三株鸡传染性支气管炎病毒优势流行毒株全基因组分析及其致病性OA北大核心CSTPCD

The genetic evolution and pathogenicity of isolated infectious bronchitis virus(IBV)strains in the laboratory were studied to investigate the prevalence of IBV and the pathogenic characteristics of dominant strains,and to provide reference for the development of new vaccines.In this study,the complete S1 nucleotide sequences of 60 strains IBV were analyzed,and three dominant genotypes were selected for whole genome sequencing analysis,named MH20,KC and JS96 strains.JS96 strain with higher virulence was selected for SPF chicken pathogenicity experiment.The results of genetic evolution analysis show that GI-19 is the main epidemic strain in China,accounting for about 53.57％of cases.At the same time,variants were emerging,and GVI(new genotype)was obviously prevalent.The whole genome sequencing showed that the complete genome of the three isolated strains had the highest similarity with QX-like strains(more than 97％),but the sequence homology with vaccine strains and classical strains was low,only about 77％.Epitope analysis also showed that there were differences in the number and sequence of B cell epitopes among the isolates,vaccine strains and classical strains.The pathogenicity of JS96 in 1-day-old SPF chickens was higher than that in 15-day-old SPF chickens,and the mortality rate of 1-day-old SPF chickens was 100％.Significant growth retardation and obvious symptoms were observed in some 15-day-old SPF chickens.This study shows that QX-like IBV strain is the main epidemic strain of IBV at present,which has strong pathogenicity to young chickens,is prone to Ⅰ gene recombination,has low similarity with S protein of vaccine strain and classical strain,and has poor adaptability,so it is urgent to select appropriate vaccines and develop new vaccines in order to control the current epidemic of IBV and reduce losses in the poultry industry.