Abstract

Large yellow croaker (Larimichthys crocea), an economically important marine fish in China, has suffered from serious vibriosis, which has resulted in great economic losses for the large yellow croaker industry. Vaccination has been considered to be a safe and effective method to prevent and control vibriosis. However, due to the complex diversity and serotypes of the Vibrio genus, the progress of Vibrio vaccine development is still slow. In this study, we prepared recombinant Vibrio dihydrolipoamide dehydrogenase (rDLD) protein and investigated its potential as a candidate to be a subunit vaccine against Vibrio. The lysozyme activity and the rDLD-specific antibody level in sera of large yellow croakers immunized with rDLD were significantly higher than those in the control group, and the transcript levels of proinflammatory cytokines (IL-6, IL-8, IL-1β), MHC IIα/β, CD40, CD8α, IL-4/13A, and IL-4/13B were significantly up-regulated in the spleen and head kidney of large yellow croakers immunized with rDLD, suggesting that rDLD could induce both specific and nonspecific immune responses in this species. In addition, rDLD protein increased the survival rate of large yellow croakers against Vibrio alginolyticus and Vibrio parahaemolyticus, with the relative percent of survival (RPS) being 74.5% and 66.9%, respectively. These results will facilitate the development of a potential subunit vaccine against Vibrio in large yellow croaker aquaculture.

Highlights

  • Publisher’s Note: MDPI stays neutralLarge yellow croaker (Larimichthys crocea) is an economically important marine fish species in China, with the largest annual yield in Chinese farmed marine fish species [1].vibriosis caused by Vibrio alginolyticus, Vibrio harveyi, and Vibrio parahaemolyticus has broken out frequently and resulted in tremendous economic losses for the large yellow croaker aquaculture [2,3,4]

  • The recombinant plasmid pET28a-Dihydrolipoamide dehydrogenase (DLD) was transformed into E. coli BL21 cells to produce recombinant Vibrio dihydrolipoamide dehydrogenase (rDLD) fusion protein with a 6 × His tag

  • The lysates of E. coli cells harboring recombinant pET28a-DLD or empty pET28a were centrifuged at 12,000× g and supernatants and sediments of cell lysates were separated by SDS-PAGE

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Summary

Introduction

Large yellow croaker (Larimichthys crocea) is an economically important marine fish species in China, with the largest annual yield in Chinese farmed marine fish species [1]. Subunit vaccines are recognized as effective tools for the prevention and control of fish diseases in aquaculture. They are typically prepared from viral capsid proteins and bacterial with regard to jurisdictional claims in published maps and institutional affiliations. DLD could be recognized by antisera of several bacteria, including Neisseria meningitidis, V. alginolyticus, and V. harveyi [20,21] These studies indicated that DLD may be a common antigen and could be used as a candidate protein for developing a subunit vaccine. We used rDLD as a vaccine antigen to investigate its protective effect on large yellow croaker, an economically important marine fish in China [22].

Bacterial Strains and Animals
Expression and Purification of Recombinant DLD Protein
Immunization of Large Yellow Croaker with Recombinant DLD Protein
Determination of Lysozyme Activity in Serum of Large Yellow Croaker
Determination of Antibody Titer in Serum of Large Yellow Croaker
Expression Analysis of Immune-Related Genes by Real-Time PCR
Challenge Experiment of Large Yellow Croaker
Statistical Analysis
Expression and Purification of rDLD Protein
The rDLD-Induced Expression of Immune- Related Genes In Vivo
The rDLD-Induced Expression of Immune-Related Genes In Vivo
Vaccine

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