title: A divalent DNA vaccine based on Sia10 and OmpU induces cross protection against Streptococcus iniae and Vibrio anguillarum in Japanese flounder.
abstract: Streptococcosis and vibriosis caused by Streptococcus iniae and Vibrio anguillarum respectively have affected fish culture industries around the world. Previous studies have indicated that the S. iniae antigen Sia10 and the V. anguillarum outer membrane protein OmpU, when used as DNA vaccines, induce protection in turbot (Scophthalmus maximus) and Asian seabass (Lates calcarifer) respectively. In this study, with an effort to develop effective vaccines against S. iniae and V. anguillarum, we constructed three DNA vaccines based on Sia10 and OmpU and examined their immune effects in a model of Japanese flounder (Paralichthys olivaceus), which in China is known to suffer from both streptococcosis and vibriosis. Of the three DNA vaccines constructed in this study, pIDSia10 and pIDOmpU express Sia10 and OmpU respectively, while pSiVa1 expresses Sia10 and OmpU as two individual proteins translated from a single bicistronic mRNA transcript. At 7 and 28 days post-vaccination, vaccine plasmids and expression of the vaccine-encoding genes were detected in the muscle, spleen, kidney, and liver of the vaccinated fish. Immunocolloidal gold electron microscopy detected production of Sia10 and OmpU proteins in pIDSia10- and pIDOmpU-vaccinated fish respectively, while both Sia10 and OmpU proteins were detected in pSiVa1-vaccinated fish. At one and two months post-vaccination, fish vaccinated with pIDSia10 and pSiVa1 exhibited comparable relative percent of survival (RPS) rates (80%-87%) following lethal S. iniae challenge. Similar protection rates were produced by fish vaccinated with pIDOmpU and pSiVa1 following lethal V. anguillarum challenge. Immunological analysis showed that (i) all vaccines induced specific serum antibody production which enhanced complement-mediated bactericidal activity, and (ii) pSiVa1 modulated the expression of a wide spectrum of immune relevant genes in a time-dependent manner. Together these results indicate that pSiVa1 is an effective bivalent vaccine that induces strong cross protection in flounder against S. iniae and V. anguillarum.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Sun
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Chun-sheng
authors.initials: CS
authors.lastname: Liu
authors.forename: Reng
authors.initials: R
authors.lastname: Qiu
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D001770:Blood Bactericidal Activity; D056738:Cross Protection; D005393:Fish Diseases / Q000276:immunology / Q000517:prevention & control*; D005432:Flounder; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D011897:Random Allocation; D013290:Streptococcal Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D013291:Streptococcus / Q000276:immunology; D019444:Vaccines, DNA / Q000276:immunology; D014733:Vibrio / Q000276:immunology; D014735:Vibrio Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D019444:Vaccines, DNA