Monophosphoryl Lipid A-based Adjuvant to Promote the Immunogenicity of Multivalent Meningococcal Polysaccharide Conjugate Vaccines

Activation of the adaptive immune system requires the engagement of costimulatory pathways in addition to B and T cell Ag receptor signaling, and adjuvants play a central role in this process. Many Gram-negative bacterial polysaccharide vaccines, including the tetravalent meningococcal conjugate vaccines (MCV4) and typhoid Vi polysaccharide vaccines, do not incorporate adjuvants. The immunogenicity of typhoid vaccines is due to the presence of associated TLR4 ligands in these vaccines. Because the immunogenicity of MCV4 is poor and requires boosters, I hypothesized that TLR4 ligands are absent in MCV4 and that incorporation of a TLR4 ligand-based adjuvant would improve their immunogenicity. Consistent with this hypothesis, two Food and Drug Administration-approved MCV4 vaccines, MENVEO and MenQuadfi, lack TLR4 ligands. Admixing monophosphoryl lipid A, a TLR4 ligand-based adjuvant formulation named "Turbo" with MCV4 induced significantly improved IgM and IgG responses to all four meningococcal serogroup polysaccharides in adult and aged mice after a single immunization. Furthermore, in infant mice, a single booster was sufficient to promote a robust IgG response and 100% seroconversion when MCV4 was adjuvanted with Turbo. Turbo upregulated the expression of the costimulatory molecules CD40 and CD86 on B cells, and Turbo-driven adjuvanticity is lost in mice deficient in CD40 and CD86. These data suggest that Turbo induces the required costimulatory molecules for its adjuvant activity and that incorporation of Turbo could make bacterial polysaccharide vaccines more immunogenic, minimize booster requirements, and be cost-effective, particularly for those individuals in low- and middle-income and disease-endemic countries.

Exploring the variables influencing the immune response of traditional and innovative glycoconjugate vaccines

Vaccines are cost-effective tools for reducing morbidity and mortality caused by infectious diseases. The rapid evolution of pneumococcal conjugate vaccines, the introduction of tetravalent meningococcal conjugate vaccines, mass vaccination campaigns in Africa with a meningococcal A conjugate vaccine, and the recent licensure and introduction of glycoconjugates against S. Typhi underlie the continued importance of research on glycoconjugate vaccines. More innovative ways to produce carbohydrate-based vaccines have been developed over the years, including bioconjugation, Outer Membrane Vesicles (OMV) and the Multiple antigen-presenting system (MAPS). Several variables in the design of these vaccines can affect the induced immune responses. We review immunogenicity studies comparing conjugate vaccines that differ in design variables, such as saccharide chain length and conjugation chemistry, as well as carrier protein and saccharide to protein ratio. We evaluate how a better understanding of the effects of these different parameters is key to designing improved glycoconjugate vaccines.

Cross reacting material (CRM197) as a carrier protein for carbohydrate conjugate vaccines targeted at bacterial and fungal pathogens

This paper gives an overview of conjugate glycovaccines which contain recombinant diphtheria toxoid CRM197 as a carrier protein. A special focus is given to synthetic methods used for preparation of neoglycoconjugates of CRM197 with oligosaccharide epitopes of cell surface carbohydrates of pathogenic bacteria and fungi. Syntheses of commercial vaccines and laboratory specimen on the basis of CRM197 are outlined briefly.

Intranasal administration of BReC-CoV-2 COVID-19 vaccine protects K18-hACE2 mice against lethal SARS-CoV-2 challenge

SARS-CoV-2 is a viral respiratory pathogen responsible for the current global pandemic and the disease that causes COVID-19. All current WHO approved COVID-19 vaccines are administered through the muscular route. We have developed a prototype two-dose vaccine (BReC-CoV-2) by combining the Receptor Binding Domain (RBD) antigen, via conjugation to Diphtheria toxoid (EcoCRM^®). The vaccine is adjuvanted with Bacterial Enzymatic Combinatorial Chemistry (BECC), BECC470. Intranasal (IN) administration of BreC-CoV-2 in K18-hACE2 mice induced a strong systemic and localized immune response in the respiratory tissues which provided protection against the Washington strain of SARS-CoV-2. Protection provided after IN administration of BReC-CoV-2 was associated with decreased viral RNA copies in the lung, robust RBD IgA titers in the lung and nasal wash, and induction of broadly neutralizing antibodies in the serum. We also observed that BReC-CoV-2 vaccination administered using an intramuscular (IM) prime and IN boost protected mice from a lethal challenge dose of the Delta variant of SARS-CoV-2. IN administration of BReC-CoV-2 provided better protection than IM only administration to mice against lethal challenge dose of SARS-CoV-2. These data suggest that the IN route of vaccination induces localized immune responses that can better protect against SARS-CoV-2 than the IM route in the upper respiratory tract.

Developing an Effective Glycan-based Vaccine for Streptococcus Pyogenes

Streptococcus pyogenes is a primary infective agent that causes approximately 700 million human infections each year, resulting in more than 500,000 deaths. Carbohydrate-based vaccines are proven to be one of the most promising subunit vaccine candidates, as the bacterial glycan pattern(s) are different from mammalian cells and show increased pathogen serotype conservancy than the protein components. In this review we highlight reverse vaccinology for use in the development of subunit vaccines against S. pyogenes, and report reproducible methods of carbohydrate antigen production, in addition to the structure-immunogenicity correlation between group A carbohydrate epitopes and alternative vaccine antigen carrier systems. We also report recent advances used to overcome hurdles in carbohydrate-based vaccine development.

A Decade of Fighting Invasive Meningococcal Disease: A Narrative Review of Clinical and Real-World Experience with the MenACWY-CRM Conjugate Vaccine

The quadrivalent A, C, W and Y meningococcal vaccine conjugated to nontoxic mutant of diphtheria toxin (MenACWY-CRM) has been licensed since 2010 for the prevention of invasive meningococcal disease (IMD), an uncommon but life-threatening condition. Here, we summarize the experience accrued with MenACWY-CRM during the first decade since its licensure, by providing an overview of clinical trials investigating the safety, immunogenicity and co-administration of MenACWY-CRM with other vaccines as well as presenting real-world evidence regarding the impact of MenACWY-CRM vaccination on carriage and IMD incidence. MenACWY-CRM has demonstrated an acceptable clinical safety profile across a wide range of age groups; no safety concerns have been reported in special populations, such as immunocompromised infants and toddlers, or pregnant women. MenACWY-CRM has also been proven to be immunogenic in various age groups and geographic settings, and a booster dose has been shown to elicit strong anamnestic responses in all studied populations, irrespective of the vaccine used for priming. With no clinically relevant vaccine interactions reported, MenACWY-CRM is being conveniently integrated into existing vaccination programs for various age and risk groups; this possibility of co-administration helps improving vaccine coverage and streamlining the healthcare process of fighting preventable infectious diseases. Vaccination of adolescents and adults has been proven to reduce nasopharyngeal carriage for serogroups C, W and Y, which is an important element in reducing transmission. Real-world evidence indicates that MenACWY-CRM can reduce IMD incidence even in high-exposure groups. When combined with vaccines against serogroup B meningococci, MenACWY-CRM can offer protection against five of the most common serogroups responsible for IMD, which is an important advantage in the continuously evolving landscape of meningococcal serogroup epidemiology.

Invasive meningococcal disease is an uncommon but life-threatening infection that appears as meningitis and/or sepsis. It is caused by Neisseria meningitidis, a bacteria commonly present in the throat or nose. Vaccination with MenACWY-CRM (Menveo, GSK) helps to prevent invasive meningococcal disease caused by four of the most common N. meningitidis serogroups (A, C, W and Y). This vaccine has been licensed for 10 years: we summarized here all available evidence gathered since the vaccine has been available in general practice, from clinical development to real-world experience. Information gained during clinical trials of MenACWY-CRM confirms that vaccination is well tolerated, has an acceptable safety profile and would induce significant protection when given to individuals of various ages such as infants, toddlers, children, adolescents and adults, and when administered at the same time as routine or traveler vaccinations as well as vaccines against serogroup B meningococci (4CMenB). Vaccination with MenACWY-CRM has been shown to decrease the number of serogroup C, W and Y meningococci found in the nose and throat in adolescents and adults as well as the occurrence of invasive meningococcal disease in a high-exposure population from a real-world setting. MenACWY-CRM can conveniently be integrated into most of the existing vaccination schedules for various age and risk groups. When combined with vaccination against serogroup B meningococci, MenACWY-CRM can contribute to providing protection against five of the most common serogroups responsible for invasive meningococcal disease.

Immunogenicity and safety of different schedules of the meningococcal ABCWY vaccine, with assessment of long-term antibody persistence and booster responses - results from two phase 2b randomized trials in adolescents

The meningococcal serogroup B (MenB) protein vaccine, 4CMenB, combined with MenA, MenC, MenW and MenY polysaccharide-protein conjugates for a pentavalent MenABCWY vaccine, can potentially protect against most causative agents of invasive meningococcal disease worldwide. Two phase 2b, randomized, multicenter studies were conducted (NCT02212457, NCT02946385) to assess the immunogenicity and safety of the MenABCWY vaccine as well as antibody persistence and response to a booster dose 2 years after the last vaccination, compared to 4CMenB vaccination. Participants (10 − 18 years), randomized (3:3:2:2:2:2), received the 4-component 4CMenB vaccine according to a 0–2 month (M) schedule or MenABCWY according to a 0–2, 0–6, 0-2-6, 0–1, or 0–11 M schedule. All participants received 5 injections (at M0, M1, M2, M6 and M12) with either the study vaccines or placebo/hepatitis A vaccine. Follow-on participants (4CMenB-0-2, MenABCWY-0-2, MenABCWY-0-6 and MenABCWY-0-2-6 groups) received one dose of either 4CMenB (4CMenB-0-2 group) or MenABCWY and newly enrolled, age-matched, meningococcal vaccine-naïve adolescents (randomized 1:1) received 2 doses (0–2 M) of either 4CMenB or MenABCWY. MenABCWY vaccination was immunogenic against MenB test strains. Non-inferiority for all 4 components of the 4CMenB vaccine could not be demonstrated for the 0–2 M schedule. Antibodies persisted up to 2 years post-MenABCWY vaccination and a booster dose induced an anamnestic response as higher titers were observed in follow-on participants compared to the first-dose response in vaccine-naïve participants. MenABCWY had a clinically-acceptable safety profile, not different from that of 4CMenB.

Peptide-Protein Conjugation and Characterization to Develop Vaccines for Group A Streptococcus

Peptide conjugates have been widely used for developing vaccines that prevent common bacterial infections for which peptides alone are either ineffective or provide only short-term protection. Among several carrier proteins, diphtheria toxoid and CRM₁₉₇ (a genetically detoxified diphtheria toxin) are considered safe and have been used in several licensed vaccines. For developing a vaccine against group A streptococcus (GAS), antigens from conserved region of M protein and the IL-8 protease, SpyCEP, have been identified. In this chapter, we describe a method for producing peptide-conjugate subunit GAS vaccines, which involves maleimide conjugation of peptides to a carrier protein and their subsequent characterization.

Cocrystal structure of meningococcal factor H binding protein variant 3 reveals a new crossprotective epitope recognized by human mAb 1E6

The 4 component meningococcus B vaccine (4CMenB) vaccine is the first vaccine containing recombinant proteins licensed for the prevention of invasive meningococcal disease caused by meningococcal serogroup B strains. 4CMenB contains 3 main recombinant proteins, including the Neisseria meningitidis factor H binding protein (fHbp), a lipoprotein able to bind the human factor H. To date, over 1000 aa sequences of fHbp have been identified, and they can be divided into variant groups 1, 2, and 3, which are usually not crossprotective. Nevertheless, previous characterizations of a small set (n = 10) of mAbs generated in humans after 4CMenB immunization revealed 2 human Fabs (huFabs) (1A12, 1G3) with some crossreactivity for variants 1, 2, and 3. This unexpected result prompted us to examine a much larger set of human mAbs (n = 110), with the aim of better understanding the extent and nature of crossreactive anti-fHbp antibodies. In this study, we report an analysis of the human antibody response to fHbp, by the characterization of 110 huFabs collected from 3 adult vaccinees during a 6-mo study. Although the 4CMenB vaccine contains fHbp variant 1, 13 huFabs were also found to be crossreactive with variants 2 and 3. The crystal structure of the crossreactive huFab 1E6 in complex with fHbp variant 3 was determined, revealing a novel, highly conserved epitope distinct from the epitopes recognized by 1A12 or 1G3. Further, functional characterization shows that human mAb 1E6 is able to elicit rabbit, but not human, complement-mediated bactericidal activity against meningococci displaying fHbp from any of the 3 different variant groups. This functional and structural information about the human antibody response upon 4CMenB immunization contributes to further unraveling the immunogenic properties of fHbp. Knowledge gained about the epitope profile recognized by the human antibody repertoire could guide future vaccine design.-Bianchi, F., Veggi, D., Santini, L., Buricchi, F., Bartolini, E., Lo Surdo, P., Martinelli, M., Finco, O., Masignani, V., Bottomley, M. J., Maione, D., Cozzi, R. Cocrystal structure of meningococcal factor H binding protein variant 3 reveals a new crossprotective epitope recognized by human mAb 1E6.

Current trends in targeted therapy for drug-resistant infections

Escalating antibiotic resistance is now a serious menace to global public health. It may be led to the emergence of "postantibiotic age" in which most of infections are untreatable. At present, there is an essential need to explore novel therapeutic strategies as a strong and sustainable pipeline to combat antibiotic-resistant infections. This review focuses on recent advances in this area including therapeutic antibodies, antimicrobial peptides, vaccines, gene therapy, genome editing, and phage therapy for tackling drug-resistant infections.

An update of clinical experience with the quadrivalent meningococcal ACWY-CRM conjugate vaccine

INTRODUCTION

Menveo, quadrivalent meningococcal ACWY-CRM conjugate vaccine, was first licensed in 2010 in the United States and has a long track record of immunogenicity and safety in all age groups, including infants from 2 months of age.

AREAS COVERED

This review presents clinical and post-marketing experience with MenACWY-CRM from 32 studies conducted in 20 countries that included individuals aged from 2 months to 75 years.

EXPERT COMMENTARY

This decade has seen an increased number of countries reporting serogroup W ST-11 clonal complex outbreaks of invasive meningococcal disease. As infant vaccination programs targeting the meningococcus are reevaluated, the role of quadrivalent meningococcal vaccines including MenACWY-CRM will be expanded. MenACWY-CRM was immunogenic in all populations and age groups studied, regardless of country of origin. MenACWY-CRM can be coadministered with many routinely used infant, toddler and adolescent vaccines, and traveler vaccines in adults, allowing for flexible use within national immunization programs and recommendations. Antibody persistence has been demonstrated up to 5 years post vaccination in all age groups. Booster doses induced robust increases in antibody titers for all four serogroups, indicative of effective priming and induction of immunological memory. The acceptable safety profile of MenACWY-CRM has been confirmed in large post-marketing safety studies.

Meningococcal C conjugate vaccine effectiveness before and during an outbreak of invasive meningococcal disease due to Neisseria meningitidis serogroup C/cc11, Tuscany, Italy

INTRODUCTION

In Tuscany, Italy, where a universal immunization program with monovalent meningococcal C conjugate vaccine (MCC) was introduced in 2005, an outbreak of invasive meningococcal disease (IMD) due to the hypervirulent strain of Neisseria meningitidis C/cc11 occurred in 2015-2016, leading to an immunization reactive campaign using either the tetravalent (ACWY) meningococcal conjugate or the MCC vaccine. During the outbreak, IMD serogroup C (MenC) cases were also reported among vaccinated individuals. This study aimed to characterize meningococcal C conjugate vaccines (MenC-vaccines) failures and to estimate their effectiveness since the introduction (2005-2016) and during the outbreak (2015-2016).

METHODS

MenC cases and related vaccine-failures were drawn from the National Surveillance System of Invasive Bacterial Disease (IBD) for the period 2006-2016. A retrospective cohort-study, including the Tuscany' population of the birth-cohorts 1994-2014, was carried out. Based on annual reports of vaccination, person-years of MenC-vaccines exposed and unexposed individuals were calculated by calendar-year, birth-cohort, and local health unit. Adjusted (by birth-cohort, local health unit, and calendar-year) risk-ratios (ARR) of MenC invasive disease for vaccinated vs unvaccinated were estimated by the Poisson model. Vaccine-effectiveness (VE) was estimated as: VE = 1-ARR.

RESULTS

In the period 2006-2016, 85 MenC-invasive disease cases were reported; 61 (71.8%) from 2015 to 2016. Twelve vaccine failures occurred, all of them during the outbreak. The time-interval from immunization to IMD onset was 20 days in one case, from 9 months to 3 years in six cases, and ≥7 years in five cases. VE was, 100% (95%CI not estimable, p = 0.03) before the outbreak (2006-2014) and 77% (95%CI 36-92, p < 0.01) during the outbreak; VE was 80% (95%CI 54-92, p < 0.01) during the overall period.

CONCLUSIONS

In Tuscany, MenC-vaccine failures occurred exclusively during the 2015-2016 outbreak. Most of them occurred several years after vaccination. VE during the outbreak-period was rather high supporting an effective protection induced by MenC-vaccines.

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

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

Immunoinformatics Approach in Designing Epitope-based Vaccine Against Meningitis-inducing Bacteria (Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae Type b)

Meningitis infection is one of the major threats during Hajj season in Mecca. Meningitis vaccines are available, but their uses are limited in some countries due to religious reasons. Furthermore, they only give protection to certain serogroups, not to all types of meningitis-inducing bacteria. Recently, research on epitope-based vaccines has been developed intensively. Such vaccines have potential advantages over conventional vaccines in that they are safer to use and well responded to the antibody. In this study, we developed epitope-based vaccine candidates against various meningitis-inducing bacteria, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b. The epitopes were selected from their protein of polysaccharide capsule. B-cell epitopes were predicted by using BCPred, while T-cell epitope for major histocompatibility complex (MHC) class I was predicted using PAProC, TAPPred, and Immune Epitope Database. Immune Epitope Database was also used to predict T-cell epitope for MHC class II. Population coverage and molecular docking simulation were predicted against previously generated epitope vaccine candidates. The best candidates for MHC class I- and class II-restricted T-cell epitopes were MQYGDKTTF, MKEQNTLEI, ECTEGEPDY, DLSIVVPIY, YPMAMMWRNASNRAI, TLQMTLLGIVPNLNK, ETSLHHIPGISNYFI, and SLLYILEKNAEMEFD, which showed 80% population coverage. The complexes of class I T-cell epitopes–HLA-C*03:03 and class II T-cell epitopes–HLA-DRB1*11:01 showed better affinity than standards as evaluated from their ΔGbinding value and the binding interaction between epitopes and HLA molecules. These peptide constructs may further be undergone in vitro and in vivo testings for the development of targeted vaccine against meningitis infection.

Preclinical studies on new proteins as carrier for glycoconjugate vaccines

Glycoconjugate vaccines are made of carbohydrate antigens covalently bound to a carrier protein to enhance their immunogenicity. Among the different carrier proteins tested in preclinical and clinical studies, five have been used so far for licensed vaccines: Diphtheria and Tetanus toxoids, the non-toxic mutant of diphtheria toxin CRM197, the outer membrane protein complex of Neisseria meningitidis serogroup B and the Protein D derived from non-typeable Haemophilus influenzae. Availability of novel carriers might help to overcome immune interference in multi-valent vaccines containing several polysaccharide-conjugate antigens, and also to develop vaccines which target both protein as well saccharide epitopes of the same pathogen. Accordingly we have conducted a study to identify new potential carrier proteins. Twenty-eight proteins, derived from different bacteria, were conjugated to the model polysaccharide Laminarin and tested in mice for their ability in inducing antibodies against the carbohydrate antigen and eight of them were subsequently tested as carrier for serogroup meningococcal C oligosaccharides. Four out of these eight were able to elicit in mice satisfactory anti meningococcal serogroup C titers. Based on immunological evaluation, the Streptococcus pneumoniae protein spr96/2021 was successfully evaluated as carrier for serogroups A, C, W, Y and X meningococcal capsular saccharides.

Safety and immunogenicity of meningococcal ACWY CRM197-conjugate vaccine in children, adolescents and adults in Russia

Neisseria meningitidis is the leading cause of bacterial invasive infections in people aged <15 years in the Russian Federation. The aim of this phase III, multicenter, open-label study was to assess the immunogenicity and safety of the quadrivalent meningococcal CRM197-conjugate vaccine MenACWY when administered to healthy Russian subjects aged 2 years and above. A total of 197 subjects were immunized with a single dose of the vaccine, and serogroup-specific serum bactericidal activity was measured pre and 1-month post-vaccination with human complement (hSBA) serum titers. Regardless of baseline serostatus, 1 month after a single dose of MenACWY-CRM197 85% (95%CI, 79-90%) of subjects showed serologic response against serogroup A, 74% (67-80%) against serogroup C, 60% (53-67%) against serogroup W, and 83% (77-88%) against serogroup Y. The percentage of subjects with hSBA titers ≥ 1:8 1 month after vaccination was 89% (83-93%) against serogroup A, 84% (78-89%) against serogroup C, 97% (93-99%) against serogroup W, and 88% (82-92%) against serogroup Y. Comparable results were obtained across all subjects: children (2 to 10 years), adolescents (11 to 17 years), and adults (≥18 years). The MenACWY-CRM197 vaccine showed an acceptable safety profile and was well tolerated across all age groups, with no serious adverse events or deaths reported during the study. In conclusion, a single dose of meningococcal MenACWY-CRM197 vaccine is immunogenic and has an acceptable safety profile, provides a broad protection against the most frequent epidemic serogroups, and is a suitable alternative to currently available unconjugated monovalent or bivalent polysaccharide vaccines in Russia.

Antibody persistence 5 years after vaccination at 2 to 10 years of age with Quadrivalent MenACWY-CRM conjugate vaccine, and responses to a booster vaccination

BACKGROUND

In a multi-center extension study, children 2-10 years of age, initially vaccinated with one or two doses (2-5 year-olds) or one dose (6-10 year-olds) of quadrivalent meningococcal CRM197-conjugate vaccine (MenACWY-CRM), were assessed five years later for antibody persistence and booster response using serum bactericidal assay with human complement (hSBA).

METHODS

Children 7-10 and 11-15 years of age, who received MenACWY-CRM in the original study, and age-matched vaccine-naïve children, were enrolled in this extension study. After an initial blood draw, children received one dose of MenACWY-CRM as booster or primary dose, with a second blood draw 28 days later.

RESULTS

hSBA titers decreased five years after primary vaccination, but were higher than in non-vaccinated controls against serogroups C, W and Y, with substantial proportions having titers ≥8: 7-22% for A, 32-57% for C, 74-83% for W, and 48-54% for Y. Previously-vaccinated children demonstrated booster responses to revaccination against all four serogroups. Responses to primary vaccination in vaccine-naïve controls were lower and similar to primary responses observed in the original study. All vaccinations were generally well tolerated, with no safety concern raised.

CONCLUSIONS

Approximately half the children vaccinated as 2-10 year-olds maintained protective antibodies against serogroups C, W and Y five years later, but fewer did against serogroup A. Declining titers five years after vaccination and robust booster responses suggest that five years may be an appropriate interval to revaccinate children, subject to epidemiology and delivery considerations.

Neisseria meningitidis factor H-binding protein fHbp: a key virulence factor and vaccine antigen

Neisseria meningitidis is a leading cause of meningitis and sepsis worldwide. The first broad-spectrum multicomponent vaccine against serogroup B meningococcus (MenB), 4CMenB (Bexsero(®)), was approved by the EMA in 2013, for prevention of MenB disease in all age groups, and by the US FDA in January 2015 for use in adolescents. A second protein-based MenB vaccine has also been approved in the USA for adolescents (rLP2086, Trumenba(®)). Both vaccines contain the lipoprotein factor H-binding protein (fHbp). Preclinical studies demonstrated that fHbp elicits a robust bactericidal antibody response that correlates with the amount of fHbp expressed on the bacterial surface. fHbp is able to selectively bind human factor H, the key regulator of the alternative complement pathway, and this has important implications both for meningococcal pathogenesis and for vaccine design. Here, we review the functional and structural properties of fHbp, the strategies that led to the design of the two fHbp-based vaccines and the data generated during clinical studies.

Safety and immunogenicity of typhoid fever and yellow fever vaccines when administered concomitantly with quadrivalent meningococcal ACWY glycoconjugate vaccine in healthy adults

BACKGROUND

Compact and short pre-travel immunization schedules, which include several vaccinations in a single visit, are desirable for many travelers. However, concomitant vaccination could potentially compromise immunogenicity and/or safety of the individual vaccines and, therefore, possible vaccine interferences should be carefully assessed. This article discusses the immunogenicity and safety of travel vaccines for typhoid fever (TF) and yellow fever (YF), when administered with or without a quadrivalent meningococcal glycoconjugate ACWY-CRM vaccine (MenACWY-CRM).

METHODS

Healthy adults (18-≤60 years) were randomized to one of three vaccine regimens: TF + YF + MenACWY-CRM (group I; n = 100), TF + YF (group II; n = 101), or MenACWY-CRM (group III; n = 100). Immunogenicity at baseline and 4 weeks post-vaccination (day 29) was assessed by serum bactericidal assay using human complement (hSBA), enzyme-linked immunosorbent assay (ELISA), or a neutralization test. Adverse events (AEs) and serious adverse events (SAEs) were collected throughout the study period.

RESULTS

Non-inferiority of post-vaccination geometric mean concentrations (GMCs) and geometric mean titers (GMTs) was established for TF and YF vaccines, respectively, when given concomitantly with MenACWY-CRM vaccine versus when given alone. The percentages of subjects with seroprotective neutralizing titers against YF on day 29 were similar in groups I and II. The antibody responses to meningococcal serogroups A, C, W-135, and Y were within the same range when MenACWY-CRM was given separately or together with TF and YF vaccines. The percentage of subjects reporting AEs was the same for TF and YF vaccines with or without MenACWY-CRM vaccine. There were no reports of SAEs or AEs leading to study withdrawals.

CONCLUSIONS

These data provide evidence that MenACWY-CRM can be administered with typhoid Vi polysaccharide vaccine and live attenuated YF vaccine without compromising antibody responses stimulated by the individual vaccines. MenACWY-CRM can, therefore, be incorporated into travelers' vaccination programs without necessitating an additional clinic visit (NCT01466387).

Carrier priming with CRM 197 or diphtheria toxoid has a different impact on the immunogenicity of the respective glycoconjugates: biophysical and immunochemical interpretation

Glycoconjugate vaccines play an enormous role in preventing infectious diseases. The main carrier proteins used in commercial conjugate vaccines are the non-toxic mutant of diphtheria toxin (CRM197), diphtheria toxoid (DT) and tetanus toxoid (TT). Modern childhood routine vaccination schedules include the administration of several vaccines simultaneously or in close sequence, increasing the concern that the repeated exposure to conjugates based on these carrier proteins might interfere with the anti-polysaccharide response. Extending previous observations we show here that priming mice with CRM197 or DT does not suppress the response to the carbohydrate moiety of CRM197 meningococcal serogroup A (MenA) conjugates, while priming with DT can suppress the response to DT-MenA conjugates. To explain these findings we made use of biophysical and immunochemical techniques applied mainly to MenA conjugates. Differential scanning calorimetry and circular dichroism data revealed that the CRM197 structure was altered by the chemical conjugation, while DT and the formaldehyde-treated form of CRM197 were less impacted, depending on the degree of glycosylation. Investigating the binding and avidity properties of IgGs induced in mice by non-conjugated carriers, we found that CRM197 induced low levels of anti-carrier antibodies, with decreased avidity for its MenA conjugates and poor binding to DT and respective MenA conjugates. In contrast, DT induced high antibody titers able to bind with comparable avidity both the protein and its conjugates but showing very low avidity for CRM197 and related conjugates. The low intrinsic immunogenicity of CRM197 as compared to DT, the structural modifications induced by glycoconjugation and detoxification processes, resulting in conformational changes in CRM197 and DT epitopes with consequent alteration of the antibody recognition and avidity, might explain the different behavior of CRM197 and DT in a carrier priming context.

Immunogenicity and safety of a single dose of a CRM-conjugated meningococcal ACWY vaccine in children and adolescents aged 2-18 years in Taiwan: results of an open label study

BACKGROUND

MenACWY-CRM (Menveo®, Novartis Vaccines, Siena, Italy) is a quadrivalent meningococcal conjugate vaccine developed to help prevent invasive meningococcal disease caused by Neisseria meningitidis serogroups A, C, W, and Y. It is approved within the European Union in persons >2 years of age and in persons from 2 months to 55 years of age in the United States, among other countries. Little is known about the immunogenicity and safety of this vaccine in Taiwanese children >2 years and adolescents. This study assessed the immunogenicity and safety of a single injection of MenACWY-CRM vaccine in Taiwanese subjects aged 2-18 years old.

METHODS

In this phase III, multicentre, open-label study 341 subjects received one dose of MenACWY-CRM. Immunogenicity measures were rates of seroresponse (defined as the proportion of subjects with a postvaccination hSBA ≥1:8 if the prevaccination (baseline) titre was <1:4, or at least a fourfold higher hSBA titre than baseline if the prevaccination titre was ≥1:4), percentages of subjects with serum bactericidal activity (hSBA) ≥1:8 for serogroups A, C, W and Y and hSBA geometric mean titres (GMTs). Local and systemic reactions and all adverse events (AEs) were recorded for 7 days, and medically attended AEs for 1 month post-vaccination.

RESULTS

Seroresponse rates after MenACWY-CRM vaccination at Day 29 for the serogroups A, C, W, and Y were 83%, 93%, 50%, and 65%, respectively. At Day 29 the percentages of subjects with hSBA ≥1:8 against all four serogroups A, C, W and Y were: 83%, 96%, 96% and 82%, respectively. GMTs against all serogroups rose by ≥7-fold from baseline to Day 29. The vaccine was well tolerated.

CONCLUSIONS

A single dose of MenACWY-CRM demonstrated a robust immune response, and an acceptable safety profile in Taiwanese children and adolescents.

Immunogenicity and safety of a quadrivalent meningococcal polysaccharide CRM conjugate vaccine in infants and toddlers

OBJECTIVES

This phase III study assessed the safety and immunogenicity of MenACWY-CRM, a quadrivalent meningococcal conjugate vaccine, administered with routine vaccines starting at 2 months of age.

METHODS

Healthy infants received MenACWY-CRM in a two- or three-dose primary infant series plus a single toddler dose. In addition, a two-dose toddler catch-up series was evaluated. Immune responses to MenACWY-CRM were assessed for serum bactericidal activity with human complement (hSBA). Reactogenicity and safety results were collected systematically.

RESULTS

After a full infant/toddler series or two-dose toddler catch-up series, MenACWY-CRM elicited immune responses against the four serogroups in 94-100% of subjects. Noninferiority of the two- versus three-dose MenACWY-CRM infant dosing regimen was established for geometric mean titers for all serogroups. Following the three-dose infant primary series, 89-98% of subjects achieved an hSBA ≥ 8 across all serogroups. Immune responses to concomitant routine vaccines given with MenACWY-CRM were noninferior to responses to routine vaccines alone, except for pertactin after the two-dose infant series. Noninferiority criteria were met for all concomitant antigens after the three-dose infant series.

CONCLUSIONS

MenACWY-CRM vaccination regimens in infants and toddlers were immunogenic and well tolerated. No clinically meaningful effects of concomitant administration with routine infant and toddler vaccines were observed.

Co-administration of a meningococcal glycoconjugate ACWY vaccine with travel vaccines: a randomized, open-label, multi-center study

BACKGROUND

Potential interactions between vaccines may compromise the immunogenicity and/or safety of individual vaccines so must be assessed before concomitant administration is recommended. In this study, the immunogenicity and safety of travel vaccines against Japanese encephalitis (JEV) and rabies (PCECV) administered together with or without a quadrivalent meningococcal glycoconjugate ACWY-CRM vaccine were evaluated (NCT01466387).

METHOD

Healthy adults aged 18 to ≤60 years were randomized to one of four vaccine regimens: JEV + PCECV + MenACWY-CRM, JEV + PCECV, PCECV or MenACWY-CRM. Immunogenicity at baseline and 28 days post-complete vaccination was assessed by serum bactericidal assay using human complement or neutralization tests. Adverse events (AEs) were collected throughout the study period.

RESULTS

JEV + PCECV + MenACWY-CRM was non-inferior to JEV + PCECV. Post-vaccination seroprotective neutralizing titers or concentrations were achieved in 98-99% (JE) and 100% (rabies) of subjects across the vaccine groups. Antibody responses to vaccine meningococcal serogroups were in the same range for MenACWY-CRM and JEV + PCECV + MenACWY-CRM. Rates of reporting of AEs were similar for JEV + PCECV and JEV + PCECV + MenACWY-CRM.

CONCLUSIONS

MenACWY-CRM was administered with an inactivated adjuvanted JE and a purified chick embryo cell-culture rabies vaccine without compromising immunogenicity or safety of the individual vaccines. These data provide evidence that MenACWY-CRM could be effectively incorporated into travel vaccination programs.

TRIAL NUMBER

NCT01466387.

Meningococcal serogroups A, C, W-135, and Y tetanus toxoid conjugate vaccine: a new conjugate vaccine against invasive meningococcal disease

Invasive meningococcal disease is a serious infection that occurs worldwide. It is caused by Neisseria meningitidis, of which six serogroups (A, B, C, W-135, X, and Y) are responsible for most infections. The case fatality rate of meningococcal disease remains high and can lead to significant sequelae. Vaccination remains the best strategy to prevent meningococcal disease. Polysaccharide vaccines were initially introduced in the late 1960s but their limitations (poor immunogenicity in infants and toddlers and hyporesponsiveness after repeated doses) have led to the development and use of meningococcal conjugate vaccines, which overcome these limitations. Two quadrivalent conjugated meningococcal vaccines – MenACWY-DT (Menactra^®) and MenACWY-CRM₁₉₇ (Menveo^®) – using diphtheria toxoid or a mutant protein, respectively, as carrier proteins have already been licensed in the US. Recently, a quadrivalent meningococcal vaccine conjugated to tetanus toxoid (MenACWY-TT; Nimenrix^®) was approved for use in Europe in 2012. The immunogenicity of MenACWY-TT, its reactogenicity and safety profile, as well as its coadministration with other vaccines are discussed in this review. Clinical trials showed that MenACWY-TT was immunogenic in children above the age of 12 months, adolescents, and adults, and has an acceptable reactogenicity and safety profile. Its coadministration with several other vaccines that are commonly used in children, adolescents, and adults did not affect the immunogenicity of MenACWY-TT or the coadministered vaccine, nor did it affect its reactogenicity and safety. Other studies are now ongoing in order to determine the immunogenicity, reactogenicity, and safety of MenACWY-TT in infants from the age of 6 weeks.

Review of meningococcal vaccines with updates on immunization in adults

Meningococcal disease is a serious and global life-threatening disease. Six serogroups (A, B, C, W-135, X, and Y) account for the majority of meningococcal disease worldwide. Meningococcal polysaccharide vaccines were introduced several decades ago and have led to the decline in the burden of disease. However, polysaccharide vaccines have several limitations, including poor immunogenicity in infants and toddlers, short-lived protection, lack of immunologic memory, negligible impact on nasopharyngeal carriage, and presence of hyporesponsiveness after repeated doses. The chemical conjugation of plain polysaccharide vaccines has the potential to overcome these drawbacks. Meningococcal conjugate vaccines include the quadrivalent vaccines (MenACWY-DT, MenACWY-CRM, and MenACWY-TT) as well as the monovalent A and C vaccines. These conjugate vaccines were shown to elicit strong immune response in adults. This review addresses the various aspects of meningococcal disease, the limitations posed by polysaccharide vaccines, the different conjugate vaccines with their immunogenicity and reactogenicity in adults, and the current recommendations in adults.

Paediatric travel medicine: vaccines and medications

The paediatric aspects of travel medicine can be complex, and individual advice is often required. Nonetheless, children are much more likely to acquire common infections than exotic tropical diseases whilst travelling. Important exceptions are malaria and tuberculosis, which are more frequent and severe in children. Overall, travellers' diarrhoea is the most common illness affecting travellers. This review discusses vaccines and medications that may be indicated for children who are travelling overseas. It focuses on immunizations that are given as part of the routine schedule, as well as those that are more specific to travel. Malaria and travellers' diarrhoea are also discussed.

The Long Road to an Effective Vaccine for Meningococcus Group B (MenB)

Neisseria meningitidis infection can cause life-threatening meningitis and meningococcal septicaemia. Over the past 40 years, vaccines against most of the main meningococcal serogroups have offered increasingly good protection from disease, with one major exception in the developed world: serogroup B meningococcus (MenB). In the United States, MenB accounts for about a quarter of cases of meningococcal meningitis, with the bulk of the rest caused by meningococcus serogroups C (MenC) and Y (MenY). In the UK, where a vaccine against MenC is widely used, MenB is now responsible for nearly 90% of cases of invasive meningococcal disease. Recent attempts to create a universal MenB vaccine have been thwarted by the variability of the surface proteins of MenB and by the similarity of the MenB capsule to human glycoproteins. This review discusses current meningococcal vaccine strategies and their limitations with regard to MenB, and examines a promising new strategy for the rational design of a MenB vaccine. Thanks to a fusion of a rational reverse genetics approach and a membrane vesicle approach, a MenB vaccine, 4CMenB (Bexsero(®)), has finally gained regulatory approval in Europe and could be in clinical use by the end of 2013.

Meningococcal polysaccharide A O-acetylation levels do not impact the immunogenicity of the quadrivalent meningococcal tetanus toxoid conjugate vaccine: results from a randomized, controlled phase III study of healthy adults aged 18 to 25 years

In this study, we compared the immunogenicities of two lots of meningococcal ACWY-tetanus toxoid conjugate vaccine (MenACWY-TT) that differed in serogroup A polysaccharide (PS) O-acetylation levels and evaluated their immunogenicities and safety in comparison to a licensed ACWY polysaccharide vaccine (Men-PS). In this phase III, partially blinded, controlled study, 1,170 healthy subjects aged 18 to 25 years were randomized (1:1:1) to receive one dose of MenACWY-TT lot A (ACWY-A) (68% O-acetylation), MenACWY-TT lot B (ACWY-B) (92% O-acetylation), or Men-PS (82% O-acetylation). Immunogenicity was evaluated in terms of serum bactericidal activity using rabbit complement (i.e., rabbit serum bactericidal activity [rSBA]). Solicited symptoms, unsolicited adverse events (AEs), and serious AEs (SAEs) were recorded. The immunogenicities, in terms of rSBA geometric mean titers, were comparable for both lots of MenACWY-TT. The vaccine response rates across the serogroups were 79.1 to 97.0% in the two ACWY groups and 73.7 to 94.1% in the Men-PS group. All subjects achieved rSBA titers of ≥1:8 for all serogroups. All subjects in the two ACWY groups and 99.5 to 100% in the Men-PS group achieved rSBA titers of ≥1:128. Pain was the most common solicited local symptom and was reported more frequently in the ACWY group (53.9 to 54.7%) than in the Men-PS group (36.8%). The most common solicited general symptoms were fatigue and headache, which were reported by 28.6 to 30.3% and 26.9 to 31.0% of subjects, respectively. Two subjects reported SAEs; one SAE was considered to be related to vaccination (blighted ovum; ACWY-B group). The level of serogroup A PS O-acetylation did not affect vaccine immunogenicity. MenACWY-TT (lot A) was not inferior to Men-PS in terms of vaccine response and was well tolerated.

Ontology representation and analysis of vaccine formulation and administration and their effects on vaccine immune responses

BACKGROUND

A vaccine is a processed material that if administered, is able to stimulate an adaptive immune response to prevent or ameliorate a disease. A vaccination process may protect the host against subsequent exposure to an infectious agent and result in reduced disease or total prevention of the disease. Vaccine formulation and administration methods may affect vaccine safety and efficacy significantly.

RESULTS

In this report, the detailed classification and definitions of vaccine components and vaccine administration processes are represented using OWL within the framework of the Vaccine Ontology (VO). Different use cases demonstrate how different vaccine formulations and routes of vaccine administration affect the protection efficacy, general immune responses, and adverse events following vaccination. For example, vaccinations of mice with Brucella abortus vaccine strain RB51 using intraperitoneal or intranasal administration resulted in different protection levels. As shown in the vaccine adverse event data provided by US FDA, live attenuated and nonliving vaccines are usually administered in different routes and have different local and systematic adverse effect manifestations.

CONCLUSIONS

Vaccine formulation and administration route can independently or collaboratively affect host response outcomes (positive protective immunity or adverse events) after vaccination. Ontological representation of different vaccine and vaccination factors in these two areas allows better understanding and analysis of the causal effects between different factors and immune responses.

MenACWY-TT vaccine for active immunization against invasive meningococcal disease

Meningococcal disease remains a significant global cause of morbidity and mortality despite the availability of polysaccharide and conjugate vaccines. The implementation of monovalent meningococcal serogroup C vaccine in developed countries has significantly decreased the incidence of meningococcal disease, while the recent introduction of monovalent serogroup A conjugate vaccine in the African meningitis belt aims to reduce the incidence of high endemic disease in this area. Three quadrivalent meningococcal vaccines have already been licensed; a polysaccharide (MenACWY-PS) and two conjugated (MenACWY-DT and MenACWY-CRM) vaccines. An investigational MenACWY-TT vaccine is described in this article. Clinical trials in infants older than 9 months of age, toddlers, children, adolescents and adults have indicated that this vaccine is well tolerated and immunogenic. The inclusion of a spacer molecule coupled with the polysaccharide (for serogroups A and C) and tetanus toxoid as the carrier protein aims to elicit robust immune responses. The tolerability of this vaccine is comparable to that of polysaccharide quadrivalent vaccines and monovalent meningococcal serogroup C vaccines. More importantly, the immunogenicity, antibody persistence and induction of immune memory aim to provide protection to a wide range of susceptible subjects.

Vaccination of travelers: how far have we come and where are we going?

Vaccine recommendations are a prominent part of health preparations before international travel. We review progress made in the past decade regarding vaccines used primarily by persons traveling from high-income countries to low- and middle-income countries. The combined hepatitis A-B vaccine, the recently licensed Vero cell-derived Japanese encephalitis vaccine and conjugated quadrivalent meningococcal vaccines are discussed. This article provides updates on yellow fever vaccine-associated visceral and neurologic adverse events, indications for influenza vaccine in travelers, the rapid immunization schedule for tick-borne encephalitis vaccine, schedules for postexposure rabies prophylaxis, and new insights about oral cholera vaccines following the outbreak in Haiti. The future should bring vaccines for serogroup B Neiserria meningitidis, dengue and malaria, as well as an inactivated yellow fever vaccine.

NCI, NHLBI/PBMTC first international conference on late effects after pediatric hematopoietic cell transplantation: persistent immune deficiency in pediatric transplant survivors

Defective immune reconstitution is a major barrier to successful hematopoietic cell transplantation (HCT), and has important implications in the pediatric population. There are many factors that affect immune recovery, including stem cell source and graft-versus-host disease (GVHD). Complete assessment of immune recovery, including T and B lymphocyte evaluation, innate immunity, and response to neoantigens, may provide insight as to infection risk and optimal time for immunizations. The increasing use of cord blood grafts requires additional study regarding early reconstitution and impact upon survival. Immunization schedules may require modification based upon stem cell source and immune reconstitution, and this is of particular importance as many children have been incompletely immunized, or not at all, before school entry. Additional studies are needed in children post-HCT to evaluate the impact of differing stem cell sources upon immune reconstitution, infectious risks, and immunization responses.

Safety and immunogenicity of a novel quadrivalent meningococcal CRM-conjugate vaccine given concomitantly with routine vaccinations in infants

BACKGROUND

In phase II studies, MenACWY-CRM elicited robust immunologic responses in young infants. We now present results from our pivotal phase III infant immunogenicity/safety study.

METHODS

In this open-label phase III study, we randomized full-term 2-month-old infants to 4 doses of MenACWY-CRM coadministered with routine vaccines at 2, 4, 6, and 12 months of age or with routine vaccines alone. We monitored for local and systemic reactions and serious adverse events among all study participants and evaluated for sufficiency of the immune responses to MenACWY-CRM through serum bactericidal activity assay with human complement.

RESULTS

Bactericidal antibodies were present in 94% to 100% of subjects against each of the serogroups in MenACWY-CRM after the 4-dose series and were 67% to 97% after the first 3 doses. Geometric mean titers were higher after the fourth dose of MenACWY-CRM compared with a single dose of MenACWY-CRM at 12 months of age for all serogroups (range of ratios, 4.5-38). Responses to 3 doses of routine vaccines coadministered with MenACWY-CRM were noninferior to routine vaccinations alone, except for small differences in pneumococcal serotype 6B responses after dose 3 but not dose 4 and pertactin after dose 3. Inclusion of MenACWY-CRM did not affect the safety or reactogenicity profiles of the routine infant vaccine series.

CONCLUSIONS

A 4-dose series of MenACWY-CRM was highly immunogenic and well tolerated in young infants, and it can be coadministered with routine infant vaccines. Substantial immunity was conferred after the first 3 doses administered at 2, 4, and 6 months of age.

Pre-clinical evaluation of a 15-valent pneumococcal conjugate vaccine (PCV15-CRM197) in an infant-rhesus monkey immunogenicity model

The incidence of invasive pneumococcal disease (IPD), caused by the approximately 91 serotypes of Streptococcus pneumoniae (PN), varies geographically and temporally as a result of changing epidemiology and vaccination patterns as well as due to regional measurement differences. Prevnar(®) (Pfizer), the first licensed pneumococcal conjugate vaccine (PCV), comprises polysaccharides (PS) from 7 serotypes conjugated to the mutant diphtheria toxin carrier protein, CRM197. In the United States and elsewhere, this vaccine has been highly efficacious in reducing the incidence of IPD caused by vaccine serotypes, however, the incidence of non-vaccine serotypes (e.g., 19A, 22F, and 33F) has increased, resulting in the need for vaccines with higher valencies. In response, 10- and 13-valent PCVs have recently been licensed. To further increase serotype coverage, we have developed a 15-valent PCV containing PS from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F conjugated to CRM197 and formulated on aluminum phosphate adjuvant. Vaccine immunogenicity was evaluated in infant rhesus monkeys since they, like human infants, respond poorly to unconjugated PN PS. Infant (2-3 month old) rhesus monkeys were vaccinated three times with PCV-15 or Prevnar(®) at 2 month intervals, and serotype-specific IgG antibodies were measured using a multiarray electrochemiluminescence (ECL) assay. The results indicate that antibody responses to PCV-15 and Prevnar(®) were comparable for the 7 common serotypes and that post-vaccination responses to PCV-15 were >10-fold higher than baseline for the 8 additional serotypes.

Safety, immunogenicity and dose ranging of a new Vi-CRM₁₉₇ conjugate vaccine against typhoid fever: randomized clinical testing in healthy adults

Background

Typhoid fever causes more than 21 million cases of disease and 200,000 deaths yearly worldwide, with more than 90% of the disease burden being reported from Asia. Epidemiological data show high disease incidence in young children and suggest that immunization programs should target children below two years of age: this is not possible with available vaccines. The Novartis Vaccines Institute for Global Health developed a conjugate vaccine (Vi-CRM₁₉₇) for infant vaccination concomitantly with EPI vaccines, either starting at 6 weeks with DTP or at 9 months with measles vaccine. We report the results from a Phase 1 and a Phase 2 dose ranging trial with Vi-CRM₁₉₇ in European adults.

Methodology

Following randomized blinded comparison of single vaccination with either Vi-CRM₁₉₇ or licensed polysaccharide vaccines (both containing 25·0 µg of Vi antigen), a randomised observer blinded dose ranging trial was performed in the same center to compare three concentrations of Vi-CRM₁₉₇ (1·25 µg, 5·0 µg and 12·5 µg of Vi antigen) with the polysaccharide vaccine.

Principal Findings

All vaccines were well tolerated. Compared to the polysaccharide vaccine, Vi-CRM₁₉₇ induced a higher incidence of mild to moderate short lasting local pain. All Vi-CRM₁₉₇ formulations induced higher Vi antibody levels compared to licensed control, with clear dose response relationship.

Conclusions

Vi-CRM₁₉₇ did not elicit safety concerns, was highly immunogenic and is therefore suitable for further clinical testing in endemic populations of South Asia.

Trial Registration

ClinicalTrials.gov NCT01123941 NCT01193907

Critical appraisal of a quadrivalent CRM(197) conjugate vaccine against meningococcal serogroups A, C W-135 and Y (Menveo) in the context of treatment and prevention of invasive disease

Worldwide, invasive meningococcal disease affects about 500,000 people annually. Case fatality in developed countries averages 10%, and higher rates are reported in less prosperous regions. According to the World Health Organization, the most important pathogenic serogroups are A, B, C, W-135, X, and Y. Clinical features of invasive meningococcal disease make diagnosis and management difficult. Antibiotic measures are recommended for prophylaxis after exposure and for treatment of invasive meningococcal disease cases; however, resistant strains may be emerging. Vaccines are generally regarded as the best preventative measure for invasive meningococcal disease. Polysaccharide vaccines against serogroups A, C, W-135, and Y using protein conjugation technology have clear advantages over older plain polysaccharide formulations without a protein component. The first quadrivalent meningococcal conjugate vaccine (MenACWY-D) was licensed in the US in 2005. More recently, MenACWY-CRM (Menveo^®) was licensed in Europe, the US, the Middle East, and Latin America. MenACWY-CRM uses cross-reactive material 197, a nontoxic mutant of diphtheria toxin, as the carrier protein. MenACWY-CRM offers robust immunogenicity in all age groups, with a tolerability profile similar to that of a plain polysaccharide vaccine. Given its potential for protecting persons from infancy to old age, MenACWY-CRM offers the opportunity to protect broad populations against invasive meningococcal disease. The most optimal strategy for use of the vaccine has to be assessed country by country on the basis of local epidemiology, individual health care systems, and need.