Age-dependent differences in SARS-CoV-2 entry-factor expression and innate immune responses between pediatric and adult liver organoids

This study used normal liver organoids derived from paediatric and adult donors to compare the infectivity and host immune responses to SARS CoV 2 wild type (WT) and Omicron (BA.1/BA.2) variants, aiming to explore the possible role of SARS CoV 2 in paediatric acute hepatitis.

Methods

Liver organoids were established from adjacent normal tissues of three adult patients with hepatocellular carcinoma and three paediatric patients with hepatoblastoma, collected between February and December 2022. Organoids were infected with SARS-CoV 2 WT, Omicron BA.1 or BA.2 at a multiplicity of infection (MOI) of 0.1. Viral loads in supernatants and intracellular viral RNA were quantified by RT qPCR at 24 and 48 hours post infection (hpi).

At 48 hpi, RNA seq was performed to profile transcriptomic changes and pathway enrichment. Additionally, single cell RNA seq data were used to compare baseline expression of SARS CoV 2 entry associated genes between paediatric and adult hepatocytes. Results Paediatric hepatocytes showed significantly higher basal expression of entry related genes, including ASGR1, KREMEN1, CTSB, CTSL, and VIM, than adult cells.

Both paediatric and adult liver organoids were permissive to WT and Omicron, but Omicron BA.1/BA.2 yielded higher intracellular viral RNA levels than WT, with notably higher intracellular viral RNA burden in paediatric organoids. RNA seq revealed that Omicron infection induced a more robust innate immune and inflammatory response in paediatric organoids—encompassing interferon signalling, RIG I like receptor and Toll like receptor pathways—alongside relative downregulation of adaptive immune-pathway transcripts.

In adult organoids, transcriptomic divergence between Omicron and WT was less pronounced. Compared with adults, Omicron infected paediatric organoids upregulated interferon γ signalling and innate immune system components, while downregulating adaptive immune-pathway transcripts; key receptors such as ACE2 and TMPRSS4 remained consistently higher in paediatric organoids across all viral strains.