The susceptibility of macrophages to human immunodeficiency virus type 1 X4 isolates dependson their activation state

The demonstration that macrophages express CXCR4 has led to a reexamination of their susceptibility to human immunodeficiency (HIV)-1 X4 strains. Here, we examined the susceptibility to X4 HIV-1Lai of two previously characterized macrophage populations, obtained either as 1) adherent cells of five-day cultures of blood mononuclear cells (PBMC), followed by two days without nonadherent PBMC nor added cytokines (MDM-5d); or 2) as adherent cells recovered from one-hour incubation of PBMC, which were cultured for seven days with macrophage colony-stimulating factor (MDM-MCSF). Exposing MDM-5d or MDM-MCSF to HIV-1Lai did not lead to productive infection, as indicated by a lack of (MDM-MCSF) or low (MDM-5d) viral p24 levels in culture supernatants. However, MDM-5d vigorously transmitted HIV-1Lai to autologous T lymphocytes, which was not the case of HIV-1Lai-exposed MDM-MCSF. PCR analysis of the LTR RU5 region showed that X4 HIV-1Lai entered into both types of macrophages in the same manner as R5 HIV-1BaL. However, in contrast to MDM-5d, there was a block of HIV-1Lai retrotransciption in MDM-MCSF. Cytokine profile analysis of the two types of macrophages showed that TNF-α, IL-6 and RANTES levels were higher in MDM-5d than in MDM-MSCF, while the IL10 level was higher in MDM-MCSF, both producing similar IL16 levels. Altogether, these data indicate that HIV-1 X4 strains enter into macrophages but that their replication is blocked thereafter in a different manner according to the activation status of the cells.