几种中国鸡传染性支气管炎致弱毒株对流行毒株CK/CH/LDL/97Ⅰ保护作用的评价

Evaluation of the protection conferred by several avian infectious bronchitis attenuated vaccines against the field strain CK/CH/LDL97Ⅰ in China

选择2株鸡传染性支气管炎异种致弱毒株CK/CH/LHLJ/04ⅤF110、tl/CH/LDT3/03 F120和1株同种毒株CK/CH/LDL97ⅠF115,研究其对中国流行强毒株CK/CH/LDL97Ⅰ的保护效果。首先对不同毒株及参考毒株的S1基因进行比较和系统进化树分析,研究了CK/CH/LDL97Ⅰ与其他病毒的基因型关系。结果显示,CK/CH/LDL97Ⅰ属于有别于其他IBV毒株的一个独立的基因群。在此基础上,通过血清抗体检测、攻毒后发病率、死亡率、临床症状、病理变化观察以及气管和肾脏中病毒分离等方面研究了同种致弱毒株和异种致弱毒株对CK/CH/LDL97Ⅰ的免疫效力。结果显示,同种致弱毒株对CK/CH/LDL97Ⅰ强毒的攻击可提供100%的临床和病毒分泌的保护性。异种毒株tl/CH/LDT3/03 F120可提供100%的临床保护,但呼吸道病毒检出率达50%,表明对呼吸系统的保护效果不好。异种毒株CK/CH/LHLJ/04ⅤF110免疫组临床发病率为50%,气管样品病毒检出率为100%,可见临床和对病毒分泌的保护效果均较差。

The present study investigated the genotypic relationship between CK/CH/LDL/97 I strains and reference IBVs based on S1 gene comparisons, and the protection provided by vaccination with attenuated homologous and heterologous strains. Phylogenetic analysis and the comparison of S1 showed.that CK/CH/LDL/97 I -type virus might be a new serotype compared to vaccine strains and other types of IBV isolates in China. Protection efficacy was evaluated by serum antibody detection, morbidity, mortality, clinical symptom, pathological lesion and virus re-isolation from the kidney and trachea of the challenged chicks. The results showed that complete protection was provided by the homologous strain CK/CH/LDL97 I FllS. However,though tl/CH/LDT3/03 P120 strain could afford fully protection for clinical symptom,5 tracheas were positive for virus recovery by RT PCR detection in the chicks inoculated with tl/CH/LDT3/03 F120. Therefore, partially respiratory protection was provided by this heterologous strain tl/CH/LDT3/03 F120. The chicks inoculated with CK/CH/LHLJ/04 V F110 strain showed morbidity as high as 50% post challenge with virulent CK/CH/LDL97 I strain. The tissue samples were detected and the results showed that the detection rate was 100% for trachea. Thus,the heterologous strain CK/CH/LHIJ/04 V F110 provided poor protection of respiratory and clinical response against CK/CH/LDL/97 I challenge.