T-Cell Dysfunction in HIV-1–Infected Patients With Impaired Recovery of CD4 Cells Despite Suppression of Viral Replication

HIV immunological non-responders are characterized by extensive immunosenescence and impaired lymphocyte cytokine production capacity

Introduction

Immunological non-responders (INR) are people living with HIV (PLHIV) who fail to fully restore CD4+ T-cell counts despite complete viral suppression with antiretroviral therapy (ART). INR are at higher risk for non-HIV related morbidity and mortality. Previous research suggest persistent qualitative defects.

Methods

The 2000HIV study (clinical trials NTC03994835) enrolled 1895 PLHIV, divided in a discovery and validation cohort. PLHIV with CD4 T-cell count <350 cells/mm3 after ≥2 years of suppressive ART were defined as INR and were compared to immunological responders (IR) with CD4 T-cell count >500 cells/mm3. Logistic and rank based regression were used to analyze clinical data, extensive innate and adaptive immunophenotyping, and ex vivo monocyte and lymphocyte cytokine production after stimulation with various stimuli.

Results

The discovery cohort consisted of 62 INR and 1224 IR, the validation cohort of 26 INR and 243 IR. INR were older, had more advanced HIV disease before starting ART and had more frequently a history of non-AIDS related malignancy. INR had lower absolute CD4+ T-cell numbers in all subsets. Activated (HLA-DR+, CD38+) and exhausted (PD1+) subpopulations were proportionally increased in CD4 T-cells. Monocyte and granulocyte immunophenotypes were comparable. INR lymphocytes produced less IL-22, IFN-γ, IL-10 and IL-17 to stimuli. In contrast, monocyte cytokine production did not differ. The proportions of CD4+CD38+HLA-DR+ and CD4+PD1+ subpopulations showed an inversed correlation to lymphocyte cytokine production.

Conclusions

INR compared to IR have hyperactivated and exhausted CD4+ T-cells in combination with lymphocyte functional impairment, while innate immune responses were comparable. Our data provide a rationale to consider the use of anti-PD1 therapy in INR.

Multi-omics in HIV: searching insights to understand immunological non-response in PLHIV

Antiretroviral therapy (ART) induces persistent suppression of HIV-1 replication and gradual recovery of T-cell counts, and consequently, morbidity and mortality from HIV-related illnesses have been significantly reduced. However, in approximately 30% of people living with HIV (PLHIV) on ART, CD4+ T-cell counts fail to normalize despite ART and complete suppression of HIV viral load, resulting in severe immune dysfunction, which may represent an increased risk of clinical progression to AIDS and non-AIDS events as well as increased mortality. These patients are referred to as "immune inadequate responders", "immunodiscordant responders" or "immune nonresponders (INR)". The molecular mechanisms underlying poor CD4+ T-cell recovery are still unclear. In this sense, the use of omics sciences has shed light on possible factors involved in the activity and metabolic dysregulation of immune cells during the failure of CD4+ T-cell recovery in INR. Moreover, identification of key molecules by omics approaches allows for the proposal of potential biomarkers or therapeutic targets to improve CD4+ T-cell recovery and the quality of life of these patients. Hence, this review aimed to summarize the information obtained through different omics concerning the molecular factors and pathways associated with the INR phenotype to better understand the complexity of this immunological status in HIV infection.

Cellular and molecular insights into incomplete immune recovery in HIV/AIDS patients

Highly active antiretroviral therapy (ART) can effectively inhibit virus replication and restore immune function in most people living with human immunodeficiency virus (HIV). However, an important proportion of patients fail to achieve a satisfactory increase in CD4⁺ T cell counts. This state is called incomplete immune reconstitution or immunological nonresponse (INR). Patients with INR have an increased risk of clinical progression and higher rates of mortality. Despite widespread attention to INR, the precise mechanisms remain unclear. In this review, we will discuss the alterations in the quantity and quality of CD4⁺ T as well as multiple immunocytes, changes in soluble molecules and cytokines, and their relationship with INR, aimed to provide cellular and molecular insights into incomplete immune reconstitution.

Decreased CD73+ Double-Negative T Cells and Elevated Level of Soluble CD73 Correlated With and Predicted Poor Immune Reconstitution in HIV-Infected Patients After Antiretroviral Therapy

Although extensive use of antiretroviral therapy (ART) has made great progress in controlling HIV replication and improving CD4+ T cell recovery, the immune reconstitution remained insufficient in some patients, who were defined as poor immunological responders (PIRs). These PIRs were at a high risk of AIDS-related and non-AIDS complications, resulting in higher morbidity and mortality rate. Thus, it is a major challenge and urgently needed to distinguish PIRs early and improve their immune function in time. Immune activation is a key factor that leads to impaired immune reconstitution in people living with HIV (PLWH) who are receiving effective ART. Double negative T cells (DNT) were reported to associate with the control of immune activation during HIV infection. However, the precise mechanisms by which DNT cells exerted their suppressive capacity during HIV infection remained puzzled. CD73, both a soluble and a membrane-bound form, display immunosuppressive effects through producing adenosine (ADO). Thus, whether DNT cells expressed CD73 and mediated immune suppression through CD73-ADO pathway needs to be investigated. Here, we found a significant downregulation of CD73 expression on DNT cells in treatment-naïve PLWH (TNs) compared to healthy controls, accompanied with increased concentration of sCD73 in plasma. Both the frequency of CD73+ DNT cells and the level of plasma sCD73 recovered after ART treatment. However, PIRs showed decreased percentage of CD73+ DNT cells compared to immunological responders (IRs). The frequency of CD73+ DNT cells was positively correlated with CD4+ T cell count and CD4/CD8 ratio, and negatively correlated with immune activation in PLWH. The level of sCD73 also showed a negative correlation to CD4+ T cell count and CD4/CD8 ratio. More importantly, in the present cohort, a higher level of sCD73 at the time of initiating ART could predict poor immune reconstitution in PLWH after long-term ART. Our findings highlighted the importance of CD73+ DNT cells and sCD73 in the disease progression and immune reconstitution of PLWH, and provided evidences for sCD73 as a potential biomarker of predicting immune recovery.

Determinants of suboptimal CD4+ T cell recovery after antiretroviral therapy initiation in a prospective cohort of acute HIV-1 infection

Introduction

Up to 30% of individuals treated with antiretroviral therapy (ART) during chronic HIV fail to recover CD4 counts to >500 cells/mm³ despite plasma viral suppression. We investigated the frequency and associations of suboptimal CD4 recovery after ART started during acute HIV infection (AHI).

Methods

Participants who started ART in Fiebig I to V AHI with ≥48 weeks of continuous documented HIV‐RNA < 50 copies/mL were stratified by CD4 count at latest study visit to suboptimal immune recovery (SIR; CD4 < 350 cells/mm³), intermediate immune recovery (IIR; 350 ≤ CD4 < 500) and complete immune recovery (CIR; CD4 ≥ 500). Clinical and laboratory parameters were assessed at pre‐ART baseline and latest study visit. Additional inflammatory and neurobehavioral endpoints were examined at baseline and 96 weeks.

Results

Of 304 participants (96% male, median 26 years old) evaluated after median 144 (range 60 to 420) weeks of ART initiated at median 19 days (range 1 to 62) post‐exposure, 3.6% (n = 11) had SIR and 14.5% (n = 44) had IIR. Pre‐ART CD4 count in SIR compared to CIR participants was 265 versus 411 cells/mm³ (p = 0.002). Individuals with SIR or IIR had a slower CD4 rate of recovery compared to those with CIR. Timing of ART initiation by Fiebig stage did not affect CD4 count during treatment. Following ART, the CD8⁺T cell count (p = 0.001) and CD4/CD8 ratio (p = 0.047) were lower in SIR compared to CIR participants. Compared to the CIR group at week 96, the combined SIR and IIR groups had higher sCD14 (p = 0.008) and lower IL‐6 (p = 0.04) in plasma, without differences in neuropsychological or psychiatric indices.

Conclusions

Despite immediate and sustained treatment in AHI, suboptimal CD4 recovery occurs uncommonly and is associated with low pre‐ART CD4 count as well as persistent low CD8 count and CD4/CD8 ratio during treatment.

Role of Kupffer Cells in Driving Hepatic Inflammation and Fibrosis in HIV Infection

While the interactions between HIV and various liver cell populations have been explored, the relevance of these interactions when patients are well-controlled on ART is less clear. Therefore, we focus this perspective on HIV-related alterations that may drive hepatic inflammation and fibrosis in aviremic patients, with a focus on Kupffer cells and Hepatic Stellate Cells. Persistent CD4+ T cell depletion in the gut resulting in increased gut permeability has been postulated to play a role in systemic immune activation in HIV patients. The liver, with its unique location, remains the gatekeeper between the gut and the systemic circulation. The resident liver macrophage, Kupffer cell, is responsible for clearing and responding to these products. We propose that changes in Kupffer cell biology, in the context of HIV infection, creates a mileu that drives hepatic inflammation and fibrosis in response to microbial translocation. Targeting these pathways may be helpful in improving liver-related outcomes in HIV patients.

Definition of Immunological Nonresponse to Antiretroviral Therapy: A Systematic Review

BACKGROUND

Terms and criteria to classify people living with HIV on antiretroviral therapy who fail to achieve satisfactory CD4 T-cell counts are heterogeneous, and need revision and summarization.

METHODS

We performed a systematic review of PubMed original research articles containing a set of predefined terms, published in English between January 2009 and September 2018. The search retrieved initially 1360 studies, of which 103 were eligible. The representative terminology and criteria were extracted and analyzed.

RESULTS

Twenty-two terms and 73 criteria to define the condition were identified. The most frequent term was "immunological nonresponders" and the most frequent criterion was "CD4 T-cell count <350 cells/µL after ≥24 months of virologic suppression." Most criteria use CD4+ T-cell counts as a surrogate, either as an absolute value or as a change after a defined period of time [corrected]. Distinct values and time points were used. Only 9 of the 73 criteria were used by more than one independent research team. Herein we propose 2 criteria that could help to reach a consensus.

CONCLUSIONS

The high disparity in terms and criteria here reported precludes data aggregation and progression of the knowledge on this condition, because it renders impossible to compare data from different studies. This review will foster the discussion of terms and criteria to achieve a consensual definition.

Two types of poor immunological responder showing distinct responses to long-term HAART

OBJECTIVES

Most previous studies on poor immunological responders (PIRs) have been performed on one cohort at one time-point following highly active antiretroviral therapy (HAART). The aim of this study was to investigate whether there are different subtypes of PIR and whether a certain population might achieve better immune reconstitution following longer HAART.

METHODS

This study was designed as an ambispective cohort study, including a 4-5-year retrospective study and a 2-year prospective follow-up investigation. Thymic output, activated T cell and regulatory T cell (Treg) subset frequencies, expression levels of interferon-stimulated genes, and plasma concentrations of neopterin were determined at 4-5 years and 6-7 years following HAART initiation.

RESULTS

PIRs were subdivided into two populations after 4-5 years of HAART, according to the kinetics of T cell recovery. Type II PIRs exhibited a significantly lower percentage of naïve CD4⁺ T cells and CD31⁺ naïve CD4⁺ T cells compared with type I PIRs. After an additional 2 years of HAART treatment, type I PIRs showed a better outcome than type II PIRs. Furthermore, it was found that 2 years of additional HAART could persistently improve thymic output.

CONCLUSIONS

The two PIR subgroups are different in terms of immune characteristics and the response to prolonged HAART.

Preserved immune functionality and high CMV-specific T-cell responses in HIV-infected individuals with poor CD4+ T-cell immune recovery

Poor CD4⁺ T-cell recovery after cART has been associated with skewed T-cell maturation, inflammation and immunosenescence; however, T-cell functionality in those individuals has not been fully characterized. In the present study, we assessed T-cell function by assessing cytokine production after polyclonal, CMV and HIV stimulations of T-cells from ART-suppressed HIV-infected individuals with CD4⁺ T-cell counts >350 cells/μL (immunoconcordants) or <350 cells/μL (immunodiscordants). A group of HIV-uninfected individuals were also included as controls. Since CMV co-infection significantly affected T-cell maturation and polyfunctionality, only CMV⁺ individuals were analyzed. Despite their reduced and skewed CD4⁺ T-cell compartment, immunodiscordant individuals showed preserved polyclonal and HIV-specific responses. However, CMV response in immunodiscordant participants was significantly different from immunoconcordant or HIV-seronegative individuals. In immunodiscordant subjects, the magnitude of IFN-γ⁺ CD8⁺ and IL-2⁺ CD4⁺ T-cells in response to CMV was higher and differently associated with the CD4⁺ T-cell maturation profile., showing an increased frequency of naïve, central memory and EMRA CMV-specific CD4⁺ T-cells. In conclusion, CD4⁺ and CD8⁺ T-cell polyfunctionality was not reduced in immunodiscordant individuals, although heightened CMV-specific immune responses, likely related to subclinical CMV reactivations, may be contributing to the skewed T-cell maturation and the higher risk of clinical progression observed in those individuals.

Dendritic cells primed with a chimeric plasmid containing HIV-1-gag associated with lysosomal-associated protein-1 (LAMP/gag) is a potential therapeutic vaccine against HIV

The decline in number and function of T cells is a hallmark of HIV infection, and preservation or restoration of HIV-specific cellular immune response is a major goal of AIDS treatment. Dendritic cells (DCs) play a key role in the initiation and maintenance of the immune response, and their use as a vaccine vehicle is a promising strategy for enhancing vaccine efficacy. We evaluated the potential of DC-mediated immunization with a DNA vaccine consisting of HIV-1-p55gag (gag, group-specific antigen) associated to lysosomal associated protein (LAMP) sequence (LAMP/gag vaccine). Immunization of mice with mouse DCs transfected with LAMP/gag (Lg-mDCs) stimulated more potent B- and T-cell responses than naked DNA or DCs pulsed with inactivated HIV. Anti-Gag antibody levels were sustained for at least 3 mo after immunization, and recall T-cell responses were also strongly detected at this time point. Human DCs transfected with LAMP/gag (Lg-hDCs) were also activated and able to stimulate greater T-cell response than native gag-transfected DCs. Coculture between Lg-hDCs and T lymphocytes obtained from patients with HIV resulted in upregulation of CD38, CD69, HLA-DR, and granzyme B by CD4(+) and CD8(+) T cells, and increased IFN-γ and TNF-α production. These results indicate that the use of LAMP/gag-DC may be an efficient strategy for enhancing immune function in patients with HIV.-Lucas, C. G. D. O., Matassoli, F. L., Peçanha, L. M. T., Santillo, B. T., Oliveira, L. M. D. S., Oshiro, T. M., Marques, E. T. D. A., Jr., Oxenius, A., de Arruda, L. B. Dendritic cells primed with a chimeric plasmid containing HIV-1-gag associated with lysosomal-associated protein-1 (LAMP/gag) is a potential therapeutic vaccine against HIV.

Systemic Cytokine Levels Do Not Predict CD4(+) T-Cell Recovery After Suppressive Combination Antiretroviral Therapy in Chronic Human Immunodeficiency Virus Infection

Background. Subjects on suppressive combination antiretroviral therapy (cART) who do not achieve robust reconstitution of CD4⁺ T cells face higher risk of complications and death. We studied participants in the Women's Interagency HIV Study with good (immunological responder [IR]) or poor (immunological nonresponder [INR]) CD4⁺ T-cell recovery after suppressive cART (n = 50 per group) to determine whether cytokine levels or low-level viral load correlated with INR status.

Methods. A baseline sample prior to viral control and 2 subsequent samples 1 and 2 years after viral control were tested. Serum levels of 30 cytokines were measured at each time point, and low-level human immunodeficiency virus (HIV) viral load and anti-HIV antibody levels were measured 2 years after viral suppression.

Results. There were minimal differences in cytokine levels between IR and INR subjects. At baseline, macrophage inflammatory protein-3β levels were higher in IR subjects; after 1 year of suppressive cART, soluble vascular endothelial growth factor-R3 levels were higher in IR subjects; and after 2 years of suppressive cART, interferon gamma-induced protein 10 levels were higher in INR subjects. Very low-level HIV viral load and anti-HIV antibody levels did not differ between IR and INR subjects.

Conclusions. These results imply that targeting residual viral replication might not be the optimum therapeutic approach for INR subjects.

Discordant responses to cART in HIV-1 patients in the era of high potency antiretroviral drugs: clinical evaluation, classification, management prospects

The goal of antiretroviral treatment (ART) in HIV-1 patients is immune reconstitution following control of viral replication. CD4+ cell number/proportions are a crude but essential correlate of immune reconstitution. Despite suppression of HIV replication, a fraction of ART-treated patients still fails to fully reconstitute CD4+ T cell numbers (immunological nonresponders, INRs). New drugs, regimens and treatment strategies led to increased efficacy, lower side effects and higher virological success rates in clinical practice. The multitude of described immune defects and clinical events accompanying INR opposed to the marginal effect of antiretroviral intensification or immunotherapy trials underline the need for continuing efforts at understanding the mechanisms that underlie INR. Here, we reassess INR definition, frequency, and the achievements of active clinical and translational research suggesting a shared definition for insufficient, partial and complete CD4+ cell number recovery thus improving homogeneity in patient selection and mechanism identification.

Increased Regulatory T-Cell Percentage Contributes to Poor CD4(+) Lymphocytes Recovery: A 2-Year Prospective Study After Introduction of Antiretroviral Therapy

Background. The primary aim of this study was to determine the impact of regulatory T cells (Tregs) percentage on immune recovery in human immunodeficiency virus (HIV)-infected patients after antiretroviral therapy introduction.

Methods. A 2-year prospective study was conducted in HIV-1 chronically infected naive patients with CD4 count <500 cells/mm³. Regulatory T cells were identified as CD4⁺CD25^highCD127^low cells among CD4⁺ lymphocytes. Effect of Treg percentage at inclusion on CD4 evolution overtime was analyzed using a mixed-effect Poisson regression for count data.

Results. Fifty-eight patients were included (median CD4 = 293/mm³, median Treg percentage = 6.1%). Percentage of Treg at baseline and CD4 nadir were independently related to the evolution of CD4 absolute value according to time: (1) at any given nadir CD4 count, 1% increase of initial Treg was associated with a 1.9% lower CD4 absolute value at month 24; (2) at any given Treg percentage at baseline, 10 cell/mm³ increase of CD4 nadir was associated with a 2.4% increase of CD4 at month 24; and (3) both effects did not attenuate with time. The effect of Treg at baseline on CD4 evolution was as low as the CD4 nadir was high.

Conclusions. Regulatory T-cell percentage at baseline is a strong independent prognostic factor of immune recovery, particularly among patients with low CD4 nadir.

Regulatory T cells in HIV-infected immunological nonresponders are increased in blood but depleted in lymphoid tissue and predict immunological reconstitution

BACKGROUND

HIV-infected immunological nonresponders fail to immune reconstitute despite optimal treatment. We hypothesized that regulatory T cells (Tregs) are involved in immunological reconstitution. Tregs and Treg subpopulations were measured in blood and Foxp3 cells in lymphoid tissue, and the impact of Tregs on immunological reconstitution was determined.

METHODS

HIV-infected individuals on combination antiretroviral therapy for a minimum of 2 years were included. The study population included 14 immunological nonresponders (INR; CD4 T-cell count <200 cells/μL), 33 intermediate responders (CD4 T-cell count 200-500 cells/μL), 30 responders (CD4 T-cell count >500 cells/μL), and 34 healthy controls. Tregs, Treg subpopulations, and intracellular staining for interleukin 10 in peripheral blood were measured using flow cytometry. Foxp3 cells in lymphoid tissue were evaluated using immunolabeling. The CD4 T-cell count was determined at inclusion and after 1 year of follow-up.

RESULTS

INR displayed high percentage of Tregs and activated Tregs in peripheral blood accompanied by a high percentage of Tregs expressing interleukin 10, whereas numbers of Foxp3 cells in lymphoid tissue were low. In contrast, responders resembled healthy controls. Finally, in INR, high level of Tregs in blood and Foxp3 cells in lymphoid tissue were associated with higher level of immunological reconstitution after 1 year of follow-up.

CONCLUSIONS

In conclusion, altered distribution of Tregs was found in INR. Interestingly, high level of Tregs predicted higher level of immunological reconstitution suggesting a role for Tregs in immunological reconstitution.

Immunodiscordant responses to HAART--mechanisms and consequences

A relevant fraction of HIV-1-infected individuals (ranging from 15 to 30%) presenting virologically successful highly active antiretroviral therapy fail to recover CD4 T-cell counts. These individuals, called immunodiscordant or immunological nonresponders, are at increased risk of clinical progression and death. Although older age, lower nadir CD4 T-cell count and HCV co-infection are some of clinical predictive factors, immunological mechanisms rely on impaired thymic production and accumulation of apoptosis-prone CD4 T cells. Indeed, immunodiscordant individuals may show increased tissue fibrosis and damage of gut-associated lymphoid tissue that results in higher hyperactivation, inflammation and immunosenescence, altered Treg/Th17 ratio and increased T-cell death. A better knowledge of the final pathogenic mechanism and factors influencing CD4 T-cell recovery will help to select the optimal therapeutic strategies for them.

Association between discordant immunological response to highly active anti-retroviral therapy, regulatory T cell percentage, immune cell activation and very low-level viraemia in HIV-infected patients

The mechanisms sustaining the absence of complete immune recovery in HIV-infected patients upon long-term effective highly active anti-retroviral therapy (HAART) remain elusive. Immune activation, regulatory T cells (T(regs)) or very low-level viraemia (VLLV) have been alternatively suspected, but rarely investigated simultaneously. We performed a cross-sectional study in HIV-infected aviraemic subjects (mean duration of HAART: 12 years) to concomitantly assess parameters associated independently with inadequate immunological response. Patients were classified as complete immunological responders (cIR, n = 48) and inadequate immunological responders (iIR, n = 39), depending on the CD4(+) T cell count (> or < 500/mm(3)). Clinical and virological data (including very low-level viraemia) were collected. In parallel, immunophenotyping of CD4(+) lymphocytes, including T(reg) subsets, and CD8(+) T cells was performed. Percentages of activated CD4(+) T cells, T(regs), effector T(regs) and terminal effector T(regs) were found to be significantly elevated in iIR. Neither the percentage of activated CD8(+) T cells nor VLLV were found to be associated with iIR. In the multivariate analysis, nadir of CD4(+) T cell count and percentage of T(regs) were the only two parameters associated independently with iIR [odds ratio (OR) = 2·339, P = 0·001, and OR = 0·803, P = 0·041]. We present here the largest study investigating simultaneously the immune response to long-term HAART, activation of CD4(+) and CD8(+) T cells, T(reg) percentages and very low-level viraemia. Causative interactions between T(regs) and CD4(+) T cells should now be explored prospectively in a large patients cohort.

Evaluation of the pharmacogenetics of immune recovery in treated HIV-infected patients

INTRODUCTION

Combination antiretroviral therapy has markedly improved the survival rate and quality of life in patients infected with HIV due to the powerful suppressor effect that current antiretroviral drugs have on the viral load. Consequently, the immune system undergoes a substantial qualitative and quantitative improvement; and this leads to an increase in the absolute CD4(+) T-lymphocyte count and the restoration of lost T-cell responses against certain opportunistic pathogens. Unfortunately, not all patients who successfully suppress plasma viremia experience sufficient CD4(+) T-cell gain and these patients, in turn, are associated with worse outcomes. Pharmacogenetic studies have been used to investigate how a patient's genetic predisposition may affect their response to antiretroviral drugs.

AREAS COVERED

This article reviews the investigations that have been published on the association between host genetic determinants of CD4(+) T-cell gain in treated HIV-infected patients. Studies were identified through a PubMed database search. Longitudinal studies into pharmacogenetic association were specifically selected.

EXPERT OPINION

While the possibility of genetic predisposition to HIV therapeutics has potential, most studies provide inconsistent data. Inconsistency is often due to partial genetic evaluation, different categorization of poor immune recovery or due to small numbers of patients evaluated. Currently, studies still belong to the research laboratory stage and more studies are required to improve our understanding.

Impaired CD4⁺ T cell stimulation of NK cell anti-fibrotic activity may contribute to accelerated liver fibrosis progression in HIV/HCV patients

BACKGROUND & AIMS

HIV/HCV co-infection is characterized by a faster progression to liver fibrosis compared to HCV mono-infection. Epidemiologic studies found an association between low CD4(+) T cell counts and advanced stages of liver fibrosis. However, the mechanisms underlying this association remain unclear. CD4(+) T cells critically modulate NK cell activity. Of note, NK cells have been shown to display anti-fibrotic activity via killing of activated hepatic stellate cells (HSC). Thus, we speculated that CD4(+) T cells might modulate fibrosis progression by interacting with NK cells.

METHODS

NK cells from HCV(+) (n=35), HIV(+)/HCV(+) (n=28), HIV(+) (n=8) patients, and healthy controls (n=30) were used in this study. NK cells were cultured in the presence or absence of supernatants from CD3/CD28-stimulated CD4(+) cells. Then, NK cells were co-incubated with activated HSC and studied for degranulation, IFN-γ secretion, and induction of HSC apoptosis.

RESULTS

Following incubation with CD4(+) T cell supernatants, NK cells displayed a significantly increased activity against primary HSC as compared to unstimulated NK cells. This effect was, at least in part, mediated via an IL-2 dependent upregulation of NKG2D expression. HCV/HIV co-infection was associated with an impaired IL-2 secretion of CD4(+) T cells resulting in an ineffective stimulation of anti-fibrotic NK cell function.

CONCLUSIONS

Here, we show that CD4(+) T cells are able to stimulate anti-fibrotic NK cell activity via IL-2 mediated upregulation of NKG2D. HIV-induced loss of CD4(+) T cells together with an impaired activity of CD4(+) T cells may contribute to accelerate progression of liver fibrosis observed in co-infection.

Impact of highly active antiretroviral therapy initiation on CD4(+) T-cell repopulation in duodenal and rectal mucosa

OBJECTIVE

The objective of this study was to assess the effects of HAART initiation on CD4(+) T-cell repopulation and T-cell immune activation in rectal and duodenal mucosa.

DESIGN

The effects of HAART on the gastrointestinal tract remain controversial, and studies have reached different conclusions regarding its effectiveness at restoring mucosal CD4(+) T cells depending upon time of initiation, duration of treatment and gastrointestinal tract region studied.

METHODS

We obtained blood, rectal biopsies and duodenal biopsies from 14 chronically infected individuals at baseline and at 4-9 months post-HAART initiation. We examined CD4(+) T-cell frequencies in blood, rectum and duodenum at both time points, and performed a detailed assessment of CD4(+) T-cell phenotype, immune activation marker expression and HIV-specific CD8(+) T-cell responses in blood and rectal mucosa.

RESULTS

CD4(+) T-cell percentages increased significantly in blood, rectal and duodenal mucosa after 4-9 months of HAART (P = 0.02, 0.0005, 0.0002), but remained lower than in uninfected controls. HIV-specific CD8(+) T-cell responses in blood and rectal mucosa declined following HAART initiation (P = 0.0015, 0.021). CD8(+) T-cell coexpression of CD38 and HLA-DR in blood and mucosa, as well as plasma sCD14, declined significantly. CD28 expression on blood and mucosal CD8(+) T cells increased, whereas programmed death receptor-1 expression on blood HIV-specific CD4(+) and CD8(+) T cells decreased.

CONCLUSION

Within the first months of HAART, limited CD4(+) T-cell reconstitution occurs in small and large intestinal mucosa. Nevertheless, decreased immune activation and increased CD28 expression suggest rapid immunological benefits of HAART despite incomplete CD4(+) T-cell reconstitution.

CD4⁺ and CD8⁺ regulatory T cells (Tregs) are elevated and display an active phenotype in patients with chronic HCV mono-infection and HIV/HCV co-infection

The aim of this study was to examine regulatory T cells (Tregs) in peripheral blood and liver tissue in patients with chronic hepatitis C virus (HCV) mono-infection and in patients with HIV/HCV co-infection. In a cross-sectional study were included 51 patients with chronic HCV infection, 24 patients with HIV/HCV co-infection and 24 healthy individuals. CD4⁺ and CD8⁺ Tregs were determined using flow cytometry. Fibrosis was examined by transient elastography. Inflammation, fibrosis and Tregs were determined in liver biopsies from 12 patients. Increased frequency of CD4⁺ and CD8⁺ Tregs was found in HIV/HCV co-infected patients [median: 6.4% (IQR: 5.7-6.9) and 1.0% (0.7-1.2), respectively] compared to HCV mono-infected patients [5.6% (4.2-6.3), P = 0.01 and 0.5% (0.3-0.7), P < 0.001, respectively]. Furthermore, HCV mono-infected patients had increased frequencies of Tregs compared with healthy controls (P < 0.05). However, no associations between the frequency of Tregs and fibrosis were found. Furthermore, characterization of CD4⁺ Tregs using CD45RA demonstrated a higher frequency of activated Tregs in both HCV mono-infected and HIV/HCV co-infected patients compared with healthy controls. Finally, number of intrahepatic Tregs was associated with both peripheral CD8⁺ Tregs and intrahepatic inflammation. In conclusion, HCV mono-infected patients and particularly HIV/HCV co-infected patients have increased the frequency of CD4⁺ and CD8⁺ Tregs compared with healthy controls. Furthermore, CD4⁺ Tregs in infected patients displayed an active phenotype. Tregs were not associated with fibrosis, but a positive correlation between intrahepatic Tregs and inflammation was found. Taken together, these results suggest a role for Tregs in the pathogenesis of chronic HCV infection.

Immunosenescence and HIV

PURPOSE OF REVIEW

The present review discusses the interplay between HIV infection and other environmental factors (e.g. co-infection with CMV) in the acceleration of the aging process of the immune system, leading to 'immunosenescence.'

RECENT FINDINGS

Basic studies in cell biology demonstrate that replicative senescence is a common pathway of many cell lineages, including those of the immune system, characterized by activation of a unique pro-inflammatory secretory program. In the setting of HIV disease, this process is accelerated, resulting in an immunosuppressed state that diminishes the ability of the immune system to contain virus while at the same time facilitating viral replication and spread. Clinically, these changes result in a lower capacity to respond to new infections as well as an increased frequency of age-associated end-organ disease (e.g. cardiovascular complications, cancer, and neurologic disease).

SUMMARY

Accelerated immunosenescence in the setting of HIV disease is associated with increased morbidity and mortality, prompting the need for more investigation into its causes, diagnosis, and treatment.

Severe immune dysregulation affects CD4⁺CD25(hi)FoxP3⁺ regulatory T cells in HIV-infected patients with low-level CD4 T-cell repopulation despite suppressive highly active antiretroviral therapy

We hypothesized that CD4(+)CD25(hi)FoxP3(+) regulatory T cells (Tregs) could be involved in the high immune activation existing in patients with low-level CD4 T-cell repopulation under suppressive high active antiretroviral therapy (hereafter, "LLR patients"). Sixteen LLR patients, 18 human immunodeficiency virus (HIV)-infected controls (hereafter, "HIV controls"), and 16 healthy subjects were included. The frequency of CD4(+)CD25(hi)FoxP3(+) and HIV-specific Treg suppressive function were assessed. Relationships between Treg and CD4/CD8 activation (HLA-DR/CD38) and the frequency of naive CD4 T-cells were assessed. Low-level patients showed a higher Treg frequency but reduced HIV-specific immunosuppressive functions than HIV controls. Whereas in healthy subjects a strong negative correlation between Tregs and activated CD8 T cells emerged (r = -0.75, P < .001), it appeared disrupted in both HIV-infected groups (r = -0.06 and P = .83 for LLR patients; r = -0.11 and P = .68 for and HIV controls). Nevertheless, in LLR patients, Tregs negatively correlated with naive CD4 T cells (r = -0.60, P = .01), whereas there was no such correlation in HIV controls (r = -0.19, P = .46) or healthy subjects (r = -0.10, P = .73). Remarkably, a higher ratio of Tregs to naive CD4 T cells was observed in LLR patients than in HIV controls (P = .001) and healthy subjects (P < .001). We conclude that LLR patients have important alterations in immunoregulation involving CD4(+)CD25(hi)FoxP3(+) Tregs. In this scenario, the role of Tregs seems to be more related to the control of the naive CD4 T-cell homeostatic proliferation, rather than to the immune activation.

Incomplete immune recovery in HIV infection: mechanisms, relevance for clinical care, and possible solutions

Treatment of HIV-infected patients with highly active antiretroviral therapy (HAART) usually results in diminished viral replication, increasing CD4+ cell counts, a reversal of most immunological disturbances, and a reduction in risk of morbidity and mortality. However, approximately 20% of all HIV-infected patients do not achieve optimal immune reconstitution despite suppression of viral replication. These patients are referred to as immunological nonresponders (INRs). INRs present with severely altered immunological functions, including malfunction and diminished production of cells within lymphopoetic tissue, perturbed frequencies of immune regulators such as regulatory T cells and Th17 cells, and increased immune activation, immunosenescence, and apoptosis. Importantly, INRs have an increased risk of morbidity and mortality compared to HIV-infected patients with an optimal immune reconstitution. Additional treatment to HAART that may improve immune reconstitution has been investigated, but results thus far have proved disappointing. The reason for immunological nonresponse is incompletely understood. This paper summarizes the known and unknown factors regarding the incomplete immune reconstitution in HIV infection, including mechanisms, relevance for clinical care, and possible solutions.

HIV-1/mycobacterium tuberculosis coinfection immunology: how does HIV-1 exacerbate tuberculosis?

Human immunodeficiency virus type 1 (HIV) and Mycobacterium tuberculosis have become intertwined over the past few decades in a "syndemic" that exacerbates the morbidity and mortality associated with each pathogen alone. The severity of the coinfection has been extensively examined in clinical studies. The extrapolation of peripheral evidence from clinical studies has increased our basic understanding of how HIV increases susceptibility to TB. These studies have resulted in multiple hypotheses of how HIV exacerbates TB pathology through the manipulation of granulomas. Granulomas can be located in many tissues, most prominently the lungs and associated lymph nodes, and are made up of multiple immune cells that can actively contain M. tuberculosis. Granuloma-based research involving both animal models and clinical studies is needed to confirm these hypotheses, which will further our understanding of this coinfection and may lead to better treatment options. This review examines the data that support each hypothesis of how HIV manipulates TB pathology while emphasizing a need for more tissue-based experiments.

Preclinical evaluation of HIV-1 therapeutic ex vivo dendritic cell vaccines expressing consensus Gag antigens and conserved Gag epitopes

BACKGROUND

Dendritic cell (DC) therapy is a promising technology for the treatment of HIV infected individuals. HIV-1 Gag- and Nef RNA-loaded DC have previously been shown to induce immune responses ex vivo following coculture with autologous lymphocytes. However, polyfunctionality and memory responses following coculture have not been evaluated. In addition, little is known regarding whether specific HIV-1 proteome components, such as highly conserved regions of the HIV-1, could enhance clinical responses following DC therapy.

METHODOLOGY AND PRINCIPAL FINDINGS

To determine the breadth of the immune responses to antigen loaded DC, we analyzed polyfunctional T cell response ex vivo to Gag RNA loaded DC. Blood samples were used to generate monocyte derived DC, which were then matured and cocultured with autologous lymphocytes. We found that cytokine-matured DC loaded with Gag RNA was able to induce Gag-specific IFN-γ and IL-2 responses after a 12-day coculture. We characterized these responses by polyfunctional intracellular cytokine staining and evaluation of T cell memory phenotypes. Central memory CD8+ T cells were induced ex vivo after DC coculture from each of 3 patients, and the effector memory pool was increased by DC coculture from 2 patients. We also observed a decrease in the terminal effector and intermediate CD8+ T cell pool and an increase in the naïve/other population. There was a reduction in terminal effector and intermediate CD4+ T cells, and a corresponding increase in naïve/other CD4+ T cells. Finally, we evaluated conserved regions of Gag as a novel DC therapy immunogen and found that a conserved element (CE) p24 Gag antigen elicited IFN-γ and IL-2 responses comparable to those induced by a full-length Gag antigen.

CONCLUSIONS

We showed that RNA-loaded DC therapy induced a polyfunctional T cell response ex vivo, supporting the use of such DC-therapy for HIV infection. However, the central and effector memory phenotypes of T cells did not appear to be enhanced during coculture with Gag RNA-loaded DC. Furthermore, comparable antigen-specific responses were induced in HIV infected individuals using full-length Gag or only conserved elements of the Gag p24 protein. This indicates that immune responses can be focused onto the conserved elements of Gag in the absence of other Gag components.