title: Safety and immunogenicity of an oral DNA vaccine encoding Sip of Streptococcus agalactiae from Nile tilapia Oreochromis niloticus delivered by live attenuated Salmonella typhimurium.
abstract: Attenuated Salmonella typhimurium SL7207 was used as a carrier for a reconstructed DNA vaccine against Streptococcus agalactiae. A 1.02 kb DNA fragment, encoding for a portion of the surface immunogenic protein (Sip) of S. agalactiae was inserted into pVAX1. The recombinant plasmid pVAX1-sip was transfected in EPC cells to detect the transient expression by an indirect immunofluorescence assay, together with Western blot analysis. The pVAX1-sip was transformed by electroporation into SL7207. The stability of pVAX1-sip into Salmonella was over 90% after 50 generations with antibiotic selection in vitro while remained stable over 80% during 35 generations under antibiotic-free conditions. The LD50 of SL/pVAX1-sip was 1.7 × 10(11) CFU/fish by intragastric administration which indicated a quite low virulence. Tilapias were inoculated orally at 10(8) CFU/fish, the recombinant bacteria were found present in intestinal tract, spleens and livers and eventually eliminated from the tissues 4 weeks after immunization. Fish immunized at 10(7), 10(8) and 10(9) CFU/fish with different immunization times caused various levels of serum antibody and an effective protection against lethal challenge with the wild-type strain S. agalactiae. Integration studies showed that the pVAX1-sip did not integrate with tilapia chromosomes. The DNA vaccine SL/pVAX1-sip was proved to be safe and effective in protecting tilapias against S. agalactiae infection.
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: L Y
authors.initials: LY
authors.lastname: Huang
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China. Electronic address: kywangsicau@126.com.
authors.forename: K Y
authors.initials: KY
authors.lastname: Wang
authors.affiliation: Animal Health Research Institute of Tongwei Co., Ltd., Chengdu, Sichuan 610041, People's Republic of China.
authors.forename: D
authors.initials: D
authors.lastname: Xiao
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China; Department of Aquaculture, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: D F
authors.initials: DF
authors.lastname: Chen
authors.affiliation: Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: Y
authors.initials: Y
authors.lastname: Geng
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: E L
authors.initials: EL
authors.lastname: Wang
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: J L
authors.initials: JL
authors.lastname: Huang
authors.affiliation: Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
authors.forename: G Y
authors.initials: GY
authors.lastname: Xiao
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial / Q000276:immunology* / Q000378:metabolism; D023681:Cichlids; D005393:Fish Diseases / Q000517:prevention & control*; D010957:Plasmids / Q000378:metabolism; D012486:Salmonella typhimurium / Q000378:metabolism*; D022541:Streptococcal Vaccines / Q000009:adverse effects / Q000276:immunology*; D013292:Streptococcus agalactiae / Q000276:immunology* / Q000378:metabolism; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; C414463:SIP protein, Streptococcus group B; D022541:Streptococcal Vaccines; D019444:Vaccines, DNA
keywords: Attenuated Salmonella typhimurium; DNA vaccine; Oral immunization; Streptococcus agalactiae sip gene; Tilapia