Understanding the role of the purinergic receptor P2X3 during influenza infection in the lung

Purinergic receptors play an important role in the response to infectious diseases by sensing damage-associated molecular patterns (DAMPs). The P2X family of purinergic receptors is known to recognize extracellular ATP (eATP) at different affinities. One of these receptors, P2X3, shows high affinity for eATP, but its role in modulating responses to infectious diseases has not been studied. Using the pulmonary infection model with influenza virus PR8 strain on wild type (WT) and P2RX3-deficient (P2RX3-KO) mice, we aimed to discover the role of P2RX3 in influenza infection in the lungs. We found that there was not a significant difference in the severity of disease in WT and P2RX3-KO mice during the acute phase, but there was more fibrotic tissue visible in P2RX3-KO mice lungs on day 40 post infection (p.i.) using Masson’s trichrome staining. To further investigate these differences, we analyzed myeloid cell populations and flu-specific lymphocytes in the infected lungs. We found that there was a significant decrease in the number of antigen-specific CD4+ T cells in the lungs of P2RX3-KO mice after 7 days p.i. After performing t-SNE (t-distributed stochastic neighbor embedding) analysis on CD4+ T cells of P2RX3-KO and WT mice, we discovered that P2RX3-KO mice had a population of cells which was not present in the WT mice. This population showed high expression of most proteins such as T-bet and BCL6, which is not characteristic of the typical Th1 population induced by influenza virus. Using in vitro activation and differentiation of Th1 CD4+ T cells from WT and P2RX3-KO mice, we found that P2RX3-KO CD4+ T cells had greater expression of markers related to Tfh (T follicular helper cells), such as ICOS and CXCR5, and overall hyperactivation, demonstrating irregular Th1 differentiation. Taken together, these results suggest that P2RX3 may be linked to the maintenance of “healthy” CD4+ T cells and may be important in preventing fibrosis in influenza infection.