We now see recombinant variants like the Omicron XE. These are not variants that have gotten some mutations. Instead, they contain a combination of genetic material from many variants, producing a new version of the SARS-CoV-2 virus. So far, at least 1,179 cases of Omicron XE have been identified in the UK (this was the number in the most recent update from the UK Health and Safety Service published on 8 April). The majority of these cases were in the south and east of England. There have also been reports of a handful of cases elsewhere around the world, most likely due to international travel. So how much should we worry about the omicron XE? Although we do not know much about it yet, what we do know does not indicate that there is cause for serious concern. Let’s take a look.
What are recombinant variants?
When viruses multiply, they sometimes make mistakes in their genetic code that lead to individual mutations. Often, these mutations do not lead to any change in the structure of the virus – called “silent mutations”. Some mutations, however, can offer an advantage. For example, mutations that occur in the spike protein (the part of the SARS-CoV-2 virus that is responsible for infecting our cells) can make the virus more contagious than previous variants. We have seen repetitive mutations in the disturbing variants that produce spike proteins. Recombination is a different process in which two different variants infect the same cell, in the same individual, at the same time. From there, they can combine their genetic material, resulting in a virus that has a mixture of genes from both “parent” viruses that infect. This recombinant variant can then spread to other people – as happened with Omicron XE. Recombination occurs when two different variants infect the same cell at the same time. Grace C. Roberts, author In fact, multiple recombinant variants have been identified worldwide by PANGOLIN (SARS-CoV-2 genealogy surveillance by the Covid-19 genetics UK consortium). At least three of them – XD, XE and XF – have been identified in the UK Some recombinants, such as the XD and XF, are combinations of the Delta variant with the Omicron genealogies. You may have heard of these hybrids, which have been named “Deltakron”. XE, however, is a combination of two Omicron strains: BA.1 and BA.2.
Why are different variants combined?
Genetic recombination of viruses is not a new phenomenon. It occurs regularly with viruses such as influenza and HIV. Indeed, one of the suggested origins of the original SARS-CoV-2 virus is from a recombination event in bats. Evolutionarily, recombination offers viruses an advantage, as it allows for faster and more significant changes in the virus, compared to the slower process of obtaining mutations through replication errors. Recombinant viruses can cause significant changes in their behavior, such as increased infectivity, escape of our existing immunity to the virus, or drug resistance. Like bug-based mutations, however, some recombinant viruses do not show obvious differences from their parent viruses. We know that Omicron XE has the majority of its genetic information, including pin protein, from the Omicron BA.2 subtype, which is the dominant variant in the UK at the moment. It is therefore possible that the characteristics of Omicron XE (such as transmissibility, disease severity and vaccine efficacy) are similar to those of BA.2. But it is prudent for scientists to continue to monitor and study Omicron XE, as it is a genetically different virus from its parents. Initial data for the Omicron XE variant indicate that the growth rate (ie the rate of new infections in the population) is slightly higher than that of Omicron BA.2. However, because there are only a small number of XE infections at present, the data we have on this are limited and it is difficult to draw solid conclusions at this time. It is reassuring to know that BA.2 is no more severe than BA.1 and that Omicron variants as a whole tend to cause less severe disease than previous SARS-CoV-2 variants. But they are very contagious. The need for up-to-date vaccines is becoming increasingly pressing as all current vaccines are based on the original Wuhan strain. Data have shown that the more changes in spike protein the next variants have, the less effective our current vaccines are in preventing infection. That said, vaccines are still very effective in preventing serious illness or death from Covid-19. Of course, we need more research to understand the features of this new Omicron XE strain. But for now, it looks a lot like the current SARS-CoV-2 strains. As we all know, it is not the first variant of the virus and it is very unlikely to be the last. This article was originally published in The Conversation by Grace C Roberts at the University of Leeds. Read the original article here.
