Coronavirus infection and demyelination. Sequence conservation of the S-gene during persistent infection of Lewis-rats.
Coronaviruses display a large phenotypic variability, which may be an important factor for diversification and selection. Previous studies have demonstrated that the S-protein is an essential determinant of virulence and pathogenicity. Therefore we studied the S-gene as an indicator molecule for selection processes employing two different MHV-JHM variants. First, Lewis-rats were infected with MHV-JHM-Pi, a variant that causes demyelinating disease after several weeks p.i. It was not possible to isolate infectious MHV-JHM-Pi from such rats, although viral proteins were expressed. The S-gene was rescued directly from brain tissue employing RT-PCR technology. The amplicons were sequenced in bulk or at the level of single clones. We detected no evidence for an increase of S-gene mutants during the length of time. Only few mutations were found at the clonal level. The changes were distributed throughout the analysed S-gene fragments without a predilection in their location. The frequency of mutation remained low within a range of 0.03 to 0.5 mutations per thousand nucleotides. As a second approach, we sequenced the S-genes of viruses isolated from brain tissue infected with MHV-JHM-ts43. Infection of adult Lewis rats with that mutant resulted several weeks to months p.i. in demyelinating encephalomyelitis. The S-gene of this virus contains an insertion of 423 bp in the S1 region, which is identical to a polymorphic region described for MHV-4. In contrast to JHM-Pi, infectious MHV-JHM-ts43 was readily to isolate from brain tissue. The S-gene sequences of virus isolated 45-106 days p.i. from diseased rats were identical with that of the input virus. These results show, that during a persistent infection of Lewis-rats the S-gene was highly conserved.
Federal Research Centre for Virus Diseases of Animals, Isle of Riems.
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Wege
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Stühler
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Lassmann
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Wege
D000818:Animals; D002460:Cell Line; D018352:Coronavirus Infections / Q000821:virology*; D003711:Demyelinating Diseases / Q000821:virology*; D014644:Genetic Variation; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D006517:Murine hepatitis virus / Q000235:genetics* / Q000472:pathogenicity; D051381:Rats; D011917:Rats, Inbred Lew; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000235:genetics*; D014774:Virulence; D017735:Virus Latency
D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus