Mechanistic Insights into Poloxamer 188-Mediated Stabilization of AAV8 Capsids Using Coarse-Grained Molecular Dynamics.

Purpose

Aggregation of adeno-associated virus (AAV) during manufacturing and storage remains a challenge in gene therapy formulation. This study evaluates how varying Poloxamer188 (P188) concentrations affect the structural stability and aggregation behavior of two full AAV8 capsids.

Methods

Coarse-grained molecular dynamics simulations of AAV8 capsids with P188 were performed for 4000 ns at 300 K. Center-of-mass (COM) separation, residue-level contacts, surface coverage, van der Waals interactions, radius of gyration (Rg), relative shape anisotropy (k2), and simulation snapshots were analyzed.

Results

Persistent capsid association was not observed in systems containing 10 or 24 P188 molecules (0.15% and 0.35% w/v), whereas systems containing 2 or 5 P188 molecules (0.03% and 0.07% w/v) showed delayed association relative to the surfactant-free system. Capsid surface coverage increased with P188 loading. Polyethylene oxide (EO) segments associated with the capsid surface early and persistently, followed by gradual polypropylene oxide (PO) engagement, indicating a preferential/sequential interaction mechanism. Higher P188 loadings showed negligible van der Waals attraction, consistent with steric shielding. Chain-resolved Rg and k2 profiles indicated initial conformational rearrangement followed by stabilization of distinct surface-associated P188 conformations, with varying spatial extension and shape anisotropy.

Conclusions

These findings provide mechanistic insight into the stabilizing effect of P188 on AAV via concentration-dependent surface coverage and steric hindrance that minimize capsid-capsid interactions associated with aggregation. The reported concentrations are nominal finite-box values defined by discrete P188 molecule counts and represent comparative simulation conditions rather than experimentally derived formulation thresholds. These findings provide a molecular basis for understanding P188-mediated AAV stabilization and for guiding formulation optimization.