Project Number: 5348-32000-024-00
Project Type: Appropriated

Start Date: Oct 01, 2006
End Date: Sep 30, 2011

Objective:
This Project is comprosed of four objectives designed to address key areas of research related to malignant catarrhal fever (MCF) and its causative viruses, particularly ovine herpesvirus 2 (OvHV-2). Discovery of new viruses in the MCF virus group necessitates extension of current nucleic acid based diagnostic tests with an emphasis on developing rapid and reliable assays for use by veterinary diagnosticians. In addition this project seeks to define basic virus-host interactions at the molecular level in order to identify how OvHV-2 causes disease so that control strategies, including immunological based methods such as vaccination, can be developed to protect clinically susceptible ruminants. These four objectives include 1) extend nucleic acid based diagnostic tests to include newly discovered members in the MCF virus group; 2) define host-virus interactions in sheep and develop an in vitro propagation system for OvHV-2; 3) define OvHV-2 gene expression within MCF lesions; and 4) develop an immunological control strategy for MCF in clinically susceptible ruminants.

Approach:
Extend current nucleic acid-based tests for clinical diagnosis of MCF by validating the recently developed real-time PCR using a large set of defined field samples from animals with clinical MCF and by developing DNA microarray-based PCR for detection and differentiation of MCF group viruses. MCF pathogenesis will be studied in three phases: 1) characterize lesion development in bison during preclinical and clinical stages; 2) determine OvHV-2 genes that are highly expressed during preclinical and clinical stages using a gene expression microarray containing all 73 OvHV-2 open reading frames; and 3) define the role of OvHV-2 gene products in MCF lesion development by developing an infectious OvHV-2 bacterial artificial chromosome (BAC) clone and testing the pathogenicity of infectious OvHV-2 BAC clones in bison, with the deletion of genes associated with lesion development. In developing an immunological control strategy for MCF in clinically susceptible ruminants, we will first characterize bison MHC class I and class II haplotypes and determine any association between MHC specific alleles and MCF resistance/susceptibility. For analysis of immune responses to OvHV-2 and development of vaccines for protection of animals from MCF losses, we will determine if animals that survive initial low dose infection with OvHV-2 are resistant to clinical MCF after a subsequent high dose challenge using our recently established animal model, bison. We will also determine which immune response dominates in the animals that survive the challenge, and finally evaluate vaccine candidates for protection against MCF in clinically susceptible ruminants. BSL-1; 9/04/06. Replacing 5348-32000-018-00D October, 2006.