用冷适应的方法致弱鸡肾型传染性支气管炎病毒

Studies on the attenuation of infectious bronchitis virus by cold-adaptation

用冷适应的方法 (病毒经囊液接种鸡胚后于 32℃孵化 48h) ,将已鉴定的北京地区鸡肾型传染性支气管炎病毒 (IBV)分离株 Tu,Da,Xi和 Hu分别通过鸡胚传代减毒致弱 ,在一定代次时接种敏感鸡作毒力测定试验 ,结果表明 ,Tu株在传至 46代时 ,Xi株在传至 5 1代时对雏鸡的毒性已大为降低 ,并且分别回归 SPF雏鸡 5代和 3代后不出现返强现象。毒价测定 Tu46和 Xi51 的 EID50 值分别为 10 - 6.3 6/ 0 .2 m l和 10 - 6.70 / 0 .2 m l,而且 Tu株出现稳定增高的趋势。它抵抗同源强毒攻击的最小免疫剂量为 10 - 2 × 0 .5 m l。此外 ,对弱毒株免疫后的雏鸡用标准强毒株Gray攻击以衡量其免疫原性 ,结果 Tu46具有 90 %的保护率。间接 EL ISA对免疫后的抗体水平检测结果反映 ,Tu46免疫鸡体内血清抗体的消长呈规律性变化 ,并在免疫后 2 0天出现最高峰。综合结果表明 ,作者培育的 IBV- Tu46株具有对雏鸡安全、毒价高及较好的免疫原性的特点 ,有希望成为供生产使用的疫苗。

Using cold-adaptation,four identified strains Tu,Hu,Da and Xi of avian nephropathogenic infectious bronchitis virus isolated in Beijing area were attenuated by passing in the embryonating chicken eggs at 32℃ for 48hrs.These attenuated viruses were inoculated into susceptive chickens for examination of potential pathogenicity. Results showed that strain Tu and strain Xi were non-pathogenic for chickens after passaging 46 and 51 respectively and non-reversion of virulence through five and three serial passages in SPF chickens.The titers (EID 50) of Tu 46 and Xi 51 strains were 10 -6.36/0.2 ml,10 -6.70/0.2 ml respectively.When challenged with the original Tu,its minimum immunity dose was 10 -2×0.5 ml. While challenged with highly virulent strain of IBV(Gray),Tu 46 could provid chickens with a very good protection(90%).The antibody of vaccinated chickens changed dynamically and the peak titer was detected by indirect ELISA at 20th day post immunization.The results of the study demonstrated the attenuated IBV-Tu 46 strain could be used as a vaccine candidate.