Fine mapping of Trypanosoma cruzi epitopes using high-density peptide chips: alanine and length scans.

CARLOS A BUSCAGLIA; JAIME ALTCHEH; LEONEL E BRACCO; FERNÁN AGÜERO

Resistencia

Otro; XXX reunión de la Sociedad Argentina de Protozoología; 2018

Sociedad Argentina de Protozoología

Chagas Disease is a major health problem in America for which no vaccine for large-scale public health interventions are yet available. Accurate diagnosis is essential for the early identification, follow up and prevent non-vector transmission. Diagnosis is routinely performed using serological methods, which require well characterized antigens. Although available tests give satisfactory results, the production of reliable reagents remains laborious and expensive. We have conducted a large-scale screening of T. cruzi linear B-cell epitopes using high-density peptide chips, leading to the identification of ~200 novel antigens. Based on these results we have developed a multiepitope diagnostic test that have excellent diagnostic performance (Mucci J, et al 2017). For each epitope, understanding which residues are important for antibody binding can lead to improved diagnostic reagents. For example, this may help identify if these key residues are conserved in other T. cruzi sequenced strains and isolates. To obtain improve the serological characterization of known antigens, we performed a number of epitope-mapping experiments using high-density peptide arrays. First, we performed Alanine scans for 276 different protein antigens (506 antibody-binding peaks/epitopes) that had been reactive in at least one of several peptide chip assays. This experiment is based on permuting an alanine in each position of the sequence to be studied, hence assessing the impact of replacing each original amino acid on the reactivity of each peptide sequence. Secondly, we performed a length scan on selected peptides, to analyze how the length of an epitope-containing peptide may affect the antibody-binding in these assays. For this, we have performed complete length scans of the C-terminal portion of 58 proteins belonging to the trans-sialidase super family of T. cruzi antigens. This length scan was performed by scanning these sequences with peptides of lengths 7 to 18. This work led to the identification of precise residue positions in epitopes that play a fundamental role in the seroreactivity of the corresponding antigens.