Asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering for stability comparison of virus-like particles in different solution environments

The stabilities of two commercially available virus like particles, CHO-HBsAg expressed by Chinese hamster ovary (CHO) cells and Hans-HBsAg expressed by Hansenula polymorpha (Hans), were compared using AF4-MALLS under different treatment processes. The initial molecular weight and hydrodynamic diameter of CHO-HBsAg measured with AF4-MALLS were 4727 kDa and 29.4 nm, while those of Hans-HBsAg were 3039 kDa and 22.8 nm respectively. In salt solution of 2 M ammonium sulfate, the molecular weight and size of CHO-HBsAg had little change, and its antigenicity remained 95%, while those of Hans-HBsAg changed greatly, resulting in aggregation and 75% antigenicity loss. In freeze-thaw operations, Hans-HBsAg aggregated heavily. Most of the aggregates precipitated and the rest soluble aggregates reached 105-106 kDa in molecular weight. The antigenicity of Hans-HBsAg decreased to 26.9% after five freeze-thaw cycles. For CHO-HBsAg, there was no obvious aggregation in freeze-thaw, and the antigenicity retained above 98%. In heating process, Hans-HBsAg gradually aggregated to large particles with temperature and the antigenicity decreased to 10% when the temperature reached 80 °C. In contrast, CHO-HBsAg would not aggregate with temperature, remained 92% antigenicity at 80 °C. The study demonstrated that CHO-HBsAg appeared to be a superior vaccine antigen in term of particle stability and constant antigenicity, which are important in production, transportation and storage.