Vaccine antigens are usually available only as dilute solutions, which are difficult to formulate into various novel delivery systems, which often require highly concentrated antigens. To address this problem, we have utilized tangential flow filtration (TFF), a simple and scalable process to prepare highly concentrated vaccine antigens. Here, we describe the optimization of TFF to concentrate hemagglutinin (HA) of egg-derived influenza antigens, from 2008 to 2009 seasonal vaccine, to concentrations up to 28 mg/mL. Concentrated antigen was evaluated by single radial immunodiffusion and reversed-phase high-performance liquid chromatographic analysis for the estimation of the HA content and a range of assays including size exclusion, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and bicinchoninic acid assay for protein characterization. In addition, the concentrated antigens retained their immunogenicity, confirmed by the induction of immune responses comparable to that of unprocessed antigen in a mouse model. The liquid concentrates were stable for up to 4 weeks, which could allow subsequent formulation into novel delivery technologies. Hence, we have used influenza HA to demonstrate that the fast, robust, and scalable approach of TFF can be used to concentrate antigens for use in novel delivery approaches. Moreover, the concentration process could be applicable for a variety of antigens and a wide range of novel vaccine delivery applications.
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