Potent Neutralization of SARS-CoV-2 by Hetero-bivalent Alpaca Nanobodies Targeting the Spike Receptor-Binding Domain

  Dr. Huan Ma et al’s manuscript titled with ‘Potent Neutralization of SARS-CoV-2 by Hetero-bivalent Alpaca Nanobodies Targeting the Spike Receptor-Binding Domain’ was published online at Journal of Virology on 3^th Mar, 2021. Congratulations.

https://pubmed.ncbi.nlm.nih.gov/33658349/

  The co-first authors of this paper are Huan Ma and Weihong Zeng. Prof. Tengchuan Jin and Prof. Yan Xiang are corresponding authors. Congratulations to all authors.

Keywords: SARS-CoV-2; COVID-19; Nanobody; Antibody; Alpaca; Hetero-bivalent.

Abstract:

  Cellular entry by SARS-CoV-2 requires the binding between the receptor-binding domain (RBD) of the viral Spike protein and the cellular angiotensin-converting enzyme 2 (ACE2). As such, RBD has become the major target for vaccine development, while RBD-specific antibodies are pursued as therapeutics. Here, we report the development and characterization of SARS-CoV-2 RBD-specific VHH/nanobody (Nb) from immunized alpacas. Seven RBD-specific Nbs with high stability were identified using phage display. They bind to SARS-CoV-2 RBD with affinity K_D ranging from 2.6 to 113 nM, and six of them can block RBD-ACE2 interaction. The fusion of the Nbs with IgG1 Fc resulted in homodimers with greatly improved RBD-binding affinities (K_D ranging from 72.7 pM to 4.5 nM) and nanomolar RBD-ACE2 blocking abilities. Furthermore, the fusion of two Nbs with non-overlapping epitopes resulted in hetero-bivalent Nbs, namely aRBD-2-5 and aRBD-2-7, with significantly higher RBD binding affinities (KD of 59.2 pM and 0.25 nM) and greatly enhanced SARS-CoV-2 neutralizing potency. The 50% neutralization dose (ND50) of aRBD-2-5 and aRBD-2-7 was 1.22 ng/mL (∼0.043 nM) and 3.18 ng/mL (∼0.111 nM), respectively. These high-affinity SARS-CoV-2 blocking Nbs could be further developed into therapeutics as well as diagnostic reagents for COVID-19.