomplished as described above. Example 4: DeAd vector The present invention also encompasses the use of partially deleted adenoviral (DeAd) vectors into which the transgene and nucleic acid encoding the immunosuppressant molecule (IL-10, vIL-10/TGFβ) is inserted and is explained more fully in regard to construction of a DeAd vector from an adenovirus of serotype 2 (Ad2). The Ad 2 DeAd genome is modified using conventional molecular cloning methods (See, e.g. Ausubel, F.M. et al., eds., 1987-1996, Current Protocols in Molecular Biology, John Wiley & Sons, Inc. New York; Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, 2d Ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York; Glover, D.M. (ed.), DNA Cloning: A Practical Approach, MRL Press, Ltd., Oxford, U.K. Vol. I, II, 1985, incorporated herein by reference) to achieve a vector with the characteristics as shown in Fig 1. Nucleotides between 358 and 6038 (numbering and sequence of Ad2 available from GenBank) of the adenovirus genome are deleted to remove the El coding region, the pIX gene, the pIVa2 gene, and the MLP promoter. The E2A coding region is deleted by removal of nucleotides 22666 to 23960; this removes the first ATG of the E2A protein encoding sequence, as well as a large portion of the protein coding region, without affecting genes encoded by the opposite strand of the virus. The E3 region is deleted by removal of nucleotides 27971 to 30937; this removes all E3 coding regions. The E4 region is deleted by removal of nucleotides 32815 to 35977; this removes all E4 coding regions. Through these deletions, the transgene packaging size of the vector is increased to approximately 12kb. The DeAd vector genome is further modified by positioning the dimerizer controlled promoter, the ecdysone controlled promoter, or the tetracycline doxycycline controlled promoter (Fontana et al., J. Immunol. 143:3230. 1995) in place of the MLP, i.e., just upstream from position 6038 (Fig. 9). Example 5 - Construction of a DeAd Vector Containing a nucleic acid molecule(s) encoding an immunomodulatory molecule(s and a CFTR Transgene. a human α-galactosidase A Transgene. an EPO Transgene. a Factor IX Transgene. a Factor VIII Transgene. or lacZ Reporter Gene and Transfer of the Gene to Recipient Cells A DeAd vector comprising the a nucleic acid(s) encoding for an immunomodulatory molecule(s) such as IL-10, vIL-10, TGFβ, and baculo virus p35 with fasL, and a functional CFTR encoding transgene for transferring a functional CFTR coding sequence (Riordan et al., Science 245:1066-1073, 1989; U.S. Patent No. 5,876,974) to cells of an individual with cystic fibrosis, nucleic acid encoding human α-galactosidase A (e.g. U.S. Patent No. 5,658,567; PCT/US98/22886, filed October 29, 1998) the nucleic acid encoding erythropoietin (EPO) (U.S. Patent 4,703,008), the factor IX coding sequence (U.S. Patent 4,994,371), or the factor VIII coding sequence with the B chain present or deleted (Toole et al., PNAS USA 55:5939, 1986), is constructed by cloning the relevant nucleic acid (transgene encoding CFTR, α- galactosidase A EPO, factor IX or factor VIII) operably linked to a promoter, such as the CMV promoter, CMV-derived promoter, the PGK promoter, α-1 antitrypsin promoter, the K19 promoter, or other promoter suitable for expression of the nucleic acid (transgene or immunomodulatory molecule), preferably the CMV promoter, into the region downstream of position 358 in the DeAd vector or any other suitable cloning site, as disclosed in the international application PCT/US99/09590 filed April 30, 1999, incorporated herein by reference, using conventional cloning techniques (Ausubel, F.M. et al., eds., 1987-1996, Current Protocols in Molecular Biology, John Wiley & Sons, Inc. New York; Sambrook et al., 1989, Molecular Cloning, A Laboratory Manual, 2d Ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York; Glover, D.M. (ed.), 1985, DNA Cloning: A Practical Approach, MRL Press, Ltd., Oxford, U.K. Vol. I, II; or as described in U.S. Patent No. 5,670,488, Armentano et al., J. Virol. 71: 2408-2416, 1997, Rich et al., Hum. Gene Ther. 4: 461-476, 1993, all of which are incorporated herein by reference. DeAd vectors comprising a nucleic acid encoding an immunomodulatory molecule, such as IL-10, vIL-10, TGFβ and p35 with fasL, and the CFTR transgene are propagated in any of the producer cell lines, as disclosed in the international application PCT/US99/09590 filed April 30, 1999, incorporated herein by reference, released from the cells by suitable techniques, such as cell lysis and purified by CsCl gradient centrifugation as described in Zabner et al., Nature Genetics 6:75-83, 1994, incorporated herein by reference. The DeAd/CFTR vector is administered via DCs to pretreat a host and also administered to a host subsequent to pretreatment as described above in Example 3. For in vivo administration, the DeAd/CFTR vector is administered by aerosol or other topical administration method to airway epithelia cells of a suitable animal (e.g. cotton rats, primates) or to individuals with cystic fibrosis (see, e.g. U.S. Patent No. 5,670,488 and Zabner et al., J. Clin. Invst. 97: 1504- 1511, 1996, incorporated herein by reference). Expression of the CFTR transgene in treated cells, animals and individuals is detected by measurement of vector specific CFTR mRNA transcript (see, e.g. Kaplan et al., Hum. Gene Ther. 8:45-56, 1997, incorporated herein by reference) or phenotypic alteration (monitored by the presence of a functional chloride ion channel produced by the functional CFTR) in recipient cells (U.S. Patent No. 5,670,488 and Zabner et al, 1996, supra, Jiang et al., Hum. Gene Ther. 8: 671-680, 1997, incorporated herein by reference). Expression of the EPO, factor IX and factor VIII transgenes in host cells transfected with DeAd vectors comprising said transgenes and an immunomodulatory molecule, such as IL-10, vIL-10, TGFβ and p35 with fasL, may be detected by any means known to those of skill in the art, including detection of RNA transcripts and protein production. Phenotypic alterations correlating with expression of the relevant transgene may also be assessed. For example, expression of EPO is measured by increased RBC production in an individual; expression of factors IX and VIII are monitored by measuring clotting in the individual. Similarly, a DeAd vector comprising a nucleic acid encoding an immunomodulatory molecule and a lacZ reporter gene encoding β-galactosidase is made. Effective gene transfer expression of the lacZ gene from the DeAd/lacZ vector to target cells or tissues is detected using an X-gal assay as disclosed in (Armentano et al., J. Virol. 71:2408-2416, 1997; Rich et al., Hum. Gene Ther. 4: 461-476, 1993; U.S. Patent No. 5,670,488, incorporated herein by reference). A DeAd/αgalA vector is constructed, as disclosed in the international application PCT/US99/09590 filed April 30, 1999, incorporated herein by reference, by inserting a transgene encoding human α-galactosidase A operably linked to a promoter into the DeAd vector and also inserting a heterologous nucleic acid encoding an immunomodulatory molecule(s), such as IL-10, vIL-10, TGFβ, and baculovirus p35 with fasL operably linked to a promoter (any promoter described herein or other suitable promoter may be used to drive the expression of any of the nucleic acids). Fibrolasts from normal and Fabry individuals, infected with DeAd/αgalA vectors produce enzymatically active α-galactosidase A may be assayed in cell lysates and spent culture medium using the fluorescent substrate 4-methylumbnelliferyl-α- D-galactopyranoside (4-mu-α-gal). The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. Various references are cited herein, the disclosures of which are incorporated by reference in their entireties.

Claims: WHAT IS CLAIMED 1. A recombinant adenoviral vector comprising an adenovirus genome from which at least the adenovirus El region has been deleted, wherein at least one heterologous nucleic acid encoding an immunomodulatory molecule is inserted into said deletion, wherein said vector delivers the heterologous nucleic acid encoding the immunomodulatory molecule to and expresses the heterologous nucleic acid encoding the immunomodulatory molecule in antigen presenting cells, and wherein said vector reduces or evades the host immune response from the cells of said individual. 2. The vector of Claim 1, in which the heterologous nucleic acid encoding an immunomodulatory molecule is selected from the group consisting of genes for baculovirus p35, fasL/CD95 ligand, viral interleukin 10 and TGFβ. 3. The vector of Claim 1, further comprising a heterologous nucleic acid encoding a transgene coding for a biologically active molecule. 4. The vector of Claim 3, wherein the transgene coding for a biologically active molecule is selected from the group consisting of genes for lysosomal enzymes, hormones, growth factors, cytokines, antigens, CFTR, αl-antitrypsin, adenosine deaminase, thymidine kinase, gplOO, MART-1 and TRP-2, factor VIII, factor IX, factor VII and Von Willebrand factor. 5. The vector of Claim 1, in which the heterologous nucleic acid encoding the immunomodulatory molecule is operably linked to expression control sequences. 6. The vector of Claim 3, in which the transgene is operably linked to expression control sequences. 7. The vector in Claim 5 and Claim 6 wherein the expression control sequences include the cytomegalovirus immediate early promoter and cytomegalovirus immediate early-derived promoter. 8. The vector of Claim 1 wherein the adenovirus E3 region has been deleted. 9. The vector of Claim 8 wherein the vector comprises two heterologous nucleic acids encoding immunomodulatory molecules, one inserted into the deletion in the El region and the other inserted into the deletion of the E3 region. 10. The vector of claim 9 wherein the vector comprises the heterologous nucleic acid encoding fasL is inserted into the deletion in the El region and the heterologous nucleic acid encoding baculovirus p35 is inserted into the deletion of the E3 region. 11. The vector of Claim 8 wherein the vector comprises a heterologous nucleic acid encoding an immunomodulatory molecule and a transgene. 12. The vector of Claim 11 comprising a transgene, a heterologous nucleic acid encoding fasL and further comprising a third heterologous nucleic acid encoding baculovirus p35. 13. The vector of Claim 11 wherein the transgene is inserted into the deletion in the El region and the heterologous nucleic acid encoding the immunomodulatory molecule is inserted into the deletion in the E3 region. 14. The vector of Claim 1 wherein the antigen presenting cells are dendritic cells. 15. A method for inducing tolerance in a host to at least one adenovirus antigen and/or transgene product comprising (a) infecting antigen presenting cells with a first adenoviral vector comprising heterologous nucleic acids wherein the gene products of said heterologous nucleic acids suppress or lyse T cells contacted by said antigen presenting cells, (b) pretreating the host with said adenoviral vector-infected antigen presenting cells, and (c) administering to said host pretreated with said adenoviral vector-infected antigen presenting cells a second adenoviral vector comprising a transgene coding for a biologically active molecule wherein the host immune response to said second adenoviral vector is minimized or eliminated. 16. The first adenoviral vector of Claim 14 wherein said first adenoviral vector is the 16. The first adenoviral vector of Claim 14 wherein said first adenoviral vector is the vector selected from the group consisting of the vector of Claims 2-13. 17. The second adenoviral vector of Claim 14 wherein said second adenoviral vector comprises the transgene contained in the first adenoviral vector of Claim 14. 18. The vector of Claims 1-16 wherein the vector backbone is selected from the group consisting of the DeAd vector, an E1/E3 -deleted adenoviral vector, an El/E3/E4-deleted adenoviral vector and a PAV vector.

Inventors: SCARIA ABRAHAM, SCARIA, ABRAHAM
Applicants: GENZYME CORP, GENZYME CORPORATION
Application year: 2000
Main classification: C12N15
IPC codes: A61K35, A61K38, A61K48, A61P43, C12N15