Emergence of SARS-CoV-2 variant JN.1 raises concerns about increased transmissibility and immune evasion

The emergence of the JN.1 variant of SARS-CoV-2 has caused global concern due to its distinct genetic characteristics and increased infectiousness. Carrying more than 30 Spike protein mutations, including the Leu455Ser mark, JN.1 has substantial potential for immune evasion.

Japanese researchers have revealed the global dominance of JN.1, as it surpasses other variants in terms of reproduction number. New findings indicate JN.1’s robust resistance to immunity, highlighting the urgent need for research strategies to address its threat to public health.

Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed a global threat. The emergence of the BA.2.86 variant, a sub-variant of the omicron, has raised significant concerns due to its large number of mutations.

Discovered in August 2023, this variant differs significantly from other existing types, such as the omicron XBB (including EG.5.1 and HK.3). Compared to XBB and BA.2, BA.2.86 has more than 30 mutations in its spike protein, contributing to its ability to effectively evade immune system defenses.

Over time, the BA.2.86 variant of SARS-CoV-2 has undergone alterations, giving rise to a new variant called JN.1 (BA.2.86.1.1) at the end of 2023. JN.1 is characterized by a specific mutation in its spike protein – Leu455Ser – as well as mutations in other parts of the virus.

This mutation, similar to Leu455Phe previously identified in variants like HK.3, has been associated with increased transmissibility and the ability to evade immune responses. Due to its distinctive mutation profile, indicating a high potential for immune evasion and transmissibility, the study of the virological properties of JN.1 has become imperative.

In their new study, Japanese researchers used genomic surveillance data from France, the United Kingdom and Spain, uncovering new findings regarding the virological properties of the JN.1 variant of SARS-CoV-2. Professor Kei Sato from the Institute of Medical Sciences at the University of Tokyo, Japan, led the research team, which included Dr Yu Kaku, Kaho Okumura and Dr Jumpei Ito.

The study, published in Lancet infectious diseaseshighlights the potential of the variant to become the dominant lineage and alerts the global health community.

The research team used a Bayesian multinomial logistic model to estimate the relative effective reproductive number of JN.1 compared to other variants, including BA.2.86.1 and HK.3.

Strikingly, the reproductive number of JN.1 exceeds that of its counterparts in all three countries studied, suggesting potential global dominance in the near future. By the end of November 2023, JN.1 had already surpassed HK.3 in France and Spain, marking a significant shift in the SARS-CoV-2 variant landscape.

What is concerning for public health is that JN.1 not only spreads easily, but also appears to be resistant to immunity. Initial experiments using blood from rodents infected or vaccinated against BA.2.86 showed that these rodents demonstrated effective neutralization of BA.2.86 and JN.1, called a cross-reactive immune response.

However, when comparing breakthrough infections in people whose virus overcomes immunity, JN.1 was found to be more difficult to neutralize than BA.2.86. Particularly noteworthy was the finding that JN.1 was strongly resistant to the XBB.1.5 vaccine, making it one of the most immune variants discovered so far.

Regarding the implications of this study, Professor Kei Sato said: “Our results will help people understand the risk of the SARS-CoV-2 JN.1 variant, including its potential to cause outbreaks worldwide. »

As the international community grapples with the current challenges posed by the COVID-19 pandemic, this research highlights the importance of continued vigilance in monitoring and understanding the evolving landscape of SARS-CoV-2 variants.

“One of the reasons it is difficult to control viral infections is due to the ability of viruses to mutate and evolve. Through research into SARS-CoV-2, understanding the principles of viral evolution and outbreaks could lead to insights not only for controlling COVID-19. 19 but also to manage various infectious diseases, including future pandemics”, concludes Professor Kei Sato.