STAT1 Controls the Functionality of Influenza-Primed CD4 T Cells but Therapeutic STAT4 Engagement Maximizes Their Antiviral Impact

• Published in: The Journal of immunology (1950) 2023-05, Vol.210 (9), p.1292-1304
• Main Authors: Finn, Caroline M, Dhume, Kunal, Prokop, Emily, Strutt, Tara M, McKinstry, K Kai
• Format: Article
• Language: English
• Subjects: Animals; Antiviral Agents - metabolism; CD4-Positive T-Lymphocytes; Cell Differentiation; Humans; Influenza, Human; Interferon-gamma - metabolism; Mice; STAT1 Transcription Factor - metabolism; STAT4 Transcription Factor - metabolism; T-Box Domain Proteins - metabolism; Th1 Cells; Transcription Factors - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.2200407

It is generally accepted that influenza A virus (IAV) infection promotes a Th1-like CD4 T cell response and that this effector program underlies its protective impact. Canonical Th1 polarization requires cytokine-mediated activation of the transcription factors STAT1 and STAT4 that synergize to maximize the induction of the "master regulator" Th1 transcription factor, T-bet. Here, we determine the individual requirements for these transcription factors in directing the Th1 imprint primed by influenza infection in mice by tracking virus-specific wild-type or T-bet-deficient CD4 T cells in which STAT1 or STAT4 is knocked out. We find that STAT1 is required to protect influenza-primed CD4 T cells from NK cell-mediated deletion and for their expression of hallmark Th1 attributes. STAT1 is also required to prevent type I IFN signals from inhibiting the induction of the Th17 master regulator, Rorγt, in Th17-prone T-bet-/- cells responding to IAV. In contrast, STAT4 expression does not appreciably impact the phenotypic or functional attributes of wild-type or T-bet-/- CD4 T cell responses. However, cytokine-mediated STAT4 activation in virus-specific CD4 T cells enhances their Th1 identity in a T-bet-dependent manner, indicating that influenza infection does not promote maximal Th1 induction. Finally, we show that the T-bet-dependent protective capacity of CD4 T cell effectors against IAV is optimized by engaging both STAT1 and STAT4 during Th1 priming, with important implications for vaccine strategies aiming to generate T cell immunity.