Objective The aim of the study was to develop a purification procedure on Pichia pastoris GS115/Fab expressing human anti-HBsAg Fab fragment. Methods Purity and yield ratio and conjugated activity of purified Fab fragment were analyzed with three purified ways of goat anti human Fab affinity chromatography and 14F7 monoclonal antibody affinity column, as well as Ion exchange Size exclusion column. Results 98% purity was reached through 14F7 monoclonal antibody column, and 95% purity was gained after goat anti human Fab fragment column. But yield ratio of the two affinity columns was low, being 35% and 55%, respectively. ForIon exchange Size exclusion column, purity and yield ratio of Fab fragment were very good, being 93.8% and 80% or more, respectively. Results of ELISA analysis showed that purified Fab fragment through three columns could bind to HBsAg specifically. Conclusion The purification process of recombinant anti-HBsAg Fab fragment was established. It lays a foundation for industrialization and clinical research of human anti-HBsAg Fab fragment.

AIM: To purify and refold the inclusion body of a human anti-HBsAg scFv with a 6?His tag, and to determine the affinity constant of the purified recombinant product.METHODS: Solubilizing in buffers containing urea or guanidine hydrochloride (GuHCl), the inclusion body was purified by IMAC, and then refolded by dialysis against urea or GuHCl, at the same time, Ni 2+ charged chelate column was utilized for in situ refolding. The affinity constant of the refolded scFv, polished by immune-affinity chromatography, was determined by non-competitive ELISA. RESULTS: The refolded scFv with highest specific bioactivity was produced by dialysis against GuHCl. Under this condition, the recovery of target protein reached (61.08?1 45)%. The affinity constant of the polished scFv was confirmed to be(2.30?0.32) ?10 7 L/mol. CONCLUSION: The inclusion body studied in this paper can be refolded efficiently under optimal dialysis condition in vitro . The antigen-binding property of this recombinant scFv is not affected by the purification tag fused to the N terminal of the protein.