Polysialosides Outperform Sulfated Analogs for Binding with SARS-CoV-2.

Area of Science:

• Biochemistry
• Virology
• Materials Science

Background:

• Polysialosides and polysulfates are known to interact with the SARS-CoV-2 spike protein's receptor binding domain (RBD).
• A detailed comparison of their binding affinities and synergistic antiviral effects is lacking.

Purpose of the Study:

• To synthesize and characterize polysialosides for their binding affinities to SARS-CoV-2 spike proteins.
• To investigate the role of functional groups (sialo, sulfo, carboxyl) in binding interactions.
• To evaluate the antiviral efficacy of potent polysialoside binders against SARS-CoV-2 replication.

Main Methods:

• Synthesis of dendritic polyglycerol-based polysialosides, polysulfates, and polycarboxylates.
• Microscale thermophoresis to determine binding affinities (dissociation constant, K_d) to spike proteins and virus particles.
• Explicit-solvent all-atom molecular dynamics simulations and ensemble docking studies.
• In vitro antiviral assays to measure inhibition of SARS-CoV-2 replication.

Main Results:

• Polysialosides dPG₅₀₀SA_0.55 and dPG₅₀₀SA_0.25 exhibited nanomolar binding affinities (K_d = 4.78 nm and 10.85 nm, respectively), binding ≈500 times stronger than polysulfated analogs.
• The presence of sulfate groups in heteromultivalent compounds weakened binding, while polycarboxylated analogs showed no binding.
• Molecular dynamics and docking revealed stronger interactions of sialosides with the SARS-CoV-2 RBD compared to sulfates.
• The most affine binder, dPG₅₀₀SA_0.55, inhibited SARS-CoV-2 (WT, D614G) replication by up to 98.6% at 0.5 µm.

Conclusions:

• Sialoside interactions with the SARS-CoV-2 RBD are stronger than sulfate interactions.
• Dendritic polyglycerol-based polysialosides are potent inhibitors of SARS-CoV-2 replication.
• These findings identify polysialosides as promising candidates for antiviral therapies against SARS-CoV-2.