Poliomyelitis. II. Propagation of MEFl Strain of Poliomyelitis Virus in Developing Chick Embryo by Yolk Sac Inoculation. ∗

Summary

1. The MEFl-A strain of human poliomyelitis virus(10), after 119 serial passages in suckling hamsters, has been maintained in one passage series for 41 consecutive generations and in a second series for 38 generations in the developing chick embryo by the yolk sac route of inoculation. Both lines of passages are still in progress. 2. The identity of the chick embryo adapted virus with human poliomyelitis virus was established by mouse neutralization tests in which anti-Lansing type immune sera from 3 different sources were used; by the ability of the passage virus to stimulate the formation of antibodies in monkeys which neutralize known virulent strains of Lansing type poliomyelitis virus; and by the ability of monkeys to withstand intracerebral challenge with known virulent strains of poliomyelitis virus after they had survived inoculation with the chick embryo passage virus. The identity of the passage virus was further established by its ability to induce typical symptoms and histopathologic lesions in monkeys following intracerebral inoculation.