Abstract
BackgroundThe front line molecules from filarial worms and other nematodes or helminthes are their Excretory-Secretory (ES) products. Their interaction with the host cells, proteins and immune system accounts for the skin and eye pathology or hyposensitivity observed in human onchocerciasis. ES products and adult worms’ crude extracts from Onchocerca ochengi, a filarial nematode that infects the African zebu cattle, were utilized in the present study as a model for studying Onchocerca volvulus that causes river blindness in man.MethodsThe ES products were generated from adult male and female worms in vitro and analyzed with poly acrylamide gel electrophoresis (PAGE) and enzyme-linked immunosorbent assay (ELISA) using sera from Onchocerca-infected cattle and humans. The cattle sera were collected from a herd that had been exposed for six years to natural transmission of Onchocerca spp. The expressed reactivity was evaluated and differences analyzed statistically using Kruskal-Wallis rank and Chi-square tests.ResultsThe gel electrophoretic analyses of 156 ES products from O. ochengi female and male worms and of two somatic extracts from three females and 25 males revealed differences in the protein pattern showing pronounced bands at 15, 30–50 and 75 kDa for male ES proteins and 15, 25 and 40–75 kDa for somatic extracts, respectively and less than 100 kDa for female worms. Proteins in the ES products and somatic extracts from female and male Onchocerca ochengi worms were recognized by IgG in sera from both Onchocerca-exposed cattle and humans. Bovine serum antibodies reacted more strongly with proteins in the somatic extracts than with those in the ES products. Interestingly, the reaction was higher with male ES products than with ES products from female worms, suggesting that the males which migrate from one nodule to another are more exposed to the host immune system than the females which remain encapsulated in intradermal nodules.ConclusionsThis study demonstrates that O. ochengi ES products and, in particular, extracts from male filariae may represent a good source of immunogenic proteins and potential vaccine candidates.
Highlights
The front line molecules from filarial worms and other nematodes or helminthes are their ExcretorySecretory (ES) products
Harvesting and analysis of ES products Three hundred and ten worm cultures generated by adult females or males of O. ochengi were collected in 2 ml of culture medium of which 250 ES products could be analysed
The performed enzyme-linked immunosorbent assay (ELISA) analyses demonstrated the antigenicity of Onchocerca spp. proteins
Summary
The front line molecules from filarial worms and other nematodes or helminthes are their ExcretorySecretory (ES) products. Onchocerciasis, commonly known as river blindness, remains a health problem for countries in tropical Africa, Latin America and the Arabian Peninsula This filarial disease is caused by Onchocerca volvulus and nowadays affects 15.5 million people worldwide [1]. Intra and interspecific regulatory mechanisms of the worm-population are based on such putative ESproducts which may be used by the sedentary female worms to attract male worms for reproduction Such molecules can be collected in worm cultures as in-vitro excretory-secretory (ES) products [12]. Due to their close relationship, O. ochengi possesses a high number of proteins homologous to those of the human parasite O. volvulus as evidenced on SDS-gels [13, 14]. Their closeness with regards to the elicitation of immune mechanisms was proven via the successful immunization of cattle against O. ochengi using live third-stage larvae (L3) of the human parasite O. volvulus [15]
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