Human immunodeficiency virus infection of monocytes: relationship to Fc-gamma receptors and antibody-dependent viral enhancement.

Antibodies that augment human immunodeficiency virus (HIV) infectivity of monocytes through Fc receptor (FcR) type III for IgG have been found in the blood of sero-positive patients and immunized chimpanzees. This study investigated the effect of acute and chronic HIV infection, as well as protein kinase C activators capable of up-regulating latent HIV, on the expression of these receptors. In addition, the frequency of this antibody-dependent enhancement (ADE) phenomenon was estimated using purified IgG from HIV-1 seropositive individuals at various clinical stages of infection. The existence of an FcR-dependent pathway for ADE of HIV-1 infection in peripheral blood monocytes and promonocytic U937 cells was confirmed in sera from a small subset of patients, and the phenomenon extended to FcR types I and II. The level of ADE activity was minimal, however, and no relationship between the presence or magnitude of the ADE phenomenon and clinical stage was uncovered. Finally, perturbations which activate a latent HIV infection were shown to concomitantly up-regulate FcR on infected and uninfected cells. This suggests a positive feedback loop linking up-regulation of latent infection, enhanced expression of low affinity HIV receptors such as FcR, and viral spread.