NK cells control HIV-1 infection of macrophages through soluble factors and cellular contacts in the human decidua.

BACKGROUND: During the first trimester of pregnancy, HIV-1 in utero transmission is rare despite the permissivity of the placenta and the decidua (the uterine mucosa during pregnancy) to infection. In the decidua from the first trimester of pregnancy, macrophages (dMs) are the HIV-1 main target cells. Decidual natural killer (dNK) cells account for 70 % of decidual leukocytes. They display distinct phenotype and functions compared to peripheral NK cells. At the periphery, NK cells are involved in the control of HIV-1 infection. In this study, we investigate whether human decidual natural killer (dNK) cells control dM HIV-1 infection. RESULTS: Autologous cocultures of infected dMs with dNK cells reveal that dNK cells strongly inhibit dM HIV-1 infection. The addition of dNK cells to dMs at different times after infection suggests that the control occurs before the complete establishment of the infection. Double chamber cocultures show that cellular contacts are necessary for an optimal control of infection. Nevertheless, soluble factors secreted by dMs and dNK cells in double chamber cocultures partially inhibit dM HIV-1 infection, indicating that soluble factors have also a role in the control of infection. IFN-γ secretion is increased in infected and uninfected cocultures. We show that IFN-γ is involved in the control of dM HIV-1 infection by dNK cells. CONCLUSIONS: These results demonstrate that human dNK cells inhibit efficiently HIV-1 infection in dMs in vitro, and highlight the role of innate immune determinants in the control of HIV-1 transmission.

Identification of a new human immunodeficiency virus type 1 distinct from group M and group O.

A highly divergent HIV-1 isolate, designated YBF 30, was obtained in 1995 from a 40-year-old Cameroonian woman with AIDS. Depending on the genes studied, phylogenetic analysis showed that YBF30 branched either with SIVcpz-gab or between SIVcpz-gab and HIV-1 group M. The structural genes and tat, vpr, and nef of YBF30 are approximately equidistant from those of HIV-1 group M and SIVcpz-gab. In contrast, vif and rev are closer to HIV-1 group M, and vpu is highly divergent. Using a YBF30 V3 loop peptide enzyme immunoassay, we screened 700 HIV-1-positive sera collected in Cameroon; three reacted strongly with the YBF30 peptides and one was confirmed as being related to YBF30 by genetic analysis of a pol fragment. YBF30 is as distinct from SIVcpz-gab as it is from HIV-1 group M and can thus be considered as the prototype strain of a new human immunodeficiency virus group.

Vaccine protection of chimpanzees against challenge with HIV-1-infected peripheral blood mononuclear cells.

Because human immunodeficiency virus (HIV) can be transmitted as cell-free virus or as infected cells (cell-associated virus), vaccines must protect against infection by both viral forms. Vaccine-mediated protection of nonhuman primates against low doses of cell-free HIV-1, HIV-2, or simian immunodeficiency virus (SIV) has been demonstrated. It is now shown that multiple immunizations of chimpanzees with HIV-1 antigens protected against infection with cell-associated virus. Protection can persist for extended periods (one animal had not been exposed to viral antigens for 1 year before challenge). These results show that it is possible to elicit long-lasting protective immunity against cell-associated HIV-1.

Prevalence of antibodies to lymphadenopathy-associated retrovirus in African patients with AIDS.

The presence of antibodies to lymphadenopathy-associated retrovirus (LAV) was determined by a radioimmunoprecipitation assay and by an enzyme-linked immunosorbent solid assay of sera from Zairian patients with the acquired immune deficiency syndrome (AIDS) in 1983. Thirty-five of 37 patients (94 percent) and 32 of 36 patients (88 percent), respectively, were seropositive by the two tests. In a control group of 26 patients, six (23 percent) showed positive results in these tests. Of these six control patients, five had clinically demonstrable infectious diseases and a low ratio of T4 to T8 lymphocytes. In addition, sera collected from a control group of Zairian mothers in 1980 were positive for LAV in 5 of 100 cases. Other serologic data suggest that LAV was present as early as 1977 in Zaire.

Selective tropism of lymphadenopathy associated virus (LAV) for helper-inducer T lymphocytes.

Lymphadenopathy associated virus ( LAV ) has been isolated from patients with the acquired immunodeficiency syndrome (AIDS) or lymphadenopathy syndrome. Since the immune deficiency in AIDS seems to be primarily related to the defect of the helper-inducer T lymphocyte subset, the possibility that LAV is selectively tropic for this subset was investigated. Fractionation of T lymphocytes was achieved by cellular affinity chromatography with monoclonal antibodies. In a hemophilic patient who was a healthy carrier of LAV , reverse transcriptase activity and virus particles detected by electron microscopy were found only in cultures of helper-inducer lymphocytes. When infected with LAV in vitro, lymphocyte subsets from normal individuals yielded similar results. Virus production was associated with impaired proliferation, modulation of T3-T4 cell markers, and the appearance of cytopathic effects. The results provide evidence for the involvement of LAV in AIDS.

Adaptation of lymphadenopathy associated virus (LAV) to replication in EBV-transformed B lymphoblastoid cell lines.

A strain of lymphadenopathy associated retrovirus ( LAV ) passaged in vitro was used to infect a lymphoblastoid cell line obtained by transformation with Epstein-Barr virus of B lymphocytes from a healthy donor. The virus produced from this line (B- LAV ) was also able to grow at a high rate in some other lymphoblastoid lines and in a Burkitt lymphoma line. This adapted strain retained the biochemical, ultrastructural, and antigenic characteristics of the original strain, as well as its tropism for normal T4+ lymphocytes. It is thus possible to grow LAV in large quantities that can be used for the preparation of diagnostic reagents. The interaction between such a human retrovirus and Epstein-Barr virus, a DNA virus, may have some implication for the pathology of the acquired immunodeficiency syndrome and related diseases.

Antibodies to the core protein of lymphadenopathy-associated virus (LAV) in patients with AIDS.

Lymphadenopathy-associated virus ( LAV ), a human T- lymphotrophic retrovirus isolated from a homosexual man with lymphadenopathy, has been causally associated with acquired immunodeficiency syndrome (AIDS). A sensitive and specific radioimmunoprecipitation test was developed for the detection of antibodies to the major core protein of LAV , p25 (molecular weight 25,000). Antibody to LAV p25 was found in the serum of 51 of 125 AIDS patients, 81 of 113 patients with lymphadenopathy syndrome, 0 of 70 workers at the Centers for Disease Control (some of whom had handled specimens from AIDS patients), and 0 of 189 random blood donors. Of a group of 100 homosexual men from San Francisco whose serum was obtained in 1978, only one had antibody to LAV p25; in contrast, of a group of 50 homosexual men in the same community whose serum was obtained in 1984, 12 had antibodies to LAV p25.

Isolation of a T-lymphotropic retrovirus from a patient at risk for acquired immune deficiency syndrome (AIDS).

A retrovirus belonging to the family of recently discovered human T-cell leukemia viruses (HTLV), but clearly distinct from each previous isolate, has been isolated from a Caucasian patient with signs and symptoms that often precede the acquired immune deficiency syndrome (AIDS). This virus is a typical type-C RNA tumor virus, buds from the cell membrane, prefers magnesium for reverse transcriptase activity, and has an internal antigen (p25) similar to HTLV p24. Antibodies from serum of this patient react with proteins from viruses of the HTLV-I subgroup, but type-specific antisera to HTLV-I do not precipitate proteins of the new isolate. The virus from this patient has been transmitted into cord blood lymphocytes, and the virus produced by these cells is similar to the original isolate. From these studies it is concluded that this virus as well as the previous HTLV isolates belong to a general family of T-lymphotropic retroviruses that are horizontally transmitted in humans and may be involved in several pathological syndromes, including AIDS.

Replication of the human immunodeficiency virus 1 and impaired differentiation of T cells after in vitro infection of bone marrow immature T cells.

HIV-1 infection in vitro of normal bone marrow mononuclear cells (BMMC) depleted of mature T cells was studied. BMMC depleted of either CD3, CD2, or both could replicate HIV-1 irrespective of the presence of macrophages/monocytes. Infected bone marrow cells were shown to differentiate during the culture into CD3+, CD4+, CD8+, and CD1+ cells, whereas noninfected BMMC gave rise to CD3+, CD4+, and CD8+ cells. Moreover, 9-14% of the cells also expressed the viral proteins p24 and gp120 on their surface. Double staining studies revealed that 72 and 83% of the CD4+ cells expressed the gp120 and p24, respectively, suggesting that virus replication occurred in CD4+ cells. T cell colony growth from infected BMMC, either unfractionated or depleted of mature T cells, was impaired in a time-dependent manner, and the differentiation capacity of T cell precursors was abnormal. Colony cells displayed an immature cell phenotype (CD1+ cells) and the viral proteins gp120 and/or p24 could also be detected on CD1+ cells. In addition, pooled colony cells derived from infected CD2- and CD3-depleted BMMC could infect normal mitogen-activated lymphocytes in coculture experiments. These findings strongly suggest that HIV-1 can infect immature bone marrow T cells and be transmitted to the progeny, but the massive viral replication occurs only when the cells differentiate toward CD4+ cells.

Down modulation of TNF-alpha mRNA placental expression by AZT used for the prevention of HIV-1 mother-to-child transmission.

Mechanisms of HIV-1 in utero mother-to-child transmission (MTCT) protection provided by AZT are not completely understood. The placental cytokine network is involved in the control of HIV-1 in utero transmission but the effect of AZT on this network is unknown. To evaluate the effects of AZT on placental cytokine expression, the chorionic villi from HIV-1 uninfected women term placentae were cultured with 0, 100, and 2,000 ng/ml AZT. Tissue fragments were harvested at days 1, 4, and 7 to determine the level of cytokine mRNA by real-time RT-PCR. The viability and morphology of the placental histocultures were monitored by the expression of beta-human chorionic gonadotropin (beta-hCG) gene, lipopolysaccharide (LPS) activation, and microscopic examination. AZT at 2,000 ng/ml significantly down-regulated TNF-alpha mRNA expression at day 1 and day 4, but had no effect on beta-hCG, stromal cell-derived factor 1 (SDF-1), and IL-10 gene expression. AZT did not induce any deleterious impact on placental tissue structure. Furthermore, activation of chorionic villi by LPS for 24 h up-regulated IL-10 and TNF-alpha mRNA expression. Down-regulation of TNF-alpha mRNA could represent a mechanism through which AZT can decrease the risk of HIV-1 MTCT, in addition to its direct effect on HIV-1 replication.

The local environment orchestrates mucosal decidual macrophage differentiation and substantially inhibits HIV-1 replication.

Macrophages from the decidua basalis (dM), the main uterine mucosa during pregnancy, are weakly permissive to HIV-1 infection. Here, we investigated the mechanisms underlying this natural control. We show, by using freshly purified decidual macrophages and ex vivo human decidual explants, that the local decidual environment influences dM differentiation and naturally protects these cells from HIV-1 infection. Interferon (IFN)-γ, present in the decidual tissue, contributes to maintenance of the dM phenotype and restricts HIV-1 infection by mechanisms involving the cyclin-dependent kinase inhibitor p21Cip1/Waf1. We also found that activation of Toll-like receptors 7 and 8 expressed by dM reinforces the low permissivity of dM to HIV-1 by restricting viral replication and inducing secretion of cytokines in the decidual environment, including IFN-γ, that shape dM plasticity. A major challenge for HIV-1 eradication is to control infection of tissue-resident macrophages in the female reproductive tract. Our findings provide clues to the development of novel strategies to prevent HIV-1 macrophage infection.

Purification and identification of a CD25 expression inhibitory protein from cell-free supernatants of chronically HIV-infected promonocytic cells.

The CD25 (IL-2-R alpha) cell surface glycoprotein expressed transiently during T-cell activation is implicated in the high affinity IL-2 receptor. This paper shows that cell-free supernatants from chronically HIV-infected promonocytic cells spontaneously produce a soluble factor which inhibits CD25 expression on PHA-activated human PBMC. We purified the CD25 expression inhibitory activity by a factor 12,350, using XM50 ultrafiltration, Superose 12 molecular sieving chromatography and MonoQ anion-exchange chromatography. Then we associated this activity to one single spot (M(r) 29,000, pI 6.8) on an O'Farrell two-dimensional gel. Our data demonstrate that this protein (M(r) 29,000, pI 6.8) is released from HIV-infected promonocytic cells and suggest that this factor is a new monokine regulating the T-cell activation process.

Cis elements and trans-acting factors involved in the RNA dimerization of the human immunodeficiency virus HIV-1.

The retroviral genome consists of two identical RNA molecules joined at their 5' ends by the Dimer Linkage Structure (DLS). To study the mechanism of dimerization and the DLS of HIV-1 RNA, large amounts of bona fide HIV-1 RNA and of mutants have been synthesized in vitro. We report that HIV-1 RNA forms dimeric molecules and that viral nucleocapsid (NC) protein NCp15 greatly activates dimerization. Deletion mutagenesis in the RNA 5' 1333 nucleotides indicated that a small domain of 100 nucleotides, located between positions 311 to 415 from the 5' end, is necessary and sufficient to promote HIV-1 RNA dimerization. This dimerization domain encompasses an encapsidation element located between the 5' splice donor site and initiator AUG of gag and shows little sequence variations in different strains of HIV-1. Furthermore, cross-linking analysis of the interactions between NC and HIV-1 RNA (311 to 415) locates a major contact site in the encapsidation element of HIV-1 RNA. The genomic RNA dimer is tightly associated with nucleocapsid protein molecules in avian and murine retroviruses, and this ribonucleoprotein structure is believed to be the template for reverse transcription. Genomic RNA-protein interactions have been analyzed in human immunodeficiency virus (HIV) virions and results showed that NC protein molecules are tightly bound to the genomic RNA dimer. Since retroviral RNA dimerization and packaging appear to be under the control of the same cis element, the encapsidation sequences, and trans-acting factor, the NC protein, they are probably related events in the course of virion assembly.

Evaluation of the placental environment with a new in vitro model of histocultures of early and term placentae: determination of cytokine and chemokine expression profiles.

We aimed to set up and validate a new in vitro model of placental histocultures, for the evaluation of cytokine and chemokine profiles of the placental environment, over a long culture period. Micro-explant cultures from 6 early and 6 term placentae were set up on collagen sponge gel supports at a liquid/air interface. At various times during culture, we analyzed tissue morphology and cell death by microscopy and quantified beta-hCG production and mRNA levels for beta-hCG and insulin-like 4 (INSL4). Levels of IL-6, LIF, TNF alpha, IL-10, IFN-gamma, IL-16 and RANTES in the medium were measured by ELISA on days 1, 4 and 7 of culture. SDF-1 mRNA expression was determined by real-time PCR at the same time points. Histocultures from early and term placentae remained viable until day 10. High levels of IL-6 and LIF production, low levels of TNF alpha, IL-10 and IFN-gamma production and significant SDF-1 expression were observed. These data indicate that placental histoculture is a suitable and reliable in vitro model for studying the placental environment.

HIV-induced, HIV-specific in vitro antibody response by B-cells from HIV-seropositive individuals.

OBJECTIVE: Recent studies have shown that B-cells from HIV-infected patients can secrete anti-HIV antibodies in vitro and that they represent 20-40% of immunoglobulin (Ig)-secreting B-cells in vivo. This study was designed to investigate the precise role of HIV in this in vitro antibody production. DESIGN AND METHODS: B-cells from HIV-infected patients [asymptomatic, n = 28; symptomatic (AIDS), n = 14], from seronegative adult volunteers (n = 22) and subjects at high risk for HIV infection (n = 15) were cultured in vitro in the presence of pokeweed mitogen, Staphylococcus aureus cowan or HIV, and T-cells or interleukins (IL). Non-specific Ig production and specific anti-HIV antibody (Ab) production were measured by enzyme-linked immunosorbent and Western blot assays. RESULTS: We found that HIV induced a specific response in cultured B-cells from seropositive patients, in contrast with cultured B-cells from uninfected normal individuals. The characteristics of the HIV-induced response differed from those of a spontaneous or a mitogen-induced response. Anti-HIV Ab production was optimal on day 8-10, when B-cells were cultured with recombinant IL-2 and recombinant interferon-alpha in the presence of infectious virus or recombinant gp160 Env protein. The anti-HIV Ab were mainly directed against Env proteins. Interaction of HIV with B-cells involved surface IgG but not CD4 antigen. Autologous CD8+ T-cells had a non-specific inhibitory effect. Both CD5+ and CD5- B-cells produced anti-HIV Ab. No anti-HIV Ab production was observed in B-cells from high-risk HIV-seronegative individuals. CONCLUSION: HIV (infectious virus or gp160) can induce B-cells from infected patients to secrete specific anti-HIV Ab in vitro.

Antibody-dependent cellular cytotoxicity against HIV-1 in sera of immunized chimpanzees.

After immunization of chimpanzees against HIV antigens, antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC) were evaluated and compared with anti-HIV-antibody levels detected by enzyme-linked immunosorbent assay (ELISA) and neutralizing antibody titers. Adult chimpanzees were immunized with different HIV-1 (LAV-BRU) antigen preparations: recombinant vaccinia virus (rVV) expressing gp160, p25 or p27nef; formalin- and beta-propiolactone-inactivated whole virus (inHIV); soluble recombinant gp160 either associated or not associated with other HIV proteins; a 25-mer peptide from the V3 region of gp120 coupled with KLH (V3-KLH). Immunization with the various rVV mixtures induced no or borderline ADCC increase above preimmune serum levels. Stronger and more sustained reactivity was elicited by inHIV. Purified HIV antigens elicited ADCC activity when the chimpanzees were naive; ADCC increased or remained at the same level when the animals had been preimmunized with rVV and/or inHIV. This type of reactivity apparently did not depend on whether gp160 alone or mixed with other proteins was used for immunization. The injection of V3-KLH resulted in only little, if any, recall ADCC response. ELISA antibody titers significantly correlated with ADCC and neutralizing antibody titers, but serum ADCC was independent of neutralizing antibody titers, an indication that the two latter serum activities are mediated by independent antibodies. Therefore, ADCC is elicited in the same manner as other antibody activities by the immunization of chimpanzees with inHIV or with purified recombinant HIV antigen preparations. The results obtained from the three chimpanzees of this series, which were subsequently challenged with infectious virus through the intravenous route, suggest that serum ADCC may be considered for vaccination purposes.

Staphylococcal superantigens activate HIV-1 replication in naturally infected monocytes.

OBJECTIVES: To study the effects of microbial superantigens, Staphylococcal exotoxins (SE), on HIV replication in monocytes following binding to and signalling through major histocompatibility complex (MHC) class II molecules. METHODS: We investigated the effects of SE on HIV replication and monokine production in three different in vitro models of monocyte culture: chronically infected monocytic cell line U1, acute infection of normal monocytes by different HIV-1 strains, and naturally-infected monocytes from seropositive patients. p24 antigen, interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha production was measured by specific enzyme-linked immunosorbent assay (ELISA). RESULTS: Staphylococcal enterotoxin B and toxic shock syndrome toxin-1 (1-1000 ng/ml) are powerful inducers of HIV-1 expression in U1 cells pretreated with granulocyte macrophage colony stimulating factor. SE induce viral replication in short-term cultures (days 6-21) of monocytes infected in vitro by HIVBa-L, HIVLAI, or naturally infected in vivo. Induction of HIV expression requires direct interactions of SE with MHC class II molecules but not T-cell receptor binding and T-cell-monocyte contact. Anti-TNF-alpha and anti-IL-6 neutralizing monoclonal antibodies inhibit by over 61% SE-induced HIV replication. CONCLUSIONS: Using SE we have linked two important pathways for the regulation of HIV replication in monocytes, namely signalling through MHC class II molecules and monokine production potentially mediated by induction of the pleiotropic cellular transcription factor NF-kappa B. In HIV-infected patients bacterial infections are common and could be an important cofactor in the immunopathogenesis of AIDS by inducing HIV replication in latently infected monocytes. Their prevention might emerge as beneficial in these patients.

Serological and virological characterization of HIV-1 group O infection in Cameroon.

OBJECTIVES: To study the presence of HIV-1 group O infection among HIV-infected people in Cameroon and to further characterize the HIV-1 group O infections. DESIGN AND METHODS: During a 2-year survey (1994-1995), all samples tested positive in screening methods in the National Reference and Public Health Laboratory, Centre Pasteur, Yaoundé, Cameroon were identified as HIV-1 group M, HIV-1 group O or HIV-2 by using a serological algorithm. HIV-1 group M and HIV-1 group O were distinguished on the basis of competitive enzyme-linked immunosorbent assay (ELISA) reactivity against gp41 group M recombinant protein. HIV-1 group O infections were confirmed by using group O-specific V3 synthetic peptides. HIV-1 group O strains were isolated by lymphocyte cocultures, proviral DNA was amplified with specific primers, and sequencing was performed on the C2V3 and gag regions. RESULTS: Of the 8,331 screened samples, 3,193 were HIV-reactive, 2,376 (74%) of which were considered to belong to group M. The 817 (26%) that had reacted poorly or not at all against group M gp41 were further characterized: 10 were confirmed as HIV-2 and 82 as HIV-1 group O, the others being indeterminate (n = 285) or negative (n = 440). The frequency of group O relative to group M ranged from 1% in Far North province to 6.3% in the capital. There was no difference in sex, age or frequency of clinical manifestations between group M and group O infections. Group O infection was confirmed in a subset of cases by polymerase chain reaction (n = 14), with perfect concordance. Sequencing and phylogenetic analyses confirmed the high variability inside group O. CONCLUSIONS: Group O and group M epidemiological patterns are known to be similar so the reason for the lower prevalence of group O remains to be found. The wide distribution of group O infection in all Cameroonian provinces underlines the importance of further characterizing the epidemic spread and diffusion of this group.

Nucleotide sequence of HIV1-NDK: a highly cytopathic strain of the human immunodeficiency virus.

A highly cytopathic strain of HIV1, named HIV1-NDK, has been isolated from a Zaïrian patient affected with AIDS. This isolate is 10(4) times more cytopathic and infectious than the prototype. To correlate the high cytopathic properties of this strain with genetic variations, we have cloned and sequenced the genome of this isolate. The principal feature which could be drawn from the fine analysis of the HIV1-NDK sequence is that the variability is not clustered in one particular region but rather spread out all along the genome. Only minor differences seem to be responsible for the acute biological effect of HIV1-NDK.

A randomized, placebo-controlled, blind anti-AIDS clinical trial: safety and immunogenicity of a specific anti-IFN alpha immunization.

HIV-induced cytokine dysregulation, including overproduction of the antiproliferative and cytolytic IFN alpha cytokine, represents a major component of the immune disorders characterizing AIDS. To block the overproduction of IFN alpha we designed an AIDS vaccine combination which included both an anti-HIV and/or an anti-IFN alpha immunization. The safety and immunogenicity of this multicomponent vaccine were tested in mice, Cercopithecus, two HIV noninfected individuals, and six HIV-1 seropositive immunocompromised patients enrolled in a 1-year open clinical trial. We now report the result of a 9-month short-term randomized, blind, placebo-controlled clinical trial (Phase I/II) performed in HIV-1 patients (22 individuals) to confirm safety/tolerance of the anti-IFN alpha vaccine and its immunogenicity and to evaluate whether the complex vaccine initially used could be simplified by removal of HIV component(s). Three groups of patients received inactivated IFN alpha (i-IFN alpha) associated with the immunomodulator P40 with HIV-1 antigens (groups B and C) or without (group A), and one group (D) was placebo. The clinical follow-up documented among those receiving i-IFN-alpha showed that none developed AIDS and/or required antiretroviral chemotherapy. Viral load did not increase and CD4 cell count as well as cell-mediated immunity (CMI) stabilized or even significantly increased in group A. Immunogenicity of the preparations was determined by a positive delayed-type hypersensitivity (DTH) reaction to i-IFN alpha and the presence of serum antibodies to i-IFN alpha and to HIV-1 peptides, occurring only in treated patients. As previously planned, based on these safety data, the trial has been extended for an additional year and all patients were switched to protocol A (i-IFN alpha+P40). This second period of the trial, now open and ongoing, should allow us to evaluate further the innocuity of the i-IFN alpha preparation and whether anti-IFN alpha vaccine could provide a long-lasting CD4 cell count as well as CMI stabilization.