Characterization of Small Plaque Mutants of Mouse Hepatitis Virus, JHM Strain

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Abstract
Two small plaque mutants designated 1a and 2c were isolated from DBT mouse brain tumor cells persistently infected with the JHM strain of mouse hepatitis virus. Unlike wild-type JHM, the 2 mutants grew more slowly with no prominent cell fusion. The buoyant densities of the mutants were slightly lower and 2c was revealed to have fewer peplomers than JHM by electron microscopy. Purified JHM contained 5 polypeptides with MW of 260,000, 105,000 (GP105), 65,000, 60,000 (P60) and 23,000 (GP23). P60 and GP23 were common to JHM and the mutants; 1a contained 3 other specific polypeptides with MW of 180,000 (GP180), 110,000 and 95,000 (GP95); 2c had GP180, GP105, GP95 and a peptide of MW 175,000. All these polypeptides were glycosylated, except for P60. After bromelain treatment, all these viruses lost the peplomers and contained P60 and another new 18,000-dalton polypeptide.