Isolation and Characterization of Vaccine Candidate Genes Including CSP and MSP1 in Plasmodium yoelii

Malaria is an infectious disease affecting humans, which is transmitted by the bite of Anopheles mosquitoes harboring sporozoites of parasitic protozoans belonging to the genus Plasmodium. Despite past achievements to control the protozoan disease, malaria still remains a significant health threat up to now. In this study, we cloned and characterized the full-unit Plasmodium yoelii genes encoding merozoite surface protein 1 (MSP1), circumsporozoite protein (CSP), and Duffy-binding protein (DBP), each of which can be applied for investigations to obtain potent protective vaccines in the rodent malaria model, due to their specific expression patterns during the parasite life cycle. Recombinant fragments corresponding to the middle and C-terminal regions of PyMSP1 and PyCSP, respectively, displayed strong reactivity against P. yoelii-infected mice sera. Specific native antigens invoking strong humoral immune response during the primary and secondary infections of P. yoelii were also abundantly detected in experimental ICR mice. The low or negligible parasitemia observed in the secondary infected mice was likely to result from the neutralizing action of the protective antibodies. Identification of these antigenic proteins might provide the necessary information and means to characterize additional vaccine candidate antigens, selected solely on their ability to produce the protective antibodies.

Apoptosis of non-parasitised red blood cells in Plasmodium yoelii malaria

Recently, while studying erythrocytic apoptosis during Plasmodium yoelii infection, we observed an increase in the levels of non-parasitised red blood cell (nRBC) apoptosis, which could be related to malarial anaemia. Therefore, in the present study, we attempted to investigate whether nRBC apoptosis is associated with the peripheral RBC count, parasite load or immune response. To this end, BALB/c mice were infected with P. yoelii 17XL and nRBC apoptosis, number of peripheral RBCs, parasitaemia and plasmatic levels of cytokines, nitric oxide and anti-RBC antibodies were evaluated at the early and late stages of anaemia. The apoptosis of nRBCs increased at the late stage and was associated with parasitaemia, but not with the intensity of the immune response. The increased percentage of nRBC apoptosis that was observed when anaemia was accentuated was not related to a reduction in peripheral RBCs. We conclude that nRBC apoptosis in P. yoelii malaria appears to be induced in response to a high parasite load. Further studies on malaria models in which acute anaemia develops during low parasitaemia are needed to identify the potential pathogenic role of nRBC apoptosis.

Expression of non-TLR pattern recognition receptors in the spleen of BALB/c mice infected with Plasmodium yoelii and Plasmodium chabaudi chabaudi AS

The spleen plays a crucial role in the development of immunity to malaria, but the role of pattern recognition receptors (PRRs) in splenic effector cells during malaria infection is poorly understood. In the present study, we analysed the expression of selected PRRs in splenic effector cells from BALB/c mice infected with the lethal and non-lethal Plasmodium yoelii strains 17XL and 17X, respectively, and the non-lethal Plasmodium chabaudi chabaudi AS strain. The results of these experiments showed fewer significant changes in the expression of PRRs in AS-infected mice than in 17X and 17XL-infected mice. Mannose receptor C type 2 (MRC2) expression increased with parasitemia, whereas Toll-like receptors and sialoadhesin (Sn) decreased in mice infected with P. chabaudi AS. In contrast, MRC type 1 (MRC1), MRC2 and EGF-like module containing mucin-like hormone receptor-like sequence 1 (F4/80) expression decreased with parasitemia in mice infected with 17X, whereas MRC1 an MRC2 increased and F4/80 decreased in mice infected with 17XL. Furthermore, macrophage receptor with collagenous structure and CD68 declined rapidly after initial parasitemia. SIGNR1 and Sn expression demonstrated minor variations in the spleens of mice infected with either strain. Notably, macrophage scavenger receptor (Msr1) and dendritic cell-associated C-type lectin 2 expression increased at both the transcript and protein levels in 17XL-infected mice with 50% parasitemia. Furthermore, the increased lethality of 17X infection in Msr1 -/- mice demonstrated a protective role for Msr1. Our results suggest a dual role for these receptors in parasite clearance and protection in 17X infection and lethality in 17XL infection.

The antiplasmodial effect of the extracts and formulated capsules of Phyllanthus amarus on Plasmodium yoelii infection in mice

OBJECTIVE@#To investigate the antiplasmodial activity of the extracts of Phyllanthus amarus (P. amarus) on Plasmodium yoelii (P. yoelii) (a resistant malaria parasite strain used in animal studies) infection in mice.@*METHODS@#The aqueous and ethanol extracts of the whole plant of Phyllanthus amarus was administered to Swiss albino mice at doses of 200 mg/kg/day, 400 mg/kg/day, 800 mg/kg/day and 1600 mg/kg/day and the prophylactic and chemotherapeutic effect of the extracts against P. yoelii infection in mice was investigated and compared with those of standard antimalaria drugs used in the treatment of malaria parasite infection. Acute toxicity test was carried out in mice to determine the safety of the plant extract when administered orally.@*RESULTS@#The results showed that the extracts demonstrated a dose-dependent prophylactic and chemotherapeutic activity with the aqueous extracts showing slightly higher effect than the ethanol extract. The antiplasmodial effects of the extracts were comparable to the standard prophylactic and chemotherapeutic drugs used in chloroquine resistant Plasmodium infection although the activity depended on the dose of the extract administered. The extracts showed prophylactic effect by significantly delaying the onset of infection with the suppression of 79% at a dose of 1600 mg/kg/day.@*CONCLUSIONS@#The results obtained indicate that the extracts of the whole plant of P. amarus possess repository and chemotherapeutic effects against resistant strains of P. yoelii in Swiss albino mice. The findings justify the use of the extract of P. amarus in traditional medicine practice, for the treatment of malaria infections.

In vivo antimalarial activity of leaves of Plectranthus amboinicus (lour) spreng on Plasmodium berghei yoelii.

An invivo study of aqueous extract of the leaves of Plectranthus amboinicus on Plasmodium berghei yoelii was conducted on laboratory infected albino mice and compared with standard drug chloroquine. Reduction of parasitemia at 250 mg/kg and 500 mg/kg of aqueous extract for 24 hrs, 48 hrs, 72 hrs and 96 hrs were determined. The reduction of parasitemia after 96 hrs was 100%, 67.9% and 76.2% for standard, 250 mg/kg and 500 mg/kg of aqueous extract respectively. The isolation of active principle responsible for the reduction of parasitemia may give a promising drug molecule.

Studies on drug metabolizing enzymes during arteether treatment of Plasmodium yoelii nigeriensis infected mice cerebral microvessels.

Human cerebral malaria is caused by a protozoan parasitic with no cure till date. The isolation of brain capillaries i.e. microvessels has permitted the in vitro study related to cerebral function. Microvessels were isolated from normal and P. yoelii infected mice brain cortex and subjected to biochemical characterization by the following enzyme markers viz alkaline phosphatase, gamma-glutamyI transpeptidase and monoamine oxidase and electron microscopically. Limited studies have been carried out in relation to drug metabolizing enzymes in cerebral microvessels of rodents. The present studies have been carried out in relation to status of drug metabolizing enzymes during P. yoelii infection in cerebral microvessels of mice. The data obtained depicted a clear cut impairment of cytochrome P450 (a terminal monooxygenase) and related indices viz b5, benzopyrene hydroxylase, aminopyrene-n-demethylase, aniline hydroxylase except NADH cytochrome e reductase which increased during P. yoelii infection in mice as compared to normal. Further the oral drug administration (arteether) treatment brought back the altered MFO system normal a week alter cessation of drug treatment.

Malaria parasite developmental analyses by the nested polymerase chain reaction method: an implication for the evaluation of mosquito infection rates in epidemiological studies.

A malaria mosquito vector, Anopheles saperoi, and a non-vector, Aedes albopictus, were allowed to feed on mice infected with murine malaria, Plasmodium yoelii nigeriensis, and were subsequently monitored for the development of parasites by the nested polymerase chain reaction (PCR) method, using Plasmodium genus-specific primer pairs. The mosquitos were divided into two parts, head/thorax and abdomen, for DNA analyses. The parasite DNA and murine DNA for each mosquito were examined in parallel. In both groups of mosquitos, murine DNA was detected up to 4 days post-blood meal in both the head/thorax and abdomen. After 4 days, the murine DNA fell below detectable limits. Murine DNA and parasite DNA remained undigested for the first 4 days post-blood meal. Parasite DNA was detected in the abdomen of 25% (3/12) of Ae. albopictus on day five and 10% (1/10) on day six, after murine DNA had fallen below detectable limits. Parasite DNA was not detected in the head/thorax of Ae. albopictus on those days or afterwards in either the head/thorax or abdomen, demonstrating that the parasite detected on days 5 and 6 in the abdomen degenerated and did not develop into mature oocysts or sporozoites. In the vector An. saperoi, parasite DNA was detected continuously in the head/thorax and abdomen for many days after the murine DNA had fallen below detectable limits. The detection rate of parasite DNA in the head/thorax of An. saperoi increased gradually from day 8 post blood meal until it reached a maximum level of 71.4% (15/21 12 days post-infection. Parasite DNA in abdomen reached its maximum level of 81% (17/21) 10 days post-blood meal. The implications of these results for the design and interpretation of epidemiological surveys is discussed.

Protective immune mechanisms induced by cellular vaccine made of the erythrocytic Plasmodium yoelii / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the characteristics of protective immunity against Plasmodium yoelii (P.y.) infection by asexual blood-stages cellular vaccine.</p><p><b>METHODS</b>The particulate vaccines were constructed by saponin or double-distilled-water lysed parasitic red blood cells and inoculated into BALB/c mice by intraperitoneal injection (i.p.). Each group was challenged by the lethal erythrocytic P.y. parasites, and then their parasitemia and survival rates were detected. Expressions of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) were detected by RT-PCR. ELISA showed the serum antibodies against the malaria challenge and their-subclasses. Special membrane protein was recognized by immunofluorescence assay.</p><p><b>RESULTS</b>The vaccination with saponified erythrocytic parasites protected the immunized mice against P.y. challenge, while double-distilled-water lysed vaccine did not (P < 0.01). This protection was characterized by the increase of both IFN-gamma/IgG2a and IL-4/IgG1. Meanwhile, MHC class I alpha chain molecule was recognized on the membrane of infected-erthythrocyte.</p><p><b>CONCLUSION</b>Saponified P.y. asexual blood-stage cellular vaccine has a significantly high protective immunity against this lethal P.y. malaria, and the immunity may be associated with the expression levels of IgG2a and IFN-gamma. MHC class I alpha chain on infected erythrocytes may play an important role in the successful immunization.</p>

Morphological characteristics of Plasmodium yoelii schizonts in ghost erythrocytes / 中国医学科学院学报

<p><b>OBJECTIVE</b>To observe the morphological characteristics of Plasmodium yoelii schizogony in their ghost erythrocytes.</p><p><b>METHODS</b>Saponify, hypotonic shock, and electron microscopy were used to observe the different fashions of erythrocytic parasites and their characteristic organellae in ghost erythrocytes.</p><p><b>RESULTS</b>The malarial parasites and their fine structures were dramatically well preserved in the ghost erythrocytes, such as the ring-like early trophozoites, the brassiere-like early schizonts, the emerging buds on the surface of late schizonts, and the grape-cluster like late schizonts. The cytostome, food vacuole, and crystallized malarial pigments were found in the early trophozoites. The proliferations of nucleoplasma and nuclear membrane as well as and the clot-like nuclear division were followed by the budding during the schizogony.</p><p><b>CONCLUSION</b>The saponify technique that makes the erythrocytic malaria parasites and their fine organellae to be dramatically revealed in their ghost erythrocytes, may be a useful method in the Plasmodium biological research and anti-malaria immunological researches.</p>

Immunity of peritoneal monocytes against Plasmodium yoelii infected erythrocytes / 中国医学科学院学报

<p><b>OBJECTIVE</b>To test the immunity of peritoneal monocytes against Plasmodium yoelii infected red blood cells (target cells).</p><p><b>METHODS</b>Saponinized Plasmodium yoelii infected red blood cells (SPRBC, Ghost erythrocyte) were used to immunize mice i.p twice. Three weeks later, the infected red blood cells were injected i.p.; 90 min later, the total peritoneal cells were isolated and washed for scanning electromicroscopy to observe the effects of the peritoneal monocyte to the target cell.</p><p><b>RESULTS</b>The peritoneal cells of the immunized mice were activated after 90 min of the challenge of target cells. The size of the cell was not even and the pili on the cell surface turned to be long and densed. Cell interconnections were found among the cells. In some peritoneal monocytes, their cell plasma were scattered (omlette-like) or with the shape as "cellular bomb". The scattered or the sheeted pili and spredding cell plasma could adhere to the target cells which were perforated densely and damaged.</p><p><b>CONCLUSION</b>The protective adaptive immunity exists in the peritoneal monocytes of immunized mice.</p>

Mining microorganism EST databases in the quest for new proteins

Microorganisms with large genomes are commonly the subjects of single-round partial sequencing of cDNA, generating expressed sequence tags (ESTs). Usually there is a great distance between gene discovery by EST projects and submission of amino acid sequences to public databases. We analyzed the relationship between available ESTs and protein sequences and used the sequences available in the secondary database, clusters of orthologous groups (COG), to investigate ESTs from eight microorganisms of medical and/or economic relevance, selecting for candidate ESTs that may be further pursued for protein characterization. The organisms chosen were Paracoccidioides brasiliensis, Dictyostelium discoideum, Fusarium graminearum, Plasmodium yoelii, Magnaporthe grisea, Emericella nidulans, Chlamydomonas reinhardtii and Eimeria tenella, which have more than 10,000 ESTs available in dbEST. A total of 77,114 protein sequences from COG were used, corresponding to 3,201 distinct genes. At least 212 of these were capable of identifying candidate ESTs for further studies (E. tenella). This number was extended to over 700 candidate ESTs (C. reinhardtii, F. graminearum). Remarkably, even the organism that presents the highest number of ESTs corresponding to known proteins, P. yoelii, showed a considerable number of candidate ESTs for protein characterization (477). For some organisms, such as P. brasiliensis, M. grisea and F. graminearum, bioinformatics has allowed for automatic annotation of up to about 20 of the ESTs that did not correspond to proteins already characterized in the organism. In conclusion, 4093 ESTs from these eight organisms that are homologous to COG genes were selected as candidates for protein characterization

Molecular cloning of Plasmodium yoelii dynamin-like protein (PyDyn) gene and the immunological character of its domains / 中国医学科学院学报

<p><b>OBJECTIVE</b>To identify and clone a new full ORF gene of PyDyn (Plasmodium yoelii dynamin-like protein), and examine the protection of their expression products.</p><p><b>METHOD</b>Using the P. yoelii Genome technology and RT-PCR.</p><p><b>RESULTS</b>The full ORF gene of PyDyn was amplified from mRNA of the erythrocytic stage of P. yoelii., three domains of PyDyn were expressed in E. coli., and the fairly positive immunogenicity of them was showed by IFA. The full ORF gene of PyDyn was 2,433 bp and encode 811 amino acids. Its Gene Bank access number is AF458071. PyDyn belongs to the dynamin-like protein family according to its property.</p><p><b>CONCLUSION</b>The new full ORF gene of PyDyn is obtained and identified; their expressed domains are probably new candidates for malaria vaccine.</p>

Trypsin and aminopeptidase activities in blood-fed females Anopheles dirus (Diptera: Culicidae) of differing susceptibility to Plasmodium yoelii nigeriensis.

Midgut proteolytic enzymes contribute to the success or failure of Plasmodium infection of the mosquito. The present study investigated trypsin and aminopeptidase activities in the midgut of two strains of Anopheles dirus selected for susceptibility and refractoriness to Plasmodium yoelii nigeriensis. At intervals of 6 hours following a bloodmeal, the midguts of fully engorged female mosquitos were dissected, homogenized, and assayed for enzyme activity. No differences trypsin activity (nmole/min) were observed between the two strains throughout the course of blood digestion. By contrast, the aminopeptidase activity measured at 0 to 18 hours post-feeding was the same for the two strains, but at 24, 30 and 36 hours significantly less activity was observed in the refractory females. The results suggest neither trypsin nor aminopeptidase plays a role in the limitation of parasite development.

Ovary specific immune response during Plasmodium yoelii yoelii infection in malaria vector Anopheles stephensi (Diptera:Insecta).

Innate immune related polypeptides expression during three gonotrophic cycles in the ovaries of major disease vector mosquito A. stephensi has been analyzed following infection by malaria parasite, P. yoelii yoelii. Seventeen polypeptides were induced in the ovaries of various stages due to parasitic infection. Most of proteins were induced systemically during early stages of infection suggesting the possibility of immune related signalling process. The reduction in the quantity of protein contents in infected mosquitoes has been ascribed to the repression of seven polypeptides and in turn correlated with the fecundity reduction. The mechanism of these responses and their significance for malaria transmission and fecundity reduction are discussed.

Investigação de possíveis danos funcionais persistentes causados pela exposição pré-natal ao trifenil hidróxido de estanho (TPTH)tp / Inquiry of possible persistent functional damages caused by the prenatal exposition to the hidróxido trifenil of I tin (TPTH)tp

TPTH é um biocida usado em tintas de navios, na preservação da madeira e no preparo de pesticidas. Neste estudo verificamos se ocorrem alterações do desenvolvimento pós-natal em decorrência da exposição pré-natal em decorrência da exposição pré-natal ao TPTH e se animais adultos que haviam sido expostos in utero ao TPTH apresentam maior vulnerabilidade à infecção por plasmodium yoelli. Camundongos foram acasalados e as fêmeas grávidas foram expostas ao TPTH (0;7,5; 15 e 30mg/kg/dia; N=20/grupo) por via oral do dia 6 ao dia 17 de gestação. Ao nascimento, os filhotes foram identificados e pesados individualmente nos dias 1, 5, 10, 15 e 20 pós-natal. Diariamente, parâmetros físicos do desenvolvimento pós-natal foram avaliados. Ao desmame, 1 fêmea e 1 macho de cada ninhada foram infectados com P. yoelii (1,0 x 10ø hemácias parasitadas (HP)/animal, por via i.p.). O restante dos filhotes permaneceu em observação até completarem 6 semanas de idade, quando 1 nova fêmea e 1 novo macho de cada ninhada foram infectados (1,0 x 10 HP/animal). O curso temporal da infecção foi avaliado. Após 33 dias de infecção, os animais foram sacrificados e timo, fígado e baço foram pesados. Animais não infectados foram sacrificados com 8 semanas de vida. A exposição in utero ao TPTH(15 e 30 mg/kg) causou um aumento na incidência de perdas pré- e peri-/pós-natais. Como conseqüência, observou-se, nestes níveis de dose, uma drástica redução do número de ninhadas viáveis ao nascimento e ao desmame. Dentre os efeitos induzidos in utero pelo TPTH, os mais marcantes foram: i. redução do peso médio corporal dos filhotes ao nascimento, ii. diminuição da razão entre o número de fêmeas e machos, ao nascimento e ao longo do desenvolvimento pós-natal, indicando maior vulnerabilidade feminina aos efeitos induzidos in utero elo TPTH e iii. altaração do curso temporal da infecção por P. yoelli, bem como, inibição dos aumentos de peso do baço e do figado, mediados por este parasita, o que indica maior vulnerabilidade do hospedeiro à infecção em decorrência da exposição pré-natal ao TPTH. Os dados do presente estudo mostram que a exposição in utero ao TPTH induz o aparecimento de alterações do desenvolvimento pós-natal e pode causar danos funcionais persistentes, que interferem com processos de defesa do organismo adulto com a infecção murina por P. yoelii.

Possibility of false-positive detection for sporozoites in mosquitos (Diptera: Culicidae) by nested polymerase chain reaction using Plasmodium yoelii genomic DNA.

Anopheles stephensi Liston and An. saperoi Bohart and Ingram infected with the rodent malaria parasite Plasmodium yoelii nigeriense. They were examined 12 and 19 days after blood feeding for sporozoites in head with anterior thorax (HT) and oocysts in abdomen with posterior thorax (AB) by light microscopy and by the nested polymerase chain reaction (nested PCR-based on the amplification of the sequences of the small subunit ribosomal RNA gene). The detection rate of parasite DNA by nested PCR in HT samples 12 days after blood feeding was similar to that by microscopic method. However, in HT samples 19 days after blood feeding, the rate by the PCR method was higher than that by the microscopic method. The incidence of sporozoites in salivary glands of infected mosquitos for 12 days after blood sucking was examined by the PCR method. Parasite DNA in HT of Aedes albopictus Skuse (a non vector for the rodent malaria) as well as An. stephensi and An. saperoi was detected for up to 4 days after feeding on mouse with the rodent malaria parasites. The results indicate that when the PCR method is used for detection of sporozoites of human malaria in mosquitos collected in the field, there are possibilities of including false-positive data for mosquitos that have just or recently fed on human blood infected with malaria (erythrocytic form).

Midgut specific immune response of vector mosquito Anopheles stephensi to malaria parasite Plasmodium.

Innate immune-related polypeptides expression in midgut in the ageing vector mosquito A. stephensi following infection by malaria parasite, Plasmodium yoelii yoelii has been studied. Twenty polypeptides were induced by an infected blood meal during various stages of adult life. A 24 kDa polypeptide was induced generally in most of the stages. Maximum parasite induced polypeptides i.e. 22, 33, 111, 122, 127, 140, 143 and 146 kDa were found in 5 days of post blood feeding (PBF) which coincides with the presence of oocysts on the midgut. However, in addition, three polypeptides in 11 days PBF and 8 polypeptides in 20 days PBF were also induced due to parasite infection in aged mosquitoes. Quantitatively, the amount of soluble proteins in the midgut in oocyst-sporozoite-positive mosquitoes was always less as compared to their normal counterparts. The parasite evidently elicits defined immune responses by inducing specific polypeptides in the midgut of the mosquito.

Análise dos mecanismos imunológicos gerados pela imunizaçäo experimental contra doença de Chagas e malária / Analysis of the immunological mechanisms generated by experimental immunization against Chagas' disease and malaria

Durante a tese de Mestrado, eu descrevi que a imunizaçao de camundongos BALB/c com um plasmídio contendo o gene da trans-sialidase foi capaz de induzir imunidade protetora contra a infecçao pelo Trypanosoma cruzi. Baseados nos resultados obtidos anteriormente, a primeira parte deste trabalho teve o intuito de analisar a imunidade celular induzida pela vacinaçao genética com o gene da TS. Observamos em animais imunizados a presença de esplenócitos CD4+ e CD8+ específicos para a TS e que produziam IFN-g, mas nao IL-4 ou IL-10. Posteriormente, estes linfócitos T foram caracterizados a nível clonal, e os clones de linfócitos T CD4+ citotóxicos secretavam IFN-g mas nao IL-4 ou IL-10, sendo definido portanto como Th1. Obtivemos também clones Th2 secretores de IL-4 e IL-10, mas nao de IFN-g Todos os clones T CDB+ gerados apresentaram atividade citotóxica in vitro e foram capazes de secretar IFN-g, mas nao IL-4 ou IL-10. 0 mais importante foi o fato que clones T CD4+ Th1 ou CD8+ Tc1 foram capazes de inibir, respectivamente, o desenvolvimento in vitro do T. cruzi em culturas de macrófagos ou fibroblastos infectados. Estes resultados mostraram que a imunizaçao genética é capaz de induzir linfócitos T CD4+ Th1 e CD8+ Tc1 potencialmente protetores, reforçando assim a possibilidade do uso desta estratégia de imunizaçao no desenvolvimento de uma vacina preventiva ou terapêutica contra doença de Chagas. Na segunda parte deste trabalho, reavaliamos a capacidade da imunizaçao com plasmídios contendo o gene da proteína do circumsporozoíta (CS) de Plasmodium yoelii com o intuito de aprofundar os estudos dos mecanismos imunológicos induzidos pela vacinaçao genética contra malária experimental. Entretanto, ao contrário do que está descrito na literatura, fomos incapazes de induzir imunidade protetora contra a infecçao experimental. A ausência de proteçao em nossos experimentos nao estava relacionada com a falta de resposta imune. Entretanto, observamos que os anticorpos induzidos pela imunizaçao com o gene da proteína CS nao foram capazes de inibir a penetraçao de esporozoítas em culturas de hepatócitos. Além de anticorpos, observamos a presença de linfócitos T CD8+ produtores de IFN-g e capazes de reconhecer o epítopo citotóxico da proteína CS. 0 número destas células produtoras de IFN-g no baço de animais imunizados foi semelhante ao descrito por outros grupos utilizando o mesmo gene. Nossos resultados sugerem que a...

Malaria vaccine development: Various immunization regimens for efficient induction of protective anti-malaria immunity

A malária permanece como a maior causa de morbidade e mortalidade humana em todo o mundo, devido à inexist6encia de medidas de controle eficientes para esta infecçäo. Considera-se que a vacinaçäo pode ser um meio eficaz que complementará outras estratégias de prevençäo e controle desta doença no futuro. Embora a possibilidade de uma vacina contra a malária tenha sido demonstrada nos anos 70, o desenvolvimento de uma facina universalmente eficaz contra esta parasitose tem sido uma difícil tarefa devido a diversos problemas complexos. Um dos aspectos é a complexidade do ciclo de vida do parasita, o qual envolve diferentes estágios que possuem antígenos específicos. Muitos antígenos parasitários têm sido investigados como candidatos potenciais à vacinaçäo, e a busca continua, com antígenos adicionais, sendo recentemente indentificados e caracterizados. Alguns desses antígenos estágio-específicos säo capazes de induzir respostas imunoprotetoras celular e humoral no hospedeiro. Todavia, essas respostas imunoprotetoras säo geralmente restritas geneticamente, adicionando outra dificuldade ao desenvolvimento de uma vacina universalmente eficaz. Por fim, o antígeno estágio-específico deve ser introduzido no hospedeiro utilizando-se um sistema de liberaçäo que possa induzir eficientemente respostas protetoras contra os respectivos estágios. No presente trabalho, revemos as diversas tentativas visando a induçäo de imunidade protetora contra todos os estágios do parasita, levando em consideraçäo os aspectos mencionados acima, que säo os antígenos protetores estágio-específicos, as respostas imunoprotetoras do hospedeiro, e os sistemas de liberaçäo antigênica.

Glucose transport in cerebral microvessels during Plasmodium yoelii nigeriensis infection in mice.

Plasmodium yoelii infected cerebral micro vessels of mice registered a significant increase in D-[U-14C] Glucose transport as compared to normal microvessels which was found to be time, temperature and concentration dependent. Metabolic inhibitors galactose, manose, 2-deoxy glucose and D-glucose showed noticeable inhibition of the same.