Regulation of interleukin 12 and interleukin 10 expression in vaccinia virus-infected human monocytes and U-937 cell line.

Regulation of IL-12 and IL-10 production in normal human monocytes infected with vaccinia virus (VV) was analysed. IL-12 and IL-10 mRNAs were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and IL-12 and IL-10 protein by ELISA. RT-PCR analysis revealed a marked-up regulation of IL-12 (p40) and IL-10 expression in virally infected cells compared with that from control (non-infected) cells at 24 h post-infection (p.i.). IL-12 transcripts occurred earlier (at 4 h p.i.) than IL-10 mRNA. A significant increase in IL-12 and IL-10 secretion into the medium was caused by the virus, and even a much more pronounced increase in both interleukins expression (mRNAs and proteins) followed LPS or Staphylococcus aureus treatment. Vaccinia virus infection did not alter IL-10 secretion and IL-10 mRNA content (or even cause a decrease) in a human monocytic cell line U937. Undetectable levels of IL-12 protein were found in the cell line although the transcripts were present in the cells at first hours p.i. It appears now that vaccinia virus transiently and sequentially induces IL-12 and IL-10 in human monocytes. Copyright 2000 Academic Press.