CHARACTERISTICS OF 2 NEW AVIAN TUMOR VIRUS SUBGROUPS

Avian tumor viruses capable of growing in cells resistant to the A and B subgroups can be assigned to two new subgroups, C and D. Members of subgroup C are virus B77, Rous-associated viruses types 7 and 49, and a clone-purified line of Prague strain Rous sarcoma virus. These agents plate with equal efficiency in types C O, C A, C B, and C AB chick embryo fibroblast cultures but are excluded from type C BC chicken cells. Rous-associated viruses of subgroup C interfere with sarcoma viruses of that subgroup but do not interfere with sarcoma viruses of subgroups A and B. Conversely, subgroup A and B Rous-associated viruses are unable to interfere alone or in combination with challenge viruses of subgroup C. Neutralization tests and fluorescent antibody staining indicate immunological relatedness of subgroup C viruses and antigenic distinctness from subgroups A and B. Of the subgroup C sarcoma viruses only B77 is oncogenic in hamsters. Members of subgroup D are cloned derivatives of the Schmidt-Ruppin and Carr Zilber strains of Rous sarcoma virus, Carr Zilber-associated virus, and Rous-associated virus type 50. These viruses form foci in C O, C A, C B, C AB, and C BC chick embryo fibroblast cultures. However, their plating efficiency is significantly reduced in all cell types resistant to subgroup B. All subgroup D sarcoma viruses are highly oncogenic for the newborn hamster. The associated viruses are capable of interfering with the sarcoma viruses of subgroup D, but this interference is not seen in all genetic types of chicken cells. The associated viruses of subgroup D also interfere with subgroup B sarcoma viruses, and subgroup B Rous-associated virus induces resistance to subgroup D. Interference does not take place between subgroups A or C and subgroup D. The members of subgroup D are also related immunologically, as indicated by the high incidence and degree of cross reactions in neutralization and fluorescent antibody tests. It appears that the previously described subgroups A and B represent mainly avian tumor viruses of the Western Hemisphere, whereas subgroups C and D are largely composed of viruses propagated in European laboratories. © 1969.