HIV-1 induces human monocyte-derived macrophages to produce C3 and to fix C3 on their surface.

Complement components, particularly C3, are known to be involved in the pathogenesis of AIDS and macrophages may serve as a source of C3 at sites of infection. We investigated whether the interaction between HIV-1 and monocytes has any effect on C3 production by the cells. Monocytes isolated from the blood of healthy volunteers were incubated with monocytotropic and T lymphocytotropic HIV-1 strains or with recombinant gp160 and cultured in serum-free medium up to 7 days. Supernatants were tested for secreted C3 by enzyme-linked immunosorbent assay. Our data show that monocytes cultured with either the monocytotropic or the T lymphocytotropic HIV-1 strains produce C3 in large amounts. The effect of both viruses is dose dependent and the amount of C3 induced by HIV was up to 20-fold higher than in the control samples. C3 production was also enhanced by gp160, the envelope protein of the virus. Secretion of IL-6 by the cells was also measured and found to be elevated up to threefold as a consequence of the interaction with the virus. HIV-1-activated monocyte-derived macrophages acquired the capacity to cleave exogenous C3 and to fix generated C3 fragments on their cell membrane.