New zealand epidemic strain meningococcal B outer membrane vesicle vaccine in children aged 16-24 months

Increase of invasive meningococcal serogroup W disease in Europe, 2013 to 2017

BackgroundThe total incidence of invasive meningococcal disease (IMD) in Europe has been declining in recent years; however, a rising incidence due to serogroup W (MenW), predominantly sequence type 11 (ST-11), clonal complex 11 (cc11), was reported in some European countries.AimThe aim of this study was to compile the most recent laboratory surveillance data on MenW IMD from several European countries to assess recent trends in Europe.MethodsIn this observational, retrospective study, IMD surveillance data collected from 2013-17 by national reference laboratories and surveillance units from 13 European countries were analysed using descriptive statistics.ResultsThe overall incidence of IMD has been stable during the study period. Incidence of MenW IMD per 100,000 population (2013: 0.03; 2014: 0.05; 2015: 0.08; 2016: 0.11; 2017: 0.11) and the proportion of this serogroup among all invasive cases (2013: 5% (116/2,216); 2014: 9% (161/1,761); 2015: 13% (271/2,074); 2016: 17% (388/2,222); 2017: 19% (393/2,112)) continuously increased. The most affected countries were England, the Netherlands, Switzerland and Sweden. MenW was more frequent in older age groups (≥ 45 years), while the proportion in children (< 15 years) was lower than in other age groups. Of the culture-confirmed MenW IMD cases, 80% (615/767) were caused by hypervirulent cc11.ConclusionDuring the years 2013-17, an increase in MenW IMD, mainly caused by MenW cc11, was observed in the majority of European countries. Given the unpredictable nature of meningococcal spread and the epidemiological potential of cc11, European countries may consider preventive strategies adapted to their contexts.

The Global Evolution of Meningococcal Epidemiology Following the Introduction of Meningococcal Vaccines

Invasive meningococcal disease (IMD) caused by Neisseria meningitidis is associated with high morbidity and mortality. Although IMD incidence is highest in infants, a second peak occurs in adolescents/young adults. The incidence of IMD and the predominant disease-causing meningococcal serogroups vary worldwide. Epidemiologic data have guided the development of meningococcal vaccines to reduce the IMD burden. In Europe, serogroup C IMD has been substantially reduced since the introduction of a serogroup C conjugate vaccine. Serogroup B predominates in Europe, although cases of serogroup Y IMD have been increasing in recent years. In the United States, declines in serogroup C and Y disease have been observed in association with the introduction of quadrivalent (serogroups ACWY) meningococcal conjugate vaccines; serogroup B persists and is now the most common cause of outbreak associated disease. In the African meningitis belt, a conjugate vaccine for serogroup A has been effective in decreasing meningitis associated with that serogroup. Outbreaks of the previously rare serogroup X disease have been reported in this region since 2006. In recent years, outbreaks of serogroup B IMD, for which vaccines have only recently been approved by the U.S. Food and Drug Administration and the European Medicines Agency, have occurred in Europe and the United States. Targeting meningococcal vaccination to adolescents/young adults may reduce the morbidity and mortality associated with IMD and has the potential to impact the larger community through herd benefits.

Factors associated with reported pain on injection and reactogenicity to an OMV meningococcal B vaccine in children and adolescents

Pain on vaccine injection and subsequent site reactions of pain and swelling may influence confidence in vaccines and their uptake. This study aimed to identify factors associated with reported pain on injection and reactogenicity following administration of a strain specific meningococcal B outer membrane vesicle vaccine. A retrospective analysis of data was conducted from a phase II single center randomized observer-blind study that evaluated the safety, reactogenicity and immunogenicity of this vaccine in 2 cohorts of healthy 8 to 12 y old children. Vaccine administration technique was observed by an unblinded team member and the vaccine administrator instructed on standardized administration. Participants kept a daily diary to record local reactions (erythema, induration and swelling) and pain for 7 d following receipt of the vaccine. Explanatory variables were cohort, vaccine, age, gender, ethnicity, body mass index, atopic history, history of frequent infections, history of drug reactions, pain on injection, vaccinator, school population socioeconomic status, serum bactericidal antibody titer against the vaccine strain NZ98/254, and total IgG. Univariate and multivariable analyses were conducted using ordinal logistic regression for factors relating to pain on injection and reactogenicity. Perceived pain on injection was related to vaccine formulation, vaccine administrator and ethnicity. Reactogenicity outcomes varied with ethnicity and vaccine administrator. Maintaining community and parental confidence in vaccine safety without drawing attention to differences between individuals and groups is likely to become increasingly difficult. Vaccine administration technique alone has the potential to significantly reduce pain experienced on injection and local vaccine reactions.

Immune responses to a recombinant, four-component, meningococcal serogroup B vaccine (4CMenB) in adolescents: a phase III, randomized, multicentre, lot-to-lot consistency study

BACKGROUND

For decades, a broadly effective vaccine against serogroup B Neisseria meningitidis (MenB) has remained elusive. Recently, a four-component recombinant vaccine (4CMenB) has been developed and is now approved in Europe, Canada, Australia and some Latin American countries. This phase III, randomized study evaluated the lot consistency, early immune responses and the safety profile of 4CMenB in 11 to 17-year-old adolescents in Australia and Canada (NCT01423084).

METHODS

In total, 344 adolescents received two doses of one of 2 lots of 4CMenB, 1-month apart. Immunogenicity was assessed before, 2-weeks and 1-month following the second vaccination. Serum bactericidal activity using human complement (hSBA) was measured against three reference strains 44/76-SL, 5/99 and NZ98/254, selected to express one of the vaccine antigens; Neisseria adhesin A (NadA), factor H binding protein (fHbp) and porin A (PorA) containing outer membrane vesicle (OMV), respectively. Responses to the Neisseria heparin binding antigen (NHBA) were assessed with enzyme linked immunosorbent assay (ELISA). Local and systemic reactions were recorded for 7 days following each vaccination; unsolicited adverse events were monitored throughout the study.

RESULTS

Immunological equivalence of the two lots of 4CMenB was established at 1-month. At baseline, ≤7% of participants had hSBA titers ≥5 to all three reference strains. Two weeks following the second dose of 4CMenB, all participants had hSBA titers ≥5 against fHbp and NadA compared with 84-96% against the PorA reference strains. At 1-month, corresponding proportions were 99%, 100% and 70-79%, respectively. Both lots were generally well tolerated and had similar adverse event profiles.

CONCLUSIONS

Two doses of 4CMenB had an acceptable safety profile and induced a robust immune response in adolescents. Peak antibody responses were observed at 14 days following vaccination. While a substantial non-uniform antigen-dependent early decline in antibody titers was seen thereafter, a significant percentage of participants continued to maintain protective hSBA titers at 1-month.

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.

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.

Global practices of meningococcal vaccine use and impact on invasive disease

A number of countries now include meningococcal vaccines in their routine immunization programs. This review focuses on different approaches to including meningococcal vaccines in country programs across the world and their effect on the burden of invasive meningococcal disease (IMD) as reflected by pre and post-vaccine incidence rates in the last 20 years. Mass campaigns using conjugated meningococcal vaccines have lead to control of serogroup C meningococcal disease in the UK, Canada, Australia, Spain, Belgium, Ireland, and Iceland. Serogroup B disease, predominant in New Zealand, has been dramatically decreased, partly due to the introduction of an outer membrane vesicle (OMV) vaccine. Polysaccharide vaccines were used in high risk people in Saudi Arabia and Syria and in routine immunization in China and Egypt. The highest incidence region of the meningitis belt initiated vaccination with the serogroup A conjugate vaccine in 2010 and catch-up vaccination is ongoing. Overall results of this vaccine introduction are encouraging especially in countries with a moderate to high level of endemic disease. Continued surveillance is required to monitor effectiveness in countries that recently implemented these programs.

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.

A bivalent Neisseria meningitidis recombinant lipidated factor H binding protein vaccine in young adults: results of a randomised, controlled, dose-escalation phase 1 trial

Neisseria meningitidis is a leading cause of meningitis and septicaemia, but a broadly-protective vaccine against endemic serogroup B disease is not licensed and available. The conserved, outer-membrane lipoprotein factor H binding protein (fHBP, also known as LP2086) is expressed as one of two subfamily variants in virtually all meningococci. This study investigated the safety, tolerability, and immunogenicity of a recombinant-expressed bivalent fHBP (r-fHBP) vaccine in healthy adults. Participants (N=103) aged 18-25 years were recruited into three ascending dose level cohorts of 20, 60, and 200μg of a bivalent r-fHBP vaccine formulation and randomised to receive vaccine or placebo at 0, 1, and 6 months. The vaccine was well tolerated. Geometric mean titres (GMTs) for r-fHBP subfamily-specific IgG antibodies increased 19-168-fold from pre-vaccination to post-dose 2 in a dose level-dependent manner. In addition, robust serum bactericidal assay using human complement (hSBA) responses for strains expressing both homologous and heterologous fHBP variants were observed. After three vaccinations, 16-52% of the placebo group and 47-90%, 75-100%, and 88-100%, of the 20, 60, and 200μg dose levels, respectively, had seroprotective (≥ 1:4) hSBA titres against six serogroup B strains. The bivalent r-fHBP vaccine was well tolerated and induced robust bactericidal activity against six diverse serogroup B strains in young adults at the 60 and 200μg dose levels.

Empirical evaluation of age groups and age-subgroup analyses in pediatric randomized trials and pediatric meta-analyses

BACKGROUND

An important step toward improvement of the conduct of pediatric clinical research is the standardization of the ages of children to be included in pediatric trials and the optimal age-subgroups to be analyzed.

METHODS

We set out to evaluate empirically the age ranges of children, and age-subgroup analyses thereof, reported in recent pediatric randomized clinical trials (RCTs) and meta-analyses. First, we screened 24 RCTs published in Pediatrics during the first 6 months of 2011; second, we screened 188 pediatric RCTs published in 2007 in the Cochrane Central Register of Controlled Trials; third, we screened 48 pediatric meta-analyses published in the Cochrane Database of Systematic Reviews in 2011. We extracted information on age ranges and age-subgroups considered and age-subgroup differences reported.

RESULTS

The age range of children in RCTs published in Pediatrics varied from 0.1 to 17.5 years (median age: 5; interquartile range: 1.8-10.2) and only 25% of those presented age-subgroup analyses. Large variability was also detected for age ranges in 188 RCTs from the Cochrane Central Register of Controlled Trials, and only 28 of those analyzed age-subgroups. Moreover, only 11 of 48 meta-analyses had age-subgroup analyses, and in 6 of those, only different studies were included. Furthermore, most of these observed differences were not beyond chance.

CONCLUSIONS

We observed large variability in the age ranges and age-subgroups of children included in recent pediatric trials and meta-analyses. Despite the limited available data, some age-subgroup differences were noted. The rationale for the selection of particular age-subgroups deserves further study.

Reducing inequalities with vaccines: New Zealand's MeNZB vaccine initiative to control an epidemic

Disadvantaged children of Māori and Pacific origin in New Zealand carry an inequitable burden of infectious diseases, many of which are preventable, some by vaccine. Immunisation is recognised in the developing world as a cheap, effective and efficient means of reducing inequalities. The MeNZB immunisation programme delivered in 2004-2006 towards the expected natural end of a projected 15-year epidemic appears to have had an effect (difficult to prove conclusively) on reducing the disproportionate burden of meningococcal disease carried by this group of children. It was delayed by the late engagement of the New Zealand Ministry of Health, fully briefed from 1996, leading to unnecessary and potentially avoidable deaths and sequelae, many lifelong. Further, failure to adequately assess vaccine effectiveness means that the contribution of MeNZB to the observed reduction in disease, particularly in those aged less than five years, will never be reliably known. However, the MeNZB campaign has at least left a legacy: the National Immunisation Register, which should enable New Zealand to minimise the 'vaccine inverse care law' and contribute to reducing ethnic inequity in the burden of vaccine preventable diseases.

Recombinant protein meningococcal serogroup B vaccine combined with outer membrane vesicles

INTRODUCTION

Meningococcal infection is a major cause of morbidity and mortality worldwide. Infection with Neisseria meningitidis is most common in young children, teenagers and people with certain medical conditions. Effective polysaccharide and glycoconjugate vaccines for serogroups A, C, W135 and Y have been developed. A similar capsular polysaccharide approach for serogroup B (MenB) has by most been judged as unsuitable, hence, no broad coverage vaccine has been licensed to date. The novel vaccine Bexsero (previously 4CMenB) has been developed and proven safe and immunogenic in clinical trials.

AREAS COVERED

The authors outline the constituents of Bexsero and immunogenicity and safety data from preclinical and clinical trials published in peer-reviewed literature, meeting proceedings and publicly-available clinical trial websites from 2000 to 2010.

EXPERT OPINION

Bexsero is well tolerated with a proven safety profile, and has demonstrated a robust immune response across different age groups against a range of diverse MenB strains. These data suggest that Bexsero has the ability to provide protection in infants, who are at the greatest risk of developing meningococcal disease.

Immunogenicity of two investigational serogroup B meningococcal vaccines in the first year of life: a randomized comparative trial

BACKGROUND

An investigational vaccine against serogroup B meningococcal (MenB) disease containing 3 main recombinant proteins (factor H-binding protein, Neisserial adhesion A, and Neisserial heparin-binding antigen) has been developed. We evaluated the immunogenicity and reactogenicity of a 3-dose course of this vaccine administered alone (recombinant MenB [rMenB]) or combined with the outer membrane vesicle (OMV) component of the vaccine used in New Zealand (rMenB+OMV).

METHODS

A randomized, single-blind, comparative study of 60 healthy infants enrolled at 6 to 8 months of age and immunized with rMenB or rMenB+OMV at day 0, day 60, and at age 12 months. Blood samples obtained at baseline and 1 month following the second and third doses of vaccine were analyzed for serum bactericidal antibody (SBA) using human complement (hSBA) against 7 MenB strains. The putative correlate of protection was an hSBA titer of ≥4.

RESULTS

The per-protocol analysis included 24 of 30 participants randomized to each group. After 3 doses of rMenB+OMV, 90% or more of participants had an hSBA titer ≥4 for 5 MenB strains, with 70% of participants having an hSBA titer ≥4 for a sixth strain. rMenB alone was immunogenic for only 3 strains. Both vaccines were well tolerated.

CONCLUSIONS

Three doses of rMenB+OMV in the second half of infancy induce bactericidal antibodies against strains expressing vaccine antigens, demonstrating the potential for broader vaccine prevention of MenB disease. This vaccine is now in phase III clinical trials.

Challenges and progress in the development of a serogroup B meningococcal vaccine

Serogroup B meningococci cause the majority of the meningococcal disease burden in developed countries. Production of an effective and safe vaccine for serogroup B organisms has been hampered by the poor immunogenicity of the capsular polysaccharide that defines this group of bacteria. Previous efforts have focused on outer membrane vesicle vaccines, which have been implemented successfully during clonal outbreaks. However, the search for a universal vaccine against endemic polyclonal serogroup B meningococcal disease continues. In this review, we have highlighted recent development of outer membrane vesicle vaccines and progress in the evaluation of recombinant outer membrane protein vaccines.

Immunogenicity and tolerability in infants of a New Zealand epidemic strain meningococcal B outer membrane vesicle vaccine

BACKGROUND

An outer membrane vesicle meningococcal vaccine (MeNZB), was developed for the New Zealand epidemic strain of Neisseria meningitidis B:4:P1.7-2,4.

METHODS

A phase II, randomized, observer blind, controlled study evaluating the safety, reactogenicity, and immunogenicity of MeNZB administered with routine New Zealand immunizations at 6 weeks, 3 months, and 5 months of age (n = 375). Group 1 (n = 250) received 25 mug MeNZB and routine immunizations with a fourth MeNZB dose given at 10 months (n = 51). Group 2 (n = 125) received routine immunizations only. Sero-response was a > or =4-fold rise in vaccine strain serum bactericidal antibody titer compared with baseline or a titer of at least 1:8 for baselines <1:4. Reactogenicity was monitored for 7 days after vaccination.

RESULTS

Sero-response in Group 1 was achieved in 53% (95% Confidence interval [CI]: 46-59, n = 239) and 69% (95% CI: 54-80, n = 45) with geometric mean antibody titers of 9 (95% CI: 7-10) and 22 (95% CI: 12-39) after the third and fourth doses, respectively. No negative interference by MeNZB on routine immunizations was detected. There were no serious adverse events judged to be vaccine related.

CONCLUSIONS

In this group of New Zealand infants, 4 MeNZB doses were required to demonstrate titers comparable with those achieved after 3 doses in older children. MeNZB was safe when used concomitantly with routine New Zealand immunizations to 5 months of age.

Genetically modified L3,7 and L2 lipooligosaccharides from Neisseria meningitidis serogroup B confer a broad cross-bactericidal response

Currently available Neisseria meningitidis serogroup B (MenB) vaccines are based on outer membrane vesicles (OMVs) that are obtained from wild-type strains. They are purified with the aim of decreasing the lipooligosaccharide (LOS) content and hence reduce the reactogenicity of the vaccine even though LOS is a potential protective antigen. In <2-year-old children, these MenB vaccines confer protection only against strains expressing homologous PorA, a major and variable outer membrane protein. Our objective was to develop a safe LOS-based vaccine against MenB. To this end, we used modified porA knockout strains expressing genetically detoxified (msbB gene-deleted) L2 and L3,7 LOSs, allowing the production of LOS-enriched OMVs. The vaccine-induced antibodies were found to be bactericidal against nearly all invasive strains, irrespective of capsular serogroup. In addition, we have also demonstrated that LOS lacking the terminal galactose (with a lgtB mutation; truncated L3 LOS), but not LOS produced without the galE gene, induced a bactericidal antibody response in mice similar to that seen for LOS containing the full lacto-N-neotetraose (L3,7 LOS). In conclusion, a bivalent detoxified LOS OMV-based vaccine demonstrated the potential to afford a broad cross-protection against meningococcal disease.

Binding of complement factor H (fH) to Neisseria meningitidis is specific for human fH and inhibits complement activation by rat and rabbit sera

Complement factor H (fH), a molecule that downregulates complement activation, binds to Neisseria meningitidis and increases resistance to serum bactericidal activity. We investigated the species specificity of fH binding and the effect of human fH on downregulating rat (relevant for animal models) and rabbit (relevant for vaccine evaluation) complement activation. Binding to N. meningitidis was specific for human fH (low for chimpanzee fH and not detected with fH from lower primates). The addition of human fH decreased rat and rabbit C3 deposition on the bacterial surface and decreased group C bactericidal titers measured with rabbit complement 10- to 60-fold in heat-inactivated sera from human vaccinees. Administration of human fH to infant rats challenged with group B strain H44/76 resulted in an fH dose-dependent increase in CFU/ml of bacteria in blood 8 h later (P < 0.02). At the highest fH dose, 50 microg/rat, the geometric mean number of CFU per ml was higher than that in control animals (1,050 versus 43 [P < 0.005]). The data underscore the importance of binding of human fH for survival of N. meningitidis in vitro and in vivo. The species specificity of binding of human fH adds another mechanism toward our understanding of why N. meningitidis is strictly a human pathogen.

Bactericidal antibody responses elicited by a meningococcal outer membrane vesicle vaccine with overexpressed factor H-binding protein and genetically attenuated endotoxin

BACKGROUND

Outer membrane vesicle (OMV) vaccines from mutant Neisseria meningitidis strains engineered to overexpress factor H-binding protein (fHbp) have elicited broadly protective serum antibody responses in mice. The vaccines investigated were not treated with detergents to avoid extracting fHbp, which is a lipoprotein. Because of their high endotoxin content, the vaccines would not be safe to administer to humans.

METHODS

We prepared a native OMV vaccine from a strain engineered to overexpress fHbp and in which the gene encoding LpxL1 was inactivated, which reportedly decreases endotoxin activity.

RESULTS

The OMV vaccine from the mutant had a similar or lower ability to induce the expression of proinflammatory cytokines by human peripheral blood mononuclear cells, compared with a detergent-extracted wild-type OMV, and 1000-10,000-fold lower activity than a native wild-type OMV. In mice, the OMV vaccine from the mutant elicited higher serum bactericidal antibody responses to a panel of heterologous N. meningitidis strains than did a control multicomponent recombinant protein vaccine or a detergent-extracted OMV vaccine that has been demonstrated to confer protection against meningococcal disease in humans.

CONCLUSIONS

The data illustrate the potential to develop a broadly immunogenic native OMV vaccine that has decreased endotoxin activity and is potentially suitable for testing in humans.

Immunogenicity, reactogenicity, and safety of a P1.7b,4 strain-specific serogroup B meningococcal vaccine given to preteens

New Zealand (NZ) has experienced a Neisseria meningitidis serogroup B epidemic since 1991. MeNZB, a strain-specific outer membrane vesicle vaccine made using an NZ epidemic strain isolate, NZ98/254 (B:4:P1.7b,4), from two manufacturing sites, the Norwegian Institute of Public Health (NIPH) and Chiron Vaccines (CV; now Novartis), was evaluated for safety, immunogenicity, and reactogenicity in this observer-blind trial with 8- to 12-year-old children. In year 1, cohort A (n = 302) was randomized 4:1 for receipt of NIPH-MeNZB or MenBvac (Norwegian parent vaccine strain 44/76; B:15:P1.7,16). In year 2, cohort B (n = 313) was randomized 4:1 for receipt of CV-MeNZB or NIPH-MeNZB. Participants all received three vaccinations 6 weeks apart. Local and systemic reactions were monitored for 7 days. Seroresponse was defined as a fourfold or greater rise in the serum bactericidal antibody titer from the baseline titer as measured by a serum bactericidal assay. Those with baseline titers of <1:4 required titers of >/=1:8 to serorespond. Intention-to-treat (ITT) and per protocol (PP) analyses are presented. In cohort A, 74% (ITT) and 73% (PP) of NIPH-MeNZB recipients demonstrated seroresponses against NZ98/254 after three doses, versus 32% (ITT and PP) of MenBvac recipients. In cohort B, seroresponses against NZ98/254 after three doses occurred in 79% (ITT and PP) of CV-MeNZB versus 75% (ITT) and 76% (PP) of NIPH-MeNZB recipients. Vaccines were tolerable, with no vaccine-related serious adverse events. In conclusion, the NZ strain meningococcal B vaccine (MeNZB) from either manufacturing site was immunogenic against New Zealand epidemic vaccine strain meningococci with no safety concerns when given in three doses to these 8- to 12-year-old children.

Additive and synergistic bactericidal activity of antibodies directed against minor outer membrane proteins of Neisseria meningitidis

Neisseria meningitidis serogroup B is a major cause of bacterial meningitis in younger populations. The available vaccines are based on outer membrane vesicles obtained from wild-type strains. In children less than 2 years old they confer protection only against strains expressing homologous PorA, a major, variable outer membrane protein (OMP). We genetically modified a strain in order to eliminate PorA and to overproduce one or several minor and conserved OMPs. Using a mouse model mimicking children's PorA-specific bactericidal activity, it was demonstrated that overproduction of more than one minor OMP is required to elicit antibodies able to induce complement-mediated killing of strains expressing heterologous PorA. It is concluded that a critical density of bactericidal antibodies needs to be reached at the surface of meningococci to induce complement-mediated killing. With minor OMPs, this threshold is reached when more than one antigen is targeted, and this allows cross-protection.

The bactericidal/permeability-increasing protein (BPI) in infection and inflammatory disease

Gram-negative bacteria (GNB) and their endotoxin present a constant environmental challenge. Endotoxins can potently signal mobilization of host defenses against invading GNB but also potentially induce severe pathophysiology, necessitating controlled initiation and resolution of endotoxin-induced inflammation to maintain host integrity. The bactericidal/permeability-increasing protein (BPI) is a pluripotent protein expressed, in humans, mainly neutrophils. BPI exhibits strong antimicrobial activity against GNB and potent endotoxin-neutralizing activity. BPI mobilized with neutrophils in response to invading GNB can promote intracellular and extracellular bacterial killing, endotoxin neutralization and clearance, and delivery of GNB outer membrane antigens to dendritic cells. Tissue expression by dermal fibroblasts and epithelia could further amplify local levels of BPI and local interaction with GNB and endotoxin, helping to constrain local tissue infection and inflammation and prevent systemic infection and systemic inflammation. This review article focuses on the structural and functional properties of BPI with respect to its contribution to host defense during GNB infections and endotoxin-induced inflammation and the genesis of autoantibodies against BPI that can blunt BPI activity and potentially contribute to chronic inflammatory disease.