Evaluation of methods for detection of asymptomatic individuals infected with Leishmania infantum in the state of Piauí, Brazil

Abstract

Background Visceral Leishmaniasis in humans presents with fever, anemia, and splenomegaly and can be lethal if not treated. Nevertheless, the majority of Leishmania infantum -infected individuals does not manifest symptoms and remain so provided they are not immunosuppressed. In this work, the performance of different tests was evaluated to detect asymptomatic individuals who were living in Teresina, Piauí state, Brazil, an endemic area for VL. Methodology L . infantum -specific antibodies were detected by ELISA and two different rapid immunochromatographic (IC) diagnostic tests, Kalazar Detect and OnSite, and parasitic loads were detected by real time PCR [qPCR]. Additionally, we measured levels of the biomarkers monokine induced by IFN-γ (MIG) and IFN-γ-induced protein 10 (IP-10) before and after stimulation of whole blood with soluble Leishmania antigen [SLA]. Principal findings Kalazar Detect and OnSite detected, respectively, 76% and 64% of patients presenting with active Visceral Leishmaniasis; 50% and 57% of patients remained positive in these tests, respectively, after treatment. Of the healthy participants in the study who were living in the endemic area, only 1.7% were positive with both of the IC tests. On the other hand, reactivity in ELISA tests revealed that 13% of these individuals presented asymptomatic infections; among VL patients, 84% presenting with active disease were reactive in ELISA, and after treatment, 55.5% were seropositive. L . infantum DNA was present in the blood of 37.9% of infected individuals living in the endemic area, while IP-10 and MIG biomarkers were detected in 26.7% of them. The greatest concordance of positivity occurred between ELISA and qPCR. Conclusion The association of different techniques can detect asymptomatic infections, however, more research is necessary to develop ideal biomarkers that are simple to use in the clinic and in field studies in areas endemic for Visceral Leishmaniasis.

Improved Performance of ELISA and Immunochromatographic Tests Using a New Chimeric A2-Based Protein for Human Visceral Leishmaniasis Diagnosis

“…However, no VL case was positive on the IgM test, and one patient diagnosed with Mycobacterium infection was IgM positive [ 39 ], disclosing, therefore, the sensitivity and specificity of anti- Leishmania IgM antibodies for VL diagnosis. In 2019, Porcino et al [ 42 ] also evaluated the ICT Kalazar Detect and Onsite Leishmania IgG/IgM Combo Rapid Test performance and obtained 76% and 64% sensitivities, respectively, in patients with active VL.…”

Whole Blood Stimulation Assay as a Treatment Outcome Monitoring Tool for VL Patients in Ethiopia: A Pilot Evaluation

“…The Leishmania-specific whole blood stimulation assay has also been evaluated in different endemic areas of Leishmania spp. for the detection of subjects with asymptomatic infection [36,38,39]. However, specificity problems of the soluble Leishmania antigens used, in particular crossreactivity with similar pathogens like Trypanosoma cruzi and Toxoplasma gondii, could be problematic when targeting a diagnostic or predictive tool in coendemic countries, which may be of lesser concern for its development as a test-of-cure.…”

Prospection of immunological biomarkers for characterization and monitoring of asymptomatic Leishmania (Leishmania) infantum infection

“…Therefore, we believe that the baseline profile of circulating biomarkers presented by the AS group characterizes the asymptomatic infection. Moreover, studies using antigen-stimulated cells have identified and suggested the use of biomarkers, such as CXCL-10 and CXCL9 chemokines (Ibarra-Meneses et al ., 2017; Porcino et al ., 2019) and IL-12, IL-2, IFN- γ , IL-17A, IL-22, IL-4 and IL-10 cytokines (Peruhype-Magalhães et al ., 2005; Pitta et al ., 2009; Romano et al ., 2009; Ibarra-Meneses et al ., 2017) for the detection of L. infantum -infected individuals. These studies clearly show that asymptomatic VL individuals have specific immune response profiles that differ from uninfected individuals living in areas endemic for VL and from patients with active VL.…”

“…Different studies have shown basal immunological biomarker levels in asymptomatic VL infections (Peruhype-Magalhães et al ., 2006; Khoshdel et al ., 2009; Costa et al ., 2012). On the other hand, studies using antigen-stimulated cells have identified and suggested the use of biomarkers, such as CXCL-10 and CXCL9 chemokines (Ibarra-Meneses et al ., 2017; Porcino et al ., 2019) and IL-12, IL-2, IFN- γ , IL-17A, IL-22, IL-4, and IL-10 cytokines (Peruhype-Magalhães et al ., 2005; Pitta et al ., 2009; Ibarra-Meneses et al ., 2017), for the detection of L. infantum -infected individuals. These findings corroborate the hypothesis that cell immunity is present and usually persists for several years.…”