Effects of antiserum to Trypanosoma cruzi on the uptake and rate of killing of vector-borne, metacyclic forms of the parasite by macrophages

Kierszenbaum F., Lima M. F. and Wirth J. J. 1985. Effects of antiserum to Trypanosoma cruzi on the uptake and rate of killing of vector-borne, metacyclic forms of the parasite by macrophages. International Journal for Parasitology15: 409–413. The contribution of phagocytic function to host defense against infection with metacyclic forms of Trypanosoma cruzi isolated from insect vectors was investigated in mice passively transferred with anti-T. cruzi serum. The protective effect resulting from the passive transfers was significantly reduced by administration of either silica or cobra venom factor (CVF). A more pronounced curtailment of the protective effect was seen when both silica and CVF were administered to the mice. This effect was greater than that calculated by adding the effects produced by silica and CVF alone. In in vitro experiments, presence of anti-T. cruzi antibodies enhanced the capacity of mouse macrophages to take up the metacyclic organisms and increased the proportion of macrophages associating with the parasites. Increased macrophage-parasite association was also seen when either the flagellates or the macrophages were preincubated with the antiserum. Antibody-treated metacyclic forms of T. cruzi were more rapidly cleared by untreated macrophages than parasites pretreated with normal mouse serum. These results support a role for macrophages in host defense against the form of T. cruzi responsible for natural infections and emphasize the role played by anti-T. cruzi antibodies. The combined effect of the silica and CVF treatments suggests that C activity may contribute to the protective action of antibodies through its opsonic properties, though a concomitant role for C-dependent immune lysis cannot be ruled out. These results highlight the protective role of antibodymediated mechanisms against infection with the form of T. cruzi responsible for natural infections.