Co-infection in embryonated chicken eggs with H7N9 and H9N2 viruses

H7N9 and H9N2 viruses had been co-circulating in China. While H7N9 and H9N2 viruses share homologous internal genes, the reassortment patterns of different H9N2 viruses co-infected with the H7N9 virus in vitro have not been evaluated experimentally. Here, we aimed to characterize viral progenies generated after co-infection of H7N9 and H9N2 viruses of different genetic lineages in eggs. A/silkie Chicken/Hong Kong/1772/2014(H7N9) (designated as HK1772) represents the Pearl River Delta lineage H7N9 viruses. There are four genetically and antigenically divergent H9N2 viruses that represent two main lineages or genotypes of H9N2 viruses in Asia. A/quail/Hong Kong/G1/1997 (H9N2) (designated as G1) is the G1-like lineage prototype virus. Other H9N2 viruses are Y280-like viruses. A/silkie chicken/Hong Kong/YU335/2007(H9N2) (designated as YU335) belonged to the subdominant H9N2 genotype. A/chicken/Zhejiang/ HJ/2007(H9N2 (designated as HJ) is the G57 prototype strain. A/chicken/Beijing/16/2013 (H9N2) (designated as BJ16) represents the G57 viruses circulating in China. Three 10-day old embryonated chicken eggs were infected with 1000 plaque-forming units (pfu) of H7N9 virus and 1000 pfu of one of the four H9N2 viruses. Allantoic fluid was harvested at 16 hours post-infection. Samples were analyzed by the next generation sequencing.