nef-deleted HIV-1 inhibits phagocytosis by monocyte-derived macrophages in vitro but not by peripheral blood monocytes in vivo.
OBJECTIVE
HIV-1 infection impairs a number of macrophage effector functions, but the mechanism is unknown. We studied the role of HIV-1 Nef in modulating phagocytosis by human monocytes and monocyte-derived macrophages (MDM).


METHODS
Using a flow cytometric assay, phagocytosis of Mycobacterium 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) HIV-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 equivalent 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), irrespective of CD4 counts and HIV viral load. In contrast, in vitro infection 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 alter phagocytic capacity.


CONCLUSIONS
This study provides evidence demonstrating the complex indirect effect of Nef 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 macrophages can directly impair function, independent of Nef.
Kedzierska
K
K
AIDS Pathogenesis Research Unit, Macfarlane Burnet Centre, Fairfield, Victoria, Australia.
Mak
J
J
Jaworowski
A
A
Greenway
A
A
Violo
A
A
Chan
H T
HT
Hocking
J
J
Purcell
D
D
Sullivan
J S
JS
Mills
J
J
Crowe
S
S
D018791:CD4 Lymphocyte Count; D015331:Cohort Studies; D018274:Electroporation; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D017353:Gene Deletion; D015754:Genes, nef; D015658:HIV Infections / Q000276:immunology* / Q000821:virology; D015497:HIV-1 / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D008264:Macrophages / Q000276:immunology* / Q000821:virology; D009000:Monocytes / Q000276:immunology* / Q000821:virology; D010587:Phagocytosis; D019562:Viral Load
D005456:Fluorescent Dyes; D016650:Fluorescein-5-isothiocyanate