Development and characterization of microsatellite loci for the tropical tree pathogen Botryosphaeria rhodina

Nineteen simple sequence repeat (SSR) markers were developed for the pathogen and blue stain fungus Botryosphaeria rhodina. Eight pairs were found to be polymorphic among isolates collected from Pinus spp., whereas a further five pairs were polymorphic when isolates from Pinus spp. were compared with those from Eucalyptus spp. Nine isolates of B. rhodina collected from pines and eucalypts in South Africa, Mexico and Indonesia were used to demonstrate the range of the markers. Testing the markers yielded preliminary evidence that relationships among isolates are more closely linked to host than to geographical origin.     

Thioredoxin reductase is essential for viability in the fungal pathogen Cryptococcus neoformans

Thioredoxin reductase (TRR1) is an important component of the thioredoxin oxidative stress resistance pathway. Here we show that it is induced during oxidative and nitrosative stress and is preferentially localized to the mitochondria in Cryptococcus neoformans. The C. neoformans TRR1 gene encodes the low-molecular-weight isoform of the thioredoxin reductase enzyme, which shares little homology with that of its mammalian host. By replacing the endogenous TRR1 promoter with an inducible copper transporter promoter, we showed that Trr1 appears to be essential for viability of this pathogenic fungus, making it a potential antifungal target.     

Neglected tropical disease vaccines

The neglected tropical diseases or ‘NTDs’ represent the most common infections of the world's one billion poorest people. Unlike the better known acute or emerging infections, the NTDs are generally chronic and disabling (and often disfiguring) conditions. The long-term disability they cause has been revealed as a major reason why poor people in developing countries cannot escape the poverty trap. Because NTDs are associated with poverty, vaccines against these conditions are sometimes referred to as antipoverty vaccines. However, despite their global public health and economic importance, such vaccines have largely been ignored by industry and today are predominantly being produced through the activities of non-profit product development partnerships (PDPs). The Human Hookworm Vaccine Initiative based at the Sabin Vaccine Institute is one such PDP developing two antipoverty vaccines for hookworm and schistosomiasis, respectively. It has been proposed to combine these vaccines in order to target polyparasitic co-infections leading to severe anemia. Ultimately, to ensure global access of a multivalent anthelminthic vaccine, it may be linked to deworming programs through vaccine-linked chemotherapy. This would be an important step towards achieving the Millennium Development Goals for sustainable poverty reduction by 2015.     

Practical methods for chemical inactivation of Creutzfeldt-Jakob disease pathogen

Chemical inactivation of pathogen of Creutzfeldt-Jakob disease (CJD) was examined using the mouse-adapted CJD strain. A high concentration of formic acid, guanidine compounds, trichloroacetate and phenol prevented CJD transmission. NaOH between 0.25 and 2 N lengthened the incubation periods. Sodium dodecyl sulfate (SDS) in a concentration between 1 and 3% did not alter incubation at room temperature but did completely block the transmission after boiling for 3 min in 3% SDS. This method is recommended for practical disinfection.     

The reactive oxygen species network pathways: an essential prerequisite for perception of pathogen attack and the acquired disease resistance in plants

Availability of complete Arabidopsis(Arabidopsis thaliana) and rice(Oryza sativa) genome sequences, together with molecular recourses of functional genomics and proteomics have revolutionized our understanding of reactive oxygen species (ROS) signalling network mediating disease resistance in plants. So far, ROS have been associated with aging, cellular and molecular alteration in animal and plant cells. Recently, concluding evidences suggest that ROS network is essential to induce disease resistance and even to mediate resistance to multiple stresses in plants. ROS are obligatory by-products emerging as a result of normal metabolic reactions. They have the potential to be both beneficial and harmful to cellular metabolism. Their dual effects on metabolic reactions are dosage specific. In this review we focus our attention on cellular ROS level to trigger beneficial effects on plant cells responding to pathogen attack. By exploring the research related contributions coupled with data of targeted gene disruption, and RNA interference approaches, we show here that ROS are ubiquitous molecules of redox-pathways that play a crucial role in plant defence mechanism. The molecular prerequisites of ROS network to activate plant defence system in response to pathogen infections are here underlined. Bioinformatic tools are now available to scientists for high throughput analysis of cellular metabolisms. These tools are used to illustrate crucial ROS-related genes that are involved in the defence mechanism of plants. The review describes also the emerging findings of ROS network pathways to modulate multiple stress resistance in plants.     

Red coloration in young tropical leaves associated with reduced fungal pathogen damage

The adaptive significance of red coloration in tropical forest leaves remains unclear. In vivo assays show that there is a significant negative correlation between anthocyanin pigments in young leaves and fungal pathogen damage. This supports a previous hypothesis that anthocyanins may protect young leaves from fungal damage during the vulnerable period of leaf expansion.     

Identification of the pathogen responsible for tea white scab disease

Tea white scab disease commonly occurs in high-altitude tea-growing areas worldwide. Both Elsinoe leucospila and Phyllosticta theaefolia have been reported as the pathogen responsible for this disease. To conclusively identify the causative agent, samples were collected from plants infected with tea white scab disease in high-altitude tea gardens in southern China. Fungal isolates obtained from the infected material were identified based on morphological characteristics, comparisons of ITS, 18S rDNA, RPB2 and LSU sequences, and pathogenicity tests. Both Elsinoe sp. and Phyllosticta sp. were isolated from the collected samples with rates of 6% and 35%, respectively. On potato dextrose agar medium, Phyllosticta sp. grew faster and sporulated more than E. leucospila. However, only E. leucospila caused symptoms similar to those of tea white scab disease. In contrast, Phyllosticta sp. infections resulted in large necrotic spots. Therefore, E. leucospila appears to be the pathogen responsible for tea white scab disease, whereas Phyllosticta sp. is a hyperparasitic fungus that infects the diseased plant tissue. The high isolation rate of Phyllosticta sp. due to its rapid growth and considerable sporulation may have led to the erroneous identification of this fungus as the cause of tea white scab disease. Our findings may be useful for future investigations of this disease, particularly regarding the development of improved prevention and/or control measures.     

Periplasmic disulphide bond formation is essential for cellulase secretion by the plant pathogen Erwinia chrysanthemi

Secretion to the cell exterior of cellulase EGZ and of at least six pectinases enables the Gram-negative Erwinia chrysanthemi to cause severe plant disease. The C-terminal cellulose-binding domain (CBD) of EGZ was found to contain a disulphide bond which forms, in the periplasm, between residues Cys-325 and Cys-382. Dithiothreitol (DTT)-treatment of native EGZ showed that the disulphide bond was dispensable, both for catalysis and cellulose binding. Adding DTT to E. chrysanthemi cultures led to immediate arrest of secretion of EGZ which accumulated in the periplasm where the CBD was eventually proteolysed. Site-directed mutagenesis that affected Cys residues involved in disulphide bond formation resulted in molecules that were catalytically active and able to bind to cellulose but were no longer secreted, Instead they accumulated in the periplasm. Interestingly, the region around EGZ Cys-325 is conserved in two pectinases secreted by the same pathway as EGZ. We conclude that the conserved Cys, and possibly adjacent residues, bear essential information for EGZ to be secreted and that periplasmic disulphide bond formation is an obligatory step which provides a pre-folded functional form of EGZ with secretion competence.     

Development of a new platform for neglected tropical disease surveillance

An expanded global focus on the control and elimination of neglected tropical diseases (NTDs) has called attention to the need to develop and validate surveillance strategies that are cost effective and can be integrated across diseases. Here, we describe a multiplex tool for the sensitive detection of antibody responses to NTDs as well as vaccine preventable diseases, malaria, and waterborne and zoonotic infections. The assay platform is robust, can be performed with either serum or dried blood spots and can be adapted to local epidemiological conditions and public health priorities. Multiplex assays open the door to conducting routine serosurveillance for NTDs through demographic health surveillance or malaria indicator surveys.     

Data base management system for lymphatic filariasis--a neglected tropical disease

Background

Researchers working in the area of Public Health are being confronted with large volumes of data on various aspects of entomology and epidemiology. To obtain the relevant information out of these data requires particular database management system. In this paper, we have described about the usages of our developed database on lymphatic filariasis.

Methods

This database application is developed using Model View Controller (MVC) architecture, with MySQL as database and a web based interface. We have collected and incorporated the data on filariasis in the database from Karimnagar, Chittoor, East and West Godavari districts of Andhra Pradesh, India.

Conclusion

The importance of this database is to store the collected data, retrieve the information and produce various combinational reports on filarial aspects which in turn will help the public health officials to understand the burden of disease in a particular locality. This information is likely to have an imperative role on decision making for effective control of filarial disease and integrated vector management operations.     

A global alliance against tropical disease

The tenth annual meeting of the National Institute of Allergy and Infectious Diseases Internal Centers for Tropical Disease Research was held, 7-9 May 2001, in Bethesda, MD, USA.     

The plasmids of Borrelia burgdorferi: essential genetic elements of a pathogen

The spirochete Borrelia burgdorferi, the causative agent of Lyme disease, has an unusual genome comprised of a linear chromosome and the largest plasmid complement of any characterized bacterium. Certain plasmid-encoded elements are required for virulence and viability, both in vitro and in vivo. The genetic tools to manipulate B. burgdorferi are sufficiently developed for precise molecular genetic investigations. B. burgdorferi now represents a prime system with which to address basic questions of plasmid biology and plasmid contributions to bacterial virulence and disease pathogenesis.     

The phenolic hydroxyl group of carvacrol is essential for action against the food-borne pathogen Bacillus cereus

The natural antimicrobial compound carvacrol shows a high preference for hydrophobic phases. The partition coefficients of carvacrol in both octanol-water and liposome-buffer phases were determined (3.64 and 3.26, respectively). Addition of carvacrol to a liposomal suspension resulted in an expansion of the liposomal membrane. Maximum expansion was observed after the addition of 0.50 micromol of carvacrol/mg of L-alpha-phosphatidylethanolamine. Cymene, a biological precursor of carvacrol which lacks a hydroxyl group, was found to have a higher preference for liposomal membranes, thereby causing more expansion. The effect of cymene on the membrane potential was less pronounced than the effect of carvacrol. The pH gradient and ATP pools were not affected by cymene. Measurement of the antimicrobial activities of compounds similar to carvacrol (e.g., thymol, cymene, menthol, and carvacrol methyl ester) showed that the hydroxyl group of this compound and the presence of a system of delocalized electrons are important for the antimicrobial activity of carvacrol. Based on this study, we hypothesize that carvacrol destabilizes the cytoplasmic membrane and, in addition, acts as a proton exchanger, thereby reducing the pH gradient across the cytoplasmic membrane. The resulting collapse of the proton motive force and depletion of the ATP pool eventually lead to cell death.     

The tetraspanin gene ClPLS1 is essential for appressorium-mediated penetration of the fungal pathogen Colletotrichum lindemuthianum

Conservation of the molecular mechanisms controlling appressorium-mediated penetration during evolution was assessed through a functional study of the ClPLS1 gene from Colletotrichum lindemuthianum orthologous to the MgPLS1 from Magnaporthe grisea, involved in penetration peg development. These two plant-pathogenic Pyrenomycetes differentiate appressoria to penetrate into plant tissues. We showed that ClPLS1 is a functional homologue of MgPLS1 in M. grisea. Loss of ClPLS1 function had no effect on vegetative growth, conidiation or on appressorium differentiation and maturation. However, Clpls1::hph mutants are non-pathogenic on either intact or wounded bean leaves, as a result of a defect in the formation and/or positioning of the penetration pore and consequently in the formation of the penetration peg. These observations suggest that the fungal tetraspanins control a conserved appressorial function that could be required for the correct localization of the site where the penetration peg emerges.     

Capsule independent uptake of the fungal pathogen Cryptococcus neoformans into brain microvascular endothelial cells

Cryptococcosis is a life-threatening fungal disease with a high rate of mortality among HIV/AIDS patients across the world. The ability to penetrate the blood-brain barrier (BBB) is central to the pathogenesis of cryptococcosis, but the way in which this occurs remains unclear. Here we use both mouse and human brain derived endothelial cells (bEnd3 and hCMEC/D3) to accurately quantify fungal uptake and survival within brain endothelial cells. Our data indicate that the adherence and internalisation of cryptococci by brain microvascular endothelial cells is an infrequent event involving small numbers of cryptococcal yeast cells. Interestingly, this process requires neither active signalling from the fungus nor the presence of the fungal capsule. Thus entry into brain microvascular endothelial cells is most likely a passive event that occurs following 'trapping' within capillary beds of the BBB.     

JNK1 is not essential for TNF-mediated joint disease

Tumour necrosis factor (TNF) signalling molecules are considered as promising therapeutic targets of antirheumatic therapy. Among them, mitogen-activated protein kinases are thought to be of central importance. Herein, we investigate the role in vivo of TNF-α signalling through c-Jun N-terminal kinase (JNK)1 in destructive arthritis. Human TNF transgenic (hTNFtg) mice, which develop inflammatory arthritis, were intercrossed with JNK1-deficient (JNK1 ^-/-) mice. Animals (n = 35) of all four genotypes (wild-type, JNK1 ^-/-, hTNFtg, JNK1 ^-/-hTNFtg) were assessed for clinical and histological signs of arthritis. Clinical features of arthritis (swelling and decreased grip strength) developed equally in hTNFtg and JNK1 ^-/-hTNFtg mice. Histological analyses revealed no differences in the quantity of synovial inflammation and bone erosions or in the cellular composition of the synovial infiltrate. Bone destruction and osteoclast formation were observed to a similar degree in hTNFtg and JNK1 ^-/-hTNFtg animals. Moreover, cartilage damage, as indicated by proteoglycan loss in the articular cartilage, was comparable in the two strains. Intact phosphorylation of JNK and c-Jun as well as expression of JNK2 in the synovial tissue of JNK1 ^-/-hTNFtg mice suggests that signalling through JNK2 may compensate for the deficiency in JNK1. Thus, JNK1 activation does not seem to be essential for TNF-mediated arthritis.