探讨原始抗原效应对禽类流感病毒感染及免疫应答的影响

In the past a few years, great efforts have been made to develop universal influenza vaccines targeting both homologous and heterologous influenza virus infections. However, rational design of universal vaccine relies on thorough understanding of the host immune response following infection or immunization. Previously, we found that following 2009 novel influenza H1N1 infection or vaccination, human developed broadly cross-reactive humoral immune responses. We hypothesize that this is due to the activation of rare cross-reactive memory B cells derived from previous exposure. On the other hand, the immune history, including infection and immunization, may impair the secondary immune response, this effect is named as “original antigenic sin” (OAS). In this study, we will focus on the following scientific questions: (1) Does the OAS response to influenza infection exist in poultry? (2) How to alleviate the OAS effect and improve the immune response to heterologous virus infection? (3) Could heterologous influenza vaccination/infection induce more broadly cross-reactive monoclonal antibodies than homologous influenza vaccination/infection? This study will provide experimental basis for the development of universal vaccine and rational design of immunization strategies.

可刺激机体产生针对不同亚型流感病毒保护性免疫的通用型流感疫苗是近期研究热点。过往研究发现2009甲型流感病毒H1N1感染或免疫后，机体产生体液免疫应答具有广泛交叉反应性。推测与机体已有的少数具有交叉反应性的记忆B细胞被激活并迅速增殖分化有关。然而，既往感染或疫苗接种史可能会削弱后续的免疫应答，即出现原始抗原效应（original antigenic sin，OAS)，影响免疫效果。本课题将（1）探讨禽类是否存在OAS效应及在禽类中记忆性免疫对异源病毒免疫应答的影响。（2）探索可能削弱OAS效应、促进机体对异源病毒产生保护性免疫应答的途径。（3）从感染了与免疫原同源或异源的流感病毒小鼠中制备单克隆抗体，对单克隆抗体进行解析，比较同源与异源流感病毒感染后抗体的交叉保护作用，推测具有广泛交叉保护作用的抗原表位。本研究将为开发通用型流感疫苗以及合理设计疫苗接种程序提供一定实验依据。

为了探讨禽类流感病毒感染或者疫苗接种史对于后续免疫效果的影响，本课题以两株血清学交叉反应性较弱的H9N2禽流感病毒作为研究对象，通过比较鸡免疫后血清中抗体的反应特异性，发现禽类在感染过一株禽流感病毒之后，对后续接触的病毒抗体反应会受到抑制，其诱导的体液免疫应答也只针对第一株病毒。本研究验证了禽类存在OAS效应的假说。接下来，探讨了可能减弱OAS效应的途径。通过活毒感染，OAS效应被显著削弱，机体不仅产生了针对异源的体液免疫应答，而且对于异源病毒的攻毒也产生了免疫保护作用。实验成功制备了3株针对H9N2血凝素蛋白的单克隆抗体。发现两株抗体均具有血凝抑制活性，说明识别位点位于HA球部受体结合部位。通过对单克隆抗体进行分析，确定了HA基因受体结合区1处氨基酸位点及1处糖基化位点对抗原性起关键作用。本研究将为开发通用型流感疫苗以及合理设计疫苗接种程序提供一定实验依据。