Epitope-specific antibody responses in market-stressed calves to bovine herpesvirus type 1

Evaluation of a blocking enzyme-linked immunosorbent assay for serological diagnosis of Bovine herpesvirus 1

Bovine herpesvirus 1 (BoHV-1) is an infectious agent of concern in the international export of bovine products; it is endemic in the United States, but it has been eradicated in many countries of the European Union (EU). For export of semen to the EU, accurate assessment of BoHV-1 status of the bull is required and is usually accomplished by measuring the level of antibody to the virus. The gold standard is virus neutralization (VN) using overnight incubation with the virus, a test approved by the World Organization for Animal Health (OIE). Enzyme-linked immunosorbent assay (ELISA) is also approved for international trade. The lone U.S. Department of Agriculture-approved commercial ELISA was compromised with specificity problems, which necessitated the development of a different ELISA. Of 4 monoclonal antibodies evaluated, 1 directed against glycoprotein C of BoHV-1 was found to be the most reliable. One hundred twenty-eight characterized positive samples and 334 negative serum samples were tested. The blocking ELISA showed 97.7% sensitivity and 99.4% specificity as compared with OIE VN. The Wisconsin Veterinary Diagnostic Laboratory ELISA fulfills the OIE requirement for a blocking or competitive ELISA to qualify animals for export to BoHV-1-free countries.

Immunogenicity and protective efficacy of a gE, gG and US2 gene-deleted bovine herpesvirus-1 (BHV-1) vaccine

The efficacy and safety of a gene-deleted bovine herpesvirus-1 (BHV-1) vaccine was determined in a bovine herpesvirus challenge trial in calves. Three different doses of the vaccine were administered intramuscularly at 10(5), 10(6) and 10(7) PFU/ml and compared to a commercial vaccine and non vaccinated control calves. Challenge was performed by intranasal aerosolization with the Cooper strain of BHV-1 (3 x 10(4) PFU/ml). The non-vaccinated calves shed significantly (P < 0.05) more virus than all other groups on days 4, 8 and 10 post challenge. By day 14 post challenge, antibody titers for BHV-1 of calves vaccinated with 10(7) PFU/ml were significantly (P < 0.05) higher than the commercial or non-vaccinated calves. Clinical scores of non-vaccinated calves were significantly (P < 0.05) higher than all other groups on days 4-14 post challenge. With both radioimmunoprecipitation and competitive enzyme-linked immunosorbent assays (C-ELISA), calves in the gene-deleted vaccine groups mounted comparable specific responses against gB, gC and gD post vaccination as calves in the commercial vaccine group, but in a dose dependent manner. These data suggest that the gene-deleted BHV-1 vaccine tested may be used as an effective vaccine in controlling BHV-1 infections.