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Research Project: Reducing Impacts of Disease on Rainbow Trout Aquaculture Production

Location: Office of The Director

Project Number: 5090-31320-005-000-D
Project Type: In-House Appropriated

Start Date: Jan 1, 2020
End Date: Dec 31, 2024

Rainbow trout are an important recreational and food fish species in the U.S., and it is thus important to improve disease resistance and improve methods for combatting outbreaks of disease to increase production and profitability of U.S. aquaculture. This research plan will focus on the following three Objectives and their supporting Sub-Objectives: Objective 1: Identify virulence factors in pathogenic flavobacterium species and develop strategies to control disease. • Sub-Objective 1.A: Isolate and characterize F. columnare mutants and identify virulence factors associated with disease in rainbow trout. • Sub-Objective 1.B: Develop vaccines to control columnaris disease. • Sub-Objective 1.C: Develop improved genetic manipulation techniques for F. psychrophilum, which causes bacterial cold-water disease. Objective 2: Characterize salmonid antimicrobial peptides and evaluate their biocidal effects against pathogens. • Sub-Objective 2.A: Identify new antimicrobial peptides by mining the rainbow trout big data sets and characterize their actions and regulation. • Sub-Objective 2.B: Characterize the immunomodulatory actions of new trout AMPs in vitro. • Sub-Objective 2.C: Assess effects of new rainbow trout AMPs on flavobacterial biofilms. Objective 3: Identify rhabdoviral virulence factors and develop strategies to reduce pathogenesis in salmonids. • Sub-Objective 3.A: Identify and characterize potential viral targets and strategies for vaccine development. • Sub-Objective 3.B: Characterize the involvement of stress granule formation and function in pathogen response and the establishment of protective immunity in fish cell-lines.

Objective 1: For this objective, our scientific aim is to develop genetic techniques to characterize F. psychrophilum and F. columnare virulence mechanisms. Using these genetic techniques, genes encoding specific secreted proteins and components of flavobacterial secretion systems will be mutated and the effects of these modifications on bacterial pathogenesis will be evaluated using in vitro and in vivo systems. Data from these approaches will improve understanding of host-pathogen interactions and generate attenuated bacterial strains for vaccine development. Objective 2: For this objective, our scientific aim is to identify and characterize new antimicrobial peptides (AMPs) in rainbow trout, understand their actions against flavobacterial and rhabdoviral pathogens, and ascertain their physiological control to improve health of rainbow trout. Using established in vitro systems with trout cell-lines, biological actions of AMPs will be assessed and ability of AMPs to kill important flavobacterial and rhabdoviral pathogens, and flavobacterial biofilms, will be characterized. Objective 3: For this objective, our scientific aim is to understand the innate immune response and components of virulence in two important rainbow trout rhabdoviruses (IHNV and VHSV). Work will involve sequential characterization of the effects of critical rhabdoviral proteins, and modifications to these proteins, on the stress response and host immunity using trout cell-lines, in vitro. The goal is to characterize components of rhabodoviral virulence and how these components (viral proteins) influence host response as a means to identify possible viral targets for new vaccine candidates. Developing new vaccine candidates based on improved understanding of rainbow trout antiviral immune functions should advance our abilities to combat these pathogens in rainbow trout.