Detection of antibodies to the nonstructural 3C proteinase of hepatitis A virus

Hepatitis A virus (HAV) infection can stimulate the production of antibodies to structural and nonstructural proteins of the virus. However, vaccination with an inactivated vaccine produces antibodies exclusively to the structural proteins. Current diagnostic assays, such as the Abbott HAVAB test, used to determine exposure to HAV detect antibodies only to the structural proteins and as a result are not able to distinguish between a natural infection and vaccination with an inactivated virus. Therefore, an ELISA was developed that is specific for antibodies to the nonstructural protein 3C of HAV and thus serves to document the occurrence of viral replication. Antibodies to the proteinase were not detected by this assay in serum from HAVAB-seropositive primates that were immunized with inactivated HAV. However, antibodies to the proteinase were detected in the serum of all primates experimentally infected with virulent HAV and in the serum of naturally infected humans.