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. â¿¢ Sub-Objective 1.A: Isolate and characterize F. columnare mutants and identify virulence factors associated with disease in rainbow trout. â¿¢ Sub-Objective 1.B: Develop vaccines to control columnaris disease. â¿¢ 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. â¿¢ Sub-Objective 2.A: Identify new antimicrobial peptides by mining the rainbow trout big data sets and characterize their actions and regulation. â¿¢ Sub-Objective 2.B: Characterize the immunomodulatory actions of new trout AMPs in vitro. â¿¢ 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. â¿¢ Sub-Objective 3.A: Identify and characterize potential viral targets and strategies for vaccine development. â¿¢ 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.