The S7 gene and VP7 protein are highly conserved among temporally and geographically distinct American isolates of epizootic hemorrhagic disease virus

Arthropod-borne Animal Diseases Research Laboratory, USDA, ARS, P.O. Box 3965, Laramie, WY 82071, USA.
Virus Research (Impact Factor: 2.32). 09/2003; 94(2):129-33. DOI: 10.1016/S0168-1702(03)00166-7
Source: PubMed


Complete sequences of genome segment 7 (S7) from six isolates of epizootic hemorrhagic disease virus serotype 1 (EHDV-1) and 37 isolates of serotype 2 (EHDV-2) were determined. These isolates were made between 1978 and 2001 from the southeast, mid-Atlantic, Midwest and intermountain United States. Analysis of the S7 sequence similarities showed 98.1% identity among the EHDV-1 isolates and 91.0% identity among the EHDV-2 isolates. Comparison of the deduced amino acid similarities showed an even greater degree of similarity among the isolates (100% among the EHDV-1 isolates and 98.9% identity among the EHDV-2 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 the two groups at the amino acid level. The ratio of non-synonymous to synonymous nucleotide indicates a strong selection for silent substitutions. There was no evidence for reassortment between EHDV-1 and EHDV-2 isolates. The high degree of conservation of S7 gene codons and the VP7 protein, suggests that little variation is allowed in preserving the function of this protein. The high degree of conservation also validates the use of diagnostic tests for EHDV based on S7 and VP7.

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    • "Thus, the most likely explanation is that these animals are in the early stages of infection, when there is circulating virus but no detectable antibody production. An alternative explanation, that the C-ELISA does not detect antibodies in some infected animals due to mutation in the epitope of the VP7 antigen recognised by the monoclonal antibody used to inhibit bovine antibodies in the assay, is possible but unlikely due to the highly conserved nature of this antigen (Mecham et al., 2003). "
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    • "However, whether these chimeric protein–protein, protein–RNA, or possibly even RNA–RNA interactions affect the fitness level (e.g., replication, assembly, and transmissibility) of EHDV-6 (Indiana) relative to non-heterotypic viruses is unknown and requires further study. Additionally, whether similarly structured reassortant viruses derived from sympatric endemic serotypes (e.g., VP7 of EHDV-1 and VP2/VP5 of EHDV-2) may also circulate in the United States has not been investigated extensively (Mecham et al., 2003). Analysis of partial VP2, VP5, and VP7 sequences from 14 EHDV-6 (Indiana) isolates (see Table 3 for list) recovered in the United States Table 1 Genomic characteristics of EHDV-6 (Indiana), showing the length of the open reading frames (ORFs) and untranslated regions (UTRs) of each segment, along with the predicted length and molecular weights (MW) of the cognate proteins. "
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