Activation of Vgamma9Vdelta2 T cells by non-peptidic antigens induces the inhibition of subgenomic HCV replication

Characterization of Expanded Gamma Delta T Cells from Atypical X-SCID Patient Reveals Preserved Function and IL2RG-Mediated Signaling

Abnormally high γδ T cell numbers among individuals with atypical SCID have been reported but detailed immunophenotyping and functional characterization of these expanded γδ T cells are limited. We have previously reported atypical SCID phenotype caused by hypomorphic IL2RG (NM_000206.3) c.172C > T;p.(Pro58Ser) variant. Here, we have further investigated the index patient's abnormally large γδ T cell population in terms of function and phenotype by studying IL2RG cell surface expression, STAT tyrosine phosphorylation and blast formation in response to interleukin stimulation, immunophenotyping, TCRvγ sequencing, and target cell killing. In contrast to his ⍺β T cells, the patient's γδ T cells showed normal IL2RG cell surface expression and normal or enhanced IL2RG-mediated signaling. Vδ2 + population was proportionally increased with a preponderance of memory phenotypes and high overall tendency towards perforin expression. The patient's γδ T cells showed enhanced cytotoxicity towards A549 cancer cells. His TCRvγ repertoire was versatile but sequencing of IL2RG revealed a novel c.534C > A; p.(Phe178Leu) somatic missense variant restricted to γδ T cells. Over time this variant became predominant in γδ T cells, though initially present only in part of them. IL2RG-Pro58Ser/Phe178Leu variant showed higher cell surface expression compared to IL2RG-Pro58Ser variant in stable HEK293 cell lines, suggesting that somatic p.(Phe178Leu) variant may at least partially rescue the pathogenic effect of germline p.(Pro58Ser) variant. In conclusion, our report indicates that expansion of γδ T cells associated with atypical SCID needs further studying and cannot exclusively be deemed as a homeostatic response to low numbers of conventional T cells.

γδ T cells: The potential role in liver disease and implications for cancer immunotherapy

The γδ T cell subset was discovered over 30 years ago, yet continues to be an exciting and challenging component of the adaptive immune response. While γδ T cells represent a very small fraction of all T cells in humans, γδ T cells have a vital effect on human immunity, serving as a bridge between the innate and adaptive immune systems. The characteristics of γδ T cells include recognition of non-MHC restrictive antigens, as well as the ability to secrete an abundance of cytokines, suggesting that γδ T cells have high antitumor activity. As such, they have gained ample attention with respect to tumor immunotherapy in the last decade. The γδ T cell subset comprises up to ∼15-20% of the T-lymphocyte population in the liver, although the liver is recognized as an immune organ with primary immune functions, the role of γδ T cells in liver disease has not been established. Herein, we present a comprehensive overview of molecular mechanisms underlying immune γδ T cell activity in liver disease, including immune liver injury, viral hepatitis, cirrhosis, and hepatocellular carcinoma, and review γδ T cell-based clinical immunotherapeutic approaches.

Human Vδ2 T Cells and Their Versatility for Immunotherapeutic Approaches

Gamma/delta (γδ) T cells are innate-like immune effectors that are a critical component linking innate and adaptive immune responses. They are recognized for their contribution to tumor surveillance and fight against infectious diseases. γδ T cells are excellent candidates for cellular immunotherapy due to their unique properties to recognize and destroy tumors or infected cells. They do not depend on the recognition of a single antigen but rather a broad-spectrum of diverse ligands through expression of various cytotoxic receptors. In this manuscript, we review major characteristics of the most abundant circulating γδ subpopulation, Vδ2 T cells, their immunotherapeutic potential, recent advances in expansion protocols, their preclinical and clinical applications for several infectious diseases and malignancies, and how additional modulation could enhance their therapeutic potential.

Defying convention in the time of COVID-19: Insights into the role of γδ T cells

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is a complex disease which immune response can be more or less potent. In severe cases, patients might experience a cytokine storm that compromises their vital functions and impedes clearance of the infection. Gamma delta (γδ) T lymphocytes have a critical role initiating innate immunity and shaping adaptive immune responses, and they are recognized for their contribution to tumor surveillance, fighting infectious diseases, and autoimmunity. γδ T cells exist as both circulating T lymphocytes and as resident cells in different mucosal tissues, including the lungs and their critical role in other respiratory viral infections has been demonstrated. In the context of SARS-CoV-2 infection, γδ T cell responses are understudied. This review summarizes the findings on the antiviral role of γδ T cells in COVID-19, providing insight into how they may contribute to the control of infection in the mild/moderate clinical outcome.

Role of Vγ9vδ2 T lymphocytes in infectious diseases

The T cell receptor Vγ9Vδ2 T cells bridge innate and adaptive antimicrobial immunity in primates. These Vγ9Vδ2 T cells respond to phosphoantigens (pAgs) present in microbial or eukaryotic cells in a butyrophilin 3A1 (BTN3) and butyrophilin 2A1 (BTN2A1) dependent manner. In humans, the rapid expansion of circulating Vγ9Vδ2 T lymphocytes during several infections as well as their localization at the site of active disease demonstrates their important role in the immune response to infection. However, Vγ9Vδ2 T cell deficiencies have been observed in some infectious diseases such as active tuberculosis and chronic viral infections. In this review, we are providing an overview of the mechanisms of Vγ9Vδ2 T cell-mediated antimicrobial immunity. These cells kill infected cells mainly by releasing lytic mediators and pro-inflammatory cytokines and inducing target cell apoptosis. In addition, the release of chemokines and cytokines allows the recruitment and activation of immune cells, promoting the initiation of the adaptive immune response. Finaly, we also describe potential new therapeutic tools of Vγ9Vδ2 T cell-based immunotherapy that could be applied to emerging infections.

In Acute Dengue Infection, High TIM-3 Expression May Contribute to the Impairment of IFNγ Production by Circulating Vδ2 T Cells

γδ T cells are innate cells able to quickly eliminate pathogens or infected/tumoral cells by their antiviral and adjuvancy activities. The role of γδ T cells during Dengue Viral Infection (DENV) infection is not fully elucidated. Nevertheless, human primary γδ T cells have been shown to kill in vitro DENV-infected cells, thus highlighting their possible antiviral function. The aim of this work was to characterize the phenotype and function of Vδ2 T cells in DENV patients. Fifteen DENV patients were enrolled for this study and peripheral blood mononuclear cells (PBMC) were used to analyze Vδ2-T-cell frequency, differentiation profile, activation/exhaustion status, and functionality by multiparametric flow cytometry. Our data demonstrated that DENV infection was able to significantly reduce Vδ2-T-cell frequency and to increase their activation (CD38 and HLA-DR) and exhaustion markers (PD-1 and TIM-3). Furthermore, Vδ2 T cells showed a reduced capability to produce IFN-γ after phosphoantigenic stimulation that can be associated to TIM-3 expression. Several studies are needed to depict the possible clinical impact of γδ-T-cell impairment on disease severity and to define the antiviral and immunoregulatory activities of γδ T cells in the first phases of infection.

Crosstalk between γδ T cells and the microbiota

The role of the microbiota in the development and function of γδ T cells-a T cell subset characterized by a T cell receptor composed of one γ-chain and one δ-chain-has been investigated in multiple organs in mice and humans. Interactions between the microbiota and γδ T cells affect both tissue homeostasis and disease pathologies. Notably, microbiota-induced interleukin-17 (IL-17)-producing-γδ T cells can mediate a range of immunological processes, from metabolic disorders to neuroinflammation via the gut-brain axis. However, the bidirectional interactions between γδ T cells and the microbiota have not been fully determined. In this Perspective, we dissect the roles of microbiota in modulating γδ T cell development and function, and evaluate the evidence for γδ T cell selection of commensal communities. We also discuss the potential implications of these cells in health and disease and the major open questions and research avenues in the field.

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.

Diverse Functions of γδ T Cells in the Progression of Hepatitis B Virus and Hepatitis C Virus Infection

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are primary risk factors for a wide spectrum of liver diseases that severely affect human health. The liver is an immunological organ that has an abundance of immune cells. Thus, various innate or adaptive immune cells are involved in the progression of HBV or HCV infection. Among those cells, a unique kind of immune cell, the γδ T cell, contributes to promoting or inhibiting the progression of liver diseases. To reveal the diverse roles of γδ T cells in HBV or HCV infection, the properties and functions of these cells in human and mouse models are analyzed. Here, we briefly describe the characteristics and functions of γδ T cells subsets in liver diseases. Then, we fully discuss the diverse roles of γδ T cells in the progression of HBV or HCV infection, including stages of acute infection, chronic infection, liver cirrhosis, and hepatocellular carcinoma. Finally, the functions and existing problems of γδ T cells in HBV or HCV infection are summarized. A better understanding of the function of γδ T cells during the progression of HBV and HCV infection will be helpful for the treatment of virus infection.

A Cell for the Ages: Human γδ T Cells across the Lifespan

The complexity of the human immune system is exacerbated by age-related changes to immune cell functionality. Many of these age-related effects remain undescribed or driven by mechanisms that are poorly understood. γδ T cells, while considered an adaptive subset based on immunological ontogeny, retain both innate-like and adaptive-like characteristics. This T cell population is small but mighty, and has been implicated in both homeostatic and disease-induced immunity within tissues and throughout the periphery. In this review, we outline what is known about the effect of age on human peripheral γδ T cells, and call attention to areas of the field where further research is needed.

Role of γδ T cells in controlling viral infections with a focus on influenza virus: implications for designing novel therapeutic approaches

BACKGROUND

Influenza virus infection is among the most detrimental threats to the health of humans and some animals, infecting millions of people annually all around the world and in many thousands of cases giving rise to pneumonia and death. All those health crises happen despite previous and recent developments in anti-influenza vaccination, suggesting the need for employing more sophisticated methods to control this malign infection. Main body The innate immunity modules are at the forefront of combating against influenza infection in the respiratory tract, among which, innate T cells, particularly gamma-delta (γδ) T cells, play a critical role in filling the gap needed for adaptive immune cells maturation, linking the innate and adaptive immunity together. Upon infection with influenza virus, production of cytokines and chemokines including CCL3, CCL4, and CCL5 from respiratory epithelium recruits γδ T cells at the site of infection in a CCR5 receptor-dependent fashion. Next, γδ T cells become activated in response to influenza virus infection and produce large amounts of proinflammatory cytokines, especially IL-17A. Regardless of γδ T cells' roles in triggering the adaptive arm of the immune system, they also protect the respiratory epithelium by cytolytic and non-cytolytic antiviral mechanisms, as well as by enhancing neutrophils and natural killer cells recruitment to the infection site.

CONCLUSION

In this review, we explored varied strategies of γδ T cells in defense to influenza virus infection and how they can potentially provide balanced protective immune responses against infected cells. The results may provide a potential window for the incorporation of intact or engineered γδ T cells for developing novel antiviral approaches or for immunotherapeutic purposes.

Lymphocyte Landscape after Chronic Hepatitis C Virus (HCV) Cure: The New Normal

Chronic HCV (CHC) infection is the only chronic viral infection for which curative treatments have been discovered. These direct acting antiviral (DAA) agents target specific steps in the viral replication cycle with remarkable efficacy and result in sustained virologic response (SVR) or cure in high (>95%) proportions of patients. These treatments became available 6–7 years ago and it is estimated that their real impact on HCV related morbidity, including outcomes such as cirrhosis and hepatocellular carcinoma (HCC), will not be known for the next decade or so. The immune system of a chronically infected patient is severely dysregulated and questions remain regarding the immune system’s capacity in limiting liver pathology in a cured individual. Another important consequence of impaired immunity in patients cleared of HCV with DAA will be the inability to generate protective immunity against possible re-infection, necessitating retreatments or developing a prophylactic vaccine. Thus, the impact of viral clearance on restoring immune homeostasis is being investigated by many groups. Among the important questions that need to be answered are how much the immune system normalizes with cure, how long after viral clearance this recalibration occurs, what are the consequences of persisting immune defects for protection from re-infection in vulnerable populations, and does viral clearance reduce liver pathology and the risk of developing hepatocellular carcinoma in individuals cured with these agents. Here, we review the recent literature that describes the defects present in various lymphocyte populations in a CHC patient and their status after viral clearance using DAA treatments.

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.

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.

Activated γδ T cells exhibit cytotoxicity and the capacity for viral clearance in patients with acute hepatitis B

γδ T cells are a unique population of lymphocytes that have regulatory roles in patients with chronic hepatitis B (CHB); however, their role in acute hepatitis B (AHB) infection remains unclear. Phenotype and function of γδ T cells were analyzed in 29 AHB patients, 28 CHB patients, and 30 healthy controls (HCs) using immunofunctional assays. Compared with HCs and CHB patients, decreased peripheral and increased hepatic γδ T cells were found in AHB patients. Increased hepatic γδ T cells in AHB patients were attributed to elevated hepatic chemokine levels. Peripheral γδ T cells exhibited highly activated and terminally differentiated memory phenotype in AHB patients. Consistently, peripheral γδ T cells in AHB patients showed increased cytotoxic capacity and enhanced antiviral activity which was further proved in longitudinal study. Activated γδ T cells in AHB patients exhibited increased cytotoxicity and capacity for viral clearance associated with liver injury and the control of infection.

Tissue-Resident Innate and Innate-Like Lymphocyte Responses to Viral Infection

Infection is restrained by the concerted activation of tissue-resident and circulating immune cells. Recent discoveries have demonstrated that tissue-resident lymphocyte subsets, comprised of innate lymphoid cells (ILCs) and unconventional T cells, have vital roles in the initiation of primary antiviral responses. Via direct and indirect mechanisms, ILCs and unconventional T cell subsets play a critical role in the ability of the immune system to mount an effective antiviral response through potent early cytokine production. In this review, we will summarize the current knowledge of tissue-resident lymphocytes during initial viral infection and evaluate their redundant or nonredundant contributions to host protection or virus-induced pathology.

γδ T Lymphocytes: An Effector Cell in Autoimmunity and Infection

γδ T cells are non-conventional lymphocytes which show several properties of innate immune cells. They present a limited TCR repertoire and circulate as cells with a pre-activated phenotype thus being able to generate rapid immune responses. γδ T cells do not recognize classical peptide antigens, their TCRs are non-MHC restricted and they can respond to pathogen-associated molecular patterns and to cytokines in absence of TCR ligands. They also recognize self-molecules induced by stress, which indicate infection and cellular transformation. All these features let γδ T cells act as a first line of defense in sterile and non-sterile inflammation. γδ T cells represent 1–10% of circulating lymphocytes in the adult human peripheral blood, they are widely localized in non-lymphoid tissues and constitute the majority of immune cells in some epithelial surfaces, where they participate in the maintenance of the epithelial barriers. γδ T cells produce a wide range of cytokines that orchestrate the course of immune responses and also exert high cytotoxic activity against infected and transformed cells. In contrast to their beneficial role during infection, γδ T cells are also implicated in the development and progression of autoimmune diseases. Interestingly, several functions of γδ T cells are susceptible to modulation by interaction with other cells. In this review, we give an overview of the γδ T cell participation in infection and autoimmunity. We also revise the underlying mechanisms that modulate γδ T cell function that might provide tools to control pathological immune responses.

Protective Role of γδ T Cells in Different Pathogen Infections and Its Potential Clinical Application

γδ T cells, a subgroup of T cells based on the γδ TCR, when compared with conventional T cells (αβ T cells), make up a very small proportion of T cells. However, its various subgroups are widely distributed in different parts of the human body and are attractive effectors for infectious disease immunity. γδ T cells are activated and expanded by nonpeptidic antigens (P-Ags), major histocompatibility complex (MHC) molecules, and lipids which are associated with different kinds of pathogen infections. Activation and proliferation of γδ T cells play a significant role in diverse infectious diseases induced by viruses, bacteria, and parasites and exert their potential effector function to effectively eliminate infection. It is well known that many types of infectious diseases are detrimental to human life and health and give rise to high incidence of illnesses and death rate all over the world. To date, there is no comprehensive understanding of the correlation between γδ T cells and infectious diseases. In this review, we will focus on the various subgroups of γδ T cells (mainly Vδ1 T cells and Vδ2 T cells) which can induce multiple immune responses or effective functions to fight against common pathogen infections, such as Mycobacterium tuberculosis, Listeria monocytogenes, influenza viruses, HIV, EBV, and HBV. Hopefully, the gamma-delta T cell study will provide a novel effective way to treat infectious diseases.

Unique and Common Features of Innate-Like Human Vδ2+ γδT Cells and Mucosal-Associated Invariant T Cells

Mucosal-associated invariant T (MAIT) cells are innate-like T cells abundant in humans that can be activated in a TCR-independent manner by inflammatory and antiviral cytokines. In humans, the capacity for TCR-independent activation is functionally linked to a transcriptional program that can be identified by the expression of the C-type lectin receptor, CD161. In addition to MAIT cells, it has been demonstrated that a subset of γδT cells expresses CD161 and can be activated by TCR-independent cytokine stimulation. In this study, we sought to clarify the nature of cytokine-responsive human γδT cells. We could link CD161 expression on Vδ2⁺ versus Vδ1⁺ γδT cells to the observation that Vδ2⁺ γδT cells, but not Vδ1⁺ γδT cells, robustly produced IFN-γ upon stimulation with a variety of cytokine combinations. Interestingly, both CD161⁺ and CD161^- Vδ2⁺ γδT cells responded to these stimuli, with increased functionality within the CD161⁺ subset. This innate-like responsiveness corresponded to high expression of PLZF and IL-18Rα, analogous to MAIT cells. Vδ2⁺ γδT cells in human duodenum and liver maintained a CD161⁺ IL-18Rα⁺ phenotype and produced IFN-γ in response to IL-12 and IL-18 stimulation. In contrast to MAIT cells, we could not detect IL-17A production but observed higher steady-state expression of Granzyme B by Vδ2⁺ γδT cells. Finally, we investigated the frequency and functionality of γδT cells in the context of chronic hepatitis C virus infection, as MAIT cells are reduced in frequency in this disease. By contrast, Vδ2⁺ γδT cells were maintained in frequency and displayed unimpaired IFN-γ production in response to cytokine stimulation. In sum, human Vδ2⁺ γδT cells are a functionally distinct population of cytokine-responsive innate-like T cells that is abundant in blood and tissues with similarities to human MAIT cells.

Human γδ T Cell Receptor Repertoires in Peripheral Blood Remain Stable Despite Clearance of Persistent Hepatitis C Virus Infection by Direct-Acting Antiviral Drug Therapy

Human γδ T cells can contribute to clearance of hepatitis C virus (HCV) infection but also mediate liver inflammation. This study aimed to understand the clonal distribution of γδ T cells in peripheral blood of chronic HCV patients and following HCV clearance by interferon-free direct-acting antiviral drug therapies. To this end, γδ T cell receptor (TCR) repertoires were monitored by mRNA-based next-generation sequencing. While the percentage of Vγ9⁺ T cells was higher in patients with elevated liver enzymes and a few expanded Vδ3 clones could be identified in peripheral blood of 23 HCV-infected non-cirrhotic patients, overall clonality and complexity of γδ TCR repertoires were largely comparable to those of matched healthy donors. Monitoring eight chronic HCV patients before, during and up to 1 year after therapy revealed that direct-acting antiviral (DAA) drug therapies induced only minor alterations of TRG and TRD repertoires of Vγ9⁺ and Vγ9^- cells. Together, we show that peripheral γδ TCR repertoires display a high stability (1) by chronic HCV infection in the absence of liver cirrhosis and (2) by HCV clearance in the course of DAA drug therapy.

Intrahepatic Vγ9Vδ2 T-cells from HCV-infected patients show an exhausted phenotype but can inhibit HCV replication

Hepatitis C virus (HCV) persistence results from inefficiencies of both innate and adaptive immune responses to eradicate the infection. A functional impairment of circulating Vγ9Vδ2 T-cells was described but few data are available on Vγ9Vδ2 T-cells in the liver that, however, represents the battlefield in the HCV/host interaction. Aim of this work was to compare circulating and intrahepatic Vγ9Vδ2 T-cells in chronic HCV-infected patients (HCV^pos) and in HCV-negative (HCV^neg) subjects. Phenotypic and functional analysis was performed by flow cytometry. Anti-HCV activity was analyzed by using an in vitro autologous liver culture system. Independently from HCV infection, the liver was enriched of Vγ9Vδ2 T-cells expressing an effector/activated phenotype. In contrast, an enrichment of PD-1 expressing Vγ9Vδ2 T-cells was observed both in the peripheral blood and in the liver of HCV^pos patients, probably due to a persistent antigenic stimulation. Moreover, a lower frequency of IFN-γ producing Vγ9Vδ2 T-cells was observed in the liver of HCV^pos patients, suggesting a functional impairment in the cytokine production in HCV^pos liver. Despite this hypo-responsiveness, intrahepatic Vγ9Vδ2 T-cells are able to exert an anti-HCV activity after specific stimulation. Altogether, our data show that HCV infection induced a dysregulation of intrahepatic Vγ9Vδ2 T cells that maintain their anti-HCV activity after specific stimulation. A study aimed to evaluate the mechanisms of the antiviral activity may be useful to identify new pathways able to improve Vγ9Vδ2 T-cells intrahepatic function during HCV infection.

Age dependent differences in the kinetics of γδ T cells after influenza vaccination

Immunosenescence is a hallmark of the aging immune system and is considered the main cause of a reduced vaccine efficacy in the elderly. Although γδ T cells can become activated by recombinant influenza hemagglutinin, their age-related immunocompetence during a virus-induced immune response has so far not been investigated. In this study we evaluate the kinetics of γδ T cells after vaccination with the trivalent 2011/2012 northern hemisphere seasonal influenza vaccine. We applied multi-parametric flow cytometry to a cohort of 21 young (19-30 years) and 23 elderly (53-67 years) healthy individuals. Activated and proliferating γδ T cells, as identified by CD38 and Ki67 expression, were quantified on the days 0, 3, 7, 10, 14, 17, and 21. We observed a significantly lower number of activated and proliferating γδ T cells at baseline and following vaccination in elderly as compared to young individuals. The kinetics changes of activated γδ T cells were much stronger in the young, while corresponding changes in the elderly occurred slower. In addition, we observed an association between day 21 HAI titers of influenza A and the frequencies of Ki67+ γδ T cells at day 7 in the young. In conclusion, aging induces alterations of the γδ T cell response that might have negative implications for vaccination efficacy.

Different features of Vδ2 T and NK cells in fatal and non-fatal human Ebola infections

Background

Human Ebola infection is characterized by a paralysis of the immune system. A signature of αβ T cells in fatal Ebola infection has been recently proposed, while the involvement of innate immune cells in the protection/pathogenesis of Ebola infection is unknown. Aim of this study was to analyze γδ T and NK cells in patients from the Ebola outbreak of 2014–2015 occurred in West Africa, and to assess their association with the clinical outcome.

Methodology/Principal findings

Nineteen Ebola-infected patients were enrolled at the time of admission to the Ebola Treatment Centre in Guinea. Patients were divided in two groups on the basis of the clinical outcome. The analysis was performed by using multiparametric flow cytometry established by the European Mobile Laboratory in the field. A low frequency of Vδ2 T-cells was observed during Ebola infection, independently from the clinical outcome. Moreover, Vδ2 T-cells from Ebola patients massively expressed CD95 apoptotic marker, suggesting the involvement of apoptotic mechanisms in Vδ2 T-cell loss. Interestingly, Vδ2 T-cells from survivors expressed an effector phenotype and presented a lower expression of the CTLA-4 exhaustion marker than fatalities, suggesting a role of effector Vδ2 T-cells in the protection. Furthermore, patients with fatal Ebola infection were characterized by a lower NK cell frequency than patients with non fatal infection. In particular, both CD56^bright and CD56^dim NK frequency were very low both in fatal and non fatal infections, while a higher frequency of CD56^neg NK cells was associated to non-fatal infections. Finally, NK activation and expression of NKp46 and CD158a were independent from clinical outcome.

Conclusions/Significances

Altogether, the data suggest that both effector Vδ2 T-cells and NK cells may play a role in the complex network of protective response to EBOV infection. Further studies are required to characterize the protective effector functions of Vδ2 and NK cells.

Human Ebola infection presents a high lethality rate and is characterized by a paralysis of the immune response. The definition of the protective immune profile during Ebola infection represents a main challenge useful in vaccine and therapy design.

In particular, the protective/pathogenetic involvement of innate immune cells during Ebola infection in humans remains to be clarified. Nineteen Ebola-infected patients were enrolled at the time of admission to the Ebola Treatment Center in Guinea, and the profiling of innate immunity was correlated with the clinical outcome. Our results show that both effector Vδ2 T-cells and NK cells were associated with survival, suggesting their involvement in the complex network of protective response to EBOV infection.

Co-Expansion of Cytokine-Induced Killer Cells and Vγ9Vδ2 T Cells for CAR T-Cell Therapy

Gamma delta (γδ) T cells and cytokine-induced killer (CIK) cells, which are a heterogeneous population of T lymphocytes and natural killer T (NKT) cells, have been separately expanded ex vivo and shown to be capable of targeting and mediating cytotoxicity against various tumor cells in a major histocompatibility complex-unrestricted manner. However, the co-expansion and co-administration of these immune cells have not been explored. In this study we describe an efficient method to expand simultaneously both CIK and Vγ9Vδ2 T cells, termed as CIKZ cells, from human peripheral blood mononuclear cells (PBMCs) using Zometa, interferon-gamma (IFN-γ), interleukin 2 (IL-2), anti-CD3 antibody and engineered K562 feeder cells expressing CD64, CD137L and CD86. A 21-day culture of PBMCs with this method yielded nearly 20,000-fold expansion of CIKZ cells with γδ T cells making up over 20% of the expanded population. The expanded CIKZ cells exhibited antitumor cytotoxicity and could be modified to express anti-CD19 chimeric antigen receptor (CAR), anti-CEA CAR, and anti-HER2 CAR to enhance their specificity and cytotoxicity against CD19-, CEA-, or HER2-positive tumor cells. The tumor inhibitory activity of anti-CD19 CAR-modified CIKZ cells was further demonstrated in vivo in a Raji tumor mouse model. The findings herein substantiate the feasibility of co-expanding CIK and γδ cells for adoptive cellular immunotherapy applications such as CAR T-cell therapy against cancer.

Functional dichotomy of Vδ2 γδ T cells in chronic hepatitis C virus infections: role in cytotoxicity but not for IFN-γ production

Vδ2 γδ (Vδ2) T cells, a major human γδ T cell subset, exhibit broad anti-tumor and anti-infective activity; however, their precise role in chronic hepatitis C virus (HCV) infections remains unclear. In this study, we analyzed the phenotype and function of Vδ2 T cells in 43 HCV-infected patients compared to 39 healthy controls (HCs). Vδ2 T cells from HCV-infected patients were activated and differentiated into effector cells. Vδ2 T cells in patients expressed significantly higher levels of natural killer (NK) cell markers CD56 and CD16 than in HCs, acquiring cytotoxic NK-like phenotype. The Vδ2 T cell phenotype was associated with increased cytolytic effector molecules expression in HCV-infected patients with elevated serum ALT levels. Surprisingly, Vδ2 T cells in patients had a markedly impaired capacity to produce IFN-γ. Further in vitro and in vivo analysis showed that interferon-α, which was induced during HCV infection, caused Vδ2 T cell function bias toward cytotoxicity. These results suggest a functional dichotomy for Vδ2 T cells in chronic HCV infections: a role in cytotoxicity but not for IFN-γ production, which may contribute to both the liver inflammation and HCV persistence.

Dual Effects of Cellular Immunotherapy in Inhibition of Virus Replication and Prolongation of Survival in HCV-Positive Hepatocellular Carcinoma Patients

Immune cells play an important role in the development and progression of hepatitis C virus (HCV) and hepatocellular carcinoma (HCC). We conducted a retrospective study to evaluate the influence of adoptive cellular immunotherapy (CIT) on viral load and progression-free survival (PFS) for HCC patients infected with HCV. Patients (n = 104) were divided into a control group (conventional therapy, n = 73) and study group (combination of CIT and conventional therapy, n = 31). Autologous mononuclear cells were induced into natural killer, γδT, and cytokine-induced killer cells and infused intravenously to study group patients. More patients had shown viral load decrease or were stable in study group (100% versus 75%) (p = 0.014). The median PFS of the study group and control group was 16 and 10 months, respectively (p = 0.0041), and only CIT was an independent prognostic factor for PFS (hazard ratio, 0.422; p = 0.005). Three patients developed transient moderate fever after infusion, and there were no significant differences in alanine aminotransferase and aspartate aminotransferase levels before and after treatment in both groups. Our results show that CIT contributes to improvement of prognosis and inhibition of viral replication in HCV-related HCC patients, without impairment of liver function.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

Modulation of sterol biosynthesis regulates viral replication and cytokine production in influenza A virus infected human alveolar epithelial cells

Highly pathogenic H5N1 viruses continue to transmit zoonotically, with mortality higher than 60%, and pose a pandemic threat. Antivirals remain the primary choice for treating H5N1 diseases and have their limitations. Encouraging findings highlight the beneficial effects of combined treatment of host targeting agents with immune-modulatory activities. This study evaluated the undefined roles of sterol metabolic pathway in viral replication and cytokine induction by H5N1 virus in human alveolar epithelial cells. The suppression of the sterol biosynthesis by Simvastatin in human alveolar epithelial cells led to reduction of virus replication and cytokine production by H5N1 virus. We further dissected the antiviral role of different regulators of the sterol metabolism, we showed that Zometa, FPT inhibitor III, but not GGTI-2133 had anti-viral activities against both H5N1 and H1N1 viruses. More importantly, FPT inhibitor III treatment significantly suppressed cytokine production by H5N1 virus infected alveolar epithelial cells. Since both viral replication itself and the effects of viral hyper-induction of cytokines contribute to the immunopathology of severe H5N1 disease, our findings highlights the therapeutic potential of FPT inhibitor III for severe human H5N1 diseases. Furthermore, our study is the first to dissect the roles of different steps in the sterol metabolic pathway in H5N1 virus replication and cytokine production.

Synergistic anti-tumor effects of zoledronic acid and radiotherapy against metastatic hepatocellular carcinoma

A 72-year-old man with advanced hepatocellular carcinoma and decompensated hepatitis C virus-related cirrhosis suffered from a metastatic femoral fracture. After undergoing radiotherapy, he was only treated with supportive care, except for the administration of zoledronic acid (ZA). Thereafter, the initially elevated serum α-fetoprotein and des-gamma carboxyprothrombin levels declined to within the normal ranges. Hepatic and metastatic adrenal tumors, distant from the radiation field, exhibited a surprising regression. ZA is known to inhibit the activity of osteoclasts, bone-residential macrophages, and has been reported to have a direct anti-tumor effect. ZA may adjust the immunological milieu in tumor microenvironments by inhibiting the tumor-associated macrophages. Because radiotherapy can enhance the presentation of tumor-associated antigens, ZA and radiotherapy may exert synergistic anti-tumor effects.

Gamma Delta T-lymphocytes in Hepatitis C and Chronic Liver Disease

Discovered 30 years ago, gamma delta (γδ) T-lymphocytes remain an intriguing and enigmatic T-cell subset. Although in humans they comprise a small fraction of the total circulating T-lymphocyte pool, they represent an important T-cell subset in tissues such as the liver, with roles bridging the innate and adaptive immune systems. The associations of γδ T-lymphocytes with chronic liver disease have been explored – however, there remain conflicting data as to whether these T-cells are pathogenic or protective. In patients with some forms of liver disease, their expansion in the periphery and especially in the liver may indeed help pathogen clearance, while in other conditions their presence may, in contrast, contribute to disease progression. γδ T-cells can also express CD161, a C-type lectin, and such cells have been found to be involved in the pathogenesis of inflammatory disease. CD161+ T-cells of diverse subsets are known to be enriched in the livers of patients with chronic hepatitis C. This article serves to provide a review of the γδ T-cell population and its role in hepatitis C and other chronic liver diseases, and also explores a potential role of the CD161+ γδ T-cells in liver diseases.

γδ T cells and their potential for immunotherapy

Vγ9Vδ2 (also termed Vγ2Vδ2) T cells, a major human peripheral blood γδ T cell subset, recognize microbial (E)-4-hydroxy-3-methylbut-2-enyl diphosphate and endogenous isopentenyl diphosphate in a TCR-dependent manner. The recognition does not require specific accessory cells, antigen uptake, antigen processing, or MHC class I, class II, or class Ib expression. This subset of T cells plays important roles in mediating innate immunity against a wide variety of infections and displays potent and broad cytotoxic activity against human tumor cells. Because γδT cells express both natural killer receptors such as NKG2D and γδ T cell receptors, they are considered to represent a link between innate and adaptive immunity. In addition, activated γδ T cells express a high level of antigen-presenting cell-related molecules and can present peptide antigens derived from destructed cells to αβ T cells. Utilizing these antimicrobial and anti-tumor properties of γδ T cells, preclinical and clinical trials have been conducted to develop novel immunotherapies for infections and malignancies. Here, we review the immunological properties of γδ T cells including the underlying recognition mechanism of nonpeptitde antigens and summarize the results of γδ T cell-based therapies so far performed. Based on the results of the reported trials, γδ T cells appear to be a promising tool for novel immunotherapies against certain types of diseases.

Human Vγ9Vδ2-T cells efficiently kill influenza virus-infected lung alveolar epithelial cells

γδ-T cells play an indispensable role in host defense against different viruses, including influenza A virus. However, whether these cells have cytotoxic activity against influenza virus-infected lung alveolar epithelial cells and subsequently contribute to virus clearance remains unknown. Using influenza virus-infected A549 cells, human lung alveolar epithelial cells, we investigated the cytotoxic activity of aminobisphosphonate pamidronate (PAM)-expanded human Vγ9Vδ2-T cells and their underlying mechanisms. We found that PAM could selectively activate and expand human Vγ9Vδ2-T cells. PAM-expanded human Vγ9Vδ2-T cells efficiently killed influenza virus-infected lung alveolar epithelial cells and inhibited virus replication. The cytotoxic activity of PAM-expanded Vγ9Vδ2-T cells was dependent on cell-to-cell contact and required NKG2D activation. Perforin-granzyme B, tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas-Fas ligand (FasL) pathways were involved in their cytotoxicity. Our study suggests that targeting γδ-T cells by PAM can potentially offer an alternative option for the treatment of influenza virus.

In vivo interferon-alpha/ribavirin treatment modulates Vγ9Vδ2 T-cell function during chronic HCV infection

In chronic hepatitis C virus (HCV) infection, treatment failure and defective host immune response highly demand improved therapy strategies. Vγ9Vδ2 T-cells represent a good target for HCV immunotherapy, since phosphoantigen (PhAg)-activated Vγ9Vδ2 T-lymphocytes are able to inhibit subgenomic HCV replication by interferon (IFN)-γ release. A profound impairment of IFN-γ production by Vγ9Vδ2 T-cells during chronic HCV infection was previously shown. Interestingly, in vitro IFN-α partially restored Vγ9Vδ2 T-cells responsiveness to PhAg, by stabilizing IFN-γ-mRNA. To verify how in vivo IFN-α/ribavirin (RBV) treatment could affect Vγ9Vδ2 T-cells phenotype and responsiveness to PhAg in HCV-infected patients, 10 subjects underwent a longitudinal study before and after treatment. IFN-α/RBV therapy did not significantly modify Vγ9Vδ2 T-cell numbers and differentiation profile. Interestingly, Vγ9Vδ2 T-cell responsiveness remained unmodified until 3 weeks of therapy, but dropped after 1 month, suggesting that repeated in vivo IFN-α administration in the absence of T-cell receptor (TCR)-mediated signals results in Vγ9Vδ2 T-cell anergy. The present work defines the window of possible application of combined strategies targeting Vγ9Vδ2 T-cells during chronic HCV infection; specifically, the first 3 weeks from the beginning of treatment may represent the optimal time to target Vγ9Vδ2 T-cells in vivo, since their function in terms of IFN-γ production is preserved.

Role of gamma-delta T-cells in cancer: another opening door to immunotherapy

The gamma-delta (γδ) T-cells are a subset of T-lymphocytes characterized by the presence of a surface antigen recognition complex type 2. Those γδ T-cells represent 2-5 % of peripheral T-cells only, but they are common in organs and mucosae, acting as a first defense system in the entries to the organism. The γδ T-cells take part on immune response by direct cytolysis, development of memory phenotypes, and modulation of immune cells, and they have been implied in autoimmune disorders, immune deficiencies, infections, and tumor diseases. We reported the role of γδ T-cells in oncology, focusing in their potential applications for cancer treatment. Experimental designs and clinical trials in the treatment of solid malignancies are extensively reviewed.

Interferon-α improves phosphoantigen-induced Vγ9Vδ2 T-cells interferon-γ production during chronic HCV infection

In chronic HCV infection, treatment failure and defective host immune response highly demand improved therapy strategies. Vγ9Vδ2 T-cells may inhibit HCV replication in vitro through IFN-γ release after Phosphoantigen (PhAg) stimulation. The aim of our work was to analyze Vγ9Vδ2 T-cell functionality during chronic HCV infection, studying the role of IFN-α on their function capability. IFN-γ production by Vγ9Vδ2 T-cells was analyzed in vitro in 24 HCV-infected patients and 35 healthy donors (HD) after PhAg stimulation with or without IFN-α. The effect of in vivo PhAg/IFN-α administration on plasma IFN-γ levels was analyzed in M. fascicularis monkeys. A quantitative analysis of IFN-γ mRNA level and stability in Vγ9Vδ2 T-cells was also evaluated. During chronic HCV infection, Vγ9Vδ2 T-cells showed an effector/activated phenotype and were significantly impaired in IFN-γ production. Interestingly, IFN-α was able to improve their IFN-γ response to PhAg both in vitro in HD and HCV-infected patients, and in vivo in Macaca fascicularis primates. Finally, IFN-α increased IFN-γ-mRNA transcription and stability in PhAg-activated Vγ9Vδ2 T-cells. Altogether our results show a functional impairment of Vγ9Vδ2 T-cells during chronic HCV infection that can be partially restored by using IFN-α. A study aimed to evaluate the antiviral impact of PhAg/IFN-α combination may provide new insight in designing possible combined strategies to improve HCV infection treatment outcome.

Type 1 responses of human Vγ9Vδ2 T cells to influenza A viruses

γδ T cells are essential constituents of antimicrobial and antitumor defenses. We have recently reported that phosphoantigen isopentenyl pyrophosphate (IPP)-expanded human Vγ9Vδ2 T cells participated in anti-influenza virus immunity by efficiently killing both human and avian influenza virus-infected monocyte-derived macrophages (MDMs) in vitro. However, little is known about the noncytolytic responses and trafficking program of γδ T cells to influenza virus. In this study, we found that Vγ9Vδ2 T cells expressed both type 1 cytokines and chemokine receptors during influenza virus infection, and IPP-expanded cells had a higher capacity to produce gamma interferon (IFN-γ). Besides their potent cytolytic activity against pandemic H1N1 virus-infected cells, IPP-activated γδ T cells also had noncytolytic inhibitory effects on seasonal and pandemic H1N1 viruses via IFN-γ but had no such effects on avian H5N1 or H9N2 virus. Avian H5N1 and H9N2 viruses induced significantly higher CCL3, CCL4, and CCL5 production in Vγ9Vδ2 T cells than human seasonal H1N1 virus. CCR5 mediated the migration of Vγ9Vδ2 T cells toward influenza virus-infected cells. Our findings suggest a novel therapeutic strategy of using phosphoantigens to boost the antiviral activities of human Vγ9Vδ2 T cells against influenza virus infection.

The aminobisphosphonate pamidronate controls influenza pathogenesis by expanding a gammadelta T cell population in humanized mice

As shown in humanized mice, a population of Vγ9Vδ2 T cells can reduce the severity and mortality of disease caused by infection with human and avian influenza viruses.

There are few antiviral drugs for treating influenza, and the emergence of antiviral resistance has further limited the available therapeutic options. Furthermore, antivirals are not invariably effective in severe influenza, such as that caused by H5N1 viruses. Thus, there is an urgent need to develop alternative therapeutic strategies. Here, we show that human Vγ9Vδ2 T cells expanded by the aminobisphosphonate pamidronate (PAM) kill influenza virus–infected cells and inhibit viral replication in vitro. In Rag2^−/−γc^−/− immunodeficient mice reconstituted with human peripheral mononuclear cells (huPBMCs), PAM reduces disease severity and mortality caused by human seasonal H1N1 and avian H5N1 influenza virus, and controls the lung inflammation and viral replication. PAM has no such effects in influenza virus–infected Rag2^−/−γc^−/− mice reconstituted with Vγ9Vδ2 T cell–depleted huPBMCs. Our study provides proof-of-concept of a novel therapeutic strategy for treating influenza by targeting the host rather than the virus, thereby reducing the opportunity for the emergence of drug-resistant viruses. As PAM has been commonly used to treat osteoporosis and Paget’s disease, this new application of an old drug potentially offers a safe and readily available option for treating influenza.

Polysaccharides isolated from Açaí fruit induce innate immune responses

The Açaí (Acai) fruit is a popular nutritional supplement that purportedly enhances immune system function. These anecdotal claims are supported by limited studies describing immune responses to the Acai polyphenol fraction. Previously, we characterized γδ T cell responses to both polyphenol and polysaccharide fractions from several plant-derived nutritional supplements. Similar polyphenol and polysaccharide fractions are found in Acai fruit. Thus, we hypothesized that one or both of these fractions could activate γδ T cells. Contrary to previous reports, we did not identify agonist activity in the polyphenol fraction; however, the Acai polysaccharide fraction induced robust γδ T cell stimulatory activity in human, mouse, and bovine PBMC cultures. To characterize the immune response to Acai polysaccharides, we fractionated the crude polysaccharide preparation and tested these fractions for activity in human PBMC cultures. The largest Acai polysaccharides were the most active in vitro as indicated by activation of myeloid and γδ T cells. When delivered in vivo, Acai polysaccharide induced myeloid cell recruitment and IL-12 production. These results define innate immune responses induced by the polysaccharide component of Acai and have implications for the treatment of asthma and infectious disease.

gammadelta T cells in cancer immunotherapy: current status and future prospects

gammadelta T lymphocytes are a distinct T-cell subset that display unique features with respect to T-cell receptor (TCR) gene usage, tissue tropism and antigen recognition. Phosphoantigens contributed by a dysregulated mevalonate pathway or the bacterial nonmevalonate pathway and aminobisphosphonates are capable of activating Vgamma9Vdelta2 T cells. With the aid of synthetic phosphoantigens, large-scale expansion of gammadelta T cells and their adoptive transfer into human hosts is now possible. The present review summarizes triumphs and tribulations of clinical trials using gammadelta T-cell immunotherapy. Adoptive transfer of phosphoantigen-activated gammadelta T cells or coadministration with aminobisphosphonates/cytokines/monoclonal antibodies appear to be promising approaches for cancer immunotherapy. It can be predicted that a comprehensive understanding of the molecular interactions of this unique T-cell subset with other key immune regulators (dendritic cells and regulatory T cells) will provide an impetus to bring this modality of treatment from bench to bedside.

Phosphoantigen-expanded human gammadelta T cells display potent cytotoxicity against monocyte-derived macrophages infected with human and avian influenza viruses

BackgroundInfluenza virus is a cause of substantial annual morbidity and mortality worldwide. The potential emergence of a new pandemic strain (eg, avian influenza virus) is a major concern. Currently available vaccines and anti-influenza drugs have limited effectiveness for influenza virus infections, especially for new pandemic strains. Therefore, there is an acute need to develop alternative strategies for influenza therapy. γδ T cells have potent antiviral activities against different viruses, but no data are available concerning their antiviral activity against influenza viruses

MethodsIn this study, we used virus-infected primary human monocyte-derived macrophages (MDMs) to examine the antiviral activity of phosphoantigen isopentenyl pyrophosphate (IPP)–expanded human Vγ9Vδ2 T cells against influenza viruses

ResultsVγ9Vδ2 T cells were selectively activated and expanded by IPP from peripheral blood mononuclear cells. IPP-expanded Vγ9Vδ2 T cells efficiently killed MDMs infected with human (H1N1) or avian (H9N2 or H5N1) influenza virus and significantly inhibited viral replication. The cytotoxicity of Vγ9Vδ2 T cells against influenza virus–infected MDMs was dependent on NKG2D activation and was mediated by Fas–Fas ligand and perforin–granzyme B pathways

ConclusionOur findings suggest a potentially novel therapeutic approach to seasonal, zoonotic avian, and pandemic influenza—the use of phosphoantigens to activate γδ T cells against influenza virus infections

Activated V gamma 9V delta 2 T cells trigger granulocyte functions via MCP-2 release

Vgamma9Vdelta2 T cells display a broad antimicrobial activity by directly killing infected cells and by inducing an effective adaptive immune response. The activation of Vgamma9Vdelta2 T cells by aminobisphosphonate drugs such as zoledronic acid (ZOL) results in a massive release of cytokines and chemokines that may induce a bystander activation of other immune cells. The aim of this work was to evaluate the ability of soluble factors released by ZOL-activated Vgamma9Vdelta2 T cells to induce granulocyte activation. We showed that soluble factors released by ZOL-stimulated Vgamma9Vdelta2 T cells activate granulocytes by inducing their chemotaxis, phagocytosis, and alpha-defensins release. Proteomic analysis allowed us to identify a number of cytokines and chemokines specifically released by activated Vgamma9Vdelta2 T cells. Moreover, MCP-2 depletion by neutralizing Ab revealed a critical role of this chemokine in induction of granulocyte alpha-defensins release. Altogether, these data show a Vgamma9Vdelta2-mediated activation of granulocytes through a bystander mechanism, and confirm the wide ability of Vgamma9Vdelta2 T-lymphocytes in orchestrating the immune response. In conclusion, an immune modulating strategy targeting Vgamma9Vdelta2 T cells may represent a key switch to induce an effective and well-coordinated immune response, and can be proposed as a way to strengthen the immune competence during infectious diseases.

Response of gammadelta T Cells to plant-derived tannins

Many pharmaceutical drugs arc isolated from plants used in traditional medicines, and new plant-derived pharmaceutical drugs continue to be identified. Relevant to this review, different plant-derived agonists for gammadelta T cells are described that impart effector functions upon distinct subsets of these cells. Recently, plant tannins have been defined as one class of gammadelta T cell agonist and appear to preferentially activate the mucosal population. Mucosal gammadelta T cells function to modulate tissue immune responses and induce epithelium repair. Select tannins, isolated from apple peel, rapidly induce immune gene transcription in gammadelta T cells, leading to cytokinc production and increased responsiveness to secondary signals. Activity of these tannin preparations tracks to the procyanidin fraction, with the procyanidin trimer (C1) having the most robust activity defined to date. The response to the procyanidins is evolutionarily conserved in that responses are seen with human, bovine, and murine gammadelta T cells, although human cells show less selectivity. Procyanidin-induced responses described in this review likely account for the expansion of mucosal gammadelta T cells seen in mice and rats fed soluble extracts of tannins. Use of procyanidins to activate gammadelta T cells may represent a novel approach for the treatment of tissue damage and autoimmune diseases.

Characteristics of circulating T cell receptor gamma-delta T cells from individuals chronically infected with hepatitis B virus (HBV): an association between V(delta)2 subtype and chronic HBV infection

BACKGROUND

To date, few studies have been conducted to determine whether T cell receptor (TCR) gammadelta T cells are involved in hepatitis B virus (HBV) infection. This study was performed to assess the quantity and immune function of TCRgammadelta T cells in the blood of patients with chronic HBV infection and to analyze the relationship between proportions of TCRgammadelta T cells and both proportions of other immune cells and clinical parameters.

METHODS

Flow cytometry was used to detect the proportions of TCRgammadelta T cells and other immune cells in the peripheral blood of 46 asymptomatic carriers (AsCs) of HBV, 95 patients with chronic hepatitis B (CHB), and 29 healthy donors (HDs). The immune functions of TCRgammadelta T cells from 5 AsCs, 6 patients with CHB, and 5 HDs were assessed by cytokine secretion and cytotoxity assays.

RESULTS

The difference in the proportion of the V(delta)2 T cell subtype between HDs and patients was significant. For the patients, the proportion of V(delta)2 T cells was negatively correlated with alanine aminotransferase, aspartate aminotransferase, and total bilirubin levels. The differences in interferon (IFN)-gamma secretion and cytotoxicity between patients and HDs were significant.

CONCLUSIONS

The proportion of circulating V(delta)2 T cells was significantly decreased in patients with chronic HBV infection, and this was accompanied by a strong immune response in the liver. IFN-gamma secretion and TCRgammadelta T cell cytotoxicity was lower in patients than in HDs.

Human gamma delta T cells: candidates for the development of immunotherapeutic strategies

A numerically small subset of human T lymphocytes expresses a gamma delta T cell receptor (TCR). These gamma delta T cells share certain effector functions with alpha beta T cells as well as with NK cells and NKT cells. The major peripheral blood gamma delta T cell subset in healthy adults expresses a Vgamma9Vdelta2 TCR, which recognizes small phosphorylated metabolites referred to as phosphoantigens. Vdelta1 gamma delta T cells mainly occur in the intestine. They recognize the stress-induced MICA/B and CD1c. Furthermore, gamma delta T cells express a variety of NK cell and pattern-recognition receptors which are responsible for the "fine-tuning" of effector functions. In recent years, gamma delta T cells start to emerge as a rewarding target for immunotherapeutic strategies against viral infections and cancer. A better understanding of factors that modulate gamma gamma delta T cell function will further eluminate the potential of these cells.

Cytotoxic effects of human peripheral blood γδT cells on the tumor cells of digestive system in vitro

AIM: To investigate the cytotoxic effects of human peripheral blood γδT cells on the tumor cell lines of digestive system.

METHODS: The γδT cells in peripheral blood of healthy volunteers were expanded using interleukin-2 (IL-2) and isopentenyl pyrophodphate (IPP) in PRMI 1640 medium. After 10 days, the purity of γδT cells was analyzed by flow cytometry. The cytotoxic activity of the purified γδT cells against human gastric cancer cells, pancreatic carcinoma cells and hepatocellular carcinoma cells were tested in different effector-to-target ratios.

RESULTS: After peripheral blood mononuclear cells were cultured for 10 days, the γδT cells were expanded rapidly from 4.21% to 70.35%. Cytotoxic activities of the purified γδT cells against human gastric cancer cells, pancreatic carcinoma cells and hepatocellular carcinoma cells were 61%, 50% and 59% respectively at the effecter-to-target cell ratio of 40∶1. The cytotoxic activities of the attached γδT cells on tumor cells were higher than those of the suspended γδT (50%, 37% and 37%, respectively) and CIK (45%, 34% and 40%, respectively) cells.

CONCLUSION: The purified human peripheral blood γδT cells show a highly-efficient cytotoxicity against the tumor cells of digestive system. The attached γδT cells are more efficient than the suspended γδT and CIK cells. γδT cells may be another important group of immune effector cells in the adoptive immunotherapy for cancer.