Further studies on in vitro and in vivo assays of hemorrhagic enteritis virus (HEV)

Isolation of hemorrhagic enteritis virus (HEV) from spleens of infected turkeys in the MDTC-RP19 lymphoblastoid cell line was compared with detection of HEV antigen in the same spleens using the agar gel precipitation (AGP) test. A concordance of 80% was found between the two assays. Virus isolation had a sensitivity of 84% and a specificity of 88% compared with the AGP test. RP19 cells were also susceptible to infection with several other avian adenoviruses, but such infection was easily differentiated from that of HEV by a fluorescent-antibody (FA) test. Turkeys required 10(2) tissue-culture-infectious doses (TCID) to develop HE-specific lesions and 10(5) TCID to be killed. On the other hand, as little as 10 TCID of apathogenic HEV protected the poults against challenge with virulent HEV. The enzyme-linked immunosorbent assay (ELISA) for detection of HEV antibody was improved by using virus-infected RP19 cells as antigen. The ELISA appears to be more sensitive than the serum-neutralization test.

Shedding of enteric coronavirus in adult cattle

Electron microscopic examination of fecal specimens from adult dairy cows indicated seasonal coronavirus shedding. Fifty-two cows from a 300 cow herd were monitored for shedding of coronavirus. Approximately 50% to 60% of the cows monitored shed coronavirus during the winter months (November to March) of the first year of the study. During 2 subsequent years of monitoring the same cows, 20% to 30% of the cows shed coronavirus during the winter months. Virus shedding was not detected during the summer months (July to September). Half of the cows monitored were vaccinated with a modified-live rotavirus-coronavirus-Escherichia coli combination vaccine; however, vaccination did not influence seasonal shedding of coronavirus, as compared with shedding in the nonvaccinated cows. In nonvaccinated cows that calved in the winter months, the incidence of coronavirus shedding increased from 20% to 30% during the last 2 months of gestation to 65% to 70% at parturition. In vaccinated cows, the incidence of shedding did not increase at parturition.

Characteristics of Australian human enteric coronavirus-like particles: comparison with human respiratory coronavirus 229E and duodenal brush border vesicles

The polypeptide profiles of highly purified coronavirus-like particles (CVLPs) proved to be very different from that of human respiratory coronavirus 229E and showed the particles not to be coronaviruses. Differences in polypeptide profiles and morphology between the CVLPs and duodenal brush border vesicles suggested that the CVLPs were also not such vesicles. Although they shared some basic overall similarity, the polypeptide profiles of three different but possibly antigenically identical CVLP preparations from Central Australian Aborigines were very dissimilar in detail. At least 38, 39 and 48 bands respectively were observed on the three profiles. At least 46 bands were visible on the polypeptide profile of CVLPs from a Vietnamese immigrant to Australia, and it also differed in detail from those of the Central Australian CVLPs. Indications of antigenic difference were obtained between Central Australian CVLPs and CVLPs from India, Kiribati, South Africa and Vietnamese immigrants to Australia. Antigenic difference was also suggested between the Central Australian CVLPs and those from one distant location within Australia, but antigenic similarity with those from another was indicated.

Humoral immune response of cats to virulent and avirulent feline infectious peritonitis virus isolates

Isolates of feline infectious peritonitis virus (FIPV) vary in their degree of virulence and have antigenically and functionally different peplomer glycoproteins. We tested the most virulent isolate, FIPV-79-1146 and the avirulent isolate, FIPV-UCD-2 in vivo in order to better understand the pathogenesis of FIP. Specific pathogen free cats were inoculated with either FIPV-79-1146 or FIPV-UCD-2. After 28 days cats which had received FIPV-79-1146 were either dead or showing clinical signs of FIP. The FIPV-UCD-2 inoculated cats seroconverted but remained healthy and were then divided into three groups. One group was not manipulated, one group received a second dose of FIPV-UCD-2, and the third group received FIPV-79-1146. One month later all FIPV-UCD-2 cats which had subsequently received FIPV-79-1146 were dead of FIP while the FIPV-UCD-2 inoculated cats remained healthy. Antibody mediated immune enhancement of FIP disease was not observed. Serum neutralization assays demonstrated that only those cats which received FIPV-79-1146 developed neutralizing antibodies to FIPV-79-1146. However, all cats except uninoculated controls developed neutralizing titers to FIPV-UCD-2. Competition ELISAs were used to analyze the specific humoral immune responses of cats to structural polypeptides of the viruses.

Probing for the human coronavirus OC43 in multiple sclerosis

Tissues acquired at autopsy from four patients with MS and biopsies from one patient with a probable diagnosis of MS were probed for the presence of OC43 RNA. This human coronavirus was not detected.

Detection of transmissible gastroenteritis coronavirus antigens by a sandwich enzyme-linked immunosorbent assay technique

A new sandwich enzyme-linked immunosorbent assay, using monoclonal and polyclonal antibodies, was developed to detect transmissible gastroenteritis virus antigens from cell culture and from intestinal wash or feces obtained from experimentally infected pigs. This technique was shown to be suitable for the detection of virulent field strain unadapted to cell culture. Cross reactions had not been observed with other enteric pathogens, rotavirus, porcine epizootic diarrhea virus, and Escherichia coli.

Prevalence of K88, K99, and 987P pili of Escherichia coli in neonatal pigs with enteric colibacillosis

One hundred nineteen live neonatal pigs with diarrhea less than or equal to 2 weeks old were euthanatized, and frozen sections of their ilea were submitted to an indirect fluorescent antibody technique to identify K88, K99, and 987P pili (also referred to as F-4, F-5, and F-6 pili, respectively) in Escherichia coli. Ten-centimeter ileal sections were used to determine numbers of lactose-fermenting bacteria. Of 52 pigs in which E coli pili were found, 14 had K88 (27%), 23 had K99 (44%), 13 had 987P (25%), and 2 had K88 and K99 simultaneously (4%). Numbers of lactose-fermenting bacteria were significantly (P less than or equal to 0.05) higher in pigs with piliated E coli than in pigs without piliated E coli. Results of this study indicated that piliated E coli are a major cause of enteric disease in neonatal swine in Michigan, and that in pigs less than or equal to 2 weeks of age, K99 was the most frequently encountered pilus antigen.

An ion-exchange capture technique for routine identification of faecal viruses by electron microscopy

Faecal specimens from 520 patients with non-bacterial, gastroenteritis were examined by electron microscopy using four methods. These were (1) a direct dip method, (2) low-speed centrifugation, (3) ultracentrifugation and (4) a calcium phosphate method. The calcium phosphate method combined with low-speed centrifugation (750 X g, 2,100 X g) was considered overall best. The calcium phosphate method makes it possible to handle a large number of faecal specimens by saving considerable time and labour.

Two enzyme immunoassays for the detection of antibody to rodent coronaviruses

Two enzyme immunoassays for detection of antibody to rodent coronaviruses were compared. Mouse hepatitis virus (MHV), strain JHM, antigen was in the form of formalin-fixed, infected 17 C1 1 cells. This antigen detected antibody to the homologous strain of MHV as well as to two heterologous MHV strains and a serologically related rat coronavirus, sialodacryodenititis virus. Antibody titers in assays using horseradish peroxidase (HRP)-conjugated or ureiase-conjugated anti-mouse IgG were substantially higher than in an indirect immunofluorescence assay. The ureiase assay was somewhat more sensitive than the HRP assay. MHV-JHM antigen was stable under a variety of storage conditions for at least two months.

[Morphology of coronaviruses from different species of monkeys in the Sukhumi nursery]

The ultrastructure of coronaviruses from 46 out of 111 monkeys examined (baboons, macaques, green monkeys, langurs) was studied by negative staining in homogenates of different parts of the intestinal tract, pancreatic gland, liver, kidneys, lungs, heart, and brain. Because of marked pleomorphism of coronaviruses it is suggested that morphological variants of the viruses may be distinguished. No relationship between pleomorphism of virus particles and species differences of monkeys and their organ pathology was established. Morphological signs distinguishing simian coronaviruses from those of man were noted.

Detection of transmissible gastroenteritis virus in feces from pigs by reversed passive hemagglutination

A reversed passive hemagglutination (RPHA) method was developed for the detection of transmissible gastroenteritis (TGE) virus in the fecal specimens from pigs. Ovine erythrocytes fixed with glutaraldehyde and treated with tannic acid were coated with anti-TGE virus swine antibodies, which were purified by affinity chromatographic technique linked with purified TGE virus. The RPHA test was done by the Microtiter method. Erythrocytes coated with purified specific antibodies were agglutinated by TGE virus, but not by porcine rotavirus or porcine enterovirus. The reaction was specifically inhibited by antiserum against TGE virus, confirming the specificity of the reaction. A litter of seven 3-day-old pigs was orally inoculated with TGE virus, and fecal specimens were obtained once a day and serum was obtained every 4th day. With the RPHA test, TGE virus was detected in the diarrheal feces; all of the inoculated pigs developed virus-neutralization antibody for the TGE virus. The RPHA test detected TGE virus in feces from pigs with naturally occurring diarrhea. The RPHA test detected TGE virus in 5 of 6 fecal specimens (80%), whereas the positive rate was only 50% (3/6) for the immunofluorescent staining of primary cultures of porcine kidney cells inoculated with the specimens. The advantages of the RPHA method are simplicity, high sensitivity, and rapid to do.

Enteric coronavirus in symptomless homosexuals

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Structural proteins of human respiratory coronavirus OC43

The human respiratory coronavirus OC43 was grown on a human rectal tumor cell line and was isotopically labeled with amino acids, glucosamine, and orthophosphate to analyze virion structural proteins. Four major protein species were resolved by electrophoresis and many of their properties were deduced from digestion studies using proteolytic enzymes. The four proteins are: A 190 kDa protein, the presumed peplomeric protein, that was glycosylated and proteolytically cleavable by trypsin into subunits of 110 and 90 kDa. The subunits each represent a different amino acid sequence on the basis of peptide mapping; a 130 kDa protein that was glycosylated and behaved as a disulfide-linked dimer of 65 kDa molecules. It is the apparent virion hemagglutinin on the basis of digestion studies with trypsin, bromelain and pronase; a 55 kDa nucleocapsid protein that was phosphorylated; a 26 kDa matrix protein that was glycosylated. The 190, 130, 55 and 26 kDa species can therefore be designated P, H, N and M, respectively. They exist in molar ratios of 4:1:33:33, and are calculated to be present at the rate of 88, 22, 726, and 726 molecules per virion, respectively.

Isolation of a porcine respiratory, non-enteric coronavirus related to transmissible gastroenteritis

A porcine respiratory, non-enteric virus which is related to the coronavirus transmissible gastroenteritis virus (TGEV) has been isolated in pigs and in cell culture. The isolate was designated TLM 83. It has become very widespread and enzootic among the swine population in Belgium and in other swine raising countries. It causes an infection of the lungs and appears to spread by aerogenic route. It does not replicate in the enteric tract. The experimental infection in conventional and gnotobiotic pigs in isolation remains subclinical. The infection, either experimental or in the field, results in the formation of antibodies which neutralise the classical enteric TGEV. Based on this relationship, this virus is assumed to be a new TGEV-related porcine respiratory coronavirus or TGEV itself which has totally lost its tropism for the enteric tract.

Coronaviruses associated with outbreaks of transmissible enteritis of turkeys in Quebec: hemagglutination properties and cell cultivation

Coronaviruses were observed by electron microscopy in the intestinal contents of turkeys in Quebec flocks where repeated outbreaks of enteritis occurred. Three isolates could be serially propagated in turkey embryos inoculated by the amniotic route with clarified intestinal contents. Purification and concentration of viral particles contained in intestinal contents of infected embryos were achieved by precipitation with polyethylene glycol and ultracentrifugation on sucrose density gradients. Three particle types were demonstrated: intact virions with a density of 1.18 to 1.20 g/ml and incomplete particles with densities of 1.14 and 1.24 g/ml. Hemagglutination of rabbit and guinea pig erythrocytes was demonstrated with the intact viral particles; the hemagglutinin was not dependent on incubation temperature. All the isolates were antigenically related, as shown by hemagglutination-inhibition. The turkey coronaviruses did not cross-react with antisera against coronaviruses of avian infectious bronchitis, porcine transmissible enteritis, bovine neonatal calf diarrhea, or mouse hepatitis. One of the Quebec isolates was shown to induce syncytia formation on its third passage in primary chicken-embryo kidney cell cultures. Electron-microscopic examination of infected cell-culture fluids revealed characteristics coronavirus particles identical to those found in intestinal contents of infected turkeys.

[Research on coronaviruses in water. I. Adsorption and elution of the coronavirus on glass powder]

The purpose of the research was to determine under what conditions enteric coronaviruses from water can be optimally concentrated by acid-pH adsorption on glass-powder followed by alkaline-pH elution. The 14C labelled bovine enteric coronavirus was grown on HRT18 cell monolayers and purified. Virus adsorption was studied in relation to pH: optimal adsorption yield--between 50 to 75% (mean value: 62%)--was obtained at pH less than or equal to 3.5. Elution was made comparatively with a 0.05 M glycine solution and a 3% beef extract solution. Virus elution occurred mostly at alkaline pH with a maximum yield between 38 and 55% for pH values between 9 and 11. Owing to the sensitivity of coronavirus to acid (pH 3) and alkaline pH (pH greater than or equal to 10), adsorption was optimal at pH 3.3 and elution at pH 9. Under such conditions, the overall efficiency of the method appears to stand between 24 and 28%.