Establishment of an enzyme-linked immunosorbent assay for Getah virus infection in horses using a 20-mer synthetic peptide for the E2 glycoprotein as an antigen.

An enzyme-linked immunosorbent assay (ELISA) using a synthetic peptide for the E2 glycoprotein was developed for the serodiagnosis of Getah virus infection in horses. To identify an immunogenic epitope, a series of 20-mer peptides (n = 22) for the E2 protein was screened with pooled sera from horses infected with Getah virus. Peptide P11 (PTEEEIDMHTPPDIPDITLL) showed the strongest reaction. ELISA using P11 (E2-P11-ELISA) detected increased antibody levels in all seven experimentally infected horses and in five out of nine vaccinated horses. Out of 28 naturally infected horses, 25 were seronegative in their acute sera but turned seropositive in their convalescent sera. For the remaining three horses whose acute sera were seropositive, an endpoint method with serial dilutions detected a ≥ 4-fold increase in titer between paired sera. The concordance between E2-P11-ELISA and a virus-neutralization test in terms of seropositivity was assessed using a series of 220 horse sera, resulting in almost perfect agreement, with a kappa coefficient value of 0.865. E2-P11-ELISA had a sensitivity of 93.3% (95% CI 86.6-97.1%) and a specificity of 95.0% (95% CI 92.5-96.4%). This highly sensitive and specific E2-P11-ELISA should be useful for serodiagnosis of Getah virus infection in horses.