Avaliação da capacidade inibitória de segmentos conservados da leishmanolisina sobre a interação entre Leishmania (Viannia) braziliensis e macrófagos humanos

Abstract

Introduction: Leishmaniasis comprises a wide range of diseases caused by protozoa of the genus Leishmania, having as host the domesticated animals, mainly dogs in peridomiciles, and transmitted to the human through the bite of the sandflies (of the genus Lutzomyia, the major vector for the transmission of the disease in the Americas). The clinical presentations of the disease vary according to the parasite and the immunopathological status of the infected host, from the visceral, mucocutaneous or cutaneous forms. In Brazil, most of the reported cases of leishmaniasis occur by the Leishmania (Viannia) braziliensis species, mainly in the North and Northeast regions, making it a public health problem. In this sense, in this current study we performed laboratory experiments involving leishmanolysin, or GP63, the most abundant glycoprotein on the surface of the protozoa, an important virulence factor for the infection and capable of stimulating the production of cytokines through the Th1 immune response. Previous studies have shown that this glycoprotein has conserved segments among the parasites, being the main targets of the study. Objective: Evaluate the contribution of conserved segments of the GP63 glycoprotein in the interaction of the parasite with the host cell. Methodology: Laboratory evaluations were carried out on the inhibition of monocyte derived macrophages (MDM) infection by parasites at the Serviço de Imunologia (SIM) of the Hospital Universitário Professor Edgard Santos (C - HUPES), Universidade Federal da Bahia (UFBA), in Salvador - Bahia. Healthy donors who agreed to participate in the study, signing the free informed term of consent (FITC), were included to obtain the MDM, and the isolates of Leishmania (Viannia) braziliensis were previously obtained by aspirating the skin lesion in patients with Cutaneous Leishmaniasis located in Corte de Pedra - Bahia. The MDM in culture were incubated with specimens of Leishmania (Viannia) braziliensis and synthetic peptides of GP63 corresponding to the conserved segments, and the determination of the percentage of infection in the experiments involving parasites, peptides and MDM were performed under an optical microscope. Statistical analysis and comparison of results employed variance analysis, considering significant of p <0.05. The interpretation of the dose response curve was performed through linear and non-linear regressions, and Dunnett’s post-test was used for multiple comparisons between each peptide and its concentrations. Results: The inhibition assays at the concentrations of 0, 100, 200 and 300 Um showed significance (p < 0,05) in all peptides, except HEVAH and SRYD in the concentration of 100 Um in relation to the control group. The dose-response effect of the SRYD and HEVAH peptides were r = -0.113 (SRYD) and r = -0.1634 (HEVAH), and there was a change in the infection state with the other peptides: k = -0.015 (PAVGNIPA), k = -0.007 (KAREQYGC) and k = -0.010 (CONCATÂMERO). Discussion: The inhibition of infection using synthetic peptides has already been described in the literature, and it is possible to verify the participation of the SRYD and HEVAH segments in the inhibition of the in vitro infection, being able to infer the same for the other peptides. Conclusion: The use of conserved segments reduces the infection of the parasite in the host cell, indicating that they are possible targets in immunoprophylaxis approaches against leishmaniasis.