Quantitation of antibody to hepatitis A antigen by immune electron microscopy

A set of precipitin reactions was performed by immune electron microscopy (IEM) with hepatitis A antigen (HA Ag) and varying quantities of antibody to HA A q (anti-HA). Serial dilution of anti-HA resulted in progressive diminution in IEM antibody rating. These data, together with a highly significant correlation between IEM ratings and immune adherence hemagglutination (IAHA) titers on 92 coded serum samples, confirm that quantitative serology development can be performed by IEM. To demonstrate the different kinetics of antibody development by IEM and IAHA, we used both techniques to test for anti-HA in longitudinally collected sera from a chimpanzee experimentally infected with hepatitis A virus. Detection of anti-HA was possible by IEM during acute hepatitis, but IAHA anti-HA was not observed until approximately 4 weeks later. Six weeks after acute illness, IEM ratings reached a plateau beyond which IAHA titers continued to rise gradually. Peak titers were achieved 11 months after inoculation.