Comparison of the antibody response to transmissible gastroenteritis virus and porcine respiratory coronavirus, using monoclonal antibodies to antigenic sites A and X of the S glycoprotein.

Pigs were inoculated with various strains of transmissible gastroenteritis virus (TGEV) or with porcine respiratory coronavirus (PRCV), and antigenic site-specific antibody responses were compared. A blocking-ELISA was used to study to what extent antibodies in convalescent sera interfered with the binding of monoclonal antibodies (MAB) 57.16 or 57.110 to the attenuated TGEV/Purdue virus. Monoclonal antibody 57.16 is directed against the A site on the peplomer, neutralizes virus, and recognizes TGEV and PRCV. Monoclonal antibody 57.110 is directed against the X site on the peplomer, but does not neutralize virus, and recognizes only TGEV. Antibodies directed against TGEV and PRCV could be detected in a blocking ELISA, using MAB 57.16 as a conjugate. Antibodies directed against both viruses were detectable as early as 1 week after inoculation. Antibody titers correlated well with those in a virus-neutralization test. Antibodies against TGEV could be detected in a blocking ELISA, using MAB 57.110 as a conjugate. Such antibodies were not induced by a PRCV infection. In the blocking ELISA, using MAB 57.110 as a conjugate, antibodies were detectable as early as 2 weeks after inoculation. There was a significant difference between antibody titers reached after infection with various TGEV strains, however. This difference is ascribed to a variation of the antigenic site defined by MAB 57.110 in TGEV strains. Conditions for a differential test for TGE serodiagnosis, and for serologic discrimination between TGEV- and PRCV-infected pigs, are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)