免疫鸡血清新城疫病毒抗体水平与攻毒保护效果的相关性研究

Correlation Between the Serum Antibody Level Against Newcastle Disease Virus and Protective Effi cacy Against Challenges in Vaccinated Chickens

为了明确不同血清新城疫病毒(NDV)抗体水平对鸡的保护效果,本研究采用重组NDV灭活疫苗(A-Ⅶ株)对鸡进行免疫,通过交叉血凝抑制(HI)试验比较A-Ⅶ株与La Sota株间的血清学差异,并采用NDV标准强毒株F_(48)E_(8)和基因Ⅶ型强毒株JSC0804对不同抗体水平免疫鸡进行了攻毒保护试验。结果显示:抗A-Ⅶ株血清用A-Ⅶ株抗原测得的平均HI抗体效价显著高于La Sota株抗原(P<0.01),约高1.5log2,而抗La Sota株血清用La Sota株抗原测得的平均HI抗体效价稍高于A-Ⅶ株抗原,但无显著差异(P>0.05),表明2种疫苗株存在一定的血清学差异。在试验条件下,所有免疫鸡经点眼滴鼻攻毒后均未表现明显临床症状,但存在不同程度的排毒现象,排毒率总体上随抗体效价升高呈逐渐下降趋势。A-Ⅶ株疫苗免疫鸡血清HI抗体效价分别达≥13log_(2)和≥14log_(2)时可完全阻止F_(48)E_8株和JSC0804株排毒。免疫鸡排毒一般仅限于攻毒后5 d内。本研究阐明了免疫鸡的抗体水平和免疫保护效果的相关性,为新城疫免疫控制提供了依据。

To investigate the protective efficacy of different antibody levels against Newcastle disease virus(NDV),chickens were vaccinated with inactivated recombinant genotypeVII NDV-matched A-VIIstrain vaccine.The serological differences between two vaccine strains of A-VIIstrain and LaSota strain were compared by cross hemagglutination inhibition(HI)test,and protection experiments against challenges with standard virulent NDV strain F_(48)E_(8)and virulent genotype VII strain JSC0804 were carried out in vaccinated chickens of different antibody levels.The results showed the mean HI antibody titer against A-VII strain of anti-A-VII strain hyperimmune sera was significantly higher(about 1.5log_(2))than that against LaSota strain(P<0.01).However,the mean HI antibody titer against La Sota strain of anti-La Sota strain hyperimmune sera was slightly higher than that against A-VII strain but showed no significant difference(P>0.05).This result suggested there were some serological differences between two vaccine strains.Under the experimental conditions,none of vaccinated chicken showed any clinical signs after being challenged intranasally and intraocularly.However,varying degrees of virus shedding were detected.The shedding rates generally decreased with the increase of antibody titers.When the serum HI antibody titers against A-VII strain of the vaccinated chickens reached≥13log_(2)(challenge with F_(48)E_(8)strain)or≥14log_(2)(challenge with JSC0804 strain),virus shedding was completely inhibited.The virus shedding in the vaccinated chickens was detectable generally within 5 days post-challenge.This study elucidated the correlation between the serum antibody level and protection effcacy in vaccinated chickens,providing a basis for immune control of Newcastle disease.