Synergistic protection by specific antibodies and interferon against infection by Trypanosoma cruzi in vitro.

Trypanosoma cruzi infects many mammalian cell types in vitro, including fibroblasts and macrophages. We have analyzed and compared the infection of mouse 3T3 fibroblasts and J774 macrophage-like tumor cells by cloned Y-A1.2 T. cruzi trypomastigotes. The effects of T. cruzi-specific antibodies and of interferon (IFN) on infection were considered. Specific antibodies protected 3T3 fibroblasts from infection by T. cruzi, but increased the relative infectivity for J774 cells due to binding of the opsonized parasite to J774 Fc receptors. It was also apparent that IFN-alpha, beta (produced by fibroblasts) and IFN-gamma (produced by T lymphocytes) activated trypanocidal activities in both 3T3 and J774 cells, although IFN-gamma was 100 to 2000 times more effective than IFN-alpha, beta on the basis of IFN antiviral units added per culture. When anti-T. cruzi antibodies and IFN-alpha, beta or IFN-gamma were used jointly, a synergistic protective effect was observed with both 3T3 fibroblasts and J774 cells. These results suggest that B and T lymphocytes might collaborate in vivo in the protection against T. cruzi infections by the production of anti-trypomastigote antibodies and IFN-gamma, respectively.