新城疫病毒HI抗体效价与流行株感染排毒之间的相关性

Relationship between HI Antibody Titer and Newcastle Disease Virus Shedding in Chickens Infected with the Prevalent Strain

为了分析免疫鸡群中新城疫强毒感染流行的原因,明确抗体效价与流行株感染排毒率之间的关系,本研究以LaSota为抗原制备新城疫灭活疫苗,并以0.02mL和0.4mL的量分别免疫3周龄的SPF鸡10只。免疫后7、14、21d分别测定免疫鸡血清中的抗体HI效价。免疫后21d以基因Ⅶd亚型新城疫流行株JS5/05进行攻毒,攻毒后每天观察试验鸡的临床症状,并于攻毒后3、5、7d采集试验鸡的喉气管与泄殖腔棉拭样品进行病毒分离,结果显示,免疫3周后0.02mL和0.4mL疫苗免疫组鸡的血清HI抗体平均效价分别为5.4log2和8.2log2;0.02mL免疫组在攻毒后的排毒率达到100%,且排毒时间较长,而0.4mL免疫组在攻毒后的排毒率明显降低,且排毒时间较短。上述结果表明新城疫抗体效价与流行株感染排毒率之间存在明显的负相关。

To elucidate the infection and epidemic of virulent Newcastle disease virus （NDV） in the vaccinated chicken flocks, the relationship between hemagglutination inhibition （HI） antibody titers of serum and virus shedding post-infection was evaluated in this study. Thirty chickens were randomly and averagely divided into 3 groups. The chickens in group 1 and 2 were injected by 0.02 mL and 0.4 mL La Sota-based oil-emulsion vaccine respectively, while the chickens in group 3 were injected by 0.4 mL PBS as the negative control. Sera samples were taken on day 7, 14 and 21 post-immunization （pi）and subjected to HI assays. Three weeks pi,the chickens were challenged by 105 ELD50 of genotype VII NDV strain JS5/05 and were monitored daily for overt clinical signs post-challenge （pc）.Oropharyngeal and cloacal swabs were collected on day 3,5 and 7 pc for virus isolation. The results showed that the mean HI antibody titer of chickens in group 1 and 2 was 5.41og2 and 8.21og2 at day 21 pi,respectively. The positive isolation of the virus from swabs in group 1 was higher than that group 2,and the virus shedding period in group I was longer than that group 2,which displayed the negative relationship between HI antibody titers and virus shedding.