Virus-like antigen associated with hepatitis A: investigations in children's acute hepatitis.

Stool specimens, collected from 8 children with viral hepatitis [5 of type A, presumably, and 3 of type B (HBsAg-positive)] during the acute phase, were examined in the electron microscope. The presence of 27-nm virus-like particles, aggregated by the convalescent serum of a chimpanzee infected with MS-1 and not by the serum of the same animal drawn before infection, was detected by immune electron microscopy (IEM) in the stools of 3 out of the 5 children with suspected hepatitis A. The virus-like particles (HA-Ag) present in the stools were aggregated by the serum drawn from the corresponding subject during convalescence and not by that obtained in the acute phase of the disease. Employing as antigen a stool particle preparation purified by isopycnic banding in cesium cloride, it was pointed out that, in all 5 children with suspected hepatitis A, antibodies capable to cause the aggregation of HA-Ag particles, appeared. Anti-HA antibodies turned out to be present also in three lots of commercial immunoglobulins. In the three subjects with type B hepatitis (HBsAg-positive) neither virus-like particles with a 27-nm diameter were observed, nor anti-HA antibodies appeared in the convalescent serum.