Identification and screening of effective protective antigens for channel catfish against Streptococcus iniae.

Yajun Wang,Kaiyu Wang,Erlong Wang,Weimin Lai,Cunbin Shi,Yang He,Ping Ouyang,Jun Wang,Xiaoli Huang,Yi Geng,Defang Chen,Qian Yang

doi:10.18632/oncotarget.16475

Yajun Wang, Kaiyu Wang + Show 10 more

Open Access

https://doi.org/10.18632/oncotarget.16475

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Abstract

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.

Highlights

Channel catfish (Ictalurus punctatus) is a highly adaptive species extensively cultured worldwide that is the leading aquaculture species in China and accounts for more than 60% of aquaculture production in the United States [1]
Three candidate protective immunogens of S. iniae DGX07 isolated from diseased channel catfish were identified and analyzed
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

Summary

Introduction

Channel catfish (Ictalurus punctatus) is a highly adaptive species extensively cultured worldwide that is the leading aquaculture species in China and accounts for more than 60% of aquaculture production in the United States [1]. It had been demonstrated that S. iniae could entry into the fish through the olfactory organ (i.e. nares inoculation) [20, 23], injured skin [21] and the gills [24]. The skin abrasion, gills, nasal mucosa and gastrointestinal (GI) tract are the portals for S. iniae to entry into the fish, which reported in tilapia and hybrid striped bass [20, 23, 24]. As for channel catfish, whether the routes of entry of S. iniae is similar to tilapia and hybrid striped bass or similar to another bacterial pathogen, Edwardsiella ictaluri via the gills [25] and the olfactory organ mucosa [26] need further investigation

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