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PubMed1990

Expression of swine transmissible gastroenteritis virus envelope antigens on the surface of infected cells: epitopes externally exposed.

The peplomer protein (S) and the transmembrane protein (M) of transmissible gastroenteritis virus (TGEV) of swine were identified by iodination and serologically on the surface of infected cells. Of a total of 4 monoclonal antibodies (mAb) directed against four antigenic sites of S protein (Correa et al., 1988), 3 specific for sites A, B and D attached to the plasma membrane of infected cells, as disclosed by indirect immunofluorescence and by complement-mediated cytolysis. Four of the mAbs assayed were specific for the viral protein M and two of them gave plasma membrane immunofluorescence and mediated cytolysis in the presence of complement. The viral nucleoprotein N could not be demonstrated on the surface of infected cells either by iodination or employing 3 mAbs against this protein. Finally, a time course infection experiment demonstrated that S and M proteins were expressed on the surface of infected cells at 4 h after infection, before infective virus was released from infected cells.

Animals↗

PubMed1983

Lactogenic immunity to transmissible gastroenteritis virus induced by a subunit immunogen.

A subunit prepared from transmissible gastroenteritis (TGE) virus and used to immunize 24 gilts prior to farrowing induced production of specific antibody in the serum and milk. Challenge of pigs, two to seven days of age and suckling on the vaccinated gilts, with the Illinois strain of TGE virus resulted in morbidity of 28% and mortality of 4% as compared with 100 and 73%, respectively, for control piglets. Piglets nursing on a sow which had been immunized approximately 10 months previously were not protected, indicating that lactogenic immunity may be of short duration. Revaccination of this animal resulted in an anamnestic response.

Animals↗

PubMed1990

Sequence of the S gene from a virulent British field isolate of transmissible gastroenteritis virus.

Subgenomic mRNA from a virulent field isolate of porcine transmissible gastroenteritis virus (TGEV), strain FS772/70, was used to produce cDNA. The cDNA from three overlapping clones was sequenced by the chain termination method and two open reading frames (ORFs) were identified. The largest ORF, 4350bp, encoded a polypeptide of 1449 amino acids of relative molecular mass (Mr) 159811, which contained 33 potential N-linked glycosylation sites, a cysteine-rich region, and a potential transmembrane region. The C-terminal half of this ORF showed homology to the S proteins of four other coronaviruses. The other ORF consisted of the 3'-end of a gene with homology to the carboxyl terminus of the F2 subunit of infectious bronchitis virus (IBV) RNA polymerase.

Amino Acid Sequence↗

PubMed1991

Expression and cellular localisation of porcine transmissible gastroenteritis virus N and M proteins by recombinant vaccinia viruses.

Porcine transmissible gastroenteritis virus (TGEV) nucleoprotein and integral membrane protein genes were cloned into the vaccinia virus insertion vector, pGS20, in the correct orientation for expression under the control of the vaccinia P7.5K promoter. Recombinant vaccinia viruses were generated by in vivo homologous recombination of the insertion vector with the WR strain of vaccinia virus. Nucleoprotein (N) expressed by both recombinant vaccinia virus and TGEV had a relative molecular mass (Mr) of 47,000 and was susceptible to degradation at the C-terminus yielding discrete breakdown products. The integral membrane protein (M) expressed by a recombinant vaccinia virus and TGEV was sensitive to endoglycosidase H reducing the mature polypeptide of Mr 29,000 to a species of Mr 27,000. Expression of M by recombinant vaccinia virus was inhibited during early infection due to a cryptic vaccinia virus transcriptional termination signal within the TGEV coding sequence. Indirect immunofluorescence showed that both N and M were only localised in the cell cytoplasm of either TGEV or recombinant vaccinia virus immunoprecipitated specific TGEV antigens from lysates of TGEV infected cells but had little significant TGEV neutralising activity in vitro.

Acetylglucosaminidase↗

PubMed2002

Binding of transmissible gastroenteritis coronavirus to cell surface sialoglycoproteins.

The surface glycoprotein S of transmissible gastroenteritis virus (TGEV) has two binding activities. (i) Binding to porcine aminopeptidase N (pAPN) is essential for the initiation of infection. (ii) Binding to sialic acid residues on glycoproteins is dispensable for the infection of cultured cells but is required for enteropathogenicity. By comparing parental TGEV with mutant viruses deficient in the sialic acid binding activity, we determined the contributions of both binding activities to the attachment of TGEV to cultured cells. In the presence of a functional sialic acid binding activity, the amount of virus bound to two different porcine cell lines was increased sixfold compared to the binding of the mutant viruses. The attachment of parental virus was reduced to levels observed with the mutants when sialic acid containing inhibitors was present or when the cells were pretreated with neuraminidase. In virus overlay binding assays with immobilized cell surface proteins, the mutant virus only recognized pAPN. In addition, the parental virus bound to a high-molecular-mass sialoglycoprotein. The recognition of pAPN was sensitive to reducing conditions and was not dependent on sialic acid residues. On the other hand, binding to the sialic acid residues of the high-molecular-mass glycoprotein was observed regardless of whether the cellular proteins had been separated under reducing or nonreducing conditions. We propose that binding to a surface sialoglycoprotein is required for TGEV as a primary attachment site to initiate infection of intestinal cells. This concept is discussed in the context of other viruses that use two different receptors to infect cells.

Animals↗

PubMed2001

The membrane M protein carboxy terminus binds to transmissible gastroenteritis coronavirus core and contributes to core stability.

The architecture of transmissible gastroenteritis coronavirus includes three different structural levels, the envelope, an internal core, and the nucleocapsid that is released when the core is disrupted. Starting from purified virions, core structures have been reproducibly isolated as independent entities. The cores were stabilized at basic pH and by the presence of divalent cations, with Mg(2+) ions more effectively contributing to core stability. Core structures showed high resistance to different concentrations of detergents, reducing agents, and urea and low concentrations of monovalent ions (<200 mM). Cores were composed of the nucleoprotein, RNA, and the C domain of the membrane (M) protein. At high salt concentrations (200 to 300 mM), the M protein was no longer associated with the nucleocapsid, which resulted in destruction of the core structure. A specific ionic interaction between the M protein carboxy terminus and the nucleocapsid was demonstrated using three complementary approaches: (i) a binding assay performed between a collection of M protein amino acid substitution or deletion mutants and purified nucleocapsids that led to the identification of a 16-amino-acid (aa) domain (aa 237 to 252) as being responsible for binding the M protein to the nucleocapsid; (ii) the specific inhibition of this binding by monoclonal antibodies (MAbs) binding to a carboxy-terminal M protein domain close to the indicated peptide but not by MAbs specific for the M protein amino terminus; and (iii) a 26-residue peptide, including the predicted sequence (aa 237 to 252), which specifically inhibited the binding. Direct binding of the M protein to the nucleoprotein was predicted, since degradation of the exposed RNA by RNase treatment did not affect the binding. It is proposed that the M protein is embedded within the virus membrane and that the C region, exposed to the interior face of the virion in a population of these molecules, interacts with the nucleocapsid to which it is anchored, forming the core. Only the C region of the M protein is part of the core.

Amino Acid Sequence↗

PubMed1996

Tropism of human adenovirus type 5-based vectors in swine and their ability to protect against transmissible gastroenteritis coronavirus.

The infection of epithelia] swine testicle and intestinal porcine epithelial (IPEC-1) cell lines by adenovirus type 5 (Ad5) has been studied in vitro by using an Ad5-luciferase recombinant containing the firefly luciferase gene as a reporter. Porcine cell lines supported Ad5 replication, showing virus titers, kinetics of virus production, and luciferase expression levels similar to those obtained in human 293 cells, which constitutively express the 5'-end 11% of the Ad5 genome. The tropism of Ad5-based vectors in swine and its ability to induce an efficient immune response against heterologous antigens expressed by foreign genes inserted in these vectors has been determined. Ad5 vectors replicate and express heterologous antigens in porcine lungs and mediastinal and mesenteric lymph nodes. Significant levels of heterologous antigen expression were also demonstrated in the small intestine (jejunum and ileum), but Ad5 replication in this organ was very poor, suggesting that Ad vectors undergo an abortive replication in the porcine small intestine. The tissues infected by Ad5 were dependent on the inoculation route. The oronasal route appeared to be best for inoculation of bronchus-associated lymphoid tissue infection, while the intraperitoneal route was best for gut-associated lymphoid tissue infection. Epithelial cells of bronchioles, macrophages, type II pneumocytes, and follicular dendritic cells were identified as targets for Ad5, while epithelial cells of the intestine were not infected by Ad5. Viruses with a deletion from 79.5 to 84.8 map units in the E3 region, with or without heterologous inserted genes, replicated to lower levels in porcine tissues than did wild-type Ad5. It was also shown that an Ad5 recombinant expressing the four antigenic sites (A, B, C, and D) of transmissible gastroenteritis coronavirus (TGEV) spike protein induced in swine immune responses which neutralized TGEV infectivity. In addition, porcine serum from Ad-TGEV-immune animals provide passive protection when mixed with fully virulent TGEV and orally administered to highly susceptible newborn piglets. These results taken together indicate that swine may be a good animal model for human Ad5 lung infection to aid in the evaluation of candidate adenovirus vaccines and that Ad5 may be suitable as a recombinant viral vaccine or for other applications in swine.

Adenoviruses, Human↗

PubMed1974

Transmissible gastroenteritis. Mechanisms responsible for diarrhea in an acute viral enteritis in piglets.

We studied 3-wk-old piglets 40 h after experimental infection with transmissible gastroenteritis (TGE) virus to identify the mechanisms of diarrhea in this disease and to better understand infectious diarrhea in humans. Using continuous segmental marker perfusion in four regions along the gut, we found significant increases in net intraluminal accumulation of water and electrolytes only in the proximal jejunum, the region infected by the virus. In this jejunal segment studied in vivo, unidirectional sodium flux, extracellular fluid (ECF) to lumen, significantly increased, lumen to ECF significantly decreased, compared with matchfed littermates. The standard perfusate rendered hypertonic by adding mannitol (450 mosmol/kg), in the same segment of normal pigs, caused only an increase in ECF to lumen flux of sodium. TGE did not alter gross villous structure or intraluminal bacteria, bile salts, lactate, pH, or osmolality. Epithelial cell migration was accelerated in the jejunum of infected pigs. Isolated in suspension, these cells from TGE pigs exhibited increased active and passive sodium efflux, cells from mannitol-perfused pigs exhibited only increased active sodium efflux. In this viral enteritis, altered sodium transport occurring in the jejunum, the region of the intestine infected appears to be associated with defective epithelial cell function. The precise nature of the abnormalities in sodium transport, their relationship to disturbances of transport of other solutes, and to virus epithelial cell interaction remain to be defined.

Animals↗

PubMed1979

Determinants of diarrhea in viral enteritis. The role of ion transport and epithelial changes in the ileum in transmissible gastroenteritis in piglets.

To understand mechanisms of viral diarrhea further, we studied ileal ion transport in vitro in relation to mucosal changes and epithelial differentiation in transmissible gastroenteritis in piglets, an invasive viral enteritis thought to involve mainly proximal intestine. In infected pigs, at the height of diarrhea, short-circuited ileal epithelium failed actively to transport Na+ and Cl-, and there was a defect of glucose-mediated Na+ transport. The Cl- secretory response to theophylline remained intact. Conductance measurements indicate that paracellular permeability may be reduced and transcellular transport may be altered. A mucosal lesion was observed at the time of the transport changes, characterized by villus blunting, crypt hyperplasia, and immature crypt-type enterocytes on the villus epithelium, deficient in disaccharidase and (Na+, K+)ATPase activity but rich in thymidine kinase. Consideration of the major determinants of diarrhea in this invasive enteritis must take into account not only altered mucosal function and differentiation but also the extent of intestinal involvement, including the ileum, a major site of fluid absorption in the intestine.

Animals↗

PubMed1975

Passive immunity in transmissible gastroenteritis of swine: intramuscular injection of pregnant swine with a modified live-virus vaccine.

Nine pregnant swine were intramuscularly injected with a modified live-virus transmissible gastroenteritis (TGE) vaccine at approximately 6 and 2 weeks before parturition. The TGE antibody levels in milk whey rapidly decreased within a few days after parturition, and the antibodies were mainly, if not solely, of the immunoglobulin G (IgG) class. Nursing newborn pigs were challenge exposed with virulent TGE virus when 2 to 4 days old. All pigs in 8 of the 9 litters became affected with typical signs of TGE. Of the pigs nursing vaccinated sows, 55% died, and of the 9 vaccinated sows, 8 became affected after challenge exposure of their litters. Subsequently, the antibody titers in serum and milk markedly increased in all 9 sows, with the antibody in milk being predominantly of the immunoglobulin A (IgA) class. Serum samples of prenursing newborn pigs from vaccinated sows did not contain detectable TGE antibodies. The capability of the vaccinated sows to provide only limited passive immunity to their suckling pigs was considered to be due mainly to the low titer and class (IgG) of TGE antibody existing in the milk of the sows at the time the newborn pigs were challenge exposed.

Animals↗

PubMed1977

Efficacy of isolated colostral IgA, IgG, and IgM(A) to protect neonatal pigs against the coronavirus of transmissible gastroenteritis.

To ascertain what class of immunoglobulin (Ig; IgA, IgG, or IgM) is most efficacious in protection, a large quantity of colostrum from sows immunized with virulent transmissible gastroenteritis (TGE) virus was fractionated by chromatographic and gel filtration methods. The isolated IgG, IgA, and IgM(A) had specific virus-neutralizing activities of 1:7.6, 1:342, and 1:302 per milligram of protein, respectively. Each Ig was fed to groups of hysterectomy-derived colostrum-deprived neonatal pigs before and after exposure (challenge) with virulent TGE virus. The 7 pigs fed IgG survived the challenge exposure, but 2 of 7 fed IgA and 1 of 7 fed IgM(A) died of TGE. Three of the survivor pigs that had been fed IgG and 2 of the survivor pigs that had been fed IgA had increased serum antibody titers between 8 and 19 days after challenge exposure, but none of the survivor pigs fed IgM(A) had TGE antibody. In contrast, 12 of 14 virus-control pigs died of TGE and the 2 survivors had antibody conversion. The data show that all 3 Ig classes in immune colostrum will protect neonatal pigs against exposure with virulent TGE virus.

Animals↗

PubMed1975

The polypeptide structure of transmissible gastroenteritis virus.

The polypeptides of purified preparations of the coronavirus responsible for transmissible gastroenteritis of pigs have beem examined by polyacrylamide gel electrophoresis. Four major polypeptides, VPI (mol. wt. 200000), VP2 (50 000), VP3 (30000) and VP4 (28500) and two minor polypeptides, VPIa (105000) and VPIb (80500) have been reproducibly demonstrated in the virion, of which VPI, VP3 and VP4 contain carbohydrate. Treatment of the virion with the proteolytic enzyme bromelain removes the surface projections and VPI, thus identifying this glycopolypeptide as the major structural component of the projection.

Bromelains↗

PubMed1981

Serum immunoglobulin A antibody response in swine infected with transmissible gastroenteritis virus, as determined by indirect immunoperoxidase antibody test.

Using an immunoperoxidase antibody test, the serum immunoglobulin (Ig) A antibody titer was determined in swine naturally infected with transmissible gastroenteritis (TGE; group A), swine inoculated orally with high-virulent TGE virus (group B), and swine inoculated IM (group C) or orally (group D) with low-virulent TGE virus. Studies were then made on the relationship between active immunity to TGE and the serum IgA antibody titer. In group A swine, serum IgA antibody and virus-neutralizing (VN) antibody were absent in the serum collected in the acute stage, but were detected from the serum collected in the convalescent stage. In group B swine, serum IgA antibody and VN antibody began to be detected on postinoculation day (PID) 7 and were still detectable on PID 100. In group C and D swine, VN antibody was detected, but serum IgA antibody was not. Swine were inoculated orally with high-virulent TGE virus and were challenge exposed orally with the same strain of virus on PID 18, 21, 80, and 120 (group E). None of group E swine manifested clinical signs of infection. Their serum IgA antibody titers ranged from 2 to 512 at the time of inoculation. Swine were inoculated IM with low-virulent TGE virus and intranasally with the same virus on PID 60 (group F). They were challenge exposed with the high-virulent strain of TGE virus on PID 140, 200, and 260 (80, 140, and 200 days after the 2nd inoculation). At the time of challenge exposure, IgA antibody was undetected in serum at a 1:2 dilution. All group F swine had severe diarrhea 3 to 4 days after inoculation. Many of them vomited at the same time. In these swine, villous atrophy was observed in the jejunal portion of the small intestine. The VN antibody titer of porcine serum obtained at the time of challenge exposure was higher than was that determined in the group E swine. Seemingly, serum IgA antibody titer determined by the immunoperoxidase antibody test may be an indicator of active immunity to TGE.

Administration, Oral↗

PubMed1982

Changes in gut-associated lymphoid tissues of the small intestine of eight-week-old pigs infected with transmissible gastroenteritis virus.

The responses of the interepithelial lymphocytes (IEL) and aggregated lymph nodules (ALN; Peyer's patches) of the small intestines of 8-week-old pigs to transmissible gastroenteritis virus (TGEV) infection were characterized at 12, 18, and 24 hours after pigs were inoculated. There was no significant difference in numbers of IEL between control and TGEV-infected pigs at 12 and 18 hours. However, in pigs examined at 24 hours, there was a significant decrease in the number of IEL in the duodenum and cranial portion of the jejunum and an increase of IEL numbers in the nuclear level of the intestinal epithelium. Number and distribution were unchanged in the middle portion of the jejunum and the ileum. Microscopic changes in TGEV-infected pigs included microulceration of the dome epithelium (DE) over the ALN, especially in the cranial portion of the intestine, and villous atrophy in the entire length of the small intestine. Generally, TGEV was found by means of peroxidase-antiperoxidase staining in areas where microscopic lesions occurred. Electron microscopy revealed that M cells and ordinary microvillus-covered epithelial cells in the DE embraced one or more lymphocytes, and formed a specialized cell complex or DE complex. Most of the lymphocytes in the DE complex possessed many organelles indicative of an active cell state. The TGEV was found between microvilli, in the cytoplasmic vesicles of M cells and microvillus-covered epithelial cells in the DE, and in the cytoplasm of macrophages and lymphocytes and some degenerated cells of unidentified origin in the domes of the ALN. The virus was also commonly found in cytoplasmic vesicles of macrophages and degenerated cells in the intestinal lumen near the base of the dome of the ALN.

Animals↗

PubMed1996

Induction of protective immunity against transmissible gastroenteritis virus after exposure of neonatal pigs to porcine respiratory coronavirus.

OBJECTIVE: To test the ability of porcine respiratory coronavirus (PRCV) to induce protective immunity to antigenically related transmissible gastroenteritis virus (TGEV) in neonatal pigs. DESIGN: Neonatal pigs were exposed to PRCV when they were 2, 4, or 6 days old and challenge-exposed to virulent TGEV at 10 days of age. ANIMALS: 34 hysterectomy-derived, colostrum-deprived pigs. PROCEDURE: After challenge exposure, clinical signs were observed, body weight, antibody response, and virus shedding were measured, and mortality was determined. RESULTS: After exposure to PRCV, principals had a slightly slower rate of weight gain than did controls; with 1 exception (a PRCV-exposed pig that was dyspneic for 1 day), principals and controls remained clinically normal until shortly after challenge exposure, when all pigs became listless and anorectic and developed watery diarrhea. However, by day 3, most of the pigs that had been exposed to PRCV when they were either 2 or 4 days old began to recover and most (15/18) survived. Conversely, the clinical condition of most of the other pigs worsened and most (14/16) died. Pigs exposed to PRCV when they were 2 or 4 days old also differed from all other pigs in that they had serum virus-neutralizing antibodies for PRCV and TGEV at the time of challenge exposure. CONCLUSIONS: The PRCV can induce protective immunity to TGEV in neonatal pigs and such immunity develops at or about 6 days after exposure to PRCV. Moreover, protective immunity may be coincident with the appearance of virus-neutralizing antibody. CLINICAL RELEVANCE: Exposure to PRCV should enhance a TGE herd vaccination program.

Aging↗

PubMed1975

The influence of pH on the growth and stability of transmissible gastroenteritis virus in vitro.

The influence of pH on the growth of transmissible gastroenteritis virus (TGEV) in adult pig thyroid cell culture, and on the stability of the virus was studied. At pH 7.2 and 100 fold higher than those at pH 8.0. The adsorption, penetration and uncoating steps of the viral replicative cycle were shown to be unaffected by pH variation. Synthesis of TGEV RNA during the first 12 hours post infection was found to be unaffected by pH variation between the range 6.5-8.0. After 12 hours breakdown of this RNA appeared to occur in cultures held at pH 7.2 and 8.0 but not at pH 6.5. When incubated at 37 degrees C for 24 hours the virus infectivity was found to be least affected by pH 6.5 but when kept at 4 degrees C for the same length of time, the virus infectivity remained constant between pH 5.0 and pH 8.0.

Animals↗

PubMed1977

Detection of transmissible gastroenteritis virus neutralising antibody in cats.

High titres of neutralizing activity to transmissible gastroenteritis virus (TGEV), a porcine coronavirus, were found in sera and peritoneal fluids from cats infected with feline infectious peritonitis (FIP). A small proportion of cats, from a hospital population unaffected by FIP, also had neutralising activity. Procedures to remove non-specific viral inhibitors, including treatment by heat inactivation, trypsin, sulphydryl reagent and kaolin absorption were unsuccessful. The active component was unable to neutralise another porcine coronavirus, haemagglutinating encephalomyelitis virus or the porcine enterovirus, Talfan. Gel filtration of feline sera and peritoneal fluid demonstrated high levels of the neutralising activity in the area corresponding to 7S IgG, which could be removed by absorption with specific anti-IgG serum and these properties are suggested to be consistent with those of antibody. These findings imply that there is a coronavirus in cats which is antigenically related to TGEV and its possible nature is discussed.

Animals↗

PubMed1992

Antigenic structure of transmissible gastroenteritis virus nucleoprotein.

A group of 11 monoclonal antibodies (MAbs) raised against transmissible gastroenteritis virus (TGEV) was used to study the antigenic structure of the virus nucleoprotein (N). To identify the regions recognized by MAbs, DNA fragments derived from the N-coding region of the TGEV strain FS772/70 were cloned into pUR expression plasmids and the antigenicity of the resulting fusion proteins was analyzed by immunoblotting. A major antigenic domain was identified, covering the first 241 amino acid residues of N, within which an epitope (residues 57-117) was also found. A second antigenic domain extended from residues 175 to 360 of the nucleoprotein, within which a subsite was characterized within the region covering residues 241-349. MAb DA3 recognized a linear epitope which mapped within residues 360 and 382 at the carboxy terminus of the nucleoprotein. The binding of the majority of the MAbs (8 out of 11) to large fusions, but not to smaller fragments included in them, suggests a conformational dependence of the MAb binding sites. Our data show that the use of fusions in Western blot experiments is a useful approach to map not only linear epitopes but more complex antigenic structures found in the nucleoprotein of the TGEV.

Antibodies, Monoclonal↗