No abstract

To disclose the mechanism of cellular injury following porcine circovirus (PCV) infection, 12 pigs were examined by the terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) method and immunohistochemistry. Histologically, the lymphoid tissues were characterized by marked apoptosis of lymphocytes, lymphocyte depletion, and macrophages and giant cells containing numerous inclusion bodies with or without apoptotic bodies. Immunohistochemically, there were many lysozyme-positive macrophages in the lymphoid follicles, while the number of CD79a-positive B lymphocytes was scanty. Apoptotic cells, which were proved to be TUNEL positive, revealed CD79a positivity. Although detectable mainly in the cytoplasm of macrophages, PCV antigens were found also in the nuclei of macrophages and apoptotic lymphocytes. Ultrastructurally, the presence of PCV virions was confirmed in apoptotic bodies phagocytosed by macrophages. These findings suggested that lymphocyte depletion with apoptotic death of B lymphocytes was caused by PCV, and that some of the inclusion bodies were phagolysosomes derived from the apoptosis. Thus, PCV may trigger the development of wasting disease syndrome by producing an immunocompromised state in pigs.

No abstract

Previous serolgoical studies strongly suggested Akabane virus to be the etiologic agent of epizootic abortion and congenital arthrogryposis-hydranencephaly in cattle, and this view was further corroborated in this study by the isolation of the virus from an aborted fetus in an epizootic of the disease and from a fetus extracted froma cow which was suggested by serologic tests to have a recent infection with the virus. The latter fetus had histological changes of encephalomyelitis and polymyositis, and specific antigens of Akabane virus was shown by the immunofluorescent technique in brain tissues as well as skeletal muscular tissues. The virus was recovered from various fetal tissues and fluids, and in relatively large amounts from brain, spinal cord, cerebral fluid, skeletal muscles and fetal placenta. The intracranial inoculation of suckling mice, 1-2 days of age, was the most sensitive system for Akabane virus isolation and HmLu-1, a continuous cell line from hamster lung, seemed almost as sensitive as suckling mice.