RECOGNITION OF AN IMMUNOGENETICALLY SELECTED TRYPANOSOMA-CRUZI ANTIGEN BY SEROPOSITIVE CHAGASIC HUMAN SERA

If the H-2 congenic mouse strains A.SW (H-2(s)) and A.CA (H-2(f)), are infected with Trypanosoma cruzi, a 45 kDa protein (Tc45), present in cultured epimastigotes and blood trypomastigotes, is recognized only b y the A.SW strain sera. In order to explore the possibility that among seropositive humans the response to Tc45 is also highly variable, 81 chagasic human sera (as defined by the HemAve agglutination test, Poly chaco S.A.I.C., Buenos Aires, Argentina) were tested in a direct (epim astigote antigenic complex directly bound to the solid phase) and indi rect immunoradiometric assay (IRMA) (Tc45, from a partially purified p reparation, bound to the solid phase, by means of a monoclonal antibod y). Sixty nine of these sera reacted in both the direct and indirect a ssays, 11 were negative in both assays (these samples may correspond t o false positives detected by the commercial agglutination test) and o nly one reacted with the antigenic complex but not with Tc45. Reactivi ty of the human sera with the epimastigote antigenic extract was relat ively homogenous, while reactivity with Tc45 was extremely variable. N o statistical correlation was determined between the two variables. Gi ven the high variability of the human response to Tc45, ranging from n egative to highly positive, together with the immunogenetic restrictio n previously described in the murine model. me speculate that human MH C may also modulate the response to this molecule. (C) 1997 Elsevier S cience B.V. All rights reserved.