Modelling severe COVID-19 in TLR3-mutated hiPSCs-derived lung organoids.

Area of Science:

• Immunology
• Genetics
• Virology
• Stem Cell Biology

Background:

• Clinical COVID-19 outcomes are influenced by host genetic factors, including inborn errors of immunity.
• Toll-like receptor 3 (TLR3) plays a crucial role in innate immunity and viral recognition.

Purpose of the Study:

• To investigate the functional impact of a heterozygous nonsense mutation in the TLR3 gene on host-virus interactions in a patient-derived model.
• To establish and utilize human lung organoids (hLORGs) derived from induced pluripotent stem cells (hiPSCs) for studying COVID-19 pathogenesis.

Main Methods:

• Generation of hiPSCs from a patient with a TLR3 mutation (p.Trp769*).
• Differentiation of hiPSCs into hLORGs.
• Infection of hLORGs with pseudotyped and live SARS-CoV-2.
• Analysis using RNA-sequencing (RNA-Seq) and quantitative polymerase chain reaction (qPCR).

Main Results:

• TLR3-mutated hLORGs exhibited reduced basal expression of TLR3 and downstream signaling genes.
• Infection led to significant upregulation of fibrinogen genes (FGA, FGG) in TLR3-mutated hLORGs, correlating with severe COVID-19.
• TLR3 expression remained inducible upon viral infection, despite the loss-of-function mutation.

Conclusions:

• Patient-derived hLORGs accurately recapitulate the pathophysiological features observed in the patient.
• This model serves as a valuable platform for investigating host-SARS-CoV-2 interactions.
• The model facilitates the testing of targeted therapies for individuals with genetic predispositions to severe COVID-19.