Combination of Epstein-Barr virus scaffold (BdRF1/VCA-p40) and small capsid protein (BFRF3/VCA-p18) into a single molecule for improved serodiagnosis of acute and malignant EBV-driven disease.

Current single Epstein-Barr virus (EBV) markers fail to reach 100% sensitivity for serodiagnosis of acute and malignant diseases associated with EBV infection. Previous study had identified immunodominant epitopes of VCA-p40 and VCA-p18, and indicated that these two VCA antigens may have diagnostic value for EBV-related diseases. A recombinant protein of the full-length BdRF1 fused to the immunodominant domain of BFRF3 as 6-his tagged protein in Escherichia coli was developed. The recombinant protein was extracted in 8M urea solution and purified by metal-affinity chromatography yielding a 55 kDa product (VCA-p40+18). VCA-p40+18 blot-strips examined for IgM reactivity in infectious mononucleosis samples yielded 100% sensitivity and specificity, with improved reactivity compared with IgM/VCA-p18-ELISAs. A recent study described a synthetic peptide-based IgA/[EBNA1+VCA-p18]-ELISA (IgA/EBV-ELISA), with a sensitivity of 90% for diagnosing nasopharyngeal carcinoma. Immunoblot analysis of biopsy-confirmed nasopharyngeal carcinoma cases with low or negative IgA/EBV-ELISA showed 100% IgG reactivity to VCA-p40 and VCA-p18 proteins. Evaluation of VCA-p40+18 as an additional marker for screening and diagnosis of nasopharyngeal carcinoma was carried out. The data showed positive IgA/VCA-p40+18 reactivity by ELISA for 63.6% (14 of 22) nasopharyngeal carcinoma samples that were missed by peptide-based IgA/EBV-ELISA, suggested VCA-p40+18 as an improved marker for nasopharyngeal carcinoma serodiagnosis. The VCA-p40+18 may be combined with an EBNA1 synthetic peptide as an antigen mixture in one or separate IgA ELISA for improved nasopharyngeal carcinoma serodiagnosis. Copyright (c) 2010 Elsevier B.V. All rights reserved.