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Front. Vet. Sci., 08 August 2022
Sec. Veterinary Infectious Diseases
Volume 9 - 2022 |

Functional characterization of Vibrio alginolyticus T3SS regulator ExsA and evaluation of its mutant as a live attenuated vaccine candidate in zebrafish (Danio rerio) model

 Weijie Zhang1, 2, Liangchuan Chen1, 2,  Haiyun Feng1, 2,  Junlin Wang1, 2, Fuyuan Zeng1, 2, Xing Xiao1, 2,  Jichang Jian1, 2, Na Wang3 and Huanying Pang1, 2
  • 1Fisheries College, Guangdong Ocean University, China
  • 2Guangdong Provincial Key Laboratory of Aquatic Animal Disease Control and Healthy Culture & Key Laboratory of Control for Diseases of Aquatic Economic Animals of Guangdong Higher Education Institutes, China
  • 3Chinese Academy of Inspection and Quarantine, China

Vibrio alginolyticus, a Gram-negative bacterium, is an opportunistic pathogen of both marine animals and humans, resulting in significant losses in the aquaculture industry. Type III secretion system (T3SS) is a crucial virulence mechanism of V. alginolyticus. In this study, the T3SS regulatory gene exsA, which was cloned from V. alginolyticus wild-type strain HY9901, is 861 bp encoding a protein of 286 amino acids. The ΔexsA was constructed by homologous recombination and Overlap-PCR. Although there was no difference in growth between HY9901 and ΔexsA, the ΔexsA exhibited significantly decreased extracellular protease activity and biofilm formation. Besides, the ΔexsA showed a weakened swarming phenotype and an ~100-fold decrease in virulence to zebrafish. Antibiotic susceptibility testing showed the HY9901ΔexsA was more sensitive to kanamycin, minocycline, tetracycline, gentamicin, doxycycline and neomycin. Compared to HY9901 there were 541 up-regulated genes and 663 down-regulated genes in ΔexsA, screened by transcriptome sequencing. qRT-PCR and β-galactosidase reporter assays were used to analyze the transcription levels of hop gene revealing that exsA gene could facilitate the expression of hop gene. Finally, Danio rerio, vaccinated with ΔexsA through intramuscular injection, induced a relative percent survival (RPS) value of 66.7% after challenging with HY9901 wild type strain. qRT-PCR assays showed that vaccination with ΔexsA increased the expression of immune-related genes, including GATA-1, IL6, IgM, and TNF-α in zebrafish. In summary, these results demonstrate the importance of exsA in V. alginolyticus and provide a basis for further investigations into the virulence and infection mechanism.

Keywords: type Ⅲ secretory system, Characteristics, live attenuated vaccine,, Vibrio alginolyticus, exsA gene

Citation: Zhang W, Chen L, Feng H, Wang J, Zeng F, Xiao X, Jian J, Wang N and Pang H (2022). Functional characterization of Vibrio alginolyticus T3SS regulator ExsA and evaluation of its mutant as a live attenuated vaccine candidate in zebrafish (Danio rerio) model. Front. Vet. Sci. 9:1158. doi: 10.3389/fvets.2022.938822

Received:08 May 2022; Accepted: 14 Jul 2022;
Published online: 08 Aug 2022.

Edited by:

Kun Li, Nanjing Agricultural University, China

Reviewed by:

Xiaojian Gao, Yangzhou University, China
Xinyu Zhu, Duke University, United States  

Copyright: © 2022 Zhang, Chen, Feng, Wang, Zeng, Xiao, Jian, Wang and Pang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: