TRYPANOSOMA-CRUZI ANTIGEN-SPECIFIC ANTIBODY-RESPONSE IN IMMUNIZED MICE DURING ACUTE AND CHRONIC INFECTION

Preimmunization with living attenuated Corpus Christi strain Trypanosoma cruzi renders otherwise susceptible C3H(He) mice resistant and enhances the resistance of C57BL/6J mice to infection with the virulent Brazil strain. Antibody titers determined by enzyme-linked immunosorbent assay were higher in immunized and subsequently infected mice compared to those immunized alone. Elevated levels of anti-T. cruzi antibodies were maintained through day 300 of infection. Sera from groups of normal, immunized, immunized and infected, and infected mice show reactivities to parasite antigens that range from 25 to 160 kDa by western blot analysis. Electrophoretically separated antigen extracts from Corpus Christi and Brazil strains of parasites have essentially identical banding patterns when reacted with mouse sera from the above-mentioned groups. However, antibodies that bind parasite antigens of 75 and 77 kDa are found in the sera of mice that can survive infection but not in those that will succumb to infection. These antibodies are present 21 days after infection in preimmunized C3H and B/6 mice and on day 42 of infection in the genetically resistant, unimmunized, B/6 mice. A reaction to a 65-68-kDa triplet band is found similarly in immunized and infected C3H mice, but resistant B/6 mice were found to be unresponsive to this glycoprotein during infection. In addition, antibodies were elicited to a 31-kDa parasite antigen in all mice infected with the Brazil strain regardless of preimmunization status. These data show that antibodies with specificity for the 75- and 77-kDa antigens correlate with protection against virulent parasites and may confer this protection.