Search tips
Search criteria

Results 1-17 (17)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  Phylogenetically Driven Sequencing of Extremely Halophilic Archaea Reveals Strategies for Static and Dynamic Osmo-response 
PLoS Genetics  2014;10(11):e1004784.
Organisms across the tree of life use a variety of mechanisms to respond to stress-inducing fluctuations in osmotic conditions. Cellular response mechanisms and phenotypes associated with osmoadaptation also play important roles in bacterial virulence, human health, agricultural production and many other biological systems. To improve understanding of osmoadaptive strategies, we have generated 59 high-quality draft genomes for the haloarchaea (a euryarchaeal clade whose members thrive in hypersaline environments and routinely experience drastic changes in environmental salinity) and analyzed these new genomes in combination with those from 21 previously sequenced haloarchaeal isolates. We propose a generalized model for haloarchaeal management of cytoplasmic osmolarity in response to osmotic shifts, where potassium accumulation and sodium expulsion during osmotic upshock are accomplished via secondary transport using the proton gradient as an energy source, and potassium loss during downshock is via a combination of secondary transport and non-specific ion loss through mechanosensitive channels. We also propose new mechanisms for magnesium and chloride accumulation. We describe the expansion and differentiation of haloarchaeal general transcription factor families, including two novel expansions of the TATA-binding protein family, and discuss their potential for enabling rapid adaptation to environmental fluxes. We challenge a recent high-profile proposal regarding the evolutionary origins of the haloarchaea by showing that inclusion of additional genomes significantly reduces support for a proposed large-scale horizontal gene transfer into the ancestral haloarchaeon from the bacterial domain. The combination of broad (17 genera) and deep (≥5 species in four genera) sampling of a phenotypically unified clade has enabled us to uncover both highly conserved and specialized features of osmoadaptation. Finally, we demonstrate the broad utility of such datasets, for metagenomics, improvements to automated gene annotation and investigations of evolutionary processes.
Author Summary
The ability to adjust to changing osmotic conditions (osmoadaptation) is crucial to the survival of organisms across the tree of life. However, significant gaps still exist in our understanding of this important phenomenon. To help fill some of these gaps, we have produced high-quality draft genomes for 59 osmoadaptation “experts” (extreme halophiles of the euryarchaeal family Halobacteriaceae). We describe the dispersal of osmoadaptive protein families across the haloarchaeal evolutionary tree. We use this data to suggest a generalized model for haloarchaeal ion transport in response to changing osmotic conditions, including proposed new mechanisms for magnesium and chloride accumulation. We describe the evolutionary expansion and differentiation of haloarchaeal general transcription factor families and discuss their potential for enabling rapid adaptation to environmental fluxes. Lastly, we challenge a recent high-profile proposal regarding the evolutionary origins of the haloarchaea by showing that inclusion of additional genomes significantly reduces support for a proposed large-scale horizontal gene transfer into the ancestral haloarchaeon from the bacterial domain. This result highlights the power of our dataset for making evolutionary inferences, a feature which will make it useful to the broader evolutionary community. We distribute our genomic dataset through a user-friendly graphical interface.
PMCID: PMC4230888  PMID: 25393412
2.  Mannosylation of Virus-Like Particles Enhances Internalization by Antigen Presenting Cells 
PLoS ONE  2014;9(8):e104523.
Internalization of peptides by antigen presenting cells is crucial for the initiation of the adaptive immune response. Mannosylation has been demonstrated to enhance antigen uptake through mannose receptors, leading to improved immune responses. In this study we test the effect of surface mannosylation of protein-based virus-like particles (VLP) derived from Rabbit hemorrhagic disease virus (RHDV) on uptake by murine and human antigen presenting cells. A monomannoside and a novel dimannoside were synthesized and successfully conjugated to RHDV VLP capsid protein, providing approximately 270 mannose groups on the surface of each virus particle. VLP conjugated to the mannoside or dimannoside exhibited significantly enhanced binding and internalization by murine dendritic cells, macrophages and B cells as well as human dendritic cells and macrophages. This uptake was inhibited by the inclusion of mannan as a specific inhibitor of mannose specific uptake, demonstrating that mannosylation of VLP targets mannose receptor-based uptake. Consistent with mannose receptor-based uptake, partial retargeting of the intracellular processing of RHDV VLP was observed, confirming that mannosylation of VLP provides both enhanced uptake and modified processing of associated antigens.
PMCID: PMC4133192  PMID: 25122183
3.  Application of Next-Generation Sequencing to Identify Genes and Mutations Causing Autosomal Dominant Retinitis Pigmentosa (adRP) 
The goal of our research is to identify genes and mutations causing auto-somal dominant retinitis pigmentosa (adRP). For this purpose we established a cohort of more than 250 independently ascertained families with adRP in the Houston Laboratory for Molecular Diagnosis of Inherited Eye Diseases. Affected members of each family were screened for disease-causing mutations in genes and gene regions that are commonly associated with adRP. By this approach, we detected mutations in 65 % of the families, leaving 85 families that are likely to harbor mutations outside of the “common” regions or in novel genes. Of these, 32 families were tested by several types of next-generation sequencing (NGS), including (a) targeted polymerase chain reaction (PCR) NGS, (b) whole exome NGS, and (c) targeted retinal-capture NGS. We detected mutations in 11 of these families (31 %) bringing the total detected in the adRP cohort to 70 %. Several large families have also been tested for linkage using Afymetrix single nucleotide polymorphism (SNP) arrays.
PMCID: PMC4121110  PMID: 24664689
Retinitis pigmentosa; Next-generation sequencing; Linkage mapping; Mutation prevalence; Retinal gene capture; Whole-exome sequencing
4.  Decreased basal chloride secretion and altered cystic fibrosis transmembrane conductance regulatory protein, Villin, GLUT5 protein expression in jejunum from leptin-deficient mice 
Patients with diabetes and obesity are at increased risk of developing disturbances in intestinal function. In this study, we characterized jejunal function in the clinically relevant leptin-deficient ob/ob mouse, a model of diabetes and obesity. We measured transepithelial short circuit current (Isc), across freshly isolated segments of jejunum from 12-week-old ob/ob and lean C57BL/6J (female and male) mice. The basal Isc was significantly decreased (~30%) in the ob/ob mice (66.5±5.7 μA/cm2 [n=20]) (P< 0.05) compared with their lean counterparts (95.1±9.1 μA/cm2 [n=19]). Inhibition with clotrimazole (100 μM, applied bilaterally) was significantly reduced in the ob/ob mice (−7.92%±3.67% [n=15]) (P<0.05) compared with the lean mice (10.44%±7.92% [n=15]), indicating a decreased contribution of Ca2+-activated K+ (KCa) channels in the ob/ob mice. Inhibition with ouabain (100 μM, applied serosally) was significantly reduced in the ob/ob mice (1.40%±3.61%, n=13) (P< 0.05) versus the lean mice (18.93%±3.76% [n=18]), suggesting a potential defect in the Na+/K+-adenosine triphosphate (ATP)ase pump with leptin-deficiency. Expression of cystic fibrosis transmembrane conductance regulatory protein (CFTR) (normalized to glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) was significantly decreased ~twofold (P<0.05) in the ob/ob mice compared with the leans, whilst crypt depth was unchanged. Villi length was significantly increased by ~25% (P<0.05) in the ob/ob mice compared with the leans and was associated with an increase in Villin and GLUT5 expression. GLUT2 and SGLT-1 expression were both unchanged. Our data suggests that reduced basal jejunal Isc in ob/ob mice is likely a consequence of reduced CFTR expression and decreased activity of the basolateral KCa channel and Na+/K+-ATPase. Understanding intestinal dysfunctions in ob/ob jejunum may allow for the development of novel drug targets to treat obesity and diabetes.
PMCID: PMC4112754  PMID: 25092993
intestinal secretion; transport; ob/ob; obese; diabetes; small intestine
5.  Synapse Maturation by Activity-Dependent Ectodomain Shedding of SIRPα 
Nature neuroscience  2013;16(10):10.1038/nn.3516.
Formation of appropriate synaptic connections is critical for proper functioning of the brain. After initial synaptic differentiation, active synapses are stabilized by neural activity-dependent signals to establish functional synaptic connections. However, the molecular mechanisms underlying activity-dependent synapse maturation remain to be elucidated. Here we show that activity-dependent ectodomain shedding of SIRPα mediates presynaptic maturation. Two target-derived molecules, FGF22 and SIRPα, sequentially organize the glutamatergic presynaptic terminals during the initial synaptic differentiation and synapse maturation stages, respectively, in the mouse hippocampus. SIRPα drives presynaptic maturation in an activity-dependent fashion. Remarkably, neural activity cleaves the extracellular domain of SIRPα, and the shed ectodomain, in turn, promotes the maturation of the presynaptic terminal. This process involves CaM kinase, matrix metalloproteinases, and the presynaptic receptor CD47. Finally, SIRPα-dependent synapse maturation has significant impacts on synaptic function and plasticity. Thus, ectodomain shedding of SIRPα is an activity-dependent trans-synaptic mechanism for the maturation of functional synapses.
PMCID: PMC3820962  PMID: 24036914
6.  A mitochondria-targeted mass spectrometry probe to detect glyoxals: implications for diabetes☆ 
Free Radical Biology & Medicine  2014;67(100):437-450.
The glycation of protein and nucleic acids that occurs as a consequence of hyperglycemia disrupts cell function and contributes to many pathologies, including those associated with diabetes and aging. Intracellular glycation occurs after the generation of the reactive 1,2-dicarbonyls methylglyoxal and glyoxal, and disruption of mitochondrial function is associated with hyperglycemia. However, the contribution of these reactive dicarbonyls to mitochondrial damage in pathology is unclear owing to uncertainties about their levels within mitochondria in cells and in vivo. To address this we have developed a mitochondria-targeted reagent (MitoG) designed to assess the levels of mitochondrial dicarbonyls within cells. MitoG comprises a lipophilic triphenylphosphonium cationic function, which directs the molecules to mitochondria within cells, and an o-phenylenediamine moiety that reacts with dicarbonyls to give distinctive and stable products. The extent of accumulation of these diagnostic heterocyclic products can be readily and sensitively quantified by liquid chromatography–tandem mass spectrometry, enabling changes to be determined. Using the MitoG-based analysis we assessed the formation of methylglyoxal and glyoxal in response to hyperglycemia in cells in culture and in the Akita mouse model of diabetes in vivo. These findings indicated that the levels of methylglyoxal and glyoxal within mitochondria increase during hyperglycemia both in cells and in vivo, suggesting that they can contribute to the pathological mitochondrial dysfunction that occurs in diabetes and aging.
•A mitochondria-targeted mass spectrometric probe, MitoG, has been developed to measure glyoxal and methylglyoxal.•Using MitoG we show that mitochondrial glyoxal and methylglyoxal can be measured in hyperglycemic cells.•MitoG can also be used in vivo to infer mitochondrial glyoxal and methylglyoxal production in a mouse model of type I diabetes.•These findings suggest that the accumulation of glyoxal and methylglyoxal within mitochondria may contribute to mitochondrial dysfunction in diabetes.
PMCID: PMC3978666  PMID: 24316194
Mitochondria; Exomarker; Methylglyoxal; Glyoxal; Hyperglycemia; MitoG; Free radicals
7.  A Monte Carlo-based framework enhances the discovery and interpretation of regulatory sequence motifs 
BMC Bioinformatics  2012;13:317.
Discovery of functionally significant short, statistically overrepresented subsequence patterns (motifs) in a set of sequences is a challenging problem in bioinformatics. Oftentimes, not all sequences in the set contain a motif. These non-motif-containing sequences complicate the algorithmic discovery of motifs. Filtering the non-motif-containing sequences from the larger set of sequences while simultaneously determining the identity of the motif is, therefore, desirable and a non-trivial problem in motif discovery research.
We describe MotifCatcher, a framework that extends the sensitivity of existing motif-finding tools by employing random sampling to effectively remove non-motif-containing sequences from the motif search. We developed two implementations of our algorithm; each built around a commonly used motif-finding tool, and applied our algorithm to three diverse chromatin immunoprecipitation (ChIP) data sets. In each case, the motif finder with the MotifCatcher extension demonstrated improved sensitivity over the motif finder alone. Our approach organizes candidate functionally significant discovered motifs into a tree, which allowed us to make additional insights. In all cases, we were able to support our findings with experimental work from the literature.
Our framework demonstrates that additional processing at the sequence entry level can significantly improve the performance of existing motif-finding tools. For each biological data set tested, we were able to propose novel biological hypotheses supported by experimental work from the literature. Specifically, in Escherichia coli, we suggested binding site motifs for 6 non-traditional LexA protein binding sites; in Saccharomyces cerevisiae, we hypothesize 2 disparate mechanisms for novel binding sites of the Cse4p protein; and in Halobacterium sp. NRC-1, we discoverd subtle differences in a general transcription factor (GTF) binding site motif across several data sets. We suggest that small differences in our discovered motif could confer specificity for one or more homologous GTF proteins. We offer a free implementation of the MotifCatcher software package at
PMCID: PMC3542263  PMID: 23181585
Motif; Monte Carlo; ChIP-seq; ChIP-chip; Comparative genomics; MEME; STAMP; TFB
8.  Synthesis and Toll-Like Receptor 4 (TLR4) Activity of Phosphatidylinositol Dimannoside Analogues 
Journal of Medicinal Chemistry  2011;54(20):7268-7279.
A series of five PIM2 analogues were synthesized and tested for their ability to activate primary macrophages and modulate LPS signaling. Structural changes included replacement of the fatty acid esters of the phosphatidyl moiety of PIM2 with the corresponding ether or amide. An AcPIM2 analogue possessing an ether linkage was also prepared. The synthetic methodology utilized an orthogonally protected chiral myo-inositol starting material that was conveniently prepared from myo-inositol in just two steps. Important steps in the synthetic protocols included the regio- and α-selective glycosylation of inositol O-6 and introduction of the phosphodiester utilizing phosphoramidite chemistry. Replacement of the inositol core with a glycerol moiety gave compounds described as phosphatidylglycerol dimannosides (PGM2). Biological testing of these PIM compounds indicated that the agonist activity was TLR4 dependent. An ether linkage increased agonist activity, removal of the inositol ring enhanced antagonist activity and the presence of an additional lipid chain enhanced LPS-induced cytokine production in primary macrophages. Furthermore, the interruption of the LPS-induced TLR4/MD-2 2:2 signaling complex formation by PIM2 represents a previously unidentified mechanism involved in the bioactivity of PIM molecules.
PMCID: PMC3280216  PMID: 21936536
9.  A quasi-experimental evaluation of an interpersonal communication intervention to increase insecticide-treated net use among children in Zambia 
Malaria Journal  2012;11:313.
This paper presents results from an evaluation of the effect of a community health worker (CHW) –based, interpersonal communication campaign (IPC) for increasing insecticide-treated mosquito net (ITN) use among children in Luangwa District, Zambia, an area with near universal coverage of ITNs and moderate to low malaria parasite prevalence.
A quasi-experimental community randomized control trial was conducted from 2008 to 2010. CHWs were the unit of randomization. Cross-sectional data were collected from houses in both 2008 and 2010 using simple random sampling of a complete household enumeration of the district. A difference-in -differences approach was used to analyse the data.
ITN use among children <5 years old in households with ≥1 ITN increased overall from 54% in 2008 to 81% in 2010 (χ2 = 96.3, p <0.01); however, there was no difference in increase between the treatment and control arms in 2010 (p >0.05). ITN use also increased among children five to 14 years old from 37% in 2008 to 68% in 2010. There was no indication that the CHW-based intervention activities had a significant effect on increasing ITN use in this context, over and above what is already being done to disseminate information on the importance of using an ITN to prevent malaria infection.
ITN use increased dramatically in the district between 2008 and 2010. It is likely that IPC activities in general may have contributed to the observed increase in ITN use, as the increased observed in this study was far higher than the increase observed between 2008 and 2010 malaria indicator survey (MIS) estimates. Contamination across control communities, coupled with linear settlement patterns and subsequent behavioural norms related to communication in the area, likely contributed to the observed increase in net use and null effect in this study.
PMCID: PMC3459708  PMID: 22958441
Evaluation; Insecticide-treated net (ITN); Interpersonal communication campaign (IPC); Community health worker (CHW); Malaria; Zambia
10.  Estimates of child deaths prevented from malaria prevention scale-up in Africa 2001-2010 
Malaria Journal  2012;11:93.
Funding from external agencies for malaria control in Africa has increased dramatically over the past decade resulting in substantial increases in population coverage by effective malaria prevention interventions. This unprecedented effort to scale-up malaria interventions is likely improving child survival and will likely contribute to meeting Millennium Development Goal (MDG) 4 to reduce the < 5 mortality rate by two thirds between 1990 and 2015.
The Lives Saved Tool (LiST) model was used to quantify the likely impact that malaria prevention intervention scale-up has had on malaria mortality over the past decade (2001-2010) across 43 malaria endemic countries in sub-Saharan African. The likely impact of ITNs and malaria prevention interventions in pregnancy (intermittent preventive treatment [IPTp] and ITNs used during pregnancy) over this period was assessed.
The LiST model conservatively estimates that malaria prevention intervention scale-up over the past decade has prevented 842,800 (uncertainty: 562,800-1,364,645) child deaths due to malaria across 43 malaria-endemic countries in Africa, compared to a baseline of the year 2000. Over the entire decade, this represents an 8.2% decrease in the number of malaria-caused child deaths that would have occurred over this period had malaria prevention coverage remained unchanged since 2000. The biggest impact occurred in 2010 with a 24.4% decrease in malaria-caused child deaths compared to what would have happened had malaria prevention interventions not been scaled-up beyond 2000 coverage levels. ITNs accounted for 99% of the lives saved.
The results suggest that funding for malaria prevention in Africa over the past decade has had a substantial impact on decreasing child deaths due to malaria. Rapidly achieving and then maintaining universal coverage of these interventions should be an urgent priority for malaria control programmes in the future. Successful scale-up in many African countries will likely contribute substantially to meeting MDG 4, as well as succeed in meeting MDG 6 (Target 1) to halt and reverse malaria incidence by 2015.
PMCID: PMC3350413  PMID: 22455864
11.  A workflow for genome-wide mapping of archaeal transcription factors with ChIP-seq 
Nucleic Acids Research  2012;40(10):e74.
Deciphering the structure of gene regulatory networks across the tree of life remains one of the major challenges in postgenomic biology. We present a novel ChIP-seq workflow for the archaea using the model organism Halobacterium salinarum sp. NRC-1 and demonstrate its application for mapping the genome-wide binding sites of natively expressed transcription factors. This end-to-end pipeline is the first protocol for ChIP-seq in archaea, with methods and tools for each stage from gene tagging to data analysis and biological discovery. Genome-wide binding sites for transcription factors with many binding sites (TfbD) are identified with sensitivity, while retaining specificity in the identification the smaller regulons (bacteriorhodopsin-activator protein). Chromosomal tagging of target proteins with a compact epitope facilitates a standardized and cost-effective workflow that is compatible with high-throughput immunoprecipitation of natively expressed transcription factors. The Pique package, an open-source bioinformatics method, is presented for identification of binding events. Relative to ChIP-Chip and qPCR, this workflow offers a robust catalog of protein–DNA binding events with improved spatial resolution and significantly decreased cost. While this study focuses on the application of ChIP-seq in H. salinarum sp. NRC-1, our workflow can also be adapted for use in other archaea and bacteria with basic genetic tools.
PMCID: PMC3378898  PMID: 22323522
12.  Comparison of Lives Saved Tool model child mortality estimates against measured data from vector control studies in sub-Saharan Africa 
BMC Public Health  2011;11(Suppl 3):S34.
Insecticide-treated mosquito nets (ITNs) and indoor-residual spraying have been scaled-up across sub-Saharan Africa as part of international efforts to control malaria. These interventions have the potential to significantly impact child survival. The Lives Saved Tool (LiST) was developed to provide national and regional estimates of cause-specific mortality based on the extent of intervention coverage scale-up. We compared the percent reduction in all-cause child mortality estimated by LiST against measured reductions in all-cause child mortality from studies assessing the impact of vector control interventions in Africa.
We performed a literature search for appropriate studies and compared reductions in all-cause child mortality estimated by LiST to 4 studies that estimated changes in all-cause child mortality following the scale-up of vector control interventions. The following key parameters measured by each study were applied to available country projections: baseline all-cause child mortality rate, proportion of mortality due to malaria, and population coverage of vector control interventions at baseline and follow-up years.
The percent reduction in all-cause child mortality estimated by the LiST model fell within the confidence intervals around the measured mortality reductions for all 4 studies. Two of the LiST estimates overestimated the mortality reductions by 6.1 and 4.2 percentage points (33% and 35% relative to the measured estimates), while two underestimated the mortality reductions by 4.7 and 6.2 percentage points (22% and 25% relative to the measured estimates).
The LiST model did not systematically under- or overestimate the impact of ITNs on all-cause child mortality. These results show the LiST model to perform reasonably well at estimating the effect of vector control scale-up on child mortality when compared against measured data from studies across a range of malaria transmission settings. The LiST model appears to be a useful tool in estimating the potential mortality reduction achieved from scaling-up malaria control interventions.
PMCID: PMC3231908  PMID: 21501453
13.  Barriers to Insecticide-Treated Mosquito Net Possession 2 Years after a Mass Free Distribution Campaign in Luangwa District, Zambia 
PLoS ONE  2010;5(11):e13129.
Background and Methods
Roll Back Malaria set the goal of 100% of households in malaria endemic countries in Africa owning an insecticide-treated mosquito net (ITN) by 2010. Zambia has used mass free distribution campaigns and distribution through antenatal care (ANC) clinics to achieve high coverage.
Methodology and Principal Findings
We conducted a probability survey of 801 households in 2008 to assess factors associated with households that lacked an ITN after mass distribution. Community perceptions of barriers to ITN access were also obtained from in-depth interviews with household heads that reported not owning an ITN. Nearly 74% of households in Luangwa district reported owning ≥1 ITN. Logistic regression showed households without a child <5 years old during the ITN distribution campaigns were twice as likely to not have an ITN as those with a child <5 during distribution (Adjusted odds ratio (AOR)  = 2.43; 95% confidence interval (CI): 1.67–3.55). Households without a woman who attended an ANC in the past 2 years were more likely to be without ITNs compared to households with a woman who attended an ANC in the past 2 years (AOR  = 1.52; 95% CI: 1.04–2.21). In-depth interviews with heads of households without an ITN revealed that old age was a perceived barrier to receiving an ITN during distribution, and that ITNs wore out before they could be replaced.
Conclusions and Significance
Delivery of a large number of ITNs does not translate directly into 100% household coverage. Due to their design, current ITN distribution strategies may miss households occupied by the elderly and those without children or ANC access. ITN distribution strategies targeting the elderly, those with limited access to distribution points, and others most likely to be missed are necessary if 100% ITN coverage of households is to be achieved.
PMCID: PMC2978084  PMID: 21085711
14.  Large scale physiological readjustment during growth enables rapid, comprehensive and inexpensive systems analysis 
BMC Systems Biology  2010;4:64.
Rapidly characterizing the operational interrelationships among all genes in a given organism is a critical bottleneck to significantly advancing our understanding of thousands of newly sequenced microbial and eukaryotic species. While evolving technologies for global profiling of transcripts, proteins, and metabolites are making it possible to comprehensively survey cellular physiology in newly sequenced organisms, these experimental techniques have not kept pace with sequencing efforts. Compounding these technological challenges is the fact that individual experiments typically only stimulate relatively small-scale cellular responses, thus requiring numerous expensive experiments to survey the operational relationships among nearly all genetic elements. Therefore, a relatively quick and inexpensive strategy for observing changes in large fractions of the genetic elements is highly desirable.
We have discovered in the model organism Halobacterium salinarum NRC-1 that batch culturing in complex medium stimulates meaningful changes in the expression of approximately two thirds of all genes. While the majority of these changes occur during transition from rapid exponential growth to the stationary phase, several transient physiological states were detected beyond what has been previously observed. In sum, integrated analysis of transcript and metabolite changes has helped uncover growth phase-associated physiologies, operational interrelationships among two thirds of all genes, specialized functions for gene family members, waves of transcription factor activities, and growth phase associated cell morphology control.
Simple laboratory culturing in complex medium can be enormously informative regarding the activities of and interrelationships among a large fraction of all genes in an organism. This also yields important baseline physiological context for designing specific perturbation experiments at different phases of growth. The integration of such growth and perturbation studies with measurements of associated environmental factor changes is a practical and economical route for the elucidation of comprehensive systems-level models of biological systems.
PMCID: PMC2880973  PMID: 20470417
15.  Role of Phosphatidylinositol Mannosides in the Interaction between Mycobacteria and DC-SIGN▿ †  
Infection and Immunity  2009;77(10):4538-4547.
The C-type lectin dendritic cell (DC)-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) is the major receptor on DCs for mycobacteria of the Mycobacterium tuberculosis complex. Recently, we have shown that although the mannose caps of the mycobacterial surface glycolipid lipoarabinomannan (ManLAM) are essential for the binding to DC-SIGN, genetic removal of these caps did not diminish the interaction of whole mycobacteria with DC-SIGN and DCs. Here we investigated the role of the structurally related glycolipids phosphatidylinositol mannosides (PIMs) as possible ligands for DC-SIGN. In a binding assay with both synthetic and natural PIMs, DC-SIGN exhibited a high affinity for hexamannosylated PIM6, which contains terminal α(1→2)-linked mannosyl residues identical to the mannose cap on ManLAM, but not for di- and tetramannosylated PIM2 and PIM4, respectively. To determine the role of PIM6 in the binding of whole mycobacteria to DC-SIGN, a mutant strain of M. bovis bacillus Calmette-Guérin deficient in the production of PIM6 (ΔpimE) was created, as well as a double knockout deficient in the production of both PIM6 and the mannose caps on LAM (ΔpimE ΔcapA). Compared to the wild-type strain, both mutant strains bound similarly well to DC-SIGN and DCs. Furthermore, the wild-type and mutant strains induced comparable levels of interleukin-10 and interleukin-12p40 when used to stimulate DCs. Hence, we conclude that, like ManLAM, PIM6 represents a bona fide DC-SIGN ligand but that other, as-yet-unknown, ligands dominate in the interaction between mycobacteria and DCs.
PMCID: PMC2747922  PMID: 19651855
16.  Protective efficacy of interventions for preventing malaria mortality in children in Plasmodium falciparum endemic areas 
International Journal of Epidemiology  2010;39(Suppl 1):i88-i101.
Background Insecticide-treated mosquito nets (ITNs) and indoor-residual spraying (IRS) are recommended strategies for preventing malaria in children. While their impact on all-cause child mortality is well documented, their impact on reducing malaria-attributable mortality has not been quantified. While the impact of intermittent preventive therapy in pregnant women (IPTp) and ITNs in pregnancy for improving birth outcomes is also well established, their impact on preventing neonatal or child mortality has not been quantified.
Methods We performed two systematic literature reviews in Plasmodium falciparum endemic settings; one to estimate the effect of ITNs and IRS on preventing malaria-attributable mortality in children 1–59 months, and another to estimate the effect of ITNs and IPTp on preventing neonatal and child mortality through improvements in birth outcomes.
Results We estimate the protective efficacy (PE) of ITNs and IRS on reducing malaria-attributable mortality 1–59 months to be 55%, with a range of 49–61%, in P. falciparum settings. We estimate malaria prevention interventions in pregnancy (IPTp and ITNs) to have a pooled PE of 35% (95% confidence interval: 23–45%) on reducing the prevalence of low birth weight (LBW) in the first or second pregnancy in areas of stable P. falciparum transmission.
Conclusion This systematic review quantifies the PE of ITNs for reducing malaria-attributable mortality in children, and the PE of IPTp and ITNs during pregnancy for reducing LBW. It is assumed the impact of IRS is equal to that of ITNs on reducing malaria-attributable mortality in children. These data will be used in the Lives Saved Tool (LiST) model for estimating the impact of malaria prevention interventions. These data support the continued scale-up of these malaria prevention interventions in endemic settings that will prevent a considerable number of child deaths due directly and indirectly to malaria.
PMCID: PMC2845865  PMID: 20348132
Systematic review; malaria prevention; child mortality; insecticide-treated mosquito nets; indoor-residual spraying; intermittent preventive therapy in pregnant women
17.  Phenyl 2,3-O-isopropyl­idene-1-thio-α-d-rhamnopyran­oside 
In the title compound, C15H20O4S, a dioxolane ring is fused to the pyran ring of the sugar which carries a thio­phenyl substituent on the anomeric C atom. The dioxolane ring adopts an envelope conformation and the pyran ring system a distorted 4 C 1 chair. The structure is stabilized by O—H⋯O hydrogen bonds, forming centrosymmetric dimers that generate an R 2 2(10) ring motif. Additional C—H⋯O inter­actions form an extended network. Two C atoms of the phenyl ring are disordered over two positions; the site occupancy factors are ca. 0.7 and 0.3.
PMCID: PMC2914986  PMID: 21200806

Results 1-17 (17)