Leidos Life Sciences, Leidos Inc., Frederick, MD, United States.
EpiVax Inc., Providence, RI, United States.
Front Immunol. 2021 Jul 7;12:690348. doi: 10.3389/fimmu.2021.690348. eCollection 2021.
The hurdles to effective blood stage malaria vaccine design include immune evasion tactics used by the parasite such as redundant invasion pathways and antigen variation among circulating parasite strains. While blood stage malaria vaccine development primarily focuses on eliciting optimal humoral responses capable of blocking erythrocyte invasion, clinically-tested (Pf) vaccines have not elicited sterile protection, in part due to the dramatically high levels of antibody needed. Recent development efforts with non-redundant, conserved blood stage antigens suggest both high antibody titer and rapid antibody binding kinetics are important efficacy factors. Based on the central role of helper CD4 T cells in development of strong, protective immune responses, we systematically analyzed the class II epitope content in five leading Pf blood stage antigens (RH5, CyRPA, RIPR, AMA1 and EBA175) using , , and methodologies. We employed T cell epitope analysis to enable identification of 67 HLA-restricted class II epitope clusters predicted to bind a panel of nine HLA-DRB1 alleles. We assessed a subset of these for HLA-DRB1 allele binding , to verify the predictions. All clusters assessed (40 clusters represented by 46 peptides) bound at least two HLA-DR alleles . The overall epitope prediction to HLA-DRB1 allele binding accuracy was 71%. Utilizing the set of RH5 class II epitope clusters (10 clusters represented by 12 peptides), we assessed stimulation of T cells collected from HLA-matched RH5 vaccinees using an IFN-γ T cell recall assay. All clusters demonstrated positive recall responses, with the highest responses - by percentage of responders and response magnitude - associated with clusters located in the N-terminal region of RH5. Finally, a statistically significant correlation between epitope predictions and IFN-γ recall response was found when accounting for HLA-DR matches between the epitope predictions and donor HLA phenotypes. This is the first comprehensive analysis of class II epitope content in RH5, CyRPA, RIPR, AMA1 and EBA175 accompanied by HLA binding validation for all five proteins and T cell response confirmation for RH5.
有效血阶段疟疾疫苗设计的障碍包括寄生虫使用的免疫逃避策略,如冗余入侵途径和循环寄生虫株之间的抗原变异。虽然血阶段疟疾疫苗开发主要集中在诱导能够阻断红细胞入侵的最佳体液反应,但经过临床测试的 Pf 疫苗并未引起无菌保护,部分原因是需要极高水平的抗体。最近对非冗余、保守的血阶段抗原的开发努力表明,高抗体滴度和快速抗体结合动力学都是重要的疗效因素。基于辅助性 CD4 T 细胞在发展强大、保护性免疫反应中的核心作用,我们系统地分析了五种领先 Pf 血阶段抗原(RH5、CyRPA、RIPR、AMA1 和 EBA175)中的 II 类表位含量,使用、和方法。我们采用 T 细胞表位分析来识别 67 个 HLA 限制性 II 类表位簇,这些簇预测与一组 9 个 HLA-DRB1 等位基因结合。我们评估了其中的一部分 HLA-DRB1 等位基因结合,以验证预测。所有评估的簇(由 46 个肽代表的 40 个簇)与至少两个 HLA-DR 等位基因结合。总体预测对 HLA-DRB1 等位基因结合的准确性为 71%。利用 RH5 II 类表位簇集(由 12 个肽代表的 10 个簇),我们使用 IFN-γ T 细胞回忆测定评估了来自 RH5 疫苗接种者 HLA 匹配的 T 细胞的刺激。所有簇均表现出阳性回忆反应,其中最高的反应 - 以反应者的百分比和反应幅度为特征 - 与位于 RH5 N 端区域的簇相关。最后,在考虑表位预测与供体 HLA 表型之间的 HLA-DR 匹配时,发现 表位预测与 IFN-γ 回忆反应之间存在统计学显著相关性。这是 RH5、CyRPA、RIPR、AMA1 和 EBA175 中 II 类表位含量的首次全面分析,同时对所有五种蛋白质进行 HLA 结合验证,并对 RH5 进行 T 细胞反应确认。
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