Common variants in Alzheimer’s disease and risk stratification by polygenic risk scores

Funder: Funder: Fundación bancaria ‘La Caixa’ Number: LCF/PR/PR16/51110003 Funder: Grifols SA Number: LCF/PR/PR16/51110003 Funder: European Union/EFPIA Innovative Medicines Initiative Joint Number: 115975 Funder: JPco-fuND FP-829-029 Number: 733051061Genetic discoveries of Alzheimer's disease are the drivers of our understanding, and together with polygenetic risk stratification can contribute towards planning of feasible and efficient preventive and curative clinical trials. We first perform a large genetic association study by merging all available case-control datasets and by-proxy study results (discovery n = 409,435 and validation size n = 58,190). Here, we add six variants associated with Alzheimer's disease risk (near APP, CHRNE, PRKD3/NDUFAF7, PLCG2 and two exonic variants in the SHARPIN gene). Assessment of the polygenic risk score and stratifying by APOE reveal a 4 to 5.5 years difference in median age at onset of Alzheimer's disease patients in APOE ɛ4 carriers. Because of this study, the underlying mechanisms of APP can be studied to refine the amyloid cascade and the polygenic risk score provides a tool to select individuals at high risk of Alzheimer's disease

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Large-scale identification of pathogenicity factors in "Bartonella" by signature-tagged mutagenesis

Bartonellae are bacterial pathogens uniquely adapted to cause intraerythrocytic infection in their mammalian reservoir hosts. In the case of human-specific Bartonella bacilliformis and Bartonella quintana, the intraerythrocytic bacteremia leads to the clinical manifestations of Oroya fever and trench fever, respectively. Here, we adapted large-scale signature-tagged mutagenesis (STM) for the first time to Bartonella, allowing us to screen for pathogenicity factors required for infection of the mammalian reservoir host in vivo. A total of 3084 STM mutants of rat-specific B. tribocorum were screened in a rat infection model for these criteria. After two rounds of screening, 130 mutants showed severe attenuation compared to wild-type B. tribocorum. We mapped the transposon insertion sites of these mutants to 80 different genes, and categorized them according to their putative function. Besides already described pathogenicity factors responsible for interaction with the host, like the two type IV secretion systems VirB-D4 and Trw, we discovered factors previously unlinked to pathogenesis. These belong to diverse functional classes, like transport, gene-expression regulation, cell envelope integrity, or metabolism. A quarter of the identified genes are (conserved) hypothetical coding for novel pathogenicity factors. We have used an additional PCR-screening approach on the entire mutant library to test for the level of mutational saturation and to identify non-essential genes in a pathogenicity island encoding 18 gene products related to the process of type IV secretion

Additional file 1: of Variability in contact precautions to control the nosocomial spread of multi-drug resistant organisms in the endemic setting: a multinational cross-sectional survey

Table S1. Country of workplace of the 213 survey participants (number of respondents per country). Table S2. Survey respondents affiliations (n = 213). Table S3. MRSA contact precaution measures according to professional background. Table S4. GRE contact precaution measures according to professional background. Table S5. ESBL-E. coli contact precaution measures according to professional background. Table S6. ESBL-non-E. coli contact precaution measures according to professional background. Table S7. CR-E. coli contact precaution measures according to professional background. Table S8. CRE contact precaution measures according to professional background. Table S9. MRD P. aeruginosa contact precaution measures according to professional background. Table S10. MRD A. baumannii contact precaution measures according to professional background. Table S11. Indication and specification for contact precautions (CP) and isolation (cont. Next page) after deduplication*. Table S12. Other specific requirements for CP, results after deduplication*. Table S13. Characteristics of respondents that indicated “unknown” compared to respondents that provided any other answer. (DOCX 78 kb

Variability in contact precautions to control the nosocomial spread of multi-drug resistant organisms in the endemic setting: a multinational cross-sectional survey

Abstract Background Definitions and practices regarding use of contact precautions and isolation to prevent the spread of gram-positive and gram-negative multidrug-resistant organisms (MDRO) are not uniform. Methods We conducted an on-site survey during the European Congress on Clinical Microbiology and Infectious Diseases 2014 to assess specific details on contact precaution and implementation barriers. Results Attendants from 32 European (EU) and 24 non-EU countries participated (n = 213). In EU-respondents adherence to contact precautions and isolation was high for Methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Enterobacteriaceae, and MDR A. baumannii (84.7, 85.7, and 80%, respectively) whereas only 68% of EU-respondents considered any contact precaution measures for extended-spectrum-beta-lactamase (ESBL) producing non-E. coli. Between 30 and 45% of all EU and non-EU respondents did not require health-care workers (HCW) to wear gowns and gloves at all times when entering the room of a patient in contact isolation. Between 10 and 20% of respondents did not consider any rooming specifications or isolation for gram-positive MDRO and up to 30% of respondents abstain from such interventions in gram-negative MDRO, especially non-E. coli ESBL. Understaffing and lack of sufficient isolation rooms were the most commonly encountered barriers amongst EU and non-EU respondents. Conclusion The effectiveness of contact precautions and isolation is difficult to assess due to great variation in components of the specific measures and mixed levels of implementation. The lack of uniform positive effects of contact isolation to prevent transmission may be explained by the variability of interpretation of this term. Indications for contact isolation require a global definition and further sound studies

The Trw Type IV Secretion System of Bartonella Mediates Host-Specific Adhesion to Erythrocytes

Bacterial pathogens typically infect only a limited range of hosts; however, the genetic mechanisms governing host-specificity are poorly understood. The alpha-proteobacterial genus Bartonella comprises 21 species that cause host-specific intraerythrocytic bacteremia as hallmark of infection in their respective mammalian reservoirs, including the human-specific pathogens Bartonella quintana and Bartonella bacilliformis that cause trench fever and Oroya fever, respectively. Here, we have identified bacterial factors that mediate host-specific erythrocyte colonization in the mammalian reservoirs. Using mouse-specific Bartonella birtlesii, human-specific Bartonella quintana, cat-specific Bartonella henselae and rat-specific Bartonella tribocorum, we established in vitro adhesion and invasion assays with isolated erythrocytes that fully reproduce the host-specificity of erythrocyte infection as observed in vivo. By signature-tagged mutagenesis of B. birtlesii and mutant selection in a mouse infection model we identified mutants impaired in establishing intraerythrocytic bacteremia. Among 45 abacteremic mutants, five failed to adhere to and invade mouse erythrocytes in vitro. The corresponding genes encode components of the type IV secretion system (T4SS) Trw, demonstrating that this virulence factor laterally acquired by the Bartonella lineage is directly involved in adherence to erythrocytes. Strikingly, ectopic expression of Trw of rat-specific B. tribocorum in cat-specific B. henselae or human-specific B. quintana expanded their host range for erythrocyte infection to rat, demonstrating that Trw mediates host-specific erythrocyte infection. A molecular evolutionary analysis of the trw locus further indicated that the variable, surface-located TrwL and TrwJ might represent the T4SS components that determine host-specificity of erythrocyte parasitism. In conclusion, we show that the laterally acquired Trw T4SS diversified in the Bartonella lineage to facilitate host-restricted adhesion to erythrocytes in a wide range of mammals

The Trw Type IV Secretion System of Bartonella Mediates Host-Specific Adhesion to Erythrocytes

Bacterial pathogens typically infect only a limited range of hosts; however, the genetic mechanisms governing host-specificity are poorly understood. The alpha-proteobacterial genus Bartonella comprises 21 species that cause host-specific intraerythrocytic bacteremia as hallmark of infection in their respective mammalian reservoirs, including the human-specific pathogens Bartonella quintana and Bartonella bacilliformis that cause trench fever and Oroya fever, respectively. Here, we have identified bacterial factors that mediate host-specific erythrocyte colonization in the mammalian reservoirs. Using mouse-specific Bartonella birtlesii, human-specific Bartonella quintana, cat-specific Bartonella henselae and rat-specific Bartonella tribocorum, we established in vitro adhesion and invasion assays with isolated erythrocytes that fully reproduce the host-specificity of erythrocyte infection as observed in vivo. By signature-tagged mutagenesis of B. birtlesii and mutant selection in a mouse infection model we identified mutants impaired in establishing intraerythrocytic bacteremia. Among 45 abacteremic mutants, five failed to adhere to and invade mouse erythrocytes in vitro. The corresponding genes encode components of the type IV secretion system (T4SS) Trw, demonstrating that this virulence factor laterally acquired by the Bartonella lineage is directly involved in adherence to erythrocytes. Strikingly, ectopic expression of Trw of rat-specific B. tribocorum in cat-specific B. henselae or human-specific B. quintana expanded their host range for erythrocyte infection to rat, demonstrating that Trw mediates host-specific erythrocyte infection. A molecular evolutionary analysis of the trw locus further indicated that the variable, surface-located TrwL and TrwJ might represent the T4SS components that determine host-specificity of erythrocyte parasitism. In conclusion, we show that the laterally acquired Trw T4SS diversified in the Bartonella lineage to facilitate host-restricted adhesion to erythrocytes in a wide range of mammals