Immune resistance to Trypanosoma cruzi: synergy of specific antibodies and recombinant interferon gamma in vivo.

The protective effects of interferon gamma (IFN-gamma) against infection by Trypanosoma cruzi were studied in vitro and in vivo in a murine model of infection. The possible synergy between IFN-gamma and trypomastigote-specific antibodies in the rejection of the parasite was also considered. Our results in vitro indicate that IFN-gamma activates macrophages to reject the parasite and this mechanism may lead to a decrease in parasitaemia in vivo. Finally, IFN production in vivo after infection by T. cruzi was compared among mice from different genetic backgrounds. Reduced parasitaemia and extended survival correlated with the early production of circulating IFN-gamma and anti-trypomastigote antibodies after infection. The appearance of an unusual type of circulating IFN in response to infection by T. cruzi was also detected; this IFN was resistant to neutralization by antibodies to IFN-alpha/beta and to IFN-gamma.