Eukaryotic expression of recombinant human centromere autoantigen and its use in a novel ELISA for diagnosis of CREST syndrome.

The cDNA coding for the human full-length centromere protein B (CENP-B) was isolated from a liver cDNA library by oligonucleotide screening and extended at the 5' and 3' ends by linker addition. The cDNA was inserted into a modified baculovirus transfer vector which mediated high-level expression of recombinant human CENP-B with a histidine-hexapeptide as affinity ligand at its N-terminus in infected Spodoptera frugiperda (Sf9) insect cells. Based on the histidine-hexapeptide moiety, the recombinant CENP-B was purified to homogeneity by single-step affinity chromatography using metal chelating matrix. An ELISA established with the eukaryotically expressed and purified recombinant human full-length CENP-B demonstrated its excellent specificity, sensitivity and reproducibility for the measurement of autoantibodies directed to the human CENP-B (ACA-B) representing a diagnostic marker for CREST syndrome, an autoimmune rheumatic disease. In this study, all pathological sera from patients (n = 80) with serologically and clinically diagnosed CREST were positively assayed for ACA-B, whereas 399 sera obtained from blood donors and 82 out of 84 sera from patients with autoimmune rheumatic disorders which were unrelated to CREST were negative in the ELISA.