Inhibition of tumor necrosis factor-alpha transcription by Epstein-Barr virus

Tumor necrosis factor-alpha (TNF-alpha), which is produced mainly by monocyte/macrophage cells, has diverse physiological functions on lymphoid cells. Moreover, it has been shown that TNF-alpha exhibits antiviral activities. Here we report that Epstein-Barr virus (EBV), a B lymphotropic human herpes virus that interacts intimately with the immune system, exerts a strong inhibitory effect on TNF-alpha production by lipopolysaccharide-treated peripheral blood leukocytes as well as by monocytic cell lines, HL-60 and U-937. Flow cytometric analysis following staining with OKB7 monoclonal antibody showed that about 20% of cells from these monocytic lines express the CR2 antigen. Direct binding of fluorescein isothiocyanate-labeled EBV indicated that the virus binds to approximately 22% of cells of both monocytic lines. However, no virus-specific antigens were detected in the infected cells by immunofluorescence, suggesting that the infection was of the abortive type. The use of UV- or heat-inactivated EBV and inhibitory effect on TNF-alpha synthesis. These results suggest that infectious virus is necessary to obtain such an inhibitory effect. Analysis of TNF-alpha mRNA by polymerase chain reaction amplification indicated that the EBV suppressive effect is manifested at the transcriptional level. In contrast, EBV did not inhibit interleukin 1 mRNA production by these cells. These results indicate that EBV interacts directly with monocytes/macrophages to exert its immunomodulatory effect.