马链球菌兽疫亚种IdeZ抗体降解酶特性研究

Characteristics of IgG degradation enzyme IdeZ in Streptococcus equi ssp. zooepidimicus

本实验室前期研究通过基因组序列比对发现SEZ ATCC 35246株Ide Z基因与化脓链球菌抗体降解蛋白IdeS基因有较高同源性。为进一步了解马链球菌兽疫亚种(SEZ)中Ide Z基因编码蛋白的生物学功能及其可能在细菌抵抗吞噬过程中的作用,本研究利用pCold-SUMO重组系统表达可溶性重组蛋白IdeZ,采用体外模拟抗体降解的试验检测IdeZ蛋白降解IgG抗体的活性。结果显示,在37℃条件下,IdeZ蛋白表现出高效的抗体降解活性,体外反应10 min即可用SDS-PAGE检测到IgG降解产物;借助巨噬细胞Raw264.7细胞模型,体外模拟巨噬细胞吞噬SEZ试验检测IdeZ蛋白对抗体介导的巨噬细胞吞噬SEZ活性的影响,结果显示,IdeZ蛋白可有效抑制SEZ免疫小鼠血清或其纯化的IgG的吞噬功能。表明IdeZ蛋白有助于SEZ抵抗巨噬细胞的吞噬功能。本研究为进一步揭示SEZ抵抗巨噬细胞吞噬机制提供了新的切入点。

Streptococcus equi ssp. zooepidimicus （SEZ） has the ability of anti-phagocytosis. This pathogen causes swine streptococcosis. SEZ ATCC35246 IdeZ gene has high homology with the IgG-degrading enzyme of Streptococcus pyogene （IdeS） gene. In present study, we expressed and purified the recombinant IdeZ protein through His trap and molecular sieve chromatography. In vitro test results showed that the IdeZ protein was able to digest IgG at 37℃ within 10 min after incubation with IgG as 1：100 （m/m）. With the Raw264.7 macrophage cell model, we found that IdeZ decreased the oposonization of anti-SEZ serum or its purified IgG and suppressed the phagocytosis of macrophage to SEZ. This study provides valuable reference in illustrating the anti-phagocytosis mechanism based on antibody digestion in SEZ.