Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2003
Publication Date: 8/1/2003
Citation: Mecham, J.O., Stallknecht, D., Wilson, W.C. 2003. The s7 gene and vp7 protein are highly conserved among temporally and geographically distinct american isolates of epizootic hemorrhagic disease virus. Virus Research 94:129-133. Interpretive Summary: Epizootic hemorrhagic disease virus (EHDV) infects both wild and domestic ungulates. Two serotypes of this virus, designated EHDV-1 (New Jersey strain) and EHDV-2 (Alberta strain), are present in the United States. These viruses often cause fatal hemorrhagic disease in wild North American ruminants, including white-tailed deer, mule deer and pronghorn antelope; and there is evidence that they may cause bluetongue-like illness in cattle. The natural variation and evolution among these viruses is unknown. Such information would be useful in understanding the etiology of periodic outbreaks of disease and infection that occur in both wild and domestic animals. In addition, understanding variation among these viruses would be useful in the development of diagnostic tests. We report the sequence analysis of the S7 viral gene that encodes the VP7 viral protein. This gene and protein are the basis for many diagnostic tests for EHDV. Comparison of the sequence of this gene from a number of geographically and temporally distinct virus isolates indicates that this gene and the protein it encodes are highly conserved. This suggests that there are constraints on variation that can occur in this gene and still maintain function of the encoded protein. This also validates the use of diagnostic tests for EHDV based on S7 and VP7.
Technical Abstract: Complete sequences of the S7 gene from 37 isolates of epizootic hemorrhagic disease virus, serotype 2 (EHDV-2) and six isolates of serotype 1 (EHDV-1) were determined. These isolates were made between 1978 and 2001 from the southeast, mid-Atlantic, Midwest and intermountain United States. Analysis of the sequence similarities indicated a high degree of conservation in the S7 gene (91.0% identity among the EHDV-2 isolates, and 98.1% identity among the EHDV-1 isolates). Comparison of the predicted amino acid similarities showed an even greater degree of similarity among the isolates (98.9% identity among the EHDV-2 isolates, and 100% among the EHDV-1 isolates). There was only 75.8% identity between the EHDV-1 and EHDV-2 isolates at the nucleic acid level; however, there was 93.7% identity between all the isolates of the two serotypes at the amino acid level. The ratio of non-synonymous to synonymous nucleotide changes implies saturation with synonymous changes. There was no evidence for reassortment between serotypes. The high degree of conservation of the S7 gene and the VP7 protein that it encodes, suggests an important function for the VP7 protein. This high degree of conservation also validates the use of diagnostic tests for EHDV based on S7 and VP7.