Binding activity of HBsAg particles from chronic HBsAg carriers to polystyrene beads coated with polymerized human serum albumin: diagnostic relevance of the assay.

The binding activity of HBsAg particles to polystyrene beads coated with polymerized human serum albumin (pHSA) was studied by radioimmunoassay in 48 patients with chronic HBsAg carrier state. The pHSA assay was positive in all 16 HBeAg-positive patients and in 22 HBeAg-negative HBsAg carriers with chronic hepatitis. Asymptomatic, "healthy" HBsAg carriers did not react in the pHSA assay. Mean binding activity was significantly higher in the HBeAg-positive group (P/N ratio 39.3) than in HBeAg-negative carriers with chronic hepatitis in various stages (P/N ratio 19.2). Fractionation of five representative HBeAg-positive sera by density gradient ultracentrifugation in cesium chloride yielded three peaks of HBsAg particles at 1.28, 1.22 and. 1.18 g/ml. The first HBsAg peak contained Dane particles and exhibited strong reactivity in pHSA assay. The second and third peaks, both consisting of 22 nm particles, reacted differently in pHSA assay. While about half of the HBsAg particles in the second peak were bound, reaction in the third HBsAg peak was predominantly negative. Intrahepatic HBsAg was detectable with the immunofluorescence technique in 19 of 22 HBsAg carriers. HBcAg was found in seven of 10 HBeAg-positive cases and in three of 16 HBeAg-negative patients with chronic hepatitis. The diagnostic value of pHSA assay might be seen in differentiation between HBeAg-negative chronic HBsAg carriers with liver disease or "healthy" carrier state.