Advances in Serological Diagnosis of Chagas' Disease by Using Recombinant Proteins

Abstract

Advances in serological diagnosis of Chagas disease by using recombinant proteins Conventional serology to determine specific antibodies against Trypanosoma cruzi, the etiologic agent of Chagas disease, presents different sensitivities and selectivities, depending on the immunological technique used to perform the determination (Salles et al 1996). Since the emergence of recombinant DNA technology, many groups have prepared and assessed protein molecules to be used as antigens, which have been heterologically expressed, mainly in Escherichia coli cells. This technology has the advantage of allowing the exclusive evaluation of defined antigens for specific antibodies determination, in the absence of other components that usually occur when the antigen has been obtained by standard purification methods from native sources. Once these molecules have been distinctly specified, they can be massively produced as a highly unvarying, homogeneous chemical. This are desirable attributes when producing analytical chemicals for infectious diseases diagnosis, since they allow standardizing tests. To enhance even more diagnostic chemicals production, researchers have proposed using multiepitope molecules, obtained by the fusion of fragments that show noteworthy diagnostic properties (Aguirre et al 2006, Camussone et al 2009). The use of these molecules has proved to lead to homogeneous and reproducible antigen attachment to the surfaces of enzyme-linked-immunosorbent-assays (ELISA), bioelectrodes, or latex particles (Camussone et al 2009, Belluzzo et al 2011, Gonzalez et al 2010). The reason for this is that when using a single molecule to sensitize the surface, lesser protein competition for the active sites occurs than it does when using protein mixtures. Moreover, when sensitizing surfaces with multiepitope constructions, a greater number of specific binding sites are exposed to react with the target antibodies (Camussone et al 2009). Therefore, when using this kind of capturing molecule, the freely available epitopes proportion is increased. In the proposed book chapter we will discus the convenience of using recombinant antigens to evaluate chagasic specific antibodies, for the diverse cases that commonly occur in the clinical practice, namely: 1) Diagnosis of chronic disease and screening for transfusion and transplantation: We will discuss the utility of defined antigens when they are used isolated, in mixtures or fused, taking into account the sensitivity an specificity reported by several authors. We will mainly focus in the ability of particular antigens to distinguish between infections caused by T. cruzi and Leishmania sp, considering the needs of the regions where these diseases are co-endemic. 2) Parasitological cure In the book chapter we will analyze the recombinant antigens value to efficiently determine parasitological cure of Chagas´ disease. Conventional serology displays sera negativization of the largest part of the patients treated during the acute phase of the infection, ca. 80%. Though, the percentage diminishes to less than 10% when patients are treated during the chronic phase of the illness. Other studies have shown that the assessment of lytic antibodies may correlate better with parasitological cure (Krettli et al 1979). However, one disadvantage of this assay is the need to be performed on trypomastigote culture, a fact that impedes the test to be straightforwardly performed in clinical diagnostic labs. That is the reason for which several recombinant antigens have been proposed and assessed by ELISA, to determine if patients which respond to therapy serorevert specific antibodies against those molecules. 3) Prognosis and evolution of the chronic disease Specific antibodies have been proposed to be used as markers of different stages of Chagas? disease. We propose to discuss the potential usefulness of recombinant antigens to evaluate the different clinical stages by determining and/or quantifying specific antibodies. 4) Infection by congenital transmission We will talk about the diagnosis of this kind of infection, mostly considering the literature published on it. The distinctly feature of serological analysis to accurately diagnose neonate infection is the need to monitor the newborns from chagasic mothers for a 6 to 9 months period. The reason for this is that maternal antibody transference exists during pregnancy. Although this is the conventional recommended protocol when using both conventional serology and recombinant antigens from commercially available tests, we will analyze the actual possibility to shorten the neonate follow-up time when using recombinant antigens.