Exploring Highly Conserved Regions of SARS-CoV-2 Spike S2 Subunit as Targets for Fusion Inhibition Using Chimeric...

Area of Science:

• Virology
• Protein Engineering
• Immunology

Background:

• COVID-19 pandemic necessitates new strategies beyond vaccines due to waning immunity and emerging SARS-CoV-2 variants.
• The SARS-CoV-2 spike protein's S2 subunit, specifically the heptad repeat 1 (HR1) and heptad repeat 2 (HR2) regions, is critical for viral entry and a promising therapeutic target.
• Existing vaccine-induced or natural immunity against SARS-CoV-2 is challenged by viral evolution.

Purpose of the Study:

• To design and characterize chimeric proteins that mimic the S2 HR1 region's structure.
• To evaluate the binding affinity of these mimetic proteins to the HR2 region.
• To assess the potential of these proteins to inhibit SARS-CoV-2 infection in vitro.

Main Methods:

• Design of chimeric proteins imitating the trimeric coiled-coil conformation of the S2 HR1 region.
• Biophysical characterization of the designed proteins, including conformational analysis and oligomerization assessment.
• In vitro assays to determine binding affinity to HR2 peptides and SARS-CoV-2 inhibition efficacy.

Main Results:

• HR1 mimetic proteins exhibited conformational heterogeneity and formed oligomers.
• Full-length HR1 mimetic proteins demonstrated high affinity for HR2 peptides and significant SARS-CoV-2 inhibitory activity.
• Smaller HR1 subdomain mimetics showed reduced HR2 binding and lacked inhibitory effects.

Conclusions:

• Full-length HR1 mimetic proteins hold therapeutic potential for combating SARS-CoV-2 infection.
• Protein structural integrity and conformation are critical for effective HR2 binding and viral inhibition.
• These findings offer insights for developing robust protein-based strategies against SARS-CoV-2 and future viral threats.