title: A teleost complement factor Ba possesses antimicrobial activity and inhibits bacterial infection in fish.
abstract: Complement factor B (Bf) is a component of the complement system. Following activation of the alternative pathway of the complement system, factor B is cleaved into Ba and Bb fragments. In fish, the Bf of rainbow trout is known to act as a C3 convertase, but the function of the Ba fragment is essentially unknown. In this study, we examined the expression patterns of tongue sole Cynoglossus semilaevis Bf (named CsBf) and the biological activity of the Ba fragment of CsBf (named CsBa). CsBf possesses the conserved domains of Bf and shares 39.9%-56.4% sequence identities with other fish Bf. CsBf expression was high in liver, muscle, and heart, and low in intestine, blood, and kidney. Bacterial infection significantly induced CsBf expression in kidney, spleen, and liver in a time-dependent manner. Recombinant CsBa (rCsBa) exhibited apparent binding capacities to bacteria and tongue sole peripheral blood leukocytes, and binding of rCsBa to bacteria inhibited bacterial growth. When overexpressed in tongue sole, CsBa significantly reduced bacterial dissemination in fish tissues. Together these results indicate for the first time that a fish Ba possesses antibacterial effect as well as immune cell-binding capacity, and thus probably plays a role in host immune defense against bacterial infection.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Xue-Peng
authors.initials: XP
authors.lastname: Li
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China. Electronic address: lsun@qdio.ac.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism; D058491:Bacterial Load; D048708:Cell Growth Processes; D003001:Cloning, Molecular; D011415:Complement Factor B / Q000235:genetics / Q000378:metabolism*; D003170:Complement Pathway, Alternative; D020594:Edwardsiella / Q000276:immunology*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D005412:Flatfishes / Q000276:immunology*; D015870:Gene Expression; D016905:Gram-Negative Bacterial Infections / Q000276:immunology* / Q000628:therapy; D007113:Immunity, Innate; D011549:Pseudomonas / Q000276:immunology*; D014733:Vibrio / Q000276:immunology*
chemical_list: D000890:Anti-Infective Agents; D029941:Fish Proteins; D011415:Complement Factor B
keywords: Antimicrobial; Bacterial infection; Complement factor B; Cynoglossus semilaevis