Adaptation of Type I Strain of Poliomyelitis Virus to Mice and Cotton Rats

Abstract
A mixture of 2 strains (Sickle and Mahoney strains) of type I poliomyelitis virus was adapted to mice (PRI strain) and to cotton rats, following passages through tissue cultures. Several sublines were obtained, some of which could be propagated in rodents either by the intraspinal or the intracerebral route. The cytopathic titer in tissue culture of the various sublines was of similar magnitude but the infectivity for mice and cotton rats varied considerably. A subline was obtained which proved to be completely avirulent for rhesus and cynomolgus monkeys.