Onchocerciasis and Immunity in Humans: Enhanced T Cell Responsiveness to Parasite Antigen in Putatively Immune Individuals

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Abstract
To identify possible immune mechanisms in human onchocerciasis, we compared a group of 12 individuals who had no clinical or parasitological evidence of infection, despite ongoing exposure to the parasite, with a group of 16 individuals from the same area who had active Onchocerca volvulus infection. Despite having less parasite-specific serum antibody, the infection-free (“putatively immune”) individuals showed greater lymphocyte responsiveness, especially interleukin-2 (lL-2) production, to O. volvulus antigen (OVA) than did the infected subjects; lymphocyte responses (including IL-2 production) to mitogens and nonparasite antigen in both study groups were equivalent and normal. Our findings define differences in parasite-specific T cell subpopulations between infected and putatively immune subjects that could be a central element in developing or maintaining protective immunity to O. volvulus infection.