Elite controllers display higher activation on central memory CD8 T cells than HIV patients successfully on HAART

T Cell Homeostasis Disturbances in a Cohort of Long-Term Elite Controllers of HIV Infection

Elite controllers (ECs) are people living with HIV (PLWH) able to control HIV replication without antiretroviral therapy and have been proposed as a model of a functional HIV cure. Much evidence suggests that this spontaneous control of HIV has a cost in terms of T cell homeostasis alterations. We performed a deep phenotypic study to obtain insight into T cell homeostasis disturbances in ECs maintaining long-term virologic and immunologic control of HIV (long-term elite controllers; LTECs). Forty-seven PLWH were included: 22 LTECs, 15 non-controllers under successful antiretroviral therapy (onART), and 10 non-controllers not receiving ART (offART). Twenty uninfected participants (UCs) were included as a reference. T cell homeostasis was analyzed by spectral flow cytometry and data were analyzed using dimensionality reduction and clustering using R software v3.3.2. Dimensionality reduction and clustering yielded 57 and 54 different CD4 and CD8 T cell clusters, respectively. The offART group showed the highest perturbation of T cell homeostasis, with 18 CD4 clusters and 15 CD8 clusters significantly different from those of UCs. Most of these alterations were reverted in the onART group. Interestingly, LTECs presented several disturbances of T cell homeostasis with 15 CD4 clusters and 13 CD8 clusters different from UC. Moreover, there was a specific profile of T cell homeostasis alterations associated with LTECs, characterized by increases in clusters of naïve T cells, increases in clusters of non-senescent effector CD8 cells, and increases in clusters of central memory CD4 cells. These results demonstrate that, compared to ART-mediated control of HIV, the spontaneous control of HIV is associated with several disturbances in CD4 and CD8 T cell homeostasis. These alterations could be related to the existence of a potent and efficient virus-specific T cell response, and to the ability to halt disease progression by maintaining an adequate pool of CD4 T cells.

Slow progression of pediatric HIV associates with early CD8+ T cell PD-1 expression and a stem-like phenotype

HIV nonprogression despite persistent viremia is rare among adults who are naive to antiretroviral therapy (ART) but relatively common among ART-naive children. Previous studies indicate that ART-naive pediatric slow progressors (PSPs) adopt immune evasion strategies similar to those described in natural hosts of SIV. However, the mechanisms underlying this immunophenotype are not well understood. In a cohort of early-treated infants who underwent analytical treatment interruption (ATI) after 12 months of ART, expression of PD-1 on CD8+ T cells immediately before ATI was the main predictor of slow progression during ATI. PD-1+CD8+ T cell frequency was also negatively correlated with CCR5 and HLA-DR expression on CD4+ T cells and predicted stronger HIV-specific T lymphocyte responses. In the CD8+ T cell compartment of PSPs, we identified an enrichment of stem-like TCF-1+PD-1+ memory cells, whereas pediatric progressors and viremic adults had a terminally exhausted PD-1+CD39+ population. TCF-1+PD-1+ expression on CD8+ T cells was associated with higher proliferative activity and stronger Gag-specific effector functionality. These data prompted the hypothesis that the proliferative burst potential of stem-like HIV-specific cytotoxic cells could be exploited in therapeutic strategies to boost the antiviral response and facilitate remission in infants who received early ART with a preserved and nonexhausted T cell compartment.

Role of Early Life Cytotoxic T Lymphocyte and Natural Killer Cell Immunity in Paediatric HIV Cure/Remission in the Anti-Retroviral Therapy Era

Only three well-characterised cases of functional cure have been described in paediatric HIV infection over the past decade. This underlines the fact that early initiation of combination antiretroviral therapy (cART), whilst minimising the size of the viral reservoir, is insufficient to achieve cure, unless other factors contribute. In this review, we consider these additional factors that may facilitate functional cure in paediatric infection. Among the early life immune activity, these include HIV-specific cytotoxic T-lymphocyte (CTL) and natural killer (NK) cell responses. The former have less potent antiviral efficacy in paediatric compared with adult infection, and indeed, in early life, NK responses have greater impact in suppressing viral replication than CTL. This fact may contribute to a greater potential for functional cure to be achieved in paediatric versus adult infection, since post-treatment control in adults is associated less with highly potent CTL activity, and more with effective antiviral NK cell responses. Nonetheless, antiviral CTL responses can play an increasingly effective role through childhood, especially in individuals expressing then 'protective' HLA-I molecules HLA-B*27/57/58:01/8101. The role of the innate system on preventing infection, in shaping the particular viruses transmitted, and influencing outcome is discussed. The susceptibility of female fetuses to in utero mother-to-child transmission, especially in the setting of recent maternal infection, is a curiosity that also provides clues to mechanisms by which cure may be achieved, since initial findings are that viral rebound is less frequent among males who interrupt cART. The potential of broadly neutralising antibody therapy to facilitate cure in children who have received early cART is discussed. Finally, we draw attention to the impact of the changing face of the paediatric HIV epidemic on cure potential. The effect of cART is not limited to preventing AIDS and reducing the risk of transmission. cART also affects which mothers transmit. No longer are mothers who transmit those who carry genes associated with poor immune control of HIV. In the cART era, a high proportion (>70% in our South African study) of transmitting mothers are those who seroconvert in pregnancy or who for social reasons are diagnosed late in pregnancy. As a result, now, genes associated with poor immune control of HIV are not enriched in mothers who transmit HIV to their child. These changes will likely influence the effectiveness of HLA-associated immune responses and therefore cure potential among children.

CTL Clonotypes with Higher TCR Affinity Have Better Ability to Reduce the HIV Latent Reservoir

The success of the shock and kill strategy for the HIV cure depends both on the reactivation of the latent reservoir and on the ability of the immune system to eliminate infected cells. As latency reversal alone has not shown any impact in the size of the latent reservoir, ensuring that effector CTLs are able to recognize and kill HIV-infected cells could contribute to reservoir reduction. In this study, we investigated which functional aspects of human CTLs are associated with a better capacity to kill HIV-infected CD4⁺ T cells. We isolated Gag- and Nef-specific CTL clones with different TCR sequences from the PBMC of donors in acute and chronic infection. High-affinity clonotypes that showed IFN-γ production preserved even when the CD8 coreceptor was blocked, and clones with high Ag sensitivity exhibited higher efficiency at reducing the latent reservoir. Although intrinsic cytotoxic capacity did not differ according to TCR affinity, clonotypes with high TCR affinity showed a better ability to kill HIV-infected CD4⁺ T cells obtained from in vivo-infected PBMC and subjected to viral reactivation. Strategies aiming to specifically boost and maintain long-living memory CTLs with high TCR affinity in vivo prior to latency-reversing treatment might improve the efficacy of the shock and kill approach to reduce the latent reservoir.

Harnessing CD8+ T Cells Under HIV Antiretroviral Therapy

Antiretroviral therapy (ART) has transformed HIV from a fatal disease to a chronic condition. In recent years there has been considerable interest in strategies to enable HIV-infected individuals to cease ART without viral rebound, either by purging all cells infected harboring replication-competent virus (HIV eradication), or by boosting immune responses to allow durable suppression of virus without rebound (HIV remission). Both of these approaches may need to harness HIV-specific CD8⁺ T cells to eliminate infected cells and/or prevent viral spread. In untreated infection, both HIV-specific and total CD8⁺ T cells are dysfunctional. Here, we review our current understanding of both global and HIV-specific CD8⁺ T cell immunity in HIV-infected individuals with durably suppressed viral load under ART, and its implications for HIV cure, eradication or remission. Overall, the literature indicates significant normalization of global T cell parameters, including CD4/8 ratio, activation status, and telomere length. Global characteristics of CD8⁺ T cells from HIV⁺ART⁺ individuals align more closely with those of HIV-seronegative individuals than of viremic HIV-infected individuals. However, markers of senescence remain elevated, leading to the hypothesis that immune aging is accelerated in HIV-infected individuals on ART. This phenomenon could have implications for attempts to prime de novo, or boost existing HIV-specific CD8⁺ T cell responses. A major challenge for both HIV cure and remission strategies is to elicit HIV-specific CD8⁺ T cell responses superior to that elicited by natural infection in terms of response kinetics, magnitude, breadth, viral suppressive capacity, and tissue localization. Addressing these issues will be critical to the success of HIV cure and remission attempts.

Class-modeling analysis reveals T-cell homeostasis disturbances involved in loss of immune control in elite controllers

BACKGROUND

Despite long-lasting HIV replication control, a significant proportion of elite controller (EC) patients may experience CD4 T-cell loss. Discovering perturbations in immunological parameters could help our understanding of the mechanisms that may be operating in those patients experiencing loss of immunological control.

METHODS

A case-control study was performed to evaluate if alterations in different T-cell homeostatic parameters can predict CD4 T-cell loss in ECs by comparing data from EC patients showing significant CD4 decline (cases) and EC patients showing stable CD4 counts (controls). The partial least-squares-class modeling (PLS-CM) statistical methodology was employed to discriminate between the two groups of patients, and as a predictive model.

RESULTS

Herein, we show that among T-cell homeostatic alterations, lower levels of naïve and recent thymic emigrant subsets of CD8 cells and higher levels of effector and senescent subsets of CD8 cells as well as higher levels of exhaustion of CD4 cells, measured prior to CD4 T-cell loss, predict the loss of immunological control.

CONCLUSIONS

These data indicate that the parameters of T-cell homeostasis may identify those EC patients with a higher proclivity to CD4 T-cell loss. Our results may open new avenues for understanding the mechanisms underlying immunological progression despite HIV replication control, and eventually, for finding a functional cure through immune-based clinical trials.

Human Immunodeficiency Virus Type-1 Elite Controllers Maintain Low Co-Expression of Inhibitory Receptors on CD4+ T Cells

Human immunodeficiency virus type-1 (HIV-1) elite controllers (ELCs) represent a unique population that control viral replication in the absence of antiretroviral therapy (cART). It is well established that expression of multiple inhibitory receptors on CD8+ T cells is associated with HIV-1 disease progression. However, whether reduced co-expression of inhibitory receptors on CD4+ T cells is linked to natural viral control and slow HIV-1 disease progression remains undefined. Here, we report on the expression pattern of numerous measurable inhibitory receptors, associated with T cell exhaustion (programmed cell death-1, CTLA-4, and TIGIT), on different CD4+ T cell memory populations in ELCs and HIV-infected subjects with or without long-term cART. We found that the co-expression pattern of inhibitory receptors was significantly reduced in ELCs compared with HIV-1 cART-treated and viremic subjects, and similar to healthy controls. Markers associated with T cell exhaustion varied among different memory CD4+ T cell subsets and highest levels were found mainly on transitional memory T cells. CD4+ T cells co-expressing all inhibitory markers were positively correlated to T cell activation (CD38+ HLA-DR+) as well as the transcription factors Helios and FoxP3. Finally, clinical parameters such as CD4 count, HIV-1 viral load, and the CD4/CD8 ratio all showed significant associations with CD4+ T cell exhaustion. We demonstrate that ELCs are able to maintain lower levels of CD4+ T cell exhaustion despite years of ongoing viral replication compared with successfully cART-treated subjects. Our findings suggest that ELCs harbor a “healthy” state of inhibitory receptor expression on CD4+ T cells that might play part in maintenance of their control status.

Immunological and virological characterization of HIV-1 viremia controllers in the North Region of Brazil

Background

A rare phenotype of clinical non-progressors to AIDS is not well understood and the new protocol for universal treatment, may block the understanding of viral control thus it is crucial to define this controversial group.

Methods

A cohort of 30 persons followed a criteria for viremia control groups 1 (VC1; n = 2) and 2 (VC2; n = 7) and non-viral controllers (NC; n = 21) including number of years of diagnosis, LTCD4⁺, LTCD8⁺ counts, plasma viral load and the absence of ART; 241 uninfected control persons were matched to age and sex. Infected persons were regularly examined and submitted to two or three annual laboratory measurements. Polymorphisms and allele frequencies of CCR5Δ32 and SDF1–3’A were detected in the genomic DNA. Plasma levels of cytokines (IL-2, IL-4, IL-5, IL-9, IL-10, IL-13, IL-17 and IFN-y) were measured.

Results

The group investigated is originated from a miscigenetic population and demographic and social characteristics were not significantly relevant. LTCD4⁺ median values were higher among VC than NC, but significantly lower than uninfected controls. Evolution of LTCD4⁺ and LTCD8⁺ counts, showed a slight increase of LTCD4⁺ among VC, but a significant decrease in the NC. The percentage of annual change in LTCD4⁺ was also significantly different between the groups. LTCD4⁺/LTCD8⁺ ratio was inverted but not significant among the VC, thus the ratio may be a useful biomarker for the VC. A clear signature indicated a change from Th1 to Th2 cytokine profiles from VC to NC, respectively.

Conclusions

The knowledge of viral controllers characteristics in different population groups is important to define a strict universal definition for the sake of learning about the pathogenesis of HIV-1. Data on LTCD4⁺ seems to be stable and repetitive from published data, but the LTCD8⁺ response and the significance of LTCD4⁺/LTCD8⁺ ratio values are in need to further exploration as biomarkers. The change from Th1 to Th2 cytokine profile may help to design and adjust specific treatment protocols for the group.

CD4+ T cells with an activated and exhausted phenotype distinguish immunodeficiency during aviremic HIV-2 infection

HIV type 2 (HIV-2) represents an attenuated form of HIV, in which many infected individuals remain ‘aviremic’ without antiretroviral therapy. However, aviremic HIV-2 disease progression exists, and in the current study, we therefore aimed to examine if specific pathological characteristics of CD4⁺ T cells are linked to such outcome.

TIGIT Marks Exhausted T Cells, Correlates with Disease Progression, and Serves as a Target for Immune Restoration in HIV and SIV Infection

HIV infection induces phenotypic and functional changes to CD8⁺ T cells defined by the coordinated upregulation of a series of negative checkpoint receptors that eventually result in T cell exhaustion and failure to control viral replication. We report that effector CD8⁺ T cells during HIV infection in blood and SIV infection in lymphoid tissue exhibit higher levels of the negative checkpoint receptor TIGIT. Increased frequencies of TIGIT⁺ and TIGIT⁺ PD-1⁺ CD8⁺ T cells correlated with parameters of HIV and SIV disease progression. TIGIT remained elevated despite viral suppression in those with either pharmacological antiretroviral control or immunologically in elite controllers. HIV and SIV-specific CD8⁺ T cells were dysfunctional and expressed high levels of TIGIT and PD-1. Ex-vivo single or combinational antibody blockade of TIGIT and/or PD-L1 restored viral-specific CD8⁺ T cell effector responses. The frequency of TIGIT⁺ CD4⁺ T cells correlated with the CD4⁺ T cell total HIV DNA. These findings identify TIGIT as a novel marker of dysfunctional HIV-specific T cells and suggest TIGIT along with other checkpoint receptors may be novel curative HIV targets to reverse T cell exhaustion.

HIV-1 infection contributes substantially to global morbidity and mortality, with no immediate promise of an effective vaccine. One major obstacle to vaccine development and therapy is to understand why HIV-1 replication persists in a person despite the presence of viral specific immune responses. The emerging consensus has been that these immune cells are functionally ‘exhausted’ or anergic, and thus, although they can recognize HIV-1 specific target cells, they are unable to effectively keep up with rapid and dynamic viral replication in an individual. We have identified a novel combination pathway that can be targeted, TIGIT and PD-L1which may be responsible, at least in part, for making these immune cells dysfunctional and exhausted and thus unable to control the virus. We show that by blocking the TIGIT and PD-L1 pathway, we can reverse the defects of these viral specific immune cells. Our findings will give new directions to vaccines and therapies that will potentially reverse these dysfunctional cells and allow them to control HIV-1 replication, but also serve in “Shock and Kill” HIV curative strategies.

Large granular lymphocytes are universally increased in human, macaque, and feline lentiviral infection

Large granular lymphocytes (LGLs) have only been anecdotally reported in HIV infection. We previously reported an LGL lymphocytosis in FIV-infected cats associated with a rise in FIV proviral loads and a marked neutropenia that persisted during chronic infection. Extensive immunophenotyping of peripheral blood mononuclear cells in cats chronically infected with FIV were identified LGLs as CD8lo(+)FAS(+); this cell population expanded commensurate with viral load. CD8lo(+)FAS(+) cells expressed similar levels of interferon-γ compared to CD8lo(+)FAS(+) cells from FIV-naive control animals, yet CD3ɛ expression, which was increased on total CD8(+) T cells in FIV-infected cats, was decreased on CD8lo(+)FAS(+) cells. Down-modulation of CD3 expression was reversed after culturing PBMC for 3 days in culture with ConA/IL-2. We identified CD8lo(+)FAS(+) LGLs to be polyclonal T cells lacking CD56 expression. Blood smears from HIV-infected individuals and SIVmac239-infected rhesus macaques revealed increased LGLs compared to HIV/SIV negative counterparts. In humans, there was no correlation with viral load or treatment and in macaques the LGLs arose in acute SIV infection with increases in viremia. This is the first report describing and partially characterizing LGL lymphocytosis in association with lentiviral infections in three different species.

Evaluation of rapid progressors in HIV infection as an extreme phenotype

DESIGN

Rapid CD4 cell loss represents an HIV phenotype used to identify causal variants of accelerated disease progression. The optimal rate and threshold for identifying this extreme phenotype in recently infected individuals is unclear.

METHODS

Using a cohort of patients with known dates of HIV-1 seroconversion (SC), CASCADE (Concerted Action on SeroConversion on AIDS and Death in Europe), we identified proportions experiencing nadir CD4 cell levels within 1 year of SC, and assessed their mean AIDS-free survival time at 10-year follow-up and hazard of AIDS/death, compared with those whose CD4 remained >500 cells per cubic millimeter. Follow-up was censored at December 31, 1996 to avoid bias due to combination antiretroviral therapy initiation.

RESULTS

Of 4876 individuals, 2.8%, 7.3%, and 24.9% experienced ≥1 CD4 <100, 200, and 350 cells per cubic millimeter, respectively, within 1 year of SC. Minimum CD4 levels of 30, 166, 231, and 506 cells per cubic millimeter were experienced during this period by 1%, 5%, 10%, and 50% of individuals, respectively. Mean (95% confidence interval) AIDS-free survival at 10 years follow-up was 2.9 (2.3 to 3.6), 5.5 (5.0 to 6.1), 6.7 (6.5 to 7.0), 7.4 (7.2 to 7.6), and 8.1 (7.9 to 8.3), for those with minimum counts ≤100, 100-200, 200-350, 350-500, >500 cells per cubic millimeter, respectively. Using counts of >500 cells per cubic millimeter as reference, the hazard ratios (95% confidence interval) of AIDS/death were 15.0 (11.9 to 18.9), 3.6 (2.9 to 4.5), 2.1 (1.8 to 2.4), and 1.5 (1.3 to 1.7), respectively. The hazard ratio increased to 37.5 (26.5 to 53.1) when a minimum CD4 count <100 was confirmed within 1 year of SC.

CONCLUSION

At least 1 CD4 ≤100 cells per cubic millimeter within the first year of SC identifies a rare group of individuals at high risk of disease progression and could form the basis for defining the rapid progressor phenotype.

Immune activation is associated with increased gut microbial translocation in treatment-naive, HIV-infected children in a resource-limited setting

BACKGROUND

Gut damage resulting in microbial translocation (MT) is considered a major cause of immune activation (IA) in HIV infection, but data in children are limited, particularly in the absence of antiretroviral therapy.

METHODS

Sixty perinatally HIV-infected, antiretroviral therapy-naive children, aged 2-12 years, were evaluated for plasma levels of lipopolysaccharide, DNA sequences encoding bacterial 16 second ribosomal DNA (16S rDNA) and soluble CD14 concurrently with markers of CD4 and CD8 T-cell IA and immune exhaustion (IE), CD4 counts, and plasma viral load. At study entry, participants were classified into immune categories (ICs): IC1 (CD4% > 25), IC2 (CD4% 15-25), and IC3 (CD4% < 15). Age-matched HIV-uninfected children served as controls. Data were evaluated at study entry and at 12 months.

RESULTS

Levels of MT, IA, and IE were increased in patients as compared with controls, were highest in patients in IC3 group, and did not change over 12 months. MT products lipopolysaccharide and 16S rDNA correlated with each other and each correlated with plasma viral load, soluble CD14, and T-cell IA and IE. There was a correlation of IA with IE. CD4 counts and percentage were inversely correlated with MT products and underlying CD4 activation.

CONCLUSIONS

In a natural history cohort of HIV-infected children not on therapy, MT was more pronounced in the most severely immunocompromised patients and was associated with IA. Strategies to reduce MT may help to reduce IA and prevent CD4 depletion.

An evaluation of HIV elite controller definitions within a large seroconverter cohort collaboration

Background

Understanding the mechanisms underlying viral control is highly relevant to vaccine studies and elite control (EC) of HIV infection. Although numerous definitions of EC exist, it is not clear which, if any, best identify this rare phenotype.

Methods

We assessed a number of EC definitions used in the literature using CASCADE data of 25,692 HIV seroconverters. We estimated proportions maintaining EC of total ART-naïve follow-up time, and disease progression, comparing to non-EC. We also examined HIV-RNA and CD4 values and CD4 slope during EC and beyond (while ART naïve).

Results

Most definitions classify ∼1% as ECs with median HIV-RNA 43–903 copies/ml and median CD4>500 cells/mm³. Beyond EC status, median HIV-RNA levels remained low, although often detectable, and CD4 values high but with strong evidence of decline for all definitions. Median % ART-naïve time as EC was ≥92% although overlap between definitions was low. EC definitions with consecutive HIV-RNA measurements <75 copies/ml with follow-up≥ six months, or with 90% of measurements <400 copies/ml over ≥10 year follow-up preformed best overall. Individuals thus defined were less likely to progress to endpoint (hazard ratios ranged from 12.5–19.0 for non-ECs compared to ECs).

Conclusions

ECs are rare, less likely to progress to clinical disease, but may eventually lose control. We suggest definitions requiring individuals to have consecutive undetectable HIV-RNA measurements for ≥ six months or otherwise with >90% of measurements <400 copies/ml over ≥10 years be used to define this phenotype.

A candidate anti-HIV reservoir compound, auranofin, exerts a selective 'anti-memory' effect by exploiting the baseline oxidative status of lymphocytes

Central memory (T_CM) and transitional memory (T_TM) CD4⁺ T cells are known to be the major cellular reservoirs for HIV, as these cells can harbor a transcriptionally silent form of viral DNA that is not targeted by either the immune system or current antiretroviral drug regimens. In the present study, we explored the molecular bases of the anti-HIV reservoir effects of auranofin (AF), a pro-oxidant gold-based drug and a candidate compound for a cure of AIDS. We here show that T_CM and T_TM lymphocytes have lower baseline antioxidant defenses as compared with their naive counterpart. These differences are mirrored by the effects exerted by AF on T-lymphocytes: AF was able to exert a pro-differentiating and pro-apoptotic effect, which was more pronounced in the memory subsets. AF induced an early activation of the p38 mitogen-activated protein kinase (p38 MAPK) followed by mitochondrial depolarization and a final burst in intracellular peroxides. The pro-differentiating effect was characterized by a downregulation of the CD27 marker expression. Interestingly, AF-induced apoptosis was inhibited by pyruvate, a well-known peroxide scavenger, but pyruvate did not inhibit the pro-differentiating effect of AF, indicating that the pro-apoptotic and pro-differentiating effects involve different pathways. In conclusion, our results demonstrate that AF selectively targets the T_CM/T_TM lymphocyte subsets, which encompass the HIV reservoir, by affecting redox-sensitive cell death pathways.

Cell-Mediated Immunity in Elite Controllers Naturally Controlling HIV Viral Load

The natural course of human immunodeficiency virus (HIV) infection is characterized by high viral load, depletion of immune cells, and immunodeficiency, ultimately leading to acquired immunodeficiency syndrome phase and the occurrence of opportunistic infections and diseases. Since the discovery of HIV in the early 1980s a naturally selected population of infected individuals has been emerged in the last years, characterized by being infected for many years, with viremia constantly below detectable level and poor depletion of immune cells. These individuals are classified as “elite controllers (EC) or suppressors” and do not develop disease in the absence of anti-retroviral therapy. Unveiling host factors and immune responses responsible for the elite status will likely provide clues for the design of therapeutic vaccines and functional cures. Scope of this review was to examine and discuss differences of the cell-mediated immune responses between HIV+ individuals with disease progression and EC.

Disease Progression in HIV-1-Infected Viremic Controllers

BACKGROUND

The mechanism of CD4 T-cell decline in HIV-1 infection is unclear, but the association with plasma viral RNA load suggests viral replication is involved. Indeed, viremic controller patients with low viral RNA loads typically maintain high CD4 T-cell counts. Within a local cohort of 86 viremic controllers, we identify a subgroup (18 "discord controllers") with low CD4 T-cell counts that present clinical uncertainty. The underlying mechanism accounting for CD4 T-cell decline in the face of low or undetectable plasma (RNA) viral load remains unresolved. The objective of this study was to investigate the viral and host immune system dynamics in discord controllers by measuring cellular HIV-1 DNA load, T-cell populations, and T-cell activation markers.

METHODS

We compared discord controllers (viral RNA load <2000 copies/mL, <450 CD4 T-cells/mm) with typical controllers (viral RNA load <2000 copies/mL, >450 CD4 T-cells/mm) and progressors (viral RNA load >10,000 copies/mL, <450 CD4 T-cells/mm). We quantified CD4/CD8 naive/central memory/effector memory subsets (CD45RA/RO ± CD62L), activation levels (CD38HLA-DR), and HIV-1 DNA load.

RESULTS

Discord controllers resembled progressors showing high viral DNA load, depletion of naive CD4 T-cells, and higher activation in all CD4 T-cell subsets, compared with typical controllers. They were similar to typical controllers with lower CD8 T-cell activation compared with progressors.

CONCLUSIONS

Our data are consistent with a relationship between CD4 T-cell activation and disease progression. HIV-1 DNA load may be a better marker of viral replication and disease progression than viral RNA load. Lower level CD8 T-cell activation correlates with low viral RNA load but not with disease progression or viral DNA load.

T-cell subset distribution in HIV-1-infected patients after 12 years of treatment-induced viremic suppression

OBJECTIVE

Residual immune activation and skewed T cell maturation may contribute to excess comorbidity and mortality in successfully treated HIV-infected patients, and long-term effects of combination antiretroviral therapy (cART) on immune reconstitution remain a debated issue. Quantitative T cell reconstitution and activation and its association with residual viremia in patients with 12 years of viremic suppression were investigated.

DESIGN

Blood samples collected cross-sectionally from 71 HIV-infected patients with cART-induced viremic suppression through 12 years were compared with samples from 16 healthy controls.

METHODS

Several different subsets of naive, memory, and activated T cells were analyzed in fresh whole blood by 6-color flowcytometry, and ultrasensitive quantification of HIV RNA was performed.

RESULTS

HIV-infected patients had lower absolute and relative CD4 T cell counts and higher absolute and relative CD8 T cell counts than controls. HIV-infected patients had lower concentrations of naive CD4 cells than controls, but proportions were similar. HIV-infected patients had higher concentrations of CD8 T cells than controls in all the examined subsets but only a higher proportion of CD8 cells in the intermediately differentiated and activated subsets. Residual viremia did not correlate to proportions of naive CD4, CD4 recent thymic emigrants, or activated CD8 T cells.

CONCLUSIONS

This study demonstrated some degree of T cell imbalance even after 12 years of successful cART. Large longitudinal studies are needed to establish whether these discrete changes have clinical relevance.

The role of lipopolysaccharide as a marker of immune activation in HIV-1 infected patients: a systematic literature review

Background

Recent observational studies suggest a role for lipopolysaccharide (LPS) as a marker of immune activation in HIV-infected patients, with potential repercussions on the effectiveness of antiretroviral regimens.

Object

A systematic review of LPS as a marker of immune activation in HIV-1 infected patients.

Data sources

MEDLINE register of articles and international conference proceedings.

Review methods

Case–control studies comparing the role of plasma LPS as a marker of immune activation in HIV-infected patients versus HIV negative subjects.

Data synthesis

Two hundred and six articles were selected using MEDLINE, plus 51 studies presented at international conferences. Plasma LPS is a marker of immune activation in HIV-infected patients, determining the entry of central memory CD4+ T cells into the replication cycle and finally generating cell death. Plasma LPS probably results from immune-mediated alterations of the intestinal barrier, which can occur soon after HIV seroconversion. LPS is a likely marker of disease progression, as it drives chronic monocyte activation, and some studies suggest that hyperexpression of CCR5 receptors, related to LPS plasma levels, could be responsible for monocyte trafficking in the brain compartment and for the appearance of HIV-associated neurocognitive disorders. Long-term combination antiretroviral therapy (cART) generally reduces LPS concentrations, but rarely to the same levels as in the control group. This phenomenon probably depends on ongoing but incomplete repair of the mucosal barrier. Only in patients achieving maximal viral suppression (i.e. viral load < 2.5 cp/ml) are LPS levels comparable to healthy donors. In successfully treated patients who did not restore CD4+ T cells, one hypothesis is that the degree of residual microbial translocation, measured by LPS, alters the turnover of CD4+ T cells.

Conclusions

LPS is a marker of microbial translocation, responsible for chronic immune activation in HIV-infected patients. Even in successfully treated patients, LPS values are rarely normal. Several studies suggest a role for LPS as a negative predictive marker of immune restoration in patients with blunted CD4 T cell gain.

Thirty Years with HIV Infection-Nonprogression Is Still Puzzling: Lessons to Be Learned from Controllers and Long-Term Nonprogressors

In the early days of the HIV epidemic, it was observed that a minority of the infected patients did not progress to AIDS or death and maintained stable CD4+ cell counts. As the technique for measuring viral load became available it was evident that some of these nonprogressors in addition to preserved CD4+ cell counts had very low or even undetectable viral replication. They were therefore termed controllers, while those with viral replication were termed long-term nonprogressors (LTNPs). Genetics and virology play a role in nonprogression, but does not provide a full explanation. Therefore, host differences in the immunological response have been proposed. Moreover, the immunological response can be divided into an immune homeostasis resistant to HIV and an immune response leading to viral control. Thus, non-progression in LTNP and controllers may be due to different immunological mechanisms. Understanding the lack of disease progression and the different interactions between HIV and the immune system could ideally teach us how to develop a functional cure for HIV infection. Here we review immunological features of controllers and LTNP, highlighting differences and clinical implications.

CD4+ T cell depletion in human immunodeficiency virus (HIV) infection: role of apoptosis

Human immunodeficiency virus (HIV) infection is principally a mucosal disease and the gastrointestinal (GI) tract is the major site of HIV replication. Loss of CD4+ T cells and systemic immune hyperactivation are the hallmarks of HIV infection. The end of acute infection is associated with the emergence of specific CD4+ and CD8+ T cell responses and the establishment of a chronic phase of infection. Abnormal levels of immune activation and inflammation persist despite a low steady state level of viremia. Although the causes of persistent immune hyperactivation remain incompletely characterized, physiological alterations of gastrointestinal tract probably play a major role. Failure to restore Th17 cells in gut-associated lymphoid tissues (GALT) might impair the recovery of the gut mucosal barrier. This review discusses recent advances on understanding the contribution of CD4+ T cell depletion to HIV pathogenesis.