Identification of pseudorabies virus-exposed swine with a gI glycoprotein enzyme-linked immunosorbent assay

A monoclonal antibody specific for the gI glycoprotein of virulent pseudorabies virus was produced and used to affinity purify gI glycoprotein. The purified gI was used in an enzyme-linked immunosorbent assay (ELISA) that identified and differentiated field virus-exposed animals from animals vaccinated with gI-deleted virus. The gI ELISA was evaluated by comparing it with the virus neutralization test and with a standard ELISA which does not distinguish between vaccinated and naturally infected animals. Pigs vaccinated with a gI-deleted vaccine were seropositive by the virus neutralization or standard ELISA but were seronegative in the gI ELISA. Nonvaccinated and vaccinated animals were detected as seropositive in the gI ELISA only after exposure to gI-containing field virus. Exposed animals were detected as early as day 7 and for as long as 141 days after field virus exposure. As little as 10(2.7) PFU of field virus was sufficient to seroconvert negative animals in the gI ELISA. Pseudorabies virus-seronegative animals which received multiple doses of gI-deleted vaccine remained seronegative in the gI ELISA. The use of this test to monitor swine for pseudorabies virus infection would offer significant benefits towards eradication of the disease.