Immunologic and virologic findings in a bull chronically infected with noncytopathic bovine viral diarrhea virus.

Depressed lymphocyte blastogenesis in response to mitogen stimulation, depressed iodination of protein by neutrophils, and enhanced ingestion of Staphylococcus aureus by neutrophils were detected in a bull with chronic bovine viral diarrhea (BVD). Before developing chronic BVD, the bull was vaccinated with a killed cytopathic BVD virus. Neutralizing antibodies specific for the vaccine virus were detected in serum specimens obtained from the bull immediately before death. A noncytopathic BVD virus was isolated from the spleen after death. The immunologic and virologic findings in this bull supported reported research findings on the pathogenetic mechanisms involved in chronic BVD and mucosal disease.