Antigenic relationships between Bovine viral diarrhea virus 1 and 2 and HoBi virus: possible impacts on diagnosis and control.

The emergence of a newly recognized group of pestiviruses in cattle, the HoBi-like viruses, requires an evaluation of the available diagnostic tools and vaccines. The present study compared antigenic characteristics of Bovine viral diarrhea virus 1 and 2 (BVDV-1, -2) strains and HoBi virus. This comparison was based on detection of HoBi virus and antibodies against it by commercial enzyme-linked immunosorbent assays (ELISAs) and the level of cross-neutralizing antibodies present in sera from animals vaccinated with BVDV. Reactivity with a panel of monoclonal antibodies (mAbs) revealed greater cross-reactivity between BVDV species (BVDV-1, -2) and HoBi epitopes within E(rns) and NS2/3 proteins than between epitopes located in the E2 glycoprotein. The results suggest that a diagnostic test designed to detect both BVDV species and HoBi could be based on E(rns) or NS2/3 epitopes, while variation among E2 epitopes could be exploited in tests for differentiation of pestivirus species. The threshold of detection of HoBi virus by an antigen-capture ELISA kit based on detection of E(rns) was statistically similar to that for BVDV. In contrast, 2 commercial ELISA kits designed to detect antibodies against BVDV missed 22.2% and 77.7%, respectively, of serum samples harboring HoBi virus-neutralizing antibodies. In addition, sera of calves vaccinated with BVDV-1 and -2 presented low neutralizing activity against HoBi virus. The results demonstrate that in spite of antigenic similarities, HoBi virus is antigenically distinct from both BVDV species. Detection and control of HoBi virus infections in cattle would thus require the development of new diagnostic reagents and reformulation of current vaccines.