Chagas Urine Nanoparticle Test Correlates with Parasitemia Levels

By LabMedica International staff writers
Posted on 13 Mar 2016

Early diagnosis of reactivated Chagas disease in human immunodeficiency virus (HIV) patients could be lifesaving. In Latin America, the diagnosis is made by microscopical detection of the Trypanosoma cruzi parasite in the blood, a diagnostic test that lacks sensitivity.

A novel nanotechnology based on the use of nano-porous particles that contain high affinity chemical baits (trypan blue) in the inner core is proposed for concentration and preservation of antigens in urine. This technology, known as Chagas urine nanoparticle test or Chunap, has been applied in the direct diagnosis of congenital Chagas disease with excellent agreement with standard diagnostic tests.

Image: The Chagatest ELISA recombinant v 3.0 assay kit for the diagnosis of Trypanosoma cruzi infected individuals (Photo courtesy of Wiener Lab).

Image: Trypanosoma cruzi trypomastigote in a thin blood smear stained with Giemsa. Note the more anterior location of the nucleus (Photo courtesy of Centers for Disease Control and Prevention).

An international team of scientists led by those at the Universidad Peruana Cayetano Heredia (Lima, Peru) evaluated samples of 31 T. cruzi-infected HIV and 24 T. cruzi uninfected individuals from Cochabamba and Santa Cruz, in Bolivia. Confirmation of T. cruzi infection was based on positive results by two or more of the following commercial tests: Chagatest ELISA and Chagatest ELISA recombinant v 3.0 (Wienner Lab; Rosario, Argentina) and the PolyChaco indirect hemagglutination test (IHA) (Laboratorio Lemos; Buenos Aires, Argentina). Patients were asked to provide the first urine of the day before ingestion of liquids, where midstream specimens were collected. Urinalysis was done using urine test strip.

The concentration of T. cruzi antigens was accomplished using hydrogel nano-porous particles. Electrophoresis and Western Blot analysis of the antigens were performed. Antigen levels were determined by densitometry of western blots. The presence of any of the five diagnostic bands (22 kDa, 42 kDa, 58 kDa, 75 kDa, and 82 kDa) was considered as a positive result. In each experiment they included a negative control, a urine sample of healthy volunteer, and a positive control, 10 mL of healthy volunteer urine sample containing 1 ng of T. cruzi excreted-secreted antigen.

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 quantitative polymerase chain reaction (qPCR), and negative parasitemia (undetectable by microscopy and qPCR). The percentage of positive results detected by Chunap was: 7/7 (100%) in cases of reactivation, 11/12 (91.7%) in cases of moderate parasitemia, and 5/12 (41.7%) in cases of negative parasitemia. Chunap specificity was found to be 91.7%. A cut-off of greater than 105 pg was chosen to determine patients with reactivation of Chagas disease (7/7). Antigenuria levels were 36 times higher in patients with CD4+ lymphocyte counts below 200/mL. The study was published on February 26, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Universidad Peruana Cayetano Heredia
Wiener Lab
Laboratorio Lemos