Chagas' disease is a major health and economic problem caused by the protozoan Trypanosoma cruzi. Multiple independently evolving clones define a complex parasite population that can be arranged into two broad genetic lineages termed T. cruzi I and II. These lineages have different evolutionary origin and display distinct ecological and biological traits. Here we describe a novel molecule termed TSSA for trypomastigote small surface antigen that provides the first immunological marker allowing discrimination between lineages. TSSA is a surface, glycosylphosphatidyl inositol (GPI)-anchored mucin-like protein, highly antigenic during the infection. TSSA sequences from different parasite isolates reveal a population dimorphism that perfectly matches with the two T. cruzi lineages. Interestingly, this dimorphism is restricted to the central region of the molecule, which comprises the immunodominant B cell epitopes. This sequence variability has a major impact on TSSA antigenicity, leading to no immunological cross-reactivity between both isoforms for antibodies present either in immunization or infection sera. Furthermore, the absolute seroprevalence for TSSA in confirmed Chagasic patients is restricted to T. cruzi II isoform, strongly suggesting that human infections are due to this particular subgroup. Even though association of T. cruzi II with Chagas' disease has been proposed based on molecular markers, this is the first immunological evidence supporting this hypothesis. The implications of these results for the future research on Chagas' disease could be envisaged.

A thick coat of mucin-like glycoproteins covers the surface of Trypanosoma cruzi and plays a crucial role in parasite protection and infectivity and host immunomodulation. The appealing candidate genes coding for the mucins of the mammal-dwelling stages define a heterogeneous family termed TcMUC, which comprises up to 700 members, thus precluding a genetic approach to address the protein core identity. Here, we demonstrate by multiple approaches that the TcMUC II genes code for the majority of trypomastigote mucins. These molecules display a variable, non-repetitive, highly O-glycosylated central domain, followed by a short conserved C terminus and a glycosylphosphatidylinositol anchor. A simultaneous expression of multiple TcMUC II gene products was observed. Moreover, the C terminus of TcMUC II mucins, but not their central domain, elicited strong antibody responses in patients with Chagas' disease and T. crusi infected animals. This highly diverse coat of mucins may represent a refined parasite strategy to elude the mammalian host immune system.Trypanosoma cruzi is the etiologic agent of Chagas' disease, which is of major medical and economical significance in Latin America (1). The T. cruzi life cycle involves distinct stages in both the mammalian host and the hematophagous insect vector (2). Within the insect, two major developmental forms can be observed: replicative epimastigotes and metacyclic trypomastigotes. The latter form brings the infection into humans when released on the skin or mucosa after the insect blood meal. Following cell invasion, metacyclic trypomastigotes differentiate into amastigotes, which, after several divisions, transform into cell-derived trypomastigotes, which are then released into the bloodstream. This stage is able to invade a wide variety of nucleated cells, thus propagating the infection.A thick coat of glycoproteins covers the surface of all these developmental stages (3-11). The major protein components of this coat have been identified as glycosylphosphatidylinositol (GPI) 1 -anchored molecules enriched in Thr, Ser, and Pro residues that serve as a scaffold for the extensive addition of O-glycans (5, 8 -10, 12). This particular feature enables their classification as mucin-like proteins by analogy to mammalian mucins (13). Mucins play a key role in parasite protection and infectivity and modulation of the host immune response throughout the T. cruzi life cycle (14 -16). The mucin coat of the cell-derived trypomastigotes (tGPI-mucins) is composed of an undefined mixture of molecules ranging from 60 to 220 kDa (6, 7, 9) and sharing the stage-specific, sialic acid-containing epitope Ssp-3, critical for mammalian cell attachment/invasion (17, 18). tGPI-mucins or their GPI moieties are potent inducers of nitric oxide and pro-inflammatory cytokines by macrophages (15,19). Major protective lytic antibodies directed against ␣-galactosyl epitopes present in tGPI-mucins have been described in sera from chronic Chagas' disease patients (6, 7, 9, 11).Recently, substantial informatio...

Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi and is one of the most important endemic problems in Latin America. Lately, it has also become a health concern in the United States and Europe. Currently, a diagnosis of Chagas' disease and the screening of blood supplies for antiparasite antibodies are achieved by conventional serological tests that show substantial variation in the reproducibility and reliability of their results. In addition, the specificity of these assays is curtailed by antigenic crossreactivity with sera from patients affected by other endemic diseases, such as leishmaniasis. Here we used a highly sensitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) to evaluate a recombinant protein core of a mucin-like molecule (termed trypomastigote small surface antigen [TSSA]) for the detection of specific serum antibodies in a broad panel of human sera. The same samples were evaluated by CL-ELISA using as the antigen either a mixture of native T. cruzi trypomastigote mucins or an epimastigote extract and, for further comparison, by conventional serologic tests, such as an indirect hemagglutination assay and indirect immunofluorescence assay. TSSA showed ϳ87% sensitivity among the seropositive Chagasic panel, a value which was increased up to >98% when only parasitologically positive samples were considered. More importantly, TSSA showed a significant increase in specificity (97.4%) compared to those of currently used assays, which averaged 80 to 90%. Overall, our data demonstrate that recombinant TSSA may be a useful antigen for the immunodiagnosis of Chagas' disease.