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 102.7 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.

No abstract

Cats exposed to feline infectious peritonitis virus (FIPV) or feline enteric coronavirus (FECV) cannot be differentiated by serological analysis. Three synthetic peptides and an E. coli recombinant fusion protein generated from FIPV 79-1146 spike gene sequence were produced. Coronavirus positive cat sera reacted to peptide aa 950-990 but were non-reactive to aa137-151 and aa 150-180 peptides as demonstrated by ELISA. Amino acid sequence 97-222 expressed as a galk fusion protein in E. coli was tested against coronavirus positive cat sera by western blot analysis. Only sera from cats exposed to the FIPV type-II strains DF-2 or 79-1146 that were exhibiting signs of FIP recognized the fusion protein. Sera from FECV exposed cats did not recognize the 97-222 fusion protein in western blot analysis.