** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MAREK'S DISEASE (MD) IS A CANCER OF CHICKENS FOR WHICH A VACCINE INJECTED INTO THE EGGS OF CHICKENS PRIOR TO HATCH PROVIDES LIFELONG PREVENTION OF THIS CANCER. MD IS CAUSED BY A VIRUS (MAREK'S DISEASE VIRUS, MDV) AND THE VACCINES THAT PREVENT MD ARE COMPOSED OF RELATED VIRUSES THAT DO NOT CAUSE DISEASE. HOW THESE RELATED VIRUSES TRAIN THE IMMUNE SYSTEM TO PROVIDE SUCH A LONGLASTING ANTI-VIRAL/ANTI-CANCER RESPONSE IS CURRENTLY UNKNOWN, AS THE VACCINE VIRUSES HAVE VERY LIMITED REPLICATION IN COMMERCIAL CHICKENS DUE TO MATERNAL ANTIBODIES AND THEIR HAVING BEEN BRED FOR RESISTANCE TO MD. IT IS OUR HYPOTHESIS THAT SMALL VESICLES (THE SIZE OF VIRUSES) PRODUCED BY SOME INFECTED CELLS IN THE BODY OF THE CHICKENS PROVIDE THIS LIFELONG PROTECTION FROM MD. THESE SMALL VESICLES, TERMED EXOSOMES, CONTAIN PROTEINS, LIPIDS, DNAS AND RNAS THAT WE BELIEVE CARRY BITS OF THE VIRUS WHICH THEN PROVIDE THESE TO SPECIALIZED CELLS OF THE IMMUNE SYSTEM THAT PATTERN THE WAY THE BODY RESPONDS TO CHALLENGE IN THE FIELD.AS DISEASE-CAUSING MDVS CAN BE FOUND IN MOST, IF NOT ALL CHICKEN HOUSES IN THE US, IN THE FORM OF INFECTIOUS DANDER (DEAD SKIN CELLS), CHALLENGE WITH MDV IS CONSIDERED TO BE HIGHLY LIKELY DURING THE LIFE OF THE CHICKEN.EXOSOMES ARE INCREDIBLY PREVALENT (~TEN BILLION PER ML OF SERUM) IN ALL BIOLOGICAL FLUIDS (SERUM, TEARS, URINE, SEMEN, LYMPH, ETC.). TO UNDERSTAND HOW EXOSOMES CONFER IMMUNE PROTECTION, WE HAVE BEEN EXAMINING THEIR UPTAKE BY A PHAGOCYTIC CELL LINE THAT HAS BEEN TREATED WITH CHEMICALS AND PROTEINS TO BECOME DENDRITIC CELLS (DCS), A POPULATION ESSENTIAL FOR THE PROPER PATTERNING OF IMMUNTY. IN THE PROPOSED WORK, WE TRY TO IDENTIFY WHETHER THESE CELLS, ONCE TREATED WITH EXOSOMES FROM THE SERUM OF BIRDS WHICH HAVE BEEN VACCINATED AND HAVE SURVIVED CHALLENGE WITH HIGHLY-VIRULENT MDVS, WILL STIMULATE IMMUNE CELLS TO BECOME ACTIVATED. WE ALSO PLAN TO DETERMINE IF THESE EXOSOMES CAN WORK TOGETHER WITH VACCINES OR CAN BE USED AS VACCINES THEMSELVES TO AUGMENT OR PREVENT DISEASE IN CHICKENS THAT WILL THEN BE CHALLENGED WITH A HIGHLY-VIRULENT MDV.IN ADDITION, SINCE CANCER CELLS PRODUCE EXOSOMES THAT HAVE BEEN ASSOCIATED WITH PROGRESSION AND DISSEMINATION (METASTASIS), WE PLAN TO USE EXOSOMES ISOLATED FROM THE SERUM OF TUMOR-BEARING CHICKENS TO DETERMINE IF THESE ALTER OR PREVENT APPROPRIATE PATTERNING OF THE IMMUNE RESPONSE. TO DO THIS, WE WILL BE TREATING THE PHAGOCYTIC CELL LINE (IN THE VARIOUS FORMS PATTERNED BY CYTOKINES) WITH KNOWN AGONISTS (SPECIFIC INDUCERS) OF DIFFERENT TYPES OF INNATE IMMUNE RESPONSES (INFLAMMATION, INTERFERON RESPONSES, ETC.) AND THEN MEASURE THEIR EFFECTS COMPARED TO NON-TREATED CONTROLS (FOR WHICH WE HAVE SIGNIFICANT DATA SHOWING WHAT A NORMAL RESPONSE WOULD BE). IN ADDITION, WE PLAN TO DETERMINE IF ADMINISTRATION OF THESE EXOSOMES FROM TUMOR-BEARING BIRDS AFFECTS MD VACCINES AND PREVENTS THEM FROM PROVIDING PROTECTION FROM CHALLENGE.FINALLY, WE WANT TO TRY AND UNDERSTAND WHAT CELLS IN THE BODY ARE INFECTED BY MDV BUT,THEN PRODUCE THE EXOSOMES WHICH HELP TO PROVIDE PROTECTION. PRELIMINARY STUDIES SUGGEST THAT PHAGOCYTIC CELLS DO IN FACT BECOME INFECTED, BUT THAT THEY DO NOT BECOME INFECTIOUS (ABLE TO TRANSMIT INFECTION). WE PLAN TO STUDY THIS VIRUS-HOST CELL INTERACTION IN ORDER TO BETTER UNDERSTAND HOW MD VACCINES PRODUCE EXOSOMES THAT GIVE RISE TO SYSTEMIC PROTECTION. THIS WORK IS FUNDAMENTAL TO OUR UNDERSTANDING OF HOW MD VACCINES WORK AND MY YIELD INSIGHT INTO THE DEVELOPMENT OF VACCINES FOR HUMAN VIRUS-INDUCED MALIGNANCIES.