Scientists at the University of Texas at Austin (USA) have found that the SARS-CoV-2 coronavirus accumulates genetic mutations, one of which made it more infectious, and the other makes it difficult for the immune system to function. This is reported in an article published in the mBIO magazine.
During the first wave of the pandemic, 71 percent of viruses isolated from COVID-19 patients in Houston had the D614G mutation affecting the spike protein (S-protein), the study found. In the second wave, the prevalence of this variant increased to 99.9 percent, reflecting the trend observed around the world.
It is known that viruses with the D614G mutation are transmitted much faster than viruses without it and provoke large outbreaks of the disease. However, some experts have suggested that the new mutation does not increase the infectiousness of the coronavirus, and the spread of the strain is explained by the founder's effect, when viruses with D614G first reached Europe and North America, where they began to dominate other strains.
Scientists tested various genetic variants of the S-protein to measure its stability and see how well it binds to the host cell receptor and neutralizing antibodies. The researchers confirmed that D614G does not increase the pathogenicity of the virus. At the same time, they revealed signs of natural selection, which indicates the effect of mutation on the fitness of the virus. This confirms that D614G is likely to increase the infectivity of SARS-CoV-2.
The researchers also found a rare mutation that results in decreased recognition by the neutralizing monoclonal antibody CR3022. This mutation is rare and does not make the disease worse in infected patients. In total, experts have noted 285 mutations in the coronavirus, although most of them do not significantly affect the severity of COVID-19.