Key Laboratory of Diagnostic Medicine designated by the Ministry of Education, Department of Laboratory Medicine, Chongqing Medical University, Chongqing 400016, People's Republic of China.
Exp Biol Med (Maywood). 2012 Jun;237(6):694-702. doi: 10.1258/ebm.2012.011383. Epub 2012 Jun 22.
Streptococcus pneumoniae resides on the mucosal surface of the upper respiratory tract and is ready to spread and trigger clinical diseases. Hence the vaccine that can eliminate the nasopharyngeal colonization was thought to be an ideal protective strategy against pneumococcal invasive diseases. Caseinolytic protease X (ClpX), a pneumococcal caseinolytic protease ATPase subunit, was shown to be a non-transmembrane protein by bioinformatics analysis. Consistent with the in silico prediction, the secretory expression of ClpX, instead of surface exposure, was further confirmed by flow cytometry and Western blot. Furthermore, ClpX was highly conserved in nine different serotypes of S. pneumoniae at both gene and protein concentrations. In addition, the anti-ClpX IgG antibody levels in human serum samples were much higher in healthy children, compared with pediatric patients, and displayed an age-related increase. Finally, ClpX protein antigen was introduced to BALB/c mice through a mucosal route, and protection against nasopharyngeal colonization and lethal infection caused by different S. pneumoniae serotypes was successfully elicited. Our findings suggest that ClpX is a potential candidate antigen that could be incorporated in pneumococcal protein vaccines.
肺炎链球菌定植于上呼吸道的黏膜表面，随时准备传播并引发临床疾病。因此，能够消除鼻咽部定植的疫苗被认为是预防肺炎球菌侵袭性疾病的理想保护策略。生物信息学分析显示，裂合蛋白酶 X（ClpX）是一种肺炎链球菌的裂合蛋白酶 ATP 酶亚基，是非跨膜蛋白。与计算机预测一致，ClpX 的分泌表达（而非表面暴露）通过流式细胞术和 Western blot 进一步得到证实。此外，ClpX 在 9 种不同血清型的肺炎链球菌中，无论是在基因水平还是蛋白浓度上都高度保守。此外，与肺炎患儿相比，健康儿童血清样本中的抗 ClpX IgG 抗体水平要高得多，且呈现出与年龄相关的增长。最后，ClpX 蛋白抗原通过黏膜途径被引入 BALB/c 小鼠体内，成功诱导了针对不同血清型肺炎链球菌的鼻咽部定植和致死性感染的保护作用。我们的研究结果表明，ClpX 是一种有潜力的候选抗原，可以被纳入肺炎球菌蛋白疫苗中。
