Vgamma9Vdelta2 T cell-mediated non-cytolytic antiviral mechanisms and their potential for cell-based therapy

Vγ9Vδ2 T-cells Are Potent Inhibitors of SARS-CoV-2 Replication and Represent Effector Phenotypes in Patients With COVID-19

Vγ9Vδ2 T cells play a key role in the innate immune response to viral infections through butyrophilin 3A (BTN3A). Here, we report blood Vγ9Vδ2 T cells decreased in clinically mild COVID-19 compared to healthy volunteers, and this was maintained up to 28 days and in the recovery period. Terminally differentiated Vγ9Vδ2 T cells tended to be enriched on the day of diagnosis, 28 days after, and during the recovery period. These cells showed cytotoxic and inflammatory activities following anti-BTN3A activation. BTN3A upregulation and Vγ9Vδ2 T-cell infiltration were observed in a lung biopsy from a fatal SARS-CoV-2 infection. In vitro, SARS-CoV-2 infection increased BTN3A expression in macrophages and lung cells that enhanced the anti-SARS-CoV-2 Vγ9Vδ2 T-cell cytotoxicity and interferon-γ and tumor necrosis factor-α. Increasing concentrations of anti-BTN3A lead to viral replication inhibition. Altogether, we report Vγ9Vδ2 T cells are important in the immune response against SARS-CoV-2 infection and activation by anti-BTN3A antibody may enhance their response. Clinical Trials Registration. NCT04816760.

Harnessing Unconventional T Cells and Innate Lymphoid Cells to Prevent and Treat Hematological Malignancies: Prospects for New Immunotherapy

Unconventional T cells and innate lymphoid cells (ILCs) make up a heterogeneous set of cells that characteristically show prompt responses toward specific antigens. Unconventional T cells recognize non-peptide antigens, which are bound and presented by diverse non-polymorphic antigen-presenting molecules and comprise γδ T cells, MR1-restricted mucosal-associated invariant T cells (MAITs), and natural killer T cells (NKTs). On the other hand, ILCs lack antigen-specific receptors and act as the innate counterpart to the T lymphocytes found in the adaptive immune response. The alteration of unconventional T cells and ILCs in frequency and functionality is correlated with the onset of several autoimmune diseases, allergy, inflammation, and tumor. However, depending on the physio-pathological framework, unconventional T cells may exhibit either protective or pathogenic activity in a range of neoplastic diseases. Nonetheless, experimental models and clinical studies have displayed that some unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic markers. In fact, cell-mediated immune response in tumors has become the focus in immunotherapy against neoplastic disease. This review concentrates on the present knowledge concerning the function of unconventional T cell sets in the antitumor immune response in hematological malignancies, such as acute and chronic leukemia, multiple myeloma, and lymphoproliferative disorders. Moreover, we discuss the possibility that modulating the activity of unconventional T cells could be useful in the treatment of hematological neoplasms, in the prevention of specific conditions (such as graft versus host disease), and in the formulation of an effective anticancer vaccine therapy. The exact knowledge of the role of these cells could represent the prerequisite for the creation of a new form of immunotherapy for hematological neoplasms.

γδ T Cells Activated in Different Inflammatory Environments Are Functionally Distinct

γδ T cells are important immunoregulatory cells in experimental autoimmune uveitis (EAU), and the activation status of γδ T cells determines their disease-enhancing or inhibitory effects. Because γδ T cells can be activated via various pathways, we questioned whether the nature of their activation might impact their function. In this study, we show that γδ T cells activated under different inflammatory conditions differ greatly in their functions. Whereas anti-CD3 treatment activated both IFN-γ⁺ and IL-17⁺ γδ T cells, cytokines preferentially activated IL-17⁺ γδ T cells. γδ T cells continued to express high levels of surface CD73 after exposure to inflammatory cytokines, but they downregulated surface CD73 after exposure to dendritic cells. Although both CD73^high and CD73^low cells have a disease-enhancing effect, the CD73^low γδ T cells are less inhibitory. We also show that polarized activation not only applies to αβ T cells and myeloid cells, but also to γδ T cells. After activation under Th17-polarizing conditions, γδ T cells predominantly expressed IL-17 (gdT17), but after activation under Th1 polarizing conditions (gdT1) they mainly expressed IFN-γ. The pro-Th17 activity of γδ T cells was associated with gdT17, but not gdT1. Our results demonstrate that the functional activity of γδ T cells is strikingly modulated by their activation level, as well as the pathway through which they were activated.

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.

Extreme immunotherapy: emergency immunology to defeat pandemics

The ongoing global COVID-19 pandemic has thrown into sharp relief the gap between modern biology's ability to investigate and respond to a novel pathogen and modern medicine's ability to marshal effective front-line interventions to limit its immediate health impact. While we have witnessed the rapid development of innovative vaccines against SARS-CoV-2 using novel molecular platforms, these have yet to alter the pandemic's long-term trajectory in all but a handful of high-income countries. Health workers at the clinical front lines have little more in their clinical armamentarium than was available a century ago-chiefly oxygen and steroids-and yet advances in modern immunology and immunotherapeutics suggest an underuse of extant and effective, if unorthodox, therapies, which we now call "Extreme Immunotherapies for Pandemics (EIPs)."

Cheap and Commonplace: Making the Case for BCG and γδ T Cells in COVID-19

Antigen-specific vaccines developed for the COVID-19 pandemic demonstrate a remarkable achievement and are currently being used in high income countries with much success. However, new SARS-CoV-2 variants are threatening this success via mutations that lessen the efficacy of antigen-specific antibodies. One simple approach to assisting with this issue is focusing on strategies that build on the non-specific protection afforded by the innate immune response. The BCG vaccine has been shown to provide broad protection beyond tuberculosis disease, including against respiratory viruses, and ongoing studies are investigating its efficacy as a tool against SARS-CoV-2. Gamma delta (γδ) T cells, particularly the Vδ2 subtype, undergo rapid expansion after BCG vaccination due to MHC-independent mechanisms. Consequently, γδ T cells can produce diverse defenses against virally infected cells, including direct cytotoxicity, death receptor ligands, and pro-inflammatory cytokines. They can also assist in stimulating the adaptive immune system. BCG is affordable, commonplace and non-specific, and therefore could be a useful tool to initiate innate protection against new SARS-CoV-2 variants. However, considerations must also be made to BCG vaccine supply and the prioritization of countries where it is most needed to combat tuberculosis first and foremost.

Augmented Th17-stimulating activity of BMDCs as a result of reciprocal interaction between γδ and dendritic cells

Our previous studies demonstrated that γδ T cells have a strong regulatory effect on Th17 autoimmune responses in experimental autoimmune uveitis (EAU). In the current study, we show that reciprocal interactions between mouse γδ T cells and dendritic cells (DCs) played a major role in γδ regulation of Th17 responses. Mouse bone marrow-derived dendritic cells (BMDCs) acquired an increased ability to enhance Th17 autoimmune responses after exposure to γδ T cells; meanwhile, after exposure, a significant portion of the BMDCs expressed CD73 - a molecule that is fundamental in the conversion of immunostimulatory ATP into immunosuppressive adenosine. Functional studies showed that CD73+ BMDCs were uniquely effective in stimulating the Th17 responses, as compared to CD73- BMDCs; and activated γδ T cells are much more effective than non-activated γδ T cells at inducing CD73+ BMDCs. As a result, activated γδ T cells acquired greater Th17-enhancing activity. Treatment of BMDCs with the CD73-specific antagonist APCP abolished the enhancing effect of the BMDCs. γδ T cells more effectively induced CD73+ BMDCs from the BMDCs that were pre-exposed to TLR ligands, and the response was further augmented by adenosine. Moreover, BMDCs acquired increased ability to stimulate γδ activation after pre-exposure to TLR ligands and adenosine. Our results demonstrated that both extra-cellular adenosine and TLR ligands are critical factors in augmented Th17 responses in this autoimmune disease, and the reciprocal interactions between γδ T cells and DCs play a major role in promoting Th17 responses.

Next Generation Sequencing-Based Identification of T-Cell Receptors for Immunotherapy Against Hepatocellular Carcinoma

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) remains a global health concern, and HBV proteins may be ideal targets for T cell-based immunotherapy for HCC. There is a need for fast and efficient identification of HBV-specific T cell receptors (TCRs) for the development of TCR-transduced T (TCR-T) cell-based immunotherapy. Two widely employed TCR identification approaches, T cell clonal expansion and single-cell sequencing, involve a TCR singularization process for the direct identification of Vα and Vβ pairs of TCR chains. Clonal expansion of T cells is well known to have tedious time and effort requirements due to the use of T cell cultures, whereas single-cell sequencing is limited by the requirements of cell sorting and the preparation of a single-cell immune-transcriptome library as well as the massive cost of the whole procedure. Here, we present a next-generation sequencing (NGS)-based HBV-specific TCR identification that does not require the TCR singularization process. Conclusion: Two pairing strategies, ranking-based strategy and α-β chain mixture-based strategy, have proved to be useful for NGS-based TCR identification, particularly for polyclonal T cells purified by a peptide-major histocompatibility complex (pMHC) multimer-based approach. Functional evaluation confirmed the specificity and avidity of two identified HBV-specific TCRs, which may potentially be used to produce TCR-T cells to treat patients with HBV-related HCC.

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.

Making a case for using γδ T cells against SARS-CoV-2

Intensive worldwide efforts are underway to determine both the pathogenesis of SARS-CoV-2 infection and the immune responses in COVID-19 patients in order to develop effective therapeutics and vaccines. One type of cell that may contribute to these immune responses is the γδ T lymphocyte, which plays a key role in immunosurveillance of the mucosal and epithelial barriers by rapidly responding to pathogens. Although found in low numbers in blood, γδ T cells consist the majority of tissue-resident T cells and participate in the front line of the host immune defense. Previous studies have demonstrated the critical protective role of γδ T cells in immune responses to other respiratory viruses, including SARS-CoV-1. However, no studies have profoundly investigated these cells in COVID-19 patients to date. γδ T cells can be safely expanded in vivo using existing inexpensive FDA-approved drugs such as bisphosphonate, in order to test its protective immune response to SARS-CoV-2. To support this line of research, we review insights gained from previous coronavirus research, along with recent findings, discussing the potential role of γδ T cells in controlling SARS-CoV-2. We conclude by proposing several strategies to enhance γδ T cell's antiviral function, which may be used in developing therapies for COVID-19.

Human Zika infection induces a reduction of IFN-γ producing CD4 T-cells and a parallel expansion of effector Vδ2 T-cells

The definition of the immunological response to Zika (ZIKV) infection in humans represents a key issue to identify protective profile useful for vaccine development and for pathogenesis studies. No data are available on the cellular immune response in the acute phase of human ZIKV infection, and its role in the protection and/or pathogenesis needs to be clarified. We studied and compared the phenotype and functionality of T-cells in patients with acute ZIKV and Dengue viral (DENV) infections. A significant activation of T-cells was observed during both ZIKV and DENV infections. ZIKV infection was characterized by a CD4 T cell differentiation toward effector cells and by a lower frequency of IFN-γ producing CD4 T cells. Moreover, a substantial expansion of CD3⁺CD4⁻CD8⁻ T-cell subset expressing Vδ2 TCR was specifically observed in ZIKV patients. Vδ2 T cells presented a terminally differentiated profile, expressed granzyme B and maintained their ability to produce IFN-γ. These findings provide new knowledge on the immune response profile during self-limited infection that may help in vaccine efficacy definition, and in identifying possible immuno-pathogenetic mechanisms of severe infection.

Functional Conversion and Dominance of γδ T Subset in Mouse Experimental Autoimmune Uveitis

We have previously shown that activated γδ T cells have a much stronger proinflammatory effect in the development of experimental autoimmune uveitis than their nonactivated counterparts. Our present study explored γδ T cell subsets are functionally distinct in autoimmune pathogenesis and determined the pathogenic contribution of biased Vγ4⁺ γδ T cell activation in this disease. By systematically comparing two major peripheral γδ T cell subsets, the Vγ1⁺ and the Vγ4⁺ cells, we found that the Vγ4⁺ cells were readily activated in B6 mice during experimental autoimmune uveitis development, whereas Vγ1⁺ cells remained nonactivated. Cytokines that were abundantly found in the serum of immunized mice activated Vγ4⁺, but did not activate Vγ1⁺, cells. The Vγ4⁺ cells had a strong proinflammatory activity, whereas the Vγ1⁺ cells remained nonactivated when tested immediately after isolation from immunized mice. However, when the Vγ1⁺ cells were activated in vitro, they promoted inflammation. Our results demonstrated that activation is a major factor in switching the enhancing and inhibiting effects of both Vγ1⁺ and Vγ4⁺ γδ T cell subsets, and that γδ T cell subsets differ greatly in their activation requirements. Whether the enhancing or inhibiting function of γδ T cells is dominant is mainly determined by the proportion of the γδ T cells that are activated versus the proportion not activated.

A Subset of Protective γ9δ2 T Cells Is Activated by Novel Mycobacterial Glycolipid Components

γ₉δ₂ T cells provide a natural bridge between innate and adaptive immunity, rapidly and potently respond to pathogen infection in mucosal tissues, and are prominently induced by both tuberculosis (TB) infection and bacillus Calmette Guérin (BCG) vaccination. Mycobacterium-expanded γ₉δ₂ T cells represent only a subset of the phosphoantigen {isopentenyl pyrophosphate [IPP] and (E)-4-hydroxy-3-methyl-but-2-enylpyrophosphate [HMBPP]}-responsive γ₉δ₂ T cells, expressing an oligoclonal set of T cell receptor (TCR) sequences which more efficiently recognize and inhibit intracellular Mycobacterium tuberculosis infection. Based on this premise, we have been searching for M. tuberculosis antigens specifically capable of inducing a unique subset of mycobacterium-protective γ₉δ₂ T cells. Our screening strategy includes the identification of M. tuberculosis fractions that expand γ₉δ₂ T cells with biological functions capable of inhibiting intracellular mycobacterial replication. Chemical treatments of M. tuberculosis whole-cell lysates (MtbWL) ruled out protein, nucleic acid, and nonpolar lipids as the M. tuberculosis antigens inducing protective γ₉δ₂ T cells. Mild acid hydrolysis, which transforms complex carbohydrate to monomeric residues, abrogated the specific activity of M. tuberculosis whole-cell lysates, suggesting that a polysaccharide was required for biological activity. Extraction of MtbWL with chloroform-methanol-water (10:10:3) resulted in a polar lipid fraction with highly enriched specific activity; this activity was further enriched by silica gel chromatography. A combination of mass spectrometry and nuclear magnetic resonance analysis of bioactive fractions indicated that 6-O-methylglucose-containing lipopolysaccharides (mGLP) are predominant components present in this active fraction. These results have important implications for the development of new immunotherapeutic approaches for prevention and treatment of TB.

CD73 Expressed on γδ T Cells Shapes Their Regulatory Effect in Experimental Autoimmune Uveitis

γδ T cells can either enhance or inhibit an adaptive immune response, but the mechanisms involved are not fully understood. Given that CD73 is the main enzyme responsible for conversion of AMP into the immunosuppressive molecule adenosine, we investigated its role in the regulatory function of γδ T cells in experimental autoimmune uveitis (EAU). We found that γδ T cells expressed different amounts of CD73 during the different stages of EAU and that low CD73 expression on γδ T cells correlated with enhanced Th17 response-promoting activity. Functional comparison of CD73-deficient and wild-type B6 (CD73+/+) mice showed that failure to express CD73 decreased both the enhancing and suppressive effects of γδ T cells on EAU. We also demonstrated that γδ T cells expressed different amounts of CD73 when activated by different pathways, which enabled them to either enhance or inhibit an adaptive immune response. Our results demonstrate that targeting CD73 expression on γδ T cells may allow us to manipulate their pro- or anti-inflammatory effect on Th17 responses.

Loss of Intra-Epithelial Endocervical Gamma Delta (GD) 1 T Cells in HIV-Infected Women

PROBLEM

Human gamma delta (GD) T cells play a well-documented role in epithelial barrier surveillance and protection. Two subsets of GD T cells, defined by the use of either the Vdelta2 (GD2) or Vdelta1 (GD1) TCR, predominate. We hypothesized that endocervical GD T cells play important role in lower genital tract anti-HIV immune responses.

METHOD OF STUDY

HIV-infected (n = 18) and HIV-uninfected (n = 19) pre-menopausal women participating in the WIHS cohort were recruited. Frequency and phenotype of GD T cells were determined in endocervical cytobrush samples and peripheral blood by multicolor flow cytometry.

RESULTS

We found depletion of GD2 cells in the blood of HIV-infected women as well as significant decrease in the frequency of endocervical GD1 cells compared to uninfected women.

CONCLUSION

We report for the first time, the GD1 cells are a predominant endocervical T-cell subset that is significantly decreased in HIV-infected women.

The Therapeutic Effect of Pamidronate on Lethal Avian Influenza A H7N9 Virus Infected Humanized Mice

A novel avian influenza virus H7N9 infection occurred among human populations since 2013. Although the lack of sustained human-to-human transmission limited the epidemics caused by H7N9, the late presentation of most patients and the emergence of neuraminidase-resistant strains made the development of novel antiviral strategy against H7N9 in urgent demands. In this study, we evaluated the potential of pamidronate, a pharmacological phosphoantigen that can specifically boost human Vδ2-T-cell, on treating H7N9 virus-infected humanized mice. Our results showed that intraperitoneal injection of pamidronate could potently decrease the morbidity and mortality of H7N9-infected mice through controlling both viral replication and inflammation in affected lungs. More importantly, pamidronate treatment starting from 3 days after infection could still significantly ameliorate the severity of diseases in infected mice and improve their survival chance, whereas orally oseltamivir treatment starting at the same time showed no therapeutic effects. As for the mechanisms underlying pamidronate-based therapy, our in vitro data demonstrated that its antiviral effects were partly mediated by IFN-γ secreted from human Vδ2-T cells. Meanwhile, human Vδ2-T cells could directly kill virus-infected host cells in a perforin-, granzyme B- and CD137-dependent manner. As pamidronate has been used for osteoporosis treatment for more than 20 years, pamidronate-based therapy represents for a safe and readily available option for clinical trials to treat H7N9 infection.

Roles of the adenosine receptor and CD73 in the regulatory effect of γδ T cells

The adenosine A2A receptor (A2AR), the main functional adenosine receptor on murine T cells, plays a unique role in the attenuation of inflammation and tissue damage in vivo. Here, we showed that, of the immune cell types tested, activated γδ T cells expressed the highest levels of A2AR mRNA and that A2AR ligation inhibited αβ T cell activation, but enhanced γδ T cell activation. We also showed that the inhibitory effect of an adenosine receptor agonist on autoreactive T cells was prevented by addition of a low percentage of activated γδ T cells. Furthermore, compared to resting cells, activated γδ T cells expressed significantly lower levels of CD73, an enzyme involved in the generation of extracellular adenosine. Exogenous AMP had a significant inhibitory effect on autoreactive T cell responses, but only in the presence of CD73+ γδ T cells, and this effect was abolished by a CD73 inhibitor. Our results show that expression of increased amounts of A2AR allows γδ T cells to bind adenosine and thereby attenuate its suppressive effect, while decreased expression of CD73 results in less generation of adenosine in the inflammatory site. Together, these events allow activated γδ T cells to acquire increased proinflammatory activity, leading to augmented autoimmune responses.

In vitro effects of bisphosphonates on chemotaxis, phagocytosis, and oxidative burst of neutrophil granulocytes

OBJECTIVES

Bisphosphonate-associated osteonecrosis of the jaws is a serious side effect that mainly occurs in patients receiving highly potent, nitrogen-containing bisphosphonates. Usually the diagnosis is made due to exposed bone and a nonhealing wound. Neutrophil granulocytes are essential for sufficient wound healing; therefore, the influence of different bisphosphonates on neutrophil granulocytes was the focus of this study.

MATERIAL AND METHODS

The effect of nitrogen-containing bisphosphonates (ibandronate, pamidronate, and zoledronate) and one non-nitrogen-containing bisphosphonate (clodronate) on chemotaxis, phagocytosis, and oxidative burst of neutrophil granulocytes in human whole blood was analyzed using standard cytometric flow assays.

RESULTS

Chemotaxis of neutrophils was reduced by almost 50 % when cells were treated with ibandronate and zoledronate. All tested nitrogen-containing bisphosphonates moderately increased the percentage of phagocytizing neutrophils, whereas the percentage of oxidizing cells was extremely affected. Zoledronate increased the oxidative burst activity even at low concentrations. Treatment with ibandronate and pamidronate reached the same level, but only in at least 10 times the higher concentrations. The maximal burst activity of a single cell reached nearly 150 % compared to control. In this case, zoledronate also caused maximal effects even at low concentrations. Clodronate did not show any effects.

CONCLUSION

The results show a proinflammatory effect of the nitrogen-containing effect on neutrophil granulocytes which might contribute to the development of osteonecrosis.

CLINICAL RELEVANCE

The altered neutrophil defense might play a key role in the pathogenesis of bisphosphonate-associated osteonecrosis of the jaws, although the underlying causation between inflammatory reaction and the development of necrosis is yet unknown.

Characterization of γδT cells in naïve and HIV-infected chimpanzees and their responses to T-cell activators in vitro

BACKGROUND

γδT cells are effector cells that eliminate cancer and virus-infected cells. Chimpanzees are an endangered species that can naturally and experimentally be infected with SIV and HIV, respectively, but no information about the functionality of γδT cells during chronic lentiviral infection is currently available.

METHODS

Healthy and HIV-infected chimpanzee γδT cells were characterized by flow cytometry. γδT subsets were studied after stimulation with T-cell activators, and the release of cytokines was analyzed by Luminex assay.

RESULTS

γδT-cell subsets, Vδ1 and Vδ2Vγ9, showed different patterns in the expression of CD4, CD195, CD159a, and CD159c. Stimulation of γδT cells resulted in increased levels of CD4 and HLA-DR, which is more pronounced in Vδ1 T cells. Distinct cytokine patterns were found between healthy and HIV-infected chimpanzees.

CONCLUSIONS

Analyses of major chimpanzee γδT subsets show similarities to human γδT cells and suggest different functionality and roles in their immune response against HIV infection.

IL-23 receptor expression on γδ T cells correlates with their enhancing or suppressive effects on autoreactive T cells in experimental autoimmune uveitis

We have previously reported that, depending on their activation status, mouse γδ T cells can either enhance or inhibit the activity of IL-17(+) autoreactive T cells in experimental autoimmune uveitis. In this study, we showed that γδ T cells in naive C57BL/6 (B6) mouse do not express the IL-23R, whereas in immunized mice, it is expressed on >50% of γδ T cells. In vitro studies showed that IL-23R expression on γδ T cells is modulated by their state of activation, as weakly activated γδ T cells expressed the IL-23R, but highly activated γδ T cells did not. Functional studies showed that IL-23R(+) γδ T cells had the strongest suppressive effect on IL-17(+) autoreactive T cells, and that this effect was inhibited when the IL-23R was blocked by anti-IL-23R Ab or in the presence of excessive amounts of exogenous IL-23. We conclude that the balance between the enhancing and inhibitory effects of γδ T cells is regulated by their level of IL-23R expression. The expression of variable IL-23R levels allows γδ T cells to have different regulatory effects on adaptive immune responses, conceivably as a result of αβ and γδ T cells competing for IL-23.

Vγ9Vδ2-T lymphocytes have impaired antiviral function in small-for-gestational-age and preterm neonates

Preterm and small-for-gestational-age (SGA) neonates are vulnerable groups that are susceptible to various microbial infections. Vγ9Vδ2-T cells are critical components of the host immune system and have been demonstrated to play an important role in the defense against viral infection in adults. However, the characteristics of Vγ9Vδ2-T cells in children, especially the preterm and SGA populations, are poorly understood. Here, we examined the frequency and antiviral function of Vγ9Vδ2-T cells in neonates, including preterm, SGA and full-term babies. When compared to adults, neonates had a significantly lower percentage of Vγ9Vδ2-T cells in the blood. Upon influenza virus stimulation, neonatal Vγ9Vδ2-T cells, especially from preterm and SGA babies, showed markedly decreased and delayed antiviral cytokine responses than those of adults. In addition, the antiviral responses of neonatal Vγ9Vδ2-T cells were positively correlated with gestational age and birth weight. Finally, a weaker expansion of Vγ9Vδ2-T cells by isopentenyl pyrophosphate (IPP) was shown in neonates than the expansion in adults. Our data suggest that the depressed antiviral activity and decreased frequency of Vγ9Vδ2-T cells may likely account for the high susceptibility to microbial infection in neonates, particularly in preterm and SGA babies. Improving Vγ9Vδ2-T-cell function of neonates may provide a new way to defend against virus infection.

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.

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.

Activated gammadelta T cells promote the activation of uveitogenic T cells and exacerbate EAU development

PURPOSE

To determine how the activation of γδ T cells affects the generation of uveitogenic αβ T cells and the development of experimental autoimmune uveitis (EAU).

METHODS

γδ T cells were isolated from B6 mice immunized with the uveitogenic peptide IRBP(1-20) and αβ T cells from immunized TCR-δ(-/-) mice. Resting γδ T cells were prepared by culture of separated γδ T cells in cytokine-free medium for 3 to 5 days, when they showed downregulation of CD69 expression. Activated γδ T cells were prepared by incubating resting γδ T cells with anti-γδ TCR (GL3) for 2 days. Responder αβ T cells were cocultured with immunizing antigen and antigen-presenting cells. The numbers of antigen-specific T cells expressing IL-17 or IFN-γ were determined by intracellular staining followed by FACS analysis after stimulation, with or without the addition of purified γδ T cells. The cytokines in the culture medium were measured by ELISA.

RESULTS

Highly enriched γδ T cells exert widely different effects on autoreactive αβ T cells in EAU, depending on the activation status of the γδ T cells. Whereas nonactivated γδ T cells had little effect on the activation of interphotoreceptor retinoid-binding protein-specific αβ T cells in vitro and in vivo, activated γδ T cells promoted the generation of uveitogenic T cells and exacerbated the development of EAU.

CONCLUSIONS

The functional ability of γδ T cells is greatly influenced by their activation status. Activated γδ T cells exacerbate EAU through increased activation of uveitogenic T cells.

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.

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.

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.

Select plant tannins induce IL-2Ralpha up-regulation and augment cell division in gammadelta T cells

Gammadelta T cells are innate immune cells that participate in host responses against many pathogens and cancers. Recently, phosphoantigen-based drugs, capable of expanding gammadelta T cells in vivo, entered clinical trials with the goal of enhancing innate immune system functions. Potential shortcomings of these drugs include the induction of nonresponsiveness upon repeated use and the expansion of only the Vdelta2 subset of human gammadelta T cells. Vdelta1 T cells, the major tissue subset, are unaffected by phosphoantigen agonists. Using FACS-based assays, we screened primary bovine cells for novel gammadelta T cell agonists with activities not encompassed by the current treatments in an effort to realize the full therapeutic potential of gammadelta T cells. We identified gammadelta T cell agonists derived from the condensed tannin fractions of Uncaria tomentosa (Cat's Claw) and Malus domestica (apple). Based on superior potency, the apple extract was selected for detailed analyses on human cells. The apple extract was a potent agonist for both human Vdelta1 and Vdelta2 T cells and NK cells. Additionally, the extract greatly enhanced phosphoantigen-induced gammadelta T cell expansion. Our analyses suggest that a tannin-based drug may complement the phosphoantigen-based drugs, thereby enhancing the therapeutic potential of gammadelta T cells.

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.