Identification of Polyvalent Vaccine Candidates From Extracellular Secretory Proteins in Vibrio alginolyticus.

Ming Jiang,Yu-Ming Peng,Xuan-Xian Peng,Su-Fang Kuang,Hui Li,Jian-Jun Tao

doi:10.3389/fimmu.2021.736360

Abstract

Bacterial infections cause huge losses in aquaculture and a wide range of health issues in humans. A vaccine is the most economical, efficient, and environment-friendly agent for protecting hosts against bacterial infections. This study aimed to identify broad, cross-protective antigens from the extracellular secretory proteome of the marine bacterium Vibrio alginolyticus. Of the 69 predicted extracellular secretory proteins in its genome, 16 were randomly selected for gene cloning to construct DNA vaccines, which were used to immunize zebrafish (Danio rerio). The innate immune response genes were also investigated. Among the 16 DNA vaccines, 3 (AT730_21605, AT730_22220, and AT730_22910) were protective against V. alginolyticus infection with 47–66.7% increased survival compared to the control, while other vaccines had lower or no protective effects. Furthermore, AT730_22220, AT730_22910, and AT730_21605 also exhibited cross-immune protective effects against Pseudomonas fluorescens and/or Aeromonas hydrophila infection. Mechanisms for cross-protective ability was explored based on conserved epitopes, innate immune responses, and antibody neutralizing ability. These results indicate that AT730_21605, AT730_22220, and AT730_22910 are potential polyvalent vaccine candidates against bacterial infections. Additionally, our results suggest that the extracellular secretory proteome is an antigen pool that can be used for the identification of cross-protective immunogens.

Highlights

Aquaculture presents an opportunity to increase food production in the face of a growing demand for high protein diets [1]
We identified immunogens from bacterial extracellular secretory proteins and found that the secretory proteins represent a novel pool of targets to search for antigens inducing immune protective response [30]
The fish were acclimated in 25 L opencircuit water tanks with aeration for two weeks and tested free of Vibrio species, A. hydrophila and P. fluorescens through zebrafish homogenates cultured in thiosulphate‐citrate‐bile salts‐sucrose agar medium (TCBS) for Vibrio and glutamate starch phenol red agar medium (GSP) for Pseudomonas and Aeromonas, respectively

Summary

Introduction

Aquaculture presents an opportunity to increase food production in the face of a growing demand for high protein diets [1]. The increasing development of finfish aquaculture has affected the environment and human health. These effects are related to the widespread and unrestricted use of antibiotics as additives in the fish food industry, especially in developing countries [2]. The. Polyvalent Vaccines of Secretory Proteins unchecked use of antibiotics leads to their accumulation in the aquatic environment and aquatic products, as well as the emergence of antibiotic-resistant bacteria [3, 4]. The use of vaccines has emerged as a superior strategy to cope with bacterial infection without using antibiotics [16,17,18]

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