Comparison of the effects of 3'-azidothymidine with those of neutralizing antibodies on simian immunodeficiency virus infection in macrophages.

We previously showed that simian immunodeficiency virus-infected macaque macrophages contacting uninfected CD4+ lymphocytes caused extensive cell fusion and synthesis of phlogistic cytokines. In this study, macaque macrophage cultures inoculated with SIVmac251 and treated simultaneously with 10 microM 3'-azidothymidine (AZT) became infected and produced small amounts of viral antigen (p27) but failed to fuse with CD4+ CEM174 cells. When AZT was added 1 to 3 days after virus inoculation, the infected cells caused fusion and the release of tumor necrosis factor and produced increasing amounts of p27. In contrast, neutralizing antibodies prevented infection when added at the time of virus inoculation, and they were much more effective than AZT in limiting virus replication, fusion cytopathic effect, and cytokine production when added up to 3 days postinoculation. Neutralizing antibodies may be more effective than AZT in reducing the virus load in the macrophage population and in preventing both cell fusion and the production of potentially pathogenic cytokines.