Research Article: Use of a Chagas Urine Nanoparticle Test (Chunap) to Correlate with Parasitemia Levels in T. cruzi/HIV Co-infected Patients

Date Published: February 26, 2016

Publisher: Public Library of Science

Author(s): Yagahira E. Castro-Sesquen, Robert H. Gilman, Carolina Mejia, Daniel E. Clark, Jeong Choi, Melissa J. Reimer-McAtee, Rosario Castro, Edward Valencia-Ayala, Jorge Flores, Natalie Bowman, Ricardo Castillo-Neyra, Faustino Torrico, Lance Liotta, Caryn Bern, Alessandra Luchini, Alain Debrabant.

Abstract: BackgroundEarly diagnosis of reactivated Chagas disease in HIV patients could be lifesaving. In Latin America, the diagnosis is made by microscopical detection of the T. cruzi parasite in the blood; a diagnostic test that lacks sensitivity. This study evaluates if levels of T. cruzi antigens in urine, determined by Chunap (Chagas urine nanoparticle test), are correlated with parasitemia levels in T. cruzi/HIV co-infected patients.Methodology/Principal FindingsT. cruzi antigens in urine of HIV patients (N = 55: 31 T. cruzi infected and 24 T. cruzi serology negative) were concentrated using hydrogel particles and quantified by Western Blot and a calibration curve. Reactivation of Chagas disease was defined by the observation of parasites in blood by microscopy. Parasitemia levels in patients with serology positive for Chagas disease were classified as follows: High parasitemia or reactivation of Chagas disease (detectable parasitemia by microscopy), moderate parasitemia (undetectable by microscopy but detectable by qPCR), and negative parasitemia (undetectable by microscopy and qPCR). The percentage of positive results detected by Chunap was: 100% (7/7) in cases of reactivation, 91.7% (11/12) in cases of moderate parasitemia, and 41.7% (5/12) in cases of negative parasitemia. Chunap specificity was found to be 91.7%. Linear regression analysis demonstrated a direct relationship between parasitemia levels and urine T. cruzi antigen concentrations (p<0.001). A cut-off of > 105 pg was chosen to determine patients with reactivation of Chagas disease (7/7). Antigenuria levels were 36.08 times (95% CI: 7.28 to 64.88) higher in patients with CD4+ lymphocyte counts below 200/mL (p = 0.016). No significant differences were found in HIV loads and CD8+ lymphocyte counts.ConclusionChunap shows potential for early detection of Chagas reactivation. With appropriate adaptation, this diagnostic test can be used to monitor Chagas disease status in T. cruzi/HIV co-infected patients.

Partial Text: Chagas disease, caused by the protozoan Trypanosoma cruzi, affects an estimated 7.8 million people in the Americas [1]. Similar to HIV infection, Chagas disease is most prevalent in the adult population [2]. Massive rural-to-urban migration throughout has brought many cases of chronic Chagas disease into the city where patients are at risk for acquisition of HIV. This has created conditions for emergence of T. cruzi/HIV co-infection as a significant public health problem in the Americas.

Reactivation of Chagas disease in HIV patients is a serious medical condition, which is often life-threatening. Early diagnosis of Chagas reactivation and prompt treatment can be life-saving. However, current methods are based on microscopy that have sub-optimal sensitivity that do not detect reactivation until parasite loads are very high. A sensitive, non-invasive test is needed to monitor increase in parasitemia levels and predict risk of reactivation. In this study we introduce the potential use of a nanoparticle-based tool to monitor T. cruzi infection in urine of HIV patients.



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