W162 - Immunomodulatory Effect of G. Lamblia Proteins in an Antigen Processing and Presentation Model in Vitro

Abstract Text: G. lamblia causes the gastrointestinal parasitosis giardiasis, colonizing the small intestine. In the intestine, antigens are continuously carried out by antigen-presenting cells (APCs), which endocytose and present peptides through their Major Histocompatibility Complex (MHC) molecules to T cells, promoting the detection of pathogens as well as favoring the induction of intestinal immune tolerance. During infection, G. lamblia secretes molecules that may modulate the host's response. Therefore, the aim of this study is to evaluate the potential immunomodulatory effect of G. lamblia in an antigen processing and presentation model in vitro. The model used was the APC (M12.C3.F6), hen egg lysozyme (HEL) as the antigen, and the T cell hybridoma 3A9, which is specific to HEL (epitope 48-61). Its activation promotes the secretion of IL-2 into the medium. To evaluate the activation of the 3A9 hybridoma, the IL-2-dependent CTLL2 cell line was used. Subsequently, the potential modulation exerted by a protein lysate from G. lamblia trophozoites was analyzed. The MTT assay was employed to analyze cell viability and proliferation. Our results showed that G. lamblia lysate induces inhibition in the processing and presentation assay by reducing the activation of the 3A9 hybridoma, therefore, lowering the secretion of IL-2 to the medium. Additionally, the lysate concentrations use (12.5 and 25 ug/mL) did not affect the viability of the participant cells, confirming that the effect was due to the potential modulation of the proteins present in G. lamblia lysate. Future experiments aim to elucidate the possible modulation mechanisms conducted by G. lamblia proteins.