Background

Legionella pneumophila is a Gram-negative intracellular bacterium and the cause of an atypical pneumonia in humans – legionnaire's disease. Immunological assessment of bacterial antigens clarifies the way that host may develop protection against the pathogen. Lipopolysaccharide (LPS) is the main antigen of Gram-negative bacteria but is less studied because of its carbohydrate nature. Here, we immunized mice with detoxified LPS in combination with immunogenic proteins and looked into the result of bacterial challenge.

Methods

LPS of L. pneumophila was extracted by hot phenol-water method. Purified LPS was detoxified by sodium hydroxide alkaline procedure. BALB/c mice were immunized mainly with non-covalent combination of detoxified LPS (dLPS) and either of recombinant FlaA or PAL separately. Afterwards, specific serum IgG was assessed by ELISA. Mice were challenged intravenously with sublethal dose of L. pneumpphila then splenocytes were cultured. Cytokine responses of splenocytes were analyzed by ELISA.

Results

Polysaccharide antigen did not elicit significant serum IgG. Combination of the dLPS with recombinant FlaA and PAL led to risen IgG and its subclasses (IgG1, IgG2a and IgG2b) against polysaccharide. Mice immunized with combination of the dLPS and recombinant proteins showed significant elevation of cytokine responses in splenocyte culture after being challenged with L. pneumophila.

Conclusions

Our results suggest that combination of polysaccharide antigen derived from Legionella LPS may confer raised cell-mediated responses against the pathogen when combined with Th-1 stimulating protein antigens. Although not covalently bond, Legionella detoxified LPS combination with recombinant FlaA and PAL effectively elicited Th-1 type cytokines and humoral responses against L. pneumophila in BALB/c mice.

中文翻译：

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用非共价结合重组鞭毛蛋白 A 和肽聚糖相关脂蛋白的解毒脂多糖进行疫苗接种后，小鼠中针对嗜肺军团菌的有效 T 细胞介导的免疫反应。

背景

嗜肺军团菌是一种革兰氏阴性细胞内细菌，是人类非典型肺炎（军团病）的病因。细菌抗原的免疫学评估阐明了宿主可能对病原体产生保护的方式。脂多糖 (LPS) 是革兰氏阴性菌的主要抗原，但由于其碳水化合物性质，研究较少。在这里，我们用解毒的 LPS 和免疫原性蛋白质对小鼠进行了免疫，并研究了细菌攻击的结果。

方法

L. pneumophila LPS采用热酚水法提取。纯化的LPS通过氢氧化钠碱性程序解毒。BALB/c 小鼠主要用解毒 LPS (dLPS) 和重组 FlaA 或 PAL 的非共价组合进行免疫。之后，通过ELISA评估特异性血清IgG。用亚致死剂量的嗜肺军团菌静脉内攻击小鼠，然后培养脾细胞。通过ELISA分析脾细胞的细胞因子反应。

结果

多糖抗原没有引起显着的血清 IgG。dLPS 与重组 FlaA 和 PAL 的组合导致针对多糖的 IgG 及其亚类（IgG1、IgG2a 和 IgG2b）升高。用 dLPS 和重组蛋白联合免疫的小鼠在受到嗜肺军团菌攻击后，脾细胞培养物中的细胞因子反应显着升高。

结论

我们的研究结果表明，当与 Th-1 刺激蛋白抗原结合时，来自军团菌LPS 的多糖抗原的组合可能会提高细胞介导的针对病原体的反应。虽然不是共价键，但军团菌解​​毒 LPS 与重组 FlaA 和 PAL 的组合在 BALB/c 小鼠中有效地引发了 Th-1 型细胞因子和针对嗜肺军团菌的体液反应。