Evaluation of the performance of rK28 and rK39 antigens used in the serological diagnosis of canine and human visceral leishmaniasis

• Grant number: 24/15199-1
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: October 01, 2025
• End date: March 31, 2029
• Field of knowledge: Health Sciences - Medicine - Pathological Anatomy and Clinical Pathology
• Principal Investigator: Maria Carmen Arroyo Sanchez
• Grantee: Bruna Ramos dos Santos
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Human visceral leishmaniasis (HVL), a serious disease that is potentially fatal to humans, has an extensive geographical distribution and affects susceptible communities in various regions of the world. It is caused by Leishmania (Leishmania) donovani (anthroponotic cycle) and L. (L.) infantum (zoonotic cycle). In VL caused by L. (L.) infantum, the dog (Canis familiaris) is the main peridomiciliary reservoir, and identifying infected dogs is an essential step in controlling transmission to humans. Although there are specific diagnostic and treatment methods for HVL, a large part of the population has limited access to these procedures, increasing mortality rates. Advances in the field of VL diagnosis have been driven by the development of serological tests using recombinant antigens, which have become important tools and ensure greater sensitivity and specificity. In this context, Rapid Diagnostic Tests (RDTs) stand out for their economic efficiency, speed in obtaining results and greater access to remote areas and those with fewer economic resources, although they can present some limitations such as variations in performance, depending on the location, and cross-reactivity. Currently, the Ministry recommends using the RDT based on rK39 for human diagnosis and, for dogs, the TR DPP® Canine Visceral Leishmaniasis immunochromatographic test for screening, followed by ELISA-L. major-like for confirming TR-positive cases. However, the culture of L. major-like for the preparation of total antigen is a limiting factor, which could be remedied by using assays based on recombinant antigens. This study aims to compare the performance (sensitivity, specificity, cross-reactivity) of the methods recommended by the Ministry of Health for diagnosing HVL and CVL with the performance of commercial RDTs-rK39 tests and with ELISA-rK28 and ELISA-rK39, using samples from different locations in Brazil: human and canine patients with VL diagnosed by parasitological examination and PCR; healthy individuals and dogs; human and canine patients with other infectious diseases. Based on the data generated in this project, we intend to propose practical strategies to improve the diagnosis of human and canine VL, which may involve adjustments to the testing protocols or considerations about the interpretation of the results.