The SARS-CoV-2 receptor-binding domain preferentially recognizes blood group A

Abstract

1. The RBD of SARS-CoV-2 shares sequence similarity with an ancient lectin family known to bind blood group antigens.

2. SARS-CoV-2 RBD binds the blood group A expressed on respiratory epithelial cells, directly linking blood group A and SARS-CoV-2.

Graphical abstract

Figure 1.

SARS-CoV-2 shares significant similarity to human galectins. (A) Structural representation of SARS-CoV-2 RBD (Protein Data Bank [PDB] ID: 6VXX), human galectin-4N-terminal domain (PDB: 5DUW), and human galectin-9N-terminal domain (PDB ID: 3LSD); β-sheet structures shown in red or green, α-helix shown in cyan. (B) Sequence alignment (Uniport align program) of SARS-CoV-2 RBD, human galectin-4N-terminal domain (galectin-4N) and human galectin-9 N-terminal domain (galectin-9N) indicating fully conserved residues (dark gray [*]), highly conserved residues (gray [:]), lowly conserved residues (light gray [.]); the galectin carbohydrate binding pocket is highlighted in light red. (C) Flow cytometric analysis of blood group A, B, or O type human RBCs after incubation with SARS-CoV-2 RBD for 1 hour followed by detection with anti-His antibody. (D) Flow cytometric analysis of HEK293 T cells alone or HEK293 T cells stably transduced to express ACE2 after a 1-hour incubation with the SARS-CoV-2 RBD and detection with anti-His antibody. (E) Flow cytometric examination of blood group A RBCs after incubation with anti-A antibody. Secondary antibody alone served as a control.

Figure 2.

SARS-CoV-2 RBD preferentially binds type I blood group A antigen. (A) Representation of human blood group antigens present on respiratory epithelium (type I) and RBCs (type II). Type I vs type II structures differ based on the linkage between the galactose and N-acetylglucosamine (type I: galactose β1-3 N-acetylglucosamine; type II: galactose β1-4 N-acetylglucosamine). (B-C) ABO(H) glycan microarray data obtained after incubation of SARS-CoV-2 RBD (B) or SARS-CoV RBD (C) with the corresponding glycans shown. Data are representative of 2 independent experiments. Error bars represent mean ± standard deviation. Statistics were generated by one-way analysis of variance with a post hoc Tukey’s multiple comparison. RFU, relative fluorescence unit. ***P < .001 for comparison between RBD binding to A type I vs all other glycans.