Immune recognition of Onchocerca volvulus proteins in the human host and animal models of onchocerciasis.

Onchocerca volvulus is a tissue-dwelling, vector-borne nematode parasite of humans and is the causative agent of onchocerciasis or river blindness. Natural infections of BALB/c mice with Litomosoides sigmodontis and of cattle with Onchocerca ochengi were used as models to study the immune responses to O. volvulus-derived recombinant proteins (OvALT-2, OvNLT-1, Ov103 and Ov7). The humoral immune response of O. volvulus-infected humans against OvALT-2, OvNLT-1 and Ov7 revealed pronounced immunoglobulin G (IgG) titres which were, however, significantly lower than against the lysate of O. volvulus adult female worms. Sera derived from patients displaying the hyperreactive form of onchocerciasis showed a uniform trend of higher IgG reactivity both to the single proteins and the O. volvulus lysate. Sera derived from L. sigmodontis-infected mice and from calves exposed to O. ochengi transmission in a hyperendemic area also contained IgM and IgG1 specific for O. volvulus-derived recombinant proteins. These results strongly suggest that L. sigmodontis-specific and O. ochengi-specific immunoglobulins elicited during natural infection of mice and cattle cross-reacted with O. volvulus-derived recombinant antigens. Monitoring O. ochengi-infected calves over a 26-month period, provided a comprehensive kinetic of the humoral response to infection that was strictly correlated with parasite load and occurrence of microfilariae.

Anthelmintic activity of phenolic acids from the axlewood tree Anogeissus leiocarpus on the filarial nematode Onchocerca ochengi and drug-resistant strains of the free-living nematode Caenorhabditis elegans.

The effect of three phenols (ellagic, gentisic and gallic acids) from the axlewood tree Anogeissus leiocarpus on Onchocerca ochengi and drug-resistant strains of Caenorhabditis elegans, a model organism for research on nematode parasites, is investigated. Worms were incubated in different concentrations of phenols and their survival was monitored after 48 h. Among the three acids, ellagic acid strongly affected the survival of O. ochengi microfilariae, O. ochengi adults, a wild-type C. elegans and anthelmintic-resistant strains of C. elegans, namely albendazole (CB3474), levamisole (CB211, ZZ16) and ivermectin (VC722, DA1316), with LC50 values ranging from 0.03 mm to 0.96 mm. These results indicate that the binding of ellagic acid in the worm differs from that of resistant strains of C. elegans. The efficacy of both gallic and gentisic acids was not significantly changed in resistant strains of C. elegans treated with levamisole (ZZ16, LC50= 9.98 mm, with gallic acid), albendazole (CB3474, LC50= 7.81 mm, with gentisic acid) and ivermectin (DA1316, LC50= 10.62 mm, with gentisic acid). The efficacy of these three pure compounds is in accordance with the use of A. leiocarpus from its locality of origin. The in vivo toxicity data reveal that the thresholds are up to 200 times higher than the determined LC50 values. Thus, ellagic acid could be a potential option for the treatment of nematode infections, even in cases of drug resistance towards established anthelmintic drugs.