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In Silico Analyses Indicate a Lower Potency for Dimerization of TLR4/MD-2 as the Reason for the Lower Pathogenicity
1Syntacoll GmbH, 93342 Saal an der Donau, Germany.
Abstract:
The SARS-CoV-2 Omicron variants have replaced all earlier variants, due to increased infectivity and effective evasion from infection- and vaccination-induced neutralizing antibodies. Compared to earlier variants of concern (VoCs), the Omicron variants show high TMPRSS2-independent replication in the upper airway organs, but lower replication in the lungs and lower mortality rates. The shift in cellular tropism and towards lower pathogenicity of Omicron was hypothesized to correlate with a lower toll-like receptor (TLR) activation, although the underlying molecular mechanisms remained undefined. In silico analyses presented here indicate that the Omicron spike protein has a lower potency to induce dimerization of TLR4/MD-2 compared to wild type virus despite a comparable binding activity to TLR4. A model illustrating the molecular consequences of the different potencies of the Omicron spike protein vs. wild-type spike protein for TLR4 activation is presented. Further analyses indicate a clear tendency for decreasing TLR4 dimerization potential during SARS-CoV-2 evolution via Alpha to Gamma to Delta to Omicron variants.
Insights
Omicron variants evade immunity and infect airways more efficiently. Their spike protein shows reduced ability to activate Toll-like Receptor 4 (TLR4), potentially explaining lower pathogenicity compared to earlier SARS-CoV-2 strains.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- SARS-CoV-2 Omicron variants exhibit increased infectivity and immune evasion.
- Omicron shows distinct tropism, replicating more in upper airways and less in lungs than prior variants.
- Lower pathogenicity of Omicron suggests a link to reduced Toll-like Receptor (TLR) activation, but mechanisms are unclear.
Purpose of the Study:
- To investigate the molecular mechanisms behind Omicron's reduced pathogenicity.
- To determine if Omicron's spike protein has altered interactions with TLR4.
- To model the impact of spike protein variations on TLR4 activation during SARS-CoV-2 evolution.
Main Methods:
- In silico analyses of spike protein interactions with TLR4/MD-2 complex.
- Computational modeling of TLR4 dimerization.
- Comparative analysis of spike protein variants (Wild Type, Alpha, Gamma, Delta, Omicron).
Main Results:
- Omicron spike protein demonstrates lower potency in inducing TLR4/MD-2 dimerization compared to wild-type.
- Binding affinity of Omicron spike to TLR4 is comparable to wild-type.
- A trend of decreasing TLR4 dimerization potential was observed across SARS-CoV-2 variants from Alpha to Omicron.
Conclusions:
- Reduced TLR4 activation by Omicron spike protein may contribute to its lower pathogenicity.
- Spike protein evolution in SARS-CoV-2 correlates with diminished TLR4 dimerization capacity.
- These findings provide molecular insights into the changing tropism and virulence of SARS-CoV-2 variants.
