Analysis of protective antigen and virulence factors of Lactococcus garvieae, fish bacterial pathogen

摘要：研究了garvieae乳球菌的细胞表面结构。发现了鸡胸草的高发育荚膜菌株（KG9408）和微荚膜菌株（MS93003）两种类型的细胞荚膜菌株，它们携带纤维状成分，从细胞表面突出。而一种染色剂（NSS9319）在其细胞表面既没有细胞荚膜也没有纤维状结构。高度发育的细胞荚膜菌株对鱼的毒力高于微荚膜菌株和非荚膜菌株。与KG9408、MS93003和NSS9310菌株相比，噬菌体对这3株菌株的敏感性明显不同。用福尔马林灭活的鸡乳球菌KG9408和MS93003免疫黄尾鱼对鸡乳球菌感染产生免疫保护作用。而接种NSS9310也能诱导免疫保护，但保护水平显著低于KG9408和ms93003。免疫NSS9310诱导保护作用。KG9408和MS93003黄尾鱼免疫血清被动免疫对黄尾鱼具有较强的保护作用，感染后细菌清除迅速。用兔抗KG9408和MS93003血清及黄尾抗KG9408和MS93003血清对鸡乳杆菌提取的蛋白进行免疫印迹分析，发现与KG9408和MS93003血清一样，未检出NSS9310中的部分条带。

ABSTRACT : Strains of Lactococcus garvieae were examined for the presence of cell surface structures. Two types of cell capsular strains such as highly developed capsule (KG9408) and micro-capsule (MS93003) of L. garvieae were found, carrying fimbrie-like components, projecting from cell surface. While one stain (NSS9319) has neither cell capsular nor fimbrie-like structures on its cell surface. Highly developed cell capsular strain indicated higher virulence to fish than that of micro-capsular or non-capsular strain. Bacteriphage susceptibilities to these three strains were clearly distinguished from KG9408 to MS93003 and NSS9310 strains. Immune protection against Lactococcus garvieae infection was induced in yellowtail, Seriola guinqueradiata immunized with formalin-killed L. garvieae KG9408 and MS93003. However immune protection was also induced by immunization of NSS9310, the level of protection was significantly lower than that of KG9408 andMS93003. protection was induced by immunization of NSS9310. Passive immunization with yellowtail immune sera raised against KG9408 and MS93003 conferred strong protection to yellowtail with the rapid bacterial clearance after the infection of L. garvieae. Immunoblotting analysis of proteins extracted from L. garvieae strains using rabbit anti-KG9408 and MS93003 serum, and yellowtail anti-KG9408 and MS93003 serum indicated that some bands from NSS9310 were not detected as seen in KG9408 and MS93003 strains.