Associations between diabetes-related genetic risk scores and residual beta cell function in type 1 diabetes: the GUTDM1 study.

AIMS/HYPOTHESIS: Use of genetic risk scores (GRS) may help to distinguish between type 1 diabetes and type 2 diabetes, but less is known about whether GRS are associated with disease severity or progression after diagnosis. Therefore, we tested whether GRS are associated with residual beta cell function and glycaemic control in individuals with type 1 diabetes. METHODS: Immunochip arrays and TOPMed were used to genotype a cross-sectional cohort (n=479, age 41.7 ± 14.9 years, duration of diabetes 16.0 years [IQR 6.0-29.0], HbA1c 55.6 ± 12.2 mmol/mol). Several GRS, which were originally developed to assess genetic risk of type 1 diabetes (GRS-1, GRS-2) and type 2 diabetes (GRS-T2D), were calculated. GRS-C1 and GRS-C2 were based on SNPs that have previously been shown to be associated with residual beta cell function. Regression models were used to investigate the association between GRS and residual beta cell function, assessed using the urinary C-peptide/creatinine ratio, and the association between GRS and continuous glucose monitor metrics. RESULTS: Higher GRS-1 and higher GRS-2 both showed a significant association with undetectable UCPCR (OR 0.78; 95% CI 0.69, 0.89 and OR 0.84: 95% CI 0.75, 0.93, respectively), which were attenuated after correction for sex and age of onset (GRS-2) and disease duration (GRS-1). Higher GRS-C2 was associated with detectable urinary C-peptide/creatinine ratio (≥0.01 nmol/mmol) after correction for sex and age of onset (OR 6.95; 95% CI 1.19, 40.75). A higher GRS-T2D was associated with less time below range (TBR) (OR for TBR<4% 1.41; 95% CI 1.01 to 1.96) and lower glucose coefficient of variance (ß -1.53; 95% CI -2.76, -0.29). CONCLUSIONS/INTERPRETATION: Diabetes-related GRS are associated with residual beta cell function in individuals with type 1 diabetes. These findings suggest some genetic contribution to preservation of beta cell function.

Networks of gut bacteria relate to cardiovascular disease in a multi-ethnic population: the HELIUS study.

AIMS: Gut microbiota have been linked to blood lipid levels and cardiovascular diseases (CVDs). The composition and abundance of gut microbiota trophic networks differ between ethnicities. We aim to evaluate the relationship between gut microbiotal trophic networks and CVD phenotypes. METHODS AND RESULTS: We included cross-sectional data from 3860 individuals without CVD history from 6 ethnicities living in the Amsterdam region participating in the prospective Healthy Life in Urban Setting (HELIUS) study. Genetic variants were genotyped, faecal gut microbiota were profiled, and blood and anthropometric parameters were measured. A machine learning approach was used to assess the relationship between CVD risk (Framingham score) and gut microbiota stratified by ethnicity. Potential causal relationships between gut microbiota composition and CVD were inferred by performing two-sample Mendelian randomization with hard CVD events from the Pan-UK Biobank and microbiome genome-wide association studies summary data from a subset of the HELIUS cohort (n = 4117). Microbial taxa identified to be associated with CVD by machine learning and Mendelian randomization were often ethnic-specific, but some concordance across ethnicities was found. The microbes Akkermansia muciniphila and Ruminococcaceae UCG-002 were protective against ischaemic heart disease in African-Surinamese and Moroccans, respectively. We identified a strong inverse association between blood lipids, CVD risk, and the combined abundance of the correlated microbes Christensenellaceae-Methanobrevibacter-Ruminococcaceae (CMR). The CMR cluster was also identified in two independent cohorts and the association with triglycerides was replicated. CONCLUSION: Certain gut microbes can have a potentially causal relationship with CVD events, with possible ethnic-specific effects. We identified a trophic network centred around Christensenellaceae, Methanobrevibacter, and various Ruminococcaceae, frequently lacking in South-Asian Surinamese, to be protective against CVD risk and associated with low triglyceride levels.

Dopamine pathway and Parkinson's risk variants are associated with levodopa-induced dyskinesia.

Background: Levodopa-induced dyskinesia (LID) is a common adverse effect of levodopa, one of the main therapeutics used to treat the motor symptoms of Parkinson's disease (PD). Previous evidence suggests a connection between LID and a disruption of the dopaminergic system as well as genes implicated in PD, including GBA1 and LRRK2. Objectives: To investigate the effects of genetic variants on risk and time to LID. Methods: We performed a genome-wide association study (GWAS) and analyses focused on GBA1 and LRRK2 variants. We also calculated polygenic risk scores including risk variants for PD and variants in genes involved in the dopaminergic transmission pathway. To test the influence of genetics on LID risk we used logistic regression, and to examine its impact on time to LID we performed Cox regression including 1,612 PD patients with and 3,175 without LID. Results: We found that GBA1 variants were associated with LID risk (OR=1.65, 95% CI=1.21-2.26, p=0.0017) and LRRK2 variants with reduced time to LID onset (HR=1.42, 95% CI=1.09-1.84, p=0.0098). The fourth quartile of the PD PRS was associated with increased LID risk (ORfourth_quartile=1.27, 95% CI=1.03-1.56, p=0.0210). The third and fourth dopamine pathway PRS quartiles were associated with a reduced time to development of LID (HRthird_quartile=1.38, 95% CI=1.07-1.79, p=0.0128; HRfourth_quartile=1.38, 95% CI=1.06-1.78, p=0.0147). Conclusions: This study suggests that variants implicated in PD and in the dopaminergic transmission pathway play a role in the risk/time to develop LID. Further studies will be necessary to examine how these findings can inform clinical care.

Polygenic risk scores for prediction of cancer-associated venous thromboembolism in the UK Biobank cohort study.

BACKGROUND: Guidelines recommend thromboprophylaxis for patients with cancer at high risk of venous thromboembolism (VTE). Polygenic risk scores may improve VTE prediction but have not yet been evaluated in patients with cancer. OBJECTIVES: We assessed the performance of the 5-, 37-, 297-, extended 297- (additionally including factor V Leiden and prothrombin G20210A), and 100-single-nucleotide polymorphism (SNP) scores in predicting cancer-associated VTE in the UK Biobank, a population-based, prospective cohort study. METHODS: The primary outcome was VTE during 12 months after cancer diagnosis. Cancer and VTE diagnosis were based on ICD-10 codes. Discrimination was evaluated by c-indices and subdistribution hazard ratios in the upper vs 3 lower quartiles of the scores in a competing risk model. As a comparison, the c-index was calculated for the Khorana cancer type risk classification. RESULTS: Of 36 150 patients with cancer (median age, 66 years; 48.7% females), 1018 (2.8%) developed VTE. C-indices at 12 months ranged from 0.56 (95% CI, 0.54-0.58) for the 5-SNP to 0.60 (95% CI, 0.58-0.62) for the extended 297-SNP scores. The subdistribution hazard ratios ranged from 1.36 (95% CI, 1.19-1.56) for the 5-SNP to 1.90 (95% CI, 1.68-2.16) for the extended 297-SNP scores and were consistent after adjusting for cancer type. For the Khorana cancer type classification, the c-index was 0.60 (95% CI, 0.58-0.61), which increased to 0.65 (95% CI, 0.63-0.67, +0.05; 95% CI, 0.04-0.07) when combined with the extended 297-SNP score. CONCLUSION: These findings demonstrate that polygenic VTE risk scores can identify patients with cancer with a 1.9-fold higher VTE risk independent of cancer type. Combined clinical-genetic scores to improve cancer-associated VTE prediction should be evaluated further.

FHL2 Genetic Polymorphisms and Pro-Diabetogenic Lipid Profile in the Multiethnic HELIUS Cohort.

Type 2 diabetes mellitus (T2D) is a prevalent disease often accompanied by the occurrence of dyslipidemia. Four and a half LIM domains 2 (FHL2) is a scaffolding protein, whose involvement in metabolic disease has recently been demonstrated. The association of human FHL2 with T2D and dyslipidemia in a multiethnic setting is unknown. Therefore, we used the large multiethnic Amsterdam-based Healthy Life in an Urban Setting (HELIUS) cohort to investigate FHL2 genetic loci and their potential role in T2D and dyslipidemia. Baseline data of 10,056 participants from the HELIUS study were available for analysis. The HELIUS study contained individuals of European Dutch, South Asian Surinamese, African Surinamese, Ghanaian, Turkish, and Moroccan descent living in Amsterdam and were randomly sampled from the municipality register. Nineteen FHL2 polymorphisms were genotyped, and associations with lipid panels and T2D status were investigated. We observed that seven FHL2 polymorphisms associated nominally with a pro-diabetogenic lipid profile including triglyceride (TG), high-density and low-density lipoprotein-cholesterol (HDL-C and LDL-C), and total cholesterol (TC) concentrations, but not with blood glucose concentrations or T2D status in the complete HELIUS cohort upon correcting for age, gender, BMI, and ancestry. Upon stratifying for ethnicity, we observed that only two of the nominally significant associations passed multiple testing adjustments, namely, the association of rs4640402 with increased TG and rs880427 with decreased HDL-C concentrations in the Ghanaian population. Our results highlight the effect of ethnicity on pro-diabetogenic selected lipid biomarkers within the HELIUS cohort, as well as the need for more large multiethnic cohort studies.

Gut microbiome associations with host genotype vary across ethnicities and potentially influence cardiometabolic traits.

Previous studies in mainly European populations have reported that the gut microbiome composition is associated with the human genome. However, the genotype-microbiome interaction in different ethnicities is largely unknown. We performed a large fecal microbiome genome-wide association study of a single multiethnic cohort, the Healthy Life in an Urban Setting (HELIUS) cohort (N = 4,117). Mendelian randomization was performed using the multiethnic Pan-UK Biobank (N = 460,000) to dissect potential causality. We identified ethnicity-specific associations between host genomes and gut microbiota. Certain microbes were associated with genotype in multiple ethnicities. Several of the microbe-associated loci were found to be related to immune functions, interact with glutamate and the mucus layer, or be expressed in the gut or brain. Additionally, we found that gut microbes potentially influence cardiometabolic health factors such as BMI, cholesterol, and blood pressure. This provides insight into the relationship of ethnicity and gut microbiota and into the possible causal effects of gut microbes on cardiometabolic traits.

Pneumococcal genetic variability in age-dependent bacterial carriage.

The characteristics of pneumococcal carriage vary between infants and adults. Host immune factors have been shown to contribute to these age-specific differences, but the role of pathogen sequence variation is currently less well-known. Identification of age-associated pathogen genetic factors could leadto improved vaccine formulations. We therefore performed genome sequencing in a large carriage cohort of children and adults and combined this with data from an existing age-stratified carriage study. We compiled a dictionary of pathogen genetic variation, including serotype, strain, sequence elements, single-nucleotide polymorphisms (SNPs), and clusters of orthologous genes (COGs) for each cohort - all of which were used in a genome-wide association with host age. Age-dependent colonization showed weak evidence of being heritable in the first cohort (h2 = 0.10, 95% CI 0.00-0.69) and stronger evidence in the second cohort (h2 = 0.56, 95% CI 0.23-0.87). We found that serotypes and genetic background (strain) explained a proportion of the heritability in the first cohort (h2serotype = 0.07, 95% CI 0.04-0.14 and h2GPSC = 0.06, 95% CI 0.03-0.13) and the second cohort (h2serotype = 0.11, 95% CI 0.05-0.21 and h2GPSC = 0.20, 95% CI 0.12-0.31). In a meta-analysis of these cohorts, we found one candidate association (p=1.2 × 10-9) upstream of an accessory Sec-dependent serine-rich glycoprotein adhesin. Overall, while we did find a small effect of pathogen genome variation on pneumococcal carriage between child and adult hosts, this was variable between populations and does not appear to be caused by strong effects of individual genes. This supports proposals for adaptive future vaccination strategies that are primarily targeted at dominant circulating serotypes and tailored to the composition of the pathogen populations.

A Genetic Map of the Modern Urban Society of Amsterdam.

Genetic differences between individuals underlie susceptibility to many diseases. Genome-wide association studies (GWAS) have discovered many susceptibility genes but were often limited to cohorts of predominantly European ancestry. Genetic diversity between individuals due to different ancestries and evolutionary histories shows that this approach has limitations. In order to gain a better understanding of the associated genetic variation, we need a more global genomics approach including a greater diversity. Here, we introduce the Healthy Life in an Urban Setting (HELIUS) cohort. The HELIUS cohort consists of participants living in Amsterdam, with a level of diversity that reflects the Dutch colonial and recent migration past. The current study includes 10,283 participants with genetic data available from seven groups of inhabitants, namely, Dutch, African Surinamese, South-Asian Surinamese, Turkish, Moroccan, Ghanaian, and Javanese Surinamese. First, we describe the genetic variation and admixture within the HELIUS cohort. Second, we show the challenges during imputation when having a genetically diverse cohort. Third, we conduct a body mass index (BMI) and height GWAS where we investigate the effects of a joint analysis of the entire cohort and a meta-analysis approach for the different subgroups. Finally, we construct polygenic scores for BMI and height and compare their predictive power across the different ethnic groups. Overall, we give a comprehensive overview of a genetically diverse cohort from Amsterdam. Our study emphasizes the importance of a less biased and more realistic representation of urban populations for mapping genetic associations with complex traits and disease risk for all.

Evaluation of the Khorana, PROTECHT, and 5-SNP scores for prediction of venous thromboembolism in patients with cancer.

BACKGROUND: The Khorana score is a validated tool to identify cancer patients at higher risk of venous thromboembolism (VTE). OBJECTIVE: We compared its predictive performance to that of the clinical PROTECHT and the polygenic 5-SNP scores in patients who participated in the Dutch CPCT-02 study. PATIENTS/METHODS: Data on VTE and its risk factors were retrospectively collected for 2729 patients with advanced stage solid tumors planned for systemic cancer treatment. Patients were followed for 6 months. Overall discriminatory performance of the scores was evaluated by time-dependent c-indices. The scores were additionally evaluated dichotomously in competing risk models. RESULTS: A total of 160 (5.9%) patients developed VTE during follow-up. Time-dependent c-indices at 6 months for the Khorana, PROTECHT, and 5-SNP scores were 0.57 (95% confidence interval [CI]: 0.55-0.60), 0.60 (95% CI: 0.57-0.62), and 0.54 (95% CI: 0.51-0.57), respectively. The dichotomous scores classified 9.6%, 16.8%, and 9.5% as high-risk, respectively. VTE risk was about 2-fold higher among high-risk patients than low-risk patients for the Khorana (subdistribution hazard ratio [SHR] 1.9, 95% CI: 1.3-3.0), PROTECHT (SHR 2.1, 95% CI: 1.5-3.0), and 5-SNP scores (SHR 1.7, 95% CI: 1.03-2.8). The sensitivity at 6 months was 16.6% (95% CI: 10.5-22.7), 28.9% (95% CI: 21.5-36.3), and 14.9% (95% CI: 8.5-21.2), respectively. CONCLUSIONS: Performance of the PROTECHT or 5-SNP score was not superior to that of the Khorana score. The majority of cancer patients who developed VTE during 6-month follow-up were not identified by these scores. Future directions for studies on cancer-associated VTE prediction may include combined clinical-genetic scores.

Whole genome sequencing identifies variants associated with sarcoidosis in a family with a high prevalence of sarcoidosis.

OBJECTIVE: We studied genetic risk factors associated with sarcoidosis within a family with a high prevalence of this disease. METHODS: We studied 41 members of a family with a high rate of sarcoidosis, including an index patient with treatment-resistant neurosarcoidosis. Whole genome sequencing was performed for six affected family members and variations associated with loss of function were filtered out as candidate genes. Findings were validated by using amplicon sequencing within all 41 family members with DNA available and candidate genes were screened on absence and presence within the sarcoidosis affected and non-affected. RESULTS: Family members (n = 61) from 5 generations were available for participation including 13 subjects diagnosed with sarcoidosis (20%). Analyses identified 36 candidate variants within 34 candidate genes. Variations within three of these genes (JAK2, BACH2, and NCF1) previously have been associated with autoimmune diseases. CONCLUSIONS: We identified 34 genes with a possible role in the etiology of sarcoidosis, including JAK2. Our results may suggest evaluation of JAK inhibitors in treatment-resistant sarcoidosis. Key Points • JAK2 has a potential role in the etiology of sarcoidosis and is a potential therapeutic target. • We identified 33 additional candidate genes of which BACH2 and NCF1 have been previously associated with autoimmune disease.

Genetic Variation in Neisseria meningitidis Does Not Influence Disease Severity in Meningococcal Meningitis.

Neisseria meningitidis causes sepsis and meningitis in humans. It has been suggested that pathogen genetic variation determines variance in disease severity. Here we report results of a genome-wide association study of 486 N. meningitidis genomes from meningococcal meningitis patients and their association with disease severity. Of 369 meningococcal meningitis patients for whom clinical data was available, 44 (12%) had unfavorable outcome and 24 (7%) died. To increase power, thrombocyte count was used as proxy marker for disease severity. Bacterial genetic variants were called as k-mers, SNPs, insertions and deletions and clusters of orthologous genes (COGs). Population-level meningococcal genetic variation did not explain variance in disease severity (unfavorable outcome or thrombocyte count) in this cohort (h2 = 0.0%; 95% confidence interval: 0.0-0.9). Genetic variants in the bacterial uppS gene represented the top signal associated with thrombocyte count (p-value = 9.96e-07) but this did not reach statistical significance. We did not find an association between previously published variants in lpxL1, fHbp, and tps genes and unfavorable outcome or thrombocyte count. A power analysis based on simulated phenotypes based on real genetic data from 880 N. meningitidis genomes showed that we would be able to detect a continuous phenotype with h2 > = 0.5 with the population size available in this study. This rules out a major contribution of pathogen genetic variation to disease severity in meningococcal meningitis, and shows that much larger sample sizes are required to find specific low-effect genetic variants modulating disease outcome in meningococcal meningitis.

Diversification in immunogenicity genes caused by selective pressures in invasive meningococci.

We studied population genomics of 486 Neisseria meningitidis isolates causing meningitis in the Netherlands during the period 1979-2003 and 2006-2013 using whole-genome sequencing to evaluate the impact of a hyperendemic period of serogroup B invasive disease. The majority of serogroup B isolates belonged to ST-41/44 (41 %) and ST-32 complex (16 %). Comparing the time periods, before and after the decline of serogroup B invasive disease, there was a decrease of ST-41/44 complex sequences (P=0.002). We observed the expansion of a sub-lineage within ST-41/44 complex sequences being associated with isolation from the 1979-2003 time period (P=0.014). Isolates belonging to this sub-lineage expansion within ST-41/44 complex were marked by four antigen allele variants. Presence of these allele variants was associated with isolation from the 1979-2003 time period after correction for multiple testing (Wald test, P=0.0043 for FetA 1-5; P=0.0035 for FHbp 14; P=0.012 for PorA 7-2.4 and P=0.0031 for NHBA two peptide allele). These sequences were associated with 4CMenB vaccine coverage (Fisher's exact test, P<0.001). Outside of the sub-lineage expansion, isolates with markedly lower levels of predicted vaccine coverage clustered in phylogenetic groups showing a trend towards isolation in the 2006-2013 time period (P=0.08). In conclusion, we show the emergence and decline of a sub-lineage expansion within ST-41/44 complex isolates concurrent with a hyperendemic period in meningococcal meningitis. The expansion was marked by specific antigen peptide allele combinations. We observed preliminary evidence for decreasing 4CMenB vaccine coverage in the post-hyperendemic period.

Residual Variation Intolerance Score Detects Loci Under Selection in Neuroinvasive Listeria monocytogenes.

Listeria monocytogenes is a Gram-positive bacterium that can be found in a broad range of environments, including soil, food, animals, and humans. L. monocytogenes can cause a foodborne disease manifesting as sepsis and meningo-encephalitis. To evaluate signals of selection within the core genome of neuroinvasive L. monocytogenes strains, we sequenced 122 L. monocytogenes strains from cerebrospinal fluid (CSF) of Dutch meningitis patients and performed a genome-wide analysis using Tajima's D and ω (dN/dS). We also evaluated the residual variation intolerance score (RVIS), a computationally less demanding methodology, to identify loci under selection. Results show that the large genetic distance between the listerial lineages influences the Tajima's D and ω (dN/dS) outcome. Within genetic lineages we detected signals of selection in 6 of 2327 loci (<1%), which were replicated in an external cohort of 105 listerial CSF isolates from France. Functions of identified loci under selection were within metabolism pathways (lmo2476, encoding aldose 1-epimerase), putative antimicrobial resistance mechanisms (lmo1855, encoding PBPD3), and virulence factors (lmo0549, internalin-like protein; lmo1482, encoding comEC). RVIS over the two genetic lineages showed signals of selection in internalin-like proteins loci potentially involved in pathogen-host interaction (lmo0549, lmo0610, and lmo1290). Our results show that RVIS can be used to detect bacterial loci under selection.

Joint sequencing of human and pathogen genomes reveals the genetics of pneumococcal meningitis.

Streptococcus pneumoniae is a common nasopharyngeal colonizer, but can also cause life-threatening invasive diseases such as empyema, bacteremia and meningitis. Genetic variation of host and pathogen is known to play a role in invasive pneumococcal disease, though to what extent is unknown. In a genome-wide association study of human and pathogen we show that human variation explains almost half of variation in susceptibility to pneumococcal meningitis and one-third of variation in severity, identifying variants in CCDC33 associated with susceptibility. Pneumococcal genetic variation explains a large amount of invasive potential (70%), but has no effect on severity. Serotype alone is insufficient to explain invasiveness, suggesting other pneumococcal factors are involved in progression to invasive disease. We identify pneumococcal genes involved in invasiveness including pspC and zmpD, and perform a human-bacteria interaction analysis. These genes are potential candidates for the development of more broadly-acting pneumococcal vaccines.

Sequencing of the variable region of rpsB to discriminate between Streptococcus pneumoniae and other streptococcal species.

The vast majority of streptococci colonizing the human upper respiratory tract are commensals, only sporadically implicated in disease. Of these, the most pathogenic is Mitis group member, Streptococcus pneumoniae Phenotypic and genetic similarities between streptococci can cause difficulties in species identification. Using ribosomal S2-gene sequences extracted from whole-genome sequences published from 501 streptococci, we developed a method to identify streptococcal species. We validated this method on non-pneumococcal isolates cultured from cases of severe streptococcal disease (n = 101) and from carriage (n = 103), and on non-typeable pneumococci from asymptomatic individuals (n = 17) and on whole-genome sequences of 1157 pneumococcal isolates from meningitis in the Netherlands. Following this, we tested 221 streptococcal isolates in molecular assays originally assumed specific for S. pneumoniae, targeting cpsA, lytA, piaB, ply, Spn9802, zmpC and capsule-type-specific genes. Cluster analysis of S2-sequences showed grouping according to species in line with published phylogenies of streptococcal core genomes. S2-typing convincingly distinguished pneumococci from non-pneumococcal species (99.2% sensitivity, 100% specificity). Molecular assays targeting regions of lytA and piaB were 100% specific for S. pneumoniae, whereas assays targeting cpsA, ply, Spn9802, zmpC and selected serotype-specific assays (but not capsular sequence typing) showed a lack of specificity. False positive results were over-represented in species associated with carriage, although no particular confounding signal was unique for carriage isolates.

Differences in Inflammation Patterns Induced by African and Asian Burkholderia pseudomallei Isolates in Mice.

AbstractBurkholderia pseudomallei is the causative agent of melioidosis, an emerging tropical disease of high mortality. Sub-Saharan Africa represents potential melioidosis "hotspots"; however, to date, only a few cases have been reported. Here in, we compared the inflammatory patterns induced by a B. pseudomallei strain recently isolated from a fatal Gabonese case with the Thai reference strain B. pseudomallei-1026b and Burkholderia thailandensis-E264. Ex vivo, no differences were observed in terms of cellular responsiveness between strains. However, when compared with the B. pseudomallei-1026b strain, the Gabonese isolate was significantly less virulent in terms of bacterial dissemination, inflammatory response, and organ damage in mice. Genomic comparison between strains showed differences in regions containing a fimbriae/adhesion virulence protein. In addition to a lack of microbiology facilities, differences in virulence of Burkholderia strains might contribute to the diverse global clinical occurrence of melioidosis.

Large scale genomic analysis shows no evidence for pathogen adaptation between the blood and cerebrospinal fluid niches during bacterial meningitis.

Recent studies have provided evidence for rapid pathogen genome diversification, some of which could potentially affect the course of disease. We have previously described such variation seen between isolates infecting the blood and cerebrospinal fluid (CSF) of a single patient during a case of bacterial meningitis. Here, we performed whole-genome sequencing of paired isolates from the blood and CSF of 869 meningitis patients to determine whether such variation frequently occurs between these two niches in cases of bacterial meningitis. Using a combination of reference-free variant calling approaches, we show that no genetic adaptation occurs in either invaded niche during bacterial meningitis for two major pathogen species, Streptococcus pneumoniae and Neisseria meningitidis. This study therefore shows that the bacteria capable of causing meningitis are already able to do this upon entering the blood, and no further sequence change is necessary to cross the blood-brain barrier. Our findings place the focus back on bacterial evolution between nasopharyngeal carriage and invasion, or diversity of the host, as likely mechanisms for determining invasiveness.

Mannose-binding lectin-associated serine protease 2 (MASP-2) contributes to poor disease outcome in humans and mice with pneumococcal meningitis.

BACKGROUND: Pneumococcal meningitis is the most common and severe form of bacterial meningitis. Fatality rates are substantial, and long-term sequelae develop in about half of survivors. Disease outcome has been related to the severity of the pro-inflammatory response in the subarachnoid space. The complement system, which mediates key inflammatory processes, has been implicated as a modulator of pneumococcal meningitis disease severity in animal studies. METHODS: We investigated mannose-binding lectin-associated serine protease (MASP-2) levels in cerebrospinal fluid (CSF) samples derived from the diagnostic lumbar puncture, which was available for 307 of 792 pneumococcal meningitis episodes included in our prospective nationwide cohort study (39%), and the association between these levels and clinical outcome. Subsequently, we studied the role of MASP-2 in our experimental pneumococcal meningitis mouse model using Masp2 -/- mice and evaluated the potential of adjuvant treatment with MASP-2-specific monoclonal antibodies in wild-type (WT) mice. RESULTS: MASP-2 levels in cerebrospinal fluid of patients with bacterial meningitis were correlated with poor functional outcome. Consistent with these human data, Masp2-deficient mice with pneumococcal meningitis had lower cytokine levels and increased survival compared to WT mice. Adjuvant treatment with MASP-2-specific monoclonal antibodies led to reduced complement activation and decreased disease severity. CONCLUSIONS: MASP-2 contributes to poor disease outcome in human and mice with pneumococcal meningitis. MASP-2-specific monoclonal antibodies can be used to attenuate the inflammatory response in pneumococcal meningitis.

Variation of 46 Innate Immune Genes Evaluated for their Contribution in Pneumococcal Meningitis Susceptibility and Outcome.

Pneumococcal meningitis is the most common and severe form of bacterial meningitis. Early recognition of the pathogen and subsequent innate immune response play a vital role in disease susceptibility and outcome. Genetic variations in innate immune genes can alter the immune response and influence susceptibility and outcome of meningitis disease. Here we conducted a sequencing study of coding regions from 46 innate immune genes in 435 pneumococcal meningitis patients and 416 controls, to determine the role of genetic variation on pneumococcal meningitis susceptibility and disease outcome. Strongest signals for susceptibility were rs56078309 CXCL1 (p=4.8e-04) and rs2008521 in CARD8 (p=6.1e-04). For meningitis outcome the rs2067085 in NOD2 (p=5.1e-04) and rs4251552 of IRAK4 were the strongest associations with unfavorable outcome (p=6.7e-04). Haplotype analysis showed a haplotype block, determined by IRAK4 rs4251552, significantly associated with unfavorable outcome (p=0.004). Cytokine measurements from cerebrospinal fluid showed that with the IRAK4 rs4251552 G risk allele had higher levels of IL-6 compared to individuals with A/A genotype (p=0.04). We show that genetic variation within exons and flanking regions of 46 innate immunity genes does not yield significant association with pneumococcal meningitis. The strongest identified signal IRAK4 does imply a potential role of genetic variation in pneumococcal meningitis.