title: Construction of a Streptococcus iniae sortase A mutant and evaluation of its potential as an attenuated modified live vaccine in Nile tilapia (Oreochromis niloticus).
abstract: Streptococcus iniae is a major Gram-positive aquatic pathogen, which causes invasive diseases in cultured fish worldwide. The identification of potential virulence determinants of streptococcal infections will help to understand and control this disease, but only a few have been confirmed in S. iniae. Sortase A (srtA) is the key enzyme that anchors pre-mature cell wall-attached proteins to peptidoglycan and it can affect the correct positioning of surface proteins, as well as the course of Gram-positive bacterial infection, thereby making it a potential target in the study of virulence factors and disease control. In this study, the 759 bp srtA gene was cloned from pathogenic S. iniae TBY-1 strain and the mutant strain TBY-1ΔsrtA was constructed via allelic exchange mutagenesis. We found that srtA shares high similarities with sortase A from other Streptococcus spp. Direct survival rate assay and challenge experiments were performed, which showed that the mutant strain TBY-1ΔsrtA had a lower survival capacity in healthy tilapia blood and it was less virulent than the wild type strain in tilapia, thereby indicating that the deletion of sortase A affects the virulence and infectious capacity of S. iniae. The mutant strain TBY-1ΔsrtA was used as a live vaccine, which was administered via intraperitoneal injection, and it provided the relative percent survival value of 95.5% in Nile tilapia, thereby demonstrating its high potential as an effective attenuated live vaccine candidate.
authors.affiliation: State Key Laboratory of Bio-control, Key Laboratory for Aquatic Products Safety of Ministry of Education, Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, 135 Xingang West Road, Haizhu District, Guangzhou 510275, Guangdong Province, PR China. Electronic address: wangjfox@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.affiliation: Hubei Province Key Laboratory of Pathogenic Microorganism, Medical College, China Three Gorges University, 8 Daxue Road, Xiling District, Yichang 443002, Hubei Province, PR China. Electronic address: zoulili@mail3.sysu.edu.cn.
authors.forename: L L
authors.initials: LL
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Bio-control, Key Laboratory for Aquatic Products Safety of Ministry of Education, Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, 135 Xingang West Road, Haizhu District, Guangzhou 510275, Guangdong Province, PR China. Electronic address: lianxing@mail.sysu.edu.cn.
authors.forename: A X
authors.initials: AX
authors.lastname: Li
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001428:Bacterial Vaccines / Q000276:immunology*; D023681:Cichlids; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000378:metabolism; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013290:Streptococcal Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D013291:Streptococcus / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity; D014613:Vaccines, Attenuated / Q000276:immunology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D014613:Vaccines, Attenuated; D037521:Virulence Factors; D019881:Aminoacyltransferases; C120542:sortase A; D003546:Cysteine Endopeptidases
keywords: Attenuated live vaccine; Sortase A; Streptococcus iniae; Tilapia