The substitution of T271A in PB2 protein could enhance the infectivity and pathogenicity of Eurasian avian-like H1N1 swine influenza viruses in mice

Abstract BackgroundCurrently, Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses (SIVs) are widely prevalent in pigs in China, with sporadic human cases reported as well. As one of the key molecular makers detected in avian H5N1 and H 7N9 viruses and pandemic H1N1 2009 virus, contributions of T271A in PB2 protein to the EA H1N1 viruses are still unknown. In this study, we investigated the effects of residue 271 in PB2 protein on the viral properties of EA H1N1 viruses.MethodsInfectivity, replication, virulence and pathogenicity of the recombinant viruses containing A or T in position 271 in PB2 protein were studied in cells and mice.ResultsThe results showed that the substitution PB2-T271A increased the viral replication in mammalian and avian cell lines. In addition, the mutation enhanced the viral infectivity, virulence and pathogenicity in mice. The viral titers of lung tissue in the rgHuN271A virus were higher than that of the rgHuN271T at 1, 4, and 7 dpi. The MID50 of the rgHuN271A and rgHuN271T virus were 101.1 TCID50 and 101.9 TCID50, respectively. Besides, the substitution of PB2-T271A enhanced the viral polymerase activity in mammalian cells.ConclusionsThe pathogenicity and replication of EA H1N1 virus containing 271A in PB2 protein were higher than the EA H1N1 virus containing 271T in PB2 protein in vivo and in vitro. Therefore, the PB2-T271A mutation should be continually monitored in influenza viruses circulating in pigs and humans.