Influenza A Virus Infection Model

Primary human lung fibroblasts (IMR-90s, Coriell Institute for Medical Research, Camden, USA) were cultured in Dulbecco’s modified Eagle’s medium (DMEM, Sigma Aldrich, Taufkirchen, Germany) with 10 % fetal bovine serum (FBS, PAN Biotech, Aidenbach, Germany), and 1 % penicillin/streptomycin (P/S, Lonza, Basel, Schweiz).
Human monocyte-derived macrophages (hMDM) were isolated from healthy donors by using Histopaque (Sigma Aldrich) and separated by density gradient centrifugation, plated in monocyte attachment medium (Promocell, Heidelberg, Germany) for 2 h and cultivated in M1-Macrophage Generation Medium DXF (Promocell) for 7 d.
Madin-Darby canine kidney (MDCK) cells were cultured in Eagle minimum essential medium (EMEM, Sigma Aldrich) with 10 % FBS and 1 % P/S.
In vitro infections were performed using influenza A virus/IAV/H1N1/Puerto Rico/8/1934 (PR8). For the in vivo model the mouse-adapted strain influenza A virus/IAV/H1N1/vi0084/2016 was used. Ex vivo infections utilized the mouse-adapted H1N1 influenza A virus strain HA-G222-mpJena/5258 [15 (link)]. To identify plaque-forming units (PFU), standard plaque assay was performed as described previously [16 (link)].