Congenital chagas disease: Development and assessment of a specific IgM capture-based assay for diagnosis of transmission

PEVERENGO, LUZ MARÍA; RODELES, LUZ MARÍA; MALDONADO, CAMILA; BALLERING, GRISELDA; PUJATO, NAZARENA; D?AMICO, INDIRA; VICCO, MIGUEL HERNÁN; GARCIA, LUCIANA; JURADO, LAURA; ALTCHEH, JAIME; MARCIPAR, IVÁN

ACTA TROPICA

ELSEVIER SCIENCE BV

Año: 2021 vol. 213

0001-706X

Transplacental transmission by Trypanosoma cruzi (T. cruzi) infection can beeffectively treated if parasiticide drugs are administered as early as possible duringchildhood. Therefore, an ideal situation would be to diagnose the infection near birth inorder to avoid the loss of patients during the subsequent follow-up. This situation isdesirable due to the maximum benefit of drugs in early stages which, consequently,implies a relevant contribution to eliminate mother-to-child transmission. However,available techniques for that purpose have limitations as being operator-dependent(microhematocrit), require several months follow-up (IgG detection) or specializedlaboratories (PCR). In this study we propose to detect specific IgM antibodies (Ab) bydeveloping a capture-based ELISA employing an improved antigen (Ag) to diagnosethe transplacental transmission of T. cruzi , and in consequence, to enhance accessto effective treatment. Firstly, a new chimera Ag (CP4) was obtained from the fusion ofCP1 and CP3 protein, carrying FRA, SAPA, MAP, TSSAII/V/VI and TcD Ag from T.cruzi . Then, we optimized the assay by capturing IgM Ab with a polyclonal anti-IgMAb and evaluating three Ag formulations to detect specific IgM bound. The formulationswere formed as follows: i) F1: CP1 and CP3; ii) F2: CP1, CP3, B13 and P2β; iii) F3: byCP4. Detection of Ab-binding Ag was carried out using an anti-His Ab since all Ag wereexpressed with a His-tag. The evaluation panel consisted of sera from verticallyinfected children under 1-year-old (6 younger than 15 days, 7 older) and samples fromnon-infected children of women with chronic Chagas Disease. The ELISA assayemploying CP4 showed better performance with notable high sensitivity and specificity(92.3% and 93.9%, respectively). Positive and negative likelihood ratios of the test(15.2 and 0.082) suggest its potential clinical relevance in term of post-test probabilityof infection. We developed a standardized and non-operator dependent test to detectspecific anti- T. cruzi IgM Ab. Although increased sample size is needed for itsvalidation, our results indicate that this capture-based technique employing CP4 Agcan certainly improve the diagnosis of connatal infection.