Antibody-Mediated Neutralization of Authentic SARS-CoV-2 B.1.617 Variants Harboring L452R and T478K/E484Q

Viruses. 2021 Aug 26;13(9):1693. doi: 10.3390/v13091693.


The capacity of convalescent and vaccine-elicited sera and monoclonal antibodies (mAb) to neutralize SARS-CoV-2 variants is currently of high relevance to assess the protection against infections. We performed a cell culture-based neutralization assay focusing on authentic SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta), B.1.427/B.1.429 (Epsilon), all harboring the spike substitution L452R. We found that authentic SARS-CoV-2 variants harboring L452R had reduced susceptibility to convalescent and vaccine-elicited sera and mAbs. Compared to B.1, Kappa and Delta showed a reduced neutralization by convalescent sera by a factor of 8.00 and 5.33, respectively, which constitutes a 2-fold greater reduction when compared to Epsilon. BNT2b2 and mRNA1273 vaccine-elicited sera were less effective against Kappa, Delta, and Epsilon compared to B.1. No difference was observed between Kappa and Delta towards vaccine-elicited sera, whereas convalescent sera were 1.51-fold less effective against Delta, respectively. Both B.1.617 variants Kappa (+E484Q) and Delta (+T478K) were less susceptible to either casirivimab or imdevimab. In conclusion, in contrast to the parallel circulating Kappa variant, the neutralization efficiency of convalescent and vaccine-elicited sera against Delta was moderately reduced. Delta was resistant to imdevimab, which, however, might be circumvented by combination therapy with casirivimab together.

Keywords: B.1.617.1; B.1.617.2; BNT2b2; Epsilon; Kappa; SARS-CoV-2; corona virus; delta; mRNA1273; monoclonal antibodies; vaccination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Amino Acid Substitution
  • Antibodies, Neutralizing / immunology*
  • Antibodies, Viral / immunology*
  • COVID-19 / immunology*
  • COVID-19 / virology*
  • Cell Line
  • Genotype
  • Host-Pathogen Interactions
  • Humans
  • Mutation*
  • Neutralization Tests
  • SARS-CoV-2 / genetics*
  • SARS-CoV-2 / immunology*


  • Antibodies, Neutralizing
  • Antibodies, Viral