Advances occurred during the last years in the diagnosis of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis infection, have prompted increased survival rates of patients. However, limitations related to the inefficiency of an early detection still remain: some techniques and laboratory methods do not have enough specificity, most instruments are expensive, and require handling by trained staff. In order to contribute to a prompt and effective diagnosis of tuberculosis, we report the development of a portable, user-friendly and low-cost biosensor device for its early detection. By using a label-free miniaturized Surface Plasmon Resonance (SPR) biosensor, we have established a direct immunoassay for the direct detection and quantification of the Heat shock protein X (HspX) of Mtb, a well-established biomarker of this pathogen, directly in pre-treated sputum samples. The method relies on highly specific monoclonal antibodies which are previously immobilized on the plasmonic sensor surface. This technology allows the direct detection of the biomarker without amplification steps, showing a Limit of Detection (LOD) of 0.63 ng mL-1 and a Limit of Quantification (LOQ) of 2.12 ng mL-1. The direct analysis in pre-treated sputum shows significant differences in the HspX concentration in patients with tuberculosis (with concentration levels in the order of 116-175 ng mL-1) compared with non-tuberculosis infected patients (values below the LOQ of the assay).

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Recently, Plasmodium vivax has been related to nearly 81% of malaria cases reported in Central America and the Mediterranean. Due to the difficulty of culturing this parasite species in vitro, most studies on P. vivax have focused on the identification of new antigens by homology comparison with P. falciparum vaccine candidate proteins. In this study, we have identified and characterized a Pf41 homologue in P. vivax, hence named Pv41, by following such approach and using web-available bioinformatics databases, molecular techniques and immunochemistry assays. Pv41 protein is a 384-amino-acid-long antigen encoded by a single exon that exhibits two s48/45 domains characteristic of gametocyte surface proteins. We have also demonstrated Pv41 transcription and expression during late intra-erythrocytic parasite stages and defined its subcellular localization on the parasite surface.

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