Functional and ultrastructural changes in neutrophils from mares and foals experimentally inoculated with a respiratory tract strain of equine herpesvirus-1.

Neutrophils isolated from venous blood of adult and foal ponies inoculated with equine herpesvirus-1 were evaluated by in vitro function tests and by electron microscopy. Foals had fever and severe neutropenia 24 hours after inoculation; increased neutrophil random migration under agarose and decreased antibody-dependent cell-mediated cytotoxicity were significant at 24 hours, but values had returned to preinoculation levels by 72 hours. Mares had fever and leukopenia of less severity, increases in neutrophil migration, and longer persistence of primary granule release than were seen in foals. Reduced migration and degranulation, and a decrease in antibody-dependent cell-mediated cytotoxicity seen with neutrophils from foals, as compared with mares, may relate to the high susceptibility of foals to equine herpesvirus-1 infection.