RESUMEN
Erythrocytes infected with the human malaria parasite Plasmodium falciparum become structurally and antigenically modified as a consequence of intracellular parasite development. The new antigens that appear on the surface of the infected erythrocyte originate from parasite-encoded proteins and by modification of the erythrocyte membrane protein band 3. Here, we show that anti-peptide antibodies generated against an amino acid sequence (YETFSKLIKIFQDH) of human band 3, and previously identified as mediating adhesion of infected erythrocytes to CD36, recognized P. falciparum-infected erythrocytes. In addition, sera from individuals living in a malaria endemic area (and who are presumably immune) contained immunoglobulins specific for this region of band 3. The anti-peptide antibodies reacted with the surface excrescences (knobs) on falciparum-infected erythrocytes. In uninfected erythrocytes, the band 3 region was cryptic and its exposure on the falciparum-infected erythrocyte surface required clustering of band 3 protein. Thus, a parasite-induced modification of band 3 promotes adhesion and induces antigenic changes in the P. falciparum-infected erythrocyte.
Asunto(s)
Proteína 1 de Intercambio de Anión de Eritrocito , Antígenos de Protozoos/inmunología , Eritrocitos/parasitología , Plasmodium falciparum/patogenicidad , Ácido 4,4'-Diisotiocianostilbeno-2,2'-Disulfónico/metabolismo , Secuencia de Aminoácidos , Animales , Proteína 1 de Intercambio de Anión de Eritrocito/química , Proteína 1 de Intercambio de Anión de Eritrocito/genética , Proteína 1 de Intercambio de Anión de Eritrocito/inmunología , Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Anticuerpos Antiprotozoarios/inmunología , Antígenos de Protozoos/química , Antígenos de Protozoos/metabolismo , Adhesión Celular , Membrana Eritrocítica/química , Membrana Eritrocítica/inmunología , Eritrocitos/fisiología , Humanos , Malaria Falciparum/inmunología , Malaria Falciparum/parasitología , Ratones , Plasmodium falciparum/inmunología , ConejosRESUMEN
The role of the erythrocyte anion exchanger, band 3 protein (AE1), in the adhesion of Plasmodium falciparum-infected erythrocytes to CD36 and thrombospondin (TSP) was studied. Two specific anion exchange inhibitors that bind covalently to different regions of the band 3 molecule affected cytoadherence in dissimilar ways. Modification of lysine 539 by diisothiocyanostilbene sulfonic acid (DIDS) resulted in a significant reduction in the adhesive properties of parasitized erythrocytes for CD36, but not TSP, whereas treatment with fluorescein-5-maleimide, which modifies lysine 430, was without effect on both TSP and CD36 binding. The adhesive properties of the DIDS binding region (DBR) was demonstrated by competition experiments using synthetic peptides and by direct interaction of such peptides with CD36 transfected CHO cells. The results suggest that host membrane proteins such as AE1 contribute to the adhesion of malaria-infected erythrocytes to CD36.
Asunto(s)
Proteína 1 de Intercambio de Anión de Eritrocito/química , Proteína 1 de Intercambio de Anión de Eritrocito/metabolismo , Antígenos CD36/metabolismo , Eritrocitos/parasitología , Plasmodium falciparum/fisiología , Plasmodium falciparum/patogenicidad , Secuencia de Aminoácidos , Animales , Proteína 1 de Intercambio de Anión de Eritrocito/genética , Sitios de Unión , Antígenos CD36/genética , Células CHO , Adhesión Celular , Cricetinae , Eritrocitos/inmunología , Humanos , Técnicas In Vitro , Malaria Falciparum/sangre , Malaria Falciparum/inmunología , Malaria Falciparum/parasitología , Datos de Secuencia Molecular , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Trombospondinas/metabolismo , TransfecciónRESUMEN
Sequestration in the microvessels of the deep tissues is a signal characteristic of the human malaria Plasmodium falciparum. The adhesion of P. falciparum-infected cells to the post-capillary endothelial cells in various tissues contributes to both the pathology of the disease (i.e. organ infarcts and coma) and parasite survival (i.e. the microaerophilic environment favors plasmodial growth while avoiding passage through and destruction in the spleen). This report identifies a conformational change in a region of band 3 protein involved in the enhanced adhesiveness of P. falciparum-infected erythrocytes.
Asunto(s)
Proteína 1 de Intercambio de Anión de Eritrocito/química , Eritrocitos/parasitología , Plasmodium falciparum/patogenicidad , Naranja de Acridina , Animales , Adhesión Celular , Humanos , Malaria Falciparum/parasitología , Malaria Falciparum/patología , Conformación ProteicaRESUMEN
Infected erythrocytes containing the more mature stages of the human malaria Plasmodium falciparum may adhere to endothelial cells and uninfected red cells. These phenomena, called sequestration and rosetting, respectively, are involved in both host pathogenesis and parasite survival. This review provides a critical summary of recent advances in the characterization of the molecules of the infected red blood cell involved in adhesion, i.e. parasite-encoded molecules (PfEMP1, MESA, rifins, stevor, clag 9, histidine-rich protein), a modified host membrane protein (band 3) and exofacial exposure of phosphatidylserine, as well as receptors on the endothelium, i.e. thrombospondin, CD36, ICAM-1 (intercellular adhesion molecule), and chondroitin sulfate.
Asunto(s)
Adhesión Celular , Endotelio Vascular/fisiología , Eritrocitos/fisiología , Eritrocitos/parasitología , Malaria/fisiopatología , Plasmodium falciparum/fisiología , Animales , Endotelio Vascular/citología , Humanos , Malaria/parasitología , Proteínas de la Membrana/metabolismo , Proteínas Protozoarias/metabolismoRESUMEN
Monoclonal antibodies recognizing proteins localized to a unique subcellular compartment within the malaria parasite are described in this report. These monoclonal antibodies recognize Plasmodium falciparum proteins of 68, 45 and 22 kDa proteins which are also conserved in rodent Plasmodium species. Co-localization studies indicate that these proteins are located in a brefeldin A-induced compartment which was previously proposed to be an early step in the export of proteins from the parasite into the infected erythrocyte. COPII coat proteins, Sar1p and Sec31p, and the endoplasmic reticulum-associated chaperone, BiP, all partially co-localize with the 68 and 22 kDa proteins, thus suggesting that this subcellular compartment has some similarities to the endoplasmic reticulum or that this compartment represents a domain of the endoplasmic reticulum. The 68 and 22 kDa proteins are highly soluble in non-ionic detergent and are likely to be located within the lumen of a membrane-bound compartment. These proteins found within this subcellular compartment are present throughout the blood stage from very early rings to segmenters. The results of this study further substantiate the existence of an alternate secretory pathway in the malaria parasite which plays a role in the export of proteins into the host erythrocyte.
Asunto(s)
Proteínas de Choque Térmico , Orgánulos/química , Plasmodium falciparum/química , Proteínas Protozoarias/análisis , Proteínas de Saccharomyces cerevisiae , Animales , Anticuerpos Monoclonales/inmunología , Anticuerpos Antiprotozoarios/inmunología , Proteínas Portadoras/análisis , Retículo Endoplásmico/química , Chaperón BiP del Retículo Endoplásmico , Técnica del Anticuerpo Fluorescente , Immunoblotting , Chaperonas Moleculares/análisis , Fosfoproteínas/análisis , Plasmodium falciparum/crecimiento & desarrollo , Plasmodium falciparum/ultraestructura , Proteínas Protozoarias/química , Proteínas Protozoarias/inmunología , Proteínas Protozoarias/metabolismo , Solubilidad , Proteínas de Transporte VesicularRESUMEN
Los merozoítos del parásito Plasmodium falciparum contienen en su superficie los fragmentos producidos por el primer procesamiento proteolítico de la proteína MSP-1 (merozoite surface protein-1). Dichos fragmentos tienen pesos moleculares relativos aproximados de 83, 42, 38 y 28-30 kDa, respectivamente. En este estudio se describe la producción y caracterización de un anticuerpo monoclonal, denominado 8F4, que reconoce la proteína MSP-1 dadas las siguientes características del antígeno: 1) localización subcelular, 2) peso molecular relativo, 3) período de expresión durante el ciclo eritrocítico, 4) tipo de asociación con la membrana plasmática del parásito y 5) presencia de epítopes compartidos con MSP-1. Adicionalmente, se estableció que 8F4 reconoce el fragmento de 28-30 kDa, producto del primer procesamiento proteolítico de MSP-1. Los análisis realizados permiten confirmar que MSP-1 subíndice 28-30 no permanece en la superficie del merozoíto después de ocurrida la invasión, lo cual sugiere que hace parte del complejo de polipéptidos que es liberado por el merozoíto previamente al evento de la invasión. 8F4 es el primer anticuerpo monoclonal reportado hasta el momento que reconoce específicamente este fragmento
Asunto(s)
Anticuerpos Monoclonales , Proteína 1 de Superficie de Merozoito , Plasmodium falciparum , Formación de AnticuerposRESUMEN
Little is known about the molecular mechanisms underlying the release of merozoites from malaria infected erythrocytes. In this study membranous structures present in the culture medium at the time of merozoite release have been characterized. Biochemical and ultrastructural evidence indicate that membranous structures consist of the infected erythrocytes membrane, the parasitophorous vacuolar membrane and the residual body containing electron dense material. These are subcellular compartments expected in a structure that arises as a consequence of merozoite release from the infected cell. Ultrastrutural studies show that a novel structure extends from the former parasite compartment to the membrane. Since these membrane modifications are detected only after merozoites have been released from the infected erythrocyte, it is proposed that they might play a role in the release of merozoites from the host cell.
Asunto(s)
Animales , Eritrocitos/parasitología , Membrana Eritrocítica/parasitología , Plasmodium falciparum/crecimiento & desarrollo , Malaria Falciparum , Fusión de MembranaRESUMEN
Aunque el efecto de la temperatura en la transformación axénica de Leishmania ha sido ampliamente estudiado, el papel que esta variable juega en la transformación del parásito intracelular se desconoce. El objetivo del presente trabajo fue evaluar si la transformación intracelular de promastigotes en amastigotes ocurre a bajas temperaturas. Cuando se infectaron macrófagos murinos de la línea celular J-774 a dos temperaturas diferentes (24 y 33§C), se observaron formas intracelulares de Leishmania amazonensis a las dos temperaturas. Los parásitos intracelulares producidos se compararon mediante criterios morfológicos, inmunológicos y ultraestructurales. Los resultados indican que los parásitos obtenidos en infecciones a 33§C son similares morfológica, inmunológica y ultraestructuralmente con las formas intracelulares obtenidas in vivo conocidas como amastigotes; sin embargo, los parásitos producidos a temperaturas más bajas (24§C) no tienen similitud antigénica ni ultraestructural con los anteriores. Se concluye que la temperatura cumple un papel relevante en la transformación de la forma extracelular de Leishmania amazonensis hacia la forma intracelular durante su invasión a macrófagos murinos