Nucleotide sequence of the gene encoding the membrane protein of human coronavirus 229 E

Infectious RNA transcribed in vitro from a cDNA copy of the human coronavirus genome cloned in vaccinia virus

The 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.

Detection of human coronavirus 229E-specific antibodies using recombinant fusion proteins

Human coronaviruses are known to be a common cause of respiratory infections in man. However, the diagnosis of human coronavirus infections is not carried out routinely, primarily because the isolation and propagation of these viruses in tissue culture is difficult and time consuming. The aim of this study was to evaluate the use of recombinant, bacterial expressed proteins in the serodiagnosis of coronavirus infections. Two proteins were examined: the human coronavirus 229E nucleocapsid protein (N), expressed as a fusion protein in the vector pUR and the coronavirus 229E surface glycoprotein (S), expressed as a fusion protein in the vector pROS. The recombinant proteins were used as antigens in Western blot (WB) assays to detect the 229E-specific IgG antibodies and the results were compared with a standard serological method, indirect immunofluorescence. Serum samples of 51 paediatric patients, suffering from acute respiratory illness, and 10 adults, voluntarily infected with human coronavirus, were tested. The serum samples of the adult group had coronavirus-specific IgG antibodies in both test systems. In contrast, only 8/51 sera of the paediatric group were positive for coronavirus-specific IgG by both WB and IF and 20/51 sera were positive by WB, but not by IF. The overall incidence of human coronavirus infections in the paediatric age group was 55% evaluated by WB analysis and 16% evaluated by IF. This study shows that recombinant human coronavirus 229E proteins are suitable reagents for the epidemiological screening of coronavirus 229E infections.

Identification of the membrane protein of porcine epidemic diarrhea virus

Sequence information on the genome of porcine epidemic diarrhea virus(PEDV) has only recently been determined. In contrast, very little is known about the viral proteins. In the present report we have identified the membrane glycoprotein (M) of PEDV by use of rabbit anti-peptide sera and transient expression of the cloned M gene in Vero cells and by expression in the baculovirus system. The native M protein of PEDV is incorporated into virions, is N-glycosylated, and migrates with a relative mobility (Mr) of 27 k in polyacrylamide gels. In contrast, the M protein synthesized by recombinant baculoviruses migrates with a Mr of 23 k, that is, with identical mobility as the deglycosylated product of PEDV. Thus, it appears that M protein specified by the recombinant baculovirus is poorly, if at all, glycosylated. Using monoclonal antibodies and rabbit and rabbit antipeptide sera specific for the N and C termini of the M protein, we were able to show that a 19 k band detected in PEDV-infected cells but not in virions represented a fragment of M from which the C terminus had been cleaved off. Finally, by electron microscopy and immunogold labelling, the relative orientation of M within the virion envelope was determined as NexoCcyt. In conclusion, all of these data strongly support the hypothesis that PEDV should be classified with the group I coronaviruses.

Sequence analysis of human coronavirus 229E mRNAs 4 and 5: evidence for polymorphism and homology with myelin basic protein

Human coronaviruses (HCV) are important pathogens responsible for respiratory, gastrointestinal and possibly neurological disorders. To better understand the molecular biology of the prototype HCV-229E strain, the nucleotide sequence of the 5'-unique regions of mRNAs 4 and 5 were determined from cloned cDNAs. Sequence analysis of the cDNAs synthesized from mRNA 4 revealed a major difference with previously published results. However, polymerase chain reaction amplification of this region showed that the sequenced cDNAs were produced from minor RNA species, an indication of possible genetic polymorphism in this region of the viral genome. The mutated messenger RNA 4 contains two ORFs: (1) ORF4a consisting of 132 nucleotides which potentially encodes a 44-amino acid polypeptide of 4653 Da; this coding sequence is preceded by a consensus transcriptional initiation sequence, CUAAACU, similar to the ones found upstream of the N and M genes; (2) ORF4b of 249 nucleotides potentially encoding an 83-amino acid basic and leucine-rich polypeptide of 9550 Da. On the other hand, mRNA 5 contains one single ORF of 231 nucleotides which could encode a 77-amino acid basic and leucine-rich polypeptide of 9046 Da. This putative protein presents a significant degree of amino acid homology (33%) with its counterpart found in transmissible gastroenteritis coronavirus (TGEV). The proteins in the two different viruses exhibit similar molecular weights and are extremely hydrophobic. Interestingly, a sequence homology of five amino acids was found between the protein encoded by ORF4b of HCV-229E and an immunologically important region of human myelin basic protein.

Another triple-spanning envelope protein among intracellularly budding RNA viruses: the torovirus E protein

The nucleotide sequence of the Berne virus envelope (E) protein gene was determined and its 26.5K translation product was identified by in vitro transcription and translation. Computer analysis of the protein sequence revealed the characteristics of a class III membrane protein lacking a cleaved signal sequence but containing three successive transmembrane alpha-helices in the N-terminal half, much the same as the coronavirus membrane (M) protein. The disposition of the E protein in the membrane was studied by in vitro translation in the presence of microsomes and by subsequent proteinase K digestion. Only small portions of either end of the polypeptide were found to be exposed on opposite sides of the vesicle membranes. Experiments with a hybrid E protein (EM) containing the C-terminal tail of a coronavirus M protein, to which an anti-peptide serum was available, showed that this C-terminus was present at the cytoplasmic side of the membrane, which is another similarity to the coronavirus M protein. Immunofluorescence experiments indicated that the EM protein, expressed by a recombinant vaccinia virus, accumulated in intracellular membranes, predominantly those of the endoplasmic reticulum. The common features of the torovirus E and the coronavirus M protein support our hypothesis that an evolutionary relationship exists between these groups of intracellularly budding viruses.

Characterization of a nucleic acid probe for the diagnosis of human coronavirus 229E infections

A cDNA copy of the HCV229E nucleocapsid protein gene was isolated and characterized. Sequence analysis predicts a nucleocapsid polypeptide of 389 amino acids with a molecular weight (mol. wt.) of 43,450. Single strand RNA probes derived from the cDNA copy hybridize specifically to HCV229E RNA and approximately 50 pg of intracellular viral RNA can be readily detected. The application of nucleic acid hybridization as a routine procedure for the diagnosis of HCV229E infection is discussed.