Suppression of LPS-inducible cytotoxicity in cytomegalovirus-infected THP-1 monocytic cell cultures does not correlate with a decrease in TNF-alpha antigen.

We document suppression of tumor necrosis factor alpha (TNF-alpha)-associated cytotoxic activity in a human monocytic cell line (THP-1) infected with the mycoplasma free human cytomegalovirus (CMV) strain AD169. Addition of lipopolysaccharide (LPS) to cell cultures that had been infected with CMV for 24 h resulted in a significant reduction in released cytotoxic activity to mouse L929 cells at 3-22 h post-LPS compared with mock-infected cultures. However, using an ELISA to measure TNF-alpha antigen levels in these culture supernatants, we found infected cultures had significantly higher TNF-alpha antigen levels than in mock-infected cultures following LPS induction. CMV alone also induced TNF-alpha release and possibly TNF-alpha inhibitor(s) which may have blocked TNF-alpha associated cytotoxic activity in CMV-infected THP-1 cell culture supernatants.