Macedo, Bruna de Gois

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 Extracellular ATP (eATP) is a danger signal released by inflamed tissues, and can be sensed by immune cells via P2RX7. P2RX7 promotes lung pathology induced by influenza infection, by inducing exacerbated numbers of lung CD4+ T cells. In response to influenza, lung CD4+ T cells are comprised of a type 1 (Th1)-like population, and a subset resembling follicular helper (Tfh) CD4+ T cells; this subset is called tissue-resident helper (Trh). Trh cells amplify lung effector immune responses. Trh cells express high P2RX7 levels, and current research in our laboratory shows that P2RX7 is crucial for Trh cell establishment and subsequent lung damage. We have also found that the intensity of lung damage caused by influenza is positively correlated with P2RX7+ lung Trh cells. It is not clear, however, how concomitant exposure to influenza and type 2 immunity-inducing lung allergens (a common clinical occurrence in the United States) affect P2RX7+ lung Trh cells and their resultant tissue damage. We investigated this, using House Dust Mite (HDM) allergen exposure together with Influenza (PR8) infection. HDM/PR8 co-exposure induced worsening of lung inflammation, compared to single exposure to PR8. This inflammation had type 1 characteristics (i.e. parenchymal immune cell accumulation and absence of mucus). The increased lung damage generated by HDM/PR8 exacerbated the generation of influenza-specific P2RX7+ lung Trh cells. The accumulation of lung Trh cells (and subsequent tissue damage) caused by HDM/PR8 was abolished in T cell-specific P2RX7-knockout mice. Our results suggest that local inflammation, eATP release and sensing, and lung Trh cells together dictate the intensity of lung damage, regardless of the nature of the lung disease agent. R01AI170649

Abstract Tissue-derived extracellular ATP (eATP) is a “danger signal” sensed by immune cells via purinergic receptors (e.g. P2RX7). In addition, healthy cells can export eATP through transmembrane channels, such as the hemichannel Pannexin-1 (Panx1). CD8+ T cells express Panx1 constitutively throughout developmental and immune response stages. However, the biological role of Panx1 in CD8+ T cells is undefined. Here, we used genetic and pharmacological tools to address this question. T-cell specific Panx1 deletion did not affect CD8+ T cell thymic development. In contrast, CD8+ T cell responses to viral infection (LCMV) are impaired by Panx1 inhibition or deletion. This is true for effector expansion of CD8+ T cells and for the survival of memory CD8+ T cells. Using adoptive transfer of tamoxifen-conditional Panx1 knockout LCMV-specific (P14) cells into LCMV-infected mice, we showed that memory CD8+ T cell survival requires sustained Panx1 – except for small intestinal-resident cells. Mechanistically, Panx1 promotes memory CD8+ T cell survival via P2RX7, which also favors memory CD8+ T cells - as suggested by our data with Panx1/P2RX7-double knockout P14 cells. The role of Panx1 for effector CD8+ T cell expansion, however, is unlikely to be via P2RX7 since this receptor does not have a role in effector CD8+ T cells. Our transcriptional and metabolic data suggests that, while memory CD8+ T cells require Panx1 for optimal mitochondrial function and expression of pro-memory genes, effector CD8+ T cells lacking Panx1 had decreased activation of the glycolytic pathway. Collectively, these results suggest that, in response to acute virus, Panx1 induces CD8+ T cell effector expansion and memory survival through distinct metabolic pathways. Supported by grants from NIH (R00 AI139381, NIAID).

Abstract Expression of the purinergic receptor P2RX7 by CD8+ T cells promotes the generation of memory populations following acute infections. However, data suggest that P2RX7 may limit the efficacy of antitumor responses. Herein, we show that P2RX7 is beneficial for optimal melanoma control in a mouse CD8+ T-cell adoptive transfer model. Tumor-specific P2rx7–/– CD8+ T cells exhibited impaired mitochondrial maintenance and function but did not display signs of overt exhaustion early in the antitumor response. However, as the tumor burden increased, the relative frequency of P2RX7-deficient CD8+ T cells declined within the tumor; this correlated with reduced proliferation, increased apoptosis, and mitochondrial dysfunction. Extending these studies, we found that the transient in vitro stimulation of P2RX7 using the ATP analogue BzATP led to enhanced B16 melanoma control by CD8+ T cells. These findings are in keeping with the concept that extracellular ATP (eATP) sensing by P2RX7 on CD8+ T cells is required for their ability to efficiently eliminate tumors by promoting mitochondrial fitness and underscore the potential for P2RX7 stimulation as a novel therapeutic treatment to enhance tumor immunotherapy.