Antigenic Differentiation of Equine Herpes Virus-l (EHV-1) Isolates of Indian Origin using Monoclonal Antibodies

170-174A panel of seven monoclonal antibodies (Mabs) (5 non-neutralizing and 2 neutralizing) raised against 140 kDa polypeptide of EHV-l strain (Hisar-90-7) were used for antigenic characterization of five Indian isolates and compared with reference strain (592) of EHV-l. Jind-96 and Hisar-90-7 were antigenically indistinguishable from reference strain in indirect enzyme-linked immunosorbent assay (ELISA) using 5 non-neutralizing Mabs. The antigenic differences were observed in three EHV-l isolates i.e. Tohana-96-2, Delhi-98 and Raj-98 as they failed to react with 5,4, and 1 of five non-neutralizing Mabs, respectively. While all the six virus isolates were neutralized with Mab 9C4 in virus neutralization test (VNT), two (Tohana-96-2 and Raj-98) of the 6 viral isolates were not neutralized with one Mab, 1H6. However, EHV -1isolates could not be differentiated on western blot analysis as all the Mabs reacted with a 140 kDa protein in these isolates. The findings of the ELISA and VNT using 7 Mabs indicate that initial isolates (Hisar-90-7 and Jind-96) are antigenically closer to reference strain (592) and there is emergence of antigenically different isolates (Tohana-96-2, Delhi-98 and Raj-98) subsequently. The study also establishes that more than one antigenically different strains of EHV-1 are circulating in equines of northern India