Lymphoblastoid cells transfected with c-myc: Downregulation of EBV-lytic antigens and impaired response of autologous CD4+ T cells in vitro

Abstract

Normal EBV-positive lymphoblastoid B-cell lines (LCL) were transfected with vectors containing the c-myc oncogene (pHEBO-Eμ-myc) or control vectors (pHEBO-Eμ) and analyzed for the expression of EBV-lytic and latent antigens. While EBV-latent antigens were normal in the c-myc transfectants, there was an almost complete downregulation of EBV-lytic antigens, including BZLF1, EA(D), gp340 and VCA. These observations were consistently repeated on 6 different LCLs transfected with c-myc. Unlike control LCLs, the c-myc transfectants did not release infectious EBV. PCR analysis demonstrated that BZLF1 mRNA was virtually absent in c-myc transfectants, possibly suggesting that the deregulated c-myc imposed a block in the EBV-lytic cycle at this particular level. c-myc transfectants failed to sustain the proliferative response of autologous CD4+ T-cell clones with specificity for EBV-lytic antigens. However, they regained this capacity after incubation with ultraviolet-inactivated EBV or gp340 antigen in vitro, also indicating that their antigen-presenting capacities were not impaired. c-myc transfectants failed to elicit a secondary proliferative response by autologous CD4+ T cells purified from the peripheral blood of EBV-seropositive donors. Exposure of c-myc transfectants to UV-inactivated EBV again resulted in a proliferative CD4+ T-cell response comparable to that elicited by the control LCLs. Collectively, our data provide evidence for the remarkable ability of an oncogene to influence the life cycle of a virus and to modify the antigenicity of the infected cells.