Molecular and Biochemical Parasitology

Liverpool, United Kingdom

Molecular and Biochemical Parasitology

Liverpool, United Kingdom

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Mendonca L.R.,Federal University of Bahia | Veiga R.V.,Federal University of Bahia | Dattoli V.C.C.,Federal University of Bahia | Figueiredo C.A.,Federal University of Bahia | And 7 more authors.
PLoS Neglected Tropical Diseases | Year: 2012

Background: Toxocara canis and T. cati are parasites of dogs and cats, respectively, that infect humans and cause human toxocariasis. Infection may cause asthma-like symptoms but is often asymptomatic and is associated with a marked eosinophilia. Previous epidemiological studies indicate that T. canis infection may be associated with the development of atopy and asthma. Objectives: To investigate possible associations between Toxocara spp. seropositivity and atopy and childhood wheezing in a population of children living in non-affluent areas of a large Latin American city. Methods: The study was conducted in the city of Salvador, Brazil. Data on wheezing symptoms were collected by questionnaire, and atopy was measured by the presence of aeroallergen-specific IgE (sIgE). Skin prick test (SPT), total IgE and peripheral eosinophilia were measured. Toxocara seropositivity was determined by the presence of anti-Toxocara IgG antibodies, and intestinal helminth infections were determined by stool microscopy. Findings: Children aged 4 to 11 years were studied, of whom 47% were seropositive for anti-Toxocara IgG; eosinophilia >4% occurred in 74.2% and >10% in 25.4%; 59.6% had elevated levels of total IgE; 36.8% had sIgE≥0.70 kU/L and 30.4% had SPT for at least one aeroallergen; 22.4% had current wheezing symptoms. Anti-Toxocara IgG was positively associated with elevated eosinophils counts, total IgE and the presence of specific IgE to aeroallergens but was inversely associated with skin prick test reactivity. Conclusion: The prevalence of Toxocara seropositivity was high in the studied population of children living in conditions of poverty in urban Brazil. Toxocara infection, although associated with total IgE, sIgE and eosinophilia, may prevent the development of skin hypersensitivity to aeroallergens, possibly through increased polyclonal IgE and the induction of a modified Th2 immune reaction. © 2012 Mendonça et al.


Hastings I.M.,Molecular and Biochemical Parasitology | Nsanzabana C.,University of California at San Francisco | Smith T.A.,Swiss Tropical and Public Health Institute
American Journal of Tropical Medicine and Hygiene | Year: 2010

We compare, contrast, and evaluate methods to quantify genetic markers of antimalarial drug resistance. Frequency estimates should be reported along with crude prevalence. There are four main potential methods to estimate frequencies in blood samples: simple counting of single nucleotide polymorphisms (SNPs) and haplotypes in samples with multiplicity of infection (MOI) = 1; SNP counting in samples with MOI ≤ 2; SNP and haplotypes counting in samples with unambiguous genotypes; statistical inference using SNP and MOI data from all samples. Large differences between the methods became apparent when analyzing field data with high MOI. Simple counting dramatically reduced sample size and estimate precision, and we show that analysis of unambiguous samples is biased, leaving maximum likelihood or similar statistical inference as the only practical option. It is essential to account for genotyping missing minor clones; ignoring this phenomenon resulted in a 2-fold underestimation of SNPs and haplotypes present at low frequencies. Copyright © 2010 by The American Society of Tropical Medicine and Hygiene.


Figueiredo C.A.,Federal University of Bahia | Amorim L.D.,Federal University of Bahia | Alcantara-Neves N.M.,Federal University of Bahia | Matos S.M.A.,Federal University of Bahia | And 4 more authors.
Journal of Allergy and Clinical Immunology | Year: 2013

Background: It has been proposed that improved hygiene and reduced experience of infections in childhood influences the development of allergic diseases. The mechanisms by which the hygiene operates are not well established but are underpinned by two apparently incompatible immunologic paradigms, the balance of TH1 versus TH2 cytokines and IL-10-mediated regulation of TH2 cytokines. Objective: This study defined immunologic phenotypes with the use of latent class analysis and investigated their associations with environmental factors, markers of allergy and asthma, in a Latin American population. Methods: We studied 1127 children living in urban Brazil. Data on wheeze and environmental exposures were collected with standardized questionnaires. Atopy was measured by specific IgE in serum and skin prick test reactivity to aeroallergens. Cytokines were measured in culture after the stimulation of peripheral blood leukocytes with mitogen. Infections with pathogens were assessed by serology and stool examinations. Children were classified as having high or low burden of infection. Latent class analysis was used to identify immune phenotypes on the basis of cytokine production. Logistic regression was used to evaluate the adjusted effects of environment and burden of infection on the immunologic phenotypes and the effect of the phenotypes on atopy and asthma. Results: Three phenotypes were identified, labeled underresponsive, intermediate, and responsive. Children of more educated mothers, living in improved environmental conditions, and with a low burden of infection were significantly more likely to have the responsive phenotype. The responsive phenotype was significantly associated with an increased prevalence of atopy but not asthma. Conclusion: Our findings contribute to a better understanding of the immune mechanisms by which the hygiene hypothesis operates in urban Latin America. © 2013 American Academy of Allergy, Asthma & Immunology.


Tamarozzi F.,Molecular and Biochemical Parasitology | Tendongfor N.,University of Buea | Tendongfor N.,Research Foundation for Tropical Diseases and Environment | Enyong P.A.,Research Foundation for Tropical Diseases and Environment | And 6 more authors.
Parasites and Vectors | Year: 2012

Background: Anti-Wolbachia treatment with doxycycline is effective in sterilising and killing adult Onchocerca volvulus nematodes, proving superior to ivermectin and of great potential as an alternative approach for the treatment and control of onchocerciasis, particularly in areas of Loa loa co-endemicity. Nevertheless, the length of the required treatment poses potential logistical problems and risk of poor compliance, raising a barrier to the use of doxycycline in Mass Drug Administration (MDA) strategies. In 2007 and 2008 a feasibility trial of community-directed treatment with doxycycline was carried out in two health districts in Cameroon, co-endemic for O. volvulus and L. loa. With 17,519 eligible subjects, the therapeutic coverage was 73.8% with 97.5% compliance, encouraging the feasibility of using doxycycline community-directed delivery in restricted populations of this size. The current study evaluated the effectiveness of this community-directed delivery of doxycycline four years after delivery. Findings. Infection with O. volvulus was evaluated by skin biopsy and nodule palpation. Of the 507 subjects recruited, 375 had completed the treatment with doxycycline followed by one or two rounds of annual ivermectin MDA and 132 received one or two rounds of annual ivermectin MDA alone. Statistically significant lower microfilarial prevalence (17.0% [doxycycline plus ivermectin group], 27.0% [ivermectin only group], p = 0.014) and load (p = 0.012) were found in people that had received doxycycline followed by ivermectin compared to those who received ivermectin only. Conclusions: This study demonstrates the long-term effectiveness of doxycycline treatment delivered with a community-directed strategy even when evaluated four years after delivery in an area of ongoing transmission. This finding shows that a multi-week course of treatment is not a barrier to community-delivery of MDA in restricted populations of this size and supports its implementation to compliment existing control strategies for onchocerciasis, where needed. © 2012 Tamarozzi et al; licensee BioMed Central Ltd.


Fatih F.A.,St George's, University of London | Siner A.,University Malaysia Sarawak | Ahmed A.,University Malaysia Sarawak | Woon L.C.,Hospital Sarikei | And 6 more authors.
Malaria Journal | Year: 2012

Background: Cytoadherence of infected red blood cells to brain endothelium is causally implicated in malarial coma, one of the severe manifestations of falciparum malaria. Cytoadherence is mediated by specific binding of variant parasite antigens, expressed on the surface of infected erythrocytes, to endothelial receptors including, ICAM-1, VCAM and CD36. In fatal cases of severe falciparum malaria with coma, blood vessels in the brain are characteristically congested with infected erythrocytes. Brain sections from a fatal case of knowlesi malaria, but without coma, were similarly congested with infected erythrocytes. The objective of this study was to determine the binding phenotype of Plasmodium knowlesi infected human erythrocytes to recombinant human ICAM-1, VCAM and CD36. Methods. Five patients with PCR-confirmed P. knowlesi malaria were recruited into the study with consent between April and August 2010. Pre-treatment venous blood was washed and cultured ex vivo to increase the proportion of schizont-infected erythrocytes. Cultured blood was seeded into Petri dishes with triplicate areas coated with ICAM-1, VCAM and CD36. Following incubation at 37°C for one hour the dishes were washed and the number of infected erythrocytes bound/mm 2 to PBS control areas and to recombinant human ICAM-1 VCAM and CD36 coated areas were recorded. Each assay was performed in duplicate. Assay performance was monitored with the Plasmodium falciparum clone HB3. Results: Blood samples were cultured ex vivo for up to 14.5 h (mean 11.3 ± 1.9 h) to increase the relative proportion of mature trophozoite and schizont-infected red blood cells to at least 50% (mean 65.8 17.51%). Three (60%) isolates bound significantly to ICAM-1 and VCAM, one (20%) isolate bound to VCAM and none of the five bound significantly to CD36. Conclusions: Plasmodium knowlesi infected erythrocytes from human subjects bind in a specific but variable manner to the inducible endothelial receptors ICAM-1 and VCAM. Binding to the constitutively-expressed endothelial receptor CD36 was not detected. Further work will be required to define the pathological consequences of these interactions. © 2012 Fatih et al; licensee BioMed Central Ltd.


Sarkies P.,Imperial College London | Selkirk M.E.,Imperial College London | Jones J.T.,James Hutton Institute | Blok V.,James Hutton Institute | And 11 more authors.
PLoS Biology | Year: 2015

Small RNA pathways act at the front line of defence against transposable elements across the Eukaryota. In animals, Piwi interacting small RNAs (piRNAs) are a crucial arm of this defence. However, the evolutionary relationships among piRNAs and other small RNA pathways targeting transposable elements are poorly resolved. To address this question we sequenced small RNAs from multiple, diverse nematode species, producing the first phylum-wide analysis of how small RNA pathways evolve. Surprisingly, despite their prominence in Caenorhabditis elegans and closely related nematodes, piRNAs are absent in all other nematode lineages. We found that there are at least two evolutionarily distinct mechanisms that compensate for the absence of piRNAs, both involving RNA-dependent RNA polymerases (RdRPs). Whilst one pathway is unique to nematodes, the second involves Dicer-dependent RNA-directed DNA methylation, hitherto unknown in animals, and bears striking similarity to transposon-control mechanisms in fungi and plants. Our results highlight the rapid, context-dependent evolution of small RNA pathways and suggest piRNAs in animals may have replaced an ancient eukaryotic RNA-dependent RNA polymerase pathway to control transposable elements. © 2015 Sarkies et al.


Landmann F.,University of California at Santa Cruz | Voronin D.,Molecular and Biochemical Parasitology | Sullivan W.,University of California at Santa Cruz | Taylor M.J.,Molecular and Biochemical Parasitology
PLoS Pathogens | Year: 2011

Filarial nematodes maintain a mutualistic relationship with the endosymbiont Wolbachia. Depletion of Wolbachia produces profound defects in nematode development, fertility and viability and thus has great promise as a novel approach for treating filarial diseases. However, little is known concerning the basis for this mutualistic relationship. Here we demonstrate using whole mount confocal microscopy that an immediate response to Wolbachia depletion is extensive apoptosis in the adult germline, and in the somatic cells of the embryos, microfilariae and fourth-stage larvae (L4). Surprisingly, apoptosis occurs in the majority of embryonic cells that had not been infected prior to antibiotic treatment. In addition, no apoptosis occurs in the hypodermal chords, which are populated with large numbers of Wolbachia, although disruption of the hypodermal cytoskeleton occurs following their depletion. Thus, the induction of apoptosis upon Wolbachia depletion is non-cell autonomous and suggests the involvement of factors originating from Wolbachia in the hypodermal chords. The pattern of apoptosis correlates closely with the nematode tissues and processes initially perturbed following depletion of Wolbachia, embryogenesis and long-term sterilization, which are sustained for several months until the premature death of the adult worms. Our observations provide a cellular mechanism to account for the sustained reductions in microfilarial loads and interruption of transmission that occurs prior to macrofilaricidal activity following antibiotic therapy of filarial nematodes. © 2011 Landmann et al.


Vollmer J.,University of Bonn | Schiefer A.,University of Bonn | Schneider T.,University of Bonn | Julicher K.,University of Bonn | And 5 more authors.
International Journal of Medical Microbiology | Year: 2013

Obligate Wolbachia endobacteria have a reduced genome and retained genes are hypothesized to be crucial for survival. Although intracellular bacteria do not need a stress-bearing peptidoglycan cell wall, Wolbachia encode proteins necessary to synthesize the peptidoglycan precursor lipid II. The activity of the enzymes catalyzing the last two steps of this pathway was previously shown, and Wolbachia are sensitive to inhibition of lipid II synthesis. A puzzling characteristic of Wolbachia is the lack of genes for l-amino acid racemases essential for lipid II synthesis. Transcription analysis showed the expression of a possible alternative racemase metC, and recombinant Wolbachia MetC indeed had racemase activity that may substitute for the absent l-Ala racemase. However, enzymes needed to form mature peptidoglycan are absent and the function of Wolbachia lipid II is unknown. Inhibition of lipid II biosynthesis resulted in enlargement of Wolbachia cells and redistribution of Wolbachia peptidoglycan-associated lipoprotein, demonstrating that lipid II is required for coordinated cell division and may interact with the lipoprotein. We conclude that lipid II is essential for Wolbachia cell division and that this function is potentially conserved in the Gram-negative bacteria. © 2013 Elsevier GmbH.


Hartkoorn R.C.,University of Liverpool | Kwan W.S.,University of Liverpool | Shallcross V.,University of Liverpool | Chaikan A.,University of Liverpool | And 9 more authors.
Pharmacogenetics and Genomics | Year: 2010

OBJECTIVE: OATP1B1 and OATP1B3 are major hepatic drug transporters whilst OATP1A2 is mainly located in the brain but is also located in liver and several other organs. These transporters affect the distribution and clearance of many endobiotics and xenobiotics and have been reported to have functional single nucleotide polymorphisms (SNPs). We have assessed the substrate specificities of these transporters for a panel of antiretrovirals and investigated the effects of SNPs within these transporters on the pharmacokinetics of lopinavir. METHODS: SLCO1A2, SLCO1B1 and SLCO1B3 were cloned, verified and used to generate cRNA for use in the Xenopuslaevis oocyte transport system. Using the oocyte system, antiretrovirals were tested for their substrate specificities. Plasma samples (n=349) from the Liverpool therapeutic drug monitoring registry were genotyped for SNPs in SLCO1A2, SLCO1B1 and SLCO1B3 and associations between SNPs and lopinavir plasma concentrations were analysed. RESULT: Antiretroviral protease inhibitors, but not non-nucleoside reverse transcriptase inhibitors, are substrates for OATP1A2, OATP1B1 and OATP1B3. Furthermore, ritonavir was not an inhibitor of OATP1B1. The 521T>C polymorphism in SLCO1B1 was significantly associated with higher lopinavir plasma concentrations. No associations were observed with functional variants of SLCO1A2 and SLCO1B3. CONCLUSION: These data add to our understanding of the factors that contribute to variability in plasma concentrations of protease inhibitors. Further studies are now required to confirm the association of SLCO1B1 521T>C with lopinavir plasma concentrations and to assess the influence of other polymorphisms in the SLCO family. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Antao T.,Molecular and Biochemical Parasitology | Beaumont M.A.,University of Bristol
Bioinformatics | Year: 2011

Motivation: Dominant markers (DArTs and AFLPs) are commonly used for genetic analysis in the fields of evolutionary genetics, ecology and conservation of genetic resources. The recent prominence of these markers has coincided with renewed interest in detecting the effects of local selection and adaptation at the level of the genome.Results: We present Mcheza, an application for detecting loci under selection based on a well-evaluated FST-outlier method. The application allows robust estimates to be made of model parameters (e.g. genome-wide average, neutral FST), provides data import and export functions, iterative contour smoothing and generation of graphics in an easy to use graphical user interface with a computation engine that supports multicore processors for enhanced performance. Mcheza also provides functionality to mitigate common analytical errors when scanning for loci under selection. © The Author 2011. Published by Oxford University Press.

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