** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE UNITED STATES' ANNUAL FOREIGN TRADE DEFICIT FOR SEAFOOD EXCEEDS ~$6 BILLION. CONSEQUENTLY, AQUACULTURE IS POISED TO BECOMEA MAJOR U.S. GROWTH INDUSTRY WITHIN THE NEXT FEW DECADES. HOWEVER, DISEASE AND HEALTH MANAGEMENT PROBLEMS ARE ONE OF THEMAJOR HURDLES FOR THE DEVELOPING AQUACULTURE INDUSTRY IN THE US AND WORLDWIDE. IN THAT REGARD, THE DEVELOPMENT OF THERAPEUTICSOLUTIONS AND FISH VACCINES ARE SIGNIFICANTLY HAMPERED BY THE LACK OF BASIC AND TRANSLATIONAL KNOWLEDGE WE HAVE ON THE SITESWERE IMMUNE RESPONSES ARE INDUCED IN FISH. THUS, IN THIS PROJECT WE WILL SPECIFICALLY FOCUS ON THE STUDY OF NOVEL FISH LYMPHOIDAREAS WHERE ANTIBODY RESPONSES ARE GENERATED. IN ADDITION, WHILE FISH ARE KNOWN TO MOUNT MEMORY ANTIBODY RESPONSES, HOWAND WHERE THESE RESPONSES OCCUR REMAINS ILL UNDERSTOOD AND THIS PROJECT WILL INVESTIGATE THE MECHANISMS BY WHICH MEMORYRESPONSES ARE GENERATED IN FISH. FINALLY, WHILE FISH VACCINES ARE KNOWN TO PROTECT MANY FISH FARMED SPECIES, INCLUDING SALMONAND CATFISH, MANY VACCINES INDUCE LESS THAN OPTIMAL PROTECTION RESPONSES AGAINST A NUMBER OF PATHOGENS. THUS, THERE IS A BIGNEED TO IMPROVE THE EFFICACY OF MANY CURRENT FISH VACCINES. THE CAPACITY OF VACCINES TO GENERATE STRONG IMMUNE RESPONSESAGAINST A PATHOGEN DEPENDS ON HOW EFFECTIVELY THE ADJUVANT CONTAINED IN THE VACCINE WILL ACTIVATE THE FISH IMMUNE SYSTEM.ADJUVANTS ARE COMPOUNDS REQUIRED FOR THE OPTIMAL ACTIVATION OF THE FISH IMMUNE SYSTEM. TO DATE THERE IS ONLY ADJUVANT APPROVEDFOR USE IN FISH VACCINES, NAMELY MINERAL OIL. WHILE MINERAL OIL IS SAFE FOR THE CONSUMER, IN SOME SPECIES SUCH AS SALMONIT INDUCES SOME LESIONS IN THE FISH PERITONEAL CAPACITY. THUS, THERE IS A NEED TO DEVELOP NEW AND SAFER ADJUVANTS FOR FISH.ALL OF THE ABOVE MENTIONED OBJECTIVES WILL BE ACHIEVED BY STUDYING HOW AND WHERE FISH INDUCE IMMUNE RESPONSES TO A NUMBEROF ANTIGENS AND PATHOGENS. TO EVALUATE FISH ANTIBODY RESPONSES, WE WILL ANALYZE IN WHICH ORGANS THE ANTIBODY RESPONSE IS BEINGINDUCED. THIS WILL BE DONE THROUGH MICROSCOPY STUDIES AS WELL AS THE ANALYSIS OF ANTIBODY GENERATION AGAINST THE ANTIGENS ANDPATHOGENS USED. MOREOVER, WE WILL USE DIFFERENT TYPES OF ADJUVANT FORMULATIONS WITH THE GOAL TO EVALUATE WHICH ADJUVANT INDUCESAFE AND OPTIMAL ANTIBODY RESPONSES AGAINST THE STUDIED ANTIGENS AND PATHOGENS.IT IS EXPECTED THAT THE PROPOSED STUDIES WILL HAVE SIGNIFICANT CONSEQUENCES FOR THE FUTURE DEVELOPMENT OF KNOWLEDGE-BASEDADJUVANTS AND VACCINES THAT INDUCE LONG LASTING MEMORY RESPONSES IN FISH FARMED SPECIES. MOREOVER, THE EXPERIMENTS PROPOSEDHERE TO TEST THE DIFFERENT CAPACITIES OF THE PROPOSED ADJUVANTS IN INDUCING POTENT FISH IMMUNE RESPONSES ARE SIGNIFICANT BECAUSETHESE DATA ARE EXPECTED TO IDENTIFY CORRELATES OF IMMUNE ACTIVATION AND PROTECTION THAT WILL PAVE THE ROAD FOR THE SCREENING ANDDEVELOPMENT OF NOVEL, MORE EFFICACIOUS AND SAFER ADJUVANTS FOR THE AQUACULTURE INDUSTRY.