Progressive Impairment of Monocytic Function in HIV-1-Infected Human Macrophage Hybridomas

Abstract

Using human macrophage hybridomas infected with HIV-1, we investigated monocyte function over a 5-week period after HIV-1 infection. Two clones, 63 and 30, were infected with HIV-1IIIB. Infection was documented by RT activity (15 x 10(6) cpm/ml), intracytoplasmic staining with an anti-p24 antibody, in situ hybridization with an HIV-1-specific riboprobe, and electron microscopy showing intracytoplasmic virus. Two weeks after infection, clones 63 and 30 lost expression of all class II antigens (DR, 81.7 vs. 0%; DQ, 15.6 vs. 0%; and DP, 76.9 vs. 0%) while retaining expression of class I (87.4 vs. 84.1%), LFA-1 (82.4 vs. 83.1%), and LFA-3 (79.1 vs. 74.7%) antigens when compared to uninfected cells. When tested for functional integrity, infected but not uninfected clone 63 cells failed to stimulate a tetanus-specific MHC-restricted T cell proliferative response 2 weeks after infection. Cytokine secretion and antigen processing were also perturbed as production of IL-1 was abolished 2 weeks after infection (although IL-6 secretion was augmented) and infected clone 63 cells failed to process exogenous antigen. Last, the viability of T cells cocultured with infected clone 63 was dramatically decreased 35 days after infection (85 vs. 15%). There was no evidence of transmission of HIV-1 to T cells, suggesting a toxic effect of infected clone 63. Taken together, these data suggest that altered macrophage function in our system occurs at multiple levels, which may account for the early immunological defects described in HIV-1 infection.

Impaired Regulation of HLA-DR Expression in Human Immunodeficiency Virus-Infected Monocytes

“…Extensive work has elucidated the mechanisms by which HIV-1 viral proteins interact and interfere with the normal surface expression of and antigen presentation by MHC-I (24). Consonant with these results, our macrophage hybridomas showed reduced MHC-I surface expression after infection with HIV-1 (55,68).…”

“…The diminished T-cell responses to recall antigens are in contrast to earlier studies using primary monocytes derived from HIV-1-infected patients as accessory cells. Similarly, studies using primary monocytes have found increased IL-1 secretion (61), whereas the macrophage hybridomas used in our laboratory previously exhibited decreased IL-1 production (68). One possible explanation may be the different frequencies of actual HIV-1 infection in monocytes from the peripheral blood of infected individuals versus rates of infection in our macrophage hybridomas.…”

“…Thus, in studies using primary monocytes, it is possible that normal, uninfected monocytes may mask defects in the infected subpopulation. In contrast, our human macrophage hybridomas were nearly uniformly infected with HIV-1, as measured by reverse transcriptase activity, in situ hybridization, intracytoplasmic staining, and electron microscopic studies, as well as by p24 assays (68).…”

“…Cytokine profiles of T cells cocultured with infected hybridoma cells in the presence of mitogens revealed a complete absence of IL-2 secretion. Antigen-specific immune responses, however, were found to be diminished when HIV-1-infected macrophage hybridomas were used as antigen-presenting cells (52,68). Exogenous IL-2 restored the capacity of the T cells to be stimulated in response to mitogens but not to specific antigen (88).…”

Induction of Apoptosis by HIV-1-Infected Monocytic Cells

“…We have been interested in studying HIV-1 monocyte interactions using a series of human monocyte and macrophage hybridomas obtained by fusing monocytes and macrophages with a mutagenized U937 promonocytic cell line (45)(46)(47)(48)(49)(50). We demonstrated that chronically HIV-1-infected human macrophage hybridomas induce apoptosis in CD4 ϩ and CD8 ϩ T and B cells by multiple mechanisms, including gp120, FasL expression, and the production of a soluble 6000-Da proapoptotic peptide (49).…”