Abstract
Onchocerca lupi (Spirurida: Onchocercidae) is a filarial worm parasitizing domestic carnivores and humans. Adult nematodes usually localize beneath in the sclera or in the ocular retrobulbar of infected animals, whilst microfilariae are found in the skin. Therefore, diagnosis of O. lupi is achieved by microscopic and/or molecular detection of microfilariae from skin biopsy and/or surgical removal of adults from ocular tissues of infected hosts. An urgent non-invasive diagnostic tool for the diagnosis of O. lupi in dog is mandatory. In this study, an immunoproteomic analyses was performed using a combination of immunoblotting and mass spectrometry techniques. Onchocerca lupi major antigen (Ol-MJA) and paramyosin (Ol-PARA) proteins were identified as potential biomarkers for serodiagnosis. Linear epitopes were herein scanned for both proteins using high-density peptide microarray. Sera collected from dog infected with O. lupi and healthy animal controls led to the identification of 11 immunodominant antigenic peptides (n = 7 for Ol-MJA; n = 4 for Ol-PARA). These peptides were validated using sera of dogs uniquely infected with the most important filarioids infesting dogs either zoonotic (Dirofilaria repens, Dirofilaria immitis) or not (Acanthocheilonema reconditum and Cercopithifilaria bainae). Overall, six antigenic peptides, three for Ol-MJA and for Ol-PARA, respectively, were selected as potential antigens for the serological detection of canine O. lupi infection. The molecular and proteomic dataset herein reported should provide a useful resource for studies on O. lupi toward supporting the development of new interventions (drugs, vaccines and diagnostics) against canine onchocercosis.
Highlights
Nematodes of the family Onchocercidae are common parasites of wild and domestic ungulates, carnivores and humans [1,2,3]
polyvinylidene fluoride (PVDF) membranes probed with serum samples allowed the identification of a band with a molecular mass of ~200kDa reactive with O. lupi sample and of ~100kDa reactive with O. lupi and D. repens samples (Fig 2)
The analysis of the gel band at ~200kDa identified five proteins (i.e., Actin 2, Calponin, Major antigen, Paramyosin and Muscle cell intermediate filament protein) with a total of 20 and 16 unique tryptic peptides associated to O. volvulus paramyosin (PARA) and Major antigen (MJA) proteins, respectively (Table 1)
Summary
Nematodes of the family Onchocercidae are common parasites of wild and domestic ungulates, carnivores and humans [1,2,3]. The zoonotic role of O. lupi was reported for the first time in 2011 [7] and, since on, up to 18 patients have been diagnosed positive for this parasite, worldwide (i.e., Germany, Tunisia, Hungary, Greece, Turkey, Iran and USA) [18,19,20]. The diagnosis of canine onchocercosis is achieved by detection and identification of microfilariae (mfs) in small skin biopsies, an invasive procedure not often accepted by dog owners, mainly in absence of typical clinical lesions of the infection [21, 22], and or based on the presence of ocular nodules on the eyelids, conjunctiva, and sclera of dogs [23, 24]. The molecular and proteomic dataset reported should establish large sero-surveys for mapping the distribution of the infection in endemic areas as well as in areas where information on the disease is not available
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