Adenoviral-mediated gene transfer of ICP47 inhibits major histocompatibility complex class I expression on vascular cells in vitro

Purpose: Many viruses have evolved mechanisms to evade detection by the hos t immune system. The herpes simplex gene ICP47 encodes a protein that binds to the host antigen-processing transporter, inhibiting the formation of ma jor histocompatibility complex class I(MHC-I) antigens in infected cells. M HC-I antigen expression is also important in acute allograft rejection. Thi s study was designed to quantitate the effect: of adenoviral-mediated gene transfer of ICP47 on MHC-I cell surface expression of human vascular cells. We hypothesized that the transduction of vascular cells with a replication -incompetent adenoviral vector that was expressing ICP47 (AdICP47) would in hibit constitutive and inducible MHC-I expression and thereby reduce the ra re of cytolysis of ICP47-transduced vascular cells by sensitized cytotoxic T lymphocytes (CTL). Methods:A replication-incompetent adenoviral vector, AdICP47, was created t o express ICP47 driven by the cytomegalovirus immediate early promoter. Cul tured hunan vascular endothelial and smooth muscle cells and human dermal f ibroblasts were transduced with either AdICP47 or the control empty vector Add1EI. Cell surface constitutive and gamma-interferon-induced MHC-I expres sion were quantitated by flow cytometry. A standard 4-hour chromium release cytotoxicity assay was used to determine the percent cytolysis of transduc ed and nontransduced endothelial cells by sensitized CTL. Finallly, to quan titate the specificity of the effect of ICP47 on MHC-I expression, adhesion molecule expression was quantitated in both transduced and nontransduced c ells. Results: Constitutive MHC-I expression in AdICP47-transduced endothelial ce lls was inhibited by a mean of 84% +/- 5% (SEM) in five experiments. After 48 hours of exposure to gamma-interferon, AdICP47-transduced cells exhibite d a mean of 66% +/- 8% lower MHC-I expression than nontransduced cells. Sim ilar inhibition in MHC-I expression was achieved. in AdICP47-transduced vas cular smooth muscle cells and dermal fibroblasts. Percent cytolysis of AdIC P47-transduced endothelial cells by CTL was reduced by 72%. Finally, the sp ecificity of the effect of transduction of ICP47 on vascular cell. MHC-X ex pression was confirmed by a lack of significant change in either constituti ve or tumor necrosis factor-induced vascular cell adhesion molecule/interce llular adhesion molecule expression. Conclusion: Transduction of vascular cells with AdICP47 strongly inhibits b oth constitutive and inducible MHC-I expression in human vascular cells. Ad ICP47-transduced cells exhibited a substantial reduction in cytolysis by CT L. Thus AdICP47 transduction holds promise as a technique to characterize t he role of MHC-I expression in acute vascular allograft rejection in vivo a nd as a potential therapeutic intervention.