Genome-wide scan for potential CD4+ T-cell vaccine candidates in Candida auris by exploiting reverse vaccinology and evolutionary information

Candida auris is a globally emerging fungal pathogen responsible for causing nosocomial outbreaks in healthcare associated settings. It is known to cause infection in all age groups and exhibits multi-drug resistance with high potential for horizontal transmission. Because of this reason combined with limited therapeutic choices available, C. auris infection has been acknowledged as a potential risk for causing a future pandemic, and thus seeking a promising strategy for its treatment is imperative. Here, we combined evolutionary information with reverse vaccinology approach to identify novel epitopes for vaccine design that could elicit CD4+ T-cell responses against C. auris. To this end, we extensively scanned the family of proteins encoded by C. auris genome. In addition, a pathogen may acquire substitutions in epitopes over a period of time which could cause its escape from the immune response thus rendering the vaccine ineffective. To lower this possibility in our design, we eliminated all rapidly evolving genes of C. auris with positive selection. We further employed highly conserved regions of multiple C. auris strains and identified two immunogenic and antigenic T-cell epitopes that could generate the most effective immune response against C. auris. The antigenicity scores of our predicted vaccine candidates were calculated as 0.85 and 1.88 where 0.5 is the threshold for prediction of fungal antigenic sequences. Based on our results, we conclude that our vaccine candidates have the potential to be successfully employed for the treatment of C. auris infection. However, in vivo experiments are imperative to further demonstrate the efficacy of our design.

Product review on the IMD serogroup B vaccine Bexsero®

Bexsero® is a multicomponent vaccine composed of four major proteins of Neisseria meningitidis: the fHbp, NHBA, NadA and PorA. This vaccine was licensed against invasive meningococcal disease (IMD) due to serogroup B isolates. When administered alone, Bexsero® showed a safety profile similar to other childhood vaccines. It provides an excellent immunogenicity but that requires booster doses in infants and young children. Although the vaccine does not seem to impact on acquisition of carriage of serogroup B isolates, it confers protection against isolates of serogroup B harboring distinct but cross-reactive variants of fHbp, NadA and NHBA. Primary vaccination schemes in infancy underwent a rapid increase after a toddler booster suggesting an anamnestic response and the establishment of a memory response. As Bexsero® targets sub-capsular proteins that can be conserved regardless the capsule, the vaccine can be effective against non-B isolates such as isolates of serogroups W and X.

Hospitalizations related to meningococcal infection in Spain from 1997 to 2018

Background

Baseline hospitalization, mortality, and in-hospital fatality rates for meningococcal infection are required to evaluate preventive interventions, such as the inclusion of the conjugated quadrivalent meningococcal vaccine and serogroup B based protein vaccines.

Methods

All meningococcal infection–related hospitalizations in any diagnostic position in Spain from 1st January 1997 through 31st December 2018 were analysed. The annual hospitalization rate, mortality rate and case-fatality rate were calculated.

Results

The average hospitalization rate for meningococcal infection was 1.64 (95% CI 1.61 to 1.66) hospitalizations per 100,000 inhabitants during the study period and significantly decreased from 1997 to 2018. Hospitalizations for meningococcal infection decreased significantly with age and were concentrated in children under 5 years of age (46%). The hospitalization rates reached 29 per 100,000 and 24 per 100,000 children under 1 and 2 years of age, respectively. The in-hospital case-fatality rate was 7.45% (95% CI 7.03 to 7.86). Thirty percent of the deaths occurred in children under 5 years of age, and more than half occurred in adults. The case fatality rate increased significantly with age (p < 0.001).

Conclusion

It is necessary to maintain epidemiological surveillance of meningococcal infection to determine the main circulating serogroups involved, track their evolution, and evaluate preventive measures whose effectiveness must be assessed in all age groups.

Factor H binding protein (fHbp)-mediated differential complement resistance of a serogroup C Neisseria meningitidis isolate from cerebrospinal fluid of a patient with invasive meningococcal disease

During an outbreak of invasive meningococcal disease (IMD) at the University of Southampton, UK, in 1997, two Neisseria meningitidis serogroup C isolates were retrieved from a student ('Case'), who died of IMD, and a close contact ('Carrier') who, after mouth-to-mouth resuscitation on the deceased, did not contract the disease. Genomic comparison of the isolates demonstrated extensive nucleotide sequence identity, with differences identified in eight genes. Here, comparative proteomics was used to measure differential protein expression between the isolates and investigate whether the differences contributed to the clinical outcomes. A total of six proteins were differentially expressed: four proteins (methylcitrate synthase, PrpC; hypothetical integral membrane protein, Imp; fructose-1,6-bisphosphate aldolase, Fba; aldehyde dehydrogenase A, AldA) were upregulated in the Case isolate, while one protein (Type IV pilus-associated protein, PilC2) was downregulated. Peptides for factor H binding protein (fHbp), a major virulence factor and antigenic protein, were only detected in the Case, with a single base deletion (ΔT366) in the Carrier fHbp causing lack of its expression. Expression of fHbp resulted in an increased resistance of the Case isolate to complement-mediated killing in serum. Complementation of fHbp expression in the Carrier increased its serum resistance by approximately 8-fold. Moreover, a higher serum bactericidal antibody titre was seen for the Case isolate when using sera from mice immunized with Bexsero (GlaxoSmithKline), a vaccine containing fHbp as an antigenic component. This study highlights the role of fHbp in the differential complement resistance of the Case and the Carrier isolates. Expression of fHbp in the Case resulted in its increased survival in serum, possibly leading to active proliferation of the bacteria in blood and death of the student through IMD. Moreover, enhanced killing of the Case isolate by sera raised against an fHbp-containing vaccine, Bexsero, underlines the role and importance of fHbp in infection and immunity.

Postmarketing surveillance of adverse events following meningococcal B vaccination: data from Apulia Region, 2014-19

Since the multicomponent meningococcal B vaccine introduction, the Apulian Regional Health Authority implemented postmarketing surveillance program, as provided by Italian laws.

From National Pharmacovigilance Network, we selected 4CMenB AEFIs reported in Apulia from 01 January 2014 to 31 December 2019, while the number of 4 cMen B doses administered per year was obtained from the regional immunization database (GIAVA).

For each subject who experienced an adverse event following meningococcal B vaccine (AEFIs), a predefined form was filled in.

A total of 214 AEFIs (26.5 × 100.000 doses) were reported after any dose of MenB-4 c vaccination of which 58/214 (27.1%) were classified as serious (7.2 × 100,000 doses), 145/214 (67.8%) as not serious (180 × 100,000 doses), and 11/214 (5.1%) as undefined (1.3 × 100,000 doses).

The average age of subjects who experimented and AEFI was 30 months. The majority of serious AEFIs were reported in 2- to 11-month-old children (44/57; 77.2%). A total of 31/58 (3.8 × 100,000 doses; 53.4%) serious AEFIs were reported as having a ‘consistent causal association’ with vaccination. Of these, fever/hyperpyrexia was reported in 21/31 (2.6 × 100,000 doses; 67.7%); hypotonic-hyporesponsive episode was reported in 7/31 (0.9 × 100,000 doses [add %-age]) and was the most frequent adverse event with neurological symptoms. A total of 13/31 (41.9%) serious AEFIs classified as ‘consistent causal association’ were reported after the first dose of 4cMenB, of these 5/13 (38.5%) children did not complete the vaccination schedule.

Our data seemed to confirm, in a large population, the a good safety profile of the universal mass vaccination with 4CMENB.

Post-licensure observational safety study after meningococcal B vaccine 4CMenB (Bexsero) vaccination within the routine UK immunisation program

The study investigated the safety of 4-component meningococcal serogroup B vaccination (4CMenB) in routine care. 4CMenB exposure and seizures, febrile seizures and Kawasaki disease were identified from The Health Improvement Network (THIN) database of UK electronic primary healthcare records, 2015-2018. A self-controlled case series analysis was completed. Anaphylaxis, Guillain-Barré syndrome and acute disseminated encephalomyelitis were secondary outcomes. A total of 107,231 children aged 1-18 months received ≥1 doses of 4CMenB vaccination. Most 4CMenB exposure (93%) was on the same day as other vaccines within a complete national immunisation program stage. With day 0 as day of vaccination, 43 seizures occurred in days 0-6 after 239,505 doses, and 23 febrile seizures occurred in days 0-6, and 4 Kawasaki disease cases in days 1-28 after 194,929 4CMenB doses. Adjusted incidence rate ratios including all 4CMenB exposures were 1.43 (95%CI: 1.02-2.02) for seizures and 1.72 (95%CI: 1.08-2.75) for febrile seizures. There were insufficient cases to model Kawasaki disease, and no cases of the secondary outcomes in risk periods when they may be associated with the vaccination. This study shows few cases of the outcomes after vaccination including 4CMenB with an increased risk of seizures and febrile seizures. It is not possible to attribute the finding to one specific vaccination as the majority of 4CMenB was given with other vaccinations. Trial registration: NA.

Multicomponent meningococcal serogroup B vaccination elicits cross-reactive immunity in infants against genetically diverse serogroup C, W and Y invasive disease isolates

BACKGROUND

The multicomponent meningococcal serogroup B vaccine (4CMenB) is currently indicated for active immunization against invasive meningococcal disease caused by Neisseria meningitidis serogroup B (MenB). However, genes encoding the 4CMenB antigens are also variably present and expressed in strains belonging to other meningococcal serogroups. In this study, we evaluated the ability of antibodies raised by 4CMenB immunisation to induce complement-mediated bactericidal killing of non-MenB strains.

METHODS

A total of 227 invasive non-MenB disease isolates were collected between 1 July 2007 and 30 June 2008 from England and Wales, France, and Germany; 41 isolates were collected during 2012 from Brazil. The isolates were subjected to genotypic analyses. A subset of 147 isolates (MenC, MenW and MenY) representative of the meningococcal genetic diversity of the total sample were tested in the human complement serum bactericidal antibody assay (hSBA) using sera from infants immunised with 4CMenB.

RESULTS

Serogroup and clonal complex repertoires of non-MenB isolates were different for each country. For the European panel, MenC, MenW and MenY isolates belonged mainly to ST-11, ST-22 and ST-23 complexes, respectively. For the Brazilian panel, most MenC and MenW isolates belonged to the ST-103 and ST-11 complexes, respectively, and most MenY isolates were not assigned to clonal complexes. Of the 147 non-MenB isolates, 109 were killed in hSBA, resulting in an overall coverage of 74%.

CONCLUSION

This is the first study in which 147 non-MenB serogroup isolates have been analysed in hSBA to evaluate the potential of a MenB vaccine to cover strains belonging to other serogroups. These data demonstrate that antibodies raised by 4CMenB are able to induce bactericidal killing of 109 non-MenB isolates, representative of non-MenB genetic and geographic diversity. These findings support previous evidence that 4CMenB immunisation can provide cross-protection against non-MenB strains in infants, which represents an added benefit of 4CMenB vaccination.

Comparative transcriptomics between species attributes reactogenicity pathways induced by the capsular group B meningococcal vaccine, 4CMenB, to the membrane-bound endotoxin of its outer membrane vesicle component

The capsular group B meningococcal (MenB) four component vaccine (4CMenB) has been licensed for the prevention of invasive disease caused by MenB. The vaccine causes fever in infants, particularly when given in combination (concomitant) with other routinely-administered vaccines (routine), such as the standard diphtheria, tetanus, pertussis (DTP)-containing vaccine. To assess the suitability of a mouse immunisation model to study this phenomenon, we monitored temperature in mice after a second dose of routine vaccines, with or without 4CMenB, and compared the results with those in humans. Using this mouse model, we explored the reactogenicity of 4CMenB components by measuring changes in temperature, cytokines, and gene expression induced by 4CMenB, one of its components, wild-type or attenuated endotoxin outer membrane vesicles (OMVs), or lipopolysaccharide (LPS). A significant rise (p < 0.01) in temperature was observed in mice immunised with 4CMenB, wild-type OMVs, and LPS. RNA-sequencing of mouse whole blood revealed a gene signature shared by the 4CMenB, OMV, and LPS groups consisting of bacterial pattern recognition receptors and neutrophil activation marker genes. Sequencing of neutrophils isolated after concomitant 4CMenB identified cells expressing the OMV-associated genes Plek and Lcp1. Immunisation with 4CMenB or OMVs led to increased IL-6 in serum and significant upregulation (p < 0.0001) of prostaglandin-synthesising enzymes on brain tissue. These data demonstrate the suitability of a mouse model for assessing vaccine reactogenicity and strongly indicate that the fever following vaccination with 4CMenB in human infants is induced by endotoxin contained in the OMV component of the vaccine.

Standing on the shoulders of giants: two centuries of struggle against meningococcal disease

Meningococcal disease was first clinically characterised by Gaspard Vieusseux in 1805, and its causative agent was identified by Anton Weichselbaum in 1887, who named it Diplococcus intracellularis menigitidis. From the beginning, the disease was dreaded because of its epidemic nature, predilection for previously healthy children and adolescents, and high mortality. In the last decade of the 19th century, the concept of serum therapy for toxin-related bacterial diseases was identified. This concept was applied to meningococcal disease therapy, in an independent way, by Wilhelm Kolle, August von Wasserman, and Georg Jochmann in Germany, and Simon Flexner in the USA, resulting in the first successful approach for the treatment of meningococcal disease. During the first three decades of the 20th century, serum therapy was the standard treatment for meningococcal disease. With the advent of sulphamides first and then antibiotics, serum therapy was abandoned. The great challenges that infectious diseases medicine is facing and the awaiting menaces in the future in terms of increasing antibiotic resistance, emergence of new pathogens, and re-emergence of old ones without effective therapy, make passive immunotherapy a promising tool. Acknowledging the achievements of our predecessors might teach us some lessons to bring light to our future.

Do HCWs adequately know about meningitis and 4CMenB vaccine and recommend its use to parents? A cross sectional analysis in Campania Region, Italy

Invasive meningococcal disease (IMD) is a severe disease caused by various Neisseria meningitidis serogroups that represents a serious public health problem worldwide. In Italy, serogroups B and C are the major causes of IMD. On 14 January 2013, the European Medicines Agency authorized the use of the first vaccine available to protect against meningococcal serogroup B (4CMenB). The aim of this study was to assess the IMD epidemiology knowledge and 4CMenB vaccine attitudes of healthcare workers (HCWs) with regard to recommending this vaccine for use, vaccine practices and infectious disease control in the Campania region in Italy. A cross-sectional study was conducted among 293 HCWs (49.5% physicians and 46.4% nurses)interviewed using a self-administered questionnaire. The majority of the HCWs had sufficient knowledge about the disease incidence and lethality, but they were less informed about the higher risk age categories and the serogroups most frequently involved. Additionally, their knowledge about the vaccine was poor with regard to the targeted categories and side effects. Approximately30.0% of the HCWs reported incidences of fever and pain and swelling at the injection site. Moreover,32.8% of the HCWs knew that the risk of developing adverse reactions increases when the 4CMenB vaccine is co-administered with other vaccines. Overall, all of the HCWs were convinced that vaccinations are an important instrument for preventing infectious diseases, and they were aware of their central role in promoting the 4CmenB vaccination and their need to be better informed.

Meningococcal Antigen Typing System (MATS): A Tool to Estimate Global Coverage for 4CMenB, a Multicomponent Meningococcal B Vaccine

Meningococcal Antigen Typing System (MATS) is the combination of a sandwich ELISA (Enzyme Linked Immunosorbent Assay) developed to estimate the level of expression and immunoreactivity of the antigen components (fHbp, NHBA, and NadA) of the 4CMenB vaccine (Bexsero, GSK Vaccines) in circulating, serogroup B meningococcal (MenB) strains, with the molecular typing of PorA, the main antigenic component in the outer membrane vesicles (OMV). MATS has been proven to be a good surrogate of the accepted correlate of protection for meningococcus (hSBA), thus providing a quick, conservative and reproducible method to assess vaccine coverage. The method has been successfully transferred and standardized in several public health laboratories across Europe, North America, and Australia and used to screen thousands of isolates all over the world. Here we describe the sandwich ELISA method applied to assess the expression and cross-reactivity of fHbp, NHBA, and NadA in MenB isolates.

Human protective response induced by meningococcus B vaccine is mediated by the synergy of multiple bactericidal epitopes

4CMenB is the first broad coverage vaccine for the prevention of invasive meningococcal disease caused by serogroup B strains. To gain a comprehensive picture of the antibody response induced upon 4CMenB vaccination and to obtain relevant translational information directly from human studies, we have isolated a panel of human monoclonal antibodies from adult vaccinees. Based on the Ig-gene sequence of the variable region, 37 antigen-specific monoclonal antibodies were identified and produced as recombinant Fab fragments, and a subset also produced as full length recombinant IgG1 and functionally characterized. We found that the monoclonal antibodies were cross-reactive against different antigen variants and recognized multiple epitopes on each of the antigens. Interestingly, synergy between antibodies targeting different epitopes enhanced the potency of the bactericidal response. This work represents the first extensive characterization of monoclonal antibodies generated in humans upon 4CMenB immunization and contributes to further unraveling the immunological and functional properties of the vaccine antigens. Moreover, understanding the mechanistic nature of protection induced by vaccination paves the way to more rational vaccine design and implementation.

Emerging clinical experience with vaccines against group B meningococcal disease

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

Recent Progress in the Prevention of Serogroup B Meningococcal Disease

The widespread use of meningococcal polysaccharide conjugate vaccines has highlighted the challenge of providing protection against serogroup B disease. Over a period of 4 decades, vaccine development has focused on subcapsular protein antigens, first with outer membrane vesicle (OMV) vaccines against epidemic outbreaks, and more recently on new multicomponent vaccines designed to offer better cross-protection against the antigenically diverse strains responsible for endemic disease. Because of the low incidence of meningococcal disease, the protective efficacy of these vaccines has not been determined in clinical studies, and their licensure has been based on serological data; however, the serological assays used to predict protective coverage have limitations. As a result, evidence of the effectiveness of these vaccines against different strains and the contribution of specific antigens to protection can only be provided by epidemiological analyses following their implementation in sufficiently large populations. The recent inclusion of the four-component meningococcal serogroup B (4CMenB) vaccine, Bexsero, in the infant immunization program in the UK has provided preliminary evidence that the vaccine is effective. Ongoing surveillance will provide valuable data on its longer-term impact and antigenic coverage. Further development of protein-based vaccines against meningococcal disease is anticipated to improve antigenic coverage and adjust to changes in circulating strains. At the same time, alternative immunization strategies may be explored to improve overall vaccine effectiveness by, for example, protecting the youngest infants or providing herd protection.

Kawasaki disease and immunisation: A systematic review

BACKGROUND

Kawasaki disease is a complex and potentially serious condition. It has been observed in temporal relation to immunisation.

METHODS

We conducted a systematic literature review using various reference sources to review the available evidence published in the literature.

RESULTS

We identified twenty seven publications reporting a temporal association between immunisation and Kawasaki disease. We present a systematic review of data drawn from randomised controlled trials, observational studies, case series and reports, and reviews. Overall there was a lack of standardised case definitions, making data interpretation and comparability challenging.

CONCLUSIONS

Although a temporal relationship between immunisation and Kawasaki disease is suggested, evidence for an increased risk or a causal association is lacking. Implementation of a standardised Kawasaki disease case definition would increase confidence in the findings and add value to future studies of pre- or post-licensure vaccine safety studies.

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

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

Vaccines for the prevention of meningococcal capsular group B disease: What have we recently learned?

Meningococcal disease remains a feared and devastating cause of sepsis and meningitis. Disease incidence is highest among infants and children although a significant burden of disease is experienced by adolescents, young adults and those with specific risk-factors. Prevention of disease against capsular groups A, C, W and Y; 4 of the 5 most pathogenic groups is achievable using capsular polysaccharide vaccines. It has only recently been possible to provide protection against capsular group B (MenB) strains following the licensure of a 4 component group B vaccine (4CMenB) in Europe in 2013. Following licensure, 4CMenB has been used in specific at-risk groups and in response to outbreaks of MenB disease. The largest outbreak interventions have been in students at 2 universities in the United States and for all individuals aged 2 months to 20 years of age in Quebec, Canada. The vaccine was recommended in February 2014 for implementation into the UK infant schedule at 2, 4 and 12 months of age, although it has taken over 12 months to resolve procurement discussions to enable implementation. The UK recommendation incorporates prophylactic paracetamol with infant doses when 4CMenB is administered concomitantly with routine vaccines. This is based on recent data demonstrating the ability of paracetamol to reduce fever rates to background levels without impacting immunogenicity. Post-implementation surveillance will be important to provide vaccine efficacy data as this was not possible to determine in pre-licensure studies due to the relative infrequency of MenB cases.

Evaluation of a protective effect of in ovo delivered Campylobacter jejuni OMVs

Campylobacter jejuni is the most prevalent cause of a food-borne gastroenteritis in the developed world, with poultry being the main source of infection. Campylobacter jejuni, like other Gram-negative bacteria, constitutively releases outer membrane vesicles (OMVs). OMVs are highly immunogenic, can be taken up by mammalian cells, and are easily modifiable by recombinant engineering. We have tested their usefulness for an oral (in ovo) vaccination of chickens. Four groups of 18-day-old chicken embryos (164 animals) underwent injection of wt C. jejuni OMVs or modified OMVs or PBS into the amniotic fluid. The OMVs modifications relied on overexpression of either a complete wt cjaA gene or the C20A mutant that relocates to the periplasm. Fourteen days post-hatch chicks were orally challenged with live C. jejuni strain. Cecum colonization parameters were analyzed by two-way ANOVA with Tukey post-hoc test. The wtOMVs and OMVs with wtCjaA overexpression were found to confer significant protection of chicken against C. jejuni (p = 0.03 and p = 0.013, respectively) in comparison to PBS controls and are promising candidates for further in ovo vaccine development.

Meningococcal B vaccination: real-world experience and future perspectives

Invasive meningococcal disease (IMD) represents a severe risk for health. It can be considered the most dangerous vaccine-preventable disease due to the high probability of related permanent sequelae and death. The introduction in many countries of the conjugate vaccines against A, C, W135, and Y meningococcal serogroups influenced significantly the impact of the disease. Recently, the difficulties in obtaining an effective vaccine against meningococcal serogroup B (MenB) have been get over through the reverse vaccinology, enabling the recognition of some antigens providing a response against most of circulating MenB strains worldwide. The new 4cMenB vaccine is recommended in Europe, Canada, Australia, the USA, and some Latin American countries. Even if sound data on efficacy and safety profile are available, the results in terms of effectiveness are still limited. The management of the MenB outbreaks in two US universities demonstrated the ability to quickly achieve high vaccination coverage rates and no new cases among immunized subjects were assessed. It is desirable that the opportunity to complete preventive intervention against IMD offered by the new 4cMenB vaccine should be recognized and that this vaccine is included in the vaccination schedule to complete the panel of immunization against Neisseria meningitidis.

Background Paper for the update of meningococcal vaccination recommendations in Germany: use of the serogroup B vaccine in persons at increased risk for meningococcal disease

In December 2013 Bexsero® became available in Germany for vaccination against serogroup B meningococci (MenB). In August 2015 the German Standing Committee on Vaccination (STIKO) endorsed a recommendation for use of this vaccine in persons at increased risk of invasive meningococcal disease (IMD). This background paper summarizes the evidence underlying the recommendation. Bexsero® is based on surface protein antigens expressed by about 80% of circulating serogroup B meningococci in Germany. The paper reviews available data on immunogenicity and safety of Bexsero® in healthy children and adolescents; data in persons with underlying illness and on the effectiveness in preventing clinical outcomes are thus far unavailable.STIKO recommends MenB vaccination for the following persons based on an individual risk assessment: (1) Persons with congenital or acquired immune deficiency or suppression. Among these, persons with terminal complement defects and properdin deficiency, including those under eculizumab therapy, are at highest risk with reported invasive meningococcal disease (IMD) incidences up 10,000-fold higher than in the general population. Persons with asplenia were estimated to have a ~ 20-30-fold increased risk of IMD, while the risk in individuals with other immune defects such as HIV infection or hypogammaglobulinaemia was estimated at no more than 5-10-fold higher than the background risk. (2) Laboratory staff with a risk of exposure to N. meningitidis aerosols, for whom an up to 271-fold increased risk for IMD has been reported. (3) Unvaccinated household (-like) contacts of a MenB IMD index case, who have a roughly 100-200-fold increased IMD risk in the year after the contact despite chemoprophylaxis. Because the risk is highest in the first 3 months and full protective immunity requires more than one dose (particularly in infants and toddlers), MenB vaccine should be administered as soon as possible following identification of the serogroup of the index case.

Cellular Immune Responses in Humans Induced by Two Serogroup B Meningococcal Outer Membrane Vesicle Vaccines Given Separately and in Combination

MenBvac and MeNZB are safe and efficacious outer membrane vesicle (OMV) vaccines against serogroup B meningococcal disease. Antibody responses have previously been investigated in a clinical trial with these two OMV vaccines given separately (25 μg/dose) or in combination (12.5 and 12.5 μg/dose) in three doses administered at 6-week intervals. Here, we report the results from analyzing cellular immune responses against MenBvac and MeNZB OMVs in terms of antigen-specific CD4(+)T cell proliferation and secretion of cytokines. The proliferative CD4(+)T cell responses to the combined vaccine were of the same magnitude as the homologous responses observed for each individual vaccine. The results also showed cross-reactivity in the sense that both vaccine groups receiving separate vaccines responded to both homologous and heterologous OMV antigen when assayed for antigen-specific cellular proliferation. In addition, a multiplex bead array assay was used to analyze the presence of Th1 and Th2 cytokines in cell culture supernatants. The results showed that gamma interferon, interleukin-4 (IL-4), and IL-10 responses could be detected as a result of vaccination with both the MenBvac and the MeNZB vaccines given separately, as well as when given in combination. With respect to cross-reactivity, the cytokine results paralleled the observations made for proliferation. In conclusion, the results demonstrate that cross-reactive cellular immune responses involving both Th1 and Th2 cytokines can be induced to the same extent by different tailor-made OMV vaccines given either separately or in combination with half the dose of each vaccine.

Type VI secretion system sheaths as nanoparticles for antigen display

The bacterial type 6 secretion system (T6SS) is a dynamic apparatus that translocates proteins between cells by a mechanism analogous to phage tail contraction. T6SS sheaths are cytoplasmic tubular structures composed of stable VipA-VipB (named for ClpV-interacting protein A and B) heterodimers. Here, the structure of the VipA/B sheath was exploited to generate immunogenic multivalent particles for vaccine delivery. Sheaths composed of VipB and VipA fused to an antigen of interest were purified from Vibrio cholerae or Escherichia coli and used for immunization. Sheaths displaying heterologous antigens generated better immune responses against the antigen and different IgG subclasses compared with soluble antigen alone. Moreover, antigen-specific antibodies raised against sheaths presenting Neisseria meningitidis factor H binding protein (fHbp) antigen were functional in a serum bactericidal assay. Our results demonstrate that multivalent nanoparticles based on the T6SS sheath represent a versatile scaffold for vaccine applications.

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

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

Vasculitis as an adverse event following immunization - Systematic literature review

BACKGROUND

Several types of vasculitis have been observed and reported in temporal association with the administration of various vaccines. A systematic review of current evidence is lacking.

OBJECTIVE

This systematic literature review aimed to assess available evidence and current reporting practice of vasculitides as adverse events following immunization (AEFI).

METHODS

We reviewed the literature from 1st January 1994 to 30th June 2014. This review comprises randomized controlled trials, observational studies, case series, case reports, reviews and comments regardless of vaccine and target population.

RESULTS

The initial search resulted in the identification of 6656 articles. Of these, 157 articles were assessed for eligibility and 75 studies were considered for analysis, including 6 retrospective/observational studies, 2 randomized controlled trials, 7 reviews, 11 case series, 46 case reports and 3 comments. Most of the larger, higher quality studies found no causal association between vaccination and subsequent development of vasculitis, including several studies on Kawasaki disease and Henoch-Schönlein purpura (IgA vasculitis). Smaller case series reported a few cases of vasculitis following BCG and vaccines against influenza and hepatitis. Only 24% of the articles reported using a case definition of vasculitis.

CONCLUSIONS

Existing literature does not allow establishing a causative link between vaccination and vasculitides. Further investigations were strengthened by the use of standardized case definitions and methods for data collection, analysis and presentation to improve data comparability and interpretation of vasculitis cases following immunization.

Persistence of specific bactericidal antibodies at 5 years of age after vaccination against serogroup B meningococcus in infancy and at 40 months

BACKGROUND

The multicomponent serogroup B meningococcal (4CMenB) vaccine induces antibodies against indicator strains of serogroup B meningococcus under various schedules. We investigated the persistence of antibodies in 5-year-old children 18-20 months after their last dose (at about 3.5 years of age).

METHODS

We assessed 5-year-old children who received the 4CMenB vaccine or a recombinant protein vaccine in a previous randomized trial. We also recruited 50 vaccine-naive 5-year-olds and administered 2 doses of 4CMenB to each child. We measured serum bactericidal antibody titres against 4 indicator strains of serogroup B meningococcus matched to each individual vaccine component and against 4 mismatched strains.

RESULTS

Of those who received the 4CMenB vaccine at 2, 4, 6, 12 and 40 months (n = 16), the percentage with protective antibody titres (≥ 1:4) at 60 months ranged from 44% to 88% against matched strains and from 13% to 81% against mismatched strains. Loss of protective titres was also observed for those who received the 4CMenB vaccine at 12, 40 and 42 months (n = 5) (80%-100% against matched strains, 60%-100% against mismatched strains) or at 40 and 42 months (n = 29) (31%-100% against matched strains, 41%-81% against mismatched strains). Administering the 4CMenB vaccine to 5-year-old children yielded protective titres against matched strains in 92%-100% and against mismatched strains in 59%-100%. The majority of these children reported injection-site pain (40/50 [80%] after dose 1, 39/46 [85%] after dose 2) and erythema (47/50 [94%] and 40/46 [87%], respectively); rates of fever were low (5/50 [10%] and 2/46 [4%], respectively).

INTERPRETATION

Waning of immunity by 5 years of age occurred after receipt of the 4CMenB vaccine in infancy, even with an additional booster at 40 months. The 4CMenB vaccine is immunogenic and was fairly well tolerated by 5-year-old children, although injection-site pain was noteworthy.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT01027351.

Clonal analysis of meningococci during a 26 year period prior to the introduction of meningococcal serogroup C vaccines

Meningococcal disease remains a public health burden in the UK and elsewhere. Invasive Neisseria meningitidis, isolated in Scotland between 1972 and 1998, were characterised retrospectively to examine the serogroup and clonal structure of the circulating population. 2607 isolates causing invasive disease were available for serogroup and MLST analysis whilst 2517 were available for multilocus sequence typing (MLST) analysis only. Serogroup distribution changed from year to year but serogroups B and C were dominant throughout. Serogroup B was dominant throughout the 1970s and early 1980s until serogroup C became dominant during the mid-1980s. The increase in serogroup C was not associated with one particular sequence type (ST) but was associated with a number of STs, including ST-8, ST-11, ST-206 and ST-334. This is in contrast to the increase in serogroup C disease seen in the 1990s that was due to expansion of the ST-11 clonal complex. While there was considerable diversity among the isolates (309 different STs among the 2607 isolates), a large proportion of isolates (59.9%) were associated with only 10 STs. These data highlight meningococcal diversity over time and the need for ongoing surveillance during the introduction of new meningococcal vaccines.

Vibrio cholerae ghosts (VCG) exert immunomodulatory effect on dendritic cells for enhanced antigen presentation and induction of protective immunity

BACKGROUND

We previously showed that the Vibrio cholerae ghost platform (VCG; empty V. cholerae cell envelopes) is an effective delivery system for vaccine antigens promoting the induction of substantial immunity in the absence of external adjuvants. However, the mechanism by which these cell envelopes enhance immunity and stimulate a predominantly Th1 cellular and humoral immune response has not been elucidated. We hypothesized that the immunostimulatory ability of VCG involves dendritic cell (DC) activation.

OBJECTIVE

The aims of this study were: a) to investigate the ability of DCs [using mouse bone marrow-derived DCs (BMDCs) as a model system] to take up and internalize VCGs; b) to evaluate the immunomodulatory effect of internalized VCGs on DC activation and maturation and their functional capacity to present chlamydial antigen to naïve and infection-sensitized CD4+ T cells and; c) to evaluate the ability of VCGs to enhance the protective immunity of a chlamydial antigen.

RESULTS

VCGs were efficiently internalized by DCs without affecting their viability and modulated DC-mediated immune responses. VCG-pulsed DCs showed increased secretion of proinflammatory cytokines and expression of co-stimulatory molecules associated with DC maturation in response to stimulation with UV-irradiated chlamydial elementary bodies (UV-EBs). Furthermore, this interaction resulted in effective chlamydial antigen presentation to infection-sensitized but not naïve CD4+ T cells and enhancement of protective immunity.

CONCLUSIONS

The present study demonstrated that VCGs activate DCs leading to the surface expression of co-stimulatory molecules associated with DC activation and maturation and enhancement of protective immunity induced by a chlamydial antigen. The results indicate that the immunoenhancing activity of VCG for increased T-cell activation against antigens is mediated, at least in part, through DC triggering. Thus, VCGs could be harnessed as immunomodulators to target antigens to DCs for enhancement of protective immunity against microbial infections.

Neisseria meningitidis: pathogenesis and immunity

The recent advances in cellular microbiology, genomics, and immunology has opened new horizons in the understanding of meningococcal pathogenesis and in the definition of new prophylactic intervention. It is now clear that Neissera meningitidis has evolved a number of surface structures to mediate interaction with host cells and a number of mechanisms to subvert the immune system and escape complement-mediated killing. In this review we report the more recent findings on meningococcal adhesion and on the bacteria-complement interaction highlighting the redundancy of these mechanisms. An effective vaccine against meningococcus B, based on multiple antigens with different function, has been recently licensed. The antibodies induced by the 4CMenB vaccine could mediate bacterial killing by activating directly the classical complement pathway or, indirectly, by preventing binding of fH on the bacterial surface and interfering with colonization.

Novel aspects of atypical haemolytic uraemic syndrome and the role of eculizumab

The haemolytic uraemic syndrome (HUS) is part of a spectrum of thrombotic microangiopathies. The most common etiologies of HUS are the ones seen in childhood caused by an infection of Shiga toxin-producing Escherichia coli, HUS caused by an infection with Streptococcus pneumoniae and HUS due to abnormalities in the alternative pathway of the complement system. In the past decade, enormous progress has been made in understanding the pathogenesis in the latter group of patients. The analysis of genes that encode for complement regulatory proteins and the development of assays for measuring the activity of ADAMTS13 and the detection of antibodies against factor H contributed significantly to the diagnostic tools in patients with HUS. These assays have made it possible to clearly differentiate between thrombotic thrombocytopenic purpura and various forms of HUS. With the introduction of eculizumab, a monoclonal anti-C5 inhibitor, in the clinical arena as effective treatment of most complement-mediated forms of HUS, a new era of treatment in HUS has begun. We review the recent advances in HUS, with the focus on treatment. We discuss unsolved questions, which should be addressed in future studies.

Human factor H (FH) impairs protective meningococcal anti-FHbp antibody responses and the antibodies enhance FH binding

The meningococcal 4CMenB vaccine (Bexsero; Novartis) contains four antigens that can elicit serum bactericidal activity, one of which is factor H (FH)-binding protein (FHbp). FHbp specifically binds human complement FH. When humans are immunized, FHbp is expected to form a complex with FH, which could affect immunogenicity and safety. Wild-type mice (whose FH does not bind to FHbp) and human FH transgenic mice were immunized with three doses of 4CMenB, and their responses were compared. There were no significant differences between the serum bactericidal responses of transgenic and wild-type mice to strains with all of the antigens mismatched for 4CMenB except PorA or NadA. In contrast, against a strain mismatched for all of the antigens except FHbp, the transgenic mice had 15-fold weaker serum bactericidal antibody responses (P = 0.0006). Binding of FH downregulates complement. One explanation for the lower anti-FHbp serum bactericidal activity in the transgenic mice is that their postimmunization serum samples enhanced the binding of FH to FHbp, whereas the serum samples from the wild-type mice inhibited FH binding. Control antiserum from transgenic mice immunized with a low-FH-binding mutant FHbp (R41S) vaccine inhibited FH binding. Two 4CMenB-vaccinated transgenic mice developed serum IgM autoantibodies to human FH. Thus, human FH impairs protective serum anti-FHbp antibody responses, in part by skewing the antibody repertoire to FHbp epitopes outside the FH binding site. FHbp vaccines that bind FH may elicit FH autoantibodies. Mutant FHbp antigens with low FH binding could improve protection and, potentially, vaccine safety in humans.

IMPORTANCE

Two serogroup B meningococcal vaccines contain a novel antigen called factor H (FH)-binding protein (FHbp). FHbp specifically binds human FH, a plasma protein that downregulates complement. One vaccine (4CMenB; Novartis) is licensed in Europe, Canada, and Australia. When humans are immunized, FHbp can complex with FH. We compared the immunogenicity of 4CMenB vaccine in wild-type mice, whose own FH does not bind to FHbp, and human FH transgenic mice. Transgenic mice had respective antibody responses similar to those of wild-type mice to 4CMenB antigens that do not bind FH. However, the protective antibody responses of the transgenic mice to FHbp were impaired, largely because the antibodies did not inhibit but rather enhanced the binding of FH to FHbp. Two transgenic mice developed serum IgM autoantibodies to FH. Mutant FHbp antigens with low FH binding likely will elicit greater protection in humans than FHbp vaccines that bind FH and have a lower risk of FH autoantibodies.

Concurrent meningococcal and herpes simplex infection in a non-immunocompromised child

A previously well 11-month-old infant presented with lethargy, a blanching rash, vomiting and diarrhoea. She was diagnosed with suspected gastroenteritis and discharged. The patient deteriorated and re-presented 24 h later with lumbar puncture (LP) confirming Neisseria meningitidis. Following an initial good response to ceftriaxone, the patient then developed a blistering facial rash on day 3 for which topical aciclovir was started with no improvement. She subsequently developed fever and redeveloped a rising C reactive protein (CRP). A CT of the head on day 6 was normal, however a repeat LP on day 7 showed persistently raised cerebrospinal fluid (CSF), white cell count (WCC), high proteins and low CSF glucose. A CSF viral PCR confirmed concurrent herpes simplex virus (HSV) type 1 for which parenteral aciclovir was started. The patient responded well to bacterial and viral anti-infective treatments and was subsequently discharged on day 16 with no neurological sequelae.

Molecular and serological diversity of Neisseria meningitidis carrier strains isolated from Italian students aged 14 to 22 years

Neisseria meningitidis is an obligate human commensal that commonly colonizes the oropharyngeal mucosa. Carriage is age dependent and very common in young adults. The relationships between carriage and invasive disease are not completely understood. In this work, we performed a longitudinal carrier study in adolescents and young adults (173 subjects). Overall, 32 subjects (18.5%) had results that were positive for meningococcal carriage in at least one visit (average monthly carriage rate, 12.1%). Only five subjects tested positive at all four visits. All meningococcal isolates were characterized by molecular and serological techniques. Multilocus sequence typing, PorA typing, and sequencing of the 4CMenB vaccine antigens were used to assess strain diversity. The majority of positive subjects were colonized by capsule null (34.4%) and capsular group B strains (28.1%), accounting for 23.5% and 29.4% of the total number of isolates, respectively. The fHbp and nhba genes were present in all isolates, while the nadA gene was present in 5% of the isolates. The genetic variability of the 4CMenB vaccine antigens in this collection was relatively high compared with that of other disease-causing strain panels. Indications about the persistence of the carriage state were limited to the time span of the study. All strains isolated from the same subject were identical or cumulated minor changes over time. The expression levels and antigenicities of the 4CMenB vaccine antigens in each strain were analyzed by the meningococcal antigen typing system (MATS), which revealed that expression can change over time in the same individual. Future analysis of antigen variability and expression in carrier strains after the introduction of the MenB vaccine will allow for a definition of its impact on nasopharyngeal/oropharyngeal carriage.