A Single Amino Acid at Position 431 of the PB2 Protein Determines the Virulence of H1N1 Swine Influenza Viruses in Mice

Abstract

The frequent reassortment among different influenza viruses in pigs adds complexity to the epidemiology of swine influenza. The diverse viral virulence phenotypes underline the need to investigate the possible genetic determinants for evaluating the pandemic potential to human public health. Here, we found that multiple genotypes of influenza viruses cocirculate in the swine population in Liaoning Province, China. Furthermore, we pinpointed a single amino acid at position 431 in the PB2 protein which plays a critical role in the virulence of H1N1 viruses in mice and found that the alteration of viral polymerase activities is the cause of the different virulence. Our study further indicated that the virulence of influenza virus is a polygenic trait, and the newly identified virulence-related residue in the PB2 provides important information for broadening knowledge on the genetic basis of viral virulence of influenza viruses.

Prevalence, Genetics and Evolutionary Properties of Eurasian Avian-like H1N1 Swine Influenza Viruses in Liaoning

“…The amino acids at positions 251, 271, 588, 431, 590, and 591 of the PB2 protein suggested that these viruses could adapt to mammalian hosts [ 13 , 31 , 32 , 33 ], but 627E and 701N indicated the relatively low pathogenicity of these viruses [ 34 , 35 ].…”

“…The EA H1N1 SIV was first detected in Liaoning in 2006 and became prevalent gradually. Since 2014, reassortant EA H1N1 or H1N2 SIVs have been detected in Liaoning [ 13 ]. From 2014 to 2016, three different recombinated EA H1N1 SIVs have been identified, including two triple reassortants and one double reassortant, as shown in Figure 5 .…”

“…The G1 virus became predominant in 2016 [ 12 ], whereas the G2 virus has not been found since 2018 in other parts of China. The G2 virus was predominant in Liaoning in 2015 [ 13 ], but the G1 virus was detected for the first time during our surveillance in Liaoning. It seems that the emergence and epidemic trend of SIV was comparably backward, which might be due to the lack of extensive surveillance in Liaoning province after 2016.…”

“…As a result, tens of large pig farms have been built in Liaoning province in recent years. As the pig population increases rapidly, the epidemiological situation of SIVs in Liaoning is becoming more and more complicated [ 13 ]. In this study, we performed extensive SIV surveillance in Liaoning province in 2020.…”

Immune Escape Adaptive Mutations in Hemagglutinin Are Responsible for the Antigenic Drift of Eurasian Avian-Like H1N1 Swine Influenza Viruses

“…Avian-like H1N1 SIV was first isolated from pigs in 1979 in Belgium ( 5 ) and has since spread to many European and Asian countries ( 6 – 8 ); for this reason, it is referred to as Eurasian avian-like H1N1 SIV (EA H1N1 SIV). After the reintroduction of the human pandemic 2009/H1N1 virus to pigs, multiple genotypes of reassortant H1N1 and H1N2 SIVs bearing the hemagglutinin (HA) gene of EA H1N1 SIV have replaced the pure EA H1N1 SIV and are currently prevalent in swine populations in China ( 9 – 13 ). Sporadic infections caused by EA H1N1 or EA H1N1-like viruses and antigenic variation within these viruses pose new potential threats to public health and also present new challenges to the pig industry ( 10 , 12 , 14 – 19 ).…”