Washington: Scientists have assessed the genome sequences of the novel coronavirus from more than 27,000 individuals with COVID-19, and found that the virus has mutated minimally since the beginning of the outbreak in China in December 2019, suggesting one vaccine would be sufficient to combat global infections. The study, published in the journal PNAS, characterised the diversification of the novel coronavirus SARS-CoV-2 since the beginning of the pandemic by aligning 18,514 independent virus genome sequences sampled from individuals in 84 countries, and scanned them for variations.
According to the scientists, including those from the Walter Reed Army Institute of Research (WRAIR) in the US, the analyses reveal low estimates of genetic differentiation of the virus following the initial outbreak in Wuhan, China. Based on the study, they said, so far, the SARS-CoV-2 genome has evolved through a mostly random process rather than through adaptation to the human hosts it encounters.
Earlier studies had pointed to the domination of a mutant form of the virus in several parts of the world in which a molecule aspartic acid — denoted as D — in the viral spike protein, which it uses to enter host cells, is replaced by another molecule glycine (G). However, the scientists behind the current study said this 'D614G' mutation cannot be seen as evidence of the virus adapting to humans. "Like other reports, we noticed that the D614G mutation in the Spike has rapidly increased in frequency since the beginning of the epidemic, but we could not link this mutation to specific adaptive forces," said Morgane Rolland, a co-author of the study from WRAIR.
"When viruses replicate and spread in the population, we expect to see some mutations and some can become fixed very rapidly in an epidemic just by random chance," Rolland added. The scientists said linking genotypes of the different strains to their traits is complicated, adding that more research is needed to fully understand the functional consequences of the D614G mutation in SARS-CoV-2. Given the low level of genetic variation, the researchers said, a promising vaccine candidate would likely be equally efficacious against all currently circulating strains of the novel coronavirus.
"Viral diversity has challenged vaccine development efforts for other viruses such as HIV, influenza and dengue, but global samples show SARS-CoV-2 to be less diverse than these viruses," Rolland said. "We can therefore be cautiously optimistic that viral diversity should not be an obstacle for the development of a broadly protective vaccine against COVID-19 infection," she added. The researchers believe the current findings may lead to the development of a vaccine that is rapidly scalable and universally applicable to all populations.
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