Demonstration of real-time and accelerated stability of hepatitis E vaccine with a combination of different physicochemical and immunochemical methods.

Hepatitis E, which is caused by infection with hepatitis E virus (HEV), is a global health problem in both developed and developing countries. An efficacious hepatitis E vaccine was licensed (by China) in 2011 with a trade name of Hecolin®. The antigen contained in this vaccine is a truncated version of the sole capsid protein encoded by open reading frame 2, which is designated p239. In this study, the real-time and real-condition stability and accelerated stability of five lots of hepatitis E vaccine products at the end of the designated shelf life, were assessed by a well-established quality analysis platform. The protein integrity of p239 that was recovered from the vaccine lots was demonstrated using CE-SDS, LC-MS and MALDI-TOF MS. The particle characteristics of the recovered vaccine antigen were assessed by TEM and HPSEC. The immunogenicity of hepatitis E vaccines was assessed by a mouse potency assay, which is part of product release and stability testing. Several methods were employed to assess the antigenicity of vaccines with or without adjuvant dissolution. Specifically, the well-established methods of sandwich ELISA and surface plasma resonance (SPR)-based BIAcore were used with unique murine monoclonal antibodies. Most interesting, two 'dissolution-free' immunoassays were also used for in situ antigenicity assessment of the vaccines. In addition to the confirmation of vaccine stability at the end of expiry dating, i.e., after storage in recommended conditions (2-8 °C) for 36 months, the mouse potency assay and sandwich ELISA were used to assess the accelerated stability of prefilled syringes to demonstrate the feasibility of out-of-cold-chain storage. In summary, molecular and functional characterization confirmed the shelf life stability of the vaccine at the end of expiry dating and the feasibility of transporting the hepatitis E vaccine for a given period of time out of cold chains.