Ultrastructural studies on the pathogenesis of poliomyelitis in monkeys infected with poliovirus

Poliovirus was inoculated intraspinally into cynomolgus monkeys to determine whether nerve cell damage in the central nervous system (CNS) is due primarily to virus multiplication in the neuron or to secondary effects of virus multiplication in the supporting cells. Electron-microscopically, the development of cytopathogenesis and of membrane-bound vesicles and virus particles in the neurons of the CNS in monkeys infected with poliovirus was compared with that of infected cultured cynomolgus monkey kidney (CMK) cells. The structure of membrane-bound vesicles in cytoplasm of damaged motoneuron was examined and found to be similar to the vesicles in infected cultured CMK cells. Virus-like particles were detected occasionally around or within membrane-bound vesicles in the cytoplasm of degenerating motoneurons as well as cultured CMK cells, although intracytoplasmic crystals were not detected in the neuron. No virus particles or membrane-bound vesicles were found in astrocyte foot plates, microglia, oligodendrocytes, axons, vascular endothelial, and inflammatory cells. In addition, poliovirus antigen was detected only in the nerve cells of the CNS by the immunoperoxidase technique, although specific staining was never found in the supporting tissues. From the present results we suggest that membrane-bound vesicles in the cytoplasm of the motoneuron are closely correlated with virus multiplication and that damage of the nerve cell is due to the direct action of the poliovirus.