高致病性猪繁殖与呼吸综合征活疫苗(HuN4-F112株)诱导特异性IFN-γ^+T细胞反应的研究

Detection of specific IFN-γ^+ T cells response to highly pathogenic PRRS attenuated live vaccine(HuN4-F112) in pigs

为研究高致病性猪繁殖与呼吸综合征(PRRS)活疫苗(HuN4-F112株)诱导的特异性IFN-γ+T细胞反应与其保护作用的相关性,本研究将25头45日龄PRRSV阴性健康仔猪随机均分为5组,第1～3组分别于0 d、7 d、14 d免疫HuN4-F112疫苗(1头份/头,106.0TCID50),第4组为攻毒对照组,第1～4组于21 d用PRRSV强毒株HuN4-F5攻毒(3 mL/头,104.0TCID50),第5组为空白对照组。疫苗免疫后1周～2周产生部分保护,3周产生完全保护,第1～4组保护率分别为5/5、2/5、2/5和0/5。中和抗体检测显示免疫组免疫后7 d和14 d所有猪只均未检测到中和抗体,免疫后第21 d第1组4头猪检测到低效价(≤1∶8)的中和抗体。疫苗免疫后血清中IFN-γ含量略有升高,但变化不大,整体都处于较低的水平。采用酶联免疫斑点技术(ELISpot)检测PRRSV特异性IFN-γ+T细胞反应。免疫组免疫后7 d、14 d、21 d百万外周血单个核细胞中IFN-γ+T细胞频数分别为0±0、0±2、5±8,组间和组内统计分析显示差异不显著。结果表明在HuN4-F112株疫苗早期保护中,IFN-γ参与的特异性细胞免疫反应较弱,在早期免疫阶段难以发挥主要作用。本研究为了解PRRSV疫苗免疫保护机制提供参考,同时,也提示需要采用更多的指标和方法来评价该疫苗诱导的免疫反应。

To investigate the relationship between IFN-γ^＋T T cells response and the protective immunity against porcine reproductive and respiratory syndrome （PRRS） with highly pathogenic PRRS vaccine （HuN4-F112） strain, PRRSV specific IFN-γ^＋T T cells response induced by HuN4-F112 vaccine was evaluated. In the present study, twenty-five PRRSV-free piglets were divided into 5 groups randomly. Group 1 to 3 were immunized with HuN4-FII2 on 0, 7, 14 day respectively. Group 1 to 4 were challenged with HuN4-F5 on 21 day, and Groun 5 was served as blank control. The results showed that protection rates of mroun 1to 4 were 5/5, 3/5, 1/5 and 0/5. The IFN-γ^＋T cells in PBMCs were detected on 7, 14 and 21 days post immunization, respectively. But no significant difference was found in both inter-group and intra-group. The result indicated that IFN-γ^＋T cells response was fairly weak, which was unable to play an important role in the early stage of the vaccine protective immunity. Therefore, other cytokines need to be considered for future studies on early immunization agaist PRRSV infection.