Role of T cells in vaccine-mediated immunity against Marek’s Disease

Authors: Heidari, Mohammad; Zhang, Huanmin; SUNKARA, LAKSHMI - Clemson University; AHMAD, SYED MUDASIR - University Of Kashmir

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2023
Publication Date: 2/28/2023
Citation: Heidari, M., Zhang, H., Sunkara, L.T., Ahmad, S. 2023. Role of T cells in vaccine-mediated immunity against Marek’s Disease. Viruses. 15. Article 648. https://doi.org/10.3390/v15030648.
DOI: https://doi.org/10.3390/v15030648

Interpretive Summary: Marek’s disease (MD) is a highly contagious disease of domestic chickens characterized by weight loss, depression and lymphoma formation in visceral organs. Although vaccines have been successful in controlling MD, the molecular mechanism of vaccine-mediated protection is not well known. To provide insight into the possible role of T cells (Cellular components of immune system) in immunity induced by vaccination, we depleted circulating T cells through intravenous injection of anti-chicken T cells monoclonal antibodies and challenged the birds 10 days post vaccination after recovery of T cell populations post treatment. There was no clinical signs or tumor development associated with birds vaccinated in the absence of specific circulating T cell population and challenged post treatment. The vaccinated birds with total depletion of circulating T cells, however, were severely emaciated, with atrophied spleens and bursas. These birds were also tumor free at termination with no virus particles detected in the collected tissues. Data indicates that T lymphocytes do not play a critical role in vaccinemediated protection against Marek’s disease virus-induced tumor development. This study sheds light onto mechanism of vaccination and paves the road for development of recombinant vaccines that modulates the innate immune system.

Technical Abstract: Marek’s disease virus (MDV) is a highly cell-associated oncogenic alpha-herpesvirus and the etiological agent of T cell lymphomas in chickens known as Marek’s disease (MD). Clinical signs of MD include neurological disorders, immunosuppression, and lymphomas in visceral organs, peripheral nerves, and skin. Although vaccination has greatly reduced the economic losses from MD, the molecular mechanism of vaccine-induced protection is largely unknown. To shed light on the possible role of T cells in immunity induced by vaccination, we vaccinated birds after depletion of circulating T cells through intravenous injection of anti-chicken CD4 and CD8 monoclonal antibodies and challenged them post vaccination after recovery of T cell populations post treatment. There was no clinical signs or tumor development associated with birds vaccinated in the absence of either CD4+ or CD8+ T cells and challenged post treatment. The vaccinated birds with combined depletion of CD4+ and CD8+ T cells, however, were severely emaciated, with atrophied spleen and bursa. These birds were also tumor free at termination with no virus particles detected in the collected tissues. Data indicates that CD4+ and CD8+ T lymphocytes do not play a critical role in vaccine-mediated protection against MDV-induced tumor development. This study sheds light onto mechanism of vaccination and paves the road for development of recombinant vaccines that modulates the innate immune system.