禽流感病毒进化研究进展

禽流感是禽流行性感冒的简称,是由正黏病毒科中的A型流感病毒亚型引起的禽类传染性疾病,被国际兽疫局定为A类传染病。不仅是鸡,其它一些家禽和野鸟都能感染禽流感。禽流感流感病毒,它是一种有包膜、单股负链、分节段RNA病毒。共分为8个节段,其中与抗原变异关系密切的是HA、NA。流感病毒主要通过抗原漂移和抗原转换来逃避机体免疫系统的攻击。由点突变造成的抗原漂移可导致流感每年的季节性流行,而抗原变异造成的抗原转换则可能产生新的亚型。本文通过对禽流感病毒基因组研究,禽流感病毒跨种属感染概况和变异机制等方面做一下综述,从而可以更好认识禽流感病毒和防止禽流感爆发。

Complete Genome Sequencing and Genetic Variation Analysis of Two H9N2 Subtype Avian Influenza Virus Strains

[Objective] The study aimed to investigate the genetic variation characters of entire sequences between two H9N2 subtype avian influenza virus strains and other reference strains.[Method] The entire sequences of 8 genes were obtained by using RT-PCR,and these sequences were analyzed with that of six H9N2 subtype avian influenza isolates in homology comparison and genetic evolution relation.[Result] The results showed that the nucleotide sequence of entire gene of the strain shared 91.1%-95.4% homology with other seven reference strains,and PG08 shared the highest homology 91.3% with C/BJ/1/94;ZD06 shared the highest homology 92.3% with D/HK/Y280/97.HA cleavage sites of two H9N2 subtype avian influenza virus isolated strains were PARSSR/GLF,typical of mildly pathogenic avian influenza virus.[Conclusion] Phylogenetic tree for entire gene of eight strains showed that the genetic relationship was the closest between ZD06 and C/Pak/2/99 strains,which belonged to the Eurasian lineage;PG08 shared the highest homology 91.3% with ZD06,it may be the product of gene rearrangements of other sub-lines.

Molecular Characterization of Avian-like H1N1 Swine Influenza A Viruses Isolated in Eastern China, 2011

Currently, three predominant subtypes of influenza virus are prevalent in pig populations worldwide： H1N1, H3N2, and H1N2. European avian-Hke H1N1 viruses, which were initially detected in European pig populations in 1979, have been circulating in pigs in eastern China since 2007. In this study, six influenza A viruses were isolated from 60 swine lung samples collected from January to April 2011 in eastern China. Based on whole genome sequencing, molecular characteristics of two isolates were determined. Phylogenetic analysis showed the eight genes of the two isolates were closely related to those of the avian-like H1N1 viruses circulating in pig populations, especially similar to those found in China. Four potential glycosylation sites were observed at positions 13, 26, 198, 277 in the HA1 proteins of the two isolates. Due to the presence of a stop codon at codon 12, the isolates contained truncated PB1-F2 proteins. In this study, the isolates contained 591Q, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The isolates also had a D rather than E at position 92 of the NS1, a marker of mammalian adaptation. Both isolates contained the GPKV motif at the PDZ ligand domain of the 3＇ end of the NS1, a characteristic marker of the European avian-like swine viruses since about 1999, which is distinct from those of avian, human and classical swine viruses. The M2 proteins of the isolates have the mutation （S31N）, a characteristic marker of the European avian-like swine viruses since about 1987, which may confer resistance to amantadine and rimantadine antivirals. Our findings further emphasize the importance of surveillance on the genetic diversity of influenza A viruses in pigs, and raise more concerns about the occurrence of cross-species transmission events.

Ecology of avian influenza viruses in migratory birds wintering within the Yangtze River wetlands

Migratory birds are considered natural reservoirs of avian influenza A viruses(AIVs).To further our viral ecology knowledge and understand the subsequent risk posed by wild birds,we conducted a 4-year surveillance study of AIVs in the bird wintering wetlands of the Yangtze River,China.We collected over8000 samples and isolated 122 AIV strains.Analyses were then carried out with 108 novel sequenced genomes and data were deposited in GISAID and other public databases.The results showed that the Yangtze River wintering wetlands functioned as a mixing ground,where various subtypes of AIVs were detected harboring a high diversity of nucleotide sequences;moreover,a portion of AIV gene segments were persistent inter-seasonally.Phylogenetic incongruence presented complex reassortment events and distinct patterns among various subtypes.In addition,we observed that viral gene segments in wintering wetlands were closely related to known North American isolates,indicating that intercontinental gene flow occurred.Notably,highly pathogenic H5 and low pathogenic H9 viruses,which usually circulate in poultry,were found to have crossed the poultry/wild bird interface,with the viruses introduced to wintering birds.Overall,this study represented the largest AIV surveillance effort of wild birds within the Yangtze River wintering wetlands.Surveillance data highlighted the important role of wintering wild birds in the ecology of AIVs and may enable future early warnings of novel AIV emergence.