两株H5N1亚型禽流感病毒的基因分析及其在不同宿主中致病性的比较

为了解两株高致病性禽流感病毒(HPAIV)的分子特征及其对不同宿主的致病性,本研究对DK/HuN/4/08和CK/GX/2/09进行全基因组序列的测定,分析结果表明:两个病毒分离株HA基因的裂解位点均具有HPAIV特有的基序(341RRR(R)KR345/346),并且均属于Clade2.3.2分支,基因组同源性在97.4%～98.3%之间。致病性试验显示,两个病毒分离株均能够以106EID50感染量在3 d内引起鸡全部死亡,并且各脏器均检测到高滴度的病毒含量;两者在SPF鸭中呈现不同的致病性,CK/GX/2/09在4 d内可以使感染鸭100%死亡,而DK/HuN/4/08只引起25%的死亡率;同样在小鼠试验中,两者致病力差异与在鸭体中的反应一致,其MLD50分别为1.63 log10EID50和6.2 log10EID50。本研究表明,这两株遗传背景相似的HPAIV在鸡、鸭和小鼠中的致病性不同,为进一步利用反向遗传技术研究这两株病毒对水禽和哺乳动物致病力差异的分子机制奠定了基础。

Genetic analysis and pathogenicity of 2 H5N1 subtype avian influenza virus isolates in different hosts

Avian influenza virus(AIV) of DK/HuN/4/08 and CK/GX/2/09 were isolated from live poultry markets in southern China.Sequencing analysis indicated that the viruses were categorized as highly pathogenic AIV(HPAIV) with the typical HA cleavage site of 341RRR(R)KR345/346,and bored the same HA gene of clade 2.3.2,sharing 97.4% to 98.3% homology in the whole genome.Six week-old SPF chickens were inoculated intranasally with 106 EID50 viruses,and results showed that isolates were both highly pathogenic to SPF chickens.However,CK/GX/2/09 was also high pathogenicity to ducks,resulting in 100% mortality,while DK/HuN/4/08 was low pathogenic to ducks with 25% mortality when four week-old SPF ducks were inoculated intranasally with 106 EID50 viruses.Meanwhile,the virus titration results showed that DK/HuN/4/08 and CK/GX/2/09 were different in pathogenicity to mice with 6.2 Log10 EID50 and 1.63 Log10 EID50,respectively,when six week-old BALB/c mice were inoculated intranasally with 106 EID50.In conclusion,the two isolates with similar genomic characteristics had distinct pathogenicity in ducks and mice,which could be used to further study the pathogenic mechanisms of H5N1 AIV in aquatic birds and mammals by reverse genetic technology.