Legionella pneumophila is a Gram-negative intracellular bacterium and causes legionnaire's disease an –atypical pneumonia in humans. 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 and O-antigen polysaccharide in combination with bovine serum albumin (BSA) and explored the immunological responses of mice to the bacterial infection.

LPS of L. pneumophila was extracted by hot phenol-water method. Purified LPS was detoxified by sodium hydroxide alkaline procedure. O-polysaccharide antigen (OPS) obtained by acetic acid treatment of LPS. BALB/c mice were immunized mainly with non-covalent combination of detoxified LPS (dLPS) or OPS with BSA separately. Pure polysaccharide antigens did not elicit significant serum IgG against LPS. Combination of the dLPS and OPS with BSA resulted in risen IgG and its subclasses (IgG1 and IgG2a) against lipopolysaccharide. Mice were challenged intravenously with sublethal dose of L. pneumpphila. Then, splenocytes were cultured and cytokine responses of splenocytes to pathogenic Legionella was studied by ELISA. Mice immunized with combination of the dLPS or OPS and BSA showed significant elevation of cytokine responses to pathogenic L. pneumophila.

Our results suggest that combination of the polysaccharide antigen derived from Legionella LPS may confer raised cell-mediated responses against the pathogen when combined with a protein antigen which is capable of eliciting cell-mediated responses. Although not covalently bond, Legionella polysaccharides combined with BSA effectively elicited Th-1 type cytokines and humoral responses against L. pneumophila in BALB/c mice.

嗜肺军团菌是革兰氏阴性细胞内细菌，可导致军团菌病和人类非典型肺炎。脂多糖（LPS）是革兰氏阴性细菌的主要抗原，但由于其碳水化合物性质而被研究较少。在这里，我们用解毒的LPS和O-抗原多糖结合牛血清白蛋白（BSA）免疫小鼠，并探索了小鼠对细菌感染的免疫反应。

用热酚水法提取嗜肺乳杆菌的LPS 。通过氢氧化钠碱法将纯化的LPS解毒。通过LPS的乙酸处理获得的O-多糖抗原（OPS）。主要用解毒的LPS（dLPS）或OPS与BSA的非共价组合分别免疫BALB / c小鼠。纯多糖抗原未引起针对LPS的显着血清IgG。dLPS和OPS与BSA的组合导致针对脂多糖的IgG及其亚类（IgG1和IgG2a）升高。用亚致死剂量的肺炎乳杆菌静脉内攻击小鼠。然后，培养脾细胞，并且脾细胞对致病军团菌的细胞因子反应通过ELISA进行了研究。免疫的小鼠用的DLP或OPS的组合和BSA表现出细胞因子的反应致病显著海拔嗜肺军团菌。

我们的结果表明，与军团菌属LPS衍生的多糖抗原结合时，与能引起细胞介导的反应的蛋白抗原结合，可提高针对病原体的细胞介导的反应。尽管不是共价键，军团菌多糖与BSA结合有效地诱导了BALB / c小鼠的Th-1型细胞因子和针对肺炎链球菌的体液反应。