iScience (Jul 2024)

A cryptic site in class 5 epitope of SARS-CoV-2 RBD maintains highly conservation across natural isolates

  • Lingyan Cui,
  • Tingting Li,
  • Miaolin Lan,
  • Ming Zhou,
  • Wenhui Xue,
  • Sibo Zhang,
  • Hong Wang,
  • Minqing Hong,
  • Yali Zhang,
  • Lunzhi Yuan,
  • Hui Sun,
  • Jianghui Ye,
  • Qingbing Zheng,
  • Yi Guan,
  • Ying Gu,
  • Ningshao Xia,
  • Shaowei Li

Journal volume & issue
Vol. 27, no. 7
p. 110208

Abstract

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Summary: The emergence of SARS-CoV-2 variants raises concerns about the efficacy of existing COVID-19 vaccines and therapeutics. Previously, we identified a conserved cryptic class 5 epitope of SARS-CoV-2 receptor binding domain (RBD) by two cross-neutralizing antibodies 7D6 and 6D6. Intriguingly, this site remains resistant to substantial mutations occurred in ever-changing SARS-CoV-2 subvariants. As compared to class 3 antibody S309, 6D6 maintains broad and consistent neutralizing activities against SARS-CoV-2 variants. Furthermore, 6D6 effectively protected hamster from the virulent Beta strain. Sequence alignment of approximately 6 million documented SARS-CoV-2 isolates revealed that 6D6 epitope maintains an exceptionally high conservation rate (99.92%). Structural analysis demonstrated that all 33 mutations accumulated in XBB.1.5 since the original strain do not perturb the binding 6D6 to RBD, in line with the sequence analysis throughout the antigenicity evolution of SARS-CoV-2. These findings suggest the potential of this epitope serving as a critical determinant for vaccines and therapeutic design.

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