Immunity to Onchocerca volvulus. Serum mediated leucocyte adherence to infective larvae in vitro

Leucocyte adherence to infective larvae of Onchocerca volvulus in the presence of serum was evaluated using sera from four clinically distinct groups of patients with Onchocerciasis from an area hyperendemic for the disease. Significant cellular adherence to infective larvae occurred for the most part in the presence of sera obtained from subjects with either no microfilaridemia and few or no palpable nodules. These patients had, as well, the highest serum titres of specific anti-O. volvulus IgG antibodies. In contrast, sera from subjects with many palpable nodules and heavy skin infiltration with microfilariae (generalised disease) did not mediate significant adherence of leucocytes to infective larvae targets. Further, this group had the lowest serum levels of specific anti-O. volvulus antibodies of the IgG isotype. The findings are in keeping with the hypothesis that specific protective immunity may occur in O. volvulus infections.