Genetic polymorphisms in host response to meningococcal infection: The role of susceptibility and severity genes

Low Levels of Factor H Family Proteins During Meningococcal Disease Indicate Systemic Processes Rather Than Specific Depletion by Neisseria meningitidis

Neisseria meningitidis, the causative agent of meningococcal disease (MD), evades complement-mediated clearance upon infection by ‘hijacking’ the human complement regulator factor H (FH). The FH protein family also comprises the homologous FH-related (FHR) proteins, hypothesized to act as antagonists of FH, and FHR-3 has recently been implicated to play a major role in MD susceptibility. Here, we show that the circulating levels of all FH family proteins, not only FH and FHR-3, are equally decreased during the acute illness. We did neither observe specific consumption of FH or FHR-3 by N. meningitidis, nor of any of the other FH family proteins, suggesting that the globally reduced levels are due to systemic processes including dilution by fluid administration upon admission and vascular leakage. MD severity associated predominantly with a loss of FH rather than FHRs. Additionally, low FH levels associated with renal failure, suggesting insufficient protection of host tissue by the active protection by the FH protein family, which is reminiscent of reduced FH activity in hemolytic uremic syndrome. Retaining higher levels of FH may thus limit tissue injury during MD.

Systems Biology Modeling of the Complement System Under Immune Susceptible Pathogens

The complement system is assembled from a network of proteins that function to bring about the first line of defense of the body against invading pathogens. However, complement deficiencies or invasive pathogens can hijack complement to subsequently increase susceptibility of the body to infections. Moreover, invasive pathogens are increasingly becoming resistant to the currently available therapies. Hence, it is important to gain insights into the highly dynamic interaction between complement and invading microbes in the frontlines of immunity. Here, we developed a mathematical model of the complement system composed of 670 ordinary differential equations with 328 kinetic parameters, which describes all three complement pathways (alternative, classical, and lectin) and includes description of mannose-binding lectin, collectins, ficolins, factor H-related proteins, immunoglobulin M, and pentraxins. Additionally, we incorporate two pathogens: (type 1) complement susceptible pathogen and (type 2) Neisseria meningitidis located in either nasopharynx or bloodstream. In both cases, we generate time profiles of the pathogen surface occupied by complement components and the membrane attack complex (MAC). Our model shows both pathogen types in bloodstream are saturated by complement proteins, whereas MACs occupy <<1.0% of the pathogen surface. Conversely, the MAC production in nasopharynx occupies about 1.5-10% of the total N. meningitidis surface, thus making nasal MAC levels at least about eight orders of magnitude higher. Altogether, we predict complement-imbalance, favoring overactivation, is associated with nasopharynx homeostasis. Conversely, orientating toward complement-balance may cause disruption to the nasopharynx homeostasis. Thus, for sporadic meningococcal disease, our model predicts rising nasal levels of complement regulators as early infection biomarkers.

Deconvolution of intergenic polymorphisms determining high expression of Factor H binding protein in meningococcus and their association with invasive disease

Neisseria meningitidis is a strictly human pathogen and is the major cause of septicemia and meningitis worldwide. Factor H binding protein (fHbp) is a meningococcal surface-exposed lipoprotein that binds the human Complement factor H allowing the bacterium to evade the host innate immune response. FHbp is also a key antigen in two vaccines against N. meningitidis serogroup B. Although the fHbp gene is present in most circulating meningococcal strains, level of fHbp expression varies among isolates and has been correlated to differences in promoter sequences upstream of the gene. Here we elucidated the sequence determinants that control fHbp expression in globally circulating strains. We analyzed the upstream fHbpintergenic region (fIR) of more than 5800 strains representative of the UK circulating isolates and we identified eleven fIR sequence alleles which represent 88% of meningococcal strains. By engineering isogenic recombinant strains where fHbp expression was under the control of each of the eleven fIR alleles, we confirmed that the fIR sequence determines a specific and distinct level of expression. Moreover, we identified the molecular basis for variation in expression through polymorphisms within key regulatory regions that are known to affect fHbp expression. We experimentally established three expression groups, high–medium–low, that correlated directly with the susceptibility to killing mediated by anti-fHbp antibodies and the ability of the meningococcal strain to survive within human serum. By using this sequence classification and information about the variant, we predicted fHbp expression in the panel of UK strains and we observed that strains with higher expressing fIR alleles are more likely associated with invasive disease. Overall, our findings can contribute to understand and predict vaccine coverage mediated by fHbp as well as to shed light on the role of this virulence factor in determining an invasive phenotype.

Complement plays a key role in the immunity against Neisseria meningitidis. The meningococcus uses the Factor H binding protein (fHbp), to bind a negative regulator of the alternative complement pathway, factor H, to its surface thus preventing complement deposition and lysis. The use of fHbp as an antigen in two licensed vaccines highlights its public health relevance. Therefore the levels of this antigen produced by the bacterium are pivotal on the one hand for the survival of N. meningitidis in blood and on the other hand for the susceptibility to vaccine-induced killing antibodies. Here, we identify the predominant nucleotide sequences that drive distinct levels of the fHbp antigen in circulating meningococcal strains. We cluster them into distinct groups with increasing levels and observe that strains expressing higher fHbp amounts are associated with invasive disease. Our findings show that the nucleotide sequence of the fHbp promoter can be used for the prediction of antigen levels of any given strain and consequently for both the assessment of its sensitivity to killing by fHbp antibodies and its likelihood to cause invasive disease.

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.

The Inflammatory and Hemostatic Response in Sepsis and Meningococcemia

Meningococcemia is notorious for evasion of the host immune system and its rapid progression to fulminant disease, and serves as a unique model for pediatric sepsis. Illness severity is determined by complex interplays among host, pathogen, and environment. The inflammatory host response, including proinflammatory and anti-inflammatory responses in innate and adaptive immunity, skews toward a proinflammatory state. This leads to endothelial dysfunction and activation of the hemostatic response, which may lead to disseminated intravascular coagulation. This article reviews the pathogenesis of sepsis, in particular the inflammatory and hemostatic response in meningococcal sepsis.

Human genetics of meningococcal infections

Neisseria meningitidis is a leading cause of bacterial septicaemia and meningitis worldwide. Meningococcal disease is rare but can be life threatening with a tendency to affect children. Many studies have investigated the role of human genetics in predisposition to N. meningitidis infection. These have identified both rare single-gene mutations as well as more common polymorphisms associated with meningococcal disease susceptibility and severity. These findings provide clues to the pathogenesis of N. meningitidis, the basis of host susceptibility to infection and to the aetiology of severe disease. From the multiple discoveries of monogenic complement deficiencies to the associations of complement factor H and complement factor H-related three polymorphisms to meningococcal disease, the complement pathway is highlighted as being central to the genetic control of meningococcal disease. This review aims to summarise the current understanding of the host genetic basis of meningococcal disease with respect to the different stages of meningococcal infection.

Identification of regulatory variants associated with genetic susceptibility to meningococcal disease

Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA – a NF-kB subunit, master regulator of the response to infection – under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes.

Neutrophil Extracellular Traps in Children With Meningococcal Sepsis

OBJECTIVES

Children with meningococcal sepsis are highly at risk for fulminant disease, multiple organ failure, and death. Recently, neutrophil extracellular traps levels have been indicated as a marker for severity in different kinds of sepsis. Our aim was to study the role of neutrophil extracellular traposis in meninogococcal sepsis in children.

DESIGN

We measured myeloperoxidase-DNA, a marker for neutrophil extracellular traps, in serum of meningococcal sepsis patients upon admission to PICU, at 24 hours, and at 1 month and studied the association with clinical outcome. Subsequently, we tested whether Neisseria meningitidis, isolated from children with meningococcal sepsis, were able to induce neutrophil extracellular traposis, using confocal microscopy live imaging.

SETTING

We used enzyme-linked immunosorbent assays to measure myeloperoxidase-DNA in patient serum. We also included inflammatory markers that were previously measured in this group.

PATIENTS

We included exclusively children with meningococcal sepsis.

INTERVENTIONS

From each patient, serum was collected for analysis.

MEASUREMENTS AND MAIN RESULTS

Myeloperoxidase-DNA levels at admission (n = 35; median, 0.21 AU/mL; interquartile range, 0.12-0.27) and at 24 hours (n = 39; median, 0.14 AU/mL; interquartile range, 0.09-0.25) were significantly higher than the myeloperoxidase-DNA levels after 1 month (controls: n = 36; median, 0.07 AU/mL; interquartile range, 0.05-0.09; p < 0.001). We did not observe a correlation between myeloperoxidase-DNA levels and mortality, cell-free DNA, or other inflammatory markers. In addition, N. meningitidis are fast and strong inducers of neutrophil extracellular traposis.

CONCLUSIONS

Children admitted to PICU for meningococcal sepsis have higher neutrophil extracellular traps levels at admission and after 24 hours than controls. Neutrophil extracellular traps levels were not associated with outcome, cell-free DNA, or other inflammatory markers. These neutrophil extracellular traps may be induced by N. meningitidis, since these are strong neutrophil extracellular traposis inducers.

Life-threatening infections in children in Europe (the EUCLIDS Project): a prospective cohort study

BACKGROUND

Sepsis and severe focal infections represent a substantial disease burden in children admitted to hospital. We aimed to understand the burden of disease and outcomes in children with life-threatening bacterial infections in Europe.

METHODS

The European Union Childhood Life-threatening Infectious Disease Study (EUCLIDS) was a prospective, multicentre, cohort study done in six countries in Europe. Patients aged 1 month to 18 years with sepsis (or suspected sepsis) or severe focal infections, admitted to 98 participating hospitals in the UK, Austria, Germany, Lithuania, Spain, and the Netherlands were prospectively recruited between July 1, 2012, and Dec 31, 2015. To assess disease burden and outcomes, we collected demographic and clinical data using a secured web-based platform and obtained microbiological data using locally available clinical diagnostic procedures.

FINDINGS

2844 patients were recruited and included in the analysis. 1512 (53·2%) of 2841 patients were male and median age was 39·1 months (IQR 12·4-93·9). 1229 (43·2%) patients had sepsis and 1615 (56·8%) had severe focal infections. Patients diagnosed with sepsis had a median age of 27·6 months (IQR 9·0-80·2), whereas those diagnosed with severe focal infections had a median age of 46·5 months (15·8-100·4; p<0·0001). Of 2844 patients in the entire cohort, the main clinical syndromes were pneumonia (511 [18·0%] patients), CNS infection (469 [16·5%]), and skin and soft tissue infection (247 [8·7%]). The causal microorganism was identified in 1359 (47·8%) children, with the most prevalent ones being Neisseria meningitidis (in 259 [9·1%] patients), followed by Staphylococcus aureus (in 222 [7·8%]), Streptococcus pneumoniae (in 219 [7·7%]), and group A streptococcus (in 162 [5·7%]). 1070 (37·6%) patients required admission to a paediatric intensive care unit. Of 2469 patients with outcome data, 57 (2·2%) deaths occurred: seven were in patients with severe focal infections and 50 in those with sepsis.

INTERPRETATION

Mortality in children admitted to hospital for sepsis or severe focal infections is low in Europe. The disease burden is mainly in children younger than 5 years and is largely due to vaccine-preventable meningococcal and pneumococcal infections. Despite the availability and application of clinical procedures for microbiological diagnosis, the causative organism remained unidentified in approximately 50% of patients.

FUNDING

European Union's Seventh Framework programme.

Case-Control Study of Risk Factors for Meningococcal Disease in Chile

An outbreak of meningococcal disease with a case-fatality rate of 30% and caused by predominantly serogroup W of Neisseria meningitidis began in Chile in 2012. This outbreak required a case−control study to assess determinants and risk factors for infection. We identified confirmed cases during January 2012−March 2013 and selected controls by random sampling of the population, matched for age and sex, resulting in 135 case-patients and 618 controls. Sociodemographic variables, habits, and previous illnesses were studied. Analyses yielded adjusted odds ratios as estimators of the probability of disease development. Results indicated that conditions of social vulnerability, such as low income and overcrowding, as well as familial history of this disease and clinical histories, especially chronic diseases and hospitalization for respiratory conditions, increased the probability of illness. Findings should contribute to direction of intersectoral public policies toward a highly vulnerable social group to enable them to improve their living conditions and health.

How many single-nucleotide polymorphisms (SNPs) must be tested in order to prove susceptibility to bacterial meningitis in children? Analysis of 11 SNPs in seven genes involved in the immune response and their effect on the susceptibility to bacterial meningitis in children

The aim of this study is to describe the prevalence of single single-nucleotide polymorphisms (SNPs) as well as their combinations in genes encoding proteins involved in the immune response in children with bacterial meningitis. The prospective study group consisted of 39 children with bacterial meningitis and 49 family members surveyed between 2012 and 2016. Eleven SNPs in seven genes involved in immune response were analysed. The mean number of minor frequency alleles (MAF) of studied SNPs was lowest in the control group and highest in patients with pneumococcal meningitis. We found that carrying ≥6 MAF of studied SNPs was associated with an increased risk of pneumococcal meningitis. The prevalence of risky variants was noted to be higher in patients with pneumococcal meningitis as compared to the control group. In conclusion, genetic factors are a relevant factor in determining the susceptibility to bacterial meningitis. A statistically significant cumulative effect of mutated variants on increasing the risk of bacterial meningitis was detected. Combining all three SNPs in MBL2 improves the prediction of susceptibility to pneumococcal meningitis. Analysis of risky alleles can help indicate people prone to the disease who are ‘gene-immunocompromised’.

Analysis of TLR2, TLR4, and TLR9 single nucleotide polymorphisms in children with bacterial meningitis and their healthy family members

BACKGROUND

The aim was to analyse TLR2 rs5743708, TLR2 rs4696480, TLR4 rs4986790, TLR9 rs5743836, and TLR9 rs352140 single nucleotide polymorphisms (SNPs) in children with pneumococcal and meningococcal meningitis and their family members.

METHODS

The study group consisted of 39 children with bacterial meningitis (25 with meningococcal meningitis and 14 with pneumococcal meningitis) and 49 family members. Laboratory test results and the course of the diseases were analyzed. Genomic DNA was extracted from 1.2ml of peripheral blood in order to analyze the five SNPs.

RESULTS

Patients with pneumococcal and meningococcal meningitis showed a similar male/female ratio, mean age, and duration of symptoms. There were no statistically significant differences in biochemical markers between the two groups. All patients possessed at least one polymorphic variant of the analyzed SNPs. The most common SNP was TLR9 rs352140, detected in 89.7% of patients. No significant differences in SNP frequency were found between patients, family members, and the general population.

CONCLUSIONS

The allele frequencies in the population studied are in accordance with the literature data. The study did not find an association between the analyzed SNPs and susceptibility to bacterial meningitis. The role of SNPs in genes coding toll-like receptors and the interactions between them in controlling inflammation in the central nervous system needs further evaluation.

Natural resistance to Meningococcal Disease related to CFH loci: Meta-analysis of genome-wide association studies

Meningococcal disease (MD) remains an important infectious cause of life threatening infection in both industrialized and resource poor countries. Genetic factors influence both occurrence and severity of presentation, but the genes responsible are largely unknown. We performed a genome-wide association study (GWAS) examining 5,440,063 SNPs in 422 Spanish MD patients and 910 controls. We then performed a meta-analysis of the Spanish GWAS with GWAS data from the United Kingdom (combined cohorts: 897 cases and 5,613 controls; 4,898,259 SNPs). The meta-analysis identified strong evidence of association (P-value ≤ 5 × 10⁻⁸) in 20 variants located at the CFH gene. SNP rs193053835 showed the most significant protective effect (Odds Ratio (OR) = 0.62, 95% confidence interval (C.I.) = 0.52–0.73; P-value = 9.62 × 10⁻⁹). Five other variants had been previously reported to be associated with susceptibility to MD, including the missense SNP rs1065489 (OR = 0.64, 95% C.I.) = 0.55–0.76, P-value = 3.25 × 10⁻⁸). Theoretical predictions point to a functional effect of rs1065489, which may be directly responsible for protection against MD. Our study confirms the association of CFH with susceptibility to MD and strengthens the importance of this link in understanding pathogenesis of the disease.

Characteristics of a new meningococcal serogroup B vaccine, bivalent rLP2086 (MenB-FHbp; Trumenba®)

Neisseria meningitidis is a common cause of bacterial meningitis, often leading to permanent sequelae or death. N. meningitidis is classified into serogroups based on the composition of the bacterial capsular polysaccharide; the 6 major disease-causing serogroups are designated A, B, C, W, X, and Y. Four of the 6 disease-causing serogroups (A, C, Y, and W) can be effectively prevented with available quadrivalent capsular polysaccharide protein conjugate vaccines; however, capsular polysaccharide conjugate vaccines are not effective against meningococcal serogroup B (MnB). There is no vaccine available for serogroup X. The public health need for an effective serogroup B vaccine is evident, as MnB is the most common cause of meningococcal disease in the United States and is responsible for almost half of all cases in persons aged 17 to 22 years. In fact, serogroup B meningococci were responsible for the recent meningococcal disease outbreaks on college campuses. However, development of a suitable serogroup B vaccine has been challenging, as serogroup B polysaccharide-based vaccines were found to be poorly immunogenic. Vaccine development for MnB focused on identifying potential outer membrane protein targets that elicit broadly protective immune responses across strains from the vast number of proteins that exist on the bacterial surface. Human factor H binding protein (fHBP; also known as LP2086), a conserved surface-exposed bacterial lipoprotein, was identified as a promising vaccine candidate. Two recombinant protein-based serogroup B vaccines that contain fHBP have been successfully developed and licensed in the United States under an accelerated approval process: bivalent rLP2086 (MenB-FHbp; Trumenba®) and 4CMenB (MenB-4 C; Bexsero®). This review will focus on bivalent rLP2086 only, including vaccine components, mechanism of action, and potential coverage across serogroup B strains in the United States.

N. meningitidis and TLR Polymorphisms: A Fascinating Immunomodulatory Network

N. meningitidis infections represent a global health problem that can lead to the development of serious permanent sequelae. Although the use of antibiotics and prevention via vaccination have reduced the incidence of meningococcal disease, our understanding regarding N. meningitidis pathogenesis is still limited, especially of those mechanisms responsible for IMD and fulminant or deadly septic shock. These severe clinical presentations occur in a limited number of subjects, whereas about 10% of healthy individuals are estimated to carry the bacteria as a commensal. Since TLR activation is involved in the defense against N. meningitidis, several studies have highlighted the association between host TLR SNPs and a higher susceptibility and severity of N. meningitidis infections. Moreover, TLR SNPs induced variations in immunological responses and in their persistence upon vaccination against meningococcal disease. In the absence of mass vaccination programs, the early identification of risk factors for meningococcal disease would be recommended in order to start immunization strategies and antibiotic treatment in those subjects carrying the risk variants. In addition, it could allow us to identify individuals with a higher risk for severe disease and sequelae in order to develop a personalized healthcare of high-risk subjects based on their genomic profile. In this review, we have illustrated important preliminary correlations between TLR variants and meningococcal susceptibility/severity and with vaccine-induced immune responses.

A complement C5 gene mutation, c.754G>A:p.A252T, is common in the Western Cape, South Africa and found to be homozygous in seven percent of Black African meningococcal disease cases

Patients with genetically determined deficiency of complement component 5 are usually diagnosed because of recurrent invasive Neisseria meningitidis infections. Approximately 40 individual cases have been diagnosed worldwide. Nevertheless, reports of the responsible genetic defects have been sporadic, and we know of no previous reports of C5 deficiency being associated with a number of independent meningococcal disease cases in particular communities. Here we describe C5 deficiency in seven unrelated Western Cape, South African families. Three different C5 mutations c.55C>T:p.Q19X, c.754G>A:p.A252T and c.4426C>T:p.R1476X were diagnosed in index cases from two families who had both presented with recurrent meningococcal disease. p.Q19X and p.R1476X have already been described in North American Black families and more recently p.Q19X in a Saudi family. However, p.A252T was only reported in SNP databases and was not associated with disease until the present study was undertaken in the Western Cape, South Africa. We tested for p.A252T in 140 patients presenting with meningococcal disease in the Cape Town area, and found seven individuals in five families who were homozygous for the mutation p.A252T. Very low serum C5 protein levels (0.1-4%) and correspondingly low in vitro functional activity were found in all homozygous individuals. Allele frequencies of p.A252T in the Black African and Cape Coloured communities were 3% and 0.66% and estimated homozygosities are 1/1100 and 1/22,500 respectively. In 2012 we reported association between p.A252T and meningococcal disease. Molecular modelling of p.A252T has indicated an area of molecular stress in the C5 molecule which may provide a mechanism for the very low level in the circulation. This report includes seven affected families indicating that C5D is not rare in South Africa.

Role of factor H binding protein in Neisseria meningitidis virulence and its potential as a vaccine candidate to broadly protect against meningococcal disease

Neisseria meningitidis is a Gram-negative microorganism that exists exclusively in humans and can cause devastating invasive disease. Although capsular polysaccharide-based vaccines against serogroups A, C, Y, and W135 are widely available, the pathway to a broadly protective vaccine against serogroup B has been more complex. The last 11 years has seen the discovery and development of the N. meningitidis serogroup B (MnB) outer membrane protein factor H binding protein (fHBP) as a vaccine component. Since the initial discovery of fHBP, a tremendous amount of work has accumulated on the diversity, structure, and regulation of this important protein. fHBP has proved to be a virulence factor for N. meningitidis and a target for functional bactericidal antibodies. fHBP is critical for survival of meningococci in the human host, as it is responsible for the primary interaction with human factor H (fH). Binding of hfH by the meningococcus serves to downregulate the host alternative complement pathway and helps the organism evade host innate immunity. Preclinical studies have shown that an fHBP-based vaccine can elicit serum bactericidal antibodies capable of killing MnB, and the vaccine has shown very encouraging results in human clinical trials. This report reviews our current knowledge of fHBP. In particular, we discuss the recent advances in our understanding of fHBP, its importance to N. meningitidis, and its potential role as a vaccine for preventing MnB disease.

[Impact of corticosteroids in the immediate management of invasive meningococcal disease associated with hyperinvasive strains of the ST-11 clonal complex in children]

OBJECTIVES

We used data from the Groupe de pathologie infectieuse pédiatrique and Association clinique et thérapeutique infantile du Val-de-Marne (GPIP/ACTIV) National Survey of Bacterial Meningitis in children and the National Reference Center for Meningococci (CNRM) microbiological data to assess the potential impact of corticosteroids on the immediate management of invasive meningococcal disease (IMD) associated with different genotypes, including highly pro-inflammatory strains of the ST-11 clonal complex (genotype ST-11).

METHODS

From 2001 to 2009, 259 pediatric wards and 168 microbiology laboratories distributed throughout France prospectively included all under-18-year-old patients with IMD (meningitis or purpura fulminans). The strains were sent to the CNRM for genotyping. We linked the ACTIV clinical data of IMD cases, where information on corticosteroid therapy was available, to strains isolated by the CRNM.

RESULTS

A total of 1981 IMD cases were identified during the 8-year study, 805 cases (712 [88.5%] bacterial meningitis and 93 [11.5%] purpura fulminans) had steroid treatment data (33.8% received corticosteroids). The genotype of the strains was available for 410 patients (24.4% related to genotype ST-11; 100 patients). For all cases and regardless of the corticosteroids, mortality was significantly associated with the genotype ST-11 (OR=2.39, 95% CI [1.29; 4.42], P=0.004). For all cases and regardless of the genotypes of the isolates, mortality was also significantly higher for children with than without corticosteroid therapy (12.7% versus 4.5%, P<0.001). However, this treatment had been prescribed more frequently in severe cases, including shock, PF, coma and/or mechanical ventilation. For children who did not receive corticosteroids, the mortality rate was significantly higher with genotype ST-11 compared to other genotypes (OR=4.68 [1.91, 11.46], P=0.001). This difference disappeared in children who received corticosteroids.

CONCLUSION

This study indicates that in the absence of corticosteroids, higher mortality in invasive meningococcal disease is associated with the ST-11 clonal complex strains. This suggests a possible positive effect of corticosteroid therapy depending on the genotype of the strain involved.

Genetic variants in toll-like receptor 2 (TLR2), TLR4, TLR9, and FCγ receptor II are associated with antibody response to quadrivalent meningococcal conjugate vaccine in HIV-infected youth

This study examined the association of host genetic variants with the antibody response to the quadrivalent meningococcal conjugate vaccine (MCV4) in HIV-infected youth. Genetic variants associated with severity of meningococcal disease, including the IgG Fc receptor (FCγRII)-A484T, interleukin-10 (IL-10)-A1082G, -C819T, and -C627A, IL-4-C589T, mannose binding lectin-2 (MBL2)-A/O, -H/L, -P/Q, and -X/Y, toll-like receptor 2 (TLR2)-G2408A, TLR4-A12874G and -C13174T, and TLR9-T1237C and -T1486C were determined by real-time PCR (RT-PCR) for 271 HIV-infected subjects (median, 17 years). Response was defined as a ≥4-fold increase from entry in bactericidal antibody titers to each serogroup. Generalized estimating equation (GEE) models were used to evaluate the association of allelic variants with the immunologic response to all serogroups within each subject with and without adjusting for CD4 percentage and HIV viral load. At week 4, but not after, subjects with TLR2-2408-G/A versus -G/G genotypes and the TLR4-12874-A/A genotype were more likely to achieve a ≥4-fold increase overall in the four serogroups (unadjusted P of 0.006 and adjusted P of 0.008 and unadjusted P of 0.008 and adjusted P of 0.019, respectively). At week 28, the TLR9-1237 T allele was associated with enhanced antibody response (T allele versus C/C, unadjusted P of 0.014 and adjusted P of 0.009), which was maintained at week 72 (unadjusted and adjusted P of 0.008). At week 72, the FcγRII-131Arg allotype was associated with a ≥4-fold increase in antibody titer versus those with His/His (unadjusted P of 0.009; adjusted P of <0.001). These findings suggest that for HIV-infected youth, the initial antibody response to MCV4 is associated with variants in TLR2 and TLR4 while the long-term response is associated with genetic polymorphisms in TLR9 and FcγRIIa.

Corticosteroid therapy in genotype ST-11 meningococcal infections

Corticosteroid treatment for meningococcal disease is debated. We report a high risk of death (odds ratio 4.68, 95% confidence interval: 1.91-11.46; P = 0.001) without corticosteroid treatment when meningococcal disease is provoked by isolates belonging to the hyperinvasive genotype ST-11. Genotypes of meningococcal isolates should be considered with corticosteroids therapy for meningococcal disease.

Meningococcal disease: clinical presentation and sequelae

The clinical spectrum of invasive meningococcal disease is diverse with meningitis and/or septicaemia being the commonest modes of presentation. The severity of manifestations of meningococcal infection ranges from bacteraemia, associated with mild non-specific symptoms, to fulminant sepsis with multiorgan failure and death in approximately 10-15% of cases. Localised infections (such as conjunctivitis or septic arthritis) as well as chronic disease may be the sole clinical manifestations but can also lead to disseminated fulminant disease. Among survivors, disabling long-term sequelae can complicate meningococcal disease and result in potentially devastating effects on the quality of life of survivors, most of whom are infants, children and adolescents. The only rational approach to the prevention of meningococcal disease and the associated human suffering is through vaccination.

Revealing the molecular signatures of host-pathogen interactions

Advances in sequencing technology and genome-wide association studies are now revealing the complex interactions between hosts and pathogen through genomic variation signatures, which arise from evolutionary co-existence.

A functional microsatellite of the macrophage migration inhibitory factor gene associated with meningococcal disease

Macrophage migration inhibitory factor (MIF) is an abundantly expressed proinflammatory cytokine playing a critical role in innate immunity and sepsis and other inflammatory diseases. We examined whether functional MIF gene polymorphisms (-794 CATT(5-8) microsatellite and -173 G/C SNP) were associated with the occurrence and outcome of meningococcal disease in children. The CATT(5) allele was associated with the probability of death predicted by the Pediatric Index of Mortality 2 (P=0.001), which increased in correlation with the CATT(5) copy number (P=0.04). The CATT(5) allele, but not the -173 G/C alleles, was also associated with the actual mortality from meningoccal sepsis [OR 2.72 (1.2-6.4), P=0.02]. A family-based association test (i.e., transmission disequilibrium test) performed in 240 trios with 1 afflicted offspring indicated that CATT(5) was a protective allele (P=0.02) for the occurrence of meningococcal disease. At baseline and after stimulation with Neisseria meningitidis in THP-1 monocytic cells or in a whole-blood assay, CATT(5) was found to be a low-expression MIF allele (P=0.005 and P=0.04 for transcriptional activity; P=0.09 and P=0.09 for MIF production). Taken together, these data suggest that polymorphisms of the MIF gene affecting MIF expression are associated with the occurrence, severity, and outcome of meningococcal disease in children.