Cellular microRNA Expression Correlates with Susceptibility of Monocytes/Macrophages to HIV-1 Infection

Although both monocytes and macrophages possess essential requirements for HIV-1 entry, peripheral blood monocytes are infrequently infected with HIV-1 in vivo and in vitro. In contrast, tissue macrophages and monocyte-derived macrophages in vitro are highly susceptible to infection with HIV-1 R5 tropic strains. We investigated intracellular anti–HIV-1 factors that contribute to differential susceptibility of monocytes/macrophages to HIV-1 infection. Freshly isolated monocytes from peripheral blood had significantly higher levels of the anti–HIV-1 microRNAs (miRNA, miRNA-28, miRNA-150, miRNA-223, and miRNA-382) than monocyte-derived macrophages. The suppression of these anti–HIV-1 miRNAs in monocytes facilitates HIV-1 infectivity, whereas increase of the anti–HIV-1 miRNA expression in macrophages inhibited HIV-1 replication. These findings provide compelling and direct evidence at the molecular level to support the notion that intracellular anti–HIV-1 miRNA-mediated innate immunity may have a key role in protecting monocytes/macrophages from HIV-1 infection.