Several oral bacteria, including Prevotella melaninogenica (Pm), have aquaporin (AQP) proteins homologous to human AQP5, a major water channel protein targeted in Sjogren's syndrome. This study aimed to understand the antigenic characteristics that induce autoantibodies against an AQP5 “E” epitope (AQP5E) in a mouse model using C57BL/6 mice. Immunization with a PmE-L peptide derived from Pm AQP, which contains amino acid mismatches both at the B- and T-cell epitopes, efficiently induced anti-AQP5E autoantibodies accompanied by increased germinal center (GC) B and follicular helper T cells in the draining lymph nodes. However, PmE, a peptide lacking a T-cell epitope, and AQP5E-L, an AQP5-derived self-peptide, hardly induced either anti-AQP5E autoantibodies or GC responses. Surprisingly, OTII-AQP5E, a peptide that replaced the self T-cell epitope of AQP5E-L with an ovalbumin-derived foreign T-cell epitope, was not any better than AQP5E-L in the induction of anti-AQP5E autoantibodies and GC response, despite the substantial expansion of CD4⁺ T cells and production of anti-OTII-AQP5E antibodies. The complex of biotinylated PmE-L peptide and highly immunogenic streptavidin (SA) induced a strong extrafollicular B-cell response skewed toward the expansion of SA-specific B cells. However, the expansion of AQP5E-specific GC B cells was limited, resulting in the inefficient induction of anti-AQP5E autoantibodies. Collectively, our results have demonstrated that anti-AQP5E autoantibody production is only allowed when foreign B- and T-cell epitopes drive a strong GC response of AQP5E-specific B cells for affinity maturation. This study helps explain why cross-reactive anti-AQP5 autoantibodies are not produced during the immune response to Pm in most healthy people.

中文翻译：

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小鼠模型中抗水通道蛋白 5 自身抗体生产的要求

包括黑色素普雷沃菌(Pm) 在内的多种口腔细菌具有与人类 AQP5 同源的水通道蛋白 (AQP)，AQP5 是干燥综合征的主要水通道蛋白。本研究旨在了解在使用 C57BL/6 小鼠的小鼠模型中诱导针对 AQP5“E”表位 (AQP5E) 的自身抗体的抗原特征。使用源自 Pm AQP 的 PmE-L 肽进行免疫，该肽在 B 细胞和 T 细胞表位均含有氨基酸错配，可有效诱导抗 AQP5E 自身抗体，同时增加生发中心 (GC) B 和滤泡辅助 T 细胞的数量。引流淋巴结。然而，PmE（一种缺乏T细胞表位的肽）和AQP5E-L（一种AQP5衍生的自肽）几乎不诱导抗AQP5E自身抗体或GC反应。令人惊讶的是，OTII-AQP5E（一种用卵清蛋白衍生的外源 T 细胞表位取代 AQP5E-L 自身 T 细胞表位的肽）在诱导抗 AQP5E 自身抗体和 GC 反应方面并不比 AQP5E-L 更好。 ，尽管 CD4 ⁺ T 细胞大幅扩增并产生抗 OTII-AQP5E 抗体。生物素化 PmE-L 肽和高免疫原性链霉亲和素 (SA) 的复合物诱导强烈的滤泡外 B 细胞反应，偏向于 SA 特异性 B 细胞的扩增。然而，AQP5E特异性GC B细胞的扩增受到限制，导致抗AQP5E自身抗体的诱导效率低下。总的来说，我们的结果表明，只有当外源 B 和 T 细胞表位驱动 AQP5E 特异性 B 细胞产生强烈的 GC 反应以实现亲和力成熟时，才允许产生抗 AQP5E 自身抗体。这项研究有助于解释为什么大多数健康人在对 Pm 的免疫反应过程中不会产生交叉反应性抗 AQP5 自身抗体。