In vitro differentiation of virulent and attenuated polioviruses by their growth characteristics on ms cells

Abstract

The MS character of poliovirns particles is described. Strains that produced relatively large plaques, up to 6 mm. in diameter, on a monkey stable (MS) Downloaded from on December 2, 2016 Published January 1, 1959 22 VIRULENT AND ATTENUATED POLIOVIRUSES cell line, were classified as MS+. Such strains were found to include the highly virulent poliovirus strains. Attenuated strains appeared deficient in this gene, for they produced tiny plaques less than 1 ram. in size, or no visible plaques at all; they were considered as MS mutants. Strains of maximum neurovirulence for the monkey possessed the MS+ and d + characters, while those of greatest attenuation were MS d. Strains possessing the MS d+ character showed high or intermediate attenuation. Virulent strains grew equally well in MS or primary monkey kidney (MK) cells. Attenuated strains gave lower titers in MS cultures than in MK cultures. While MS cells after infection with a virulent virus yielded about 100 to 200 PFU per cell, only one PFU per MS cell was detected after infection with an attenuated virus. © 1959, Rockefeller University Press., All rights reserved.