Early Γδ Research Articles

IL-18R signaling is required for γδ T cell response and confers resistance to Trypanosoma cruzi infection.

IFN-γ-producing γδ T cells have been suggested to play an important role in protection against infection with Trypanosoma cruzi. However, little is known about the mechanisms leading to functional differentiation of this T cell subset in this model. In the current work, we investigated the possibility that the IL-18/MyD88 pathway is central for the generation of effector γδ T cells, playing a role for resistance against infection. We found that splenic γδ+ CD3+ cells were rapidly expanded (10-14 days post infection), which was accompanied by an early γδ T cell infiltration into the heart. In the following days, intracardiac parasitism was reduced, the protective immunity being accompanied by decreased γδ T cells tissue infiltration. As predicted, there was a drastic reduction of γδ T cells in Myd88- and Il18r1-deficient mice, both transgenic strains displaying a susceptible phenotype with increased intracardiac parasitism. In vivo and in vitro assays confirmed that IL-18R deficiency hampered γδ T cell proliferation. Further characterization revealed that T. cruzi infection up-regulates IL-18R expression in WT γδ+ T cell population whereas Il18r1-/- mice showed impaired generation of cytotoxic GzB+ and IFN-γ-producing γδ T cells. Consistently, in vitro cytotoxicity assay confirmed that cytolytic function was impaired in Il18r1-deficient γδ T cells. As a proof of concept, adoptive transfer of WT γδ T cells rescues Il18r1-deficient mice from susceptibility, reducing parasitemia and abrogating the mortality. Collectively, our findings implicate the IL-18R-MyD88 signaling in the mechanisms underlying generation of immunoprotective γδ T cells response in experimental Trypanosoma cruzi infection.

High-dose post-transplant cyclophosphamide impairs γδ T-cell reconstitution after haploidentical haematopoietic stem cell transplantation using low-dose antithymocyte globulin and peripheral blood stem cell graft.

ObjectivesHaploidentical haematopoietic cell transplantation (Haplo‐HCT) using peripheral blood stem cell (PBSC) grafts and post‐transplant cyclophosphamide (PTCy) is being increasingly used; however, data on immunological reconstitution (IR) are still scarce.MethodsThis retrospective study evaluated T‐cell immunological reconstitution in 106 adult patients who underwent allogeneic haematopoietic cell transplantation for haematologic malignancies between 2013 and 2016.ResultsAt D30, while conventional T cells reached similar median counts in Haplo‐HCT recipients (n = 19) and controls (n = 87), γδ and Vδ2+ T‐cell median counts were significantly lower in Haplo‐HCT recipients and it persists at least until D360 for Vδ2+ T cells. PTCy induces a significant reduction in early γδ and Vδ2+ T‐cell proliferation at D 7. At one year, the rate of increase in Epstein–Barr virus (EBV) viral load was significantly higher in Haplo‐HCT recipients as compared to controls (61% versus 34%, P = 0.02). In multivariate analysis, a higher γδ T‐cell count (> 4.63 μL−1) at D30 was the only independent parameter significantly associated with a reduced risk of increase in EBV viral load (RR 0.34; 95% CI, 0.15–0.76, P = 0.009).ConclusionImmunological reconstitution of γδ T cells is significantly delayed after Haplo‐HCT using PTCy and low‐dose ATG and is associated with an increased risk of increase in EBV viral load.

γδ T cells are involved in acute HIV infection and associated with AIDS progression.

BackgroundEarly diagnosis is vital to HIV control. γδ T cells play critical roles in viral infections, but their activation in acute HIV infected patients and follow up to 18 months has not been described.MethodsChanges in γδ T cells, including subsets, function and activation, in treated and untreated acutely HIV-infected patients (n = 79) were compared by cytotoxicity assay and flow cytometry with healthy controls (n = 21) at month 0, 6, 12 and 18.ResultsIn acutely HIV-infected patients, Vδ1 cell proportion was elevated (P = 0.027) with Vδ2 population reduced (P = 0.002). Effector and central memory γδ T cell factions were decreased (P = 0.006 and P = 0.001, respectively), while proportion of terminal γδ T cells increased (P = 0.002). γδ T cell cytotoxicity was compromised over time. Fraction of IL-17-producing cells increased (P = 0.008), and IFN-γ-producing cells were unaffected (P = 0.115). Elevation of a microbial translocation marker, sCD14, was associated with γδ T cell activation (P = 0.001), which increased in a time-dependent manner, correlating with CD4/CD8 T cell activation set-points and CD4 counts. Antiretroviral therapy did not affect these changes.Conclusionsγδ T cell subpopulation and functions change significantly in acute HIV infection and over time. Early γδ T cell activation was associated with CD4/CD8 T cell activation set-points, which predict AIDS progression. Therefore, γδ T cell activation represents a potential surrogate marker of AIDS progression.

Elevated Gamma Delta T Cell Recovery Following Hematopoietic Stem Cell Transplantation Associated with Improved Long Term Overall Survival in Pediatric Patients with Acute Leukemia

Abstract 227Recent studies show that accelerated γΔ T cell reconstitution after hematopoietic stem cell transplantation (HSCT) is associated with improved overall survival (OS) though the mechanisms have not been elucidated. Here, we confirm that early γΔ T cell recovery after HSCT is an independent predictor for improving OS and event free survival (EFS). Moreover, patients with robust γΔ T cell recovery after HSCT appear to be protected from increased risk of serious life threatening infections, and acute gut and chronic graft versus host disease (GVHD). More importantly, we show that γΔ T cell recovery dynamics are independent from those of classical αβ T cells. We evaluated 102 consecutive pediatric patients with acute leukemia undergoing HSCT at St. Jude Children’s Research Hospital from 1996–2011. The median age of the patients was 10.5 ± 5.9 yrs. (range, 0.6–25.2) and median follow up was 2.7±1.8 yrs. (range 0.2–6.0). There were 57% males, 43% females and 59% with ALL and 41% with AML. There were 14 patients with elevated γΔ T cells (≥1.75×105 cells/ml) and 88 with low/normal γΔ T cells (<1.75×105 cells/ml). There were no significant differences between the two groups with respect to age, sex, disease or donor source, p=0.7, 0.5, 1 and 0.07 respectively. Fours years after HSCT, OS was significantly higher for patients in the elevated group compared to the patients in the low/normal group, 93% and 60%, respectively, p=0.0173. Survival without relapse or graft failure (EFS) was significantly higher in the elevated group compared to the low/normal group, 85.7% and 58.0%, respectively. Since T cell reconstitution following HSCT is age dependent, we determined if γΔ T cell recovery correlated with age and/or CD3+ cells. Multivariate analysis showed no correlation between the number of CD3+ and γΔ T cells. In fact, 13 of 14 patients that recovered with increased number of γΔ T cells had normal or low numbers of CD3+ cells. Thus, γΔ T cell recovery is not a simple correlate of T cell reconstitution. Because γΔ T cells play a central role in maintaining intestinal epithelium integrity, we evaluated the incidence of gut GVHD. We found a significant lower rate of gut GVHD in the elevated group compared to the low/normal group, 0% and 17% respectively. Furthermore, the number of γΔ T cells in patients with cGVHD (2.3 x105 cells/ml) was significantly lower compared to patients without cGVHD (6.2 x105 cells/ml), p=0.01. This suggests that γΔ T cell may protect against gut and cGVHD. Since accumulating evidence suggests that γΔ T cells contribute to both innate and adaptive immune responses during infections, we evaluated the rate and types of infection between the two groups. We found a significant lower incidence of infection in the elevated group compared to the low/normal group, 21% and 54% respectively p=0.02. Furthermore, the elevated group had only viral infections while the low/normal group had viral, bacterial and fungal infections. Recent studies suggested that γΔ T cells could contribute to surveillance of CMV reactivation after HSCT through cooperation with anti-CMV IgG. Evaluation of CMV infections found no significant decrease in the incidence of CMV infection in the elevated group compared to the low/normal group, 14% and 2%. In summary, this is the first reported study of γΔ T cell recovery after HSCT in pediatric patients and adds new insights into the role γΔ T cells by evaluating the relationship of the most common complications such as relapse, GVHD and infections. Disclosures:No relevant conflicts of interest to declare.

Tuberculosis Immunity: Opportunities from Studies with Cattle

Mycobacterium tuberculosis and M. bovis share >99% genetic identity and induce similar host responses and disease profiles upon infection. There is a rich history of codiscovery in the development of control measures applicable to both human and bovine tuberculosis (TB) including skin-testing procedures, M. bovis BCG vaccination, and interferon-γ release assays. The calf TB infection model offers several opportunities to further our understanding of TB immunopathogenesis. Recent observations include correlation of central memory immune responses with TB vaccine efficacy, association of SIRPα + cells in ESAT-6:CFP10-elicited multinucleate giant cell formation, early γδ T cell responses to TB, antimycobacterial activity of memory CD4+ T cells via granulysin production, association of specific antibody with antigen burden, and suppression of innate immune gene expression in infected animals. Partnerships teaming researchers with veterinary and medical perspectives will continue to provide mutual benefit to TB research in man and animals.

Aggravation of intestinal inflammation by depletion/deficiency of γδ T cells in different types of IBD animal models

The role of gammadelta T cells in inflammatory bowel disease (IBD) is still controversial. Although gammadelta T cells induce IBD in immunodeficient animals, others suggest a protective role of gammadelta T cells. Therefore, this study was conducted in order to elucidate the effect of gammadelta T cell depletion/deficiency on different IBD animal models. Mice depleted of or deficient in gammadelta T cells were exposed to dextran sodium sulfate (DSS) in order to induce colitis. In addition, gammadelta T cells were depleted in mice with terminal ileitis (TNFDeltaARE) or colitis due to interleukin 2 deficiency (IL-2 ko). Finally, DSS-induced colitis was studied in mice deficient in interferon gamma (IFN-gamma ko) upon gammadelta T cell depletion. Depletion of gammadelta T cells aggravated DSS-induced colitis and terminal ileitis of TNFDeltaARE mice. Exacerbated DSS-induced colitis was also found in gammadelta T cell-deficient mice. IL-2 ko mice showed increased mortality upon early (starting at 4 wk of age) but not late depletion (starting at 8 wk of age). Early gammadelta T cell depletion or deficiency resulted in increased IFN-gamma production by both lamina propria lymphocytes and splenocytes in every model investigated herein. In IFN-gamma ko mice, gammadelta T cell depletion did not affect the development and course of DSS-induced colitis. The protective effect of gammadelta T cells in IBD was confirmed in various IBD animal models. Particularly, during the early phase of intestinal inflammation, gammadelta T cells appear to be important. The mechanism seems to involve the control of IFN-gamma production and epithelial regeneration.