Development of Peptide-Based Lineage-Specific Serology for Chronic Chagas Disease: Geographical and Clinical Distribution of Epitope Recognition

Abstract

BackgroundChagas disease, caused by infection with the protozoan Trypanosoma cruzi, remains a serious public health issue in Latin America. Genetically diverse, the species is sub-divided into six lineages, known as TcI–TcVI, which have disparate geographical and ecological distributions. TcII, TcV, and TcVI are associated with severe human disease in the Southern Cone countries, whereas TcI is associated with cardiomyopathy north of the Amazon. T. cruzi persists as a chronic infection, with cardiac and/or gastrointestinal symptoms developing years or decades after initial infection. Identifying an individual's history of T. cruzi lineage infection directly by genotyping of the parasite is complicated by the low parasitaemia and sequestration in the host tissues.Methodology/Principal FindingsWe have applied here serology against lineage-specific epitopes of the T. cruzi surface antigen TSSA, as an indirect approach to allow identification of infecting lineage. Chagasic sera from chronic patients from a range of endemic countries were tested by ELISA against synthetic peptides representing lineage-specific TSSA epitopes bound to avidin-coated ELISA plates via a biotin labelled polyethylene glycol-glycine spacer to increase rotation and ensure each amino acid side chain could freely interact with their antibodies. 79/113 (70%) of samples from Brazil, Bolivia, and Argentina recognised the TSSA epitope common to lineages TcII/TcV/TcVI. Comparison with clinical information showed that a higher proportion of Brazilian TSSApep-II/V/VI responders had ECG abnormalities than non-responders (38% vs 17%; p<0.0001). Among northern chagasic sera 4/20 (20%) from Ecuador reacted with this peptide; 1/12 Venezuelan and 1/34 Colombian samples reacted with TSSApep-IV. In addition, a proposed TcI-specific epitope, described elsewhere, was demonstrated here to be highly conserved across lineages and therefore not applicable to lineage-specific serology.Conclusions/SignificanceThese results demonstrate the considerable potential for synthetic peptide serology to investigate the infection history of individuals, geographical and clinical associations of T. cruzi lineages.

Mapping Antigenic Motifs in the Trypomastigote Small Surface Antigen from Trypanosoma cruzi

“…As previously shown (11), when used under more stringent conditions, a minimal fraction of Chagas-negative serum samples from patients affected by autoimmune and/or other endemic coinfection diseases reacted against bacterium-derived contaminants and/or the GST motif in TSSA-CL . On the other hand, p30-50 may contribute to improve the robustness of TSSA-based serologic methods in molecular epidemiology studies (17,18). The use of a more defined reagent lacking most of the sequences conserved across TSSA isoforms (14) may diminish its level of cross-recognition by antibodies elicited toward a different TSSA isoform.…”

“…Interstrain polymorphisms were shown to be focused on the central region of TSSA (12,14) and to have a major impact on its immunogenicity and antigenicity (11,12,16). Different attempts at using TSSA polymorphisms to design parasite lineage-specific serologic reagents as an indirect approach to allow for the typification of infecting T. cruzi strains have been undertaken (17,18). Although these methods can be improved, they showed good concordance with genotyping techniques (17) and support the differential predominance of T. cruzi lineages causing human infections in distinct areas that are endemic for the parasite (13,19,20).…”

Putting Infection Dynamics at the Heart of Chagas Disease

“…New detection tools continue to be developed. For example, nucleic acid aptamers to identify T. cruzi secreted antigens in serum may surpass the sensitivity of PCR [24], and lineage-specific serology has the potential to define historical exposure to different parasite subtypes [25]. …”

The crucial role of the Instituto Evandro Chagas in Chagas disease research

“…The international collaborators produced a large body of relevant published work, and an assessment of the wider geographical distributions and ecological associations of the six genetic lineages of T. cruzi 26,27,28,29,30,31,32,33,34 ( Figure 7). Most recently, this work has included the development of peptide-based T. cruzi lineage-specific serology for discovery of the reservoir hosts of TcII, TcV and TcVI 35,36 . This later research is beyond the scope of the current text but updates can be found in key recent reviews or by searches with appropriate keywords in PubMed [26][27][28][29][30][31][32][33][34] .…”