Malaria ist eine schwerwiegende Krankheit, die jährlich über eine Million Menschen tötet. Die zunehmende Resistenzbildung gegenüber den verwendeten Medikamenten macht die Entwicklung neuer Antimalariamittel dringend notwendig. Daher sind die Vitamin B6 Synthese und der Shikimatweg von besonderem Interesse, da diese beiden Synthesewege nur im Parasiten und nicht im Menschen vorkommen. Unter der Voraussetzung, dass diese essentiell für den Parasiten sind, böten sie ideale Ansatzpunkte zur Entwicklung neuer Antimalariamittel. Voraus gegangene Studien haben gezeigt, dass Plasmodium falciparum in der Lage ist, PLP de novo mittels eines bifunktionalen Enzymkomplex, bestehend aus den Proteinen Pdx1 und Pdx2, zu synthetisieren. Pdx1 stellt dabei die eigentliche Synthase dar, während Pdx2 als Glutaminase-Partner das benötigte Ammoniumion für den heterocyclen Ring bereitstellt. Zusätzlich dazu verfügt der Parasit auch über einen salvage pathway um PLP zu „recyclen“, in dem der Pyridoxalkinase PdxK eine Schlüsselfunktion zufällt. Knockout Studien der pdx1 im Mausmalariasystem P. berghei haben gezeigt, dass PbPdx1 für eine optimale Entwicklung der Blutstadien benötigt wird, nicht jedoch für deren Überleben. Im Rahmen dieser Arbeit habe ich die Effekte eines pbpdxK(-) Knockouts in demselben System untersucht. Es konnte eine monoklonale Knockoutlinie generiert werden, was zeigte, dass PbPdxK nicht essentiell für das Überleben des Parasiten in den Blutstadien ist. Die Entwicklung während des Blutstadiums war von dem pbpdxK(-) Knockout nicht betroffen. Allerdings zeigte sich im Moskitostadium eine drastische Reduktion der Sporozoitenzahl sowohl in den Mitteldärmen als auch in den Speicheldrüsen. Dieses Ergebnis legt nahe, dass PbPdxK essentiell für das Überleben der Sporozoiten ist. Daneben wurde versucht, die Gene pfpdx1, pfpdx2 sowie pfpdxK in P. falciparum 3D7 durch Verwendung der single cross over Strategie auszuschalten. Es konnte jedoch für keines der genannten Konstrukte eine Integration in die jeweiligen Genloci anhand von PCR-Analysen nachgewiesen werden. Ebenso scheiterte der Versuch, durch Rekombination eines komplementären Genabschnitts die Funktion des Gens zu rekonstituieren. Daher bleibt es unklar, ob pfpdx1, pfpdx2 und pfpdxK durch Knockout Strategien auszuschalten sind oder nur für Genmanipulationen nicht zugänglich sind. Die Kultivierung von P. falciparum 3D7 Parasiten in Vitamin B6 depletiertem Medium hatte keinen Effekt auf deren Wachstum. Eine anschließende Analyse der Proteinextrakte zeigte eine erhöhte Expression der PfPdxK, während sich das Expressionslevel der PfPdx1 nicht veränderte. Es scheint, dass der Parasit in der Lage ist Vitamin B6 Mangel durch vermehrte Nutzung des salvage pathways vollständig zu kompensieren. Frühere Arbeiten zeigten, dass der C-Terminus der Pdx1 in die Aktivität des PLP Synthasekomplexes involviert ist. Aus diesem Grund wurden verschiedene C-terminale Deletionsmutanten der PfPdx1 konstruiert und dabei bis zu 30 Aminosäuren entfernt. Diese Analysen ergaben, dass der C-Terminus vier verschiedene Funktionen besitzt: das Assembly der Pdx1 Untereinheiten zum Dodekamer, die Bindung des Pentosesubstrats Ribose 5-Phosphat, die Bildung des Intermediats I320 und schließlich die PLP Synthese. Diese unterschiedlichen Funktionen wurden durch verschiedene Deletionsvarianten identifiziert. Darüber hinaus waren alle Deletionsvarianten in der Lage, die Glutaminase Pdx2 zu aktivieren, was zeigt, dass das Dodekamer nicht Vorraussetzung für die Glutaminaseaktivität ist. Aufgrund der geringen PLP Syntheseaktivität in vitro wurde vermutet, dass der PfPdx1/PfPdx2 Komplex durch einen zusätzlichen Faktor aktiviert wird. Daher wurde versucht, mittels Yeast 2-Hybrid, basierend auf einer PCR-amplifizierten P. falciparum 3D7 cDNA-Bibliothek als bait und PfPdx1 als prey, einen Interaktionspartner zu identifizieren. Mehrere Klone wurden gewonnen, die alle einen Bereich des Mal13P1.540, einem putativen Hsp70 Proteins, enthielten. Jedoch scheiterten alle Versuche, die Protein-Protein-Interaktion mit rekombinant exprimierten Protein zu bestätigen. Ebenso war es nicht möglich, das vollständige Mal13P1.540 rekombinant zu exprimieren sowie dessen Lokalisation in vivo zu bestimmen. Daher bleibt die Interaktion von PfPdx1 und Mal13P1.540 ungeklärt. Neben der Vitamin B6 Biosynthese konnten auch einige Gene des Shikimatweges in Plasmodium identifiziert werden. In P. berghei konnten der C-terminale Teil der 3-Dehydroquinatsynthase (2) sowie die Shikimatkinase (5) und die 5-Enoylpyruvylshikimat 3-Phosphatsynthase (6) in einem open reading frame (ORF) identifiziert werden, der dieselbe genetische Organisation aufweisen wie der Arom-Komplex der Hefen. Mit Hilfe eines Komplementationsassay wurde die Funktionalität dieses ORFs überprüft. Dazu wurden S. cerevisiae BY4741Δaro1, ein Hefestamm ohne funktionalen Arom-Komplex, mit dem Pb2_6_5_ABC Fragment transformiert. Die so transformierten Hefen waren nicht in der Lage, auf Mangelplatten ohne aromatische Aminosäuren zu wachsen, was zeigte, dass das Pb2_6_5_ABC Konstrukt den BY4741Δaro1 Phänotyp nicht komplementieren konnte. Der Versuch, mit Hilfe des Baculovirussytems rekombiant exprimiertes Protein zu erhalten, verlief erfolglos. Ebenso war es nicht möglich, Teile des Proteins für Immunisierungen zu exprimieren. Daher bleibt die Funktionalität des Pb2_6_5_ABC Konstruktes ungeklärt. / Malaria is a serious burden of mankind causing over one million deaths a year. In view of the raising number of resistances to common drugs there is an urgent need for the development of new antimalarial drugs. In this respect, the vitamin B6 biosynthesis and the shikimate pathway are of particular interest, since these synthesis pathways are only present in the malarial parasites and not in their human host. Given their essentiality for the parasite, they would represent ideal targets for antimalarial drug development. Previous studies revealed that Plasmodium falciparum is able to produce PLP de novo through a bifunctional enzyme complex composed of the proteins Pdx1 and Pdx2, of which Pdx1 is the actual synthase and Pdx2 the glutaminase partner providing the nitrogen for the ring system. In addition, the parasites possess a salvage pathway for PLP, of which pyridoxal kinase, PdxK, is a key player. Knockout studies of the pdx1 in the rodent malaria system P. berghei showed, that pbpdx1 is required for the optimal development of parasite blood stages but is not essential for parasite survival. Here, I investigated the effect of a pbpdxK(-) knockout in the same system. A monoclonal knockout strain was obtained, indicating that PbPdxK is not essential for the survival of the parasite. Blood stages were not affected by the knockout. However, in the mosquito stages pbpdxK(-) showed a tremendous reduction of sporozoites numbers in the midgut and in the salivary glands, indicating that PbPdxK is essential for the survival of sporozoites. It was then also tried to knockout pfpdx1, pfpdx2 and pfpdxK in the P. falciparum 3D7 strain by using the single cross over strategy. However, no integration of the constructs in the corresponding gene locus could be detected by a PCR approach. Also an approach to complement the loss of endogenous gene function by generating a functional gene copy upon recombination failed. Thus, it remains unclear if pfpdx1, pfpdx2 and pfpdxK can be knocked out or are inaccessible for gene targeting in P. falciparum. Cultivation of P. falciparum 3D7 parasites in medium deficient of vitamin B6 showed no effect on the growth rate of the parasites. Analysis of protein extracts of these parasites revealed an upregulation of PfPdxK expression, whereas the level of PfPdx1 remained stable. Thus it seems that the parasite is fully able to compensate vitamin B6 malnutrition by the increased usage of the salvage pathway. Previous studies on the activity of the PLP synthase complex indicated that the C-terminal end of Pdx1 is involved in PLP formation. Therefore several C-terminal deletion mutants of PfPdx1 were constructed, removing up to 30 amino acids. These analyses revealed that the C-terminus has four distinct functionalities: assembly of the Pdx1 monomers, binding of the pentose substrate (ribose 5-phosphate), formation of the reaction intermediate I320, and finally PLP synthesis. Deletions of distinct C-terminal regions distinguish between these individual functions. All variants were able to activate the glutaminase PfPdx2, indicating that the dodecameric structure is not a prerequisite for Pdx2 activation. Due to the low PLP synthase activity in vitro it was assumed that the PfPdx1/PfPdx2 complex maybe activated by an additional protein. Hence a yeast 2-hybrid assay was performed, using PfPdx1 as prey and a PCR-amplified cDNA-library of P. falciparum 3D7 as bait. Several clones were detected on high stringency plates, containing all a region of Mal13P1.540, a putative Hsp70 protein. Trials to confirm protein-protein interaction with recombinantly produced proteins failed as well as protein expression of full length Mal13P1.540. It was also not possible to determine the localisation of Mal13P1.540 in vivo. Thus, an interaction of PfPdx1 with Mal13P1.540 could so far not be verified. Besides the vitamin B6 biosynthesis, some genes of the shikimate pathway were identified in Plasmodium. In P. berghei, the C-terminal part of the dehydroquinatesynthase (2) as well as the shikimate kinase (5) and 5-enoylpyruvylshikimate 3-phosphatesynthase (6) were found in a single open reading frame having the same organisation as the arom-complex of yeast. To proof the functionality of these genes a complementation assay with S. cerevisiae BY4741Δaro1 with the Pb2_6_5_ABC construct, comprising the above mentioned genes, was performed. However, transformded yeast strains were not able to grow on minimal media without aromatic amino acids, indicating that they were not able to produce chorismate. Recombinant expression of this constructs in the baculovirussystem did not yield any detectable protein. Expression of parts of this protein for immunisation was also not successful. Hence, the functionality of this protein remains to be established.

A malária mata mais de um milhão de pessoas por ano, sendo uma das doenças infecciosas mais relevantes e um grande problema de saúde pública. Além disso, o surgimento de cepas resistentes aos quimioterápicos utilizados faz necessário o estudo de novos alvos para tratamentos contra esta doença. No nosso laboratório foi demonstrada a biossíntese de isoprenóides, em P. falciparum pela via MEP. Sabe-se que substâncias inibidoras da biossíntese de isoprenóides, dentre essas os terpenos, apresentam atividade antimalárica. Levando em consideração o anterior, nós avaliamos o potencial antimalárico do álcool perilico (POH) em P. falciparum e P. berghei. Nossos resultados demonstraram que o POH teve efeito inibitório contra o crescimento do P. falciparum in vitro, nas cepas 3D7 e K1 com uma IC50 de 4,8 ± 0,5 &mu;M, e 10,41±2,33 &mu;M, respectivamente. Além disso, o POH não teve efeito tóxico na linhagem celular Vero. Ainda, Comprovamos que o POH inibiu a farnesilação de proteinas entre 20 e 37 KDa de P. falciparum. Por outro lado, os experimentos in vivo não mostraram eficácia do tratamento do POH contra PbGFP em camundongos Balb/c. Em contraste, foi demostrada a eficácia do POH na de malária cerebral experimental (MCE), , indicando uma redução na taxa de incidência da MCE no grupo tratado com POH, comparado o não tratado ( P<0,05). Além disso, o POH reduziu a inflamação no cérebro dos animais tratados, uma vez que teve uma redução significativa na adesão de leucócitos aos vasos cerebrais (P<0.001), como também, o numero de hemorragias foi menor comparados com os animais não tratados. (P<0.0001). Portanto, os resultados obtidos nesta pesquisa abrem novas alternativas no estudo do mecanismo de ação do POH como um terpeno com grande potencial para tratar MC. / Malaria kills over one million people a year worldwide, and is one of the most important infectious diseases and a major public health problem. Furthermore, the emergence of resistant strains to chemotherapeutic agents used, make it necessary to study new targets for treatments against this disease. In our laboratory we have demonstrated the isoprenoids biosynthesis in P. falciparum, by the MEP pathway. It is known that the substances that inhibit isoprenoid biosynthesis, among these terpenes, have antimalarial activity in vitro and in vivo. Considering this, we evaluate the antimalarial potential of PA (POH) in P. falciparum and P. berghei. Our results showed that the POH had inhibitory effect against the growth of strains 3D7 and K1 of P. falciparum in vitro, with an IC50 of 4.8 &mu;M ± 0.5, and 10.41 ± 2.33 &mu;M, respectively. Furthermore, the POH had no toxic effect on cell line Vero. Moreover, the POH proved that inhibited proteins farnesylation from 20 to 37 kDa of P.falciparum. On the other hand, in vivo experiments did not show efficacy on treatment against POH PbGFP in BALB/c mice. In contrast, the effectiveness of POH in the experimental cerebral malaria (MCE) was demonstrated, indicating a reduction in the incidence rate of MCE in the group treated with POH, compared with of untreated animals (P <0.05). In addition, the POH reduced inflammation in the brain of treated animals, since it had a significant reduction in leukocyte adhesion to cerebral vessels (P <0.001), as also the number of bleeding was lower compared to untreated animals (P<0.0001). Therefore, the results obtained in this work provide new alternatives to study the POH\'s mechanism of action as a terpene with great potential to treat MC.

A malária mata mais de um milhão de pessoas por ano, sendo uma das doenças infecciosas mais relevantes e um grande problema de saúde pública. Além disso, o surgimento de cepas resistentes aos quimioterápicos utilizados faz necessário o estudo de novos alvos para tratamentos contra esta doença. No nosso laboratório foi demonstrada a biossíntese de isoprenóides, em P. falciparum pela via MEP. Sabe-se que substâncias inibidoras da biossíntese de isoprenóides, dentre essas os terpenos, apresentam atividade antimalárica. Levando em consideração o anterior, nós avaliamos o potencial antimalárico do álcool perilico (POH) em P. falciparum e P. berghei. Nossos resultados demonstraram que o POH teve efeito inibitório contra o crescimento do P. falciparum in vitro, nas cepas 3D7 e K1 com uma IC50 de 4,8 ± 0,5 &mu;M, e 10,41±2,33 &mu;M, respectivamente. Além disso, o POH não teve efeito tóxico na linhagem celular Vero. Ainda, Comprovamos que o POH inibiu a farnesilação de proteinas entre 20 e 37 KDa de P. falciparum. Por outro lado, os experimentos in vivo não mostraram eficácia do tratamento do POH contra PbGFP em camundongos Balb/c. Em contraste, foi demostrada a eficácia do POH na de malária cerebral experimental (MCE), , indicando uma redução na taxa de incidência da MCE no grupo tratado com POH, comparado o não tratado ( P<0,05). Além disso, o POH reduziu a inflamação no cérebro dos animais tratados, uma vez que teve uma redução significativa na adesão de leucócitos aos vasos cerebrais (P<0.001), como também, o numero de hemorragias foi menor comparados com os animais não tratados. (P<0.0001). Portanto, os resultados obtidos nesta pesquisa abrem novas alternativas no estudo do mecanismo de ação do POH como um terpeno com grande potencial para tratar MC. / Malaria kills over one million people a year worldwide, and is one of the most important infectious diseases and a major public health problem. Furthermore, the emergence of resistant strains to chemotherapeutic agents used, make it necessary to study new targets for treatments against this disease. In our laboratory we have demonstrated the isoprenoids biosynthesis in P. falciparum, by the MEP pathway. It is known that the substances that inhibit isoprenoid biosynthesis, among these terpenes, have antimalarial activity in vitro and in vivo. Considering this, we evaluate the antimalarial potential of PA (POH) in P. falciparum and P. berghei. Our results showed that the POH had inhibitory effect against the growth of strains 3D7 and K1 of P. falciparum in vitro, with an IC50 of 4.8 &mu;M ± 0.5, and 10.41 ± 2.33 &mu;M, respectively. Furthermore, the POH had no toxic effect on cell line Vero. Moreover, the POH proved that inhibited proteins farnesylation from 20 to 37 kDa of P.falciparum. On the other hand, in vivo experiments did not show efficacy on treatment against POH PbGFP in BALB/c mice. In contrast, the effectiveness of POH in the experimental cerebral malaria (MCE) was demonstrated, indicating a reduction in the incidence rate of MCE in the group treated with POH, compared with of untreated animals (P <0.05). In addition, the POH reduced inflammation in the brain of treated animals, since it had a significant reduction in leukocyte adhesion to cerebral vessels (P <0.001), as also the number of bleeding was lower compared to untreated animals (P<0.0001). Therefore, the results obtained in this work provide new alternatives to study the POH\'s mechanism of action as a terpene with great potential to treat MC.

O Antígeno-1 de Membrana Apical (AMA-1) de merozoítas de Plasmodium é um dos principais candidatos a compor uma vacina contra a malária. A função biológica de AMA-1 não é totalmente conhecida, entretanto, existem evidências que sugerem a participação dessa proteína na ligação a eritrócitos de diferentes espécies de Plasmodium. O objetivo deste estudo foi investigar a participação de AMA-1 de P. vivax (PvAMA-1) na ligação a eritrócitos humanos utilizando células COS-7 transfectadas com plasmídios recombinantes codificando diferentes regiões do ectodomínio de PvAMA-1. Para isso, os genes que codificam os domínios I-II ou III de PvAMA-1 foram inseridos no vetor pDisplay-EGFP, que permite a expressão das proteínas recombinantes em fusão com a porção N-terminal da Proteína Fluorescente Verde (GFP). Em paralelo, utilizamos construções contendo os genes que codificam a região C-terminal de 19 kDa da Proteína 1 de Superfície do Merozoíta (PvMSP119) e a região II da Duffy Binding Protein (PvDBP-RII). As quatro construções foram utilizadas para transfectar células COS-7 na presença de lipofectamina. A eficiência das transfecções transientes foi confirmada por imunofluorescência utilizando anticorpos específicos. Em seguida, estudamos a participação dos diferentes domínios de PvAMA-1 na ligação aos eritrócitos. Nossos resultados mostraram que os domínios contíguos I-II, ao contrário do domínio III, foram capazes de se ligar a eritrócitos in vitro. Essa ligação foi específica, pois soros de indivíduos infectados por P. vivax e soros policlonais de camundongos contendo anticorpos anti-PvAMA-1 foram capazes de inibir essa ligação em 82,0% e 79,8%, respectivamente. Além disso, anticorpos monoclonais dirigidos contra o domínio II dessa proteína foram capazes de inibir parcialmente essa ligação. Após o tratamento de eritrócitos com tripsina ou quimiotripsina, estas células perderam grande parte de sua capacidade de ligação, sugerindo que o receptor para PvAMA-1 tenha constituição predominantemente protéica. Em conjunto, nossos resultados podem servir de base para futuros estudos visando um melhor entendimento da função de anticorpos gerados durante a infecção natural ou induzidos após vacinação com PvAMA-1. / The Apical Membrane Antigen (AMA-1) of Plasmodium merozoites is one of the main candidates to be part of a vaccine against malaria. The biological function of AMA-1 is unknown. However, there are evidences that suggest the participation of this protein in the interaction with erythrocytes (RBC) of different Plasmodium species. Using transfected COS-7 cells with recombinant plasmids encoding different portions of the PvAMA-1 ectodomain, our aim was to identify possible domains of PvAMA-1 able to interact with human RBC. The genes that encoded domains I and II in combination or domain III of PvAMA-1 were cloned into the pDisplay-EGFP vector. This vector allows expression of the protein fused to the N-terminus of enhanced green fluorescent protein (GFP). In parallel, we also used constructions containing the genes that encoded the 19 kDa C-terminal region of Merozoite Surface Protein 1 (PvMSP119) and region II of the Duffy Binding Protein (PvDBP-RII). Constructions were used to transiently transfect COS-7 cells. The efficiency of expression of all constructs was confirmed by immunofluorescence assay using specific antibodies. After that, we studied the participation of the different domains of PvAMA-1 in the binding to human RBC. We found that COS-7 cells expressing domains I-II, but not domain III, bound to human RBC in vitro. This binding was specific, because sera from malaria-infected patients and mouse polyclonal sera containing antibodies to PvAMA-1 were able to block the adhesion by 82.0% and 79.8%, respectively. Moreover, monoclonal antibodies directed against domain II were partially inhibitory in the cytoadherence assays. The receptor recognized on the surface of COS-7 cells expressing the domains I and II was partially removed after human RBC were treated with trypsin or chymotrypsin, suggesting that its composition is predominantly protein. In conclusion, our results can be used as basis for future studies aimed at better understating the function of the antibodies generated during the natural infection or after vaccination with PVAMA-1.

The human immune-regulatory protein, complement receptor type 1 (CR1, CD35), occurs on erythrocytes where it serves as the immune adherence receptor. It interacts with C3b, C4b, C1q and mannan-binding lectin (MBL). It additionally binds the Plasmodium falciparum protein, Rh4, in the non-sialic acid-dependent erythrocye-invasion pathway, and is also important for rosetting, via an interaction with P. falciparum erythrocyte membrane protein 1 (PfEMP1). A C3b/C4b, and PfEMP1 binding site lies in CCP modules 15-17 (out of 30 in CR1), while polymorphisms that afford advantage to some populations in dealing with severe malaria occur in CCPs 24-25, begging the question central to this thesis – do these polymorphism modulate function, and if so how? We hypothesized that the CR1 architecture apposes CCPs 15-17 and CCPs 24-25 using the exceptionally long linker between CCPs 21 and 22 as a hinge, thus polymorphic variants in CCPs 24-25 modulate functionality in CCPs 15-17. To test this, a panel of recombinant CR1 protein fragments (CCPs 21, 21-22, 20-23, 15-17, 17, 10-11, 17-25, 15-25 and 24-25) were produced in Pichia pastoris along with polymorphic forms of the relevant constructs. After purification, biophysical and biological methods were used to assess whether the linker does indeed act as a hinge, and the comparative abilities of the CCPs 15-25 variants (along with soluble CR1 (sCR1), CCPs 1-3 and the panel of CR1 fragments) to interact with a range of ligands were measured. We found no evidence from NMR for face-to-face contacts between CCPs 21 and 22 that would be consistent with the long linker permitting a 180-degree bend between them. Indeed, based on scattering and analytical ultracentrifugation data, CCPs 20-23 form an extended rather than a bent-back structure. All of the four Knops blood-group variants of the CCPs 15-25 proteins produced similar results according to dynamic light scattering and AUC indicating no structural difference or change in self-association state between variants. In addition, based on the data collected from surface plasmon resonance (SPR), ELISA and fluid-phase cofactor (for factor I) assays, there were no evidence of any difference between the polymorphic forms with respect to their interactions with C3b, C4b, C1q and MBL. Only weak interaction was observed for sCR1, and all CCPs 15-25 variants, with the relevant part of PfEMP1, and there was no measurable difference amongst the variants in disrupting rosettes. The sCR1-Rh4.9 interaction was confirmed by SPR; affinities measured between the binding domain of Rh4 and the panel of CR1 fragments identified CCPs 1-3 (site 1) as the main interaction site. It seemed unlikely therefore that CCPs 24 and 25 could modulate Rh4 binding; indeed none of the four CR1 15-25 variants bound Rh4.9 appreciably. Thus we concluded that allotypic variations in CCPs 24-25 have no measurable effect on the architecture as well as binding of CR1 to its host or parasite ligands The inferred selective pressure acting on these variants likely arise from some other (i.e. besides malaria) geographically localised infectious diseases.

Malaria persists today as a significant burden for a large part of the world. However, over the past few decades, a concerted effort by governments, non-governmental organizations, researchers, and community health workers worldwide has yielded progress in reducing the deadly impact of this disease. Today, some of these gains are threatened by the rise of antimalarial drug resistance, a recurring problem that has impeded global malaria reduction efforts before. Research on Plasmodium falciprum resistance to the numerous antimalarial compounds used today and in the past has made significant progress on determining which specific mutations modulate drug susceptibility and to what degree they do so. To gain a comprehensive understanding of drug resistance, we need to elucidate how and why it arises. Therefore, it is important to elucidate whether some malaria parasites acquire resistance-conferring mutations faster than others and why the native function of the genetic factors involved lend themselves to modulating drug resistance. For instance, resistance to multiple antimalarial therapies has repeatedly emerged in Southeast Asia. We investigated the long-held hypothesis that this was due to the ability of these parasites to mutate significantly faster than non-Southeast Asian strains. Elucidating whether this hypermutability phenotype accurately represents Southeast Asian parasite evolvability is important, as it can inform when resistance would be expected to next arise, particularly in the Greater Mekong Subregion in Southeast Asia. Here, we have adapted a fluctuation assay to Plasmodium falciparum and determined that some contemporaneous Cambodian parasites exhibit a mild mutator, but not a hypermutator, phenotype. We also show that this is likely driven by mutations in DNA repair genes carried predominantly by multidrug resistant Southeast Asian parasites. One of the most common genes in which drug resistance-conferring mutations occurs is the P. falciparum chloroquine resistance transporter (pfcrt). Mutations in pfcrt are associated with parasite susceptibility to many of the antimalarial compounds that have been used in a clinical setting to date. However, beyond its role in drug resistance, little is known about the native function of PfCRT. To facilitate the study of pfcrt, we have designed a zinc-finger nuclease (ZFN)-based gene engineering system that introduces a single double-strand break in intron 1 of pfcrt. Our ZFN strategy enables replacing nearly any endogenous pfcrt locus with a user-defined recombinant pfcrt allele. We show that our method of pfcrt allelic replacement is fast, efficient, and reliable. We used this system to generate a unique mutant parasite encoding a pfcrt-L272F mutation, which enlarges the parasite digestive vacuole, the lysosome-like organelle used to catabolize host-derived hemoglobin for amino acid salvage. Our results provide clear evidence that PfCRT is associated with the terminal steps of hemoglobin degradation, overall parasite fitness, and the balance of osmolytes across the digestive vacuole membrane. Bringing clarity to the native function of PfCRT can reveal how and why this single genetic factor has been and continues to be involved in the resistance to many different antimalarial compounds.

Made available in DSpace on 2015-04-11T13:38:50Z (GMT). No. of bitstreams: 1 Cynthia Ferreira.pdf: 1778547 bytes, checksum: ba2b6be94cabf06f34f677dac25cf356 (MD5) Previous issue date: 2013-11-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / In the legal Amazon, the Amazon state registered 180.290 malaria cases in 2006, that fact carries in huge economic and social impact for the region. The diagnosis is traditionally performed by the method of the giemsa stained thick blood smear, however low-level parasitemias and mixed infections are frequently not detected. These disadvantages justify the use of more sensitive and specific methodologies as the Polimerase Chain Reaction (PCR). The elevated cost of this method is one of the factors that prevent your utilization as routine in the different endemic regions. The PCR method is a technic that has been already implemented alternatively for drug monitoring, detections of mixed infections and genotyping studies. The present work had for goal the molecular characterization of Plasmodium falciparum and P. vivax field isolates of 12 endemic areas in Amazon state: Manaus, Careiro, Borba, Autazes, Itacoatira, Presidente Figueiredo, Barcelos, São da Cachoeira, Coari, Tefé, Guajará and Humaitá. The samples were obtained by microscopy diagnosis and the study of mixed infections was done through nested-PCR. Additionally was standardized methodology in real time to hasten and to give more reliability to the samples diagnosis used in studies developed by the malaria management of the Fundação de Medicina Tropical do Amazonas (FMTAM). The genes used to P. falciparum´s characterization were pfcrt and pfatp6, and for P. vivax was used the gene pvmdr, using the automatic sequencing and for genotiping assays using Real Time probes detection. All P. falciparum samples analyzed for the gene pfcrt demonstrated similar genetic profile to 7G8 strain control, which has the mutation K76T, proving the resistant phenotype observed in previous studies. For the gene pfatp6 were described 3 distinct haplotypes, with mutations identified in the positions 1204, 1888 and 2694. The analysis of the gene pvmdr in P. vivax identified mutations in codons 976 and 1076 in 11 samples of 100 total analyzed, distributed among four areas, Autazes, Coari, Manaus and Tefé. The identification of Plasmodium population´s genetic profile circulating in Amazon region is an important tool to understand the transmission dynamics of malaria and essential for constant monitoring the disease control actions / Na Amazônia legal, o estado do Amazonas registrou 180.290 casos de malária no ano de 2006, fato que acarreta em grande impacto econômico e social para a região. O diagnóstico é tradicionalmente realizado pela técnica da gota espessa (G.E.), no entanto fatores como a redução de sensibilidade em baixas parasitemias e dificuldade no diagnóstico de infecções mistas justificam a adoção de metodologias com maior sensibilidade e especificidade. Através da técnica de reação em cadeia da polimerase (PCR) esses objetivos podem ser alcançados, no entanto, o elevado custo ainda é um fator que impede sua utilização como rotina nas diferentes regiões endêmicas. Alternativamente, para monitoramento da resposta terapêutica, identificação de infecções mistas e estudos de genotipagem, esta técnica já é implementada. Este trabalho teve por objetivo a caracterização molecular de isolados de Plasmodium falciparum e P. vivax de 12 localidades endêmicas do estado do Amazonas: Manaus, Careiro, Borba, Autazes, Itacoatira, Presidente Figueiredo, Barcelos, São Gabriel da Cachoeira, Coari, Tefé, Guajará e Humaitá. As amostras foram obtidas segundo diagnóstico da G.E. no entanto foi feito o estudo de infecções mistas, não detectadas, através de PCR, e adicionalmente foi padronizada metodologia em tempo real para agilizar e dar maior confiabilidade aos diagnósticos de amostras utilizadas em estudos desenvolvidos pela gerência de malária da Fundação de Medicina Tropical do Amazonas (FMTAM). Os genes utilizados para caracterização do P. falciparum foram o pfcrt e pfatp6, e para o estudo de P. vivax utilizou-se o gene pvmdr. Como metodologia adotou-se o sequenciamento automático e a genotipagem utilizando sondas em sistema de PCR em Tempo Real. Todas as amostras de P. falciparum analisadas para o gene pfcrt demonstraram perfil genético semelhante à cepa 7G8, que contem a mutação K76T, comprovando o fenótipo resistente observado em estudos anteriores. Para o gene pfatp6 foram descritos 3 haplótipos distintos, com mutações identificadas nas posições 1204, 1888 e 2694. A análise do gene mdr de P. vivax identificou mutações nos códons 976 e 1076 em 11 amostras de um total de 100 analisadas, distribuídas entre os munícipios de Autazes, Coari, Manaus e Tefé. A identificação do perfil genético de populações de Plasmodium circulantes na Amazônia é uma importante ferramenta para o entendimento da dinâmica de transmissão da malária e para o constante monitoramento das ações de controle da doença

Orientador: Ricardo Luiz Dantas Machado / Banca: Ana Elizabete Silva / Banca: Karin Kirchgatter / Resumo: Plasmodium vivax é a espécie mais prevalente de malária no Brasil. O processo co-evolutivo parasita-hospedeiro pode ser visto como uma "ferramenta", na qual trocas genéticas adaptativas podem influenciar na diversidade da população. Objetivo: Investigar polimorfismos de genes envolvidos na resposta imune humoral visando identificar possíveis associações com a malária. Material e Métodos: a amostra foi constiuída por 103 pacientes com malária vivax não complicada e como grupo controle 97 indíviduos não-maláricos. A identificação dos SNPs -726T>C no gene CD40L, -1 C>T no gene CD40 e -871C>T no gene BLYS foram efetuadas pelo método de PCR-RFLP. As frequências genotípicas, alélicas e de indivíduos portadores de cada alelo foram estimadas por contagem direta. Também foram comparadas as frequências genotípicas observadas com as esperadas segundo o teorema de Hardy e Weinberg. Resultados: As freqüências genotípicas e alélicas para esses SNPs não diferiram estatisticamente entre pacientes e indivíduos do grupo controle. A combinação dos genótipos entre os genes CD40 e BLYS e entre CD40L e BLYS não revelou interação gênica na população estudada. Não foi observada associação entre resposta imune humoral e parasitemia nos indivíduos maláricos com os polimorfismos dos genes investigados. Ambos os genes se encontram em equilíbrio de Hardy e Weinberg. Conclusões: Os resultados deste estudo sugerem que as variantes genéticas analisadas nos genes CD40, CD40L e BLYS não afetam a funcionalidade das moléculas de modo que possa interferir na susceptibilidade a doença, mas estas variantes podem influenciar o curso clínico em vez de simplesmente aumentar ou diminuir a susceptibilidade / Abstract: Plasmodium vivax is the most prevalent malaria species in Brazil. The parasite-host coevolutionary process can be viewed as an 'arms race', in which adaptive genetic changes in one are eventually matched by alterations in the other. Objectives: following the candidate gene approach we analyzed the CD40, CD40L and BLYS genes that participate in B-cell co-stimulation, for associations with P. vivax malaria. Methods: the study sample included 97 patients and 103 controls. We extracted DNA using the extraction and purification commercial kit and identified the following SNPs: -1C>T in the CD40 gene, -726T>C in the CD40L gene and the -871C>T in the BLyS gene using PCR-RFLP. We analyzed the genotype and allele frequencies by direct counting. We also compared the observed with the expected genotype frequencies using the Hardy-Weinberg Equilibrium. Results: The allele and genotype frequencies for these SNPs did not differ statistically between patient and control groups. Gene-gene interactions were not observed between the CD40 and BLYS and between the CD40L and BLYS genes. Overall, the genes were in Hardy-Weinberg Equilibrium. Significant differences were not observed among the frequencies of antibody responses against P. vivax sporozoite and erythrocytic antigens and the CD40 and BLYS genotypes Conclusions: the results of this study show that, although the investigated CD40, CD40L and BLYS alleles differ functionally, this variation does not alter the functionality of the molecules in a way that would interfere in susceptibility to the disease. Significance: The variants of these genes may influence the clinical course rather than simply increase or decrease susceptibility / Mestre

Plasmodium vivax agente etiológico de la malaria, exhibe una gran variabilidad genética durante episodios recurrentes de la enfermedad. Esta recurrencia es informada como de baja prevalencia asociada con la malaria asintomática. Así mismo los episodios recurrentes (reinfecciones o relapsos) a menudo pueden ser confundidos por resistencia a fármacos como la cloroquina. Por lo tanto el objetivo principal de este estudio fue relacionar los patrones de recurrencia y la resistencia con la variabilidad genética de P. vivax. En este estudio se evaluaron las muestras secuenciales de individuos provenientes de una región endémica del Perú (Mazán-Iquitos), diagnosticados previamente con malaria, por microscopía, durante seguimientos activos y sometidos a un régimen de tratamiento estándar con cloroquina. La genotipificación realizada en base al gen pvmsp3-α, utilizando el Nested PCR y la digestión enzimática, permitió identificar una alta variabilidad genética de P. vivax, a partir de la cual, se identificaron los patrones de recurrencia, establecidos como relapsos, a partir de estadios latentes o hipnozoitos homólogos (con haplotipos idénticos) y reinfecciones (con haplotipos diferentes). Los rangos de tiempo permitieron una identificación más precisa, observándose mayores frecuencias de relapsos por hipnozoitos homólogos antes de los 90 días post-primera evaluación y mayores frecuencias de reinfecciones después de este periodo. Así mismo las recurrencias en el primer periodo de tiempo, por haplotipos diferentes, pueden deberse también a hipnozoitos heterólogos. Complementando el estudio, el análisis de secuenciamiento del gen pvmdr1, permitió identificar SNPs, codificantes de mutaciones no sinónimas, relacionadas con resistencia a cloroquina. Estos SNPs, a través del software U-Melt (análisis in sílico), presentaron variaciones en las temperaturas de fusión. Finalmente los resultados de cuantificación relativa con qPCR Real Time no mostraron diferencias significativas en el número de copias del gen pvmdr1. Palabras clave: Cloroquina, Genotipificación, Haplotipos, Hipnozoito, Malaria Asintomática, Recurrencia, Variabilidad. / --- Plasmodium vivax etiologic agent of malaria has a large genetic variability during recurrent episodes of the disease. This recurrence is reported as low prevalence associated with asymptomatic malaria. Also recurrent episodes (reinfection or relapse) can often be mistaken for drug resistance as chloroquine. Therefore the main objective of this study was to correlate the patterns of recurrence and resistance to the genetic variability of P. vivax. In this study, we evaluated the sequential samples of individuals from an endemic region of Peru (Mazán-Iquitos), previously diagnosed with malaria microscopy during active follows and subjected to a standard treatment regimen with chloroquine. Genotyping based on the pvmsp3-α gene, using Nested PCR and enzymatic digestion, identified high genetic variability of P. vivax, from which were identified recurrence patterns established as relapse, from latent stages or homologous hypnozoites (with identical haplotypes) and reinfections (with different haplotypes). The time ranges allow more accurate identification, with higher frequency of relapses by homologous hypnozoites before 90 days post-first evaluation and higher frequencies of reinfection after this period. Also recurrences in the first period of time, for different haplotypes may also be due to heterologous hypnozoites. Complementing the study, the sequencing analysis of the gene pvmdr1, identified SNPs, encoding nonsynonymous mutations related to resistance to chloroquine. These SNPs, through U-Melt software (in sílico analysis), showed variations in the melting temperatures. Finally the results of relative cuantification with Real Time qPCR no showed significant differences in copy number of the pvmdr1 gene.} Keywords: Chloroquine, Genotyping, Haplotypes, Hipnozoite, Recurrence, Asymptomatic Malaria, Variability. / Tesis

Infection with Plasmodium species leads to nearly 400,000 deaths a year despite widespread use of mosquito bed nets, insecticides, and anti-malarial drugs. To date, there is not a licensed vaccine capable of providing complete protection from Plasmodium infection to vaccinees. Whole parasite vaccination of humans and rodents can achieve complete protection in vaccines, but the dose of sporozoites, number of administrations, and production concerns in generating these types of vaccines will likely prevent these approaches from achieving worldwide use. However, the protective immunological responses against Plasmodium parasites engendered by these vaccination approaches can be studied and aid in the development of advanced subunit vaccines against Plasmodium. Using rodent models of malaria to elucidate the features of protective immunity engendered by whole parasite vaccination, it has been repeatedly shown that CD8 T cell responses directed against liver-stage parasite antigens can provide complete protection with some contribution by CD4 T cells and antibody responses depending on the model system studied. However, the quantatitive and qualitative requirements for CD8 T cell immunity against Plasmodium remains largely undefined. To enhance our understanding of how to generate protective immunity against Plasmodium, I have utilized rodent models of malaria to study the superior protection afforded from single-dose vaccination with virulent sporozoites administered under prophylatic chloroquine-cover, referred to as chemoprophylaxis sporozoites (CPS) vaccination, compared to the well-studied approach of administering radiation-attenuated Plasmodium sporozoites (RAS). RAS vaccination has long been considered the “gold standard” in vaccination due the ability of RAS vaccination to engender complete protection following sporozoite challenge of vaccinated humans and rodents. However, CPS vaccination is arguably a superior vaccination approach since it can achieve protection through less vaccine administrations relative to RAS vaccination, but the immunological basis of this enhanced CPS vaccine-induced immune response was unclear. In my study, I utilized a stringent host/parasite model to find that C57Bl/6 mice administered CPS vaccination with P. yoelii sporozoites elicit substantially higher parasite-specific CD8 T cell responses than RAS vaccination, but CPS-induced CD8 T cells were not necessary for protection following liver-stage sporozoite or blood-stage parasite challenge. CPS vaccination resulted in a low grade, transient parasitemia shortly following cessation of chloroquine treatment, which lead to the generation of potent antibody responses to blood-stage parasites; this blood-stage parasite-specific antibody response correlated with sterilizing protection in sporozoite challenged CPS-vaccinated mice. Therefore, my data provide a mechanistic basis for enhanced protective immunity elicited by single-dose CPS vaccination in a rodent model that is independent of CD8 T cells. The other portion of my work examines how CD8 T cell specificity impacts protective capacity against Plasmodium. I show that robust CD8 T cell responses of similar phenotype are mounted following prime-boost immunization against three novel Plasmodium berghei protein-derived epitopes in addition to a previously described protective, immunodominant epitope. I show that only CD8 T cells specific to sporozoite surface-expressed protein-derived epitopes, but not the intracellular protein-derived epitopes, are efficiently recognized by sporozoite-infected hepatocytes in vitro. These results suggest that antigenic targets must be efficiently presented by infected hepatocytes for CD8 T cells to eliminate liver-stage Plasmodium infection and proteins expressed on the surface of sporozoites may be good target antigens for protective CD8 T cells. Collectively, my work highlights the ability to generate protective CD8 T cell independent and dependent immunity against Plasmodium infections, whether achieved through potent blood-stage-specific antibody responses, or via numerically large monospecific CD8 T cell responses that target parasite antigens that are efficiently presented during liver-stage infection. These studies are relevant in understanding how to efficiency engender protective immunity against Plasmodium, and could aid in the advancement of subunit vaccination approaches that generate immunity through the priming of responses from multiple arms of the immune response, targeting both the liver- and blood-stages of Plasmodium.