Declan T. Bradley

Complement in age-related macular degeneration: a focus on function.

Age-related macular degeneration (AMD) is an inflammatory disease, which causes visual impairment and blindness in older people. The proteins of the complement system are central to the development of this disease. Local and systemic inflammation in AMD are mediated by the deregulated action of the alternative pathway of the complement system. Variants in complement system genes alter an individuals risk of developing AMD. Recent studies have shown how some risk-associated genetic variants alter the function of the complement system. In this review, we describe the evolution of the complement system and bring together recent research to form a picture of how changes in complement system genes and proteins affect the function of the complement cascade, and how this affects the development of AMD. We discuss the application of this knowledge to prevention and possible future treatments of AMD.

A variant in LDLR is associated with abdominal aortic aneurysm

Background—Abdominal aortic aneurysm (AAA) is a common cardiovascular disease among older people and demonstrates significant heritability. In contrast to similar complex diseases, relatively few genetic associations with AAA have been confirmed. We reanalyzed our genome-wide study and carried through to replication suggestive discovery associations at a lower level of significance. Methods and Results—A genome-wide association study was conducted using 1830 cases from the United Kingdom, New Zealand, and Australia with infrarenal aorta diameter ≥30 mm or ruptured AAA and 5435 unscreened controls from the 1958 Birth Cohort and National Blood Service cohort from the Wellcome Trust Case Control Consortium. Eight suggestive associations with P<1×10−4 were carried through to in silico replication in 1292 AAA cases and 30 503 controls. One single-nucleotide polymorphism associated with P<0.05 after Bonferroni correction in the in silico study underwent further replication (706 AAA cases and 1063 controls from the United Kingdom, 507 AAA cases and 199 controls from Denmark, and 885 AAA cases and 1000 controls from New Zealand). Low-density lipoprotein receptor (LDLR) rs6511720 A was significantly associated overall and in 3 of 5 individual replication studies. The full study showed an association that reached genome-wide significance (odds ratio, 0.76; 95% confidence interval, 0.70–0.83; P=2.08×10−10). Conclusions—LDLR rs6511720 is associated with AAA. This finding is consistent with established effects of this variant on coronary artery disease. Shared causal pathways with other cardiovascular diseases may present novel opportunities for preventative and therapeutic strategies for AAA.

Abdominal Aortic Aneurysm Genetic Associations: Mostly False? A Systematic Review and Meta-analysis

OBJECTIVE/BACKGROUND Many associations between abdominal aortic aneurysm (AAA) and genetic polymorphisms have been reported. It is unclear which are genuine and which may be caused by type 1 errors, biases, and flexible study design. The objectives of the study were to identify associations supported by current evidence and to investigate the effect of study design on reporting associations. METHODS Data sources were MEDLINE, Embase, and Web of Science. Reports were dual-reviewed for relevance and inclusion against predefined criteria (studies of genetic polymorphisms and AAA risk). Study characteristics and data were extracted using an agreed tool and reports assessed for quality. Heterogeneity was assessed using I(2) and fixed- and random-effects meta-analyses were conducted for variants that were reported at least twice, if any had reported an association. Strength of evidence was assessed using a standard guideline. RESULTS Searches identified 467 unique articles, of which 97 were included. Of 97 studies, 63 reported at least one association. Of 92 studies that conducted multiple tests, only 27% corrected their analyses. In total, 263 genes were investigated, and associations were reported in polymorphisms in 87 genes. Associations in CDKN2BAS, SORT1, LRP1, IL6R, MMP3, AGTR1, ACE, and APOA1 were supported by meta-analyses. CONCLUSION Uncorrected multiple testing and flexible study design (particularly testing many inheritance models and subgroups, and failure to check for Hardy-Weinberg equilibrium) contributed to apparently false associations being reported. Heterogeneity, possibly due to the case mix, geographical, temporal, and environmental variation between different studies, was evident. Polymorphisms in nine genes had strong or moderate support on the basis of the literature at this time. Suggestions are made for improving AAA genetics study design and conduct.

Genetic susceptibility to invasive meningococcal disease: MBL2 structural polymorphisms revisited in a large case-control study and a systematic review.

Invasive infection caused by Neisseria meningitidis is a worldwide public health problem. Previous reports have indicated that carriage of common ‘defective’ structural polymorphisms of the host mannose‐binding lectin gene (MBL2) greatly increases an individual’s risk of developing the disease. We report the largest case–control study so far to investigate the effect of these polymorphisms in meningococcal disease (296 PCR‐positive cases and 5196 population controls, all of European ancestry) and demonstrate that no change in risk is associated with the polymorphisms overall or in any age‐defined subgroup. This finding contrasts with two smaller studies that reported an increase in risk. A systematic review of all studies of MBL2 polymorphisms in people of European ancestry published since 1999, including 24 693 individuals, revealed a population frequency of the combined ‘defective’MBL2 allele of 0.230 (95% confidence limits: 0.226–0.234). The past reported associations of increased risk of meningococcal disease were because of low ‘defective’ allele frequencies in their study control populations (0.13 and 0.04) that indicate systematic problems with the studies. The data from our study and all other available evidence indicate that MBL2 structural polymorphisms do not predispose children or adults to invasive meningococcal disease.

The Effectiveness of Disaster Risk Communication: A Systematic Review of Intervention Studies

INTRODUCTION A disaster is a serious disruption to the functioning of a community that exceeds its capacity to cope within its own resources. Risk communication in disasters aims to prevent and mitigate harm from disasters, prepare the population before a disaster, disseminate information during disasters and aid subsequent recovery. The aim of this systematic review is to identify, appraise and synthesise the findings of studies of the effects of risk communication interventions during four stages of the disaster cycle. METHODS We searched the Cochrane Central Register of Controlled Trials, Embase, MEDLINE, PsycInfo, Sociological Abstracts, Web of Science and grey literature sources for randomised trials, cluster randomised trials, controlled and uncontrolled before and after studies, interrupted time series studies and qualitative studies of any method of disaster risk communication to at-risk populations. Outcome criteria were disaster-related knowledge and behaviour, and health outcomes. RESULTS Searches yielded 5,224 unique articles, of which 100 were judged to be potentially relevant. Twenty-five studies met the inclusion criteria, and two additional studies were identified from other searching. The studies evaluated interventions in all four stages of the disaster cycle, included a variety of man-made, natural and infectious disease disasters, and were conducted in many disparate settings. Only one randomised trial and one cluster randomised trial were identified, with less robust designs used in the other studies. Several studies reported improvements in disaster-related knowledge and behaviour. DISCUSSION We identified and appraised intervention studies of disaster risk communication and present an overview of the contemporary literature. Most studies used non-randomised designs that make interpretation challenging. We do not make specific recommendations for practice but highlight the need for high-quality randomised trials and appropriately-analysed cluster randomised trials in the field of disaster risk communication where these can be conducted within an appropriate research ethics framework.

A novel GUCY2D mutation, V933A, causes central areolar choroidal dystrophy.

PURPOSE To identify the genetic cause of central areolar choroidal dystrophy (CACD) in a large Northern Irish family. METHODS We previously reported linkage of the locus for CACD in this family to an interval of approximately 5 cM on chromosome 17p13 flanked by polymorphic markers D17S1810 and CHLC GATA7B03. We undertook sequence capture, massively parallel sequencing and computational alignment, base-calling and annotation to identify a causative mutation. Conventional sequencing was used to confirm the RESULTS Results. Deep sequencing identified a single-base substitution in guanylate cyclase 2D, membrane (retina-specific) gene (GUCY2D). The novel mutation segregated with the disease phenotype and resulted in substitution of valine by alanine at position 933, within the catalytic domain of the protein. It altered a motif that is strongly conserved in a large number of distantly related proteins across several species and was predicted to have a damaging effect on protein activity. CONCLUSIONS Mutations in GUCY2D have previously been associated with dominant cone-rod dystrophies (CORD6) and recessive forms of Lebers congenital amaurosis. This is the first report of a GUCY2D mutation causing CACD and adds to our understanding of genotype-phenotype correlation in this heterogeneous group of choroidoretinal dystrophies.

Rare CFH mutations and early-onset age-related macular degeneration

Editor, F actor H (FH), one of the most abundant proteins in human blood is the key inhibitory regulator of the complement system. The complement factor H (CFH) gene which encodes it is highly polymorphic within and between populations: haplotypes carrying functional variants, including deletion of CFHR3-CFHR1 (CNP147) and rs1061170 (Y402H), alter risk of age-related macular degeneration (AMD) and autoimmune disease (Bradley et al. 2011). The common form of FH protein is composed of 20 repetitive short consensus repeat (SCR) units which are folded to form a protein with several active sites. Rare mutations in the FH N-terminal SCRs have recently been reported to cause early-onset familial AMD in two families (Yu et al. 2014). We conducted a pooled next-generation sequencing (NGS) experiment using fragmented and indexed DNA from 35 AMD cases. All cases and controls for this study were recruited and described previously (Hughes et al. 2007). DNA was retrieved from the Anonymised DNA, RNA and Serum Bank in the Centre for Public Health at Queen’s University Belfast, under ethical approval of the Office for Research Ethics Committees Northern Ireland (reference 11/NI/0139). Patients were of European descent and had neovascular AMD in at least one eye, but no details about the clinical course or treatment were available. A total of 5 Mb, including CFH, was targeted using a Nimblegen SeqCap EZ library and sequenced on a HiSeq 2000 (Illumina). Paired-end reads (100 bp) were aligned to hg19 human reference sequence with the Burroughs Wheeler Aligner 0.5.9 aln algorithm. Sorting and indexing was performed with SAMtools 0.1.14. Genome Analysis Toolkit was used to recalibrate, realign and call polymorphisms, and sequence was viewed in Integrative Genomics Viewer. We identified a novel missense mutation,CFH P139A, for which the G allele contributed 13 of 1061 reads from the pooled DNA (Fig. 1A) and verified it in a single contributing individual by Sanger sequencing (Fig. 1B). It was not found in a further 181 AMD cases or 151 elderly controls. The individual had neovascular AMDwith onset at the age of 55 years and carried an otherwise low-risk genetic background (two protective copies of CFH rs800292 [62I] and heterozygous for the common ARMS2 rs10490924 risk allele). Only two patients in our database of 303 cases had a disease onset at a younger age than this individual. The P139A mutation is located near the C-terminal end of SCR2 and changes a highly conserved amino acid. It is predicted to be damaging by both SIFT and PolyPhen-2. Modelling suggests that the SCR2-SCR3 junction is crucial for the docking of complement factor I (FI) into the groove formed between FH SCRs 1 to 3 and C3b (Roversi et al. 2011). Disruption of the interaction between FH and FI is expected to inhibit decay of C3b and therefore to result in a greater level of alternative pathway activation.We cannot conduct protein studies as ourDNA collection is anonymized, and we have

Susceptibility to Invasive Meningococcal Disease: Polymorphism of Complement System Genes and Neisseria meningitidis Factor H Binding Protein

Background Neisseria meningitidis can cause severe infection in humans. Polymorphism of Complement Factor H (CFH) is associated with altered risk of invasive meningococcal disease (IMD). We aimed to find whether polymorphism of other complement genes altered risk and whether variation of N. meningitidis factor H binding protein (fHBP) affected the risk association. Methods We undertook a case-control study with 309 European cases and 5,200 1958 Birth Cohort and National Blood Service cohort controls. We used additive model logistic regression, accepting P<0.05 as significant after correction for multiple testing. The effects of fHBP subfamily on the age at infection and severity of disease was tested using the independent samples median test and Student’s T test. The effect of CFH polymorphism on the N. meningitidis fHBP subfamily was investigated by logistic regression and Chi squared test. Results Rs12085435 A in C8B was associated with odds ratio (OR) of IMD (0.35 [95% CI 0.19–0.67]; P = 0.03 after correction). A CFH haplotype tagged by rs3753396 G was associated with IMD (OR 0.56 [95% CI 0.42–0.76], P = 1.6x10−4). There was no bacterial load (CtrA cycle threshold) difference associated with carriage of this haplotype. Host CFH haplotype and meningococcal fHBP subfamily were not associated. Individuals infected with meningococci expressing subfamily A fHBP were younger than those with subfamily B fHBP meningococci (median 1 vs 2 years; P = 0.025). Discussion The protective CFH haplotype alters odds of IMD without affecting bacterial load for affected heterozygotes. CFH haplotype did not affect the likelihood of infecting meningococci having either fHBP subfamily. The association between C8B rs12085435 and IMD requires independent replication. The CFH association is of interest because it is independent of known functional polymorphisms in CFH. As fHBP-containing vaccines are now in use, relationships between CFH polymorphism and vaccine effectiveness and side-effects may become important.

Coding polymorphisms in the genes of the alternative complement pathway and abdominal aortic aneurysm.

Variants in the genes of the alternative complement pathway are associated with risk of numerous inflammatory diseases. Abdominal aortic aneurysm is associated with inflammation and is a common cause of illness and death among European populations. This study tested 49 single nucleotide polymorphisms, including common putatively functional polymorphisms, in the genes of the alternative complement cascade (CFH, CFB, CFD, CFI, properdin, CR1, CR1L, CR2, CD46, vitronectin, C3, C5, C6, C7, C8A, C8B, C8G and C9). The study group were 434 cases with infra‐renal aortic diameter ≥30 mm and 378 disease‐free controls from two UK centres, all with self‐reported European ancestry. There was no evidence for significant association with presence or size of aneurysm following correction for multiple testing. This study suggests that variation in the genes of the alternative pathway is not an important cause of abdominal aortic aneurysm development.

Reasons for non-participation in the Northern Ireland Bowel Cancer Screening Programme: a qualitative study.

Objectives To identify the reasons why some people do not participate in bowel cancer screening so that steps can be taken to improve informed decision-making. Design Qualitative study, using focus groups with thematic analysis of data to identify, analyse and report patterns. Transcripts were repeatedly read and inductively coded using a phenomenological perspective, and organised into key themes. Setting Belfast and Armagh, two areas of Northern Ireland with relatively low uptake of bowel cancer screening. Participants Ten women and 18 men in three single-gender focus groups (two male and one female), each with 9–10 participants. Study participants were recruited by convenience sampling from the general public and were eligible for, but had not taken part in, the Northern Ireland Bowel Cancer Screening Programme. Results Key themes identified were fear of cancer; the test procedure; social norms; past experience of cancer and screening; lack of knowledge or understanding about bowel cancer screening; and resulting behaviour towards the test. Fear about receiving bad news and reluctance to conduct the test themselves were reactions that participants seemed willing to overcome after taking part in open discussion about the test. Conclusions We identified barriers to participation in bowel cancer screening and used these insights to develop new materials to support delivery of the programme. Some of the issues raised have been identified in other UK settings, suggesting that knowledge about barriers, and strategies to improve uptake, may be generalisable.