DETECTION OF HUMAN PARVOVIRUS-B19-SPECIFIC IGM AND IGG ANTIBODIES USING A RECOMBINANT VIRAL VP1 ANTIGEN EXPRESSED IN INSECT CELLS AND ESTIMATION OF TIME OF INFECTION BY TESTING FOR ANTIBODY AVIDITY

Sera from patients with symptoms of recent human parvovirus B19 (B19) infection were tested for B19-specific IgM in an immunofluorescence as say (IFA) using insect cells expressing B19 recombinant VPI coat prote in as an antigen. A highly significant correlation (P<0.001) was found between titres obtained in the IgM IFA and the units obtained in an I gM antibody-capture RIA using plasma derived native B19 antigen. An Ig G IFA using the recombinant antigen was performed on 57 sera and the a ntibody avidity determined. There was a highly significant correlation (P<0.001) between the relative amounts of low avidity B19-specific Ig G antibodies and time after onset of illness. This finding allows the detection of IgG to be used for diagnosing acute infection.