THROUGHOUT THE WORLD, INCLUDING THE US, CATTLE ARE ESSENTIAL FOOD ANIMALS AND ARE ALSO UTILIZED FOR MILK PRODUCTION. BOVINE HERPESVIRUS 1 (BOHV-1) IS AN IMPORTANT CAUSATIVE AGENT OF ABORTION AND COFACTOR FOR BOVINE RESPIRATORY DISEASE (BRD). BOHV-1 USUALLY INFECTS CATTLE VIA THE NOSE, EYE, OR MOUTH; BUT CAN ALSO BE SEXUALLY TRANSMITTED. BOHV-1 GROWTH IN CATTLE LEADS TO TISSUE DAMAGE IN THE EYES AND NOSE, FEVER, NASAL CONGESTION, AND SWELLING OF THE UPPER RESPIRATORY TRACT. A WEEK OR SO AFTER INFECTION, VIRUS GROWTH IS STOPPED BY THE BOVINE'S IMMUNE SYSTEM. BY THIS TIME, BOHV-1 HAS SPREAD TO THE PERIPHERAL NERVOUS SYSTEM WHERE IT PERSISTS IN NEURONS FOR THE LIFE OF CATTLE: THIS PROCESS IS KNOWN AS LATENCY. STRESS CAN DISRUPT LATENCY, WHICH LEADS TO VIRUS SPREAD TO OTHER COWS: THIS PROCESS IS KNOWN AS REACTIVATION FROM LATENCY. WE RECENTLY FOUND THAT PROGESTERONE, A HORMONE ESSENTIAL FOR MAINTAINING PREGNANCY IN COWS, PROMOTES VIRAL GENE EXPRESSION AND GROWTH OF THE VIRUS. STUDIES IN THIS GRANT ARE FOCUSED ON UNDERSTANDING HOW PROGESTERONE PROMOTES VIRUS SPREAD TO THE REPRODUCTIVE TRACT OF INFECTED CALVES; AND WHETHER PROGESTERONE CAN INITIATE REACTIVATION FROM LATENCY. ADDITIONAL STUDIES WILL EXAMINE THE COOPERATIVE EFFECT CORTICOSTEROIDS AND PROGESTERONE HAVE ON VIRAL GROWTH IN CALVES AND REACTIVATION FROM LATENCY. FINALLY, STUDIES WILL TEST HOW PROGESTERONE AND CORTICOSTEROIDS STIMULATE VIRAL GENE EXPRESSION. IF BOHV-1 VACCINES CAN BE DEVELOPED THAT PREVENT SPREAD TO REPRODUCTIVE TISSUES AND DO NOT REACTIVATE FROM LATENCY VIA INCREASED PROGESTERONE AND STRESS, WE MAY REDUCE ABORTIONS IN PREGNANT COWS.