Polysorbates and poloxamer rescue filter-induced serotype-dependent loss of AAVs

Adeno-associated viruses (AAVs) are the leading viral vector for in-vivo gene therapy, and their use is expected to grow rapidly in the next decade. While AAVs are promising tools for treating many genetic diseases, vectors are vulnerable to adsorptive losses to surfaces due to the low concentrations (10-100 μg/mL) during manufacturing, storage, and administration. Here, we examined the filter-induced loss of two AAV serotypes of Clade E and Clade C as a function of the filter type (materials of composition such as polyvinylidene (PVDF), polyethersulfone (PES), and nylon), pore size (0.22 vs 0.45 μm), pH and ionic strength of the formulation, and hydrophobicity and ionic charge of the AAVs. Our results show that both the AAV serotype and the filter used result in varied amounts of adsorptive losses. Increased hydrophobicity of the AAV or the filter resulted in increased levels of adsorption. Altering formulation pH from 5 - 8 or ionic strength from 50 mM - 180 mM NaCl did not have a significant impact on adsorption loss. Additionally, no change in adsorptive loss was observed with an increase in the filter pore size. Three surfactants (polysorbate 20 (PS20), polysorbate 80 (PS80), and poloxamer 188 (P188)) are observed to rescue the filter-dependent loss of AAVs, but to different minimum concentrations. P188 was found to be the most efficient in the case of nylon filters, whereas PS20 is the most efficient with PES filters. A comparison of empty vs. full capsids shows that empty capsids can be used to optimize formulation parameters for full capsids. This study highlights the importance of surfactants in mitigating filter-dependent surface-induced losses observed during AAV manufacturing processes.