Development of a focus-reduction neutralizing test for detecting equine herpesvirus type-1-neutralizing antibodies.

Virus-neutralizing (VN) testing is essential for evaluating virus-specific immunity in equine herpesvirus type-1 (EHV-1) infection. We developed a focus-reduction neutralization test (FRNT) for EHV-1 using 96-well plates for faster large-scale testing with sufficient sensitivity. We used an overlay medium containing Avicel (FMC Biopolymer), a microcrystalline cellulose with lower viscosity than the methylcellulose. The foci were visualized by immuno-staining with anti-EHV-1 gp14 monoclonal antibody. The FRNT successfully detected seroconversion in horses experimentally infected with EHV-1 (n = 3) and in those infected naturally (n = 16). The FRNT for EHV-1 was high-throughput and time saving. The FRNT can be used in large-scale seroepidemiological studies of EHV-1 and in evaluating vaccine efficacy.