Edwardsiella tarda sialidase: pathogenicity involvement and vaccine potential.
Bacterial sialidases are a group of glycohydrolases that are known to play an important role in invasion of host cells and tissues. In this study, we examined in a model of Japanese flounder (Paralichthys olivaceus) the potential function of NanA, a sialidase from the fish pathogen Edwardsiella tarda. NanA is composed of 670 residues and shares low sequence identities with known bacterial sialidases. In silico analysis indicated that NanA possesses a sialidase domain and an autotransporter domain, the former containing five Asp-boxes, a RIP motif, and the conserved catalytic site of bacterial sialidases. Purified recombinant NanA (rNanA) corresponding to the sialidase domain exhibited glycohydrolase activity against sialic acid substrate in a manner that is pH and temperature dependent. Immunofluorescence microscopy showed binding of anti-rNanA antibodies to E. tarda, suggesting that NanA was localized on cell surface. Mutation of nanA caused drastic attenuation in the ability of E. tarda to disseminate into and colonize fish tissues and to induce mortality in infected fish. Likewise, cellular study showed that the nanA mutant was significantly impaired in the infectivity against cultured flounder cells. Immunoprotective analysis showed that rNanA in the form of a subunit vaccine conferred effective protection upon flounder against lethal E. tarda challenge. rNanA vaccination induced the production of specific serum antibodies, which enhanced complement-mediated bactericidal activity and reduced infection of E. tarda into flounder cells. Together these results indicate that NanA plays an important role in the pathogenesis of E. tarda and may be exploited for the control of E. tarda infection in aquaculture.
Department of Marine Biology, Ocean University of China, Qingdao, China.
Ren-ping
RP
Jin
Yong-hua
YH
Hu
Bo-guang
BG
Sun
Xiao-hua
XH
Zhang
Li
L
Sun
D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology*; D018929:Cell Culture Techniques / Q000662:veterinary; D020609:Edwardsiella tarda / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005393:Fish Diseases / Q000276:immunology / Q000517:prevention & control*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D005432:Flounder; D007274:Injections, Intraperitoneal / Q000662:veterinary; D008856:Microscopy, Fluorescence / Q000662:veterinary; D008969:Molecular Sequence Data; D007652:Oxo-Acid-Lyases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000276:immunology; D016415:Sequence Alignment / Q000662:veterinary; D020539:Sequence Analysis, Protein / Q000662:veterinary; D022223:Vaccines, Subunit / Q000276:immunology; D014614:Vaccines, Synthetic / Q000276:immunology; D014774:Virulence
D001428:Bacterial Vaccines; D029941:Fish Proteins; D011994:Recombinant Proteins; D022223:Vaccines, Subunit; D014614:Vaccines, Synthetic; D007652:Oxo-Acid-Lyases; C018728:N-acetylneuraminate lyase