GAMMA-IFN AND MACROPHAGE RESPIRATORY BURST IN CALOMYS CALLOSUS CHALLENGED WITH TRYPANOSOMA-CRUZI BLOOD-STREAM AND METACYCLIC FORMS

Parasitemia levels of Calomys callosus inoculated with a high dose (HB T) of 4 x 10(3) Trypanosoma cruzi strain M226 bloodstream trypomastigo tes (BT) exceeded those with the same inoculum of metacyclic trypomast igotes (MT) while a similar parasitemia was obtained with a low dose ( LBT) of 5 X 10(2) of BT. Serum IFN-gamma levels during the acute phase of infection were higher in the LBT inoculated group when compared wi th the group inoculated with HBT, while the IFN-gamma levels in MT ino culated animals were close to uninfected controls. Spontaneous liberat ion of H2O2 of peritoneal macrophages explanted from animals on days 2 1 and 28 after infection was comparable to that of controls for HBT an d LBT groups while that of the MT inoculated group was significantly h igher. Phorbol Myristate Acetate (PMA) stimulation resulted in high H2 O2 liberation specially in the infected groups. In vitro challenge wit h BT suppressed the small amount of spontaneous H2O2 release, while MT challenge stimulated this release to a limited degree in infected gro ups. In this animal model, interacting with a parasite strain isolated from the same host, macrophage activation as measured by H2O2 release was low, while the same strain had been previously observed to result in hyperactivation of mouse macrophages. We suggest that this distinc tive behavior may be due to a host-parasite adaptation.