**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HYPERVIRULENT AEROMONAS HYDROPHILA (VAH) IS A SIGNIFICANT PATHOGEN IN FRESHWATER AQUACULTURE.SINCE 2009,EPIDEMIC OUTBREAKS OF MOTILE AEROMONAS SEPTICEMIA CAUSED BY VAHHAVE RESULTED IN DEVASTATING LOSSES IN SOUTHEASTERN AQUACULTURE PRODUCTION FACILITIES, AND THESE LOSSES HAVE HAD A PARTICULARLY DELETERIOUS IMPACT IN THE ALABAMA CATFISH AQUACULTURE SECTOR WHICH IS VITAL TO THE ECONOMY OF THE STATE'S MOST ECONOMICALLY DEPRESSED COUNTIES.THIS RESEARCH WILL ADVANCE VACCINE DEVELOPMENT TARGETING VAH AND VAH-RELATED MOTILE AEROMONAS SEPTICEMIA (VMAS). VACCINATION IS A KEYSTONE OF DISEASE PREVENTION IN AQUATIC PRODUCTION SYSTEMS AND COULD PROVE AN EFFECTIVE PREVENTIVE METHOD AGAINST VMAS. HOWEVER, VACCINE DEVELOPMENT IS A SLOW PROCESS, LARGELY DUE TO THE TIME REQUIRED TO IDENTIFY AND VALIDATE A SUITABLY EFFECTIVE ANTIGEN THAT WILL STIMULATE A STRONG PROTECTIVE IMMUNE RESPONSE IN VACCINATED CATFISH. THIS RESEARCH WILL SIGNIFICANTLY SPEED UP THIS PROCESS BY PRE-SCREENING TARGETED BACTERIAL PROTEINS IDENTIFIED BY MULTI-OMICS (PROTEIN AND GENE EXPRESSION) RESEARCH APPROACHES. THIS PROJECTWILL IDENTIFY PROMISING RECOMBINANT PROTEIN VACCINE CANDIDATES THAT STIMULATE ROBUST HUMORAL ADAPTIVE IMMUNITY IN CATFISH BY USING PRELIMINARYDATA TO SELECT PROTEINS WITH HIGH POTENTIAL AS VACCINE CANDIDATES, AND TO DEVELOP A LATEX-MICROSPHERE-BASED AGGLUTINATION ASSAY PLATFORM TO RAPIDLY SCREEN THESE IMMUNOGENIC TARGETS FOR ANTIGENICITY.NEW PRELIMINARY DATA GENERATED THROUGH OUR RESEARCHHAS IDENTIFIED PROTEINS THAT ARE HIGHLY EXPRESSED AND/OR SECRETED BY VAH, AND HAS IDENTIFIED MULTIPLE HIGH-PRIORITY VACCINE CANDIDATE PROTEINS. USING RECOMBINANT PROTEIN TECHNOLOGIES AND METHODS, MULTIPLE SURFACE-EXPRESSED RECOMBINANT VAH PROTEINS WILL BE SCREENED FOR THE ABILITY TO INDUCE CATFISH IGM ANTIBODY RESPONSE THROUGH LATEX AGGLUTINATION ASSAYS USING SERUM FROM CATFISH PREVIOUSLY INFECTED WITH VAH. HIGHLY IMMUNOGENIC RECOMBINANT PROTEINS IDENTIFIED DURING THIS RESEARCH WILL BE USED IN THE DEVELOPMENT OF SUBUNIT AND MULTIVALENT SUBUNIT VACCINES.AN EFFECTIVE VACCINE WILL OFFER AN AFFORDABLE, DURABLE PROTECTION OPTION TO PRODUCERS AND SIGNIFICANTLY DECREASE THE STAGGERING LOSSES RESULTING FROM VMAS EACH YEAR.