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PubMed1977

Immunoglobulin classes of antibodies in milk of swine after intranasal exposure to pseudorabies virus or transmissible gastroenteritis virus.

Experiments were conducted to evaluate whether infection of the respiratory tract of pregnant swine with pseudorabies (Pr) virus would induce the secretion of immunoglobulin A (IgA) antibodies in their milk as was observed after enteric infection with transmissible gastroenteritis (TGE) virus. The immune response of sows to Pr virus inoculated intranasally and to TGE virus inoculated orally/intranasally or via a natural infection was studied. Emphasis was placed upon titers and Ig classes of Pr and TGE virus-neutralizing antibodies in colostrum and milk. All animals exposed to Pr virus (alone or in combination with TGE virus) developed Pr-neutralizing antibody titers in both serum and milk. Pr antibody titers were generally higher in colostrum than in serum, but the opposite was true in milk compared with serum, with milk titers declining markedly during lactation. In contrast, TGE antibody titers in milk from experimentally or naturally infected sows usually remained higher than the corresponding serum titers and persisted at relatively constant levels throughout lactation. Gel filtration studies of milk indicated that the antibody activity against Pr virus was associated almost entirely with IgG fractions, with small amounts of antibody detectable in IgM fractions in colostrum from two of nine sows. By comparison, TGE antibodies were primarily of the IgA class, with varying but lesser amounts of antibody associated with the IgG class. Such results suggest that viral infection of the intestinal tract of the sow, but not the upper respiratory tract, stimulates the secretion of IgA antibodies in the milk.

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↗
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↗
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↗
PubMed1979

Methanol precipitation of transmissible gastroenteritis virus.

Methanol precipitation of transmissible gastroenteritis virus was tested at Ph 4.0, 5.0, 6.0, and 7.0 and at methanol concentrations of 15%, 25%, and 30%. Supernatant and precipitate fractions were tested for complement-fixing and agar-diffusion soluble antigens and plaque-forming units, and were examined by electron microscopy. Virus could be obtained free of detectable agar-diffusion antigens and most of the complement-fixing antigens. Most of the virions were without peplomers after methanol treatment but they retained infectivity.

Animals↗
PubMed1981

Thermal inactivation studies of a coronavirus, transmissible gastroenteritis virus.

The thermolability of transmissible gastroenteritis virus (TGEV) was studied between 31 and 55 degrees C using two different strains. The loss of infectivity followed first order kinetics except at the highest temperature. The values of the thermodynamic parameters indicated that the mechanisms involved above and below 45 degrees C are clearly distinct. The rates of inactivation were greater at alkaline than at neutral pH, yet the name of the reaction appeared unchanged. Using four independent stocks of mutagenized virus, we failed to select thermal-resistant mutants by survivor selection at 38 degrees C. In contrast, thermal-resistant mutants were consistently obtained at 54 degrees C. However, the latter did not show any increased stability at 38 degrees C, confirming the fact that a different inactivation process takes place at high and at physiological temperatures.

Coronaviridae↗
PubMed1976

Isolation of subviral components from transmissible gastroenteritis virus.

Exposure of purified transmissible gastroenteritis virus, a porcine coronavirus, to non-ionic detergents resulted in the removal of the surface projections and greater than 98% of the virus lipid. Virus RNA was associated with a subviral particle which had a sedimentation coefficient of 650S, compared with 495S for the intact virion, and which banded in Cs2SO4 gradients at 1-295 g/ml. Negatively stained preparations of subviral particles were shown by electron microscopy to contain spherical particles of 60 to 70 nm diam., similar in appearance to those derived from oncornaviruses. Polyacrylamide gel electrophoresis of the polypeptides from isolated subviral particles showed that these structures contained three of the four major virus structural proteins, the arginine-rich polypeptide VP2 and the two membrane glycopolypeptides VP2 and 4. The detergent-liberated surface projections, composed of a single species of sulphated glycopolypeptide, VPI, were isolated by rate-zonal centrifugation through sucrose gradients followed by precipitation with ammonium sulphate in the presence of bovine serum albumin.

Arginine↗
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↗
PubMed1986

Effect of recombinant DNA-derived bovine alpha-1 interferon on transmissible gastroenteritis virus infection in swine.

Recombinant DNA-derived bovine interferon alpha 1-1 (BoIFN) inhibited replication of both vesicular stomatitis virus and transmissible gastroenteritis virus in cultures of swine testicular cells. Newborn pigs were orally inoculated with BoIFN and subsequently had interferon in their gastric contents and serum; however, interferon was found only occasionally in intestinal washings. Incubation of BoIFN with gastric contents from a newborn suckling pig did not affect antiviral activity, whereas intestinal (small intestine) contents from the same animal inactivated BoIFN within 1 minute. Beginning at 6 hours of age, newborn, colostrum-deprived pigs were given 1 mg of BoIFN orally every 12 hours. These pigs were not protected against challenge exposure to virulent transmissible gastroenteritis virus at 48 hours of age; disease and mortality were similar for these pigs and for control pigs not given BoIFN prior to challenge exposure. The BoIFN did not impair growth rate of pigs and did not cause obvious disease or lesions.

Administration, Oral↗
PubMed1981

[Morphology of coronaviruses-- electron microscopic demonstration by negative contrast technic of the transmissible gastroenteritis virus of swine].

This contribution to the morphology of corona virus is based on the use of electron microscopy in a negative contrast investigation of the virus of transmissible gastroenteritis of swine. Viruses of transmissible gastro-enteritis are spherical or, in rare cases, pleomorphous particles of typical corona virus structure. The viruses investigated by the authors were 132 nm in diameter. The surface projections, consisting of a flattened knob and conical shaft, are 18 nm in length. Internal bodies, 50 +/- 2 nm in diameter, occur as "filled" or "empty" particles. The thickness of all internal bodies and virus membranes is 8 +/- 1 nm. Differences were found to exist between virus of transmissible gastro-enteritis and particles similar to corona virus and isolated from faecal samples. A first comparison had been made for that purpose. Those differences were relating to shape and size of individual particles and to morphological setup of surface projections.

Animals↗
PubMed1976

In vitro differentiation and pH sensitivity of field and cell culture-attentuated strains of transmissible gastroenteritis virus.

Characteristics of four transmissible gastroenteritis (TGE) virus field strains (Miller, Purdue, Bl, and V203) and four cell culture-attenuated strains (Purdue, SH, CKp, and Bl) were studied to find methods of differentiation between the two groups of viruses. TGE field virus strains did not replicate as well as attenuated strains at 37 C and could not be passaged serially for more than four to six passages at 33 C. There were clear differences in plaque size when the strains were compared. Field strains had average plaque sizes ranging from 3.59 to 3.15 mm, whereas attenuated strains induced plaques that were larger than 4.2 mm. Variations were observed in stability of strains at pH 3.0. Field strains and cell culture-attenuated strains CKp-270 and SH-114 were reduced in titer by about 1 log10. A reduction of about 3 log10, however, was obtained with cell culture strains B1-300 and Purdue-113.

Cell Line↗
PubMed1979

Humoral and cellular responses in swine exposed to transmissible gastroenteritis virus.

Swine exposed to attenuated transmissible gastroenteritis virus had higher virus-neutralizing antibody titers than did swine exposed to virulent virus. The cellular response, measured by the direct leukocyte migration-inhibition (LMI) procedure, was greater in swine exposed to virulent virus than in swine exposed to the attenuated virus. Leukocytes from exposed swine were inhibited more in the LMI procedure in the presence of the homologeous sensitizing antigen than in the presence of the heterologous viral antigen. The humoral response measured by virus neutralizing reached a peak 21 days after exposure, and the cellular response measured by LMI reached a peak 28 days after exposure.

Animals↗
PubMed1980

Genome of porcine transmissible gastroenteritis virus.

The Purdue strain of transmissible gastroenteritis virus, a porcine coronavirus, was grown to titers of greater than 10(8) PFU/ml in a swine testicle cell line, and the RNA was isotopically labeled with [3H]uridine. The RNA was extracted from purified virus and was found to have the following properties. (i) It consisted primarily of a homogeneous large-molecular-weight species which electrophoretically migrated with an apparent molecular weight of 6.8 X 10(6) under denaturing conditions. (ii) It migrated electrophoretically at the same rate on nondenaturing gels before and after heat denaturation, suggesting that it does not consist of subunits. (iii) It was susceptible to pancreatic RNase A digestion in high (0.3 M) NaCl. (iv) It was polyadenylated to the extent that greater than 60% of the native RNA bound to oligodeoxythymidilic acid-cellulose under conditions of high (0.5 M) NaCl. RNA extracted from virions was infectious. This coronavirus can therefore be characterized as a positive-strand RNA virus.

Animals↗
PubMed2006

Complete genomic sequences, a key residue in the spike protein and deletions in nonstructural protein 3b of US strains of the virulent and attenuated coronaviruses, transmissible gastroenteritis virus and porcine respiratory coronavirus.

Transmissible gastroenteritis virus (TGEV) isolates that have been adapted to passage in cell culture maintain their infectivity in vitro but may lose their pathogenicity in vivo. To better understand the genomic mechanisms for viral attenuation, we sequenced the complete genomes of two virulent TGEV strains and their attenuated counterparts: virulent TGEV Miller M6 and attenuated TGEV Miller M60 and virulent TGEV Purdue and attenuated TGEV Purdue P115, together with the ISU-1 strain of porcine respiratory coronavirus (PRCV-ISU-1), a naturally occurring TGEV deletion mutant with an altered respiratory tropism and reduced virulence. Pairwise comparison at both the nucleotide (nt) and amino acid (aa) levels between virulent and attenuated TGEV strains identified a common change in nt 1753 of the spike gene, resulting in a serine to alanine mutation at aa position 585 of the spike proteins of the attenuated TGEV strains. Alanine was also present in this protein in PRCV-ISU-1. Particularly noteworthy, the serine to alanine mutation resides in the region of the major antigenic site A/B (aa 506-706) that elicits neutralizing antibodies and within the domain mediating the cell surface receptor aminopeptidase N binding (aa 522-744). Comparison of the predicted polypeptide products of ORF3b showed significant deletions in the naturally attenuated PRCV-ISU-1 and TGEV Miller M60; these deletions occurred at a common break point, suggesting a related mechanism of recombination that may affect viral virulence or tropism. Sequence comparisons at both genomic and protein levels indicated that PRCV-ISU-1 had a closer relationship with TGEV Miller strains than Purdue strains. Phylogenetic analyses showed that virulence is an evolutionarily labile trait in TGEV and that TGEV strains as a group share a common ancestor with PRCV.

Amino Acid Sequence↗
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↗