Serogroup B meningococcal vaccines—an unfinished story

4CMenB Vaccination to Prevent Meningococcal B Disease in Vietnam: Expert Review and Opinion

An advisory board meeting was held with experts in Vietnam (Hanoi, August 2022), to review the evidence on invasive meningococcal disease (IMD) epidemiology, clinical management, and meningococcal vaccines to reach a consensus on recommendations for meningococcal vaccination in Vietnam. IMD is a severe disease, with the highest burden in infants and children. IMD presents as meningitis and/or meningococcemia and can progress extremely rapidly. Almost 90% of deaths in children occur within the first 24 h, and disabling sequelae (e.g., limb amputations and neurological damage) occur in up to 20% of survivors. IMD patients are often hospitalized late, due to mild and nonspecific early symptoms and misdiagnosis. Difficulties related to diagnosis and antibiotic misuse mean that the number of reported IMD cases in Vietnam is likely to be underestimated. Serogroup B IMD is predominant in many regions of the world, including Vietnam, where 82% of IMD cases were due to serogroup B (surveillance data from 2012 to 2021). Four component meningococcal B vaccine (4CMenB) is used in many countries (and is part of the pediatric National Immunization Program in 13 countries), with infant vaccination starting from two months of age, and a 2 + 1 dosing schedule. Experts recommend 4CMenB vaccination as soon as possible in Vietnam, starting from two months of age, with a 2 + 1 dosing schedule, and at least completing one dose before 6 months of age.

Conjugation of a Toll-like Receptor Agonist to Glycans of an HIV Native-like Envelope Trimer Preserves Neutralization Epitopes

Small molecule adjuvants are attractive for enhancing broad protection and durability of immune responses elicited by subunit vaccines. Covalent attachment of an adjuvant to an immunogen is particularly attractive because it simultaneously delivers both entities to antigen presenting cells resulting in more efficient immune activation. There is, however, a lack of methods to conjugate small molecule immune potentiators to viral glycoprotein immunogens without compromising epitope integrity. We describe herein a one-step enzymatic conjugation approach for the covalent attachment of small molecule adjuvants to N -linked glycans of viral glycoproteins. It involves the attachment of an immune potentiator to CMP-Neu5AcN 3 by Cu(I)-catalyzed azide-alkyne 1,3-cycloaddition followed by sialyltransferase-mediated transfer to N -glycans of a viral glycoprotein. The method was employed to modify a native-like HIV envelope trimer with a Toll-like receptor 7/8 agonist. The modification did not compromise Env-trimer recognition by several broadly neutralization antibodies. Electron microscopy confirmed structural integrity of the modified immunogen.

Immune responses of meningococcal B outer membrane vesicles in middle-aged mice

The elderly are more likely to die when infected with Neisseria meningitidis. Aging is associated with immune system dysfunctions that impair responses to vaccines and infections. Therefore, immunization of middle-aged individuals could be beneficial. This study aims to evaluate the immunogenicity of N. meningitidis B outer membrane vesicles (OMVs) complexed to two different adjuvants. Middle-aged BALB/c and A/Sn mice were immunized and subsequent immune response was assessed by ELISA, immunoblotting and ELISpot. IgG levels were similar between the animals immunized with OMVs complexed to adjuvants. A total of 235 days after the last immunization only A/Sn mice presented higher IgG levels than those observed in the baseline, especially the group immunized with OMVs and aluminum hydroxide. The predominant IgG subclasses were IgG2a and IgG2b. Immunization with the three-dose regimen generated IgG antibodies that recognized a variety of antigens present in the homologous and heterologous meningococcal OMVs evaluated. There was an increase in the frequency of antigen-specific IFN-γ secreting splenocytes, after in vitro stimulation, in mice immunized with OMVs and adjuvants compared to the control group, almost 1 year after the last immunization. Both adjuvants showed similar performance. Immunization of middle-aged mice has generated a robust immune response and it appears to be advantageous.

Immunogenicity of the UK group B meningococcal vaccine (4CMenB) schedule against groups B and C meningococcal strains (Sched3): outcomes of a multicentre, open-label, randomised controlled trial

BACKGROUND

The use of the multicomponent meningococcal vaccine 4CMenB in the UK schedule at 2, 4, and 12 months of age has been shown to be 59·1% effective at preventing invasive group B meningococcal disease. Here, we report the first data on the immunogenicity of this reduced-dose schedule to help to interpret this effectiveness estimate.

METHODS

In this multicentre, parallel-group, open-label, randomised clinical trial, infants aged up to 13 weeks due to receive their primary immunisations were recruited via child health database mailouts in Oxfordshire and via general practice surgeries in Gloucestershire and Hertfordshire. Infants were randomly assigned (1:1) with permuted block randomisation to receive a 2 + 1 (2, 4, and 12 months; group 1) or 1 + 1 (3 and 12 months; group 2) schedule of the 13-valent pneumococcal conjugate vaccine (PCV13). All infants also received 4CMenB at 2, 4, and 12 months of age, and had blood samples taken at 5 and 13 months. Participants and clinical trial staff were not masked to treatment allocation. Proportions of participants with human complement serum bactericidal antibody (hSBA) titres of at least 4 were determined for group B meningococcus (MenB) reference strains 5/99 (Neisserial Adhesin A [NadA]), NZ98/254 (porin A), and 44/76-SL (factor H binding protein [fHbp]). Geometric mean titres (GMTs) with 95% CIs were also calculated, and concomitant vaccine responses (group C meningococcus [MenC], Haemophilus influenzae b [Hib], tetanus, diphtheria, and pertussis) were compared between groups. The primary outcome was PCV13 immunogenicity, with 4CMenB immunogenicity and reactogenicity as secondary outcomes. All individuals by randomised group with a laboratory result were included in the analysis. The study is registered on the EudraCT clinical trials database, 2015-000817-32, and ClinicalTrials.gov, NCT02482636, and is complete.

FINDINGS

Between Sept 22, 2015, and Nov 1, 2017, of 376 infants screened, 213 were enrolled (106 in group 1 and 107 in group 2). 204 samples post-primary immunisation and 180 post-boost were available for analysis. The proportion of participants with hSBA of at least 4 was similar in the two study groups. For strain 5/99, all participants developed hSBA titres above 4 in both groups and at both timepoints. For strain 44/76-SL, these proportions were 95·3% (95% CI 88·5-98·7) or above post-priming (82 of 86 participants in group 1), and 92·4% (84·2-97·2) or above post-boost (73 of 79 participants in group 1). For strain NZ98/254, these proportions were 86·5% (78·0-92·6) or above post-priming (83 of 96 participants in group 2) and 88·6% (79·5-94·7) or above post-boost (70 of 79 participants in group 1). The MenC rabbit complement serum bactericidal antibody (rSBA) titre in group 1 was significantly higher than in group 2 (888·3 vs 540·4; p=0·025). There was no significant difference in geometric mean concentrations between groups 1 and 2 for diphtheria, tetanus, Hib, and pertussis post-boost. A very small number of children did not have a protective response against 44/76-SL and NZ98/254. Local and systemic reactions were similar between the two groups, apart from the 3 month timepoint when one group received an extra dose of PCV13 and recorded more systemic reactions.

INTERPRETATION

These data support the recent change to the licensed European schedule for 4CMenB to add an infant 2 + 1 schedule, as used in the routine UK vaccine programme with an effectiveness of 59·1%. When compared with historical data, our data do not suggest that effectiveness would be higher with a 3 + 1 schedule, however a suboptimal boost response for bactericidal antibodies against vaccine antigen fHbp suggests a need for ongoing surveillance for vaccine breakthroughs due to fHbp-matched strains. Changing from a 2 + 1 to a 1 + 1 schedule for PCV13 for the UK is unlikely to affect protection against diphtheria, tetanus, and Hib, however an unexpected reduction in bactericidal antibodies against MenC seen with the new schedule suggests that ongoing surveillance for re-emergent MenC disease is important.

FUNDING

Bill & Melinda Gates Foundation and the National Institute for Health Research.

Meningococcal Serogroup B Disease in Vaccinated Children

BACKGROUND

Neisseria meningitidis serogroup B (MenB) is the most frequent cause of invasive meningococcal disease (IMD) in Spain. The multicomponent vaccine against MenB (4CMenB) was approved in Spain in January 2014.

METHODS

We present 4 cases of children who developed MenB-associated IMD despite previous vaccination with 4CMenB. Extensive immunologic diagnostic work-up was performed in order to rule out any immunodeficiency. Also, molecular characterization of the MenB strain was conducted to determine whether bacterial antigens matched vaccine antigens.

RESULTS

Among the 4 patients (2 girls), 2 had previous risk factors for IMD (recurrent bacterial meningitis of unknown origin and treatment with eculizumab). All patients developed meningitis, but only 2 developed septic shock; they were all cured without sequelae. No other primary or secondary immunodeficiencies were detected. MenB sequence type 213 was identified in 3 cases. With the exception of neisserial heparin-binding antigen peptide 465 present in 1 isolate, the rest of the isolated strains harbored vaccine antigen variants that did not match antigen variants included in the vaccine.

CONCLUSIONS

We present 4 children who developed MenB-associated IMD despite previous vaccination with 4CMenB. In 2 cases, the antibodies induced by 4CMenB likely were not effective against the isolated strains. A high level of suspicion for IMD seems advisable regardless of the patient's vaccination history.

Biology of the Gonococcus: Disease and Pathogenesis

Neisseria gonorrhoeae infection is a major public health problem worldwide. The increasing incidence of gonorrhea coupled with global spread of multidrug-resistant isolates of gonococci has ushered in an era of potentially untreatable infection. Gonococcal disease elicits limited immunity, and individuals are susceptible to repeated infections. In this chapter, we describe gonococcal disease and epidemiology and the structure and function of major surface components involved in pathogenesis. We also discuss the mechanisms that gonococci use to evade host immune responses and the immune responses following immunization with selected bacterial components that may overcome evasion. Understanding the biology of the gonococcus may aid in preventing the spread of gonorrhea and also facilitate the development of gonococcal vaccines and treatments.

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.

Evaluation of intranasal and subcutaneous route of immunization in neonatal mice using DODAB-BF as adjuvant with outer membrane vesicles of Neisseria meningitis B

BACKGROUND

The Neisseria meningitidis bacterium is a Gram-negative diplococcus that can be classified into different serogroups according to the capsular structure. Six of them (A, B, C, W, X, Y) are responsible for causing Invasive Meningococcal Disease (IMD). The strategies for the development of a vaccine for serogroup B have been directed to the use of outer membrane vesicles (OMVs). The aim of this study was to evaluate the immunogenicity of antigenic determinants from OMVs of N. meningitidis B complexed with two different adjuvants: DODAB-BF and aluminum hydroxide (alum), comparing the evaluation of intranasal and subcutaneous route of immunization.

METHODS

We used prime-boost immunization for the first time in outbred neonatal mice evaluating the cellular and humoral immune response.

RESULTS

Immunoblot, ELISA DOT-ELISA and ELISpot were used universal methods of antibody detection, in order to detect the humoral and cellular immune response in male and female mice. Immunoblot analyzes the specificity of antibodies with the homologous N. meningitidis strain. ELISA served to quantify and compare the titers of antibodies in the serum of mice immunized with DODAB-BF + OMVs and alum + OMVs for IgG, IgG1, and IgG2a. Intranasal immunization produced a mixed response in the T helper cells Th1 and Th2, while subcutaneous immunization exhibited a Th1 profile. The DOT-ELISA identified cross-reactivity with DODAB-BF to different serogroups of N. meningitidis (B, C, W, and Y) that was not observed with alum. ELISpot analyzed IFN-γ- and IL-4 and the results showed the response directly to Th1 and Th2 profile.

CONCLUSION

Our findings indicate that DODAB-BF can be an alternative adjuvant for mucosal cell activation with OMVs of N. meningitidis B and that DODAB-BF was similar to aluminum hydroxide as an adjuvant for subcutaneous immunization.

A deeper mining on the protein composition of VA-MENGOC-BC®: An OMV-based vaccine against N. meningitidis serogroup B and C

The protein composition of an Outer Membrane Vesicle (OMV) preparation that constitutes the active pharmaceutical ingredient of VA-MENGOC-BC®, an effective vaccine against Neisseria meningitidis serogroups B, and C is presented. This preparation has a high lipid content and five abundant membrane proteins (FetA, PorA, PorB, RmpM, and Opc), constituting approximately 70% of the total protein mass. The protein composition was determined by combining the use of the Hexapeptide Ligand Library and an orthogonal tandem fractionation of tryptic peptides by reverse-phase chromatography at alkaline and acid pH. This approach equalizes the concentration of tryptic peptides derived from low- and high-abundance proteins as well as considerably simplifying the number of peptides analyzed by LC-MS/MS, enhancing the possibility of identifying low-abundance species. Fifty-one percent of the proteins originally annotated as membrane proteins in the genome of the MC58 strain were identified. One hundred and sixty-eight low-abundance cytosolic proteins presumably occluded within OMV were also identified. Four (NadA, NUbp, GNA2091, and fHbp), out of the five antigens constituting the Bexsero® vaccine, were detected in this OMV preparation. In particular, fHbp is also the active principle of the Trumenba® vaccine developed by Pfizer. The HpuA and HpuB gene products (not annotated in the MC58 genome) were identified in the CU385 strain, a clinical isolate that is used to produce this OMV. Considering the proteins identified here and previous work done by our group, the protein catalogue of this OMV preparation was extended to 266 different protein species.

Emerging clinical experience with vaccines against group B meningococcal disease

The prevention of paediatric bacterial meningitis and septicaemia has recently entered a new era with the availability of two vaccines against capsular group B meningococcus (MenB). Both of these vaccines are based on sub-capsular proteins of the meningococcus, an approach that overcomes the challenges set by the poorly immunogenic MenB polysaccharide capsule but adds complexity to predicting and measuring the impact of their use. This review describes the development and use of MenB vaccines to date, from the use of outer membrane vesicle (OMV) vaccines in MenB outbreaks around the world, to emerging evidence on the effectiveness of the newly available vaccines. While recent data from the United Kingdom supports the potential for protein-based vaccines to provide direct protection against MenB disease in immunised children, further research is required to understand the breadth and duration of this protection. A more detailed understanding of the impact of immunisation with these vaccines on nasopharyngeal carriage of the meningococcus is also required, to inform both their potential to induce herd immunity and to preferentially select for carriage of strains not susceptible to vaccine-induced antibodies. Although a full understanding of the potential impact of these vaccines will only be possible with this additional information, the availability of new tools to prevent the devastating effect of invasive MenB disease is a significant breakthrough in the fight against childhood sepsis and meningitis.

Exploring the population-level impact of MenB vaccination via modeling: Potential for serogroup replacement

Various meningococcal conjugate vaccines exist against serogroups A, C, W and Y. A new protein-based vaccine targeting serogroup B (MenB) is also now available. The potential of such vaccines to drive serogroup replacement is considered a possible public health concern when implementing nationwide routine immunization programmes. The aim of this work was to investigate if and how serogroup replacement may occur following widespread vaccination with a MenB vaccine that may protect against carriage. To that end, we built a dynamic transmission model with age and serogroup stratification, focusing on European settings where most invasive meningococcal disease (IMD) cases are caused by serogroups B and C. For illustration purposes, the model was employed in 2 such settings: UK (England and Wales) and Czech Republic. Preliminary model-based projections suggest that, under strong serogroup competition for colonization, vaccine-induced serogroup replacement may occur even with a relatively low vaccine efficacy against serogroup B carriage (e.g., 20%), with potential subsequent increase in serogroup C IMD. The magnitude and speed of the model-projected serogroup C IMD increase depend on the MenB vaccination strategy, vaccine efficacy against carriage and the extent of any potential cross-protection against other serogroups. These analyses are neither exhaustive nor definitive, and focused on simulating potential population-level trends in IMD post-vaccination, under certain assumptions. Due to present inherent limitations and uncertainties, this study has limited quantitative value and is best regarded as an explorative qualitative modeling approach, to complement and challenge the current status quo, and suggest areas where collecting additional data may be essential.

Phase variation of Opa proteins of Neisseria meningitidis and the effects of bacterial transformation

Opa proteins are major proteins involved in meningococcal colonization of the nasopharynx and immune interactions. Opa proteins undergo phase variation (PV) due to the presence of the 5'-CTCTT-3' coding repeat (CR) sequence. The dynamics of PV of meningococcal Opa proteins is unknown. Opa PV, including the effect of transformation on PV, was assessed using a panel of Opa-deficient strains of Neisseria meningitidis. Analysis of Opa expression from UK disease-causing isolates was undertaken. Different opa genes demonstrated variable rates of PV, between 6.4 × 10(-4) and 6.9 × 10(-3) per cell per generation. opa genes with a longer CR tract had a higher rate of PV (r(2) = 0.77, p = 0.1212). Bacterial transformation resulted in a 180-fold increase in PV rate. The majority of opa genes in UK disease isolates (315/463, 68.0%) were in the 'on' phase, suggesting the importance of Opa proteins during invasive disease. These data provide valuable information for the first time regarding meningococcal Opa PV. The presence of Opa PV in meningococcal populations and high expression of Opa among invasive strains likely indicates the importance of this protein in bacterial colonization in the human nasopharynx. These findings have potential implications for development of vaccines derived from meningococcal outer membranes.

Regulation of capsule in Neisseria meningitidis

Neisseria meningitidis, a devastating pathogen exclusive to humans, expresses capsular polysaccharides that are the major meningococcal virulence determinants and the basis for successful meningococcal vaccines. With rare exceptions, the expression of capsule (serogroups A, B, C, W, X, Y) is required for systemic invasive meningococcal disease. Changes in capsule expression or structure (e.g. hypo- or hyper-encapsulation, capsule "switching", acetylation) can influence immunologic diagnostic assays or lead to immune escape. The loss or down-regulation of capsule is also critical in meningococcal biology facilitating meningococcal attachment, microcolony formation and the carriage state at human mucosal surfaces. Encapsulated meningococci contain a cps locus with promoters located in an intergenic region between the biosynthesis and the conserved capsule transport operons. The cps intergenic region is transcriptionally regulated (and thus the amount of capsule expressed) by IS element insertion, by a two-component system, MisR/MisS and through sequence changes that result in post-transcriptional RNA thermoregulation. Reversible on-off phase variation of capsule expression is controlled by slipped strand mispairing of homo-polymeric tracts and by precise insertion and excision of IS elements (e.g. IS1301) in the biosynthesis operon. Capsule structure can be altered by phase-variable expression of capsular polymer modification enzymes or "switched" through transformation and homologous recombination of different polymerases. Understanding the complex regulation of meningococcal capsule has important implications for meningococcal biology, pathogenesis, diagnostics, current and future vaccine development and vaccine strategies.

Predicted Strain Coverage of a New Meningococcal Multicomponent Vaccine (4CMenB) in Spain: Analysis of the Differences with Other European Countries

Background

A novel meningococcal multicomponent vaccine, 4CMenB (Bexsero^®), has been approved in Europe, Canada, Australia and US. The potential impact of 4CMenB on strain coverage is being estimated by using Meningococcal Antigen Typing System (MATS), an ELISA assay which measures vaccine antigen expression and diversity in each strain. Here we show the genetic characterization and the 4CMenB potential coverage of Spanish invasive strains (collected during one epidemiological year) compared to other European countries and discuss the potential reasons for the lower estimate of coverage in Spain.

Material and Methods

A panel of 300 strains, a representative sample of all serogroup B Neisseria meningitidis notified cases in Spain from 2009 to 2010, was characterized by multilocus sequence typing (MLST) and FetA variable region determination. 4CMenB vaccine antigens, PorA, factor H binding protein (fHbp), Neisseria Heparin Binding Antigen (NHBA) and Neisserial adhesin A (NadA) were molecularly typed by sequencing. PorA coverage was assigned to strain with VR2 = 4. The levels of expression and cross-reactivity of fHbp, NHBA and NadA were analyzed using MATS ELISA.

Findings

Global estimated strain coverage by MATS was 68.67% (95% CI: 47.77–84.59%), with 51.33%, 15.33% and 2% of strains covered by one, two and three vaccine antigens, respectively. The predicted strain coverage by individual antigens was: 42% NHBA, 36.33% fHbp, 8.33% PorA and 1.33% NadA. Coverage within the most prevalent clonal complexes (cc) was 70.37% for cc 269, 30.19% for cc 213 and 95.83% for cc 32.

Conclusions

Clonal complexes (cc) distribution accounts for variations in strain coverage, so that country-by-country investigations of strain coverage and cc prevalence are important. Because the cc distribution could also vary over time, which in turn could lead to changes in strain coverage, continuous detailed surveillance and monitoring of vaccine antigens expression is needed in those countries where the multicomponent vaccine is introduced. This is really important in countries like Spain where most of the strains are predicted to be covered by only one vaccine antigen and the chance for escape mutants to emerge with vaccine use is higher. Based on the observed data, cc213 should receive special attention as it is associated with low predicted strain coverage, and has recently emerged in Spain.

Impact of Reducing Complement Inhibitor Binding on the Immunogenicity of Native Neisseria meningitidis Outer Membrane Vesicles

Neisseria meningitidis recruits host human complement inhibitors to its surface to down-regulate complement activation and enhance survival in blood. We have investigated whether such complement inhibitor binding occurs after vaccination with native outer membrane vesicles (nOMVs), and limits immunogenicity of such vaccines. To this end, nOMVs reactogenic lipopolysaccharide was detoxified by deletion of the lpxl1 gene (nOMVlpxl1). nOMVs unable to bind human complement factor H (hfH) were generated by additional deletions of the genes encoding factor H binding protein (fHbp) and neisserial surface protein A (NspA) (nOMVdis). Antibody responses elicited in mice with nOMVdis were compared to those elicited with nOMVlpxl1 in the presence of hfH. Results demonstrate that the administration of human fH to mice immunized with fHbp containing OMVlpxl1 decreased immunogenicity against fHbp (but not against the OMV as a whole). The majority of the OMV-induced bactericidal immune response (OMVlpxl1 or OMVdis) was versus PorA. Despite a considerable reduction of hfH binding to nOMVdis, and the absence of the vaccine antigen fHbp, immunogenicity in mice was not different from nOMVlpxl1, in the absence or presence of hfH (serum bactericidal titers of 1:64 vs 1:128 after one dose in the nOMVdis and nOMVlpxl1-immunized groups respectively). Therefore, partial inhibition of fH binding did not enhance immunity in this model.

Cost-effectiveness analysis of a multicomponent meningococcal serogroup B vaccine in hypothetic epidemic situation in a middle-income country

NmenB vaccine (4CMenB) is now available, but studies on the cost-effectiveness of vaccine introduction in a country outbreak situation are lacking. The aim of this study was to evaluate the cost-effectiveness of 4CMenB in the context of a hypothetical epidemic outbreak in Chile. We analyzed the direct and indirect costs of acute disease, sequelae and death for each case of meningococcal disease (MD) based on information obtained during the latest NmenB outbreak in Santiago, Chile, occurring between 1993-1999, with an incidence of 5.9/100,000 inhabitants and a mortality of 7.3%. We analyzed the cost of a mass vaccination campaign, considering one dose of 4CMenB for population between 12 months and 25 y of age and 3 doses for infants. Cost-effectiveness analysis was based on 80% and 92% 4CMenB immunogenicity for individual's bellow and over 12 months respectively. Sensitivity analysis was applied to different vaccine costs.

RESULTS

The total cost of the epidemic was USD $59,967,351, considering individual cost of each acute case (USD$2,685), sequelae (USD$2,374) and death (USD $408,086). In Chile, the 4CMenB mass vaccination strategy would avoid 215 cases, 61 sequelae, and 16 deaths per year. The strategy would be cost-effective at a vaccine dose cost ≤ of USD$18.

CONCLUSIONS

Implementation of a mass vaccination campaign to control a hypothetical NmenB outbreak in Chile would be cost-effective at a vaccine cost per dose ≤ of USD$18. This is the first report of a cost-effectiveness analysis for use of 4CMenB as a single intervention strategy to control an epidemic outbreak of NmenB.

The multicomponent meningococcal serogroup B vaccine (4CMenB): origin, composition, health impact and unknown aspects

Neisseria meningitidis serogroup B is the main cause for meningococcal invasive disease in many parts of the world. Since 2013, a new multicomponent vaccine against meningococcal serogroup B (4CMenB) has been licensed in Europe, Australia, Canada, Chile, Uruguay, USA and Brazil with different immunization schedules. Clinical trials involving adults, adolescents, children and infants showed 4CMenB has a good immunogenicity and safety profile. Strain coverage estimates are similar to or better than other recently approved vaccines, ranging from 66% in Canada to 91% in Unites States. Some points still remain to be clarified such as the best immunization strategy, the effect of 4CMenB on carriage, the long-term persistence of protective bactericidal antibodies titers, long-term safety outcomes, the possible emergence of N. meningitidis escape mutants and the vaccine cost–effectiveness. In this review, we focus on the vaccine composition, clinical trials and suggested schedules, safety data, potential strain coverage and future challenges.

Extracellular Vesicles: Role in Inflammatory Responses and Potential Uses in Vaccination in Cancer and Infectious Diseases

Almost all cells and organisms release membrane structures containing proteins, lipids, and nucleic acids called extracellular vesicles (EVs), which have a wide range of functions concerning intercellular communication and signaling events. Recently, the characterization and understanding of their biological role have become a main research area due to their potential role in vaccination, as biomarkers antigens, early diagnostic tools, and therapeutic applications. Here, we will overview the recent advances and studies of Evs shed by tumor cells, bacteria, parasites, and fungi, focusing on their inflammatory role and their potential use in vaccination and diagnostic of cancer and infectious diseases.

The impact of aggregating serogroups in dynamic models of Neisseria meningitidis transmission

Background

Neisseria meningitidis (Nm) is a pathogen of multiple serogroups that is highly prevalent in many populations. Serogroups associated with invasive meningococcal disease (IMD) in Canada, for example, include A, B, C, W-135, X and Y. IMD is a rare but serious outcome of Nm infection, and can be prevented with vaccines that target certain serogroups. This has stimulated the development of dynamic models to evaluate vaccine impact. However, these models typically aggregate the various Nm serogroups into a small number of combined groups, instead of modelling each serogroup individually. The impact of aggregation on dynamic Nm model predictions is poorly understood. Our objective was to explore the impact of aggregation on dynamic model predictions.

Methods

We developed two age-structured agent-based models--a 2-strain model and a 4-strain model--to simulate vaccination programs in the Canadian setting. The 2-strain model was used to explore two different groupings: C, versus all other serogroups combined; and B, versus all other serogroups combined. The 4-strain model used the four groupings: C, B, Neisseria lactamica, versus all other serogroups combined. We compared the predicted impact of monovalent C vaccine, quadrivalent ACWY vaccine (MCV-4), and monovalent B vaccine (4CMenB) on the prevalence of serogroup carriage under these different models.

Results

The 2-strain and 4-strain models predicted similar overall impacts of vaccines on carriage prevalence, especially with respect to the vaccine-targeted serogroups. However, there were some significant quantitative and qualitative differences. Declines in vaccine-targeted serogroups were more rapid in the 2-strain model than the 4-strain model, for both the C and the 4CMenB vaccines. Sustained oscillations, and evidence for multiple attractors (i.e., different types of dynamics for the same model parameters but different initial conditions), occurred in the 4-strain model but not the 2-strain model. Strain replacement was also more pronounced in the 4-strain model, on account of the 4-strain model spreading prevalence more thinly across groups and thus enhancing competitive interactions.

Conclusions

Simplifying assumptions like aggregation of serogroups can have significant impacts on dynamic model predictions. Modellers should carefully weigh the advantages and disadvantages of aggregation when formulating models for multi-strain pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1015-8) contains supplementary material, which is available to authorized users.

Multivalent meningococcal serogroup B vaccines: challenges in predicting protection and measuring effectiveness

Vaccines targeting Neisseria meningitidis serogroup B (MenB) have been attempted for 40 years. Monovalent outer membrane vesicle vaccines targeted at epidemic outbreaks have been successfully developed. Newer vaccines aim to induce antibodies to cross-reactive antigens, such as factor H binding protein (rLP2086) or a mix of outer membrane vesicle, factor H binding protein and other minor antigens (4CMenB). The true protective coverage among circulating MenB isolates afforded by these vaccines is unknown. Carefully conducted Phase IV post-implementation evaluations designed to measure specific effectiveness against major circulating MenB clonal lineages are needed to address the critical question of which antigens are linked to protection. Progress with whole-genome sequencing and bio-informatics may allow the composition of antigen mozaics based on two major outer membrane proteins: PorA and FetA.

Identification of Outer Membrane Vesicles Derived from Orientia tsutsugamushi

Orientia tsutsugamushi, a causative pathogen of Scrub typhus, is a gram-negative intracellular bacterium. Outer membrane vesicles (OMVs) are produced from the membrane of bacteria and play many roles related to the survival of the pathogen. However, there have been no reports confirming whether O. tsutsugamushi indeed produce OMVs. O. tsutsugamushi boryong was cultured in ECV-304 cells for the purification of OMVs. Western blot analysis and immunoenrichment using anti-O. tsutsugamushi monoclonal antibody and electron microscopy were employed for identification and characterization of OMVs. We confirm the presence of OMVs derived from O. tsutsugamushi, and also found that those OMVs contain a major surface antigen of 56-kDa protein and variant immunogenic antigens.

Meningococcal serogroup B vaccine (4CMenB): Booster dose in previously vaccinated infants and primary vaccination in toddlers and two-year-old children

OBJECTIVE

The multicomponent, recombinant serogroup B vaccine, 4CMenB, is approved in Europe, Canada and Australia from two months of age. We investigated persistence to booster doses at 12 months of age following infant vaccination, and immune response to catch-up vaccination of toddlers and children up to two years of age.

METHODS

We assessed persistence of immune responses after one year in participants vaccinated as infants, and responses to two doses at 12-15 or 24-26 months of age in vaccine-naïve children, as serum bactericidal activity with human complement (hSBA) against indicator strains for four vaccine antigens. Adverse events were recorded after each vaccination.

RESULTS

High antibody titers were induced against all four 4CMenB components following booster vaccination in infant-primed toddlers and after two doses in previously unvaccinated toddlers or two-year-olds. Antibodies waned over 12 months, particularly those against NZ OMV. Systemic reactogenicity in toddlers was lower than in infants, and lower again in vaccine-naïve two-year-olds. Local reactogenicity was common in all groups.

CONCLUSIONS

Four infant or two toddler 4CMenB vaccinations elicit immune responses believed to be protective for the first two years of life, which can be boosted. Reactogenicity is lower in toddlers than in infants.

Group B meningococcal vaccine science and policy

Capsular group B Neisseria meningitidis is one of the leading causes of death in developed countries. A new vaccine (4CMenB) has recently been developed which was found to have an acceptable safety profile in clinical studies and to be immunogenic. This review examines the evidence supporting the licensure of the 4CMenB vaccine and discusses recommendations for its use.

Health and economic outcomes of introducing the new MenB vaccine (Bexsero) into the Italian routine infant immunisation programme

Introduction

In January 2013 a novel type of multicomponent protein-based vaccine against group B meningococcal disease was licensed by the European Medicines Agency. With the widespread use of the meningococcal serogroup C conjugate vaccines, serogroup B remains now the major cause of bacterial meningitis and septicaemia in young children in Europe. The aim of this study is to investigate the health and the economic outcomes of MenB vaccine introduction into the Italian routine mass vaccination programme.

Methods

The present work is structured in two main parts. Firstly, we assess the epidemiological burden of group B meningococcal disease using official hospitalisation and notification data from two of the most populated Italian regions (Lombardia and Piemonte) during a 6-year study period (2007-2012). Secondly, we evaluate the cost-effectiveness of the immunisation programme in Italy from the public health payer perspective under base case parameters assumptions and performing a comprehensive sensitivity analysis to assess the robustness and the uncertainty of our model results.

Results

MenB serotype is responsible for 59% of the 341 cases of Invasive Meningococcal Disease in Lombardia and Piemonte. Incidence rate for MenB infection is estimated to be 0.21/100,000/y resulting at the highest level in children ≤4 years of age. Although the new MenB vaccine can potentially prevent about one third of the disease cases in the Italian population, model results show this strategy is unlikely to be cost-effective (ICER value over €350,000/QALY) with a vaccine that prevents disease only. These results are robust under most of the sensitivity scenarios except when allowing for lower discount rates.

Discussion

The introduction of the novel vaccine into the routine immunisation schedule needs to be carefully evaluated. The new MenB vaccine has the potential to reduce the disease burden at the population level. However, from the Italian Health Service perspective, the immunisation programme is unlikely to be cost-effective at the current incidence levels and vaccine price.

Recognition of Neisseria meningitidis by the long pentraxin PTX3 and its role as an endogenous adjuvant

Long pentraxin 3 (PTX3) is a non-redundant component of the humoral arm of innate immunity. The present study was designed to investigate the interaction of PTX3 with Neisseria meningitidis. PTX3 bound acapsular meningococcus, Neisseria-derived outer membrane vesicles (OMV) and 3 selected meningococcal antigens (GNA0667, GNA1030 and GNA2091). PTX3-recognized microbial moieties are conserved structures which fulfil essential microbial functions. Ptx3-deficient mice had a lower antibody response in vaccination protocols with OMV and co-administration of PTX3 increased the antibody response, particularly in Ptx3-deficient mice. Administration of PTX3 reduced the bacterial load in infant rats challenged with Neisseria meningitidis. These results suggest that PTX3 recognizes a set of conserved structures from Neisseria meningitidis and acts as an amplifier/endogenous adjuvant of responses to this bacterium.

The capsular group B meningococcal vaccine, 4CMenB : clinical experience and potential efficacy

INTRODUCTION

Capsular group B meningococcal disease is a leading cause of childhood meningitis and septicaemia. Up to 10% of sufferers die, and sequelae remain in > 30% of survivors. A vaccine, four component meningococcal group B ( 4CMenB ), designed with the aim to induce broad coverage against this highly variable bacterium, has been licensed in countries including in the European Union, Canada and Australia.

AREAS COVERED

Immunogenicity and safety data, published in peer-reviewed literature between 2004 and 2014, are presented in the context of the recent recommendation for the use of the vaccine in infants in the UK.

EXPERT OPINION

4CMenB induces significant reactogenicity when administered with routine infant vaccines, in particular with respect to fever rates. Fevers can be somewhat reduced using paracetamol. The efficacy of the vaccine is unknown but has been extrapolated from effectiveness data obtained from use of one of its components in New Zealand, immunogenicity data from clinical trials and estimation of coverage from in vitro studies. These data suggest that the vaccine will prevent a proportion of invasive meningococcal disease cases in infants and young children. Implementation and well-planned post-marketing surveillance will address uncertainties over field effectiveness.

Variability of genes encoding surface proteins used as vaccine antigens in meningococcal endemic and epidemic strain panels from Norway

Surface-expressed protein antigens such as factor H-binding protein (fHbp), Neisserial adhesin A (NadA), Neisserial heparin-binding antigen (NHBA) and Porin protein A (PorA); all express sequence variability that can affect their function as protective immunogens when used in meningococcal serogroup B vaccines like the recently-approved 4CMenB (Bexsero(®)). We assessed the sequence variation of genes coding for these proteins and two additional proteins ("fusion partners" to fHbp and NHBA) in pathogenic isolates from a recent low incidence period (endemic situation; 2005-2006) in Norway. Findings among strains from this panel were contrasted to what was found among isolates from a historic outbreak (epidemic situation; 1985-1990). Multilocus sequence typing revealed 14 clonal complexes (cc) among the 66 endemic strains, while cc32 vastly predominated in the 38-strain epidemic panel. Serogroup B isolates accounted for 50/66 among endemic strains and 28/38 among epidemic strains. Potential strain-coverage ("sequence match") for the 4CMenB vaccine was identified among the majority (>70%) of the endemic serogroup B isolates and all of the epidemic serogroup B isolates evaluated. Further information about the degree of expression, surface availability and the true cross-reactivity for the vaccine antigens will be needed to fully characterize the clinical strain-coverage of 4CMenB in various geographic and epidemiological situations.

Identification of vaccine antigens using integrated proteomic analyses of surface immunogens from serogroup B Neisseria meningitidis

Meningococcal surface proteins capable of evoking a protective immune response are candidates for inclusion in protein-based vaccines against serogroup B Neisseria meningitidis (NmB). In this study, a 2-dimensional (2-D) gel-based platform integrating surface and immune-proteomics was developed to characterize NmB surface protein antigens. The surface proteome was analyzed by differential 2-D gel electrophoresis following treatment of live bacteria with proteinase K. Alongside, proteins recognized by immune sera from mice challenged with live meningococci were detected using 2-D immunoblots. In combination, seventeen proteins were identified including the well documented antigens PorA, OpcA and factor H-binding protein, previously reported potential antigens and novel potential immunogens. Results were validated for the macrophage infectivity potentiator (MIP), a recently proposed NmB vaccine candidate. MIP-specific antisera bound to meningococci in whole-cell ELISA and facilitated opsonophagocytosis and deposition of complement factors on the surface of meningococcal isolates of different serosubtypes. Cleavage by proteinase K was confirmed in western blots and shown to occur in a fraction of the MIP expressed by meningococci suggesting transient or limited surface exposure. These observations add knowledge for the development of a protein NmB vaccine. The proteomic workflow presented here may be used for the discovery of vaccine candidates against other pathogens.

BIOLOGICAL SIGNIFICANCE

This study presents an integrated proteomic strategy to identify proteins from N. meningitidis with desirable properties (i.e. surface exposure and immunogenicity) for inclusion in subunit vaccines against bacterial meningitis. The effectiveness of the method was demonstrated by the identification of some of the major meningococcal vaccine antigens. Information was also obtained about novel potential immunogens as well as the recently described potential antigen macrophage infectivity potentiator which can be useful for its consideration as a vaccine candidate. Additionally, the proteomic strategy presented in this study provides a generic 2-D gel-based platform for the discovery of vaccine candidates against other bacterial infections.

Does binding of complement factor H to the meningococcal vaccine antigen, factor H binding protein, decrease protective serum antibody responses?

Factor H binding protein (fHbp) is a principal antigen in a multicomponent meningococcal vaccine recently licensed in Europe for prevention of serogroup B diseases. The protein recruits the complement downregulator, factor H (fH), to the bacterial surface, which enables the organism to resist complement-mediated bacteriolysis. Binding is specific for human fH. In preclinical studies, mice and rabbits immunized with fHbp vaccines developed serum bactericidal antibody responses, which in humans predict protection against developing meningococcal disease. These studies, however, were in animals whose fH did not bind to the vaccine antigen. Here we review the immunogenicity of fHbp vaccines in human fH transgenic mice. The data suggest that animals with high serum human fH concentrations have impaired protective antibody responses. Further, mutant fHbp vaccines with single amino acid substitutions that decrease fH binding are superior immunogens, possibly by unmasking epitopes in the fH binding site that are important for eliciting serum bactericidal antibody responses. Humans immunized with fHbp vaccines develop serum bactericidal antibody, but achieving broad coverage in infants required incorporation of additional antigens, including outer membrane vesicles, which increased rates of fever and local reactions at the injection site. The experimental results in transgenic mice predict that fHbp immunogenicity can be improved in humans by using mutant fHbp vaccines with decreased fH binding. These results have important public health implications for developing improved fHbp vaccines for control of serogroup B meningococcal disease and for development of vaccines against other microbes that bind host molecules.

Lipopolysaccharide modifications of a cholera vaccine candidate based on outer membrane vesicles reduce endotoxicity and reveal the major protective antigen

The causative agent of the life-threatening gastrointestinal infectious disease cholera is the Gram-negative, facultative human pathogen Vibrio cholerae. We recently started to investigate the potential of outer membrane vesicles (OMVs) derived from V. cholerae as an alternative approach for a vaccine candidate against cholera and successfully demonstrated the induction of a long-lasting, high-titer, protective immune response upon immunization with OMVs using the mouse model. In this study, we present immunization data using lipopolysaccharide (LPS)-modified OMVs derived from V. cholerae, which allowed us to improve and identify the major protective antigen of the vaccine candidate. Our results indicate that reduction of endotoxicity can be achieved without diminishing the immunogenic potential of the vaccine candidate by genetic modification of lipid A. Although the protective potential of anti-LPS antibodies has been suggested many times, this is the first comprehensive study that uses defined LPS mutants to characterize the LPS-directed immune response of a cholera vaccine candidate in more detail. Our results pinpoint the O antigen to be the essential immunogenic structure and provide a protective mechanism based on inhibition of motility, which prevents a successful colonization. In a detailed analysis using defined antisera, we can demonstrate that only anti-O antigen antibodies, but not antibodies directed against the major flagellar subunit FlaA or the most abundant outer membrane protein, OmpU, are capable of effectively blocking the motility by binding to the sheathed flagellum and provide protection in a passive immunization assay.

Dynamics of childhood invasive meningococcal disease in Israel during a 22-year period (1989-2010)

AIM

To describe the dynamics in the incidence of childhood invasive meningococcal disease (IMD) in Israel during a 22-year period (1989-2010).

METHODS

A longitudinal prospective surveillance in all 27 medical centers with pediatric services in Israel. All cases of children <15 years old with positive blood/cerebrospinal fluid (CSF) culture for Neisseria meningitidis were reported. Demographic, clinical, and bacteriological data were recorded. Meningococcal vaccine was not routinely given to Israeli children during the study period.

RESULTS

The mean age ± standard deviation (SD) among the 743 cases was 40.7 ± 40.2 months. The mean yearly incidence/100,000 was 2.0 ± 0.8. Age-specific incidences were 8.7 ± 2.8, 2.9 ± 1.5, and 0.8 ± 0.5 for children <1, 1-4, and >4 years old, respectively. The overall incidence decreased significantly from 3.7 in 1989 to 1.5 in 2010. Meningitis constituted 69.2 % of all cases. The most common serogroups were: B (76.9 %), C (10.9 %), Y (8.0 %), and W(135) (2.9 %). 78.6 % of all serogroup B isolates were from children <5 years old (p < 0.01). Serogroup C was found mainly in children ≥5 years old (63.4 %). The case fatality rates (CFRs) for children <1, 1-4, >4 years old, and the total study population were 9.2, 12.3, 7.7, and 9.9 %, respectively. CFRs were higher for children without meningitis (14.9 %) compared to children with meningitis (7.9 %) (p < 0.01).

CONCLUSIONS

Overall, and for serogroups B and W135, childhood IMD rates decreased significantly in Israel during the study period, without routine vaccine usage. The most common serogroup in all age groups was B, which was most prevalent in children <5 years old. No change in the trend of the overall CFR was noted during the study period.

Immunogenicity and safety of an investigational multicomponent, recombinant, meningococcal serogroup B vaccine (4CMenB) administered concomitantly with routine infant and child vaccinations: results of two randomised trials

BACKGROUND

Meningococcal serogroup B disease disproportionately affects infants. We assessed lot-to-lot consistency, safety and immunogenicity, and the effect of concomitant vaccination on responses to routine vaccines of an investigational multicomponent vaccine (4CMenB) in this population.

METHODS

We did primary and booster phase 3 studies between March 31, 2008, and Aug 16, 2010, in 70 sites in Europe. We used two series of sponsor-supplied, computer-generated randomisation envelopes to allocate healthy 2 month-old infants to receive routine vaccinations (diphtheria-tetanus-acellular pertussis, inactivated poliovirus, hepatitis B plus Haemophilus influenzae type b, and seven-valent pneumococcal vaccine) at 2, 4, and 6 months of age alone, or concomitantly with 4CMenB or serogroup C conjugate vaccine (MenC) in: 1) an open-label, lot-to-lot immunogenicity and safety substudy of three 4CMenB lots compared with routine vaccines alone (1:1:1:1, block size eight); or 2) an observer-blind, lot-to-lot safety substudy of three 4CMenB lots compared with MenC (1:1:1:3, block size six). At 12 months, 4CMenB-primed children from either substudy were randomised (1:1, block size two) to receive 4CMenB booster, with or without measles-mumps-rubella-varicella (MMRV) vaccine. Immunogenicity was assessed by serum bactericidal assay with human complement (hSBA) against serogroup B test strains, and on randomly selected subsets of serum samples for routine vaccines; laboratory personnel were masked to assignment. The first coprimary outcome was lot-to-lot consistency (hSBA geometric mean ratio of all lots between 0·5 and 2·0), and the second was an immune response (hSBA titre ≥5) for each of the three strains. The primary outcome for the booster study was immune response to booster dose. Immunogenicity data for 4CMenB were for the modified intention-to-treat population, including all infants from the open-label substudy who provided serum samples. The safety population included all participants who contributed safety data after at least one dose of study vaccine. These trials are registered with ClinicalTrials.gov, numbers NCT00657709 and NCT00847145.

FINDINGS

We enrolled 2627 infants in the open-label phase, 1003 in the observer-blind phase, and 1555 in the booster study. Lot-to-lot consistency was shown for the three 4CMenB lots, with the lowest 95% lower confidence limit being 0·74 and the highest upper limit being 1·33. Of 1181–1184 infants tested 1 month after three 4CMenB doses (all lots pooled), 100% (95% CI 99–100) had hSBA titres of 5 or more against strains selective for factor H binding protein and neisserial adhesin A, and 84% (82–86) for New Zealand outer-membrane vesicle. In a subset (n=100), 84% (75–91) of infants had hSBA titres of 5 or more against neisseria heparin binding antigen. At 12 months of age, waning titres were boosted by a fourth dose, such that 95–100% of children had hSBA titres of 5 or more for all antigens, with or without concomitant MMRV. Immune responses to routine vaccines were much the same with or without concomitant 4CMenB, but concomitant vaccination was associated with increased reactogenicity. 77% (1912 of 2478) of infants had fever of 38·5°C or higher after any 4CMenB dose, compared with 45% (295 of 659) after routine vaccines alone and 47% (228 of 490) with MenC, but only two febrile seizures were deemed probably related to 4CMenB.

INTERPRETATION

4CMenB is immunogenic in infants and children aged 12 months with no clinically relevant interference with routine vaccines, but increases reactogenicity when administered concomitantly with routine vaccines. This breakthrough vaccine offers an innovative solution to the major remaining cause of bacterial meningitis in infant and toddlers.

FUNDING

Novartis Vaccines and Diagnostics.

Vaccines against meningococcal serogroup B disease containing outer membrane vesicles (OMV): lessons from past programs and implications for the future

The utility of wild-type outer membrane vesicle (wtOMV) vaccines against serogroup B (MenB) meningococcal disease has been explored since the 1970s. Public health interventions in Cuba, Norway and New Zealand have demonstrated that these protein-based vaccines can prevent MenB disease. Data from large clinical studies and retrospective statistical analyses in New Zealand give effectiveness estimates of at least 70%. A consistent pattern of moderately reactogenic and safe vaccines has been seen with the use of approximately 60 million doses of three different wtOMV vaccine formulations. The key limitation of conventional wtOMV vaccines is their lack of broad protective activity against the large diversity of MenB strains circulating globally. The public health intervention in New Zealand (between 2004–2008) when MeNZB was used to control a clonal MenB epidemic, provided a number of new insights regarding international and public-private collaboration, vaccine safety surveillance, vaccine effectiveness estimates and communication to the public. The experience with wtOMV vaccines also provide important information for the next generation of MenB vaccines designed to give more comprehensive protection against multiple strains.

Predicted strain coverage of a meningococcal multicomponent vaccine (4CMenB) in Europe: a qualitative and quantitative assessment

BACKGROUND

A novel multicomponent vaccine against meningococcal capsular group B (MenB) disease contains four major components: factor-H-binding protein, neisserial heparin binding antigen, neisserial adhesin A, and outer-membrane vesicles derived from the strain NZ98/254. Because the public health effect of the vaccine, 4CMenB (Novartis Vaccines and Diagnostics, Siena, Italy), is unclear, we assessed the predicted strain coverage in Europe.

METHODS

We assessed invasive MenB strains isolated mainly in the most recent full epidemiological year in England and Wales, France, Germany, Italy, and Norway. Meningococcal antigen typing system (MATS) results were linked to multilocus sequence typing and antigen sequence data. To investigate whether generalisation of coverage applied to the rest of Europe, we also assessed isolates from the Czech Republic and Spain.

FINDINGS

1052 strains collected from July, 2007, to June, 2008, were assessed from England and Wales, France, Germany, Italy, and Norway. All MenB strains contained at least one gene encoding a major antigen in the vaccine. MATS predicted that 78% of all MenB strains would be killed by postvaccination sera (95% CI 63-90, range of point estimates 73-87% in individual country panels). Half of all strains and 64% of covered strains could be targeted by bactericidal antibodies against more than one vaccine antigen. Results for the 108 isolates from the Czech Republic and 300 from Spain were consistent with those for the other countries.

INTERPRETATION

MATS analysis showed that a multicomponent vaccine could protect against a substantial proportion of invasive MenB strains isolated in Europe. Monitoring of antigen expression, however, will be needed in the future.

FUNDING

Novartis Vaccines and Diagnostics.