Delayed-type hypersensitivity reactions to Onchocerca volvulus antigens inexposed and non-exposed African individuals

Although considered of critical importance, the mode of helper T-lymphocyte function in Onchocerca volvulus infection is still unclear including the r ole of the Th1/Th2 dichotomy. We studied the delayed-type hypersensitivity (DTH) reaction, which is the classical Th1 response, to O. volvulus antigen s in Africans exposed and not exposed to the infection. DTH reactions were found in a small percentage of patients with generalized onchocerciasis, bu t in a high percentage of patients with localized onchocerciasis, in putati vely immune subjects, and also in non-exposed individuals, which may be due to cross-reactivity with other nematodes. These findings support the notio ns of (i) prenatal influence of maternal O. volvulus infection preventing d evelopment of Th1 responses and/or (ii) suppression of Th1 responses by the infection itself.