USE OF RECOMBINANT HUMAN PARVOVIRUS-B19 ANTIGENS IN SEROLOGICAL ASSAYS

Aims-To compare the sensitivity, specificity, and practicality of reco mbinant proteins in serological tests for the detection of human parvo virus B19 IgG and IgM. Method-Indirect enzyme linked immunosorbent ass ays using B19 structural proteins expressed in Escherichia coli were d eveloped for the detection of B19 specific IgG and IgM (rELISA-G and r ELISA-M). Cells infected with baculovirus expressing B19 structural pr oteins were also used in an indirect immunofluorescence assay for IgG and IgM antibodies (IFA-G and IFA-M). Antibody capture radioimmunoassa ys for IgG and IgM (GACRIA and MACRIA) were used as comparative assays .Results-Twenty nine pools of intravenous immunoglobulin were clearly positive for B19 IgG by rELISA-G and contained low IgG titres by GACRI A. From 113 samples tested by all methods, sensitivities of 92% (77/84 ) and 97% (68/70) were obtained for ELISA and immunofluorescence, resp ectively, when compared with GACRIA. One hundred and sixteen samples f rom patients presenting with rash or arthralgia were compared by MACRI A, rELISA-M, and IFA-M. Sensitivities of both recombinant tests were m ore than 95%. Despite pre-treatment to remove IgG or rheumatoid factor , false positive results were a problem in the rELISA-M but were not s een with the IFA-M. Conclusions-The limited supply of native antigen h as severely restricted the wide application of serology for parvovirus B19. The use of recombinant antigens permitted the introduction of lo cal screening tests which had many advantages, including quicker resul ts and relief of the burden on the Reference Laboratory. The use of rE LISA-M for sensitivity and IFA-M for specificity and confirmation prov ed a useful and practical combination for diagnosis of recent infectio n with B19, and rELISA-G allowed the immune response to be determined in selected populations.