Chronicle of an outbreak foretold: meningococcal meningitis W135 in Burkina Faso

Trends in Neisseria meningitidis serogroups amongst patients with suspected cerebrospinal meningitis in the meningitis belt of Ghana: a 5-year retrospective study

BACKGROUND

Serogroup A Neisseria meningitidis was the major cause of meningococcal meningitis epidemics in the African meningitis belt before 2010 when the monovalent meningococcal A conjugate vaccine (MenAfriVac) was introduced in the region. Therefore, this study aimed to establish the trends in N. meningitidis serogroups from 2016 to 2020 in Ghana's meningitis belt.

METHODS

Polymerase chain reaction (PCR) confirmed laboratory results of suspected cases of cerebrospinal meningitis from January, 2016 to March, 2020 were obtained from the Tamale Public Health Laboratory. The data were subjected to trend analysis using Statistical Package for the Social Sciences version 25. Differences between discrete variables were analyzed using the Cochran-Armitage trend test.

RESULTS

Of the 2,426 suspected cases, 395 (16.3%) were confirmed positive for N. meningitidis using PCR. Serogroup X showed a significant upward trend (P < 0.01), and serogroup W showed a downward trend (P < 0.01). However, no significant trend was observed for any other serogroup.

CONCLUSION

This study showed the emergence of serogroup X, a non-vaccine type, as the predominant N. meningitidis serogroup in the wake of a declining serogroup W in Ghana's meningitis belt.

Pneumococcal vaccine implementation in the African meningitis belt countries: the emerging need for alternative strategies

Introduction: Besides meningococcal disease, the African meningitis belt (AMB) region is also affected by pneumococcal disease. Most AMB countries have introduced pneumococcal conjugate vaccines (PCV) following a schedule of three primary doses without a booster or a catch-up campaign. PCV is expected to help control pneumococcal disease through both direct and indirect effects. Whether and how fast this will be achieved greatly depends on implementation strategies. Pre-PCV data from the AMB indicate high carriage rates of the pneumococcus, not only in infants but also in older children, and a risk of disease and death that spans lifetime. Post-PCV data highlight the protection of vaccinated children, but pneumococcal transmission remains important, resulting in a lack of indirect protection for unvaccinated persons.Areas covered: A non-systematic literature review focused on AMB countries. Relevant search terms were used in PubMed, and selected studies before and after PCV introduction were summarized narratively to appraise the suitability of current PCV programmatic strategies.Expert opinion: The current implementation strategy of PCV in the AMB appears suboptimal regarding the generation of indirect protection. We propose and discuss alternative programmatic strategies, including the implementation of broader age group mass campaigns, to accelerate disease control in this high transmission setting.

Emergence of Neisseria meningitidis W135 in Cote d'Ivoire: laboratory based-surveillance

OBJECTIVES

To describe the emergence of Neisseria meningitidis (Nm) W135 in Côte d’Ivoire and its characteristics compared to NmA.

METHODS

Data on Nm samples isolated at the National Reference Center for meningitis in Côte d’Ivoire between 2007 and 2012 were analyzed. Socio-demographic data and biological information on the samples were extracted from the database. Categorical variables, such as sex and the serotype of the bacteria, were compared using the Fisher exact test, while the distribution of continuous variables, such as age, was compared using the Wilcoxon test.

RESULTS

Among the 175 Nm samples, 57 were NmA, 4 were NmB, 13 were NmC, and 99 were NmW135. The geographical distribution of NmA and NmW135 did not show a significant difference according to age or sex. NmW135 was more common than NmA in the northern health districts of Cote d’Ivoire (85.9 vs. 45.5%; p<0.001). No sample of NmA has been isolated since 2009, while 95% of the type W135 samples were isolated between 2010 and 2012.

CONCLUSIONS

This study highlighted the emergence of NmW135 in Côte d’Ivoire, as well as the simultaneous disappearance of NmA. It is important to improve laboratory-based surveillance of meningitis to assess trends in the circulation of bacteria and to detect the emergence of new serogroups earlier.

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.

Impact of MenAfriVac in nine countries of the African meningitis belt, 2010-15: an analysis of surveillance data

BACKGROUND

In preparation for the introduction of MenAfriVac, a meningococcal group A conjugate vaccine developed for the African meningitis belt, an enhanced meningitis surveillance network was established. We analysed surveillance data on suspected and confirmed cases of meningitis to quantify vaccine impact.

METHODS

We compiled and analysed surveillance data for nine countries in the meningitis belt (Benin, Burkina Faso, Chad, Côte d'Ivoire, Ghana, Mali, Niger, Nigeria, and Togo) collected and curated by the WHO Inter-country Support Team between 2005 and 2015. The incidence rate ratios (IRRs) of suspected and confirmed cases in vaccinated and unvaccinated populations were estimated with negative binomial regression models. The relative risk of districts reaching the epidemic threshold of ten per 100 000 per week was estimated according to district vaccination status.

FINDINGS

The incidence of suspected meningitis cases declined by 57% (95% CI 55-59) in vaccinated compared with unvaccinated populations, with some heterogeneity observed by country. We observed a similar 59% decline in the risk of a district reaching the epidemic threshold. In fully vaccinated populations, the incidence of confirmed group A disease was reduced by more than 99%. The IRR for non-A serogroups was higher after completion of MenAfriVac campaigns (IRR 2·76, 95% CI 1·21-6·30).

INTERPRETATION

MenAfriVac introduction has led to substantial reductions in the incidence of suspected meningitis and epidemic risk, and a substantial effect on confirmed group A meningococcal meningitis. It is important to continue strengthening surveillance to monitor vaccine performance and remain vigilant against threats from other meningococcal serogroups and other pathogens.

FUNDING

World Health Organization.

Nationwide Trends in Bacterial Meningitis before the Introduction of 13-Valent Pneumococcal Conjugate Vaccine-Burkina Faso, 2011-2013

BACKGROUND

Following introduction of Haemophilus influenzae type b vaccine in 2006 and serogroup A meningococcal conjugate vaccine in 2010, Streptococcus pneumoniae (Sp) became the leading cause of bacterial meningitis in Burkina Faso. We describe bacterial meningitis epidemiology, focusing on pneumococcal meningitis, before 13-valent pneumococcal conjugate vaccine (PCV13) introduction in the pediatric routine immunization program in October 2013.

METHODS

Nationwide population-based meningitis surveillance collects case-level demographic and clinical information and cerebrospinal fluid (CSF) laboratory results. Sp infections are confirmed by culture, real-time polymerase chain reaction (rt-PCR), or latex agglutination, and CSF serotyped using real-time and conventional PCR. We calculated incidence rates in cases per 100,000 persons, adjusting for age and proportion of cases with CSF tested at national reference laboratories, and case fatality ratios (CFR).

RESULTS

During 2011-2013, 1,528 pneumococcal meningitis cases were reported. Average annual adjusted incidence rates were 26.9 (<1 year), 5.4 (1-4 years), 7.2 (5-14 years), and 3.0 (≥15 years). Overall CFR was 23% and highest among children aged <1 year (32%) and adults ≥30 years (30%). Of 1,528 cases, 1,036 (68%) were serotyped: 71% were PCV13-associated serotypes, 14% were non-PCV13-associated serotypes, and 15% were non-typeable by PCR. Serotypes 1 (45%) and 12F/12A/12B/44/46 (8%) were most common. Among children aged <1 year, serotypes 5 (15%), 6A/6B (13%) and 1 (12%) predominated.

CONCLUSIONS

In Burkina Faso, the highest morbidity and mortality due to pneumococcal meningitis occurred among children aged <1 year. The majority of cases were due to PCV13-associated serotypes; introduction of PCV13 should substantially decrease this burden.

Global epidemiology of capsular group W meningococcal disease (1970-2015): Multifocal emergence and persistence of hypervirulent sequence type (ST)-11 clonal complex

Following an outbreak in Mecca Saudi Arabia in 2000, meningococcal strains expressing capsular group W (W) emerged as a major cause of invasive meningococcal disease (IMD) worldwide. The Saudi Arabian outbreak strain (Hajj clone) belonging to the ST-11 clonal complex (cc11) is similar to W cc11 causing occasional sporadic disease before 2000. Since 2000, W cc11 has caused large meningococcal disease epidemics in the African meningitis belt and endemic disease in South America, Europe and China. Traditional molecular epidemiologic typing suggested that a majority of current W cc11 burden represented global spread of the Hajj clone. However, recent whole genome sequencing (WGS) analyses revealed significant genetic heterogeneity among global W cc11 strains. While continued spread of the Hajj clone occurs in the Middle East, the meningitis belt and South Africa have co-circulation of the Hajj clone and other unrelated W cc11 strains. Notably, South America, the UK, and France share a genetically distinct W cc11 strain. Other W lineages persist in low numbers in Europe, North America and the meningitis belt. In summary, WGS is helping to unravel the complex genomic epidemiology of group W meningococcal strains. Wider application of WGS and strengthening of global IMD surveillance is necessary to monitor the continued evolution of group W lineages.

Genomic Epidemiology of Hypervirulent Serogroup W, ST-11 Neisseria meningitidis

Neisseria meningitidis is a leading bacterial cause of sepsis and meningitis globally with dynamic strain distribution over time. Beginning with an epidemic among Hajj pilgrims in 2000, serogroup W (W) sequence type (ST) 11 emerged as a leading cause of epidemic meningitis in the African ‘meningitis belt’ and endemic cases in South America, Europe, Middle East and China. Previous genotyping studies were unable to reliably discriminate sporadic W ST-11 strains in circulation since 1970 from the Hajj outbreak strain (Hajj clone). It is also unclear what proportion of more recent W ST-11 disease clusters are caused by direct descendants of the Hajj clone. Whole genome sequences of 270 meningococcal strains isolated from patients with invasive meningococcal disease globally from 1970 to 2013 were compared using whole genome phylogenetic and major antigen-encoding gene sequence analyses. We found that all W ST-11 strains were descendants of an ancestral strain that had undergone unique capsular switching events. The Hajj clone and its descendants were distinct from other W ST-11 strains in that they shared a common antigen gene profile and had undergone recombination involving virulence genes encoding factor H binding protein, nitric oxide reductase, and nitrite reductase. These data demonstrate that recent acquisition of a distinct antigen-encoding gene profile and variations in meningococcal virulence genes was associated with the emergence of the Hajj clone. Importantly, W ST-11 strains unrelated to the Hajj outbreak contribute a significant proportion of W ST-11 cases globally. This study helps illuminate genomic factors associated with meningococcal strain emergence and evolution.

•

Genomic characterization of serogroup W ST-11 of Neisseria meningitidis.

.

•

Epidemic W ST-11 strain (Hajj clone) emerged through recombination affecting virulence genes.

•

Both the Hajj clone and W ST-11 strains unrelated to the Hajj outbreak have persisted globally.

Neisseria meningitidis, a bacterial cause of frequently fatal brain (meningitis) and blood stream (sepsis) infections, has variable strain distribution over time. Serogroup W sequence type 11 (W ST-11) lineage is associated on one hand with strains causing only rare (sporadic) disease cases, and the Hajj clone – a major global cause of epidemic and endemic meningococcal disease. In this study we analyzed complete genome sequences of a global collection of 270 W ST-11 isolates causing meningococcal disease from 1970-2013. The Hajj clone acquired novel gene sequences within genes involved in nitrogen metabolism (nitrogen oxide reductase, nitrite reductase) and evasion of human immune response (factor H binding protein). These genes may be the cause of increased virulence of the Hajj clone and can be used to trace continuing spread of the clone. These results shed light on mechanisms of meningococcal strain emergence.

Continuing effectiveness of serogroup A meningococcal conjugate vaccine, Chad, 2013

In 2011, vaccination with a serogroup A meningococcal polysaccharide conjugate vaccine was implemented in 3 of 23 regions in Chad. Cases of meningitis declined dramatically in vaccinated areas, but an epidemic continued in the rest of Chad. In 2012, the remaining Chad population was vaccinated, and the epidemic was halted.

Spatio-temporal factors associated with meningococcal meningitis annual incidence at the health centre level in Niger, 2004-2010

BACKGROUND

Epidemics of meningococcal meningitis (MM) recurrently strike the African Meningitis Belt. This study aimed at investigating factors, still poorly understood, that influence annual incidence of MM serogroup A, the main etiologic agent over 2004-2010, at a fine spatial scale in Niger.

METHODOLOGY/PRINCIPAL FINDINGS

To take into account data dependencies over space and time and control for unobserved confounding factors, we developed an explanatory Bayesian hierarchical model over 2004-2010 at the health centre catchment area (HCCA) level. The multivariate model revealed that both climatic and non-climatic factors were important for explaining spatio-temporal variations in incidence: mean relative humidity during November-June over the study region (posterior mean Incidence Rate Ratio (IRR) = 0.656, 95% Credible Interval (CI) 0.405-0.949) and occurrence of early rains in March in a HCCA (IRR = 0.353, 95% CI 0.239-0.502) were protective factors; a higher risk was associated with the percentage of neighbouring HCCAs having at least one MM A case during the same year (IRR = 2.365, 95% CI 2.078-2.695), the presence of a road crossing the HCCA (IRR = 1.743, 95% CI 1.173-2.474) and the occurrence of cases before 31 December in a HCCA (IRR = 6.801, 95% CI 4.004-10.910). At the study region level, higher annual incidence correlated with greater geographic spread and, to a lesser extent, with higher intensity of localized outbreaks.

CONCLUSIONS

Based on these findings, we hypothesize that spatio-temporal variability of MM A incidence between years and HCCAs result from variations in the intensity or duration of the dry season climatic effects on disease risk, and is further impacted by factors of spatial contacts, representing facilitated pathogen transmission. Additional unexplained factors may contribute to the observed incidence patterns and should be further investigated.

Meningococcal serogroup W135 in the African meningitis belt: epidemiology, immunity and vaccines

In the sub-Saharan African meningitis belt there is a region of hyperendemic and epidemic meningitis stretching from Senegal to Ethiopia. The public health approaches to meningitis epidemics, including those related to vaccine use, have assumed that Neisseria meningitidis serogroup A will cause the most disease. During 2001 and 2002, the first large-scale epidemics of serogroup W135 meningitis in sub-Saharan Africa were reported from Burkina Faso. The occurrence of N. meningitidis W135 epidemics has led to a host of new issues, including the need for improved laboratory diagnostics for identifying serogroups during epidemics, an affordable supply of serogroup W135-containing polysaccharide vaccine for epidemic control where needed, and re-evaluating the long-term strategy of developing a monovalent A conjugate vaccine for the region. This review summarizes the existing data on N. meningitidis W135 epidemiology, immunology and vaccines as they relate to meningitis in sub-Saharan Africa.

Epidemiological changes in meningococcal meningitis in Niger from 2008 to 2011 and the impact of vaccination

Background

The epidemiology of bacterial meningitis in the African ‘meningitis belt’ changes periodically. In order to design an effective vaccination strategy, we have examined the epidemiological and microbiological patterns of bacterial meningitis, and especially that of meningococcal meningitis, in Niger during the period 2008–2011. During this period a mass vaccination campaign with the newly developed meningococcal A conjugate vaccine (MenAfriVac®) was undertaken.

Method

Cerebrospinal fluid samples were collected from health facilities throughout Niger and analysed by culture, seroagglutination and/or speciation polymerase chain reaction, followed by genogrouping PCR for Neisseria meningitidis infections. A sample of strains were analysed by multi-locus sequence typing.

Results

N. meningitidis serogroup A cases were prevalent in 2008 and 2009 [98.6% and 97.5% of all N. meningitidis cases respectively]. The prevalence of serogroup A declined in 2010 [26.4%], with the emergence of serogroup W Sequence Type (ST) 11 [72.2% of cases], and the serogroup A meningococcus finally disappeared in 2011. The geographical distribution of cases N. meningitidis serogroups A and W within Niger is described.

Conclusion

The substantial decline of serogroup A cases that has been observed from 2010 onwards in Niger seems to be due to several factors including a major polysaccharide A/C vaccination campaign in 2009, the introduction of MenAfriVac® in 10 districts at risk in December 2010, the natural dynamics of meningococcal infection and the persistence of serogroup A sequence-type 7 for about 10 years. The emergence of serogroup W strains suggests that there may be a need for serogroup W containing vaccines in Niger in the coming years.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Development of a glycoconjugate vaccine to prevent meningitis in Africa caused by meningococcal serogroup X

Neisseria meningitidis is a major cause of bacterial meningitis worldwide, especially in the African meningitis belt, and has a high associated mortality. The meningococcal serogroups A, W, and X have been responsible for epidemics and almost all cases of meningococcal meningitis in the meningitis belt over the past 12 y. Currently no vaccine is available against meningococcal X (MenX). Because the development of a new vaccine through to licensure takes many years, this leaves Africa vulnerable to new epidemics of MenX meningitis at a time when the epidemiology of meningococcal meningitis on the continent is changing rapidly, following the recent introduction of a glycoconjugate vaccine against serogroup A. Here, we report the development of candidate glycoconjugate vaccines against MenX and preclinical data from their use in animal studies. Following optimization of growth conditions of our seed MenX strain for polysaccharide (PS) production, a scalable purification process was developed yielding high amounts of pure MenX PS. Different glycoconjugates were synthesized by coupling MenX oligosaccharides of varying chain length to CRM197 as carrier protein. Analytical methods were developed for in-process control and determination of purity and consistency of the vaccines. All conjugates induced high anti-MenX PS IgG titers in mice. Antibodies were strongly bactericidal against African MenX isolates. These findings support the further development of glycoconjugate vaccines against MenX and their assessment in clinical trials to produce a vaccine against the one cause of epidemic meningococcal meningitis that currently cannot be prevented by available vaccines.

Immunogenicity and safety of a quadrivalent meningococcal serogroups A, C, W-135 and Y tetanus toxoid conjugate vaccine (MenACWY-TT) administered to adults aged 56 Years and older: results of an open-label, randomized, controlled trial

Background

The burden of invasive meningococcal disease is substantial in older adults in whom the case fatality rate is high. Travelers to regions with high rates of meningococcal disease, such as Hajj pilgrims, are at increased risk of meningococcal infection, and disease transmission from travelers to their close contacts has been documented. In younger individuals, meningococcal conjugate vaccines offer advantages over polysaccharide vaccines in terms of duration of protection and boostability, and induction of herd immune effects through reductions in nasopharyngeal carriage of meningococci. To date, few data are available evaluating meningococcal conjugate vaccine use in adults >55 years of age.

Objective

To evaluate the immunogenicity and safety of quadrivalent meningococcal serogroups A, C, W-135 and Y vaccine with all serogroups conjugated to tetanus toxoid (MenACWY-TT, Nimenrix™, GlaxoSmithKline, Belgium) and a licensed quadrivalent polysaccharide vaccine (MenPS, Mencevax™ GlaxoSmithKline, Belgium) in adults >55 years of age.

Methods

This was a phase IIIb, open-label, randomized (3:1), controlled study conducted at one study center in Lebanon. A total of 400 healthy adults between 56 and 103 years of age without previous MenPS or tetanus toxoid vaccination within the previous 5 years or meningococcal conjugate vaccination at any time previously were included. They received a single-dose vaccination with MenACWY-TT or MenPS with blood sampling before and 1 month after vaccination. The main outcome measures were serum bactericidal activity (rabbit complement source: rSBA) vaccine response (VR) rate [rSBA titer of ≥1:32 in initially seronegative subjects (rSBA titer <1:8); ≥4-fold increase in subjects with pre-vaccination rSBA titers between 1:8 and 1:128, and ≥2-fold increase in subjects with pre-vaccination rSBA titers ≥1:128]. The percentages of subjects with rSBA titers ≥1:8 and ≥1:128 and rSBA geometric mean titers (GMTs) were assessed. Solicited adverse events were recorded for 4 days following vaccination, and all other adverse events, including the incidence of new onset chronic diseases, were recorded for 31 days after vaccination.

Results

One month after a single dose of MenACWY-TT, the rSBA VR rate in the MenACWY-TT group was 76.6 % for serogroup A, 80.3 % for serogroup C, 77.5 % for serogroup W-135 and 81.9 % for serogroup Y. VR rates in the MenPS group were 91.7, 84.8, 87.1 and 89.1 %, respectively. One month after vaccination, ≥93.2 % of subjects in the MenACWY-TT group and ≥93.9 % in the MenPS group had rSBA titers ≥1:128. In each group, GMTs increased by ≥13-fold for each serogroup. rSBA VR and GMTs tended to be lower in subjects who were over 65 years compared to 56–65 years of age. Only 6.3 % of MenACWY-TT recipients had anti-TT ≥0.1 IU/ml prior to vaccination, increasing to 28.1 % post-vaccination. The rSBA GMTs were 1.9- to 4-fold higher in anti-TT responders. Each local and general solicited symptom was reported by no more than 3.0 % of subjects in either group. No serious adverse events were considered vaccine related.

Conclusion

In adults 56 years of age and older, MenACWY-TT was immunogenic, with a vaccine response rate ≥76 % and with ≥93 % of subjects achieving rSBA titers ≥1:128 against all four serogroups after a single dose. MenACWY-TT induced low anti-TT concentrations in this population, which deserves further study.

Electronic supplementary material

The online version of this article (doi:10.1007/s40266-013-0065-0) contains supplementary material, which is available to authorized users.

Significant sequelae after bacterial meningitis in Niger: a cohort study

BACKGROUND

Beside high mortality, acute bacterial meningitis may lead to a high frequency of neuropsychological sequelae. The Sahelian countries belonging to the meningitis belt experience approximately 50% of the meningitis cases occurring in the world. Studies in Africa have shown that N. meningitidis could cause hearing loss in up to 30% of the cases, exceeding sometimes measles. The situation is similar in Niger which experiences yearly meningitis epidemics and where rehabilitation wards are rare and hearing aids remain unaffordable. The aim of this study was to estimate the frequency of neuropsychological sequelae after acute bacterial meningitis in four of the eight regions of Niger.

METHODS

Subjects exposed to acute bacterial meningitis were enrolled into a cohort with non exposed subjects matched on age and gender. Consenting subjects were interviewed during inclusion and at a control visit two months later. If clinical symptoms or psychological troubles persisted at both visits among the exposed subjects with a frequency significantly greater than that observed among the non exposed subjects, a sequelae was retained. The comparison of the frequency of sequelae between non exposed and exposed subjects to bacterial meningitis was also calculated using the Fisher exact test.

RESULTS

Three persisting functional symptoms were registered: headaches, asthenia, and vertigo among 31.3, 36.9, and 22.4% respectively of the exposed subjects. A significant motor impairment was retrieved among 12.3% of the exposed versus 1.6% of the non exposed subjects. Hearing loss significantly disabled 31.3% of the exposed subjects and 10.4% exhibited a serious deafness.

CONCLUSIONS

This study carried out in Niger confirms two serious neurological sequelae occurring at high frequencies after bacterial meningitis: severe and profound hearing loss and motor impairment. Cochlear implantation and hearing aids are too expensive for populations living in developing countries. Neurological sequelae occurring after meningitis should sensitize African public health authorities on the development of rehabilitation centers. All these challenges can be met through existing strategies and guidelines.

Meningococcal carriage in the African meningitis belt

A meningococcal serogroup A polysaccharide/tetanus toxoid conjugate vaccine (PsA-TT) (MenAfriVac#x2122;) is being deployed in countries of the African meningitis belt. Experience with other polysaccharide/protein conjugate vaccines has shown that an important part of their success has been their ability to prevent the acquisition of pharyngeal carriage and hence to stop transmission and induce herd immunity. If PsA-TT is to achieve the goal of preventing epidemics, it must be able to prevent the acquisition of pharyngeal carriage as well as invasive meningococcal disease and whether PsA-TT can prevent pharyngeal carriage needs to be determined. To address this issue, a consortium (the African Meningococcal Carriage (MenAfriCar) consortium) was established in 2009 to investigate the pattern of meningococcal carriage in countries of the African meningitis belt prior to and after the introduction of PsA-TT. This article describes how the consortium was established, its objectives and the standardised field and laboratory methods that were used to achieve these objectives. The experience of the MenAfriCar consortium will help in planning future studies on the epidemiology of meningococcal carriage in countries of the African meningitis belt and elsewhere.

Un vaccin conjugué contenant un polysaccharide du sérogroupe A méningococcique et une anatoxine du tétanos (PsA-TT) (MenAfriVac™) est en cours de déploiement dans les pays de la ceinture africaine de la méningite. L’ expérience avec d’ autres vaccins conjugués polysaccharide/protéine a montré qu’ une partie importante de leur succès a été leur capacité à empêcher l’ acquisition du portage pharyngé et donc à arrêter la transmission et à induire une immunité de group. Si PsA-TT doit d’ atteindre l’ objectif de prévenir les épidémies, il devrait être en mesure d’ empêcher l’ acquisition du portage pharyngé ainsi que la méningococcie invasive et le fait que PsA-TT puisse empêcher le portage pharyngé devrait être déterminé. Pour résoudre ce problème, le consortium MenAfriCar (Consortium Africain du Portage Méningococcique) a été établi en 2009 pour étudier le mode de portage du méningocoque dans les pays de la ceinture africaine de la méningite avant et après l’ introduction de PsA-TT. Cet article décrit comment le consortium a été établi, ses objectifs et les méthodes de laboratoire et de terrain standardisées qui ont été utilisées pour atteindre ces objectifs. L’ expérience du consortium MenAfriCar aidera à planifier les futures études sur l’ épidémiologie du portage du méningocoque dans les pays de la ceinture africaine de la méningite et d’ ailleurs.

Se está utilizando una vacuna meningocócica conjugada (MenAfriVac™) de polisacárido del serogrupo A / tétano toxoide (PsA-TT) en países del cinturón Africano de meningitis. Las experiencias obtenidas con otras vacunas conjugadas polisacárido/proteína han demostrado que una parte importante de su éxito se debe a su habilidad para prevenir la colonización faríngea de los portadores, acabando por lo tanto con la transmisión, y a la de inducir la protección de rebaño. Si PsA-TT ha de cumplir el objetivo de prevenir epidemias, debe ser capaz de prevenir el estado de portador faríngeo, al igual que la enfermedad invasiva por meningococo, y para ello es necesario determinar si la PsA-TT puede prevenir la colonización faríngea. Con el fin de abordar esta cuestión se estableció un consorcio africano en el 2009 - el MenAfriCar (African Meningococcal Carriage Consortium) – para investigar los patrones del estado de portador de meningococo en países del cinturón Africano de la meningitis, antes y después de la introducción de PsA-TT. Este artículo describe como se estableció el consorcio, sus objetivos y los métodos estandarizados de campo y de laboratorio que se utilizaron para alcanzarlos. La experiencia del consorcio MenAfriCar ayudará en la planificación de estudios futuros sobre la epidemiología del estado de portador de meningococo, tanto en países del cinturón Africano de la meningitis como en otros lugares del mundo.

Biochemical and biophysical characterization of the sialyl-/hexosyltransferase synthesizing the meningococcal serogroup W135 heteropolysaccharide capsule

Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis and sepsis. Crucial virulence determinants of pathogenic Nm strains are the polysaccharide capsules that support invasion by hindering complement attack. In NmW-135 and NmY the capsules are built from the repeating units (→ 6)-α-D-Gal-(1 → 4)-α-Neu5Ac-(2 →)n and (→ 6)-α-D-Glc-(1 → 4)-α-Neu5Ac-(2 →)n, respectively. These unusual heteropolymers represent unique examples of a conjugation between sialic acid and hexosyl-sugars in a polymer chain. Moreover, despite the various catalytic strategies needed for sialic acid and hexose transfer, single enzymes (SiaDW-135/Y) have been identified to form these heteropolymers. Here we used SiaDW-135 as a model system to delineate structure-function relationships. In size exclusion chromatography active SiaDW-135 migrated as a monomer. Fold recognition programs suggested two separate glycosyltransferase domains, both containing a GT-B-fold. Based on conserved motifs predicted folds could be classified as a hexosyl- and sialyltransferase. To analyze enzyme properties and interplay of the two identified glycosyltransferase domains, saturation transfer difference NMR and mutational studies were carried out. Simultaneous and independent binding of UDP-Gal and CMP-Sia was seen in the absence of an acceptor as well as when the catalytic cycle was allowed to proceed. Enzyme variants with only one functionality were generated by site-directed mutagenesis and shown to complement each other in trans when combined in an in vitro test system. Together the data strongly suggests that SiaDW-135 has evolved by fusion of two independent ancestral genes encoding sialyl- and galactosyltransferase activity.

Priorities for research on meningococcal disease and the impact of serogroup A vaccination in the African meningitis belt

For over 100 years, large epidemics of meningococcal meningitis have occurred every few years in areas of the African Sahel and sub-Sahel known as the African meningitis belt. Until recently, the main approach to the control of these epidemics has been reactive vaccination with a polysaccharide vaccine after an outbreak has reached a defined threshold and provision of easy access to effective treatment but this approach has not prevented the occurrence of new epidemics. Meningococcal conjugate vaccines, which can prevent meningococcal carriage and thus interrupt transmission, may be more effective than polysaccharide vaccines at preventing epidemics. Because the majority of African epidemics have been caused by serogroup A meningococci, a serogroup A polysaccharide/tetanus toxoid protein conjugate vaccine (PsA-TT) has recently been developed. Results from an initial evaluation of the impact of this vaccine on meningococcal disease and meningococcal carriage in Burkina Faso have been encouraging. To review how the research agenda for meningococcal disease in Africa has been changed by the advent of PsA-TT and to define a new set of research priorities for study of meningococcal infection in Africa, a meeting of 41 scientists was held in Dakar, Senegal on April 24th and 25th 2012. The research recommendations developed during the course of this meeting are presented in this paper. The need for enhanced surveillance for meningitis in defined populations with good diagnostic facilities in African countries at risk of epidemics was identified as the highest priority. This is needed to determine the duration of protection against serogroup A meningococcal disease provided by PsA-TT and to determine the risk of disease and carriage caused by meningococci of other serogroups. Other research areas given high priority included identification and validation of serological correlates of protection against meningococcal disease and carriage, development of improved methods for detecting carriage and epidemiological studies aimed at determining the reasons underlying the peculiar epidemiology of meningococcal disease in the African meningitis belt. Minutes and working papers from the meeting are provided in supplementary tables and some of the presentations made at the meeting are available on the MenAfriCar consortium website (www.menafricar.org) and on the web site of the Centers for Disease Control (www.cdc.gov).

The immunogenicity and safety of an investigational meningococcal serogroups A, C, W-135, Y tetanus toxoid conjugate vaccine (ACWY-TT) compared with a licensed meningococcal tetravalent polysaccharide vaccine: a randomized, controlled non-inferiority study

Immunogenicity and safety of ACWY-TT compared with licensed ACWY polysaccharide vaccine (MenPS) in healthy adults, and lot-to-lot consistency of three ACWY-TT lots were evaluated in a phase 3, open, controlled study. Adults aged 18–55 y were randomized to receive ACWY-TT (one of three lots) or MenPS. Serum bactericidal antibodies (rSBA) were measured pre- and 1 mo post-vaccination. Adverse events (AEs) were assessed 4 d (solicited symptoms) and 31 d (unsolicited symptoms) post-vaccination. Serious AEs were reported up to 6 mo after vaccination. The number of vaccinated subjects was 1247 (ACWY-TT, n = 935; MenPS, n = 312). ACWY-TT lot-to-lot consistency and non-inferiority of ACWY-TT as compared with MenPS groups were demonstrated according to pre-specified criteria. The percentages of subjects with a vaccine response (VR = rSBA titer ≥ 1:32 in initially seronegative; ≥ 4-fold increase in initially seropositive) to ACWY-TT vs. MenPS were 80.1%/69.8% (serogroup A), 91.5%/ 92.0% (C), 90.2%/85.5% (W-135), 87.0%/78.8% (Y). Exploratory analyses showed that for serogroups A, W-135 and Y, VR rates and GMTs were significantly higher for ACWY-TT compared with MenPS. For each serogroup, ≥ 98.0% of subjects had rSBA titers ≥ 1:128. Grade 3 solicited AEs were reported in ≤ 1.6% of subjects in any group. The immunogenicity of ACWY-TT vaccine was non-inferior to MenPS for all four serogroups in adults, with significantly higher VR rates to serogroups A, W-135 and Y and an acceptable safety profile. Consistency of 3 ACWY-TT production lots was demonstrated. These data suggest that, if licensed, ACWY-TT conjugate vaccine may be used for protection against invasive meningococcal disease in healthy adults.

 

This study is registered at clinicaltrials.gov NCT00453986

Epidemiology and prevention of meningococcal disease: a critical appraisal of vaccine policies

Meningococcal disease is characterized by a marked variation in incidence and serogroup distribution by region and over time. In several European countries, Canada and Australia, immunization programs, including universal vaccination of infants or toddlers with catch-up campaigns in children and adolescents, aimed at controlling disease caused by meningococcal serogroup C have been successful in reducing disease incidence through direct and indirect protection. More recently, meningococcal conjugate vaccines targeting disease caused by serogroups A, C, W-135 and Y have been licensed and are being used in adolescent programs in the USA and Canada while a mass immunization campaign against serogroup A disease has been implemented in Africa. Positive results from clinical trials using vaccines against serogroup B disease in various age groups suggest the possibility of providing broader protection against serogroup B disease than is provided by the currently used outer membrane vesicle vaccines. The purpose of our review of meningococcal epidemiology and assessment of existing policies is to set the stage for future policy decisions. Vaccination policies to prevent meningococcal disease in different regions of the world should be based on quality information from enhanced surveillance systems.

Neisseria meningitidis: biology, microbiology, and epidemiology

Neisseria meningitidis (the meningococcus) causes significant morbidity and mortality in children and young adults worldwide through epidemic or sporadic meningitis and/or septicemia. In this review, we describe the biology, microbiology, and epidemiology of this exclusive human pathogen. N.meningitidis is a fastidious, encapsulated, aerobic gram-negative diplococcus. Colonies are positive by the oxidase test and most strains utilize maltose. The phenotypic classification of meningococci, based on structural differences in capsular polysaccharide, lipooligosaccharide (LOS) and outer membrane proteins, is now complemented by genome sequence typing (ST). The epidemiological profile of N. meningitidis is variable in different populations and over time and virulence of the meningococcus is based on a transformable/plastic genome and expression of certain capsular polysaccharides (serogroups A, B, C, W-135, Y and X) and non-capsular antigens. N. meningitidis colonizes mucosal surfaces using a multifactorial process involving pili, twitching motility, LOS, opacity associated, and other surface proteins. Certain clonal groups have an increased capacity to gain access to the blood, evade innate immune responses, multiply, and cause systemic disease. Although new vaccines hold great promise, meningococcal infection continues to be reported in both developed and developing countries, where universal vaccine coverage is absent and antibiotic resistance increasingly more common.

Seroprevalence of serum bactericidal antibodies against group W135 and Y meningococci in England in 2009

Serological surveillance has been used in the United Kingdom to inform vaccine policy for several infections, including those with group C meningococci. Meningococcal conjugate vaccines, containing capsular groups A, W135, and Y in addition to C, are now available, but their use in the United Kingdom is restricted to at-risk groups and travelers to areas of endemicity. The aim of this study was to establish a baseline for natural immunity for groups W135 and Y. Serum samples collected in 2009 from individuals of all ages were obtained from the Health Protection Agency Seroepidemiology Unit, which collects residual sera from participating laboratories across the country. Serum bactericidal antibody (SBA) activity against two reference strains, representing groups Y (strain M03 241125) and W135 (strain M01 240070), was determined with 1,191 sera using a standardized complement-mediated SBA assay, with complement derived from baby rabbits (rSBA). The age-specific geometric mean titers (GMTs) and percentages of individuals with rSBA titers of ≥ 8 were calculated, together with 95% confidence intervals (CI). Overall, 18.4% and 19.6% had rSBA titers of ≥ 8 for groups W135 and Y, respectively. Antibody prevalence varied by age. In general, rSBA titers were low for younger children, with serum samples from 7% and 13% of children under 5 years achieving titers of ≥ 8 against groups W135 and Y, respectively. GMTs peaked for 20- to 24-year-olds for group W135 (GMT, 7.1; 95% CI, 4.7, 10.9) and for 30- to 44-year-olds for group Y (GMT, 8.6; 95% CI, 5.9, 12.7). Unlike seroprevalence against group B meningococci, there was not an obvious peak in SBA titers in samples from teenagers. Natural immunity against group W135 and Y meningococci in England appears to be low.

The changing and dynamic epidemiology of meningococcal disease

The epidemiology of invasive meningococcal disease continues to change rapidly, even in the three years since the first Meningococcal Exchange Meeting in 2008. Control of disease caused by serogroup C has been achieved in countries that have implemented meningococcal C or quadrivalent meningococcal ACWY conjugate vaccines. Initiation of mass immunization programs with meningococcal A conjugate vaccines across the meningitis belt of Africa may lead to the interruption of cyclical meningococcal epidemics. A meningococcal B vaccination program in New Zealand has led to a decreased incidence of high rates of endemic serogroup B disease. Increases in serogroup Y disease have been observed in certain Nordic countries which, if they persist, may require consideration of use of a multiple serogroup vaccine. The imminent availability of recombinant broadly protective serogroup B vaccines may provide the tools for further control of invasive meningococcal disease in areas where serogroup B disease predominates. Continued surveillance of meningococcal disease is essential; ongoing global efforts to improve the completeness of reporting are required.

Epidemiology, molecular characterization and antibiotic resistance of Neisseria meningitidis from patients ≤15 years in Manhiça, rural Mozambique

Background

The epidemiology of meningococcal disease in Mozambique and other African countries located outside the “meningitis belt” remains widely unknown. With the event of upcoming vaccines microbiological and epidemiological information is urgently needed.

Methods

Prospective surveillance for invasive bacterial infections was conducted at the Manhiça District hospital (rural Mozambique) among hospitalized children below 15 years of age. Available Neisseria meningitidis isolates were serogrouped and characterized by Multilocus Sequence Typing (MLST). Antibiotic resistance was also determined.

Results

Between 1998 and 2008, sixty-three cases of confirmed meningococcal disease (36 meningitis, 26 sepsis and 1 conjunctivitis) were identified among hospitalized children. The average incidence rate of meningococcal disease was 11.6/100,000 (8/100,000 for meningitis and 3.7/100,000 for meningococcemia, respectively). There was a significant rise on the number of meningococcal disease cases in 2005–2006 that was sustained till the end of the surveillance period. Serogroup was determined for 43 of the 63 meningococcal disease cases: 38 serogroup W-135, 3 serogroup A and 2 serogroup Y. ST-11 was the most predominant sequence type and strongly associated with serogroup W-135. Two of the three serogroup A isolates were ST-1, and both serogroup Y isolates were ST-175. N. meningitidis remained highly susceptible to all antibiotics used for treatment in the country, although the presence of isolates presenting intermediate resistance to penicillin advocates for continued surveillance.

Conclusions

Our data show a high rate of meningococcal disease in Manhiça, Mozambique, mainly caused by serogroup W-135 ST-11 strains, and advocates for the implementation of a vaccination strategy covering serogroup W-135 meningococci in the country.

Immunogenicity of a single dose of tetravalent meningococcal serogroups A, C, W-135, and Y conjugate vaccine administered to 2- to 10-year-olds is noninferior to a licensed-ACWY polysaccharide vaccine with an acceptable safety profile

BACKGROUND

Meningococcal disease remains an important cause of invasive bacterial infections in children less than 5 years of age. Immunogenicity and safety of the investigational ACWY vaccine conjugated with tetanus toxoid (ACWY-TT, GlaxoSmithKline Biologicals) were evaluated in 1501 healthy 2- to 10-year-old children in the Philippines, India, Lebanon, and Saudi Arabia.

METHODS

Children were randomized (3:1) to receive ACWY-TT or licensed tetravalent meningococcal polysaccharide vaccine (Mencevax, GlaxoSmithKline, Men-PS). Diary cards were used to collect solicited symptoms for 4 days after vaccination. Serious adverse events were reported for 6 months. Serum bactericidal activity (rSBA, rabbit complement) was measured before and 1 month after vaccination in the first 75% of subjects enrolled in each country.

RESULTS

The statistical criteria for noninferiority in terms of rSBA vaccine responses were reached. Exploratory analyses showed that postvaccination rSBA titers ≥ 1:8 and ≥ 1:128 were significantly higher after ACWY-TT than Men-PS for serogroups C, W-135, and Y, and rSBA vaccine responses and geometric mean antibody titers were significantly higher for all 4 serogroups after administration of ACWY-TT. Noninferiority in terms of incidences of grade 3 general symptoms was not demonstrated. ACWY-TT was well tolerated with grade 3 events reported in <1% of subjects per group. No serious adverse events were considered related to vaccination.

CONCLUSION

ACWY-TT was immunogenic in children between 2 to 10 years of age with a clinically acceptable safety profile that resembled licensed Men-PS. These data support a positive benefit/risk ratio for the ACWY-TT vaccine.

Infections of people with complement deficiencies and patients who have undergone splenectomy

The complement system comprises several fluid-phase and membrane-associated proteins. Under physiological conditions, activation of the fluid-phase components of complement is maintained under tight control and complement activation occurs primarily on surfaces recognized as "nonself" in an attempt to minimize damage to bystander host cells. Membrane complement components act to limit complement activation on host cells or to facilitate uptake of antigens or microbes "tagged" with complement fragments. While this review focuses on the role of complement in infectious diseases, work over the past couple of decades has defined several important functions of complement distinct from that of combating infections. Activation of complement in the fluid phase can occur through the classical, lectin, or alternative pathway. Deficiencies of components of the classical pathway lead to the development of autoimmune disorders and predispose individuals to recurrent respiratory infections and infections caused by encapsulated organisms, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. While no individual with complete mannan-binding lectin (MBL) deficiency has been identified, low MBL levels have been linked to predisposition to, or severity of, several diseases. It appears that MBL may play an important role in children, who have a relatively immature adaptive immune response. C3 is the point at which all complement pathways converge, and complete deficiency of C3 invariably leads to severe infections, including those caused by meningococci and pneumococci. Deficiencies of the alternative and terminal complement pathways result in an almost exclusive predisposition to invasive meningococcal disease. The spleen plays an important role in antigen processing and the production of antibodies. Splenic macrophages are critical in clearing opsonized encapsulated bacteria (such as pneumococci, meningococci, and Escherichia coli) and intraerythrocytic parasites such as those causing malaria and babesiosis, which explains the fulminant nature of these infections in persons with anatomic or functional asplenia. Paramount to the management of patients with complement deficiencies and asplenia is educating patients about their predisposition to infection and the importance of preventive immunizations and seeking prompt medical attention.

Neurological disorders in complex humanitarian emergencies and natural disasters

Complex humanitarian emergencies include the relatively acute, severe, and overwhelming health consequences of armed conflict, food scarcity, mass displacement, and political strife. Neurological manifestations of complex humanitarian emergencies are important and underappreciated consequences of emergencies in populations worldwide. This review critically assesses the existing knowledge of the range of neurological disorders that accompany complex humanitarian emergencies and natural disasters in both the acute phase of crisis and the "long shadow" that follows.

Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis

The epidemiology of bacterial meningitis has changed as a result of the widespread use of conjugate vaccines and preventive antimicrobial treatment of pregnant women. Given the significant morbidity and mortality associated with bacterial meningitis, accurate information is necessary regarding the important etiological agents and populations at risk to ascertain public health measures and ensure appropriate management. In this review, we describe the changing epidemiology of bacterial meningitis in the United States and throughout the world by reviewing the global changes in etiological agents followed by specific microorganism data on the impact of the development and widespread use of conjugate vaccines. We provide recommendations for empirical antimicrobial and adjunctive treatments for clinical subgroups and review available laboratory methods in making the etiological diagnosis of bacterial meningitis. Finally, we summarize risk factors, clinical features, and microbiological diagnostics for the specific bacteria causing this disease.

Evidence for capsule switching between carried and disease-causing Neisseria meningitidis strains

Changing antigenic structure such as with capsule polysaccharide is a common strategy for bacterial pathogens to evade a host immune system. The recent emergence of an invasive W:2a:P1.7-2,4 sequence type 11 (ST-11) strain of Neisseria meningitidis in New Zealand, an uncommon serogroup/serotype in New Zealand disease cases, was investigated for its genetic origins. Molecular typing of 107 meningococcal isolates with similar serotyping characteristics was undertaken to determine genetic relationships. Results indicated that the W:2a:P1.7-2,4 strain had emerged via capsule switching from a group C strain (C:2a:P1.7-2,4). Neither the upstream nor downstream sites of recombination could be elucidated, but sequence analysis demonstrated that at least 45 kb of DNA was involved in the recombination, including the entire capsule gene cluster. The oatWY gene carried by the W:2a:P1.7-2,4 strain contained the insertion sequence element IS1301, one of five variants of oatWY found in group W135 strains belonging to the carriage-associated ST-22 clonal complex. This suggested that the origin of the capsule genes carried by the invasive W:2a:P1.7-2,4 strain is carriage associated. These results provide novel evidence for the long-standing dogma that disease-associated strains acquire antigenic structure from carriage-associated strains. Moreover, the capsule switch described here has arisen from the exchange of the entire capsule locus.

Global epidemiology of meningococcal disease

As reviewed in this paper, meningococcal disease epidemiology varies substantially by geographic area and time. The disease can occur as sporadic cases, outbreaks, and large epidemics. Surveillance is crucial for understanding meningococcal disease epidemiology, as well as the need for and impact of vaccination. Despite limited data from some regions of the world and constant change, current meningococcal disease epidemiology can be summarized by region. By far the highest incidence of meningococcal disease occurs in the meningitis belt of sub-Saharan Africa. During epidemics, the incidence can approach 1000 per 100,000, or 1% of the population. Serogroup A has been the most important serogroup in this region. However, serogroup C disease has also occurred, as has serogroup X disease and, most recently, serogroup W-135 disease. In the Americas, the reported incidence of disease, in the range of 0.3-4 cases per 100,000 population, is much lower than in the meningitis belt. In addition, in some countries such as the United States, the incidence is at an historical low. The bulk of the disease in the Americas is caused by serogroups C and B, although serogroup Y causes a substantial proportion of infections in some countries and W-135 is becoming increasingly problematic as well. The majority of meningococcal disease in European countries, which ranges in incidence from 0.2 to 14 cases per 100,000, is caused by serogroup B strains, particularly in countries that have introduced serogroup C meningococcal conjugate vaccines. Serogroup B also predominates in Australia and New Zealand, in Australia because of the control of serogroup C disease through vaccination and in New Zealand because of a serogroup B epidemic. Based on limited data, most disease in Asia is caused by serogroup A and C strains. Although this review summarizes the current status of meningococcal disease epidemiology, the dynamic nature of this disease requires ongoing surveillance both to provide data for vaccine formulation and vaccine policy and to monitor the impact of vaccines following introduction.

Amino acid 310 determines the donor substrate specificity of serogroup W-135 and Y capsule polymerases of Neisseria meningitidis

The capsular polysaccharides of serogroup W-135 and Y meningococci are sialic acid-containing heteropolymers, with either galactose or glucose as the second sugar residue. As shown previously, sequences of the predicted enzymes that catalyse capsule polymerization, i.e. SiaD(W-135) and SiaD(Y), differ in only a few amino acids. By in vitro assays with purified recombinant proteins, SiaD(W-135) and SiaD(Y) were now confirmed to be the capsule polymerases harbouring both hexosyltransferase and sialyltransferase activity. In order to identify amino acids crucial for substrate specificity of the capsule polymerases, polymorphic sites were narrowed down by DNA sequence comparisons and subsequent site-directed mutagenesis. Serogroup-specific amino acids were restricted to the N-terminal part of the proteins. Exclusively amino acid 310, located within the nucleotide recognition domain of the enzymes' predicted hexosyltransferase moiety, accounted for substrate specificity as shown by immunochemistry and in vitro activity assay. Pro-310 determined galactosyltransferase activity that resulted in a serogroup W-135 capsule and Gly-310 determined glucosyltransferase activity that resulted in a serogroup Y capsule. In silico analysis revealed a similar amino acid-based association in other members of the same glycosyltransferase family irrespective of the bacterial species.

Systematic review: Impact of meningococcal vaccination on pharyngeal carriage of meningococci

OBJECTIVE

To investigate the effect of meningococcal vaccines on pharyngeal carriage of meningococci.

METHODS

Systematic review. MEDLINE and EMBASE were searched for relevant studies. Controlled trials and observational studies which used comparison groups or compared carriage rates before and after vaccination were included in the review.

RESULTS

Twenty-nine studies satisfied the inclusion criteria. Twenty-five studies reported the effect of a polysaccharide vaccine, one the effect of a serogroup C conjugate vaccine and three the impact of serogroup B outer-membrane vaccines on overall and/or serogroup-specific meningococcal carriage rates. Ten studies of meningococcal polysaccharide vaccines found reduced serogroup-specific carriage; seven of these focussed on high-risk groups and had a short follow-up period. Only one of five studies of civilian populations in Africa showed a significantly reduced carriage. Many studies had methodological shortcomings. The one study which assessed the effect of a meningococcal conjugate vaccine on carriage showed a significant impact. Three studies of serogroup B outer-membrane protein vaccines showed no effect on carriage.

CONCLUSIONS

A few well-designed trials of the impact of meningococcal vaccines on carriage have been undertaken. Such studies should be an essential component of the evaluation of new meningococcal vaccines, particularly those introduced to control epidemic meningococcal disease in Africa.

Meningococcal A, C, Y and W-135 polysaccharide-protein conjugate vaccines

Serogroup C meningococcal conjugate vaccines, first launched in the UK in 1999, have been used successfully in Australia, Canada and several other European countries. Combination conjugate vaccines, containing more than one meningococcal polysaccharide, have been developed to broaden protection against the disease. A tetravalent meningococcal A, C, Y and W-135 conjugate vaccine was licensed for use in 11-55 year old adolescents and adults in the US in January 2005, and subsequently also in 2-11 year old children in Canada in May 2006. This article discusses the different glycoconjugate meningococcal vaccines which have been developed and the potential for their use to control disease caused by serogroups A, C, Y and W-135 of Neisseria meningitidis.

Genetic diversification of Neisseria meningitidis during waves of colonization and disease in the meningitis belt of sub-Saharan Africa

Although Neisseria meningitidis is a highly variable organism, most invasive disease is caused by a minority of genotypes. Hypervirulent lineages have been identified and their pandemic spread has been traced. During a longitudinal meningococcal colonization study in a district of northern Ghana clonal waves of carriage and disease were observed. Genetic diversification of genoclouds was analysed by pulsed field gel electrophoretic (PFGE) analysis of isolates from healthy carriers and from meningitis patients. Even during the limited time of persistence in the district, microevolution of the dominating genoclouds took place. Population genomic analyses are required to understand the genetic basis for the emergence of new lineages with epidemic potential, which is of crucial importance for the development of long-term global vaccination strategies against meningococcal disease.

The epidemiology of Neisseria meningitidis meningitis in Togo during 2003–2005

Few reports documenting the epidemiology of Neisseria meningitidis (Nm) serogroup W135 exist, and none from Togo. During 2003-2005, we conducted acute bacterial meningitis surveillance at three major reference hospitals in Togo. Of 116 Nm identified, 83 (71%) were NmA, 23 (20%) were NmW135, and 10 (9%) did not have a serogroup identified. Nine percent of NmW135 cases and 35% of NmA cases occurred among those aged 15 years or older. The two hospitals in central Togo reported 23% of all Nm cases and 78% of NmW135 cases. Twelve of the 23 NmW135 cases occurred during February-March 2003, while the remaining 11 occurred sporadically over the remaining 18 months of the study. NmW135 meningitis showed pronounced temporal and geographic clustering and occurred almost exclusively among those younger than 15 years old. By the 2004-2005 epidemic season, NmW135 had largely disappeared from Togo for unknown reasons.

Risk mapping and early warning systems for the control of meningitis in Africa

Epidemics of meningococcal meningitis in Africa have plagued the continent for over a century. These epidemics have a strong association with the environment and efforts are being made to develop models to predict both their location and their incidence. This review describes the predictive models based on climate/environmental information currently available, describes work in progress, and presents evidence that the distribution of the epidemics is changing in a pattern that is compatible with changes in the environment. Discussion of priorities for research in the context of the new conjugate vaccines in Africa is also provided.

Molecular surveillance of meningococcal meningitis in Africa

Analysis of meningococcal strains recovered from outbreaks and epidemics in the African meningitis belt, using molecular methods, has demonstrated for nearly 20 years the dominance among serogroup A organisms of a single clone complex, the sequence type 5 (ST-5) complex. However, a shift was observed since the mid-1990s when ST-5 gradually was replaced by ST-7 in all countries of the region. Since 2001, outbreaks caused by serogroup W135 strains belonging to the ST-11 complex became an additional problem. Monitoring of the clones responsible for meningococcal disease provides important insights on the biology and epidemiology of this most serious pathogen.

Preparedness for infectious threats: public-private partnership to develop an affordable vaccine for an emergent threat: the trivalent Neisseria meningitidis ACW135 polysaccharide vaccine

With the emergence of epidemic Neisseria meningitidis W135 meningitis in Burkina Faso during early 2002, the public health community was faced with the challenge of providing access to an appropriate and affordable vaccine in time for the upcoming 2003 epidemic season. Recognizing the implications of the emergent threat, the World Health Organization developed a strategy, established a public-private partnership to provide the needed vaccine, and then ensured that a stockpile was available for future use. The trivalent N meningitidis ACW135 polysaccharide vaccine that resulted is now one of the primary tools for epidemic response in African meningitis belt countries. It will remain so for the foreseeable future and until appropriate and affordable conjugate vaccines become part of national immunization programs in the region.

Epidemiological and molecular characteristics of a highly lethal pneumococcal meningitis epidemic in Burkina Faso

BACKGROUND

Public health and clinical strategies for meningitis epidemics in sub-Saharan Africa usually assume that Neisseria meningitidis infection causes most disease.

METHODS

During 24 months from 2002 to 2005, we collected clinical and laboratory information for suspected acute bacterial meningitis cases from 3 districts in Burkina Faso. Streptococcus pneumoniae was identified by culture, polymerase chain reaction, or antigen detection in cerebrospinal fluid. Pneumococcal genotyping was performed on strains using multilocus variable-number tandem repeat typing and multilocus sequence typing.

RESULTS

Samples of cerebrospinal fluid were collected from 1686 persons; 249 (15%) had S. pneumoniae identified (annual incidence, 14 cases per 100,000 persons). Of these patients, 115 (46%) died, making S. pneumoniae the most commonly identified organism and responsible for two-thirds of deaths due to bacterial meningitis. During the meningitis epidemic season, an average of 38 cases of S. pneumoniae infection were identified each month, compared with an average of 8.7 cases during other months. Of 48 pneumococci that were tested, 21 (44%) were identified as serotype 1, and the remaining 27 (56%) were identified as 15 different serogroups and/or serotypes. Both serotype 1 and other serogroups and/or serotypes were seasonal. The genotypes of serotype 1 isolates were closely related but diversified over the study period and were similar to, but not identical to, the predominant genotypes found previously in Ghana.

CONCLUSIONS

Intervention strategies during the epidemic season in Burkina Faso (and perhaps elsewhere) must now account for pneumococcal meningitis occurring in an epidemic pattern similar to meningococcal meningitis. Although a serotype 1 clone was commonly isolated, over half of the cases were caused by other serogroups and/or serotypes, and genetic diversification increased over a relatively short period.