IFITM3 Clusters on Virus Containing Endosomes and Lysosomes Early in the Influenza A Infection of Human Airway Epithelial Cells

Kummer, Susann; Avinoam, Ori; Kräusslich, Hans-Georg

Viruses 2019, 11, x FOR PEER REVIEW 6 of 17 space, both in the uninfected A549 cells and in the IAV-infected cells with a dim or absent NP signal. Importantly, the productively infected cells exhibiting strong nuclear NP signals again exhibited a weak IFITM3 signal, even after the pretreatment with hIFNα. Comparing the non-treated and hIFNαpretreated IAV-infected A549 cells lacking a strong nuclear NP signal, we observed an increased IFITM3 signal in both cases, partially colocalizing with vesicular structures. Vesicular localization appeared more obvious in the absence of a hIFNα pretreatment with a less diffuse cytosolic signal. Blocking IFNα with a neutralizing antibody during the IAV infection of A549 cells resulted in increased infection rates, and a concomitant minimal increase of the IFITM3 signal ( Figure 1C ).