Heightened innate immune responses in the respiratory tract of COVID-19 2 patients

ABSTRACT

The outbreaks of 2019 novel coronavirus disease (COVID-19) caused by SARS-CoV44 2 infection has posed a severe threat to global public health. It is unclear how the human 45 immune system responds to this infection. Here, we used metatranscriptomic 46 sequencing to profile immune signatures in the bronchoalveolar lavage fluid of eight 47 COVID-19 cases. The expression of proinflammatory genes, especially chemokines, 48 was markedly elevated in COVID-19 cases compared to community-acquired 49 pneumonia patients and healthy controls,suggesting that SARS-CoV-2 infection causes 50 hypercytokinemia. Compared to SARS-CoV, which is thought to induce inadequate 51 interferon (IFN) responses, SARS-CoV-2 robustly triggered expression of numerous 52 IFN-inducible genes (ISGs). These ISGs exhibit immunopathogenic potential, with 53 overrepresentation of genes involved in inflammation. The transcriptome data was also 54 used to estimate immune cell populations, revealing increases in activated dendritic 55 cells and neutrophils. Collectively, these host responses to SARS-CoV-2 infection 3 56 could further our understanding of disease pathogenesis and point towards antiviral 57 strategies.