Neutralizing antibodies to bovine herpesvirus types 1 (BoHV-1) and 5 (BoHV-5) and its subtypes

This study was carried out to determine whether the sensitivity of serum neutralization (SN) tests would be affected by the use of distinct subtypes of bovine herpesvirus 1 (BoHV-1) and 5 (BoHV-5) as test challenge viruses. Bovine sera collected from a randomized sample (n=287) were tested in a 24h incubation SN against three type 1 viruses (BoHV-1.1 strains "Los Angeles" (LA) and "EVI 123"; BoHV-1.2a strain "SV 265") and three type 5 viruses (BoHV-5a strain "EVI 88"; BoHV-5b strain "A 663" and BoHV-5c "ISO 97"). SN sensitivity varied greatly depending on the test challenge virus used in the test, particularly when results against each virus were considered individually, where it ranged from 77% (detecting 80 out of 104 antibody-positive sera) with ISO 97 to 91% (95/104) with BoHV-1.1 strain LA. All tests to single viruses revealed a significantly low sensitivity (McNemar's; p<0.05). Maximum sensitivity (104/104) was achieved when positive results to a particular combination of four of the challenge viruses (LA+EVI 123+SV 265+A 663) or some combinations of five viruses (or all six viruses) were added cumulatively. These results provide evidence for no association between any particular virus type/subtype and higher SN sensitivity. In addition, it was clearly shown that when SN is performed with single test challenge viruses, sensitivity can vary so significantly that might compromise control or eradication efforts. Performing SN against a number of different viruses demonstrated to improve significantly the test's sensitivity.