To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.

To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.

[ ABSTRACT ] AIM: To investigate the toxicity and reproductive effect of vascular endothelial growth factor ( VEGF)/basic fibroblast growth factor ( bFGF) complex peptide vaccine ( VBP3) on the female-mice.METHODS:The VBP3 was purified with Ni-NTA affinity chromatography.The female BALB/c mice were immunized with the purified VBP3.The antibody titer in the serum was detected by ELISA.The data of the body weight and the organ weight of the par-ent mice were gathered and analyzed, and the pathological changes of the organs were observed with HE staining to investi-gate the toxicity of VBP3.To investigate the toxicity of VBP3 in the F1 mice, the parent immunized female mice were ma-ted with the parent non-immunized male mice.After the F1 mice were born, the survival rate was calculated, the change of the body weight and the organ weight of the F1 mice were also determined.The pathological changes of the organs in F1 mice were also observed with HE staining.RESULTS: In the parent mice, high titers of the antibodies were detected against VEGF and bFGF, and no difference of the body weight, the organ weight and the pathological change between the immunized mice and control mice was found.In the F1 mice, a low titer of anti-bFGF antibody was detected compared with blank group.The survival rate in control group was higher than that in immunized group.In the 2 groups of the F1 mice, no obvious difference of the weight of the spleen, kidney, lung and heart was observed, and there was some difference in the weight of liver between the 2 groups.The results of the HE staining in the F1 mice showed some difference in the liver between the 2 groups.CONCLUSION:VEGF/bFGF complex peptide vaccine has no obvious organ toxicity in the parent female mice, but has some side effects on the reproductive and the healthy processes of F1 mice.