Functional diversity in GII.4 norovirus entry: HBGA binding and capsid clustering dynamics

Area of Science:

• Virology
• Cell Biology
• Gastroenterology

Background:

• Human noroviruses (HuNoVs), particularly GII.4 strains, are the primary cause of viral gastroenteritis globally.
• Current therapeutic options for HuNoV infections are limited, with no approved vaccines or antivirals available.

Purpose of the Study:

• To investigate whether the cell entry mechanism of the GII.4 Sydney 2012 strain is conserved across other GII.4 variants.
• To compare the early binding and entry processes of multiple GII.4 variants.

Main Methods:

• Utilized wild-type and mutant GII.4 virus-like particles (VLPs) for comparative analysis.
• Employed modified human intestinal enteroid cultures to study VLP-cell interactions.
• Investigated the role of specific VP1 residues (V333, R339) and lipid raft components in viral entry.

Main Results:

• Identified two distinct phenotypes among GII.4 variants: clustering and nonclustering.
• Clustering variants, including GII.4 Sydney, showed enhanced membrane wounding and endocytosis, dependent on histo-blood group antigen (HBGA) binding.
• Specific VP1 residues (V333, R339) were critical for capsid clustering and efficient cell entry, independent of HBGA binding itself.
• Viral entry was driven by lipid raft remodeling, regulated by cholesterol and ceramides, and independent of host protein glycosylation.

Conclusions:

• A dichotomy exists between clustering and nonclustering GII.4 variants, with clustering strains demonstrating superior entry competence.
• Understanding these strain-specific entry mechanisms provides insights into HuNoV pathogenesis.
• This research may aid in identifying cellular receptors and developing targeted therapeutics for norovirus infections.