The γδ T-cell receptor repertoire is reconstituted in HIV patients after prolonged antiretroviral therapy

Intravenous Bacillus Calmette-Guérin (BCG) Induces a More Potent Airway and Lung Immune Response than Intradermal BCG in Simian Immunodeficiency Virus-infected Macaques

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the leading causes of death due to an infectious agent. Coinfection with HIV exacerbates M. tuberculosis infection outcomes in people living with HIV. Bacillus Calmette-Guérin (BCG), the only approved TB vaccine, is effective in infants, but its efficacy in adolescents and adults is limited. In this study, we investigated the immune responses elicited by BCG administered via i.v. or intradermal (i.d.) routes in SIV-infected Mauritian cynomolgus macaques (MCM) without the confounding effects of M. tuberculosis challenge. We assessed the impact of vaccination on T cell responses in the airway, blood, and tissues (lung, thoracic lymph nodes, and spleen), as well as the expression of cytokines, cytotoxic effectors, and key transcription factors. Our results showed that i.v. BCG induces a robust and sustained immune response, including tissue-resident memory T cells in lungs, polyfunctional CD4+ and CD8αβ+ T cells expressing multiple cytokines, and CD8αβ+ T cells and NK cells expressing cytotoxic effectors in airways. We also detected higher levels of mycobacteria-specific IgG and IgM in the airways of i.v. BCG-vaccinated MCM. Although i.v. BCG vaccination resulted in an influx of tissue-resident memory T cells in lungs of MCM with controlled SIV replication, MCM with high plasma SIV RNA (>105 copies/ml) typically displayed reduced T cell responses, suggesting that uncontrolled SIV or HIV replication would have a detrimental effect on i.v. BCG-induced protection against M. tuberculosis.

Vδ1 Effector and Vδ2 γδ T-Cell Subsets Shift in Frequency and Are Linked to Plasma Inflammatory Markers During Antiretroviral Therapy-Suppressed HIV Infection

BACKGROUND

Chronic inflammation is prevalent with antiretroviral therapy (ART)-suppressed human immunodeficiency virus (HIV) infection and one immune cell subset putatively driving this phenomenon is TIGIT+ γδ T cells.

METHODS

To elucidate γδ T-cell phenotypic diversity, spectral flow cytometry was performed on blood lymphocytes from individuals of a HIV and aging cohort and data were analyzed using bioinformatic platforms. Plasma inflammatory markers were measured and correlated with γδ T-cell subset frequencies.

RESULTS

Thirty-nine distinct γδ T-cell subsets were identified (22 Vδ1+, 14 Vδ2+, and 3 Vδ1-Vδ2-Vγ9+) and TIGIT was nearly exclusively found on the Vδ1+CD45RA+CD27- effector populations. People with ART-suppressed HIV infection (PWH) exhibited high frequencies of distinct clusters of Vδ1+ effectors distinguished via CD8, CD16, and CD38 expression. Among Vδ2+ cells, most Vγ9+ (innate-like) clusters were lower in PWH; however, CD27+ subsets were similar in frequency between participants with and without HIV. Comparisons by age revealed lower 'naive' Vδ1+CD45RA+CD27+ cells in older individuals, regardless of HIV status. Plasma inflammatory markers were selectively linked to subsets of Vδ1+ and Vδ2+ cells.

CONCLUSIONS

These results further elucidate γδ T-cell subset complexity and reveal distinct alterations and connections with inflammatory pathways of Vδ1+ effector and Vδ2+ innate-like subsets during ART-suppressed HIV infection.

γδ T cells mediate robust anti-HIV functions during antiretroviral therapy regardless of immune checkpoint expression

Objectives

Although antiretroviral therapy (ART) efficiently suppresses HIV viral load, immune dysregulation and dysfunction persist in people living with HIV (PLWH). γδ T cells are functionally impaired during untreated HIV infection, but the extent to which they are reconstituted upon ART is currently unclear.

Methods

Utilising a cohort of ART-treated PLWH, we assessed the frequency and phenotype, characterised in vitro functional responses and defined the impact of immune checkpoint marker expression on effector functions of both Vδ1 and Vδ2 T cells. We additionally explore the in vitro expansion of Vδ2 T cells from PLWH on ART and the mechanisms by which such expanded cells may sense and kill HIV-infected targets.

Results

A matured NK cell-like phenotype was observed for Vδ1 T cells among 25 ART-treated individuals (PLWH/ART) studied compared to 17 HIV-uninfected controls, with heightened expression of 2B4, CD160, TIGIT and Tim-3. Despite persistent phenotypic perturbations, Vδ1 T cells from PLWH/ART exhibited strong CD16-mediated activation and degranulation, which were suppressed upon Tim-3 and TIGIT crosslinking. Vδ2 T cell degranulation responses to the phosphoantigen (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate at concentrations up to 2 ng mL-1 were significantly impaired in an immune checkpoint-independent manner among ART-treated participants. Nonetheless, expanded Vδ2 T cells from PLWH/ART retained potent anti-HIV effector functions, with the NKG2D receptor contributing substantially to the elimination of infected cells.

Conclusion

Our findings highlight that although significant perturbations remain within the γδ T cell compartment throughout ART-treated HIV, both subsets retain the capacity for robust anti-HIV effector functions.

Impact of BCG vaccination on the repertoire of human γδ T cell receptors

Introduction

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection is a serious threat to human health. Vaccination with BCG prevents the development of the most severe forms of TB disease in infants and was recently shown to prevent Mtb infection in previously uninfected adolescents. γδ T cells play a major role in host defense at mucosal sites and are known to respond robustly to mycobacterial infection. However, our understanding of the effects of BCG vaccination on γδ T cell responses is incomplete.

Methods

In this study we performed γδ T cell receptor (TCR) repertoire sequencing of samples provided pre- and post-BCG vaccination from 10 individuals to identify specific receptors and TCR clones that are induced by BCG.

Results

Overall, there was no change in the diversity of γTCR or δTCR clonotypes in post- vs pre-BCG samples. Furthermore, the frequencies of TCR variable and joining region genes were minimally modulated by BCG vaccination at either the γTCR or δTCR loci. However, the γTCR and δTCR repertoires of individuals were highly dynamic; a median of ~1% of γTCR and ~6% of δTCR in the repertoire were found to significantly expand or contract in post- vs pre-BCG comparisons (FDR-q < 0.05). While many of the clonotypes whose frequency changed after BCG vaccination were not shared among multiple individuals in the cohort, several shared (i.e., "public") clonotypes were identified with a consistent increase or decrease in frequency across more than one individual; the degree of sharing of these clonotypes was significantly greater than the minimal sharing that would be expected among γTCR and δTCR repertoires. An in vitro analysis of Mtb antigen-reactive γδ T cells identified clonotypes that were similar or identical to the single-chain γTCRs and δTCRs that changed consistently after BCG vaccination; pairings of γTCRs and δTCRs that increased after BCG vaccination were significantly over-represented among the Mtb-reactive γδ T cells (p = 1.2e-6).

Discussion

These findings generate hypotheses about specific γδTCR clonotypes that may expand in response to BCG vaccination and may recognize Mtb antigens. Future studies are required to validate and characterize these clonotypes, with an aim to better understand the role of γδ T cells in Mtb immunity.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

How to Train Your Dragon: Harnessing Gamma Delta T Cells Antiviral Functions and Trained Immunity in a Pandemic Era

The emergence of viruses with pandemic potential such as the SARS-CoV-2 coronavirus causing COVID-19 poses a global health challenge. There is remarkable progress in vaccine technology in response to this threat, but their design often overlooks the innate arm of immunity. Gamma Delta (γδ) T cells are a subset of T cells with unique features that gives them a key role in the innate immune response to a variety of homeostatic alterations, from cancer to microbial infections. In the context of viral infection, a growing body of evidence shows that γδ T cells are particularly equipped for early virus detection, which triggers their subsequent activation, expansion and the fast deployment of antiviral functions such as direct cytotoxic pathways, secretion of cytokines, recruitment and activation of other immune cells and mobilization of a trained immunity memory program. As such, γδ T cells represent an attractive target to stimulate for a rapid and effective resolution of viral infections. Here, we review the known aspects of γδ T cells that make them crucial component of the immune response to viruses, and the ways that their antiviral potential can be harnessed to prevent or treat viral infection.

The Unknown Unknowns: Recovering Gamma-Delta T Cells for Control of Human Immunodeficiency Virus (HIV)

Recent advances in γδ T cell biology have focused on the unique attributes of these cells and their role in regulating innate and adaptive immunity, promoting tissue homeostasis, and providing resistance to various disorders. Numerous bacterial and viral pathogens, including human immunodeficiency virus-1 (HIV), greatly alter the composition of γδ T cells in vivo. Despite the effectiveness of antiretroviral therapy (ART) in controlling HIV and restoring health in those affected, γδ T cells are dramatically impacted during HIV infection and fail to reconstitute to normal levels in HIV-infected individuals during ART for reasons that are not clearly understood. Importantly, their role in controlling HIV infection, and the implications of their failure to rebound during ART are also largely unknown and understudied. Here, we review important aspects of human γδ T cell biology, the effector and immunomodulatory properties of these cells, their prevalence and function in HIV, and their immunotherapeutic potential.

Comparable Vδ2 Cell Functional Characteristics in Virally Suppressed People Living with HIV and Uninfected Individuals

Crosstalk between innate and adaptive pathways is a critical component to developing an effective, lasting immune response. Among natural effector cells, innate-like γδ T cells promote immunity by facilitating communication between the two compartments and exerting cytotoxic effector functions. Dysregulation of γδ T cell populations is a byproduct of primary Humanimmunodeficiency virus (HIV) infection. This is most pronounced in the depletion and loss of function within cells expressing a Vγ9Vδ2 TCR (Vδ2 cells). Whether or not prolonged viral suppression mediated by antiretroviral therapy (ART) can reverse these effects has yet to be determined. In this study, we present evidence of similar Vδ2 cell functional responses within a cohort of people living with HIV (PLWH) that has been stably suppressed for >1 year and uninfected donors. Through the use of aminobisphosphonate drugs, we were able to generate a comprehensive comparison between ex vivo and expanded Vδ2 cells within each group. Both groups had largely similar compositions of memory and effector phenotypes, post-expansion TCR repertoire diversity, and cytotoxic capabilities. Our findings support the notion that ART promotes the recovery of Vδ2 polyfunctionality and provides insight for strategies aiming to reconstitute the full immune response after infection with HIV.

Reversal of Immunity After Clearance of Chronic HCV Infection-All Reset?

Chronic viral infections cause deterioration of our immune system. However, since persistent infections rarely can be eliminated, the reinvigoration capacity of an exhausted immune system has remained largely elusive. Chronic hepatitis C virus (HCV) infection can since some years be effectively cured with novel direct acting antiviral agents. Thus, it is now possible to study reversal of immunity in patients that are cured from a long-lasting chronic infection. We here highlight recent developments in the analysis of various immune cell populations during and after clearance of HCV infection. Surprisingly, whereas reinvigoration of certain immune traits clearly can be seen, many features of immune exhaustion persist over time after viral elimination. Thus, a long-term chronic insult might result in irreversible damage to our immune system. This will be important to consider in therapeutic vaccination efforts against chronic infection and in the development of immunotherapy based strategies against cancer.

Human γδ TCR Repertoires in Health and Disease

The T cell receptor (TCR) repertoires of γδ T cells are very different to those of αβ T cells. While the theoretical TCR repertoire diversity of γδ T cells is estimated to exceed the diversity of αβ T cells by far, γδ T cells are still understood as more invariant T cells that only use a limited set of γδ TCRs. Most of our current knowledge of human γδ T cell receptor diversity builds on specific monoclonal antibodies that discriminate between the two major subsets, namely Vδ2⁺ and Vδ1⁺ T cells. Of those two subsets, Vδ2⁺ T cells seem to better fit into a role of innate T cells with semi-invariant TCR usage, as compared to an adaptive-like biology of some Vδ1⁺ subsets. Yet, this distinction into innate-like Vδ2⁺ and adaptive-like Vδ1⁺ γδ T cells does not quite recapitulate the full diversity of γδ T cell subsets, ligands and interaction modes. Here, we review how the recent introduction of high-throughput TCR repertoire sequencing has boosted our knowledge of γδ T cell repertoire diversity beyond Vδ2⁺ and Vδ1⁺ T cells. We discuss the current understanding of clonal composition and the dynamics of human γδ TCR repertoires in health and disease.

Identification of the Ligands of TCRγδ by Screening the Immune Repertoire of γδT Cells From Patients With Tuberculosis

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection is a serious threat to human health. γδT cells, which are characterized by major histocompatibility complex (MHC) non-restriction, are rapidly activated and initiate anti-infectious immune responses in the early stages of Mtb infection. However, the mechanism underlying the recognition of Mtb by γδT cells remains unclear. In this study, we characterized the pattern of the human T-cell receptor (TCR) γδ complementary determinant region 3 (CDR3) repertoire in TB patients by using high-throughput immune repertoire sequencing. The results showed that the diversity of CDR3δ was significantly reduced and that the frequency of different gene fragments (V/J), particularly the V-segment of the δ-chain, was substantially altered, which indicate that TB infection-related γδT cells, especially the δ genes, were activated and amplified in TB patients. Then, we screened the Mtb-associated epitopes/proteins recognized by γδT cells using an Mtb proteome chip with dominant CDR3δ peptides as probes. We identified the Mtb protein Rv0002 as a potential ligand capable of stimulating the activation and proliferation of γδT cells. Our findings provide a further understanding of the mechanisms underlying γδT cell-mediated immunity against Mtb infection.

Persistent gamma delta T-cell dysfunction in chronic HCV infection despite direct-acting antiviral therapy induced cure

Immune dysfunction is a hallmark of chronic HCV infection and viral clearance with direct antivirals recover some of these immune defects. TCRVγ9Vδ2 T-cell dysfunction in treated HCV patients however is not well studied and was the subject of this investigation. Peripheral blood cells from patients who had achieved sustained virologic response (SVR) or those who had relapsed after interferon-free therapy were phenotyped using flow cytometry. Functional potential of Vγ9Vδ2 T cells was tested by measuring proliferation in response to aminobisphosphonate zoledronic acid, and cytotoxicity against HepG2 hepatoma cell line. TCR sequencing was performed to analyse impact of HCV infection on Vδ2 T-cell repertoire. Vγ9Vδ2 cells from patients were activated and therapy resulted in reduction of CD38 expression on these cells in SVR group. Relapsed patients had Vδ2 cells with persistently activated and terminally differentiated cytotoxic phenotype (CD38⁺ CD45RA⁺ CD27^- CD107a⁺ ). Irrespective of outcome with therapy, majority of patients had persistently poor Vδ2 T-cell proliferative response to zoledronate along with lower expression of CD56, which identifies anti-tumour cytotoxic subset, relative to healthy controls. There was no association between the number of antigen reactive Vγ2-Jγ1.2 TCR rearrangements at baseline and levels of proliferation indicating nonresponse to zoledronate is not due to depletion of phosphoantigen responding chains. Thus, HCV infection results in circulating Vγ9Vδ2 T cells with a phenotype equipped for immediate effector function but poor cytokine response and expansion in response to antigen, a functional defect that may have implications for susceptibility for carcinogenesis despite HCV cure.

High Activation of γδ T Cells and the γδ2pos T-Cell Subset Is Associated With the Onset of Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome, ANRS 12153 CAPRI NK

Background: Human Immunodeficiency Virus 1 (HIV-1) and Mycobacterium Tuberculosis (Mtb) co-infected patients are commonly at risk of immune reconstitution inflammatory syndrome (IRIS) when initiating antiretroviral treatment (ART). Evidence indicates that innate immunity plays a role in TB-IRIS. Here, we evaluate the phenotype of Gamma-delta (γδ) T cells and invariant Natural Killer (iNK) T cells in tuberculosis-associated IRIS.

Methods: Forty-eight HIV+/TB+ patients (21 IRIS) and three control groups: HIV–/TB– (HD, n = 11), HIV+/TB– (n = 26), and HIV–/TB+ (n = 22) were studied. Samples were taken at ART initiation (week 2 of anti-tuberculosis treatment) and at the diagnosis of IRIS for HIV+/TB+; before ART for HIV+/TB-, and at week 2 of anti-tuberculosis treatment for HIV–/TB+ patients. γδ T cells and Invariant natural killer T (iNKT) cells were analyzed by flow cytometry.

Results: Before ART, IRIS, and non-IRIS patients showed a similar proportion of γδ^pos T and iNKT cells. HLA-DR on γδ^pos T cells and δ2^posγδ^pos T cells was significantly higher in TB-IRIS vs. non-IRIS patients and controls (p < 0.0001). NKG2D expression on γδ^pos T cells and the δ2^posγδ^pos T cell subset was lower in HIV+/TB+ patients than controls. CD158a expression on γδ^pos T cells was higher in TB-IRIS than non-IRIS (p = 0.02), HIV+/TB–, and HIV–/TB- patients.

Conclusion: The higher activation of γδ^posT cells and the γδ2^posγδ^pos T cell subset suggests that γδ T cells may play a role in the pathogenesis of TB-IRIS.

γδ T-cell responses during HIV infection and antiretroviral therapy

HIV infection is associated with a rapid and sustained inversion of the Vδ1:Vδ2 T‐cell ratio in peripheral blood. Studies of antiretroviral therapy (ART)‐treated cohorts suggest that ART is insufficient to reconstitute either the frequency or function of the γδ T‐cell subset. Recent advances are now beginning to shed light on the relationship between microbial translocation, chronic inflammation, immune ageing and γδ T‐cell immunology. Here, we review the impact of acute, chronic untreated and treated HIV infection on circulating and mucosal γδ T‐cell subsets and highlight novel approaches to harness γδ T cells as components of anti‐HIV immunotherapy.

A comprehensive immune repertoire study for patients with pulmonary tuberculosis

BACKGROUND

Tuberculosis (TB) is a major global health problem and has replaced HIV as the leading cause of death from a single infectious agent.

METHODS

Here, we applied high throughput sequencing to study the immune repertoire of nine pulmonary tuberculosis patients and nine healthy control samples.

RESULTS

Tuberculosis patients and healthy controls displayed significantly different high express clones and distinguishable sharing of CDR3 sequences. The TRBV and TRBJ gene usage showed higher expression clones in patients than in controls and we also found specific high express TRBV and TRBJ gene clones in different groups. In addition, six highly expressed TRBV/TRBJ combinations were detected in the CD4 group, 21 in the CD8 group and 32 in the tissue group.

CONCLUSION

In conclusion, we studied the patients with tuberculosis as well as healthy control individuals in order to understand the characteristics of immune repertoire. Sharing of CDR3 sequences and differential expression of genes was found among the patients with tuberculosis which could be used for the development of potential vaccine and targets treatment.

Next generation sequencing reveals changes of the γδ T cell receptor repertoires in patients with pulmonary tuberculosis

Tuberculosis (TB) is a severe global threat to human health. The immune protection initiated by γδ T cells play an important role in mycobacterial infection. Vaccines for Mycobacterium tuberculosis (Mtb) based on γδ T cells provide a novel approach for TB control. In our previous studies, we found a preponderant complementarity-determining region 3 (CDR3) sequence of the γδ T cell receptor (TCR) in TB patients, and successfully identified a tuberculosis antigen that can effectively activate γδ T cells with a reverse genetic strategy. However, due to the throughput limitation of the method we used, the information we obtained about the γδ TCR repertoire and preponderant CDR3 sequences was limited. In this study, we introduced next generation sequencing (NGS) to study the γδ TCR CDR3 repertoires in TB patients. We found that the CDR3δ tended to be more polyclonal and CDR3γ tended to be longer in TB patients; the γδ T cells expressing CDR3 sequences using a Vγ9-JγP rearrangement expanded significantly during Mtb infection. We also identified new preponderant CDR3 sequences during Mtb infection. This study comprehensively characterized the γδ T cell receptor repertoire changes, and provides useful information for the development of new vaccines and adjuvants against TB.

Interleukin-18 activates Vγ9Vδ2+ T cells from HIV-positive individuals: recovering the response to phosphoantigen

The study aimed to identify an immunoregulatory factor that restores the phosphoantigen response of Vγ9Vδ2⁺ T cells from HIV-positive individuals on antiretroviral therapy. It was designed to characterize the effects of interleukin-18 (IL-18) on proliferation and effector function in Vγ9Vδ2 T cells from HIV-negative individuals and test whether exogenous IL-18 reconstitutes the Vγ9Vδ2 T-cell response to phosphoantigen from HIV-positive donors. Vγ9Vδ2 T cells from HIV-negative individuals responded strongly to phosphoantigen or aminobisphosphonate stimulation of peripheral blood mononuclear cells (PBMC), whereas cells with similar T-cell receptor profiles from HIV-positive individuals only responded to aminobisphosphonate. Interleukin-18 was higher after aminobisphosphonate stimulation due to activation of the inflammasome pathway. Both IL-18 and IL-18 receptor levels were measured and the activity of exogenous IL-18 on HIV-negative and HIV-positive PBMC was evaluated in terms of Vγ9Vδ2 T-cell proliferation, memory subsets, cytokine expression and CD107a expression. Interleukin-18 stimulation increased proliferation, enhanced the accumulation of effector memory cells, and increased expression of cytotoxic markers in HIV-negative controls. When Vγ9Vδ2 T cells from HIV-positive individuals were stimulated with isopentenyl pyrophosphate in the presence of IL-18, there was increased proliferation, accumulation of memory cells, and higher expression of CD56, NKG2D and CD107a (markers of cytotoxic effector phenotype). Interleukin-18 stimulation specifically expanded the Vγ9-JγP⁺ subset of Vγ9Vδ2 T cells, as was expected for normal responses to phosphoantigen. Interleukin-18 is a potent stimulator of Vγ9Vδ2 T-cell proliferation and effector function. Therapies directed at reconstituting Vγ9Vδ2 T-cell activity in HIV-positive individuals should include stimulators of IL-18 or direct cytokine supplementation.

Evolution and function of the TCR Vgamma9 chain repertoire: It's good to be public

Lymphocytes expressing a T cell receptor (TCR) composed of Vgamma9 and Vdelta2 chains represent a minor fraction of human thymocytes. Extrathymic selection throughout post-natal life causes the proportion of cells with a Vgamma9-JP rearrangement to increase and elevates the capacity for responding to non-peptidic phosphoantigens. Extrathymic selection is so powerful that phosphoantigen-reactive cells comprise about 1 in 40 circulating memory T cells in healthy adults and the subset expands rapidly upon infection or in response to malignancy. Skewing of the gamma delta TCR repertoire is accompanied by selection for public gamma chain sequences such that many unrelated individuals overlap extensive in their circulating repertoire. This type of selection implies the presence of a monomorphic antigen-presenting molecule that is an object of current research but remains incompletely defined. While selection on a monomorphic presenting molecule may seem unusual, similar mechanisms shape the alpha beta T cell repertoire including the extreme examples of NKT or mucosal-associated invariant T cells (MAIT) and the less dramatic amplification of public Vbeta chain rearrangements driven by individual MHC molecules and associated with resistance to viral pathogens. Selecting and amplifying public T cell receptors whether alpha beta or gamma delta, are important steps in developing an anticipatory TCR repertoire. Cell clones expressing public TCR can accelerate the kinetics of response to pathogens and impact host survival.

γδ T Cells in HIV Disease: Past, Present, and Future

Human immunodeficiency virus (HIV) type 1 dysregulates γδ T cells as part of an immune evasion mechanism. Nearly three decades of research defined the effects of HIV on γδ T cells and how this impacts disease. With highly effective antiretroviral therapy providing virus suppression and longer survival, we expected a return to normal for γδ T cells. This is not the case. Even in patients with CD4 T cell reconstitution, normal γδ T cell levels and function are not recovered. The durable damage to Vδ2 T cells is paralleled by defects in NK, CD8 T cells, and dendritic cells. Whether these consequences of HIV stem from similar or distinct mechanisms are not known and effective means for recovering the full range of cellular immunity have not been discovered. These unanswered questions receive too little attention in the overall program of efforts to cure HIV this disease. Approved drugs capable of increasing Vδ2 T cell function are being tested in clinical trials for cancer and hold promise for restoring normal function in patients with HIV disease. The impetus for conducting clinical trials will come from understanding the significance of γδ T cells in HIV disease and what might be gained from targeted immunotherapy. This review traces the history and current progress of AIDS-related research on γδ T cells. We emphasize the damage to γδ T cells that persists despite effective virus suppression. These chronic immune deficits may be linked to the comorbidities of AIDS (cancer, cardiovascular disease, metabolic disease, and others) and will hinder efforts to eradicate HIV by cytotoxic T or NK cell killing. Here, we focus on one subset of T cells that may be critical in the pathogenesis of HIV and an attractive target for new immune-based therapies.

Distortion of memory Vδ2 γδ T cells contributes to immune dysfunction in chronic HIV infection

γδ T cells play important roles in innate immunity as the first-line of defense against infectious diseases. Human immunodeficiency virus (HIV) infection disrupts the balance between Vδ(1) T cells and Vδ(2) T cells and causes dysfunction among γδ T cells. However, the biological mechanisms and clinical consequences of this disruption require further investigation. In this study, we performed a comprehensive analysis of phenotype and function of memory γδ T cells in cohorts of Chinese individuals with HIV infection. We found a dynamic change in memory Vδ(2) γδ T cells, skewed toward an activated and terminally differentiated effector memory phenotype T(EMRA) Vδ(2) γδ T cell, which may account for the dysfunction of Vδ(2) γδ T cells in HIV disease. In addition, we found that IL-17-producing γδ T cells were significantly increased in HIV-infected patients with fast disease progression and positively correlated with HLA-DR(+) γδ T cells and CD38(+)HLA-DR(+) γδ T cells. This suggests the IL-17 signaling pathway is involved in γδ T-cell activation and HIV pathogenesis. Our findings provide novel insights into the role of Vδ(2) T cells during HIV pathogenesis and represent a sound basis on which to consider immune therapies with these cells.

Levels of CD56+TIM-3- effector CD8 T cells distinguish HIV natural virus suppressors from patients receiving antiretroviral therapy

Prolonged antiretroviral therapy (ART) with effective HIV suppression and reconstitution of CD4 T cells, fails to restore CD8 T cell lytic effector function that is needed to eradicate the viral reservoir. Better understanding of the phenotype and function of circulating CD8 cells in HIV patients will contribute to new targeted therapies directed at increasing CD8 T cell lytic effector function and destruction of the viral reservoir. We show that CD8 T cells from ART treated patients had sharply reduced expression of CD56 (neural cell adhesion molecule-1), a marker associated with cytolytic function whereas elite patients who control HIV in the absence of ART had CD56+ CD8 T cell levels similar to uninfected controls. The CD56+ CD8 T cells had higher perforin upregulation as well as degranulation following stimulation with HIV gag peptides compared with CD56 negative CD8 T cells. Elite patients had the highest frequencies of perforin producing CD56+ CD8 T cells among all HIV+ groups. In patients receiving ART we noted high levels of the exhaustion marker TIM-3 on CD56+ CD8 T cells, implying that defective effector function was related to immune exhaustion. CD56+ CD8 T cells from elite or treated HIV patients responded to PMA plus ionomycin stimulation, and expressed transcription factors T-bet and EOMES at levels similar to uninfected controls. Consequently, the lytic effector defect in chronic HIV disease is due to immune exhaustion and quantitative loss of CD56+ CD8 T cells and this defect is not repaired in patients where viremia is suppressed and CD4 T cells are recovered after ART.

Reconstituting the cytotoxic CD56+ subset of CD8+ T cells through new interventions might improve the lytic effector capacity and contribute to reducing the viral reservoir. Our initial studies indicate that IL-15 treatment partly reverses the CD56 defect, implying that myeloid cell defects could be targeted for immune therapy during chronic HIV disease.

The potential role of CD16+ Vγ2Vδ2 T cell-mediated antibody-dependent cell-mediated cytotoxicity in control of HIV type 1 disease

Increasing evidence has suggested that HIV infection severely damages the Vγ2Vδ2 (Vδ2) T cells that play an important role in the first-line host response to infectious disease. However, little is known about Vδ2 T cell-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) in HIV disease. We found that although the CD16(+) Vδ2 T cell subset hardly participated in phosphoantigen responses dominated by the CD16(-) Vδ2 T cell subset, the potency of the ADCC function of Vδ2 T cells was correlated with the frequency of the CD16(+) subset. Thus, two distinct and complementary Vδ2 T cell subsets discriminated by CD16 were characterized to explore the respective impacts of HIV-1 infection on them. HIV-1 disease progression was not only associated with the phosphoantigen responsiveness of the CD16(-) Vδ2 subset, but also with the ability of the CD16(+) Vδ2 subset to kill antibody-coated target cells. Furthermore, both of the two Vδ2 functional subsets could be partially restored in HIV-infected patients with antiretroviral therapy. Notably, in the context of an overall HIV-mediated Vδ2 T cell depletion, despite the decline of phosphoantigen-responsive CD16(-) Vδ2 cells, CD16(+) Vδ2 cell-mediated ADCC was not compromised but exhibited a functional switch with dramatic promotion of degranulation in the early phase of HIV infection and chronic infection with slower disease progression. Our study reveals functional characterizations of the two Vδ2 T cell subsets with different activation pathways during HIV-1 infection and provides a rational direction for activating the CD16(+) Vδ2 T cells capable of mediating ADCC as a means to control HIV-1 disease.