Department of Virology, Medical University of Vienna, Vienna, Austria.
Department of Statistics, Protein Informatics Group, University of Oxford, Oxford, United Kingdom Section of Biosimulation and Bioinformatics, Medical University of Vienna, Vienna, Austria.
J Virol. 2014 Jul;88(14):7828-42. doi: 10.1128/JVI.00196-14. Epub 2014 Apr 30.
Tick-borne encephalitis (TBE) virus is endemic in large parts of Europe and Central and Eastern Asia and causes more than 10,000 annual cases of neurological disease in humans. It is closely related to the mosquito-borne yellow fever, dengue, Japanese encephalitis, and West Nile viruses, and vaccination with an inactivated whole-virus vaccine can effectively prevent clinical disease. Neutralizing antibodies are directed to the viral envelope protein (E) and an accepted correlate of immunity. However, data on the specificities of CD4(+) T cells that recognize epitopes in the viral structural proteins and thus can provide direct help to the B cells producing E-specific antibodies are lacking. We therefore conducted a study on the CD4(+) T cell response against the virion proteins in vaccinated people in comparison to TBE patients. The data obtained with overlapping peptides in interleukin-2 (IL-2) enzyme-linked immunosorbent spot (ELISpot) assays were analyzed in relation to the three-dimensional structures of the capsid (C) and E proteins as well as to epitope predictions based on major histocompatibility complex (MHC) class II peptide affinities. In the C protein, peptides corresponding to two out of four alpha helices dominated the response in both vaccinees and patients, whereas in the E protein concordance of immunodominance was restricted to peptides of a single domain (domain III). Epitope predictions were much better for C than for E and were especially erroneous for the transmembrane regions. Our data provide evidence for a strong impact of protein structural features that influence peptide processing, contributing to the discrepancies observed between experimentally determined and computer-predicted CD4(+) T cell epitopes. Importance: Tick-borne encephalitis virus is endemic in large parts of Europe and Asia and causes more than 10,000 annual cases of neurological disease in humans. It is closely related to yellow fever, dengue, Japanese encephalitis, and West Nile viruses, and vaccination with an inactivated vaccine can effectively prevent disease. Both vaccination and natural infection induce the formation of antibodies to a viral surface protein that neutralize the infectivity of the virus and mediate protection. B lymphocytes synthesizing these antibodies require help from other lymphocytes (helper T cells) which recognize small peptides derived from proteins contained in the viral particle. Which of these peptides dominate immune responses to vaccination and infection, however, was unknown. In our study we demonstrate which parts of the proteins contribute most strongly to the helper T cell response, highlight specific weaknesses of currently available approaches for their prediction, and demonstrate similarities and differences between vaccination and infection.
蜱传脑炎（TBE）病毒在欧洲和中、东欧的大部分地区流行，每年导致 1 万多例人类神经系统疾病。它与蚊媒传播的黄热病、登革热、日本脑炎和西尼罗河病毒密切相关，接种灭活全病毒疫苗可有效预防临床疾病。中和抗体针对病毒包膜蛋白（E），是公认的免疫相关物。然而，缺乏针对识别病毒结构蛋白表位的 CD4+T 细胞特异性的相关数据，而这些表位可以为产生 E 特异性抗体的 B 细胞提供直接帮助。因此，我们比较了接种疫苗者和 TBE 患者的病毒粒子蛋白的 CD4+T 细胞反应，进行了这项研究。用白细胞介素-2（IL-2）酶联免疫斑点（ELISpot）检测分析重叠肽获得的数据，与衣壳（C）和 E 蛋白的三维结构以及基于主要组织相容性复合体（MHC）Ⅱ类肽亲和力的表位预测相关联。在 C 蛋白中，两个α螺旋中的两个肽对应于两种疫苗接种者和患者的反应，而 E 蛋白的免疫优势一致性仅限于一个结构域（结构域 III）的肽。C 蛋白的表位预测比 E 蛋白更好，特别是对于跨膜区的预测错误。我们的数据提供了证据，证明了影响肽加工的蛋白质结构特征具有很强的影响力，这有助于解释在实验确定和计算机预测的 CD4+T 细胞表位之间观察到的差异。重要性：蜱传脑炎病毒在欧洲和亚洲的大部分地区流行，每年导致 1 万多例人类神经系统疾病。它与黄热病、登革热、日本脑炎和西尼罗河病毒密切相关，接种灭活疫苗可有效预防疾病。疫苗接种和自然感染都会诱导形成中和病毒感染力并介导保护的病毒表面蛋白抗体。合成这些抗体的 B 淋巴细胞需要其他淋巴细胞（辅助性 T 细胞）的帮助，辅助性 T 细胞识别来自病毒颗粒中包含的蛋白质的小肽。然而，这些肽中哪些主导疫苗接种和感染的免疫反应尚不清楚。在我们的研究中，我们展示了哪些蛋白质部分对辅助性 T 细胞反应贡献最大，突出了目前用于预测这些肽的方法的具体弱点，并展示了疫苗接种和感染之间的相似性和差异。
