The presence of avian leukosis virus group-specific antibodies in chicken sera

Abstract

Experiments designed to investigate by complement-fixation inhibition tests the group-specific antibody response to an injected dose of either subgroup A or subgroup B strains of avian leukosis virus (ALV) were carried out in chickens 2 1 2 , 6, and 23–25 weeks of age. Many 2 1 2 and 6-week-old birds responded with group-specific (gs) antibody whereas the antibody response of birds injected at 23–25 weeks was very poor. Birds congenitally infected with an ALV of subgroup A were immunologically tolerant to the gs antigen and did not respond with gs antibody whether the challenge virus was subgroup A or B. A comparison between neutralizing and gs antibody activity in 70 immune chicken sera showed: (1) the greatest number of sera containing gs antibody were those with titers of neutralizing antibody > 1 1000 , (2) all gs-positive sera had titers of neutralizing antibody > 1 200 , and (3) only 56% of the sera with high neutralizing activity contained gs antibody. Fractionation of two chicken sera containing gs antibody was carried out to separate the IgM and IgG fractions. The gs antibody activity, as well as most of the neutralizing activity, was found in the IgG fractions.