Induction of IL-6 and IL-10 production by recombinant HIV-1 envelope glycoprotein 41 (gp41) in the THP-1 human monocytic cell line.

Elevated levels of circulating monokines (IL-6, IL-1, and TNF alpha) have been seen in HIV-1 infection, and the overproduction of these cytokines could contribute to AIDS pathogenesis in various ways. In previous work, we had seen that exposure of human monocytes to HIV-1, including inactivated, noninfectious HIV, led to rapid IL-6 gene expression and secretion. To investigate cytokine production in response to components of HIV by monocytes/macrophages, production of IL-6 and IL-10 were examined in a human monocytic cell line, THP-1, stimulated by HIV proteins. IL-6 production was induced in THP-1 cells by a detergent lysate of HIV, particularly fractions at molecular weight of 25-50 kDa. Recombinant HIV envelope glycoprotein 41 (gp41), but not gp120 or p24, also was seen to induce significant IL-6 production by THP-1 cells. These results suggest that gp41, transmembrane protein, is the primary HIV-encoded protein involved in inducing IL-6 production. IL-10 was also produced with delayed kinetics, following IL-6 production in THP-1 cells stimulated by gp41. To investigate a possible regulatory role for IL-10 in HIV-induced monokine production, recombinant IL-10 was added to gp41-exposed THP-1 cells. IL-10 inhibited gp41-induced IL-6 production and reduced the expression of IL-6 mRNA. When anti-human IL-10 neutralizing antibody was added to THP-1 cells, IL-6 production was enhanced. These results suggest that the IL-6 production may be downregulated by endogenously produced IL-10 and that IL-10 may downregulate cytokine production by HIV-activated monocytes via an autoregulatory mechanism.

Cell-mediated immune response to human immunodeficiency virus (HIV) type 1 in seronegative homosexual men with recent sexual exposure to HIV-1.

Although human immunodeficiency virus (HIV) type 1 infection is efficiently transmitted by sexual intercourse, some individuals whose sexual behavior places them at extremely high risk for infection have nevertheless remained HIV-1-seronegative. An investigation was undertaken to determine whether such individuals have circulating T helper cells that are sensitized to HIV-1. Five very high risk men who had recent sexual exposure to HIV-1 were studied. Peripheral blood mononuclear cells from all 5 produced interleukin (IL)-2 in culture in response to synthetic amphipathic HIV-1 envelope peptides. One of the 5 high-risk men has subsequently seroconverted, while 4 have remained seronegative. All were initially culture-negative, and those who have remained seronegative were also virus-negative by polymerase chain reaction (PCR) testing 10 months after they were first studied. These results demonstrate that a cell-mediated immune response to HIV-1 can be detected in the absence of a humoral immune response in individuals recently exposed to HIV-1. Furthermore, IL-2 production by T cells in response to synthetic peptides may be a more sensitive test for exposure to HIV-1 than antibody, lymphoproliferation, or PCR tests.

Serum and effector-cell antibody-dependent cellular cytotoxicity (ADCC) activity remains high during human immunodeficiency virus (HIV) disease progression.

The activity of both serum and effector cell antibody-dependent cellular cytotoxicity (ADCC) against human immunodeficiency virus (HIV-1, HIV) was assessed in HIV-infected individuals. The goal was to relate ADCC levels with the stage or progression of HIV disease. Serial serum samples, usually collected at 6-month intervals, from individuals at defined stages of HIV disease (seroconversion, the HIV-seropositive period before AIDS, and around the time of clinical AIDS diagnosis) were tested. HIV-coated CEM tumor cells were used as targets. Effector-cell ADCC activity was evaluated using fresh peripheral blood mononuclear cells (PBMC) from HIV-infected individuals at different stages of HIV disease. Samples were obtained from male homosexual participants in the Multicenter AIDS Cohort Study (MACS). In seroconverters, ADCC-inducing HIV-specific antibodies were detected at the time that the ELISA antibody test was first positive. Within several months, serum ADCC activity stabilized in each individual. In 29 HIV-seroprevalent individuals (HIV seropositive on their first visit), serum ADCC activity remained constant regardless of whether the individual's HIV disease was stable (high stable CD4; n = 9) or rapidly deteriorating (sharply declining CD4, n = 10; AIDS progressors, n = 10). With respect to effector-cell activity, PBMC from HIV-infected individuals with or without AIDS were capable of mediating ADCC with heterologous and usually with autologous sera. Although the level of NK cytotoxic activity and the level of antibody-armed effector cell activity have been reported to decline as disease progresses, our results support previous observations that ADCC effector-cell activity against antibody-coated targets does not decline in HIV infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Human immunodeficiency virus type 1 infection in homosexual men who remain seronegative for prolonged periods.

Infection with the human immunodeficiency virus type 1 (HIV-1), as demonstrated by viral cultures, has been described in some patients before antibodies to HIV-1 can be detected, but the duration and frequency of such latent infections are uncertain. We selected prospectively a cohort of 133 seronegative homosexual men who continued to be involved in high-risk sexual activity, and we cultured 225 samples of their peripheral-blood lymphocytes, using mitogen stimulation to activate the integrated HIV-1 genome. HIV-1 was isolated in blood samples from 31 of the 133 men (23 percent), 27 of whom have remained seronegative for up to 36 months after the positive culture. The other four men seroconverted 11 to 17 months after the isolation of HIV-1. In three of them, we studied cryopreserved lymphocytes obtained earlier, using the polymerase chain reaction to amplify small amounts of viral DNA, and we demonstrated that HIV-1 provirus had been present 23, 35, and 35 months before seroconversion. We conclude that HIV-1 infection in homosexual men at high risk may occur at least 35 months before antibodies to HIV-1 can be detected. A prolonged period of latency in such infections may be more common than previously recognized; the degree of infectiousness during such periods is unknown.

Induction of IL-6 (B cell stimulatory factor-2/IFN-beta 2) production by HIV.

Polyclonal B cell activation is commonly observed in AIDS and in infection with HIV. The effect of HIV on the induction of B cell stimulatory factor 2 (BSF-2) production was examined, since BSF-2 plays an essential role in the differentiation of activated B cells to Ig-secreting cells. Increased BSF-2 mRNA levels and increased BSF-2 secretion were observed soon after exposure of mononuclear cells isolated from healthy donors to both "live" and inactivated HIV. HIV-induced BSF-2 production was seen in monocyte/macrophages, but not in T cells. These results suggest that the HIV-induced overproduction of BSF-2 might contribute to the polyclonal B cell activation seen in AIDS and in infection with HIV.

Analysis of false positive HIV-1 serologic testing in Kenya.

Sera of 95 mothers and 129 children from Nairobi, Kenya, collected in 1976, and of 466 adults and 193 children of Embu District, Kenya, collected in 1984 and 1985, were analyzed for the presence of human immunodeficiency virus type 1 (HIV-1) antibodies. Although no HIV-1 seropositivity was demonstrated by western blot analysis in both study groups, 7% of Nairobi mothers and 10% of adult females from Embu District had false positive results by enzyme immunoassay (EIA) compared with less than 1% seroreactivity rates observed in adult males and children. False positive results were not due to simian T lymphotropic virus type III (STLV-IIIAGM)/human T lymphotropic virus type IV (HTLV-IV) seropositivity. Sixty-one percent of the HIV-1 EIA reactive sera could not be explained by cytotoxic activity to lymphocytes bearing the HLA-DR4 or HLA-DQw3 phenotype. We conclude that false positive HIV EIA tests are frequently encountered in East Africa. Seroprevalence rates in rural Africa must be interpreted with caution due to the decreased specificity of HIV EIAs.

A simple and rapid method for preparation of HIV-expressing targets for functional assays.

Standardized samples of target cells expressing viral antigen are necessary to perform reproducible and comparable functional assays for immune responses to human immunodeficiency virus (HIV-1). HIV-infected cultured cell lines show wide variability in the number of HIV-expressing cells and in the amount of viral antigen per cell. They, as well as cells coated with the infectious virus, are a biohazard. 0.015% v/v beta-propiolactone (BPL) in buffered solution at pH 7.5 inactivates the infectivity of HIV but retains its antigenicity. BPL-inactivated HIV easily binds to T4 receptor bearing T-lymphocytes in a 30 min incubation at 22 degrees C. The process of adsorption is dose-dependent and results in a standardized and reproducible sample of target cells. Applications for the method are demonstrated and include: (1) preparation of target cells for assay of antibody-dependent cellular cytotoxicity (ADCC), and (2) characterization of antisera to HIV for their capacity to block HIV binding to cells.

Selective alterations in immunoregulatory lymphocyte subsets in early HIV (human T-lymphotropic virus type III/lymphadenopathy-associated virus) infection.

In order to characterize the effects of HIV (human T-lymphotropic virus type III/lymphadenopathy-associated virus) on the immune system, Leu8- and Leu8+ subsets of CD4 and CD8 cells were studied in seropositive homosexually active men without acquired immune deficiency syndrome (AIDS). Controls included both heterosexual men and HIV-seronegative homosexually active men. The decrease in CD4 levels, observed in HIV-seropositive men who were asymptomatic, as well as in those who had persistent generalized lymphadenopathy or constitutional symptoms of HIV infection, occurred proportionally in both the Leu8- and the Leu8+ CD4 subsets. This observation, that HIV infection does not selectively diminish either subset of CD4 cells, indicates that the selective loss of T cell-mediated functions which accompanies the development of AIDS is not related to preferential loss of the Leu8+ CD4 subset. Among CD8 cells, however, HIV infection resulted in a threefold elevation in the number of Leu8- CD8 cells, while the number of Leu8+ CD8 cells remained constant. The increase in Leu8- CD8 cells was present in recent seroconverters, persistently seropositive men, and patients with AIDS. We propose that the increase in Leu8- CD8 cells represents an HIV-specific cytotoxic T-cell response. These cells may operate by killing infected CD4 cells, thereby partially controlling viral infection while simultaneously contributing to the destruction of the immune system.

Leukemia derived growth factors produced by human malignant T-lymphoid cell lines.

An autocrine (noninterleukin 2) growth factor, which we term leukemia derived growth factor (LDGF), has previously been found in the culture supernatant of the human malignant T-lymphoid cell line MOLT-4f. We now show that two other human malignant T-lymphoid cell lines, CCRF-CEM and CCRF-HSB-2 also produce such a factor. All three factors, i.e., the LDGF from MOLT-4f, CCRF-CEM, and CCRF-HSB-2 are similar to each other both in biological activity and in physicochemical characteristics. In addition to their autocrine activity, these LDGFs stimulate the growth of other malignant T-lymphoid cell lines, but they do not stimulate B-lymphoblastoid or myeloid cell lines. The results therefore suggest that these LDGFs are T-cell specific.