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Background: Canine distemper caused by canine distemper virus that belongs to the Morbillivirus genus of the Paramyxoviridae family is still a global epidemic significant infectious disease, especially in pet dogs in China and serious harm to the development of the dog industry. It has been known that apoptosis caused by the canine distemper virus can show in culture cells, lymphoid tissues, and the cerebellum. However, its occurrence in brain tissue cells remains unclear. To investigate the relationship among canine distemper infecting brain tissues, apoptosis in brain tissue cells, and demyelinating pathogenesis was investigated., Methods: 16 naturally infected dogs that exhibited clinical signs of CD and tested positive for the anti-CDV monoclonal antibody and six healthy dogs that served as the control, were used in the research. Brain specimens were divided into the cerebrum, brain stem, and cerebellum embedded in paraffin and made the sections respectively. Approximately 5 µm-thick sections were stained by hematoxylin-eosin, methyl green pyronin, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique, and immunohistochemistry. CDV nucleocapsid protein was detected by immune streptavidin-biotinylated peroxidase complex., Results: Alterations in the brain tissues of CDV-infected dogs involved both various cells and nerve fibers. CDV had varying degrees of cytotropism to all brain tissue cells; apoptosis also occurred in all brain cells, especially in the endothelia of cerebral vessels, astrocytes, oligodendrocytes, and ependymal cells, the more serious infection, the more obvious apoptosis. Serious infections also involved the pyramidal and Purkinje cells. The nervous fibers exhibited demyelinating lesions (showed small multifocal vacuole), and some axonal neuron atrophy gradually disappeared (formed large vacuole)., Conclusions: Apoptosis in brain tissue cells was mainly related to the propagation path and cytotropism of CDV. The apoptosis of astrocytes, oligodendrocytes, and some neurons may play a significant role in the demyelinating pathogenesis in dogs with acute canine distemper. A lot of diverse nervous signs shown in the clinic may be related to different neuron apoptosis., (© 2021. The Author(s).)

Infectious bursal disease virus (IBDV) is a very important small RNA virus in the family of Birnaviridae, which can cause severe immunosuppressive effects and pathological damages in young chickens. It can replicate in bursal lymphocytes and impede the growth and development of B cells, finally causing bursal lymphocytes apoptosis. Previous results have shown that protocatechuic acid (PCA) as an important phenolic compound could effectively improve the survival rate of chickens infected with IBDV. The current study aimed to explore how PCA influenced the pathogenesis of IBDV, especially lymphocyte apoptosis in the process of IBDV infection. The results showed that PCA could effectively alleviate bursal pathological changes at the early stage of IBDV invasion. Moreover, bursal lymphocyte apoptosis for tissue section samples was largely elevated by PCA by using the terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) method while the bursal lymphocyte apoptosis ratio was also increased by PCA by flow cytometry in the early stage of IBDV infection in vivo. Meanwhile, PCA could promote non-lymphocyte apoptosis in vitro. Further study displayed that the potential mechanisms mainly relied on regulation of the expressions of pro-apoptotic protein Bax and anti-apoptotic Bcl-2, thus speeding up the process of IBDV-infected cell apoptosis and preventing virus infection. Meanwhile, the results displayed that the PI3K/Akt and NF kappa B signal pathways might play an important role in promoting cell apoptosis after IBDV infection. Overall, PCA as a potent antiviral drug precursor is expected to be applied in the poultry industry as a substitute for clinical antiviral application., (Copyright © 2018. Published by Elsevier Ltd.)