Isolation of a Non-Neurotropic Variant of Type I Poliomyelitis Virus

Following the adaptation of Type I, Mahoney strain, poliomyelitis virus to mice, further passages in tissue cultures, mice, and alternate monkey skin to tissue cultures resulted in the establishment of 4 passage lines of virus, 3 of which appear to be distinct variants. These strains have been designated as LS, LS-a, LS-b and LS-c and are differentiated on the basis of their range of host reactions. LS and LS-a react similarly and are so-called mouse and monkey spinal variants. LS-b is a mouse cerebral strain and LS-c is a non-neurotropic strain which is avirulent for both mice and monkeys by all routes. These variants have unaltered antigenic and tissue culture characteristics. Preliminary experiments with the LS-c strain have shown it to be capable of inducing good antibody titers and a high degree of resistance to virulent virus challenge in monkeys. There is suggestive evidence that continued skin passages of the LS-c strain may yield a dermal poliomyelitis virus variant.