In this week’s brief Research Tracker we look at the emerging information about the new UK variant.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
Information on the UK variant, currently called B 1.1.7 or VUI-202012/01, is still emerging. Originally detected in the UK in September, it is now being reported in several European countries and Australia. There are no reports of it from the US, but their level of viral genome sequencing is low, so it may be present there (and elsewhere) too.
The variant has only just hit the headlines because of the rapid pace at which it is spreading in the UK in recent weeks. There are still many uncertainties associated with this variant. There is, though, confidence that it does not lead to more serious disease.
Is the variant more transmissible?
There is concern that this variant has a selective advantage that enables it to spread more quickly compared to other variants. This has yet to be proven, but available data suggests that that might be the case.
The UK’s New and Emerging Respiratory Virus Threats Advisory Group assessed available information on 18 December and had “moderate confidence that VUI-202012/01 demonstrates a substantial increase in transmissibility compared to other variants.”
There is discussion that the more rapid spread may be due to more younger people becoming affected, but this too requires further study.
A large number of mutations
A preliminary genomic analysis of the variant (not peer-reviewed) identified 14 amino acid replacement mutations, three deletions of amino acids, and six mutations that didn’t change amino acids. Eight of the amino acid changes are in the spike protein. This is a very large number of mutations.
Some of these mutations have been seen previously in other viruses, but not all of them in a single variant.
The amino acid replacement N501Y in the spike protein is a particular focus of attention. This involves the more commonly seen asparagine (“N” in amino candid code) being replaced by tyrosine (“Y”) at position 501 in the spike protein. It has been shown in earlier research to affect binding to the ACE2 receptor and, perhaps in conjunction with some of the other mutations, may have enhanced transmissibility. The 501Y change is also associated with higher viral loads, compared with viruses having N501.
A pre-print paper from South Africa describes another variant 501Y.V2, with 8 mutations, that also has the N501Y mutation.
Another mutation seen in B.1.1.7 - the deletion of the amino acids at positions 69 and 70 in the spike protein - has been found in a range of viral variants. In one case, involving an immunocompromised patient with a long lasting infection, this deletion was associated, along with another mutation, with evasion of neutralising antibodies. However, there is no evidence that the deletion usually enables the virus to escape the immune response.
Will vaccines still be effective?
The impact on vaccine effectiveness is unknown, but considered to be relatively small. There is no indication at this stage that the B.1.1.7 variant is resistant to Pfizer’s, Moderna’s or other vaccines. But neither is there data to demonstrate that there is no effect.
Laboratory experiments are underway to assess all of these issues.
Why so many mutations?
SARS-CoV-2 and other coronaviruses have a relatively low mutation rate for RNA viruses. Mutations occur when the virus replicates and the changes are not detected or corrected.
The large numbers of changes in B.1.1.7, 501Y.V2, and several other variants, are thought to be due to two factors. Firstly, prolonged infection in some people leads to many cycles of virus replication and so more chances of mutation.
Secondly, exposure to a variety of neutralising antibodies during this prolonged infection provides a strong selective pressure (called antigenic selection) where certain mutations may provide an advantage.
The analyses of both the UK and South African variants suggest this hypothesis may account for the large number of changes. However, this has yet to be proven.
Standard practices still apply
Keeping your distance, avoiding crowded spaces and events, good hand washing, mask wearing, and isolating if unwell remain effective means of reducing the chance of becoming infected or transmitting the virus.