Epidemic meningitis, meningococcaemia, and Neisseria meningitidis

Invasive Meningococcal Disease: What We Should Know, Before It Comes Back

Background

Invasive meningococcal disease (IMD), sepsis and/or meningitis continues to be a public health problem, with mortality rates ranging from 5% to 16%. The aim of our study was to further knowledge about IMD with a large series of cases occurring over a long period of time, in a cohort with a high percentage of adult patients.

Methods

Observational cohort study of patients with IMD between 1977 hand 2013 at our hospital, comparing patients with only sepsis and those with meningitis and several degrees of sepsis. The impact of dexamethasone and prophylactic phenytoin was determined, and an analysis of cutaneous and neurological sequelae was performed.

Results

A total of 527 episodes of IMD were recorded, comprising 57 cases of sepsis (11%) and 470 of meningitis with or without sepsis (89%). The number of episodes of IMD decreased from 352 of 527 (67%) in the first to 20 of 527 (4%) in the last quarter (P < .001). Thirty-three patients died (6%): 8 with sepsis (14%) and 25 with meningitis (5%) (P = .02). Cutaneous and neurological sequelae were present in 3% and 5% of survivors of sepsis and meningitis, respectively. The use of dexamethasone was safe and resulted in less arthritis, and patients given prophylactic phenytoin avoided seizures.

Conclusions

The frequency of IMD has decreased sharply since 1977. Patients with sepsis only have the highest mortality and complication rates, dexamethasone use is safe and can prevent some arthritis episodes, and prophylactic phenytoin might be useful in a selected population. A rapid response and antibiotic therapy may help improve the prognosis.

Cost Effectiveness of Meningococcal Serogroup B Vaccination in College-Aged Young Adults

INTRODUCTION

Neisseria meningitidis serogroup B is the most common form of meningococcal infection in young adults in the U.S. Vaccines have recently become available, but it is not clear that the benefits outweigh the costs. The purpose of this study was to assess cost effectiveness and determine potentially favorable conditions for universal vaccination.

METHODS

Costs and benefits of universal vaccination at college entry versus no universal vaccination with an outbreak response were estimated in 2018 in the context of a mid-sized U.S.-based 4-year college from both a health sector and a societal perspective. Probability, cost, and utility data were obtained from the published literature. Costs (2015 U.S.$) and benefits were discounted at 3%. One-way and multivariable probabilistic sensitivity analyses were performed including variations in the specific vaccine used. Further testing of the model's parameters at extremes was used to identify favorable conditions for universal vaccination.

RESULTS

The incremental cost per quality-adjusted life year gained with universal vaccination was $13.9 million under the health sector perspective and $13.8 million under the societal perspective, each perspective was compared with a willingness-to-pay threshold of $150,000 per quality-adjusted life year. Multivariable probabilistic sensitivity analysis showed that universal vaccination was not the preferred strategy for <$15 million per quality-adjusted life year. Under an extremely favorable model, a universal vaccination strategy became cost effective for vaccine series costing <$65.

CONCLUSIONS

This study demonstrates that universal vaccination at college entry is not cost effective. The rarity of N. meningitidis serogroup B contributes to the lack of cost effectiveness for universal vaccination.

Genetic Meningococcal Antigen Typing System (gMATS): A genotyping tool that predicts 4CMenB strain coverage worldwide

BACKGROUND

The Meningococcal Antigen Typing System (MATS) was developed to identify meningococcus group B strains with a high likelihood of being covered by the 4CMenB vaccine, but is limited by the requirement for viable isolates from culture-confirmed cases. We examined if antigen genotyping could complement MATS in predicting strain coverage by the 4CMenB vaccine.

METHODS

From a panel of 3912 MATS-typed invasive meningococcal disease isolates collected in England and Wales in 2007-2008, 2014-2015 and 2015-2016, and in 16 other countries in 2000-2015, 3481 isolates were also characterized by antigen genotyping. Individual associations between antigen genotypes and MATS coverage for each 4CMenB component were used to define a genetic MATS (gMATS). gMATS estimates were compared with England and Wales human complement serum bactericidal assay (hSBA) data and vaccine effectiveness (VE) data from England.

RESULTS

Overall, 81% of the strain panel had genetically predictable MATS coverage, with 92% accuracy and highly concordant results across national panels (Lin's accuracy coefficient, 0.98; root-mean-square deviation, 6%). England and Wales strain coverage estimates were 72-73% by genotyping (66-73% by MATS), underestimating hSBA values after four vaccine doses (88%) and VE after two doses (83%). The gMATS predicted strain coverage in other countries was 58-88%.

CONCLUSIONS

gMATS can replace MATS in predicting 4CMenB strain coverage in four out of five cases, without requiring a cultivable isolate, and is open to further improvement. Both methods underestimated VE in England. Strain coverage predictions in other countries matched or exceeded England and Wales estimates.

Development of meningococcal polysaccharide conjugate vaccine that can elicit long-lasting and strong cellular immune response with hepatitis B core antigen virus-like particles as a novel carrier protein

Neisseria meningitidis caused meningitis is life-threatening acute infection with high fatality and high frequency of severe sequelae. Meningococcal capsular polysaccharides can be used to prevent meningococcal disease; while conjugating the polysaccharides to carrier protein was found necessary to improve the immunogenicity and induce memory responses in infants and young children. Nevertheless, repeated administration of glycoconjugate vaccines might lead to carrier-induced epitope suppression due to limited number of carrier proteins. Here in this study, full-length hepatitis B core antigen virus-like particles (HBc VLPs) was used as a novel potential carrier protein for conjugation of meningococcal group C polysaccharides (CPS) with heterobifunctional polyethylene glycol (PEG) of different length (2, 5 and 10 kDa) as linkers. The physiochemical properties of the CPS-PEG-HBc conjugate vaccines were fully characterized. The TEM, DLS, native agarose gel electrophoresis, and HPLC analyses all confirmed the successful conjugation. As compared to plain CPS and the physical mixture of CPS and HBc, the immunization with the conjugate vaccines can generate about 10 times increase in CPS specific IgG titers with a significant boosting effect. HBc conjugation induced a shift to a Th1 cellular immune type response, as assessed by the increased IgG2a subclass production. In addition, vaccination of the conjugate vaccines elicited much enhanced avidity functional antibody and long-lasting immunological memory. IgG titers elicited by CPS-P2k-HBc, CPS-P5k-HBc and CPS-P10k-HBc at week 18 maintained 38.1%, 17.9% and 33.3% of their peak values. All these results demonstrated that HBc VLPs can be used as potential carrier protein to develop polysaccharide conjugate vaccines effective in eliciting long-lasting and strong cellular immune response.

Experience implementing a university-based mass immunization program in response to a meningococcal B outbreak

Neisseria meningitidis serogroup B (MenB) has caused several recent outbreaks of meningococcal disease on US college campuses. In January 2015, a case of MenB was reported at a university in Oregon, culminating in an outbreak with a total of 7 cases (including 1 fatality) identified over a 5-month period. In response to the outbreak, the university organized a mass immunization campaign with 4 "opt-in" immunization clinics. The preparation, challenges, and resources required for organization and implementation of a mass immunization program in response to an outbreak at a large public university are discussed herein. Based on the logistical challenges as well as resource expenditures associated with planning and executing a mass immunization effort, this experience illustrates that proactive, routine immunization of incoming students is the best strategy for MenB outbreak prevention.

In Vitro Models for Studying the Interaction of Neisseria meningitidis with Human Brain Endothelial Cells

Bacterial meningitis is a serious, life-threatening infection of the central nervous system (CNS). To cause meningitis, bacteria must interact with and penetrate the meningeal blood-cerebrospinal fluid barrier (mB/CSFB), which comprises highly specialized brain endothelial cells. Neisseria meningitidis (meningococcus) is a leading cause of bacterial meningitis, and examination meningococcus' interaction with the BBB is critical for understanding disease progression. To examine specific interactions, in vitro mB/CSFB models have been developed and employed and are of great importance because in vivo models have been difficult to produce considering Neisseria meningitidis is exclusively a human pathogen. Most in vitro blood-brain barrier and mB/CSF models use primary and immortalized brain endothelial cells, and these models have been used to examine bacterial-mB/CSFB interactions by a variety of pathogens. This chapter describes the use of past and current in vitro brain endothelial cells to model Neisseria meningitidis interaction with the mB/CSFB, and inform on the standard operating procedure for their use.

Meningococcal Antigen Typing System (MATS): A Tool to Estimate Global Coverage for 4CMenB, a Multicomponent Meningococcal B Vaccine

Meningococcal Antigen Typing System (MATS) is the combination of a sandwich ELISA (Enzyme Linked Immunosorbent Assay) developed to estimate the level of expression and immunoreactivity of the antigen components (fHbp, NHBA, and NadA) of the 4CMenB vaccine (Bexsero, GSK Vaccines) in circulating, serogroup B meningococcal (MenB) strains, with the molecular typing of PorA, the main antigenic component in the outer membrane vesicles (OMV). MATS has been proven to be a good surrogate of the accepted correlate of protection for meningococcus (hSBA), thus providing a quick, conservative and reproducible method to assess vaccine coverage. The method has been successfully transferred and standardized in several public health laboratories across Europe, North America, and Australia and used to screen thousands of isolates all over the world. Here we describe the sandwich ELISA method applied to assess the expression and cross-reactivity of fHbp, NHBA, and NadA in MenB isolates.

Diagnosis of Meningococcal Infection Using Internally Controlled Multiplex Real-Time PCR

Neisseria meningitidis (Nm) is a leading cause of invasive infections associated with high mortality and morbidity, notably meningitis and septicemia. Etiological rapid diagnosis is key for the preventive management of invasive meningococcal disease (IMD). However, conventional methods for diagnosis are time-consuming and could be hampered by the difficulties in culturing the isolates from clinical specimens especially due to early antibiotic treatment. Therefore, sensitive, specific and rapid non-culture-based methods are valuable for early diagnosis, effective therapy, and prevention. Here we describe a real-time PCR multiplex assays for the detection of Nm targeting the meningococcal-specific gene crgA, coding for a LysR-like transcriptional regulator, and six serogroup-specific (A, B, C, W, X, Y) Nm capsular genes, using a Qiagen column-based method for the optimum isolation of DNA from clinical specimens. Internal quality controls were included to monitor extraction of DNA, inhibition and the technical validation of the PCR as well.

Development of a PCR algorithm to detect and characterize Neisseria meningitidis carriage isolates in the African meningitis belt

Improved methods for the detection and characterization of carried Neisseria meningitidis isolates are needed. We evaluated a multiplex PCR algorithm for the detection of a variety of carriage strains in the meningitis belt. To further improve the sensitivity and specificity of the existing PCR assays, primers for gel-based PCR assays (sodC, H, Z) and primers/probe for real-time quantitative PCR (qPCR) assays (porA, cnl, sodC, H, E, Z) were modified or created using Primer Express software. Optimized multiplex PCR assays were tested on 247 well-characterised carriage isolates from six countries of the African meningitis belt. The PCR algorithm developed enabled the detection of N. meningitidis species using gel-based and real-time multiplex PCR targeting porA, sodC, cnl and characterization of capsule genes through sequential multiplex PCR assays for genogroups (A, W, X, then B, C, Y and finally H, E and Z). Targeting both porA and sodC genes together allowed the detection of meningococci with a sensitivity of 96% and 89% and a specificity of 78% and 67%, for qPCR and gel-based PCR respectively. The sensitivity and specificity ranges for capsular genogrouping of N. meningitidis are 67% - 100% and 98%-100% respectively for gel-based PCR and 90%-100% and 99%-100% for qPCR. We developed a PCR algorithm that allows simple, rapid and systematic detection and characterisation of most major and minor N. meningitidis capsular groups, including uncommon capsular groups (H, E, Z).

A Longitudinal Epidemiology Study of Meningococcal Carriage in Students 13 to 25 Years Old in Quebec

Disease caused by Neisseria meningitidis is associated with serious complications and a high fatality rate. Asymptomatic individuals can harbor the bacterium in the throat, a state known as “carriage,” which can lead to person-to-person spread of the pathogen. This study examined N. meningitidis carriage from 2010 to 2013 among 2 groups in the Quebec City region: ninth-grade students (aged 13 to 15 years), who were also followed in their last year of high school (eleventh grade/college entry; 16 to 18 years), and university students (18 to 25 years); both groups have been shown in some other geographic regions to have high rates of carriage. This study demonstrated that N. meningitidis carriage rates were higher among university students in dormitories than ninth-grade and eleventh-grade/college entry students. Understanding carriage rates in these age groups leads to better strategies to control N. meningitidis by targeting vaccination to those responsible for transmission within the population.

Neisseria meningitidis carriage data are necessary to inform serogroup B (NmB) immunization program implementation. This longitudinal study compared detection methods to measure N. meningitidis throat carriage prevalence in Quebec from November 2010 to December 2013 using cultured swab isolates and direct swab PCR from students in ninth grade (aged 13 to 15 years; n = 534) and eleventh grade/college entry (16 to 18 years; n = 363) and in university students in dormitories (18 to 25 years; n = 360) at 3 time points per group. Meningococcal and NmB carriage rates were lower in ninth- and eleventh-grade/college entry students than university students, regardless of methodology. Genotyping cultured isolates by PCR detected NmB and non-NmB in 2.1% and 7.3% of ninth-grade students, in 1.7% and 7.2% of eleventh-grade/college entry students, and in 7.5% and 21.9% of university students, respectively. NmB acquisition rates were 1.9, 0.7, and 3.3 per 1,000 person-months across respective age groups. Most NmB isolates (94.7%, 76.9%, and 86.8%, respectively) expressed subfamily A factor H binding-protein (fHBP) variants. The most common non-NmB serogroups were NmY (1.7%/1.1%) from ninth grade and eleventh grade/college entry and NmW (2.8%) from university students. Genomic analyses detected disease-associated sequence types in carriage isolates, and carriage could persist for months. This is the largest longitudinal carriage study in Canada and the first to report fHBP variants in NmB carriage isolates in healthy Canadians. These data contribute to identification of the optimal window for NmB vaccination in precollege adolescents and provide a baseline for investigating NmB vaccination effects on carriage in this population.

IMPORTANCE Disease caused by Neisseria meningitidis is associated with serious complications and a high fatality rate. Asymptomatic individuals can harbor the bacterium in the throat, a state known as “carriage,” which can lead to person-to-person spread of the pathogen. This study examined N. meningitidis carriage from 2010 to 2013 among 2 groups in the Quebec City region: ninth-grade students (aged 13 to 15 years), who were also followed in their last year of high school (eleventh grade/college entry; 16 to 18 years), and university students (18 to 25 years); both groups have been shown in some other geographic regions to have high rates of carriage. This study demonstrated that N. meningitidis carriage rates were higher among university students in dormitories than ninth-grade and eleventh-grade/college entry students. Understanding carriage rates in these age groups leads to better strategies to control N. meningitidis by targeting vaccination to those responsible for transmission within the population.

Concomitant administration of a fully liquid ready-to-use DTaP-IPV-HB-PRP-T hexavalent vaccine with a meningococcal ACWY conjugate vaccine in toddlers

Invasive meningococcal disease caused by Neisseria meningitidis is a life-threatening disease. Several countries now include meningococcal serogroup C (MenC) conjugate and, more recently, a meningococcal serogroup ACWY conjugate (MenACWY) vaccination in their national immunization schedules. DTaP-IPV-HB-PRP-T is a hexavalent vaccine that provides protection against six diseases. The phase III, open-label, randomised, multicentre study enrolled healthy toddlers who received the DTaP-IPV-HB-PRP-T vaccine (at 2, 3 and 4 months) with or without a MenC vaccine (at 2 and 4 months) in the primary series study. At 12 months of age, 312 toddlers were randomised to receive DTaP-IPV-HB-PRP-T co-administered with MenACWY-TT vaccine (Group A; n = 104); DTaP-IPV-HB-PRP-T vaccine alone (Group B; n = 105); or MenACWY-TT vaccine alone (Group C; n = 103). At 12 months of age, there were no notable differences in terms of antibody persistence for any DTaP-IPV-HB-PRP-T vaccine antigen, whether MenC-TT conjugate vaccine was co-administered or not during the primary series. Following booster vaccination, immune responses to DTaP-IPV-HB-PRP-T and MenACWY-TT vaccines were not affected by co-administration. One month after vaccination, the immune responses elicited by both vaccines were high, whether administered concomitantly or separately. The administration of MenC vaccine during infancy did not preclude the use of a MenACWY-TT vaccine for booster vaccination. Even though the reactogenicity after co-administration was somewhat higher, the results of this study support the concomitant administration of the DTaP-IPV-HB-PRP-T vaccine with a MenACWY-TT conjugate vaccine when given from 12 months of age. The clinical trial registration numbers are: clinicaltrial.gov: NCT01839175; EudraCT: 2012-005547-24.

Heteroresistance to the model antimicrobial peptide polymyxin B in the emerging Neisseria meningitidis lineage 11.2 urethritis clade: mutations in the pilMNOPQ operon

Clusters of Neisseria meningitidis (Nm) urethritis among primarily heterosexual males in multiple US cities have been attributed to a unique non-encapsulated meningococcal clade (the US Nm urethritis clade, US_NmUC) within the hypervirulent clonal complex 11. Resistance to antimicrobial peptides (AMPs) is a key feature of urogenital pathogenesis of the closely related species, Neisseria gonorrhoeae. The US_NmUC isolates were found to be highly resistant to the model AMP, polymyxin B (PmB, MICs 64-256 µg ml^-1 ). The isolates also demonstrated stable subpopulations of heteroresistant colonies that showed near total resistant to PmB (MICs 384-1024 µg ml^-1 ) and colistin (MIC 256 µg ml^-1 ) as well as enhanced LL-37 resistance. This is the first observation of heteroresistance in N. meningitidis. Consistent with previous findings, overall PmB resistance in US_NmUC isolates was due to active Mtr efflux and LptA-mediated lipid A modification. However, whole genome sequencing, variant analyses and directed mutagenesis revealed that the heteroresistance phenotypes and very high-level AMP resistance were the result of point mutations and IS1655 element movement in the pilMNOPQ operon, encoding the type IV pilin biogenesis apparatus. Cross-resistance to other classes of antibiotics was also observed in the heteroresistant colonies. High-level resistance to AMPs may contribute to the pathogenesis of US_NmUC.

Meningococcemia Masquerading as a Nonspecific Flu-Like Syndrome

Neisseria meningitidis is a cause of bacterial meningitis and meningococcemia worldwide. Rarely, it causes invasive disease with significant lifelong sequela if survived. Early clinical recognition is key as meningococcemia is an easily treatable disease, yet mortality is 50% if it is left untreated. In this case review, we present a classic case of meningococcemia, with an atypical presentation.

Meningococcal disease in adolescents and young adults: a review of the rationale for prevention through vaccination

Invasive meningococcal disease (IMD) caused by Neisseria meningitidis is characterized by high mortality and morbidity. While IMD incidence peaks in both infants and adolescents/young adults, carriage rates are often highest in the latter age groups, increasing IMD risk and the likelihood of transmission. Effective vaccines are available for 5 of 6 disease-causing serogroups. Because adolescents/young adults represent a significant proportion of cases, often have the highest carriage rate, and have characteristically low vaccination adherence, efforts should be focused on educating this population regarding long-term consequences of infection and the importance of meningococcal vaccination in prevention. This review describes the role of adolescents/young adults in meningococcal transmission and the clinical consequences and characteristics of IMD in this population. With a focus on countries with advanced economies that have specific meningococcal vaccination recommendations, the epidemiology of meningococcal disease and vaccination recommendations in adolescents/young adults will also be discussed.

Initial validation of a simulation model for estimating the impact of serogroup A Neisseria meningitidis vaccination in the African meningitis belt

We previously developed a mathematical simulation of serogroup A Neisseria meningitidis (NmA) transmission in Burkina Faso, with the goal of forecasting the relative benefit of different vaccination programs. Here, we revisit key structural assumptions of the model by comparing how accurately the different assumptions reproduce observed NmA trends following vaccine introduction. A priori, we updated several of the model's parameters based on recently published studies. We simulated NmA disease under different assumptions about duration of vaccine-induced protection (including the possibility that vaccine-induced protection may last longer than natural immunity). We compared simulated and observed case counts from 2011-2017. We then used the best-fit model to forecast the impact of different vaccination strategies. Our updated model, with the assumption that vaccine-induced immunity lasts longer than immunity following NmA colonization, was able to reproduce observed trends in NmA disease. The updated model predicts that, following a mass campaign among persons 1-29 years of age, either routine immunization of 9 month-old children or periodic mini-campaigns among children 1-4 years of age will lead to sustained control of epidemic NmA in Burkina Faso. This validated model can help public health officials set policies for meningococcal vaccination in Africa.

Chronic meningococcemia: a report of 26 cases and literature review

Chronic meningococcemia is defined by blood culture(s) positive for Neisseria meningitidis, symptoms duration > 7 days, and neither meningitis nor shock on admission. This series of 26 consecutive cases illustrates that this is a rare disease (< 5% of meningococcemia, < 0.05 cases per 100,000 inhabitants per year), mostly affecting young adults, males, with no predisposing condition. Major symptoms include fever, rash, and arthralgia. Median time between symptoms onset, and diagnosis is 28 days. Most patients fully recover with a 1-week course of parenteral betalactams.

Development and Assessment of a Diagnostic DNA Oligonucleotide Microarray for Detection and Typing of Meningitis-Associated Bacterial Species

Meningitis is commonly caused by infection with a variety of bacterial or viral pathogens. Acute bacterial meningitis (ABM) can cause severe disease, which can progress rapidly to a critical life-threatening condition. Rapid diagnosis of ABM is critical, as this is most commonly associated with severe sequelae with associated high mortality and morbidity rates compared to viral meningitis, which is less severe and self-limiting. We have designed a microarray for detection and diagnosis of ABM. This has been validated using randomly amplified DNA targets (RADT), comparing buffers with or without formamide, in glass slide format or on the Alere ArrayTube^TM (Alere Technologies GmbH) microarray platform. Pathogen-specific signals were observed using purified bacterial nucleic acids and to a lesser extent using patient cerebral spinal fluid (CSF) samples, with some technical issues observed using RADT and glass slides. Repurposing the array onto the Alere ArrayTube^TM platform and using a targeted amplification system increased specific and reduced nonspecific hybridization signals using both pathogen nucleic and patient CSF DNA targets, better revealing pathogen-specific signals although sensitivity was still reduced in the latter. This diagnostic microarray is useful as a laboratory diagnostic tool for species and strain designation for ABM, rather than for primary diagnosis.

Societal costs due to meningococcal disease: a national registry-based study

Purpose

Limited detailed evidence exists on the societal costs of meningococcal disease. The objective of this study was to estimate the average 5-year societal cost of events attributable to meningococcal disease in Denmark.

Methods

The study was based on the nationwide Danish registries. Incident patients diagnosed with meningococcal disease were identified and each matched with two controls, using direct matching on age, gender, and level of education. Siblings constituted a secondary control population where one patient was matched with one sibling control without meningococcal disease. Costs related to health care in the primary and secondary sectors, prescription medicine, municipality home care services and costs of production loss, ie, estimated loss of yearly earnings, were included (1997–2015).

Results

The incidence of meningococcal disease fluctuated between 1980 and 2015. The average attributable societal costs were highest the first year after diagnosis, with costs equaling USD 18,920 per event in the primary study population (matched controls) and USD 16,169 in the secondary study population (sibling controls). Hospital admission costs accounted for 65% and production loss for 30%; however, having a lifetime perspective and including loss due to premature death further increase the costs of meningococcal disease events.

Conclusion

The costs of meningococcal disease are substantial, and the estimated costs of event may be informative in evaluating the impact of preventive interventions targeting meningococcal disease.

Compartmental models for seasonal hyperendemic bacterial meningitis in the African meningitis belt

The pathophysiological mechanisms underlying the seasonal dynamic and epidemic occurrence of bacterial meningitis in the African meningitis belt remain unknown. Regular seasonality (seasonal hyperendemicity) is observed for both meningococcal and pneumococcal meningitis and understanding this is critical for better prevention and modelling. The two principal hypotheses for hyperendemicity during the dry season imply (1) an increased risk of invasive disease given asymptomatic carriage of meningococci and pneumococci; or (2) an increased transmission of these bacteria from carriers and ill individuals. In this study, we formulated three compartmental deterministic models of seasonal hyperendemicity, featuring one (model1-'inv' or model2-'transm'), or a combination (model3-'inv-transm') of the two hypotheses. We parameterised the models based on current knowledge on meningococcal and pneumococcal biology and pathophysiology. We compared the three models' performance in reproducing weekly incidences of suspected cases of acute bacterial meningitis reported by health centres in Burkina Faso during 2004-2010, through the meningitis surveillance system. The three models performed well (coefficient of determination R2, 0.72, 0.86 and 0.87, respectively). Model2-'transm' and model3-'inv-transm' better captured the amplitude of the seasonal incidence. However, model2-'transm' required a higher constant invasion rate for a similar average baseline transmission rate. The results suggest that a combination of seasonal changes of the risk of invasive disease and carriage transmission is involved in the hyperendemic seasonality of bacterial meningitis in the African meningitis belt. Consequently, both interventions reducing the risk of nasopharyngeal invasion and the bacteria transmission, especially during the dry season are believed to be needed to limit the recurrent seasonality of bacterial meningitis in the meningitis belt.

Dioctadecyldimethylammonium bromide (DODAB-BF) as a new adjuvant for maternal-fetal immunization in mice against Neisseria meningitidis: evaluation of humoral response

Neisseria meningitidis bacterium is a Gram-negative diplococcus. Among their serogroups, the B is one of the main causes of invasive meningococcal disease. Newborns and children are particularly susceptible to this infection because of their immune systems that are still maturing and relatively inexperienced. Thus, further studies on the use of maternal immunization for protection against this disease are needed. The purpose of this study was to evaluate the potential immunogenic antigens from the outer membrane of N. meningitidis serogroup B in outbred mice and the influence of maternal immunization in the offspring, and analyze the adjuvant effect of bilayer fragments of dioctadecyldimethylamonium bromide (DODAB-BF) and hydroxide aluminium (alum) in enhancing antibodies production and transference to offspring. IgG and IgG1, IgG2a and IgG2b subclasses of antibodies in serum from immunized mice and controls were quantified and compared. Immunization by subcutaneous and intramuscular routes exhibited evidence of IgG, and both adjuvants promoted the production of IgG1 and IgG2b that were transferred to the offspring. These antibodies also showed specificity with the outer membrane vesicles from homologous strain and were capable to cross react with different strains. The use of DODAB-BF seems to enhance immune response on mothers and offspring and may have immunological advantages.

Meningococcal Group A, C, W, and Y Tetanus Toxoid Conjugate Vaccine: A Review of Clinical Data in Adolescents

MenACWY-TT (Nimenrix) is a quadrivalent meningococcal vaccine containing polysaccharides from serogroups A, C, W, and Y conjugated to a tetanus toxoid carrier protein. MenACWY-TT is licensed in some countries as a three-dose primary series in individuals as young as 6 weeks of age and as a single dose in individuals ≥12 months of age. MenACWY-TT use is supported by long-term immunogenicity and safety across age groups, including data from several phase 2, 3, and 4 clinical studies in adolescents and young adults. Adolescents are an important population in the epidemiology, transmission, and prevention of invasive meningococcal disease, with this age-based population having the highest risk for carriage and transmission as well as one of the highest risks of disease. This age group is emerging as a target population in meningococcal vaccination programs globally, as vaccinating adolescents and young adults could potentially not only decrease disease rates directly for those vaccinated but also indirectly for unvaccinated individuals by decreasing carriage and eliciting herd protection. This review will consider available data for MenACWY-TT in adolescents, including safety and immunogenicity, booster and memory responses, persistence, and coadministration with other vaccines, with an emphasis on the rationale for use of MenACWY-TT and other quadrivalent meningococcal vaccines in adolescents to address the changing epidemiology of meningococcal disease.

Structures of NHBA elucidate a broadly conserved epitope identified by a vaccine induced antibody

Neisserial heparin binding antigen (NHBA) is one of three main recombinant protein antigens in 4CMenB, a vaccine for the prevention of invasive meningococcal disease caused by Neisseria meningitidis serogroup B. NHBA is a surface-exposed lipoprotein composed of a predicted disordered N-terminal region, an arginine-rich region that binds heparin, and a C-terminal domain that folds as an anti-parallel β-barrel and that upon release after cleavage by human proteases alters endothelial permeability. NHBA induces bactericidal antibodies in humans, and NHBA-specific antibodies elicited by the 4CMenB vaccine contribute to serum bactericidal activity, the correlate of protection. To better understand the structural bases of the human antibody response to 4CMenB vaccination and to inform antigen design, we used X-ray crystallography to elucidate the structures of two C-terminal fragments of NHBA, either alone or in complex with the Fab derived from the vaccine-elicited human monoclonal antibody 5H2, and the structure of the unbound Fab 5H2. The structures reveal details on the interaction between an N-terminal β-hairpin fragment and the β-barrel, and explain how NHBA is capable of generating cross-reactive antibodies through an extensive conserved conformational epitope that covers the entire C-terminal face of the β-barrel. By providing new structural information on a vaccine antigen and on the human immune response to vaccination, these results deepen our molecular understanding of 4CMenB, and might also aid future vaccine design projects.

Structure-Function Relationships of the Neisserial EptA Enzyme Responsible for Phosphoethanolamine Decoration of Lipid A: Rationale for Drug Targeting

Bacteria cause disease by two general mechanisms: the action of their toxins on host cells and induction of a pro-inflammatory response that can lead to a deleterious cytokine/chemokine response (e.g., the so-called cytokine storm) often seen in bacteremia/septicemia. These major mechanisms may overlap due to the action of surface structures that can have direct and indirect actions on phagocytic or non-phagocytic cells. In this respect, the lipid A (endotoxin) component of lipopolysaccharide (LPS) possessed by Gram-negative bacteria has been the subject of literally thousands of studies over the past century that clearly identified it as a key virulence factor in endotoxic shock. In addition to its capacity to modulate inflammatory responses, endotoxin can also modulate bacterial susceptibility to host antimicrobials, such as the host defense peptides termed cationic antimicrobial peptides. This review concentrates on the phosphoethanolamine (PEA) decoration of lipid A in the pathogenic species of the genus Neisseria [N. gonorrhoeae and N. meningitidis]. PEA decoration of lipid A is mediated by the enzyme EptA (formerly termed LptA) and promotes resistance to innate defense systems, induces the pro-inflammatory response and can influence the in vivo fitness of bacteria during infection. These important biological properties have driven efforts dealing with the biochemistry and structural biology of EptA that will facilitate the development of potential inhibitors that block PEA addition to lipid A.

Meningococcemia complicated by myocarditis in a 16-year-old young man: a case report

Fulminant meningococcemia is a relatively rare life-threatening disease caused by Neisseria meningitidis. The clinical presentation is varied, but, when associated with myocarditis, it carries a particularly poor prognosis. We report a case of a patient with fulminant meningococcemia who subsequently developed severe myocardial dysfunction and successfully recovered within a period of 7 days of hospitalization. A 15-year-old girl presented with headache, fever, body ache for 1 day and few ecchymotic rash over her body for 3 hours. Blood cultures confirmed infection with N. meningitidis. After 2 days in the hospital, the patient developed dyspnea, elevated jugular venous pressure and shock. The patient was managed with intravenous ceftriaxone, furosemide and norepinephrine. Over the next 4 days the patient rapidly improved. Meningococcemia complicated by myocarditis has an extremely poor prognosis with high mortality. Our case suggests that recovery from a severe myocardial dysfunction can occur rapidly within a few days. Prompt recognition and management in this case might have contributed to the patient's rapid recovery from myocarditis.

Genotypic and Phenotypic Characterization of the O-Linked Protein Glycosylation System Reveals High Glycan Diversity in Paired Meningococcal Carriage Isolates

Species within the genus Neisseria display significant glycan diversity associated with the O-linked protein glycosylation (pgl) systems due to phase variation and polymorphic genes and gene content. The aim of this study was to examine in detail the pgl genotype and glycosylation phenotype in meningococcal isolates and the changes occurring during short-term asymptomatic carriage. Paired meningococcal isolates derived from 50 asymptomatic meningococcal carriers, taken about 2 months apart, were analyzed with whole-genome sequencing. The O-linked protein glycosylation genes were characterized in detail using the Genome Comparator tool at the https://pubmlst.org/ database. Immunoblotting with glycan-specific antibodies (Abs) was used to investigate the protein glycosylation phenotype. All major pgl locus polymorphisms identified in Neisseria meningitidis to date were present in our isolate collection, with the variable presence of pglG and pglH, both in combination with either pglB or pglB2 We identified significant changes and diversity in the pgl genotype and/or glycan phenotype in 96% of the paired isolates. There was also a high degree of glycan microheterogeneity, in which different variants of glycan structures were found at a given glycoprotein. The main mechanism responsible for the observed differences was phase-variable expression of the involved glycosyltransferases and the O-acetyltransferase. To our knowledge, this is the first characterization of the pgl genotype and glycosylation phenotype in a larger strain collection. This report thus provides important insight into glycan diversity in N. meningitidis and into the phase variability changes that influence the expressed glycoform repertoire during meningococcal carriage.IMPORTANCE Bacterial meningitis is a serious global health problem, and one of the major causative organisms is Neisseria meningitidis, which is also a common commensal in the upper respiratory tract of healthy humans. In bacteria, numerous loci involved in biosynthesis of surface-exposed antigenic structures that are involved in the interaction between bacteria and host are frequently subjected to homologous recombination and phase variation. These mechanisms are well described in Neisseria, and phase variation provides the ability to change these structures reversibly in response to the environment. Protein glycosylation systems are becoming widely identified in bacteria, and yet little is known about the mechanisms and evolutionary forces influencing glycan composition during carriage and disease.

Meningococcal Quadrivalent Tetanus Toxoid Conjugate Vaccine (MenACWY-TT; Nimenrix®): A Review

MenACWY-TT (Nimenrix^®) is a quadrivalent meningococcal tetanus toxoid conjugate vaccine licensed in Europe for active immunisation of individuals aged ≥ 6 weeks against invasive disease caused by Neisseria meningitidis capsular groups A, C, W and Y. MenACWY-TT is the first quadrivalent conjugate vaccine to be approved in Europe for use in infants as young as 6 weeks of age. Numerous phase II-IIIb clinical studies showed that intramuscular MenACWY-TT administered as primary or booster vaccination was highly immunogenic for all four vaccine capsular groups and had an acceptable reactogenicity profile in individuals aged 6 weeks to ≥ 56 years. MenACWY-TT is as immunogenic and safe as other previously licensed monovalent capsular group C or quadrivalent capsular groups A, C, W and Y meningococcal vaccines and can be coadministered with other routine vaccines without adversely affecting the immunogenicity or safety profiles of either vaccine. Current data indicate that primary and booster vaccination with MenACWY-TT is a valuable and safe option for broadening meningococcal protection against four capsular groups across a broad age range, starting as early as 6 weeks of age.

Optimal use of meningococcal serogroup B vaccines: moving beyond outbreak control

Neisseria meningitidis is a major cause of meningitis and septicemia globally. Vaccines directed against N. meningitidis serogroup B (MenB) have been used to control sporadic and sustained disease in industrialized and non-industrialized countries. Early outer membrane vesicle (OMV) vaccines effectively reduced MenB disease in countries such as Norway, New Zealand, and France; however, these vaccines were highly specific for their targeted outbreak strain, did not elicit a durable immune response, and were ineffective for widespread use due to the diversity of MenB-disease-causing isolates. Recently developed recombinant protein-based MenB vaccines that target conserved surface proteins have the potential to induce a broader immune response against the diversity of disease-causing strains. Given the deleterious consequences and sporadic nature of MenB disease, the use of optimal vaccination strategies is crucial for prevention. Reactive vaccination strategies used in the past have significant limitations, including delayed implementation, substantial use of resources, and time constraints. The broad coverage potential of recombinant protein-based MenB vaccines suggests that routine use could result in a reduced burden of disease. Despite this, routine use of MenB vaccines is currently limited in practice.

Single-dose oral ciprofloxacin prophylaxis as a response to a meningococcal meningitis epidemic in the African meningitis belt: A 3-arm, open-label, cluster-randomized trial

BACKGROUND

Antibiotic prophylaxis for contacts of meningitis cases is not recommended during outbreaks in the African meningitis belt. We assessed the effectiveness of single-dose oral ciprofloxacin administered to household contacts and in village-wide distributions on the overall attack rate (AR) in an outbreak of meningococcal meningitis.

METHODS AND FINDINGS

In this 3-arm, open-label, cluster-randomized trial during a meningococcal meningitis outbreak in Madarounfa District, Niger, villages notifying a suspected case were randomly assigned (1:1:1) to standard care (the control arm), single-dose oral ciprofloxacin for household contacts within 24 hours of case notification, or village-wide distribution of ciprofloxacin within 72 hours of first case notification. The primary outcome was the overall AR of suspected meningitis after inclusion. A random sample of 20 participating villages was enrolled to document any changes in fecal carriage prevalence of ciprofloxacin-resistant and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae before and after the intervention. Between April 22 and May 18, 2017, 49 villages were included: 17 to the control arm, 17 to household prophylaxis, and 15 to village-wide prophylaxis. A total of 248 cases were notified in the study after the index cases. The AR was 451 per 100,000 persons in the control arm, 386 per 100,000 persons in the household prophylaxis arm (t test versus control p = 0.68), and 190 per 100,000 persons in the village-wide prophylaxis arm (t test versus control p = 0.032). The adjusted AR ratio between the household prophylaxis arm and the control arm was 0.94 (95% CI 0.52-1.73, p = 0.85), and the adjusted AR ratio between the village-wide prophylaxis arm and the control arm was 0.40 (95% CI 0.19‒0.87, p = 0.022). No adverse events were notified. Baseline carriage prevalence of ciprofloxacin-resistant Enterobacteriaceae was 95% and of ESBL-producing Enterobacteriaceae was >90%, and did not change post-intervention. One limitation of the study was the small number of cerebrospinal fluid samples sent for confirmatory testing.

CONCLUSIONS

Village-wide distribution of single-dose oral ciprofloxacin within 72 hours of case notification reduced overall meningitis AR. Distributions of ciprofloxacin could be an effective tool in future meningitis outbreak responses, but further studies investigating length of protection, effectiveness in urban settings, and potential impact on antimicrobial resistance patterns should be carried out.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02724046.

Immunogenicity and safety of MenACWY-TT, a meningococcal conjugate vaccine, co-administered with routine childhood vaccine in healthy infants: A phase III, randomized study

BACKGROUND

Invasive meningococcal disease has a high burden in young children, particularly during infancy. We investigated the immunogenicity and safety of a quadrivalent meningococcal conjugated vaccine (MenACWY-TT) co-administered with routine vaccines in healthy infants.

METHODS

In this phase IIIb study (NCT01340898) conducted in 2 centers in Lebanon and Mexico, 750 infants were randomized (2:1:1) to receive MenACWY-TT according to 3 schedules: 3+1 (at ages 2, 4, 6 and 15-18 months; group ACWY3+1); 1+1 (at 6 and 15-18 months; group ACWY1+1) or single-dose at 15-18 months (group ACWY1). All infants received PHiD-CV and DTPa-IPV/Hib at ages 2, 4, 6, 15-18 months. Immune responses to MenACWY-TT were assessed by rSBA and hSBA at 7 months (groups ACWY3+1, ACWY1+1) and pre- and post-vaccination at 15-18 months of age (all groups). Immune responses to co-administered vaccines, reactogenicity and safety were also evaluated.

RESULTS

Immunogenicity of MenACWY-TT at 1 month post-primary vaccination was demonstrated in group ACWY3+1: the lower limit of the 95% confidence interval for the percentage of infants with rSBA titers ≥8 was >80% for each serogroup. At 7 months of age, ≥93.9% of MenACWY-TT-primed infants had rSBA titers ≥8. Post-MenACWY-TT vaccination at age 15-18 months, ≥96.3% of participants in all groups had rSBA titers ≥8, regardless of the number of doses received previously. The percentage of infants with hSBA titers ≥4 were ≥87.2% and ≥89.7% at post-primary and booster/single-dose vaccination, respectively. Immune responses to PHiD-CV and DTPa-IPV/Hib did not seem impacted by co-administration with MenACWY-TT in infancy. The incidence of all adverse events was similar among groups. Serious adverse events were reported for 63/750 children in all groups; none were considered vaccine-related by investigators.

CONCLUSION

Primary vaccination with 3 or 1 dose(s) of MenACWY-TT when co-administered with routine pediatric vaccines in infants is immunogenic and well-tolerated.

Changing Pattern of Childhood Epidemic Cerebrospinal Meningitis in North-Western Nigeria

Introduction

Nigeria lies within the meningitis belt which extends from the Gambia, Senegal through Nigeria to Eritrea; however, outbreaks have been shown to extend further south involving countries such as Angola and Namibia. Epidemic outbreaks are often recorded every 8-12 years averaging in a 10 yearly circle however endemic cases still occurs.

Materials and Methods

The study was retrospective; all results of cerebrospinal fluid (CSF) samples of children with cases of meningitis from January 2010 to December 2010 were collected from the register of the microbiology laboratory of General Hospital Gusau. Relevant information such as their age, sex, CSF macroscopy/microscopy reports, latex particle agglutination test report, and CSF culture report were retrieved and entered into a pro forma.

Results

There were 89 (73%) males and 33 (27%) females with male to female ratio of 2.7:1. The age ranged from 2 months to 14 years; the mean was 6.27 ± 4.00 years. Meningitis was mostly recorded from January to April. W135 was the most common serotype identified. Majority of the samples (54) which were nonreactive for any of the tested antigens had clear CSF (36), while among those that reacted; the W135 group had a high proportion of cases that had turbid CSF (44); (Fisher's exact test = 30.650, P = 0.000). Majority of the samples (99) had no cell count; although those of the W135 group had higher cell counts followed by those in the nonreactive group (Fisher's exact test = 11.226, P = 0.181).

Conclusion

Meningitis was highest between January and April, and W135 was the most common serotype.

Vaccination strategies for the prevention of meningococcal disease

Routine prophylactic vaccination and mass vaccination strategies have been used to control both endemic and epidemic disease caused by Neisseria meningitidis globally. This review discusses real-world examples of these vaccination strategies, their implementation, and outcomes of these efforts, with the overall goal of providing insights on how to achieve optimal control of meningococcal disease through vaccination in varied settings. Tailoring immunization programs to fit the needs of the target population has the potential to optimally reduce disease incidence.

Progress toward the global control of Neisseria meningitidis: 21st century vaccines, current guidelines, and challenges for future vaccine development

The control of meningitis, meningococcemia and other infections caused by Neisseria meningitidis is a significant global health challenge. Substantial progress has occurred in the last twenty years in meningococcal vaccine development and global implementation. Meningococcal protein-polysaccharide conjugate vaccines to serogroups A, C, W, and Y (modeled after the Haemophilus influenzae b conjugate vaccines) provide better duration of protection and immunologic memory, and overcome weak immune responses in infants and young children and hypo-responsive to repeated vaccine doses seen with polysaccharide vaccines. ACWY conjugate vaccines also interfere with transmission and reduce nasopharyngeal colonization, thus resulting in significant herd protection. Advances in serogroup B vaccine development have also occurred using conserved outer membrane proteins with or without OMV as vaccine targets. Challenges for meningococcal vaccine research remain including developing combination vaccines containing ACYW(X) and B, determining the ideal booster schedules for the conjugate and MenB vaccines, and addressing issues of waning effectiveness.

Impact of meningococcal vaccination on carriage and disease transmission: A review of the literature

Colonization of the human nasopharyngeal tract by the bacterium Neisseria meningitidis is usually asymptomatic, but life-threatening meningococcal disease with a clinical presentation of meningitis, septicemia, or more rarely, gastrointestinal symptoms, can develop. Invasive meningococcal disease (IMD) can be fatal within 24 hours, but IMD is vaccine-preventable. Vaccines used to protect against IMD caused by 5 of the 6 most common serogroups (A, B, C, W, and Y) may also influence carriage prevalence in vaccinated individuals. Lower carriage among vaccinated people may reduce transmission to nonvaccinated individuals to provide herd protection against IMD. This article reviews observational and clinical studies examining effects of vaccination on N. meningitidis carriage prevalence in the context of mass vaccination campaigns and routine immunization programs. Challenges associated with carriage studies are presented alongside considerations for design of future studies to assess the impact of vaccination on carriage.

Global epidemiology of serogroup B meningococcal disease and opportunities for prevention with novel recombinant protein vaccines

BACKGROUND

Meningococcal disease (MD) is a major cause of meningitis and sepsis worldwide, with a high case fatality rate and frequent sequelae. Neisseria meningitidis serogroups A, B, C, W, X and Y are responsible for most of these life-threatening infections, and its unpredictable epidemiology can cause outbreaks in communities, with significant health, social and economic impact. Currently, serogroup B is the main cause of MD in Europe and North America and one of the most prevalent serogroups in Latin America. Mass vaccination strategies using polysaccharide vaccines have been deployed since the 1970s and the use of conjugate vaccines has controlled endemic and epidemic disease caused by serogroups A, C, W and Y and more recently serogroup B using geographically-specific outer membrane vesicle based vaccines. Two novel protein-based vaccines are a significant addition to our armamentarium against N. meningitidis as they provide broad coverage against highly diverse strains in serogroup B and other groups. Early safety, effectiveness and impact data of these vaccines are encouraging. These novel serogroup B vaccines should be actively considered for individuals at increased risk of disease and to control serogroup B outbreaks occurring in institutions or specific regions, as they are likely to save lives and prevent severe sequelae. Incorporation into national programs will require thorough country-specific analysis.

Combined Chemical Synthesis and Tailored Enzymatic Elongation Provide Fully Synthetic and Conjugation-Ready Neisseria meningitidis Serogroup X Vaccine Antigens

Studies on the polymerization mode of Neisseria meningitidis serogroup X capsular polymerase CsxA recently identified a truncated construct that can be immobilized and used for length controlled on-column production of oligosaccharides. Here, we combined the use of a synthetic acceptor bearing an appendix for carrier protein conjugation and the on-column process to a novel chemo-enzymatic strategy. After protein coupling of the size optimized oligosaccharide produced by the one-pot elongation procedure, we obtained a more homogeneous glycoconjugate compared to the one previously described starting from the natural polysaccharide. Mice immunized with the conjugated fully synthetic oligomer elicited functional antibodies comparable to controls immunized with the current benchmark MenX glycoconjugates prepared from the natural capsule polymer or from fragments of it enzymatically elongated. This pathogen-free technology allows the fast total in vitro construction of predefined bacterial polysaccharide fragments. Compared to conventional synthetic protocols, the procedure is more expeditious and drastically reduces the number of purification steps to achieve the oligomers. Furthermore, the presence of a linker for conjugation in the synthetic acceptor minimizes manipulations on the enzymatically produced glycan prior to protein conjugation. This approach enriches the methods for fast construction of complex bacterial carbohydrates.

Invasive meningococcal disease without meningitis: a forgotten diagnosis

Neisseria meningitidis, a Gram-negative diplococcus, is an uncommon cause of pneumonia. There have been only about 344 cases reported worldwide from 1906 to 2015. To our knowledge, there have been only 3 cases reported in the USA in the past 2 decades. We present a case of a 72-year-old male with a past medical history of severe COPD, obstructive sleep apnea, and stage I lung cancer status post-stereotactic body radiation therapy 1 year ago, who was admitted with a 6-day history of productive cough with yellowish sputum, shortness of breath, extreme myalgias, and fatigue. Chest X-ray revealed an infiltrative process in the left lower lung field and left-sided pleural effusion. Blood cultures grew beta-lactamase-negative N. meningitidis after 24 hours. Our patient was initially treated with broad-spectrum antibiotics, which were later switched to amoxicillin to complete a total of 14 days of antibiotics. Diagnosing meningococcal pneumonia requires a high level of suspicion, as sputum cultures may be falsely positive due to asymptomatic carriage of the organism in the upper respiratory tract in up to 10% of outpatient population. We highlight this case as early recognition and treatment is critical. The case fatality rate for N. meningitidis pneumonia has been reported to be higher compared with meningococcal meningitis.

Whole-Genome Sequencing of Emerging Invasive Neisseria meningitidis Serogroup W in Sweden

Invasive disease caused by Neisseria meningitidis serogroup W (MenW) has historically had a low incidence in Sweden, with an average incidence of 0.03 case/100,000 population from 1995 to 2014. In recent years, a significant increase in the incidence of MenW has been noted in Sweden, to an average incidence of 0.15 case/100,000 population in 2015 to 2016. In 2017 (1 January to 30 June), 33% of invasive meningococcal disease cases (7/21 cases) were caused by MenW. In the present study, all invasive MenW isolates from Sweden collected in 1995 to June 2017 (n = 86) were subjected to whole-genome sequencing to determine the population structure and to compare isolates from Sweden with historical and international cases. The increase of MenW in Sweden was determined to be due to isolates belonging to the South American sublineage of MenW clonal complex 11, namely, the novel U.K. 2013 lineage. This lineage was introduced in Sweden in 2013 and has since been the dominant lineage of MenW.

Increase of Neisseria meningitidis W:cc11 invasive disease in Chile has no correlation with carriage in adolescents

Neisseria meningitidis is a human exclusive pathogen that can lead to invasive meningococcal disease or may be carried in the upper respiratory tract without symptoms. The relationship between carriage and disease remains poorly understood but it is widely accepted that decreasing carriage by immunization should lead to a reduction of invasive cases. Latin America has experienced an increased incidence of serogroup W invasive cases of Neisseria meningitidis in the last decade. Specifically in Chile, despite low total incidence of invasive cases, serogroup W has become predominant since 2011 and has been associated with elevated mortality. Expecting to gain insight into the epidemiology of this disease, this study has used molecular typing schemes to compare Neisseria meningitidis isolates causing invasive disease with those isolates collected from adolescent carriers during the same period in Chile. A lower carriage of the serogroup W clonal complex ST-11/ET37 than expected was found; whereas, the same clonal complex accounted for 66% of total invasive meningococcal disease cases in the country that year. A high diversity of PorA variable regions and fHbp peptides was also ascertained in the carrier isolates compared to the invasive ones. According to the results shown here, the elevated number of serogroup W invasive cases in our country cannot be explained by a rise of carriage of pathogenic isolates. Overall, this study supports the idea that some strains, as W:cc11 found in Chile, possess an enhanced virulence to invade the host. Notwithstanding hypervirulence, this strain has not caused an epidemic in Chile. Finally, as genetic transfer occurs often, close surveillance of Neisseria meningitidis strains causing disease, and particularly hypervirulent W:cc11, should be kept as a priority in our country, in order to prepare the best response to face genetic changes that could lead to enhanced fitness of this pathogen.

Meningococcal disease and vaccination: Knowledge and acceptability among adolescents in Italy

This study aimed to evaluate the knowledge, attitudes and practice about invasive meningococcal disease and the relative vaccine for adolescent in Italy. A cross-sectional study was conducted from March to May 2017 among a sample of 771 adolescents in the geographic area of Naples (Italy). A self-administered anonymous questionnaire was used to collect demographics, knowledge about meningitis and preventive measures, perceived risk for contracting meningitis, attitude towards the utility of meningococcal vaccine, and adolescents' willingness to receive a meningococcal vaccine. 85.2% of participants have heard about meningitis, 57.2% knew that adolescents are a susceptible population but only 30.3% knew that meningitis is transmitted by respiratory droplets. Moreover, 40.5% of adolescents knew that meningitis is a vaccine-preventable disease and that adolescents could be vaccinated. This knowledge was significantly greater among female participants, among those who talk with parents about vaccinations, among who have received information about vaccinations from physicians, among who have positive attitude towards the utility of information received on vaccinations and among who don't feel the need of additional information about meningitis. As regard the attitudes, 25.7% of adolescents thought that the vaccine was very useful. Males, adolescent aged 11-13 years, those who had the positive attitude towards the utility of information received about vaccinations and those who had received at least one vaccination in the last year were more likely to have this attitude. The our finding identifies the need to improve adolescents' knowledge about meningitis and its related vaccinations, through correct health education, in order to have a good acceptance of vaccination.

An epidemic of meningococcal disease in children in North Norway in the 1970s and 1980s was dominated by a hypervirulent group B strain

AIM

We examined children hospitalised for invasive meningococcal disease, a leading cause of paediatric sepsis, in Troms County, North Norway, from 1973 to 2016, including the epidemic in the 1970s and 1980s.

METHODS

This study was a retrospective review of children under the age of 15 years who were hospitalised for meningococcal disease at the University Hospital of North Norway and Harstad Hospital. We studied hospital and bacteriological records to determine the incidence rates and phenotypes involved.

RESULTS

There were 300 cases under 15 years and an incidence rate of 17 per 100,000 cases for 1973-2016. This was broken down into the following: 1973-1980 (n = 130, 49), 1981-1990 (n = 129, 39), and 1991-2016 (n = 41, 4.7), respectively. There were 21 (7%) deaths. Phenotype B:15:P1.7,16 was more common than the other phenotypes in the epidemic period before 1990 than after 1990 (p = 0.02) and had a significantly lower mortality rate than the other phenotypes (p = 0.04). Later years showed a more heterogenous phenotype distribution. Serogroup B was the dominant serogroup.

CONCLUSION

The B:15:P1.7,6 strain was more prevalent during the Norwegian epidemic of invasive meningococcal disease, but had a significantly lower mortality rate. The phenotype distribution was more heterogeneous after 1990. The dominant serogroup was B.

Human protective response induced by meningococcus B vaccine is mediated by the synergy of multiple bactericidal epitopes

4CMenB is the first broad coverage vaccine for the prevention of invasive meningococcal disease caused by serogroup B strains. To gain a comprehensive picture of the antibody response induced upon 4CMenB vaccination and to obtain relevant translational information directly from human studies, we have isolated a panel of human monoclonal antibodies from adult vaccinees. Based on the Ig-gene sequence of the variable region, 37 antigen-specific monoclonal antibodies were identified and produced as recombinant Fab fragments, and a subset also produced as full length recombinant IgG1 and functionally characterized. We found that the monoclonal antibodies were cross-reactive against different antigen variants and recognized multiple epitopes on each of the antigens. Interestingly, synergy between antibodies targeting different epitopes enhanced the potency of the bactericidal response. This work represents the first extensive characterization of monoclonal antibodies generated in humans upon 4CMenB immunization and contributes to further unraveling the immunological and functional properties of the vaccine antigens. Moreover, understanding the mechanistic nature of protection induced by vaccination paves the way to more rational vaccine design and implementation.

Challenges and opportunities for meningococcal vaccination in the developing world

Meningococcal disease continues to be a life threatening infection with high morbidity and mortality even in appropriately treated patients. Meningococcal vaccination plays a major role in the control of the disease; however, implementing vaccination remains problematic in the developing world. The objective of this review is to identify the challenges facing the use of meningococcal vaccines in the developing world in order to discuss the opportunities and available solutions to improve immunization in these countries. Inadequate epidemiologic information necessary to implement vaccination and financial challenges predominate. Multiple measures are needed to achieve the successful implementation of meningococcal conjugate vaccination programs that protect against circulating serogroups in developing countries including enhanced surveillance systems, financial support and aid through grants, product development partnerships that are the end result of effective collaboration and communication between different interdependent stakeholders to develop affordable vaccines, and demonstration of the cost-effectiveness of new meningococcal vaccines.

Interplay Between Virulence and Variability Factors as a Potential Driver of Invasive Meningococcal Disease

Neisseria meningitidis (Nm) is frequently found in the upper respiratory tract of the human population. Despite its prevalence as a commensal organism, Nm can occasionally invade the pharyngeal mucosal epithelium causing septicemia and life-threatening disease. A number of studies have tried to identify factors that are responsible for the onset of a virulent phenotype. Despite this however, we still miss clear causative elements. Several factors have been identified to be associated to an increased susceptibility to meningococcal disease in humans. None of them, however, could unambiguously discriminate healthy carrier from infected individuals. Similarly, comparative studies of virulent and apathogenic strains failed to identify virulence factors that could explain the emergence of the pathogenic phenotype. In line with this, a recent study of within host evolution found that Nm accumulates genomic changes during the asymptomatic carriage phase and that these are likely to contribute to the shift to a pathogenic phenotype. These results suggest that the presence of virulence factors in the meningococcal genome is not a sufficient condition for developing virulent traits, but is rather the ability to promote phenotypic variation, through the stochastic assortment of the repertoire of such factors, which could explain the occasional and unpredictable onset of IMD. Here, we present a series of argumentations supporting the hypothesis that invasive meningococcal disease comes as a result of the coexistence of bacterial virulence and variability factors in a plot that can be further complicated by additional latent factors, like host pre-existing immune status and genetic predisposition.

Impact of meningococcal C conjugate vaccination programs with and without catch-up campaigns in adolescents: Lessons learned from Bahia, Brazil

The significant increase in the incidence rates and ongoing outbreaks of serogroup C meningococcal (MenC) disease, associated with the sequence type-103 complex, motivated the incorporation of the meningococcal C conjugate (MCC) vaccine in the routine immunization program in the State of Bahia, Brazil in early 2010, targeting children younger than 5 years of age. In its capital, Salvador, the program also included a catch-up campaign for individuals 10-24 years of age. We performed an observational, ecological study, analyzing data collected from 2007 to 2015, to compare the impact of these two immunization strategies on meningococcal disease incidence and mortality rates. In Salvador, following the vaccination program, a dramatic early impact on MenC disease and mortality rates could be observed, with significant reductions in incidence rates of MenC disease in all age groups, including individuals that were too old to have been vaccinated, indicating the presence of herd protection. Compared to the pre-vaccine period, a virtual disappearance of MenC disease was observed in 2015. However, in the state of Bahia (excluding the city of Salvador), no herd protection could be observed, with significant impact only among vaccine-eligible children within 5 years of introduction of the MCC vaccination program. These results highlight the importance of catch-up campaigns, including adolescents and young adults, to induce herd protection compared to immunization strategies restricted to infants and young children. This information is crucial for identifying optimal immunization policies and future strategies, focused on adolescents, to optimize the impact of MCC vaccination programs.

Vaccine prevention of meningococcal disease in Africa: Major advances, remaining challenges

Africa historically has had the highest incidence of meningococcal disease with high endemic rates and periodic epidemics. The meningitis belt, a region of sub-Saharan Africa extending from Senegal to Ethiopia, has experienced large, devastating epidemics. However, dramatic shifts in the epidemiology of meningococcal disease have occurred recently. For instance, meningococcal capsular group A (NmA) epidemics in the meningitis belt have essentially been eliminated by use of conjugate vaccine. However, NmW epidemics have emerged and spread across the continent since 2000; NmX epidemics have occurred sporadically, and NmC recently emerged in Nigeria and Niger. Outside the meningitis belt, NmB predominates in North Africa, while NmW followed by NmB predominate in South Africa. Improved surveillance is necessary to address the challenges of this changing epidemiologic picture. A low-cost, multivalent conjugate vaccine covering NmA and the emergent and prevalent meningococcal capsular groups C, W, and X in the meningitis belt is a pressing need.