Cryptococcus neoformans chitin synthase 3 plays a critical role in dampening host inflammatory responses

Cryptococcus neoformans is the most common disseminated fungal pathogen in AIDS patients, resulting in ∼200,000 deaths each year. There is a pressing need for new treatments for this infection, as current antifungal therapy is hampered by toxicity and/or the inability of the host’s immune system to aid in resolution of the disease. An ideal target for new therapies is the fungal cell wall. The cryptococcal cell wall is different from the cell walls of many other pathogenic fungi in that it contains chitosan. Strains that have decreased chitosan are less pathogenic and strains that are deficient in chitosan are avirulent and can induce protective responses. In this study, we investigated the host responses to a chs3Δ strain, a chitosan-deficient strain, and found that mice inoculated with the chs3Δ strain all died within 36 h and that death was associated with an aberrant hyperinflammatory immune response driven by neutrophils, indicating that chitosan is critical in modulating the immune response to Cryptococcus.Cryptococcus neoformans infections are significant causes of morbidity and mortality among AIDS patients and the third most common invasive fungal infection in organ transplant recipients. One of the main interfaces between the fungus and the host is the fungal cell wall. The cryptococcal cell wall is unusual among human-pathogenic fungi in that the chitin is predominantly deacetylated to chitosan. Chitosan-deficient strains of C. neoformans were found to be avirulent and rapidly cleared from the murine lung. Moreover, infection with a chitosan-deficient C. neoformans strain lacking three chitin deacetylases (cda1Δcda2Δcda3Δ) was found to confer protective immunity to a subsequent challenge with a virulent wild-type counterpart. In addition to the chitin deacetylases, it was previously shown that chitin synthase 3 (Chs3) is also essential for chitin deacetylase-mediated formation of chitosan. Mice inoculated with the chs3Δ strain at a dose previously shown to induce protection with the cda1Δcda2Δcda3Δ strain die within 36 h after installation of the organism. Mortality was not dependent on viable fungi, as mice inoculated with a heat-killed preparation of the chs3Δ strain died at the same rate as mice inoculated with a live chs3Δ strain, suggesting that the rapid onset of death was host mediated, likely caused by an overexuberant immune response. Histology, cytokine profiling, and flow cytometry indicate a massive neutrophil influx in the mice inoculated with the chs3Δ strain. Mice depleted of neutrophils survived chs3Δ inoculation, indicating that death was neutrophil mediated. Altogether, these studies lead us to conclude that Chs3, along with chitosan, plays critical roles in dampening cryptococcus-induced host inflammatory responses

Seed systems of rice and finger millet in Nepal, between formality and informality

In Nepal, more than 90% of cereal seed flows from informal systems and there are regions and groups of farmers that are not connected at all to any seed networks with external seed supply. Nepal's agricultural policies and formal institutions are promoting the development of the formal seed system. However, knowledge gaps exist on the opportunities and challenges for smallholder farmers when formal seed systems are becoming accessible. This study identified impacts of different seed systems on agrobiodiversity, seed value chains and livelihood of smallholder farmers in Ghanpokhara, a mid-hill region of Nepal. A survey was conducted in 40 farm households (rice and finger millet), numerous key informants and experts involved in Nepal's seed systems were interviewed and extensive literature review was done. Four different seed systems were identified: the formal system, the intermediary system, the informal system and the no seed supply system (except local seeds). The latter was found in Ghanpokhara for rice and finger millet. Although (seed and crop) markets can be found not too far away, farmers in the study site appear to be locked off from the formal seed system. Their interest to purchase new seed seems to be high, but their awareness about potential benefits of quality seed is low, and they have limited access to information and new seed. The present research also found that varietal diversity along the continuum of seed systems is highest in informal seed systems. Besides numerous benefits, increasingly formal seed systems bear also disadvantages (and risks) for small-holder farmers: higher costs of input, dependency from formal seed sources and changes in crop genetic diversity, among others. The recommendations derived from this study are: extension service should be promoted in remote areas, more resources should be made available for farmers' training on seed production, selection and storage techniques. Furthermore, the organisation in farmer groups for seed production should be facilitated (socially inclusive) in order to produce good quality seed of farmer preferred varieties locally and in sufficient quantity

The Decay of Disease Association with Declining Linkage Disequilibrium: A Fine Mapping Theorem

Several important and fundamental aspects of disease genetics models have yet to be described. One such property is the relationship of disease association statistics at a marker site closely linked to a disease causing site. A complete description of this two-locus system is of particular importance to experimental efforts to fine map association signals for complex diseases. Here, we present a simple relationship between disease association statistics and the decline of linkage disequilibrium from a causal site. Specifically, the ratio of Chi-square disease association statistics at a marker site and causal site is equivalent to the standard measure of pairwise linkage disequilibrium, r2. A complete derivation of this relationship from a general disease model is shown. Quite interestingly, this relationship holds across all modes of inheritance. Extensive Monte Carlo simulations using a disease genetics model applied to chromosomes subjected to a standard model of recombination are employed to better understand the variation around this fine mapping theorem due to sampling effects. We also use this relationship to provide a framework for estimating properties of a non-interrogated causal site using data at closely linked markers. Lastly, we apply this way of examining association data from high-density genotyping in a large, publicly-available data set investigating extreme BMI. We anticipate that understanding the patterns of disease association decay with declining linkage disequilibrium from a causal site will enable more powerful fine mapping methods and provide new avenues for identifying causal sites/genes from fine-mapping studies

Cell wall composition in Cryptococcus neoformans is media dependent and alters host response, inducing protective immunity

INTRODUCTION: OBJECTIVE: The purpose of this study was to determine how different media influenced the amount of chitin and chitosan in the cell wall, which in turn impacted the cell wall architecture and host response. METHODS: Yeast extract, peptone, and dextrose (YPD) and yeast nitrogen base (YNB) are two commonly used media for growing Cryptococcus before use in in vitro or in vivo experiments. As a result, RESULTS: We observed that the growth of wild-type CONCLUSION: These findings emphasize the importance of culture media and pH during growth in shaping the content and organization of th

Pharmacognostic evaluation of Achyranthes coynei: Leaf

AbstractAchyranthes coynei Sant., (Amaranthaceae) is a rare, medicinal shrub, endemic to India. The plant especially, leaves are used in treatment of various disorders by folk healers. It has been scientifically evaluated for its antimicrobial and antioxidant properties. Pharmacognostic studies have not been carried out so far in this plant. So, the present study was undertaken to evaluate pharmacognostic characters of leaf of A. coynei. The studies were carried out in terms of morphological, microscopic characters and physicochemical parameters using standard methods. Leaf size (15–23 × 7–10 cm) and petiole nature (pink above and green beneath) were the distinguishing morphological character observed in the present study. Transverse section of leaf and petiole showed presence of long, multi-cellular, warty trichomes with pointed apex and short, glandular trichomes with blunt apex on thick walled epidermis; conjoint, collateral closed, endarch vascular bundles; rosette crystals of calcium oxalate in ground tissue. Ash and extractive values, micro and macro elements and nutritive factors were estimated. Leaf powder showed fluorescence under the influence of different solvents. Preliminary phytochemical screening showed the presence of alkaloids, saponins and triterpenoids. High Performance Thin Layer Chromatorgraphic (HPTLC) analysis yielded eight bands in leaf extract. The study forms the first report on pharamcognostic characters for A. coynei, which could be useful for identification and authentication of the plant