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

Manchang T., Ajonina-Ekoti I., Ndjonka D., Eisenbarth A., Achukwi M., Renz A., Brattig N., Liebau E., Breloer M.

Abstract

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.