Abstract
Seven serologically and immunologically distinct types of foot-and-mouth disease virus (FMDV) are known; these types can be subdivided into numerous subtypes. Recently, we reported on polynucleotide sequence homologies among the ribonucleic acids (RNA's) of FMDV types A, O and C (Dietzschold et al. 1971). Making use of saturation and competition experiments various degrees (44 to 65%) of base sequence homologies between different types were obtained. This report is concerned with similar studies but using subtypes and mutants of FMDV, type O. We felt that there is a need especially for quantitative data on genetic relationships between different subtypes, because the serological classification is not always congruent with a classification based on immunological properties (Wittmann, 1964). Furthermore, it appeared interesting to compare in cross-annealing experiments wild-type virus with mutants reacting identically in serological tests.
The experiments were performed with radioactive labelled FMDV RNA of five O-subtypes and five mutants of subtype O1 which were hybridized with denatured unlabelled FMDV-specific double-stranded RNA of the respective virus-strains.