An immunoproteomic approach for identification of clinical biomarkers of Whipple's disease

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Abstract
Whipple's disease (WD) is a chronic multisystemic infection, caused by the bacterium Tropheryma whipplei. The main clinical presentations are classic WD (CWD) with histologic lesions in the gastrointestinal tract, endocarditis, and isolated neurologic infection. The current strategy for diagnosis remains invasive.The present study aimed to select the protein candidates for serological diagnosis of WD. The first step was to identify candidate proteins by an immunoproteomic approach combining 2-DE using a total extract of a T. whipplei, immunoblotting, and MS. The second step was to validate the discovered biomarkers using a recombinant protein-based ELISA. Serum samples from 18 patients with WD and from 54 control individuals were tested. A sugar ABC transporter, TWT328 (sensitivity (Se) 61%, specificity (Sp) 87%, positive predictive value (PPV) 61%, negative predictive value (NPV) 87%, and positive likelihood ratio (PLR) 4.69) was the best marker for development of serodiagnosis for CWD. We also obtained a reproducible immunoreactive protein pattern for patients with isolated neurological infection due to T. whipplei (Se 100%, Sp 93%, PPV 55.5%, NPV 100%, and PLR 13.51) as an encouraging step towards noninvasive diagnosis of this particular manifestation. Nine recombinant candidates have been successfully screened with serum samples. Results from these ELISA assays skewed with those obtained with immunoblots.