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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21 - 32 of 32 results
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Inter- and intra-variant genetic heterogeneity of human coronavirus OC43 strains in France
Human coronavirus OC43 (HCoV-OC43) causes acute, self-limited respiratory infections. A close relationship between bovine coronaviruses (BCoVs) and HCoV-OC43 has recently been demonstrated. This study includes seven clinical, non-cell culture-adapted, contemporary HCoV-OC43 strains detected in France in 2003. By using RT-PCR and clonal sequencing of the S1 gene of HCoV-OC43, the inter-variant heterogeneity of the HCoV-OC43 circulating strains was studied and the intra-variant diversity was assessed by investigation of a quasispecies cloud. This paper brings to the forefront a high genetic diversity of circulating HCoV-OC43 variants. Genetically different groups are defined among the variants described in this study. One of these variants holds characteristics of an outlier and presents a deletion of 12 nt, also found in BCoV strains. Moreover, the presence of HCoV-OC43 as a quasispecies cloud in vivo during an acute respiratory-tract illness was discovered. It has also been revealed that quasispecies-cloud sizes are similar for the two viral populations tested.
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Interaction of severe acute respiratory syndrome-associated coronavirus with dendritic cells
More LessSevere acute respiratory syndrome (SARS) of humans is caused by a novel coronavirus of zoonotic origin termed SARS-associated coronavirus (SARS-CoV). The virus induces severe injury of lung tissue, as well as lymphopenia and destruction of the architecture of lymphatic tissue by as-yet-unknown mechanisms. In this study, the interaction of SARS-CoV with dendritic cells (DCs), the key regulators of immune responses, was analysed. Monocyte-derived DCs were infected with SARS-CoV and analysed for viability, surface-marker expression and alpha interferon (IFN-α) induction. SARS-CoV infection was monitored by quantitative RT-PCR, immunofluorescence analysis and recovery experiments. SARS-CoV infected both immature and mature DCs, although replication efficiency was low. Immature DCs were activated by SARS-CoV infection and by UV-inactivated SARS-CoV. Infected DCs were still viable on day 6 post-infection, but major histocompatibility complex class I upregulation was missing, indicating that DC function was impaired. Additionally, SARS-CoV infection induced a delayed activation of IFN-α expression. Therefore, it is concluded that SARS-CoV has the ability to circumvent both the innate and the adaptive immune systems.
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Isolation of avian infectious bronchitis coronavirus from domestic peafowl (Pavo cristatus) and teal (Anas)
Coronavirus-like viruses, designated peafowl/China/LKQ3/2003 (pf/CH/LKQ3/03) and teal/China/LDT3/2003 (tl/CH/LDT3/03), were isolated from a peafowl and a teal during virological surveillance in Guangdong province, China. Partial genomic sequence analysis showed that these isolates had the S–3–M–5–N gene order that is typical of avian coronaviruses. The spike, membrane and nucleocapsid protein genes of pf/CH/LKQ3/03 had >99 % identity to those of the avian infectious bronchitis coronavirus H120 vaccine strain (Massachusetts serotype) and other Massachusetts serotype isolates. Furthermore, when pf/CH/LKQ3/03 was inoculated experimentally into chickens (specific-pathogen-free), no disease signs were apparent. tl/CH/LDT3/03 had a spike protein gene with 95 % identity to that of a Chinese infectious bronchitis virus (IBV) isolate, although more extensive sequencing revealed the possibility that this strain may have undergone recombination. When inoculated into chickens, tl/CH/LDT3/03 resulted in the death of birds from nephritis. Taken together, this information suggests that pf/CH/LKQ3/03 might be a revertant, attenuated vaccine IBV strain, whereas tl/CH/LDT3/03 is a nephropathogenic field IBV strain, generated through recombination. The replication and non-pathogenic nature of IBV in domestic peafowl and teal under field conditions raises questions as to the role of these hosts as carriers of IBV and the potential that they may have to transmit virus to susceptible chicken populations.
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Infectious RNA transcribed in vitro from a cDNA copy of the human coronavirus genome cloned in vaccinia virus
More LessThe coronavirus genome is a positive-strand RNA of extraordinary size and complexity. It is composed of approximately 30000 nucleotides and it is the largest known autonomously replicating RNA. It is also remarkable in that more than two-thirds of the genome is devoted to encoding proteins involved in the replication and transcription of viral RNA. Here, a reverse-genetic system is described for the generation of recombinant coronaviruses. This system is based upon the in vitro transcription of infectious RNA from a cDNA copy of the human coronavirus 229E genome that has been cloned and propagated in vaccinia virus. This system is expected to provide new insights into the molecular biology and pathogenesis of coronaviruses and to serve as a paradigm for the genetic analysis of large RNA virus genomes. It also provides a starting point for the development of a new class of eukaryotic, multi-gene RNA vectors that are able to express several proteins simultaneously.
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Identification and subcellular localization of a 41 kDa, polyprotein 1ab processing product in human coronavirus 229E-infected cells.
More LessThe translation products of the human coronavirus (HCV) 229E open reading frames 1a and 1b, the polyproteins 1a and 1ab, are processed by virus- encoded proteinases. One of the key enzymes in this process is a chymotrypsin-like enzyme, the 3C- like proteinase. In this study we have identified an ORF 1b-encoded, 41 kDa processing product in HCV 229E-infected cells by using a monoclonal antibody with defined specificity. We show that this polypeptide is released from polyprotein 1ab by 3C-like proteinase-mediated cleavage of the peptide bonds Gln-6110/Gly-6111 and Gln-6458/Ser- 6459. Also, we have investigated the subcellular localization of the 41 kDa processing product. Immunofluorescence microscopy revealed a punctate, perinuclear distribution of the 41 kDa polypeptide in infected cells and an identical subcellular localization was observed for three additional pp1ab-derived polypeptides. In contrast, the virus nucleocapsid protein showed a homogeneous cytoplasmic localization.
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Identification of residues critical for the human coronavirus 229E receptor function of human aminopeptidase N.
More LessAminopeptidase N (APN) is the major cell surface receptor for group 1 coronaviruses. In this study, we have isolated and characterized a feline APN cDNA and shown that the transfection of human embryonic kidney cells with this cDNA renders them susceptible to infection with the feline coronavirus feline infectious peritonitis virus, the human coronavirus (HCV) 229E and the porcine coronavirus porcine transmissible gastroenteritis virus. By using chimeric APN genes, assembled from porcine and feline sequences, we have shown that, analogously to the human APN protein, a region within the amino-terminal part of the feline APN protein (encompassing amino acids 132–295) is essential for its HCV 229E receptor function. Furthermore, by comparing the relevant feline, human and porcine APN sequences, we were able to identify a hypervariable stretch of eight amino acids that are more closely related in the feline and human APN proteins than in the porcine APN molecule. Using PCR- directed mutagenesis, we converted this stretch of amino acids within the porcine APN molecule to the corresponding residues of the human APN molecule. These changes were sufficient to convert porcine APN into a functional receptor for HCV 229E and thus define a small number of residues that are critically important for the HCV 229E receptor function of human APN.
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An immunodominant CD4+ T cell site on the nucleocapsid protein of murine coronavirus contributes to protection against encephalomyelitis
More LessThe murine coronavirus neurotropic strain JHM (MHV-JHM) nucleocapsid (N) protein induces a strong T-helper cell response in Lewis rats. It has been shown previously that N-specific CD4+ T cells can confer protection against acute disease upon transfer to otherwise lethally infected rats. To define the major antigenic regions that elicit this T cell response, truncated fragments of N protein were expressed from a bacterial expression vector and employed as T cell antigens. Lymphocytes from either MHV-JHM-infected or immunized rats were stimulated in culture with virus antigen, grown and tested for their specificity to the N protein fragments. The carboxy-terminally located C4-N fragment (95 amino acids) induced the most pronounced proliferative response irrespective of whether the lymphocyte culture was derived from immunized or MHV-JHM-infected rats. We established T cell lines specific for the truncated N protein fragments and tested their potential to mediate protection by transfer experiments. Only the T cell line C4-N and the T cell line specific for the full-length N protein were protective. By contrast, all truncated N protein fragments elicited a humoral immune response and contained antigenic sites recognized by antibodies from diseased rats.
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Identification of a New Membrane-associated Polypeptide Specified by the Coronavirus Infectious Bronchitis Virus
More LessNucleotide sequences from the third open reading frame of mRNA D (D3) of infectious bronchitis virus (IBV) were expressed in bacteria as part of a fusion protein with β-galactosidase. Antiserum raised in rabbits against this fusion protein immunoprecipitated from IBV-infected chick kidney or Vero cells a polypeptide of 12·4K, the size expected for a D3- encoded product. The D3 polypeptide is apparently non-glycosylated, and appears to be associated with the membrane fraction of infected cells, as judged by cell fractionation and immunofluorescence.
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Identification of the Coronavirus MHV-JHM mRNA 4 Product
More LessSummaryA bacterial expression vector was constructed to encode a fusion protein which had, at its carboxy terminus, a polypeptide encoded within the 5′ proximal open reading frame of the coronavirus MHV-JHM mRNA 4. This polypeptide was isolated and used to produce an antiserum. The antiserum reacted specifically with a 15000 M r polypeptide synthesized in MHV-JHM-infected cells, or in vitro translations of infected cell poly(A) RNA enriched for mRNA 4. These results demonstrate the translational activity of mRNA 4 during infection, identify conclusively the translation product and provide a means to investigate the synthesis and function of this protein.
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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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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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