Characterization of human immune responses to the cytosolic superoxide dismutase and glutathione S-transferase from Onchocerca volvulus

Abstract

In onchocerciasis patients and in O. volvulus-exposed individuals without signs of onchocerciasis, T- and B-cell responses to two recombinantly expressed O. volvulus enzymes were analysed and compared to responses to total protein extract of adult parasites. The cytosolic enzymes Cu/Zn superoxide dismutase 1 (OvSOD1) and glutathione S-transferase 2 (OvGST2) represent 2 detoxifying molecules which may play an important role in parasite defense against host-induced oxidative stress. The T-cell response to the two recombinant proteins was analysed by investigating the cytokine responses of peripheral blood mononuclear cells. Induction of IL-5 at the mRNA level and IL-5 and IL-10 at the protein level was demonstrated in patients with the generalized form of onchocerciasis and endemic normals without clinical manifestations. IFN-γ was not found to be induced by either antigen. This pattern of lymphokine expression is indicative of a Th2-type response. Compared to patients with the generalized form, a higher level of cytokine induction was observed in the group of endemic normals. Low but significant IgG levels were observed against OvSOD1 in patients with onchocerciasis; higher antibody levels were found against OvGST2 in patients and endemic normals. The highest IgG levels were detected against the crude O. volvulus extract. These results indicate that the two recombinant O. volvulus proteins induce moderate T and B cell responses.