2011 Annual Report 1a.Objectives (from AD-416) This project is comprised of two objectives designed to address key areas of research related to malignant catarrhal fever (MCF) in bison. These two objectives include:. 1)defining ovine herpesvirus 2 gene expression within MCF lesions and. 2)developing an immunological control strategy for MCF in clinically susceptible ruminants. 1b.Approach (from AD-416) ARS and cooperator have recently developed an animal model (bison), in which the infection and disease can be ready induced by aerosol transmission. The first objective of the project focuses on MCF pathogenesis by characterization of lesion development in bison during preclinical and clinical stages and determination of viral genes that are highly expressed during preclinical and clinical stages using a gene expression microarray. The second objective emphasizes the development of an immunological control strategy for MCF in clinically susceptible ruminants. In this objective, bison MHC class I haplotypes will be determined. Immune responses to the virus will be analyzed in bison that survive initial low dose infection and a subsequent high dose challenge. Overall an immunological control strategy will be developed and vaccine candidates evaluated using the animal model. 3.Progress Report During FY 2011, the principal investigator of the project, working with the scientists at the Animal Disease Research Unit, USDA-ARS and with faculty at Washington State University, participated in a series of studies on determination of OvHV-2 replication and host response in rabbits in comparison with bison. The lesion development in experimentally infected rabbits during preclinical and clinical stages was examined, and viral and host gene expressions during infection were determined. The data revealed that there is a similarity in OvHV-2 replication and host response between rabbits and bison, suggesting that rabbits can be used as a research model for MCF vaccine development and pathogenesis studies. Meanwhile, we are in preparation of an experiment to determine AlHV-2 infectivity in bison, a non-pathogenic MCF virus from African antelope (hartebeest or topi), which will be used as an MCF vaccine backbone. This project, under specific cooperative agreement, has been closely monitored by the parl, the lead scientist of the parent project. The lead scientist had occasional onsite visits and discussions about the project with the principal investigator (PI) at the University of Wyoming. Regular conference calls have been scheduled between the lead scientist and the PI to discuss research progress and problems, in addition to frequent email communications.