Abstract
BackgroundAfter the occurrence of 2009 pandemic H1N1, close attention has been paid to the H1N1 subtype swine influenza viruses (H1N1 SIV) by scientific communities in many countries. A large-scale sequence analysis of the NCBI Influenza Virus Resource Database on H1N1 SIVs submitted primarily by scientists in China during 1992 to 2011 was performed. The aims of this study were to elucidate the genetic and evolutionary characteristics of H1N1 SIVs, to identify and unify the lineages and genetic characteristics of the H1N1 SIVs isolated in mainland China.ResultsMost of the strains were isolated during the period of 2008 to 2010 from Guangdong and Shandong provinces, China. Based on the phylogenetic and genotypic analyses, all of the H1N1 SIV strains can be classified into 8 lineages and 10 genotypes. All strains were of the characteristics of low pathogenic influenza viruses. The viruses of different lineage are characterized with different amino acid residues at the receptor-binding sites. Viruses containing PB2 genes of the classical swine, early seasonal human and recent seasonal human lineage might be more infectious to human. Some genotypes were directly related with human influenza viruses, which include strains that harbored genes derived from human influenza viruses.ConclusionsPhylogenetic diversity and complexity existed in H1N1 SIVs isolated in mainland China. These H1N1 SIV strains were closely related to other subtype influenza viruses, especially to human influenza viruses. Moreover, it was shown that, novel lineages and genotypes of H1N1 SIVs emerged recently in mainland China. These findings provided new and essential information for further understanding of the genetic and evolutionary characteristics and monitoring the H1N1 SIVs in mainland China.
Highlights
After the occurrence of 2009 pandemic H1N1, close attention has been paid to the H1N1 subtype swine influenza viruses (H1N1 SIV) by scientific communities in many countries
As pigs raised in increasing numbers continually in many provinces of mainland China, H1N1 SIVs might become more prevalent in the nation
In the phylogenetic trees of the HA and NA gene of the H1N1 SIVs (Figures 1, 2), it indicated that the HA and NA gene of H1N1 SIVs in mainland China mainly fall into five lineages, the classical swine (CS) lineage, the early seasonal human (ESH) lineage, the recent seasonal human (RSH) lineage, the Eurasian avian-like (EA) lineage, and the 2009 human (2009H) lineage
Summary
After the occurrence of 2009 pandemic H1N1, close attention has been paid to the H1N1 subtype swine influenza viruses (H1N1 SIV) by scientific communities in many countries. A large-scale sequence analysis of the NCBI Influenza Virus Resource Database on H1N1 SIVs submitted primarily by scientists in China during 1992 to 2011 was performed. Influenza A viruses have been isolated from humans and a number of animals including birds, dogs, seals, horses, and swine [2]. Swine influenza viruses cause significant economic losses in animal husbandry, human disease [12], and occasionally give rise to human pandemics [13]. The 2009 pandemic H1N1, a new swine-origin influenza A (H1N1) virus, caused the latest human pandemic [14,15]. After the occurrence of the 2009 pandemic H1N1, the virus was repeatedly introduced back into pigs in many countries [16,17,18]
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