Effect of ivermectin on serum dependent cellular interactions to Dipetalonema viteae microfilariae

The effects of ivermectin (Iv) on the filarial infection has been investigated using Dipetalonema viteae--Mastomys natalensis model system. In vitro, Iv (3 micrograms/ml) had no effect on the microfilariae (mf) in the presence or absence of serum from normal or infected Mastomys (NMS, IMS). However, the sera promoted cell-mediated cytotoxicity with macrophages or eosinophils to the mf when Iv was added at 3 ng/ml. Sera isolated from normal or infected Mastomys after subcutaneous treatment with Iv (100 micrograms/kg) (Iv-NMS, Iv-IMS) also induced cellular cytotoxicity to the mf in vitro. Available evidence suggests that Iv mediates the cellular cytotoxicity by complement activation by alternative pathway. Iv treatment of D. viteae infected Mastomys resulted in an initial mobilization of the mf into circulation followed by the death of both the mf and adults in vivo. There was enhanced antibody level in Iv treated infected animals and antibody dependent cellular cytotoxicity mediated by IgM seems to be predominantly involved in elimination of the mf. The serum containing these antibodies was effective in clearing the circulating mf from Mastomys on passive immunization. Thus, Iv seems to synergize host immune factors against D. viteae infection.