Molecular Assembly and Stability of Human Hepatitis B Virus Surface Antigen Vaccine

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Vaccines superior to the conventional ones can now be produced in principle using gene engineering technique. Human hepatitis B virus surface antigen vaccine derived from yeast(y-HBsAg vaccine)is, however, the first and only successful outcome of the introduction of the engineering technique into vaccine production. Its efficacy is believed to be derived from the particular nature and high stability of the assembly composed mainly of protein polypeptides and lipids. The present research project was motivated from our belief that the mode of assembly of the constituents and the source of the stability must be understood to provide basic knowledge hopefully leading to production other efficient vaccines through the approach.The y-HBsAg vaccine particles were found to be spherical, and homogeneous with respect to their size having radius of about 19 nm as judged from dynamic light scattering, small-angle X-ray scattering and electron microscopy. No regular structure was detected in the vaccine particle by small-angle X-ray scattering. The vaccine particle was eluted from a TSK-Gel G600OPW column as a symmetrical peak. Monitoring of the elution gave molar mass estimate of 5, 040 kg/mol for the vaccine particle of the target in the present study of which constituent polypeptide has 9 additional amino acid residues in the N-terminal side compared to the polypeptide of the virus surface antigen. The molar mass of the vaccine particle consisted of the latter polypeptide was estimated to be 4, 640 kg/ mol. The vaccine particle was stable against heating up to 8OﾟC. The constituent polypeptide also showed stability against heating in the presence of SDS. Isoelectric point of the particle was estimated to be 4.0 to 4.2 by electrophoretic light scattering in free solution. It is hoped that these results and approaches can play a role of guidepost for future characterization of vaccine particles expected to be developed in near future using gene engineering technique.