Coronaviruses
Coronaviruses are a large family of viruses that can infect a range of hosts. They are known to cause diseases including the common cold, Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) in humans.
In January 2020, China saw an outbreak of a new coronavirus strain now named SARS-CoV-2. Although the animal reservoir for the SARS and MERS viruses are known, this has yet to have been confirmed for SARS-CoV-2. All three strains are transmissible between humans.
To allow the widest possible distribution of relevant research, the Microbiology Society has brought together articles from across our portfolio and made this content freely available.
Image credit: "MERS-CoV" by NIAID is licensed under CC BY 2.0, this image has been modified.
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241 - 260 of 298 results
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The Predicted Primary Structure of the Peplomer Protein E2 of the Porcine Coronavirus Transmissible Gastroenteritis Virus
More LessSummaryThe complete nucleotide sequence of cloned cDNAs containing the E2 glycoproteinencoding region of the genome of transmissible gastroenteritis virus (TGEV) has been determined. A single large translatable frame of 4·3 kb starting at 8·2 kb from the 3′ end of the genome was identified. Its deduced amino acid sequence contains the characteristic features of a coronavirus peplomer protein: (i) the precursor polypeptide of TGEV E2 is 1447 residues long (i.e. 285 longer than the avian infectious bronchitis coronavirus spike protein); (ii) partial N-terminal sequencing demonstrated that a putative secretory signal sequence of 16 amino acids is absent in the virion-associated protein; (iii) the predicted mol. wt. of the apoprotein is 158K; most of the 32 potential N-glycosylation sites available in the sequence are presumed to be functional to account for the difference between this and the experimentally determined value (200K to 220K); (iv) a typical hydrophobic sequence near the C terminus is likely to be responsible for anchoring the peplomer to the virion envelope.
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Rat Glial C6 Cells are Defective in Murine Coronavirus Internalization
More LessSummaryRat C6 glial cells were resistant to infection by several strains of murine coronaviruses. The restriction was not at the adsorption stage, since virus adsorbed to the C6 cells in a similar manner to mouse L cells which supported a lytic infection. The virus could not be internalized by the C6 cells. However, if the virus was introduced into the C6 cells by polyethylene glycol fusion, viral replication occurred and progeny virions were released from the infected cells. These studies indicated that the C6 cells were restrictive to coronavirus replication by preventing the early penetration stage of the viral replicative cycle.
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Sequence and N-terminal Processing of the Transmembrane Protein E1 of the Coronavirus Transmissible Gastroenteritis Virus
More LessSummarySequencing 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 M r value.
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Intracellular RNAs of the Feline Infectious Peritonitis Coronavirus Strain 79-1146
More LessSUMMARYIn Felis catus whole foetus D cells infected with feline infectious peritonitis virus (FIPV), strain 79–1146, six virus-specific, poly(A)-containing RNA species of about 20, 9·6, 5·2, 3·8, 2·8 and 1·6 kb were found. By translation in vitro the 3·8 and 2·8 kb RNAs were shown to encode the 25K envelope protein and the 45K nucleocapsid protein, respectively. The partial map of the FIPV genome was compared with genomic maps of porcine, murine and avian coronaviruses. Differences in these maps suggest that transcription units have been lost or gained during coronavirus divergence.
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Induction of Demyelination by a Temperature-sensitive Mutant of the Coronavirus MHV-A59 is Associated with Restriction of Viral Replication in the Brain
More LessSUMMARYThe neurovirulence of eight temperature-sensitive (ts) mutants of mouse hepatitis virus strain A59 in 4-week-old BALB/c mice was investigated. Whereas a dose of 100 p.f.u. of wild-type virus killed mice within a week, a 1000-fold higher dose of ts mutants did not. Three ts mutants induced demyelinating disease in the central nervous system (CNS). The pathology of the demyelinating disease caused by one mutant, designated ts-342, was studied in detail. Pathological changes, starting 3 days post-inoculation (p.i.), were characterized by inflammation and demyelination in the CNS. Antibody responses directed against all virus-specific structural proteins were present at 7 days p.i. No virus particles were observed by electron microscopy at 14 days p.i. However, macrophages and lymphocytes were abundant in the areas of demyelination. The growth kinetics in vivo of wild-type virus, ts-342 and a revertant of ts-342 were compared. Wild-type virus and the revertant replicated rapidly in the brain and spread to the liver causing a lethal hepatitis. Ts-342, however, replicated to a much lesser extent within the brain and could not be detected in the blood or liver. The ts lesion in the genome of ts-342 seems, therefore, to determine the outcome of the infection.
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Completion of the Sequence of the Genome of the Coronavirus Avian Infectious Bronchitis Virus
More LessSUMMARYThe nucleotide sequence determination of the genome of the Beaudette strain of the coronavirus avian infectious bronchitis virus (IBV) has been completed. The complete sequence has been obtained from 17 overlapping cDNA clones, the 5′-most of which contains the leader sequence (as determined by direct sequencing of the genome) and the 3′-most of which contains the poly(A) tail. Approximately 8 kilobases at the 3′ end of this sequence have already been published. These contain the sequences of mRNAs A to E within which are the genes for the spike, the membrane and the nucleocapsid polypeptides: the main structural components of the virion. The remainder of the sequence, equivalent to the ‘unique’ region of mRNA F, is some 20 kilobases in length and is thought to code for a polymerase or polymerases which are involved in the replication of the genome and the production of the subgenomic messenger RNAs. This sequence contains two large open reading frames, potentially coding for polypeptides of molecular weights 441000 and 300000. Unlike other large open reading frames in the virus, the 300000 open reading frame appears to have no subgenomic RNA associated with it which would allow it to be at the 5′ end of an mRNA species. Because of this, and because of the characteristics of the sequence in the region immediately upstream of its start codon, other mechanisms of translation, such as ribosome slippage, must be postulated.
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Nucleotide Sequence of the Gene Encoding the Surface Projection Glycoprotein of Coronavirus MHV-JHM
More LessSUMMARY
Sequences encoding the surface projection glycoprotein of the coronavirus, murine hepatitis virus (MHV), strain JHM, have been cloned into pAT153 using cDNA produced by priming with specific oligonucleotides on infected cell RNA. The regions of three clones pJMS1010, pJS112 and pJS92, which together encompass the surface protein gene have been sequenced by the chain termination method. The sequence of the primary translation product, deduced from the DNA sequence, predicts a polypeptide of 1235 amino acids with a molecular weight of 136600. This polypeptide displays the features characteristic of a group 1 membrane protein; an amino-terminal signal sequence and carboxy-terminal membrane and cytoplasmic domains. There are 21 potential glycosylation sites in the polypeptide and a cysteine-rich region in the vicinity of the transmembrane domain. During maturation proteolytic processing of the polypeptide occurs and at positions 624 to 628 the sequence Arg-Arg-Ala-Arg- Arg is found, which is similar to a number of basic sequences involved in the cleavage of enveloped RNA virus glycoproteins. The fusogenic properties of the MHV surface protein do not appear to correlate with a strongly hydrophobic region at the putative amino terminus of the carboxy-terminal cleavage product.
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Comparison of the Spike Precursor Sequences of Coronavirus IBV Strains M41 and 6/82 with that of IBV Beaudette
More LessSummaryThe nucleotide sequences of the spike precursor genes of infectious bronchitis virus strains M41 and 6/82 have been determined and compared with that of the Beaudette strain which we have previously sequenced. The two Massachusetts strains, M41 and Beaudette, were found to be remarkably similar, having only 3.7% of the amino acids different. The situation with 6/82, one of the new field isolates, is quite different and this strain had 13.8% of its amino acids different from Beaudette. The differences identified are discussed in terms of the structural features of the spike protein.
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Antigenic Structure of Transmissible Gastroenteritis Virus. II. Domains in the Peplomer Glycoprotein
More LessSummaryThe antigenic structure of the peplomer glycoprotein E2 of the porcine transmissible gastroenteritis coronavirus (TGEV) was explored using a panel of 23 hybridoma antibodies (MAbs). The topography of the epitopes was established by means of a competition radioimmunoassay. Four main antigenic sites, termed A, B, C and D, were thus clearly delineated. Most of the neutralization-mediating determinants were found to cluster in the A-B area, which has been shown to be highly conserved among TGEV strains. Cooperative enhancement of binding to sites B and D was observed following attachment of MAbs relevant to site A. Additional epitopes were identified on E2 by MAbs that selectively recognized its intracellular precursor. Functional mapping was also performed using neutralization-resistant variants. Analysis of their reactivity confirmed part of the epitope linkages defined by the first approach. The overall lower frequency of such variants altered at site A suggested that some of the epitopes may play an essential function.
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Coronavirus IBV: Removal of Spike Glycopolypeptide S1 by Urea Abolishes Infectivity and Haemagglutination but Not Attachment to Cells
More LessSummaryUrea has been used to remove the S1 spike glycopolypeptide from avian infectious bronchitis virus (IBV) strains M41 and Beaudette, without removing the S2 spike-anchoring glycopolypeptide. Reduction of the pH to 2.9 did not cause release of S1 although some S1 was released spontaneously from IBV Beaudette at pH 7.4. Virus that lacked S1 was no longer infectious or able to cause haemagglutination (HA). However, radiolabelled IBV that lacked S1 attached to erythrocytes and chick kidney cells to the same or similar extent as did intact virus. Treatment of IBV with a phospholipase C preparation, required to make IBV cause HA, did not increase binding of IBV to erythrocytes. The results indicate that while the attachment to cells of virus that lacks S1 is qualitatively different from that of intact virus, the decline in infectivity is the consequence of the loss of some other spike function.
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Coronavirus IBV: Virus Retaining Spike Glycopolypeptide S2 but Not S1 Is Unable to Induce Virus-neutralizing or Haemagglutination-inhibiting Antibody, or Induce Chicken Tracheal Protection
More LessSummaryAvian infectious bronchitis coronavirus (IBV) inactivated by β-propiolactone induce partial protection of the trachea in up to 40% of chickens following one intramuscular inoculation 4 to 6 weeks prior to challenge. Retention of an intact tracheal ciliated epithelium 4 days after challenge was the criterion of protection. There was no correlation between protection and serum titres of virus-neutralizing (VN) and haemagglutination-inhibiting (HI) antibody, which were maximal at about 4 weeks after inoculation. Virus from which the S1 but not the S2 (spike-anchoring) spike glycopolypeptide had been removed by urea did not induce protection or VN or HI antibody. Four intramuscular inoculations of monomeric S1 induced VN and HI antibody in two and four chickens respectively. These results indicate that VN and HI antibodies are induced primarily by S1, that intact spikes are a major requirement for the induction of protective immunity and that this propertyis probably associated with S1.
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Antigenic Structure of Transmissible Gastroenteritis Virus. I. Properties of Monoclonal Antibodies Directed against Virion Proteins
More LessSummaryThirty-two hybridoma cell lines producing monoclonal antibodies (MAbs) against the three major structural proteins of transmissible gastroenteritis virus (TGEV) have been isolated. Radioimmunoprecipitation of intracellular viral polypeptides showed that 17 hybridomas recognized both the peplomer protein [E2, 220 × 103 mol. wt. (220K)] and a lower mol. wt. species (E′2, 175K), which was characterized as a precursor of E2. Six MAbs selectively immunoprecipitated the E′2 protein. Four hybridomas were directed against the low mol. wt. envelope protein (E1, 29K), and three against the nucleoprotein (N, 47K). All major neutralization-mediating determinants were found to be carried by the peplomers. Several anti-E2 MAbs displayed an intrinsic neutralizing activity close to that of the most potent anti-TGEV polyclonal reagents tested (including ascitic fluid of feline infectious peritonitis virus-infected cats). None of the anti-E′2 MAbs induced significant neutralization, although this protein might be incorporated to some extent into the virions. Immunofluorescence patterns obtained with MAbs directed against either the envelope glycoproteins or the nucleocapsid revealed distinctly different distributions of these antigens within the cells. Comparison of nine TGEV strains using our panel of MAbs confirmed their close antigenic relationship, but revealed the occurrence of distinct antigenic differences.
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Survival Characteristics of Airborne Human Coronavirus 229E
More LessSUMMARYThe survival of airborne human coronavirus 229E (HCV/229E) was studied under different conditions of temperature (20 ± 1 °C and 6 ± 1 °C) and low (30 ± 5%), medium (50 ± 5%) or high (80 ± 5%) relative humidities (RH). At 20 ± 1 °C, aerosolized HCV/229E was found to survive best at 50% RH with a half-life of 67.33 ± 8.24 h while at 30% RH the virus half-life was 26.76 ± 6.21 h. At 50% RH nearly 20% infectious virus was still detectable at 6 days. High RH at 20 ± 1 °C, on the other hand, was found to be the least favourable to the survival of aerosolized virus and under these conditions the virus half-life was only about 3 h; no virus could be detected after 24 h in aerosol. At 6 ± 1 °C, in either 50% or 30% RH conditions, the survival of HCV/229E was significantly enhanced, with the decay pattern essentially similar to that seen at 20 ± 1 °C. At low temperature and high RH (80%), however, the survival pattern was completely reversed, with the HCV/229E half-life increasing to 86.01 ± 5.28 h, nearly 30 times that found at 20 ± 1 °C and high RH. Although optimal survival at 6 °C still occurred at 50% RH, the pronounced stabilizing effect of low temperature on the survival of HCV/229E at high RH indicates that the role of the environment on the survival of viruses in air may be more complex and significant than previously thought.
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Sequencing of Coronavirus IBV Genomic RNA: Three Open Reading Frames in the 5′ ‘Unique’ Region of mRNA D
More LessSUMMARYThe nucleotide sequence of a genomic cDNA clone corresponding to the 5′ terminal domain of mRNA D of the Beaudette strain of infectious bronchitis virus (IBV) has been determined. This region contains three open reading frames which predict polypeptides of molecular weights 6700 s(6.7K), 7.4K and 12.4K. The predicted 12.4K polypeptide has a codon usage very similar to that predicted for the products of the IBV nucleocapsid, membrane and spike genes. The sequence also predicts a hydrophobic, potentially membrane-anchoring, region in the N terminal half of the 12.4K polypeptide, and a hydrophilic C terminus.
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Chronic Shedding of Bovine Enteric Coronavirus Antigen-Antibody Complexes by Clinically Normal Cows
More LessSUMMARYUsing an ELISA for the detection of virus-specific immune complexes, ten cows were found to be shedding bovine enteric coronavirus. The shedding patterns from five of these animals were followed for a period of 12 weeks, and all were found to be chronically shedding virus. Despite the presence of both faecal and serum antibody the infection was not cleared; therefore, the role of cell-mediated immunity (CMI) was investigated by immunosuppressing the chronically shedding cows with dexamethasone. No major role for CMI in maintaining the chronic infection could be determined, although immunosuppression did result in a temporary reduction in the shedding of virus-specific immune complexes.
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Cloning and Sequencing of the Gene Encoding the Spike Protein of the Coronavirus IBV
SUMMARYRNA sequences encoding the surface projection (spike) of the coronavirus infectious bronchitis virus, strain Beaudette, have been cloned into pBR322 using cDNA primed with a specific oligonucleotide. A 5.3 kilobase viral insert in the clone pMB179 has been identified. The region of this clone coding for the spike gene has been sequenced by the chain termination method, and we present here the first report of DNA sequence data for a coronavirus spike protein, the protein which forms the characteristic ‘corona’ after which the group is named. The amino acid sequence of the primary translation product, deduced from the DNA sequence, predicts a polypeptide of 1162 amino acids with a molecular weight of 127006. This has many interesting features which confirm and extend our knowledge of this recently characterized membrane glycoprotein. The polypeptide is subsequently cleaved to S1 and S2, and partial amino acid analysis of the amino-terminus of the S1 polypeptide has been employed to locate the position of this terminus of S1 within the large open reading frame. The amino acid analysis also reveals the presence of an 18 amino acid putative signal sequence on the primary translation product which is not present on the mature S1 polypeptide.
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Coding Sequence of Coronavirus MHV-JHM mRNA 4
More LessSUMMARYA coding sequence at the 5′ end of mRNA 4 of the coronavirus MHV-JHM was determined by M13/chain-terminator sequencing of cloned cDNA. An open reading frame of 417 bases with the potential to encode a polypeptide of mol. wt. 15200 (139 residues) was identified. The 3′ end of the open reading frame overlapped by 16 bases the start of an open reading frame found in mRNA 5. The translation product of mRNA 4 was predicted to be a basic polypeptide rich in threonine. It had a large hydrophobic region near the amino terminus and a basic carboxy terminus. An intracellular, virus-specific polypeptide, which has been previously described as having a mol. wt. of 14000 to 14500 has the size and charge characteristics of such a translation product.
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Coronavirus MHV-JHM mRNA 5 Has a Sequence Arrangement which Potentially Allows Translation of a Second, Downstream Open Reading Frame
More LessSUMMARYThe sequence of a 5′-proximal region of mRNA 5 of coronavirus MHV-JHM was determined by chain-terminator sequencing of cDNA subcloned in M13. The sequence contained two long open reading frames of 321 bases and 264 bases, overlapping by five bases but in different frames. Both open reading frames are initiated by AUG codons in sequence contexts that are relatively infrequently used as initiator codons. The smaller, downstream open reading frame encoded a neutral protein (mol. wt. 10200) with a hydrophobic amino terminus. The larger, 5′-proximal open reading frame encoded a basic protein (mol. wt. 12400) which lacks internal methionine residues. With the exception of the AUG codon initiating the downstream open reading frame, no internal AUG codons were found within the sequence covered by the upstream open reading frame. These results suggest that the MHV-JHM mRNA 5 is translated to produce two proteins by a mechanism involving internal initiation of protein synthesis. Preliminary evidence is presented showing that the downstream open reading frame is functional in vivo.
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Inhibition of the Growth of Human Coronavirus 229E by Leupeptin
More LessSUMMARYThe protease inhibitor leupeptin prevented multiplication of the human coronavirus strain 229E in cultures of MRC-C cells. The IC50 of leupeptin in plaque reduction tests was 0.4 µg/ml, whereas growth of host cells was unaffected by leupeptin at 50 µg/ml. Inhibition of plaque formation could be prevented by the addition of proteases to the overlay medium. In single-cycle growth experiments, leupeptin reduced virus yield only if added within 2 h of infection, indicating its action on an early stage of virus replication.
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