Human immunodeficiency virus-1 env impairs Fc(γ) receptor-mediated phagocytosis via a cyclic adenosine monophosphate-dependent mechanism

Abstract

Human immunodeficiency virus (HIV)-1 expression in mononuclear phagocytes is associated with multiple functional defects, including phagocytosis. To assess Fc(γ) receptor (Fc(γ)R) function in cells expressing HIV-1, human promonocytic cells (U937) acutely or chronically infected with HIV-1, or stably transfected with a noninfectious reverse transcriptase (RT) defective HIV-1 provirus (Δpol), were treated with phorbol 12-myristate 13-acetate for 48 hours and tested for their ability to ingest sheep erythrocytes coated with IgG (E-IgG). HIV-1-infested or transfected U937 cells ingested 50% to 65% fewer E-IgG than controls despite normal surface expression of FcγRs. HIV-1 specifically impaired Fc(γ)R- mediated phagocytosis, as ingestion of complement-coated erythrocytes was unaffected. U937 cells transfected with an any deficient mutant of HIV-1 ingested E-IgG normally, suggesting that the expression of HIV-1 env was required for HIV-1 to inhibit Fc(γ)R-mediated phagocytosis. Expression of HIV-1 in 0937 cells was associated with an increased accumulation of intracellular cyclic adenosine monophosphate (cAMP); addition of the adenylate cyclase inhibitor 2',5'-dideoxyadenosine to these cells decreased intracellular cAMP levels to that of controls and restored Fc(γ)R-mediated phagocytosis. Addition of either interferon (IFN)-γ, or an inhibitor of cAMP-dependent protein kinase A (KT 5720) to HIV-1-transfected U937 cells also restored Fc(γ)R-mediated phagocytosis. Expression of HIV-1 induces a specific defect of Fc(γ)R function in mononuclear phagocytes that correlates with increased levels of cAMP, and can be corrected by pharmacologic manipulation.