Antibody response to related leukosis viruses induced in chickens tolerant to an avian leukosis virus.

White Leghorn chickens congenitally infected with a subgroup A avian leukosis virus ALV-F42 were challenged at various ages with the serologically related subgroup A avian leukosis viruses (ALV) RAV-1, RAV-3, and RAV-5 and their antibody responses and viremic status determined. Birds given injections of RAV-1 failed to produce neutralizing antibody to any of the pseudotype sarcoma viruses of the various ALV, whereas many birds challenged with RAV-3 or RAV-5 produced neutralizing antibody directed against the heterologous RAV-1 as well as the homologous viruses, but not against the tolerated virus ALV-F42. Virtually all birds remained viremic despite the presence of neutralizing antibody. The results suggested that a phenomenon akin to circumvention or abrogation of tolerance to ALV-F42 was effected, and that there are multiple determinants of the viral envelope antigens of ALV as measured by neutralization.