Monoclonal Antibodies to Immunodominant Epitope ofTropheryma whipplei

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Abstract
Recent isolation ofTropheryma whipplei(formerlyTrophyrema whippelii), the agent of Whipple’s disease, from the cardiac valve of a patient with Whipple’s disease endocarditis now allows the detection of reactive epitopes that could be used in a serological assay. In order to propose an enzyme-linked immunosorbent assay (ELISA) that uses recombinantT. whippleiantigen, we first determined by Western blotting of human, mouse, and rabbit antisera that the common immunodominant epitope is an 84-kDa protein. We then produced 13 monoclonal antibodies (MAbs) againstT. whipplei, 12 of which recognize this immunodominant epitope. These MAbs did not react with phylogenetically closely related bacteria or bacteria previously shown to be cross-reactive withT. whipplei, but they did react with two other strains ofT. whippleiisolated, one from an ocular sample and the other from a duodenal biopsy specimen. By confocal microscopy, the MAbs allowed detection ofT. whippleiwithin infected fibroblasts. The identification of the 84-kDa antigen with our MAbs will make it possible to develop a diagnostic antigen for use in a diagnostic ELISA for Whipple’s disease.