E protein-driven iNKT subset modulation shapes early immune responses during influenza A virus infection.

Invariant natural killer T (iNKT) cells play a critical role in the early phases of the response to influenza A virus (IAV) infection by influencing inflammation and immune regulation, but the impact of the different iNKT functional subsets (iNKT1, iNKT2, and iNKT17) in these responses is unclear. We used genetically altered mouse strains with normal numbers of iNKT cells but different iNKT subset representation (NKTWT and NKTET2) to analyze the impact of different iNKT functional subsets on IAV infection outcomes. We show that IAV-infected NKTET2 mice have reduced weight loss, diminished myeloid recruitment and activation, and a 40% reduction in lung-infected areas compared with controls. This was accompanied by lower expression of inflammatory mediators (Ifna, Isg15, Ifit1) and chemoattractants Ccl2 and Cxcl2, along with elevated levels of type III interferon (Ifnl3). Single-cell RNA sequencing analysis of iNKTs suggests that these changes are driven by quantitative differences in iNKT responses, which are predominantly type I in NKTWT mice but type 17 in NKTET2 mice. These differences correlate with higher levels of Il22b and Il1b in NKTET2 mice lungs. Altogether, our results indicate that changes in iNKT subset representation impact the outcome of IAV infections by changing the character of the early immune response, and suggests that selective activation of iNKT subsets could be used to improve vaccination strategies in the future.