Further Modification of the Mouse Adapted Type III Poliomyelitis Virus

Abstract

A further modification of the mouse-adapted Leon virus is described. With successive mouse passages the virulence for mice has spontaneously increased and the incubation period has become shorter and more constant. Passage from mice to tissue culture results in loss or marked reduction of virulence for mice. This modified virus can be employed quite satisfactorily for serum neutralization tests and makes available an additional field and laboratory tool for poliomyelitis research.