nef-deleted HIV-1 inhibits phagocytosis by monocyte-derived macrophages invitro but not by peripheral blood monocytes in vivo

Objective: HIV-1 infection impairs a number of macrophage effector function s, but the mechanism is unknown. We studied the role of HIV-1 Nef in modula ting phagocytosis by human monocytes and monocyte-derived macrophages (MDM) . Design and methods: Using a flow cytometric assay, phagocytosis of Mycobact erium avium complex (MAC) by monocytes in whole blood of Sydney Blood Bank Cohort (SBBC) members infected with a nef-deleted (Delta nef) strain of HIV -1 was compared with that of monocytes from uninfected or wild-type (WT) HI V-infected subjects. The specific impact of Nef on phagocytosis by MDM was determined by either infecting cells in vitro with Delta nef strains of HIV -1 or electroporating Nef into uninfected MDM. Results: MAC phagocytic capacity of monocytes from SBBC members was equival ent to that of cells from uninfected individuals (P = 0.81); it was greater than that of cells from individuals infected with WT HIV-1 (P < 0.0001), i rrespective of CD4 counts and HIV viral load. In contrast, in vitro infecti on of MDM with either <Delta>nef or WT strains of HIV-1 resulted in similar levels of HIV replication and equivalent impairment of phagocytosis via Fc gamma and complement receptors. Electroporation of Nef into MDM did not al ter phagocytic capacity. Conclusions: This study provides evidence demonstrating the complex indirec t effect of Nei on phagocytosis by peripheral blood monocytes (infrequently infected with HIV-1) in vivo. Conversely, the fact that MDM infected with either Delta nef or WT HIV-1 in vitro (high multiplicity of infection) show comparably impaired phagocytosis, indicates that HIV-1 infection of macrop hages can directly impair function, independent of Nef. (C) 2001 Lippincott Williams & Wilkins.