Immune recognition ofOnchocerca volvulusproteins in the human host and animal models of onchocerciasis

Abstract

AbstractOnchocerca volvulusis 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 withLitomosoides sigmodontisand of cattle withOnchocerca ochengiwere used as models to study the immune responses toO. volvulus-derived recombinant proteins (OvALT-2,OvNLT-1,Ov103 andOv7). The humoral immune response ofO. volvulus-infected humans againstOvALT-2,OvNLT-1 andOv7 revealed pronounced immunoglobulin G (IgG) titres which were, however, significantly lower than against the lysate ofO. volvulusadult 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 theO. volvuluslysate. Sera derived fromL. sigmodontis-infected mice and from calves exposed toO. ochengitransmission in a hyperendemic area also contained IgM and IgG1 specific forO. volvulus-derived recombinant proteins. These results strongly suggest thatL. sigmodontis-specific andO. ochengi-specific immunoglobulins elicited during natural infection of mice and cattle cross-reacted withO. volvulus-derived recombinant antigens. MonitoringO. 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.