B cells do not play a role in vaccine-mediated immunity against Marek’s disease

Abstract

Background Marek’s disease virus (MDV), a highly oncogenic α-herpesvirus, is the etiological agent of Marek’s disease (MD) in chickens. The antiviral activity of vaccine-induced immunity against MD reduces the level of early cytolytic infection, production of cell-free virions in the feather follicle epithelial cells (FFE), and lymphoma formation. Despite the success of several vaccines that have greatly reduced the economic losses from MD, the mechanism of vaccine-induced immunity is poorly understood. Methods To provide insight into possible role of B cells in vaccine-mediated protection, we bursectomized birds on day of hatch and vaccinated them eight days later. The birds were challenged 10 days post vaccination with or without receiving adoptive lymphocytes from age-matched control birds prior to inoculation. The study also included vaccinated/challenged and non-vaccinated challenged intact birds. Flowcytometric analysis of PBMN cells were conducted twice post bursectomy to confirm B cell depletion and assess the effect of surgery on T cell population. Immunohistochemical analysis and viral genome copy number assessment in the skin samples at termination was performed to measure the replication rate of MDV in the FFE of the skin tissues of the challenged birds. Results The non-vaccinated/challenged birds developed typical clinical signs of MD while the vaccinated/challenged and bursectomized, vaccinated/challenged groups with or without adoptive lymphocyte transfer, were fully protected with no sign of transient paralysis, weight loss, or T cell lymphomas. Immunohistochemical analysis and viral genome copy number evaluation in the skin samples revealed that unlike the vaccinated/challenged birds a significant number of virus particles were produced in the FFE of the non-vaccinated/challenged birds at termination. In the bursectomized, vaccinated/challenged groups, only a few replicating virions were detected in the skin of birds that received adoptive lymphocytes prior to challenge. Conclusions The study shows that B cells do not play a critical role in MD vaccine-mediated immunity.

Marek’s disease virus-specific T cells proliferate, express antiviral cytokines but have impaired degranulation response

“…MD is associated with metabolic dysregulation ( 4 – 7 ), immunosuppression ( 8 – 14 ), neurological disorder ( 15 ), and CD4+ lymphoma formation in chickens ( 1 , 16 ). Because of MDV’s highly cell associated nature, it is believed that virus-specific T lymphocytes are critical in control of MD ( 17 , 18 ). Vaccination inhibits MD but fails to control MDV replication and shedding ( 19 ).…”

Role of T Cells in Vaccine-Mediated Immunity against Marek’s Disease

“…Our previous study has revealed that B cells do not play an essential role in vaccine-induced protection [ 47 ].The goal of the present study was to provide insight into the role of T cells in immunity mediated by vaccination. Using specific monoclonal antibodies, birds were depleted of CD4 + , CD8 + , or combined CD4 + /CD8 + T cells followed by vaccination.…”

“…Approximately 10 mg of spleen tissues were used for DNA isolation using Qiagen DNeasy Blood and Tissue Kit according to the manufacture’s recommendation. Skin DNA isolation was performed according to previously published protocol [ 47 ].…”

Diagnosis of Marek’s Disease in Isa Brown Layer Chicken based on Anatomical Pathology and Histopathological Examination

“…The respiratory route is one-way chickens are infected by MD as they inhale contaminated air [4]. The virus of Marek's disease is transported through the lungs to the lymphoid organs by attaching to macrophages and dendritic cells that have either been infected or have phagocytized the virus [9]. Following infection of the respiratory tract, pathogenesis occurs in several stages, including the initial cytolytic phase, latent phase, and late cytolytic phase.…”

“…Despite low mortality, mild forms of Marek's disease can be immunosuppressive thus chickens are more susceptible to other diseases and potential sources of infection. Furthermore, [9] describe the clinical symptoms of MD for instance temporary paralysis, crippling, weight loss, blindness, depression, immunosuppression, and the formation of T cell lymphoma in visceral organs.…”