Identification of in vivo released products of Onchocerca with diagnostic potential, and characterization of a dominant member, the OV1CF intermediate filament

Abstract

A sensitive and specific test for the routine diagnosis of active Onchocerca infection is currently lacking. A major drawback in the development of such a test has been the paucity of knowledge of suitable parasite antigens that can serve as targets in antigen-detection assays. In the present investigation, we employed mass spectrometry, bioinformatics and molecular techniques to identify and characterize several potentially diagnostic Onchocerca antigens in the in vivo nodular fluid, which is being investigated for the first time. The majority of the 27 identified antigens lacked a secretory signal. One of them, also identified and characterized in greater detail with the aid of previously developed monoclonal antibodies (Mabs), was a dominant circulating cytoplasmic intermediate filament protein, previously identified and named, OV1CF. Although OV1CF lacks a secretory signal in its amino acid sequence and is not detected in the pure 42 h in vitro released products, it is easily detected in the in vivo nodular fluid. We conclude that these in vivo released products offer promise as diagnostics markers in onchocerciasis.