Detection of Chagas Disease by Latex Agglutination

GONZALEZ, V. D. G.; GARCIA, V. S.; VEGA, J. R.; MARCIPAR, I. S.; GUGLIOTTA, L. M.

Los Cocos, Córdoba

Simposio; V Simposio Argentino – Chileno de Polímeros - ARCHIPOL ‘09; 2009

Immunochemical analysis is applied as a powerful diagnostic tool. Many infectious diseases are routinely diagnosed when specific immunoglobulin G (IgG) antibodies against particular antigens are detected in the patient’s blood by using immunological assays. Anti-Trypanosoma cruzi IgGs are the expected antibodies to be found in chronic patients suffering from American trypanosomiasis or Chagas-Mazza’s disease. Nowadays, this pathology is considered to be the most serious American parasitosis, since about 20 million people are infected in Latin America (WHO, 2006). Although it would be desirable to detect the infection during the acute phase, it is almost impossible because of the short duration of this phase and the low parasite concentration in blood. Therefore, the parasitosis diagnosis is currently achieved during the chronic phase, when T. cruzi antibodies are detected in patient’s serum. However, serologic methods have the potential drawback of cross-reactions with related protozoans, particularly Leishmania. To enhance both sensitivity and specificity of serologic diagnosis, at least two independent tests must be conducted (Guhl et al., 2002). The most widely used assays are indirect hemagglutination (IHA), indirect immunofluorescence (IIF), and enzyme-linked immunosorbent assay (ELISA). These techniques are time-consuming and require relatively expensive kits. The development of sensitive, fast, easy-to-use, and low-cost methods is therefore of crucial importance. The latex agglutination test which involves in vitro aggregation of latex particles coated with antigen (or antibody), called latex-antigen (or –antibody) conjugate, in the presence of specific antibody (or antigen) is of great interest especially in biomedical applications (Martin and Mitchell, 1998; Park et al., 2004). This test is claimed to be the quickest and easiest method. The agglutination reaction produced during the immunoassay can be detected by either visual method or instrumental-based techniques. The visual method (Dey et al., 2007; Chen et al., 2007) is simple and cheap, without requiring special equipment. These tests are subjective and inadequate for quantification. The following instrumental techniques are generally used to detect the agglutination produced during an immunoassay: turbidimetry, nephelometry, particle recount, and light scattering. By using an appropriate apparatus, an accurate and sensitive assay is achieved, which can also be automated. Sensitivity and accuracy of the immunoassay depends on the method used to detect the agglutination (Molina-Bolívar and Galisteo-González, 2005). In this work, a latex agglutination test to detect anti-T. cruzi IgG in human sera is presented, and three different instrumental techniques (based on light scattering principles) are used to detect and monitor the agglutination process.