Differential immunogenicity of Epstein-Barr virus latent-cycle proteins for human CD4(+) T-helper 1 responses

Human CD4(+) T-helper 1 cell responses to Epstein-Barr virus (EBV) infectio n are likely to be important in the maintenance of virus-specific CD8(+) me mory and/or as antiviral effectors in their own right. The present work has used overlapping peptides as stimulators of gamma interferon release (i) t o identify CD4(+) epitopes within four EBV latent-cycle proteins, i.e., the nuclear antigens EBNA1 and EBNA3C and the latent membrane proteins LMP1 an d LMP2, and (ii) to determine the frequency and magnitude of memory respons es to these proteins in healthy virus carriers. Responses to EBNA1 and EBNA 3C epitopes were detected in the majority of donors, and in the case of EBN A1, their antigen specificity was confirmed by in vitro reactivation and cl oning of CD4(+) T cells using protein-loaded dendritic cell stimulators. By contrast, responses to LMP1 and LMP2 epitopes were seen much less frequent ly. EBV latent-cycle proteins therefore display a marked hierarchy of immun odominance for CD4(+) T-helper 1 cells (EBNA1, EBNA3C much greater than LMP 1, LMP2) which is different from that identified for the same proteins with respect to CD8(+)-T-cell responses (EBNA3C > EBNA1 > LMP2 much greater tha n LMP1). Furthermore, the range of CD4(+) memory T-cell frequencies in peri pheral blood of healthy virus carriers was noticeably lower and narrower th an the corresponding range of latent antigen-specific CD8(+)-T-cell frequen cies.