Secretion of the fungal toxin candidalysin is dependent on conserved precursor peptide sequences

The opportunistic fungal pathogen Candida albicans damages host cells via its peptide toxin, candidalysin. Before secretion, candidalysin is embedded in a precursor protein, Ece1, which consists of a signal peptide, the precursor of candidalysin and seven non-candidalysin Ece1 peptides (NCEPs), and is found to be conserved in clinical isolates. Here we show that the Ece1 polyprotein does not resemble the usual precursor structure of peptide toxins. C. albicans cells are not susceptible to their own toxin, and single NCEPs adjacent to candidalysin are sufficient to prevent host cell toxicity. Using a series of Ece1 mutants, mass spectrometry and anti-candidalysin nanobodies, we show that NCEPs play a role in intracellular Ece1 folding and candidalysin secretion. Removal of single NCEPs or modifications of peptide sequences cause an unfolded protein response (UPR), which in turn inhibits hypha formation and pathogenicity in vitro. Our data indicate that the Ece1 precursor is not required to block premature pore-forming toxicity, but rather to prevent intracellular auto-aggregation of candidalysin sequences.

Harnessing the potential of digital data for infectious disease surveillance in sub-Saharan Africa

 

Despite efforts by the WHO to support local surveillance strategies in developing countries, there is a lack of robust public health surveillance frameworks. As a result, early infectious disease outbreak detection and response remain a significant challenge for local health systems in low-resource settings such as sub-Saharan African countries. In contrast, the growing digital infrastructure, especially in the mobile phone sector, and the global availability of extensive digital data offer promising solutions to enhance and strengthen epidemiological surveillance. Yet, there is little insight into concepts of utilisation and transfer into local public health practice. Using Tanzania as an example, a novel electronic surveillance and early outbreak alert framework is being developed that links signals on emerging diseases with relevant contextual Open Data for rapid outbreak risk assessment. The concept focuses on haemorrhagic fever diseases, specifically dengue virus disease, which is increasingly spreading in sub-Saharan Africa. A data stack framework forms the core of the system, which augments electronic information on the occurrence of acute haemorrhagic fever syndrome, e.g., collected via mobile phone-based surveillance tools, with openly available socio-ecological context data specific to dengue. Preliminary results on the data and information flow within the surveillance framework are presented and strategies for an automated indicator-based risk assessment for dengue outbreaks will be discussed, supplemented by an agent-based simulation framework to model possible short-term outbreak scenarios. In addition, adequate data inputs, identified through an appraisal of various data sources available for Tanzania, are outlined. The framework could serve as a blueprint for designing locally implementable early warning and decision support systems integrated with existing digital surveillance infrastructure.

Key messages

• Digital health surveillance and Open Data offer great potential for early outbreak detection and supporting health decisions but require tailored solutions to benefit low-resource settings.

• Building on existing digital surveillance infrastructure, the framework may serve as a blueprint for designing an enhanced surveillance and decision support system for infectious disease outbreaks.

Augmented Enterocyte Damage During Candida albicans and Proteus mirabilis Coinfection

The human gut acts as the main reservoir of microbes and a relevant source of life-threatening infections, especially in immunocompromised patients. There, the opportunistic fungal pathogen Candida albicans adapts to the host environment and additionally interacts with residing bacteria. We investigated fungal-bacterial interactions by coinfecting enterocytes with the yeast Candida albicans and the Gram-negative bacterium Proteus mirabilis resulting in enhanced host cell damage. This synergistic effect was conserved across different P. mirabilis isolates and occurred also with non-albicans Candida species and C. albicans mutants defective in filamentation or candidalysin production. Using bacterial deletion mutants, we identified the P. mirabilis hemolysin HpmA to be the key effector for host cell destruction. Spatially separated coinfections demonstrated that synergism between Candida and Proteus is induced by contact, but also by soluble factors. Specifically, we identified Candida-mediated glucose consumption and farnesol production as potential triggers for Proteus virulence. In summary, our study demonstrates that coinfection of enterocytes with C. albicans and P. mirabilis can result in increased host cell damage which is mediated by bacterial virulence factors as a result of fungal niche modification via nutrient consumption and production of soluble factors. This supports the notion that certain fungal-bacterial combinations have the potential to result in enhanced virulence in niches such as the gut and might therefore promote translocation and dissemination.

Cost effectiveness of neoadjuvant chemotherapy in locally advanced operable head and neck cancer followed by surgery and postoperative radiotherapy: a Markov model-based decision analysis

INTRODUCTION

Head and neck carcinomas are among the most frequent tumor diseases and, because of different multimodal therapy options, cause enormous costs. For this reason, we examined whether in operable advanced head and neck carcinomas, neoadjuvant induction chemotherapy is cost effective in comparison with surgery followed by postoperative radio(chemo)therapy.

MATERIAL AND METHODS

A Markov model was developed with paclitaxel, cisplatin and fluorouracil as induction therapy. The legal health insurance in Germany was chosen for cost perspectives, and a willingness-to-pay limit at EUR 38,000 was set.

RESULTS

Total costs for surgery with postoperative radiochemotherapy amounted to EUR 13,999. Prior induction chemotherapy raised the costs to EUR 17,377, with a higher effectiveness by 0.1 years of life. Costs per year of life gained are EUR 33,780. The incremental cost effectiveness ratio (ICER) with variations in side effects for surgery and postoperative chemotherapy amounted to between EUR 31,520 and 36,050. With variations in side effects for induction chemotherapy, the ICER amounted to EUR 30,060-37,520. The Monte Carlo simulation disclosed cost effectiveness for 55.4% of the patients; for 44.6%, there was no cost effectiveness.

CONCLUSION

The Markov-modeled cost effectiveness analysis indicates that with operable head and neck tumors, induction therapy with paclitaxel, cisplatin and fluorouracil is cost effective.

Indications for a novel muscular dystrophy pathway. gamma-filamin, the muscle-specific filamin isoform, interacts with myotilin

gamma-Filamin, also called ABP-L, is a filamin isoform that is specifically expressed in striated muscles, where it is predominantly localized in myofibrillar Z-discs. A minor fraction of the protein shows subsarcolemmal localization. Although gamma-filamin has the same overall structure as the two other known isoforms, it is the only isoform that carries a unique insertion in its immunoglobulin (Ig)-like domain 20. Sequencing of the genomic region encoding this part of the molecule shows that this insert is encoded by an extra exon. Transient transfections of the insert-bearing domain in skeletal muscle cells and cardiomyocytes show that this single domain is sufficient for targeting to developing and mature Z-discs. The yeast two-hybrid method was used to identify possible binding partners for the insert-bearing Ig-like domain 20 of gamma-filamin. The two Ig-like domains of the recently described alpha-actinin-binding Z-disc protein myotilin were found to interact directly with this filamin domain, indicating that the amino-terminal end of gamma-filamin may be indirectly anchored to alpha-actinin in the Z-disc via myotilin. Since defects in the myotilin gene were recently reported to cause a form of autosomal dominant limb-girdle muscular dystrophy, our findings provide a further contribution to the molecular understanding of this disease.

Purification and characterization of an acetyl esterase from Aspergillus niger

Optimized acetyl esterase enzyme production conditions using Aspergillus niger ATCC 10864 in 14-L fermentation jars were determined to be 33 degrees C, 1.5 vvm aeration, and 300 rpm agitation without pH control. The acetyl esterase was purified by precipitation in 60-80% saturation in ammonium sulfate. The pellet was applied directly to a Pharmacia high-load Phenyl Sepharose column for hydrophobic interaction chromatography and purified to homogeneity in two steps. Stability and kinetic characteristics of the acetyl esterase were determined over a pH range of 4.0-7.5 and from 4 to 45 degrees C. At temperatures > 25 degrees C, stability was superior at pH values < 5.0. The temperature activity optimum was 35 degrees C, and the pH optimum was 7.0. The Vmax was determined to be 46,700 U/mg protein, and the Km was 0.023M p-nitrophenyl acetate at pH 6.5 in 0.2M phosphate buffer at 35 degrees C. The mol wt of the enzyme was 35,000 dalton by size-exclusion chromatography and SDS gel electrophoresis. The N-terminal amino acid sequence and the glycosylation composition were also determined.

Evidence for alteration of the membrane-bound ribosomes in Micrococcus luteus cells exposed to lead

Micrococcus luteus cell exposed to PB(NO3)2 contained cytosol ribosomal particles and disaggregated membranal ribosomal particles as determined by ultracentirifugation and spectral studies. Approx. 60% of the membrane ribosome fraction from lead exposed cells had a sedimentation value of 8.4S. Cytosol ribosomes from lead exposed cells as well as membranal and cytosol ribosomes from control cells were comparable by their contents of predominantly the 70S type with the 50S and 100S present in relatively small amounts. The lead content of the 8.4S component was more than 200 times higher than the components with higher sedimentation coefficients from lead exposed cells and approc. 650 times more than that of control cell ribosomes. The cells exposed to lead, however, showed no adverse effects from the lead in respect to their growth rates and cellular yields. These results indicate that lead is interacting only at specific sites of the membrane and is inducing events initiated only in strategic cellular regions. These data further substantiate that subtle changes do occur in lead exposed cells that show no obvious effects. It is assumed that these 'minor' alterations are, in toto, biologically significant.