Collectin-11, a complement pattern recognition molecule, mediates pulmonary SARS-CoV-2 neutralization and protection

Abstract

Background Collectin-11 (CL-11) is a complement-activating pattern recognition molecule with structural and functional similarities to mannose-binding lectin (MBL), produced in different tissues, including lung epithelium. Given its tissue localization and role in innate immunity, we investigated its potential to recognize and neutralize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to activate complement. Methods We produced recombinant CL-11, MBL, as well as wild-type, variant, and glycan-mutated SARS-CoV-2 Spike (S) proteins. We evaluated CL-11 binding to the S protein, complement activation, and inhibition of S protein-receptor binding using ELISA, as well as neutralization of SARS-CoV-2 in cell-based neutralization assays. Results CL-11 bound different SARS-CoV-2 S protein variants with similar binding preferences as MBL, targeting multiple glycan sites. Upon S protein binding, CL-11 mediated activation of both the lectin and alternative complement pathways, and inhibited S protein-receptor binding. Notably, CL-11 neutralized SARS-CoV-2, inhibiting infection of permissive cells. Conclusion CL-11 binds different SARS-CoV-2 variants and neutralizes SARS-CoV-2 in an antibody-independent manner, suggesting a crucial role in early-stage infection control.