Common polymorphisms in the complement system and susceptiblity to bacterial meningitis

Low serum complement level is associated with higher mortality in tuberculous meningitis: a retrospective cohort study

Purpose

We evaluated the associations between serum complement levels and tuberculous meningitis (TBM), bacterial meningitis (BM), and viral meningitis (VM), as well as the association between serum complement levels and mortality in TBM.

Methods

Background information and blood/cerebrospinal fluid analysis results were collected from 2009 to 2019. Patients who had serum complement level data collected at admission and who were diagnosed with TBM (n = 97), BM (n = 31), or VM (n = 557) were enrolled.

Results

Initial serum complement levels were significantly lower in the TBM group than the VM group in both the total population and the propensity score-matched population. In the TBM and VM groups, compared to patients with initial highest-quartile C4 level, patients in the lowest quartile (C4 < 24.3 mg/dL) had significantly greater odds of TBM diagnosis (odds ratio, 2.2; 95% confidence interval, 1.0-4.5; p = 0.038). In the TBM group, patients with the lowest-quartile C3 level (<96.9 mg/dL) experienced a significantly higher 90-day mortality rate compared to other TBM patients (hazard ratio, 19.0; 95% confidence interval, 2.1-167.4.5; p = 0.008).

Conclusion

Both serum C3 and C4 levels were significantly lower in the TBM group than in the VM group. TBM patients with lower serum C3 level had a significantly higher mortality rate than those with higher C3 level.

Synthesizing the connections between environmental disturbances and zoonotic spillover

Zoonotic spillover is a phenomenon characterized by the transfer of pathogens between different animal species. Most human emerging infectious diseases originate from non-human animals, and human-related environmental disturbances are the driving forces of the emergence of new human pathogens. Synthesizing the sequence of basic events involved in the emergence of new human pathogens is important for guiding the understanding, identification, and description of key aspects of human activities that can be changed to prevent new outbreaks, epidemics, and pandemics. This review synthesizes the connections between environmental disturbances and increased risk of spillover events based on the One Health perspective. Anthropogenic disturbances in the environment (e.g., deforestation, habitat fragmentation, biodiversity loss, wildlife exploitation) lead to changes in ecological niches, reduction of the dilution effect, increased contact between humans and other animals, changes in the incidence and load of pathogens in animal populations, and alterations in the abiotic factors of landscapes. These phenomena can increase the risk of spillover events and, potentially, facilitate new infectious disease outbreaks. Using Brazil as a study model, this review brings a discussion concerning anthropogenic activities in the Amazon region and their potential impacts on spillover risk and spread of emerging diseases in this region.

Complement component 3 mutations alter the longitudinal risk of pediatric malaria and severe malarial anemia

Severe malarial anemia (SMA) is a leading cause of childhood morbidity and mortality in holoendemic Plasmodium falciparum transmission regions. To gain enhanced understanding of predisposing factors for SMA, we explored the relationship between complement component 3 (C3) missense mutations [rs2230199 (2307C>G, Arg>Gly¹⁰²) and rs11569534 (34420G>A, Gly>Asp¹²²⁴)], malaria, and SMA in a cohort of children (n = 1617 children) over 36 months of follow-up. Variants were selected based on their ability to impart amino acid substitutions that can alter the structure and function of C3. The 2307C>G mutation results in a basic to a polar residue change (Arg to Gly) at position 102 (β-chain) in the macroglobulin-1 (MG1) domain, while 34420G>A elicits a polar to acidic residue change (Gly to Asp) at position 1224 (α-chain) in the thioester-containing domain. After adjusting for multiple comparisons, longitudinal analyses revealed that inheritance of the homozygous mutant (GG) at 2307 enhanced the risk of SMA (RR = 2.142, 95%CI: 1.229-3.735, P = 0.007). The haplotype containing both wild-type alleles (CG) decreased the incident risk ratio of both malaria (RR = 0.897, 95%CI: 0.828-0.972, P = 0.008) and SMA (RR = 0.617, 95%CI: 0.448-0.848, P = 0.003). Malaria incident risk ratio was also reduced in carriers of the GG (Gly¹⁰²Gly¹²²⁴) haplotype (RR = 0.941, 95%CI: 0.888-0.997, P = 0.040). Collectively, inheritance of the missense mutations in MG1 and thioester-containing domain influence the longitudinal risk of malaria and SMA in children exposed to intense Plasmodium falciparum transmission.

Recurrent Community-Acquired Bacterial Meningitis in Adults

BACKGROUND

Recurrent bacterial meningitis has been found to occur in about 5% of meningitis cases.

METHODS

We analyzed adults with recurrent episodes in a prospective nationwide cohort study of community-acquired bacterial meningitis.

RESULTS

Of 2264 episodes of community-acquired bacterial meningitis between 2006 and 2018, 143 (6%) were identified as recurrent episodes in 123 patients. The median age was 57 years (interquartile range [IQR], 43-66), and 57 episodes (46%) occurred in men. The median duration between the first and the current episode was 5 years (IQR, 1-15). For 82 of 123 patients (67%), it was the first recurrent episode, 31 patients had 2-5 previous episodes (25%), 2 had 6-10 episodes (2%), and 2 had >10 episodes (2%). Predisposing factors were identified in 87 of 118 patients (74%) and most commonly consisted of ear or sinus infections (43 of 120, 36%) and cerebrospinal fluid leakage (37 of 116, 32%). The most common pathogens were Streptococcus pneumoniae (93 of 143, 65%) and Haemophilus influenzae (19 of 143, 13%). The outcome was unfavorable (Glasgow outcome scale score, <5) in 24 episodes with recurrent meningitis (17%) vs 810 for nonrecurrent meningitis patients (39%, P < .001). Six of 143 died (4%) vs 362 of 2095 patients (17%, P < .001).

CONCLUSIONS

Recurrent meningitis occurs mainly in patients with ear or sinus infections and cerebrospinal fluid leakage. Predominant causative pathogens are S. pneumoniae and H. influenzae. The disease course is less severe, resulting in lower case fatality compared with nonrecurrent meningitis patients.

Follow-up evaluation of the immunological status of children admitted for acute cerebral nervous system infections: a retrospective study

Background

Acute Cerebral Nervous System Infections (ACNS) may cause death or severe complications even to promptly treated children. The role of the immune system in influencing the course and the outcome of meningitis has been studied but it is not yet completely understood. The aim of the research is to ascertain whether children who experienced ACNS infection had a normal immune system.

Methods

Patients under 18 years of age admitted at Bambino Gesù Children from January 2006 till June 2016 for meningitis were asked to participate to the follow-up study. The immune status was evaluated both clinically and by laboratory investigations.

Results

Most of the patients over 3 years at follow up had at least one immunological alteration at follow-up evaluation (74%). Considering ACNS infection etiology, certain pathogens were almost exclusive of patients affected by some immunological alteration, regardless of their age.

Discussion

Our preliminary results indicate that sub-clinical immunological defects may be associated to ACNS pediatric infections. Moreover, to the best of our knowledges, this is the first study correlating pathogens to immune evaluation in ACNS infections. It is, however, important to underline the high frequency of persistent immunological alterations in the analyzed patients. Further studies are needed to confirm our conclusions.

Conclusions

We recommend an immunological assessment at follow up evaluation in children who experienced an ACNS infection.

Person-Specific Biomolecular Coronas Modulate Nanoparticle Interactions with Immune Cells in Human Blood

When nanoparticles interact with human blood, a multitude of plasma components adsorb onto the surface of the nanoparticles, forming a biomolecular corona. Corona composition is known to be influenced by the chemical composition of nanoparticles. In contrast, the possible effects of variations in the human blood proteome between healthy individuals on the formation of the corona and its subsequent interactions with immune cells in blood are unknown. Herein, we prepared and examined a matrix of 11 particles (including organic and inorganic particles of three sizes and five surface chemistries) and plasma samples from 23 healthy donors to form donor-specific biomolecular coronas (personalized coronas) and investigated the impact of the personalized coronas on particle interactions with immune cells in human blood. Among the particles examined, poly(ethylene glycol) (PEG)-coated mesoporous silica (MS) particles, irrespective of particle size (800, 450, or 100 nm in diameter), displayed the widest range (up to 60-fold difference) of donor-dependent variance in immune cell association. In contrast, PEG particles (after MS core removal) of 860, 518, or 133 nm in diameter displayed consistent stealth behavior (negligible cell association), irrespective of plasma donor. For comparison, clinically relevant PEGylated doxorubicin-encapsulated liposomes (Doxil) (74 nm in diameter) showed significant variance in association with monocytes and B cells across all plasma donors studied. An in-depth proteomic analysis of each biomolecular corona studied was performed, and the results were compared against the nanoparticle-blood cell association results, with individual variance in the proteome driving differential association with specific immune cell types. We identified key immunoglobulin and complement proteins that explicitly enriched or depleted within the corona and which strongly correlated with the cell association pattern observed across the 23 donors. This study demonstrates how plasma variance in healthy individuals significantly influences the blood immune cell interactions of nanoparticles.

Tackling COVID-19 infection through complement-targeted immunotherapy

The complement system is an ancient part of innate immunity sensing highly pathogenic coronaviruses by mannan‐binding lectin (MBL) resulting in lectin pathway activation and subsequent generation of the anaphylatoxins (ATs) C3a and C5a as important effector molecules. Complement deposition on endothelial cells and high blood C5a serum levels have been reported in COVID‐19 patients with severe illness, suggesting vigorous complement activation leading to systemic thrombotic microangiopathy (TMA). Complement regulator gene variants prevalent in African‐Americans have been associated with a higher risk for severe TMA and multi‐organ injury. Strikingly, severe acute respiratory syndrome Coronavirus 2 (SARS‐CoV‐2)‐infected African‐Americans suffer from high mortality. These findings allow us to apply our knowledge from other complement‐mediated diseases to COVID‐19 infection to better understand severe disease pathogenesis. Here, we discuss the multiple aspects of complement activation, regulation, crosstalk with other parts of the immune system, and the options to target complement in COVID‐19 patients to halt disease progression and death.

Targeting the complement system in bacterial meningitis

Bacterial meningitis is most commonly caused by Streptococcus pneumoniae and Neisseria meningitidis and continues to pose a major public health threat. Morbidity and mortality of meningitis are driven by an uncontrolled host inflammatory response. This comprehensive update evaluates the role of the complement system in upregulating and maintaining the inflammatory response in bacterial meningitis. Genetic variation studies, complement level measurements in blood and CSF, and experimental work have together led to the identification of anaphylatoxin C5a as a promising treatment target in bacterial meningitis. In animals and patients with pneumococcal meningitis, the accumulation of neutrophils in the CSF was mainly driven by C5-derived chemotactic activity and correlated positively with disease severity and outcome. In murine pneumococcal meningitis, adjunctive treatment with C5 antibodies prevented brain damage and death. Several recently developed therapeutics target C5 conversion, C5a, or its receptor C5aR. Caution is warranted because treatment with C5 antibodies such as eculizumab also inhibits the formation of the membrane attack complex, which may result in decreased meningococcal killing and increased meningococcal disease susceptibility. The use of C5a or C5aR antagonists to specifically target the harmful anaphylatoxins-induced effects, therefore, are most promising and present opportunities for a phase 2 clinical trial.

Host genetic variability and pneumococcal disease: a systematic review and meta-analysis

Background

Pneumonia, sepsis, meningitis, and empyema due to Streptococcus pneumoniae is a major cause of morbidity and mortality. We provide a systemic overview of genetic variants associated with susceptibility, phenotype and outcome of community acquired pneumococcal pneumonia (CAP) and invasive pneumococcal disease (IPD).

Methods

We searched PubMed for studies on the influence of host genetics on susceptibility, phenotype, and outcome of CAP and IPD between Jan 1, 1983 and Jul 4, 2018. We listed methodological characteristics and when genetic data was available we calculated effect sizes. We used fixed or random effect models to calculate pooled effect sizes in the meta-analysis.

Results

We identified 1219 studies of which 60 studies involving 15,358 patients were included. Twenty-five studies (42%) focused on susceptibility, 8 (13%) on outcome, 1 (2%) on disease phenotype, and 26 (43%) on multiple categories. We identified five studies with a hypothesis free approach of which one resulted in one genome wide significant association in a gene coding for lincRNA with pneumococcal disease susceptibility. We performed 17 meta-analyses of which two susceptibility polymorphisms had a significant overall effect size: variant alleles of MBL2 (odds ratio [OR] 1·67, 95% confidence interval [CI] 1·04–2·69) and a variant in CD14 (OR 1·77, 95% CI 1·18–2·66) and none of the outcome polymorphisms.

Conclusions

Studies have identified several host genetics factors influencing risk of pneumococcal disease, but many result in non-reproducible findings due to methodological limitations. Uniform case definitions and pooling of data is necessary to obtain more robust findings.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0572-x) contains supplementary material, which is available to authorized users.

Novel and preclinical treatment strategies in pneumococcal meningitis

PURPOSE OF REVIEW

Pneumococcal meningitis is the most frequent form of bacterial meningitis in Europe and the United States. Although early antimicrobial and adjuvant therapy with dexamethasone have helped to improve disease outcome in adults, mortality and morbidity rates remain unsatisfactorily high, emphasizing the need for additional treatment options. Promising targets for adjuvant therapy have been identified recently and will be the focus of this review.

RECENT FINDINGS

Brain disease in pneumococcal meningitis is caused by direct bacterial toxicity and excessive meningeal inflammation. Accordingly, promising targets for adjuvant therapy comprise limiting the release of toxic bacterial products and suppressing inflammation in a way that maximally protects against tissue injury without hampering pathogen eradication by antibiotics. Among the agents tested so far in experimental models, complement inhibitors, matrix-metalloproteinase inhibitors, and nonbacteriolytic antibiotics or a combination of the above have the potential to more efficiently protect the brain either alone (e.g., in children and outside the high-income settings) or in addition to adjuvant dexamethasone. Additionally, new protein-based pneumococcal vaccines are being developed that promise to improve disease prevention, namely by addressing the increasing problem of serotype replacement seen with pneumococcal conjugate vaccines.

SUMMARY

Pneumococcal meningitis remains a life-threatening disease requiring early antibiotic and targeted anti-inflammatory therapy. New adjuvant therapies showed promising results in animal models but need systematic clinical testing.

Antigenicity of Bovine Pericardium Determined by a Novel Immunoproteomic Approach

Despite bovine pericardium (BP) being the primary biomaterial used in heart valve bioprostheses, recipient graft-specific immune responses remain a significant cause of graft failure. Consequently, tissue antigenicity remains the principal barrier for expanding use of such biomaterials in clinical practice. We hypothesize that our understanding of BP antigenicity can be improved by application of a combined affinity chromatography shotgun immunoproteomic approach to identify antigens that have previously been overlooked. Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) analysis of affinity chromatography purified antigens resulted in identification of 133 antigens. Most importantly, antigens were identified from all subcellular locations, including 18 integral membrane protein antigens. Critically, isoforms of several protein families were found to be antigenic suggesting the possibility that shared epitope domains may exist. Furthermore, proteins associated with immune, coagulation, and inflammatory pathways were over-represented, suggesting that these biological processes play a key role in antigenicity. This study brings to light important determinants of antigenicity in a clinically relevant xenogeneic biomaterial (i.e. BP) and further validates a rapid, high-throughput method for immunoproteomic antigen identification.

Prediction of Outcome From Adult Bacterial Meningitis in a High-HIV-Seroprevalence, Resource-Poor Setting Using the Malawi Adult Meningitis Score (MAMS)

Background.

Acute bacterial meningitis (ABM) in adults residing in resource-poor countries is associated with mortality rates >50%. To improve outcome, interventional trials and standardized clinical algorithms are urgently required. To optimize these processes, we developed and validated an outcome prediction tool to identify ABM patients at greatest risk of death.

Methods.

We derived a nomogram using mortality predictors derived from a logistic regression model of a discovery database of adult Malawian patients with ABM (n = 523 [65%] cerebrospinal fluid [CSF] culture positive). We validated the nomogram internally using a bootstrap procedure and subsequently used the nomogram scores to further interpret the effects of adjunctive dexamethasone and glycerol using clinical trial data from Malawi.

Results.

ABM mortality at 6-week follow-up was 54%. Five of 15 variables tested were strongly associated with poor outcome (CSF culture positivity, CSF white blood cell count, hemoglobin, Glasgow Coma Scale, and pulse rate), and were used in the derivation of the Malawi Adult Meningitis Score (MAMS) nomogram. The C-index (area under the curve) was 0.76 (95% confidence interval, .71–.80) and calibration was good (Hosmer-Lemeshow C-statistic = 5.48, df = 8, P = .705). Harmful effects of adjunctive glycerol were observed in groups with relatively low predicted risk of poor outcome (25%–50% risk): Case Fatality Rate of 21% in the placebo group and 52% in the glycerol group (P < .001). This effect was not seen with adjunctive dexamethasone.

Conclusions.

MAMS provides a novel tool for predicting prognosis and improving interpretation of ABM clinical trials by risk stratification in resource-poor settings. Whether MAMS can be applied to non-HIV-endemic countries requires further evaluation.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0770-9) contains supplementary material, which is available to authorized users.

Acute bacterial meningitis in adults

Over the past several decades, the incidence of bacterial meningitis in children has decreased but there remains a significant burden of disease in adults, with a mortality of up to 30%. Although the pathogenesis of bacterial meningitis is not completely understood, knowledge of bacterial invasion and entry into the CNS is improving. Clinical features alone cannot determine whether meningitis is present and analysis of cerebrospinal fluid is essential for diagnosis. Newer technologies, such as multiplex PCR, and novel diagnostic platforms that incorporate proteomics and genetic sequencing, might help provide a quicker and more accurate diagnosis. Even with appropriate antimicrobial therapy, mortality is high and so attention has focused on adjunctive therapies; adjunctive corticosteroids are beneficial in certain circumstances. Any further improvements in outcome are likely to come from either modulation of the host response or novel approaches to therapy, rather than new antibiotics. Ultimately, the best hope to reduce the disease burden is with broadly protective vaccines.

Community-acquired bacterial meningitis

Meningitis is an inflammation of the meninges and subarachnoid space that can also involve the brain cortex and parenchyma. It can be acquired spontaneously in the community - community-acquired bacterial meningitis - or in the hospital as a complication of invasive procedures or head trauma (nosocomial bacterial meningitis). Despite advances in treatment and vaccinations, community-acquired bacterial meningitis remains one of the most important infectious diseases worldwide. Streptococcus pneumoniae and Neisseria meningitidis are the most common causative bacteria and are associated with high mortality and morbidity; vaccines targeting these organisms, which have designs similar to the successful vaccine that targets Haemophilus influenzae type b meningitis, are now being used in many routine vaccination programmes. Experimental and genetic association studies have increased our knowledge about the pathogenesis of bacterial meningitis. Early antibiotic treatment improves the outcome, but the growing emergence of drug resistance as well as shifts in the distribution of serotypes and groups are fuelling further development of new vaccines and treatment strategies. Corticosteroids were found to be beneficial in high-income countries depending on the bacterial species. Further improvements in the outcome are likely to come from dampening the host inflammatory response and implementing preventive measures, especially the development of new vaccines.

Exome Array Analysis of Susceptibility to Pneumococcal Meningitis

Host genetic variability may contribute to susceptibility of bacterial meningitis, but which genes contribute to the susceptibility to this complex disease remains undefined. We performed a genetic association study in 469 community-acquired pneumococcal meningitis cases and 2072 population-based controls from the Utrecht Health Project in order to find genetic variants associated with pneumococcal meningitis susceptibility. A HumanExome BeadChip was used to genotype 102,097 SNPs in the collected DNA samples. Associations were tested with the Fisher exact test. None of the genetic variants tested reached Bonferroni corrected significance (p-value <5 × 10(-7)). Our strongest signals associated with susceptibility to pneumococcal meningitis were rs139064549 on chromosome 1 in the COL11A1 gene (p = 1.51 × 10(-6); G allele OR 3.21 [95% CI 2.05-5.02]) and rs9309464 in the EXOC6B gene on chromosome 2 (p = 6.01 × 10(-5); G allele OR 0.66 [95% CI 0.54-0.81]). The sequence kernel association test (SKAT) tests for associations between multiple variants in a gene region and pneumococcal meningitis susceptibility yielded one significant associated gene namely COL11A1 (p = 1.03 × 10(-7)). Replication studies are needed to validate these results. If replicated, the functionality of these genetic variations should be further studied to identify by which means they influence the pathophysiology of pneumococcal meningitis.

The role of complement in neurological and neuropsychiatric diseases

The complement system is a major component of innate immunity and a potent driver of inflammation. It has key roles in host defense against pathogens but can also contribute to pathology by driving inflammation and cell damage in diverse diseases. Complement has emerged as an important factor in the pathogenesis of numerous diseases of the CNS and PNS, including infectious, autoimmune and degenerative disorders, and is increasingly implicated in neuropsychiatric disease. Establishing the roles and relevance of complement in disease pathogenesis has become ever more important in recent years as new drugs targeting the complement system have reached the clinic, and the potential for using complement analytes as disease biomarkers has been recognized. In this brief review, the author summarizes the evidence implicating complement in these diseases and outlines ways in which this new understanding can be used to aid diagnosis and improve outcome.

The genetic fingerprint of susceptibility for transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) occurs frequently after hematopoietic stem cell transplantation (HSCT) and can lead to significant morbidity and mortality. There are no data addressing individual susceptibility to TA-TMA. We performed a hypothesis-driven analysis of 17 candidate genes known to play a role in complement activation as part of a prospective study of TMA in HSCT recipients. We examined the functional significance of gene variants by using gene expression profiling. Among 77 patients undergoing genetic testing, 34 had TMA. Sixty-five percent of patients with TMA had genetic variants in at least one gene compared with 9% of patients without TMA (P < .0001). Gene variants were increased in patients of all races with TMA, but nonwhites had more variants than whites (2.5 [range, 0-7] vs 0 [range, 0-2]; P < .0001). Variants in ≥3 genes were identified only in nonwhites with TMA and were associated with high mortality (71%). RNA sequencing analysis of pretransplantation samples showed upregulation of multiple complement pathways in patients with TMA who had gene variants, including variants predicted as possibly benign by computer algorithm, compared with those without TMA and without gene variants. Our data reveal important differences in genetic susceptibility to HSCT-associated TMA based on recipient genotype. These data will allow prospective risk assessment and intervention to prevent TMA in highly susceptible transplant recipients. Our findings may explain, at least in part, racial disparities previously reported in transplant recipients and may guide treatment strategies to improve outcomes.

Cerebrospinal fluid complement activation in patients with pneumococcal and meningococcal meningitis

BACKGROUND

Recent research into the treatment of bacterial meningitis has examined the innate immune system, specifically the complement system, as a potential target for adjuvant therapy. However, the effects of blocking the complement system may be pathogen dependent.

METHODS

We measured cerebrospinal fluid (CSF) levels of complement components C1q, C3a, iC3b, C5a, sC5b-9, CFH and MBL in 310 patients with pneumococcal and meningococcal meningitis from a prospective nationwide cohort study. The CSF complement component levels were successfully determined for between 289 (93%) and 307 (99%) patients, depending on available volumes of stored CSF.

RESULTS

Complement factors C1q and MBL as well as common complement pathway factors C3a, iC3b, C5a, sC5b-9 and complement regulator CFH were all elevated in patients with bacterial meningitis as compared to the controls. CSF levels of complement components C5a and sC5b-9 were higher in patients with pneumococcal meningitis compared to those with meningococcal meningitis. After correction for age, immunocompromised state and level of consciousness, the CSF concentrations of C5a and sC5b-9 remained different between causative microorganisms (P = 0.006 and P = 0.016 respectively). In pneumococcal meningitis high C5a and C5b-9 levels are associated with the occurrence of systemic complications, unfavorable outcome and death, whereas an inverse relationship between C5b-9 levels and mortality is observed in meningococcal meningitis.

CONCLUSIONS

Our study shows striking variations in complement activation depending on the pathogen responsible for the bacterial meningitis. In pneumococcal meningitis, high CSF complement levels were a strong indicator of disease severity and mortality, however in meningococcal meningitis, an inverse relationship between sC5b-9 and mortality was observed.

Update on bacterial meningitis: epidemiology, trials and genetic association studies

PURPOSE OF REVIEW

Bacterial meningitis is a life-threatening disease that continues to inflict a heavy toll. We reviewed recent advances in vaccination, randomized studies on treatment, and genetic association studies in bacterial meningitis.

RECENT FINDINGS

The incidence of bacterial meningitis has decreased after implementation of vaccines, and further implementation of existing conjugate vaccines particularly in low-income countries is expected to reduce the global disease burden. Several randomized studies have been performed recently in this field. Clinical studies showed that short duration (5 days) of antibiotic treatment is as effective as longer duration treatment in low-income countries, and that dexamethasone decreases death and neurological sequelae in high-income countries. Ongoing trials will further define the role of paracetamol, glycerol and hypothermia in bacterial meningitis. Genetic association studies identified pathophysiological mechanisms that could be counteracted in experimental meningitis, providing promising leads for future treatments.

SUMMARY

Conjugate vaccines have reduced the burden of bacterial meningitis in high-income countries, but implementation of available vaccines in low-income countries is necessary to reduce disease burden worldwide. Adjunctive dexamethasone therapy has beneficial effects in patients with bacterial meningitis but only in high-income countries. Genetic association studies may reveal targets for new treatment strategies.