#06-006

Complete

Date Full Report Received

08/13/2007

Date Abstract Report Received

09/15/2008

Investigation

Institution:
Primary Investigator: ,

Porcine circovirus type 2 (PCV2) currently is an economically important swine pathogen. Although several vaccines against PCV2 are available, it is important to understand the mechanism of PCV2 pathogenesis and develop improved vaccines. The open reading frame (ORF) 3 of porcine circovirus type 2 (PCV2) reportedly encodes a novel protein that is involved in pathogenesis, and that an ORF3-deletion PCV2 mutant is reportedly attenuated in mice. These reports have not been independently confirmed, and the results from the published mice pathogenesis study are difficult to interpret. In this study, we attempted to verify the published reports in the relevant pig model and to assess whether or not the ORF3 can be used for PCV2 vaccine development. By using an anti-peptide ORF3-specific rabbit antibody, we could not detect the expression of ORF3 protein in PCV2-infected cells. Furthermore, when pigs, the natural host of PCV2, were inoculated with a ORF3-null PCV2 mutant, we did not find significant difference in the average scores of gross or histological pathological lesions between pigs inoculated with the ORF3-null mutant and pigs inoculated with wild-type PCV2. Thus, the data from this study do not support the conclusion of previous published reports, and thus the ORF3-null PCV2 cannot be used as a vaccine candidate. Contact information: E-mail: xjmeng@vt.edu. X.J. Meng, M.D., Ph.D., Professor of Virology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA.