Veterinary Research Institute, Hudcova 70, Brno 621 00, Czech Republic.
Vet Microbiol. 2011 May 12;150(1-2):167-72. doi: 10.1016/j.vetmic.2011.01.007. Epub 2011 Jan 15.
The key process for immune response development is the recognition of bacteria by the immune system of the host based on the sensing of pathogen-associated molecular patterns (PAMP). One of the most important PAMP is the lipopolysaccharide (LPS) molecule, a complex molecule present in the outer membrane of Gram negative bacteria. In this study we were interested in how different parts of the LPS of Salmonella enterica serovar Enteritidis are recognized by porcine neutrophils. To this aim, we constructed S. Enteritidis mutants with rfaL and rfaC genes disabled in the attachment of the O-antigen and in the synthesis of the inner oligosaccharide core of LPS, respectively. We found that in the absence of serum, both the rfa mutants associated with neutrophils and stimulated them for reactive oxygen species (ROS) production significantly more than the wild-type strain. Addition of polymyxin B, which neutralized lipid A, the endotoxic moiety of LPS, effectively decreased the association of the wild-type strain and the rfaC mutant with neutrophils, but not the rfaL mutant. This indicates that the oligosaccharide core newly exposed on the surface in the rfaL mutant, protected from interaction in the wild-type strain by the O-antigen but completely absent in the rfaC mutant, may represent a new ligand for porcine neutrophils that cannot be neutralized by polymyxin B.
免疫反应发展的关键过程是宿主免疫系统基于对病原体相关分子模式（PAMP）的感知来识别细菌。最重要的 PAMP 之一是脂多糖（LPS）分子，它是革兰氏阴性菌外膜中存在的复杂分子。在这项研究中，我们感兴趣的是沙门氏菌肠炎亚种 LPS 的不同部分如何被猪中性粒细胞识别。为此，我们构建了 rfaL 和 rfaC 基因失活的沙门氏菌肠炎亚种突变体，分别在 O 抗原的附着和 LPS 内寡糖核心的合成中失活。我们发现，在没有血清的情况下，两种 rfa 突变体与中性粒细胞结合并刺激它们产生活性氧（ROS）的能力明显强于野生型菌株。添加多粘菌素 B，可中和 LPS 的内毒素部分脂多糖 A，有效降低了野生型菌株和 rfaC 突变体与中性粒细胞的结合，但 rfaL 突变体不受影响。这表明 rfaL 突变体表面新暴露的寡糖核心，由于 O 抗原的存在而免受野生型菌株的相互作用，但在 rfaC 突变体中完全缺失，可能代表了一种新的猪中性粒细胞配体，不能被多粘菌素 B 中和。
