Adaptation Of An Emergent H5N6 Avian Influenza Virus To Mice

H5N6 influenza virus was derived from combination of the H5N1 with H6N6.The H5N6 NA genes derived from H6N6 and the rest of the genes derived from H5N1.Maybe H5N1 characteristics had been passed on H5N6.Since the first time of the Hong Kong people were infected with the H5N1 subtype of highly pathogenic avian influenza(HPAI),many places and countries were constantly appearing HPAIV.And many infected people were death.In 2004,the H5N1 bird influenza virus attacked some Asian countries,and caused great economic loss and influence to the human.Many people infected by HPAIV subtype H5N1,and 60% of them were death.It was reported that H5N6 subtype of the influenza virus had made many people infection and death.It means that H5N6 avian virus has a potential threat to human's health.Therefore,the pathogenicity study of H5N6 avian influenza virus to mammals is an important thing.In this reserch,we used the avian influenza virus(A/wine/Guangdong/1/2014 H5N6)to adapt to mice.We serially passaged an H5N6 virus 4 times in BALB/c mice and sequenced the viral genome.The pathogenicity of the wildtype GD1 and mammal-adapted GD1-M-F4(F4)were compared.We found that adaption strain had higher fatality rate than the wild type virus and adaption strains replicted in the lungs,turbinate,brain and spleen.Sequencing results showed that mice adaption strain obtained the mutations of PB2-E627 K,PB1-L598 Q,HA-R293 C and M-D106 E.For further studying the function of the four amino acid mutations in mice,we rescued the viruses possessing the mutations we found.The rescued virus of PB2-627 K not only replicated in the lungs but also replicated in the turbinate,brain and spleen.The rescued virus of PB1-598 Q replicted in lung,turbinate,and brain.The rescued viruses of M-106 E and HA-239 C just replicated in the lung.And polymerase activity test revealed the PB2-E627 K and PB1-L598 Q for significantly increased the enzyme activity.We provided evidence that the mutations of HA R239 C,PB1 L598 Q,and PB2 E627 K are important for adaptation of H5N6 AIVs in mice.This study revealed the adapting molecular marker of H5N6 avian influenza virus to mice.At the same time,it can provide scientific theory basis of how avian influenza virus to break through the barrier between poultry and mammals.