Tolerance, Viral Shedding, and Neoplasia in Chickens Infected with Non-Defective Reticuloendotheliosis Viruses

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Abstract
Chickens inoculated as embryos with non-defective reticuloendotheliosis viruses (ndREV) generally developed a tolerant infection characterized by lack of immunofluorescent antibody and by a viremia that persisted through 93 wk. Chickens inoculated at hatching generally developed a non-tolerant infection characterized by antibody development that gradually waned as the chickens aged and by a transient or intermittent viremia. Although chickens tolerantly infected with ndREV strain T were immunodepressed, tolerance to ndREV did not depend on immunodepression, because 17-20 wk old chickens tolerantly infected with ndREV strain CS were normal in antibody response to sheep red blood cells and Brucella abortus and in mitogen-stimulated blastogenesis of blood lymphocytes. Tolerantly infected dams shed low levels of gs antigen and virus into eggs at high frequencies; in 2 trials, congenital transmission of virus by strain-CS-infected dams was documented in only 2 of 42 and 1 of 132 progeny chicks. Eggs and progeny chicks from non-tolerantly infected dams were always negative for virus and gs antigen. After long latent periods (17-93 wk), ndREV-infected chickens developed lymphomas involving the bursa of Fabricius and other visceral organs at high frequency and developed sarcomas, carcinomas and inflammatory nerve lesions at a lower frequency. The ability of ndREV to induce tolerant and non-tolerant infection, virus- and anti-shedding into eggs and chronic neoplastic disease resembled that of lymphoid leukosis virus, another common avian retrovirus. Certain differences in epidemiological properties of these 2 viruses are discussed.