EXPRESSION AND PURIFICATION OF AN EPSTEIN-BARR-VIRUS ENCODED 23-KDA PROTEIN AND CHARACTERIZATION OF ITS IMMUNOLOGICAL PROPERTIES

Serodiagnosis of Epstein-Barr virus (EBV) infection is currently based on the detection of antibodies to distinct EBV antigens by immunofluo rescence and enzyme-linked immunosorbent assay-based tests, or in part on the detection of heterophile antibodies by the Paul-Bunnell-Davids on heterophile assay. In the past few years, the specificity and the s ensitivity of serodiagnostic assay systems has been improved considera bly by the use of purified recombinant EBV antigens. Screening of EBV- positive sera for antigenic reactivities by immunoprecipitation with e xtracts of EBV-positive cells revealed a 23-kDa protein (p23) that was recognized by antibodies from all EBV carriers tested. Open reading f rame BLRF2 was identified as the coding region for this protein. After cloning and high-level expression of the BLRF2 open reading frame as DHFR fusion protein in Escherichia coli, the recombinant protein was p urified to near homogeneity with the help of continuous elution electr ophoresis. Sera from both EBV-positive and -negative donors were scree ned by immunoblot analysis and enzyme-linked immunosorbent assay for I gM and IgG antibodies against the EBV-encoded protein p23. Since anti- p23 antibodies were not detectable in 30 of 30 EBV-negative sera, and 294 of 302 EBV-positive sera had either IgM and/or IgG antibody respon ses to this protein, recombinant p23 seems to be a useful diagnostic m arker for EBV-infection.