Adeno-associated virus adsorption on different surfaces relevant to production of pre-clinical & clinical material

Since the concept of gene therapy was introduced in the late 1970s, recombinant Adeno-associated virus (AAV) vector has emerged as a leading drug platform for delivering treatment to patients. During the AAV production process, capsids get exposed to and interact with various surfaces including bioreactors, resins, tubing, and storage containers. These interactions potentially impact vector concentration due to surface adsorption. When evaluating drug product in both in vitro and in vivo studies, the concentration of the purified AAV vectors should be consistent. Maintaining vector concentration accuracy is critical for successful evaluation of pre-clinical and clinical-stage studies. Therefore, it is of interest to investigate the effect of contact layer adsorption on AAV concentration over time. To understand the potential effects of material surface on concentrations for two widely used serotypes, AAV8 and AAV9, this study evaluated the extent of product loss on ten commonly used contact materials: polypropylene, polystyrene, flint glass, borosilicate glass, crystal zenith, high-density polyethylene, polyethylene terephthalate glycol, polypropylene copolymer, polycarbonate, and silicon. In addition, the study examined the effect of a non-ionic copolymer surfactant, commonly used in process or in storage formulations, on adsorption. Samples and buffer controls for the two serotypes were stored in different materials in the presence and absence of the surfactant. Sample optical density (OD) measurements were used to calculate the changes in the total and in the percentage of empty capsids over time. Noticeable differences in adsorption were observed for the different serotypes and different contact layers over time when normalized to the contact area. Additionally, serotype and contact surface interactions had an impact on the percentage of empty capsids in the solution, and polypropylene showed the largest influence. Inclusion of surfactant had a variable effect depending on the surface and serotype.