Enzyme linked immunosorbent assay using recombinant HuD-autoantigen for serodiagnosis of paraneoplastic neurological syndromes

Abstract

The aim of this study was to evaluate the suitability of an ELISA employing purified recombinant HuD antigen, for detection of specific anti-HuD antibodies in sera and cerebrospinal fluid (CSF) from patients with paraneoplastic neurological syndromes (PNS). The cutoff for optical density readings was estimated by testing of 145 sera from healthy subjects. Sera from 17 patients with paraneoplastic neurological syndromes (PNS) and evidence of a clear anti-Hu band pattern in an immunoblot employing human cerebellar crude extract as antigen were tested. All 17 sera from patients with PNS revealed a clear positive result in the HuD-ELISA, demonstrating a sensitivity of 100%. Two out of 150 sera from patients with various infectious, autoimmune and neoplastic diseases (excluding PNS) showed a borderline result in the HuD-ELISA. This reveals a specificity of more than 98%. In addition 10 serum/CSF pairs from patients with anti-Hu-syndrome were adjusted to equal IgG concentrations and were tested in parallel in the HuD-ELISA. A specific antibody index (AI=ODCSF/ODserum) over 1.5 indicates intrathecal antibody synthesis. Six of ten patients revealed an AI >1.5, one was borderline (AI=1.5), and three had an AI in the range of 0.9-1.2. There appears to be a correlation between elevated AIs (>1.5) and presence of oligoclonal bands in the CSF. Due to its high specificity and sensitivity the recombinant HuD-ELISA is a suitable test for detection of anti-HuD antibodies in patients with putative PNS. In addition, the HuD-ELISA seems to be appropriate for the detection of specific intrathecal HuD-antibody synthesis.