Role of Thymus-Dependent Immune System in HVT Protection against Marek's Disease

Publisher Website
Google Scholar
Abstract
An experiment was conducted to study the role of thymus-dependent and bursa-dependent immune systems in protecting chickens against Marek''s disease (MD) using herpesvirus of turkeys (HVT). Chickens were rendered T cell-deficient (TX) by surgical thymectomy at 1 day of age and by anti-thymus serum treatment. The chicks were unable to mount graft-vs.-host reaction in embryonating eggs. A separate group of chicks were made B cell-deficient (BX) by cyclophosphamide and anti-bursal serum treatment and the chicks produced no antibodies against HVT or MD virus (MDV). A group of chicks with intact immune systems was also included. The chicks were vaccinated at 11 days of age with HVT vaccine and then challenged with MDV 3 wk post-vaccination. Vaccinated uninfected and unvaccinated MDV-infected birds of BX, TX and normal immune status were also included. Vaccinated control birds (BX, TX and normal) did not develop MD lesions. Normal and TX birds of the unvaccinated MDV-infected group developed severe MD lesions but the BX chicks did not develop gross lesions. Vaccinated and challenged normal and BX birds had no MD lesions, but TX birds had a high incidence of lesions. Thus, in the absence of thymus, the HVT vaccine fails to protect birds against MD infection. Evidently, cell-mediated immunity plays a major role in HVT vaccinmal protection against MD.