Rapid Urine Test Detects Active Visceral Leishmaniasis

A capture enzyme linked immunosorbent assays (ELISA) has been designed to detect individually each of three Leishmania infantum antigens in the urine of VL patients.

Scientists from The Forsyth Institute (Cambridge, MA, USA) in conjunction with those at DetectoGen Inc. (Grafton, MA, USA; www.detectogen.com), have developed a single assay assembled with the combination of the reagents used to individually detect three Leishmania antigens in the urine of VL patients. They combed reverse-phase high-performance liquid chromatography (RP-HPLC) with mass spectroscopy, to identify the three distinct L. infantum proteins. These were L. infantum iron superoxide dismutase 1, L. infantum tryparedoxin 1, and L. infantum nuclear transport factor 2.

In a sample of 20 confirmed and diagnosed VL patients, each L. infantum protein was identified in approximately 10 to 12 overlapping and nonoverlapping urine samples. Moreover, in one sample no leishmanial antigen could be identified by any of the three assays. None of the antigens was detected in the urine of patients with cutaneous leishmaniasis, Chagas disease, schistosomiasis, or tuberculosis (TB). The urinary antigen detection ELISA had a sensitivity of 89%, specificity of 100%, and limit of detection of 4 pg to 10 pg of antigen per mL of urine. This new urine-based assay identified 20/20 VL patients and did not react with 62 urine samples obtained from control subjects.

The authors concluded that the urine based capture ELISA is a noninvasive VL diagnostic test that can differentiate active disease from parasitic exposure and from cured VL patients. The assay will be useful for the diagnosis of VL in patients coinfected with the human immunodeficiency virus (HIV) as the conventional serological diagnosis of VL in these patients is problematic and not sensitive. It is likely that the combined capture ELISA test will be equally useful for the diagnosis of VL patients from the Old World. This prediction is based on the fact that the three antigens discovered in the urine of patients with VL from the New World are 98% homologous to the same group of proteins produced by L. donovani.

Kala-azar or VL is a serious and debilitating disease that affects economic productivity and quality of life, and is nearly 100% fatal if not treated promptly, and there are 500,000 new cases of disease per year around the world. The disease occurs on four continents and is endemic in 47 countries, with approximately 200 million people at risk of infection. Due to the deterioration of social and economic conditions and coinfection with HIV, the number of cases is increasing. Most of the approximately 50,000 deaths that occur each year due to VL occur in children. The study was published on May 30, 2013, in the Public Library of Science Neglected Tropical Diseases.

Related Links:

The Forsyth Institute
DetectoGen Inc.