Ultrastructural changes of motoneurons in monkeys infected with enterovirus 71. Brief report.

Tissues of the central nervous system (CNS) of cynomolgus monkeys were examined by electron microscopy after intraspinal inoculation of enterovirus 71 (E71). A characteristic finding was the appearance of numerous membrane-bound vesicles (Mbvs) in affected motoneurons. Similar Mbvs were also present in E71-infected cynomolgus monkey kidney (CMK) cells in culture. Virus-like particles were found within or around Mbvs in motoneurons as well as in infected CMK cells in culture. Neither Mbvs nor E71 antigens as detected by immunofluorescence were found in supporting tissues, vascular endothelium, or inflammatory cells. Quite similar findings had been seen in poliovirus infections. It was suggested that the appearance of Mbvs in the cytoplasm of motoneuron is the direct results of virus multiplication in E71 infection as in poliovirus infection.