Banca de QUALIFICAÇÃO: ANA GLÓRIA BARBOSA BEZERRA DE SOUSA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : ANA GLÓRIA BARBOSA BEZERRA DE SOUSA
DATA : 09/02/2018
HORA: 09:00
LOCAL: Sala de Reuniões do CB
TÍTULO:

EVALUATION OF THE HEMOLYTIC ACTIVITY MEASURED BY THE COMPLEMENT SYSTEM IN HUMAN ERYTHROCYTES TREATED WITH PROTEIN EXTRACTS OF Plasmodium falciparum AND ITS POSSIBLE IMPLICATIONS FOR SEVERE MALARIA

PALAVRAS-CHAVES:

Plasmodium falciparum; malaria; complement system; immunopathogenesis; hemolysis.

PÁGINAS: 70
GRANDE ÁREA: Ciências Biológicas
ÁREA: Parasitologia
RESUMO:

Malaria is an infection caused by apicomplex protozoa of the genus Plasmodium, of high prevalence and morbidity, especially in the tropical and subtropical regions of the planet. Plasmodium falciparum, considered the most aggressive, causes a series of modifications in the cellular surface of parasitized red blood cells, such as the expression of molecules responsible for the cytoadherence process, rosetting and sequestration of parasitized erythrocytes, generating serious clinical pictures and, for many times, lethal malaria. Against this, the innate defense system will use some mechanisms to control the progression of infection like the complement system. However, the exacerbated activation of this response may favor certain complications associated with P. falciparum infection. In this sense, this study evaluated the degree of hemolysis mediated by the complement of human erythrocytes sensitized with protein extracts of P. falciparum, in different concentrations, through in vitro autologous hemolytic assays, in order to establish relations between this activity and its implications for the pathogenesis of severe malaria. Protein extracts were produced from P. falciparum culture (strain 3D7) yielding an extract called crude P. falciparum extract (EBPf). In the autologous hemolytic assay, RBCs and serum, the complement source, were used for the analysis of its activation. VBS + buffer was used as a negative control and distilled water as a positive control. Inactivated human serum was also used to confirm the action of complement under the lysis of erythrocytes, in addition to the evaluation of hemolytic activity in erythrocytes with sickle cell trait, a characteristic that provides protection against the plasmodium. The same assay was performed using the enzyme neuraminidase in order to compare the profile of the hemolytic activities observed. In a treatment of a minimum concentration of 0.6 μg/ mL of EBPf, hemolysis of about 60% occurred when in presence of the complement, whereas, in the absence of the latter, the effect was considerably reduced, indicating its participation. In the red blood cells with sickle cell trait, there was a small reduction in hemolysis compared to normal red blood cells, demonstrating the influence that this genetic trait has on the parasite-host interaction. In comparison with the neuraminidase treatment, the hemolytic action profiles were close, indicating that P. falciparum probably has proteases with similar action to this enzyme, cleaving proteases sialisated on the surface of the target cell and using alternative routes of invasion under determinated situations. The SDS-PAGE stained with silver nitrate revealed an equivalent protein degradation profile between erythrocyte treatments with EBPf and neuraminidase, reinforcing this idea. A dose-response assay was performed starting from the concentration of 0,06 μg/mL, in which a reduction in hemolytic activity was observed only from the concentration of 0,03 μg/mL of EBPf, indicating that high parasitemia did not is a strictly crucial factor for the activation of the complement, being probably a biological phenomenon potentiated by other factors involved in the infectious process. Thus, it was concluded that erythrocytes sensitized with EBPf lose their ability to control complement-mediated lysis, which is one of the factors responsible for the loss of homeostasis of the individual, contributing to an exacerbated inflammatory and processgenerating characteristic signs of severe malaria.

MEMBROS DA BANCA:
Presidente - 2213126 - VALTER FERREIRA DE ANDRADE NETO
Externo ao Programa - 1375489 - ANA CLAUDIA GALVAO FREIRE GOUVEIA
Externo ao Programa - 1752367 - PAULO MARCOS DA MATTA GUEDES