Performing Department
(N/A)
Non Technical Summary
The farm-raised catfish industry dominates the aquaculture sector in the United States, and Edwardsiella ictaluri is asignificant pathogen causing enteric septicemia of catfish (ESC). There are limitations in the current therapeutic and preventative strategies against ESC. The problem is exacerbated by the increasing emergence of E. ictaluri strainesresistant to approved antimicrobials. As a result, there is an urgent, industry-defined need to provide catfish producers with a practical, safe, and efficacious treatment alternative.This proposal will determine the potential of newly constructed mutants as live attenuated vaccine candidates and explore the effectiveness of β-glucan as a vaccine adjuvant.The ultimate outcome of this project is to develop a management strategy to control ESC infection and provide insight into mechanisms of E. ictaluri pathogenesis. This project includes conducting research to evaluate the virulence of constructed mutants and assess whether β-glucan can be used as a vaccine adjuvant to improve the efficacy of the candidate vaccine strains. The study will also explore the ability of candidate vaccine strains to stimulate protective immunity of catfish against E. ictaluri.We expect the successful completion of this project will help us understand the novel virulence factors in E. ictaluri, yield a better understanding of β-glucan as an adjuvant for catfish vaccines, and lay a foundation for developing more effective live attenuated vaccines to prevent ESC. The approach implemented in this research will ensure aquaculture producers have adequate treatment options for maximum production efficiency, profitability, and sustainability.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
100%
Goals / Objectives
Edwardsiella ictaluri is the causative agent of enteric septicemia of catfish (ESC) and one of the most important pathogens affecting the catfish industry in the United States. The current preventive strategies to control ESC have limitations, and catfish operations continue to suffer significant losses because of ESC. Therefore, it is necessary to develop a safe and effective management tool to control ESC outbreaks. Our long-term goal is to support the US aquaculture industry by identifying potential intervention strategies to reduce catfish mortality associated with bacterial infections. The objective of this study is to assess the safety and efficacy of newly constructed mutants, evaluate their potential as live attenuated vaccine candidates, and investigate the effectiveness of β-glucan as a vaccine adjuvant. We will achieve our objective through the following two specific aims:Specific Aim 1. Evaluate the virulence of constructed mutants and identify the critical mutations responsible for virulence attenuation. In this aim, we will characterize the safety and efficacy of novel E. ictaluri mutants in catfish fingerlings and fry. We will evaluate for the first time the effectiveness of β-glucan as a vaccine adjuvant to improve the efficacy of our vaccine candidate and induce effective immunity. This aim will identify novel virulence factors in E. ictaluri and lay the foundation for the development of attenuated vaccine candidates to prevent ESC.Specific Aim 2. Assess the ability of the attenuated mutants to stimulate protective immunity against E. ictaluri. In this aim, we will evaluate the effects of the safest and most efficacious vaccine candidates on phagocytic cells, B cell-specific gene expression, and IgM titers. The potential candidate vaccine strains are expected to boost the immune responses of catfish such that they are better able to resist ESC infection.
Project Methods
Our efforts will be to identify critical genes responsible for E. ictaluri virulence and evaluate the potential of E. ictaluri mutants to protect catfish fingerlings and fry from E. ictaluri infections. In this project, 15 novel E. ictaluri mutants will be evaluated. To achieve this, catfish fingerlings and fry will be challenged with E. ictalurimutants followed by infection with E. ictaluri wildtype strain. Fish survival, based on statistical analysis, will be used to quantify the degree of virulence of each mutant and identify the mutant strains that provide maximum protection. The potential application of β-glucan to increase the protective efficacy of the candidate vaccine strains will be evaluated through fish challenge experiments. Our effort to assess the impact of avirulent mutant strains on the E. ictaluri burden and tissue damage will be evaluated by determining pathological changes in catfish tissues following vaccination with candidate vaccine strains.Successful vaccination requires development of immune responses to protect against further infection. Therefore, in the current grant our efforts to determine the ability of the attenuated mutants to trigger humoral immunity and expression of inflammatory genes in vaccinated catfish compared to sham-vaccinated catfish using real-time PCR. Our team will also evaluate the ability of the most promising vaccine candidate to enhance phagocytic and bactericidal activity of macrophages to eliminate E. ictaluri using ex vivo and in vivo models.