CLONING AND CHARACTERIZATION OF A GENE ENCODING A NOVEL IMMUNODOMINANT ANTIGEN OF TRYPANOSOMA-CRUZI

A Trypanosoma cruzi genomic expression library was screened with a poo l of sera obtained from chronic chagasic patients. The recombinant ant igen (Tc40) isolated from this library reacted with a large number of serum samples of chronic chagasic patients, suggesting that the presen ce of anti-Tc40 antibodies may be specifically associated to Chagas' d isease. The full-length sequence of the Tc40 gene was determined after isolation of genomic and cDNA clones. The Tc40 cDNA includes a large open reading frame (2745 bp-long) that encodes a polypeptide of 100 kD a without any homology with previously described T. cruzi sequences. I n contrast with other T. cruzi antigens whose immunodominant B-cell ep itopes are composed by amino acid repetitive motifs, Tc40 does not sho w any amino acid repetition. Antibodies against the Tc40 recombinant p rotein reacted with three native polypeptides of 100, 41 and 38 kDa wh ich are lightly associated with membranes or cytoskeleton and expresse d in all developmental stages of the parasite life cycle. A transcript of 3.9-kb was detected in Northern blot analysis which is large enoug h to encode a 100 kDa polypeptide. Tc40 genes were mapped on a chromos omal band of 1.1 Mbp and in a few copies per haploid genome in the G s train. (C) 1997 Elsevier Science B.V.