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Find video protocols related to scientific articles indexed in Pubmed.
Altered microRNA expression after infection with human cytomegalovirus leads to TIMP3 downregulation and increased shedding of metalloprotease substrates, including MICA.
J. Immunol.
PUBLISHED: 06-27-2014
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Proteolytic shedding of ligands for the NK group 2D (NKG2D) receptor is a strategy used by tumors to modulate immune recognition by NK cells and cytotoxic T cells. A number of metalloproteases, especially those of the A disintegrin and metalloprotease (ADAM) family, can mediate NKG2D ligand cleavage and this process can be modulated by expression of the thiol isomerase ERp5. In this article, we describe that an increased shedding of the NKG2D ligand MICA is observed postinfection with several strains of human CMV due to an enhanced activity of ADAM17 (TNF-? converting enzyme) and matrix metalloprotease 14 caused by a reduction in the expression of the endogenous inhibitor of metalloproteases tissue inhibitors of metalloproteinase 3 (TIMP3). This decrease in TIMP3 expression correlates with increased expression of a cellular miRNA known to target TIMP3, and we also identify a human CMV-encoded microRNA able to modulate TIMP3 expression. These observations characterize a novel viral strategy to influence the shedding of cell-surface molecules involved in immune response modulation. They also provide an explanation for previous reports of increased levels of various ADAM17 substrates in the serum from patients with CMV disease. Consistent with this hypothesis, we detected soluble MICA in serum of transplant recipients with CMV disease. Finally, these data suggest that it might be worthwhile to prospectively study ADAM17 activity in a larger group of patients to assay whether this might be a useful biomarker to identify patients at risk for development of CMV disease.
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The development of effective behaviour change interventions to support the use of malaria rapid diagnostic tests by Tanzanian clinicians.
Implement Sci
PUBLISHED: 06-09-2014
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Parasitological confirmation is now recommended for all cases of suspected malaria. The roll-out of rapid diagnostic tests (RDTs) is hoped to enable this goal in low resource settings through point of care testing. However, simply making RDTs available has not led to high uptake of the tests or adherence to results by clinicians, with malaria continuing to be overdiagnosed in many settings. We undertook to design an evidence-based intervention package that would be sufficient to support the introduction of RDTs at dispensaries in Tanzania, to be evaluated through the Targeting Artemisinin Combination Therapy (TACT) cluster randomised controlled trial.
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The practice of 'doing' evaluation: lessons learned from nine complex intervention trials in action.
Implement Sci
PUBLISHED: 05-15-2014
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There is increasing recognition among trialists of the challenges in understanding how particular 'real-life' contexts influence the delivery and receipt of complex health interventions. Evaluations of interventions to change health worker and/or patient behaviours in health service settings exemplify these challenges. When interpreting evaluation data, deviation from intended intervention implementation is accounted for through process evaluations of fidelity, reach, and intensity. However, no such systematic approach has been proposed to account for the way evaluation activities may deviate in practice from assumptions made when data are interpreted.
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High levels of sulphadoxine-pyrimethamine resistance Pfdhfr-Pfdhps quintuple mutations: a cross sectional survey of six regions in Tanzania.
Malar. J.
PUBLISHED: 04-13-2014
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In 2006, the first-line anti-malarial drug treatment in Tanzania was changed from sulphadoxine-pyrimethamine (SP) to artemether-lumefantrine (ALu), an artemisinin-based combination (ACT), since when the use of SP has been restricted for intermittent preventive treatment in pregnancy (IPTp). A number of Plasmodium falciparum mutations are known to be associated with resistance to SP, but it is not known if the prevalence of these mutations is increasing or decreasing under the conditions of reduced levels of SP use. This study reports on the current SP resistant quintuple Pfdhfr-Pfdhps mutations in six regions of Tanzania.
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Inpatient child mortality by travel time to hospital in a rural area of Tanzania.
Trop. Med. Int. Health
PUBLISHED: 03-24-2014
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To investigate the association, if any, between child mortality and distance to the nearest hospital.
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Differential induction of apoptosis, interferon signaling, and phagocytosis in macrophages infected with a panel of attenuated and nonattenuated poxviruses.
J. Virol.
PUBLISHED: 03-05-2014
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Due to the essential role macrophages play in antiviral immunity, it is important to understand the intracellular and molecular processes that occur in macrophages following infection with various strains of vaccinia virus, particularly those used as vaccine vectors. Similarities as well as differences were found in macrophages infected with different poxvirus strains, particularly at the level of virus-induced apoptosis and the expression of immunomodulatory genes, as determined by microarray analyses. Interestingly, the attenuated modified vaccinia Ankara virus (MVA) was particularly efficient in triggering apoptosis and beta interferon (IFN-?) secretion and in inducing changes in the expression of genes associated with increased activation of innate immunity, setting it apart from the other five vaccinia virus strains tested. Taken together, these results increase our understanding of how these viruses interact with human macrophages, at the cellular and molecular levels, and suggest mechanisms that may underlie their utility as recombinant vaccine vectors.
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Invasive Salmonella infections in areas of high and low malaria transmission intensity in Tanzania.
Clin. Infect. Dis.
PUBLISHED: 12-13-2013
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Background.?The epidemiology of Salmonella Typhi and invasive non-typhoidal Salmonella (NTS) differs, and prevalence of these pathogens among children in sub-Saharan Africa may vary in relation to malaria transmission intensity. Methods.?We compared the prevalence of bacteremia among febrile pediatric inpatients aged 2 months to 13 years recruited at sites of high and low malaria endemicity in Tanzania. Enrollment at Teule Hospital, the high malaria transmission site, was from June 2006 through May 2007 and at Kilimanjaro Christian Medical Centre (KCMC), the low malaria transmission site, from September 2007 through August 2008. Automated blood culture, malaria microscopy with Giemsa-stained blood films, and HIV testing were performed. Results.?At Teule, 3,639 children were enrolled compared to 467 at KCMC. Smear positive malaria was detected in 2,195 (60.3%) of 3,639 at Teule and 11 (2.4%) of 460 at KCMC (p<0.001). Bacteremia was present in 336 (9.2%) of 3,639 at Teule and 20 (4.3%) of 463 at KCMC (p<0.001). NTS was isolated in 162 (4.5%) of 3,639 children at Teule and 1 (0.2%) of 463 at KCMC (p<0.001). Salmonella Typhi was isolated from 11 (0.3%) patients at Teule and 6 (1.3%) at KCMC (p=0.008). With NTS excluded, the prevalence of bacteremia at Teule was 5.0% and at KCMC 4.1% (p=0.391). Conclusions.?Where malaria transmission was intense, invasive NTS was common and Salmonella Typhi was uncommon, while the inverse was observed at a low malaria transmission site. The relationship between these pathogens, the environment, and the host is a compelling area for further research.
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Trends in chloroquine resistance marker, Pfcrt-K76T mutation ten years after chloroquine withdrawal in Tanzania.
Malar. J.
PUBLISHED: 08-28-2013
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Plasmodium falciparum resistance to anti-malarial drugs remains a major obstacle to the control of malaria. In 2001 Tanzania replaced chloroquine (CQ) with sulphadoxine-pyrimethamine (SP) as first-line drug, which in turn was replaced by artemisinin combination therapy in 2006. SP has however, continued to be used in intermittent preventive treatment of malaria in pregnancy (IPTp) despite reports of high levels of resistance to SP due to the lack of alternatives to SP for IPTp. Recent reports have indicated recovery of CQ-susceptibility in Malawi, Kenya, Mozambique, and Tanzania based on the prevalence of wild types at codon 76 of the Pfcrt gene in indigenous P. falciparum populations. The current prevalence of this Pfcrt-76 CQ resistance marker from six regions of Tanzania mainland is hereby reported.
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Blood glucose as a predictor of mortality in children admitted to the hospital with febrile illness in Tanzania.
Am. J. Trop. Med. Hyg.
PUBLISHED: 07-01-2013
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Data from a prospective study of 3,319 children ages 2 months to 5 years admitted with febrile illness to a Tanzanian district hospital were analyzed to determine the relationship of blood glucose and mortality. Hypoglycemia (blood sugar < 2.5 mmol/L and < 45 mg/dL) was found in 105 of 3,319 (3.2%) children at admission, and low-normal blood glucose (2.5-5 mmol/L and 45-90 mg/dL) was found in 773 of 3,319 (23.3%) children. Mortality was inversely related to admission blood sugar; compared with children with an admission blood glucose of > 5 mmol/L, the adjusted odds of dying were 3.3 (95% confidence interval = 2.1-5.2) and 9.8 (95% confidence interval = 5.1-19.0) among children with admission blood glucose 2.5-5 and < 2.5 mmol/L, respectively. Receiver operating characteristic (ROC) analysis suggested an optimal cutoff for admission blood sugar of < 5 mmol/L in predicting mortality (sensitivity = 57.7%, specificity = 75.2%). A cutoff for admission blood glucose of < 5 mmol/L represents a simple and clinically useful predictor of mortality in children admitted with severe febrile illness to hospital in resource-poor settings.
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A GPI anchor explains the unique biological features of the common NKG2D-ligand allele MICA*008.
Biochem. J.
PUBLISHED: 06-19-2013
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The human MICA (MHC I-related chain A) gene, encoding a ligand for the NKG2D (NKG2-D type II integral membrane protein) receptor, is highly polymorphic. A group of MICA alleles, named MICA 5.1 (prototype, MICA*008), produce a truncated protein due to a nucleotide insertion in the transmembrane domain. These alleles are very frequent in all of the human populations studied and they have different biological properties, compared with full-length alleles, e.g. recruitment into exosomes, which makes them very potent for down-modulating the NKG2D receptor in effector immune cells. Moreover, MICA*008 is not affected by viral immune evasion mechanisms that target other MICA alleles. In the present study, we demonstrate that MICA*008 acquires a GPI (glycosylphosphatidylinositol) anchor and that this modification is responsible for many of the distinct biological features of the truncated MICA alleles, including recruitment of the protein to exosomes. MICA*008 processing is also unusual as it is observed in the endoplasmic reticulum as a Triton™ X-114 soluble protein, partially undergoing GPI modification while the rest is exocytosed, suggesting a new model for MICA*008 release. This is the first report of a GPI-anchored MICA allele. The finding that this modification occurs in both families of human NKG2D ligands, as well as in the murine system, suggests positive pressure to maintain this biochemical feature.
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Exploring mechanisms of excess mortality with early fluid resuscitation: insights from the FEAST trial.
BMC Med
PUBLISHED: 03-14-2013
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Early rapid fluid resuscitation (boluses) in African children with severe febrile illnesses increases the 48-hour mortality by 3.3% compared with controls (no bolus). We explored the effect of boluses on 48-hour all-cause mortality by clinical presentation at enrolment, hemodynamic changes over the first hour, and on different modes of death, according to terminal clinical events. We hypothesize that boluses may cause excess deaths from neurological or respiratory events relating to fluid overload.
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The genetic risk of acute seizures in African children with falciparum malaria.
Epilepsia
PUBLISHED: 03-06-2013
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It is unclear why some children with falciparum malaria develop acute seizures and what determines the phenotype of seizures. We sought to determine if polymorphisms of malaria candidate genes are associated with acute seizures.
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Point-of-care measurement of blood lactate in children admitted with febrile illness to an African District Hospital.
Clin. Infect. Dis.
PUBLISHED: 08-26-2011
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Lactic acidosis is a consistent predictor of mortality owing to severe infectious disease, but its detection in low-income settings is limited to the clinical sign of "deep breathing" because of the lack of accessible technology for its measurement. We evaluated the use of a point-of-care (POC) diagnostic device for blood lactate measurement to assess the severity of illness in children admitted to a district hospital in Tanzania.
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Decreasing incidence of severe malaria and community-acquired bacteraemia among hospitalized children in Muheza, north-eastern Tanzania, 2006-2010.
Malar. J.
PUBLISHED: 08-16-2011
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The annual incidence and temporal trend of severe malaria and community-acquired bacteraemia during a four-year period in Muheza, Tanzania was assessed.
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Association of sub-microscopic malaria parasite carriage with transmission intensity in north-eastern Tanzania.
Malar. J.
PUBLISHED: 08-08-2011
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In malaria endemic areas, individuals are frequently asymptomatic and may be undetected by conventional microscopy or newer, rapid diagnostic tests. Molecular techniques allow a more accurate assessment of this asymptomatic parasite burden, the extent of which is important for malaria control. This study examines the relative prevalence of sub-microscopic level parasite carriage and clonal complexity of infections (multiplicity of infection) over a range of endemicities in a region of north-eastern Tanzania where altitude is an established proxy of malaria transmission. The PCR prevalence was then compared against other measures of transmission intensity collected in the same area.
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Treatment guided by rapid diagnostic tests for malaria in Tanzanian children: safety and alternative bacterial diagnoses.
Malar. J.
PUBLISHED: 06-08-2011
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WHO guidelines for the treatment of young children with suspected malaria have recently changed from presumptive treatment to anti-malarial treatment guided by a blood slide or malaria rapid diagnostic test (RDT). However, there is limited evidence of the safety of this policy in routine outpatient settings in Africa.
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Mortality after fluid bolus in African children with severe infection.
N. Engl. J. Med.
PUBLISHED: 05-26-2011
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The role of fluid resuscitation in the treatment of children with shock and life-threatening infections who live in resource-limited settings is not established.
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Invasive bacterial and fungal infections among hospitalized HIV-infected and HIV-uninfected children and infants in northern Tanzania.
Trop. Med. Int. Health
PUBLISHED: 04-07-2011
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To describe the contribution of paediatric HIV and of HIV co-infections to admissions to a hospital in Moshi, Tanzania, using contemporary laboratory methods.
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Evaluation of a PfHRP2 and a pLDH-based rapid diagnostic test for the diagnosis of severe malaria in 2 populations of African children.
Clin. Infect. Dis.
PUBLISHED: 04-07-2011
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Rapid diagnostic tests (RDTs) now play an important role in the diagnosis of falciparum malaria in many countries where the disease is endemic. Although these tests have been extensively evaluated in uncomplicated falciparum malaria, reliable data on their performance for diagnosing potentially lethal severe malaria is lacking.
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Palmitoylation of MICA, a ligand for NKG2D, mediates its recruitment to membrane microdomains and promotes its shedding.
Eur. J. Immunol.
PUBLISHED: 04-06-2011
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MICA and MICB (MHC-class-I-related chain A/B) are transmembrane proteins expressed in pathological conditions that are ligands for NKG2D, an activating receptor found on cytotoxic lymphocytes. The recognition on target cells of NKG2D ligands leads to the activation of lysis and cytokine secretion by NK cells and T cells. Besides being expressed at the cell surface, MICA/B can be released as soluble proteins. Soluble NKG2D ligands downmodulate expression of the NKG2D receptor on lymphocytes, leading to a diminished cytotoxic response. Prior studies suggested that recruitment of MICA/B molecules to cholesterol-enriched microdomains was an important factor regulating the proteolytic release of these molecules. We now show that recruitment of MICA to these microdomains depends on palmitoylation of two cysteine residues that allow MICA molecules to reside in the membrane in the same domains as caveolin-1. Compared with WT molecules, nonpalmitoylated mutant MICA molecules were shed to the supernatant with low efficiency; however, both WT and mutant MICA were able to trigger NK cell cytotoxicity. These data suggest that the presence of NKG2D ligands at the plasma membrane is sufficient to activate cytotoxicity and reflect the need of different ligands to exploit different cellular pathways to reach the cell surface upon different stress situations.
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Use of an HRP2-based rapid diagnostic test to guide treatment of children admitted to hospital in a malaria-endemic area of north-east Tanzania.
Trop. Med. Int. Health
PUBLISHED: 02-14-2011
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To compare the performance of the Paracheck™ rapid diagnostic test (RDT) with microscopy for diagnosing malaria in hospitalised children.
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Likely health outcomes for untreated acute febrile illness in the tropics in decision and economic models; a Delphi survey.
PLoS ONE
PUBLISHED: 02-03-2011
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Modelling is widely used to inform decisions about management of malaria and acute febrile illnesses. Most models depend on estimates of the probability that untreated patients with malaria or bacterial illnesses will progress to severe disease or death. However, data on these key parameters are lacking and assumptions are frequently made based on expert opinion. Widely diverse opinions can lead to conflicting outcomes in models they inform.
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The human NKG2D ligand ULBP2 can be expressed at the cell surface with or without a GPI anchor and both forms can activate NK cells.
J. Cell. Sci.
PUBLISHED: 01-11-2011
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The activating immune receptor NKG2D binds to several stress-induced ligands that are structurally different. MHC-class-I-related chain (MIC) A/B molecules have a transmembrane domain, whereas most UL16 binding proteins (ULBPs) are glycosylphosphatidylinositol (GPI)-linked molecules. The significance of this variability in membrane anchors is unclear. Here, we demonstrate that ULBP2, but not ULBP1 or ULBP3, can reach the cell surface without the GPI modification. Several proteins are expressed at the cell surface as both transmembrane and GPI-linked molecules, either via alternative splicing or by the expression of linked genes. However, to our knowledge, ULBP2 is the first single mammalian cDNA that can be expressed as either a transmembrane or a GPI-anchored protein. The rate of maturation and the levels of cell surface expression of the non-GPI-linked form were lower than those of the GPI-linked ULBP2. Nonetheless, non-GPI ULBP2 was recognised by NKG2D and triggered NK cell cytotoxicity. These data show that differences in membrane attachment by NKG2D ligands are more important for regulation of their surface expression than for cytotoxic recognition by NKG2D and emphasise that detailed characterisation of the cell biology of individual NKG2D ligands will be necessary to allow targeted modulation of this system.
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Selective induction of host genes by MVA-B, a candidate vaccine against HIV/AIDS.
J. Virol.
PUBLISHED: 06-09-2010
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The aim of this study was to define the effects on antigen-presenting cells of the expression of HIV antigens from an attenuated poxvirus vector. We have analyzed the transcriptional changes in gene expression following infection of human immature monocyte-derived dendritic cells (DC) with recombinant modified vaccinia virus Ankara (MVA) expressing the genes encoding the gp120 and Gag-Pol-Nef antigens of HIV type 1 clade B (referred to as MVA-B) versus parental MVA infection. Using microarray technology and real-time reverse transcription-PCR, we demonstrated that the HIV proteins induced the expression of cytokines, cytokine receptors, chemokines, chemokine receptors, and molecules involved in antigen uptake and processing, including major histocompatibility complex (MHC) genes. Levels of mRNAs for interleukin-1, beta interferon, CCR8, and SCYA20 were higher after HIV antigen production. MVA-B infection also modulated the expression of antigen processing and presentation genes: the gene for MICA was upregulated, whereas those for HLA-DRA and HSPA5 were downregulated. Indeed, the increased expression of the gene for MICA, a glycoprotein related to major histocompatibility complex class I molecules, was shown to enhance the interaction between MVA-B-infected target cells and cytotoxic lymphocytes. The expression profiles of the genes for protein kinases such as JAK1 and IRAK2 were activated after HIV antigen expression. Several genes included in the JAK-STAT and mitogen-activated protein kinase signaling pathways were regulated after HIV antigen expression. Our findings provide the first gene signatures in DC of a candidate MVA-B vaccine expressing four HIV antigens and identified the biological roles of some of the regulatory genes, like that for MICA, which will help in the design of more effective MVA-derived vaccines.
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WHO guidelines for antimicrobial treatment in children admitted to hospital in an area of intense Plasmodium falciparum transmission: prospective study.
BMJ
PUBLISHED: 04-01-2010
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To assess the performance of WHOs "Guidelines for care at the first-referral level in developing countries" in an area of intense malaria transmission and identify bacterial infections in children with and without malaria.
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Evaluation of the Widal tube agglutination test for the diagnosis of typhoid fever among children admitted to a rural hdospital in Tanzania and a comparison with previous studies.
BMC Infect. Dis.
PUBLISHED: 03-23-2010
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The diagnosis of typhoid fever is confirmed by culture of Salmonella enterica serotype Typhi (S. typhi). However, a more rapid, simpler, and cheaper diagnostic method would be very useful especially in developing countries. The Widal test is widely used in Africa but little information exists about its reliability.
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Patient costs for paediatric hospital admissions in Tanzania: a neglected burden?
Health Policy Plan
PUBLISHED: 02-02-2010
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Tanzania has a policy of free provision of inpatient care for young children in order to promote timely access and thus reduce the current levels of mortality. However, little is known about out-of-pocket costs that may be incurred by families in seeking care for sick children. We conducted this study to identify the magnitude of these costs in relation to family income.
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Invasive salmonellosis among children admitted to a rural Tanzanian hospital and a comparison with previous studies.
PLoS ONE
PUBLISHED: 01-27-2010
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The importance of invasive salmonellosis in African children is well recognized but there is inadequate information on these infections. We conducted a fever surveillance study in a Tanzanian rural hospital to estimate the case fraction of invasive salmonellosis among pediatric admissions, examine associations with common co-morbidities and describe its clinical features. We compared our main findings with those from previous studies among children in sub-Saharan Africa.
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Differential mechanisms of shedding of the glycosylphosphatidylinositol (GPI)-anchored NKG2D ligands.
J. Biol. Chem.
PUBLISHED: 01-14-2010
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Tumor cells release NKG2D ligands to evade NKG2D-mediated immune surveillance. The purpose of our investigation was to explore the cellular mechanisms of release used by various members of the ULBP family. Using biochemical and cellular approaches in both transfectant systems and tumor cell lines, this paper shows that ULBP1, ULBP2, and ULBP3 are released from cells with different kinetics and by distinct mechanisms. Whereas ULBP2 is mainly shed by metalloproteases, ULBP3 is abundantly released as part of membrane vesicles known as exosomes. Interestingly, exosomal ULBP3 protein is much more potent for down-modulation of the NKG2D receptor than soluble ULBP2 protein. This is the first report showing functionally relevant differences in the biochemistry of the three members of the ULBP family and confirms that in depth study of the biochemical features of individual NKG2D ligands will be necessary to understand and manipulate the biology of these proteins for therapy.
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Natural killer cell cytotoxicity is suppressed by exposure to the human NKG2D ligand MICA*008 that is shed by tumor cells in exosomes.
Cancer Res.
PUBLISHED: 01-12-2010
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The MHC class I-related chain (MIC) A and MICB ligands for the activating receptor NKG2D can be shed from tumor cells, and the presence of these soluble molecules in sera is related with compromised immune response and progression of disease. Recently, thiol disulphide isomerases and members of the ADAM (a disintegrin and metalloproteinase) gene family were identified as key enzymes in mediating MICA/B shedding from cells. Here, we report shedding of the most frequently expressed MICA allele in human populations (MICA*008) into exosomes, small membrane vesicles that are secreted upon fusion with the plasma membrane. Although similar to other MICA/B molecules in the extracellular domain, the predicted transmembrane and cytoplasmic domains of MICA*008 are quite different, and this difference seemed to be critical for the mode of release from tumor cells. Treatment of natural killer (NK) cells with exosomes containing MICA*008 molecules not only triggered downregulation of NKG2D from the cell surface but also provoked a marked reduction in NK cytotoxicity that is independent of NKG2D ligand expression by the target cell. Our findings reveal a mechanism of NK suppression in cancer that may facilitate immune escape and progression.
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Azithromycin plus artesunate versus artemether-lumefantrine for treatment of uncomplicated malaria in Tanzanian children: a randomized, controlled trial.
Clin. Infect. Dis.
PUBLISHED: 09-23-2009
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Acute febrile illness is the most common cause of outpatient attendance and mortality for children in Africa. Malaria and bacterial disease are difficult to differentiate with limited diagnostic facilities. Combinations of antibiotics and antimalarials are potentially attractive for treatment of the syndrome. Azithromycin plus artesunate (AT+AS) is an effective antimalarial combination for adults in Asia.
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Quality of paediatric blood transfusions in two district hospitals in Tanzania: a cross-sectional hospital based study.
BMC Pediatr
PUBLISHED: 08-14-2009
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Blood transfusion (BT) can be lifesaving for children; however, monitoring the quality of BT is important. The current study describes the quality of paediatric BT delivered in two district hospitals in north-east Tanzania in order to identify areas for quality assurance and improvement in the administration of BT.
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Out with the old, in with the new: the utility of rapid diagnostic tests for malaria diagnosis in Africa.
Trans. R. Soc. Trop. Med. Hyg.
PUBLISHED: 07-28-2009
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After many years of development, rapid diagnostic tests (RDTs) for malaria are now being rolled out in many African countries to support the introduction of artemisinin-based combination therapies (ACT). RDTs create new opportunities both for improved care and as research tools, but it is important that the research agenda continues to address the many challenges, both operational and technical, that still need to be met. Here we review what is known and what new evidence is needed to maximise the utility of RDTs in Africa.
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Conflicting priorities: evaluation of an intervention to improve nurse-parent relationships on a Tanzanian paediatric ward.
Hum Resour Health
PUBLISHED: 06-23-2009
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Patient, or parent/guardian, satisfaction with health care provision is important to health outcomes. Poor relationships with health workers, particularly with nursing staff, have been reported to reduce satisfaction with care in Africa. Participatory research approaches such as the Health Workers for Change initiative have been successful in improving provider-client relationships in various developing country settings, but have not yet been reported in the complex environment of hospital wards. We evaluated the HWC approach for improving the relationship between nurses and parents on a paediatric ward in a busy regional hospital in Tanzania.
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Immunophoretic rapid diagnostic tests as a source of immunoglobulins for estimating malaria sero-prevalence and transmission intensity.
Malar. J.
PUBLISHED: 04-27-2009
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Sero-epidemiological methods are being developed as a tool for rapid assessment of malaria transmission intensity. Simple blood collection methods for use in field settings will make this more feasible. This paper describes validation of such a method, by analysing immunoglobulins from blood retained within immunophoretic rapid diagnostic tests (RDTs) for Plasmodium falciparum. RDTs are now widely used for the diagnosis of malaria and estimation of parasite rates, and this method represents a further use for these devices in malaria control.
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Genome-wide and fine-resolution association analysis of malaria in West Africa.
Nat. Genet.
PUBLISHED: 04-27-2009
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We report a genome-wide association (GWA) study of severe malaria in The Gambia. The initial GWA scan included 2,500 children genotyped on the Affymetrix 500K GeneChip, and a replication study included 3,400 children. We used this to examine the performance of GWA methods in Africa. We found considerable population stratification, and also that signals of association at known malaria resistance loci were greatly attenuated owing to weak linkage disequilibrium (LD). To investigate possible solutions to the problem of low LD, we focused on the HbS locus, sequencing this region of the genome in 62 Gambian individuals and then using these data to conduct multipoint imputation in the GWA samples. This increased the signal of association, from P = 4 × 10(-7) to P = 4 × 10(-14), with the peak of the signal located precisely at the HbS causal variant. Our findings provide proof of principle that fine-resolution multipoint imputation, based on population-specific sequencing data, can substantially boost authentic GWA signals and enable fine mapping of causal variants in African populations.
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Equity and coverage of insecticide-treated bed nets in an area of intense transmission of Plasmodium falciparum in Tanzania.
Malar. J.
PUBLISHED: 04-16-2009
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There is no clear consensus on the most sustainable and effective distribution strategy for insecticide treated bed nets (ITNs). Tanzania has been a leader in social marketing but it is still not clear if this can result in high and equitable levels of coverage.
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Brief residence at the plasma membrane of the MHC class I-related chain B is due to clathrin-mediated cholesterol-dependent endocytosis and shedding.
J. Immunol.
PUBLISHED: 04-04-2009
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Recognition of MHC class I-related chain (MIC) molecules on the surface of target cells by the activating receptor NKG2D leads to their lysis by immune effector cells. Up-regulation of NKG2D ligands is broadly related to stress, although the detailed molecular mechanisms that control the presence of these molecules at the plasma membrane are unclear. To investigate the posttranslational mechanisms that control surface expression of the human NKG2D ligand MICB, we studied the subcellular localization and trafficking of this molecule. We found that in several cellular systems, the expression of MICB molecules on the cell surface is accompanied by an intracellular accumulation of the molecule in the trans-Golgi network and late endosome-related compartments. Surprisingly, MICB has a much shorter half-life at the plasma membrane than MHC molecules and this depends on both recycling to internal compartments and shedding to the extracellular medium. Internalization of MICB depends partially on clathrin, but importantly, the lipid environment of the membrane also plays a crucial role in this process. We suggest that the brief residence of MICB at the plasma membrane modulates, at least in part, the function of this molecule in the immune system.
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Motivation, money and respect: a mixed-method study of Tanzanian non-physician clinicians.
Soc Sci Med
PUBLISHED: 03-28-2009
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Poor quality of care is a major concern in low-income countries, and is in part attributed to low motivation of healthcare workers. Non-physician clinicians (mid-level cadre healthworkers) are central to healthcare delivery in half of the countries in Africa, but while much is expected from these clinicians, little is known about their expectations and motivation to perform well. Understanding what motivates these healthworkers in their work is essential to provide an empirical base for policy decisions to improve quality of healthcare. In 2006-2007, we conducted a mixed-method study to evaluate factors affecting motivation, including reasons for varying levels of motivation, amongst these clinicians in Tanzania. Using a conceptual framework of internal and environmental domains known to influence healthworker motivation in low-income countries, developed from existing literature, we observed over 2000 hospital consultations, interviewed clinicians to evaluate job satisfaction and morale, then designed and implemented a survey instrument to measure work motivation in clinical settings. Thematic analysis (34 interviews, one focus group) identified social status expectations as fundamental to dissatisfaction with financial remuneration, working environments and relationships between different clinical cadres. The survey included all clinicians working in routine patient care at 13 hospitals in the area; 150 returned sufficiently complete data for psychometric analysis. In regression, higher salary was associated with internal motivation; amongst higher earners, motivation was also associated with higher qualification and salary enhancements. Salary was thus a clear prerequisite for motivation. Our results are consistent with the hypothesis that non-salary motivators will only have an effect where salary requirements are satisfied. As well as improvements to organisational management, we put forward the case for the professionalization of non-physician clinicians.
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The traffic of the NKG2D/Dap10 receptor complex during natural killer (NK) cell activation.
J. Biol. Chem.
PUBLISHED: 03-26-2009
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NKG2D is an important activating receptor for triggering the NK cell cytotoxic activity, although chronic engagement of specific ligands by NKG2D is also known to provoke decreased cell surface expression of the receptor and compromised NK cell function. We have studied the dynamics of surface NKG2D expression and how exposure to the specific ligand major histocompatibility complex class I chain-related molecule B (MICB) affects receptor traffic and fate. While in the NKL cell line and "resting" NK cells NKG2D was found principally at the cell surface, in activated primary NK cells an intracellular pool of receptor could also be found recycling to the plasma membrane. Exposure of NK cells to targets expressing MICB resulted in degradation of approximately 50% of total NKG2D protein and lysosomal degradation of the DAP10 adaptor molecule. Consistent with these observations, confocal microscopy experiments demonstrated that DAP10 trafficked to secretory lysosomes in both transfected NKL cells and in activated primary NK cells upon interaction with MICB-expressing target cells. Interestingly, polarization to the synapse of secretory lysosomes containing DAP10 was also observed. The implications of the intracellular traffic of the NKG2D/DAP10 receptor complex for NK cell activation are discussed. We propose that the rapid degradation of NKG2D/DAP10 observed coincident with recruitment of the receptor to the cytotoxic immune synapse may explain the loss of NKG2D receptor expression after chronic exposure to NKG2D ligands.
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A screening instrument to measure the prevalence of neurological disability in resource-poor settings.
Neuroepidemiology
PUBLISHED: 03-25-2009
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Very little is known about the prevalence of neurological morbidity in Africa. Much of this is due to the difficulty in performing epidemiological surveys in these settings. A screening instrument to measure neurological disease in resource-poor settings was designed by the World Health Organization in 1981, but several problems with it have subsequently been recognized.
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Assessment of urinary concentrations of hepcidin provides novel insight into disturbances in iron homeostasis during malarial infection.
J. Infect. Dis.
PUBLISHED: 03-07-2009
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Disturbances in iron homeostasis are frequently observed in individuals with malaria. To study the effect of malaria and its treatment on iron homeostasis and to provide a mechanistic explanation for observed alterations in iron distribution, we studied the course of the iron regulatory hormone hepcidin in anemic Tanzanian children with febrile Plasmodium falciparum malaria. Before initiation of antimalarial treatment, urinary concentrations of hepcidin were strongly elevated and were associated with iron maldistribution, as was suggested by the presence of hypoferremia and high serum concentrations of ferritin. Antimalarial treatment resulted in a rapid decrease in urinary concentrations of hepcidin and reversal of the hypoferremia. Exploration of regulatory pathways of hepcidin production by analysis of iron, erythropoietic, and inflammatory indices suggested that reduced erythropoietic activity and inflammation stimulated hepcidin production. We conclude that high concentrations of hepcidin explain the observed disturbances in host iron homeostasis associated with malaria and may contribute to malarial anemia and an impaired erythropoietic response to iron supplementation.
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Cutting edge: the metalloproteinase ADAM17/TNF-alpha-converting enzyme regulates proteolytic shedding of the MHC class I-related chain B protein.
J. Immunol.
PUBLISHED: 02-14-2009
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MHC class I-related chain (MIC) A/B are transmembrane proteins expressed in pathological conditions that are ligands for the activating receptor NKG2D found on cytotoxic lymphocytes. Soluble NKG2D ligands are detected in sera of patients suffering from multiple types of cancer where they are associated with reduced levels of receptor expression and compromised function of NK and CTLs. In this study, we report the identification of a metalloproteinase involved in the cleavage process of MIC; inhibition and knockdown of ADAM17/TACE blocks the shedding of these proteins. Strikingly, the recruitment of both enzyme and substrate to detergent-resistant membrane microdomains is crucial for efficient proteolysis. These findings provide a novel insight into the molecular mechanisms of MIC shedding.
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Abandoning presumptive antimalarial treatment for febrile children aged less than five years--a case of running before we can walk?
PLoS Med.
PUBLISHED: 01-09-2009
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Current guidelines recommend that all fever episodes in African children be treated presumptively with antimalarial drugs. But declining malarial transmission in parts of sub-Saharan Africa, declining proportions of fevers due to malaria, and the availability of rapid diagnostic tests mean it may be time for this policy to change. This debate examines whether enough evidence exists to support abandoning presumptive treatment and whether African health systems have the capacity to support a shift toward laboratory-confirmed rather than presumptive diagnosis and treatment of malaria in children under five.
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Age patterns of severe paediatric malaria and their relationship to Plasmodium falciparum transmission intensity.
Malar. J.
PUBLISHED: 01-07-2009
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The understanding of the epidemiology of severe malaria in African children remains incomplete across the spectrum of Plasmodium falciparum transmission intensities through which communities might expect to transition, as intervention coverage expands.
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Population pharmacokinetic and pharmacodynamic properties of intramuscular quinine in Tanzanian children with severe Falciparum malaria.
Antimicrob. Agents Chemother.
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Although artesunate is clearly superior, parenteral quinine is still used widely for the treatment of severe malaria. A loading-dose regimen has been recommended for 30 years but is still often not used. A population pharmacokinetic study was conducted with 75 Tanzanian children aged 4 months to 8 years with severe malaria who received quinine intramuscularly; 69 patients received a loading dose of 20 mg quinine dihydrochloride (salt)/kg of body weight. Twenty-one patients had plasma quinine concentrations detectable at baseline. A zero-order absorption model with one-compartment disposition pharmacokinetics described the data adequately. Body weight was the only significant covariate and was implemented as an allometric function on clearance and volume parameters. Population pharmacokinetic parameter estimates (and percent relative standard errors [%RSE]) of elimination clearance, central volume of distribution, and duration of zero-order absorption were 0.977 liters/h (6.50%), 16.7 liters (6.39%), and 1.42 h (21.5%), respectively, for a typical patient weighing 11 kg. Quinine exposure was reduced at lower body weights after standard weight-based dosing; there was 18% less exposure over 24 h in patients weighing 5 kg than in those weighing 25 kg. Maximum plasma concentrations after the loading dose were unaffected by body weight. There was no evidence of dose-related drug toxicity with the loading dosing regimen. Intramuscular quinine is rapidly and reliably absorbed in children with severe falciparum malaria. Based on these pharmacokinetic data, a loading dose of 20 mg salt/kg is recommended, provided that no loading dose was administered within 24 h and no routine dose was administered within 12 h of admission. (This study has been registered with Current Controlled Trials under registration number ISRCTN 50258054.).
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Quality of malaria microscopy in 12 district hospital laboratories in Tanzania.
Pathog Glob Health
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The WHO recommendation for parasitological diagnosis of malaria wherever possible is challenged by evidence of poor-quality microscopy in African hospitals but the reasons are not clear.
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A rapid assessment of the quality of neonatal healthcare in Kilimanjaro region, northeast Tanzania.
BMC Pediatr
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While child mortality is declining in Africa there has been no evidence of a comparable reduction in neonatal mortality. The quality of inpatient neonatal care is likely a contributing factor but data from resource limited settings are few. The objective of this study was to assess the quality of neonatal care in the district hospitals of the Kilimanjaro region of Tanzania.
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Novel, potentially zoonotic paramyxoviruses from the African straw-colored fruit bat Eidolon helvum.
J. Virol.
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Bats carry a variety of paramyxoviruses that impact human and domestic animal health when spillover occurs. Recent studies have shown a great diversity of paramyxoviruses in an urban-roosting population of straw-colored fruit bats in Ghana. Here, we investigate this further through virus isolation and describe two novel rubulaviruses: Achimota virus 1 (AchPV1) and Achimota virus 2 (AchPV2). The viruses form a phylogenetic cluster with each other and other bat-derived rubulaviruses, such as Tuhoko viruses, Menangle virus, and Tioman virus. We developed AchPV1- and AchPV2-specific serological assays and found evidence of infection with both viruses in Eidolon helvum across sub-Saharan Africa and on islands in the Gulf of Guinea. Longitudinal sampling of E. helvum indicates virus persistence within fruit bat populations and suggests spread of AchPVs via horizontal transmission. We also detected possible serological evidence of human infection with AchPV2 in Ghana and Tanzania. It is likely that clinically significant zoonotic spillover of chiropteran paramyxoviruses could be missed throughout much of Africa where health surveillance and diagnostics are poor and comorbidities, such as infection with HIV or Plasmodium sp., are common.
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Candidate human genetic polymorphisms and severe malaria in a Tanzanian population.
PLoS ONE
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Human genetic background strongly influences susceptibility to malaria infection and progression to severe disease and death. Classical genetic studies identified haemoglobinopathies and erythrocyte-associated polymorphisms, as protective against severe disease. High throughput genotyping by mass spectrometry allows multiple single nucleotide polymorphisms (SNPs) to be examined simultaneously. We compared the prevalence of 65 human SNPs, previously associated with altered risk of malaria, between Tanzanian children with and without severe malaria. Five hundred children, aged 1-10 years, with severe malaria were recruited from those admitted to hospital in Muheza, Tanzania and compared with matched controls. Genotyping was performed by Sequenom MassArray, and conventional PCR was used to detect deletions in the alpha-thalassaemia gene. SNPs in two X-linked genes were associated with altered risk of severe malaria in females but not in males: heterozygosity for one or other of two SNPs in the G6PD gene was associated with protection from all forms of severe disease whilst two SNPs in the gene encoding CD40L were associated with respiratory distress. A SNP in the adenyl cyclase 9 (ADCY9) gene was associated with protection from acidosis whilst a polymorphism in the IL-1? gene (IL1A) was associated with an increased risk of acidosis. SNPs in the genes encoding IL-13 and reticulon-3 (RTN3) were associated with increased risk of cerebral malaria. This study confirms previously known genetic associations with protection from severe malaria (HbS, G6PD). It identifies two X-linked genes associated with altered risk of severe malaria in females, identifies mutations in ADCY9, IL1A and CD40L as being associated with altered risk of severe respiratory distress and acidosis, both of which are characterised by high serum lactate levels, and also identifies novel genetic associations with severe malaria (TRIM5) and cerebral malaria(IL-13 and RTN3). Further studies are required to test the generality of these associations and to understand their functional consequences.
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Defining falciparum-malaria-attributable severe febrile illness in moderate-to-high transmission settings on the basis of plasma PfHRP2 concentration.
J. Infect. Dis.
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In malaria-endemic settings, asymptomatic parasitemia complicates the diagnosis of malaria. Histidine-rich protein 2 (HRP2) is produced by Plasmodium falciparum, and its plasma concentration reflects the total body parasite burden. We aimed to define the malaria-attributable fraction of severe febrile illness, using the distributions of plasma P. falciparum HRP2 (PfHRP2) concentrations from parasitemic children with different clinical presentations.
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Human NKG2D-ligands: cell biology strategies to ensure immune recognition.
Front Immunol
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Immune recognition mediated by the activating receptor NKG2D plays an important role for the elimination of stressed cells, including tumors and virus-infected cells. On the other hand, the ligands for NKG2D can also be shed into the sera of cancer patients where they weaken the immune response by downmodulating the receptor on effector cells, mainly NK and T cells. Although both families of NKG2D-ligands, major histocompatibility complex class I-related chain (MIC) A/B and UL16 binding proteins (ULBPs), are related to MHC molecules and their expression is increased after stress, many differences are observed in terms of their biochemical properties and cell trafficking. In this paper, we summarize the variety of NKG2D-ligands and propose that selection pressure has driven evolution of diversity in their trafficking and shedding, but not receptor binding affinity. However, it is also possible to identify functional properties common to individual ULBP molecules and MICA/B alleles, but not generally conserved within the MIC or ULBP families. These characteristics likely represent examples of convergent evolution for efficient immune recognition, but are also attractive targets for pathogen immune evasion strategies. Categorization of NKG2D-ligands according to their biological features, rather than their genetic family, may help to achieve a better understanding of NKG2D-ligand association with disease.
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Severe febrile illness in adult hospital admissions in Tanzania: a prospective study in an area of high malaria transmission.
Trans. R. Soc. Trop. Med. Hyg.
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Severe febrile illness is a major cause of adult hospital admission in Africa. Studies of non-malarial fever come largely from children or from high HIV prevalence settings. This prospective study of adult admissions with severe febrile illness in a malaria-endemic area with moderate/low HIV prevalence investigated admission diagnosis as well as final diagnosis based on results of investigations. Severe malaria was the admission diagnosis in 148/198 (74.7%) cases. Plasmodium falciparum was identified in 38/188 (20.2%) admissions and 26/198 (13.1%) were bacteraemic, with 13/25 (52%) prescribed empirical antibiotics. HIV was equally common among those with (16/37; 43.2%) and without P. falciparum (50/138; 36.2%) (p=0.44). In 6/22 (27.3%) deaths, blood cultures were positive for a pathogen, with Streptococcus pneumoniae, Escherichia coli and non-Typhi Salmonella predominating. Chest radiography was suspicious for bacterial/mycobacterial disease in 5/22 additional deaths. Systemic inflammatory response syndrome criteria were more sensitive but less specific than WHO severe malaria criteria for predicting mortality. Malaria is overdiagnosed in adults with severe febrile illness and was not associated with mortality in the absence of co-infection in this high-incidence setting. Adults with severe febrile illness should be tested for malaria and HIV using rapid, sensitive tests. Early antibiotic use should be promoted. Improved diagnostics for invasive bacterial disease are needed.
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Diagnosing severe falciparum malaria in parasitaemic African children: a prospective evaluation of plasma PfHRP2 measurement.
PLoS Med.
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In African children, distinguishing severe falciparum malaria from other severe febrile illnesses with coincidental Plasmodium falciparum parasitaemia is a major challenge. P. falciparum histidine-rich protein 2 (PfHRP2) is released by mature sequestered parasites and can be used to estimate the total parasite burden. We investigated the prognostic significance of plasma PfHRP2 and used it to estimate the malaria-attributable fraction in African children diagnosed with severe malaria.
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Utility of rapid antibody tests to exclude HIV-1 infection among infants and children aged <18 months in a low-resource setting.
J. Clin. Virol.
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Excluding HIV infection among infants and young children in resource-poor settings where nucleic acid amplification tests (NAAT) are not routinely available remains a considerable challenge.
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Sequence variation does not confound the measurement of plasma PfHRP2 concentration in African children presenting with severe malaria.
Malar. J.
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Plasmodium falciparum histidine-rich protein PFHRP2 measurement is used widely for diagnosis, and more recently for severity assessment in falciparum malaria. The Pfhrp2 gene is highly polymorphic, with deletion of the entire gene reported in both laboratory and field isolates. These issues potentially confound the interpretation of PFHRP2 measurements.
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Nasopharyngeal carriage of Streptococcus pneumoniae: prevalence and risk factors in HIV-positive children in Tanzania.
Int. J. Infect. Dis.
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Pneumococcal colonization of the nasopharynx is especially common in young children and is a pre-requisite for pneumococcal disease. Those with immunosuppression, such as HIV, are at higher risk of colonization and disease, especially at older ages. Currently, vaccination schedules are only offered to children under 6 months of age, despite the large impact of pneumococcal disease in older unvaccinated children with HIV. We conducted a study to assess the prevalence of, and risk factors for, pneumococcal carriage in HIV-positive children aged <15 years.
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