Safety and immunogenicity of an oral DNA vaccine encoding Sip of Streptococcus agalactiae from Nile tilapia Oreochromis niloticus delivered by live attenuated Salmonella typhimurium

L Y Huang; K Y Wang; D Xiao; D F Chen; Y Geng; J Wang; Y He; E L Wang; J L Huang; G Y Xiao

doi:10.1016/j.fsi.2014.02.017

Safety and immunogenicity of an oral DNA vaccine encoding Sip of Streptococcus agalactiae from Nile tilapia Oreochromis niloticus delivered by live attenuated Salmonella typhimurium

Fish Shellfish Immunol. 2014 May;38(1):34-41. doi: 10.1016/j.fsi.2014.02.017. Epub 2014 Mar 12.

Authors

L Y Huang¹, K Y Wang², D Xiao³, D F Chen⁴, Y Geng⁵, J Wang¹, Y He¹, E L Wang¹, J L Huang¹, G Y Xiao¹

Affiliations

¹ Research Center of Fish Disease, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
² 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: [email protected].
³ Animal Health Research Institute of Tongwei Co., Ltd., Chengdu, Sichuan 610041, People's Republic of China.
⁴ 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.
⁵ Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.

PMID: 24631734
DOI: 10.1016/j.fsi.2014.02.017

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.

Keywords: Attenuated Salmonella typhimurium; DNA vaccine; Oral immunization; Streptococcus agalactiae sip gene; Tilapia.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Administration, Oral
Animals
Antibodies, Bacterial
Antigens, Bacterial / immunology*
Antigens, Bacterial / metabolism
Cichlids*
Fish Diseases / prevention & control*
Plasmids / metabolism
Salmonella typhimurium / metabolism*
Streptococcal Vaccines / adverse effects
Streptococcal Vaccines / immunology*
Streptococcus agalactiae / immunology*
Streptococcus agalactiae / metabolism
Vaccines, DNA / administration & dosage
Vaccines, DNA / adverse effects
Vaccines, DNA / immunology

Substances

Antibodies, Bacterial
Antigens, Bacterial
SIP protein, Streptococcus group B
Streptococcal Vaccines
Vaccines, DNA