DEVELOPMENT OF AN IGM CAPTURE ASSAY FOR THE DIAGNOSIS OF B19 PARVOVIRUS INFECTION USING RECOMBINANT BACULOVIRUSES EXPRESSING VP1 OR VP2 ANTIGENS

Background: The clinical manifestations of human parvovirus B19 infect ion are often similar to those induced as the result of infection by o ther infectious agents such as rubella and some bacteria. Although dia gnosis of B19 infection is feasible by detection of specific antibodie s, the tests require viraemic serum as a source of antigen. This inevi tably leads to problems of reproducibility and dependence upon appropr iate high quality clinical material. Objectives: To develop a monoclon al antibody capture ELISA (MACEIA) for detecting anti-B19 IgM antibody in human sera, using recombinant baculoviruses expressing the B19 par vovirus VP1 and VP2 proteins and to compare this with MACEIA using a p lasma derived B19 antigen. Study design: Sera from 85 patients with pr oven B19 infection and the paired convalescent sera from 26 anti-B19 I gM-positive acute samples were examined for B19-specific IgM antibody by a monoclonal antibody capture assay that utilised recombinant bacul oviruses expressing B19 proteins in lieu of a plasma-derived B19 antig en. Control samples consisted of 24 anti-rubella IgM, 24 anti-EBV IgM and 102 negative sera from uninfected individuals. Results: Eighty-fou r of the 85 sera were anti-B19 IgM positive by MACEIA using recombinan t baculovirus derived B19 antigen and by indirect immunofluorescence t ests, whereas 79 were positive by MACEIA using plasma-derived antigen. Of the 26 convalescent samples which were positive as acute sera, 4 h ad become negative by 8 weeks post-infection. The expressed recombinan t baculovirus antigens had identical molecular weights to the VP1 (84 kDa) and VP2 (58 kDa) proteins of virus purified from human plasma. Re combinant baculovirus-derived VP1 antigen was as effective as VP2 part icles at detecting antibodies. Conclusions: Recombinant proteins VP1 a nd VP2, obtained from recombinant baculovirus-infected cell lysate, sh owed equal specificity to and higher sensitivity than, B19 virus purif ied from human plasma when used in MACEIA to detect B19-IgM antibody.