Apoptotic Investigation of Brain Tissue Cells in Dogs Naturally Infected by Canine Distemper Virus
Abstract 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 Seriously harm to the development of the dog industry. It has been known that Apoptosis caused by canine distemper virus can show in culture cells, lymphoid tissues and cerebellum. however, its occurrence in brain tissue cells remains unclear. In order to investigate the relationship among canine distemper infecting brain tissues, apoptosis in brain tissue cells and demyelinating pathogenesis this study was performed. Methods 16 naturally infected dogs that exhibited clinical signs of CD and tested positive for anti-CDV monoclonal antibody, as well as on six healthy dogs that served as controls were used in the research. Brain specimens were divided into cerebrum, brain stem and cerebellum that was embedded in paraffin and made the sections respectively. Approximately 5 µm-thick sections were stained by haematoxylin–eosin, methyl green pyronin, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling 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 nervous fibres. CDV had varying degrees of cytotropism to all brain tissue cells; apoptosis also occurred in all kind of cells in the brain, especially in the endothelia of cerebral vessels, astrocytes, oligodendrocytes and ependymal cells, the heavier infection, the more obvious apoptosis. Serious infections also involved the pyramidal and Purkinje cells. The nervous fibres exhibited demyelinating lesions (showed small multifocal vacuole) as well as some neuron axonal atrophy and disappeared gradually (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 clinic may be in relation to different neuron apoptosis.