2.1 Viruses
Three strains of H6N6 subtype AIV isolated from chickens were selected in this study, including A/CK/JX/20490/2014(JX20490), A/CK/ZZ/1923/2015(ZZ1923), and A/CK/ZZ/346/2014 (ZZ346). Avian influenza virus H9N2 A/DK/GX/767/2010 (GX767), which had been previously confirmed to bind to avian-like SAα-2, 3-receptor, was used as a control for receptor-binding analysis. The swine influenza virus H1N1 A/SW/GX/3843/2011 (GX3843), which was previously confirmed to be able to infect mice, was used as the positive control for the in vivomice infection study. The human virus H3N2 A/ST/602/2005 (ST602), which can effectively replicate in humans and bind to avian-like SAα-2,6-receptor, was used as the in vitro human lung infection positive control.
Three strains of the H6N6 virus and one strain of H9N2 virus were passaged in 10-day-old embryonated chicken eggs; swine influenza virus H1N1 and human virus H3N2 were cultured in MDCK cells. HA subtype was identified by the HI test, and NA subtype was identified by direct sequencing.