PTAFR and infection: To test if IAV drives upregulation of adhesion factors in cardiomyocytes, we infected human AC16 cardiomyocytes with IAV (multiplicity of infection [MOI] of 2) for 24, 48, or 72 h, and expression of platelet-activating factor receptor (PAFr), polymeric immunoglobulin receptor (pIgR), and fibronectin leucine-rich transmembrane protein 1 (FLRT1) was measured by immunoblots (Fig. 1I).