Impact of prior influenza exposures on antibody repertoires to new viral strains

描述(由申请人提供)：流感病毒在血凝素(HA)和神经氨酸酶(NA)蛋白内的抗体(Ab)结合部位迅速积累突变，这一过程被称为“抗原漂移”。由于抗原漂移，人类经常再次感染抗原性不同的流感病毒株，疫苗必须经常更新。流感疫苗未能在某些个体中激发保护性抗体反应，即使疫苗毒株与主要流通毒株很好地匹配。老年人通常有广泛的流感接触史，对流感疫苗的反应特别差。早在20世纪50年代，S就注意到，人类免疫系统优先针对以前流行的流感病毒株产生抗体反应，而不是针对较新的病毒株产生新的抗体反应。这一过程被称为“原始抗原缺陷(OAS)”，被认为是导致有大量流感暴露前病史的个体疫苗失败的原因之一。我们推测，与OAS诱导的识别HA保守区表位的抗体相比，识别位于HA顶部的可变表位的菌株特异性抗体在中和病毒方面更有效。以前对美洲国家组织的研究使用了具有显著抗原性差异的流感毒株，然而，与以前流行的流感毒株相比，人类通常更多地顺序感染或接种具有细微抗原变化的流感毒株。在这项提案中，我们将确定OAS是否是由具有中等抗原性差异的季节性流感毒株顺序感染引起的。我们将用具有明确HA抗原突变的A/波多黎各/8/34病毒依次感染小鼠和雪貂，并通过血凝抑制(HAI)、ELISA、ELISPOT、基于FACS的抗体结合和体外中和试验来鉴定OAS诱导的抗体。我们将在预先接触MF59佐剂和不使用MF59佐剂的动物中完成类似的疫苗接种实验。然后，我们将绘制抗HA单抗的精确结合足迹图，这些单抗来自顺序感染不同流感病毒株的小鼠。我们还将绘制一个 大量H3N2型单抗来自接种过疫苗的人，这些人有不同的H3N2前暴露史。最后，我们将使用小鼠模型来确定OAS诱导的小鼠和人mAb的体内中和效率。总而言之，这些研究将确定(1)季节性疫苗是否会诱发OAS，(2)OAS是否会导致预先暴露人群的疫苗效力降低，以及(3)OAS抗体谱是否可以被MF59佐剂改变。

DESCRIPTION (provided by applicant): Influenza viruses rapidly accumulate mutations in antibody (Ab) binding sites within the hemagglutinin (HA) and neuraminidase (NA) proteins, a process termed 'antigenic drift'. Due to antigenic drift, humans are frequently re-infected with antigenically distinct influenza strains and vaccines must be updated frequently. Influenza vaccines fail to elicit protective Ab responses in some individuals, even when vaccine strains are well matched to predominant circulating strains. Elderly individuals, who typically have extensive influenza exposure histories, respond particularly poorly to influenza vaccines. As early as the 1950's, it was noted that the human immune system preferentially mounts Ab responses to previously circulating influenza strains, as opposed to new Ab responses that exclusively target newer viral strains. This process, termed 'original antigenic sin (OAS)', has been proposed to contribute to vaccine failures in individuals with extensive influenza pre-exposure histories. We hypothesize that strain-specific Abs that recognize variable epitopes located on the top of HA are more efficient at neutralizing virus compared to OAS-induced Abs that recognize epitopes in conserved regions of HA. Previous studies of OAS have utilized influenza strains that have dramatic antigenic differences, however humans are more typically sequentially infected or vaccinated with influenza strains that have subtle antigenic changes compared to previously circulating strains. In this proposal, we will determine if OAS is induced by sequential infections with seasonal influenza strains with moderate antigenic differences. We will sequentially infect mice and ferrets with A/Puerto Rico/8/34 viruses with well defined HA antigenic mutations, and we will identify OAS-induced Abs through hemagglutination-inhibition (HAI), ELISA, ELISPOT, FACS-based Ab binding, and in vitro neutralization assays. We will complete similar vaccination experiments in pre-exposed animals with and without the MF59 adjuvant. We will then map the precise binding footprints of anti-HA mAbs derived from mice sequentially infected with distinct influenza strains. We will also map the binding footprints of a large panel of H3N2 mAbs derived from vaccinated humans with different H3N2 pre- exposure histories. Finally, we will determine in vivo neutralization efficiencies of OAS-induced murine and human mAbs using a mouse model. Collectively, these studies will determine (1) if seasonal vaccines induce OAS, (2) if OAS contributes to decreased vaccine efficacy in pre-exposed populations, and (3) if OAS Ab repertoires can be altered by MF59 adjuvants.