UNDERSTANDING MICROBIAL METABOLITE EFFECTS ON EBV LIFE CYCLE B CELLS AND EPITHELIAL CELLS - PROJECT SUMMARY/ABSTRACT EPSTEIN-BARR VIRUS (EBV) IS A HIGHLY PREVALENT ONCOVIRUS, INFECTING OVER 90% OF THE ADULT POPULATION WORLDWIDE AND CONTRIBUTING TO VARIOUS DISEASES INCLUDING MULTIPLE CANCERS, GASTRIC CARCINOMAS, AND AUTOIMMUNE CONDITIONS. WHILE EBV TYPICALLY REMAINS LATENT IN B CELLS THROUGHOUT AN INDIVIDUAL'S LIFE, LYTIC REACTIVATION CAN OCCUR UNDER SPECIFIC CONDITIONS, LEADING TO VIRAL PRODUCTION AND INFECTION OF ORAL EPITHELIAL CELLS, WHICH IS A CRITICAL STEP IN EBV'S PATHOGENESIS AND TRANSMISSION CYCLE. AN EMERGING BODY OF LITERATURE SUGGESTS THAT THE ORAL MICROBIOTA, PARTICULARLY THROUGH THE PRODUCTION OF SHORT-CHAIN FATTY ACIDS (SCFAS) SUCH AS PROPIONATE, BUTYRATE, ACETATE, AND VALERATE, PLAYS A CRUCIAL ROLE IN EBV REACTIVATION THROUGH THEIR ACTION AS HISTONE DEACETYLASE INHIBITORS AND EPIGENETIC MODIFIERS. HOWEVER, THE SPECIFIC MECHANISMS BY WHICH THESE MICROBIAL METABOLITES INFLUENCE EBV INFECTION AND REACTIVATION IN BOTH B CELLS AND EPITHELIAL CELLS REMAIN POORLY UNDERSTOOD. THE OVERARCHING OBJECTIVE OF THIS PROPOSAL IS TO CHARACTERIZE HOW MICROBIAL METABOLITES MODULATE EBV INFECTION AND REPLICATION ACROSS BOTH KEY STAGES OF THE VIRAL LIFE CYCLE IN B CELLS AND EPITHELIAL CELLS. OUR PRELIMINARY DATA FROM 42 BURKITT LYMPHOMA (BL) PATIENTS AND 51 AGE-MATCHED HEALTHY CONTROLS IN KENYA DEMONSTRATE THAT BL PATIENTS EXHIBIT DISTINCT ORAL MICROBIOTA PROFILES WITH DIFFERENTIAL DIVERSITY AND BACTERIAL TAXA ABUNDANCE. ADDITIONALLY, WE HAVE OBSERVED THAT METABOLITES FROM DIFFERENTIALLY ABUNDANT BACTERIA CAN MODIFY HISTONES AT THE BZLF1 PROMOTOR, ESSENTIAL FOR EBV LYTIC REACTIVATION IN B CELLS. MOREOVER, IN EPITHELIAL CELLS, EPHA2, AN IMPORTANT RECEPTOR FOR EBV ENTRY, IS UPREGULATED IN THREE SEPARATE EPITHELIAL CELL LINES IN RESPONSE TO SCFAS. THEREFORE, MY CENTRAL HYPOTHESIS OF THIS PROPOSAL IS ORAL MICROBIAL METABOLITES INFLUENCE THE EBV LIFE CYCLE THOUGH; (1) MODULATING H3K27ME3, THE SPECIFIC HISTONE MODIFICATION THAT REPRESSES BZLF1 EXPRESSION FOR VIRAL REACTIVATION AND DECREASING METHYLATION OF EBV PROMOTER REGIONS IN INFECTED B CELLS AND (2) INCREASING EPHA2 EXPRESSION TO ENHANCE VIRAL ENTRY AND VIRAL REPLICATION IN EPITHELIAL CELLS. TO TEST THIS HYPOTHESIS, I WILL UTILIZE BIOBANKED CLINICAL SAMPLES FROM OUR BL PATIENT COHORT ALONGSIDE IN VITRO CELL MODELS TO INVESTIGATE SCFAS AND OTHER NOVEL METABOLITES IN B CELLS AND SCFAS IN EPITHELIAL CELLS. THIS PROPOSED WORK WILL PROVIDE CRUCIAL INSIGHTS INTO THE RELATIONSHIP BETWEEN THE ORAL MICROBIOME AND EBV PATHOGENESIS, WITH BROADER IMPLICATIONS FOR UNDERSTANDING VIRUS-MICROBIOTA INTERACTIONS IN HUMAN DISEASE.