Omickron mutant substrain is spreading around the world - countless mutations appear again and again.
Currently, the diversity of the Omickron variant of SARS-CoV-2 is unprecedented in . This complexity makes it even more difficult to predict the upcoming wave of infection. It may even lead to "double waves" in some places, because first one variant and then another variant more than one population.
Currently, scientists have identified some mutations that evade the epidemic, which provide impetus for the spread of the variant. However, so far, some super mutant strains have appeared around the world, causing different outbreaks in different regions.
In Europe, North America and Africa, the prevalence of the Omickron branch in the BQ.1 family is rising rapidly, although overall cases appear to be declining. In Asian countries including Singapore, Bangladesh and India, a lineage called XBB has triggered a new wave of infection. Scientists are closely watching several areas where both regions are circulating to see which region has advantages.
"End of all, some variants may dominate, but it is not as decisive as it was in the past," said Cornelius Roemer, a computational biologist at the University of Basel, Switzerland.
A mutant large lineage
mutant strains that promoted the past wave of epidemics, such as alpha and delta , all come from different branches of the SARS-CoV-2 genealogy.
But since the advent of Omickron at the end of 2021, it has produced a range of submutations, including BA.2 and BA.5, triggering a global wave of infection.
Many countries use the BA.5 mutant strain as the research subject of the mutant strain in mid-2022, but most scientists think it is only a matter of time before another sub-lineage stands out.
Over the past few months, variant detectors have been combing through global SARS-CoV-2 sequencing data to identify candidates. However, what they identified was not one or two rapidly rising mutation lines, but more than a dozen viral mutation lines worthy of attention.
"This is a collection of mutations not like we have seen before," said Cao Yunlong, an immunologist at Peking University, who has been studying the immune evasion ability of mutations. Members of the
mutation lineage are from various parts of the Omickron family tree. But their rise appears to be due to a handful of shared gene mutations, most of which lead to amino acid changes in the portion of the viral spike protein called the receptor binding domain (RBD). This portion of the protein is necessary to infect cells and is a target for antibodies that provide effective immune responses.
Cao Yunlong 's team's work this month shows that RBD mutations help the virus escape infections caused by infections caused by COVID-19 vaccine and early Omickron branches (including BA.2 and BA.5).
Mutations worthy of alert
Cao Yunlong and others have observed that the more these RBD changes a variant has, the faster it grows, as measured by the number of sequences reported to the global database. For example, variants with five critical RBD changes (relative to BA.2) (e.g. BQ.1) appear to grow slowly than variants with six changes. BQ.1.1, a descendant of BQ.1, had six such changes and rapidly rose in Europe, North America and elsewhere.
The seventh RBD change seems to lead to faster growth (although scientists warn that the estimate is approximate, especially when the number of recorded sequences is small). The main "level 7" variant scientists are tracking is XBB. This subsector is a hybrid or recombinant of two Omickron subsectors, both of which are offspring of BA.2.
In the population of COVID-19 mutant strains, BQ.1.1 and XBB appear to be rising to their peak. The BQ.1 family already dominates France, and as these regions enter winter, it may trigger a wave of infection in Europe and North America. It is also a common ingredient in South Africa, Nigerian and other parts of Africa. By contrast, XBB seems likely to dominate the infection in Asia, which recently triggered a wave of infections in Asia.
Researchers are also monitoring countries where BQ.1.1 and XBB are spreading together to see which one spreads faster. In Australia, there are some early signs that XBB is gaining an advantage, Cao Yunlong noted. This seems to have happened in India as well, said
microbial scientist Rajesh Karyakarte, who is responsible for coordinating the SARS-CoV-2 gene sequencing of Maharashtra . "We will be able to tell which one survives here. We suspect XBB. The advantage of
XBB over the BQ.1 series may be due in part to changes outside the spike RBD, Cao said. The variant also has mutations in part of the genome encoding a spike protein region called the N-terminal domain (NTD). According to preliminary data from the Cao Yunlong lab, our immune system also targets this portion of the spike with neutralizing antibodies, and people recovering from BA.2 and BA.5 infections have particularly strong immune responses to NTD.
html D mutation, he said. Unpublished research by his team showed that this addition greatly enhances the ability of these variants to evade vaccination and neutralizing antibodies caused by previous infection.
Cao Yunlong says BQ.1.1 may cause a surge in cases, just that XBB surpasses it in some places. "If it turns out that XBB will eventually dominate globally, we may see some kind of double wave in Europe and North America," he said.
double immunity?
A key determinant is how much BQ.1 lineage infection protects XBB. Cao Yunlong 's team is currently working on this issue. "I have a feeling that if you get BQ.1, you might have some protection against XBB," he said. "We don't have data yet. "
Whether driven by XBB, BQ.1.1 or other members of the group, large waves of infection can disrupt society, and even minor infections can lead to long-term health effects. But researchers are paying particular attention to whether the upcoming wave will lead to large numbers of hospitalizations and deaths.
In an unpublished preliminary study of 28 people infected with XBB, the team at Karyakarte found no one had serious symptoms. Karyakarte said his colleagues in Bangladesh reported a similar pattern. Singapore recorded COVID-19 in its XBB wave. There is a slight increase in hospitalizations and deaths, but these serious effects are smaller than the waves in the past.
but Cao Yunlong said seasonality (winter weather in the northern hemisphere may promote the spread of SARS-CoV-2), previous waves of outbreaks and policies, etc., means that Singapore’s experience may not be predictable in other countries. “This may not be a blueprint for what is going to happen.”
References
1.Cao, Y. et al. Preprint at bioRxiv https://doi.org/10.1101/2022.09.15.507787 (2022).
