Ian S. Roberts

Banff '05 Meeting Report: Differential Diagnosis of Chronic Allograft Injury and Elimination of Chronic Allograft Nephropathy (‘CAN’)

The 8th Banff Conference on Allograft Pathology was held in Edmonton, Canada, 15–21 July 2005. Major outcomes included the elimination of the non‐specific term ‘chronic allograft nephropathy’ (CAN) from the Banff classification for kidney allograft pathology, and the recognition of the entity of chronic antibody‐mediated rejection. Participation of B cells in allograft rejection and genomics markers of rejection were also major subjects addressed by the conference.

Structure, assembly and regulation of expression of capsules in Escherichia coli

Many Escherichia coli strains are covered in a layer of surface‐associated polysaccharide called the capsule. Capsular polysaccharides represent a major surface antigen, the K antigen, and more than 80 distinct K serotypes result from structural diversity in these polymers. However, not all capsules consist of K antigen. Some are due to production of an extensive layer of a polymer structurally identical to a lipopolysaccharide O antigen, but distinguished from lipopolysaccharide by the absence of terminal lipid A‐core. Recent research has provided insight into the manner in which capsules are organized on the Gram‐negative cell surface, the pathways used for their assembly, and the regulatory processes used to control their expression. A limited repertoire of capsule expression systems are available, despite the fact that the producing bacteria occupy a variety of ecological niches and possess diverse physiologies. All of the known capsule assembly systems seen in Gram‐negative bacteria are represented in E. coli, as are the majority of the regulatory strategies. Escherichia coli therefore provides a variety of working models on which studies in other bacteria are (or can be) based. In this review, we present an overview of the current molecular and biochemical models for capsule expression in E. coli. By taking into account the organization of capsule gene clusters, details of the assembly pathway, and regulatory features that dictate capsule expression, we provide a new classification system that separates the known capsules of E. coli into four distinct groups.

Post-mortem imaging as an alternative to autopsy in the diagnosis of adult deaths: a validation study

Summary Background Public objection to autopsy has led to a search for minimally invasive alternatives. Imaging has potential, but its accuracy is unknown. We aimed to identify the accuracy of post-mortem CT and MRI compared with full autopsy in a large series of adult deaths. Methods This study was undertaken at two UK centres in Manchester and Oxford between April, 2006, and November, 2008. We used whole-body CT and MRI followed by full autopsy to investigate a series of adult deaths that were reported to the coroner. CT and MRI scans were reported independently, each by two radiologists who were masked to the autopsy findings. All four radiologists then produced a consensus report based on both techniques, recorded their confidence in cause of death, and identified whether autopsy was needed. Findings We assessed 182 unselected cases. The major discrepancy rate between cause of death identified by radiology and autopsy was 32% (95% CI 26–40) for CT, 43% (36–50) for MRI, and 30% (24–37) for the consensus radiology report; 10% (3–17) lower for CT than for MRI. Radiologists indicated that autopsy was not needed in 62 (34%; 95% CI 28–41) of 182 cases for CT reports, 76 (42%; 35–49) of 182 cases for MRI reports, and 88 (48%; 41–56) of 182 cases for consensus reports. Of these cases, the major discrepancy rate compared with autopsy was 16% (95% CI 9–27), 21% (13–32), and 16% (10–25), respectively, which is significantly lower (p<0·0001) than for cases with no definite cause of death. The most common imaging errors in identification of cause of death were ischaemic heart disease (n=27), pulmonary embolism (11), pneumonia (13), and intra-abdominal lesions (16). Interpretation We found that, compared with traditional autopsy, CT was a more accurate imaging technique than MRI for providing a cause of death. The error rate when radiologists provided a confident cause of death was similar to that for clinical death certificates, and could therefore be acceptable for medicolegal purposes. However, common causes of sudden death are frequently missed on CT and MRI, and, unless these weaknesses are addressed, systematic errors in mortality statistics would result if imaging were to replace conventional autopsy. Funding Policy Research Programme, Department of Health, UK.

Expression of a dominant-negative mutant TGF-β type II receptor in transgenic mice reveals essential roles for TGF-β in regulation of growth and differentiation in the exocrine pancreas

Using a dominant‐negative mutant receptor (DNR) approach in transgenic mice, we have functionally inactivated transforming growth factor‐β (TGF‐β) signaling in select epithelial cells. The dominant‐negative mutant type II TGF‐β receptor blocked signaling by all three TGF‐β isoforms in primary hepatocyte and pancreatic acinar cell cultures generated from transgenic mice, as demonstrated by the loss of growth inhibitory and gene induction responses. However, it had no effect on signaling by activin, the closest TGF‐β family member. DNR transgenic mice showed increased proliferation of pancreatic acinar cells and severely perturbed acinar differentiation. These results indicate that TGF‐β negatively controls growth of acinar cells and is essential for the maintenance of a differentiated acinar phenotype in the exocrine pancreas in vivo. In contrast, such abnormalities were not observed in the liver. Additional abnormalities in the pancreas included fibrosis, neoangiogenesis and mild macrophage infiltration, and these were associated with a marked up‐regulation of TGF‐β expression in transgenic acinar cells. This transgenic model of targeted functional inactivation of TGF‐β signaling provides insights into mechanisms whereby loss of TGF‐β responsiveness might promote the carcinogenic process, both through direct effects on cell proliferation, and indirectly through up‐regulation of TGF‐βs with associated paracrine effects on stromal compartments.

Postmortem findings after fatal anaphylactic reactions

Aims—To determine the frequency at which classic manifestations of anaphylaxis are present at necropsy after fatal anaphylactic reactions. Methods—A register has been established of fatal anaphylactic reactions in the UK since 1992, traced from the certified cause of death and other sources. Details of the previous medical history and the reaction suggest anaphylaxis as the cause of death for 130 cases; a postmortem report was available for 56. Results—The 56 deaths studied included 19 reactions to bee or wasp venom, 16 to foods, and 21 to drugs or contrast media. Death occurred within one hour of anaphylaxis in 39 cases. Macroscopic findings included signs of asthma (mucous plugging and/or hyperinflated lungs) (15 of 56), petechial haemorrhages (10 of 56), pharyngeal/laryngeal oedema (23 of 56), but for 23 of 56 there was nothing indicative of an allergic death. Mast cell tryptase was raised in 14 of 16 cases tested; three of three tested had detectable IgE specific for the suspected allergen. Conclusions—In many cases of fatal anaphylaxis no specific macroscopic findings are present at postmortem examination. This reflects the rapidity and mode of death, which is often the result of shock rather than asphyxia. Investigations that might help determine whether anaphylaxis was the cause of death had rarely been performed. In the presence of a typical clinical history, absence of postmortem findings does not exclude the diagnosis of anaphylaxis.

Increased expression of a novel Aspergillus fumigatus ABC transporter gene, atrF, in the presence of itraconazole in an itraconazole resistant clinical isolate.

Aspergillus fumigatus is the most frequent causative agent of invasive aspergillosis. Itraconazole became available in 1990 to treat invasive aspergillosis, but instances of resistance have now been described. Drug efflux was a proposed mechanism in one itraconazole resistant clinical isolate (AF72) which accumulates low levels of the drug. Drug efflux in fungi can be mediated by ATP-binding cassette transporter (ABCT) genes, such as CDR1 in Candida albicans. Using a probe derived from CDR1, a gene, atrF, was cloned from A. fumigatus. The atrF gene product (AtrF) is 1547 amino acids long and has characteristic multidrug resistance motifs. Dot blot analysis revealed that AF72 has approximately 5-fold higher levels of atrF mRNA than susceptible isolates AF10 and H06-03 in cultures with sub-minimum inhibitory concentration (sub-MIC) levels of itraconazole. atrF is the first ABCT gene cloned from A. fumigatus, whose overexpression is correlated with itraconazole resistance.

Vascular endothelial growth factor expression correlates with tumour grade and vascularity in gliomas

Vascular endothelial growth factor expression correlates with tumour grade and vascularity in gliomas

Complete Genome Sequence and Comparative Metabolic Profiling of the Prototypical Enteroaggregative Escherichia coli Strain 042

Background Escherichia coli can experience a multifaceted life, in some cases acting as a commensal while in other cases causing intestinal and/or extraintestinal disease. Several studies suggest enteroaggregative E. coli are the predominant cause of E. coli-mediated diarrhea in the developed world and are second only to Campylobacter sp. as a cause of bacterial-mediated diarrhea. Furthermore, enteroaggregative E. coli are a predominant cause of persistent diarrhea in the developing world where infection has been associated with malnourishment and growth retardation. Methods In this study we determined the complete genomic sequence of E. coli 042, the prototypical member of the enteroaggregative E. coli, which has been shown to cause disease in volunteer studies. We performed genomic and phylogenetic comparisons with other E. coli strains revealing previously uncharacterised virulence factors including a variety of secreted proteins and a capsular polysaccharide biosynthetic locus. In addition, by using Biolog™ Phenotype Microarrays we have provided a full metabolic profiling of E. coli 042 and the non-pathogenic lab strain E. coli K-12. We have highlighted the genetic basis for many of the metabolic differences between E. coli 042 and E. coli K-12. Conclusion This study provides a genetic context for the vast amount of experimental and epidemiological data published thus far and provides a template for future diagnostic and intervention strategies.

Aberrant succination of proteins in fumarate hydratase-deficient mice and HLRCC patients is a robust biomarker of mutation status

Germline mutations in the FH gene encoding the Krebs cycle enzyme fumarate hydratase predispose to hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome. FH‐deficient cells and tissues accumulate high levels of fumarate, which may act as an oncometabolite and contribute to tumourigenesis. A recently proposed role for fumarate in the covalent modification of cysteine residues to S‐(2‐succinyl) cysteine (2SC) (termed protein succination) prompted us to assess 2SC levels in our existing models of HLRCC. Herein, using a previously characterized antibody against 2SC, we show that genetic ablation of FH causes high levels of protein succination. We next hypothesized that immunohistochemistry for 2SC would serve as a metabolic biomarker for the in situ detection of FH‐deficient tissues. Robust detection of 2SC was observed in Fh1 (murine FH)‐deficient renal cysts and in a retrospective series of HLRCC tumours (n = 16) with established FH mutations. Importantly, 2SC was undetectable in normal tissues (n = 200) and tumour types not associated with HLRCC (n = 1342). In a prospective evaluation of cases referred for genetic testing for HLRCC, the presence of 2SC‐modified proteins (2SCP) correctly predicted genetic alterations in FH in every case. In two series of unselected type II papillary renal cancer (PRCC), prospectively analysed by 2SCP staining followed by genetic analysis, the biomarker accurately identified previously unsuspected FH mutations (2/33 and 1/36). The investigation of whether metabolites in other tumour types produce protein modification signature(s) that can be assayed using similar strategies will be of interest in future studies of cancer. Copyright

Listeria monocytogenes relA and hpt Mutants Are Impaired in Surface-Attached Growth and Virulence

We describe here the identification and characterization of two Listeria monocytogenes (Tn917-LTV3) relA and hpt transposon insertion mutants that were impaired in growth after attachment to a model surface. Both mutants were unable to accumulate (p)ppGpp in response to amino acid starvation, whereas the wild-type strain accumulated (p)ppGpp within 30 min of stress induction. The induction of transcription of the relA gene after adhesion was demonstrated, suggesting that the ability to mount a stringent response and undergo physiological adaptation to nutrient deprivation is essential for the subsequent growth of the adhered bacteria. The absence of (p)ppGpp in the hpt mutant, which is blocked in the purine salvage pathway, is curious and suggests that a functional purine salvage pathway is required for the biosynthesis of (p)ppGpp. Both mutants were avirulent in a murine model of listeriosis, indicating an essential role for the stringent response in the survival and growth of L. monocytogenes in the host. Taken as a whole, this study provides new information on the role of the stringent response and the physiological adaptation of L. monocytogenes for biofilm growth and pathogenesis.