Actinobacillus pleuropneumoniaesecretes the hemolytic cytotoxins ApxI, ApxII, ApxIII, and ApxIV, which cause pleurop- neumonia in swine. Of these, ApxI is the most toxic. ApxIA, a repeats-in-toxin toxin-like protein, has strong hemolytic and cytotoxic activities. This study aimed to develop an immune modulator ApxIA toxoid, with a Spytag/Spycatcher pair (SC::ST pair), in yeast ghost shells (YGSs). These YGSs were utilized as ApxIA toxoid delivery platforms for -glucan components that can be recognized by the innate immune system. The SC::ST pair was used to conjugate the ApxIA toxoid to YGSs. The YGS-SC::ST-ToxApxIA was successfully phagocytosed by RAW 264.7 macrophages cells, without any toxicity. Further investigation revealed that YGS-SC::ST-ToxApxIA led to defective immune responses, in addition to increased levels of cytokines IL-1β, TNF-α, and IL-10. A membrane proteomic analysis, to determine preferential major histocompatibility complex binding of ApxIA-derived peptides, was performed and four ApxIA peptides were successfully identified by liquid chromatography with tandem mass spectrometry analysis. The identified peptides may serve as poten- tial vaccine candidates in immunobiology studies of A. pleuropneumoniae. Our results indicate that YGS-SC::ST-ToxApxIA can prevent A. pleuropneumoniae pleuropneumonia (APP) by inducing both humoral and cellular immune responses.

中文翻译：

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SpyCatcher-SpyTagged ApxIA类毒素和免疫调节酵母鬼壳。

胸膜肺炎放线杆菌分泌溶血性细胞毒素ApxI，ApxII，ApxIII和ApxIV，它们会引起猪胸膜肺炎。其中，ApxI最有毒。ApxIA是一种毒素中的重复毒素样蛋白，具有很强的溶血和细胞毒活性。这项研究旨在开发一种在酵母鬼壳（YGSs）中具有Spytag / Spycatcher对（SC :: ST对）的免疫调节剂ApxIA类毒素。这些YGS被用作可被先天免疫系统识别的-葡聚糖成分的ApxIA类毒素递送平台。使用SC :: ST对将ApxIA类毒素与YGS缀合。YGS-SC :: ST-ToxApxIA被RAW 264.7巨噬细胞成功吞噬，没有任何毒性。进一步的研究表明，除了增加细胞因子IL-1β，TNF-α和IL-10的水平外，YGS-SC :: ST-ToxApxIA还导致免疫应答缺陷。进行了膜蛋白质组学分析，以确定ApxIA衍生肽的优先主要组织相容性复合物结合，并通过液相色谱-串联质谱分析成功鉴定了四种ApxIA肽。鉴定出的肽可能在免疫生物学研究中作为潜在的候选疫苗胸膜肺炎单胞菌。我们的结果表明，YGS-SC :: ST-ToxApxIA可以通过诱导体液和细胞免疫应答来预防胸膜肺炎放线杆菌（APP）。