Evaluated Evolution Of Avian Influenza Virus Subtype H5N1 In Zhejiang Province From 2000 To 2006

Backgrounds & ObjectivesIn 1878,avian influenza,which was termed originally as 'fowl plague',was initially recognized as an infectious disease of birds in Italy.Afterwards,outbreaks of the disease also occurred locally in European,American and South-East Asian countries. Nowadays,avian influenza spreads around world.However,it was not until 1955 that Schafer characterized these agents as influenza A viruses.When low pathogenic avian influenza virus(LPAIV)strains result in mildly respiratory symptoms among poultry. However,highly pathogenic avian influenza viruses(HPAI)lead to high risk of morbidity and mortality in human.To date,300 patients have resulted from HPAI since 1997.HPAI H5N1 strains threaten the health of human by characters of its high virulence and mutants..In this study,avian influenza virus subtype H5N1 in Zhejiang province from 2000 to 2006 was sequenced,and then evolution and recombination of stains H5N1 were evaluated by the sequences;Finally,origin and characters of stains H5N1 was speculated.Materials and MethodsThe complete genome of 9 avian influenza H5N1 virus isolated in Zhejiang province from 2000 to 2006 were sequenced by using a Big DyeTM Terminator V 3.1 Sequence Kit.The sequence of 38 stains from China mainland and other Asia countries was downloaded from NCBI database.Phylogenetic tree of avian influenza virus(H5N1) was generated by MEGA software version 4.0.ResultsThe HA gene of all these strains revealed that there were multiple basic amino acids at the cleavage site,which was typical for HPAIV.There were 11 different amino acids between HA sequence of H5N1 stains from Zhejiang and neighboring countries. But the different amino acids did not locate the domain of glycosylation.Furthermore, the stains found after 1997 were absent of 20 amino acids in HA fragment.Based on the whole genome sequence,H5N1 stains from China mainland in resent years differed from neighbouring countries,and also largely differed from H5N1 stains from Hong kong and Guangzhou in 1996 and 1997.However,several Chinese strains were close to the HongKong strains isolated in 1997 but far away from the current strains in the phylogenetic tree.ConclusionThe present study indicated that evolution of avian influenza virus subtype H5N1 by recombination of mutated fragment existed widely in poultry from Zhejiang province. A/Zhejiang/16/2006 Etc formed a separate branch with the strains isolated in China mainland in recent years,but it presented an obvious difference with the isolates in neighboring countries.Whole-Genome analysis of avian influenza H5N1 virus sequence better reflect the evolutionary relationship between strains than single gene analysis.