Pattern of epitopic reactivity of the anti-Hu antibody on HuD with and without paraneoplastic syndrome

Previous study has shown that the anti-Hu antibody titre of serum samples f rom patients with paraneoplastic encephalomyelitis/paraneoplastic sensory n euronopathy (PEM/PSN) was significantly higher than that from patients with small cell lung cancer without neurological disturbances (non-PEM/PSN). Th e aims of this study were (1) to identify the fine epitopes on HuD recognis ed by the anti-Hu antibody, (2) to determine if the pattern of epitopic rea ctivity differed between antibodies from patients with and without PEM/PSN, and (3) to determine if the pattern of epitopic reactivity correlated with the clinical features. Recombinant full length HuD and nine deletion fragm ents were constructed and immunoreacted by western blot analysis with 14 an ti-Hu serum samples from eight patients with PEM/PSN and six without PEM/PS N. All anti-Hu serum samples reacted with the deletion fragments containing amino acids (aa) 90-101 or aa 171-206. Some anti-Hu samples reacted with t he deletion fragments containing aa 223-234, aa 235-252, or aa 354-373. The re was no difference in the pattern of epitopic reactivity between patients with and without PEM/PSN. There was no correlation between the pattern of epitopic reactivity and the clinical features. The anti-Hu antibody titre f rom patients with PEM. PSN was significantly higher than from patients with out PEM/PSN, but there was overlap of their titre concentrations. In conclu sion, aa 90-101 and aa 171-206 are the major epitopes with which all anti-H u serum samples react, and aa 223-234, aa 235-252, and aa 354-373 are the m inor epitopes with which only some anti-Hu serum samples react. The analyse s suggested that the pattern of epitopic reactivity of the anti-Hu antibody on HuD was not a critical factor for the development or clinical features of PEM/PSN.