Development of an IgM capture assay for the diagnosis of B19 parvovirus infection using recombinant baculoviruses expressing VP1 or VP2 antigens

Abstract

Background: The clinical manifestations of human parvovirus B19 infection are often similar to those induced as the result of infection by other infectious agents such as rubella and some bacteria. Although diagnosis of B19 infection is feasible by detection of specific antibodies, the tests require viraemic serum as a source of antigen. This inevitably leads to problems of reproducibility and dependence upon appropriate high quality clinical material. Objectives: To develop a monoclonal antibody capture ELISA (MACEIA) for detecting anti-B19 IgM antibody in human sera, using recombinant baculoviruses expressing the B19 parvovirus VP1 and VP2 proteins and to compare this with MACEIA using a plasma derived B19 antigen. Study design: Sera from 85 patients with proven B19 infection and the paired convalescent sera from 26 anti-B19 IgM-positive acute samples were examined for B19-specific IgM antibody by a monoclonal antibody capture assay that utilised recombinant baculoviruses expressing B19 proteins in lieu of a plasma-derived B19 antigen. Control samples consisted of 24 anti-rubella IgM, 24 anti-EBV IgM and 102 negative sera from uninfected individuals. Results: Eighty-four of the 85 sera were anti-B19 IgM positive by MACEIA using recombinant baculovirus derived B19 antigen and by indirect immunofluorescence tests, whereas 79 were positive by MACEIA using plasma-derived antigen. Of the 26 convalescent samples which were positive as acute sera, 4 had become negative by 8 weeks post-infection. The expressed recombinant baculovirus antigens had identical molecular weights to the VP1 (84 kDa) and VP2 (58 kDa) proteins of virus purified from human plasma. Recombinant baculovirus-derived VP1 antigen was as effective as VP2 particles at detecting antibodies. Conclusions: Recombinant proteins VP1 and VP2, obtained from recombinant baculovirus-infected cell lysate, showed equal specificity to and higher sensitivity than, B19 virus purified from human plasma when used in MACEIA to detect B19-IgM antibody.