Trypanosoma cruzi Trypomastigote Glycosylphosphatidylinositol-Anchored Mucins And A Synthetic Alpha-Gal-Containing Neoglycoprotein As Potential Biomarkers And Vaccines For Chagas Disease

Chagas disease (CD), caused by the protozoan Trypanosoma cruzi, is a neglected tropical disease that kills or permanently disable thousands of people annually. About 6-8 million people are estimated to be infected worldwide. Although many efforts have been made for the development of an effective immunotherapy, currently there is no vaccine to prevent or treat CD in humans. Despite their toxicity, the two current drugs for CD, benznidazole (BZN) and nifurtimox (NFX), have medium-to-high efficacy in the chronic stage of the disease and could save or improve the lives of thousands of patients. However, negative seroconversion in treated patients, as measured by the conventional serology, may take 10-20 years to occur. This is one the reasons that only 0.3% of chronic CD (CCD) patients are currently being treated. Identification of biomarkers (BMKs) to evaluate early response to chemotherapy for chronic CCD has become of paramount importance because of lack of validated early BMKs for CCD therapeutic responses. Therefore, clinical and laboratorial BMKs are urgently needed for the early assessment of treatment outcomes or disease progression, thus potentially new drugs, and/or different treatment regimens could be tested. The cell surface of infective T. cruzi trypomastigote form is covered by highly immunogenic glycosylphosphatidylinositol-anchored (GPI) mucin-like glycoproteins (tGPI-mucins). Almeida and colleagues have shown in a series of publications in the last several years that CCD patients have high levels of protective antibodies (Ch anti-alpha-Gal Abs) against the terminal nonreducing alpha-Gal glycotopes expressed on tGPI-mucins or TcMUCII mucins. Those authors have also shown that Ch anti-alpha-Gal Abs correlate with parasitological cure following chemotherapy with BZN, thus negative seroconversion for those antibodies could be considered a reliable criteria of cure in contrast to PCR assay. The Ch anti-alpha-Gal Abs recognize a major and immunodominant glycotope expressed on tGPI-mucins, the trisaccharide Gal alpha(1,3)Gal beta(1,4)GlcNAc alpha (Gal alpha 3LN alpha). In this project, I aimed to validate the synthetic glycotope Gal alpha 3LN alpha covalently conjugated to a carrier protein (bovine serum albumin, BSA), giving rise to a neoglycoprotein (NGP) named NGP24b (Gal alpha 3LN alpha-BSA), as a reliable surrogate BMK for the tGPI-mucins for early assessment of treatment outcomes (Chapter 1). Moreover, I evaluated Gal alpha3LNï?¡-HSA as potential therapeutic vaccine candidate (Chapter 2) in an experimental murine transgenic model of CD that mimics human antibody responses to alpha-Gal glycotopes. Keywords: Trypanosoma cruzi; Chagas disease; diagnosis; chemotherapy; treatment follow-up; anti-alpha-Gal antibodies; biomarkers; trypomastigote mucins; synthetic neoglycoprotein; vaccine