Abstract

Mice immunized with equine herpesvirus type-1 (EHV-1) L-particles showed a significant increase (p<0.05) in serum antibody titers. Upon a booster dose four weeks later, antibody titers increased significantly. Interestingly, immunization via intravenous or intramuscular route induced significantly higher (p<0.05) antibody titers. However, mice iummunized with UV-treated L-particles, virions or immunization via intranasal route induced lower antibody titers. Upon challenge inoculation with wild-type EHV-1, our data showed there was a poor correlation between antibody titers and protection against virus replication. Therefore, the role of cell-mediated immunity towards protection was investigated. As predicted, the strongest cell-mediated immunity, as measured by delayed-hypersensitivity test, was detected in mice immunized with live virus particles. The magnitude of cell-mediated immune response correlated with the efficacy of L-particles as immunizing agent. The highest efficacy, as indicated in mice immunized via intranasal route, was highly correlated with cell-mediated immunity. A similar phenomenon was also demonstrated in mice immunized intranasally with UV-treated L-particles. However, the degree of protection was reduced when mice immunized intravenously or intramuscularly with UV-treated L-particles. In conclusion, protection conferred in these animals was highly implicated by immune cells and the least by antibodies. The route of immunization and the nature of the antigen also contributed to the efficacy of L-particles as immunizing agent. In contrast to that of herpes simplex virus type 1, our data showed EHV-1 non-infectious L-particles are highly suitable for immunization of the host against EHV-1 disease.

• Keywords: equine herpesvirus; L-particles; cell-mediated immunity; antibody response