Long-term survivors of HIV-1 infection

Long-Term Non-Progression and Broad HIV-1-Specific Proliferative T-Cell Responses

Complex mechanisms underlying the maintenance of fully functional, proliferative, HIV-1-specific T-cell responses involve processes from early T-cell development through to the final stages of T-cell differentiation and antigen recognition. Virus-specific proliferative CD4 and CD8 T-cell responses, important for the control of infection, are observed in some HIV-1(+) patients during early stages of disease, and are maintained in long-term non-progressing subjects. In the vast majority of HIV-1(+) patients, full immune functionality is lost when proliferative HIV-1-specific T-cell responses undergo a variable progressive decline throughout the course of chronic infection. This appears irreparable despite administration of potent combination antiretroviral therapy, which to date is non-curative, necessitating life-long administration and the development of effective, novel, therapeutic interventions. While a sterilizing cure, involving clearance of virus from the host, remains a primary aim, a "functional cure" may be a more feasible goal with considerable impact on worldwide HIV-1 infection. Such an approach would enable long-term co-existence of host and virus in the absence of toxic and costly drugs. Effective immune homeostasis coupled with a balanced response appropriately targeting conserved viral antigens, in a manner that avoids hyperactivation and exhaustion, may prove to be the strongest correlate of durable viral control. This review describes novel concepts underlying full immune functionality in the context of HIV-1 infection, which may be utilized in future strategies designed to improve upon existing therapy. The aim will be to induce long-term non-progressor or elite controller status in every infected host, through immune-mediated control of viremia and reduction of viral reservoirs, leading to lower HIV-1 transmission rates.

Immune and viral correlates of "secondary viral control" after treatment interruption in chronically HIV-1 infected patients

Upon interruption of antiretroviral therapy, HIV-infected patients usually show viral load rebound to pre-treatment levels. Four patients, hereafter referred to as secondary controllers (SC), were identified who initiated therapy during chronic infection and, after stopping treatment, could control virus replication at undetectable levels for more than six months. In the present study we set out to unravel possible viral and immune parameters or mechanisms of this phenomenon by comparing secondary controllers with elite controllers and non-controllers, including patients under HAART. As candidate correlates of protection, virus growth kinetics, levels of intracellular viral markers, several aspects of HIV-specific CD4+ and CD8+ T cell function and HIV neutralizing antibodies were investigated. As expected all intracellular viral markers were lower in aviremic as compared to viremic subjects, but in addition both elite and secondary controllers had lower levels of viral unspliced RNA in PBMC as compared to patients on HAART. Ex vivo cultivation of the virus from CD4+ T cells of SC consistently failed in one patient and showed delayed kinetics in the three others. Formal in vitro replication studies of these three viruses showed low to absent growth in two cases and a virus with normal fitness in the third case. T cell responses toward HIV peptides, evaluated in IFN-γ ELISPOT, revealed no significant differences in breadth, magnitude or avidity between SC and all other patient groups. Neither was there a difference in polyfunctionality of CD4+ or CD8+ T cells, as evaluated with intracellular cytokine staining. However, secondary and elite controllers showed higher proliferative responses to Gag and Pol peptides. SC also showed the highest level of autologous neutralizing antibodies. These data suggest that higher T cell proliferative responses and lower replication kinetics might be instrumental in secondary viral control in the absence of treatment.

Are long-term non-progressors very slow progressors? Insights from the Chelsea and Westminster HIV cohort, 1988-2010

Define and identify long-term non-progressors (LTNP) and HIV controllers (HIC), and estimate time until disease progression. LTNP are HIV-1⁺ patients who maintain stable CD4⁺ T-cell counts, with no history of opportunistic infection or antiretroviral therapy (ART). HIC are a subset of LTNP who additionally have undetectable viraemia. These individuals may provide insights for prophylactic and therapeutic development. Records of HIV-1⁺ individuals attending Chelsea and Westminster Hospital (1988–2010), were analysed. LTNP were defined as: HIV-1⁺ for >7 years; ART-naïve; no history of opportunistic infection and normal, stable CD4⁺ T-cell counts. MIXED procedure in SAS using random intercept model identified long-term stable CD4⁺ T-cell counts. Survival analysis estimated time since diagnosis until disease progression. Subjects exhibiting long-term stable CD4⁺ T-cell counts with history below the normal range (<450 cells/µl blood) were compared to LTNP whose CD4⁺ T-cell count always remained normal. Within these two groups subjects with HIV-1 RNA load below limit of detection (BLD) were identified. Of 14,227 patients, 1,204 were diagnosed HIV-1⁺ over 7 years ago and were ART-naïve. Estimated time until disease progression for the 20% (239) whose CD4⁺ T-cell counts remained within the normal range, was 6.2 years (IQR: 2.0 to 9.6); significantly longer than 4.0 years (IQR: 1.0 to 7.3) for patients with historical CD4⁺ T-cell count below normal (Logrank chi-squared = 21.26; p<0.001). Within a subpopulation of 312 asymptomatic patients, 50 exhibited long-term stable CD4⁺ T-cell counts. Of these, 13 were LTNP, one of whom met HIC criteria. Of the remaining 37 patients with long-term stable low CD4⁺ T-cell counts, 3 controlled HIV-1 RNA load BLD. Individuals with stable, normal CD4⁺ T-cell counts progressed less rapidly than those with low CD4⁺ T-cell counts. Few LTNP and HIC identified in this and other studies, endorse the need for universal definitions to facilitate comparison.

The emerging role of HLA-C in HIV-1 infection

Recently, genome-wide association studies have identified the major histocompatibility complex class I protein HLA-C as an important molecule that affects HIV disease progression. The association between HLA-C and HIV disease outcome was originally determined through a single nucleotide polymorphism (SNP) 35 kb upstream of the HLA-C locus. More recent work has focused on elucidating the functional significance of the -35 SNP, and several groups now have demonstrated HLA-C surface expression to be a key element in control of HIV viral load, with higher surface expression associating with slower disease progression. Most recently, control of HLA-C surface expression has been correlated with the presence of microRNA binding sites that affect HLA-C expression and control of HIV disease. This review highlights these results and explores the ways in which HLA-C surface expression could affect immune system function in the setting of HIV disease.

Daily sampling of an HIV-1 patient with slowly progressing disease displays persistence of multiple env subpopulations consistent with neutrality

The molecular evolution of HIV-1 is characterized by frequent substitutions, indels and recombination events. In addition, a HIV-1 population may adapt through frequency changes of its variants. To reveal such population dynamics we analyzed HIV-1 subpopulation frequencies in an untreated patient with stable, low plasma HIV-1 RNA levels and close to normal CD4+ T-cell levels. The patient was intensively sampled during a 32-day period as well as approximately 1.5 years before and after this period (days −664, 1, 2, 3, 11, 18, 25, 32 and 522). 77 sequences of HIV-1 env (approximately 3100 nucleotides) were obtained from plasma by limiting dilution with 7–11 sequences per time point, except day −664. Phylogenetic analysis using maximum likelihood methods showed that the sequences clustered in six distinct subpopulations. We devised a method that took into account the relatively coarse sampling of the population. Data from days 1 through 32 were consistent with constant within-patient subpopulation frequencies. However, over longer time periods, i.e. between days 1…32 and 522, there were significant changes in subpopulation frequencies, which were consistent with evolutionarily neutral fluctuations. We found no clear signal of natural selection within the subpopulations over the study period, but positive selection was evident on the long branches that connected the subpopulations, which corresponds to >3 years as the subpopulations already were established when we started the study. Thus, selective forces may have been involved when the subpopulations were established. Genetic drift within subpopulations caused by de novo substitutions could be resolved after approximately one month. Overall, we conclude that subpopulation frequencies within this patient changed significantly over a time period of 1.5 years, but that this does not imply directional or balancing selection. We show that the short-term evolution we study here is likely representative for many patients of slow and normal disease progression.

Genome-wide association scan in HIV-1-infected individuals identifying variants influencing disease course

Background

AIDS develops typically after 7–11 years of untreated HIV-1 infection, with extremes of very rapid disease progression (<2 years) and long-term non-progression (>15 years). To reveal additional host genetic factors that may impact on the clinical course of HIV-1 infection, we designed a genome-wide association study (GWAS) in 404 participants of the Amsterdam Cohort Studies on HIV-1 infection and AIDS.

Methods

The association of SNP genotypes with the clinical course of HIV-1 infection was tested in Cox regression survival analyses using AIDS-diagnosis and AIDS-related death as endpoints.

Results

Multiple, not previously identified SNPs, were identified to be strongly associated with disease progression after HIV-1 infection, albeit not genome-wide significant. However, three independent SNPs in the top ten associations between SNP genotypes and time between seroconversion and AIDS-diagnosis, and one from the top ten associations between SNP genotypes and time between seroconversion and AIDS-related death, had P-values smaller than 0.05 in the French Genomics of Resistance to Immunodeficiency Virus cohort on disease progression.

Conclusions

Our study emphasizes that the use of different phenotypes in GWAS may be useful to unravel the full spectrum of host genetic factors that may be associated with the clinical course of HIV-1 infection.

Increased breadth and depth of cytotoxic T lymphocytes responses against HIV-1-B Nef by inclusion of epitope variant sequences

Different vaccine approaches cope with HIV-1 diversity, ranging from centralized^1–4 to variability-encompassing^5–7 antigens. For all these strategies, a concern remains: how does HIV-1 diversity impact epitope recognition by the immune system? We studied the relationship between HIV-1 diversity and CD8⁺ T Lymphocytes (CTL) targeting of HIV-1 subtype B Nef using 944 peptides (10-mers overlapping by nine amino acids (AA)) that corresponded to consensus peptides and their most common variants in the HIV-1-B virus population. IFN-γ ELISpot assays were performed using freshly isolated PBMC from 26 HIV-1-infected persons. Three hundred and fifty peptides elicited a response in at least one individual. Individuals targeted a median of 7 discrete regions. Overall, 33% of responses were directed against viral variants but not elicited against consensus-based test peptides. However, there was no significant relationship between the frequency of a 10-mer in the viral population and either its frequency of recognition (Spearman's correlation coefficient ρ = 0.24) or the magnitude of the responses (ρ = 0.16). We found that peptides with a single mutation compared to the consensus were likely to be recognized (especially if the change was conservative) and to elicit responses of similar magnitude as the consensus peptide. Our results indicate that cross-reactivity between rare and frequent variants is likely to play a role in the expansion of CTL responses, and that maximizing antigenic diversity in a vaccine may increase the breadth and depth of CTL responses. However, since there are few obvious preferred pathways to virologic escape, the diversity that may be required to block all potential escape pathways may be too large for a realistic vaccine to accommodate. Furthermore, since peptides were not recognized based on their frequency in the population, it remains unclear by which mechanisms variability-inclusive antigens (i.e., constructs enriched with frequent variants) expand CTL recognition.

Correlation between HIV-1 seropositivity and prevalence of a gamma-secretase polymorphism in two distinct ethnic populations

Susceptibility for human immunodeficiency virus type 1 (HIV-1) infection may be influenced by host genetics. Recent findings with a Wistar rat model raised the possibility that the gamma-secretase pathway may be associated with an individual's susceptibility to infection. A functional single-nucleotide polymorphism (SNP) in the gamma-secretase component APH1B (Phe217Leu; rs1047552) was therefore analyzed for association with HIV-1 infection. The SNP showed a tendency for association with HIV-1 infection in a Xhosa indigenous South African Bantu study (P = 0.087), and associated significantly in a Caucasian Dutch study (P = 0.049). Together, the results suggest a role for the gamma-secretase pathway in susceptibility to HIV-1 infection.

Defective human immunodeficiency virus-specific CD8+ T-cell polyfunctionality, proliferation, and cytotoxicity are not restored by antiretroviral therapy

Identifying the functions of human immunodeficiency virus (HIV)-specific CD8+ T cells that are not merely modulated by the level of virus but clearly distinguish patients with immune control from those without such control is of paramount importance. Features of the HIV-specific CD8+ T-cell response in antiretroviral-treated patients (designated Rx <50) and untreated patients (long-term nonprogressors [LTNP]) matched for very low HIV RNA levels were comprehensively examined. The proliferative capacity of HIV-specific CD8+ T cells was not restored in Rx <50 to the level observed in LTNP, even though HIV-specific CD4+ T-cell proliferation in the two patient groups was comparable. This diminished HIV-specific CD8+ T-cell proliferation in Rx <50 was primarily due to a smaller fraction of antigen-specific cells recruited to divide and not to the numbers of divisions that proliferating cells had undergone. Exogenous interleukin-2 (IL-2) induced proliferating cells to divide further but did not rescue the majority of antigen-specific cells with defective proliferation. In addition, differences in HIV-specific CD8+ T-cell proliferation could not be attributed to differences in cellular subsets bearing a memory phenotype, IL-2 production, or PD-1 expression. Although polyfunctionality of HIV-specific CD8+ T cells in Rx <50 was not restored to the levels observed in LTNP despite prolonged suppression of HIV RNA levels, per-cell cytotoxic capacity was the functional feature that most clearly distinguished the cells of LTNP from those of Rx <50. Taken together, these data suggest that there are selective qualitative abnormalities within the HIV-specific CD8+ T-cell compartment that persist under conditions of low levels of antigen.

Association of HLA-C and HCP5 gene regions with the clinical course of HIV-1 infection

BACKGROUND

Recently, a genome-wide association analysis revealed single-nucleotide polymorphisms (SNPs) in the gene regions of HLA-C and HCP5 to be associated with viral load at set point and SNPs in the RNF39/ZNRD1 gene region to be associated with HIV-1 disease course.

METHODS

We studied whether the association of these SNPs with viral load at set point could be replicated and whether these SNPs also associated with other clinical outcomes of HIV-1 infection in 335 HIV-1-infected homosexual participants from the Amsterdam Cohort Studies on HIV infection and AIDS (ACS).

RESULTS

Significant associations between the minor allele variants of SNPs HLA-C rs9264942 and HCP5 rs2395029 and a lower viral load at set point could be replicated in the ACS. Moreover, these SNPs were significantly associated with delayed progression to AIDS, AIDS-related death, and a CD4 T-cell count below 400 cells/mul. Both minor allele variants were independent predictors of disease progression, also when a CCR5 Delta32 heterozygous genotype was included in the analysis. However, predictive value was not independent from viral load and CD4 T-cell count at set point. The SNPs in the RNF39/ZNRD1 gene region were associated with set point CD4 T-cell count but not with disease course in the ACS.

CONCLUSION

The minor allele variants of SNPs in the HLA-C and HCP5 gene regions are also in the ACS associated with a lower viral load at set point and additionally with delayed HIV-1 disease progression. The association of these SNPs with the relatively early course of infection may help unravel their mode of action.

Knowledge of their children's HIV status in HIV-positive mothers attending a genitourinary medicine clinic in the UK

OBJECTIVES

To determine whether HIV-infected mothers knew the HIV status of their children, enabling the offer of targeted testing of children at risk.

METHODS

All HIV-positive women attending the genitourinary medicine clinic at a district general hospital in the United Kingdom were asked whether they had children and the age, HIV status and residence of their children using a standardized proforma.

RESULTS

A total of 297 HIV-positive women were included in a prospective audit. Two hundred and fifty-four women had 551 offspring; 143 had a total of 217 children aged <16 years. Of those children, 118 lived in the United Kingdom. Of the 99 children living abroad, 71% were living in Zimbabwe, 21% in other African countries (Zambia, Kenya, Burundi, Malawi and South Africa) and 5% in Jamaica and other Caribbean countries. Of the 118 children living in the UK, mothers knew the HIV status in 49 (42%), of whom nine (18%) were HIV positive. A further two older offspring were also HIV positive. Mothers were aware of the HIV status in significantly fewer children staying in the country of origin: nine (9%; P<0.05), of whom four were known to be HIV positive. All HIV-positive children living in the United Kingdom were under the care of paediatricians with special expertise in paediatric HIV infection.

CONCLUSIONS

The HIV status of the majority of children of HIV-positive immigrant mothers is unknown, particularly those children who remain in their country of origin.

Slow progression of HIV-1 infection in a cohort of antiretroviral naïve hotel workers in Dar es Salaam, Tanzania as defined by their CD4 cell slopes

Data on slow progression following HIV-1 infection in Africa are sparse. From a study on the natural history of HIV-1 infection in Dar es Salaam, Tanzania, an analysis of immunological and clinical data from 237 HIV-1 seropositive individuals was performed. Annual CD4 cell determinations were carried out by flow cytometry. None was on antiretroviral treatment. CD4+ cell slopes were obtained by fitting a linear regression model. A study population of 50 individuals with >3 CD4 cell determinations and followed for >5 y had a mean follow-up of 72.7 months, and mean 5.7 CD4+ cell determinations. With a criterion of maintaining a CD4 cell count >or=500 cells/ml, 8 of the 50 (16.0%) were long-term non-progressors (LTNP). With a definition of maintaining a CD4+ cell slope <or=-10 (a loss of 10 or less cells per y), 13 (26.0%) were long-term slow progressors (LTSP). 11 of them (84.6%) had a baseline CD4 cell count <500 cells/microl and 5(38.5%) had a baseline CD4 cell count less than 350 cells/microl. An analysis of the selection bias introduced during slope determination is presented. With no selection, 24 (23.3%) would have documented slow CD4 progression among those enrolled for 5 or more y regardless of CD4 determinations.

Development and studies of the anti-R7V neutralizing antibody ELISA test: a new serological test for HIV seropositive patients

A new peptide-based ELISA test developed for the detection of anti-R7V specific antibodies in the sera of HIV seropositive patients is described. HIV virus acquires a cellular antigen at the moment the virus is released by budding, the R7V epitope. Certain patients produce anti-R7V Ab which are described as having the capacity to neutralize in vitro cell infection by HIV. Anti-R7V Ab are also detected in asymptomatic patients who have a lower likelihood of progressing to AIDS. Tested with 449 serum samples, the prevalence of anti-R7V Ab was 53.2% in HIV positive patients and 5.5% in HIV negative subjects. According to the duration of infection, the seroprevalence reaches almost 80% of non-treated long-term infected patients. Other retrospective studies were conducted on 308 HIV positive samples; the presence of anti-R7V Ab was significantly higher for 177 asymptomatic patients (64.4%) compared to the 131 symptomatic patients (35.1%). Regarding their neutralizing ability, anti-R7V antibodies were detected at the highest percentage in asymptomatic HIV-infected patients naive of treatment. Besides conventional biological parameters (CD4 and viral load), the detection of anti-R7V antibodies could be proposed to clinicians as an additional tool to manage treatment initiation and to improve the psychological state of their asymptomatic patients.

Host genetics of HIV-1 susceptibility

Susceptibility to HIV-1 and the rate of disease progression reflect the influence of the genetic diversity of the virus as well as the variation in host factors. The virus will co-evolve with the host, escaping and adapting to host-determined influences. Dominant host factors currently identified include diversity in the major histocompatibility complex class I, and alleles of chemokine, chemokine receptor and cytokine genes. Recent work proposes new variants in life cycle genes and in antiviral innate defense, which modify HIV-1 susceptibility. Comparative genomics generates information on host cell barriers that may explain the current distribution of these viruses among human and nonhuman primates. A greater understanding of the genetic basis of human susceptibility to HIV-1 contributes to an understanding of the pathogenesis of the disease, helps identify new targets for prophylaxis and vaccine development and will lead to predictive tools to identify those at risk of rapid disease progression.

Evaluation of SIV-lipopeptide immunizations administered by the intradermal route in their ability to induce antigen specific T-cell responses in rhesus macaques

Numerous clinical and experimental observations have shown that cellular immunity, in particular CD8+ T-lymphocytes, plays an important role in the control of HIV infection. We have focused on a lipopeptide vaccination strategy that has been shown to induce polyepitopic T-cell responses in both animals and humans, in order to deliver simian immunodeficiency virus (SIV) antigens to rhesus macaques. Given the relevance of antigen administration route in the development of an effective cellular immune response, this study was designed to assess SIV lipopeptide immunizations administered either by the intradermal (ID) or the intramuscular (IM) routes in their ability to elicit GAG and NEF multispecific T-lymphocytes in the rhesus macaque. Antigen specific T-cell responses were observed between 7 and 11 weeks following vaccination in both groups. Macaques immunized by the IM route yielded antigen-specific IFN-gamma secreting lymphocytes in response to no more than two pools of peptides derived from SIV-NEF. In contrast, among the four ID-immunized macaques, two presented multi-specific T-cell responses to as many as four pools of SIV-NEF and/or GAG peptides. Responses persisted 16 weeks following the vaccination protocol in one of the ID-vaccinated macaques. The induction of such responses is of great clinical relevance in the development of an effective HIV vaccine. Given the crucial role of CD8+ T-lymphocytes in HIV/SIV containment, vaccination through the intradermal route should merit high consideration in the development of an AIDS vaccine.

Specific nature of cellular immune responses elicited by chimpanzees against HIV-1

Recent epidemiologic and phylogenetic analyses suggest that in the human population human immunodeficiency virus (HIV-1) is a relatively new pathogen that arose by zoonotic transmission from chimpanzees. In humans the morbidity and mortality figures due to HIV infection are extremely high. In a very small percentage of the human population, however, individuals have been identified who were infected for more than 20 years and have no evidence of disease progression. In contrast to most infected humans, almost all chimpanzees appear to be resistant to the pathologic effects caused by lentiviruses such as HIV-1. Here we review the characteristics of the HIV-1-specific cell-mediated immune responses mounted by chimpanzees, and we postulate the mechanisms that have evolved that facilitate their resistance to acquired immunodeficiency syndrome.

Longitudinal study of humoral immune responses in HIV type 1 subtype CRF01_AE (E)-infected Thai patients with different rates of disease progression

Identification of immune correlates associated with disease progression will provide information for HIV-1 vaccine design in countries such as Thailand, where the prevalent subtypes (B and CRF01_AE [E]) are characterized. In this study, plasma viral load and humoral immune responses were measured in 20 HIV-1 subtype E-infected Thai patients with different rates of disease progression, based on CD4(+) T cell decline and clinical symptoms. Nine progressors (PRs) and 11 slower progressors (SPs) were evaluated. CD4(+) T cell counts were inversely correlated with viral load (p = 0.004) and positively correlated with p24 Ab (p = 0.022). In progressors, p24 Ab showed a significant decrease (p < 0.001) over time. V3 and gp41 Ab did not change significantly in either group. Both CD4-binding site (CD4/gp120BS) and gp120 titers correlated positively with neutralizing antibody (NAb) against both a subtype E cell line-adapted virus (NP03) and a primary isolate (TH023). However, V3 Ab correlated only with NAb against NP03 (p < 0.001). Increased NAb over time was observed more frequently in SPs as compared with PRs, against both the TH023 (p = 0.004) and NPO3 (p = 0.004) viruses. Cross-clade antibody-dependent cellular cytotoxicity was demonstrated in both groups. These data suggest that in HIV-1 subtype E infection, declining p24 Ab titer is a predictive marker of disease progression, as described for subtype B. Furthermore, in subtype E-infected patients, slower progressors retain the immune competence to develop new antibody responses to Env over time; these evolving responses may contribute to prolonged survival during HIV-1 disease progression.

Could TCR antagonism explain associations between MHC genes and disease?

Alleles of major histocompatibility complex (MHC) loci are associated with certain types of diseases, including those of infectious and autoimmune origin. MHC products can promote susceptibility or resistance to disease by stimulating or inhibiting immune responses. Recent evidence suggests that MHC-associated peptides derived from self-proteins can act as antagonists of T-cell activation, thereby inhibiting immune responses to antigens. We suggest that self-peptide-promoted antagonism might explain some associations between MHC alleles and particular chronic diseases.

HIV-1-Specific CD4 helper function in persons with chronic HIV-1 infection on antiviral drug therapy as measured by ELISPOT after treatment with an inactivated, gp120-depleted HIV-1 in incomplete Freund's adjuvant

OBJECTIVE

We hypothesized that treatment of HIV-1-seropositive study subjects receiving potent antiviral therapy with an HIV-specific immune-based therapy would increase HIV-1-specific T-helper immune function.

DESIGN

10 HIV-1-seropositive study subjects receiving antiretroviral therapy were treated with an inactivated, gp120-depleted immunogen in IFA (HIV-1 immunogen, Remune) at baseline, week 12, and week 24.

METHODS

The frequency of HIV-1 antigen-stimulated interferon-gamma (IFN-gamma)-producing cells was determined by the ELISPOT assay.

RESULTS

Study subjects significantly increased their frequency of HIV-1-stimulated (p <. 001) or p24 antigen-stimulated (p <.01) IFN-gamma-producing cells after one, two, and three treatments of HIV-1 immunogen. Depletion of CD4 cells resulted in the strongest abrogation of the IFN-gamma response. The frequency of HIV-1 (r = 0.64; p =.0002) and p24 (r = 0. 72; p <.001) antigen-stimulated IFN-gamma-producing cells in the CD8-depleted population before and after treatment was associated with the lymphocyte-proliferative response.

CONCLUSIONS

Treatment with HIV-1 immunogen significantly enhanced the frequency of HIV-1-specific IFN-gamma-producing cells. Studies are ongoing to determine the relationship between this reversal of HIV-specific anergy and virologic outcomes.

Early highly active antiretroviral therapy for acute HIV-1 infection preserves immune function of CD8+ and CD4+ T lymphocytes

Highly active antiretroviral therapy (HAART) has been advocated for the management of primary HIV-1 infection without clear understanding of its immunological effects. Here, we demonstrate that early use of HAART during primary infection preserves HIV-specific CD8(+) T cells physically and functionally while HIV-specific T cell help is sustained. We also show that even transient administration of HAART at seroconversion can preserve HIV-specific immunity. In contrast, delayed initiation of HAART is associated with a progressive loss of HIV-specific CD8(+) T cells and absent HIV-specific T cell help. These results imply that HIV-specific T help is damaged during primary HIV-1 infection. Early drug treatment, which preserves this immunity, also preserves HIV-specific CD8(+) T cells. These results have implications for understanding the early pathogenesis of HIV-1 infection and suggest that acute HIV infection should be treated aggressively and as early as possible.

Lymphoproliferative response to HIV type 1 p24 in long-term survivors of HIV type 1 infection is predictive of persistent AIDS-free infection

To establish immunologic correlates of progression to AIDS in long-term survivors of HIV-1 infection, HIV-1-specific T cell-mediated responses, together with T cell reactivity to recall antigens, were studied in frozen samples collected after 5 and 8 years of documented HIV-1 infection. Eight of 21 homosexual men, who remained asymptomatic and maintained CD4+ T cell numbers >400 cells/microl for 9 years of HIV-1 infection, progressed to AIDS (CDC 1993 definition) within 12.5 years of infection (late progressors, LPs). The remainders showed minimal deterioration of immune parameters (long-term nonprogressors, LTNPs). CD4+ T cell numbers and T cell function measured at years 5 and 8 of follow-up were comparable in the two groups. At both time points responses to recall antigens did not significantly differ between the two groups, although a significant decline of lymphoproliferative responses to Candida and tetanus toxoid was observed in LPs. Circulating HIV-1-specific cytotoxic T lymphocyte precursors were found in broad frequency ranges in both LPs and LTNPs and, similarly, no significant differences were found in comparing the breadth of serum neutralizing activity against heterologous HIV-1 primary isolates. In contrast, lymphoproliferative responses to p24gag, but not p17gag or gp160env, were detected only in LTNPs and were totally absent in LPs at both time points (p < 0.01). Our data suggest that the presence of circulating p24-specific CD4+ T cells may reflect effective viral control and be predictive of subsequent favorable clinical course in long-term asymptomatic individuals.

Conserved CTL Epitopes Shared Between HIV-Infected Human Long-Term Survivors and Chimpanzees

Certain HIV-1 infected humans that do not progress to AIDS have been documented to share particular MHC class I alleles that appear to correlate with long-term survival. HIV-1-infected chimpanzees are relatively resistant to progression to AIDS. Out of a group of 10 chimpanzees with CTL activity and nonprogressive HIV-1 infection, 2 animals with prominent cytolytic CD3+CD8+ T cell responses to HIV-1 Ags were studied in detail. Characterization of these CTL revealed that they contained the granzymes A and B, T cell intracellular Ag-1, and perforin and induced calcium-dependent cytolysis that correlated with the presence of apoptotic nuclei in target cells. These CTL responses were directed against two gagpeptides, which were found to be identical to previously described epitopes recognized in the context of HLA-B27 and HLA-B57 molecules. The latter two restriction elements occur with increased frequency in human long-term survivor cohorts. Phylogenetic comparisons revealed that the chimpanzee restriction elements, Patr-B*02and -B*03, described here do not show any obvious similarity with the HLA-B*27 and -B*57 alleles, suggesting that CTL responses to HIV-1 in distinct primate species may be controlled by different types of HLA-B-like molecules. The CTL responses in these two chimpanzees are directed, however, against highly conserved epitopes mapping across the majority of HIV-1 clades.

Neutralizing antibodies are positively associated with CD4+ T-cell counts and T-cell function in long-term AIDS-free infection

OBJECTIVES

To assess the dynamics of neutralizing antibodies (NAb) in long-term AIDS-free HIV-1-infected subjects and establish correlations with known markers of disease progression.

DESIGN

Cross-sectional study using sera collected from long-term non-progressors (LTNP) 8 years after seroconversion or study entry. Longitudinal study using sera collected from LTNP at 0, 0.5, 1, 2, 4, 6, 8 and 10 years after seroconversion and, as controls, from rapid progressors.

METHODS

Individuals with documented AIDS-free HIV-1 infection for at least 8 years were evaluated for NAb against five heterologous HIV-1 primary isolates. In the cross-sectional study, serum viral RNA levels, CD4+ T-cell numbers and T-cell function were determined on samples collected during the eighth year of follow-up. For the longitudinal study, NAb were assessed in sequential sera taken from LTNP and rapid progressors.

RESULTS

Serum neutralization titres found in individual sera differed from one HIV-1 isolate to another, were detected in 49-76% of LTNP, without correlation with the coreceptor usage of the isolate, and were positively associated with CD4+ T-lymphocyte counts (P = 0.0041) and T-cell function (P = 0.04). No correlation was found between NAb and the level of viral RNA in serum or the rate of CD4+ T-cell decline. Longitudinal analysis of sera from LTNP and rapid progressors showed that although several subjects in both groups had neutralizing activity at seroconversion, it thereafter became lower or no longer detectable. NAb were again found 1-4 years later and stably persisted in LTNP, but remained undetectable or at low levels in rapid progressors.

CONCLUSIONS

NAb were preferentially found in subjects with relatively preserved T-cell function and CD4+ T-cell numbers. In these individuals, neutralizing activity against heterologous isolates increased with time. These data suggest that the capacity to produce broadly NAb is a function of the integrity of the immune system.

Sexual and mother-to-child transmission of the human immunodeficiency virus type 1: a review

PROBLEM

Sexual and mother-to-child transmission of the human immunodeficiency virus (HIV) type 1 occurs only with a low percentage of infection. Many instances of sexual intercourse result in no transmission, and only 20% of children are infected from seropositive mothers (3% in mothers treated with azidothymidine).

METHOD OF STUDY

We analyzed the presence of HIV in various ejaculates of the same HIV-infected patients, as well as in the cervico-vaginal fluid. We have studied the mechanism of transmission from mother to child, by analyzing the cell-to-cell transmission in the trophoblast.

RESULTS

Some ejaculates collected at different times from the same HIV-infected males are free of virus, explaining the low rate of sexual transmission. We never found HIV in mobile spermatozoa. The trophoblast can be infected by HIV with a strain dependence and also transiently. By analyzing the tissue of the fetus, it was found that only some organs are infected, confirming the cell-to-cell transmission between the mother and child and not a true vertical transmission through the germinal lines.

CONCLUSIONS

HIV is not always present in the genital secretion, explaining the low rate of sexual transmission. Mother-to-child transmission occurs during pregnancy but often after the second trimester and at delivery after cell-to-cell or blood transmission, respectively.

TCR expression and clonality analysis in peripheral blood and lymph nodes of HIV-infected patients

We compared the T cell receptor (TCR) V beta gene family repertoire in peripheral blood mononuclear cells (PBMC) and lymph node (LN) cells from 7 human immunodeficiency virus (HIV)-infected patients and 3 seronegative healthy controls. Virtually all the V beta family specificities were represented in patient PBMC and LN cells, and mean values for each specificity were comparable to figures in seronegative controls. In 4 patients, however, some V beta gene segment transcripts were overrepresented in the LN compartment, compared to the peripheral blood counterpart. To ascertain whether this phenomenon was due to polyclonal or oligoclonal expansion of T cells bearing the relevant V beta gene product, we sequenced the entire CDR3 region of a panel of 238 PCR clones corresponding to the V beta transcripts expanded in LN; as control, the same regions were cloned and sequenced in patient's PBMC, and in PBMC and LN cells from seronegative individuals. This analysis disclosed preferential usage of J beta 2 genes in PBMC and LN cells from both seropositive patients and controls, regardless of the V beta gene segment considered, thus indicating that this skewness in the V beta-J beta repertoire could be a consistent feature of at least a part of the V beta repertoire in different lymphoid compartments, regardless of the pathologic conditions. In addition, in LN from HIV seropositive patients we found the presence of recurrent TCR rearrangements, accounting for 8-23% of the generated clones, in each of the 4 V beta specificities analyzed; recurrent sequences were not found in PBMC from patients nor in PBMC and LN cells from seronegative controls. These findings suggest that antigen-driven oligoclonal T cell expansions may occur in vivo in lymphoid organs of HIV seropositive patients.

A clearer distinction between HIV-1 paired isolates from peripheral blood mononuclear cells of asymptomatic carriers with and without CD8+ T-cells at nef rather than env V3 loci

In asymptomatic carriers, the vast majority of human immunodeficiency virus type 1 (HIV-1) infection is non-productive whilst the clinical stage of disease is associated with significant virus expression. Virus-specific CD8+ T-cell functions are believed to play a major role in the generation of heterogeneous virus populations and in subsequent disease progression. Here, we prepared two types of HIV-1 isolate by culturing whole and CD8+ T cell-depleted peripheral blood mononuclear cells (PBMCs) from five asymptomatic carriers. The former is expected to be escape variant populations, whereas the latter would be mixed populations including the former viruses. The analyses of Nef and Env V3 sequence variations of viruses in a total of 77 and 44 DNA clones, respectively, allowed a direct comparison to be made of the differences between the paired isolates. Comparison of Nef sequences between the paired isolates showed them to be more distinct in two carriers with a relatively stable CD4/CD8 ratio (Nos 68 and 69), than in two other carriers with similar CD4/CD8 ratios (Nos 53 and 57), or in carrier No. 67, which had an extremely lower CD4/CD8 ratio. By contrast, a distinction between the paired isolates by use of the Env V3 sequences was only apparent in the latter three carriers. These results indicate that the predominant populations of HIV-1 in Nos 68 and 69 were sensitive to selective pressure from Nef-specific CD8+ T-cells, while those in Nos 53, 57, and 67 were sensitive to pressure from V3-specific CD8+ T-cells. It is noteworthy that Nos 53 and 57 progressed to an AIDS-related complex shortly and several years after this examination. These data suggest that HIV-1-induced pathogenesis is more strongly associated with the generation of variant nef alleles than with env V3 variants, and that these arise by CD8+ T-cell pressure.

A chain section containing epitopes for cytotoxic T, B and helper T cells within a highly conserved region found in the human immunodeficiency virus type 1 Gag protein

Cell-mediated immune responses constitute a major defense against the spread of human immunodeficiency virus type 1 (HIV-1). However, multiple alterations within a particular epitope may accumulate during disease progression, allowing the virus to escape cytotoxic T lymphocytes (CTLs). Therefore, the best candidate for a peptide vaccine that would prevent the onset of the disease might be a chain section containing epitopes for the generation of CTLs in regions of conserved sequences among different HIV-1 isolates. We previously showed that immunizing mice with synthetic peptides consisting of 23-amino acids (Gag-23mer; 287-309 amino acid residues) in a highly conserved region derived from the major core protein p24 of HIV-1 generates specific CTLs as well as antibodies. Here, we identified one CTL (T-1; 291-300) and two B-cell (B-1; 290-299 and B-2; 300-309) epitopes, all of which consisted of 10 amino acids within the region. In addition, helper T cells primed by the Gag-23mer peptide were proliferated by in vitro stimulation with a 21mer (H-1; 289-309) or a 19mer (H-2; 291-309) peptide, but not with a 17mer peptide (293-309) or 19mer peptide (287-305). Immunization with the H-1 peptide generated an antibody reactive to B-1, but not B-2, whereas that with H-2 generated an antibody reactive to B-2, but not B-1. CTLs were not generated by immunization with these peptides, indicating that the entire sequence of Gag-23mer is the helper epitope for CTLs. Thus, the Gag-23mer is a chain section containing epitopes for cytotoxic T, B and helper T-cells within a highly conserved region of HIV-1 Gag protein.

Circulating cell adhesion molecules in HIV1-infected patients as indicator markers for AIDS progression

Cell adhesion molecules play an important role during immune responses. Circulating (c) forms of these molecules have been used as monitors of disease progression. In this study, we have investigated serum levels of ICAM1, ICAM2, ICAM3 and VCAM1 in HIV-infected patients. Our results showed that levels of cICAMs and cVCAM1 are increased during HIV infection. Among an HIV-infected population, the cICAM2 level was higher in the asymptomatic group compared to the AIDS group. In contrast, the cICAM1 level was higher in the AIDS group compared to the asymptomatic group. No difference between the two groups was observed in cICAM3 and cVCAM1 levels. A significant correlation was found between cICAM1, cICAM2 and cVCAM1 in both populations. We also showed that the cICAM1/cICAM2 ratio was correlated with the increase in the c beta 2 microglobulin level and the decrease in CD4 T-cell counts in the AIDS group. These results indicate that serum cCAM1 and cICAM2 in HIV infection could be additional markers to discriminate between asymptomatic and progressor patients.

Novel, cross-restricted, conserved, and immunodominant cytotoxic T lymphocyte epitopes in slow progressors in HIV type 1 infection

HIV-specific cytotoxic T lymphocytes (CTLs) play an important role in the immune response to HIV infection. Long-term nonprogressors (LTNPs) or slow progressors (SPs) in HIV infection may make qualitatively different CTL responses compared to those generated by seropositive individuals who progress to disease at a faster rate. The class I molecule HLA-B*57 has been identified as one restriction element overrepresented in SP groups studied, and, together with the closely related molecule HLA-B*58, occurs commonly in ethnic groups where HIV is most prevalent. In this study, we have identified five new HLA-B*57-restricted CTL epitopes recognized by SP donors, one of which is also HLA-B*5801 restricted. These HLA-B*57-restricted responses represent the dominant HIV-specific CTL response in each of the SP donors tested. These and other such epitopes may be an important component in future vaccine design.

CD8+ cells in HIV infection produce macrophage inflammatory protein-1 alpha and RANTES: a comparative study in long-term survivors and progressor patients

Evidence suggests that CD8+ lymphocytes are involved in the control of Human Immunodeficiency virus type 1 (HIV-1) infection by the release of HIV-suppressive factors. The human chemokines RANTES and the macrophage inflammatory protein 1 alpha (MIP-1 alpha) have been identified to be potent inhibitors of HIV in vitro. The aim of this study was to determine whether high levels of these chemokines are associated with a delayed progression of HIV disease. We have therefore analysed the in vitro production of RANTES and MIP-1 alpha from purified stimulated CD8+ cells from HIV+ long term survivors (LTS) and, as a comparison, from HIV+ patients with progressive disease. RANTES production was similar in LTS and progressors (14.06 +/- 3, 13.36 +/- 4.1 ng/ml, not statistically significant); the same cells from healthy controls show a RANTES production of 20 +/- 3.5 ng/ml (P = 0.034 versus LTS and P = 0.038 versus progressors). MIP-1 alpha production was slightly reduced in LTS (96.8 +/- 12 ng/ml) and progressors (91.6 + 17, not statistically significant between the two groups) when compared to healthy controls (109 +/- 7 ng/ml, P = 0.03). Our study suggests that resistance to HIV-1 progression in LTS may not be associated with high levels of RANTES and MIP-1 alpha production.

CC CKR5: a RANTES, MIP-1alpha, MIP-1beta receptor as a fusion cofactor for macrophage-tropic HIV-1

Human immunodeficiency virus-type 1 (HIV-1) entry requires fusion cofactors on the CD4+ target cell. Fusin, a heterotrimeric GTP-binding protein (G protein)-coupled receptor, serves as a cofactor for T cell line-tropic isolates. The chemokines RANTES, MIP-1alpha, and MIP-1beta, which suppress infection by macrophage-tropic isolates, selectively inhibited cell fusion mediated by the corresponding envelope glycoproteins (Envs). Recombinant CC CKR5, a G protein-coupled receptor for these chemokines, rendered CD4-expressing nonhuman cells fusion-competent preferentially with macrophage-tropic Envs. CC CKR5 messenger RNA was detected selectively in cell types susceptible to macrophage-tropic isolates. CC CKR5 is thus a fusion cofactor for macrophage-tropic HIV-1 strains.