Characterization of pre-s gene products in hepatitis B surface antigen.

The 20-nm particles of hepatitis B surface antigen (HBsAg) contain two minor glycoproteins, GP33 and GP36, which are probably encoded at their 55 N-terminal amino acids by the pre-s region of the viral DNA. Their 226 C-terminal amino acids are identical to the major protein P24. The 20-nm particles contained more GP33 and GP36 when the blood had a high HBsAg concentration. They were also found in relatively high amounts in HBsAg filaments and virions. Treatment with glycosidase and trypsin showed that the mannose rich glycan and the N-terminal portion of GP33 and GP36 were exposed at the surface of the HBsAg particles. The 20-nm particles containing much GP33 and GP36 did not induce higher anti-HBs titers in guinea pigs than those particles almost devoid of them.