Scientists explain why the “British” strain of coronavirus is so contagious

Scientists have figured out the mechanism of the increased infectiousness of the British mutation

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Scientists explain why the
Image Credit: EPA

Scientists from the United States, Great Britain, and Australia have described the molecular mechanisms that explain the increased infectivity of the so-called “British” strain of the SARS-CoV-2 coronavirus.

The SARS-CoV-2 B.1.1.7 variant of the coronavirus was originally discovered in England last fall and quickly spread throughout the UK and beyond, becoming the dominant strain in many European countries.

The problem stems from the fact that the “British” version of the coronavirus is easier to transmit and spread much faster, and healthcare systems were not prepared for this development.

A new study by biologists led by Thushan I de Silva from the University of Sheffield in the UK showed that increased viral transmissibility of B.1.1.7 is associated with increased expression of subgenomic RNA (sgRNA). Scientists have shown that the ORF9 protein, which is abundant in the sgRNA of the “British” strain, can regulate interferon responses.

In their work, the authors used genomic sequencing data from ARTIC Network Oxford Nanopore 4,400 positive SARS-CoV-2 samples from the nasopharynx of medical workers and hospital patients, and the results of the analyzes were compared with the previously dominant variant of coronavirus from Spain called B.1.177.

Scientists have found that variant B.1.1.7 has an increased sgRNA expression compared to B.1.177, which causes serious phenotypic changes in the SARS-CoV-2 virus.

To rule out a possible explanation for sgRNA changes during infection with differences in symptoms, the researchers collected clinical information from 2,327 patients with confirmed COVID-19. They found small differences in the onset of symptoms of B.1.177 infection and B.1.1.7 infection, which, however, according to the authors, did not affect overall results.

“It is possible that the days from the onset of symptoms in the sample may vary depending on the origin of the data, either due to changes in the sample over time or due to people seeking medical attention, which in turn could affect our sgRNA expression results,” de Silva said in a press release.

To finally confirm their conclusions, the authors used laboratory variants of pseudo-infections to see how long after the onset of the first symptoms, genetic changes occur in both variants.

Variant B.1.1.7 infections showed increased sgRNA expression as early as the first day of symptom onset. The researchers believe that mutations can be caused by recombination between sgRNA and the genome of the virus, and the result leads to a significant enrichment of the subgenomic RNA containing the ORF9b protein. The expression of sgRNA ORF9b in samples B.1.1.7 was 16 times higher than in B.1.17 variant.

Based on these results, the researchers suggest that sgRNA-containing ORF9b may mediate the interferon responses seen during SARS-CoV-2 infections and cause greater infectivity in variant B.1.17.

The authors hope that the mechanism they have identified for increasing the transmission of the “British” variant of the coronavirus will help doctors and medical services in developing methods of treatment and prevention of coronavirus.

The research results have been published on the bioRxiv and this article is a preprint and has not been certified by peer review.