RESUMEN
Chronic malaria is a major public health problem and significant challenge for disease eradication efforts. Despite its importance, the biological factors underpinning chronic malaria are not fully understood. Recent studies have shown that host metabolic state can influence malaria pathogenesis and transmission, but its role in chronicity is not known. Here, with the goal of identifying distinct modifications in the metabolite profiles of acute versus chronic malaria, metabolomics was performed on plasma from Plasmodium-infected humans and nonhuman primates with a range of parasitemias and clinical signs. In rhesus macaques infected with Plasmodium coatneyi, significant alterations in amines, carnitines, and lipids were detected during a high parasitemic acute phase and many of these reverted to baseline levels once a low parasitemic chronic phase was established. Plasmodium gene expression, studied in parallel in the macaques, revealed transcriptional changes in amine, fatty acid, lipid and energy metabolism genes, as well as variant antigen genes. Furthermore, a common set of amines, carnitines, and lipids distinguished acute from chronic malaria in plasma from human Plasmodium falciparum cases. In summary, distinct host-parasite metabolic environments have been uncovered that characterize acute versus chronic malaria, providing insights into the underlying host-parasite biology of malaria disease progression.
Asunto(s)
Aminoácidos/sangre , Aminoácidos/metabolismo , Metabolismo de los Lípidos , Lípidos/sangre , Malaria/metabolismo , Adolescente , Adulto , Anciano , Animales , Modelos Animales de Enfermedad , Ácidos Grasos/sangre , Ácidos Grasos/metabolismo , Femenino , Expresión Génica , Glicerofosfolípidos/sangre , Glicerofosfolípidos/metabolismo , Interacciones Huésped-Parásitos/fisiología , Humanos , Macaca mulatta , Malaria/genética , Masculino , Metaboloma , Persona de Mediana Edad , Parasitemia , Plasmodium , Plasmodium falciparum , Adulto JovenRESUMEN
BACKGROUND: Plasmodium knowlesi is a monkey malaria species that is becoming a serious public health concern infecting hundreds and perhaps thousands of humans in Southeast Asia. Invasion of erythrocytes by merozoites entails a cascade of molecular interactions. One step involves the adhesion of Plasmodium reticulocyte binding-like (RBL) proteins. Plasmodium knowlesi merozoites express only two RBL invasion ligands, known as Normocyte Binding Proteins (PkNBPXa and PkNBPXb). METHODS: Overlapping N-terminal regions of PkNBPXa and PkNBPXb were expressed in COS7 cells and tested for surface expression and adhesion to rhesus monkey erythrocytes. Subsequent tests to study specific receptor ligand interactions included adhesion to a panel of human and non-human primate erythrocytes, enzymatic treatment, and site directed mutagenesis. RESULTS: An N-terminal cysteine-rich region of PkNBPXb (PkNBPXb-II) exhibited specific adhesion to rhesus monkey erythrocytes. Mutation of four of five cysteines in PkNBPXb-II interfered with its surface expression on COS7 cells, suggesting disulphide bond conformation is critical for intracellular trafficking. Binding of PkNBPXb-II was abolished when rhesus erythrocytes were pre-treated with chymotrypsin, but not trypsin or neuraminidase. PkNBPXb-II also bound other Old World monkey species and gibbon erythrocytes. However, erythrocytes from other primate species including humans did not bind to PkNBPXb-II or native PkNBPXb. Importantly, unlike PkNBPXb, PkNBPXa bound human erythrocytes, and this binding was independent of the Duffy blood group determinant. CONCLUSIONS: The data reported here begins to clarify the functional domains of the P. knowlesi RBLs. A binding domain has been identified and characterized in PkNBPXb. Notably, this study demonstrates that unlike PkNBPXb, PkNBPXa can bind to human erythrocytes, suggesting that PkNBPXa may function as a ligand to enable the invasion of P. knowlesi merozoites into human cells.
Asunto(s)
Adhesión Celular , Eritrocitos/parasitología , Plasmodium knowlesi/genética , Plasmodium knowlesi/patogenicidad , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Secuencia de Aminoácidos , Animales , Asia Sudoriental , Sitios de Unión , Células COS , Chlorocebus aethiops , Clonación Molecular , Expresión Génica , Humanos , Macaca mulatta , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Alineación de SecuenciaRESUMEN
The human malaria parasite Plasmodium vivax is responsible for 25-40% of the approximately 515 million annual cases of malaria worldwide. Although seldom fatal, the parasite elicits severe and incapacitating clinical symptoms and often causes relapses months after a primary infection has cleared. Despite its importance as a major human pathogen, P. vivax is little studied because it cannot be propagated continuously in the laboratory except in non-human primates. We sequenced the genome of P. vivax to shed light on its distinctive biological features, and as a means to drive development of new drugs and vaccines. Here we describe the synteny and isochore structure of P. vivax chromosomes, and show that the parasite resembles other malaria parasites in gene content and metabolic potential, but possesses novel gene families and potential alternative invasion pathways not recognized previously. Completion of the P. vivax genome provides the scientific community with a valuable resource that can be used to advance investigation into this neglected species.
Asunto(s)
Genoma de Protozoos/genética , Genómica , Malaria Vivax/parasitología , Plasmodium vivax/genética , Secuencias de Aminoácidos , Animales , Artemisininas/metabolismo , Artemisininas/farmacología , Atovacuona/metabolismo , Atovacuona/farmacología , Núcleo Celular/genética , Cromosomas/genética , Secuencia Conservada/genética , Eritrocitos/parasitología , Evolución Molecular , Haplorrinos/parasitología , Humanos , Isocoras/genética , Ligandos , Malaria Vivax/metabolismo , Familia de Multigenes , Plasmodium vivax/efectos de los fármacos , Plasmodium vivax/patogenicidad , Plasmodium vivax/fisiología , Análisis de Secuencia de ADN , Especificidad de la Especie , Sintenía/genéticaRESUMEN
Plasmodium is dependent on glycolysis for ATP production. The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (G3PDH) plays an important role in glycolysis and is, therefore, a potential target for antimalarial drug development. The g3pdh gene of nine Plasmodium species was sequenced from genomic DNA and the type and origin determined by phylogenetic analysis. Substitutions were analyzed over a wide phylogenetic spectrum in relation to the known three-dimensional structures of the P. falciparum and human proteins. Substitutions were found within the functional domains (Rossman NAD+-binding and catalytic domains). A number of replacements within the adenosyl-binding surfaces were found to be conserved within the Chromoalveolates, others in the Apicomplexa, and still others within the genus Plasmodium, all of which were different from the human sequence. These sites may prove to be of functional importance and provide insights for drug-targeting studies, as have other regions examined in Leishmania and Toxoplasma G3PDH research.
Asunto(s)
Gliceraldehído 3-Fosfato Deshidrogenasa (NADP+)/química , Gliceraldehído 3-Fosfato Deshidrogenasa (NADP+)/genética , Filogenia , Plasmodium/genética , Secuencia de Aminoácidos , Animales , Gliceraldehído 3-Fosfato Deshidrogenasa (NADP+)/fisiología , Datos de Secuencia Molecular , Conformación Proteica , Homología de Secuencia de AminoácidoRESUMEN
Naturally acquired antibody reactivity to two major Plasmodium vivax vaccine candidates was investigated in 294 donors from three malaria-endemic communities of Rondônia state, Brazil. Antibody recognition of recombinantly expressed antigens covering five different regions of P. vivax reticulocyte binding protein 1 (PvRBP1) and region II of P. vivax Duffy binding protein (PvDBP-RII) were compared. Positive IgG responses to these antigens were significantly related to the level of malaria exposure in terms of past infections and years of residence in the endemic area when corrected for age. The highest prevalence of anti-PvRBP1 total IgG antibodies corresponded to the amino acid regions denoted PvRBP1(431-748) (41%) and PvRBP1(733-1407) (47%). Approximately one-fifth of positively responding sera had titers of at least 1:1,600. Total IgG responses to PvDBP-RII were more prevalent (67%), of greater magnitude, and acquired more rapidly than those to individual PvRBP1 antigens. Responses to both PvRBP1 and PvDBP-RII were biased toward the cytophilic subclasses IgG1 and IgG3. These data provide the first insights on acquired antibody responses to PvRBP1 and a comparative view with PvDBP-RII that may prove valuable for understanding protective immune responses to these two vaccine candidates as they are evaluated as components of multitarget blood-stage vaccines.