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）结合位点迅速积累突变，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不同的流感毒株，疫苗必须经常更新。流感疫苗在某些个体中不能引起保护性抗体反应，即使疫苗株与主要流行株很好地匹配。老年人通常有广泛的流感暴露史，对流感疫苗的反应尤其差。早在20世纪50年代，人们就注意到，人类免疫系统优先对以前流行的流感病毒株产生Ab反应，而不是只针对较新的病毒株产生新的Ab反应。这一过程被称为“原始抗原原原性罪过（OAS）”，被认为是导致具有广泛流感暴露前病史的个体接种疫苗失败的原因之一。我们假设，与oas诱导的识别HA保守区域表位的抗体相比，识别HA顶部可变表位的株特异性抗体在中和病毒方面更有效。先前对美洲国家组织的研究利用了具有显著抗原差异的流感毒株，然而，与以前流行的毒株相比，人类更典型的是依次感染或接种具有细微抗原变化的流感毒株。在这项建议中，我们将确定OAS是否由具有中等抗原差异的季节性流感毒株的顺序感染引起。我们将依次用具有明确HA抗原突变的A/Puerto Rico/8/34病毒感染小鼠和雪貂，并将通过血凝抑制（HAI）、ELISA、ELISPOT、基于facs的抗体结合和体外中和试验鉴定oas诱导的抗体。我们将在接种和不接种MF59佐剂的预暴露动物中完成类似的疫苗接种实验。然后，我们将绘制从顺序感染不同流感毒株的小鼠中提取的抗ha单抗的精确结合足迹。我们还将映射a的绑定足迹

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.