Acute measles virus (MV) infection results in a decrease in plasma human immunodeficiency virus type 1 (HIV-1) RNA levels in co-infected children. An in vitro peripheral blood mononuclear cell (PBMC) culture system was used to assess the mechanisms by which MV blocks HIV-1 replication. MV inhibited proliferation of CD4+ T lymphocytes, the target cell for HIV-1 replication. In the presence of MV, cells did not progress to G1b and S phases, steps critical for the completion of HIV-1 reverse transcription and productive replication. This block in cell-cycle progression was characterized by an increased proportion of CD4+ and HIV-1-infected cells retained in the parental generation in PBMCs co-cultured with MV and HIV-1, and decreased levels of cyclins and RNA synthesis. Early HIV-1 replication was also inhibited in the presence of MV, as measured by reduced expression of a luciferase reporter gene and lower levels of both early (LTR) and late (LTR-gag) DNA intermediates of HIV-1 reverse transcription in the presence of CCR5-tropic HIV-1. The effects of MV on lymphoproliferation and p24 antigen production were reproduced by n-butyrate and hydroxyurea, drugs that block the cell cycle in G1a and G1/S, respectively. It was concluded that MV inhibits HIV-1 productive replication in part by blocking the proliferation of CD4+ T lymphocytes.
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