关键词: 猪链球菌2型, 溶菌酶释放蛋白, 细胞融合, 细胞凋亡, 血管内皮细胞

Abstract: Streptococcus suis type 2 (SS2) mainly causes meningitis of human and pigs. Muramidase-released protein (MRP) is one of the key virulence factors of SS2. However，the pathogenic effects of MRP on microvascular endothelial cells (MEC) which makes up of brain blood barrier (BBB) is unknown to date. So the spleen microvascular endothelial cells (SMEC) from neonatal rabbit were isolated, purified, immortalized by SV40-T antigen, and used as cell model in present study. After co-incubation with electrophoretically purified MRP, two principal morphologic changes of SMEC confluent layer were revealed by light microscopy. Firstly, the confluent cell layer turned into a riddle-like structure full of giant hole. Secondly, cells were fused into syncytia which scattered in the hole, containing 10～30 nuclei. The nuclei were then released from the syncytia after an extreme condensation. And finally, the syncytia disappeared. Results of present study suggest that MRP alone is sufficient to destroy the brain blood barrier.

Key words: Streptococcus suis type 2, Muramidase-released protein, Apoptosis, Cell fusion, Microvascular endothelial cells