Repertoire and frequency of immune cells reactive to Epstein-Barr virus-derived autologous lymphoblastoid cell lines.

Answers to questions about frequency and repertoire of immune cells, relative contributions made by different types of immune cells toward the total Epstein-Barr virus (EBV)-directed response and the variation of such responses in healthy persons have been elusive because of disparities in assays, antigen presenting cells, and antigenic sources used in previous experiments. In this study, we addressed these questions using an assay that allowed direct comparison of responses generated by different types of cells of the immune system. This short-term (20-hour) ex vivo assay measured interferon-gamma production by blood cells in response to autologous EBV-transformed lymphoblastoid cell lines (LCLs). Our experiments defined the variation in responses among persons and clearly distinguished 10 healthy EBV-immune from 10 healthy EBV-naive persons. In EBV-immune persons, 33% of responding cells were CD4(+), 43.3% were CD8(+), and 12.9% were gamma-delta T cells. LCL-reactive CD8(+) T cells were only 1.7-fold more frequent than similarly reactive CD4(+)T cells. Responses by gamma-delta T cells were 6-fold higher in seropositive than in seronegative persons. Our findings emphasize the importance of CD4(+) and gamma-delta T-cell responses and have implications for immunotherapy and for identifying defects in T-cell populations that might predispose to development of EBV-associated lymphomas.

Serum IgA antibodies to Epstein-Barr virus (EBV) early lytic antigens are present in primary EBV infection.

Primary Epstein-Barr virus (EBV) infection is characterized by the presence of IgM antibodies to viral capsid antigen and the absence of antibodies to EB nuclear antigen. Here, using a flow cytometry-based assay, we investigated whether IgA antibodies are a marker for primary infection. Serum IgA antibodies in 15 individuals with primary EBV infection reacted with 15%-55.6% of HH514-16 Burkitt lymphoma cells expressing early lytic antigens (EAs), whereas IgA antibodies in serum samples from 15 healthy EBV-seropositive individuals reacted with 0.02%-2% of cells with EAs (P<.0001). IgA antibodies in primary infection were directed against the Bam Z Epstein-Barr replication activator (ZEBRA) (BZLF1) and diffuse EA (BMRF1) EAs. Thus, IgA antibodies to EBV EAs are produced during primary EBV infection and are likely to be stimulated as a result of lytic EBV replication in mucosal sites. Detection of IgA antibodies to EA may be developed into a diagnostic tool for primary EBV infection.