Fine structure of hepatitis B virus surface antigen produced by recombinant yeast: comparison with HBsAg of human origin

The ultrastructure of hepatitis B virus surface antigen (HBsAg) particles produced by recombinant yeast cells was examined using high-resolution negative staining, and ice embedding, electron microscopy. With negative staining, the HBsAg particles were spherical to slightly ovoid with a mean diameter of 27.5 nm and consisted of many subunits each 4 nm in diameter. Subunits were marked with a minute central pore. With ice embedding, particles were mostly spherical to ovoid, with a mean diameter of 23.7 nm and a 7–8 nm thick cortex surrounding an electron translucent core. Human HBsAg particles, examined using the same methods, were smaller, apparently because of molecular differences in polypeptide structure.