Interferon-regulated viral replication in chronically HIV1-infected promonocytic U937 cells

To further document the role of interferons in the restriction of HIV1 replication in cells of the monocyte/macrophage lineage, the antiviral effects of alpha-interferon (IFN alpha) were studied in chronically HIV 1-infected promonocytic cells U937, in which IFN alpha was endogenously produced or to which recombinant IFN alpha was added. Protein analysis performed after immunoprecipitation of culture media revealed that the addition of anti-IFN alpha antibody led to an increase in the production of viral particles, whereas addition of IFN alpha caused its decrease in a dose-dependent manner, indicating that IFN alpha mainly affects viral assembly and virion release. However, the treatment of HIV 1-infected cells with IFN alpha did not cause an increase in the amount of intracellular viral proteins, suggesting that this cytokine might act on other steps in the viral life cycle. No decrease in the level of the 3 main types of viral RNA was observed by Northern blot analysis, indicating that proviral transcription was not restricted by IFN alpha. Furthermore, cotransfection experiments with TAR(trans-activation responsive)-element-containing expression plasmids demonstrated that viral replication appears to be restricted at either a post-transcriptional and/or a translational level. These experiments suggest that the double-stranded (ds) inverted repeat TAR sequence present in HIV1 leader RNA may inhibit viral protein synthesis by phosphorylating the dsRNA-activated protein kinase induced by IFN. These results provide an impetus for achieving antiretroviral therapy based on the constitutive expression of IFN in monocytes and macrophages.