Long-lasting B cell convergence to distinct broadly reactive epitopes following vaccination with chimeric influenza virus hemagglutinins

In a phase I clinical trial, a chimeric hemagglutinin (cHA) immunogen induced antibody responses against the conserved HA stalk domain as designed. Here, we determined the specificity, function, and subsets of B cells induced by cHA vaccination by pairing single cell RNA-sequencing and B cell receptor repertoire sequencing. We have shown that the cHA inactivated vaccine with a squalene-based adjuvant induced a robust activated B cell and memory B cell (MBC) phenotype against two broadly neutralizing epitopes in the stalk domain. The overall specificities of the acute plasmablast (PB) and MBC responses clonally overlapped, suggesting B cell convergence to these broadly protective epitopes. At one-year post-immunization, we identified that cHA vaccination reshaped the HA-specific MBC pool to enrich for stalk-binding B cells. Altogether, these data indicate the cHA vaccine induced robust and durable B cell responses against broadly protective epitopes of the HA stalk domain, in line with serological data. MBCs (CD19+IgD-Probe+) from cHA vaccine and seasonal influenza vaccine recipients were sort purified for analysis of transcriptome and V(D)J gene usage

在一项I期临床试验中，嵌合血凝素（chimeric hemagglutinin, cHA）免疫原可如预期般诱导针对血凝素茎部保守结构域的抗体应答。本研究通过联合单细胞RNA测序与B细胞受体库测序技术，明确了cHA疫苗诱导的B细胞的特异性、功能及亚群分类。本研究证实，搭载角鲨烯佐剂的cHA灭活疫苗可针对茎部结构域的两类广谱中和表位，诱导显著活化的B细胞与记忆B细胞（memory B cell, MBC）表型。急性期浆母细胞（plasmablast, PB）与MBC应答的整体特异性存在克隆型重叠，提示B细胞向这些广谱保护性表位发生趋同应答。在免疫后一年时，本研究发现cHA疫苗可重塑HA特异性MBC库，使其富集结合茎部结构域的B细胞。综上，本研究数据表明，cHA疫苗可诱导针对HA茎部结构域广谱保护性表位的强效且持久的B细胞应答，这与血清学检测结果一致。研究人员对cHA疫苗接种者与季节性流感疫苗接种者体内的MBCs（CD19+IgD-Probe+）进行分选纯化，以开展转录组与V(D)J基因取用情况分析。