Induction of salivary antibody levels in Dutch adolescents after immunization with monovalent meningococcal serogroup C or quadrivalent meningococcal serogroup A, C, W and Y conjugate vaccine

Vaccination of Rabbits with a Cholera Conjugate Vaccine Comprising O-Specific Polysaccharide and a Recombinant Fragment of Tetanus Toxin Heavy Chain Induces Protective Immune Responses against Vibrio cholerae O1

There is a need for next-generation cholera vaccines that provide high-level and durable protection in young children in cholera-endemic areas. A cholera conjugate vaccine (CCV) is in development to address this need. This vaccine contains the O-specific polysaccharide (OSP) of Vibrio cholerae O1 conjugated via squaric acid chemistry to a recombinant fragment of the tetanus toxin heavy chain (OSP:rTTHc). This vaccine has been shown previously to be immunogenic and protective in mice and found to be safe in a recent preclinical toxicological analysis in rabbits. We took advantage of excess serum samples collected as part of the toxicological study and assessed the immunogenicity of CCV OSP:rTTHc in rabbits. We found that vaccination with CCV induced OSP-, lipopolysaccharide (LPS)-, and rTTHc-specific immune responses in rabbits, that immune responses were functional as assessed by vibriocidal activity, and that immune responses were protective against death in an established virulent challenge assay. CCV OSP:rTTHc immunogenicity in two animal model systems (mice and rabbits) is encouraging and supports further development of this vaccine for evaluation in humans.

Antibodies against Neisseria meningitidis serogroups A, C, W and Y in serum and saliva of Norwegian adolescents

INTRODUCTION

The incidence of invasive meningococcal disease (IMD) among Norwegian 16-19-year-olds was 1-7/100,000 in the decade before the COVID-19 pandemic, with serogroup Y (MenY) dominance. In contrast to many other European countries, meningococcal vaccines are not part of the national immunisation program (NIP) in Norway. This cross-sectional study aimed to measure the degree of natural immunity against Neisseria meningitidis among adolescents in Norway to evaluate the need for introducing tetravalent meningococcal conjugate vaccine (MCV4) in the NIP.

MATERIALS AND METHODS

Serum and saliva samples were collected from students in upper and lower secondary schools in Norway in 2018. Samples were analysed for meningococcal capsular polysaccharide (PS)-specific antibodies using a bead-based multiplex immunoassay. PS-specific antibody levels were linked to data on meningococcal carriage, vaccination status and risk factors for carriage (assessed with questionnaire) and analysed by linear regression of log transformed concentrations. A subset of samples from unvaccinated individuals was analysed for serum bactericidal antibodies (SBA).

RESULTS

A total of 1344 participants, median age 16 years (range 12-24), were included in the study. Overall, 60.9% of the participants were female and 1137 (84.6%) were not vaccinated with MCV4. PS-specific antibody concentrations in serum and saliva were low among unvaccinated individuals for all serogroups and only 6.7-20.0% of the subpopulation with high PS-specific antibodies assessed with SBA had protective levels. Unvaccinated MenY carriers had higher levels of MenY anti-PS IgG in serum and IgA in saliva than those not carrying MenY. Use of Swedish snus was associated with lower anti-PS IgG levels in serum and waterpipe use with lower anti-PS IgG levels in saliva.

CONCLUSION

Unvaccinated adolescents in Norway have a low degree of natural immunity against the serogroups of N. meningitidis predominating among cases of IMD in this age group. Therefore, introduction of MCV4 for adolescents in the NIP is recommended.

Scalable production and immunogenicity of a cholera conjugate vaccine

There is a need to develop cholera vaccines that are protective in young children under 5 years of age, which induce long-term immunity, and which can be incorporated into the Expanded Programme of Immunization (EPI) in cholera-endemic countries. The degree of protection afforded by currently available oral cholera vaccines (OCV) to young children is significantly lower than that induced by vaccination of older vaccine recipients. Immune responses that protect against cholera target the O-specific polysaccharide (OSP) of Vibrio cholerae, and young children have poor immunological responses to bacterial polysaccharides, which are T cell independent antigens. To overcome this, we have developed a cholera conjugate vaccine (CCV) containing the OSP of V. cholerae O1, the main cause of endemic and epidemic cholera. Here, we describe production of CCV through a scalable manufacturing process and preclinical evaluation of immunogenicity in the presence and absence of aluminum phosphate (alum) as an adjuvant. The vaccine displays V. cholerae O1 Inaba OSP in sun-burst display via single point attachment of core oligosaccharide to a recombinant tetanus toxoid heavy chain fragment (rTTHc). Two different pilot-scale production batches of non-GMP CCV were manufactured and characterized in terms of physico-chemical properties and immunogenicity. In preclinical testing, the vaccine induced OSP- and lipopolysaccharide (LPS)-specific IgG and IgM responses, vibriocidal responses, memory B cell responses, and protection in a V. cholerae O1 challenge model. The addition of alum to the administered vaccine increased OSP-specific immune responses. These results support evaluation of CCV in humans.

4CMenB vaccine and its role in preventing transmission and inducing herd immunity

INTRODUCTION

: Vaccination is the most effective method of protecting people from invasive meningococcal disease (IMD). Of all the capsular groups, B is the most common cause of invasive meningococcal disease in many parts of the world. Despite this, adolescent meningococcal B vaccine programs have not been implemented globally, partly due to the lack of evidence for herd immunity afforded by meningococcal B vaccines.

AREAS COVERED

This review aims to synthesise the available evidence on recombinant 4CMenB vaccines' ability to reduce pharyngeal carriage and therefore provide indirect (herd) immunity against IMD.

EXPERT OPINION

There is some evidence that the 4CMenB vaccine may induce cross-protection against non-B carriage of meningococci. However, the overall body of evidence does not support a clinically significant reduction in carriage of disease-associated or group B meningococci following 4CMenB vaccination. No additional cost-benefit from herd immunity effects should be included when modelling the cost-effectiveness of 4CMenB vaccine programs against group B IMD. 4CMenB immunisation programs should focus on direct (individual) protection for groups at greatest risk of meningococcal disease.

Future meningococcal B and combination vaccines being developed should consider the impact of the vaccine on carriage as part of their clinical evaluation.

Impact of MenAfriVac on Meningococcal A Meningitis in Cameroon: A Retrospective Study Using Case-by-Case-Based Surveillance Data from 2009 to 2015

Meningococcal meningitis is a public health concern in Africa. Conjugated vaccine against serogroup A Neisseria meningitidis (MenAfriVac) was used in mass vaccination and was proved to have a good impact in the meningitis belt. There is a lack of information about the impact of this intervention in Cameroon after mass vaccination was undertaken. This study aimed at filling the gap in its unknown impact in Cameroon. A retrospective longitudinal study using biological monitoring data of case-by-case-based surveillance for meningitis was obtained from the National Reference Laboratories from 1 January 2009 to 20 September 2015. Immunization coverage data were obtained from Regional Public Health Delegations where immunizations took place. We compared the risks of vaccine serogroup occurrence before and after vaccinations and calculated the global impact using Halloran's formula. Annual cases of meningitis A decreased gradually from 92 in 2011 to 34 in 2012 and then to 1 case in 2013, and since 2014, no cases have been detected. The impact was estimated at 14.48% (p=0.41) in 2012 and then at 98.63% (p < 0.0001) after the end of vaccinations in 2013. This survey confirms the effectiveness of the MenAfriVac vaccine in Cameroon as expected by the WHO. The surveillance must be pursued and enhanced to monitor coming immunizations measures with multivalent conjugated vaccines for this changing threat.

'B Part of It' School Leaver study: a repeat cross-sectional study to assess the impact of increasing coverage with meningococcal B (4CMenB) vaccine on carriage of Neisseria meningitidis

BACKGROUND

Recombinant protein-based vaccines targeting serogroup B meningococci protect against invasive disease, but impacts on carriage are uncertain. This study assessed carriage prevalence of disease-associated meningococci from 2018-2020, as the proportion of vaccinated adolescents increased following introduction of a school-based 4CMenB immunisation program.

METHODS

Eligible participants who completed high school (age 17-25) in South Australia in the previous year had an oropharyngeal swab taken and completed a risk factor questionnaire. Disease-associated meningococci (genogroups A, B, C, W, X, Y) were detected by meningococcal and genogroup-specific polymerase chain reaction.

RESULTS

The final analysis included 4104 participants in 2018, 2690 in 2019, and 1338 in 2020. The proportion vaccinated with 4CMenB increased from 43% in 2018, to 78% in 2019, and 76% in 2020. Carriage prevalence of disease-associated meningococci in 2018 was 225/4104 (5.5%). There was little difference between the carriage prevalence in 2019 (134/2690, 5.0%, adjusted odds ratio [aOR] 0.82, 95% CI 0.64-1.05) and 2020 (68/1338, 5.1% aOR 0.82, 95% CI 0.57-1.17) compared to 2018.

CONCLUSIONS

Increased 4CMenB uptake in adolescents was not associated with a decline in carriage of disease-associated meningococci. 4CMenB immunisation programs should focus on direct (individual) protection for groups at greatest risk of disease.

Effectiveness of Meningococcal Vaccines at Reducing Invasive Meningococcal Disease and Pharyngeal Neisseria meningitidis Carriage: A Systematic Review and Meta-analysis

BACKGROUND

Invasive meningococcal disease (IMD), caused by Neisseria meningitidis, leads to significant morbidity and mortality worldwide. This review aimed to establish the effectiveness of meningococcal vaccines at preventing IMD and N. meningitidis pharyngeal carriage.

METHODS

A search within PubMed, Embase, Scopus, and unpublished studies up to 1 February 2020 was conducted.

RESULTS

After removal of duplicates, 8565 studies were screened and 27 studies included. Protection was provided by meningococcal C vaccines for group C IMD (odds ratio [OR], 0.13 [95% confidence interval {CI}, .07-.23]), outer membrane vesicle (OMV) vaccines against group B IMD (OR, 0.35 [95% CI, .25-.48]), and meningococcal A, C, W, Y (MenACWY) vaccines against group ACWY IMD (OR, 0.31 [95% CI, .20-.49]). A single time series analysis found a reduction following an infant 4CMenB program (incidence rate ratio, 0.25 [95% CI, .19-.36]). Multivalent MenACWY vaccines did not reduce carriage (relative risk [RR], 0.88 [95% CI, .66-1.18]), unlike monovalent C vaccines (RR, 0.50 [95% CI, .26-.97]). 4CMenB vaccine had no effect on group B carriage (RR, 1.12 [95% CI, .90-1.40]). There was also no reduction in group B carriage following MenB-FHbp vaccination (RR, 0.98 [95% CI, .53-1.79]).

CONCLUSIONS

Meningococcal conjugate C, ACWY, and OMV vaccines are effective at reducing IMD. A small number of studies demonstrate that monovalent C conjugate vaccines reduce pharyngeal N. meningitidis carriage. There is no evidence of carriage reduction for multivalent MenACWY, OMV, or recombinant MenB vaccines, which has implications for immunization strategies.

CLINICAL TRIALS REGISTRATION

CRD42018082085 (PROSPERO).

Impact of Meningococcal B (4CMenB) Vaccine on Pharyngeal Neisseria meningitidis Carriage Density and Persistence in Adolescents

BACKGROUND

Higher density of Neisseria meningitidis carriage may be associated with transmission of the meningococcus. Our aim was to establish the impact of meningococcal B (4CMenB) vaccine on N. meningitidis carriage density.

METHODS

We compared 4CMenB vaccine to control among 913 South Australian students aged approximately 15-18 years in a cluster randomized trial who had N. meningitidis carriage at 12 months. Oropharyngeal swabs were collected at baseline and 12 months later to detect N. meningitidis carriage. Colony-forming units per milliliter (CFU/mL) were estimated by generating a standard curve that plotted quantitative polymerase chain reaction cycle threshold values against log-normalized CFU.

RESULTS

Among the 913 students with N. meningitidis carriage at 12 months, there was no difference in mean carriage density between the vaccinated (n = 434; 3.80 log CFU/mL [standard deviation {SD}, 1.29]) and control group (n = 479; 3.73 log CFU/mL [SD, 1.30]; P = .51). Higher N. meningitidis carriage density at baseline was associated with an increase in the odds of persistent carriage at 12 months (n = 504; odds ratio [OR] per 1.0 log CFU/mL increase in density, 1.36 [95% confidence interval {CI}, 1.17-1.58]; P < .001). Students with baseline carriage who were vaccinated had decreased persistent N. meningitidis carriage at 12 months compared to unvaccinated students (81/260 [31%] vs 105/244 [43%]; OR, 0.60 [95% CI, .40-.90]; P = .01).

CONCLUSIONS

4CMenB vaccine did not reduce carriage density of N. meningitidis 12 months postvaccination, despite increased carriage clearance. Higher carriage density is likely to enable transmission through prolonged periods of population exposure.

CLINICAL TRIALS REGISTRATION

NCT03089086.

Herd Protection against Meningococcal Disease through Vaccination

Reduction in the transmission of Neisseria meningitidis within a population results in fewer invasive disease cases. Vaccination with meningococcal vaccines composed of high weight capsular polysaccharide without carrier proteins has minimal effect against carriage or the acquisition of carriage. Conjugate vaccines, however, elicit an enhanced immune response which serves to reduce carriage acquisition and hinder onwards transmission. Since the 1990s, several meningococcal conjugate vaccines have been developed and, when used in age groups associated with higher carriage, they have been shown to provide indirect protection to unvaccinated cohorts. This herd protective effect is important in enhancing the efficiency and impact of vaccination. Studies are ongoing to assess the effect of protein-based group B vaccines on carriage; however, current data cast doubt on their ability to reduce transmission.

JUSTIFICATION OF SELECTION OF MEANS AND METHODS OF THE ORAL CAVITY HYGIENE IN CHILDREN WITH CYSTIC FIBROSIS

Cystic fibrosis (CF) promotes the development of gingivitis in children. The high prevalence and early manifestation of gingivitis is due to a combination of many factors. The pathogenic mechanisms of cystic fibrosis lead to disruption of normal physiological processes in the oral cavity, in particular, to a decrease in the level of salivation, to an increase in the viscosity of saliva, to a suppression of local immunity. Therefore, poor oral hygiene contributes to oral diseases. The aim of the study was to determine the level of oral hygiene in children with CF as one of the reasons for the development of gingivitis, and to select dental hygiene products that active towards factors that affect plaque. Material and methods. A total of 24 children with CF in the Ukrainian population participated in the study. The hygienic index OHI-S (J. C. Green, J. R. Wermillion, 1964) was calculated. The data were analyzed using Student’s criterions. The analysis was performed with a confidence level of 95 %. Results. The level of hygiene of the oral cavity was unsatisfactory among patients (OHI-S=2.19±0.11). Hygiene methods and dental hygiene products, to taking into account the manifestation of the pathogenesis of somatic disease, were selected. A follow-up study after 3 months revealed a significant positive trend in indicators of oral hygiene. Conclusions. This study has shown the low level of oral hygiene in children with CF. Hygienic education and motivation of these patients could help them achieve a higher level of oral health knowledge and are important starting points for the treatment and prevention of gingivitis. There was a significant improvement of the oral hygiene level after training children and after the proper selection of hygiene products. The dentists should use means and methods that have not contraindicate in patients of this category. It is recommended to monitore the hygiene indices to establish the effectiveness of the measures and necessity for individually therapy correction.

Immune surveillance for vaccine-preventable diseases

INTRODUCTION

Immunesurveillance is an important tool to monitor the protection of the population against vaccine-preventable diseases, which is currently mostly based on the detection of specific serum antibodies. However, the landscape of immune surveillance is changing, driven by emerging and evolving pathogens, changes in the age distribution of the population and scientific understanding of protective immunity, necessitating a comprehensive review.

AREAS COVERED

To anticipate these changes, reliable and high-throughput detection of antibody levels is desired to enable screening in larger population settings. Antibody levels alone do not always equate with protection and may require additional functional testing of the antibodies or immune cell-based assays. In addition, the location (systemic or locally mucosal) of the infection and whether the antibodies are induced through infection or vaccination have implications for both immune protection and assessing immune status.

EXPERT COMMENTARY

In order to perform multicenter studies on many samples for multiple antigens, more validated reference materials and wider adoption of high-throughput techniques are needed. The field of serosurveillance will also benefit from better correlates of protection and understanding of (local) mechanisms of protection. Here we give an overview of the current state-of-the-art of serosurveillance and how the field could move forward.

Parental Knowledge about Meningococcal Disease and Vaccination Uptake among 0⁻5 years Old Polish Children

In Poland, in addition to mandatory, free of charge vaccines, listed in the national immunization schedule, numerous self-paid vaccinations are recommended, including meningococcal vaccination (MV). To assess MV uptake among ≤5-year-old children and to evaluate parental knowledge and attitudes regarding invasive meningococcal disease (IMD). A cross-sectional study was conducted in 2018 among 350 parents (mean age: 32.3 years), attending three randomly selected primary care clinics in Szczecin region, Poland. Anonymous questionnaires were administered to the parents by researchers, present at the time the survey was conducted, to self-complete on a voluntary basis. Chi-square or Fisher’s exact for categorical and Mann–Whitney U test for continuous variables. Variables significantly (p < 0.05) associated with ‘good knowledge’ in the bivariate analysis were used to build a logistic regression model. It was found that the response rate was 93.4%, and MV uptake among children was 29.5%. The main knowledge sources were medical staff and media; 72.5% had ever received information about IMD. Only 18.8% of parents self-assessed their knowledge regarding IMD as good; 61.8% scored >50% in the knowledge test 58.9% knew the mode of transmission, 58.7% recognized the severity of meningitis, and 79.7% knew that bacterial meningitis is a vaccine-preventive disease. Knowledge regarding IMD was higher among parents with higher educational level (OR = 3.37; p = 0.01), from urban facilities (OR = 2.20; p = 0.02), who received previous information about IMD (OR = 2.85; p = 0.01) and self-assessed their knowledge as good (OR = 2.59; p = 0.04). Low MV coverage among children up to five years old and knowledge gaps about IMD call for awareness campaigns which may increase the coverage. Although educational interventions should cover all parents, those from provincial facilities, representing lower education level need special attention.

Use of saliva to monitor meningococcal vaccine responses: proposing a threshold in saliva as surrogate of protection

Background

Mucosal antibodies against capsular polysaccharides offer protection against acquisition and carriage of encapsulated bacteria like Neisseria meningitidis serogroup C. Measurements of salivary antibodies as replacement for blood testing has important (cost-effective) advantages, particular in studies that assess the impact of large-scale vaccination or in populations in which blood sampling is difficult. This study aimed to estimate a threshold for meningococcal IgG salivary antibody levels to discriminate between unprotected and protected vaccinated individuals.

Methods

MenA-, MenC-, MenW- and MenY-polysaccharide (PS) specific IgG levels in serum and saliva from participants in a meningococcal vaccination study were measured using the fluorescent-bead-based multiplex immunoassay. Functional antibody titers in serum against the four serogroups were measured with serum bactericidal assay using rabbit complement (rSBA). A threshold for salivary IgG was determined by analysis of ROC curves using a serum rSBA titer ≥128 as correlate of protection. The area under the curve (AUC) was calculated to quantify the accuracy of the salivary test and was considered adequate when ≥0.80. The optimal cut-off was considered adequate when salivary IgG cut-off levels provided specificity of ≥90%. True positive rate (sensitivity), positive predictive value, and negative predictive value were calculated to explore the possible use of salivary antibody levels as a surrogate of protection.

Results

The best ROC curve (AUC of 0.95) was obtained for MenC, with an estimated minimum threshold of MenC-PS specific salivary IgG ≥3.54 ng/mL as surrogate of protection. An adequate AUC (> 0.80) was also observed for MenW and MenY with an estimated minimal threshold of 2.00 and 1.82 ng/mL, respectively. When applying these thresholds, all (100%) samples collected 1 month and 1 year after the (booster) meningococcal vaccination, that were defined as protective in the saliva test for MenC, MenW and MenY, corresponded with concomitant serum rSBA titer ≥128 for the respective meningococcal serogroups.

Conclusion

The saliva test offers an alternative screening tool to monitor protective vaccine responses up to one year after meningococcal vaccination against MenC, MenW and MenY. Future (large) longitudinal vaccination studies evaluating also clinical protection against IMD or carriage acquisition are required to validate the currently proposed threshold in saliva.

B cell homeostasis is maintained during long-duration spaceflight

Long-duration spaceflights reportedly induce immune dysregulation, which is considered a risk to astronaut safety and mission success. Recent studies have examined the impact of spaceflight on markers of adaptive and innate immunity, but no study, to date, has comprehensively evaluated humoral immunity and serological markers of B cell function. The aim of this study was to characterize changes in B cell numbers and phenotypes, along with plasma Igs and polyclonal free light chains (FLCs)-near-"real-time" biomarkers of Ig synthesis-in response to an ~6-mo mission to the International Space Station (ISS). Whole-blood samples were collected before flight, during flight ("Early flight," "Mid-flight," and "Late flight"), immediately upon return, and during a recovery period (R + 18, R + 30/R + 33, and R + 60/R + 66) from 23 ISS crew members. B Cell counts and phenotypes were measured throughout the duration of the mission, along with total plasma Ig and FLC levels. There was no effect of spaceflight on the number and proportion of the different B cell subsets. There was no difference in kappa FLC between preflight samples and either in-flight or recovery samples ( P > 0.05), and only a marginal reduction was observed in lambda FLC levels upon return to Earth ( P < 0.05). Furthermore, IgG and IgM remained unchanged during and after spaceflight compared with preflight values ( P > 0.05). Of note, plasma IgA concentrations were elevated in-flight compared with baseline and recovery values ( P < 0.05). These results indicate that B cell homeostasis is maintained during long-duration spaceflight, advocating for potential in-flight vaccination as viable countermeasures against viral reactivation during exploration-class missions.