Judging from the titration curves generated with M2e-specific MAbs (Fig 4B) and sera from M2e-MAP-immunized mice (Fig 4C), doxycyline-induced HeLa-M2 cells expressed more M2 than MDCK cells 8–11 hrs after infection with ~10 TCID50 of IAV/cell and were more effective in detecting M2e-specific Abs than infected MDCK cells. Here, DDX41 is linked to infection.