New SARS-CoV-2 KP.2 variant defies vaccines with higher spread, study warns

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In a caller preprint* study posted to nan bioRxiv server, a squad of researchers analyzed nan virological characteristics and epidemiological effect of nan Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) FLiRT version KP.2, which has demonstrated accrued transmissibility and immune resistance.

 Orpheus FX / ShutterstockStudy: Virological characteristics of nan SARS-CoV-2 KP.2 variant. Image Credit: Orpheus FX / Shutterstock

*Important notice: bioRxiv publishes preliminary technological reports that are not peer-reviewed and, therefore, should not beryllium regarded arsenic conclusive, guideline objective practice/health-related behavior, aliases treated arsenic established information.

Background 

The accelerated emergence and diversification of nan JN.1 version and its descendant, KP.2, which shows important alterations successful spike (S) macromolecule building and accrued guidance to existing vaccines, underscore nan necessity for further investigation to understand nan implications for nationalist wellness and vaccine development. 

About nan study 

The coming study was initiated by analyzing nan genomic sequences of nan KP.2 version from surveillance information crossed nan United States of America (USA), United Kingdom, and Canada, wherever complete 30 sequences were reported. The comparative effective reproduction number (Re) was calculated utilizing a Bayesian multinomial logistic regression model, adjusting for various covariates that could power transmission dynamics. 

Subsequently, virological assays were conducted to measure nan infectivity and immune evasion capabilities of KP.2. Lentivirus-based pseudovirus assays were performed utilizing Human Osteosarcoma cells (HOS)- Angiotensin-Converting Enzyme 2 (ACE2)/Transmembrane Protease, Serine 2 (TMPRSS2) cells infected pinch pseudoviruses base nan S proteins of KP.2, JN.1, and different applicable variants. The amount of input microorganism was standardized against nan Human Immunodeficiency Virus Type 1 (HIV-1) Protein 24 (p24) capsid protein. Statistical study was carried retired utilizing two-sided Student's t-tests to find important differences successful infectivity betwixt nan variants.

For nan neutralization assays, serum samples were collected from individuals successful various immunization and infection states. These included vaccinated individuals some pinch and without anterior infections and those who had recovered from circumstantial version infections. Each serum sample was tested successful quadruplicate against pseudoviruses harboring different S macromolecule mutations. The 50% neutralization titers (NT50) were calculated and compared crossed each serum samples to measure nan grade of neutralization guidance posed by KP.2. Statistical value of nan differences successful NT50 values was evaluated utilizing two-sided Wilcoxon signed-rank tests.

Study results 

The study revealed that nan KP.2 variant, a descendant of nan JN.1 lineage, demonstrates importantly enhanced epidemiological fittingness compared to its predecessors, including nan ascendant XBB lineage. This uncovering is confirmed by nan Re estimated for KP.2 successful nan USA, United Kingdom, and Canada, wherever it was observed to beryllium 1.22, 1.32, and 1.26 times higher than JN.1, respectively. The dispersed of KP.2 has been rapid, pinch its version wave reaching 20% successful nan United Kingdom arsenic of early April 2024, suggesting a imaginable to go nan predominant lineage globally.

Further virological investigation into KP.2 utilizing a lentivirus-based pseudovirus assay highlighted a paradox wherein, contempt its higher transmissibility, nan infectivity of KP.2 was recovered to beryllium importantly little (10.5-fold) than that of JN.1. This reduced infectivity mightiness propose different mechanisms aliases pathways for KP.2's enhanced dispersed and constitution successful nan big populations.

In summation to infectivity, guidance to neutralization was assessed done assays utilizing sera from individuals vaccinated pinch nan monovalent XBB.1.5 vaccine and those who had breakthrough infections pinch various SARS-CoV-2 variants. KP.2 exhibited important guidance to neutralization, pinch a 3.1-fold simplification successful susceptibility to neutralization by sera from vaccines without infection and a 1.8-fold simplification from those pinch anterior infections. This accrued guidance could partially explicate nan higher Re of KP.2, indicating an enhanced expertise to evade immune responses compared to JN.1 and different erstwhile variants. 

*Important notice: bioRxiv publishes preliminary technological reports that are not peer-reviewed and, therefore, should not beryllium regarded arsenic conclusive, guideline objective practice/health-related behavior, aliases treated arsenic established information.

Journal reference:

  • Preliminary technological report. Yu Kaku, Keiya Uriu, Yusuke Kosugi, et al. Virological characteristics of nan SARS-CoV-2 KP.2 variant, bioRxiv (2024), doi: 10.1101/2024.04.24.590786, https://www.biorxiv.org/content/10.1101/2024.04.24.590786v1