Poliovirus Mutants with Altered Responses to Cystine

Abstract

SUMMARY: Three strains of poliovirus (Akron, antigenic type 1; Brooks, type 2; Mabie, type 3), which require exogenously supplied cystine (or a cystine-substitute) for optimal cytopathogenic action on monkey kidney tissue cultures, were serially passaged ten times in cystine-deficient monkey kidney tissue cultures in tubes. From various passage levels in this system were isolated three mutants of Akron, four of Brooks and two of Mabie. These nine mutants are designated the cystine-response mutants and are distinguishable from their ancestral viruses used to initiate the passage series by being relatively cystine-non-requiring. Two criteria suffice to distinguish the mutants of any strain from each other: (1) the degree of loss of requirement for cystine, and (2) the degree of inhibition by relatively high concentrations of cystine. The compositions of the virus populations in most of the passage levels were determined, and from these determinations the patterns of emergence of the mutant viruses were delineated.