[Molecular and immunologic bases for the development of a vaccine against Chagas disease].

Subcellular fractions of T. cruzi epimastigotes (Epi) were studied for their capability to induce protective or aggressive effects in animals. The flagellar fraction (F) showed the best immunoprotective properties without tissular aggression. Monoclonal antibodies were raised against F. Two of them, FCH-F8-1 and 4, were able to neutralize the infectivity of bloodstream forms, to mediate lysis by complement of cell culture derived[trypomastigotes (Tripo) and to recognize the surface of Tripo and Epi. FCH-F8-1 reacted with a 85 kDa protein from Tripo (assayed by immunoprecipitation) and with peptides of 43 kDa on Epi and Tripo (tested by immunoblotting). FCH-F8-4 recognized several proteins ranging from 50 to 150 kDa on Epi and two molecules of 15 and 48 kDa on Tripo. Mice immunized with antigens purified by affinity chromatography by using FCH-F8-4 were protected against the infection. Several recombinant clones were detected on a cDNA lambda gt11 expression library constructed from T. cruzi Epi (Tulahuén strain): three with FCH-F8-4 and two with FCH-F8-1. One clone recognized by each monoclonal antibody was studied gamma (FCH-F8-1) 1 and gamma (FCH-F8-4) 1. Both inserts were of 150 base pairs each; they detected a 3.5 and 5.0 kilobases Epi mRNA, respectively. Both inserts were sequenced, and the amino acid sequences were inferred. gamma (FCH-F8-4) 1 codified for a 19 aa peptide, PAFLGCSSRFSGSFSGVEP, and gamma (FCH-F8-1) 1 for a 29 aa peptide EFLERGRISCORHSYTSYTSCSDEHNVTPFC. The whole 19 aa peptide was synthesized. This peptide (SP4) inhibited the ELISA reactivity against the parasite of chronically infected and F immunized mouse sera.(ABSTRACT TRUNCATED AT 250 WORDS)