The SARS-CoV2 coronavirus, the etiological pathogen of the COVID-19 pandemic, is a respiratory virus belonging to the human beta-coronavirus family. Many variants of SARS-CoV-2 with improved immune capacity have emerged during the pandemic and have triggered several distinct pandemic waves around the world. The omicron variant of SARS-CoV-2 first emerged in South Africa in late 2021. The BA.2 lineage was a major descendant lineage of omicron that exhibited significantly higher transmissibility and infectivity. BA.2.86 is a notable lineage descendant of BA.2 that emerged in 2023. This variant has a greater number of spike protein mutations than previously emerged variants.
According to the prediction made by a team of scientists based on the molecular identity card, JN.1 will very quickly become the dominant COVID variant worldwide. Derived from omicron 2 (BA.2.86), it emerged at the end of 2023 and for some scientists it could represent a turning point for the virus of the same magnitude as Omicron. This variant was in fact found to be phylogenetically distinct from the circulating XBB variants (on which the updated vaccines currently in use are also based), including Eris (EG.5.1) and HK.3, which last November was already one of the XBB lineages with the highest growth advantage. Not surprisingly, at the end of November 2023, JN.1 had already surpassed HK.3 in France and Spain.
Among the various mutations possessed by the Spike protein of this variant, the one called L455S is the one that seems to allow it the greatest immune evasion, which makes it spread at the rate of a regular flu, mixing in symptomatology and incubation period. In a study just published in EuroSurveillance, scientists studied the immune escape potencies of the recent JN.1, BA.2.86 and earlier variants. The scientists collected serum samples from a total of 39 healthy individuals vaccinated and exposed to SARS-CoV-2 and evaluated the virus neutralization titers in these samples against seven different viral variants, including B.1, BA. 2, BA.5, XBB. 1.5, EG.5.1, BA.2.86 and JN.1.
Evaluation of neutralization titers revealed the highest neutralizing reactivity against ancestral B.1 variants, followed by BA.2 and BA.5 variants. This is due to pre-existing anti-SARS-CoV2 immunity induced by COVID-19 vaccination or previous coronavirus infection. Compared to the B.1 variant, the XBB.1.5 and EG.5.1 variants showed approximately 15-fold reduction in neutralization. Furthermore, no detectable neutralizing reactivity was observed against these variants in 12 of 39 participants. For the BA.2.86 variant, the reduction in neutralizing titers was 20-fold compared to the ancestral B.1 variant. Compared to the BA.2.86 variant, the JN.1 variant did not show a further reduction in neutralizing titers.
The investigation, overall, found that both BA.2.86 and JN.1 variants have comparable immune escape capabilities. Both variants have a significantly higher ability to escape pre-existing anti-SARS-CoV2 immunity than previous variants. This may explain the recent predominance of BA.2.86 and JN.1 variants. However, increased immune fitness may not be the reason for the recent increase in JN.1 cases, as the variant has no additional immune escape ability compared to the BA.2.86 variant. Possibly, there are still molecular details that escape scientists or unknown genetic and immunological determinants, but the conditions that this variant will manifest itself as an annual flu in the future are already there.
By Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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Scientific publications
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