EIAV弱毒疫苗株和强毒株诱导的特异性体液免疫应答差别

The difference in specific humoral immune responses induced with the attenuated equine infectious anemia vaccine strain and virulent strain

目的:通过研究EIAV弱毒疫苗株和强毒株在诱导多种特异性抗体方面的差异,初步探讨特异性体液免疫应答在EIAV弱毒疫苗株保护性免疫中的作用。方法:试验马匹根据接种毒株分为疫苗组和强毒隐性感染组,应用ELISA方法对血清中病毒囊膜蛋白Env和衣壳蛋白P26结合抗体的滴度、亲和力及Env结合抗体的构象依赖性进行动态实相检测,同时采用细胞蚀斑染色和逆转录酶活性检测方法对中和抗体水平进行同期检测。结果:Env和P26结合抗体的滴度、亲和力、构象依赖性及中和抗体的中和活性均存在一个缓慢上升的过程。对于P26抗体滴度及Env抗体亲和力,疫苗组和强毒隐性感染组仅在病毒接种2个月内,表现为统计学差异(P<0.05)。疫苗组从接种后14d开始,Env抗体的构象依赖性高于强毒隐性感染组(P<0.05),并持续至最后一个监测点。最明显的是,疫苗组诱导产生具有中和强毒特性毒株(EIAVDLV34)和弱毒特性毒株(EIAVFDDV)活性的中和抗体均高于强毒隐性感染组(P<0.05)。结论:弱毒疫苗株和强毒株诱导机体产生结合抗体和中和抗体的时间、水平和性质均存在明显差异,其中中和抗体和构象依赖性抗体的差异,可能是EIAV弱毒疫苗诱导保护性免疫的主要因素之一。

AIM： To disclose the potential roles of humoral immune response in the EIAV vaccine-induced protective immunity. In this study, major parameters of humoral immunity be compared between horses inoculated with the EIAV vaccine strain and the pathogenic virulent strain. METHODS： Experimental horses were randomly assigned into the group inoculated with the vaccine strain EIAVDLV （the vaccinated group） and the group inoculated with sub-morbigenous dose of virulent strain EIAVLiao （the inapparent infection group）. Humoral immunity parameters, including binding endpoint titer and avidity index of antibodies to the envelop protein （Env） and the capsid protein （P26）, and the conformation-dependent index of the Env antibody, were assayed and compared between these two groups by using ELISA. Neutralizing antibodies to the EIAV vaccine strain and a pathogenic strain were simultaneously detected by using plaque forming unite assay （PFU） and reverse transcriptase activity assay, respectively. RESULTS： In general, all humoral parameters increased with a time-dependent manner in both the vaccinated and the inapparent infection group. However, significantly higher antibody activities for P26 binding endpoint titer and Env avidity index were detected in the vaccinated group within 2 months post infection （ P 〈 0.05）. Furthermore, the conformation-dependent index of the Env antibody in the vaccinated group was significantly higher than that in the inapparent infection group throughout the entire observation period （ P 〈 0.05 ）. The most dramatic difference between these experimental groups was in the raise of the neutralizing antibody. The antibody neutralizing both the vaccine strain EIAVDLV and a virulent strain EIAVDLV34 was detected significantly earlier and in higher titers in vaccinated horses than in virulent strain-infected horses （P 〈 0.01 for EIAVFDDV and P 〈 0. 05 for EIAVDLV34 ）. CONCLUSION： Statistically significant differences in EIAV-specific binding antibodies and the neutralizing antibody are detected between animals induced with the EIAV vaccine strain and the virulent strain. Importantly, the significantly early and strong responses in the neutralizing antibody and the conformation-dependent Env antibody induced by the vaccine implicate special roles these antibodies playing in EIAV vaccine-induced immune protection.