Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: UMLS:C0024530 (malaria)
44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heat shock protein 70 (Hsp 70) and heat shock protein 40 (Hsp 40) are molecular chaperones that ensure that the proteins of the cell are properly folded and functional under both normal and stressful conditions. The malaria parasite Plasmodium falciparum is known to overproduce a heat shock protein 70 (PfHsp 70) in response to thermal stress; however, the in vivo function of this protein still needs to be explored. Using in vivo complementation assays, we found that PfHsp 70 was able to suppress the thermosensitivity of an Escherichia coli dnaK 756 strain, but not that of the corresponding deletion strain (DeltadnaK 52) or dnaK 103 strain, which produces a truncated DnaK. Constructs were generated that encoded the ATPase domain of PfHsp 70 fused to the substrate-binding domain (SBD) of E. coli DnaK (referred to as PfK), and the ATPase domain of E. coli DnaK coupled to the SBD of PfHsp 70 (KPf). PfK was unable to suppress the thermosensitivity of any of the E. coli strains. In contrast, KPf was able to suppress the thermosensitivity in the E. coli dnaK 756 strain. We also identified two key amino acid residues (V 401 and Q 402) in the linker region between the ATPase domain and SBD that are essential for the in vivo function of PfHsp 70. This is the first example of an Hsp70 from a eukaryotic parasite that can suppress thermosensitivity in a prokaryotic system. In addition, our results also suggest that interdomain communication is critical for the function of the PfHsp 70 and PfHsp 70-DnaK chimeras. We discuss the implications of these data for the mechanism of action of the Hsp70-Hsp 40 chaperone machinery.
...
PMID:Plasmodium falciparum heat shock protein 70 is able to suppress the thermosensitivity of an Escherichia coli DnaK mutant strain. 1597 16

Malaria aspartic proteases are attractive drug targets for the treatment of malaria, however, recombinant expression of active histo-aspartic proteinase (HAP) to facilitate its characterization has proven elusive. The present study reports on the first recombinant expression of soluble, active histo-aspartic proteinase from Plasmodium falciparum as a thioredoxin fusion protein. A truncated form of HAP (77p-451) was fused to thioredoxin in the pET32b(+) vector and the fusion protein (Trx-tHAP) was expressed in Escherichia coli Rosetta-gami B (DE3)pLysS. The fusion protein was partially purified from the culture medium using a combination of anion exchange and Ni(2+) affinity chromatography. Soluble tHAP was subsequently purified by enterokinase treatment and removal, followed by gel filtration chromatography. Although truncated HAP was incapable of autocatalytic activation, enterokinase digestion of partially purified fusion protein released the truncated prosegment yielding a mature form of tHAP (mtHAP). N-terminal sequencing of mtHAP indicated that enterokinase cleavage took place at Lys119-Ser120, four residues upstream of the native cleavage site (Gly123-Ser124). Initial activity tests showed that mtHAP was capable of hydrolyzing acid-denatured globin as well as cleavage of the synthetic substrate EDANS-CO-CH(2)-CH(2)-CO-ALERMFLSFP-Dap(DABCYL)-OH. Inhibition studies showed that the activity of mtHAP was completely inhibited by pepstatin A and to a lesser degree, PMSF. Using the synthetic substrate, mtHAP showed a pH optimum of 5.2, and Km=3.4 microM and kcat=1.6 x 10(-3)s(-1). The successful expression of active recombinant HAP from E. coli will accelerate the investigation of the structure-function relationships of HAP and facilitate the development of specific inhibitors with antimalarial activities.
...
PMID:Recombinant expression and partial characterization of an active soluble histo-aspartic protease from Plasmodium falciparum. 1662 75

Blood schizontocidal activity of 10 selected cis-fused cyclopenteno-1,2,4-trioxanes (namely Fenozan compound nos 6, 7, 11, 27, 32, 39, 44, 45, 48 and 51) have been re-investigated to establish their curative doses against the multidrug-resistant Plasmodium yoelii nigeriensis strain, which is lethal in Swiss mice. Freshly prepared formulations of these compounds prepared either in neutral groundnut (peanut) oil or in dimethyl sulfoxide (DMSO)-Tween-water, were compared for their antimalarial activity. Only 2 compounds, namely Fenozan derivatives 11 and 45, formulated in neutral groundnut oil for oral administration, showed highest activity with 100% cure rate in MDR P. yoelii nigeriensis-infected mice, while the DMSO-Tween-water formulations were inactive. Fenozan-48 produced 72.2% cure, when administered orally in groundnut oil (formulation) while its DMSO-Tween formulation was inactive. In the case of Fenozan 7, the oil and DMSO-Tween formulations produced 92.3 and 76.0% cures respectively. Fenozan derivatives nos 6, 27, 32, 39, 44 and 51 were not protective either in groundnut oil or DMSO-Tween oral formulations. The present study has applied more rigorous criteria for selection of active compounds, and has identified the 3,3-spirocyclopentane derivative Fenozan 11, and the 3,3-spirohydropyran derivative Fenozan 45, as potential blood schizontocides which can completely eliminate multidrug-resistant malaria infection in mice. Both these compounds are candidates for pre-clinical development. The present study advocates the preferred use of an oil vehicle for oral evaluation of potential antimalarial trioxanes/fenozans instead of the DMSO formulation, which gives inferior curative efficacy.
...
PMID:Blood schizontocidal activity of selected 1,2,4-trioxanes (Fenozans) against the multidrug-resistant strain of Plasmodium yoelii nigeriensis (MDR) in vivo. 1676 36

Adenoviral vectors based on adenovirus type 35 (rAd35) have the advantage of low natural vector immunity and induce strong, insert-specific T- and B-cell responses, making them prime-candidate vaccine carriers. However, severe vector-genome instability of E1-deleted rAd35 vectors was observed, hampering universal use. The instability of E1-deleted rAd35 vector proved to be caused by low pIX expression induced by removal of the pIX promoter, which was located in the E1B region of B-group viruses. Reinsertion of a minimal pIX promoter resulted in stable vectors able to harbour large DNA inserts (> 5 kb). In addition, it is shown that replacement of the E4-Orf6 region of Ad35 by the E4-Orf6 region of Ad5 resulted in successful propagation of an E1-deleted rAd35 vector on existing E1-complementing cell lines, such as PER.C6 cells. The ability to produce these carriers on PER.C6 contributes significantly to the scale of manufacturing of rAd35-based vaccines. Next, a stable rAd35 vaccine was generated carrying Mycobacterium tuberculosis antigens Ag85A, Ag85B and TB10.4. The antigens were fused directly, resulting in expression of a single polyprotein. This vaccine induced dose-dependent CD4+ and CD8+ T-cell responses against multiple antigens in mice. It is concluded that the described improvements to the rAd35 vector contribute significantly to the further development of rAd35 carriers for mass-vaccination programmes for diseases such as tuberculosis, AIDS and malaria.
...
PMID:Novel replication-incompetent adenoviral B-group vectors: high vector stability and yield in PER.C6 cells. 1684 8

The 42-kDa processed fragment of Plasmodium falciparum merozoite surface protein 1 (MSP-1(42)) is a prime candidate for a blood-stage malaria vaccine. Merozoite surface protein 8 contains two C-terminal epidermal growth factor (EGF)-like domains that may function similarly to those of MSP-1(42). Immunization with either MSP-1 or MSP-8 induces protection that is mediated primarily by antibodies against conformation-dependent epitopes. In a series of comparative immunogenicity and efficacy studies using the Plasmodium yoelii rodent model, we tested the ability of recombinant P. yoelii MSP-8 (rPyMSP-8) to complement rPyMSP-1-based vaccines. Unlike MSP-1, PyMSP-8-dependent protection required immunization with the full-length protein and was not induced with recombinant antigens that contained only the C-terminal EGF-like domains. Unlike PyMSP-8, the immunogenicity of the PyMSP-1 EGF-like domains was low when present as part of the rPyMSP-1(42) antigen. Immunization with a mixture of rPyMSP-1(42) and rPyMSP-8 further inhibited the antibody response to protective epitopes of rPyMSP-1(42) and did not improve vaccine efficacy. To improve PyMSP-1 immunogenicity, we produced a chimeric antigen containing the EGF-like domains of PyMSP-1 fused to the N terminus of PyMSP-8. Immunization with the chimeric rPyMSP-1/8 antigen induced high and comparable antibody responses against the EGF-like domains of both PyMSP-1 and PyMSP-8. This enhanced MSP-1-specific antibody response and the concurrent targeting of MSP-1 and MSP-8 resulted in improved, nearly complete protection against lethal P. yoelii 17XL malaria. Unexpectedly, immunization with rPyMSP-1/8 failed to protect against challenge infection with reticulocyte-restricted P. yoelii 17X parasites. Overall, these data establish an effective strategy to improve the efficacy of P. falciparum MSP-based vaccines.
...
PMID:Enhanced protection against malaria by a chimeric merozoite surface protein vaccine. 1715 95

Two Salmonella enterica serovar Typhi strains that express and export a truncated version of Plasmodium falciparum circumsporozoite surface protein (tCSP) fused to Salmonella serovar Typhi cytolysin A (ClyA) were constructed as a first step in the development of a preerythrocytic malaria vaccine. Synthetic codon-optimized genes (t-csp1 and t-csp2), containing immunodominant B- and T-cell epitopes present in native P. falciparum circumsporozoite surface protein (PfCSP), were fused in frame to the carboxyl terminus of the ClyA gene (clyA::t-csp) in genetically stabilized expression plasmids. Expression and export of ClyA-tCSP1 and ClyA-tCSP2 by Salmonella serovar Typhi vaccine strain CVD 908-htrA were demonstrated by immunoblotting of whole-cell lysates and culture supernatants. The immunogenicity of these constructs was evaluated using a "heterologous prime-boost" approach consisting of mucosal priming with Salmonella serovar Typhi expressing ClyA-tCSP1 and ClyA-tCSP2, followed by parenteral boosting with PfCSP DNA vaccines pVR2510 and pVR2571. Mice primed intranasally on days 0 and 28 with CVD 908-htrA(pSEC10tcsp2) and boosted intradermally on day 56 with PfCSP DNA vaccine pVR2571 induced high titers of serum NANP immunoglobulin G (IgG) (predominantly IgG2a); no serological responses to DNA vaccination were observed in the absence of Salmonella serovar Typhi-PfCSP priming. Mice primed with Salmonella serovar Typhi expressing tCSP2 and boosted with PfCSP DNA also developed high frequencies of gamma interferon-secreting cells, which surpassed those produced by PfCSP DNA in the absence of priming. A prime-boost regimen consisting of mucosal delivery of PfCSP exported from a Salmonella-based live-vector vaccine followed by a parenteral PfCSP DNA boosting is a promising strategy for the development of a live-vector-based malaria vaccine.
...
PMID:Enhanced immunity to Plasmodium falciparum circumsporozoite protein (PfCSP) by using Salmonella enterica serovar Typhi expressing PfCSP and a PfCSP-encoding DNA vaccine in a heterologous prime-boost strategy. 1750 96

The Plasmodium falciparum cysteine proteases falcipain-2 and falcipain-3 hydrolyze hemoglobin in an acidic food vacuole to provide amino acids for erythrocytic malaria parasites. Trafficking to the food vacuole has not been well characterized. To study trafficking of falcipains, which include large membrane-spanning prodomains, we utilized chimeras with portions of the proteases fused to green fluorescent protein. The prodomains of falcipain-2 and falcipain-3 were sufficient to target green fluorescent protein to the food vacuole. Using serial truncations, deletions, and point mutations, we showed that both a 20-amino acid stretch of the lumenal portion and a 10-amino acid stretch of the cytoplasmic portion of the falcipain-2 prodomain were required for efficient food vacuolar trafficking. Mutants with altered trafficking were arrested at the plasma membrane, implicating trafficking via this structure. Our results indicate that falcipains utilize a previously undescribed bipartite motif-dependent mechanism for targeting to a hydrolytic organelle, suggesting inhibition of this unique mechanism as a new means of antimalarial chemotherapy.
...
PMID:Falcipain cysteine proteases require bipartite motifs for trafficking to the Plasmodium falciparum food vacuole. 1756 83

An effective malaria vaccine which protects against all stages of Plasmodium infection may need to elicit robust CD8(+) and CD4(+) T cell and antibody responses. To achieve this, we have investigated strategies designed to improve the immunogenicity of DNA vaccines encoding the Plasmodium yoelii pre-erythrocytic stage antigens PyCSP and PyHEP17, by targeting the encoded proteins to the MHC Classes I and II processing and presentation pathways. For enhancement of CD8(+) T cell responses, we targeted the antigens for degradation by the ubiquitin (Ub)/proteosome pathway following the N-terminal rule. We constructed plasmids containing PyCSP or PyHEP17 genes fused to the Ub gene: plasmids where the N-terminal antigen residues were mutated from the stabilizing amino acid methionine to destabilizing arginine, plasmids where the C-terminal residues of Ub were mutated from glycine to alanine, and plasmids in which the potential hydrophobic leader sequences of the antigens were deleted. For enhancement of CD4(+) T cell and antibody responses, we targeted the antigens for degradation by the endosomal/lysosomal pathway by linking the antigen to the lysosome-associated membrane protein (LAMP). We found that immunization with DNA vaccine encoding PyHEP17 fused to Ub and bearing arginine induced higher IFN-gamma, cytotoxic and proliferative T cell responses than unmodified vaccines. However, no effect was seen for PyCSP using the same targeting strategies. Regarding Class II antigen targeting, fusion to LAMP did not enhance antibody responses to either PyHEP17 or PyCSP, and resulted in a marginal increase in lymphoproliferative CD4(+) T cell responses. Our data highlight the antigen dependence of immune enhancement strategies that target antigen to the MHC Class I and II pathways for vaccine development.
...
PMID:Targeting antigen to MHC Class I and Class II antigen presentation pathways for malaria DNA vaccines. 1760 49

Folate metabolism of the malaria parasites provides two targets for current antimalarials: dihydrofolate reductase and dihydropteroate synthase. Dihydrofolate reductase inhibitors have been used as antimalarials over the past few decades, often in combination with dihydropteroate synthase inhibitors. Resistance to these antifolate drugs developed through mutations in both target enzymes. However, limited mutation possibilities gave opportunities for the development of new drugs. Furthermore, other enzymes in the folate and related pathways are potential new targets that remain to be exploited. These include thymidylate synthase, an enzyme fused with dihydrofolate reductase in the same protein chain, serine hydroxymethyltransferase, methylene tetrahydrofolate dehydrogenase, methionine synthase and enzymes in the glycine cleavage pathway.
...
PMID:Folate metabolism as a source of molecular targets for antimalarials. 1766 90

Malaria proteases are attractive anti-malarial targets because of their roles in parasite development and infection. Falcipain-2 (FP-2), a food vacuole cysteine protease in Plasmodium falciparum, is involved in hemoglobin degradation and cleavage of cytoskeletal elements. To understand the route of trafficking and identify the signals involved in trafficking to food vacuole, we have generated transgenic parasites expressing green fluorescent protein (GFP) fusion proteins comprising of N-terminal regions of falcipain-2 fused to GFP. Using falcipain2-GFP chimeras and anti-falcipain-2 antibody, we show that falcipain-2 is trafficked through a classical vesicle mediated secretory pathway involving endoplasmic reticulum and Golgi-like apparatus. Photobleaching and confocal microscopy techniques reveal that falcipain-2 is carried to the food vacuole in the form of cytostomal vesicles. We identify an N-terminal sequence (1-120aa) of falcipain-2, sufficient for its transport to the food vacuole. Analysis of sequences of few other food vacuole targeted proteins suggests a common mechanism for protein trafficking to food vacuole of malaria parasite.
...
PMID:Food vacuole targeting and trafficking of falcipain-2, an important cysteine protease of human malaria parasite Plasmodium falciparum. 1769 13


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---