Killing Two Birds with One Stone: Discovery of Dual Inhibitors of Oxygen and Fumarate Respiration in Zoonotic Parasite, Echinococcus multilocularis

Ascofuranone (AF), a meroterpenoid isolated from various filamentous fungi, including Acremonium egyptiacum, has been reported as a potential lead candidate for drug development against parasites and cancer. In this study, we demonstrated that AF and its derivatives are potent anthelminthic agents, particularly against Echinococcus multilocularis, which is the causative agent of alveolar echinococcosis. We measured the inhibitory activities of AF and its derivatives on the mitochondrial aerobic and anaerobic respiratory systems of E. multilocularis larvae. Several derivatives inhibited complex II (succinate:quinone reductase [SQR]; IC₅₀ = 0.037 to 0.135 μM) and also complex I to III (NADH:cytochrome c reductase; IC₅₀ = 0.008 to 0.401 μM), but not complex I (NADH:quinone reductase), indicating that mitochondrial complexes II and III are the targets. In particular, complex II inhibition in the anaerobic pathway was notable because E. multilocularis employs NADH:fumarate reductase (fumarate respiration), in addition to NADH oxidase (oxygen respiration), resulting in complete shutdown of ATP synthesis by oxidative phosphorylation. A structure-activity relationship study of E. multilocularis complex II revealed that the functional groups of AF are essential for inhibition. Binding mode prediction of AF derivatives to complex II indicated potential hydrophobic and hydrogen bond interactions between AF derivatives and amino acid residues within the quinone binding site. Ex vivo culture assays revealed that AF derivatives progressively reduced the viability of protoscoleces under both aerobic and anaerobic conditions. These findings confirm that AF and its derivatives are the first dual inhibitors of fumarate and oxygen respiration in E. multilocularis and are potential lead compounds in the development of anti-echinococcal drugs.

Biochemical characterization and identification of ferulenol and embelin as potent inhibitors of malate:quinone oxidoreductase from Campylobacter jejuni

Campylobacter jejuni infection poses a serious global threat to public health. The increasing incidence and antibiotic resistance of this bacterial infection have necessitated the adoption of various strategies to curb this trend, primarily through developing new drugs with new mechanisms of action. The enzyme malate:quinone oxidoreductase (MQO) has been shown to be essential for the survival of several bacteria and parasites. MQO is a peripheral membrane protein that catalyses the oxidation of malate to oxaloacetate, a crucial step in the tricarboxylic acid cycle. In addition, MQO is involved in the reduction of the quinone pool in the electron transport chain and thus contributes to cellular bioenergetics. The enzyme is an attractive drug target as it is not conserved in mammals. As a preliminary step in assessing the potential application of MQO from C. jejuni (CjMQO) as a new drug target, we purified active recombinant CjMQO and conducted, for the first time, biochemical analyses of MQO from a pathogenic bacterium. Our study showed that ferulenol, a submicromolar mitochondrial MQO inhibitor, and embelin are nanomolar inhibitors of CjMQO. We showed that both inhibitors are mixed-type inhibitors versus malate and noncompetitive versus quinone, suggesting the existence of a third binding site to accommodate these inhibitors; indeed, such a trait appears to be conserved between mitochondrial and bacterial MQOs. Interestingly, ferulenol and embelin also inhibit the in vitro growth of C. jejuni, supporting the hypothesis that MQO is essential for C. jejuni survival and is therefore an important drug target.

Effect of geranylated dihydrochalcone from Artocarpus altilis leaves extract on Plasmodium falciparum ultrastructural changes and mitochondrial malate: Quinone oxidoreductase

Nearly half of the world's population is at risk of being infected by Plasmodium falciparum, the pathogen of malaria. Increasing resistance to common antimalarial drugs has encouraged investigations to find compounds with different scaffolds. Extracts of Artocarpus altilis leaves have previously been reported to exhibit in vitro antimalarial activity against P. falciparum and in vivo activity against P. berghei. Despite these initial promising results, the active compound from A. altilis is yet to be identified. Here, we have identified 2-geranyl-2', 4', 3, 4-tetrahydroxy-dihydrochalcone (1) from A. altilis leaves as the active constituent of its antimalarial activity. Since natural chalcones have been reported to inhibit food vacuole and mitochondrial electron transport chain (ETC), the morphological changes in food vacuole and biochemical inhibition of ETC enzymes of (1) were investigated. In the presence of (1), intraerythrocytic asexual development was impaired, and according to the TEM analysis, this clearly affected the ultrastructure of food vacuoles. Amongst the ETC enzymes, (1) inhibited the mitochondrial malate: quinone oxidoreductase (PfMQO), and no inhibition could be observed on dihydroorotate dehydrogenase (DHODH) as well as bc₁ complex activities. Our study suggests that (1) has a dual mechanism of action affecting the food vacuole and inhibition of PfMQO-related pathways in mitochondria.

Siccanin Is a Dual-Target Inhibitor of Plasmodium falciparum Mitochondrial Complex II and Complex III

Plasmodium falciparum contains several mitochondrial electron transport chain (ETC) dehydrogenases shuttling electrons from the respective substrates to the ubiquinone pool, from which electrons are consecutively transferred to complex III, complex IV, and finally to the molecular oxygen. The antimalarial drug atovaquone inhibits complex III and validates this parasite’s ETC as an attractive target for chemotherapy. Among the ETC dehydrogenases from P. falciparum, dihydroorotate dehydrogenase, an essential enzyme used in de novo pyrimidine biosynthesis, and complex III are the two enzymes that have been characterized and validated as drug targets in the blood-stage parasite, while complex II has been shown to be essential for parasite survival in the mosquito stage; therefore, these enzymes and complex II are considered candidate drug targets for blocking parasite transmission. In this study, we identified siccanin as the first (to our knowledge) nanomolar inhibitor of the P. falciparum complex II. Moreover, we demonstrated that siccanin also inhibits complex III in the low-micromolar range. Siccanin did not inhibit the corresponding complexes from mammalian mitochondria even at high concentrations. Siccanin inhibited the growth of P. falciparum with IC₅₀ of 8.4 μM. However, the growth inhibition of the P. falciparum blood stage did not correlate with ETC inhibition, as demonstrated by lack of resistance to siccanin in the yDHODH-3D7 (EC₅₀ = 10.26 μM) and Dd2-ELQ300 strains (EC₅₀ = 18.70 μM), suggesting a third mechanism of action that is unrelated to mitochondrial ETC inhibition. Hence, siccanin has at least a dual mechanism of action, being the first potent and selective inhibitor of P. falciparum complexes II and III over mammalian enzymes and so is a potential candidate for the development of a new class of antimalarial drugs.

5-Aminolevulinic acid antiviral efficacy against SARS-CoV-2 omicron variant in vitro

The coronavirus disease 2019 (COVID 19) pandemic continues to pose a threat to global health. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant (B.1.1.529) has spread rapidly worldwide and became dominant in many countries. A natural 5-aminolevulinic acid (5-ALA) with sodium ferrous citrate (SFC) has demonstrated antiviral activity in Wuhan, Alpha, Beta, Gamma, and Delta variants of SARS-CoV-2 infections in vitro. In this study, we report antiviral activity of 5-ALA, 5-ALA with SFC led to IC₅₀ of 329 and 765/191, respectively after infection with Omicron variant of SARS-CoV-2 in vitro. Our finding suggests that 5-ALA could be used as antiviral drug candidate to treat Omicron variant infected patients.

Antiviral activity of 5-aminolevulinic acid against variants of severe acute respiratory syndrome coronavirus 2

BACKGROUND

Genetic variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began to emerge in 2020 and have been spreading globally during the coronavirus disease 2019 (COVID-19) pandemic. Despite the presence of different COVID-19 vaccines, the discovery of effective antiviral therapeutics for the treatment of patients infected with SARS-CoV-2 are still urgently needed. A natural amino acid, 5-aminolevulinic acid (5-ALA), has exhibited both antiviral and anti-inflammatory activities. In a previous study, we demonstrated an in vitro antiviral effect of 5-ALA against SARS-CoV-2 infection without significant cytotoxicity. In the present study, we sought to investigate whether 5-ALA with or without sodium ferrous citrate (SFC) can inhibit in vitro both the original SARS-CoV-2 Wuhan strain and its variants, including the Alpha, Beta, Gamma and Delta strains.

METHODS

The antiviral activity of ALA with or without SFC was determined in Vero-E6 cell. The virus inhibition was quantified by real time RT-PCR.

RESULTS

Co-administration of 5-ALA and SFC inhibited the Wuhan, Alpha and Delta variants of SARS-CoV-2 with IC50 values of 235, 173 and 397 µM, respectively, and the Beta and Gamma variants with IC50 values of 1311 and 1516 µM.

CONCLUSION

Our study suggests that 5-ALA with SFC warrants accelerated clinical evaluation as an antiviral drug candidate for treating patients infected with SARS-CoV-2 variants.

Rhoptry kinase protein 39 (ROP39) is a novel factor that recruits host mitochondria to the parasitophorous vacuole of Toxoplasma gondii

Most intracellular pathogens replicate in a vacuole to avoid the defense system of the host. A few pathogens recruit host mitochondria around those vacuoles, but the molecules responsible for mitochondrial recruitment remain unidentified. It is only in the apicomplexan parasite Toxoplasma gondii, that mitochondrial association factor 1b (MAF1b) has been identified as an association factor for host mitochondria. Here, we show that rhoptry kinase family protein 39 (ROP39) induces host mitochondrial recruitment in T. gondii. We found that the abundance of ROP39 was increased on host mitochondria extracted from human foreskin fibroblasts (HFFs) infected with T. gondii. ROP39 expressed exogenously in HFFs localized on host mitochondria, indicating that it has the potential to bind to host mitochondria without assistance from other parasite factors. Confocal microscopy revealed that ROP39 colocalized with host mitochondria on the membrane of parasitophorous vacuoles, in which the parasites reside. Moreover, we observed about a 10% reduction in the level of mitochondrial association in rop39-knockout parasites compared with a parental strain.

Summary: We revealed that ROP39 recruitments host mitochondria, possibly through its kinase activity. Exploiting components involved with recruitment of host mitochondria advances the understanding of how the parasites employ mitochondrial recruitment to survive in host cells.

Exploring natural microbial resources for the discovery of anti-malarial compounds

Microorganisms in nature are highly diverse biological resources, which can be explored for drug discovery. Some countries including Brazil, Columbia, Indonesia, China, and Mexico, which are blessed with geographical uniqueness with diverse climates and display remarkable megabiodiversity, potentially provide microorganismal resources for such exploitation. In this review, as an example of drug discovery campaigns against tropical parasitic diseases utilizing microorganisms from such a megabiodiversity country, we summarize our past and on-going activities toward discovery of new antimalarials. The program was held in a bilateral collaboration between multiple Indonesian and Japanese research groups. In order to develop a new platform of drug discovery utilizing Indonesian bioresources under an international collaborative scheme, we aimed at: 1) establishment of an Indonesian microbial depository, 2) development of robust enzyme-based and cell-based screening systems, and 3) technology transfer necessary for screening, purification, and identification of antimalarial compounds from microbial culture broths. We collected, characterized, and deposited Indonesian microbes. We morphologically and genetically characterized fungi and actinomycetes strains isolated from 5 different locations representing 3 Indonesian geographical areas, and validated genetic diversity of microbes. Enzyme-based screening was developed against two validated mitochondrial enzymes from Plasmodium falciparum, dihydroorotate dehydrogenase and malate:quinone oxidoreductase, while cell-based proliferation assay was developed using the erythrocytic stage parasite of 3D7 strain. More than 17 thousands microbial culture extracts were subjected to the enzyme- and cell-based screening. Representative anti-malarial compounds discovered in this campaign are discussed, including a few isolated compounds that have been identified for the first time as anti-malarial compounds. Our antimalarial discovery campaign validated the Indonesian microbial library as a powerful resource for drug discovery. We also discuss critical needs for selection criteria for hits at each stage of screening and hit deconvolution such as preliminary extraction test for the initial profiling of the active compounds and dereplication techniques to minimize repetitive discovery of known compounds.

5-amino levulinic acid inhibits SARS-CoV-2 infection in vitro

The current COVID-19 pandemic requires urgent development of effective therapeutics. 5-amino levulinic acid (5-ALA) is a naturally synthesized amino acid and has been used for multiple purposes including as an anticancer therapy and as a dietary supplement due to its high bioavailability. In this study, we demonstrated that 5-ALA treatment potently inhibited infection of SARS-CoV-2, a causative agent of COVID-19, in cell culture. The antiviral effects could be detected in both human and non-human cells, without significant cytotoxicity. Therefore, 5-ALA is worth to be further investigated as an antiviral drug candidate for COVID-19.

Characterization of Plasmodium falciparum Pantothenate Kinase and Identification of Its Inhibitors From Natural Products

Coenzyme A (CoA) is a well-known cofactor that plays an essential role in many metabolic reactions in all organisms. In Plasmodium falciparum, the most deadly among Plasmodium species that cause malaria, CoA and its biosynthetic pathway have been proven to be indispensable. The first and rate-limiting reaction in the CoA biosynthetic pathway is catalyzed by two putative pantothenate kinases (PfPanK1 and 2) in this parasite. Here we produced, purified, and biochemically characterized recombinant PfPanK1 for the first time. PfPanK1 showed activity using pantetheine besides pantothenate, as the primary substrate, indicating that CoA biosynthesis in the blood stage of P. falciparum can bypass pantothenate. We further developed a robust and reliable screening system to identify inhibitors using recombinant PfPanK1 and identified four PfPanK inhibitors from natural compounds.

Interaction between transforming Theileria parasites and their host bovine leukocytes

Theileria are tick-transmitted parasites that cause often fatal leuko-proliferative diseases in cattle called tropical theileriosis (T. annulata) and East Coast fever (T. parva). However, upon treatment with anti-theilerial drug-transformed leukocytes die of apoptosis indicating that Theileria-induced transformation is reversible making infected leukocytes a powerful example of how intracellular parasites interact with their hosts. Theileria-transformed leukocytes disseminate throughout infected cattle causing a cancer-like disease and here, we discuss how cytokines, noncoding RNAs and oncometabolites can contribute to the transformed phenotype and disease pathology.

Structural and Biochemical Features of Eimeria tenella Dihydroorotate Dehydrogenase, a Potential Drug Target

Dihydroorotate dehydrogenase (DHODH) is a mitochondrial monotopic membrane protein that plays an essential role in the pyrimidine de novo biosynthesis and electron transport chain pathways. In Eimeria tenella, an intracellular apicomplexan parasite that causes the most severe form of chicken coccidiosis, the activity of pyrimidine salvage pathway at the intracellular stage is negligible and it relies on the pyrimidine de novo biosynthesis pathway. Therefore, the enzymes of the de novo pathway are considered potential drug target candidates for the design of compounds with activity against this parasite. Although, DHODHs from E. tenella (EtDHODH), Plasmodium falciparum (PfDHODH), and human (HsDHODH) show distinct sensitivities to classical DHODH inhibitors, in this paper, we identify ferulenol as a potent inhibitor of both EtDHODH and HsDHODH. Additionally, we report the crystal structures of EtDHODH and HsDHODH in the absence and presence of ferulenol. Comparison of these enzymes showed that despite similar overall structures, the EtDHODH has a long insertion in the N-terminal helix region that assumes a disordered configuration. In addition, the crystal structures revealed that the ferulenol binding pocket of EtDHODH is larger than that of HsDHODH. These differences can be explored to accelerate structure-based design of inhibitors specifically targeting EtDHODH.

Plasmodium falciparum multidrug resistance gene-1 polymorphisms in Northern Nigeria: implications for the continued use of artemether-lumefantrine in the region

Background

The analysis of single nucleotide polymorphism (SNPs) in drug-resistance associated genes is a commonly used strategy for the surveillance of anti-malarial drug resistance in populations of parasites. The present study was designed and performed to provide genetic epidemiological data of the prevalence of N86Y-Y184F-D1246Y SNPs in Plasmodium falciparum multidrug resistance 1 (pfmdr1) in the malaria hotspot of Northern Nigeria.

Methods

Plasmodium falciparum-positive blood samples on Whatman-3MM filter papers were collected from 750 symptomatic patients from four states (Kano, Kaduna, Yobe and Adamawa) in Northern Nigeria, and genotyped via BigDye (v3.1) terminator cycle sequencing for the presence of three SNPs in pfmdr1. SNPs in pfmdr1 were used to construct NYD, NYY, NFY, NFD, YYY, YYD, YFD and YFY haplotypes, and all data were analysed using Pearson Chi square and Fisher’s exact (FE) tests.

Results

The prevalence of the pfmdr1 86Y allele was highest in Kaduna (12.50%, ² = 10.50, P = 0.02), whilst the 184F allele was highest in Kano (73.10%, ² = 13.20, P = 0.00), and the pfmdr1 1246Y allele was highest in Yobe (5.26%, ² = 9.20, P = 0.03). The NFD haplotype had the highest prevalence of 69.81% in Kano (² = 36.10, P = 0.00), followed by NYD with a prevalence of 49.00% in Adamawa, then YFD with prevalence of 11.46% in Kaduna. The YYY haplotype was not observed in any of the studied states.

Conclusion

The present study suggests that strains of P. falciparum with reduced sensitivity to the lumefantrine component of AL exist in Northern Nigeria and predominate in the North-West region.

Theileria parasites subvert E2F signaling to stimulate leukocyte proliferation

Intracellular pathogens have evolved intricate mechanisms to subvert host cell signaling pathways and ensure their own propagation. A lineage of the protozoan parasite genus Theileria infects bovine leukocytes and induces their uncontrolled proliferation causing a leukemia-like disease. Given the importance of E2F transcription factors in mammalian cell cycle regulation, we investigated the role of E2F signaling in Theileria-induced host cell proliferation. Using comparative genomics and surface plasmon resonance, we identified parasite-derived peptides that have the sequence-specific ability to increase E2F signaling by binding E2F negative regulator Retinoblastoma-1 (RB). Using these peptides as a tool to probe host E2F signaling, we show that the disruption of RB complexes ex vivo leads to activation of E2F-driven transcription and increased leukocyte proliferation in an infection-dependent manner. This result is consistent with existing models and, together, they support a critical role of E2F signaling for Theileria-induced host cell proliferation, and its potential direct manipulation by one or more parasite proteins.

Molecular and biological analysis revealed genetic diversity and high virulence strain of Toxoplasma gondii in Japan

Toxoplasma gondii is classified into 16 haplogroups based on a worldwide genotyping study of the parasite. However, only a few isolates from Japan were included in this analysis. To conduct more precise genotyping of T. gondii, we examined the genotypes of Japanese isolates in this study. DNA sequences of 6 loci were determined in 17 Japanese isolates and compared with those of strains of 16 haplogroups. As a result, Japanese isolates were classified into four groups. We investigated the virulence of some Japanese isolates and found a highly virulent strain in mice, comparable to that of RH strain, although this Japanese isolate was sister to strains of haplogroup 2, which show moderate virulence in mice. We further investigated whether this high virulence isolate had different virulence mechanism and strategy to adapt to Japanese host from other strains by comparing the virulence-related genes, ROP5, 18 and the immunomodulatory gene, ROP16 of the isolate with those of archetypical strains (GT1, ME49 and VEG). This analysis indicated the high virulence of the isolate in mice was partly explained by gene sequences of ROP5 and ROP16. These findings lead to the elucidation of biodiversity of T. gondii and have potential to optimize the diagnostic protocol.

Selective Cytotoxicity of Dihydroorotate Dehydrogenase Inhibitors to Human Cancer Cells Under Hypoxia and Nutrient-Deprived Conditions

Human dihydroorotate dehydrogenase (HsDHODH) is a key enzyme of pyrimidine de novo biosynthesis pathway. It is located on the mitochondrial inner membrane and contributes to the respiratory chain by shuttling electrons to the ubiquinone pool. We have discovered ascofuranone (1), a natural compound produced by Acremonium sclerotigenum, and its derivatives are a potent class of HsDHODH inhibitors. We conducted a structure–activity relationship study and have identified functional groups of 1 that are essential for the inhibition of HsDHODH enzymatic activity. Furthermore, the binding mode of 1 and its derivatives to HsDHODH was demonstrated by co-crystallographic analysis and we show that these inhibitors bind at the ubiquinone binding site. In addition, the cytotoxicities of 1 and its potent derivatives 7, 8, and 9 were studied using human cultured cancer cells. Interestingly, they showed selective and strong cytotoxicity to cancer cells cultured under microenvironment (hypoxia and nutrient-deprived) conditions. The selectivity ratio of 8 under this microenvironment show the most potent inhibition which was over 1000-fold higher compared to that under normal culture condition. Our studies suggest that under microenvironment conditions, cancer cells heavily depend on the pyrimidine de novo biosynthesis pathway. We also provide the first evidence that 1 and its derivatives are potential lead candidates for drug development which target the HsDHODH of cancer cells living under a tumor microenvironment.

Fates of Evolutionarily Distinct, Plastid-type Glyceraldehyde 3-phosphate Dehydrogenase Genes in Kareniacean Dinoflagellates

The ancestral kareniacean dinoflagellate has undergone tertiary endosymbiosis, in which the original plastid is replaced by a haptophyte endosymbiont. During this plastid replacement, the endosymbiont genes were most likely flowed into the host dinoflagellate genome (endosymbiotic gene transfer or EGT). Such EGT may have generated the redundancy of functionally homologous genes in the host genome-one has resided in the host genome prior to the haptophyte endosymbiosis, while the other transferred from the endosymbiont genome. However, it remains to be well understood how evolutionarily distinct but functionally homologous genes were dealt in the dinoflagellate genomes bearing haptophyte-derived plastids. To model the gene evolution after EGT in plastid replacement, we here compared the characteristics of the two evolutionally distinct genes encoding plastid-type glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in Karenia brevis and K. mikimotoi bearing haptophyte-derived tertiary plastids: "gapC1h" acquired from the haptophyte endosymbiont and "gapC1p" inherited from the ancestral dinoflagellate. Our experiments consistently and clearly demonstrated that, in the two species examined, the principal plastid-type GAPDH is encoded by gapC1h rather than gapC1p. We here propose an evolutionary scheme resolving the EGT-derived redundancy of genes involved in plastid function and maintenance in the nuclear genomes of dinoflagellates that have undergone plastid replacements. Although K. brevis and K. mikimotoi are closely related to each other, the statuses of the two evolutionarily distinct gapC1 genes in the two Karenia species correspond to different steps in the proposed scheme.

Impact of the presence of HLA 1-locus mismatch and the use of low-dose antithymocyte globulin in unrelated bone marrow transplantation

HLA 1-locus-mismatched unrelated donors (1MMUD) have been used in allogeneic hematopoietic stem cell transplantation (allo-HCT) for patients who lack an HLA-matched donor. We retrospectively analyzed 3313 patients with acute leukemia or myelodysplastic syndrome who underwent bone marrow transplantation from an HLA allele-matched unrelated donor (MUD) or 1MMUD between 2009 and 2014. We compared the outcomes of MUD (n=2089) and 1MMUD with antithymocyte globulin (ATG) (1MM-ATG(+); n=109) with those of 1MMUD without ATG (1MM-ATG(-); n=1115). The median total dose of ATG (thymoglobulin) was 2.5 mg/kg (range 1.0-11.0 mg/kg) in the 1MM-ATG(+) group. The rates of grade III-IV acute GvHD, non-relapse mortality (NRM) and overall mortality were significantly lower in the MUD group than in the 1MM-ATG(-) group (hazard ratio (HR) 0.77, P=0.016; HR 0.74; P<0.001; and HR 0.87, P=0.020, respectively). Likewise, the rates of grade III-IV acute GVHD, NRM and overall mortality were significantly lower in the 1MM-ATG(+) group than in the 1MM-ATG(-) group (HR 0.42, P=0.035; HR 0.35, P<0.001; and HR 0.71, P=0.042, respectively). The outcome of allo-HCT from 1MM-ATG(-) was inferior to that of allo-HCT from MUD even in the recent cohort. However, the negative impact of 1MMUD disappeared with the use of low-dose ATG without increasing the risk of relapse.

Low-dose thymoglobulin as second-line treatment for steroid-resistant acute GvHD: an analysis of the JSHCT

A nationwide retrospective study for the clinical outcomes of 99 patients who had received thymoglobulin at a median total dose of 2.5 mg/kg (range, 0.5-18.5 mg/kg) as a second-line treatment for steroid-resistant acute GvHD was conducted. Of the 92 evaluable patients, improvement (complete or partial response) was observed in 55 patients (60%). Multivariate analysis demonstrated that male sex and grade III and IV acute GvHD were associated with a lower improvement rate, whereas thymoglobulin dose (<2.0, 2.0-3.9 and ⩾4.0 mg/kg) was NS. Factors associated with significantly higher nonrelapse mortality included higher patient age (⩾50 years), grade IV acute GvHD, no improvement of GvHD and higher dose of thymoglobulin (hazard ratio, 2.55; 95% confidence interval, 1.34-4.85; P=0.004 for 2.0-3.9 mg/kg group and 1.79; 0.91-3.55; P=0.093 for ⩾4.0 mg/kg group). Higher dose of thymoglobulin was associated with a higher incidence of bacterial infections, CMV antigenemia and any additional infection. Taken together, low-dose thymoglobulin at a median total dose of 2.5 mg/kg provides a comparable response rate to standard-dose thymoglobulin reported previously, and <2.0 mg/kg thymoglobulin is recommended in terms of the balance between efficacy and adverse effects.

The upstream sequence segment of the C-terminal cysteine-rich domain is required for microneme trafficking of Plasmodium falciparum erythrocyte binding antigen 175

Erythrocyte invasion is a critical step for survival of Plasmodium parasites, the causative agents of malaria, in their host and recognition of the host cell receptors by Plasmodium erythrocyte-binding-like (EBL) proteins plays an important role. Although EBL subcellular localization was shown to be closely linked to parasite virulence in the rodent model of malaria, the trafficking of EBL to micronemes, the secretory organelle in the invasive parasite is not fully understood. In this study, we assessed the impact of the deletion and amino acid replacement of Plasmodium falciparum EBL (EBA-175) using transgenic P. falciparum lines expressing modified EBA-175. We found that, in addition to a signal peptide and a cysteine rich region (region 6) to the cytoplasmic tail, a previously unrecognized sequence segment in region 5 was required for correct microneme trafficking of EBA-175. Replacement of Arg or Phe residues in this segment altered microneme trafficking, suggesting that the sequence itself contained critical information. Based on these findings, we propose that the sequence segment in region 5 is also required for the recognition of EBA-175 by the trafficking machinery to direct this protein to the microneme. Our results provide key information to clarify an as yet unidentified EBA-175 trafficking mechanism.

A Study of Trap Profiles in Thin Silicon Dioxide Films at Dielectric Breakdown Using Percolation Model

A Monte Carlo simulation of wear-out process in thin silicon dioxide films is performed to investigate the correlation between the electron trap distribution and the dielectric breakdown. Non-uniformity of the trap generation and its dependence on the stress conditions are monitored by the measurements of the charge centroid. In order to include these experimental observations into Degraeve's percolation model [IEDM Tech. Dig., pp.863-866 (1995)], we introduce exponential trap profiles decaying from the Si/SiO2 interface. Our new model successfully reproduces critical threshold voltage shifts from the information about critical charge centroids for various stress conditions. Finally, as a reasonable explanation of the stress dependent breakdown properties, we suggest that the bond strain caused by lattice mismatch at the interface is accelerated by the electric field.

Assessment of skin penetration of third-stage larvae of Strongyloides ratti

Strongyloides stercoralis infection is caused by skin penetration of third-stage larvae (L3s). We studied skin penetration of L3s of Strongyloides ratti using an in vitro assay that has been used previously to study Angiostrongylus cantonensis, an agarose membrane with a temperature gradient, and scanning electron microscopy. Our results revealed that skin penetration of L3s depended on host skin temperature. When the target temperature of the outer liquid was 37°C, more than 80% of L3s penetrated the skin, but penetration was only 60% when the target temperature was 20°C. Thirdstage larvae moved rapidly on the agarose membrane toward optimum temperature area for this parasite, which indicates that L3 has a sensor that is sensitive to temperature changes. Penetration rate for hosts such as cat (36%), dog (32%), and bird (13%) were significantly lower than that for rat (82%). Although we could not establish the reason, L3s seemed to have an ability to differentiate these hosts at the time of penetration. By using scanning electron microscopy, penetration of L3s could be observed within 10 min. We demonstrated thermotaxis of L3 of S. ratti, and this peculiar characteristic seemed to have a close relationship with the process of searching for the host.

A randomized controlled trial of plasma real-time PCR and antigenemia assay for monitoring CMV infection after unrelated BMT

Preemptive therapy is the standard strategy for preventing CMV disease after allogeneic hematopoietic SCT. In this study, unrelated BMT recipients were randomly assigned to a plasma real-time PCR group or an antigenemia group to compare the value of these monitoring tools for CMV reactivation. Ganciclovir (GCV) was started at 5 mg/kg/day when PCR reached 300 copies per ml or when antigenemia reached three positive cells per two slides. A total of 88 patients were randomized into the antigenemia group (n=45) or the PCR group (n=43). A significantly higher number of patients reached the threshold in the antigenemia group than in the PCR group (73.3 vs 44.2%, P=0.0089). However, only three patients (one in the antigenemia group and two in the PCR group) developed early CMV disease. These patients exclusively had colitis and were successfully treated with GCV or foscarnet. The median number of antigenemia-positive cells at the start of GCV was 47 in the PCR group. These findings suggest that antigenemia assay with the current cutoff was too sensitive and led to unnecessary use of GCV. However, the appropriateness of the threshold may be different by the methodology used, and therefore, it is difficult to generalize.

Myeloablative allogeneic hematopoietic stem cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia in adults: significant roles of total body irradiation and chronic graft-versus-host disease

Disease-free survival in Philadelphia chromosome-positive ALL (Ph + ALL) is very poor, and allogeneic hematopoietic stem cell transplantation (allo-HSCT) is currently considered the only procedure with curative potential. To identify factors affecting transplant outcome, we analyzed the data from 197 Ph + ALL patients aged 16 years or older who had undergone allo-HSCT. The 5-year survival rates were 34% for patients in first complete remission (CR), 21% for those in second or subsequent CR, and 9% for those with active disease (P < 0.0001). Multivariate analysis showed four pre-transplant factors as significantly associated with better survival: younger age, CR at the time of transplantation, conditioning with total body irradiation, and HLA-identical sibling donor (P < 0.0001, P < 0.0001, P = 0.0301, P = 0.0412, respectively). Severe acute GVHD increased the risk of treatment-related mortality (TRM) without diminishing the risk of relapse, whereas chronic GVHD reduced the risk of relapse without increasing the risk of TRM. Thus, patients who developed extensive chronic GVHD had better survivals (P = 0.0217), and those who developed grade III-IV acute GVHD had worse survivals (P = 0.0023) than did the others.

Nonmyeloablative stem cell transplantation with fludarabine and cyclophosphamide for patients with hematologic malignancies

We conducted a multi-center phase I/II trial of nonmyeloablative stem cell transplantation for patients with hematologic malignancies. The aim of this trial was to assess the safety and feasibility of this treatment modality for older or younger patients with significant organ dysfunction, who could not be treated with conventional high dose chemoradiotherapy. Twelve patients were treated with a conditioning regimen consisting of fludarabine and cyclophosphamide, followed by peripheral blood stem cell transplantation from human leukocyte antigen (HLA) identical siblings. Nonhematologic toxicities were mild. Median time to absolute neutrophils above 0.5 x 10(9)/l, 1.0 x 10(9)/l and platelets above 50 x 10(9)/l were 8, 10 and 12 days, respectively. Donor dominant hematopoiesis was achieved in all patients, with or without donor leukocyte infusion. The cumulative incidence of acute and chronic graft-versus-host disease (GVHD) was 75 and 56%, respectively. Only one patient experienced early death within 100 days, caused by acute GVHD complicated by fungal infection. All patients except one achieved complete remission. With a median follow-up of 330 days, expected progression-free survival is 75%. Overall survival is 76%. Our study confirms that nonmyeloablative stem cell transplantation with cyclophosphamide and fludarabine conditioning is a safe and promising treatment for elderly patients with hematologic malignancies. A further study in large-scale setting is warranted.

Good prognosis of patients with acute promyelocytic leukemia who achieved second complete remission (CR) with a new retinoid, Am80, after relapse from CR induced by all-trans-retinoic acid

A new synthetic retinoid, Am80, is effective in treating acute promyelocytic leukemia relapsed from all-trans-retinoic acid-induced complete remission (CR). We report here the long-term clinical outcomes of patients who achieved second CR with Am80. Of 24 evaluable patients, 14 achieved a second CR by Am80 therapy. Of those patients, 4 relapsed within 6 months, despite subsequent consolidation chemotherapy. Six patients underwent sibling or unrelated HLA-matched allogeneic bone marrow transplantation (BMT), and 4 are alive without relase for more than 49 months after achieving second CR. Four of 8 patients who did not receive BMT are alive without relapse for more than 49 months. Promyelocytic leukemia-retinoic acid receptor alpha (PML-RAR alpha) fusion transcript was undetectable by reverse transcriptase-polymerase chain reaction in all living patients. Therefore, if patients achieve second CR with Am80 and HLA-matched donors are available, BMT is the treatment of choice. However, it is noteworthy that CR was maintained for more than 49 months in half of the patients who did not receive BMT.

Two cases of chronic graft-versus-host disease with elevated levels of soluble Fas ligand in serum

It has recently been shown that the Fas-Fas ligand (FasL) system may be one of the pathogeneses for acute graft-versus-host disease (GVHD), and it has been reported that serum soluble Fas ligand (sFasL) increases with the presence of acute GVHD. However, there is no report on a correlation between the Fas-FasL system and chronic GVHD. We present two cases of chronic GVHD with elevated levels of serum sFasL. Its level in each case was high at the onset of chronic GVHD, but it decreased with steroid therapy. Liver dysfunction also improved as the level of serum sFasL decreased. It appears in these cases that the Fas-FasL system was related to the pathogenesis of liver damage.

A chronic myelogenous leukemia-like myeloproliferative disorder accompanied by T-cell lymphoblastic lymphoma with chromosome translocation t(8;13)(p11;q12): a Japanese case

A 40-year-old male patient presented with leukocytosis and mild splenomegaly. Bone marrow aspirate showed myeloid hyperplasia and eosinophilia resembling chronic myelogenous leukemia in the chronic phase. Cytogenetic examination of bone marrow cells revealed an unusual karyotype, t(8;13)(p11;q12), in 20/20 metaphases. Not the BCR/ABL, but the ZNF198/FGFR1 chimeric mRNA was detected by reverse transcription-polymerase chain reaction. Since 1992, 12 patients with a similar atypical myeloproliferative disorder with T-cell non-Hodgkin's lymphoma or eosinophilia, associated with a t(8;13) translocation in both bone marrow and lymph node specimens, have been described. The present case is an additional one that should be classified into this new clinicopathologic entity.

A cystatin-related gene, testatin/cresp, shows male-specific expression in germ and somatic cells from the initial stage of murine gonadal sex-differentiation

Sex-differentiation in mammals initiates at mid-gestation when the differentiation of Sertoli cells is triggered by the expression of the testis-determining gene, Sry. However, little is known about the succeeding germ-soma interaction that directs the sex-differentiation of germ cells. We carried out subtraction and differential screening between male and female gonads at 13.5 dpc (days post coitum). A novel cystatin-related gene was identified and named cresp (cystatin-related expressed in Sertoli and spermatogonia), and has recently been reported independently under the name testatin (Töhönen et al., 1998). The presumed amino acid sequence of testatin/cresp showed considerable homology to the cystatin family, but it lacked a few critical amino acid residues for the cysteine-protease inhibitory activity. A 0.7 kb RNA was detected by northern blotting specifically in the fetal and adult testes from 11.5 dpc and expression increased between 11.5 dpc and 12.5 dpc. Using RT-PCR analysis, the testatin/cresp mRNA was first detectable at 9.5 dpc in both male and female embryos but it was maintained only in the male. In females, the expression became weaker at 11.5 dpc and was undetectable after 12.0 dpc. In situ hybridization and immunohistochemical analyses, as well as single cell RT-PCR analysis, showed that the testatin/cresp mRNA was localized specifically in both the (pro)spermatogonia and Sertoli cells in the testis from 12.5 dpc to adult. Thus, expression of the testatin/cresp gene is upregulated in male gonads but downregulated in females immediately after the initiation of sex-differentiation, suggesting roles in the early developmental cascade of testis such as the germ-soma interaction.

Sweet's syndrome followed by retinoic acid syndrome during the treatment of acute promyelocytic leukemia with all-trans retinoic acid

We present here the case of a 49-year-old female with acute promyelocytic leukemia (APL) who, after first developing all-trans retinoic acid (ATRA)-related Sweet's syndrome, was later diagnosed as having retinoic acid (RA) syndrome. Preceding the RA syndrome diagnosis, she developed a fever as well as erythematous nodules on her upper arms. These symptoms were observed on day 18 of treatment with ATRA. Ten days later, she began to develop respiratory distress. There was no indication of infection, and her condition did not improve with empiric therapy. At this time, the diagnosis of RA syndrome was made, resulting in the initiation of steroid pulse therapy, and within 24 hours her elevated fever and respiratory distress improved markedly. In addition, the erythematous nodules gradually began disappearing. A skin biopsy revealed a dense dermal infiltrate consisting of neutrophils.

Three AML patients with existing or pre-existing intracerebral granulocytic sarcomas who were successfully treated with allogeneic bone marrow transplantations

We report three acute myelogenous leukemia (AML) patients who developed intracerebral granulocytic sarcomas (GS) and were successfully treated with allogeneic BMT (allo-BMT). The diagnosis of one patient was AML M2 with myelofibrosis, and the other two patients were AML M4 with eosinophilia (AML M4 Eo), according to the FAB classification. Two patients first experienced a relapse in the brain that resulted in the formation of GS, followed by a relapse in the bone marrow. The remaining patient developed an optic nerve GS after suffering a bone marrow relapse. All three patients received irradiation for the GS and systemic chemotherapy before the allo-BMT. TBI was used for conditioning, and GVHD prophylaxis was with cyclosporine (CsA) and short-term MTX in all three cases. These patients are currently 9 to 37 months post-BMT without relapse. Thus, our experience suggests that allo-BMT is an effective treatment for AML patients with existing or pre-existing intracerebral GS.

New triterpenoid saponins from Maesa japonica

New triterpenoid saponins, maejaposides A, B, C, D, and E, were isolated from the roots of Maesa japonica and were, respectively, defined to be 3-O-[beta-D-xylopyranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->2)-bet a-D-galactopyranosyl-(1-->3)] [beta-D-galactopyranosyl-(1-->2)]beta-D-glucuronopyranosides of 22alpha-[(Z)-2-hexenoyloxy]-13beta,28-oxido-olean++ +-16alpha, 28alpha-diol (1); 22alpha-[2'-methylbutanoyl]-13beta, 28-oxido-olean-16alpha,28alpha-diol (2a) and 22alpha-angeloyloxy-13beta,28-oxido-olean-16a lpha,28alpha-diol (2b); 21beta,22alpha-diangeloyloxy-13beta,28-oxido- olean-16alpha, 28alpha-diol (3); 21beta-angeloyloxy, 22alpha-(2'-methylbutanoyl)-13beta,28-oxido-olean++ +-16alpha, 28alpha-diol (4), and 21beta-angeloyloxy, 22alpha-[(Z)-2'-hexenoyl]-13beta,28-oxido-olean- 16alpha,28alpha-diol (5). Their structures were established on the basis of extensive NMR (DEPT, COSY, HOHAHA, HETCOR, HMBC, and NOESY) and ESIMS/MS studies, along with chemical degradation.

Response-oriented individualized induction therapy with six drugs followed by four courses of intensive consolidation, 1 year maintenance and intensification therapy: the ALL90 study of the Japan Adult Leukemia Study Group

Adult patients with acute lymphoblastic leukemia (ALL) were treated according to the ALL90 study, the second prospective study for ALL of the Japan Adult Leukemia Study Group (JALSG). Its characteristics included response-oriented individualized induction therapy with six drugs (doxorubicin, mitoxantrone, vincristine, prednisolone, [corrected] cyclophosphamide and L-asparaginase), and a prospective comparison between allogeneic bone marrow transplantation (allo-BMT) and chemotherapy alone in patients below 45 years of age. The protocol consisted of one or two courses of induction, four courses of consolidation, and three courses of intensification including 12 month maintenance and six times of central nervous system (CNS) prophylaxis. Of 180 evaluable patients (median age, 43), 125 (69%) achieved complete remission (CR). Predicted overall survival (OAS), event-free survival and disease-free survival (DFS) were 15, 10 and 14%, respectively at the median follow-up period of 62 months. No specific toxicities were observed. Leukocytes < 30,000/microliter, normal karyotype, and blasts < 10% in bone marrow at day 15 of induction therapy were significantly favorable prognostic factors for the achievement of CR, DFS and OAS by univariate analysis. Multivariate analysis showed leukocytes < 30,000/microliter and blasts < 10% on day 15 was a significant factor for the achievement of CR, DFS and OAS. Ph-chromosome was found in 28% (36/130) of patients examined and was one of the worst prognostic factors. All Ph positive patients were predicted to die within 600 days. Allo-BMT was not significantly superior to chemotherapy with respect to DFS (P = 0.226). The overall results were inferior to those of the former ALL87 protocol. As reasons, the older median age of 43 years old (vs. 38 years old) and lower dose intensity, especially of l-asparaginase, etc. were suggested. However, patients with good prognostic factors (leukocyte < 30,000/microliter and age < 30 years old) showed better survival than others (P < 0.0001), and the result was similar to that of older children, the high risk group of childhood ALL, suggesting that ALL could be a disease of single entity, showing higher resistance to chemotherapy as patients become older.

Ultrastructural abnormalities of bone marrow erythroblasts in refractory anemia

Ultrastructural abnormalities of erythroblasts in 30 patients with refractory anemia (RA) according to FAB classification were studied. Nuclear clefts, iron-laden mitochondria, and myelin figures in cytoplasm were most frequently observed. Eleven patients (36.7%) with nuclear clefts of erythroblasts had a higher platelet count and higher incidence of cytogenetic abnormalities linked to poor prognosis than the patients without nuclear clefts. They also had a higher frequency of leukemic transformation and shorter survival than the patients without nuclear clefts. The nuclear clefts of erythroblasts, which are the result of impairment of DNA metabolism or nuclear formation and fusion during mitosis, may be one of the adverse prognostic factors for patients with RA.

Myelodysplastic syndrome with eosinophilia in bone marrow. Gunma Haematology Study Group

Clinical features were investigated in 114 patients with de novo myelodysplastic syndrome (MDS) diagnosed over the past 10 years, and eight cases (7%) were complicated with eosinophilia in the bone marrow. Two patients had refractory anaemia (RA), five had RA with excess of blasts (RAEB), and one had RAEB in transformation. Their bone marrow cells exhibited tri-lineage dysplasia and morphological abnormalities in eosinophils. Cytogenetics revealed major karyotype abnormalities (MAKA) in five patients. Survival durations were significantly shorter than those of other MDS patients. Our study suggests that marrow eosinophilia in MDS is strongly related to the coexistence of MAKA.

Splenic lymphoma with villous lymphocytes with CD5+, CD11c+ B-cell phenotype

A 64-year-old male suffered from splenomegaly without lymphadenopathy. His WBC count on admission was 6.1 x 10(9)/l with 55% abnormal lymphocytes. No monoclonal gammopathy was detected. Abnormal cells shown in films usually had relatively abundant cytoplasm with serrated edges. Under phase-contrast microscopy, the cells displayed short, needle-like processes. The immunophenotype of peripheral blood mononuclear cells were CD19+, CD20+, CD11c+, FMC7+, CD5+, CD10-, CD25- and SIg+. The spleen histology showed a distinctive pattern of white pulp infiltration by abnormal lymphocytes with features of plasma cell differentiation. These findings were compatible with the features of splenic lymphoma with villous lymphocytes.

Ultrastructure of neutrophilic phagosome of autologous platelet in vivo in specific granule deficiency

The ultrastructure of neutrophilic phagosomes containing autologous platelets in vivo from a woman with specific granule deficiency is described. This phagosome formation was observed only when she had developed pneumonia due to Staphylococcus aureus. Therefore, the phenomenon might be induced by severe bacterial infection under an abnormal neutrophilic condition accompanied by specific granule deficiency.

Ultrastructure of plasma cells in a patient with J chain disease

Ultrastructural analysis of plasma cells was performed in a 74-year-old female patient with J chain disease. By electron microscopy, various characteristic findings were observed: lobulated nuclei, multinuclei, single sac loop-like structures, flocculent filament-like substances, nuclear inclusion bodies, cytoplasmic inclusion bodies, and multilamellar bodies. Our prior studies pointed out a poor prognosis in myeloma patients with these findings.

Agranulocytosis during treatment with fluconazole

Fluconazole, a new effective triazole antifungal agent, has been reported to cause fewer adverse reactions than amphotericin B. A patient who was diagnosed as having agranulocytosis and thrombocytopenia after treatment with fluconazole was investigated and recovered after withdrawal of the antifungal therapy. This case suggests the need for careful haematological observation during the treatment with fluconazole.