Transcriptomic Profiling of Neutrophils in SARS-CoV-2 Infected Mice

The severity of COVID-19 is linked to excessive inflammation. Neutrophils represent a critical arm of the innate immune response and are major mediators of inflammation, but their role in COVID-19 pathophysiology remains poorly understood. We conducted transcriptomic profiling of neutrophils obtained from SARS-CoV-2 infected mice, in comparison to non-infected healthy controls. In addition, we investigated the inflammasome formation potential in neutrophils from mice upon SARS-CoV-2 infection. Transcriptomic analysis of polymorphonuclear cells (PMNs), consisting mainly of mature neutrophils, revealed a striking type I interferon (IFN-I) gene signature in infected mice. Furthermore, IFN-I emerged as a priming stimulus for neutrophil inflammasomes, which was confirmed in a COVID-19 mouse model. These findings underscore the crucial role of neutrophil inflammasomes in driving inflammation during severe COVID-19. Altogether, these findings open promising avenues for targeted therapeutic interventions to mitigate the pathological processes associated with the disease. Overall design: Experimental procedures were approved by the Animal Experimental Board of Finland (license number ESAVI/28687/2020). Female BALB/c mice (7 to 8 weeks old) were transferred to a biosafety level-3 facility and acclimatized for 7 days. Mice were inoculated intranasally with SARS-CoV-2 MaVie strain or PBS (mock-infected control). Four separate experiments were conducted, involving various groups of mice that were infected, treated, and euthanized at different time points (2 and 4 days post-infection). Neutrophils were isolated from lung tissues for RNA sequencing. The sequencing libraries were prepared using the Illumina Stranded with RiboZero library preparation method, and sequencing was performed on the Illumina NextSeq platform. The study aims to understand the transcriptomic changes in neutrophils during SARS-CoV-2 infection and their role in inflammation associated with severe COVID-19.