#05-166

Complete

Date Full Report Received

02/28/2007

Date Abstract Report Received

02/28/2007

Investigation

Institution:
Primary Investigator:

We have established a set of standard protocols and reagents for whole genome PRRSV sequencing and assembly. Phylogenetic comparisons amongst 10 pairs of homologous strains confirmed several regions undergoing positive selection (changes in protein sequences assumed to be in reaction to immunological or physiological pressures) and others where essentially no changes were observed (suggesting that the observed protein sequence is highly favored for survival). we have not found any sequence changes that occur in all virus samples. This means that potential escape of a PRRSV from immunological protection is not dependent on a specific genetic change in the virus. In addition, a high ratio of transition/transversion was discovered. The significance of this observation is not yet clear, but suggests that the high rate of change characteristic of PRRSV may be due to external host cell factors, rather than a feature of the virus itself.