Novel method for detection of virus-specific CD41+ T cells indicates a decreased EBV-specific CD4+ T cell response in untreated HIV-infected subjects

Abstract

A lower function of EBV‐specific CD8+ T cells in HIV‐infected subjects could be related to a lack of specific CD4+ T cell help. Therefore, we studied EBV‐specific CD4+ T cells in both healthy donors and untreated or highly active antiretroviral therapy (HAART)‐treated HIV‐seropositive homosexual men. To this end, PBMC were stimulated with overlapping peptide pools from a latent and a lytic EBV protein, EBV nuclear antigen (EBNA)1 and EBV lytic‐switch protein ZEBRA (BZLF1), respectively. EBV‐specific CD4+ T cell frequencies measured directly ex vivo were low. To measure EBV‐specific memory CD4+ T cells, capable of both expansion and IFN‐γ production upon antigenic challenge, we developed a specific and reproducible assay, combining ex vivo expansion of specific T cells with flow cytometric analysis of IFN‐γ production. Untreated HIV‐infected individuals had a lower CD4+ T cell response to both EBNA1 and BZLF1 as compared to healthy EBV carriers and HAART‐treated HIV‐positive subjects. This suggests loss of EBV‐specific CD4+ T cells due to HIV infection, while HAART might restore this response. In addition, we found an increase in the EBNA1‐specific CD8+ T cell response in HAART‐treated subjects. Interestingly, numbers of EBV‐specific CD4+ and CD8+ T cells were inversely correlated with EBV viral load, suggesting an important role also for EBV‐specific CD4+ T cells in the control of EBV infection.