Congenital Chagas Disease: development and assessment of a specific IgM capture-based assay for diagnosis of transmission

PEVERENGO LUZ; LUZ RODELES,; CAMILA MALDONADO; BALLERING GRISELDA; PUJATO NAZARENA; D'AMICO INDIRA; MIGUEL H. VICCO,; GARCÍA LUCIANA; JURADO LAURA; ALTECH JAIME; IVÁN MARCIPAR,

ACTA TROPICA

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020

0001-706X

Transplacental transmission by Trypanosoma cruzi (T. cruzi) infection can be effectively treated if 28 parasiticide drugs are administered as early as possible during childhood. Therefore, an ideal situation 29 would be to diagnose the infection near birth in order to avoid the loss of patients during the 30 subsequent follow-up. This situation is desirable due to the maximum benefit of drugs in early stages 31 which, consequently, implies a relevant contribution to eliminate mother-to-child transmission. 32 However, available techniques for that purpose have limitations as being operator-dependent 33 (microhematocrit), require several months follow-up (IgG detection) or specialized laboratories 34 (PCR). In this study we propose to detect specific IgM antibodies (Ab) by developing a capture-based 35 ELISA employing an improved antigen (Ag) to diagnose the transplacental transmission of T. cruzi, 36 and in consequence, to enhance access to effective treatment. Firstly, a new chimera Ag (CP4) was 37 obtained from the fusion of CP1 and CP3 protein, carrying FRA, SAPA, MAP, TSSAII/V/VI and 38 TcD Ag from T. cruzi. Then, we optimized the assay by capturing IgM Ab with a polyclonal anti-IgM 39 Ab and evaluating three Ag formulations to detect specific IgM bound. The formulations were formed 40 as follows: i) F1: CP1 and CP3; ii) F2: CP1, CP3, B13 and P2β; iii) F3: by CP4. Detection of Ab-41 binding Ag was carried out using an anti-His Ab since all Ag were expressed with a His-tag. The 42 evaluation panel consisted of sera from vertically infected children under 1-year-old (6 younger than 43 15 days, 7 older) and samples from non-infected children of women with chronic Chagas Disease. 44 The ELISA assay employing CP4 showed better performance with notable high sensitivity and 45 specificity (92.3% and 93.9%, respectively). Positive and negative likelihood ratios of the test (15.2 46 and 0.082) suggest its potential clinical relevance in term of post-test probability of infection. We 47 developed a standardized and non-operator dependent test to detect specific anti-T. cruzi IgM Ab. 48 Although increased sample size is needed for its validation, our results indicate that this capture-based 49 technique employing CP4 Ag can certainly improve the diagnosis of connatal infection.