Institute of Tropical Medicine Antwerp

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    6320 research outputs found

    Human African Trypanosomiasis

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    Echinococcosis

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    Analysis of memory B cell responses and isolation of novel monoclonal antibodies with neutralizing breadth from HIV-1-infected individuals

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    BACKGROUND: The isolation of human monoclonal antibodies (mAbs) that neutralize a broad spectrum of primary HIV-1 isolates and the characterization of the human neutralizing antibody B cell response to HIV-1 infection are important goals that are central to the design of an effective antibody-based vaccine. METHODS AND FINDINGS: We immortalized IgG(+) memory B cells from individuals infected with diverse clades of HIV-1 and selected on the basis of plasma neutralization profiles that were cross-clade and relatively potent. Culture supernatants were screened using various recombinant forms of the envelope glycoproteins (Env) in multiple parallel assays. We isolated 58 mAbs that were mapped to different Env surfaces, most of which showed neutralizing activity. One mAb in particular (HJ16) specific for a novel epitope proximal to the CD4 binding site on gp120 selectively neutralized a multi-clade panel of Tier-2 HIV-1 pseudoviruses, and demonstrated reactivity that was comparable in breadth, but distinct in neutralization specificity, to that of the other CD4 binding site-specific neutralizing mAb b12. A second mAb (HGN194) bound a conserved epitope in the V3 crown and neutralized all Tier-1 and a proportion of Tier-2 pseudoviruses tested, irrespective of clade. A third mAb (HK20) with broad neutralizing activity, particularly as a Fab fragment, recognized a highly conserved epitope in the HR-1 region of gp41, but showed striking assay-dependent selectivity in its activity. CONCLUSIONS: This study reveals that by using appropriate screening methods, a large proportion of memory B cells can be isolated that produce mAbs with HIV-1 neutralizing activity. Three of these mAbs show unusual breadth of neutralization and therefore add to the current panel of HIV-1 neutralizing antibodies with potential for passive protection and template-based vaccine design

    The epidemiology of Leishmania donovani infection in high transmission foci in India

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    Summary Objective Visceral Leishmaniasis (VL) is highly prevalent in Bihar, India. India and its neighbours aim at eliminating VL, but several knowledge gaps in the epidemiology of VL may hamper that effort. The prevalence of asymptomatic infections with Leishmania donovani and their role in transmission dynamics are not well understood. We report data from a sero-survey in Bihar. Methods Demographic and immunological surveys were carried out in July and November 2006, respectively in 16 highly VL endemic foci in Muzaffarpur district in Bihar. Household and individual information was gathered and capillary blood samples were collected on filter papers. Direct agglutination test (DAT) was used to determine infected individuals (cut-off titre 1:1600). DAT results were tabulated against individual and household variables. A multivariate generalized estimating equation (GEE) model was used to study the prevalence of serologically positive individuals taking into account the clustering at household and cluster levels. Results Of study subjects 18% were DAT positive, and this proportion increased with age. Women had a significantly lower prevalence than men >14 years old. Owning domestic animals (cows, buffaloes or goats) was associated with a higher risk of being DAT positive [OR 1.16 (95% CI 1.01-1.32)], but socio-economic status was not. Conclusions Prevalence of leishmanial antibodies was high in these communities, but variable. Demographic factors (i.e. marriage) may explain the lower DAT positivity in women >14 years of age. Within these homogeneously poor communities, socio-economic status was not linked to L. donovani infection risk at the individual level, but ownership of domestic animals wa

    Effect of maternal multiple micronutrient supplements on cord blood hormones: a randomized controlled trial

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    BACKGROUND: Fetal growth improves in pregnant women who take daily maternal multiple micronutrients [United Nations International Multiple Micronutrient Preparation (UNIMMAP)] rather than iron and folic acid (IFA) alone. OBJECTIVE: Our objective was to test whether such an effect was mediated by changes in concentrations of cord hormones. DESIGN: In a double-blind, controlled trial carried out in Burkina Faso, we randomly assigned 1426 pregnant women to receive UNIMMAP or IFA supplements. We measured concentrations of insulin-like growth factor I (IGF-I), leptin, insulin, free thyroxine, and cortisol in cord serum in a subsample of 294 live single newborns. We performed mediation analysis with an Aroian test. RESULTS: UNIMMAP supplementation had no significant effect on cord hormone concentrations. However, UNIMMAP supplementation significantly affected concentrations of IGF-I (+30%; 95% CI: 8%, 52%; P = 0.009) and leptin in male newborns. In these infants, 51.1% (P = 0.08) of the effect of UNIMMAP supplementation on birth weight was mediated through IGF-I, whereas for female newborns, this proportion was negligible. UNIMMAP supplementation also increased cortisol concentrations by 36% (P = 0.009) in cord blood in primiparae (P for interaction = 0.02). Growth-retarded babies had 41.2% lower IGF-I (P < 0.0001) and 27.3% lower leptin (P = 0.04) than did infants with normal growth. Offspring of primiparae had reduced IGF-I and insulin concentrations, and their cortisol concentrations were 25% higher (P = 0.05). Male newborns had lower concentrations of IGF-I, leptin, and insulin than did female newborns. CONCLUSIONS: UNIMMAP supplementation had sex-specific effects on cord IGF-I and leptin concentrations that were of unclear clinical significance. Other pathways may have been involved in the action of UNIMMAP on fetal growth. The specific hormonal pattern in primiparae could be related to constrained fetal growth. Confirmatory studies are warranted. This trial was registered at clinicaltrials.gov as NCT0064240

    The incremental cost-effectiveness of engaging private practitioners to refer tuberculosis suspects to DOTS services in Jogjakarta, Indonesia

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    We aimed to evaluate the incremental cost-effectiveness of engaging private practitioners (PPs) to refer tuberculosis (TB) suspects to public health centers in Jogjakarta, Indonesia. Effectiveness was assessed for TB suspects notified between May 2004 and April 2005. Private practitioners referred 1,064 TB suspects, of which 57.5% failed to reach a health center. The smear-positive rate among patients reaching a health center was 61.8%. Two hundred eighty (280) out of a total of 1,306 (21.4%) new smear-positive cases were enrolled through the PPs strategy. The incremental cost-effectiveness ratio per smear-positive case successfully treated for the PPs strategy was US351.66(95351.66 (95% CI 322.84-601.33). On the basis of an acceptability curve using the National TB control program's willingness-to-pay threshold (US448.61), we estimate the probability that the PPs strategy is cost-effective at 66.8%. The strategy of engaging PPs was incrementally cost-effective, although under specific conditions, most importantly a well-functioning public directly observed treatment, short-course (DOTS) progra

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