Recombinant Salmonella expressing SspH2-EscI fusion protein limits its colonization in mice

• Main Authors: Maozhi Hu, Weixin Zhao, Wei Gao, Wenhua Li, Chuang Meng, Qiuxiang Yan, Yuyang Wang, Xiaohui Zhou, Shizhong Geng, Zhiming Pan, Guiyou Cui, Xinan Jiao
• Format: Article
• Language: English
• Published: BMC 2017-05-01
• Series: BMC Immunology
• Subjects: Salmonella; Inflammasome; SspH2-EscI; Mice; Colonization
• Online Access: http://link.springer.com/article/10.1186/s12865-017-0203-2

Abstract Background Activation of inflammasome contributes to the clearance of intracellular bacteria. C-terminus of E. coli EscI protein can activate NLRC4 (NLR family, CARD domain containing-4) inflammasome in macrophages. The purpose of this study was to determine if activation of NLRC4 inflammasome by EscI can reduce the colonization of Salmonella in mice. Results A recombinant S. typhimurium strain expressing fusion protein of the N-terminal SspH2 (a Salmonella type III secretion system 2 effector) and C-terminal EscI was constructed and designated as X4550(pYA3334-SspH2-EscI). In vitro assay showed that X4550(pYA3334-SspH2-EscI) significantly enhanced IL-1β and IL-18 secretion (P < 0.05) and pyroptotic cell death of mouse peritoneal macrophages, compared with those infected with control strain, X4550(pYA3334-SspH2). In vivo studies showed that colonization of X4550(pYA3334-SspH2-EscI) in both spleen and liver were significantly lower than that of X4550(pYA3334-SspH2) (P < 0.05). The bacterial counts of X4550(pYA3334-SspH2-EscI) in mice decreased, while those of X4550(pYA3334-SspH2) increased over the time after infection. Additionally, X4550(pYA3334-SspH2-EscI) induced a less pathological alteration in spleen and liver than X4550(pYA3334-SspH2). Conclusion Fusion protein SspH2-EscI may be translocated into macrophages and activate NLRC4 inflammasome, which limits Salmonella colonization in spleen and liver of mice.