The diverse expression of immunity in humans at distinct states of Onchocerca volvulus infection

This study examined the development and persistence of immunity in humans presenting defined states of Onchocerca volvulus infection, i.e. in exposed endemic control individuals without microfilaridermia and clinical disease, in patients with patent or post‐patent onchocerciasis, and in patients concurrently infected with Mansonella perstans. Onchocerca volvulus antigen (OvAg)‐specific cellular reactivity was significantly diminished in microfilariae (mf)‐positive patients, while the highest reactivity was measured in exposed but mf‐negative endemic controls, those being free of any clinical signs of onchocercal disease. In patients who became post‐patent, responses to OvAg were significantly augmented, but did not approach entirely the magnitude observed in endemic controls. In onchocerciasis patients with concurrent mansonelliasis, cellular unresponsiveness to OvAg persisted, even when mf of O. volvulus were eliminated permanently by repeated ivermectin therapy. Cells from mf‐positive onchocerciasis patients produced significantly less interferon‐γ (IFN‐γ) (P