糖基水解酶参与猪链球菌2型的致病作用

Glycosyl hydrolase contributes to the pathogenicity of Streptococcus suis type 2

摘要:

【背景】猪链球菌2型(Streptococcus suis serotype 2, SS2)是一种重要的人畜共患病原菌，可引起猪和人的严重感染，导致肺炎和感染性休克，甚至死亡。【目的】尽管多数毒力因子被相继发现，但其致病机制仍不清晰，寻找新的毒力因子或毒力相关基因进一步解析其致病机理依旧迫在眉睫。【方法】基于前期SS2的Tn917转座子插入突变体库的大蜡螟幼虫筛选结果，选取了一株致病性显著下降的插入突变体，其突变基因鉴定为B9H01_RS10315，编码糖基水解酶(glycosyl hydrolase, ghA)。通过构建ghA基因的缺失株(∆ghA)及回补株(C∆ghA)，进行生长观察和体内体外致病力试验，探究ghA参与的致病作用。【结果】相较于野生株，缺失株∆ghA表现出一定的生长缺陷，大蜡螟幼虫24 h致死率下降25%，对上皮细胞的黏附能力下降约50%，在全血中存活能力下降约35%，以及在细菌对细胞10倍和50倍的感染比下被吞噬细胞的吞噬增加约100%和200%。【结论】猪链球菌2型糖基水解酶GhA有助于细菌的生长，并通过促进细菌黏附、血液存活、抗吞噬能力等参与其致病过程。

关键词:猪链球菌;致病作用;毒力基因;糖基水解酶

Abstract:

[Background] Streptococcus suis serotype 2 (SS2) is a significant zoonotic pathogen responsible for severe infections in pigs and humans, resulting in pneumonia, septic shock, and even death. [Objective] Despite the diverse virulence factors identified, the underlying pathogenic mechanism of SS2 remains unclear. Therefore, it is urgent to search for new virulence factors or virulence-related genes for elucidating the pathogenic mechanism. [Methods] An insertion mutant with significantly attenuated pathogenicity in Galleria mellonella larvae was selected from the Tn917 transposon insertion mutant library of SS2, and its mutated gene was identified as B9H01_RS10315, which encoded a glycosyl hydrolase (ghA). An isogenic deletion mutant of ghA (∆ghA) and its complementary strain (C∆ghA) were constructed, and the growth and pathogenicity of the mutants were determined to reveal the pathogenic role of ghA. [Results] Compared with the wild type, ∆ghA displayed a growth defect, a 25% decrease in mortality of Galleria mellonella larvae within 24 h, a reduction of about 50% in adhesion to epithelial cells, a decrease of about 35% in survival in whole blood, and increases of about 100% and 200% in phagocytosis by phagocytes at 10:1 and 50:1 infection ratios, respectively. [Conclusion] The glycosyl hydrolase GhA promotes the growth and participates in the pathogenic process of SS2 by promoting the adhesion, improving the survival in blood, and resisting phagocytosis.

Key words:Streptococcus suis;pathogenicity;virulence gene;glycosyl hydrolase