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Infectious diseases caused by antibiotic-resistant bacteria lead to a considerable increase in human morbidity and mortality globally. This requires to search potential actinomycete isolates from undiscovered habitats as a source of effective bioactive metabolites and to synthesis metabolite-mediated antibacterial silver nanoparticles (AgNPs). The main purpose of the present study was to identify actinomycetes isolated from Thika waste dump soils that produce bioactive metabolites to synthesize antibacterial AgNPs. The synthesis of metabolite-mediated AgNP was confirmed with visual detection and a UV-vis spectrophotometer, whereas the functional groups involved in AgNP synthesis were identified using a FTIR spectrophotometer. The antibacterial activity of the metabolite-mediated AgNPs was tested by a well diffusion assay. Identification of actinomycete isolates involved in the synthesis of antibacterial AgNPs was done based on 16S rRNA gene sequence analysis. The visual detection showed that dark salmon and pale golden color change was observed due to the formation of AgNPs by KDT32 and KGT32 metabolites, respectively. The synthesis was confirmed by a characteristic UV spectra peak at 415.5 nm for KDT32-AgNP and 416 nm for KGT32-AgNP. The FTIR spectra revealed that OH, C=C, and S-S functional groups were involved in the synthesis of KDT32-AgNP, whereas OH, C=C, and C-H were involved in the formation of KGT32-AgNP. The inhibition zone results revealed that KDT32-AgNP showed 22.0 ± 1.4 mm and 19.0 ± 1.4 mm against Escherichia coli and Salmonella typhi, whereas KGT32-AgNP showed 21.5 ± 0.7 mm and 17.0 ± 0.0 mm, respectively. KDT32 and KGT32 isolates were identified as genus Streptomyces and their 16S rRNA gene sequences were deposited in the GenBank database with MH301089 and MH301090 accession numbers, respectively. Due to the bactericidal activity of synthesized AgNPs, KDT32 and KGT32 isolates can be used in biomedical applications.

13 p.-8 fig.-3 tab., Toxicity and poor adherence to treatment that favors the generation of resistance in the Leishmania parasites highlight the need to develop better alternatives. Here, we evaluated the in vitro effectiveness of hydrazone derived from chromanes 2-(2,3-dihydro-4H-1-benzothiopyran-4-ylidene) hydrazide (TC1) and 2-(2,3-dihydro- 4H-1-benzopyran-4-ylidene) hydrazide (TC2) and the mixture of triterpene saponin hederagenin-3-O-(3,4-Odiacetyl-ß-D-xylopyranosyl-(1à3)-a-L- rhamnopyranosyl-(1à2)-a-L-arabinofuranoside, hederagenin-3-O-(3,4-Odiacetyl-a-L- arabinopyranosyl-(1à3)-a-L-rhamnopyranosyl-(1à2)-a-L-arabinofuranoside and, hederagenin-3-O-(4-O-acetyl-ß-D-xylopyranosyl-(1à3)-a-L-rhamnopyranosyl-(1à2)-a-L-arabinofuranoside from Sapindus saponaria(SS) on L. braziliensis and L. pifanoi. Mixtures of TC1 or TC2 with saponin were formulated for topical application and the therapeutic effectiveness was evaluated in the model for cutaneous leishmaniasis (CL) in golden hamster.The mode of action of these compounds was tested on various parasite processes and ultrastructural parasite modifications. TC1, TC2 and SS showed moderate cytotoxicity when tested independently but toxicity was improved when tested in combination. The compounds were more active against intracellular Leishmania amastigotes. In vivo studies showed that combinations of TC1 or TC2 with SS in 1:1 ratio (w/w) cured 100% of hamsters with no signs associated with toxicity. The compounds did cause changes in the mitochondrial activity of the parasite with a decrease in ATP levels and depolarization of membrane potential and overproduction of reactive oxygen species; nevertheless, these effects were not related to alterations in membrane permeability.The phagolysosome ultrastructure was also affected impacting the survival of Leishmania but the function of the lysosome nor the pH inside the phagolysosome did not change.Lastly, there was a protease inhibition which was directly related to the decrease in the ability of Leishmania to infect and multiply inside the macrophage. The results suggest that the combination of TC1 and TC2 with SS in a 1:1 ratio is capable of curing CL in hamsters.This effect may be due to the ability of these compounds to affect parasite survival and the ability to infect new cells., The work with Sapindus saponaria had “Permission of Access to Genetic Resources and its Derived Products” issued by ANLA-Colombia (Framework Contract No.154RGE0237).

The intracellular protozoan parasites of the genus Leishmania are the causative agents of leishmaniasis, a vector-borne disease of major public health concern, estimated to affect 12 million people worldwide. The clinical manifestations of leishmaniasis are highly variable and can range from self-healing localized cutaneous lesions to life-threatening disseminated visceral disease. Once introduced into the skin by infected sandflies, Leishmania parasites interact with a variety of immune cells, such as neutrophils, monocytes, dendritic cells (DCs), and macrophages. The resolution of infection requires a finely tuned interplay between innate and adaptive immune cells, culminating with the activation of microbicidal functions and parasite clearance within host cells. However, several factors derived from the host, insect vector, and Leishmania spp., including the presence of a double-stranded RNA virus (LRV), can modulate the host immunity and influence the disease outcome. In this review, we discuss the immune mechanisms underlying the main forms of leishmaniasis, some of the factors involved with the establishment of infection and disease severity, and potential approaches for vaccine and drug development focused on host immunity.

Growing evidence shows that antioxidant proteins ofLeishmaniacould be used as vaccine candidates. In this study, we report the efficacy ofLeishmania donovaniiron superoxide dismutase B1 (LdFeSODB1) as a vaccine antigen in BALB/c mice in a DNA-protein prime-boost immunization regimen in the presence or absence of murine granulocyte macrophage colony stimulating factor (mGMCSF) DNA adjuvant. The expression study confirmed that LdFeSODB1 is expressed in mammalian cells and mGMCSF fusion mediates the secretion of the recombinant protein. Heterologous immunization with LdFeSODB1 induced a strong antibody- and cell-mediated immune response in mice. Immunization triggered a mixed Th1/Th2 response as evidenced by the ratio of IgG2a to IgG1. Antigen-stimulated spleen cells from the immunized mice produced high level IFN-γ. Multiparametric flow cytometry data showed that immunization with LdFeSODB1 induced significantly higher expression of TNF-αor IL-2 by antigen-stimulated T cells. Eight weeks afterL. majorinfection, immunization with the antigen shifted the immune response to a more Th1 type than the controls as demonstrated by IgG2a/IgG1 ratio. Moreover, IFN-γproduction by antigen-stimulated spleen cells from immunized mice remained high. The footpad swelling experiment showed that immunization with LdFeSODB1 resulted in partial protection of mice from a high doseL. majorinfection.

A simple technique to enhance the humoral immune response to intracellular protein antigens in genetic immunizations is demonstrated in mice. In this approach, the intracellular protein is intentionally secreted from expressing cells as a chimeric protein, comprising an N-terminal secreted protein fused to the intracellular protein antigen. Using the Leishmania chagasi Ldccys1 cysteine protease (411CP) as an example of an intracellular protein antigen and both human and murine granulocyte colony stimulating factor (GMCSF) as examples of N-terminal secretion competent fusion partners in chimeric proteins, a humoral response in plasmid DNA immunized mice could only be detected by Western blotting when the expressed 411CP was secreted.

Cutaneous leishmaniasis in Ethiopia is caused mainly by Leishmania aethiopica. In this study, the response of L. aethiopica to sodium stibogluconate (SSG) and liquid nitrogen in Silti has been investigated. Patients were divided into two groups by the treating physician and were treated with either liquid nitrogen or SSG. Punch biopsy samples were collected from 54 patients with mean age of 20.61 (± 9.87 SD) years for histological characterization. The histological spectrum found to be type-1, type-2, type-3 and type-4 were 37.0%, 3.7%, 37.0% and 22.2% respectively. One hundred and three patients with a mean age of 18.4 (± 11.7 SD) years were treated with liquid nitrogen. The mean duration of the lesions before the onset of treatment was 8.5 months (± 6.7 SD). Of the 103 patients 80.6% (83/103) were cured, 13.6% (14/103) were dropouts and 5.8% (6/103) did not respond. Twenty patients with a mean age of 19.55 (+1.64 SD) years were treated with Pentostam on conventional dose. Of the 20 patients 85.0% (17/20) were cured, 10.0% (2/20) were unresponsive and 5.0% (1/20) were dropouts. The per protocol cure rate for cryotherapy and Pentostam was 93.3% and 89.5% respectively. Hence, liquid nitrogen can be used as one of the treatment options especially in resource poor settings.

In this study, we tested the protective efficacy of recombinant Leishmania donovani iron superoxide dismutase B1 (SODB1) against Leishmania major infection in BALB/c mice. Mice were challenged with L. major 3 weeks after the second boost immunization with rSODB1 alone or in the presence of adjuvants. Injection of BALB/c mice with rSODB1 alone elicited both humoral and cellular immune responses. Administration of rSODB1 with CpG ODN or GLA-SE (a synthetic toll-like receptor 4 agonist) adjuvant resulted in the induction of anti-SODB1 IgG1, and more importantly of significantly high levels of IgG2a isotype. Immunization of mice with rSODB1 alone or with adjuvant induced the production of IFN-γ by splenocytes in response to stimulation with L. major soluble leishmanial antigens (SLA). Moreover, immunization protocols involving rSODB1 resulted in a significant decrease in IL-10 as compared to controls. The presence of CpG ODN or GLA-SE adjuvant in the immunization protocols resulted in a relative increase in IFN-γ in response to stimulation with rSODB1 in comparison to immunization with rSODB1 alone. Mice immunized with rSODB1 plus CpG ODN or GLA-SE, were able to partially control their Leishmania infections, as indicated by the reduction in footpad swelling and parasite numbers, compared to controls. These results suggest that immunization with recombinant SODB1 protein together with CpG ODN or GLA-SE can be potential vaccine candidate against leishmaniasis.

Cysteine proteases are crucial for general lysosomal function and for the pathogenic mechanisms of many protistan parasites. Cathepsin B cysteine proteases are currently defined by the presence of the "occluding loop" motif and have been best characterized from humans and their parasites. Though related to a variety of pathogenic excavate flagellates, oxymonads are themselves commensals. While studying this cell biologically aberrant protist lineage, we identified 11 different cathepsin B homologues. These were found to be expressed, at comparable levels to common house-keeping genes, such as elongation factor 1-alpha, alpha-tubulin, beta-tubulin, and glyceraldehyde phosphate dehydrogenase. Primary structure examination of the cathepsin B homologues identified putative signal peptide sequences, and the pre-, pro-, and mature domains of the protein. However, the occluding loop motif was either partially or entirely absent. Comparative genomics, sequence alignment, and phylogenetics of cathepsin sequences from across the diversity of eukaryotes demonstrated that absence of the occluding loop is not a feature exclusive to oxymonads, but is relatively common, suggesting that the "occluding loop" should no longer be used as the defining feature of the cathepsin B subfamily. Overall, this report identifies an abundant protein family in oxymonads, and provides insight both into the evolution and classification of cathepsin B cysteine proteases.

Cutaneous leishmaniasis (CL) is an increasing public health problem in Ethiopia. There is a concern that it is spreading with increased incidence. In this study, we used isoenzyme electrophoresis and internal transcribed spacer one (ITS1) PCR-RFLP techniques to identify Leishmania species from CL patients in Ethiopia. We obtained isolates from 55 localized cutaneous leishmaniasis (LCL), 3 diffused cutaneous leishmaniasis (DCL) and 36 biopsy samples from 34 LCL and 2 DCL cases from All Africa Leprosy and Tuberculosis Rehabilitation and Training Center (ALERT) and clinically diagnosed CL cases from Ochollo village. Both isoenzyme and ITS1 PCR-RFLP techniques showed that Leishmania aethiopica (L. aethiopica) was the aetiologic agent in all cases. Our study also showed that ITS1 PCR-RFLP could identify Leishmania species from biopsy samples and suggests the method could be used for epidemiological surveillance of leishmaniasis in Ethiopia and for species-specific diagnosis.

There is limited information on the biology and pathogenesis of Leishmania aethiopica, causative agent of cutaneous leishmaniasis (CL) in Ethiopia. In this study we have identified and characterized two cathepsin L-like cysteine protease genes, Laecpa and Laecpb, from L. aethiopica. The predicted amino acid sequence of Laecpa and Laecpb is more than 75% identical with homologous cathepsin L-like cysteine protease genes of other Leishmania species and less than 50% identical with human cathepsin L. Laecpa is expressed predominantly in the stationary, and to a lower level, during the amastigote stage while Laecpb is specifically expressed in the stationary stage of L. aethiopica development. Phylogenetic analysis showed that the two genes are grouped into separate clades which are the result of gene duplication. The isolation of these genes will be useful in developing Leishmania species specific diagnostics for molecular epidemiological studies and serves as a first step to study the role of cysteine proteases in L. aethiopica pathogenesis.

Tuberculosis remains one of the major causes of global public health problems. There is no effective vaccine for the disease until now. Many reports show that DNA vaccines are promising to induce protection against Mycobacterium tuberculosis (M. tb); however, the efficiency of DNA vaccine is limited due to inadequate delivery systems. Among others, live attenuated bacterial vectors such as Salmonella enterica typhimurium ( S. typhimurium ) have significant promise as efficient mucosal delivery vehicles for DNA vaccines. In this study, we constructed recombinant attenuated S. typhimurium DNA vaccines carrying genes encoding resuscitation promoting factor (Rpf)-like proteins of M. tb on eukaryotic expression plasmid agianst latent tuberculosis and evaluated the plasmid stability and growth curve assays of the recombinant Salmonella vaccine constructs in vitro. Four Rpf gene fragments (RpfB, RpfC, RpfD, RpfE) associated with latency were amplified from genomic DNA of the H37Rv strain of M. tb, cloned into eukaryotic expression plasmid (pVR1020) and verified by sequencing. In later studies, we will demonstrate the potential use of the Salmonella -mediated DNA constructs as candidate post-exposure vaccines against tuberculosis through testing their immunogenicity and effectiveness for oral delivery in eukaryotic systems. Key words : Latent tuberculosis, resuscitation promoting factor (Rpf), DNA vaccine, recombinant Salmonella typhimurium.

We assessed the immune response against recombinant proteins of two related, albeit functionally different, peroxidoxins fromLeishmania donovani: peroxidoxin 1 (LdPxn1) and peroxidoxin 2 (LdPxn2) in BALB/c mice. We also evaluated the effect of coadministration of TLR agonists (CpG ODN and GLA-SE) on the antigen-specific immune response. Immunization with recombinant LdPxn1 alone induced a predominantly Th2 type immune response that is associated with the production of high level of IgG1 and no IgG2a isotype while rLdPxn2 resulted in a mixed Th1/Th2 response characterized by the production of antigen-specific IgG2a in addition to IgG1 isotype. Antigen-stimulated spleen cells from mice that were immunized with rLdPxn1 produced low level of IL-10 and IL-4 and no IFN-γ, whereas cells from mice immunized with rLdPxn2 secreted high level of IFN-γ, low IL-4, and no IL-10. Coadministration of CpG ODN or GLA-SE with rLdPxn1 skewed the immune response towards a Th 1 type as indicated by robust production of IgG2a isotype. Furthermore, the presence of TLR agonists together with rLdPxn1 antigen enhanced the production of IFN-γand to a lesser extent of IL-10. TLR agonists also enhanced a more polarized Th 1 type immune response against rLdPxn2.

Giardia duodenalis infections are among the most common causes of waterborne diarrhoeal disease worldwide. At the height of infection, G. duodenalis trophozoites induce multiple pathophysiological processes within intestinal epithelial cells that contribute to the development of diarrhoeal disease. To date, our understanding of pathophysiological processes in giardiasis remains incompletely understood. The present study reveals a previously unappreciated role for G. duodenalis cathepsin cysteine proteases in intestinal epithelial pathophysiological processes that occur during giardiasis. Experiments first established that Giardia trophozoites indeed produce cathepsin B and L in strain-dependent fashion. Co-incubation of G. duodenalis with human enterocytes enhanced cathepsin production by Assemblage A (NF and S2 isolates) trophozoites, but not when epithelial cells were exposed to Assemblage B (GSM isolate) trophozoites. Direct contact between G. duodenalis parasites and human intestinal epithelial monolayers resulted in the degradation and redistribution of the intestinal epithelial cytoskeletal protein villin; these effects were abolished when parasite cathepsin cysteine proteases were inhibited. Interestingly, inhibition of parasite proteases did not prevent degradation of the intestinal tight junction-associated protein zonula occludens 1 (ZO-1), suggesting that G. duodenalis induces multiple pathophysiological processes within intestinal epithelial cells. Finally, this study demonstrates that G. duodenalis-mediated disruption of villin is, at least, in part dependent on activation of myosin light chain kinase (MLCK). Taken together, this study indicates a novel role for parasite cathepsin cysteine proteases in the pathophysiology of G. duodenalis infections.

All eukaryotes carry out glycolysis, interestingly, not all using the same enzymes. Anaerobic eukaryotes face the challenge of fewer molecules of ATP extracted per molecule of glucose due to their lack of a complete tricarboxylic acid cycle. This may have pressured anaerobic eukaryotes to acquire the more ATP-efficient alternative glycolytic enzymes, such as pyrophosphate-fructose 6-phosphate phosphotransferase and pyruvate orthophosphate dikinase, through lateral gene transfers from bacteria and other eukaryotes. Most studies of these enzymes in eukaryotes involve pathogenic anaerobes; Monocercomonoides , an oxymonad belonging to the eukaryotic supergroup Excavata, is a nonpathogenic anaerobe representing an evolutionarily and ecologically distinct sampling of an anaerobic glycolytic pathway. We sequenced cDNA encoding glycolytic enzymes from a previously established cDNA library of Monocercomonoides and analyzed the relationships of these enzymes to those from other organisms spanning the major groups of Eukaryota , Bacteria , and Archaea . We established that, firstly, Monocercomonoides possesses alternative versions of glycolytic enzymes: fructose-6-phosphate phosphotransferase, both pyruvate kinase and pyruvate orthophosphate dikinase, cofactor-independent phosphoglycerate mutase, and fructose-bisphosphate aldolase (class II, type B). Secondly, we found evidence for the monophyly of oxymonads, kinetoplastids, diplomonads, and parabasalids, the major representatives of the Excavata. We also found several prokaryote-to-eukaryote as well as eukaryote-to-eukaryote lateral gene transfers involving glycolytic enzymes from anaerobic eukaryotes, further suggesting that lateral gene transfer was an important factor in the evolution of this pathway for denizens of this environment.

Cutaneous leishmaniasis (CL) is a painful, disfiguring and debilitating disease prevalent in Ethiopia and other countries around the world. In Ethiopia, CL is primarily caused by Leishmania aethiopica and less often by L. tropica and L. major. The intracellular survival mechanisms of Leishmania parasites are still not well understood. Recently a new family of antioxidant enzymes called peroxidoxins have been identified that play an important role in parasite survival. In this study, we have identified two distinct peroxidoxin genes (Pxn1 and Pxn2) that are part of a multi-gene family in L. aethiopica. Protein sequence analysis showed that Pxn1 and Pxn2 are highly homologous to peroxidoxins from other Leishmania species. We have found that L. aethiopica Pxn1 is predominantly expressed in amastigotes and stationary phase promastigotes, whereas Pxn2 is constitutively expressed in the different stages of the parasite. This pattern of RNA expression is consistent with patterns seen in some Leishmania species, but not all. Data from this study will be helpful in enhancing vaccine strategies and drug studies targeted towards peroxidoxins.

This study was performed to characterize the genes that code for superoxide dismutase (SOD) in Leishmania aethiopica. It involved three main steps: specimen collection and parasite isolation, species identification, and molecular characterization of the SOD genes. Out of 20 skin slit specimens cultured and processed from suspected cutaneous leishmaniasis patients enrolled in the study, five (25%) were found to be positive for motile promastigotes. Isoenzyme electrophoresis and PCR-RFLP results confirmed that the isolates were L. aethiopica. Superoxide dismutase-B (SODB) genes were identified from L. aethiopica for the first time. Iron superoxide dismutase-B genes amplified from promastigotes of L. aethiopica (LaeFeSODB) were similar in size to the SODB genes of other Leishmania species. Nucleotide sequences of LaeFeSODB1 showed 95.4, 93.5, and 97.3% identity with L. donovani SODB1 (LdFeSODB1) L. major SODB1 (LmFeSODB1) and L. tropica SODB1 (LtrFeSODB1), respectively. Similarly, LaeFeSODB2 showed 95.9 and 94.1 and 97.6% identity with LdFeSODB2 and LmFeSODB2 and LtrFeSODB2, respectively. On the other hand, predicted amino acid sequence comparison indicated that LaeFeSODB1 had 91.3, 89.8, and 93.9% identity with LdFeSODB1, LmFeSODB1, and LtrFeSODB1, respectively. The difference in nucleic acid sequence of LaeFeSODB from that of LmFeSODB and LtrFeSODB can be utilized to develop specific molecular methods that help differentiate these species in places where there is an overlap in the distribution of these species. In addition, the data provide information about the situation of L. aethiopica with respect to SODB genes.

The mechanisms by which Leishmaniaparasites survive exposure to highly reactive oxygen (ROS) and nitrogen (RNS) species within phagosomes of macrophages are not well known. Recently it has been shown that RNS alone is sufficient and necessary to control Leishmania donovani infection in mice (Murray, H. W., and Nathan, C. F. (1999) J. Exp. Med. 189, 741–746). No enzymatic defense against RNS has been discovered inLeishmania to date. We have previously isolated two peroxidoxins (LcPxn1 and LcPxn2) from Leishmania chagasiand showed that recombinant LcPxn1 protein was capable of detoxifying hydrogen peroxide, hydroperoxide, and hydroxyl radicals (Barr, S. D., and Gedamu, L. (2001) J. Biol. Chem. 276, 34279–34287). In further characterizing the physiological role of peroxidoxins in Leishmania survival, we show here that recombinant LcPxn1 protein can detoxify RNS in addition to ROS, whereas recombinant LcPxn2 protein can only detoxify hydrogen peroxide. LcPxn1 and LcPxn2 are localized to the cytoplasm, and overexpression of LcPxn1 in L. chagasi parasites enhanced survival when exposed to exogenous ROS and RNS and enhanced survival within U937 macrophage cells. Site-directed mutagenesis studies revealed that the conserved Cys-52 residue is essential for detoxifying hydrogen peroxide, t-butyl hydroperoxide, and hydroxyl radicals, whereas the conserved Cys-173 residue is essential for detoxifying t-butyl hydroperoxide and peroxynitrite. This is the first report of an enzymatic defense against RNS in Leishmania.

For the first time, we have reported the establishment and serial propagation of an axenic culture of Leishmania chagasi amastigote-like forms. Parasites were characterized by microscopic evaluation and by the expression of two stage-specific genes, A2 and Ldccys2 amastigote-specific cysteine protease. The differentiated amastigote-like forms were maintained by serial cultivation.

Cathepsin B-like genes from Leishmania donovani and Leishmania chagasi have been isolated and characterized. It is a single gene, which is constitutively expressed in all the life cycle stages of the parasite. Studies using cathepsin B-specific inhibitor treatment suggested that cathepsin B does not seem to play a role in the promastigote stages of the parasite, however it aids in the parasite survival within the host macrophages. Antisense mRNA inhibition of cathepsin B gene also revealed that it plays an important role in the parasite survival within the host macrophages. Furthermore, for the first time, we have shown that Leishmania whole cell lysates as well as the recombinant cathepsin B protein cleaved human recombinant latent transforming growth factor (TGF)-β1 into a mature peptide releasing the latency associated protein, in a cell-free incubation system. Mink lung epithelial cell growth inhibition assay revealed that the cleaved TGF-β1 was biologically active, suggesting thatLeishmania cathepsin B can cleave latent TGF-β1 into mature and active form. These results suggest that cathepsin B plays an important role in Leishmania survival within the host macrophages by activating latent TGF-β1.

Background To date, no universally effective and safe vaccine has been developed for general human use. Leishmania donovani Peroxidoxin-1 (LdPxn-1) is a member of the antioxidant family of proteins and is predominantly expressed in the amastigote stage of the parasite. The aim of this study was to evaluate the immunogenicity and protective efficacy of LdPxn-1 in BALB/c mice in heterologous DNA-Protein immunization regimen in the presence of fusion murine granulocyte-macrophage colony-stimulating factor (mGMCSF) DNA adjuvant. Methodology and Principal Findings A fusion DNA of LdPxn1 and mGMCSF was cloned into a modified pcDNA vector. To confirm the expression in mammalian system, Chinese hamster ovary cells were transfected with the plasmid vector containing LdPxn1 gene. BALB/c mice were immunized twice with pcDNA-mGMCSF-LdPxn-1 or pcDNA-LdPxn1 DNA and boosted once with recombinant LdPxn-1 protein. Three weeks after the last immunization, mice were infected with Leishmania major promastigotes. The result showed that immunization with pcDNA-mGMCSF-LdPxn1 elicited a mixed Th-1/Th-2 immune response with significantly higher production of IFN-γ than controls. Intracellular cytokine staining of antigen-stimulated spleen cells showed that immunization with this antigen elicited significantly higher proportion of CD4+ T cells that express IFN-γ, TNF-α, or IL-2. The antigen also induced significantly higher proportion of multipotent CD4+ cells that simultaneously express the three Th-1 cytokines. Moreover, a significant reduction in the footpad swelling was seen in mice immunized with pcDNA-mGMCSF-LdPxn1 antigen. Expression study in CHO cells demonstrated that pcDNA-mGMCSF-LdPxn-1 was expressed in mammalian system. Conclusion The result demonstrates that immunization of BALB/c mice with a plasmid expressing LdPxn1 in the presence of mGMCSF adjuvant elicits a strong specific immune response with high level induction of multipotent CD4+ cells that mediate protection of the mice from Leishmania major infection. To our knowledge, this is the first study showing the vaccine potential of Leishmania peroxidoxin -1., Author Summary Leishmaniasis, a disease caused by protozoan parasites under the genus Leishmania, claims the lives of thousands of people annually. It mainly affects people in poor communities in Africa, Asia and South America. Although several drugs are available for the treatment of leishmaniasis, their efficacy is limited by the emergence of drug resistant parasite strains and by the inherent side-effects of some drugs. In light of these challenges, developing effective vaccine is considered as a crucial step in the control and ultimate elimination of the disease. In this study, we have evaluated the potential of the antioxidant Leishmania Peroxidoxin-1 as a candidate vaccine for leishmaniasis. The efficacy of the candidate vaccine was assessed in DNA-Protein immunization strategy in mice. We also investigated the adjuvant role of GMCSF DNA fused with the vaccine antigen in a pcDNA plasmid vector. The result showed that Leishmania Peroxidoxin-1 together with fusion GMCSF adjuvant in a pcDNA plasmid induces a partially protective immune response in mice. Further analysis of the immune response demonstrated that the antigen-adjuvant combination elicits CD4+ T cells that express IFN-γ, TNF-α, or IL-2. The antigen also induced a high frequency of CD4+ T cells that simultaneously express all the three cytokines. The study on samples taken from leishmaniasis patients showed that the recombinant Leishmania Peroxidoxin-1 protein is recognized by and elicit immune response in humans, a crucial requirement in the development of a vaccine.

Antioxidants have been implicated in protecting cells from oxygen radicals produced as a result of aerobic metabolism and in response to foreign pathogens by phagocytic cells. The mechanisms allowing pathogens to withstand the toxic prooxidant environment within the phagolysosome are poorly understood. We have cloned and characterized three antioxidant genes belonging to the 2-Cys family of peroxidoxins from Leishmania chagasi that may prove to provide these parasites with an enhanced defense mechanism against toxic oxidants. The 5′-untranslated regions and coding regions of each gene are highly conserved, whereas the 3′-untranslated regions have diverged significantly. L. chagasi peroxidoxin 1 (LcPxn1) is predominantly expressed in the amastigote stage, whereas LcPxn2 and LcPxn3 are expressed mainly in the promastigote stage, with LcPxn3 being far less abundant than LcPxn2. LcPxn2 and LcPxn3 possess a nine-amino acid extension at the carboxyl terminus, which LcPxn1 lacks. LcPxn1 appears to exist as high molecular weight multimers in vivo, and recombinant LcPxn1 was shown to detoxify hydrogen peroxide and alkyl hydroperoxides. We also present strong evidence that recombinant LcPxn1 can enzymatically detoxify hydroxyl radicals, an activity never before clearly demonstrated for a protein.

2,b Significant levels of IgG3 and IgG4 and high levels of IgG1 leishmania-specific antibody differentiated the immune states in 10 patients with visceral leishmaniasis from those of vir- tually all 20 drug-cured and 18 subclinically infected subjects, whereas the level of IgG2 antibody was nondiscriminating. The most extreme "subclinically infected" outlier subse- quently developed disease. Overall, the immune states in subclinically infected and drug-cured persons were mutually indistinguishable but were readily distinguished from those of patients. These findings may have implications for the immunologic mechanism underlying drug cure in visceral leishmaniasis.

We have isolated and characterized two superoxide dismutase (SOD) cDNAs from a Leishmania chagasi promastigote cDNA library using degenerate primers derived from conserved amino acid residues of previously isolated manganese and iron SODs. Comparison of these two L. chagasi SOD deduced amino acid sequences with previously isolated MnSOD and FeSOD amino acid sequences revealed that they have higher homology to, and complete conservation of, invariant residues found in iron-containing SODs. Southern blot analysis showed that one gene, L.c.FeSODA, is a single copy gene, whereas the other gene, L.c.FeSODB, belongs to a multi-gene family. Transcript levels and enzyme activities of L.c.FeSODA and L.c.FeSODB show differential stage expression, with higher levels present in the amastigote stage of the parasite compared to the promastigote stage. Expression of the L.c.FeSODs in an E. coli SOD null strain protected the bacteria against free radical generating agents. Overexpression of these FeSODs in L. chagasi parasites also showed enhanced protection against the free radical generating agents, paraquat and nitroprusside. The cloning, characterization and overexpression of the L.c.FeSODA and L.c.FeSODB genes and proteins demonstrates the possible role of SODs in Leishmania pathogenesis.

We have cloned and characterized two distinct cysteine protease cDNAs from Leishmania donovani chagasi. One of the cDNAs, Ldccy2, was isolated from a cDNA library prepared from total promastigote RNA while the other cDNA, Ldccys1, was isolated from a cDNA library prepared from total amastigote RNA. Ldccys2 has an open reading frame of 471 amino acids and Ldccys1 has an open reading frame of 447 amino acids. Comparison of the predicted protein sequences of the two distinct cysteine proteases with those of cysteine proteases from Leishmania pifanoi, a member of the L. mexicana complex, showed that the cysteine proteases from the two species of Leishmania are similar in their protein sequences. Each of the two cDNAs is distinct in genomic arrangement and chromosome location. Ldccys1 belongs to a family of cysteine proteases encoded by tandemly organized genes located on chromosome 7 while Ldccys2 appears to be a single cysteine protease gene located on chromosome 10. The organization of the two families of cysteine protease genes in L. donovani donovani was also found to be similar. In this species, the Lddcys1 genes are located on chromosome 5 while the Lddcys2 gene is located on chromosome 8. The Ldccys1 genes are expressed abundantly in the amastigotes recovered from infected hamsters, but at a very low level in the promastigote stage of development. On the other hand, the Ldccys2 gene is expressed both in the promastigote and amastigote stages. We have overexpressed the two cDNAs of cysteine proteases in Leishmania cells and the over-produced cysteine proteases are biologically active and are inhibited by cysteine protease inhibitors. Furthermore, the over-produced and indigenous amastigote specific cysteine protease, Ldccys1, reacted with polyclonal antibodies raised against this protein.

Transgenic tobacco plants and calli bearing the bacterialuid A gene under the transcriptional control ofrbcS, mas and CaMV35S promoter(s) were exposed to different concentrations of cadmium. The transcriptional activity of the promoters was monitored using p-nitrophenyl β-D-g1ucuronide as a substrate for the β-glucuronidase (uidA) reporter enzyme. Therbc S promoter was repressed by high concentrations of cadmium. An induction of themas promoter was seen after cadmium treatment of seedlings but not calli. The activity of the CaMV35S promoter was unaffected by cadmium in both seedlings and calli.

Recently we have demonstrated that the human hepatocellular carcinoma-derived cell lines, HepG2 and HuH7, contain gonadotropin-releasing hormone (gonadoliberin) receptors and respond to various molecular forms of gonadoliberin in terms of suppressed proliferation in vitro. This study provides the first demonstration that gonadoliberin inhibits the zinc-induced production of metallothionein mRNA in HepG2 and HuH7 cells. Administration of gonadoliberin agonist (gonadoliberin-A) inhibited the Zn-induced metallothionein mRNA level in a time-related and dose-related manner. The effect of gonadoliberin-A was found to be specific, because concomitant treatment with a gonadoliberin antagonist (gonadoliberin-ANT) blocked gonadoliberin-A inhibition of metallothionein mRNA accumulation. Furthermore, the gonadoliberin-A-induced inhibition of Zn-mediated metallothionein accumulation was found to correlate closely with suppresion of cell proliferation and [3H] thymidine uptake in these cells. It is known that the metal-binding protein metallothionein plays an important role in tumor cell pathobiology and resistance to chemotherapeutic drugs. The present findings may have important implications in the development of an effective chemotherapy for treatment of human liver cancer, in part, by improving the sensitivity of tumor cells through suppression of metallothionein production by gonadoliberin peptides.

To identify suitable promoters for expressing exogenous genes in arthritic joints, the constitutive, simian virus 40 (SV 40) and IL-1 or metal inducible, human stromelysin and metallothionein (MT) gene promoters were tested for their activity in chondrocytes and synovial fibroblasts. Transient transfection with plasmids containing the reporter chloramphenicol acetyltransferase (CAT) gene attached to these promoters showed that SV40, stromelysin and MT promoters drove CAT expression with different strengths in primary bovine chondrocytes. The MTI-F and MT-IG gene promoters were also functional in human chondrocytes. The SV40, IL-1 inducible stromelysin-1 and MT-IG driven CAT activity was also detectable in human synoviocytes. Therefore, chondrocytes and synoviocytes have the trans-acting factors necessary for transcription from the respective promoters which may be conserved in bovine and human cells. These promoters could be useful for expressing potentially therapeutic anti-inflammatory and anti-erosive genes in arthritic joints.

We have analyzed the human (h) metallothionein (MT)-IG proximal promoter region (−174 to +5) using a TATA box mutation (TATCA) and four trinucleotide mutants of the proximal MREa. Transient transfection of HepG2 cells was complemented by in vitro transcription with rat liver nuclear extracts. In both systems, mutations of the TATA box and conserved core of metal responsive element (MRE)a were detrimental to hMT-IG promoter activity suggesting that both elements make significant contributions to hMT-IG transcription. Although MRE binding factors were active in vitro, further metal activation of MT promoter activity was accomplished only by in vivo metal treatment rather than addition of zinc in vitro. Southwestern blotting identified nuclear proteins in rat liver and HepG2 cells which physically interact with MREa in a zinc-dependent manner and could be responsible for MREa function in each system. In addition, the functional effects of the TATCA mutation correlate with altered physical interaction with TATA box-binding protein as observed using DNase I protection.

In this study, the contributions of the two metal-responsive elements (MREs) of the rainbow trout (Salmo gairdnerii) metallothionein (tMT)-B gene promoter (-137 to +5) were analyzed. The effect of MRE mutations on the basal and zinc-induced activities of tMT-B promoter-reporter gene fusions were determined by transfection of a rainbow trout hepatoma (RTH-149) cell line. Together, MREa and MREb cooperate to elicit a significant response to zinc but exhibit differential basal and metal-induced activity. The MREa sequence (-62 to -51) is important for basal promoter activity and can function independently, whereas the more distal MREb (-89 to -100) mainly contributes to metal induction through cooperative interactions with MREa. The degree of basal character of the MREs is partially determined by nucleotide differences at the flexible position N of the MRE consensus TGC(G/A)CNC. In mouse L and HepG2 cells, MREa activity is conserved, but the contributions of the MREb region differ, including reduced cooperativity with MREa. There are also differences in the apparent molecular masses of the rainbow trout and mammalian nuclear factors that bind to the tMT-B promoter and MREa sequence.

The oxidative phosphorylation process is the main source of endogenous reactive oxygen species (ROS) such as superoxide in mitochondria. In mammals, manganese superoxide dismutase plays an important role in detoxification of superoxide before it interferes with mitochondrial function and causes programmed cell death. Here, we investigated the role of Leishmania donovani mitochondrial iron superoxide dismutase-A (LdFeSODA) in protecting the parasite from oxidative stress and in the control of programmed cell death events. We have shown that overexpression of LdFeSODA protects Leishmania donovani from miltefosine induced cytotoxicity and reduced mitochondrial-derived superoxide generation. Furthermore, parasites overexpressing LdFeSODA showed (i) lower level of phosphatidylserine exposure as measured by flow cytometry and fluorescent microscopy; and (ii) reduced level of TUNEL staining of parasites compared to the control parasites. Finally, prolonged incubation of the parasites with miltefosine induced the release of both cytochrome C and LdFeSODA into the cytosol as demonstrated by Western blotting and fluorescence microscopy indicating programmed cell death. The results indicate that LdFeSODA protects the mitochondria of Leishmania from oxidative stress thereby inhibiting programmed cell death.

A series of Bombyx mori nuclear polyhedrosis virus (Bm-NPV) transfer vectors has been developed containing various lengths of the polyhedrin promoter, including sequences 3' of the initiation codon. The ATG initiation codon was mutated in some of these vectors to allow for the production of authentic nonfusion proteins. The ability of the various polyhedrin promoter constructs to direct expression of foreign gene sequences was assessed using two test genes, chloramphenicol acetyl transferase (cat), and human metallothionein II. Accumulation of cat mRNA and nonfused protein was low when only polyhedrin promoter sequences to -8 (relative to the translational start site of polyhedrin mRNA) were included in the transfer vector, but cat expression was comparable with that of the wild-type polyhedrin gene when promoter sequences to +5 were present. Further addition of polyhedrin gene sequences to +26 or +94 resulted in no further increase in expression. Similar results were obtained for expression of human metallothionein II, where constructs encoding polyhedrin-metallothionein fusion proteins containing polyhedrin sequences to at least +5 resulted in high levels of mRNA and protein accumulation. The expression vectors containing the +5, +26, or +94 BmNPV polyhedrin promoter can thus be used to direct maximal levels of production of nonfused proteins (when the polyedrin ATG has been mutated) or of fusion proteins, depending on which is more suitable for a particular application. These new vectors are a useful addition to those presently available and should increase the utility of the BmNPV expression system for large-scale protein production.

In this report, we have measured the cadmium (Cd2+)-induced expression of all known metallothionein I (MT-I) mRNAs in a human hepatoma cell line, Hep G2. Among the human MT-I gene family promoters, marked sequence conservation exists; despite this, the mRNA accumulation level for each species was found to be quite unique. This differential Cd2+ induction of MT-I family members provides an ideal opportunity to assess whether the characteristic response results from subtle isoform-specific variations in promoter structure. Accordingly, we have examined the mechanism for differential expression of two isoforms, MT-IG and MT-IF, by transient transfection into Hep G2 cells. In the presence of Cd2+, MT-IG promoter activity and endogenous mRNA level were, respectively, 4.7- and 3-fold greater than those of MT-IF. This close correlation between promoter activity and mRNA accumulation strongly suggests that differential expression occurs at the level of transcription. The difference in Cd(2+)-stimulated activity was found to be conferred by 240- and 243-base pair promoter fragments spanning nucleotides -174 to +66 and -172 to +71 of the MT-IG and MT-IF genes, respectively. One of the most striking nonhomologies between the promoters is a single A (TATAAA) to C (TATCAA) transversion in the TATA motifs of MT-IG and MT-IF genes, respectively. To determine whether such a subtle change in the TATA motif could account for the marked differences in promoter function, we constructed MT-IG-TATCA and MT-IF-TATAA promoters and measured their activities in transient transfection and cell-free transcription assays. Results of both assays showed a profound difference between the two motifs that paralleled the difference in Cd(2+)-stimulated MT-IG and MT-IF mRNA levels. In summary, we have shown that differential regulation of two MT-I promoters is primarily due to a single base alteration in their TATA motifs.

In order to study the temporal and spatial regulation of a rat testis-specific heat-shock-like hst70 gene, an 0.8-kb fragment of its upstream DNA was fused to the lacZ gene and microinjected into one-cell murine embryos. Independent tgHST1 and tgHST2 transgenic mice strains were established, containing about 5-7 and 40-60 transgene copies/haploid genome, respectively. Enzyme assays in various tissues showed that transgene-encoded beta-galactosidase accumulates exclusively in testes of transgenic animals and cannot be detected until 16-17 days after birth. In-situ assays revealed that the enzyme accumulates mainly in pachytene primary spermatocytes. Our data complement previous studies on the endogenous rat hst70 and suggest that its 0.8-kb upstream region contains sufficient information to function as an active spermatogenesis-specific promoter.

A rainbow trout major heat-shock-protein-like gene (hsp 70) and corresponding cDNA clones were isolated by hybridization to heterologous hsp70 probes. DNA sequencing revealed that this gene is structurally similar to a mammalian heat-shock-cognate hsc70 gene and consists of eight introns. Northern blot and primer extension analyses showed that the corresponding mRNA is constitutively abundant in different trout tissues and salmonid cell lines. Fragments of the isolated gene containing the -900 - +30 and -217 - +58 sequence were linked to a bacterial chloramphenicol acetyltransferase reporter gene and transiently transfected into salmonid cells. The expression pattern of these constructs supports our conclusion that the isolated genomic and cDNA clones correspond to a trout heat-shock-cognate hsc70 gene.

In Ethiopia, visceral leishmaniasis (VL) is an increasing public health concern. Recently, a new outbreak of VL claimed the lives of hundreds of Ethiopians. Mapping its distribution and the identification of the causative Leishmania species is important for proper use of resources and for control planning. The choice of appropriate typing technique is the key for determining the infecting species. Here we compared three deoxyribonucleic acid (DNA) based markers. We used, for the first time, cpbE and cpbF (cpbE/F) PCR-RFLP and demonstrated that it clearly differentiates Leishmania donovani from Leishmania infantum. The cpbE/F PCR-RFLP gave identical banding pattern for all L. donovani strains irrespective of their geographic origin. With the K26 (primers) PCR-RFLP, the L. donovani strains gave a banding pattern different from L. infantum and showed variation with geographic origin. The Ethiopian isolates typed as L. donovani by the PCR-RFLP of the cpbE/F (gene) and K26 (primers) showed two types of patterns with the T2/B4 (primers) PCR-RFLP; one group with L. infantum-like and the other L. donovani-like pattern. Phylogenetic analysis using cpbE/F sequences showed variation with geographic origin of strains and the African strains of L. donovani are more distantly related to L. infantum. Moreover, the Ethiopian isolates were seen to be closely related to the Sudanese, Kenyan and Indian strains. Thus, we recommend the use of more than one marker to study the population genetics of L. donovani complex.

The sequences responsible for heavy metal-inducible expression are situated within the proximal 437 and 160 base pairs (bp) of MT-IF and MT-IG 5'-flanking sequence, respectively. Only 105 bp of proximal MT-IG 5'-flanking sequence containing a TATA box, two metal responsive elements (MREs), and three GC motifs and 147 bp of proximal MT-IF 5'-flanking sequence containing a TATCA box, four MREs, and two GC motifs were required for heavy metal-inducible expression. However, the proximal 111 bp of MT-IF 5'-flanking sequences (a TATCA box, two MREs, and two GC motifs) was not responsive to heavy metals and competes less efficiently than the 105-bp MT-IG fragment in a competition transfection analysis. The MT-IF promoter fragment containing MREc and MREd is substantially stronger and a more efficient competitor than the MT-IG promoter fragment containing MREc and MREd. Furthermore, the proximal 160 bp of MT-IG 5'-flanking sequence functions as a strong metal-inducible promoter but not as a metal-inducible enhancer. Mobility shift analysis of MT-IF and MT-IG promoter subregions suggests a correlation between protein binding to MRE sequences and MT gene expression. These data illustrate that the overall structural and functional organization of the MT-IF and MT-IG promoters are very different and that the molecular mechanisms governing differential expression levels of human MT genes are quite complex.

In this study we have demonstrated the ability of 5-azacytidine to elevate the basal level expression of the metallothionein (MT)-IF and MT-IG genes and increase the basal level expression of the MT-IIA gene in Hep G2 cells, a cell line which exhibits heavy metal inducible MT gene expression. Atomic absorption analysis of 5-azacytidine treated Hep G2 cells detected a 2-fold increase in the total cellular copper content. Pretreatment of 5-azacytidine exposed cells within hydroxyurea and cycloheximide indicated that the increase in total cellular copper content was a direct response to 5-azacytidine treatment. S1 nuclease analysis illustrated that pretreatment of Hep G2 cells with KCN, a copper specific chelator and uptake inhibitor, suppressed 5-azacytidine- and copper-inducible MT-IG gene expression. Thus, the increase in MT gene expression in response to 5-azacytidine treatment can be correlated to an increase in the total cellular copper content. Possible mechanisms on how 5-azacytidine could alter the influx/efflux of copper in Hep G2 cells are discussed.

The metallothionein (MT) gene expression profile was followed in rainbow trout during early embryo development and in liver and gonads during the period of sexual maturation. The hepatic MT mRNA levels increase at the end of sexual maturation in both male and female rainbow trout. Although both isoforms of MT mRNA accumulate in the liver, there is a preferential increase in MT-A in the female liver. Concomitantly with this increase in MT there is a redistribution of zinc and copper to MT. In the juvenile female there is an abundance of MT mRNA in the ovaries. This is correlated to high levels of zinc in the MT fraction upon Sephadex G-75 chromatography. During ovary development the MT mRNA levels and the MT-bound zinc levels drop, with an increase in zinc being bound to high-molecular-mass proteins. At ovulation most of the zinc is found in the membrane portion upon centrifugation. In contrast to the ovaries, there are no apparent changes in either trace metal distribution or MT mRNA levels during testis development. In the developing embryo there is an increase in MT-bound copper at gastrulation. This is accompanied by an increase in both isoforms of MT mRNA. At hatch both the copper and zinc levels increase in the MT fraction, with a concomitant increase in mainly MT-A mRNA. These findings indicate that the variations in MT mRNA levels during development are closely associated with metal regulation.

A lambda phage recombinant clone, 25 S, which contains a 15.5-kb EcoRI human genomic DNA fragment, has been characterized. Restriction mapping and Southern blot hybridization indicated a 3.0-kb HindIII fragment containing metallothionein (MT)-like sequences. Several interesting features were found upon comparison of this nucleotide sequence with that of other human MT genes: (1) sequences representing the 5' regulatory region, the 5' untranslated region, and the first exon are not contained in the 3.0-kb HindIII fragment; (2) the coding sequence of the second exon (amino acids 10-31 encoding a portion of the beta-domain of the MT protein) has 11 amino acid changes out of a total of 21, whereas, the third exon (amino acids 32-61, representing the complete alpha-domain of the MT protein) has only 4 amino acid substitutions; however, all cysteine residues are conserved; (3) this MT-like gene retains intron sequences and processing signals; (4) Southern blot analysis of human genomic DNA indicated this MT-like gene is located on a 10.5-kb EcoRI genomic DNA fragment; and (5) unusual AG/CT-rich repetitive elements are located within the second intron and upstream of the second exon of this MT-like gene. This gene is not expressed in response to metal induction in two human cell lines, as shown by northern blot analyses. Based on these observations, this MT-like gene represents a unique nonprocessed pseudogene of the human MT multigene family.

Exposure of a trout gonadal fibroblast (RTG-2) cell line to ZnCl2, CdCl2 and CuCl2 resulted in differential levels of accumulation of metallothionein (MT) mRNA. ZnCl2 being the most effective agent induced MT mRNA in 3 h, with 172-fold induction after 48 h and continued accumulation up to 144 h. Following CdCl2 treatment, mRNA could be detected after 24 h, reaching peak levels at 72 h. Furthermore, trout MT mRNA could be detected up to 8 days after withdrawal of extraneous ZnCl2. Using a novel technique of primer extension and DNA sequencing with total RNA as template, specificity of the trout MTa and MTb gene-specific primers was established. Primer extension studies revealed a higher response of MTa to ZnCl2 and CdCl2 compared to MTb. Insensitivity of MT mRNA induction to cycloheximide suggested that induction by the metals was independent of de novo protein synthesis. However, simultaneous exposure of cells to actinomycin D and metals completely inhibited MT mRNA synthesis implying control at the transcriptional level.

The expression of three human metallothionein genes, MT-IIA, MT-IF, and MT-IG was studied in the human hepatoblastoma (HepG2), the hepatocarcinoma (Hep3B2), the embryonic kidney (Hek 293), and the lymphoblastoid-derived (Wi-L2) cell lines. The pattern of expression of each specific MT gene in response to various heavy metals was different among the four cell lines studied indicating differential regulation of MT gene expression. The MT-IF or MT-IG and the MT-IIA genes were regulated in a cell-type specific manner in response to heavy metals and dexamethasone, respectively. DNA methylation was shown to be correlated to cell-type specific regulation of MT gene expression since 5-azacytidine treatment resulted in the expression of the MT-IF and MT-IG genes in response to cadmium and zinc in Wi-L2 cells, of the MT-IIA gene in response to dexamethasone in Wi-L2 cells, and of the MT-IG in response to zinc and copper in Hek 293 cells. Furthermore, transfection studies indicated that all the trans-acting factors necessary for the expression of these genes were present and functional in Wi-L2 and Hek 293 cells. The differential level of expression of the MT-IF and MT-IG genes in response to heavy metals in the Hek 293 cell line was shown to be correlated to their chromatin structure.

Summary An outbreak of skin lesions was reported in June 2005 in the district of Silti woreda, 150 km south of Addis Ababa, by the Christian Children's Fund (CCF) and confirmed to be cutaneous leishmaniasis (CL) by our group from the Armauer Hansen Research Institute in July 2005. A house-to-house survey of 1907 residents in three kebeles of Silti woreda conducted in April 2006 showed a prevalence of 4.8%. RFLP analysis of the internal transcribed spacer RNA (ITS1) showed that Leishmania aethiopica was the causative agent. In the survey, it was found that the age group 11–20 years was the most affected. Environmental factors such as proximity of the house to the gorge where hyraxes reside, presence of the plants Adhatoda schimperiana and Acacia spp. in the compound and sharing the same room with domestic animals were significantly associated with developing CL. The prevalence of active disease was higher in Kibet town (10.4%) compared to the rural kebeles. The identified risk factors of CL in the area need further study. The appearance of leishmaniasis in Silti, which was not known to be endemic for the disease, underlines the need to initiate a leishmaniasis control program in Ethiopia to limit its expansion.

Many reports have shown that Leishmania species are susceptible to reactive oxygen species (ROS) and reactive nitrogen species (RNS)-mediated killing. The superoxide dismutase (SOD) is one of the antioxidant defense enzymes important for parasite survival through its detoxification of superoxide into hydrogen peroxide and oxygen. The mitochondria produce numerous superoxide radicals as a by-product of cellular respiration and hence targeting of SODs to the mitochondria is critical in maintaining healthy mitochondria. This study examines the characteristic determinants for mitochondrial localization of Leishmania donovani FeSODA. We show that FeSODA is localized to the mitochondria and that the N-terminal 31 amino acid extension is important for its localization. Interestingly, further dissection of the 31 amino acid extension revealed that the first 8 amino acids of the FeSODA protein are sufficient for targeting to the mitochondria. In addition, we found that the four basic amino acid residues contained within the N-terminal extension are also important for targeting. These studies highlight important features of mitochondrial targeting sequences in kinetoplastids.

Kinetoplastid glycosomes contain a variety of metabolic activities, such as glycolysis, β-oxidation of fatty acids, lipid biosynthesis, and purine salvage. One advantage of sequestering metabolic activities is the avoidance of cellular oxidative damage by reactive oxygen species produced as a by-product of metabolism. Little is known about how glycosomes themselves withstand these toxic metabolites. We previously isolated an iron superoxide dismutase fromLeishmania chagasithat is expressed at low levels in the early logarithmic promastigote stage and increases toward the stationary promastigote and amastigote stages. We have since identified a second highly homologousLcfesodbgene that is expressed at high levels in the early logarithmic promastigote stage and decreases toward the stationary promastigote and amastigote stages. Localization studies using green fluorescent protein fusions have revealed that LcFeSODB1 and LcFeSODB2 are localized within the glycosomes by the last three amino acids of their carboxyl termini. To better understand the specific role that FeSODB plays in parasite growth and survival, a single-allele knockout of theLcfesodb1gene was generated. The parasites with these genes exhibited a significant reduction in growth when endogenous superoxide levels were increased with paraquat in culture. Furthermore, the FeSODB1-deficient parasites exhibited a significant reduction in survival within human macrophages. Our results suggest that LcFeSODB plays an important role in parasite growth and survival by protecting glycosomes from superoxide toxicity.