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Results for “Transmissible gastroenteritis”

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PubMed2007

Recombinant dimeric small immunoproteins neutralize transmissible gastroenteritis virus infectivity efficiently in vitro and confer passive immunity in vivo.

Small immunoproteins (SIPs) are single-chain molecules comprising the variable regions of an antibody assembled in a single polypeptide (scFv) and joined to the immunoglobulin heavy-chain dimerizing domain. To investigate the potential of these molecules to provide protection against enteric infections when supplied orally, SIPs were generated against Transmissible gastroenteritis virus (TGEV), a highly pathogenic porcine virus. Different variants of TGEV-specific SIPs were created, of epsilon and alpha isotypes, by exploiting the dimerizing domains epsilonCH4 and alphaCH3 of human and swine origin. Transfected cells secreted these recombinant mini-antibodies efficiently, mainly as dimers stabilized covalently by inter-chain disulphide bridges. The specificity and functionality of the recombinant TGEV-specific SIPs were determined by in vitro binding, neutralization and infection-interference assays. The neutralization indices of the TGEV-specific SIPs were all very similar to that of the original TGEV-specific mAb, thus confirming that the immunological properties have been preserved in the recombinant SIPs. In vivo protection experiments on newborn piglets have, in addition, demonstrated a strong reduction of virus titre in infected tissues of animals treated orally with TGEV-specific SIPs. It has therefore been demonstrated that it is possible to confer passive immunization to newborn pigs by feeding them with recombinant SIPs.

Animals↗

PubMed1984

Antibody-dependent and spontaneous cell-mediated cytotoxicity against transmissible gastroenteritis virus infected cells by lymphocytes from sows, fetuses and neonatal piglets.

The purpose of this study was to investigate the ontogeny in the pig of effector lymphocytes mediating antibody-dependent and spontaneous cell-mediated cytotoxicity against target cells infected with transmissible gastroenteritis virus. The same activities were also studied in sows in late pregnancy and early lactation. Peripheral blood lymphocytes and intraepithelial lymphocytes collected from piglets during the first week of life failed to mediate cytolysis as determined by chromium release assays, but significant activities developed during the second week and usually increased further by the sixth week. Peripheral blood lymphocytes collected from fetuses on the 109th gestation day failed to produce spontaneous cell-mediated cytotoxicity and only reacted in antibody-dependent cell-mediated cytotoxicity when contaminated with macrophages. The cytotoxic activities of peripheral blood lymphocytes from sows were lowest at parturition. It was concluded that impaired lymphocyte cytotoxicity in newborn piglets and parturient sows may contribute to their relatively high susceptibility to transmissible gastroenteritis.

Animals↗

PubMed2004

A corn-based delivery system for animal vaccines: an oral transmissible gastroenteritis virus vaccine boosts lactogenic immunity in swine.

Recombinant plant expression systems offer a means to produce large quantities of selected antigens for subunit vaccines. Cereals are particularly well-suited expression vehicles since the expressed proteins can be stored at relatively high concentrations for extended periods of time without degradation and dry seed can be formulated into oral vaccines suitable for commercial applications. A subunit vaccine candidate directed against porcine transmissible gastroenteritis virus and expressed in corn seed has been developed for oral delivery to swine. Here, we show that this vaccine, when administered to previously sensitized gilts, can boost neutralizing antibody levels in the animals' serum, colostrum and milk. Thus, this vaccine candidate is effective at boosting lactogenic immunity and is appropriate to pursue through large-scale field trials preceding commercialization.

Administration, Oral↗

PubMed1991

Intestinal permeability in piglets during transmissible gastroenteritis.

Macromolecular permeability of the small intestine was tested in seven three-week-old piglets infected with porcine transmissible gastroenteritis virus (TGE-strain Miller). Fourteen hours after the infection, the piglets showed loss of appetite and a profuse diarrhoea. In some animals vomiting occurred somewhat earlier. Macromolecular permeability was tested morphologically by injecting horseradish peroxidase (MW = 40,000 Da) into the jejunal lumen just distally to the Treitz' ligament in two piglets at 12 hours and in five piglets at 48 hours after the inoculation in comparison with two control piglets. After a period of 20 minutes, small segments of jejunum were taken for stereomicro-scopical, histological and ultrastructural investigations. An increased permeability for HRP together with a severe, hyper-regenerative villous atrophy was observed in the TGE-infected piglets at 48 hours after the inoculation.

Animals↗

PubMed1987

Sequence and N-terminal processing of the transmembrane protein E1 of the coronavirus transmissible gastroenteritis virus.

Sequencing of part of a clone from a transmissible gastroenteritis virus genome cDNA library led to the identification of the gene encoding the E1 matrix protein. The amino acid sequence of the primary translation product predicts a polypeptide of 262 residues which shares many features with the previously characterized murine hepatitis virus and infectious bronchitis virus E1 proteins. However, N-terminal amino acid sequencing revealed that a putative signal peptide of 17 residues was absent in the virion-associated polypeptide. The predicted mol. wt. of the mature unglycosylated product, 27,800, is in agreement with the experimental Mr value.

Amino Acid Sequence↗

PubMed1990

Infection with a new porcine respiratory coronavirus in Denmark: serologic differentiation from transmissible gastroenteritis virus using monoclonal antibodies.

In 1984 neutralizing antibodies against transmissible gastroenteritis virus (TGEV) were detected in pig herds in a small geographical area in the southern part of Denmark. No clinical symptoms were observed and accumulating epidemiological evidence gradually pointed towards a respiratory infection. In 1986 a TGE-like virus, tentatively named porcine respiratory coronavirus (PRCV), was isolated from the lungs of swine. The virus was partially characterized using monoclonal antibodies against TGEV and this showed that some (mainly nonneutralizing) epitopes of the peplomer glycoprotein E2 were absent in PRCV, whereas the major neutralizing domains were conserved. These findings allowed the design of competitive antibody immunoassays either discriminating or not discriminating the immune responses against the two viruses. However, the discriminating epitopes studied so far have shown minor immunodominance and some steric interference from nondiscriminating epitopes.

Animals↗

PubMed1992

Coronavirus infection in mink (Mustela vison). Serological evidence of infection with a coronavirus related to transmissible gastroenteritis virus and porcine epidemic diarrhea virus.

Antibodies to a transmissible gastroenteritis virus (TGEV)-related coronavirus have been demonstrated in mink sera by indirect immunofluorescence, peroxidase-linked antibody assays and immunoblotting. This is the first serological evidence of a specific coronavirus infection in mink. The putative mink coronavirus (MCV) seems to be widespread in the Danish mink population with a prevalence approaching 100%. Analysis by immunoblotting has shown that MCV is closely related to TGEV by the spike (S), matrix (M) and nucleoprotein (N) polypeptides. Furthermore, antibodies to MCV also cross-reacted with N and M polypeptides of porcine epidemic diarrhea virus (PEDV). Thus MCV may occupy an intermediate position between the TGEV group of coronavirus and PEDV. The possibility that MCV may be associated with syndromes of acute enteritis in preweaning mink is discussed.

Animals↗

PubMed1989

Sequence of the coding regions from the 3.0 kb and 3.9 kb mRNA. Subgenomic species from a virulent isolate of transmissible gastroenteritis virus.

Subgenomic mRNA from a virulent isolate of porcine transmissible gastroenteritis virus (TGEV) was used to produce cDNA clones covering the genome region from the 3' end of the peplomer gene to the start of the integral membrane protein gene. The nucleotide sequence of this area was determined using clone pTG11 and a previously reported cDNA clone pTG22. Three open reading frames (ORFs) were identified encoding putative polypeptides of relative molecular masses (Mr) 6,600, 27,600, and 9,200. The sequence encoding the Mr 9,200 polypeptide was found to be present on the "unique" 5' region of the 3.0 kb mRNA species whereas the other two ORFs mapped on the 3.9 kb mRNA species. Differences between the ORFs from this strain of TGEV and those from a previously reported avirulent strain of TGEV were compared.

Amino Acid Sequence↗

PubMed1984

Colonic compensation in transmissible gastroenteritis of swine.

Absorption of water and electrolytes by the small and large intestine was examined using a nonabsorbable marker technique in 3-day-old and 3-wk-old pigs. One-half of the pigs in each group were orally infected with transmissible gastroenteritis virus; the remaining pigs served as controls. Three-day-old control pigs concentrated the nonabsorbable fluid marker twelve fold along the small and large intestine, indicating an efficiency of about 95% in absorption of the exogenous daily fluid load presented to the intestine. In contrast, the marker concentration in infected pigs showed no change whatsoever along either the small or large intestine, indicating a complete absence of net fluid absorption or secretion in these animals. Three-week-old control pigs concentrated the marker similarly to the 3-day-old group, with the bulk of the fluid absorption occurring in the small intestine. Infected pigs in the 3-wk-old group had marked net fluid secretion in the proximal small intestine, so that about twice the fluid load was presented to the large intestine of the 3-wk-old infected pigs as compared to the 3-day-old infected group. However, in contrast to the 3-day-old infected group, the large intestine of the 3-wk-old infected pigs increased fluid absorption some six times over the control, and this compensatory response prevented diarrhea in these older animals. Analysis of luminal contents indicated that in the older pigs, unabsorbed carbohydrate was almost completely fermented to short-chain fatty acids in the colon, whereas in the younger pigs the carbohydrate passed through the colon unchanged. These results demonstrate that development of microbial digestion, together with rapid short-chain fatty acid absorption, is a primary feature responsible for the colonic compensation in the older pigs with transmissible gastroenteritis.

Age Factors↗

PubMed1986

Characterization and translation of transmissible gastroenteritis virus mRNAs.

Three protein species were identified in purified transmissible gastroenteritis virus particles (strain Purdue). They are thought to represent constituents of the peplomer (E2; molecular weights of 280,000 and 240,000), the envelope (E1; molecular weights of 28,000, 31,500, and 33,000), and the nucleocapsid (N; molecular weight of 48,000). In infected cells, proteins with molecular weights of 195,000 (E2), 48,000 (N), and 28,000 (E1) were detected. Tunicamycin, an inhibitor of N glycosylation, prevented the appearance of polypeptides with molecular weights of 195,000 and 28,000 in infected cells; instead, proteins with molecular weights of 160,000 and 25,000 were observed. One minor and five major mRNA species were detected in porcine cells after infection. Their size was determined to be 23.6 kilobases (kb) (RNA1), 8.4 kb (RNA3), 3.8 kb (RNA4), 3.0 kb (RNA5), 2.6 kb (RNA6), and 1.9 kb (RNA7). The RNAs were translated in vitro. RNA7 was shown to code for the N protein. Although complete separation of RNA6 could not be achieved, it was shown to encode an unglycosylated (molecular weight of 25,000) precursor of E1 (molecular weight of 28,000). RNA4 was translated into a nonstructural protein with a molecular weight of 24,000. Translation of RNA3 resulted in proteins with molecular weights of 250,000 and 130,000 and smaller molecules which could be precipitated with a monoclonal antibody directed against E2.

Animals↗

PubMed1990

Localization of antigenic sites of the E2 glycoprotein of transmissible gastroenteritis coronavirus.

Four antigenic sites of the E2 glycoprotein of transmissible gastroenteritis virus were defined by competitive radioimmunoassays of monoclonal antibodies (MAbs). Here, we describe the localization of these sites by testing the antigenicity of protein fragments and prokaryotic expression products of E2 gene fragments, and by sequencing of MAb-resistant (mar) mutants. Partial proteolysis of purified E2 protein allowed the isolation of a 28K fragment recognized by both site A- and site C-specific MAbs. An antiserum against this fragment bound to a synthetic peptide containing residues 1 to 18 and to an expression product containing residues 1 to 325. The same expression product was recognized by site C-specific MAbs. These data indicate that residues within the sequence 1 to 325 contribute to site C and possibly also to site A. Sequencing of mar mutants that escaped neutralization by site A-specific MAbs indicated that residues 538 and 543 also belong to site A. The binding of site-specific MAbs to expression products led directly to the localization of sites B and D, between residues 1 to 325 and 379 to 529, respectively. The first 37% of the polypeptide chain of E2 appears to be more immunogenic than the rest of the sequence.

Amino Acid Sequence↗

PubMed1992

Antigen selection and presentation to protect against transmissible gastroenteritis coronavirus.

The antigenic structure of the S glycoprotein of transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV) has been determined and correlated with the physical structure. Four antigenic sites have been defined (A, B, C, and D). The sites involved in the neutralization of TGEV are: A, D, and B, sites A and D being antigenically dominant for TGEV neutralization in vitro. These two sites have specific properties of interest: site A is highly conserved and is present in coronaviruses of three animal species, and site D can be represented by synthetic peptides. Both sites might be relevant in protection in vivo. PRCV does not have sites B and C, due to a genomic deletion. Complex antigenic sites, i.e., conformation and glycosylation dependent sites, have been represented by simple mimotopes selected from a library expressing recombinant peptides with random sequences, or by anti-idiotypic internal image monoclonal antibodies. An epidemiological tree relating the TGEVs and PRCVs has been proposed. The estimated mutation fixation rate of 7 +/- 2 x 10(-4) substitutions per nucleotide and year indicates that TGEV related coronaviruses show similar variability to other RNA viruses. In order to induce secretory immunity, different segments of the S gene have been expressed using a virulent forms of Salmonella typhimurium and adenovirus. These vectors, with a tropism for Peyer's patches may be ideal candidates in protection against TGEV.

Amino Acid Sequence↗

PubMed1990

Evidence for a porcine respiratory coronavirus, antigenically similar to transmissible gastroenteritis virus, in the United States.

A respiratory variant of transmissible gastroenteritis virus (TGEV), designated PRCV-Ind/89, was isolated from a swine breeding stock herd in Indiana. The virus was readily isolated from nasal swabs of pigs of different ages and induced cytopathology on primary porcine kidney cells and and on a swine testicular (ST) cell line. An 8-week-old pig infected oral/nasally with the respiratory variant and a contact pig showed no signs of respiratory or enteric disease. These pigs did not shed virus in feces but did shed the agent from the upper respiratory tract for approximately 2 weeks. Baby pigs from 2 separate litters (2 and 3 days old) also showed no clinical signs following oral/nasal inoculation with PRCV-Ind/89. In a third litter, 5 of 7 piglets (5 days old) infected either oral/nasally or by stomach tube developed a transient mild diarrhea with villous atrophy. However, virus was not isolated from rectal swabs or ileal homogenates of these piglets, and viral antigen was not detected in the ileum by fluorescent antibody staining even though the virus was easily recovered from nasal swabs and lung tissue homogenates. Swine antisera produced against PRCV-Ind/89 or enteric TGEV cross-neutralized either virus. In addition, an anti-peplomer monoclonal antibody, 4F6, that neutralizes TGEV also neutralized the PRCV-Ind/89 isolate. Radioimmunoassays with a panel of monoclonal antibodies indicated that the Indiana respiratory variant and the European PRCV are antigenically similar.

Animals↗

PubMed2002

Transcription regulatory sequences and mRNA expression levels in the coronavirus transmissible gastroenteritis virus.

The transcription regulatory sequences (TRSs) of the coronavirus transmissible gastroenteritis virus (TGEV) have been characterized by using a helper virus-dependent expression system based on coronavirus-derived minigenomes to study the synthesis of subgenomic mRNAs. The TRSs are located at the 5' end of TGEV genes and include a highly conserved core sequence (CS), 5'-CUAAAC-3', that is essential for mediating a 100- to 1,000-fold increase in mRNA synthesis when it is located in the appropriate context. The relevant sequences contributing to TRS activity have been studied by extending the CS 5' upstream and 3' downstream. Sequences from virus genes flanking the CS influenced transcription levels from moderate (10- to 20-fold variation) to complete mRNA synthesis silencing, as shown for a canonical CS at nucleotide (nt) 120 from the initiation codon of the S gene that did not lead to the production of the corresponding mRNA. An optimized TRS has been designed comprising 88 nt from the N gene TRS, the CS, and 3 nt 3' to the M gene CS. Further extension of the 5'-flanking nucleotides (i.e., by 176 nt) decreased subgenomic RNA levels. The expression of a reporter gene (beta-glucuronidase) by using the selected TRS led to the production of 2 to 8 microg of protein per 10(6) cells. The presence of an appropriate Kozak context led to a higher level of protein expression. Virus protein levels were shown to be dependent on transcription and translation regulation.

3' Flanking Region↗

PubMed1975

Passive immunity in transmissible gastroenteritis of swine: immunoglobulin characteristics of antibodies in milk after inoculating virus by different routes.

Pregnant swine were exposed to transmissible gastroenteritis (TGE) virus by different routes, and their serum, colostrum, and mild were examined for titer and immunoglobulin (Ig) class of antibodies. When 2 to 4 days old, the litters of most of these animals were challenged with virulent TGE virus to determine the effectiveness of passive immunity. After two oral/intranasal exposures to attenuated virus, none of the six pregnant animals became sick. TGE antibodies in milk were primarily or solely of the IgG class, although low levels of IgA antibodies were detected in three animals. Pigs in the five challenged litters received some passive immunity, the mortality being 25%. After intramuscular injection of six pregnant swine with virulent virus, two types of clinical and immunological responses were observed, presumably dependent on whether the gut was infected by an hematogenous spread of the virus. Three became sick, showing typical clinical signs of TGE, and their immunological response was characterized by the occurrence in milk of antibodies of the IgA class. A good degree (0% mortality) of passive immunity occurred upon challenge of the suckling pigs. In contrast, in three pregnant animals that did not sicken, antibody in milk was primarily of the IgG calss, and poor (69% mortality) passive immunity occurred. After intramammary injections of three pregnant swine with virulent virus, no sickness was observed and the immunological response was characterized by the occurrence in colostrum of high titers of TGE antibodies that were primarily or solely of the IgG class; good (0% mortality) passive immunity occured. The occurrence in milk of TGE antibodies of the IgA class was associated with an intestinal infection, whereas antibodies of the IgG class resulted from a parenteral antigenic stimulation. The role of antigenic stimulation of the intestinal tract for providing antibodies in milk of the IgA class is discussed. Passive immunity against intestinal infection with TGE virus was generally more complete in pigs ingesting antibodies of the IgA than of the IgG class.

Absorption↗

PubMed1975

Age-dependent resistance to transmissible gastroenteritis of swine. III. Effects of epithelial cell kinetics on coronavirus production and on atrophy of intestinal villi.

Coronavirus titers in small intestine, degree of villous atrophy and apparent rates of regeneration of intestinal villi were compared in newborn, 3-week-old and adult pigs for 1 week after they were exposed to the transmissible gastroenteritis virus of swine. The response within the newborn group was homogeneous, resulting in high virus titers, maximal villous atrophy and comparatively slow regeneration. In general, virus titers were lower, villous atrophy was less severe and regeneration more rapid in both older groups than in the newborn pigs. However, the response varied greatly in the older groups. The 3-week-old group was divided into two populations. The major population had low virus titers and developed partial villous atrophy, whereas the minor population had marked villous atrophy and virus titers comparable to those of the newborn pigs. These observations support the hyposthesis that the accelerated replacement of villous epithelium in the small intestine of pigs during the first 3 weeks contributes to the innate age-dependent resistance to transmissible gastroenteritis. The accelerated replacement of villous epithelial cells in older pigs contributes to resistance in two ways. The increased proliferative capacity of crypt epithelium results in a more rapid regeneration of atrophic villi; and the comparatively young villous absorptive cells resulting from accelerated replacement produce less virus per cell than the older ones of the newborn pig.

Age Factors↗

PubMed1976

Local and systemic cell-mediated immunity against transmissible gastroenteritis, an intestinal viral infection of swine.

The occurrence of local and systemic cell-mediated immunity (CMI) in swine against transmissible gastroenteritis (TGE) virus, a coronavirus that infects the epithelial cells of the small intestine of swine, has been investigated. Leukocyte suspensions prepared from intestinal lamina propria (LP) and spleen were each incubated with and without inactivated TGE virus. The supernatants from these cultures were tested for the presence of macrophage migration inhibition factor (MIF) by the indirect MIF test using guinea pig peritoneal exudate cells as the source of macrophages. All swine serologically negative for TGE antibodies (i.e., unexposed to TGE virus) were also negative for MIF production by lymphocytes from both sources. In 10 of 10 animals given TGE virus subcutaneously, MIF production by splenic lymphocytes was significantly greater (p less than or equal to 0.01) than by LP lymphocytes, and in 9 of 10 of these animals MIF production by LP lymphocytes was negligible (percentage of inhibition of migration less than 3%).

Animals↗

PubMed1990

Sows infected in pregnancy with porcine respiratory coronavirus show no evidence of protecting their sucking piglets against transmissible gastroenteritis.

Eighteen litters of sucking piglets were challenged with one of two strains of transmissible gastroenteritis virus (TGEV). During pregnancy, their seronegative dams had been either inoculated intranasally with porcine respiratory coronavirus (PRCV), inoculated orally with TGEV or left untreated. On the basis of weight gain, clinical signs and survival, no differences in response to challenge was detected when piglets suckled by PRCV inoculated sows were compared with those suckled by uninoculated sows. Such a difference was evident when the litters of sows successfully pre-immunized with TGEV were compared with those of uninoculated or PRCV-inoculated sows. The possibility of transplacental transmission of PRCV was investigated in two litters born to sows that had been inoculated with this virus in late pregnancy. All sixteen live-born piglets were seronegative for the virus at birth and PRCV was not isolated from tissues taken from two stillborn piglets.

Animals↗