What are these “FLiRT variants”? This is the term being used to describe a whole family of different variants—including KP.2, JN.1.7, and any other variants starting with KP or JN—that appear to have independently picked up the same set of mutations. This is called convergent evolution.
JN (alias BA.2.86.1.)
KP (alias JN.1.11.1)
At the end of March, the KP.2 variant was causing about 4% of infections in the U.S., according to the CDC, while its parental strain, JN.1, was causing over 50% of infections at that time. As of early May, KP.2 makes up about 28% of infections, overtaking JN.1 as the dominant variant.
KP.2 is one of several variants being referred to as “FLiRT variants,” named after the technical names for their mutations. The prevalence of these variants comes at a critical time, when experts are deciding how to formulate the fall COVID vaccine.
In this Q&A, Andy Pekosz, PhD, a professor in Molecular Microbiology and Immunology, explains what virologists like him are seeing, whether these variants might cause a summer wave of infections, and how people can protect themselves.
What are these “FLiRT variants”?
This is the term being used to describe a whole family of different variants—including KP.2, JN.1.7, and any other variants starting with KP or JN—that appear to have independently picked up the same set of mutations. This is called convergent evolution. They are all descendants of the JN.1 variant that has been dominant in the U.S. for the past several months.
The particular mutations that people refer to as “FLiRT”s or “FLip”s refer to specific positions in the spike protein—in this case, positions 456, 346, and 572.
Viruses like SARS-CoV-2 mutate frequently, and when they mutate to evade recognition by antibodies, this often weakens their ability to bind to the cells they want to infect. We then see mutations appear that improve that binding ability. This is a cycle we have seen many times with SARS-CoV-2. The fact that these different variants are picking up the same mutations tells virologists that this combination of mutations is helping the virus accomplish these goals most efficiently.
ttps://publichealth.jhu.edu/2024/what-to-know-about-covid-flirt-variants
- 15.6. 2024 kommenttin: (Wuhan wt virus , F456, R346 ja T572).
How do these mutations help the virus bind to cells while evading antibodies?
Two of these mutations—456 and 346—eliminate binding sites for antibodies that neutralize SARS-CoV-2. However, those same antibody binding sites are also important for the virus to bind to and enter cells. So in evading antibodies, these FLiRT variants may have also lost some ability to bind to their receptor. At the same time, the 572 mutation appears to allow the virus to more tightly bind to cells and ultimately cause an infection.
Do people who recently had COVID have any protection against infection from FLiRT variants?
A JN.1 infection should provide pretty strong protection against all the FLiRT variants. The difference between JN.1 and these variants is only one or two amino acid changes, so there are still a lot of other places antibodies can bind to. Infection from a variant older than JN.1 is less likely to offer as much protection.
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How might these variants impact plans for the COVID vaccine formula that gets updated for the fall?
This is the time of year when governing bodies like the WHO and FDA recommend a formulation for updated COVID vaccines that will roll out in early fall. Last year, the vaccines were based on the XBB.1.5 variant, and only a few months later, the JN.1 variant became the dominant variant in the U.S.
At the end of April, the WHO announced that their COVID vaccine advisory group advises using the JN.1 lineage as the antigen for the upcoming formulations of the vaccine. All of these FLiRT variants are within the JN.1 family of variants.
Here in the U.S., the FDA has postponed its meetingto determine the fall 2024 COVID vaccine from mid-May to early June. That gives them more time to see which of the FLiRT variants is becoming the dominant one so they can fine-tune the WHO recommendation to what they anticipate will be most prominent in the fall.
New COVID variants are likely to crop up after a decision is made—just as it did last summer—but the goal remains to select a formulation that, come fall, will match the circulating variants as closely as possible.
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