2011 Annual Report 1a.Objectives (from AD-416) 1) Identify epigenetic changes. 2) Evaluate the epigenetic changes in relation to Marek's disease risk in chickens. 1b.Approach (from AD-416) Profiling hypomethylation and hypermethylation changes in two unique inbred lines of chickens challenged simultaneously with Marek's disease viruses. One of the chicken lines is known resistant and the other susceptible to Marek's disease. 3.Progress Report With samples from two consecutive replicates of challenging experiments, systematic epigenetic analyses were conducted on the University of Maryland campus in collaborative efforts, and significant progresses were made in identifying genomic regions and candidates genes that confer either genetic resistant to Marek’s disease (MD), a T cell lymphoma of chickens caused by the Marek’s disease virus (MDV) or confer differentiated MD vaccinal immunity. Specific genes were characterized that reveal the underlying biological pathways for host-pathogen interactions. Furthermore, epigenetic factors including DNA methylation and microRNA were identified with differentiated patterns or expression levels between MD resistant and highly susceptible lines of chickens, thus, indicating that epigenetic factors may also be involved in disease resistance. Teleconferences were held to discuss research progress and planning experimental efforts. The collaborator, two post doctorial researchers and a graduate student from the University of Maryland came to the Avian Disease and Oncology Laboratory (ADOL) earlier this year to take part in conducting animal challenging experiments and sample gathering. All proposed studies will be finished up and this collaborative work is likely to come to an end, in accordance with the current plan, by August 31, 2012.