Covid variant JN.1 may have become dominant due to just one mutation

Last year, a mutation may have been crucial to the new coronavirus variant JN.1 that spread rapidly around the world, suggesting that the virus adapts very quickly.

“A mutation in JN.1 is key to its ability to evade antibody responses, which is why it has been able to spread globally,” Emanuele Andreano at the Tuscany Life Sciences Foundation, Italy.

JN.1 is a subvariant of the Omicron variant, first discovered in Luxembourg in August 2023. 88%accounting for 85% and 77% of recorded infections in the United States, the United Kingdom, and Australia. Its predecessor, BA.2.86, never accounted for more than 5% of known infections worldwide.

Because JN.1 and its descendants remain the most reported covid-19 variants worldwide, Andreano and his colleagues wanted to study how it had spread so widely. Genetic sequencing had previously pointed to an additional mutation in its spike protein, which the virus uses to infect host cells, compared to BA.2.86.

To learn more, Andreano and his colleagues analyzed 899 antibodies in blood samples previously collected from 14 people who had received two or three doses of the mRNA COVID-19 vaccine and had been confirmed to have been infected with previous variants of the virus.

The researchers placed these antibodies in a dish containing monkey cells along with the BA.2.86 SARS-CoV-2 virus. The results showed that 66 of the 899 antibodies were able to prevent BA.2.86 from infecting the cells. When they repeated the experiment with JN.1, only 23 antibodies were able to prevent infection.

Next, the researchers used computer simulations to test how mutations in the JN.1 spike protein help it evade neutralizing antibodies (which block the virus from entering cells). They found that mutations that replace the longer amino acid leucine with the shorter amino acid serine weakened or completely prevented the antibodies from interacting with the spike protein.

The antibodies that prevented JN.1 infection in monkey cells came from five of the 14 blood sample donors. Andreano said these people had “super hybrid” immunity, resulting from three doses of the mRNA vaccine, and had been infected once with the original SARS-CoV-2 variant found in Wuhan, China, and once with the omicron variant. Andreano said the antibodies may bind to other parts of the spike protein, away from the mutation site, to prevent JN.1 infection.

The study suggests that a single mutation may be key to JN.1’s ability to evade neutralizing antibodies. However, Andreano said it still does not cause more severe disease than previous variants.

This may be because there are many other organs in the immune system, such as T cells, which can stop the virus from causing serious illness even if they cannot prevent infection. Jonathan Ball “Overall, people’s immunity is strong,” said researchers from the Liverpool School of Tropical Medicine in the UK.

The antibodies the researchers collected were similar to those previously found in people around the world. But the study was still small and should be repeated in larger groups. Daran Bailey at the Pirbright Institute in the UK.