E-Poster with pre-recorded video presentation Lorne Infection and Immunity 2021

SARS-CoV-2 infects but does not replicate in human macrophages and triggers pro-inflammatory and anti-viral cytokine responses. (#208)

Claudia J Stocks 1 , Keng Yih Chew 2 , Kate Schroder 1 , Kirsty Short 2 , Larisa I Labzin 1
  1. Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
  2. School of Chemistry and Molecular Biology, The University of Queensland, Brisbane, QLD, Australia

Severe inflammation is a hallmark of viral disease including COVID-19.  The cellular source of the initial and ongoing inflammation in COVID-19 is unknown. Macrophages, as sentinel innate immune cells, are specialised for detecting infection and releasing potent pro-inflammatory (IL-6, TNF, IL-1b) and anti-viral cytokines (e.g. IFNb). They are recruited to the lung in large numbers during severe COVID-19. However, whether these macrophages are directly infected with SARS-CoV-2 and whether they are the source of pathogenic inflammation is unclear. Primary human monocyte derived macrophages (HMDM) are a suitable in vitro model for investigating human macrophage inflammatory responses to viral infection. HMDM did not support SARS-CoV-2 replication, as determined by viral RNA accumulation and plaque assay at MOI 5 or MOI 0.5. In contrast, pandemic H1N1 (pH1N1) 2009 Influenza A Virus (IAV) infected and replicated in HMDM. While IAV induced strong pro-inflammatory (IL-6, TNF, IL-1b) and anti-viral (IFNb, CXCL10) responses over time, indicative of detection of replicating viral RNA, SARS-CoV-2 only induced macrophage pro-inflammatory and anti-viral responses at MOI 5. Therefore, HMDM sense incoming SARS-CoV-2 virions to trigger inflammation, unlike IAV where both incoming virions and replicating virus are sensed. Blocking macrophage specific sensing pathways to block inflammation may prevent pathologic inflammation in severe COVID-19 and IAV infections.