Interaction of Group B Streptococcus sialylated capsular polysaccharides with host Siglec-like molecules dampens the inflammatory response in tilapia

文献类型： 外文期刊

第一作者： Dong, Junjian

作者： Dong, Junjian;Sun, Chengfei;Tian, Yuanyuan;Hu, Jie;Shi, Hongya;Zhang, Dengfeng;Lu, Maixin;Ye, Xing;Wei, Yuanzheng;Shi, Hongya;Lu, Maixin;Ye, Xing

作者机构：

关键词： Oreochromis niloticus; Group B Streptococcus (GBS); Sialylated capsular polysaccharides; Siglec-like; Anti-inflammatory cytokine; Proinflammatory cytokines

期刊名称：MOLECULAR IMMUNOLOGY （ 影响因子：4.407； 五年影响因子：4.227 ）

ISSN： 0161-5890

年卷期： 2018 年 103 卷

页码：

收录情况： SCI

摘要： Group B Streptococcus (GBS, S. agalactiae) infection in tilapia (Oreochromis niloticus) causes widespread death of this species and is a significant issue for the aquaculture industry. The major virulence factor for GBS is its sialylated capsular polysaccharides (CPs). These CPs interact with sialic acid-binding immunoglobulin-like lectins (Siglecs) on the host immune cells to regulate the downstream inflammatory response and evade detection. Previously, we cloned multiple Siglec-like molecules from an O. niloticus cDNA library, all of which were shown to interact with the sialylated CPs of GBS. In the present study, we investigated the effects of GBS infection on the expression of pro- and anti-inflammatory cytokines in O. niloticus as well as OnSiglec-like-transfected macrophage cells. Eukaryotic expression vectors containing full-length OnSiglec-1-like, -4b-like, -14-like were constructed and used to transfect RAW264 macrophages in vitro as well as live tilapia in vivo prior to GBS infection. The expression of the anti-inflammatory cytokine interleukin (IL)-10 and the pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha, IL-6, and interferon (INF)-beta were then analyzed by qPCR. Our results indicate that as infection progressed, IL-10 expression was significantly upregulated, while that of TNF-alpha and IL-6 were significantly downregulated in the OnSiglec-like-transfected cells. INF-beta expression was also downregulated in cells transfected with OnSiglec-1-like and -4b-like, but was not significantly effected in OnSiglec-14-like-transfected cells. Notably, the magnitude of these cytokine expression changes was greatly decreased when a Delta neuA GBS mutant was used to infect the OnSiglec-1-like-transfected cells. In GBS-infected tilapia, IL-10 expression was significantly upregulated in all tissues, whereas INF-beta expression in the spleen, kidney, and gills was significantly downregulated at 12 hpi. While the expression of TNF-alpha was slightly upregulated, this change was not significant. In GBS Delta neuA mutant-infected O. niloticus, IL-10 expression in all of the tissues was significantly lower than that observed for the wild-type GBS group, while TNF-alpha expression was higher in the mutant infected group. There was no significant difference in INF-beta expression between the two groups. Taken together, sialylated CPs on GBS appear to interact with host OnSiglec-like molecules to transmit negative regulatory signals via enhanced anti-inflammatory cytokine IL-10 production and reduced pro-inflammatory cytokine production, ultimately leading to dampening of the host immune response. The results of this study further elucidate the molecular mechanism underlying GBS infection in tilapia and also provide candidate drug target molecules.

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