Expression of Herpes Simplex Virus ICP47 and Human Cytomegalovirus US11 Prevents Recognition of Transgene Products by CD8+Cytotoxic T Lymphocytes

Autor: Stanley R. Riddell, Philip D. Greenberg, David C. Johnson, Carolina Berger, Kathe S. Watanabe, Suzanne M. Xuereb, Hans-Peter Kiem
Rok vydání: 2000
Předmět:
Zdroj: Journal of Virology. 74:4465-4473
ISSN: 1098-5514
0022-538X
DOI: 10.1128/jvi.74.10.4465-4473.2000
Popis: The development of methods to introduce genes into somatic cells has led to clinical applications of this technology including the treatment of genetic or acquired diseases, marking transferred cells to evaluate their in vivo persistence and migration, and the introduction of a suicide gene to address safety concerns in cell therapy (5, 20). However, a major obstacle to the in vivo persistence of cells modified by retroviral or adenoviral vectors is the development of a host immune response to transgene or vector-encoded proteins (47, 62). Early reports demonstrated long-term in vivo persistence of gene-modified cells transduced with retroviral vectors encoding a therapeutic gene and/or an antibiotic selection marker. However, in these studies the gene-modified cells were administered to immunocompromised hosts such as patients with primary immunodeficiency or those undergoing bone marrow transplantation and cancer chemotherapy (7, 11, 12, 25, 34, 49, 50). More recent studies in which gene-modified cells have been inoculated into immunocompetent animals and humans have shown that potent host immune responses to transgene-encoded proteins such as neomycin phosphotransferase, hygromycin phosphotransferase (Hy), herpes simplex virus (HSV) thymidine kinase (TK), and therapeutic genes may limit the in vivo persistence of transferred cells (9, 13, 23, 37, 47, 57). The immune mechanisms responsible for eliminating genetically altered cells included antibody responses to transgene products that were secreted or expressed at the cell surface and CD8+ cytotoxic T-cell responses to peptide fragments derived from intracellular proteins. These findings suggest that immunomodulatory strategies to render gene-modified cells less susceptible to host immune surveillance will be required for successful gene therapy in immunocompetent hosts. Long-term persistence of gene-modified cells could potentially be achieved by administering immunosuppressive regimens commonly used in the prevention of solid organ graft rejection, graft-versus-host disease, and autoimmune disorders. The continuous administration of both cyclosporin and cyclophosphamide, but not cyclosporin alone, prolonged in vivo gene expression following adenovirus-mediated gene transfer, although the ability of this regimen to facilitate secondary gene delivery was not tested (17, 18). However, this strategy is limited by incomplete efficacy, the risk of infectious complications, and other regimen-related toxicities. Transient and less toxic immunomodulatory approaches such as the inhibition of costimulatory interactions between T cells and antigen-presenting cells by blockade of CD28- and CD40 signaling with CTLA4Ig and monoclonal antibody (MAb) against CD40 ligand, respectively, have been evaluated in animal studies of adenovirus-mediated gene transfer to the liver and airways. This transient immunomodulation resulted in a significant prolongation of transgene expression, a decrease in the magnitude of neutralizing antibody titers to the vector, and successful secondary gene transfer in some animals (33, 61). However, these studies indicated that cellular and humoral immune responses were markedly reduced but not completely abrogated. An alternative approach to decrease the immunogenicity of gene-modified cells which do not secrete their transgene products is to inhibit the pathway by which antigens are presented to CD8+ cytotoxic T lymphocytes (CTL). This antigen presentation pathway requires intracellular degradation of the antigenic protein to peptide fragments, transport of these peptides into the endoplasmatic reticulum (ER) by the heterodimeric transporter of antigen presentation (TAP), assembly of class I major histocompatibility complex (MHC) heavy chain, β2-microglobulin, and peptide complexes within the ER lumen, and transport of this trimeric complex to the plasma membrane, where it is displayed for recognition by CTL (22). Several human herpesviruses evade recognition by CD8+ CTL by selectively interfering at discrete sites in the class I MHC antigen processing pathway (29, 44). HSV produces a cytosolic protein, ICP47, which prevents transport of peptides into the ER by the TAP complex (19, 26, 63). Human cytomegalovirus (HCMV) interferes with antigen presentation at several sites (2, 30). The HCMV US2 and US11 gene products cause reverse translocation of class I heavy chains from the ER to the cytosol, leading to their rapid degradation (58, 59). HCMV US3 binds to and retains class I MHC molecules in the ER (31) and the US6 protein blocks the TAP complex from the ER-lumenal side (3, 24). In this study, we developed retroviral vectors encoding HSV ICP47, HCMV US3, or HCMV US11 and evaluated their ability to inhibit class I MHC presentation of antigenic epitopes derived from viral proteins and transgene products expressed in gene-modified cells. Our results demonstrate that expression of ICP47 and US11 in human fibroblasts and primary T cells dramatically decreases class I MHC expression, protects from CTL-mediated lysis, and renders these cells ineffective for stimulating memory CTL responses in vitro. Thus, constitutive expression of viral inhibitory gene products could be a potential strategy to prolong transgene expression in vivo.
Databáze: OpenAIRE
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