Effectiveness of single dose rifampicin in preventing leprosy in close contacts of patients with newly diagnosed leprosy: cluster randomised controlled trial

Objective To determine the effectiveness of chemoprophylaxis using a single dose of rifampicin to prevent leprosy in close contacts.Design Single centre, double blind, cluster randomised, placebo controlled trial.SettingLeprosy control programme in two districts of northwest Bangladesh with a population of more than four million.Participants28 092 close contacts of 1037 patients with newly diagnosed leprosy. 21 711 contacts fulfilled the study requirements.Interventions A single dose of rifampicin or placebo given to close contacts in the second month of starting the index patient’s treatment, with follow-up for four years.Main outcome measure Development of clinical leprosy.Results 18 869 of the 21 711 contacts (86.9%) were followed-up at four years. Ninety one of 9452 contacts in the placebo group and 59 of 9417 in the rifampicin group had developed leprosy. The overall reduction in incidence of leprosy using a single dose of rifampicin in the first two years was 57% (95% confidence interval 33% to 72%). The groups did not differ between two and four years. The overall number needed to treat (NNT) to prevent a single case of leprosy among contacts was 297 (95% confidence interval 176 to 537). Differences were found between subgroups at two years, both in reduction of incidence and in NNT.ConclusionA single dose of rifampicin given to contacts of patients with newly diagnosed leprosy is effective at preventing the development of clinical leprosy at two years. The effect was maintained, but no difference was seen between the placebo and rifampicin groups beyond two years.Trial registration Current Controlled Trials ISRCTN61223447.     

Potentials for monitoring gene level biodiversity: using Sweden as an example

Programs for monitoring biological diversity over time are needed to detect changes that can constitute threats to biological resources. The convention on biological diversity regards effective monitoring as necessary to halt the ongoing erosion of biological variation, and such programs at the ecosystem and species levels are enforced in several countries. However, at the level of genetic biodiversity, little has been accomplished, and monitoring programs need to be developed. We define “conservation genetic monitoring” to imply the systematic, temporal study of genetic variation within particular species/populations with the aim to detect changes that indicate compromise or loss of such diversity. We also (i) identify basic starting points for conservation genetic monitoring, (ii) review the availability of such information using Sweden as an example, (iii) suggest categories of species for pilot monitoring programs, and (iv) identify some scientific and logistic issues that need to be addressed in the context of conservation genetic monitoring. We suggest that such programs are particularly warranted for species subject to large scale enhancement and harvest—operations that are known to potentially alter the genetic composition and reduce the variability of populations.     

Building protein interaction maps for Down's syndrome.

Now that the complete sequences for human chromosome 21 and the orthologous mouse genomic regions are known, reasonably complete, conserved, protein-coding gene catalogues are also available. The central issue now facing Down's syndrome researchers is the correlation of increased expression of specific, normal, chromosome 21 genes with the development of specific deficits in learning and memory. Because of the number of candidate genes involved, the number of alternative splice variants of individual genes and the number of pathways in which these genes function, a pathway analysis approach will be critical to success. Here, three examples, both gene specific and pathway related, that would benefit from pathway analysis are discussed: (1) the potential roles of eight chromosome 21 proteins in RNA processing pathways; (2) the chromosome 21 protein intersectin 1 and its domain composition, alternative splicing, protein interactions and functions; and (3) the interactions of ten chromosome 21 proteins with components of the mitogen-activated protein kinase and the calcineurin signalling pathways. A productive approach to developing gene-phenotype correlations in Down's syndrome will make use of known and predicted functions and interactions of chromosome 21 genes to predict pathways that may be perturbed by their increased levels of expression. Investigations may then be targeted in animal models to specific interactions, intermediate steps or end-points of such pathways and the downstream - perhaps amplified - consequences of gene dosage directly assessed. Once pathway perturbations have been identified, the potential for rational design of therapeutics becomes practical.     

A Short Scale for Measuring Loneliness in Large Surveys: Results From Two Population-Based Studies

Most studies of social relationships in later life focus on the amount of social contact, not on individuals' perceptions of social isolation. However, loneliness is likely to be an important aspect of aging. A major limiting factor in studying loneliness has been the lack of a measure suitable for large-scale social surveys. This article describes a short loneliness scale developed specifically for use on a telephone survey. The scale has three items and a simplified set of response categories but appears to measure overall loneliness quite well. The authors also document the relationship between loneliness and several commonly used measures of objective social isolation. As expected, they find that objective and subjective isolation are related. However, the relationship is relatively modest, indicating that the quantitative and qualitative aspects of social relationships are distinct. This result suggests the importance of studying both dimensions of social relationships in the aging process.     

Effect of Pathogen Isolate, Potato Cultivar, and Antagonist Strain on Potato Scab Severity and Biological Control

Antibiotic-producing Streptomyces spp. have shown potential in biocontrol of potato scab caused by Streptomyces scabies. However, results have been inconsistent among field trials. Pathogen isolate, antagonist strain and potato cultivar were investigated as potential sources of variation in the efficacy of potato scab biocontrol. Biocontrol success varied significantly among pathogen isolates and was not correlated with in vitro sensitivity to antibiotic inhibition. Antagonists also varied in their effectiveness as biocontrol agents, and the relative effectiveness of different antagonists varied among growing seasons. Finally, biocontrol varied among potato cultivars in the field. The diverse origins of significant variation in potato scab biocontrol suggest that consistent control in the field is likely to be difficult to achieve.     

The Y42H mutation in medium-chain acyl-CoA dehydrogenase, which is prevalent in babies identified by MS/MS-based newborn screening, is temperature sensitive.

Medium-chain acyl-CoA dehydrogenase (MCAD) is a homotetrameric flavoprotein which catalyses the initial step of the beta-oxidation of medium-chain fatty acids. Mutations in MCAD may cause disease in humans. A Y42H mutation is frequently found in babies identified by newborn screening with MS/MS, yet there are no reports of patients presenting clinically with this mutation. As a basis for judging its potential consequences we have examined the protein phenotype of the Y42H mutation and the common disease-associated K304E mutation. Our studies of the intracellular biogenesis of the variant proteins at different temperatures in isolated mitochondria after in vitro translation, together with studies of cultured patient cells, indicated that steady-state levels of the Y42H variant in comparison to wild-type were decreased at higher temperature though to a lesser extent than for the K304E variant. To distinguish between effects of temperature on folding/assembly and the stability of the native enzyme, the thermal stability of the variant proteins was studied after expression and purification by dye affinity chromatography. This showed that, compared with the wild-type enzyme, the thermostability of the Y42H variant was decreased, but not to the same degree as that of the K304E variant. Substrate binding, interaction with the natural electron acceptor, and the binding of the prosthetic group, FAD, were only slightly affected by the Y42H mutation. Our study suggests that Y42H is a temperature sensitive mutation, which is mild at low temperatures, but may have deleterious effects at increased temperatures.     

The Population Reference Sample, POPRES: a resource for population, disease, and pharmacological genetics research

Technological and scientific advances, stemming in large part from the Human Genome and HapMap projects, have made large-scale, genome-wide investigations feasible and cost effective. These advances have the potential to dramatically impact drug discovery and development by identifying genetic factors that contribute to variation in disease risk as well as drug pharmacokinetics, treatment efficacy, and adverse drug reactions. In spite of the technological advancements, successful application in biomedical research would be limited without access to suitable sample collections. To facilitate exploratory genetics research, we have assembled a DNA resource from a large number of subjects participating in multiple studies throughout the world. This growing resource was initially genotyped with a commercially available genome-wide 500,000 single-nucleotide polymorphism panel. This project includes nearly 6,000 subjects of African-American, East Asian, South Asian, Mexican, and European origin. Seven informative axes of variation identified via principal-component analysis (PCA) of these data confirm the overall integrity of the data and highlight important features of the genetic structure of diverse populations. The potential value of such extensively genotyped collections is illustrated by selection of genetically matched population controls in a genome-wide analysis of abacavir-associated hypersensitivity reaction. We find that matching based on country of origin, identity-by-state distance, and multidimensional PCA do similarly well to control the type I error rate. The genotype and demographic data from this reference sample are freely available through the NCBI database of Genotypes and Phenotypes (dbGaP).     

Mutational analysis of histidine residues in the human proton-coupled amino acid transporter PAT1

The proton-coupled amino acid transporter 1 (PAT1) represents a major route by which small neutral amino acids are absorbed after intestinal protein digestion. The system also serves as a novel route for oral drug delivery. Having shown that H⁺ affects affinity constants but not maximal velocity of transport, we investigated which histidine residues are obligatory for PAT1 function. Three histidine residues are conserved among the H⁺-coupled amino acid transporters PAT1 to 4 from different animal species. We individually mutated each of these histidine residues and compared the catalytic function of the mutants with that of the wild type transporter after expression in HRPE cells. His-55 was found to be essential for the catalytic activity of hPAT1 because the corresponding mutants H55A, H55N and H55E had no detectable l-proline transport activity. His-93 and His-135 are less important for transport function since H93N and H135N mutations did not impair transport function. The loss of transport function of His-55 mutants was not due to alterations in protein expression as shown both by cell surface biotinylation immunoblot analyses and by confocal microscopy. We conclude that His-55 might be responsible for binding and translocation of H⁺ in the course of cellular amino acid uptake by PAT1.     

Expression of recombinant murine pregnancy-associated plasma protein-A (PAPP-A) and a novel variant (PAPP-Ai) with differential proteolytic activity.

Murine pregnancy-associated plasma protein-A (PAPP-A) cDNA encoding a 1545 amino-acid protein has been cloned. We have also identified and cloned cDNA that encodes a novel variant of PAPP-A, PAPP-Ai, carrying a 29-residue highly basic insert. The point of insertion corresponds to a junction between two exons in the human PAPP-A gene. The human intron flanked by these exons does not encode a homologous corresponding insert, which is unique to the mouse. The overall sequence identity between murine and human PAPP-A is 91%, and murine PAPP-A contains sequence motifs previously described in the sequence of human PAPP-A. Through expression in mammalian cells, we show that murine PAPP-A and PAPP-Ai are active metalloproteinases, both capable of cleaving insulin-like growth factor binding protein (IGFBP)-4 and -5. Cleavage of IGFBP-4 is dramatically enhanced by the addition of IGF, whereas cleavage of IGFBP-5 is slightly inhibited by IGF, as previously established with human PAPP-A. Surprisingly, however, quantitative analyses demonstrate that the murine PAPP-Ai cleaves IGFBP-4 very slowly compared to PAPP-A, even though its ability to cleave IGFBP-5 is unaffected by the presence of the insert. By RT-PCR analysis, we find that both variants are expressed in several tissues. The level of mRNA in the murine placenta does not exceed the levels of other tissues analyzed. Furthermore, the IGFBP-4-proteolytic activity of murine pregnancy serum is not elevated. This is in striking contrast to the increase seen in human pregnancy serum, and the expression of PAPP-A in the human placenta, which exceeds other tissues at least 250-fold. Interestingly, the position of the insert of PAPP-Ai, within the proteolytic domain, lies in close proximity to the cysteine residue, which in human PAPP-A forms a disulfide bond with the proform of eosinophil major basic protein (proMBP). ProMBP functions as a proteinase inhibitor in the PAPP-A-proMBP complex, but whether any mechanistic parallel on regulation of proteolytic activity can be drawn between the insert of PAPP-Ai and the linkage to proMBP is not known. Importantly, these data support the development of the mouse as a model organism for the study of PAPP-A, which must take into account the differences between the mouse and the human.