Immune response to avian leukosis virus infection in chickens: Sequential expression of serum immunoglobulins and viral antibodies

Chickens of a 15I₅ × 7₂ cross that produces endogenous Rous associated virus (RAV-0) were infected with subgroup A lymphoid leukosis virus (RAV-1). Within 3 weeks, before RAV-1 neutralizing antibodies were detected, significantly higher levels of serum immunoglobulin G (IgG) were found in infected birds than in uninoculated hatchmates. Immunoglobulin M was significantly elevated only during the late leukotic state. Although most of the inoculated birds tested had RAV-1 neutralizing antibodies, no correlation was found between IgG levels and antibody titers. Tolerance to endogenous virus (RAV-0) and viral group-specific antigen was apparently abrogated by RAV-1 inoculation because significantly higher percentages of iodinated envelope glycoprotein (gpE) of RAV-0 and a viral structural antigen of mol. wt 19,000 daltons (p 19) were precipitated by sera from inoculated birds than from control birds.