Description

CD8 T cell and protective response induced by Marek’s disease vaccines

Hans Cheng^1,2, John Dunn¹, Supawadee Umthong^3*

¹USDA, ARS, Avian Disease and Oncology Laboratory, East Lansing, MI, USA; ²Genetics Program, Michigan State University, East Lansing, MI, USA; ³Microbiology and Molecular Genetics Program, Michigan State University, East Lansing, MI, USA

Marek’s disease (MD) is a lymphoproliferative disorder in chickens caused by Marek’s disease virus (MDV), a highly oncogenic herpesvirus. MD vaccines are widely used throughout the world and are effective in preventing tumor development but not viral infection or spread. It is unknown as to whether MD vaccines enhance the immunity of MDV-infected birds against the virus or towards the tumor. In other cancer-related viruses such as hepatitis B virus (HBV) or human papillomavirus (HPV), CD8 CTL effector function is thought to be necessary for protection by providing anti-viral effects, killing infected cells, preventing cancer formation, or/and destroying cancerous cells. The test of potential role of CD8 T cells, birds were vaccinated with SB-1, HVT, or SB-1+HVT MD vaccines at hatch, then anti-CD8 monoclonal antibody specific to the CD8 receptor administered on a weekly basis to significantly deplete CD8 T cells. At 5 days of age, the chicks were challenged with pathogenic MDV (Md5 strain). Our result shows that CD8 depletion reduced vaccinal protection in birds given SB-1 or HVT vaccines only but not when both vaccines were administered. Additional experiments are underway to explore whether CD8 response induced by vaccine immunization results in anti-virus or anti-tumor effect, which will help to elucidate the protective mechanism of MD vaccines.