The mucosal humoral immune response of the horse to infective challenge and vaccination with Equine herpesvirus-1 antigens

Equine herpesvirus-1 (ERV-1) remains a frequent cause of upper respiratory tract infection and abortion in horses worldwide. However, little is known about the local antibody response elicited in the upper airways of horses f ollowing exposure to EHV-1. This study analysed the mucosal humoral immune response of weanling foals following experimental infection with virulent E HV-1, or vaccination with either of 2 commercial vaccines. Twenty weanlings were assigned to 5 groups and were inoculated with, or vaccinated against, EHV-1 following different regimens. Finally, all weanlings were simultaneo usly challenged intranasally with virulent EHV-I Army 183 (A183). Nasal was h and serum samples were collected at regular intervals until 13 weeks afte r final challenge. Nasal washes were assayed for EHV-1-specific equine IgGa , IgGb, IgG(T), IgA, IgM and total virus-specific antibody using an indirec t, quantitative ELISA. Total serum antibody responses were also monitored, and clinical signs of EHV-disease were recorded for each individual. Virus-specific IgA dominated the mucosal antibody response elicited in wean lings inoculated with A183, being detectable at up to 3.1 mug/mg total IgA 13 weeks after challenge. Neither inactivated EHV-1 administered i.m., nor attenuated ERV-1 administered intranasally induced detectable mucosal antib odies. ERV-1-specific mucosal antibodies impeded ERV-1 plaque formation in vitro. Such virus-neutralising antibody probably contributes to a reduction of shedding of ERV-1 from the respiratory tract of virus-infected horses.