Early and persistent bone marrow hematopoiesis defect in simian/human immunodeficiency virus-infected macaques despite efficient reduction of viremia by highly active antiretroviral therapy during primary infection

The hematological abnormalities observed in human immunodeficiency virus (HIV)-infected patients appear to be mainly due to bone marrow dysfunction. A macaque models of AIDS could greatly facilitate an in vivo approach to the pathogenesis of such dysfunction. Here, we evaluated in this model the impact of infection with a pathogenic simian/human immunodeficiency virus (SHIV) on bone marrow hematopoiesis. Three groups of macaques were inoculated with 50 50% median infective doses of pathogenic SHIV 89.P, which expresses env of dual-tropic HIV type 1 (HIV-1) 89.6 primary isolate. During the primary phase of infection, animals were treated with either a placebo or highly active antiretroviral therapy (HAART) combining zidovudine, lamivudine, and indinavir, initiated 4 or 72 h postinfection (p.i.) and administered twice a day until day 28 p.i. In both placebo-treated and HAART-treated animals, bone marrow colony-forming cells (CFC) progressively decreased quite early, during the first month p.i. One year p.i., both placebo- and HAART-treated animals displayed decreases in CFC to about 56% of preinfection values. At the same time, a dramatic decrease (greater than 77%) of bone marrow CD34(+) long-term culture-initiating cells was noted in all animals were found. No statistically significant differences between placebo- and HAART-treated monkeys were found. These data argue for an early and profound alteration of myelopoiesis at the level of the most primitive CD34(+) progenitor cells during SHIV infection, independently of the level of viremia, circulating CD4(+) cell counts, or antiviral treatment.

Longitudinal analysis of CD8+ T-cell phenotype and IL-7, IL-15 and IL-16 mRNA expressionin different tissues during primary simian immunodeficiency virus infection

Infection of macaques with pathogenic isolates of simian immunodeficiency virus (SIV) represents a useful model of HIV infection that offers the unique opportunity to investigate the very early modifications that affect CD8(+) T-lymphocyte subsets and related cytokines during lentiviral infection. Herein, three cynomolgus macaques were inoculated intravenously with a pathogenic isolate of SIVmac 251. In fresh isolated mononuclear cells from blood, lymph node and bronchoalveolar lavage, we analyzed changes in the phenotype of CD8(+) T cells and we used reverse transcription-PCR to monitor the expression of IL-7, IL-15 and IL-16 mRNA. We demonstrated that an expansion of CD8(+)CD28(-) T cells occurs from the third week of infection on in the peripheral blood and in the lung, whereas CD8(+)CD28(+) T cells expand in the lymph nodes. Concomitantly, we evidenced mRNA modulations in IL-16, IL-15 and IL-7 expression in the three compartments studied. The containment of systemic viral replication was associated with an overexpression of IL-16 mRNA in the lung and in the peripheral blood. Given the immunomodulatory properties of IL-15 and IL-7 and the potential antiviral ability of IL-16, these perturbations could have important implications in early viral dissemination and HIV immunopathogenesis.

Immune responses following simian/human immunodeficiency virus (SHIV) challenge of rhesus macaques after human immunodeficiency virus (HIV)-1 third variable domain (V3) loop-based genetic immunization

Following DNA immunization of rhesus macaques with a plasmid encoding the human immunodeficiency virus (HIV)-1 third variable domain (V3) loop, presented by pseudo-viral envelope particles of hepatitis B virus, specific immune responses were induced. The primates were then inoculated with a chimeric simian/human immunodeficiency virus (SHIV). All the animals were infected, but the V3-specific immunization provided a relative attenuation of the acute phase of infection in the absence of neutralizing antibody. In all animals, SHIV-specific cytotoxic T-lymphocyte precursors (CTLp) were detected early in peripheral blood and lymph nodes. The viremia peak correlated significantly with the decrease in CD4+ T cells and with a transient increase in the percentage of natural killer cells. The infection induced an oligoclonalization of the CD8+ T-cell variable beta chain repertoire in the blood. Surprisingly, HIV envelope-specific CTLp generated by genetic immunization may be governed by distinct circulation rules compared to SHIV-specific CTLp induced by infection.

[Evaluation of the effect of early and massive tritherapy on the expression of cellular factors potentially implicated in antiretroviral therapy resistance]

Treatment of the human immunodeficiency virus (HIV) is restricted by therapeutic escape. The biological mechanisms of this chemoresistance rely notably on the modulation of cell kinase and P-glycoprotein (P-gp) expression. In this study, we investigated, in cynomolgus macaques, the roles of SHIV89.6P infection and of HAART in the mRNA expression of these cell factors. SHIV infection, or associated pathophysiological disorders, increase both thymidine kinase and thymidylate kinase mRNA expression and decrease those of P-gp. On the other hand, the expression of other cell kinases is not modulated. In parallel, HAART accentuates the decrease of P-gp expression and attenuates the increase of kinase expression. On the whole, such metabolic disorders, evidenced herein an animal model of HIV infection, could be involved in HIV-infected patients.

RANTES, IFN-gamma, CCR1, and CCR5 mRNA expression in peripheral blood, lymph node, and bronchoalveolar lavage mononuclear cells during primary simian immunodeficiency virus infection of macaques

Primary infection of macaques with pathogenic isolates of simian immunodeficiency virus (SIV) (as a model of HIV infection in humans) represents a unique opportunity to study early lentivirus/host interactions. We sought to determine whether there is a temporal relationship linking SIV replication and dissemination and the expression of the chemokine RANTES (regulated upon activation normal T cell expressed and secreted) and the SIV/HIV coreceptor CCR5 in different tissues during acute SIV infection of macaques. Four cynomolgus macaques were inoculated intravenously with a pathogenic primary isolate of SIVmac251. RT-PCR was used to monitor the expression of RANTES and CCR5 mRNA in fresh isolated mononuclear cells from blood, lymph node, and bronchoalveolar lavages. These expressions were compared to those of IFN-gamma as an indicator of the development of the immune response and to another receptor for RANTES, CCR1, which is not described as a coreceptor for SIV/HIV-1 entry. An enhancement of CCR1/CCR5 mRNA expression was noticed during primary SIVmac251 infection of macaques, mainly in tissue. In the three different compartments investigated, IFN-gamma and RANTES overexpression was noticed by the time of systemic viral replication containment. Our results put CCR5 and RANTES mRNA expression back in the context of inflammatory and immune responses to SIV primary infection.

Secretion of beta-chemokines by bronchoalveolar lavage cells during primary infection of macaques inoculated with attenuated nef-deleted or pathogenic simian immunodeficiency virus strain mac251

Primary infection of macaques with simian immunodeficiency virus (SIV) as a model of human immunodeficiency virus (HIV) infection represents a unique opportunity to investigate early lentivirus-host interactions. In order to gain insight into immunopathogenic events taking place in the lung during lentiviral infection, we analysed lymphocyte expansion in the lung and chemokine secretion by mononuclear cells obtained by bronchoalveolar lavage (BALMCs) during primary infection by a pathogenic and a non-pathogenic SIV. Two groups of cynomolgus macaques were inoculated intravenously with a fully pathogenic isolate of SIVmac251 or with an attenuated, nef-deleted, molecular clone of SIVmac251. Spontaneous MIP-1alpha, MIP-1beta and RANTES production was assessed by ELISA in supernatants of short-term cultured BALMCs. Kinetics of haematological, virological and immunological parameters were investigated simultaneously. All 11 inoculated animals became infected. Monkeys inoculated with the nef-deleted SIV clone exhibited a significantly reduced plasma virus load and a less pronounced accumulation of lymphocytes in the lung compared to monkeys infected with the pathogenic SIVmac251 isolate. Compared to pre-infection levels, we observed an increase in the levels of RANTES, MIP1-alpha and MIP1-beta production in the two groups of monkeys, by the time of peak viraemia. Strikingly, a greater enhancement of RANTES and MIP-1alpha production was detected in monkeys infected with the attenuated virus. Given the potential influence of beta-chemokines on the immune response and virus replication, such results suggest that RANTES, MIP1-alpha and MIP1-beta could contribute to the singular features of the immune response elicited during infection of macaques with an attenuated SIV.

Consequences of ddI-induced reduction of acute SIVmac251 virus load on cytokine profiles in cynomolgus macaques

This study evaluates the consequences of antiretroviral treatment of the acute simian immunodeficiency virus (SIV) primary infection on virus load and cytokine responses. Four cynomolgus macaques were inoculated intravenously with a pathogenic primary isolate (SIVmac251). Animals were pretreated with 10.8 mg/kg/day of dideoxyinosine (ddI) from 4 days before inoculation, and treatment was continued for 28 days. Proinflammatory (IL6, IL1 beta and TNF alpha) and antiinflammatory (IL10) cytokine and lymphokine (IL2, IL4 and IFN gamma) polymerase chain reaction (PCR) ratios were monitored in unmanipulated peripheral blood mononuclear cells (PBMCs) during acute infection by using a semiquantitative reverse transcription (RT)-PCR method. PBMC-associated virus loads were dramatically reduced compared to those of placebo-treated macaques. Nevertheless, a transient rise in IL6, IL1 beta, TNF alpha and IL10 mRNA expression was observed in PBMCs. IL2, IL4 and IFN gamma mRNAs were either undetectable or weakly detectable throughout the study, with no major changes. Despite a dramatic reduction in the acute viral loads in ddI-treated monkeys, early cytokine mRNA profiles were comparable to those of untreated SIVmac251-infected monkeys. Contrary to what was previously evidenced during primary infection with an attenuated SIV clone, no increase in IL2 and IL4 mRNA was detected in PBMCs of the ddI-treated monkeys, although these monkeys exhibited virus loads similar to those evidenced in macaques infected by attenuated SIV. These data indicate that differential lymphokine expression patterns found in pathogenic and Nef-truncated SIV-infected monkeys may not be strictly dependent on virus load levels.

Selective quasispecies transmission after systemic or mucosal exposure of macaques to simian immunodeficiency virus

Sexual transmission is the major cause of the AIDS epidemic. For the development of new antiviral and vaccine strategies, we therefore need to understand the mechanisms by which lentiviruses cross the mucosal barrier and the subsequent pathogenic consequences. For this purpose, experimental approaches are greatly facilitated by the development of relevant animal models. In this study, macaques were inoculated intravenously, intrarectally, or intravaginally with a pathogenic cell-free isolate of SIVmac251. Patterns of virological and immunological events significantly differed between vaginally (transient viremia, late seroconversion) and intravenously or intrarectally inoculated monkeys (persistent viremia and early seroconversion). Two weeks after infection, analysis of the env gene nucleotide sequences of proviruses recovered from PBMCs demonstrated that most of the differences were observed in the V1 loop. Three viral variants were specifically associated with vaginal transmission, whereas no such selection was evidenced after intravenous or intrarectal transmissions. These results are in favor of specific mechanisms associated with vaginal transmission, implicating viral envelope structure.

Variation in virological parameters and antibody responses in macaques after atraumatic vaginal exposure to a pathogenic primary isolate of SIVmac251

We developed an animal model for the male-to-female transmission of human immunodeficiency virus, consisting of an atraumatic vaginal application of simian immunodeficiency virus onto the intact vaginal mucosa of cynomolgus macaques. Different doses of a pathogenic isolate of SIVmac251, with or without seminal plasma, were infused into the vaginas of female macaques. Infection of macaques could be achieved after a single exposure to the virus. Two patterns of infection were underscored with no relation to the virus dose inoculated: in 50% of the monkeys, SIV was persistently recovered and a strong antibody response to SIV was evidenced in blood and vaginal secretions. In the other infected animals, SIV infection was only transiently evidenced and a weak systemic antibody response was detected. It appeared that the presence of seminal plasma may be implicated in this variability only when low doses of virus are inoculated. Sequence analysis of the env gene of SIV revealed that most of the persistently viraemic animals were infected with a viral variant different from that of transiently viraemic macaques.

Lack of interleukin 10 expression in monocyte-derived macrophages in response to in vitro infection by HIV type 1 isolates

Interleukin 10 is a pleiotropic cytokine that is overexpressed in HIV-infected patients. Here, we investigated IL-10 expression in primary cultures of monocyte-derived macrophages (MDMs) in response to in vitro infection by HIV-1/Ba-L or two macrophage-tropic HIV-1 primary isolates. Whatever the multiplicity of infection used, and in spite of high replication levels and an increase in HIV-infected cell frequency, neither significant IL-10 secretion nor IL-10 mRNA overexpression was induced in HIV-1-infected MDMs. Moreover, identical results were obtained with HIV-1-infected 1-day monocytes. These results show that MDM infection by HIV is not sufficient by itself for inducing IL-10 synthesis.

Chemoattractant factors (IP-10, MIP-1alpha, IL-16) mRNA expression in mononuclear cells from different tissues during acute SIVmac251 infection of macaques

We have used semiquantitative RT-PCR to monitor the expression of mRNA encoding chemoattractant factors IP-10, MIP-1alpha, and IL-16 in freshly isolated peripheral blood mononuclear cells (PBMCs), lymph node mononuclear cells (LNMCs), and mononuclear cells obtained after bronchoalveolar lavages (BALMCs) of two cynomolgus macaques inoculated intravenously with a pathogenic isolate of simian immunodeficiency virus, SIVmac251. Concomitant with the peak of systemic viral replication (two weeks after experimental inoculation) and proinflammatory cytokine IL-6 mRNA expression, high levels of MIP-1alpha and IP-10 mRNA were produced in LNMCs and BALMCs. In BALMCs, in which we have reported a marked progressive overexpression of IFN-gamma mRNA coinciding with an increase in the CD8+ lymphocyte percentages, we noticed a progressive overexpression of IL-16 mRNA. Our results suggest the role of chemokines IP-10, MIP-1alpha, and IL-16 in the development of inflammatory and immune responses during the early stages of lentiviral infection.

Cytokine mRNA expression in mononuclear cells from different tissues during acute SIVmac251 infection of macaques

We used semiquantitative RT-PCR to monitor the expression of mRNA encoding cytokines (IL-1 beta, IL-6, TNF-alpha, and IL-10) and IFN-gamma in fresh isolated peripheral blood mononuclear cells (PBMCs), lymph node mononuclear cells (LNMCs), and mononuclear cells obtained after bronchoalveolar lavages (BALMCs), of four cynomolgus macaques inoculated intravenously with a pathogenic isolate of simian immunodeficiency virus (SIVmac251). To investigate the effects of the viral load on the expression of the cytokines, two monkeys received 30 mg kg-1 day-1 of didanosine (ddI). The two nontreated monkeys became infected and seroconverted, whereas the ddI-treated monkeys were completely protected as demonstrated by all criteria of diagnosis of SIV infection. Concomitant with the peak of viral replication (2 weeks after the experimental inoculation), high levels of IL-6 mRNA were produced in PBMCs, LNMCs, and BALMCs of the two placebotreated infected monkeys. Overexpression of TNF-alpha and IL-10 mRNAs was sometimes observed in LNMCs and BALMCs. A progressive overexpression of IFN-gamma mRNA, starting 2 weeks after experimental inoculation, was observed in BALMCs from infected animals. Concurrently, a marked increase in the CD8+ lymphocyte percentage in the BAL fluids was detected by FACS analysis. Thus, our results emphasize the importance of a comparative study of the expression of cytokines in different tissues. They suggest the interactions of monocyte/macrophage monokine production with viral replication, as well as the role of IFN-gamma in the development of lung cellular immunity to SIV infection.

Superinfection of HIV-2-preinfected macaques after rectal exposure to a primary isolate of SIVmac251

To test the protection afforded by a weakly pathogenic HIV-2 isolate against the superinfection or development of SIV-induced disease, we intrarectally challenged six HIV-2-preinfected rhesus monkeys with a pathogenic isolate of SIVmac251. At the time of SIV challenge, none of these HIV-2-infected animals was positive for virus isolation, p27-Gag antigenemia, or HIV-2 provirus detection in PBMCs or peripheral lymph nodes. However, all monkeys exhibited anti-HIV-2 antibody titers ranging from 10(2) to 10(3). Neutralizing antibodies against the challenge SIV strain were also detected in two animals. After rectal exposure to SIVmac251, five of the six HIV-2-preinfected macaques were superinfected. SIVmac251 DNA sequences were detected repeatedly in the PBMCs of the five superinfected animals and the two controls, whereas no HIV-2 provirus was detected for 14 months postchallenge. The one monkey that resisted superinfection was negative for all SIV infection criteria. This monkey exhibited the highest anti-SIV ELISA and cross-neutralizing antibody titers on the day of SIV challenge. Preinfection with a weakly pathogenic HIV-2 ROD isolate protected one of six macaques from infection with the closely related pathogenic SIVmac251 isolate, but no protection from the progression of disease was evidenced in the other five.

Comparative interleukin (IL-2)/interferon IFN-gamma and IL-4/IL-10 responses during acute infection of macaques inoculated with attenuated nef-truncated or pathogenic SICmac251 virus

Comparison of immune responses to infection by a pathogenic or a nonpathogenic immunodeficiency virus in macaques may provide insights into pathogenetic events leading to simian AIDS. This work is aimed at exploring cytokine expression during infection by simian immunodeficiency virus (SIV). We used semiquantitative reverse transcription-PCR to monitor interleukin (IL)-2/interferon (IFN)-gamma (Th1-like), and IL-4/IL-10 (Th2-like) expression in unmanipulated peripheral blood mononuclear cells (PBMCs), during the acute phase of infection of eight cynomolgus macaques (Macaca fascicularis) with a pathogenic primary isolate of SIVmac251 (full-length nef), and of four other cynomolgus macaques by an attenuated molecular clone of SIVmac251 (nef-truncated). All the monkeys became infected, as clearly shown by the presence of infected PBMCs and by seroconversion. Nevertheless, PBMC-associated virus loads and p27 antigenemia in monkeys infected by the attenuated virus clone remained lower than those observed in animals infected with the pathogenic SIVmac251 isolate. A rise of IL-10 mRNA expression occurred in both groups of monkeys coincident with the peak of viral replication. In monkeys infected with the pathogenic SIVmac251, IL-2, IL-4, and IFN-gamma mRNAs were either weakly detectable or undetectable. On the contrary, animals infected by the attenuated virus exhibited an overexpression of these cytokine mRNAs during the first weeks after inoculation. The lack of expression of these cytokines in monkeys infected with the pathogenic primary isolate may reflect early immunodeficiency.

Interleukin 1 beta, interleukin 6, tumor necrosis factor alpha, and interleukin 10 responses in peripheral blood mononuclear cells of cynomolgus macaques during acute infection with SIVmac251

HIV infection ultimately leads to AIDS, despite the immune responses elicited soon after infection. In addition to the observed changes in lymphoid cell subsets, alteration of the cytokine network most likely accompanies and/or contributes to the lack of protective immune responses. In an attempt to delineate the early events in the immune response to lentivirus infection, we have sequentially monitored levels of proinflammatory (IL-1 beta, IL-6, and TNF-alpha) and antiinflammatory (IL-10) cytokine mRNAs in PBMCs of cynomolgus macaques during primary SIVmac infection. Eight monkeys were infected i.v. with 4 AID50 of cell-free SIVmac251. All monkeys seroconverted between days 16 and 21 postinfection (p.i.), and had detectable peripheral viremia. The viral load peaked between days 12 and 16 p.i., and fell sharply thereafter. A marked increase in the expression of IL-6 mRNA was observed in all macaques during the first weeks following infection. An increase in the levels of expression of IL-1 beta, TNF-alpha, and IL-10 mRNA was also determined in six, six, and five of the eight monkeys, respectively. While IL-6, TNF-alpha, and IL-10 increased transiently, increased levels of IL-1 beta mRNA expression were sustained over 44 days in most monkeys.

Cytokine mRNA levels in unmanipulated (ex vivo) and in vitro stimulated monkey PBMCs using a semi-quantitative RT-PCR and high sensitivity fluorescence-based detection strategy

To investigate the spectrum of cytokines expressed by peripheral blood mononuclear cells (PBMC) from cynomolgus macaques (Macaca fascicularis), we used a semi-quantitative RT-PCR to determine levels of mRNA coding for IL-1 beta, IL-2, IL-4, IL-6, IL-10, IFN-gamma, and TNF-alpha. The PCR products were labelled and quantified using a new fluorescent tag TOTO-1 (thiazole orange dimer) and an automated fluorescence-based electrophoretic instrument. Using this assay, the base line levels of cytokine mRNA expression in unmanipulated PBMCs (ex vivo) from 10 healthy monkeys were compared with the mRNA levels for the same cytokines in PBMC samples from two pre-immunized monkeys following culture with previously defined optimal concentrations of purified protein derivative (PPD), tetanus toxoid (TT) and the mitogen concanavalin A (con-A). While transcripts or IL-2, IL-4 and IFN-gamma were either low or not detected in unmanipulated PBMCs, varying levels of IL-1 beta, IL-5, IL-10, and TNF-alpha were readily detected in the same samples. With the exception of IL-10, the mitogen con-A induced the highest levels of cytokine expression, followed by levels induced by culture with TT. The levels of cytokine expression induced by PPD however, were not significantly elevated, despite the fact that the cells showed marked proliferative responses. This assay is a simple and convenient method for evaluating the levels of cytokine expression in small PBMC samples and will allow for the concurrent evaluation of immune profiles with functional immune analyses.

Functional consequences of macrophage infection by human immunodeficiency virus: bispecific antibody targeting of HIV-1-infected cells to Fc gamma RI expressing effector cells

Human monocytes/macrophages play a major role in pathogenesis of human immunodeficiency virus (HIV) infection. These cells have been suspected of acting as a reservoir for the virus and are important in viral dissemination and persistence in infected individual. Furthermore, several biologic and clinical features indicate that monocytes/macrophages from HIV-1-seropositive patients have characteristics of an activation status, including the ability to secrete high levels of cytokines. Dysregulation of the cytokine network may influence the level and the consequences of viral replication in infected monocytes/macrophages. Therefore, the development of virus-specific agents that may interfere with viral replication could help to slow down the fatal course of HIV infection. In this article, we try to further quantify the early and late kinetic patterns of the cytokine network during HIV-1 macrophage infection and report the biologic effects of virus-specific bispecific antibody (MDX-240) in HIV-1 macrophage infection.

Highly attenuated SIVmac142 is immunogenic but does not protect against SIVmac251 challenge

We report here the use of the highly attenuated SIVmac142 clone, unable to establish permanent infection of rhesus macaques, in a vaccine trial. Four rhesus macaques were immunized over a long time period with HUT-78 cells infected with wild-type SIVmac142 or, in order to reinforce the safety use of the vaccine, a deleted mutant with similar in vitro infectivity. The first two injections were done with living cells and the remaining boosts with cells emulsified in muramyl dipeptide adjuvant. Three control macaques were injected with uninfected HUT-78 cells. Over 3 years, we have been unable except once to detect viral infections by three methods. However, antibodies directed against the viral Gag proteins and envelope glycoproteins were detected by immunoblots and/or in vitro neutralization assays. All macaques were challenged intravenously with a low dose (10 animal infectious doses) of a highly pathogenic biological clone of SIVmac251 grown on macaque PBMCs. All seven animals became persistently viremic following challenge. The cell-associated viral loads of the vaccinated monkeys were not reduced relative to those of unvaccinated controls during the first weeks postchallenge even if vaccinated monkeys did not present a transient CD4 decrease. Thus, our data reinforced the notion that the efficacy of live attenuated SIV requires the establishment of persistent infection.

Tumor necrosis factor-alpha in serum of macaques during SIVmac251 acute infection

TNF secretion was explored in sera during acute SIV-infection of cynomolgus macaques. A peak of TNF was detected in sera of animals in concomitance with SIV replication. Likewise, AZT treatment delayed and reduced peaks of viral replication and TNF production. Thus, SIVmac251-infected monkey could be an excellent model to explore the interdigitation existing between HIV and TNF in acute and chronic infection and to develop new therapeutic strategies that target the production of this cytokine or its inductive effects.

Heterologous HIV-2 challenge of rhesus monkeys immunized with recombinant vaccinia viruses and purified recombinant HIV-2 proteins

In an attempt to analyse the role of anti-envelope immunity in the protection of rhesus monkeys against an HIV-2 intravenous challenge, rhesus macaques were immunized twice with recombinant HIV-2 ROD vaccinia viruses (10(8) p.f.u. each) at days 0 and 30, followed by booster injections of purified HIV-2 proteins at months 8, 9, 15 and 27. One group of five macaques was immunized with the Gag, Pol, Vif and Nef antigens, whereas a second group received the same antigens with the addition of HIV-2 Env protein. Eight months after the last boost, the animals were challenged by intravenous injection of 100 AID50 of a monkey PBMC-grown stock of HIV-2 SBL. None of the animals was protected in spite of high humoral immune responses on day of challenge as determined by ELISA and Western Blot assays.

Nef and Gag synthetic peptide priming of antibody responses to HIV type 1 antigens in mice and primates

T epitope mapping in human immunodeficiency virus proteins provides a useful tool for AIDS vaccine design. We have previously shown that four peptides selected from the Gag polyprotein of HIV-1 were able to prime mice for in vitro lymphoproliferative responses. These responses were shown to be MHC restricted, and a pool of these peptides was able to prime mice for a subsequent humoral response to HIV-1 Gag proteins. Here we show that two of these Gag peptides are able to prime the anti-HIV-1 IgG response to heat-inactivated HIV-1 in B10Sc.Cr mice. Furthermore, we extended this study in the nonhuman primate model, and show efficient priming of the IgG response to heat-inactivated HIV-1 using the pool of four Gag peptides in baboons. Further mapping of "nonself" peptides is extended to the HIV-1 Nef protein. Three potential Nef T epitopes located at positions 137-145, 98-107, and 81-95 are also shown to prime the IgG response to HIV-1 in the mouse model, although T cell proliferation to recall peptides in vitro was not detectable. Although they have not yet been defined as major helper T epitopes in humans, using classic in vitro stimulation assays, the fact that most of them are able to prime IgG responses in animals without detectable in vitro proliferative responses does not rule out their functional helper capacity in humans.

An animal model for antilentiviral therapy: effect of zidovudine on viral load during acute infection after exposure of macaques to simian immunodeficiency virus

We analyzed the kinetics of the virological and immunological events that occurred in four AZT-treated cynomolgus macaques during the acute infection that followed their exposure to the simian immunodeficiency virus (SIVmac251) grown on monkey PBMCs in a cell-free stock solution. These events included changes in the CD4+ and CD8+ T lymphocyte subsets, p27 antigenemia, infectious serum virus, and cell-associated virus loads. The kinetics of these changes proved strikingly similar to those reported in human HIV-1 infection. Four other SIV-exposed macaques were treated with placebo instead of AZT. We demonstrated that AZT does not prevent SIV infection, even when administered before SIV inoculation. However, the peaks of p27 antigenemia and of serum and cellular viremia were significantly smaller and occurred significantly later in the monkeys given AZT than in those given placebo.

Induction of humoral and cellular immunity to simian immunodeficiency virus: what are the requirements for protection?

In an effort to produce a strong humoral and cellular immune response that might protect against simian immunodeficiency virus (SIV) infection, groups of five rhesus macaques each were immunized intramuscularly at 0, 2 and 6 months with 100 micrograms of an inactivated preparation of SIV/Delta B670 in either an oil-in-water emulsion with Ribi Detox, containing mycobacterial cell wall skeleton and monophosphoryl lipid A (CWS/MPL) (group A) or a water-in-oil emulsion with incomplete Freund's adjuvant, containing CWS/MPL for the first two injections (group B). Animals were challenged with 10-100 monkey ID50 of monkey-cell-grown SIVmac251 3 months after the last injection, along with a group of four unvaccinated controls. Group B animals demonstrated the strongest immune responses following immunization, including neutralizing antibody titres against the challenge virus ranging from 160 to 320 and SIV-specific ELISA titres ranging from 10(5)-10(6) on the day of challenge, as well as strong in vitro lymphoproliferative and interleukin-2 (IL-2) production responses to the immunogen. Neutralizing antibody was not detectable in group A animals, ELISA titres were lower (10(2)-10(4)), no in vitro lymphoproliferative responses were observed, and in vitro IL-2 production was less pronounced. No protection against challenge was observed in either group. Moreover, group B animals exhibited a more pronounced clinical response following challenge than either group A animals or controls, consisting of hyperthermia and a greater degree of lymphadenopathy on day 7, followed by hypothermia and generally higher levels of serum viraemia on day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody-dependent cellular cytotoxicity and neutralization of human immunodeficiency virus type 1 by high affinity cross-linking of gp41 to human macrophage Fc IgG receptor using bispecific antibody

Human monocytes/macrophages, which express Fc receptors for IgG are involved in human immunodeficiency virus type 1 (HIV-1) infection and pathogenesis. These receptors are known to mediate numerous immunological functions including cell-mediated killing and possibly targeting of HIV to the lysophagosome monocyte-derived macrophage (MDM) entry route for virus neutralization. To study both activities in HIV-1 infection, MDM Fc gamma RI was specifically selected using bispecific antibody (Bs-Ab) containing whole human monoclonal antibody against gp41 and the Fab' fragment of murine anti-Fc gamma RI 22.2 antibody. Bs-Ab was found to mediate potent antibody-dependent cellular cytotoxicity and virus neutralization.

Evolution of the human immunodeficiency virus type 2 envelope gene in preimmunized and persistently infected rhesus macaques

The V3 and V4 domains of human immunodeficiency virus type 2 (HIV-2) env genes from 14 rhesus macaques experimentally infected by HIV-2 SBL6669/H5 were sequenced. No variation was observed in viral sequences from sera and from uncultured peripheral blood mononuclear cells during primary infection. The first mutations were detected 17 months after infection; they mainly concerned the region between the V3 and V4 domains and not those domains themselves, which are known to be hypervariable, suggesting that variation of V3 is a late event of HIV infection.

Four cross-linked HIV Gag peptides prime the immune response to HIV proteins in mice

The functional help provided by four cross-linked synthetic peptides from HIV-1 Gag structural proteins was investigated in the mouse model. These peptides, selected upon non-self-criteria, are not predicted as T epitopes by classical prediction methods such as the Rothbard consensus or the amphipathy rule. Priming mice with these peptides allows the enhancement of the antibody response to HIV-1 Gag proteins (p55, p18, p24) given in the viral particle form. Furthermore, all of them also induce spleen and lymph node cells from primed mice to proliferate in vitro, in a MHC class II restricted context. This approach may help to identify relevant immunogenic viral epitopes that may be involved in a vaccinal strategy.

Specific and non-specific immunity and protection of macaques against SIV infection

The simian immunodeficiency virus is a retrovirus closely related to the human immunodeficiency viruses; it induces an AIDS-like disease in macaques, and provides therefore an obvious animal model for anti-lentiviral drug and vaccine strategy assessments. In our experiment, we immunized rhesus macaques with a purified and formalin-inactivated whole SIVmac251 antigen preparation. Most of these monkeys were still protected for more than 4 months following a heterologous SIVsm intravenous challenge. Both virus stocks, for vaccine preparation and challenge, were provided by culture supernatants of infected T cells of human origin. Four of the protected macaques were then reimmunized with the same antigen preparation and rechallenged intravenously with a homologous rhesus cell grown SIVmac251. Unexpectedly, all animals developed clinical and biological evidence of infection by day 15 after the second challenge.

Inactivation of human immunodeficiency virus during human growth hormone production

Since human immunodeficiency virus (HIV) has been found in the brains of AIDS patients, the possibility was investigated that preparations of human growth hormone (hGH) extracted from human pituitary glands harbor infectious HIV. It was found that the procedure used for extracting hGH, i.e. a combination of acid pH and 10% ethanol, totally inactivates HIV infectivity.