Expression of δ-toxin by Staphylococcus aureus mediates escape from phago-endosomes of human epithelial and endothelial cells in the presence of β-toxin

Staphylococcus aureus is able to invade non-professional phagocytes by interaction of staphylococcal adhesins with extracellular proteins of mammalian cells and eventually resides in acidified phago-endosomes. Some staphylococcal strains have been shown to subsequently escape from this compartment. A functional agr quorum-sensing system is needed for phagosomal escape. However, the nature of this agr dependency as well as the toxins involved in disruption of the phagosomal membrane are unknown. Using a novel technique to detect vesicular escape of S. aureus, we identified staphylococcal virulence factors involved in phagosomal escape. Here we show that a synergistic activity of the cytolytic peptide, staphylococcal δ-toxin and the sphingomyelinase β-toxin enable the phagosomal escape of staphylococci in human epithelial as well as in endothelial cells. The agr dependency of this process can be directly explained by the location of the structural gene for δ-toxin within the agr effector RNAIII.     

Autophagy-related lipase FgATG15 of Fusarium graminearum is important for lipid turnover and plant infection

Autophagy is a non-selective degradation pathway in eukaryotic cells that is conserved from yeasts to humans. Autophagy is involved in the virulence of several pathogenic fungi such as Magnaporthe grisea or Colletotrichum orbiculare. In the current study, we identified and disrupted an autophagy-like lipase FgATG15 in Fusarium graminearum. We showed that FgATG15 exhibits lipase activity when heterologously expressed in P. pastoris. We used a gene deletion approach to characterize the function of the enzyme. We demonstrate that FgATG15 is involved in fungal growth and aerial hyphae production. FgATG15 is also involved in conidia production and germination, and disruption of FgATG15 led to aberrant conidia shapes. FgATG15 disruptants were reduced in storage lipid degradation under starvation conditions, implicating FgATG15's involvement in lipid turnover. Moreover, wheat head infection by the disruptants was severely attenuated, indicating the involvement of FgATG15 in pathogenesis. Additionally, we found that the deoxynivalenol levels of FgATG15 disruptants were significantly decreased compared with the wild type strain. Taken together, we show that FgATG15 is involved in numerous developmental processes and could be exploited as an antifungal target.     

Food composition of the diet in relation to changes in waist circumference adjusted for body mass index

Background

Dietary factors such as low energy density and low glycemic index were associated with a lower gain in abdominal adiposity. A better understanding of which food groups/items contribute to these associations is necessary.

Objective

To ascertain the association of food groups/items consumption on prospective annual changes in “waist circumference for a given BMI” (WC_BMI), a proxy for abdominal adiposity.

Design

We analyzed data from 48,631 men and women from 5 countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Anthropometric measurements were obtained at baseline and after a median follow-up time of 5.5 years. WC_BMI was defined as the residuals of waist circumference regressed on BMI, and annual change in WC_BMI (ΔWC_BMI, cm/y) was defined as the difference between residuals at follow-up and baseline, divided by follow-up time. The association between food groups/items and ΔWC_BMI was modelled using centre-specific adjusted linear regression, and random-effects meta-analyses to obtain pooled estimates.

Results

Higher fruit and dairy products consumption was associated with a lower gain in WC_BMI whereas the consumption of white bread, processed meat, margarine, and soft drinks was positively associated with ΔWC_BMI. When these six food groups/items were analyzed in combination using a summary score, those in the highest quartile of the score – indicating a more favourable dietary pattern –showed a ΔWC_BMI of −0.11 (95% CI −0.09 to −0.14) cm/y compared to those in the lowest quartile.

Conclusion

A dietary pattern high in fruit and dairy and low in white bread, processed meat, margarine, and soft drinks may help to prevent abdominal fat accumulation.     

Olfactory and gustatory sensitivity in adults with attention-deficit/hyperactivity disorder

Recently, research on olfactory functions in attention-deficit/hyperactivity disorder (ADHD) has become prominent, whereas gustation has never been investigated. Increased odor sensitivity was found in medication-na?ve children with ADHD, but not in adult ADHD, which might be due to a dopaminergic dysregulation presumed to underlie this disorder. Taste sensitivity, in particular bitter sensitivity as a hereditary trait, also might be altered in ADHD. To examine olfactory and gustatory functions in adult ADHD patients, we assessed odor sensitivity by Sniffin' Sticks, taste sensitivity by taste strips, and bitter sensitivity by the one-solution test in women with ADHD (n = 12), Bulimia Nervosa (n = 12), and healthy control women (n = 12). Bulimia Nervosa as second patient group was included to control for effects of impulsivity. Preliminary results indicate that ADHD patients were significantly more often classified as tasters, i.e. perceived the bitter taste as more intense, compared to both bulimic patients and healthy controls. No group differences were found with regard to general odor and taste sensitivity. It is proposed that the higher frequency of tasters in ADHD patients might underlie a genetic variation of the bitter receptor-dependent signaling pathway associated with ADHD.     

Trend in obesity prevalence in European adult cohort populations during follow-up since 1996 and their predictions to 2015

Objective

To investigate trends in obesity prevalence in recent years and to predict the obesity prevalence in 2015 in European populations.

Methods

Data of 97 942 participants from seven cohorts involved in the European Prospective Investigation into Cancer and Nutrition (EPIC) study participating in the Diogenes project (named as “Diogenes cohort” in the following) with weight measurements at baseline and follow-up were used to predict future obesity prevalence with logistic linear and non-linear (leveling off) regression models. In addition, linear and leveling off models were fitted to the EPIC-Potsdam dataset with five weight measures during the observation period to find out which of these two models might provide the more realistic prediction.

Results

During a mean follow-up period of 6 years, the obesity prevalence in the Diogenes cohort increased from 13% to 17%. The linear prediction model predicted an overall obesity prevalence of about 30% in 2015, whereas the leveling off model predicted a prevalence of about 20%. In the EPIC-Potsdam cohort, the shape of obesity trend favors a leveling off model among men (R² = 0.98), and a linear model among women (R² = 0.99).

Conclusion

Our data show an increase in obesity prevalence since the 1990ies, and predictions by 2015 suggests a sizeable further increase in European populations. However, the estimates from the leveling off model were considerably lower.     

HIV incidence and risk factors for acquisition in HIV discordant couples in Masaka, Uganda: an HIV vaccine preparedness study

Objectives

To determine the incidence of and risk factors for HIV acquisition in a cohort of HIV-uninfected partners from HIV discordant couples in Masaka, Uganda, and to establish its suitability for HIV vaccine trials.

Methods

HIV-uninfected adults living in HIV discordant couple relationships were enrolled and followed for 2 years. Interviews, medical investigations, HIV counseling and testing, syphilis and urine pregnancy (women) tests were performed at quarterly visits. Sexual risk behaviour data were collected every 6 months.

Results

495 participants were enrolled, of whom 34 seroconverted during 786.6 person-years of observation (PYO). The overall HIV incidence rate [95% confidence interval (CI)] was 4.3 [3.1–6]; and 4.3 [2.8–6.4] and 4.4 [2.5–8] per 100 PYO in men and women respectively. Independent baseline predictors for HIV acquisition were young age [18–24 (aRR = 4.1, 95% CI 1.6–10.8) and 25–34 (aRR = 2.7, 95% CI 1.2–5.8) years]; alcohol use (aRR = 2.6, 95% CI 1.1–6); and reported genital discharge (aRR = 3.4, 95% CI 1.6–7.2) in the past year. Condom use frequency in the year preceding enrolment was predictive of a reduced risk of HIV acquisition [sometimes (aRR = 0.4, 95% CI 0.2–0.8); always (aRR = 0.1, 95% CI 0.02–0.9)]. In the follow-up risk analysis, young age [18–24 (aRR = 6.2, 95% CI 2.2–17.3) and 25-34 (aRR = 2.3, 95% CI 1.1–5.0) years], reported genital discharge (aRR = 2.5, 95% CI 1.1–5.5), serological syphilis (aRR 3.2, 95% CI 1.3–7.7) and the partner being ART naïve (aRR = 4.8, 95% CI 1.4–16.0) were independently associated with HIV acquisition. There were no seroconversions among participants who reported consistent condom use during the study.

Conclusions

The study has identified important risk factors for HIV acquisition among HIV discordant couples. HIV-uninfected partners in discordant couples may be a suitable population for HIV vaccine efficacy trials. However, recent confirmation that ART reduces heterosexual HIV transmission may make it unfeasible to conduct HIV prevention trials in this population.     

Intronic CA-repeat and CA-rich elements: a new class of regulators of mammalian alternative splicing

We have recently identified an intronic polymorphic CA-repeat region in the human endothelial nitric oxide synthase (eNOS) gene as an important determinant of the splicing efficiency, requiring specific binding of hnRNP L. Here, we analyzed the position requirements of this CA-repeat element, which revealed its potential role in alternative splicing. In addition, we defined the RNA binding specificity of hnRNP L by SELEX: not only regular CA repeats are recognized with high affinity but also certain CA-rich clusters. Therefore, we have systematically searched the human genome databases for CA-repeat and CA-rich elements associated with alternative 5' splice sites (5'ss), followed by minigene transfection assays. Surprisingly, in several specific human genes that we tested, intronic CA RNA elements could function either as splicing enhancers or silencers, depending on their proximity to the alternative 5'ss. HnRNP L was detected specifically bound to these diverse CA elements. These data demonstrated that intronic CA sequences constitute novel and widespread regulatory elements of alternative splicing.     

Systematic identification of antiprion drugs by high-throughput screening based on scanning for intensely fluorescent targets

Conformational changes and aggregation of specific proteins are hallmarks of a number of diseases, like Alzheimer's disease, Parkinson's disease, and prion diseases. In the case of prion diseases, the prion protein (PrP), a neuronal glycoprotein, undergoes a conformational change from the normal, mainly alpha-helical conformation to a disease-associated, mainly beta-sheeted scrapie isoform (PrP(Sc)), which forms amyloid aggregates. This conversion, which is crucial for disease progression, depends on direct PrP(C)/PrP(Sc) interaction. We developed a high-throughput assay based on scanning for intensely fluorescent targets (SIFT) for the identification of drugs which interfere with this interaction at the molecular level. Screening of a library of 10,000 drug-like compounds yielded 256 primary hits, 80 of which were confirmed by dose response curves with half-maximal inhibitory effects ranging from 0.3 to 60 microM. Among these, six compounds displayed an inhibitory effect on PrP(Sc) propagation in scrapie-infected N2a cells. Four of these candidate drugs share an N'-benzylidene-benzohydrazide core structure. Thus, the combination of high-throughput in vitro assay with the established cell culture system provides a rapid and efficient method to identify new antiprion drugs, which corroborates that interaction of PrP(C) and PrP(Sc) is a crucial molecular step in the propagation of prions. Moreover, SIFT-based screening may facilitate the search for drugs against other diseases linked to protein aggregation.     

Molecular dynamics simulations indicate a possible role of parallel beta-helices in seeded aggregation of poly-Gln

The molecular structures of amyloid fibers characterizing neurodegenerative diseases such as Huntington's or transmissible spongiform encephalopathies are unknown. Recently, x-ray diffraction patterns of poly-Gln fibers and electron microscopy images of two-dimensional crystals formed from building blocks of prion rods have suggested that the corresponding amyloid fibers are generated by the aggregation of parallel beta-helices. To explore this intriguing concept, we study the stability of small beta-helices in aqueous solution by molecular dynamics simulations. In particular, for the Huntington aggregation nucleus, which is thought to be formed of poly-Gln polymers, we show that three-coiled beta-helices are unstable at the suggested circular geometries and stable at a triangular shape with 18 residues per coil. Moreover, we demonstrate that individually unstable two-coiled triangular poly-Gln beta-helices become stabilized upon dimerization, suggesting that seeded aggregation of Huntington amyloids requires dimers of at least 36 Gln repeats (or monomers of approximately 54 Gln) for the formation of sufficiently stable aggregation nuclei. An analysis of our results and of sequences occurring in native beta-helices leads us to the proposal of a revised model for the PrP(Sc) aggregation nucleus.