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.
Bovine papillomavirus type 12 (BPV-12, putative type BAA1) was detected in epithelial papilloma located on the tongue of an infected cow. Then, the whole genome was sequenced, and phylogenetic analysis illustrated that it should be classified as a member of the genus Xipapillomavirus. The viral genome is 7197 base pairs in length and contains five early ORFs (E1, E2, E4, E7 and E8), three late ORFs (L1, L2 and L3), and a long control region that possesses replication regulatory elements. Meanwhile, mRNA of each gene was detected in the papilloma sample. The papilloma was identified as epithelial papilloma by histological and immunohistochemical examination. Based on the genome information and pathological properties, BAA1 was designated as BPV-12 in this study.
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