Physical mapping of a 670-kb region of chromosomes XVI and XVII from the human protozoan parasite Trypanosoma cruzi encompassing the genes for two immunodominant antigens.

As part of the Trypanosoma cruzi Genome Initiative, we have mapped a large portion of the chromosomal bands XVI (2.3 Mb) and XVII (2.6 Mb) containing the highly repetitive and immunodominant antigenic gene families h49 and jl8. Restriction mapping of the isolated chromosomal bands and hybridization with chromosome specific gene probes showed that genes h49 and jl8 are located in a pair of size-polymorphic homologous chromosomes. To construct the integrated map of the chromosomes harboring the h49 and jl8 loci, we used YAC, cosmid, and lambda phage overlapping clones, and long range restriction analysis using a variety of probes (i.e., known gene sequences, ESTs, polymorphic repetitive sequences, anonymous sequences, STSs generated from the YAC ends). The total length covered by the YAC contig was approximately 670 kb, and its map agreed and was complementary to the one obtained by long-range restriction fragment analysis. Average genetic marker spacing in a 105 kb region around h49 and jl8 genes was estimated to be 6.2 kb/marker. We have detected some polymorphism in the H49/JL8 antigens-encoding chromosomes, affecting also the coding regions. The physical map of this region, together with the isolation of specific chromosome markers, will contribute in the global effort to sequence the nuclear genome of this parasite.

[Levels of anti-Gal antibodies in persons infected and non-infected with Trypanosoma cruzi. Probably induced by bacteria and by the parasite]. / Niveles de anticuerpos anti-Gal en personas infectadas y no infectadas por Trypanosoma cruzi. Probable inducción por bacterias y por el parásito.

Antibodies levels against Gal alpha 1,3 Gal epitopes were studied in 407 human sera (92 chagasic and 315 non-chagasic), by means of hemagglutination with rabbit erytrocytes reactivity of serum having high titres of anti-Gal antibodies in presence of Escherichia coli and Serratia marcescens antigen was studied by immunoelectrotransference. Finally, using a purified anti-Gal antibody, Gal alpha 1,3 Gal epitopes were identified in metacyclic forms from 12 high Andean Chilean strains of Trypanosoma cruzi. Among the chagasic sera, it was demonstrated that in 63 (68.5%) were detected antibodies anti-Gal at the same or higher titer than 1:1,600; while i the non chagasic sera only 49 (15.6%) showed and anti-Gal response at similar titers. Immunoelectrotransference showed that the sera of people infected with T. cruzi recognize antibodies present in E. coli and S. marcescens, which reinforces the idea that at least in part, these bacterias would be capable of stimulating these responses. The autoradiographic analysis using purified anti-Gal antibodies, showed differences in the Gal alpha 1,3 Gal epitopes expressed in the different strains of T. cruzi. These results suggest that anti-Gal antibodies could have a real significance on the natural immunity mechanisms and protection of human infection with T. cruzi.