Perturbations in eosinophil homeostasis following treatment of lymphatic filariasis

Treatment of patients with patent Wuchereria bancrofti infection results in an acute clinical reaction and peripheral eosinophilia. To investigate the dynamics of the eosinophil response, changes in eosinophil activation and degranulation and plasma levels of eosinophil-active chemokines and cytokin es were studied in 15 microfilaremic individuals in south India by sequenti al blood sampling before and after administration of 300 mg of diethylcarba mazine (DEC). Clinical symptoms occurred within 24 h. Plasma interleukin-5 (IL-5) and RANTES levels peaked 1 to 2 days posttreatment, preceding a peak peripheral eosinophil count at day 4. Major basic protein secretion from e osinophils paralleled IL-5 secretion, while levels of eosinophil-derived ne urotoxin peaked at day 13 after treatment. Expression of the activation mar kers HLA-DR and CD25 on eosinophils rose markedly immediately after treatme nt, while expression of VLA-4 and alpha 4 beta 7 showed an early peak withi n 24 h and a second peak at day 13. Thus, the posttreatment reactions seen in filarial infections can be divided into an early phase with killing of m icrofilariae, clinical symptomatology, increases in plasma IL-5 and RANTES levels, and eosinophil activation and degranulation and a later phase with expression of surface integrins on eosinophils, recruitment of eosinophils from the bone marrow to tissues, and clearance of parasite antigen.