MAP3K8 and infection: To determine whether Tpl2 regulates influenza virus replication, wild type (WT) and Tpl2-/- mice were infected with 104 plaque forming units (pfu) of mouse-adapted influenza virus A/HK-X31(H3N2) (X31), and viral titers in the lungs were evaluated on days 3, 5 and 7 post infection (pi).