The Trypanosoma cruzi Antigen and Epitope Atlas: antibody specificities in Chagas disease patients across the Americas

Abstract

During an infection the immune system produces pathogen-specific antibodies. These antibody repertoires become specific to the history of infections and represent a rich source of diagnostic markers. However, the specificities of these antibodies are mostly unknown. Here, using high-density peptide arrays we examined the human antibody repertoires of Chagas disease patients. Chagas disease is a neglected disease caused by Trypanosoma cruzi, a protozoan parasite that evades immune mediated elimination and mounts long-lasting chronic infections. We describe a proteome-wide search for antigens, characterised their linear epitopes, and show their reactivity on 71 individuals from diverse human populations. Using single-residue mutagenesis we revealed the core functional residues for 232 of these epitopes. Finally, we show the diagnostic performance of identified antigens on challenging samples. These datasets enable the study of the Chagas antibody repertoire at an unprecedented depth and granularity, while also providing a rich source of serological biomarkers.

Identification of highly conserved Trypanosoma cruzi antigens for the development of a universal serological diagnostic assay

“…Thus, most peptides represented private antigens recognized by a few subjects, and none of these peptides were truly universal antigens recognized by all subjects. This is in agreement with a recent study similarly based on a screen of the T. cruzi proteome, indicating that most of its antigenic regions were private, with a very limited set of antigens recognized by more than 50% of T. cruzi infected subjects from their panel [ 30 ]. Because some of these apparently shared antigens were sufficiently conserved among parasite strains to have been included in our microarray screen, we analysed their recognition by our sample pools.…”

“…Remarkably, while T. cruzi positive control samples reacted strongly with epitopes from all conventional antigens tested, serology discordant but T. cruzi positive samples showed very limited or no recognition of any of these antigens, which agrees with the failure of current serological tests to identify these samples. Even newly described epitopes thought to be recognized by 50–100% of T. cruzi infected subjects [ 30 ] failed to be reactive to our discordant positive pool, and several even did not react with our positive control pool, suggesting a limited usefulness to improve serological testing.…”

“…Thus, a first key observation from this screening was that samples from T. cruzi positive control subjects had a very different epitope recognition profile compared to samples from infected but serologically discordant subjects. Importantly, this applied to an extensively large collection of epitopes that included those from the CMV large phosphoprotein antigen, from conventional T. cruzi antigens such as several used in current tests (CA-2/B13, SAPA, TSSA, Antigen 1 or Antigen 30), from novel T. cruzi epitopes thought to be broadly recognized [ 30 ], and from many of the conserved T. cruzi proteins we evaluated.…”

“…New approaches, including the use of high-density peptide microarrays, are providing powerful opportunities to screen large number of antigens and have allowed the identification of many new parasite antigens recognized by well characterized sera [ 25 , 30–32 ]. However, the extent of conservation of many of these antigens across T. cruzi strains and DTUs and their potential recognition from samples with discordant serology is still unclear, although some have shown promise [ 30 ].…”

“…New approaches, including the use of high-density peptide microarrays, are providing powerful opportunities to screen large number of antigens and have allowed the identification of many new parasite antigens recognized by well characterized sera [ 25 , 30–32 ]. However, the extent of conservation of many of these antigens across T. cruzi strains and DTUs and their potential recognition from samples with discordant serology is still unclear, although some have shown promise [ 30 ]. Indeed, most studies aiming at identifying T. cruzi antigens only rely on well-characterized consensus samples that are clearly negative or positive for T. cruzi antibodies based on several available tests, and do not include discordant samples.…”