These data suggested that PDNS is a manifestation of disseminated intravascular coagulation in swine. For the experimental conditions reported here, combined infection with g1-TTV and PRRSV was implicated in the genesis of these lesions.
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...
Abstract. An immunohistochemistry technique was developed using fixed tissues to study the presence and location of transmissible gastroenteritis virus (TGEV) antigens in situ. Experimentally infected gnotobiotic and conventional pigs as well as pigs with natural TGEV infection were examined. The staining technique was based on detection of the major structural protein of TGEV, the nucleocapsid, by using a pool of 3 monoclonal antibodies. Formalin and periodate-lysine-paraformaldehyde (PLP)-fixed intestinal tissues from a gnotobiotic pig inoculated with virulent TGEV were used to determine optimal antibody concentrations and incubation times. The intestinal tissues remained in their respective fixatives for 6 months, and serial sections were removed at sequential times and embedded in paraffin blocks. PLP and 10% neutral buffered formalin were acceptable fixatives and preserved TGEV nucleocapsid antigenicity for up to 6 months. Formalin, in comparison with PLP as a fixative, was better for preserving original tissue morphology and provided better antigen detection. Conventional crossbred pigs were inoculated with virulent TGEV, and animals were euthanized on various postexposure days. Intestinal tissues were positive for TGEV nucleocapsid antigens on postexposure days 2, 4, and 8. The immunohistochemistry technique detected TGEV antigen in stored paraffin-embedded tissues from 14 naturally infected pigs previously confirmed as positive for TGEV using a direct immunofluorescence assay on intestinal mucosal smears, whereas 9 naturally infected pigs confirmed negative for TGEV antigen by the same immunofluorescence assay showed no staining consistent with the presence of TGEV antigen. Immunohistochemistry provides a method to detect TGEV and possibly other closely related coronaviruses such as porcine respiratory coronavirus in situ. A diagnostic test using the same fixed tissues processed for histopathology provides veterinary practitioners an alternative to delivering live pigs or refrigerated fresh intestinal samples containing infectious virus to a diagnostic laboratory. Investigators can utilize this technique to retrospectively screen fixed tissues for TGEV antigen.Transmissible gastroenteritis (TGE) virus (TGEV) belongs to the family Coronaviridae and causes enteritis in swine of all ages. Enteritis from TGEV results from destruction of villous enterocytes and villous atrophy of the small intestinal mucosa, especially within the jejunum and ileum.11 Clinical signs of TGE include anorexia, vomiting, diarrhea, and dehydration. Mortality in infected neonatal piglets approaches 100% because of severe diarrhea and dehydration.14 TGE annually costs the swine industry approximately $200 million through mortality and decreased production efficiency. ' During outbreaks of swine diarrhea, a presumptive diagnosis of TGEV can be made by evaluation of disease history and clinical signs. Histopathologic sections of formalin-fixed jejunum and ileum showing evidence of villous atrophy, although consistent with TGEV infect...
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