Purification and characterization of hepatitis B virus surface antigen particles produced in Drosophila Schneider-2 cells

The small surface antigen of hepatitis B virus (HBV) was produced in Drosop hila melanogaster Schneider-2 (DS-2) cells transfected stably using an indu cible Drosophila metallothionein promoter. Selected clonal DS-2 cell-lines expressed and secreted large quantities of HBsAg particles consisting exclu sively of non-glycosylated 25 kDa proteins. HBsAg produced by DS-2 cells ha d physical and biochemical properties very similar to 22 nm particles deriv ed from the human hepatoma cell-line PLC/PRF/5. DS-2 cell-derived HBsAg par ticles were purified near homogeneity by a strategy based on protein concen tration, precipitation and ultracentrifugation. The resulting HBsAg product was < 98% pure. A single immunisation of BALB/c mice with both DS-2 and ye ast-cell derived purified HBsAg particles without adjuvants elicited a subs tantial humoral antibody and class-I restricted cytotoxic T lymphocyte (CTL ) response. Adsorbtion of HBsAg particles to aluminium hydroxide resulted i n increased levels of HBsAg-specific antibodies. However, CTLs were not eli cited by HBsAg/Alum combinations. Thus, stably transfected DS-2 cells provi de a useful source for the production of HBV subviral particles for diagnos tic and research purposes as well as for novel vaccine development. (C) 199 9 Elsevier Science B.V. All rights reserved.