Immunolocalization of superoxide dismutase in Dirofilaria immitis adult worms

Superoxide dismutase (SOD) may not only perform a housekeeping role in filarial worms but also assist in defense against oxidants generated by host immune cells. Both Dirofilaria and Onchocerca adult filariae and microfilariae contain relatively high activities of the antioxidant enzyme SOD; adult Dirofilaria worms also secrete SOD in vitro. In addition, superoxide radicals are relatively impotent against Dirofilaria and Onchocerca microfilariae in vitro. In assessing the role of SOD, we determined the anatomic localization of SOD in D. immitis adult worms by immunolocalization at the light-microscopic level. We found that anti-D. immitis SOD did not stain parasite tissues homogeneously, in support of the hypothesis that SOD does not have only a housekeeping role and that the pattern of staining may suggest another role(s) for SOD.