Safe diagnosis of Chagas disease is the subject of research at Fiocruz Bahia

A study conducted by Fiocruz researchers suggests that the use of IBMP chimeric antigens has promising potential for the safe diagnosis of Chagas disease in regions where the protozoa Crithidia sp. LVH-60A and Trypanosoma cruzi coexist. The research, led by Fred Luciano Neves Santos, from the Gonçalo Moniz Institute (Fiocruz Bahia), was published in the journal Diagnostics and focused on the development of precise immunoassays, a method that uses antibodies to identify or quantify a substance, in the context of diagnosing Chagas disease.

On the left, a culture of parasites of the species Crithidia sp LVH60A; on the right, in vitro culture of the species Leishmania infantum (photo: Luana Rogerio/UFSCar)

The research aimed to evaluate the diagnostic potential of these chimeric antigens for detecting Chagas disease in patients infected with Crithidia sp. LVH-60A, a parasite that presents symptoms similar to those of visceral leishmaniasis. Previously collected human sera from seven patients with Crithidia sp. VH-60A and three patients with Leishmania infantum were analyzed at the Biorepository of the Laboratory of Immunology and Molecular Biology at the Federal University of Sergipe. The results indicated that these IBMP antigens showed 100% sensitivity, with specificity ranging from 87.5% to 100%, and accuracy values between 90% and 100%. No cross-reactivity was observed with Crithidia sp. LVH-60A and only one sample positive for L. infantum showed cross-reactivity with the IBMP-8.1 molecule.

The researchers emphasize that accurate and specific diagnostic methods are crucial to effectively managing and controlling infectious diseases. Chagas disease and leishmaniasis are tropical diseases that often coexist in various geographical regions of Brazil, and diagnosing them can be a challenge due to the potential for cross-reactivity in serological tests. Cross-reactivity occurs when antibodies produced in response to one pathogen mistakenly recognize antigens from another, which can lead to false-positive or inconclusive results.

The challenges in diagnosing Chagas disease are further amplified when considering Trypanosoma rangeli, Trypanosoma evansi and other members of the Trypanosomatidae family, including the genera Crithidia, Herpetomonas, Blastocrithidia and Leptomonas, as well as newly discovered species such as Crithidia sp. LVH-60A. To address this knowledge gap, the study investigated the influence of anti-Crithidia sp. LVH-60A and anti-L. infantum antibodies when diagnosing Chagas disease, using four IBMP chimeric proteins from T. cruzi as antigens.

Advances in diagnosis

The study's main limitation was the small number of samples positive for Crithidia sp. LVH-60A analyzed. However, despite this shortcoming, the importance and novelty of the data presented are evident. For the authors, recognizing and understanding cross-reactions in serological tests for Chagas disease is essential to ensure accurate diagnoses, improve patient care and strengthen the effectiveness of efforts to control Chagas disease and related illnesses.

Moreover, the knowledge obtained supports the continuous improvement of diagnostic tools, which can improve disease management and thus epidemiological surveillance by advancing diagnostic methodologies. The results suggest that using IBMP chimeric antigens is promising for the reliable diagnosis of Chagas disease in regions where Crithidia sp. LVH-60A and T. cruzi coexist, and indicate that, to confirm the findings, it is necessary to investigate with a greater number of samples positive for Crithidia sp. LVH-60A.