A rapidly spreading new variant of SARS-CoV-2, the virus that causes COVID, means that a rise in new infections may be on the horizon. While it may not be possible to completely evade immunity, this subspecies is able to evade some of our defenses thanks to boosts from mutations.
XBB.1.5 — Unofficially nicknamed “Kraken” by some scientists online — is a variant of Omicron that has attracted the attention of virologists in recent weeks due to its extremely fast spreading speed. A study by computational virologist Trevor Bedford and his team at Fred Hutchinson Cancer Center in Seattle now suggests that the reproduction number for XBB.1.5 is about 1.6. Man.
“According to the Centers for Disease Control and Prevention Nowcast estimates the variant rate, XBB.1.5. “It could lead to an increase in cases in the short term, depending on the extent of the benefit of XBB.1.5 and the various factors affecting SARS-CoV-2 transmission in general.”
Importantly, despite dozens of mutations away from the subvariant BA.5 that dominated last summer, XBB.1.5 remains a member of the Omicron family and an entirely new SARS-CoV-2 not a variant.it is also very similar to that parental pedigreeXBB — itself a combination of two strains derived from the subvariant BA.2 that dominated last spring.
The parental XBB gained prominence after causing a wave of infections in Singapore last year, but for its ability to evade the human immune system using a mutation at a site in the spike protein known as 486. worthy ofMutations at this site known to Even early variants of the pandemic have helped the virus evade detection by the immune system. Lawrence Young, professor of molecular oncology at the University of Warwick Medical School, UK, describes mutations as evolutionary trade-offs. [is a] It’s a trade-off in terms of transmissibility, in that the changes make the virus slightly less efficient at transmission,” he says.
In contrast, the main difference between XBB.1.5 and XBB is a mutation in the spike protein known as F486P. This mutation gives XBB.1.5 a major advantage, making it more infectious while maintaining XBB’s ability to sneak past human defenses. In other words, it’s more like a turbocharger, not a trade-off.
The mechanism behind the increased infectivity of XBB.1.5 is not known with certainty.But her F486P mutation in the subvariant makes the virus more effective Latches to ACE2 receptor Inside the body – “The gateway for viruses to enter cells in the nose, throat, and lungs,” says Young.
“I think there are very few studies that show a direct correlation between ACE2 binding and increased infectivity of the virus,” says Stanley Perlman, professor of microbiology and immunology at the University of Iowa. . “It’s certainly a factor, but he’s just one of many factors.”
As a result, XBB.1.5 is highly contagious while maintaining Omicron’s ability to evade the immune system. However, some experts stress that XBB.1.5’s immune evasion properties should not be overstated. According to Professor Alessandro Sette of the La Jolla Institute of Immunology, the subvariants may evade antibodies conferred by vaccines and previous exposures to some extent, but they cannot evade the immune system completely. XBB.1.5 says it will struggle to escape cell-mediated immunity conferred by killer T cells. This T-cell response in him helps prevent serious illness. There is currently no evidence to suggest that XBB.1.5 causes more or less severe disease or different symptoms compared to his previous Omicron subvariant.
“There’s been a fair amount of confusion in the conservation narrative,” Sette says. “Since antibodies are confined to specific regions of the viral spike protein, it is relatively easy for viruses to mutate and evade them. But what about cell-mediated immunity? The mechanism by which T cells recognize viruses.” is quite different.” He said that while certain SARS-CoV-2 variants can evade antibodies to varying degrees, T cells retain about 85% of their ability to fight the virus at the population level. added.
This reinforces points made by many experts during the pandemic. Immunity from vaccines or previous exposures may not prevent people from being infected multiple times, but they still help prevent serious illness.
Jake Scott, a clinical assistant professor of infectious diseases at Stanford University, isn’t worried about XBB.1.5 yet. “I think it is clear that all subvariants of Omicron are inherently less likely to lead to severe disease because they are less likely to lead to lower respiratory tract disease,” he says. “Yes, the Omicron subvariant is highly contagious, and yes, XBB.1.5 is the most contagious of the Omicron subvariants, which could lead to an increase in cases. There is absolutely no concern that COVID alone will lead to an increase in hospitalizations and deaths.”
Scott admits this is mostly speculation. “But I’m reluctant to make predictions, but I think it’s okay to be confident in a vaccine,” he says.
Sette repeats that point. “Now we have an even better bivalent booster, which is very important.”
Additionally, antiviral COVID drugs such as Paxlovid and remdesivir “should be effective against XBB.1.5,” Young said. “Both of these prevent the virus from replicating, and their critical function is unchanged in his XBB.1.5.”
