Characterization of the large size aggregation of Hepatitis B virus surface antigen (HBsAg) formed in ultrafiltration process

Abstract

This investigation focused on the structure change of Hepatitis B virus surface antigen (HBsAg) in the process of ultrafiltration (UF). Based on the assay of high performance size exclusion chromatography combining with on-line multi-angle laser light scattering (HPSEC-MALLS) and enzyme-linked immunosorbent assay (ELISA), the HBsAg assemblies were found to aggregate into large-size HBsAg aggregation with only about 20% HBsAg activity of the normal HBsAg assembly. The secondary structure of large size HBsAg aggregation was monitored by circular dichroism spectroscopy (CD) and demonstrated that the content of greek small letter alpha-helix in HBsAg decreased from 48.2% to 34.4% and the content of γ-turn increased from 29.6% to 38.7% due to aggregation. The lipid structure of large size HBsAg aggregation was also changed markedly by the assay of infrared spectroscopy (IR) at the wavenumber 1750 cm−1 which is corresponding to ester acyl.