COMPARISON BETWEEN HEPATITIS-B SURFACE-ANTIGEN (HBSAG) PARTICLES DERIVED FROM MAMMALIAN-CELLS (CHO) AND YEAST-CELLS (HANSENULA-POLYMORPHA) - COMPOSITION, STRUCTURE AND IMMUNOGENICITY

The composition, structure and immunogenicity of hepatitis B surface a ntigen (HBsAg) particles derived from Chinese hamster ovary (CHO) cell s and from cells of the yeast Hansenula polymorpha were compared. The particles were similar in size distribution (mean 20-33 nm), in shape (spherical), in gross composition (protein to lipid weight ratio of 60 :40), and in types of lipids (phospholipids much greater than sterols= sterol esters=triacyl-glycerols). Differences related to genetic engin eering and type of host cells were found in peptide and lipid composit ions. CHO-HBsAg has three peptides. S, M and L, each in two forms of g lycosylation, while the Hansenula-HBsAg has only the nonglycosylated S peptide. The electrical surface potential at the lipid/water interfac e of HBsAg derived from Hansenula is more negative than that of HBsAg derived from CHO, which was close to neutrality. Although the numbers of cysteine residues (all in the S peptides) are identical (14), 11 of them are free thiols in the CHO-HBsAg, compared with three to four in the Hansenula-HBsAg. The fact that 85% of the phospholipids are hydro lyzed by phospholipase C and that all the aminophospholipids react wit h trinitrobenzenesulfate suggests that the particles derived from both cell types are either leaky vesicles or have a lipoprotein-like struc ture. Subcutaneous injection into mice of fluorescein-isothiocyanate-l abeled HBsAg particles from both sources resulted in their accumulatio n in the marginal sinus of lymph nodes. The humoral responses to subcu taneous injection into mice of CHO- and Hansenula-HBsAg were similar; however, the cytotoxic T lymphocyte response to CHO-HBsAg was lower. ( C) 1997 Elsevier Science Ltd.