A universal vaccine for serogroup B meningococcus

Identification of novel vaccine candidates against carbapenem resistant Klebsiella pneumoniae: A systematic reverse proteomic approach

Klebsiella pneumoniae is declared as antibiotic resistant by WHO, with the critical urgency of developing novel antimicrobial therapeutics as drug resistance is the second most dangerous threat after terrorism. Besides many attempts still, there is no effective vaccine available against K. pneumoniae. By utilizing all the available proteomic data we prioritized the novel proteins ideal for vaccine development using bioinformatics tools and techniques. Among the huge data, eight proteins passed all the barriers and were considered ideal candidates for vaccine development. These include: copper silver efflux system outer membrane protein (CusC), outer membrane porin protein (OmpN), Fe⁺⁺ enterobactin transporter substrate binding protein (fepB), zinc transporter substrate binding protein (ZnuA), ribonuclease HI, tellurite resistant methyltransferase (the B), and two uncharacterized hypothetical proteins (WP_002918223 and WP_002892366). These proteins were also subjected to epitope analysis and were found best for developing subunit vaccine against K. pneumoniae. The study shows that the potential vaccine targets are sufficiently efficient being virulent, of outer membranous origin and can be proposed for the DNA third-generation vaccines development that would help to cope up infections caused by multidrug-resistant K. pneumoniae.

The Serogroup B Meningococcal Vaccine Bexsero Elicits Antibodies to Neisseria gonorrhoeae

Background

Neisseria gonorrhoeae and Neisseria meningitidis are closely-related bacteria that cause a significant global burden of disease. Control of gonorrhoea is becoming increasingly difficult, due to widespread antibiotic resistance. While vaccines are routinely used for N. meningitidis, no vaccine is available for N. gonorrhoeae. Recently, the outer membrane vesicle (OMV) meningococcal B vaccine, MeNZB, was reported to be associated with reduced rates of gonorrhoea following a mass vaccination campaign in New Zealand. To probe the basis for this protection, we assessed the cross-reactivity to N. gonorrhoeae of serum raised to the meningococcal vaccine Bexsero, which contains the MeNZB OMV component plus 3 recombinant antigens (Neisseria adhesin A, factor H binding protein [fHbp]-GNA2091, and Neisserial heparin binding antigen [NHBA]-GNA1030).

Methods

A bioinformatic analysis was performed to assess the similarity of MeNZB OMV and Bexsero antigens to gonococcal proteins. Rabbits were immunized with the OMV component or the 3 recombinant antigens of Bexsero, and Western blots and enzyme-linked immunosorbent assays were used to assess the generation of antibodies recognizing N. gonorrhoeae. Serum from humans immunized with Bexsero was investigated to assess the nature of the anti-gonococcal response.

Results

There is a high level of sequence identity between MeNZB OMV and Bexsero OMV antigens, and between the antigens and gonococcal proteins. NHBA is the only Bexsero recombinant antigen that is conserved and surfaced exposed in N. gonorrhoeae. Bexsero induces antibodies in humans that recognize gonococcal proteins.

Conclusions

The anti-gonococcal antibodies induced by MeNZB-like OMV proteins could explain the previously-seen decrease in gonorrhoea following MeNZB vaccination. The high level of human anti-gonococcal NHBA antibodies generated by Bexsero vaccination may provide additional cross-protection against gonorrhoea.

Complement in malaria: immune evasion strategies and role in protective immunity

The malaria parasite has for long been thought to escape host complement attack as a survival strategy. However, it was only recently that complement evasion mechanisms of the parasite were described. Simultaneously, the role of complement in antibody-mediated naturally acquired and vaccine-induced protection against malaria has also been reported. Such findings should be considered in future vaccine design, given the current need to develop more efficacious vaccines against malaria. Parasite antigens derived from molecules mediating functions crucial for parasite survival, such as complement evasion, or parasite antigens against which antibody responses lead to an efficient complement attack could present new candidates for vaccines. In this review, we discuss recent findings on complement evasion by the malaria parasites and the emerging role of complement in antibody-mediated protection against malaria. We emphasize that immune responses to vaccines based on complement inhibitors should not only induce complement-activating antibodies but also neutralize the escape mechanisms of the parasite.

Synergic complement-mediated bactericidal activity of monoclonal antibodies with distinct specificity

The classical complement pathway is triggered when antigen-bound immunoglobulins bind to C1q through their Fc region. While C1q binds to a single Fc with low affinity, a higher avidity stable binding of two or more of C1q globular heads initiates the downstream reactions of the complement cascade ultimately resulting in bacteriolysis. Synergistic bactericidal activity has been demonstrated when monoclonal antibodies recognize nonoverlapping epitopes of the same antigen. The aim of the present work was to investigate the synergistic effect between antibodies directed toward different antigens. To this purpose, we investigated the bactericidal activity induced by combinations of monoclonal antibodies (mAbs) raised against factor H-binding protein (fHbp) and Neisserial Heparin-Binding Antigen (NHBA), two major antigens included in Bexsero, the vaccine against Meningococcus B, for prevention from this devastating disease in infants and adolescents. Collectively, our results show that mAbs recognizing different antigens can synergistically activate complement even when each single Mab is not bactericidal, reinforcing the evidence that cooperative immunity induced by antigen combinations can represent a remarkable added value of multicomponent vaccines. Our study also shows that the synergistic effect of antibodies is modulated by the nature of the respective epitopes, as well as by the antigen density on the bacterial cell surface.

Construction and assessment of the immunogenicity and bactericidal activity of fusion protein porin A from Neisseria meningitidis serogroups A and B admixed with OMV adjuvant as a novel vaccine candidate

Objectives

The porins A and B and also outer membrane vesicles (OMVs) of Neisseria meningitidis are used for vaccine purposes. In the present study, we aimed to design a new vaccine candidate based on a fusion of PorA of serogroups A and B of N. meningitidis admixed with OMV and evaluate it in an animal model.

Materials and Methods

After bioinformatic studies, a fusion protein composed of porin A from both serogroups A and B of N. meningitidis was constructed, expressed, and purified by nickel resins. Extraction of OMV of N. meningitidis was performed using a chemical method. The mice were vaccinated subcutaneously in different groups with mixtures of PorA proteins, OMV, and Freund's adjuvants. Then, the immune responses were measured using the ELISA method. Finally, serum bactericidal activity (SBA) procedure was applied to assay the activity of the immune responses in mice.

Results

Mice received the PorA protein plus Freund's adjuvant. Mice vaccinated with PorA fusion of serogroups A+B plus Freund's adjuvant produced more IgG, IgG1, and IgG2a than combinations admixed with OMV. Furthermore, the vaccinated mice tended to direct the IgG responses toward IgG1. Sera of the mice that received PorA+Freund's and those that received PorA+OMV produced higher bactericidal activity than the controls.

Conclusion

Fusion protein porin A could be a valuable target for developing vaccines against N. meningitidis. Although, Freund's adjuvant induced the strongest IgG responses, given that Freund's adjuvant has no human use, and OMV is a human adjuvant, OMV could be considered in vaccine design against N. meningitidis.

Interest of bacterial pangenome analyses in clinical microbiology

Thanks to the progress and decreasing costs in genome sequencing technologies, more than 250,000 bacterial genomes are currently available in public databases, covering most, if not all, of the major human-associated phylogenetic groups of these microorganisms, pathogenic or not. In addition, for many of them, sequences from several strains of a given species are available, thus enabling to evaluate their genetic diversity and study their evolution. In addition, the significant cost reduction of bacterial whole genome sequencing as well as the rapid increase in the number of available bacterial genomes have prompted the development of pangenomic software tools. The study of bacterial pangenome has many applications in clinical microbiology. It can unveil the pathogenic potential and ability of bacteria to resist antimicrobials as well identify specific sequences and predict antigenic epitopes that allow molecular or serologic assays and vaccines to be designed. Bacterial pangenome constitutes a powerful method for understanding the history of human bacteria and relating these findings to diagnosis in clinical microbiology laboratories in order to optimize patient management.

Immunogenicity of trimeric autotransporter adhesins and their potential as vaccine targets

The current problem of increasing antibiotic resistance and the resurgence of numerous infections indicate the need for novel vaccination strategies more than ever. In vaccine development, the search for and the selection of adequate vaccine antigens is the first important step. In recent years, bacterial outer membrane proteins have become of major interest, as they are the main proteins interacting with the extracellular environment. Trimeric autotransporter adhesins (TAAs) are important virulence factors in many Gram-negative bacteria, are localised on the bacterial surface, and mediate the first adherence to host cells in the course of infection. One example is the Neisseria adhesin A (NadA), which is currently used as a subunit in a licensed vaccine against Neisseria meningitidis. Other TAAs that seem promising vaccine candidates are the Acinetobacter trimeric autotransporter (Ata), the Haemophilus influenzae adhesin (Hia), and TAAs of the genus Bartonella. Here, we review the suitability of various TAAs as vaccine candidates.

The Neisseria gonorrhoeae Vaccine Candidate NHBA Elicits Antibodies That Are Bactericidal, Opsonophagocytic and That Reduce Gonococcal Adherence to Epithelial Cells

Due to the continuing emergence of multidrug resistant strains of Neisseria gonorrhoeae there is an urgent need for the development of a gonococcal vaccine. We evaluated the gonococcal Neisseria heparin binding antigen (NHBA) as a potential vaccine candidate, in terms of its sequence conservation and expression in a range of N. gonorrhoeae strains, as well as its immunogenicity and the functional activity of antibodies raised to either the full length NHBA or a C-terminal fragment of NHBA (NHBA-c). The gene encoding NHBA is highly conserved and expressed in all N. gonorrhoeae strains investigated. Recombinant NHBA is immunogenic, and mice immunized with either NHBA or NHBA-c adjuvanted with either Freund's or aluminium hydroxide (alum) generated a humoral immune response, with predominantly IgG1 antibodies. Antibodies generated by both NHBA and NHBA-c antigens promoted complement activation and mediated bacterial killing via both serum bactericidal activity and opsonophagocytic activity, with slightly higher titers seen for the NHBA-c antigen. Anti-NHBA was also able to block the functional activity of NHBA by reducing binding to heparin and adherence to cervical and urethral epithelial cells. These data suggest that the gonococcal NHBA is a promising vaccine antigen to include in a vaccine to control N. gonorrhoeae.

Meningococcal factor H binding protein as immune evasion factor and vaccine antigen

Factor H binding protein (fHbp) is a key virulence factor of Neisseria meningitidis and a main component of the two licensed vaccines against serogroup B meningococcus (Bexsero and Trumenba). fHbp is a surface-exposed lipoprotein that enables the bacterium to survive in human blood by binding the human complement regulator factor H (fH). When used as vaccine, the protein induces antibodies with potent bactericidal activity. While the fHbp gene is present in the majority of N. meningitidis serogroup B isolates, the expression level varies up to 15 times between different strains and more than 700 different sequence variants have been described. Antigenically, the protein has been divided into three variants or two subfamilies. The 3D structure of fHbp alone, in combination with fH or in complex with bactericidal antibodies, has been key to understanding the molecular details of the protein. In this article, we will review the biochemical and immunological properties of fHbp, and its key role in meningococcal pathogenesis, complement regulation, and immune evasion.

An assessment of the use of Hepatitis B Virus core protein virus-like particles to display heterologous antigens from Neisseria meningitidis

Neisseria meningitidis is the causative agent of meningococcal meningitis and sepsis and remains a significant public health problem in many countries. Efforts to develop a comprehensive vaccine against serogroup B meningococci have focused on the use of surface-exposed outer membrane proteins. Here we report the use of virus-like particles derived from the core protein of Hepatitis B Virus, HBc, to incorporate antigen domains derived from Factor H binding protein (FHbp) and the adhesin NadA. The extracellular domain of NadA was inserted into the major immunodominant region of HBc, and the C-terminal domain of FHbp at the C-terminus (CFHbp), creating a single polypeptide chain 3.7-fold larger than native HBc. Remarkably, cryoelectron microscopy revealed that the construct formed assemblies that were able to incorporate both antigens with minimal structural changes to native HBc. Electron density was weak for NadA and absent for CFHbp, partly attributable to domain flexibility. Following immunization of mice, three HBc fusions (CFHbp or NadA alone, NadA + CFHbp) were able to induce production of IgG1, IgG2a and IgG2b antibodies reactive against their respective antigens at dilutions in excess of 1:18,000. However, only HBc fusions containing NadA elicited the production of antibodies with serum bactericidal activity. It is hypothesized that this improved immune response is attributable to the adoption of a more native-like folding of crucial conformational epitopes of NadA within the chimeric VLP. This work demonstrates that HBc can incorporate insertions of large antigen domains but that maintenance of their three-dimensional structure is likely to be critical in obtaining a protective response.

Understanding immunogenicity assessments for meningococcal serogroup B vaccines

Invasive meningococcal disease (IMD) is a potentially devastating infection associated with high mortality and long-term sequelae; however, vaccines are available to protect against the five common disease-causing serogroups (A, B, C, W, and Y). Because traditional field efficacy clinical trials were not feasible due to low IMD incidence that necessitates a very large number of participants, serum bactericidal antibody (SBA) assays using rabbit (rSBA) or human (hSBA) complement were established as in vitro surrogates of meningococcal vaccine efficacy and are now routinely used to support vaccine licensure. Specifically, rSBA assays have been used to evaluate responses to meningococcal capsular polysaccharide-protein conjugate vaccines against serogroups A, C, W, and Y; the accepted correlate of protection for rSBA assays is a titer ≥1:8. Importantly, because the bacterial capsular polysaccharide antigen is conserved across strains, only one test strain that expresses an invariant polysaccharide capsule for each serogroup is required to assess coverage. rSBA assays are unsuitable for subcapsular protein-based serogroup B (MenB) vaccines, and therefore, hSBA assays have been used for licensure; titers ≥1:4 are considered the correlate of protection against IMD for hSBA. In contrast to MenACWY vaccines, because bacterial surface proteins are antigenically variable, MenB vaccines must be tested with hSBA assays using multiple test strains that represent the antigenic diversity of disease-causing isolates. As this complexity regarding SBA assessment methods can make data interpretation difficult, herein we describe the use of hSBA assays to evaluate MenB vaccine efficacy and to support licensure. In addition, we highlight how the two recently approved MenB vaccines differ in their use of hSBA assays in clinical studies to demonstrate broad protection against MenB IMD.

Effect of complement Factor H on antibody repertoire and protection elicited by meningococcal capsular group B vaccines containing Factor H binding protein

Bacteria produce surface ligands for host complement regulators including Factor H (FH), which allows the bacteria to evade immunity. Meningococcal Factor H binding protein (FHbp) is both a virulence factor and a vaccine antigen. Antibodies to FHbp can neutralize its function by inhibiting binding of FH to the bacteria and confer robust complement-mediated protection. However, in the presence of human or primate FH, antibodies to FHbp do not inhibit FH binding and the protective antibody responses are decreased. This immune suppression can be overcome by modification of the FHbp antigen to decrease FH binding, which modulates the antibody repertoire to inhibit FH binding and increase protection. When FHbp is present at sufficient density on the bacterial surface, two or more antibodies can synergize to activate the complement system. Thus, modification of FHbp antigens to decrease FH binding expands the anti-FHbp antibody repertoire and increases the potential for synergistic activity.

Adsorption onto aluminum hydroxide adjuvant protects antigens from degradation

Aluminum based adjuvants are widely used in commercial vaccines, since they are known to be safe and effective with a variety of antigens. The effect of antigen adsorption onto Aluminum Hydroxide is a complex area, since several mechanisms are involved simultaneously, whose impact is both antigen and formulation conditions dependent. Moreover, the mode of action of Aluminum Hydroxide is itself complex, with many mechanisms operating simultaneously. Within the literature there are contrasting theories regarding the effect of adsorption on antigen integrity and stability, with reports of antigen being stabilized by adsorption onto Aluminum Hydroxide, but also with contrary reports of antigen being destabilized. With the aim to understand the impact of adsorption on three recombinant proteins which, following in vivo immunization, are able to induce functional bactericidal antibodies against Neisseria meningitidis type B, we used a range of physico-chemical tools, such as DSC and UPLC, along with in vitro binding of antibodies that recognize structural elements of the proteins, and supported the in vitro data with in vivo evaluation in mice studies. We showed that, following exposure to accelerated degradation conditions involving heat, the recombinant proteins, although robust, were stabilized by adsorption onto Aluminum Hydroxide and retain their structural integrity unlike the not adsorbed proteins. The measure of the Melting Temperature was a useful tool to compare the behavior of proteins adsorbed and not adsorbed on Aluminum Hydroxide and to predict protein stability.

Estimated susceptibility of Canadian meningococcal B isolates to a meningococcal serogroup B vaccine (MenB-FHbp)

BACKGROUND

Invasive meningococcal disease caused by Neisseria meningitidis serogroup B (MenB) remains a health risk in Canada and globally. Two MenB vaccines are now approved for use. An understanding of the genotype of Canadian strains and the potential strain coverage conferred by the MenB-FHbp vaccine is needed to inform immunization policies.

METHODS

Serogroup B Neisseria meningitidis strains responsible for meningococcal disease in Canada from 2006 to 2012 were collected as part of the Canadian Immunization Monitoring Program Active surveillance network. Genotypic analysis was done on MenB isolates from 2006 to 2012 with determination of fHbp surface expression for a subset of isolates: those occurring from 2010 to 2012.

RESULTS

Two clonal complexes (cc269 and cc41/44) were observed in 68.8% of the 276 isolates. A total of 50 different fHbp peptides were identified among isolates from 2006 to 2012. Surface expression of fHbp was detected on 95% of MenB isolates from 2010 to 2012 and 91% of isolates expressed fHbp at levels that are predicted to be susceptible to the bactericidal immune response elicited by the MenB-FHbp vaccine. Some regional differences were observed, particularly in isolates from British Columbia and Quebec.

CONCLUSION

The majority of MenB isolates responsible for meningococcal disease in Canada expressed fHbp at levels predicted to be sufficient for complement mediated bactericidal activity in the presence of MenB-FHbp induced serum antibodies.

Cross-reactivity with Brazilian strains of Neisseria meningitidis B after immunization with outer membrane vesicles

Background

Immunization against Neisseria meningitidis is important for public health. Vaccines composed of cross-reactivity antigens avoid strain-specific responses, ensuring more comprehensive protection.

Methods

The cross-reactivity between three strains from the last outbreak of N. meningitidis in Brazil was assessed in our studies, using enzyme-linked immunosorbent assay (ELISA) and immunoblotting assays.

Results

Both assays verifed a similar humoral response between the strains evaluated. Patterns of antigen recognition differed with each dose evaluated.

Conclusions

We observed that immunization with N. meningitidis B outer membrane vesicles (OMVs) led to the production of antibodies that recognized antigens of heterologous strains, indicating possible protection against these evaluated strains.

Does vaccination with 4CMenB convey protection against meningococcal serogroup B strains not predicted to be covered by MATS? A study of the UK clonal complex cc269

The Meningococcal Antigen Typing System (MATS) has been developed as an hSBA surrogate to evaluate potential coverage afforded by the 4-component meningococcal serogroup B vaccine (4CMenB: Bexsero, GSK). We investigated whether the lower value of MATS coverage among invasive Meningococcus serogroup B clonal complex 269 strains from the United Kingdom (53% in 2014–2015 versus 73% in 2007–2008) reflected the lower bactericidal activity of the vaccine against these isolates. A total of 34 MATS-negative strains (31 were cc269 or closely related) were tested against pooled sera from 32 or 72 4CMenB-vaccinated infants in a serum bactericidal antibody assay in presence of human complement (hSBA). All infants had received four 4CMenB doses in the first 2 y of life. Baseline sera comprised 180 pooled samples from healthy-unvaccinated 2-month-old infants. Twenty of the 34 (59%) MATS-negative strains were killed in hSBA with titers ≥4 by pooled sera from vaccinated infants. There were 13/34 strains with hSBA titers ≥4 and at least a 4-fold rise in titer with respect to pooled baseline sera, and 10/34 with hSBA titers ≥8 and at least a 4-fold rise in titer with respect to baseline. These data confirm MATS as a conservative estimate for predicting strain coverage by 4CMenB.

In silico Design of an Epitope-Based Vaccine Ensemble for Chagas Disease

Trypanosoma cruzi infection causes Chagas disease, which affects 7 million people worldwide. Two drugs are available to treat it: benznidazole and nifurtimox. Although both are efficacious against the acute stage of the disease, this is usually asymptomatic and goes undiagnosed and untreated. Diagnosis is achieved at the chronic stage, when life-threatening heart and/or gut tissue disruptions occur in ~30% of those chronically infected. By then, the drugs' efficacy is reduced, but not their associated high toxicity. Given current deficiencies in diagnosis and treatment, a vaccine to prevent infection and/or the development of symptoms would be a breakthrough in the management of the disease. Current vaccine candidates are mostly based on the delivery of single antigens or a few different antigens. Nevertheless, due to the high biological complexity of the parasite, targeting as many antigens as possible would be desirable. In this regard, an epitope-based vaccine design could be a well-suited approach. With this aim, we have gone through publicly available databases to identify T. cruzi epitopes from several antigens. By means of a computer-aided strategy, we have prioritized a set of epitopes based on sequence conservation criteria, projected population coverage of Latin American population, and biological features of their antigens of origin. Fruit of this analysis, we provide a selection of CD8⁺ T cell, CD4⁺ T cell, and B cell epitopes that have <70% identity to human or human microbiome protein sequences and represent the basis toward the development of an epitope-based vaccine against T. cruzi.

Preclinical Efficacy of a Lipooligosaccharide Peptide Mimic Candidate Gonococcal Vaccine

The global spread of multidrug-resistant strains of Neisseria gonorrhoeae constitutes a public health emergency. With limited antibiotic treatment options, there is an urgent need for development of a safe and effective vaccine against gonorrhea. Previously, we constructed a prototype vaccine candidate comprising a peptide mimic (mimitope) of a glycan epitope on gonococcal lipooligosaccharide (LOS), recognized by monoclonal antibody 2C7. The 2C7 epitope is (i) broadly expressed as a gonococcal antigenic target in human infection, (ii) a critical requirement for gonococcal colonization in the experimental setting, and (iii) a virulence determinant that is maintained and expressed by gonococci. Here, we have synthesized to >95% purity through a relatively facile and economical process a tetrapeptide derivative of the mimitope that was cyclized through a nonreducible thioether bond, thereby rendering the compound homogeneous and stable. This vaccine candidate, called TMCP2, when administered at 0, 3, and 6 weeks to BALB/c mice at either 50, 100 or 200 μg/dose in combination with glucopyranosyl lipid A-stable oil-in-water nanoemulsion (GLA-SE; a Toll-like receptor 4 and T_H1-promoting adjuvant), elicited bactericidal IgG and reduced colonization levels of gonococci in experimentally infected mice while accelerating clearance by each of two different gonococcal strains. Similarly, a 3-dose biweekly schedule (50 μg TMCP2/dose) was also effective in mice. We have developed a gonococcal vaccine candidate that can be scaled up and produced economically to a high degree of purity. The candidate elicits bactericidal antibodies and is efficacious in a preclinical experimental infection model.IMPORTANCE Neisseria gonorrhoeae has become resistant to most antibiotics. The incidence of gonorrhea is also sharply increasing. A safe and effective antigonococcal vaccine is urgently needed. Lipooligosaccharide (LOS), the most abundant outer membrane molecule, is indispensable for gonococcal pathogenesis. A glycan epitope on LOS that is recognized by monoclonal antibody (MAb) 2C7 (called the 2C7 epitope) is expressed almost universally by gonococci in vivo Previously, we identified a peptide mimic (mimitope) of the 2C7 epitope, which when configured as an octamer and used as an immunogen, attenuated colonization of mice by gonococci. Here, a homogenous, stable tetrameric derivative of the mimitope, when combined with a T_H1-promoting adjuvant and used as an immunogen, also effectively attenuates gonococcal colonization of mice. This candidate peptide vaccine can be produced economically, an important consideration for gonorrhea, which affects socioeconomically underprivileged populations disproportionately, and represents an important advance in the development of a gonorrhea vaccine.

Integrated Bioinformatic Analyses and Immune Characterization of New Neisseria gonorrhoeae Vaccine Antigens Expressed during Natural Mucosal Infection

There is an increasingly severe trend of antibiotic-resistant Neisseria gonorrhoeae strains worldwide and new therapeutic strategies are needed against this sexually-transmitted pathogen. Despite the urgency, progress towards a gonococcal vaccine has been slowed by a scarcity of suitable antigens, lack of correlates of protection in humans and limited animal models of infection. N. gonorrhoeae gene expression levels in the natural human host does not reflect expression in vitro, further complicating in vitro-basedvaccine analysis platforms. We designed a novel candidate antigen selection strategy (CASS), based on a reverse vaccinology-like approach coupled with bioinformatics. We utilized the CASS to mine gonococcal proteins expressed during human mucosal infection, reported in our previous studies, and focused on a large pool of hypothetical proteins as an untapped source of potential new antigens. Via two discovery and analysis phases (DAP), we identified 36 targets predicted to be immunogenic, membrane-associated proteins conserved in N. gonorrhoeae and suitable for recombinant expression. Six initial candidates were produced and used to immunize mice. Characterization of the immune responses indicated cross-reactive antibodies and serum bactericidal activity against different N. gonorrhoeae strains. These results support the CASS as a tool for the discovery of new vaccine candidates.

Meningococcal Group B Vaccine For The Prevention Of Invasive Meningococcal Disease Caused By Neisseria meningitidis Serogroup B

Invasive meningococcal disease (IMD) is a major public health concern because of its high case fatality, long-term morbidity, and potential to course with outbreaks. IMD caused by Nesseira meningitidis serogroup B has been predominant in different regions of the world like Europe and only recently broadly protective vaccines against B serogroup have become available. Two protein-based vaccines, namely 4CMenB (Bexsero®) and rLP2086 (Trumenba®) are currently licensed for use in different countries against MenB disease. These vaccines came from a novel technology on vaccine design (or antigen selection) using highly specific antigen targets identified through whole-genome sequence analysis. Moreover, it has the potential to confer protection against non-B meningococcus and against other Neisserial species such as gonococcus. Real-world data on the vaccine-use are rapidly accumulating from the UK and other countries which used the vaccine for control of outbreak or as part of routine immunization program, reiterating its safety and efficacy. Additional data on real-life effectiveness, long-term immunity, and eventual herd effects, including estimates on vaccine impact for cost-effectiveness assessment are further needed. Given the predominance of MenB in Europe and other parts of the world, these new vaccines are crucial for the prevention and public health control of the disease, and should be considered.

Complement in malaria immunity and vaccines

Developing efficacious vaccines for human malaria caused by Plasmodium falciparum is a major global health priority, although this has proven to be immensely challenging over the decades. One major hindrance is the incomplete understanding of specific immune responses that confer protection against disease and/or infection. While antibodies to play a crucial role in malaria immunity, the functional mechanisms of these antibodies remain unclear as most research has primarily focused on the direct inhibitory or neutralizing activity of antibodies. Recently, there is a growing body of evidence that antibodies can also mediate effector functions through activating the complement system against multiple developmental stages of the parasite life cycle. These antibody‐complement interactions can have detrimental consequences to parasite function and viability, and have been significantly associated with protection against clinical malaria in naturally acquired immunity, and emerging findings suggest these mechanisms could contribute to vaccine‐induced immunity. In order to develop highly efficacious vaccines, strategies are needed that prioritize the induction of antibodies with enhanced functional activity, including the ability to activate complement. Here we review the role of complement in acquired immunity to malaria, and provide insights into how this knowledge could be used to harness complement in malaria vaccine development.

Genetic Similarity of Gonococcal Homologs to Meningococcal Outer Membrane Proteins of Serogroup B Vaccine

The human pathogens Neisseria gonorrhoeae and Neisseria meningitidis share high genome identity. Retrospective analysis of surveillance data from New Zealand indicates the potential cross-protective effect of outer membrane vesicle (OMV) meningococcal serogroup B vaccine (MeNZB) against N. gonorrhoeae A licensed OMV-based MenB vaccine, MenB-4C, consists of a recombinant FHbp, NhbA, NadA, and the MeNZB OMV. Previous work has identified several abundantly expressed outer membrane proteins (OMPs) as major components of the MenB-4C OMV with high sequence similarity between N. gonorrhoeae and N. meningitidis, suggesting a mechanism for cross-protection. To build off these findings, we performed comparative genomic analysis on 970 recent N. gonorrhoeae isolates collected through a U.S surveillance system against N. meningitidis serogroup B (NmB) reference sequences. We identified 1,525 proteins that were common to both Neisseria species, of which 57 proteins were predicted to be OMPs using in silico methods. Among the MenB-4C antigens, NhbA showed moderate sequence identity (73%) to the respective gonococcal homolog, was highly conserved within N. gonorrhoeae, and was predicted to be surface expressed. In contrast, the gonococcal FHbp was predicted not to be surface expressed, while NadA was absent in all N. gonorrhoeae isolates. Our work confirmed recent observations (E. A. Semchenko, A. Tan, R. Borrow, and K. L. Seib, Clin Infect Dis, 2018, https://doi.org/10.1093/cid/ciy1061) and describes homologous OMPs from a large panel of epidemiologically relevant N. gonorrhoeae strains in the United States against NmB reference strains. Based on our results, we report a set of OMPs that may contribute to the previously observed cross-protection and provide potential antigen targets to guide the next steps in gonorrhea vaccine development.IMPORTANCE Gonorrhea, a sexually transmitted disease, causes substantial global morbidity and economic burden. New prevention and control measures for this disease are urgently needed, as strains resistant to almost all classes of antibiotics available for treatment have emerged. Previous reports demonstrate that cross-protection from gonococcal infections may be conferred by meningococcal serogroup B (MenB) outer membrane vesicle (OMV)-based vaccines. Among 1,525 common proteins shared across the genomes of both N. gonorrhoeae and N. meningitidis, 57 proteins were predicted to be surface expressed (outer membrane proteins [OMPs]) and thus preferred targets for vaccine development. The majority of these OMPs showed high sequence identity between the 2 bacterial species. Our results provide valuable insight into the meningococcal antigens present in the current OMV-containing MenB-4C vaccine that may contribute to cross-protection against gonorrhea and may inform next steps in gonorrhea vaccine development.

Glycointeractions in bacterial pathogenesis

Many important interactions between bacterial pathogens and their hosts are highly specific binding events that involve host or pathogen carbohydrate structures (glycans). Glycan interactions can mediate adhesion, invasion and immune evasion and can act as receptors for toxins. Several bacterial pathogens can also enzymatically alter host glycans to reveal binding targets, degrade the host cell glycans or alter the function of host glycoproteins. In recent years, high-throughput screening technologies, such as lectin, glycan and mucin microarrays, have transformed the field by identifying new bacterial-host glycointeractions, which are crucial for colonization, persistence and disease. In this Review, we discuss interactions involving both host and bacterial glycans that have a role in bacterial pathogenesis. We also highlight recent technological advances that have illuminated the glycoscience of microbial pathogenesis.

NHBA is processed by kallikrein from human saliva

Neisserial Heparin Binding Antigen (NHBA) is a surface-exposed lipoprotein of Neisseria meningitidis and a component of the Bexsero vaccine. NHBA is characterized by the presence of a highly conserved Arg-rich region involved in binding to heparin and heparan sulphate proteoglycans present on the surface of host epithelial cells, suggesting a possible role of NHBA during N. meningitidis colonization. NHBA has been shown to be cleaved by the meningococcal protease NalP and by human lactoferrin (hLF), a host protease presents in different body fluids (saliva, breast milk and serum). Cleavage occurs upstream or downstream the Arg-rich region. Since the human nasopharynx is the only known reservoir of infection, we further investigated the susceptibility of NHBA to human proteases present in the saliva to assess whether proteolytic cleavage could happen during the initial steps of colonization. Here we show that human saliva proteolytically cleaves NHBA, and identified human kallikrein 1 (hK1), a serine protease, as responsible for this cleavage. Kallikrein-related peptidases (KLKs) have a distinct domain structure and exist as a family of 15 genes which are differentially expressed in many tissues and in the central nervous system. They are present in plasma, lymph, urine, saliva, pancreatic juices, and other body fluids where they catalyze the proteolysis of several human proteins. Here we report the characterization of NHBA cleavage by the tissue kallikrein, expressed in saliva and the identification of the cleavage site on NHBA both, as recombinant protein or as native protein, when expressed on live bacteria. Overall, these findings provide new insights on NHBA as target of host proteases, highlights thepotential role of NHBA in the Neisseria meningitidis nasopharyngeal colonization, and of kallikrein as a defensive agent against meningococcal infection.

Phase-variable bacterial loci: how bacteria gamble to maximise fitness in changing environments

Phase-variation of genes is defined as the rapid and reversible switching of expression - either ON-OFF switching or the expression of multiple allelic variants. Switching of expression can be achieved by a number of different mechanisms. Phase-variable genes typically encode bacterial surface structures, such as adhesins, pili, and lipooligosaccharide, and provide an extra contingency strategy in small-genome pathogens that may lack the plethora of 'sense-and-respond' gene regulation systems found in other organisms. Many bacterial pathogens also encode phase-variable DNA methyltransferases that control the expression of multiple genes in systems called phasevarions (phase-variable regulons). The presence of phase-variable genes allows a population of bacteria to generate a number of phenotypic variants, some of which may be better suited to either colonising certain host niches, surviving a particular environmental condition and/or evading an immune response. The presence of phase-variable genes complicates the determination of an organism's stably expressed antigenic repertoire; many phase-variable genes are highly immunogenic, and so would be ideal vaccine candidates, but unstable expression due to phase-variation may allow vaccine escape. This review will summarise our current understanding of phase-variable genes that switch expression by a variety of mechanisms, and describe their role in disease and pathobiology.

Epidemiology of community-acquired bacterial meningitis

PURPOSE OF REVIEW

The epidemiology of bacterial meningitis has been dynamic in the past 30 years following introduction of conjugated vaccines against Haemophilus influenzae type B, Streptococcus pneumoniae and Neisseria meningitidis. The purpose of this review is to describe recent developments in bacterial meningitis epidemiology.

RECENT FINDINGS

The incidence of bacterial meningitis in Western countries (Finland, Netherlands, and the United States) gradually declined by 3-4% per year to 0.7-0.9 per 100 000 per year in the past 10-20 years. In African countries (Burkina Faso and Malawi), incidence rates are still substantially higher at 10-40 per 100 000 persons per year. Introduction of pneumococcal conjugate vaccines have not consistently decreased overall pneumococcal meningitis incidence because of serotype replacement. Following the introduction of serogroup A and C meningococcal vaccines, the incidence of meningococcal meningitis because of these serogroups strongly decreased. Novel outbreaks in the African meningitis belt by serogroup C and increased incidence of serogroup W in the United Kingdom and the Netherlands were observed recently.

SUMMARY

Bacterial meningitis remains an important infectious disease, despite a gradual decline in incidence after large-scale vaccination campaigns. Further development of vaccines with broader coverage is important, as is continuous surveillance of bacterial meningitis cases.

Serum Bactericidal Antibody Responses of Students Immunized With a Meningococcal Serogroup B Vaccine in Response to an Outbreak on a University Campus

Background

MenB-4C is a recently licensed meningococcal serogroup B vaccine. For vaccine licensure, short-term efficacy was inferred from serum bactericidal antibody (SBA) titers against 3 antigen-specific indicator strains, which are not necessarily representative of US disease-causing strains.

Methods

A total of 4923 students were immunized with MenB-4C in response to an outbreak at a university. Serum samples were obtained at 1.5-2 months from 106 students who received the recommended 2 doses and 52 unvaccinated students. Follow-up serum samples were obtained at 7 months from 42 vaccinated and 24 unvaccinated participants. SBA was measured against strains from 4 university outbreaks.

Results

At 1.5-2 months, the proportion of immunized students with protective titers ≥1:4 against an isolate from the campus outbreak was 93% (95% confidence interval [CI], 87%-97%) vs 37% (95% CI, 24%-51%) in unvaccinated students. The proportion with protective titers against strains from 3 other university outbreaks was 73% (95% CI, 62%-82%) vs 26% (95% CI, 14%-41%) in unvaccinated; 71% (95% CI, 61%-79%) vs 19% (95% CI, 10%-33%) in unvaccinated; and 53% (95% CI, 42%-64%) vs 9% (95% CI, 3%-22%) in unvaccinated (P < .0001 for each strain). At 7 months, the proportion of immunized students with titers ≥1:4 was 86% (95% CI, 71%-95%) against the isolate from the campus outbreak and 57% (95% CI, 41%-72%), 38% (95% CI, 24%-54%), and 31% (95% CI, 18%-47%), respectively, for the other 3 outbreak strains.

Conclusions

MenB-4C elicited short-term protective titers against 4 strains responsible for recent university campus outbreaks. By 7 months the prevalence of protective titers was <40% for 2 of the 4 outbreak strains. A booster dose of MenB-4C may be needed to maintain protective titers.

Reverse vaccinology and subtractive genomics reveal new therapeutic targets against Mycoplasma pneumoniae: a causative agent of pneumonia

Pneumonia is an infectious disease caused by bacteria, viruses or fungi that results in millions of deaths globally. Despite the existence of prophylactic methods against some of the major pathogens of the disease, there is no efficient prophylaxis against atypical agents such as Mycoplasma pneumoniae, a bacterium associated with cases of community-acquired pneumonia. Because of the morphological peculiarity of M. pneumoniae, which leads to an increased resistance to antibiotics, studies that prospectively investigate the development of vaccines and drug targets appear to be one of the best ways forward. Hence, in this paper, bioinformatics tools were used for vaccine and pharmacological prediction. We conducted comparative genomic analysis on the genomes of 88 M. pneumoniae strains, as opposed to a reverse vaccinology analysis, in relation to the capacity of M. pneumoniae proteins to bind to the major histocompatibility complex, revealing seven targets with immunogenic potential. Predictive cytoplasmic proteins were tested as potential drug targets by studying their structures in relation to other proteins, metabolic pathways and molecular anchorage, which identified five possible drug targets. These findings are a valuable addition to the development of vaccines and the selection of new in vivo drug targets that may contribute to further elucidating the molecular basis of M. pneumoniae-host interactions.

Fishing for vaccines against Vibrio cholerae using in silico pan-proteomic reverse vaccinology approach

BACKGROUND

Cholera, an acute enteric infection, is a serious health challenge in both the underdeveloped and the developing world. It is caused by Vibrio cholerae after ingestion of fecal contaminated food or water. Cholera outbreaks have recently been observed in regions facing natural calamities (i.e., earthquake in Haiti 2010) or war (i.e., ongoing civil war in Yemen 2016) where healthcare and sanitary setups have been disrupted as a consequence. Whole-cell oral cholera vaccines (OCVs) have been in market but their regimen efficacy has been questioned. A reverse vaccinology (RV) approach has been applied as a successful anti-microbial measure for many infectious diseases.

METHODOLOGY

With the aim of finding new protective antigens for vaccine development, the V. cholerae O1 (biovar eltr str. N16961) proteome was computationally screened in a sequential prioritization approach that focused on determining the antigenicity of potential vaccine candidates. Essential, accessible, virulent and immunogenic proteins were selected as potential candidates. The predicted epitopes were filtered for effective binding with MHC alleles and epitopes binding with greater MHC alleles were selected.

RESULTS

In this study, we report lipoprotein NlpD, outer membrane protein OmpU, accessory colonization factor AcfA, Porin, putative and outer membrane protein OmpW as potential candidates qualifying all the set criteria. These predicted epitopes can offer a potential for development of a reliable peptide or subunit vaccine for V. cholerae.

A Meningococcal Outer Membrane Vesicle Vaccine with Overexpressed Mutant FHbp Elicits Higher Protective Antibody Responses in Infant Rhesus Macaques than a Licensed Serogroup B Vaccine

MenB-4C (Bexsero; GlaxoSmithKline Biologicals) is a licensed meningococcal vaccine for capsular B strains. The vaccine contains detergent-extracted outer membrane vesicles (dOMV) and three recombinant proteins, of which one is factor H binding protein (FHbp). In previous studies, overexpression of FHbp in native OMV (NOMV) with genetically attenuated endotoxin (LpxL1) and/or by the use of mutant FHbp antigens with low factor H (FH) binding increased serum bactericidal antibody (SBA) responses. In this study, we immunized 13 infant macaques with 2 doses of NOMV with overexpressed mutant (R41S) FHbp with low binding to macaque FH (NOMV-FHbp). Control macaques received MenB-4C (n = 13) or aluminum hydroxide adjuvant alone (n = 4). NOMV-FHbp elicited a 2-fold higher IgG anti-FHbp geometric mean titer (GMT) than MenB-4C (P = 0.003), and the anti-FHbp repertoire inhibited binding of FH to FHbp, whereas anti-FHbp antibodies to MenB-4C enhanced FH binding. MenB-4C elicited a 10-fold higher GMT against strain NZ98/254, which was used to prepare the dOMV component, whereas NOMV-FHbp elicited an 8-fold higher GMT against strain H44/76, which was the parent of the mutant NOMV-FHbp vaccine strain. Against four strains with PorA mismatched to both of the vaccines and different FHbp sequence variants, NOMV-FHbp elicited 6- to 14-fold higher SBA GMTs than MenB-4C (P ≤ 0.0002). Two of 13 macaques immunized with MenB-4C but 0 of 17 macaques immunized with NOMV-FHbp or adjuvant developed serum anti-FH autoantibodies (P = 0.18). Thus, the mutant NOMV-FHbp approach has the potential to elicit higher and broader SBA responses than a licensed group B vaccine that contains wild-type FHbp that binds FH. The mutant NOMV-FHbp also might pose less of a risk of eliciting anti-FH autoantibodies.IMPORTANCE There are two licensed meningococcal capsular B vaccines. Both contain recombinant factor H binding protein (FHbp), which can bind to host complement factor H (FH). The limitations of these vaccines include a lack of protection against some meningococcal strains and the potential to elicit autoantibodies to FH. We immunized infant macaques with a native outer membrane vesicle (NOMV) vaccine with genetically attenuated endotoxin and overproduced mutant FHbp with low binding to FH. The NOMV-FHbp vaccine stimulated higher levels of protective serum antibodies than a licensed meningococcal group B vaccine against five of six genetically diverse meningococcal strains tested. Two of 13 macaques immunized with the licensed vaccine, which contains FHbp that binds macaque FH, but 0 of 17 macaques given NOMV-FHbp or the negative control developed serum anti-FH autoantibodies Thus, in a relevant nonhuman primate model, the NOMV-FHbp vaccine elicited greater protective antibodies than the licensed vaccine and may pose less of a risk of anti-FH autoantibody.

[From a pathogen's genome to an effective vaccine: the four-component meningococcal serogroup B vaccine]

Invasive meningococcal disease (IMD), caused by the bacterium Neisseria meningitidis, entails significant mortality and morbidity. Disease incidence is highest in infants <1 year and young children globally. In Europe, N. meningitidis serogroup B is responsible for over 50% of overall IMD cases, whereas the majority of IMD cases in Latin America is caused either by serogroup B or C. The development of an effective vaccine against serogroup B has challenged the researchers for over half a century. Serogroup B capsular polysaccharide was an inappropriate vaccine antigen, and the success of outer membrane vesicle (OMV) vaccines was restricted to homologous bacterial strains. Reverse vaccinology led to the development of a 4-component meningococcal vaccine including three novel antigens, and OMVs (4CMenB). Each vaccine component has a different target. 4CMenB has been authorised based on its immunogenicity and safety data because the low disease incidence precluded formal clinical efficacy studies. Human serum bactericidal antibody (hSBA) assay tests functional antibodies in the serum of vaccinated individuals (i.e. the vaccine immunogenicity), and is the accepted correlate of protection. Vaccine strain coverage has been assessed both through hSBA assays and a more conservative method named Meningococcal Antigen Typing System (MATS). Effectiveness data of 4CMenB have been collected in the field since 2013. The vaccine proved effective in outbreak control in North America, and recent data from the introduction of the vaccine in the United Kingdom infant national immunisation programme reveal a vaccine effectiveness of 82.9% for the first two doses, with an acceptable safety profile.

Preliminary Work Towards Finding Proteins as Potential Vaccine Candidates for Vibrio cholerae Pakistani Isolates through Reverse Vaccinology

Background and Objective: Vibrio cholerae continues to emerge as a dangerous pathogen because of increasing resistance to a number of antibiotics. This paper provides a solution to emerging antibiotic resistance by introducing novel proteins as vaccine candidates against cholera. Materials and Methods: Vibrio cholerae genome versatility is a hurdle for developing a vaccine to combat diarrhoeal infection, so its core gene information was used to determine a potential vaccine candidate. Whole genome sequence data of more than 100 Vibrio cholerae strains were used simultaneously to get core genome information. The VacSol pipeline based on reverse vaccinology was selected to address the problem of safe, cheap, temperature-stable, and effective vaccine candidates which can be used for vaccine development against Vibrio cholerae. VacSol screens vaccine candidates using integrated, well-known, and robust algorithms/tools for proteome analysis. The proteomes of the pathogens were initially screened to predict homology using BLASTp. Proteomes that are non-homologous to humans are then subjected to a predictor for localization. Helicer predicts transmembrane helices for the protein. Proteins failing to comply with the set parameters were filtered at each step, and finally, 11 proteins were filtered as vaccine candidates. Results: This selected group of vaccine candidates consists of proteins from almost all structural parts of Vibrio cholerae. Their blast results show that this filtered group includes flagellin A protein, a protein from the Zn transporter system, a lipocarrier outer membrane protein, a peptidoglycan-associated protein, a DNA-binding protein, a chemotaxis protein, a tRNA Pseuriudine synthase A, and two selected proteins, which were beta lactamases. The last two uncharacterized proteins possess 100% similarity to V. albensis and Enterobacter, respectively. Tertiary structure and active site determination show a large number of pockets on each protein. Conclusions: The most interesting finding of this study is that 10 proteins out of 11 filtered proteins are introduced as novel potential vaccine candidates. These novel vaccine candidates can result in the development of cost-effective and broad-spectrum vaccines which can be used in countries where cholera is a major contributor to diarrheal disease.

Immunogenicity profiling of protein antigens from capsular group B Neisseria meningitidis

Outer membrane vesicle (OMV)- based vaccines have been used to provide strain-specific protection against capsular group B Neisseria meningitidis infections, but the full breadth of the immune response against the components of the OMV has not been established. Sera from adults vaccinated with an OMV vaccine were used to screen 91 outer membrane proteins (OMPs) incorporated in an antigen microarray panel. Antigen-specific IgG levels were quantified pre-vaccination, and after 12 and 18 weeks. These results were compared with IgG levels from mice vaccinated with the same OMV vaccine. The repertoires of highly responding antigens in humans and mice overlapped, but were not identical. The highest responding antigens to human IgG comprised four integral OMPs (PorA, PorB, OpcA and PilQ), a protein which promotes the stability of PorA and PorB (RmpM) and two lipoproteins (BamC and GNA1162). These observations will assist in evaluating the role of minor antigen components within OMVs in providing protection against meningococcal infection. In addition, the relative dominance of responses to integral OMPs in humans emphasizes the importance of this subclass and points to the value of maintaining conformational epitopes from integral membrane proteins in vaccine formulations.

Phasevarions of bacterial pathogens - phase-variable epigenetic regulators evolving from restriction-modification systems

Phase-variable DNA methyltransferases control the expression of multiple genes via epigenetic mechanisms in a wide variety of bacterial species. These systems are called phasevarions, for phase-variable regulons. Phasevarions regulate genes involved in pathogenesis, host adaptation and antibiotic resistance. Many human-adapted bacterial pathogens contain phasevarions. These include leading causes of morbidity and mortality worldwide, such as non-typeable Haemophilus influenzae, Streptococcus pneumoniae and Neisseria spp. Phase-variable methyltransferases and phasevarions have also been discovered in environmental organisms and veterinary pathogens. The existence of many different examples suggests that phasevarions have evolved multiple times as a contingency strategy in the bacterial domain, controlling phenotypes that are important in adapting to environmental change. Many of the organisms that contain phasevarions have existing or emerging drug resistance. Vaccines may therefore represent the best and most cost-effective tool to prevent disease caused by these organisms. However, many phasevarions also control the expression of current and putative vaccine candidates; variable expression of antigens could lead to immune evasion, meaning that vaccines designed using these targets become ineffective. It is therefore essential to characterize phasevarions in order to determine an organism's stably expressed antigenic repertoire, and rationally design broadly effective vaccines.

The Development of a Vaccine Against Meningococcus B Using Reverse Vaccinology

The discovery of vaccine antigens through whole genome sequencing (WGS) contrasts with the classical hypothesis-driven laboratory-based analysis of microbes to identify components to elicit protective immunity. This radical change in scientific direction and action in vaccine research is captured in the term reverse vaccinology. The complete genome sequence of an isolate of Neisseria meningitidis serogroup B (MenB) was systematically analyzed to identify proteins predicted to be secreted or exported to the outer membrane. This identified hundreds of genes coding for potential surface-exposed antigens. These were amplified, cloned in expression vectors and used to immunize mice. Antisera against 350 recombinant antigens were obtained and analyzed in a panel of immunological assays from which 28 were selected as potentially protective based on the -antibody dependent, complement mediated- serum bactericidal activity assay. Testing of these candidate vaccine antigens, using a large globally representative strain collection of Neisseria species isolated from cases of disease and carriage, indicated that no single component would be sufficient to induce broad coverage and that a “universal” vaccine should contain multiple antigens. The final choice of antigens to be included was based on cross-protective ability, assayed by serum bactericidal activity and maximum coverage of the extensive antigenic variability of MenB strains. The resulting multivalent vaccine formulation selected consisted of three recombinant antigens (Neisserial Heparin Binding Antigen or NHBA, Factor H binding protein or fHbp and Neisseria Adhesin A or NadA). To improve immunogenicity and potential strain coverage, an outer membrane vesicle component obtained from the epidemic New Zealand strain (OMVNz) was added to the formulation to create a four component vaccine, called 4CMenB. A series of phase 2 and 3 clinical trials were conducted to evaluate safety and tolerability and to estimate the vaccine effectiveness of human immune responses at different ages and how these were affected by various factors including concomitant vaccine use and lot-to-lot consistency. 4CMenB was approved in Europe in 2013 and introduced in the National Immunization Program in the UK starting from September 2015 when the vaccine was offered to all newborns using a 2, 4, and 12 months schedule., The effectiveness against invasive MenB disease measured at 11 months after the study start and 5 months after the second vaccination was 83% and there have been no safety concerns.

Exploitation of Neisseria meningitidis Group B OMV Vaccines Against N. gonorrhoeae to Inform the Development and Deployment of Effective Gonorrhea Vaccines

Have potential clues to an effective gonorrhea vaccine been lurking in international disease surveillance data for decades? While no clinically effective vaccines against gonorrhea have been developed we present direct and indirect evidence that a vaccine is not only possible, but may already exist. Experience from Cuba, New Zealand, and Canada suggest that vaccines containing Group B Neisseria meningitides outer membrane vesicles (OMV) developed to control type-specific meningococcal disease may also prevent a significant proportion of gonorrhea. The mechanisms for this phenomenon have not yet been elucidated but we present some strategies for unraveling potential cross protective antigens and effector immune responses by exploiting stored sera from clinical trials and individuals primed with a meningococcal group B OMV vaccine (MeNZB). Elucidating these will contribute to the ongoing development of high efficacy vaccine options for gonorrhea. While the vaccine used in New Zealand, where the strongest empirical evidence has been gathered, is no longer available, the OMV has been included in the multi component recombinant meningococcal vaccine 4CMenB (Bexsero) which is now licensed and used in numerous countries. Several lines of evidence suggest it has the potential to affect gonorrhea prevalence. A vaccine to control gonorrhea does not need to be perfect and modeling supports that even a moderately efficacious vaccine could make a significant impact in disease prevalence. How might we use an off the shelf vaccine to reduce the burden of gonorrhea? What are some of the potential societal barriers in a world where vaccine hesitancy is growing? We summarize the evidence and consider some of the remaining questions.

Inhibitors of the Neisseria meningitidis PilF ATPase provoke type IV pilus disassembly

Despite the availability of antibiotics and vaccines, Neisseria meningitidis remains a major cause of meningitis and sepsis in humans. Due to its extracellular lifestyle, bacterial adhesion to host cells constitutes an attractive therapeutic target. Here, we present a high-throughput microscopy-based approach that allowed the identification of compounds able to decrease type IV pilus-mediated interaction of bacteria with endothelial cells in the absence of bacterial or host cell toxicity. Compounds specifically inhibit the PilF ATPase enzymatic activity that powers type IV pilus extension but remain inefficient on the ATPase that promotes pilus retraction, thus leading to rapid pilus disappearance from the bacterial surface and loss of pili-mediated functions. Structure activity relationship of the most active compound identifies specific moieties required for the activity of this compound and highlights its specificity. This study therefore provides compounds targeting pilus biogenesis, thereby inhibiting bacterial adhesion, and paves the way for a novel therapeutic option for meningococcal infections.

Typing complex meningococcal vaccines to understand diversity and population structure of key vaccine antigens

Background: Protein-conjugate capsular polysaccharide vaccines can potentially control invasive meningococcal disease (IMD) caused by five (A, C, W, X, Y) of the six IMD-associated serogroups.  Concerns raised by immunological similarity of the serogroup B capsule to human neural cell carbohydrates, meant that 'serogroup B substitute' vaccines target more variable subcapsular protein antigens.  A successful approach using outer membrane vesicles (OMVs) as major vaccine components had limited strain coverage. In 4CMenB (Bexsero ^®), recombinant proteins have been added to ameliorate this problem.  Methods: Scalable, portable, genomic techniques were used to investigate the Bexsero ^® OMV protein diversity in meningococcal populations. Shotgun proteomics identified 461 proteins in the OMV, defining a complex proteome. Amino acid sequences for the 24 proteins most likely to be involved in cross-protective immune responses were catalogued within the PubMLST.org/neisseria database using a novel OMV peptide Typing (OMVT) scheme. Results: Among these proteins there was variation in the extent of diversity and association with meningococcal lineages, identified as clonal complexes (ccs), ranging from the most conserved peptides (FbpA, NEISp0578, and putative periplasmic protein, NEISp1063) to the most diverse (TbpA, NEISp1690).  There were 1752 unique OMVTs identified amongst 2492/3506 isolates examined by whole-genome sequencing (WGS). These OMVTs were grouped into clusters (sharing ≥18 identical OMVT peptides), with 45.3% of isolates assigned to one of 27 OMVT clusters. OMVTs and OMVT clusters were strongly associated with cc, genogroup, and Bexsero ^® antigen variants, demonstrating that combinations of OMV proteins exist in discrete, non-overlapping combinations associated with genogroup and Bexsero ^® Antigen Sequence Type. This highly structured population of IMD-associated meningococci is consistent with strain structure models invoking host immune and/or metabolic selection. Conclusions: The OMVT scheme facilitates region-specific WGS investigation of meningococcal diversity and is an open-access, portable tool with applications for vaccine development, especially in the choice of antigen combinations, assessment and implementation.

Typing complex meningococcal vaccines to understand diversity and population structure of key vaccine antigens

Background: Protein-conjugate capsular polysaccharide vaccines can potentially control invasive meningococcal disease (IMD) caused by five (A, C, W, X, Y) of the six IMD-associated serogroups.  Concerns raised by immunological similarity of the serogroup B capsule to human neural cell carbohydrates, meant that ‘serogroup B substitute’ vaccines target more variable subcapsular protein antigens.  A successful approach using outer membrane vesicles (OMVs) as major vaccine components had limited strain coverage. In 4CMenB (Bexsero ^®), recombinant proteins have been added to ameliorate this problem. 

Methods: Scalable, portable, genomic techniques were used to investigate the Bexsero ^® OMV protein diversity in meningococcal populations. Shotgun proteomics identified 461 proteins in the OMV, defining a complex proteome. Amino acid sequences for the 24 proteins most likely to be involved in cross-protective immune responses were catalogued within the PubMLST.org/neisseria database using a novel OMV peptide Typing (OMVT) scheme.

Results: Among these proteins there was variation in the extent of diversity and association with meningococcal lineages, identified as clonal complexes (ccs), ranging from the most conserved peptides (FbpA, NEISp0578, and putative periplasmic protein, NEISp1063) to the most diverse (TbpA, NEISp1690).  There were 1752 unique OMVTs identified amongst 2492/3506 isolates examined by whole-genome sequencing (WGS). These OMVTs were grouped into clusters (sharing ≥18 identical OMVT peptides), with 45.3% of isolates assigned to one of 27 OMVT clusters. OMVTs and OMVT clusters were strongly associated with cc, genogroup, and Bexsero ^® antigen variants, demonstrating that combinations of OMV proteins exist in discrete, non-overlapping combinations associated with genogroup and Bexsero ^® Antigen Sequence Type. This highly structured population of IMD-associated meningococci is consistent with strain structure models invoking host immune and/or metabolic selection.

Conclusions:The OMVT scheme facilitates region-specific WGS investigation of meningococcal diversity and is an open-access, portable tool with applications for vaccine development, especially in the choice of antigen combinations, assessment and implementation.

PanRV: Pangenome-reverse vaccinology approach for identifications of potential vaccine candidates in microbial pangenome

BACKGROUND

A revolutionary diversion from classical vaccinology to reverse vaccinology approach has been observed in the last decade. The ever-increasing genomic and proteomic data has greatly facilitated the vaccine designing and development process. Reverse vaccinology is considered as a cost-effective and proficient approach to screen the entire pathogen genome. To look for broad-spectrum immunogenic targets and analysis of closely-related bacterial species, the assimilation of pangenome concept into reverse vaccinology approach is essential. The categories of species pangenome such as core, accessory, and unique genes sets can be analyzed for the identification of vaccine candidates through reverse vaccinology.

RESULTS

We have designed an integrative computational pipeline term as "PanRV" that employs both the pangenome and reverse vaccinology approaches. PanRV comprises of four functional modules including i) Pangenome Estimation Module (PGM) ii) Reverse Vaccinology Module (RVM) iii) Functional Annotation Module (FAM) and iv) Antibiotic Resistance Association Module (ARM). The pipeline is tested by using genomic data from 301 genomes of Staphylococcus aureus and the results are verified by experimentally known antigenic data.

CONCLUSION

The proposed pipeline has proved to be the first comprehensive automated pipeline that can precisely identify putative vaccine candidates exploiting the microbial pangenome. PanRV is a Linux based package developed in JAVA language. An executable installer is provided for ease of installation along with a user manual at https://sourceforge.net/projects/panrv2/ .

Preclinical efficacy of an anti-methamphetamine vaccine using E6020 adjuvant

BACKGROUND AND OBJECTIVE

Methamphetamine (MA) substance use disorder (SUD) does not have an efficacious pharmacotherapy. We developed a MA vaccine and investigated its potential to attenuate MA induced responses.

METHODS

We examined a novel adjuvant, E6020, a Toll-like receptor-4 (TLR-4) agonist combined with tetanus-toxoid conjugated to succinyl-methamphetamine (TT-SMA) adsorbed on aluminum hydroxide (alum). Adult BALB/c female mice received the vaccine and booster injections at weeks 0, 3, and 6. The efficacy of the vaccine was assessed by the level and affinity of anti-MA antibodies elicited, its ability to attenuate MA induced locomotor activation and its reduction in the amount of MA entering the brains of vaccinated mice.

RESULTS

The TT-SMA vaccine containing alum and E6020 adjuvant produced anti-MA antibodies with nanomolar affinities and showed threefold greater peak titer levels than without E6020 (700 vs 250 μg/ml). These antibodies significantly decreased MA-induced locomotor activation (p < .05), and reduced the brain (p < .005) MA levels following MA administration in actively immunized mice.

CONCLUSIONS

Thus, this anti-MA vaccine formulated with E6020 demonstrated effective functional protection against behavioral disruptions induced by MA.

SCIENTIFIC SIGNIFICANCE

Together, anti-MA vaccine showing a promising improvement in the efficacy of the vaccine that could be an effective candidate vaccine for methamphetamine use disorder (MUD). Furthermore, combinations of adjuvants may be a tool to design vaccines for MA dependence in humans. (Am J Addict 2019;XX:1-8).

Genome-Based Approach Delivers Vaccine Candidates Against Pseudomonas aeruginosa

High incidence, severity and increasing antibiotic resistance characterize Pseudomonas aeruginosa infections, highlighting the need for new therapeutic options. Vaccination strategies to prevent or limit P. aeruginosa infections represent a rational approach to positively impact the clinical outcome of risk patients; nevertheless this bacterium remains a challenging vaccine target. To identify novel vaccine candidates, we started from the genome sequence analysis of the P. aeruginosa reference strain PAO1 exploring the reverse vaccinology approach integrated with additional bioinformatic tools. The bioinformatic approaches resulted in the selection of 52 potential antigens. These vaccine candidates were conserved in P. aeruginosa genomes from different origin and among strains isolated longitudinally from cystic fibrosis patients. To assess the immune-protection of single or antigens combination against P. aeruginosa infection, a vaccination protocol was established in murine model of acute respiratory infection. Combinations of selected candidates, rather than single antigens, effectively controlled P. aeruginosa infection in the in vivo model of murine pneumonia. Five combinations were capable of significantly increase survival rate among challenged mice and all included PA5340, a hypothetical protein exclusively present in P. aeruginosa. PA5340 combined with PA3526-MotY gave the maximum protection. Both proteins were surface exposed by immunofluorescence and triggered a specific immune response. Combination of these two protein antigens could represent a potential vaccine to prevent P. aeruginosa infection.

An Overview of Neisseria meningitidis

Neisseria meningitidis (the meningococcus) is a member of the normal nasopharyngeal microbiome in healthy individuals, but can cause septicemia and meningitis in susceptible individuals. In this chapter we provide an overview of the disease caused by N. meningitidis and the schemes used to type the meningococcus. We also review the adhesions, virulence factors, and phase variable genes that enable it to successfully colonize the human host. Finally, we outline the history and current status of meningococcal vaccines and highlight the importance of continued molecular investigation of the epidemiology and the structural analysis of the antigens of this pathogen to aid future vaccine development.