Virus-like particles demonstrated by freeze-squeeze technique in acute-phase serum of patients with HBAg-negative hepatitis.

Electromicroscopy of fluid, squeezed from excised and frozen precipitation lines obtained by immunoelectrophoresis in agarose gels of acute-phase sera from patients with HBAg-negative hepatitis, revealed particles of 22, 27, and 31-41 nm. These precipitates and particles were not present in normal human sera and disappeared from the sera of the patients after recovery. These particles were still demonstrable after two years' storage at -20 degrees C.