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  • Diagnosis of NCC can be accomplished via

    2019-07-19

    Diagnosis of NCC can be accomplished via imaging techniques and serological confirmatory testing. The best immunodiagnostic test for NCC, the enzyme-linked immunotransfer blot EITB (Tsang et al., 1989), is based on the detection of Tacalcitol for to one or more of the 7 lentil-lectin glycoproteins (LLGP) of the T. solium metacestode. While this test is known to be 98% sensitive and 100% specific in cases of cysticercosis associated with multiple cysts, it requires specialized equipment and laboratory techniques that are not readily available in poorer settings. In contrast, enzyme-linked immunosorbent assays (ELISAs) are fast, simple, and cheap tests that can be performed in almost any laboratory. Several ELISAs have been developed for the diagnosis of cysticercosis in the past few years and, although they have not reached the sensitivity and specificity of the EITB assay and are not yet commercially available, they are quantitative, can be conducted in a high throughput manner, and are more practical for utilization in those parts of the world that have high T. solium burdens (Ishida et al., 2006; Mandal et al., 2006, 2008; Pina et al., 2011; Sahu et al., 2009; Scheel et al., 2005). Excreted/secreted antigens have long been considered good candidates for the diagnosis of parasitic infections on account of their being heavily-exposed to the host\'s immune system (Longoni et al., 2012; Meira et al., 2011; Revest et al., 2008). In some flatworms, one such excreted/secreted antigen is enolase (Bernal et al., 2004): a cytosolic and surface lyase (Gan et al., 2010) that catalyzes the conversion of 2-phosphoglycerate (2-PGA) to and from phosphoenolpyruvate (PEP) via the Embden-Meyerhof pathway (Wold, 1971). This reaction is metal-dependent and typically involves Mg2+. There are three different types of enolases (α, β, and γ) and, while all three varieties are commonly found in multicellular species (Fletcher et al., 1976), most unicellular organisms possess only one isoform in their genome, with α-enolases being the most common (Ghosh and Jacobs-Lorena, 2011). Recently, enolases have been reported to be a part of the tegument interaction of flatworms with their environments. Such a fact is pathologically relevant as enolases have been shown to facilitate cellular invasion in various prokaryotic and eukaryotic pathogens. In such instances, enolases capture extracellular environmental plasminogen, which, after being converted into its active plasmin form, functions as a potent protease capable of degrading the extracellular matrix during parasitic invasion of the host (Bergmann et al., 2005; Carneiro et al., 2004; Derbise et al., 2004; Lottenberg et al., 1994; Maldonado et al., 2006) (Ghosh and Jacobs-Lorena, 2011). Moreover, the enolases of some flatworms such as Schistosoma bovis have been shown to actually catalyze the activation of plasminogen on their own (de la Torre-Escudero et al., 2010). Because of its accessibility as well as its pathologically-relevant role in flatworms, Gan et al. expressed a recombinant Echinococcus granulosus enolase in Escherichia coli and found that it had a potential use as a vaccine candidate (Gan et al., 2010). A few years later, Wang et al. (2012) used this same recombinant enolase as the basis of an ELISA to diagnose human cystic echinococcocis and found it to be 81.25% sensitive and 100% specific (Y. Wang et al., 2012). Other flatworm enolases, such as those from T. asiatica and Schistosoma japonicum, have also shown promise as both vaccine candidates and immunodiagnostics (Du et al., 2009; Yang et al., 2010). Genomes have long been considered a rich source of data for the investigation and identification of antigens for diagnostics and vaccine development, and recently the T. solium genome became available (Pajuelo et al., 2015; Tsai et al., 2013). We searched this genome for antigens with potential utility for immunodiagnostics and identified a gene that codes for an enolase homologous to that of E. granulosus. Here we report our attempts to clone, recombinantly express, and enzymatically-characterize this enolase as well as its capacity to serve as an immunodiagnostic for porcine cysticercosis.