Human Surfactant Protein D Binds Spike Protein and Acts as an Entry Inhibitor of SARS-CoV-2 Pseudotyped Viral Particles

Human SP-D is a potent innate immune molecule whose presence at pulmonary mucosal surfaces allows its role in surveillance against pathogens. Higher levels of serum have been reported the patients with severe acute respiratory syndrome coronavirus (SARS-CoV). Studies suggested ability human to recognise spike glycoprotein SARS-CoV; interaction HCoV-229E strain leads viral inhibition bronchial epithelial (16HBE) cells. Previous studies that recombinant fragment (rfhSP-D) composed 8 Gly-X-Y repeats, neck and CRD region, can act range pathogens including influenza A Virus Respiratory Syncytial vitro , vivo ex . In this context, study was aimed examining likely protective rfhSP-D SARS-CoV-2 infection. showed dose-responsive binding S1 protein receptor domain. Importantly, inhibited HEK293T cells overexpressing angiotensin converting enzyme 2 (hACE2). The infection as an entry inhibitor further validated by use pseudotyped lentiviral particles expressing protein; ~0.5 RLU fold reduction seen following treatment (10 µg/ml). These results highlight therapeutic potential merit pre-clinical animal models.