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PubMed1993

N-acetylneuraminic acid plays a critical role for the haemagglutinating activity of avian infectious bronchitis virus and porcine transmissible gastroenteritis virus.

Porcine transmissible gastroenteritis virus (TGEV) was found to resemble avian infectious bronchitis virus (IBV) in its interaction with erythrocytes. Inactivation of the receptors on erythrocytes by neuraminidase treatment and restoration of receptors by reattaching N-acetylneuraminic acid (Neu5Ac) to cell surface components indicated that alpha 2,3-linked Neu5Ac serves as a receptor determinant for TGEV as has been reported recently for IBV. Similar to IBV, the haemagglutinating activity of TGEV is evident only after pretreatment of virus with neuraminidase indicating that inhibitors on the virion surface have to be inactivated in order to induce the HA-activity of these viruses. A model is presented to explain why the HA-activity of untreated virus is masked and how neuraminidase treatment results in the unmasking of this activity.

Bacterial Proteins↗
PubMed1988

Physicochemical properties of transmissible gastroenteritis virus hemagglutinin.

Transmissible gastroenteritis virus was readily adsorbed onto chicken erythrocytes at 4 degrees C. The hemagglutinin thus adsorbed could be eluted from the erythrocytes by incubating in phosphate buffered saline at 37 degrees C. The receptor on chicken erythrocytes for the hemagglutinin was inactivated by neuraminidase and potassium periodate, but not by trypsin, 2-mercaptoethanol and formalin. The hemagglutinin was inactivated by trypsin, papain, pepsin, alpha-amylase, phospholipase C, neuraminidase, formalin, 2-mercaptoethanol, potassium periodate, ethyl ether, chloroform, Tween-80 and beta-propiolactone, but not by sodium deoxycholate and trichlorotrifluoroethane, suggesting that the active component of the hemagglutinin involved glycoproteins. The hemagglutinin was stable at 37 degrees C or lower temperatures but not at 60 degrees C or higher temperatures. The hemagglutinin activity was resistant to ultraviolet irradiation, while the infectivity was very susceptible. The hemagglutinin and the infectivity were readily sedimented by ultracentrifugation at 45,000 x g for 60 minutes. In rate zonal centrifugation of the hemagglutinin preparation on a sucrose density gradient, the hemagglutinin activity showed a sharp peak at 1.19 g/ml coinciding with the peak of infectivity. The activity in the peak fraction seemed to be structurally associated with virus particles.

Chemical Phenomena↗
PubMed1990

Mechanisms of transmissible gastroenteritis coronavirus neutralization.

Transmissible gastroenteritis virus (TGEV) was neutralized more than 10(9)-fold with antibodies of a single specificity [monoclonal antibodies (MAbs)]. Most of the virus was neutralized in the first 2-3 min of a reversible reaction, which was followed by a second phase with a decreased neutralization rate and, in some cases, by a persistent fraction, which was a function of the MAb and of the antibody-to-virus ratio. Neutralization of TGEV is a specific event that requires the location of the epitope involved in the neutralization in the appropriate structural context, which is present in the wild-type virus but not in certain MAb escaping mutants. In neutralization of TGEV by binary combinations of MAbs specific for the same or for different antigenic sites, either no cooperation or a synergistic effect, respectively, was observed. Mechanisms of TGEV neutralization by MAbs were characterized at high, intermediate, and low antibody-to-virus ratios. Under these conditions, mainly three steps of the replication cycle were inhibited: binding of virus to the cell, internalization, and a step that takes place after internalization. In addition, virus aggregation could be responsible for the neutralization of 10 to 20% of virus infectivity.

Animals↗
PubMed1976

Vaccination of newborn pigs with an attenuated strain of transmissible gastroenteritis virus.

Clinical signs of transmissible gastroenteritis were not observed in newborn pigs orally inoculated with the high-passaged vaccinal transmissible gastroenteritis virus (TO-163 strain). Vaccinal viral multiplication in digestive tract of newborn pigs fed colostrum before inoculation and kept at 21 to 22 C was diminished, but was not diminished in those fed colostrum and kept at 10 to 11 C. Other groups of newborn pigs inoculated with the attenuated vaccinal virus and kept at 18 to 22 C or at 31 to 34 C were challenge exposed with virulent intestinal virus on the 1st, 2nd, . . ., or 6th postinoculation (PI) days. In the groups kept at 18 to 22 C, 2 of 7 inoculated pigs challenge exposed with virulent virus on the 3rd PI day, 4 of 7 pigs exposed on the 4th PI day, and all of the pigs exposed on and after the 5th PI day survived the exposure. In the groups kept at 18 to 22 C, the attenuated vaccinal virus was distributed mainly in the respiratory organs and lymphatic tissues. On the contrary, in the groups kept at 31 to 34 C, all of the pigs died in 2 to 5 days after challenge exposure, and the attenuated vaccinal virus was scarcely detected in any of the pigs.

Animals↗
PubMedDate not supplied

Interferon-alpha-producing cells are localized in gut-associated lymphoid tissues in transmissible gastroenteritis virus (TGEV) infected piglets.

Transmissible gastroenteritis virus (TGEV) infection of piglets results in a very rapid and massive release of IFN-alpha in serum and secretions. The objective of this work was to characterize the IFN-alpha-producing cells (IPC) in tissues of TGEV-infected piglets. Caesarean-derived colostrum-deprived piglets were infected orally with the TGEV virulent Miller strain and IPC were characterized in situ by immunohistochemistry, using a rabbit anti-pig IFN-alpha antiserum. IPC were almost exclusively detected in intestinal tissues and mesenteric lymph nodes (MLN), as early as 6 h post inoculation (p.i.), with a peak at 12-18 h. They disappeared by 24 h. IPC were localized between enterocytes in the small intestine epithelial layer, in the lamina propria, around the Peyer's patches and, at highest frequency, in MLN. Very few IPC were present in the spleen and popliteal lymph nodes of infected piglets. Double immunohistochemical staining for IFN-alpha and leukocyte markers on MLN cryosections showed that IPC were mainly Swine Leukocyte Antigen (SLA) class II positive, and were not stained by an anti-macrophage (SWC3a) MAb. In addition, double staining with anti-TGEV and anti-IFN-alpha MAbs showed that viral antigens were present in MLN, close to IPC. These results show for the first time the presence of IPC in gut mucosa and gut-associated lymphoid tissues in response to an enteropathogenic virus. Moreover, this work shows that IFN-alpha released in serum is likely to originate almost exclusively from gut IPC triggered locally by viral antigens to produce IFN-alpha, since there were very few IPC in spleen or peripheral lymph nodes. MHC class II molecule expression by gut-associated IPC suggests that these cells may be the in vivo mucosal counterparts of the dendritic cells recently shown to produce IFN-alpha after in vitro viral induction.

Animals↗
PubMed1976

[Transmissible Gastroenteritis in Swine (author's transl)].

Transmissible gastroenteritis or TGE is a virus diarrhoea which occurs in pigs of all ages and is associated with high mortality rates in the young piglets. Growth of virus in the columnar epithelium of the small intestine causes atrophy of the intestinal villi, malabsorption, watery diarrhoea and dehydration. Faecal excretion of virus usually continues up to fourteen days after infection but chronic carriers have been found to occur. TGE is self-limiting on the majority of pig-breeding farms but the virus may persist in particular conditions and an enzootic form of the disease will appear in this case. In typical outbreaks, the diagnosis can usually be based on clinical symptoms. When the disease runs an enzootic course, a clinical diagnosis will be out of the question. TGE should be differentiated from colibacillosis and from another virus diarrhoea, the aetiology of which is not precisely known. A rapid and correct diagnosis may be established by direct fluorescent antibody studies of frozen sections of the small intestine in infected piglets. When sows have been spontaneously infected, their offspring will be protected by lactogenic immunity. The presence of TGE antibodies of IgA class in the milk is required to ensure complete immunity of the piglets lasting for weeks on end. Intramuscular inoculation of a commercially available vaccine in sows will only stimulate the production of antibodies of the IgG class in the milk. These antibodies will merely afford short-lived immunity. The vaccine cannot prevent symptoms of disease from appearing in piglets following infection with virulent TGE virus but it does reduce mortality

Animals↗
PubMed1997

Development of PCR-based techniques to identify porcine transmissible gastroenteritis coronavirus isolates.

Sixteen isolates of transmissible gastroenteritis virus and one isolate of porcine respiratory coronavirus were characterized using RT-PCR amplification of 4 antigenic subsites in the site A epitope on the TGEV spike gene. The PCR products were digested with restriction enzymes Sau3AI and SspI and the sizes of the fragments were determined. Three different digestion patterns were observed with each enzyme. The recognition site for Sau3AI was missing in 1 isolate, was present in 13 isolates and 3 isolates had 2 sites. PCR-products with a single site had 3 different fragment sizes and the other isolates produced 2 fragments with different sizes. The SspI recognition site was not present in 5 isolates and 12 isolates had a single site that produced 2 fragments of different sizes. Based on the restriction fragment sizes, the 17 isolates were separated into 7 groups. Direct sequencing of the 455 bp nested set fragments demonstrated greater than 96% sequence homology among the 16 isolates and 100% homology in the 4 antigenic subsites in the conserved site A epitope. The groups are discussed in relation to their sequence homology and virulence. In vitro procedures have been developed to identify several porcine enteric coronavirus isolates at the strain level.

Animals↗
PubMed1975

Comparison of properties between virulent and attenuated strains of transmissible gastroenteritis virus.

Strains of transmissible gastroenteritis (TGE) virus possessing different pathogenicity were examined for stability to digestive enzymes and acid, and growth at various temperatures. In growth experiments, virus titer obtained at 37 degrees C were about equal between attenuated and virulent strains, but titers attained by the attenuated strain were higher at 30 degrees C. The attenuated virus multiplied at 28 degrees C, but the virulent virus did not at this temperature. The virulent virus was significantly stable to trypsin and pepsin, but the attenuated virus was inactivated rapidly by these proteolytic enzymes. No significant differences were observed in stability to acid between the attenuated and virulent strains. At different pH, both lost their infectivity more rapidly at 37 degrees C than at 22 degrees C.

Coronaviridae↗
PubMed1986

Critical epitopes in transmissible gastroenteritis virus neutralization.

Purified transmissible gastroenteritis (TGE) virus was found to be composed of three major structural proteins having relative molecular weights of 200,000, 48,000, and 28,000. The peplomer glycoprotein was purified by affinity chromatography with the monoclonal antibody (MAb) 1D.G3. A collection of 48 MAbs against TGE virus was developed from which 26, 10, and 3 were specific for proteins E2, N, and E1, respectively. A total of 14 neutralizing MAbs of known reactivity were E2 protein specific. In addition, MAb 1B.C11, of unknown specificity, was also neutralizing. These MAbs reduced the virus titer 10(2)- to 10(9)-fold. Six different epitopes critical in TGE virus neutralization were found, all of which were conformational based on their immunogenicity and antigenicity. Only the epitope defined by MAb 1G.A7 was resistant to sodium dodecyl sulfate treatment, although it was destroyed by incubation in the presence of both the detergent and beta-mercaptoethanol. The frequency of MAb-resistant (mar) mutants selected with four MAbs (1G.A7, 1B.C11, 1G.A6, and 1E.F9) ranged from 10(-6) to 10(-7), whereas the frequency of the putative mar mutant defined by MAb 1B.B11 was lower than 10(-9). Furthermore, the epitopes defined by these MAbs and by MAbs 1H.C2 and 1A.F10, were present in 11 viral isolated with different geographical locations, years of isolation, and passage numbers (with the exception of two epitopes absent or modified in the TOY 56 viral isolate), suggesting that the critical epitopes in TGE virus neutralization were highly conserved.

Antibodies, Monoclonal↗
PubMed1976

The detection of transmissible gastroenteritis viral antibodies by immunodiffusion.

Precipitating antibodies against transmissible gastroenteritis viral antigens were detected by the immunodiffusion test in two transmissible gastroenteritis viral hyperimmune antisera and in antiserum prepared against haemagglutinating encephalomyelitis virus but not in sera from several species of normal animals, in antisera prepared against a variety of othet viruses and bacteria or sera from swine with bacterial enteritis. When the immunodiffusion test was compared with the virus neutralization test for the detection of transmissible gastroeneritis viral antibodies in 20 swine sera certain samples which contained high titres of virus neutralizing antibodies failed to produce precipitation while other sera were positive in the immunodiffusion test although their virus neutralizing antibody titres were relatively low. Precipitating antibodies were also detected by immunodiffusion in several samples of milk whey from a sow which had been vaccinated with inactivated transmissible gastroenteritis virus.

Animals↗
PubMed1997

An overview of immunological and genetic methods for detecting swine coronaviruses, transmissible gastroenteritis virus, and porcine respiratory coronavirus in tissues.

Transmissible gastroenteritis (TGE) is an enteric disease of swine caused by a coronavirus, designated as transmissible gastroenteritis virus (TGEV). Commonly used methods for TGEV detection include viral isolation and detection of the viral antigen by indirect immunofluorescence (IFA), immunoperoxidase, and immunogold silver staining. Each of these techniques has some advantages and disadvantages. In general IFA and immunohistochemistry are preferred over viral isolation as TGEV isolation is not very reliable because not all field isolates replicate in cell cultures. The diagnosis of TGEV has become more complicated since the emergence of porcine respiratory coronavirus (PRCV). PRCV is believed to be a TGEV mutant, and can not be easily differentiated from TGEV by immunological tests. Nucleic acid probes and polymerase chain reaction (PCR) have successfully been used to detect and differentiate these viruses. These techniques can detect viral nucleic acids in the specimen but do not provide information on the cell types infected by these viruses. Recently we have developed isotopic and nonisotopic in situ hybridization techniques (ISH) for the detection of these viral nucleic acids in formalin-fixed paraffin-embedded tissues. Furthermore, this procedure can differentiate between TGEV- and PRCV-infected cells. By ISH, TGEV is detected in the mature absorptive enterocytes of tissues infected by TGEV and the crypt epithelial cells are also infected but to a lesser extent. For PRCV, the main infected cells are epithelial cells of the bronchioles, type II pneumocytes, and alveolar and septal macrophages. ISH is an excellent tool for studying molecular pathogenesis of these two viruses especially when used in combination with immunohistochemistry.

Animals↗
PubMed1978

The postulated role of feeder swine in the perpetuation of the transmissible gastroenteritis virus.

Clinical, immunofluorescence and histopathological observations were found to be an efficient approach for the confirmation of the diagnosis of transmissible gastroenteritis in feeder swine. Two cases are reported to exemplify how feeder swine exposed to points of concentration such as holding areas, sales barns and auctions can play an important role in the epizootiology of transmissible gastroenteritis. A third field case is reported as an example of an outbreak of transmissible gastroenteritis beginning in feeder swine and then spreading to baby pigs on the farm. All baby pigs died that were born during the acute phase of the outbreak in the feeder swine. Baby pigs born shortly after the clinical signs had abated in the herd, and from sows that had been exposed orally to virulent transmissible gastroenteritis virus and vaccinated with a commercial transmissible gastroenteritis vaccine ten days before farrowing, survived. This was explained by a combination of a decrease in the amount of virus shed in the environment and the immunity induced in the sows. These observations of field outbreaks of transmissible gastroenteritis combined with recently reported experimental studies lend strong support to the hypothesis of a reservoir for transmissible gastroenteritis virus in feeder pigs. This reservoir would be based principally on the transmission of the virus on a continuous basis from the feces of recently infected pigs to susceptible pigs. Clinical signs of transmissible gastroenteritis in such pigs are difficult to recognize or absent and this contributes to the importance of the reservoir in the field.

Animal Husbandry↗
PubMed2003

Binding of transmissible gastroenteritis coronavirus to brush border membrane sialoglycoproteins.

Transmissible gastroenteritis coronavirus (TGEV) is a porcine pathogen causing enteric infections that are lethal for suckling piglets. The enterotropism of TGEV is connected with the sialic acid binding activity of the viral surface protein S. Here we show that, among porcine intestinal brush border membrane proteins, TGEV recognizes a mucin-type glycoprotein designated MGP in a sialic acid-dependent fashion. Virus binding assays with cryosections of the small intestine from a suckling piglet revealed the binding of TGEV to mucin-producing goblet cells. A nonenteropathogenic mutant virus that lacked a sialic acid binding activity was unable to bind to MGP and to attach to goblet cells. Our results suggest a role of MGP in the enteropathogenicity of TGEV.

Animals↗
PubMed1975

Recovery of transmissible gastroenteritis virus from chronically infected experimental pigs.

Transmissible gastroenteritis (TGE) virus was reisolated from pulmonary and intestinal tissues from 6 of 9 chronically infected experimental pigs (principals) necropsied 30 to 104 days after inoculation. Tissue homogenates (lung and small intestine) from the principals were prepared and inoculated into 3- to 5-day-old gnotobiotic pigs. The virus reisolated from the tissue homogenates produced a milder disease on 1st passage and a more severe disease on 2nd passage. The chronically infected experimental pigs (principals) developed serum-neutralization titers to TGE of 1:30 to 1:525. There appeared to be no relationship between serum titers and reisolation of TGE virus from the 9 principals. The persistence of virus in lung or intestine to 104 days indicates the recovered (or carrier) pig may be considered the primary source of TGE virus infection.

Animals↗
PubMed1978

Small plaque variant transmissible gastroenteritis virus.

A small plaque (SP) variant transmissible gastroenteritis (TGE) virus strain that may be useful in the control of TGE in swine has been developed and tested. This strain was derived from a persistently infected swine leukocyte cell line originally infected with a virulent TGE virus. The SP viral strain was avirulent for 3-day-old susceptible pigs and pregnant gilts. The SP virus elicited protective antibody when inoculated into pregnant gilts oral/intranasally, or intramammarily, or by both of these routes. The morbidity and mortality of their passively immune suckling pigs were 62% and 14%, respectively.

Animals↗
PubMed1995

Functional domains in the spike protein of transmissible gastroenteritis virus.

The coronavirus spike protein S is assumed to mediate essential biological functions, including recognition of target cells. Earlier studies from our and other groups identified two regions of the TGEV S (220K) protein possibly implicated in such functions. The first of these corresponds to the 224 amino acid N-terminal region which is deleted in PRCV, the respiratory variant of TGEV. We have examined the pathogenicity for the newborn piglet of a series of neutralization escape mutants encoding an S protein mutated in this region. Several amino acid changes were correlated with a dramatic loss of enterovirulence, thus indicating that crucial determinants are associated with this domain of S. The second region of potential relevance is the major neutralization domain. Baculovirus-vectored expression of 150 to 220 amino acid-long stretches encompassing this region, which is encoded by both TGEV and PRCV, was performed. The resultant recombinant proteins were shown to react with the cognate antibodies and to bind APN specifically, thus localizing the receptor-binding site on the S primary structure. Altogether these data lend support to the view that a domain of S protein structurally distinct from the receptor binding site is required for the virus to express its enteric tropism.

Amino Acid Sequence↗