BIOLOGICAL PROPERTIES OF RIBONUCLEIC ACID FROM VIRULENT AND ATTENUATED POLIOVIRUS

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Abstract
The relationship of neurovirulence and viral ribonucleic acid (RNA) of type I poliovirus was studied in cell cultures and in mice. Infectious RNA was extracted by the phenol method from the following strains of type I poliovirus: Mahoney and its 2 variants, Lsa and Lsc. The Mahoney strain is highly virulent in mpnkeys both intraspinally and intracerebrally. The Lsa strain is virulent in mice intraspinally; the Lsc variant is avirulent in mice both intraspinally and intracerebrally and is highly attenuated for monkeys. Comparison of the reproductive capacity at 36[degree]C and 40[degree]C in monkey kidney cell cultures indicated that the intact Mahoney virus or its RNA formed the same number of plaques at both temperatures of incubation, while Lsc virus or its RNA failed to form plaques at 40[degree]C. Intraspinal inoculation of mice with RNA derived from Lsa virus caused synthesis of high concentrations of poliovirus, appearance of typical lesions in the spinal cord resulting in paralysis and death of the animals. Injection of RNA extracted from Lsc virus caused low virus multiplication, absence of specific lesions, illness or death. The results suggest that infective RNA from type I poliovirus carried the genetic information which determines the degree of neurovirulence.