Single intratracheal exposure to SARS-CoV-2 S1 spike protein induces acute lung injury in K18-hACE2 transgenic mice

Abstract

The SARS-CoV-2 pandemic has infected more than 85,900,000 people and provoked the death of more than 1.9 million worldwide. Therapeutic options remain limited, and vaccines may exhibit narrow efficacy, due to short supplies, delays in distribution and the emergence of new resistant strains. It is mandatory to study new therapeutic approaches that modulate the strong inflammatory response observed in the lung, prevent respiratory failure and improve outcomes. The study of SARS-CoV-2 pathogenicity in vivo is challenging due to the necessary biosafety laboratory regulations. Thus, we developed an acute lung injury model by intratracheally instilling the S1 subunit of SARS-CoV-2 Spike S protein (400 µg/kg, 2 ml/kg body weight) in K18-hACE2 transgenic mice that overexpress the human receptor for SARS-CoV-2 Spike protein S, ACE2, and investigated outcomes 72 hours later. Mice exhibited an acute decline in body weight during the first 48 hours following instillation, compared to saline-instilled controls. At 72 hours, bronchoalveolar lavage fluid demonstrated a dramatic increase in white blood cell content, particularly neutrophils, and marked proteinosis compared to controls. Histologic examination of lung tissue revealed hyaline membranes, alveolar septal thickening, and a large number of neutrophils in the interstitial and alveolar spaces of Spike protein S exposed mice. We propose that a single exposure of K18-hACE2 mice to SARS-CoV-2 Spike Protein S subunit S1 may represent a valid model of COVID-19, allow the study of the molecular mechanisms of SARS-CoV-2 induced lung injury and be useful in the investigation of potential new therapeutic approaches to the management of COVID-19 as well as future coronavirus-dependent respiratory diseases.