First Draft Genome Sequence of Balamuthia mandrillaris, the Causative Agent of Amoebic Encephalitis.

The free-living amoeba Balamuthia mandrillaris is a rare but highly lethal agent of amoebic encephalitis in humans and many other mammalian species. Here, we announce the first draft genome sequence of the original 1990 isolate cultured from the brain of a deceased mandrill baboon.

Nitric oxide synthase and cytokines gene expression analyses in Leishmania-infected RAW 264.7 cells treated with an extract of Pelargonium sidoides (Eps 7630).

A modern aqueous-ethanolic formulation of the roots of Pelargonium sidoides (Eps 7630), elaborated from the traditional herbal medicine used in areas of southern Africa, is effectively employed for the treatment of ENT and respiratory tract infections in modern phytotherapy. Previous studies have demonstrated antibacterial and immunomodulatory activities. To gain insight into the mode of action at the molecular level, gene expression analyses for the inducible nitric oxide synthase and the cytokines interleukin (IL)-1, IL-12, IL-18, tumour necrosis factor (TNF)-alpha, interferon (IFN)-alpha, and IFN-gamma, were performed using reverse transcription-polymerase chain reaction (RT-PCR). The experiments were carried out in parallel in non-infected and in Leishmania major-infected RAW 264.7 cells and the expression profiles were compared with those mediated by IFN-gamma+LPS. Eps 7630 induced low mRNA levels in non-infected cells, and it considerably up-regulated the transcript expressions in parasitised cells. Interestingly, and in contrast to activation by IFN-gamma+LPS, Eps 7630 also stimulated infected cells to produce IFN-gamma mRNA. A similar expression profile was observed for the methanol-insoluble fraction (MIF) of Eps 7630 and gallic acid, a trace constituent of the extract, while the methanol-soluble fraction and umckalin, an exclusive and representative member of the occurring coumarins, proved to be devoid of any remarkable gene-inducing capabilities. The present results provide not only convincing support for the improvement of immune functions as previously demonstrated in functional bioassays, but also evidence for activation at the transcriptional level and suggest that the underlying inducing principle is located in the MIF.

Amphotericin B.

Invasive fungal infections are a major cause of morbidity and mortality in immunodeficient individuals (such as AIDS patients) and in transplant recipients or tumor patients undergoing immunosuppressive chemotherapy. Amphotericin B is one of the oldest, yet most efficient antimycotic agents. However, its usefulness is limited due to dose-dependent side-effects, notably nephrotoxicity. In order to improve its safety margin, new pharmaceutical formulations of amphotericin B have been designed especially to reduce its detrimental effects on the kidneys. Since the 1980s, a wide variety of new amphotericin B formulations have been brought forward for clinical testing, many of which were approved and reached market value in the 1990s. This review describes and discusses the molecular genetics, pharmacological, toxicological, and clinical aspects of amphotericin B itself and many of its innovative formulations.

Natural products as antiparasitic drugs.

Natural products are not only the basis for traditional or ethnic medicine. Only recently, they have provided highly successful new drugs such as Artemisinin. Furthermore, screening natural products found in all sorts of environments such as the deep sea, rain forests and hot springs, and produced by all sorts of organisms ranging from bacteria, fungi and plants to protozoa, sponges and invertebrates, is a highly competitive field where all of the major pharmaceutical companies are encountered. Already, many new natural product groups have revealed antiparasitic properties of surprising efficacy and selectivity, as will be shown in this review for plant-derived alkaloids, terpenes and phenolics. Many novel lead structures, however, have severe chemico-physical drawbacks such as poor solubility. Here, innovative drug formulations and carrier systems might help, as discussed by the authors in another article of this series.

Formulation and biopharmaceutical issues in the development of drug delivery systems for antiparasitic drugs.

The development of really new antiparasitic drugs to market level is a very rare event. A large number of lead structures have already been screened and discarded, the market is large but poor, and the administrative barriers are increasingly high and costly. Novel antiparasitics must not only be better, they must also be substantially safer than the existing repertoire. There are two major aspects to drug development. One is the strategy of pathogen-specific biochemical intervention, the other the strategy of optimal formulation and application. This review focuses on the latter. In finding and adapting innovative and "intelligent", i.e. parasite- and disease-specific formulations and delivery systems, established but deficient drugs might be optimised, enhancing their efficiency and reducing negative side effects at relatively low cost. Further, many promising new ideas are severely hampered by the low water solubility of the antiparasitic drug. Here as well, some of the innovative drug formulation and delivery systems discussed below might offer highly efficient, while technologically simple, solutions.

Formulation of amphotericin B as nanosuspension for oral administration.

Amphotherin B was formulated in a nanosuspension as a new oral drug delivery system for the treatment of experimental visceral leishmaniasis. Amphotericin B (AmB) nanosuspensions were produced by high pressure homogenisation obtaining particles with a PCS diameter of 528 nm. Environmental stability was determined in artificial gastrointestinal fluids at different pH and electrolyte concentrations. In vivo efficacy was determined in a mouse model of visceral leishmaniasis. Following oral administration (5 mg kg(-1)), micronised amphotericin B did not show any curative effect. However, administrations of amphotericin B nanosuspension, reduced liver parasite load by 28.6% compared to untreated controls.

Antileishmanial activity of hydrolyzable tannins and their modulatory effects on nitric oxide and tumour necrosis factor-alpha release in macrophages in vitro.

A series of 27 hydrolyzable tannins and related compounds was tested for antiparasitic effects against both extracellular promastigote and intracellular amastigote Leishmania donovani organisms. In parallel, the compounds were evaluated for their immunomodulatory effects on macrophage functions, including release of nitric oxide (NO), tumour necrosis factor-alpha (TNF-alpha) and interferon (IFN)-like properties using several functional assays. Of the series of polyphenols tested, only gallic acid (54 microM NO) and its methyl ester (32 microM NO) induced murine macrophage-like RAW 264.7 cells to release NO in appreciable amounts (IFN-gamma/LPS 119 microM NO). The in vitro TNF-inducing potential of the polyphenols examined increased in the order of oligomeric ellagitannins (EC(50) > 25 microg/ml) < monomeric ellagitannins, gallotannins (EC(50) 8.5 to > 25 microg/ml) < C-glucosidic ellagitannins, dehydroellagitannins (EC(50) 0.6 - 2.8 microg/ml) at the host cell subtoxic concentration of 50 microg/ml. Furthermore, promastigotes of Leishmania donovani were assayed in the presence of these polyphenols and the results showed that none of the compounds was significantly toxic (EC(50) > 25 microg/ml) to the extracellular forms. In contrast, all polyphenols showed pronounced antileishmanial activities (EC(50) < 0.4 - 12.5 versus 7.9 microg/ml for Pentostam) against intracellular amastigotes of L. donovani residing within RAW cells. Noteworthy, most compounds exhibited low cytotoxicity against the murine host cells (EC(50) >25 microg/ml). Furthermore, some ellagitannins and the majority of dehydroellagitannins induced potent interferon-like activities as reflected by inhibition of the cytopathic effect of encephalomyocarditis virus on fibroblast L929 cells. This is the first report on hydrolyzable tannins as a new class of natural products with leishmanicidal activity including their potential for inducing the release of NO, TNF and IFN-like activity in macrophage-like RAW cells.

In vitro activity of aurones against Plasmodium falciparum strains K1 and NF54.

A series of naturally occurring aurones (e. g., Rubiaceae, Cyperaceae) was synthesized and tested for the ability to inhibit erythrocytic stages of Plasmodium falciparum strains in vitro. Some of the these compounds exhibited antiplasmodial activity in the micromol range, determined as fifty percent-inhibitory concentrations (IC(50)). Drug activity was not associated with cytotoxicity for the mammalian tumor cell lines KB and SKMel (IC(50) > 3.0 microM). The most active compound was 4,6,4'-triacetyl-3',5'-dimethoxy-2-aurone with IC(50) values of 0.007 microM and 0.18 microM for the P. falciparum strains K1 and NF54, respectively. Interestingly, the multiple drug-resistant P. falciparum strain K1 was more sensitive to tested aurones than the drug-susceptible strain NF54.

Evaluation of in vitro activity of aurones and related compounds against Cryptosporidium parvum.

The efficacy of a series of aurones, auronols and 4-methoxy-alpha-pyrones has been screened for the ability to inhibit the intracellular growth of the parasitic protist Cryptosporidium parvum using an in vitro enzyme linked immunosorbent assay (ELISA). All aurones of this series were active at 25 to 100 microM. 10 of 19 aurones inhibited the intracellular growth of C. parvum by > 90 % with moderate to no toxicity. The most active of these was 3',4',6-trihydroxy-2-[phenylmethylene]-3(2H)-benzofuranone.

Proanthocyanidins and related compounds: antileishmanial activity and modulatory effects on nitric oxide and tumor necrosis factor-alpha-release in the murine macrophage-like cell line RAW 264.7.

A series of 17 proanthocyanidins and structurally related compounds was tested for activity against Leishmania donovani amastigotes and promastigotes in vitro. Most of the polyphenols significantly inhibited the intracellular survival of L. donovani amastigotes (EC50 0.8-10.6 nM) when compared with the antileishmanial drug Pentostam (EC50 10.6 nM), but all were inactive against the extracellular form (EC50 7.8 to >86 nM). Noteworthy is that all compounds exhibited only moderate or no cytotoxicity against the murine host cells (EC50 7.8 to >56 nM; >25 microg/ml). These polyphenols were further evaluated for immunomodulatory effects on macrophage functions, including release of nitric oxide (NO), tumor necrosis factor-alpha (TNF) and interferon (IFN)-like properties using several functional assays. The results showed that all compounds induced murine RAW 264.7 cells only moderately to release NO (7-26 microM) relative to the reference stimulus IFN-gamma/LPS (119 microM). The TNF-inducing potential of the polyphenols producing 50% lysis in murine L929 cells ranged from absent to 138 U/ml at the host cell subtoxic concentration of 50 microg/ml. The highest TNF-inducing activity was associated with those flavan-3-ols with galloyl groups (98-127 U/ml). For proanthocyanidins, it appeared that an increase in the flavanyl chain length did not enhance the induction of TNF-release (32-86 U/ml and below detection limits for oligomers and polymers, respectively). With interferon-like activities, phylloflavan and a prodelphinidin polymer showed appreciable cytoprotective effects, as reflected by the inhibition of the cytopathic effect of encephalomyocarditis virus on L929 fibroblast cells (38 and 36 U/ml, respectively). All remaining compounds displayed only negligible or moderate protective effects at subtoxic concentrations up to 25 microg/ml (<5 to 12 U/ml). These results indicate that proanthocyanidins and related compounds have favorable antileishmanial activity in vitro and might be considered as beneficial immunological response modifiers provided there are no bioavailability problems.

Tannins and related compounds: killing of amastigotes of Leishmania donovani and release of nitric oxide and tumour necrosis factor alpha in macrophages in vitro.

The antileishmanial and immunomodulatory potencies of a series of 28 polyphenols were evaluated in terms of extra- and intracellular leishmanicidal activity and macrophage activation for release of nitric oxide (NO), tumour necrosis factor (TNF) and interferon (IFN)-like properties. For this, several functional bioassays were employed including an in vitro model for leishmaniasis in which murine bone marrow-derived macrophages (BMMphi) were infected with the obligate intracellular parasite Leishmania donovani, an extracellular Leishmania proliferation assay, a fibroblast-lysis assay (TNF-activity), and a biochemical assay for NO. Except for gallic acid, its methyl ester, shikimic acid and catechin (EC50 25.8-67.9 nM) all polyphenols tested significantly inhibited the intracellular survival of L. donovani amastigotes (EC50 0.4-13.9 nM) when compared with the clinically used agent, sodium stibogluconate (EC50 10.6 nM). In contrast, none of the samples proved to be directly toxic for the extracellular promastigote form of the parasite. Noteworthy, the phenolic samples showed only moderate or no cytotoxicity against the murine host cells (EC50 10 to >144 nM). Although NO is an important effector molecule in macrophage microbicidal activity, the inducing potential of the test compounds for its release was found to be very moderate ranging from 7-54 microM (IFN-gamma/LPS 119 microM). On the other hand, inhibition of NO production had no apparent effect on intracellular leishmanicidal activity of polyphenols. Their in vitro TNF-inducing potential producing 50% lysis in murine L929 cells increased in the order of simple phenols and flavanols (34-48 U/ml) < A-type proanthocyanidins (53-80 U/ml) < B-type proanthocyanidins (64-200 U/ml) < hydrolyzable tannins (287-350 U/ml) at the host cell subtoxic concentration of 50 microg/ml. Furthermore, gallic acid and some hydrolyzable tannins showed appreciable IFN-like activities (14-23 U/ml) as reflected by inhibition of the cytopathic effect of encephalomyocarditis virus on fibroblast L 929 cells. The results provide a rational basis for the recorded anti-infectious efficacy of traditionally used herbal medicines containing tannins in vivo, in the light of both only moderate direct antimicrobial activities of distinct polyphenols in vitro and the limited knowledge on their uptake in humans.

Immunomodulatory principles of Pelargonium sidoides.

Extracts and isolated constituents (coumarins and phenols) of Pelargonium sidoides DC, a plant species used in folk medicine by the Southern African native population, were evaluated for their effects on nonspecific immune functions. Although this herbal medicine is also successfully employed in modern phytotherapy in Europe to cure infectious diseases of the respiratory tract, the scientific basis of its remedial effects is still unclear. Thus, functional bioassays including an in vitro model for intracellular infection with Leishmania parasites, an extracellular Leishmania growth assay, a fibroblast-virus protection assay (IFN activity), a fibroblast-lysis assay (TNF activity) and a biochemical assay for inorganic nitric oxides (iNO) were employed. None of the test samples revealed significant activity against extracellular, promastigote Leishmania donovani, the causative agent of human visceral leishmaniasis. In contrast, apart from the coumarin samples, all the Pelargonium extracts (EC(50) <0.1-3.3 microg/mL), gallic acid (EC(50) 4.4 microg/mL) and its methyl ester (EC(50) 12.5 microg/mL) significantly reduced the intracellular survival of L. donovani amastigotes within murine macrophages. These data indicate that the samples acted indirectly on Leishmania parasites, possibly by activating leishmanicidal macrophage functions. Macrophage activation was confirmed by detection of tumour necrosis factor (TNF-alpha) and inorganic nitric oxides (iNO) in supernatants of sample-treated macrophage cultures. Synthesis of iNO is a well-known effector mechanism of macrophages against microorganisms such as Leishmania. Interestingly, blocking iNO-synthase with L-NMMA had no substantial effect on sample-induced intracellular Leishmania kill. From bioassay-guided fractionation, gallic acid and its methyl ester present in large amounts in P. sidoides and in its active extracts, were identified as the prominent immunomodulatory principle for this herbal medicine. The results, when taken together with recent reported antibacterial activity, provide a rational basis for both the traditional and the present utilization of P. sidoides in the claimed conditions.

In vitro leishmanicidal activity of naturally occurring chalcones.

A variety of chalcones have been shown to exhibit activity against Leishmania parasites. In contrast to synthetic or semisynthetic chalcones, only a few plant-derived compounds have been investigated. To provide a scientific rational for the antiprotozoal potency of plants used in ethnomedicine and containing chalcones, and in the search for new antiprotozoal drugs, we have carried out a primary screening for in vitro leishmanicidal activity of 20 chalcones isolated from plants. The compounds were tested against extracellular promastigotes of Leishmania donovani, L. infantum, L. enrietii and L. major, and against intracellular amastigote L. donovani residing within murine macrophages. Against the extracellular Leishmania (L. donovani), most compounds were active with EC(50) values between 0.07 and 2.01 microg/mL. Some of these chalcones, 2',4'-dihydroxy-4-methoxychalcone, 2'-hydroxy-3,4-dimethoxychalcone and 2-hydroxy-4,4'-dimethoxychalcone also significantly inhibited the intracellular survival of L. donovani parasites with EC(50) values between 0.39 and 0.41 microg/mL. When tested against murine bone marrow-derived macrophages as a mammalian host cell control, all compounds with antileishmanial activities also proved to be cytotoxic to varying extents (EC(50) 0.19-2.06 microg/mL). Correlations between molecular structures and antileishmanial activity are discussed in detail. Specific compounds are illustrated with emphasis on their mode of action and potential for the development of selective antiprotozoal agents.

Antileishmanial activities of aphidicolin and its semisynthetic derivatives.

Aphidicolin and a series of semisynthetic aphidicolan derivatives have been identified in in vitro tests as novel drugs with antiparasitic potential. All compounds have been tested against extracellular promastigotes of Leishmania donovani, L. infantum, L. enriettii, and L. major and against intracellular amastigotes of L. donovani in murine macrophages. The compounds showed antileishmanial activity at concentrations in the microgram range (50% effective concentration [EC(50)] = 0.02 to 1.83 microg/ml). The most active derivative (aphidicolin-17-glycinate hydrochloride) had EC(50)s of 0. 2 microg/ml against extracellular and 0.02 microg/ml against intracellular L. donovani parasites. To validate the pharmacological potential of tested drugs, pharmacological safety was determined by testing all compounds against two neoplastic cell lines (squamous carcinoma [KB] and melanoma [SK-Mel]) and against murine bone marrow-derived macrophages as host cells. With minor exceptions only for macrophages, tested aphidicolans did not show significant cytotoxicity (EC(50) > 25.0 microg/ml). Structure-activity relationships of these aphidicolan derivatives are discussed.

In vitro leishmanicidal activity of monomeric and dimeric naphthoquinones.

A series of monomeric and dimeric naphthoquinones with potential for treatment of Leishmania infections was identified in vitro using both a direct cytotoxicity assay against extracellular promastigotes of Leishmania donovani, L. infantum, L. enriettii, and L. major and a test against intracellular amastigote L. donovani residing within murine macrophages. Several naphthoquinones proved to be active at concentrations in the microgram range (EC(50) 0.9-17.0 microg/ml). When tested against a panel of human cancer cell lines (KB, SKMel, A549, MDA) and murine bone marrow culture-derived macrophages (BMMPhi) as mammalian host cell controls, compounds with anti-Leishmania-activity showed moderate (EC(50)>25 microg/ml) to pronounced (EC(50)<10 microg/ml) toxic effects.

In vitro leishmanicidal activity of monomeric and dimeric naphthoquinones.

A series of monomeric and dimeric naphthoquinones with potential for treatment of Leishmania infections was identified in vitro using both a direct cytotoxicity assay against extracellular promastigotes of Leishmania donovani, Leishmania infanturn, Leishmania enriettii, and Leishmania major and a test against intracellular amastigote L. donovani residing within murine macrophages. Several naphthoquinones proved to be active at concentrations in the microgram range (EC(50) 0.9-17.0 microg/ml). When tested against a panel of human cancer cell lines (KB, SKMel, A549, MDA) and murine bone marrow culture-derived macrophages (BMMPhi) as mammalian host cell controls, compounds with anti-Leishmania-activity showed moderate (EC(50)>25 microg/ml) to pronounced (EC(50)<10 microg/ml) toxic effects.

[Pathogenesis of pneumocystis carinii pneumonia]. / Pathogenese der Pneumocystis carinii-Pneumonie.

Pneumocystis carinii is a ubiquitous fungus and opportunistic resident of the bronchoalveolar lumen of men and a variety of other mammalian species. This microorganism replicates under immunosuppressive conditions, ultimately resulting in lethal pneumonia (PcP) if left untreated. In the past decade, considerable progress has been made concerning the understanding of the underlying pathogenic mechanisms of this infection, mostly with the help of animal models such as SCID (severe combined immunodeficiency) or gene-knock-out mice. Partially conflicting data derived from animal studies lead to the assumption that there is no single relevant model for PcP. The T cell-mediated branch of the immune system is recognised as the major component in the host's ability to resist or overcome an infection with P. carinii. Natural, nonspecific immune mechanisms involving mononuclear phagocytes and elaborating a variety of cytokines and other immunomediators play an important role in initiating the immunoresponse as well as in its effector phase, but it is the CD4+ T lymphocytes which are essential for coordinating the complete eradication of this pathogen. The biological function and immunological effects of antigens expressed on the surface of or secreted by P. carinii organisms is not yet fully known. Hopefully, characterisation of these molecules, clarification of their immunological properties and the evaluation of the interactions between humoral and cellular as well as specific and nonspecific parts of the immune system will lead to new insights into the pathogenesis of P. carinii pneumonia.

A monoclonal antibody directed against the murine macrophage surface molecule F4/80 modulates natural immune response to Listeria monocytogenes.

Whole spleen cell cultures from SCID mice release high levels of IFN-gamma when exposed to heat-killed Listeria monocytogenes (HKL). This microbe-induced and T cell-independent response depends on both macrophages (MPhi) and NK cells: HKL-stimulated MPhi release TNF-alpha and IL-12, which together activate NK cells for IFN-gamma release. We show here that this cytokine-mediated activation cascade can be modulated by a mAb against the MPhi surface glycoprotein F4/80. HKL-induced IL-12, TNF-alpha, and IFN-gamma in SCID whole spleen cell cultures was inhibited by coincubation with anti-F4/80 mAb whereas IL-1 and IL-10 were enhanced. Both effects were apparent at mRNA and protein release levels. Whereas inhibitory activities were F4/80 Ag specific, stimulatory effects were Fc dependent and nonspecific. Furthermore, cytokine inhibition by anti-F4/80 was only apparent when MPhi and NK cells were present simultaneously and in close vicinity, indicating that direct cell-to-cell contact is a prerequisite. These data suggest a novel pathway for microbe-induced MPhi/NK cell interaction involving direct cell-to-cell signaling and give the first evidence for a functional role of the MPhi surface glycoprotein F4/80.

In vitro leishmanicidal activity of aurones.

A series of aurones with drug-potential for Leishmania infections was identified in vitro using both a direct cytotoxicity assay against extracellular promastigotes of Leishmania donovani, L. infantum, L. enriettii, and L. major, and a test against intracellular amastigote forms of L. donovani residing within murine macrophages. The most active aurone (6-hydroxy-2-[phenylmethylene]-3(2H)-benzofuranone) had an EC50 of 0.45 microgram/ml in the extra-, and an EC50 of 1.40 micrograms/ml in the intracellular assay. Other aurones were active between 0.06-12.50 micrograms/ml and 0.04-7.81 micrograms/ml, respectively. When tested against murine bone marrow-derived macrophages as a mammalian host cell control, the compounds showed only moderate cytotoxicity (EC50 2.32 to > 25.0 micrograms/ml). This is the first report on aurones as a new class of natural products with leishmanicidal activity.