Presence of two interfering enteroviral agents (ECHO virus type 9 and poliovirus type 2) in the human central nervous system

Summary

A cytopathogenic and suckling-mouse pathogenic agent isolated from the CNS of an infant appeared to consist essentially of two different interfering viruses. The major component was ECHO-9 virus, the minor component was polio virus type 2. Both viruses were segregated by various methods: (1) cultivation in human papilloma cells, in which only the poliovirus multiplied, (2) plating of high dilutions of monkey kidney culture fluid, which yielded ECHO-9 single plaque progeny, (3) suckling-mouse passage. Poliomyelitis-like lesions developed after intracerebral and intraspinal inoculation of monkey kidney culture fluid containing both components, but only in monkeys that had been treated with cortisone. The CNS of these monkeys yielded mostly ECHO-9 virus, and occasionally poliovirus type 2. ECHO-9 virus was the interfering agent, which considerably suppressed the multiplication of poliovirus type 2, not only through a number of monkey kidney culture passages, but also in the CNS of monkeys. Since the high concentration of virus found in the CNS of the patient was mainly a result of a high concentration of the ECHO-9 component, the latter has apparently interfered with the poliovirus component also in the human CNS. A slight interfering effect of the poliovirus on the multiplication of ECHO-9 virus has been observed in suckling-mice. Although the ECHO-9 virus has entered the human CNS accompanied by poliovirus type 2, the neuroinvasiveness of the former, under certain conditions, is evident. Likewise, there is evidence of multiplication of this particular strain in the human and monkey CNS. The problem as to whether this virus is able to produce poliomyelitis-like lesions in the human CNS, however, remains to be solved.