Research Papers: Immunology:
Identification and screening of effective protective antigens for channel catfish against Streptococcus iniae
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Yajun Wang1,2,*, Erlong Wang1,*, Yang He1,*, Kaiyu Wang1,3, Qian Yang1, Jun Wang1, Yi Geng1,3, Defang Chen4, Xiaoli Huang4, Ping Ouyang1, Weimin Lai1 and Cunbin Shi2
1 Department of Basic Veterinary, Sichuan Agricultural University, Chengdu, Sichuan, China
2 Pearl River Fishery Research Institute, Chinese Academy of Fishery Science, Guangzhou, Guangdong, China
3 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, Sichuan, China
4 Department of Aquaculture, Sichuan Agricultural University, Chengdu, Sichuan, China
* These authors have contributed equally to this work
Kaiyu Wang, email:
Keywords: Streptococcus iniae; immunogens; immunogenicity; subunit vaccines; channel catfish; Immunology and Microbiology Section; Immune response; Immunity
Received: February 16, 2017 Accepted: March 13, 2017 Published: March 22, 2017
Vaccination is a potential approach for prevention and control of disease in fish. The use of genetically engineered vaccines is an effective method and a green intervention to control bacterial infection in aquaculture. However, efforts to develop these vaccines are limited by the lack of conserved protective antigens. In this study, three candidate immunogens (Srr, NeuA, and Hsp) of the pathogenic Streptococcus iniae strain DGX07 isolated from diseased channel catfish were identified and analyzed. Molecular cloning, expression, and purification of candidate antigen genes were carried out to obtain the candidate immunogens in the form of recombinant subunit vaccines. Western blotting was performed to evaluate immunogenicity in vitro and channel catfish were vaccinated by intraperitoneal injection and the specific antibody titers and relative percent of survival were determined to evaluate immune protection in vivo. The results showed that these three candidate immunogens were expressed correctly as recombinant proteins fused with His tags, with molecular weights of 70 kDa for Srr, 86 kDa for NeuA, and 51 kDa for Hsp, respectively. Moreover, each immunogen was predicted to be located either extracellularly or on the surface of S. iniae, and were able to offer protection against S. iniae infection in the form of recombinant subunit vaccines with adjuvant ISA763, especially Srr, with a relative percent of survival of 70% for Srr, 55% for NeuA, and 50% for Hsp, respectively.
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