Epitope type-specific IgG responses to capsid proteins VP1 and VP2 of human parvovirus B19

Temporal reactivities of IgG towards native and linear antigenic determinants in assembled capsids or isolated structural proteins of human parvovirus B19 were measured by an epitope type-specific IgG EIA and by immunoblots. Antigens used were baculovirus-expressed B19 capsids composed of the proteins VP1 and VP2 in their native proportion, VP2 alone, or a prokaryotic VP1 fusion protein. Follow-up sera after primary infection were compared with samples from previously infected persons. The IgG responses during acute and early convalescence phases were directed towards both conformational and linear epitopes of VP2. The antibodies against the linear VP2 epitopes disappeared abruptly within 6 months; however, the conformational VP2 antibodies persisted. The epitope type-specific IgG reactivity of VP1 was strikingly different from that of VP2. On the basis of these results, two novel tests were developed for patient diagnosis. Both tests are suitable for verifying the time of human parvovirus infection.