Isolation of a Heat-resistant Variant of Polio-virus

IT has been shown 1 that when preparations of MEF 1 (type II) polio-virus ( P. hominis ) are exposed to heat at 50° C., there is a marked reduction in the rate of inactivation as the exposure time is increased (see Fig. 1). Bodian et al. 2 have suggested that such a phenomenon occurring during the inactivation of polio-virus with formaldehyde may be due to (1) protection of some virus particles by aggregation, or (2) the presence of inherently resistant particles, and concluded that there was no evidence to support the latter possibility. Since either of these possibilities may explain our results with heat as the inactivating agent, they formed the basis of further experiments.