Putative receptor binding sites on alphaviruses as visualized by cryoelectron microscopy

Area of Science:

• Virology
• Structural Biology
• Immunology

Background:

• Sindbis virus and Ross River virus are alphaviruses that cause significant human disease.
• Understanding viral entry mechanisms is critical for developing antiviral therapies.
• The E2 glycoprotein is a key component of the viral envelope spike protein involved in host cell interaction.

Purpose of the Study:

• To determine the structural basis of antibody recognition on Sindbis virus and Ross River virus.
• To investigate the role of the E2 glycoprotein in viral cell-receptor interactions.

Main Methods:

• Cryoelectron microscopy was used to determine the structures of Sindbis virus and Ross River virus.
• Complexes of these viruses with Fab fragments from specific monoclonal antibodies were analyzed.
• Structural analysis focused on the binding sites of antibodies on the viral envelope spike proteins.

Main Results:

• The structures of both viruses complexed with Fab fragments were resolved.
• Antibodies were found to bind to epitopes on the E2 glycoprotein located at the outermost tip of the trimeric envelope spike.
• These binding regions are implicated in cell-receptor recognition for both viruses.

Conclusions:

• The outermost tip of the Sindbis virus and Ross River virus envelope spike is composed of the E2 glycoprotein.
• This E2-rich region is directly involved in the recognition of cellular receptors, mediating viral entry.
• Structural insights into antibody binding provide a foundation for targeted antiviral drug design.