Selection of H5N1 subtype avian influenza virus demonstrating high pathogenicity for mice

As H5N1 avian influenza virus can infect mammalian,research of vaccine against H5N1 virus became urgent.Our study aimed to examine the infectious status of recent H5N1 viruses against Balb/c mice and select a highly pathogenic H5N1 virus. We inoculated mice were intranasally with 17 strains H5N1 viruses isolated from poultry in southern China.The virulence and lethality were observed,while TCID_(50),EID_(50),mice LD_(50),and virus loading were measured;the phylogenetic tree was drawn through HA sequence analysis.Among the 17 H5N1 strains,1 was highly lethal to mice(TCID_(50)/100μl=7.2,EID_(50)/100μl=8.325,LD_(50)/100μl= 6.318≈10~2EID_(50)).Avian influenza virus NS segments were detected from lung,spleen,nose,and brain tissues of infected mice.The viral load in brain tissue was the highest,which was up to 3.56×10~(10) copies/5μl.These results indicate that most of H5N1 viruses from poultry are nonpathogenic for mice;this mouse model can be used to evaluate the cross-protection of avian influenza vaccine and also to investigate the prophylaxis and treatment of H5N1 avian influenza viruses.