Elevations in granulocyte-macrophage colony-stimulating factor and interleukin-5 levels precede posttreatment eosinophilia in onchocerciasis

The eosinophil survival assay was used to quantitate cytokines in 17 serial serum samples from 10 patients treated for onchocerciasis with diethylcarbamazine. Eosinophils isolated from normal donors were cultured for 4 days in the presence of patients' sera, and cell viability was determined. Serum specimens from 9 of 10 patients enhanced eosinophil survival from 4.8% ± 2.2% (mean ± SE) before treatment to 50.0% ± 6.4% after treatment. Survival enhancement activity peaked before posttreatment eosinophilia. Antibodies to interleukin (IL)-5, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-3 were used to block cytokine activity in 22 serum samples. Antibodies to IL-5 blocked survival in 5 samples, antibodies to GM- CSF blocked survival in 6 samples, and a combination of antibodies to IL-5 and GM-CSF blocked survival in 8 additional samples. Overall, posttreatment sera from patients treated for onchocerciasis enhanced eosinophil survival; both GM-CSF and IL-5 may promote the posttreatment eosinophilia in filarial infection.