Salgado, Caio Loureiro

Abstract Sensing of extracellular metabolites controls CD8+ T cell function. Their accumulation can occur through export by specialized molecules, such as the release channel Pannexin-1 (Panx1). Here, we report that T cell-specific Panx1 is needed for efficient CD8+ T cell responses to viral infection and cancer. Panx1 favors both the expansion of effector CD8+ T cells and the survival of memory CD8+ T cells. Our data suggests that, while memory CD8+ T cells require Panx1 for mitochondrial function, Panx1 promotes the glycolytic pathway in effector CD8+ T cells. Panx1 promotes memory CD8+ T cell survival together with the eATP sensor P2RX7. However, Panx1 induces effector CD8+ T cells independently of eATP. Rather, we found an unexpected link between Panx1, lactate export and the activation of effector CD8+ T cells. Therefore, Panx1 regulates effector and memory CD8+ T cells through export of distinct metabolites and by engaging different intracellular pathways.

Abstract Development of universal influenza (flu) vaccines requires better knowledge of lung-resident immune responses. That includes flu-specific CD4 T cells, which establish long-term lung residency and induce a diversified local protective response to subsequent infection. Tissue-resident helper (Trh) cells are a subset of lung-resident CD4 T cells that share phenotypic and functional features with follicular helper cells (Tfh). Trh cells serve to amplify lung-resident immune responses, and express high levels of the extracellular ATP (eATP) sensor P2RX7. Considering that eATP levels in the lung increase in response to flu infection, we used T cell-specific P2RX7-knockout (KO) mice to test the role of P2RX7 for CD4 T cell responses to flu. During acute phase of infection, we found that P2RX7 promotes the accumulation of flu-specific CD4 T cells inside the lung tissue. Moreover, P2RX7 promoted this establishment via induction of CXCR3 upregulation. Despite no specific defects in the Trh pool at the acute phase, T cell-specific P2RX7-KO led to a progressive decay of Trh cells. Consequently, lungs of T cell-P2RX7-KO mice had reduced lung B cell responses. Our single-cell RNAseq of lung flu-specific CD4 T cells showed reduced expression of cell survival and mitochondrial genes in P2RX7-KO Trh cells. Our findings suggest that lung eATP sensing by CD4 T cells induces lung-resident CD4 T cell accumulation in response to flu, impacting the survival of specific lung CD4 T cell subsets. National Institute of Allergy and Infectious Diseases (NIAID) (H.BdS.: R00 AI139381, R01 AI170649).

Abstract Recent studies suggest that the intestinal microenvironment regulate lung immune cells. Conversely, changes in the lung can modulate the gut immune system. Yet, mucosal-associated immune responses have been studied in a compartmentalized manner, as if there is no communication between different organs. Thus, the role of the gut-lung axis in mucosal immune responses is poorly understood. Using enterotoxigenic Escherichia coli (ETEC), we established a model of intestine-localized infection without translocation to any other tissue. In response to ETEC, type 2 innate lymphoid cells (ILC2s) and eosinophils accumulated in the intestinal lamina propria, even after bacterial clearance. In addition, oral ETEC transiently increased the numbers of ILC2 and eosinophils in the lung parenchyma. To test if oral ETEC promote lung immune responses to allergen, we exposed mice that recently cleared ETEC to intranasal papain/ovalbumin allergy induction model. Unexpectedly, ETEC-exposed mice were significantly resistant to allergen-induced lung inflammation, with reduced number of ILC2, Type 2 effector CD4+ T cells (Th2) and eosinophils. Paradoxically, oral ETEC-induced protection against lung allergen exposure was dependent on IL-33: IL-33KO mice developed partial lung inflammation in this model, and no protection induced by ETEC exposure was observed. Importantly, protection from allergy was achieved with ETEC heat-labile toxin (LT) oral exposure; we also found that the toxicity domain of LT is needed for this protection. Our results indicate that gastrointestinal bacterial infection mediators (toxins) negatively regulate the onset of allergic inflammation and may provide a novel immunological basis for the “hygiene hypothesis”. R01AI170649 FAPESP 2021/15185-2