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Updated: Feb 16, 2026
Quantifying Human Norovirus Virus-like Particles Binding to Commensal Bacteria Using Flow Cytometry
Published on: April 29, 2020
Norovirus-like VP1 particles exhibit isolate dependent stability profiles
Ronja Pogan1, Carola Schneider, Rudolph Reimer
1Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.
Abstract:
Noroviruses are the main cause of viral gastroenteritis with new variants emerging frequently. There are three norovirus genogroups infecting humans. These genogroups are divided based on the sequence of their major capsid protein, which is able to form virus-like particles (VLPs) when expressed recombinantly. VLPs of the prototypical GI.1 Norwalk virus are known to disassemble into specific capsid protein oligomers upon alkaline treatment. Here, native mass spectrometry and electron microscopy on variants of GI.1 and of GII.17 were performed, revealing differences in terms of stability between these groups. Beyond that, these experiments indicate differences even between variants within a genotype. The capsid stability was monitored in different ammonium acetate solutions varying both in ionic strength and pH. The investigated GI.1 West Chester isolate showed comparable disassembly profiles to the previously studied GI.1 Norwalk virus isolate. However, differences were observed with the West Chester being more sensitive to alkaline pH. In stark contrast to that, capsids of the variant belonging to the currently prevalent genogroup GII were stable in all tested conditions. Both variants formed smaller capsid particles already at neutral pH. Certain amino acid substitutions in the S domain of West Chester relative to the Norwalk virus potentially result in the formation of these T = 1 capsids.
Insights
Norovirus virus-like particles (VLPs) show varied stability. GI.1 variants exhibit pH-dependent disassembly, while GII.17 capsids remain stable, offering insights into norovirus gastroenteritis control.
Area of Science:
- Virology
- Structural Biology
- Biochemistry
Background:
- Noroviruses are a leading cause of viral gastroenteritis, with frequent emergence of new variants.
- Human noroviruses are classified into three genogroups based on their major capsid protein sequences.
- Recombinant expression of capsid proteins forms virus-like particles (VLPs), useful for studying viral structure and stability.
Purpose of the Study:
- To investigate the stability differences of norovirus virus-like particles (VLPs) from different genogroups and variants.
- To understand the impact of pH and ionic strength on VLP disassembly.
- To identify potential structural determinants of capsid stability.
Main Methods:
- Native mass spectrometry was employed to analyze VLP structure and disassembly.
- Electron microscopy provided high-resolution structural insights.
- VLP stability was assessed across a range of pH and ionic strength conditions using ammonium acetate solutions.
Main Results:
- Significant differences in capsid stability were observed between norovirus genogroups (GI.1 vs. GII.17) and even between variants within the same genotype.
- GI.1.1 West Chester isolate showed increased sensitivity to alkaline pH compared to the prototypical GI.1 Norwalk virus.
- GII.17 capsids demonstrated remarkable stability under all tested conditions, forming smaller particles at neutral pH.
Conclusions:
- Norovirus VLP stability is highly dependent on the specific genogroup and even strain, with implications for viral persistence and transmission.
- Amino acid substitutions, particularly in the S domain, may influence capsid assembly and stability, potentially leading to the formation of T=1 capsids.
- Understanding these stability differences is crucial for developing effective strategies against norovirus gastroenteritis.
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