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Mucosal-associated invariant T (MAIT) cells are innate-like, unconventional T cells that are present in peripheral blood and mucosal surfaces. A clear understanding of how MAIT cells in the mucosae function and their role in host immunity is still lacking. Therefore, our aim was to investigate MAIT cell distribution and their characteristics in the gastrointestinal (GI) mucosal tissue based on Vα7.2+CD161hi identification. We showed that Vα7.2+CD161hi T cells are present in both intraepithelial layer and lamina propriae of the GI mucosa, but have different abundance at each GI site. Vα7.2+CD161hi T cells were most abundant in the duodenum, but had the lowest reactivity to MR1-5-OP-RU tetramers when compared with Vα7.2+CD161hi T cells at other GI tissue sites. Striking discrepancies between MR1-5-OP-RU tetramer reactive cells and Vα7.2+CD161hi T cells were observed along each GI tissue sites. Vα7.2+CD161hi TCR repertoire was most diverse in the ileum. Similar dominant profiles of TRBV usage were observed among peripheral blood, duodenum, ileum, and colon. Some TRBV chains were detected at certain intestinal sites and not elsewhere. The frequency of peripheral blood Vα7.2+CD161hi T cells correlated with mucosal Vα7.2+CD161hi T cells in lamina propriae ileum and lamina propriae colon. The frequency of peripheral blood Vα7.2+CD161hi T cells in Helicobacter pylori-infected individuals was significantly lower than uninfected individuals, but this was not observed with gastric Vα7.2+CD161hi T cells. This study illustrates the biology of Vα7.2+CD161hi T cells in the GI mucosa and provides a basis for understanding MAIT cells in the mucosa and MAIT-related GI diseases.

Mucosal-associated invariant T (MAIT) cells are a major subset of innate-like T cells mediating protection against bacterial infection through recognition of microbial metabolites derived from riboflavin biosynthesis. Mouse MAIT cells egress from the thymus as two main subpopulations with distinct functions, namely, T-bet-expressing MAIT1 and RORγt-expressing MAIT17 cells. Previously, we reported that inducible T-cell costimulator and interleukin (IL)-23 provide essential signals for optimal MHC-related protein 1 (MR1)-dependent activation and expansion of MAIT17 cells in vivo. Here, in a model of tularemia, in which MAIT1 responses predominate, we demonstrate that IL-12 and IL-23 promote MAIT1 cell expansion during acute infection and that IL-12 is indispensable for MAIT1 phenotype and function. Furthermore, we showed that the bias toward MAIT1 or MAIT17 responses we observed during different bacterial infections was determined and modulated by the balance between IL-12 and IL-23 and that these responses could be recapitulated by cytokine coadministration with antigen. Our results indicate a potential for tailored immunotherapeutic interventions via MAIT cell manipulation.

The INPEX-led Ichthys Joint Venture has established strong partnerships with the Northern Territory Government (NTG), cultural organisations and Traditional Owner groups in the Northern Territory to deliver social and environmental offset programs. The key governance model for delivery of the offset programs is the Ichthys Project Voluntary Offset Agreement (IPVOA), which commits $91 M AUD over a 40-year period through a suite of offset programs. This paper focuses on the journey to partner with the NTG-run Aboriginal Ranger Grants Program (ARGP). Through the IPVOA, INPEX and its Ichthys Joint Venture participants will contribute $24 M AUD over 22 years, to the ARGP, for Aboriginal Ranger programs addressing specific species and their associated habitat throughout the Top End. This is the first time where industry has contributed to the ARGP to deliver positive outcomes in the NT. This has been achieved by fostering collaborative, engaging and trustworthy relationships with the Commonwealth and NT governments; engaging with the Aboriginal Land Management Advisory Group; and meeting with Aboriginal Ranger groups. The key has been finding a common ground between the perspectives and the priorities of all stakeholders for how best to deliver conservation management on country in the NT. This common ground is likely to evolve over the next 22 years as the INPEX-led Ichthys Joint Venture and NTG deliver environmental outcomes, promote a connection to country and empower Aboriginal Ranger groups to better manage their country for future generations.

BACKGROUND: Patients hospitalised with COVID-19 suffer thrombotic complications. Risk factors for poor outcomes are shared with coronary artery disease. OBJECTIVES: To investigate efficacy of an acute coronary syndrome regimen in patients hospitalised with COVID-19 and coronary disease risk factors. PATIENTS/METHODS: A randomised controlled open-label trial across acute hospitals (UK and Brazil) added aspirin, clopidogrel, low-dose rivaroxaban, atorvastatin, and omeprazole to standard care for 28-days. Primary efficacy and safety outcomes were 30-day mortality and bleeding. The key secondary outcome was a daily clinical status (at home, in hospital, on intensive therapy unit admission, death). RESULTS: 320 patients from 9 centres were randomised. The trial terminated early due to low recruitment. At 30 days there was no significant difference in mortality (intervention: 11.5% vs control: 15%, unadjusted OR 0.73, 95%CI 0.38 to 1.41, p=0.355). Significant bleeds were infrequent and not significantly different between the arms (intervention: 1.9% vs control 1.9%, p>0.999). Using a Bayesian Markov longitudinal ordinal model, it was 93% probable that intervention arm participants were more likely to transition to a better clinical state each day (OR 1.46, 95% CrI 0.88 to 2.37, Pr(Beta>0)=93%; adjusted OR 1.50, 95% CrI 0.91 to 2.45, Pr(Beta>0)=95%) and median time to discharge home was two days shorter (95% CrI -4 to 0, 2% probability that it was worse). CONCLUSIONS: Acute coronary syndrome treatment regimen was associated with a reduction in the length of hospital stay without an excess in major bleeding. A larger trial is needed to evaluate mortality.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that require MHC class I–related protein 1 (MR1) for their development. The role of MAIT cells in cancer is unclear, and to date no study has evaluated these cells in vivo in this context. Here, we demonstrated that tumor initiation, growth, and experimental lung metastasis were significantly reduced in Mr1−/− mice, compared with wild-type mice. The antitumor activity observed in Mr1−/− mice required natural killer (NK) and/or CD8+ T cells and IFNγ. Adoptive transfer of MAIT cells into Mr1−/− mice reversed metastasis reduction. Similarly, MR1-blocking antibodies decreased lung metastases and suppressed tumor growth. Following MR1 ligand exposure, some, but not all, mouse and human tumor cell lines upregulated MR1. Pretreatment of tumor cells with the stimulatory ligand 5-OP-RU or inhibitory ligand Ac-6-FP increased or decreased lung metastases, respectively. MR1-deleted tumors resulted in fewer metastases compared with parental tumor cells. MAIT cell suppression of NK-cell effector function was tumor-MR1–dependent and partially required IL17A. Our studies indicate that MAIT cells display tumor-promoting function by suppressing T and/or NK cells and that blocking MR1 may represent a new therapeutic strategy for cancer immunotherapy.Significance:Contradicting the perception that MAIT cells kill tumor cells, here MAIT cells promoted tumor initiation, growth, and metastasis. MR1-expressing tumor cells activated MAIT cells to reduce NK-cell effector function, partly in a host IL17A–dependent manner. MR1-blocking antibodies reduced tumor metastases and growth, and may represent a new class of cancer therapeutics.This article is highlighted in the In This Issue feature, p. 1

Supplementary text and figures

This study is motivated by the challenges faced by clinics in sub-Saharan Africa in allocating scarce and unreliable supply of antiretroviral drugs (ARVs) among a large pool of eligible patients. Existing discussion of ARV allocation is focused on qualitative rules for prioritizing certain socioeconomic and demographic patient segments over others at the national level. However, such prioritization rules are of limited utility in providing quantitative guidance on scaling up of treatment programs at individual clinics. In this study, we take the perspective of a clinic administrator whose objective is to maximize the quality-adjusted survival of the entire patient population in its service area by allocating scarce and unreliable supply of drugs among two activities: initiating treatment for untreated patients and continuing treatment for previously treated patients. The key trade-off underlying this allocation decision is between the marginal health benefit obtained by initiating an untreated patient on treatment and that obtained by avoiding treatment interruption of a treated patient. This trade-off has not been explicitly studied in the clinical literature, which focuses either on the incremental value obtained from initiating treatment (over no treatment) or on the value of providing continuous treatment (over interrupted treatment) but not on the difference of the two. We cast the clinic's problem as a stochastic dynamic program and provide a partial characterization of the optimal policy, which consists of dynamic prioritization of patient segments and is characterized by state-dependent thresholds. We use this structure of the optimal policy to design a simpler Two-Period heuristic and show that it substantially outperforms the Safety-Stock heuristic, which is commonly used in practice. In our numerical experiments based on realistic parameter values, the performance of the Two-Period heuristic is within 4% of the optimal policy whereas that of the Safety-Stock heuristic can be as much as 20% lower than that of the optimal policy. Our model can serve as a basis for developing a decision support tool for clinics to design their ARV treatment program scale-up plans.

Cell death mechanisms in T lymphocytes vary according to their developmental stage, cell subset and activation status. The cell death control mechanisms of mucosal-associated invariant T (MAIT) cells, a specialized T cell population, are largely unknown. Here we report that MAIT cells express key necroptotic machinery; receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein, in abundance. Despite this, we discovered that the loss of RIPK3, but not necroptotic effector MLKL or apoptotic caspase-8, specifically increased MAIT cell abundance at steady-state in the thymus, spleen, liver and lungs, in a cell-intrinsic manner. In contrast, over the course of infection with Francisella tularensis, RIPK3 deficiency did not impact the magnitude of the expansion nor contraction of MAIT cell pools. These findings suggest that, distinct from conventional T cells, the accumulation of MAIT cells is restrained by RIPK3 signalling, likely prior to thymic egress, in a manner independent of canonical apoptotic and necroptotic cell death pathways.

Background To achieve replicative immortality, most cancers develop a telomere maintenance mechanism, such as reactivation of telomerase or alternative lengthening of telomeres (ALT). There are limited data on the prevalence and clinical significance of ALT in pediatric brain tumors, and ALT-directed therapy is not available. Methods We performed C-circle analysis (CCA) on 579 pediatric brain tumors that had corresponding tumor/normal whole genome sequencing through the Open Pediatric Brain Tumor Atlas (OpenPBTA). We detected ALT in 6.9% (n = 40/579) of these tumors and completed additional validation by ultrabright telomeric foci in situ on a subset of these tumors. We used CCA to validate TelomereHunter for computational prediction of ALT status and focus subsequent analyses on pediatric high-grade gliomas (pHGGs) Finally, we examined whether ALT is associated with recurrent somatic or germline alterations. Results ALT is common in pHGGs (n = 24/63, 38.1%), but occurs infrequently in other pediatric brain tumors ( Conclusions We demonstrate that ATRX is mutated in only a subset of ALT+ pHGGs, suggesting other mechanisms of ATRX loss of function or alterations in other genes may be associated with the development of ALT in these patients. We show that germline variants in MMR are associated with the development of ALT in patients with pHGG.

T-cell receptor

T-cell immunity is important for recovery from COVID-19 and provides heightened immunity for re-infection. However, little is known about the SARS-CoV-2-specific T-cell immunity in virus-exposed individuals. Here we report virus-specific CD4+ and CD8+ T-cell memory in recovered COVID-19 patients and close contacts. We also demonstrate the size and quality of the memory T-cell pool of COVID-19 patients are larger and better than those of close contacts. However, the proliferation capacity, size and quality of T-cell responses in close contacts are readily distinguishable from healthy donors, suggesting close contacts are able to gain T-cell immunity against SARS-CoV-2 despite lacking a detectable infection. Additionally, asymptomatic and symptomatic COVID-19 patients contain similar levels of SARS-CoV-2-specific T-cell memory. Overall, this study demonstrates the versatility and potential of memory T cells from COVID-19 patients and close contacts, which may be important for host protection., T cells compose a critical component of the immune response to coronavirus infection with SARS-CoV-2. Here the authors characterise the T cell response to SARS CoV-2 in patients and their close contacts, and show the presence of SARS-CoV-2 specific T cells in the absence of detectable virus infection.

BackgroundTo achieve replicative immortality, most cancers develop a telomere maintenance mechanism, such as reactivation of telomerase or alternative lengthening of telomeres (ALT). There are limited data on the prevalence and clinical significance of ALT in pediatric brain tumors, and ALT-directed therapy is not available.MethodsWe performed C-circle analysis (CCA) on 579 pediatric brain tumors that had corresponding tumor/normal whole genome sequencing through the Open Pediatric Brain Tumor Atlas (OpenPBTA). We detected ALT in 6.9% (n=40/579) of these tumors and completed additional validation by ultrabright telomeric fociin situon a subset of these tumors. We used CCA to validateTelomereHunterfor computational prediction of ALT status and focus subsequent analyses on pediatric high-grade glioma (pHGG) Finally, we examined whether ALT is associated with recurrent somatic or germline alterations.ResultsALT is common in pHGG (n=24/63, 38.1%), but occurs infrequently in other pediatric brain tumors (ATRXmutations occur in 50% of ALT+ pHGG and in 30% of ALT-pHGG. Rare pathogenic germline variants in mismatch repair (MMR) genes are significantly associated with an increased occurrence of ALT. Conclusions: We demonstrate thatATRXis mutated in only a subset of ALT+ pHGG, suggesting other mechanisms ofATRXloss of function or alterations in other genes may be associated with the development of ALT in these patients. We show that germline variants in MMR are associated with development of ALT in patients with pHGG.Key PointsATRX alterations are frequent, but not required, for an ALT phenotype in pHGGspHGG patients with germline mismatch repair variants have higher rate of ALT + tumorsTelomereHunteris validated to predict ALT in pHGGsImportance of the StudyWe performed orthogonal molecular and computational analyses to detect the presence of alternative lengthening of telomeres in a highly characterized cohort of pediatric brain tumors. We demonstrate that many pHGG utilize ALT without a mutation in ATRX, suggesting either loss of function of ATRX via an alternative mechanism or an alternate means of development of ALT. We show that germline variants in MMR genes are significantly associated with ALT in pHGG. Our work adds to the biological understanding of the development of ALT and provides an approach to stratify patients who may benefit from future ALT-directed therapies in this patient population.