Adenovirus-mediated human immunodeficiency virus-1 Nef expression in human monocytes/macrophages and effect of Nef on downmodulation of Fcγ receptors and expression of monokines

To characterize the effect of human immunodeficiency virus-1 (HIV-1) nef expression in human monocytes/macrophage (HMO) and U937 on the levels of FcγRs, HLA antigens, and monokines, elutriated HMOs and U937 cells were transfected with an adenovirus-mediated Nef expression system. Nef-expressing cells downmodulated FcγRI, FcγRII, and upregulated HLA class I molecules. Nef-expressing HMOs, treated with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA), overexpressed tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-10. However, IL-6 was induced by LPS and inhibited by PMA. Additionally, a subpopulation of Nef-expressing HMOs underwent apoptosis. Our data suggest that HIV-1 nef downmodulated FcγRs in myeloid cells in a manner similar to that previously reported for its effect on CD4+ in T cells.