Evaluation of the Baculovirus-Expressed S Glycoprotein of Transmissible Gastroenteritis Virus (TGEV) as Antigen in a Competition ELISA to Differentiate Porcine Respiratory Coronavirus from TGEV Antibodies in Pigs

Abstract

Abstract. The spike (S) glycoprotein of the Miller strain of transmissible gastroenteritis virus (TGEV) was recently cloned and expressed in baculovirus. The recombinant S protein was used as the coating antigen in a competition (blocking) enzyme-linked immunosorbent assay (ELISA) in combination with monoclonal antibodies to the S protein epitope A (conserved on TGEV and porcine respiratory coronavirus [PRCV]) or epitope D (present on TGEV only) to differentiate PRCV-from TGEV-induced antibodies. One set (set A) of 125 serum samples were collected at different times after inoculation of caesarean-derived, colostrum-deprived (n ϭ 52) and conventional young pigs (n ϭ 73) with 1 of the 2 porcine coronaviruses or uninoculated negative controls (TGEV/PRCV/negative ϭ 75/30/20). A second set (set B) of 63 serum samples originated from adult sows inoculated with PRCV and the recombinant TGEV S protein or with mock-protein control and then exposed to virulent TGEV after challenge of their litters. Sera from set A were used to assess the accuracy indicators (sensitivity, specificity, accuracy) of the fixed-cell blocking ELISA, which uses swine testicular cells infected with the M6 strain of TGEV as the antigen source (ELISA 1) and the newly developed ELISA based on the recombinant S protein as antigen (ELISA 2). The sera from set B (adults) were tested for comparison. The plaque reduction virus neutralization test was used as a confirmatory test for the presence of antibodies to TGEV/PRCV in the test sera. The accuracy indicators for both ELISAs suggest that differential diagnosis can be of practical use at least 3 weeks after inoculation by testing the dual (acute/convalescent) samples from each individual in conjunction with another confirmatory (virus neutralization) antibody assay to provide valid and complete differentiation information. Moreover, whereas ELISA 1 had 10-20% false positive results to epitope D for PRCV-infected pigs (set A samples), no false-positive results to epitope D occurred using ELISA 2, indicating its greater specificity. The progression of seroresponses to the TGEV S protein epitopes A or D, as measured by the 2 ELISAs, was similar for both sets (A and B) of samples. Differentiation between TGEV and PRCV antibodies (based on seroresponses to epitope D) was consistently measured after the third week of inoculation.Transmissible gastroenteritis virus (TGEV), a prominent cause of neonatal diarrhea, causes death in 90-100% of seronegative pigs under 2 weeks of age and costs the US swine industry nearly $200 million/ year. 15,19 Surveys of TGEV antibodies in swine sera collected prior to the detection of porcine respiratory coronavirus (PRCV) indicated that 19-54% of swine herds in North America have antibodies, 17 but few differential serosurveys have been done since the detection of PRCV. 32 A variant of TGEV, referred to as PRCV, was isolated from pigs in Europe in 1986 and identified in the USA in 1989. 15,18,19 As reported from Iowa swine herds, a recent increase observed in TGEV/PRCV seropre...

Field Validation of a Commercial Blocking ELISA to Differentiate Antibody to Transmissible Gastroenteritis Virus (TGEV) and Porcine Respiratory Coronavirus and to Identify TGEV-Infected Swine Herds

“…3 Numerous serological ELISAs based on these epitopic differences and monoclonal antibodies have been developed to differentiate antibodies to TGEV and PRCV. 2,4,8,15,17 However, few have been validated using large numbers of field sera collected from commercial herds 18 or are commercially available for use in diagnostic laboratories.…”

Phage display for identifying peptides that bind the spike protein of transmissible gastroenteritis virus and possess diagnostic potential

“…A number of ELISA-based assays have been developed over the years for detecting TGEV, many of which have been directed at differentiating TGEV from PRCV-infected animals. Among the earlier ones, Sestak et al [32] targeted the S glycoprotein of TGEV in a competition ELISA where recombinant S protein was coated onto plates and used to capture host antibodies. Using a monoclonal Ab to epitope D and which is specific for TGEV, the investigators were able to differentiate the infectious agents.…”

A Monoclonal Antibody Against Transmissible Gastroenteritis Virus Generated via Immunization of a DNA Plasmid Bearing TGEV S1 Gene

“…ELISA is very convenient and simple, and we and others have used this method to detect various viruses or antibodies with great success. (9,(15)(16)(17)(18)(19)(20) In this study, we therefore used the MAb (1H4) as a primary antibody to detect TGEV. The result verified that the developed MAb 1H4 exclusively reacted with TGEV rather than a closely related porcine coronavirus PEDV, PRRSV, or avian coronvavirus IBV.…”