Western blot analysis was performed as previously described [36 (link)]. The primary antibodies and dilutions are: mouse anti-NP (ATCC, HB-65, 1:50), mouse anti-NS1 (Santa Cruz biotechnology, Santa Cruz, CA, USA, 1:1000), mouse anti-β-actin (Thermo Fisher Scientific, 1:3000), rabbit anti-FZD5 (ProSci, Poway, CA, USA, 1:1000).