Mutation, fitness, viral diversity, and predictive markers of disease progression in a computational model of HIV type 1 infection

The aim of this study was to develop a computational model of HIV infection able to simulate the natural history of the disease and to test predictive parameters of disease progression. We describe the results of a numerical simulation of the cellular and humoral immune response to HIV-1 infection as an adaptive pathway in a "bit-string" space. A total of 650 simulations of the HIV-1 dynamics were performed with a modified version of the Celada-Seiden immune system model. Statistics are in agreement with epidemiological studies showing a log normal distribution for the time span between infection and the development of AIDS. As predictive parameters of disease progression we found that HIV-1 accumulates "bit" mutations mainly in the peptide sequences recognized by cytotoxic CD8 T cells, indicating that cell-mediated immunity plays a major role in viral control. The viral load set point was closely correlated with the time from infection to development of AIDS. Viral divergence from the viral quasispecies that was present at the beginning of infection in long-term nonprogressors (LTNP) was found to be similar to that found in rapid progressors at the time CD4 T cells drop below the critical value of 200 cells/microl. In contrast, the diversity indicated by the number of HIV strains present at the same time was higher for rapid and normal progressors compared to LTNP, suggesting that the early immune response can make the difference. This computational model may help to define the predictive parameters of HIV dynamics and disease progression, with potential applications in therapeutic and vaccine simulations.     

Immunogenicity of a New HIV-1 DNA Construct in a BALB/c Mouse Model

Background: Cell mediated immunity, especially cytotoxic T cell responses against HIV-1 infection, plays a critical role in controlling viral replication and disease progres-sion. DNA vaccine is a novel technology which is known to stimulate strong cellular immune responses. Many DNA vaccines have been tested for HIV infection but there is still no effective vaccine against this infection. Construction of a vaccine consisting of multiple conserved and immunogenic epitopes may increase vaccine efficacy. Objective: In the present study, a DNA vaccine candidate constructed from HIV-1 P24-Nef was evaluated and cellular immune responses were assessed in murine BALB/c model. Methods: HIV-1 P24-Nef gene was cloned in pCDNA3.1 expression vector. Mice were immunized with DNA construct and IL-4 and IFN-γ evaluation was per-formed using ELISPOT. Cytotoxicity response was evaluated with Granzyme B ELIS-POT assay and lymphocyte proliferation was evaluated with LTT assay. Results: Analysis of immune responses showed that, compared to control groups, the candidate vaccine induced production of higher levels of both IL-4 and IFN-γ (p<0.05). Cytotox-icity and lymphocyte proliferation responses of mice vaccinated with the candidate vac-cine were significantly increased compared to control groups (p<0.05). Conclusion: HIV-1 P24-Nef DNA construct displayed strong immunogenicity in a murine model.     

Defective IL-2 production by HIV-1-specific CD4 and CD8 T cells in an adolescent/young adult cohort

Here we investigate the effect of viremia and the influence of HAART on the frequency and quality of HIVspecfic T cells in an adolescent/young adult cohort. Measurements of viral loads and the magnitude and quality of antiviral cellular immune responses were performed on 14 HAART-naive and 8 treated HIV-1-infected adolescents. Cross-sectional correlations between viral load and cellular immune responses were determined and data were analyzed by viral load (<4000, 4000-40,000, and >40,000 copies/ml plasma) and patient treatment status. All 22 patients showed a broad IFN-gamma ELISPOT response that was proportional to viral load (r = 0.53, p = 0.02), recognizing an average of five to eight peptide pools throughout Gag, Pol, Env, Tat, Rev, and Nef. Intracellular cytokine staining was performed with pools of overlapping peptides corresponding to HIV Gag to distinguish CD8 response from CD4 response. Among untreated patients with increased viral load there was a constant IFN-gamma CD8 response but a declining IFN-gamma CD4 response. HIV-specific IL-2 production was consistently low in CD8 cells but inversely related to viral load in CD4 cells (r = -0.52, p = 0.02). In this crosssectional analysis, time on HAART was associated with an increased frequency of antiviral IFN-gamma- and IL-2-coproducing CD4 cells (r = 0.98, p <0.001), but not of antiviral CD8 cells. Our results suggest that T cells coproducing IL-2 and IFN-gamma are a better marker for immunological competence than T cells producing IFN-gamma alone. They also suggest that HAART may be associated with an improved capacity for IL-2 production by antiviral CD4 T cells in a time-dependent manner. Longitudinal studies are clearly necessary to assess the impact of HAART on these parameters.     

Viral and cellular dynamics in HIV disease

The control mechanisms that maintain a steady-state viral load during chronic HIV-1 infection are critical to understanding the pathophysiology of HIV disease. This paper compares the conceptual features of the two alternative models of viral control, target cell limitation and immune control, with available data on the viral and cellular dynamics of HIV-1 infection and the pattern of changes induced by effective antiretroviral drug therapy. These data suggest that an antigen-driven immune response is the primary control mechanism for in vivo viral growth.     

A dendritic cell-based vaccine for treating HIV infection: background and preliminary results

Antibody response against human immunodeficiency virus-1 (HIV) is ineffective and cellular immune response is not strong enough to achieve the complete suppression or at least a strong control of viral replication in HIV- infected patients. In 2001, we showed in vitro that dendritic cells (DCs) of HIV-infected patients loaded with autologous HIV chemically inactivated by aldrithiol-2 were capable of raising an HIV-specific cellular immune response powerful enough to allow the destruction of autologous HIV- infected CD4 T cells. In 2003, we showed that simian immunodeficiency virus (SIV)-infected macaques vaccinated with inactivated SIV-loaded autologous DCs raised a strong SIV-specific cellular response. Ten months after vaccination, plasma viral load of 7 out of the 10 vaccinated monkeys remained 1000-fold lower than initially. In December 2004, we published results observed in 18 untreated HIV-infected patients vaccinated with autologous monocyte-derived DCs loaded with autologous inactivated HIV. A year following vaccination, 8 patients had a plasma viral load decrease >90%; among them, 4 had viral load <1000 copies mL(-1). Moreover, by one year, the viral load decline of the 18 patients was significantly correlated with their percentage of HIV-1-gag-specific CD8(+) T cells expressing perforin and that of HIV-1-specific CD4(+) T(H)1 cells. This is the first demonstration of the capacity of a therapeutic vaccine to induce an effective HIV-specific T cell response associated with sustained viral suppression in untreated viremic patients. The manipulation of antigen presenting cells to elicit virus-specific cellular responses is a promising tool to control persistant viral infections.     

Quantification of HIV-1-specific T-cell responses at the mucosal cervicovaginal surface

OBJECTIVE: To characterize HIV-1 specific cellular immune responses at mucosal surfaces using a rapid, sensitive enzyme-linked immuno-spot (ELISPOT) technique. DESIGN: Cervicovaginal mononuclear cells obtained from cytobrush and cervicovaginal lavage were assessed for production of interferon-gamma (IFN-gamma) in response to stimulation by HIV-1 antigens. HIV-1 specific responses were compared in a cross-sectional study of two HIV-1-positive patient groups: women not currently on antiretroviral therapy with peripheral CD4 cell counts > 250 x 10(6)/l (n = 12); and women on highly active antiretroviral therapy (HAART) (n = 9). METHODS: Mononuclear cells from peripheral blood or cervicovaginal specimens were assessed in an ELISPOT assay for responses to HIV-1 antigens expressed by recombinant vaccinia viruses. This assay detects primarily CD8 T cells and shows good correlation with MHC class I tetramer staining of cytotoxic T lymphocytes. RESULTS: HIV-1 specific IFN-gamma spot-forming cells were detected in cervicovaginal samples of one out of nine women (11%) on HAART and five out of 12 women (42%) not currently on HAART. In peripheral blood mononuclear cells, HIV-1 specific IFN-gamma spot-forming cells were significantly more numerous in women not currently on HAART than in women on HAART (P = 0.009). In most cases, antigens recognized by mucosal T cells were also recognized by PBMC; however, there were exceptions. CONCLUSIONS: HIV-1-specific antigen-reactive T cells may be detected in routine, noninvasive gynecological specimens. The results suggest that cervicovaginal HIV-1-specific T cells may be less numerous in individuals on HAART than in those not on HAART, as shown previously for HIV-1-specific cytotoxic T lymphocytes in the peripheral blood.     

Evaluation of cellular immune responses in subjects chronically infected with HIV type 1

The importance of host cellular immune responses, particularly CD8(+) cytotoxic T-lymphocyte (CTL) responses, in control of human immunodeficiency virus type 1 (HIV-1) infection has been demonstrated in many clinical studies. These studies, along with vaccination challenge studies in rhesus macaques, indicate the importance of cellular immune responses against HIV-1. Toward this end, we evaluated anti-HIV-1 cellular immune responses in a cohort of 54 subjects who were chronically infected with HIV-1. By validation of IFN-gamma ELISpot assay, we established a dual cut-off criterion for scoring a positive response. The magnitude and frequency of cellular immune responses were measured against HIV-1 antigens (Gag, Pol, Nef, Rev, and Tat), using synthetic peptides as antigens in ELISpot assay. Here we showed that HIV-1 Gag, Pol, and Nef were frequent targets of T cell responses in these subjects, whereas Tat and Rev were less frequently recognized. We further evaluated the possible association between host cellular immune responses and corresponding plasma viral loads in this cohort. By performing ranking correlation analysis, we demonstrated a positive correlation between host viral loads and ELISpot responses of HIV Gag and Pol in untreated subjects. For the subjects under antiviral regimens, however, we did not find any significant association. Our findings suggest that the high levels of ELISpot responses in chronically infected subjects were reflective of their persistent viral infection.     

Amplification of low-frequency antiviral CD8 T cell responses using autologous dendritic cells.

OBJECTIVE: To utilize the potent antigen-presenting capacity of mature dendritic cells (MDC) in order to develop a rapid, sensitive method for quantifying antigen-specific CD8 T cells present at low frequency in peripheral blood. DESIGN: Peripheral blood mononuclear cells (PBMC) were obtained from seven HIV-1-positive individuals with low to moderate CD8 T cell responses, including five on highly active antiretroviral therapy (HAART). IFN-gamma ELISPOT assays were performed using either monocytes or MDC to present antigens expressed by recombinant vaccinia viruses (r-VV). METHODS: Peripheral blood-derived monocytes were cultured for 5-6 days in the presence of IL-4 and granulocyte macrophage colony-stimulating factor, then matured in monocyte-conditioned medium. MDC were infected with r-VV and co-cultured in an ELISPOT assay with autologous monocyte-depleted PBMC. RESULTS: Relative to autologous monocytes, MDC amplified detection of antigen-specific CD8 T cells by 2-30-fold in response to antigens from HIV-1, Epstein-Barr virus and cytomegalovirus. Furthermore, antigenic specificities were revealed that had not been detected using standard ELISPOT of PBMC. CONCLUSION: This assay will prove useful for the detection of memory T cells present at low frequency, and may be of interest for identifying subdominant cytotoxic T lymphocyte epitopes. This method may have broad applications for the detection of antiviral CD8 T cell responses in patient populations in whom such responses have been difficult to detect, including HIV-1-seropositive individuals with advanced disease or undergoing HAART.     

ART-Treated Patients Exhibit an Adaptive Immune Response against the HFVAC Peptides,a Potential HIV-1 Therapeutic Vaccine (Provir/Latitude45 Study)

We proposed a new HIV-1 therapeutic vaccine based on conserved cytotoxic T lymphocyte (CTL) epitopes of archived HIV-1 DNA according to their affinity to the dominant HLA-A and -B alleles of the population investigated. Our proposal (Hla Fitted VAC, HFVAC) was composed of 15 peptides originating from the RT, gag and nef parts of proviral DNA. Our aim was to investigate baseline immune reactivity to the vaccine in HIV-1 chronically infected patients at success of antiretroviral therapy (ART) who would be eligible for a therapeutic vaccine. Forty-one patients were tested. Most of them had been infected with HIV-1 subtype B and all had been receiving successful ART for 2 to 20 years. The predominant HLA-A and -B alleles were those of a Caucasian population. ELISPOT was carried out using the HFVAC peptides. In 22 patients, the PD-1 marker was investigated on CD4+ and CD8+ T cells by flow cytometry in order to evaluate global T cell exhaustion. ELISPOT positivity was 65% overall and 69% in patients exhibiting at least one HLA allele fitting with HFVAC. The percentages of CD4+ and CD8+ T cells expressing PD-1 were high (median values 23.70 and 32.60, respectively), but did not seem to be associated with an impairment of the immune response investigated in vitro. In conclusion, reactivity to HFVAC was high in this ART-treated population with dominant HLA alleles, despite potential cellular exhaustion associated with the PD-1 marker.     

Quantitative and qualitative assessment of human immunodeficiency virus type 1 (HIV-1)-specific CD4+ T cell immunity to gag in HIV-1-infected individuals with differential disease progression: reciprocal interferon-gamma and interleukin-10 responses.

The human immunodeficiency virus type 1 (HIV-1)-specific CD4(+) T cell response was investigated in 33 untreated HIV-1-infected individuals, using highly sensitive ELISPOT assays and intracellular flow cytometry. The median frequencies of interferon (IFN)-gamma-producing HIV-1 gag-specific CD4(+) T cells did not correlate significantly with control of viral replication or progression. HIV-1 gag-specific interleukin (IL)-4-producing cells were rarely detected. Circulating frequencies of CD4(+) T cells constitutively producing IL-10, however, were significantly higher in individuals with progression or active replication. In 17 of 30 HIV-1-infected individuals, gag antigen was observed to induce IL-10 production from CD4(+) T cells. In 2 individuals, early treatment of acute HIV-1 infection "rescued" low to undetectable gag-specific IFN-gamma-producing CD4(+) T cell responses and dramatically down-regulated constitutive IL-10 production from circulating CD4(+) T cells. The detection of HIV-1-specific IL-10-inducing CD4(+) T cells in HIV-1-infected individuals suggests that HIV-1 may directly subvert specific immune responses by IL-10 induction.     

Rare and new V3 loop variants in HIV-1-positive long-term non-progressors from Rwanda

We identified uncommon amino acid substitutions in the V3 loop regions of HIV-1 strains infecting patients from Rwanda. Their frequency was greater in long-term non-progressors (LTNP) compared with late-stage patients (P = 0.006), particularly in a sequence region that has crucial interactions with the cell surface, and is highly relevant for the host's immune response. These variants might reflect a viral response to a strong immune pressure, or represent attenuated HIV-1 strains infecting LTNP in Rwanda.     

Evaluation of modified vaccinia virus Ankara as an alternative vaccine against smallpox in chronically HIV type 1-infected individuals undergoing HAART

The fear of malevolent use of variola virus by terrorists has led to the implementation of a health care worker vaccination program and to the consideration of vaccination for the general public. However, due to concerns about side effects of the classical smallpox vaccine, especially for immunocompromised individuals, a safer vaccine is urgently needed. We characterized the immunogenicity of modified vaccinia virus Ankara (MVA), one of the more promising alternative smallpox vaccines, in a cohort of 10 chronically HIV-1-infected individuals undergoing highly active antiretroviral therapy (HAART). Nine subjects received smallpox vaccination as children while one subject was never vaccinated against smallpox. All the subjects had CD4 counts >400 cells/mm(3) and 8 out of 10 had undetectable viral loads. MVA was able to elicit humoral and cellular immune responses in the majority of individuals. Vaccinia-specific antibodies were mainly of the IgG class while T cells specific to vaccinia were predominantly CD8(+). The immune responses were maintained over 1 year. Similar vaccinia specific humoral immune responses were observed when our cohort of HIV-1-infected individuals was compared to smallpox-vaccinated healthy subjects. The observed immune responses suggest that the highly attenuated MVA could be used as a substitute vaccine against smallpox in chronically HIV-1-infected individuals undergoing HAART.     

Dendritic cell amplification of HIV type 1-specific CD8+ T cell responses in exposed,seronegative heterosexual women

In the Heterosexual AIDS Transmission Study (HATS), the frequency of high-risk sexual activity and viral load in the seropositive partner were shown to correlate with HIV-1 transmission. However, these parameters could not account for the status of some exposed, seronegative (ESN) individuals who remained uninfected despite years of exposure. To test the hypothesis that antiviral immune responses are a correlate of nontransmission in this cohort, we developed two sensitive methods for assessing HIV-1-specific humoral and cell-mediated responses. To quantify T cell responses, autologous mature dendritic cells (DCs) were used as antigen-presenting cells to elicit HIV-1-specific IFN-gamma production by ELISPOT. Antibody responses to HIV-1 gp120 were assessed by combination immunoprecipitation-Western blot (IP-WB). Previous studies of this cohort, using limiting dilution analysis, did not reveal HIV-1-specific cytotoxic T lymphocyte activity. However, when autologous DCs were used to present HIV-1 antigens, T cells from three of eight ESN women (38%) responded by producing IFN-gamma. T cells from three of four seropositive partners responded to HIV-1 antigens, whereas five negative controls did not. The use of DCs as antigen-presenting cells increased sensitivity by 2- to 30-fold relative to standard ELISPOT. Using IP-WB, low levels of gp120-reactive antibodies were detected in plasma from 1 of 14 ESN women. These results support the hypothesis that HIV-1-specific T cell responses play a role in immune surveillance in this cohort of North American serodiscordant couples. This report also demonstrates the ability of dendritic cells to reveal T cell responses that might be overlooked by other methods.     

The virological and immunological consequences of structured treatment interruptions in chronic HIV-1 infection.

BACKGROUND: Some individuals with chronic HIV-1 infection have discontinued their drug therapy with consequent plasma virus rebound. In a small number of patients, a delayed or absent rebound in plasma virus load has been noted after drug cessation, apparently associated with prior drug interruptions and autologous boosting of HIV-1 specific immune responses. We hypothesized that cyclic structured treatment interruptions structured treatment interruptions (STI) could augment HIV-1 specific immune responses in chronic HIV-1 infection, which might help to control HIV-1 replication off therapy. METHODS: We initiated an STI pilot study in 10 antiretroviral treatment-naive HIV-1 chronically infected subjects with baseline CD4 T-cell counts > 500 x 10(6) cells/l and plasma viral load > 5000 copies/ml who received highly active antiretroviral therapy (HAART) for 1 year with good response (plasma viral load < 20 copies/ml for at least 32 weeks). Three cycles of HAART interruption were performed. RESULTS: In all of the patients viral load rebounded, but doubling times increased significantly between the first and third stops (P = 0.008), and by the third stop, six out of nine subjects had a virological set-point after a median 12 months off therapy that was lower than baseline before starting HAART (ranging from 0.6 log(10) to 1.3 log(10) lower than baseline) and in four it remained stable below 5000 copies/ml. Those subjects who controlled viral replication developed significantly stronger HIV-1 specific cellular immune responses than subjects lacking spontaneous decline (P < 0.05). During viral rebounds no genotypic or phenotypic changes conferring resistance to reverse trancriptase inhibitors or protease inhibitors was detected, but mean absolute CD4 T-cell counts declined significantly, although never below 450 x 10(6)/l and the mean value at 12 months off therapy was significantly higher than the pre-treatment level (P = 0.004). CONCLUSIONS: Our findings suggest that STI in chronic HIV-1 infection might augment HIV-1-specific cellular immune responses associated with a spontaneous and sustained drop in plasma viral load in some subjects but at the potential cost of lower CD4 T-cell counts.     

Cross-protection in NYVAC-HIV-1-immunized/HIV-2-challenged but not in NYVAC-HIV-2-immunized/SHIV-challenged rhesus macaques

OBJECTIVES: Immunization with attenuated poxvirus-HIV-1 recombinants followed by protein boosting had protected four of eight rhesus macaques from HIV-2SBL6669 challenge. The present study was designed to confirm this result and to conduct the reciprocal cross-protection experiment. METHODS: Twenty-four macaques were primed with NYVAC (a genetically attenuated Copenhagen vaccinia strain) recombinants with HIV-1 and HIV-2 env and gag-pol or NYVAC vector alone and boosted with homologous, oligomeric gp160 proteins or adjuvant only. Binding and neutralizing antibodies, cytotoxic T-lymphocytes (CTL) and CD8 T cell antiviral activity (CD8AA) were evaluated. One half of each immunization and control group were intravenously challenged with SHIV(HXB2) the other half was challenged with HIV-2SBL6669,. Protective outcome was assessed by monitoring virus isolation, proviral DNA and plasma viral RNA. RESULTS: Both immunization groups developed homologous binding antibodies; however, homologous neutralizing antibodies were only observed in NYVAC-HIV-2-immunized macaques. While no cross-reactive neutralizing antibodies were detected, both immunization groups displayed cross-reactive CTL. Significant CD8AA was observed for only one NYVAC-HIV-2-immunized macaque. Virological assessments verified that both NYVAC-HIV-1 and NYVAC-HIV-2 immunization significantly reduced viral burdens and partially protected against HIV-2 challenge, although cross-protection was not at the level that had been previously reported. Humoral antibody and/or CTL and CD8AA were associated with protection against homologous HIV-2 challenge, while cellular immune responses seemed more important for cross-protection. No significant protection was observed in the SHIV-challenged macaques, although NYVAC-HIV-1 immunization resulted in significantly lower viral burdens compared with controls. CONCLUSIONS: Further delineation of cross-reactive mechanisms may aid in the development of a broadly protective vaccine.     

Characterization of Immune Responses Induced by Combined Clade-A HIV-1 Recombinant Adenovectors in Mice

Background: Numerous evidences indicate that in some HIV-1 positive patients, the humoral and cellular immune responses are induced against HIV-1 proteins and this is inversely related to the progress of infection. Objective: The aim of this study was the evaluation of the Adenovectors containing HIV genes in induction of immune responses in mice. Methods: The HIV-1 genes including gag p24, rev, nef and exon-1 of tat were amplified from HIV-1 RNA (clade-A). The cDNA of each gene was cloned into a transfer vector. The transfer vector was then co-transformed into E. coli strain BJ5183 together with pAdenovector ΔE1/E3. The recombinant adenoviral construct was transfected into QBI-293A cells. Recombinant viruses were purified and titrated on 293 cell plates. Expression of transgenes was evaluated using western blotting. Then 1012 viral particles were injected into 15 groups of 5 mice and all patterns of combination of these 4 HIV-1 genes were evaluated. After 2 weeks, humoral and cellular immune responses were evaluated using ELISA, cell proliferation and ELISpot (IL-2, IL-4 and IFN-γ) assays, consecutively. Results: It was demonstrated that each gene was expressed. The response targets were mostly toward Th1, though several Th2 responses were also observed. Single injection in our study induced a good cellular response but the humoral responses were not as strong as the cellular ones. Conclusion: Considering and comparing all results and evaluating the various possible interactions revealed that simultaneous injection of tat and gag has enhanced the humoral and cellular responses.     

Combined Immunization of Mice with DNA, rMVA and rAd5 Expressing HIV-1 Structural Genes from Different Subtypes

The objective of present paper is to study the immunogenicity of combinations of multiple vector vaccines expressing HIV-1 structural genes from different subtypes. Mice were vaccinated with DNA (B'/C) and rMVA (B'/C) vaccines expressing B'/C recombinant subtype gag-pol and env genes, DNA (B') and rAd5 (B') vaccines expressing subtype B' gag gene with different combination schemes. HIV-1 Gag-specific cellular immune responses and P24- specific IgG levels were analyzed by IFN-γ enzyme-linked immunospot assay (ELISPOT) and enzyme-linked immunosorbent assay (ELISA) respectively. ELISPOT results indicated that the Gag-specific cellular immune responses induced by combination of three vaccines were much higher than that induced by combination of two vaccines. Among the groups of mice immunized with two vaccines, the groups with rAd5 booster elicited higher cellular immune responses compared with the groups with rMVA booster. All the test groups of three vaccines in combination could induce similar level of cellular immune responses, which did not correlate with the immunization order. ELISA results showed that p24- specific IgG induced by combination of three vaccines were much higher than that induced by combination of two vaccines. It indicates that the combination scheme of multiple vector vaccines maybe a promising AIDS vaccine strategy.     

CCR5 receptor expression is down-regulated in HIV type 2 infection: implication for viral control and protection

HIV-2 is known to display an attenuated phenotype in vivo with prolonged time to disease and decreased rate of transmission. Observational studies in Senegal have demonstrated protection from HIV-1 infection, although the putative mechanism for immunoprotection remains undefined. We evaluated HIV-2-seropositive women from a cohort of commercial sex workers in Dakar, Senegal and identified individuals with very low surface CCR5 receptor expression on CD4+ T cells. In vitro up-regulation of the CCR5 receptor was readily achieved. Down-regulation of the CCR5 was not correlated with activation markers (HLA-DR), beta-chemokine levels, or plasma viral loads. A correlation was observed with HIV-2-specific CD8+ T cell activity as measured by intracellular cytokine production. We postulate that down-regulation of the CCR5 receptor in HIV-2 infection contributes to slower disease course and to the protective mechanism against HIV-1 superinfection, mediated in part by HIV-2-specific cellular immune responses.     

Non-polarized cytokine profile of a long-term non-progressor HIV infected patient

The HIV-1 initial viral infection may present diverse clinical and laboratory course and lead to rapid, intermediate, or long-term progression. Among the group of non-progressors, the elite controllers are those who control the infection most effectively, in the absence of antiretroviral therapy (ART). In this paper, the TH1, TH2 and TH17 cytokines profiles are described, as well as clinical and laboratory aspects of an HIV-infected patient with undetectable viral load without antiretroviral therapy. Production of IL-6, IL-10, TNF-α, IFN-γ, and IL-17 was detected; in contrast IL-4 was identified. Host-related factors could help explain such a level of infection control, namely the differentiated modulation of the cellular immune response and a non-polarized cytokine response of the TH1 and TH2 profiles.     

Virus-specific cytotoxic T-lymphocytes in HIV-2-infected cynomolgus macaques.

OBJECTIVE: Specific cytotoxic T-lymphocytes (CTL) are induced in humans or monkeys after infection with HIV-1 or SIVmac, respectively. Since, like HIV-1, HIV-2 causes AIDS, our objective was to determine the characteristics of the HIV-2-specific CTL response. DESIGN: Since it is rarely possible to study cellular immunity in individuals, because of the small number of HIV-2-infected patients available in Europe and the necessity for co-operation in the performance of sequential CTL assays, cynomolgus macaques were infected with HIV-2. Autologous transformed B-lymphoblastoid cell lines infected with recombinant vaccinia viruses were used as target cells for cytotoxicity assays. METHODS: Recombinant vaccinia viruses expressing HIV-2 genes were constructed to infect B-lymphoblastoid cell lines from macaques. These cells were used as target cells for cytotoxicity assays with peripheral blood mononuclear cells from HIV-2BEN-infected cynomolgus macaques. To characterize the effector cells, CD8+ cells were separated with immunomagnetic beads. Major histocompatibility complex (MHC) restriction of the cytotoxic cells was determined by incubation with matched or mismatched target cells. RESULTS: HIV-2BEN-infected cynomolgus macaques raised CTL against proteins of the three major viral structural genes, gag, pol and env. The cytotoxic cells were CD8+ and their activity was MHC class I-restricted. In contrast to SIVmac-infected macaques, env-specific lysis was mediated exclusively by CD8+ cells. CTL from individual animals recognized different viral proteins and the recognition pattern varied over time. CONCLUSIONS: Like HIV-1 and SIVmac, HIV-2 induces virus-specific CTL. The variation of antigen recognition between individual animals and over time indicates that sequential experiments are necessary to determine the complete spectrum of the CTL response of infected animals. HIV-2-infected macaques represent a suitable model for investigations into the cellular immune response against HIV.