Productive infection of primary human hepatocytes with SARS-CoV-2 induces antiviral and proinflammatory responses

We read with interest the article by Luxenburger and Thimme, summarising current knowledge about hepatic sequelae in the context of SARS-CoV-2 infection.1 As acute liver injury is observed in one-third of the patients with hospitalised COVID-192 3 and chronic liver disease is associated with higher mortality rates,4 a detailed understanding of hepatic susceptibility and dysfunction in the context of SARS-CoV-2 infection is of utmost importance. Previous studies have provided evidence of hepatic infection,5-7 however, the molecular mechanisms underlying acute liver injury associated with SARS-CoV-2 infection are not well understood. Here we show that primary human hepatocytes (PHH) can be productively infected with SARS-CoV-2. Donor-specific production kinetics were observed, with de novo viral secretion from PHH increasing in a time-dependent manner for four out of six donors (figure 1A). To explore virus replication and host gene dysregulation in parallel, Illumina sequencing of time point-matched infected and uninfected PHH was performed, followed by mapping to host and virus scaffolds. Increases in viral genome coverage over time corresponded to increasing rates of secreted virus (figure 1B). On the host side, detectable messenger RNA (mRNA) expression of known or suspected SARS-CoV-2 entry factors was observed for all PHH donors (figure 1C). Despite robust viral replication, host transcriptional responses were delayed until 72 hours post infection (hpi) and correlated with specific type III and interferon-β (IFN) induction in three donors (D1-3; termed reactive), while two donors remained unreactive, even though low levels of viral replication were observed (D4-5; figure 1C). These observations imply a viral replication threshold must be crossed to trigger robust host responses in PHH. Interestingly, one donor (D6; termed pre-activated) possessed abundant IFN-encoding transcripts independent of infection status or sampling time, resulting in high baseline interferon stimulated gene expression which prevented productive infection (figure 1A-C). Of note, similar to reactive donors at 72 hpi, IFN production in the pre-activated donor was also limited to IFN-β and IFNL1-4, suggesting hepatocytes are unable to produce additional IFN types/subtypes at meaningful levels. © Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.