Meningococcal Polysaccharide Research Articles

Robust Assessment of Molecular Size Distribution of Meningococcal AC Vaccine.

The molecular size of meningococcal polysaccharides is an important physicochemical parameter that is related to immunogenicity and efficacy. A simple method for size-exclusion chromatography was developed, optimized, and applied for safe and rapid fractionation of meningococcal polysaccharide AC vaccine. Pooling of the fractions collected from size-exclusion chromatography was investigated and evaluated, rather than analyzing each fraction separately, for determining the percentages of meningococcal polysaccharide A and C that were eluted before the distribution coefficient of 0.5. Pooling is preferred rather than analyzing each fraction individually, as it is easily handled, faster, simpler, less expensive, more accurate, safe, and applicable. The developed method was validated and successfully applied for the determination of meningococcal polysaccharide vaccine serotype A and C in quality-control and commercial samples.

Association between timely initiation of hepatitis B vaccine and completion of the hepatitis B vaccine and national immunization program vaccine series

Little is known about the association between the initiation of hepatitis B vaccine (HB vaccine) at birth and completion of the HB vaccine and the national immunization program vaccine (NIPV) series in Fujian, China. A provincial survey, including children in the community and newborns in hospital, was conducted to evaluate coverage with a timely first dose of HB vaccine and the completion of three doses of HB vaccine and the NIPV series in 2013. A proportion of the samples was rechecked to investigate the relationship between the administration of a timely first dose of HB vaccine and completion of the HB vaccine series and the NIPV series (three doses of HB vaccine, one dose of Bacillus Calmette-Guérin vaccine, three doses of oral poliomyelitis vaccine, three doses of diphtheria-tetanus-pertussis vaccine, one dose of measles-containing vaccine, one dose of Japanese encephalitis attenuated live vaccine, and two doses of group A meningococcal polysaccharide vaccine). A total of 6589 subjects (including 3785 community children and 2804 hospital newborns) were included in this study; 97.34% of them received a timely first dose of HB vaccine (≤24h after birth) and 99.10% and 88.27% completed the HB vaccine series and the NIPV series, respectively. Among the 1680 children from eight counties who were rechecked, those with a timely first dose of HB vaccine had higher completion rates of the HB vaccine series and the NIPV series than those with a delayed first dose of HB vaccine (99.69% and 88.90% vs. 83.05% and 79.66%, respectively; both p<0.001). Compared to those with a delayed HB vaccine first dose, the odds ratios for completing the HB vaccine series and the NIPV series among children who received a timely first dose of HB vaccine were 65.96 (95% confidence interval (CI) 21.73-200.25) and 3.24 (95% CI 1.81-5.81), respectively. Coverage with a timely first dose of HB vaccine is high in children in the community and newborns in hospital, and timely receipt of the first dose of HB vaccine is associated with an increased likelihood of completing the HB vaccine series and the NIPV series in Fujian, China.

Mechanisms responsible for differential bactericidal activities of human and rabbit complement for Neisseria meningitidis

Polysaccharide conjugate vaccines are available to prevent disease caused by Neisseria meningitidis serogroups A, C, W and Y. Meningococcal vaccine efficacy is assessed in clinical trials using serum bactericidal assays (SBAs). Baby rabbit serum is usually used as the source of complement for SBAs as it lacks endogenous bactericidal activity compared to human serum. Previous studies have shown that SBA activities determined with rabbit (rSBA) and human (hSBA) complement correlate poorly, possibly due to different interactions between antibody subclasses and the complement source, and species-specific interaction of Neisseria meningitidis with complement regulators. The aim of this project was to investigate the mechanisms responsible for differential bactericidal activities of human and rabbit complement against Neisseria meningitidis. The serum concentration of polysaccharide-specific antibody subclasses was measured following vaccination with quadrivalent meningococcal polysaccharide vaccines; data showed that the concentration of polysaccharide-specific IgG1 antibody correlated most significantly with hSBA titres whereas the concentration of polysaccharide-specific IgM antibody correlated most significantly with rSBA titres. The interaction of human IgM and IgG subclasses with human and rabbit complement was compared at the level of C1q and C3 using both binding and functional assays. These data define important differences in the ability of human antibody subclasses to fix human and rabbit complement. Specifically, polysaccharide-specific IgM contributes significantly more to bactericidal titres in rSBAs compared to hSBAs. As a consequence, rSBAs produce misleadingly high titres in individuals with large IgM responses to vaccination. Using a series of pathway-specific inhibitors, it was shown that the alternative pathway contributes significantly more to the bactericidal activity of rabbit complement towards Neisseria meningitidis than human complement. This project provides significant insight into the difficulties and challenges associated with the interpretation of rSBA data, enhances the understanding of antibody responses to meningococcal vaccines and will support improvements in the development and testing of meningococcal vaccines.

Association of Low B Cell Count and IgG Levels With Infection, and Poor Vaccine Response With All-Cause Mortality in an Immunosuppressed Vasculitis Population.

Patients with systemic vasculitis (SV) have an increased risk of all-cause mortality, often due to infection, compared to the healthy population. We investigated whether humoral response to vaccination and biomarkers of immune dysfunction were associated with infection and death. Patients with SV in remission were vaccinated with pneumococcal 7-valent conjugate, Haemophilus influenzae type b, and meningococcal group C conjugate vaccine and meningococcal polysaccharide groups A, C, Y, and W135 vaccines. Total IgG and antibody titers against specific antigens and lymphocyte subset analysis were performed before vaccination. Postvaccination antibody titers were measured at 4 weeks and 2 years, from which an antibody response score was calculated. Infections and death following vaccination were collected prospectively following vaccination. A total of 92 patients were safely vaccinated with no increase in disease relapse, median followup 4.6 years (interquartile range [IQR] 3.6-4.8 years). Eighteen patients died at a median of 2 years and the overall infection rate was 0.4 (IQR 0.2-1.3) infections/patient/year. Reduced serum IgG, B cell count, and CD4+ cell counts predicted poor vaccine response and infection but not death. The response rates to individual vaccine antigens was highly variable, with a median response rate of 46% (IQR 39-58%) of patients responding to each individual antigen. Vaccine response, age, and reduced renal function were independent predictors of all-cause mortality in multivariate analysis. Total IgG and B cell counts predict infection and response to vaccination. Vaccination in patients with SV in remission is safe and the response predicts all-cause mortality. Vaccine response is a surrogate marker of immune system health.

Advisory Committee on Immunization Practices Recommended Immunization Schedule for Adults Aged 19 Years or Older — United States, 2016

I October 2015, the Advisory Committee on Immunization Practices (ACIP) approved the Recommended Adult Immunization Schedule: United States, 2016. This schedule summarizes ACIP recommendations for the use of vaccines routinely recommended for adults in 2 figures (Figures 1 and 2), footnotes for each vaccine (Figure 3), and a table that describes primary contraindications and precautions for commonly used vaccines for adults (Table). Details on these updates and information on other vaccines recommended for adults can be found at www.cdc.gov/vaccines/schedules. The full ACIP recommendations for each vaccine are not included in the schedule owing to space limitations but can be found at www.cdc.gov/vaccines/hcp/acip-recs /index.html. The 2016 adult immunization schedule was reviewed and approved by the American College of Physicians, American Academy of Family Physicians, American College of Obstetricians and Gynecologists, and American College of Nurse-Midwives. Changes in the 2016 adult immunization schedule from the 2015 schedule include the following new ACIP recommendations: Y Interval change for 13-valent pneumococcal conjugate vaccine (PCV13) followed by 23-valent pneumococcal polysaccharide vaccine (PPSV23) from “6 to 12 months” to “at least 1 year” for immunocompetent adults aged ≥65 years (1). Adults aged ≥19 years with anatomical or functional asplenia, cerebrospinal fluid leak, or cochlear implant or who are immunocompromised should receive PPSV23 at least 8 weeks after PCV13. Y Serogroup B meningococcal (MenB) vaccine series should be administered to persons aged ≥10 years who are at increased risk for serogroup B meningococcal disease (2). Those at increased risk include persons with anatomical or functional asplenia or persistent complement component deficiencies, microbiologists who are routinely exposed to isolates of Neisseria meningitidis, and persons identified at increased risk because of a serogroup B meningococcal disease outbreak. MenB vaccine series may be administered to adolescents and young adults aged 16 through 23 years (preferred age is 16 through 18 years) to provide short-term protection against most strains of serogroup B meningococcal disease (3). Y Nine-valent human papillomavirus (HPV) vaccine (9vHPV) was added to the 2016 adult immunization schedule. This vaccine can be used for routine vaccination against HPV as 1 of 3 HPV vaccines (bivalent HPV vaccine [2vHPV], quadrivalent HPV vaccine [4vHPV], and 9vHPV) recommended for females and 1 of 2 HPV vaccines (4vHPV and 9vHPV) recommended for males (4). Notable changes in Figures 1 and 2 are as follows: Y The row for “Meningococcal” was retitled to “Meningococcal 4-valent conjugate (MenACWY) or polysaccharide (MPSV4)” to indicate that there are 2 types of serogroup A, C, W, and Y meningococcal vaccines available for adults. Y A new row for “Meningococcal B (MenB)” was added. Y Additional text was added in several indication bars to describe reasons for alternate dosing schedules for vaccines where such designations were appropriate; for example, in the “Measles, mumps, and rubella (MMR)” indication bar that states “1 or 2 doses,” the clause “depending on indication” was added. Y The text in the “Hepatitis A” indication bar was revised from “2 doses” to “2 or 3 doses depending on vaccine” to account for the hepatitis A and hepatitis B combination vaccine that is administered in a 3-dose series. Additional clarifying changes in Figure 2 include: Y The text in the consolidated “Influenza” indication bar was simplified to “one dose annually”; readers should refer to the footnotes for additional information regarding which influenza vaccine types are recommended for different age and risk groups. Y The text in the “Pneumococcal polysaccharide (PPSV23)” indication bar was revised from “1 or 2 doses” to “1, 2, or 3 doses depending on indication” to account for the recommendation that adults aged ≥19

Fully Synthetic Self-Adjuvanting α-2,9-Oligosialic Acid Based Conjugate Vaccines against Group C Meningitis.

α-2,9-Polysialic acid is an important capsular polysaccharide expressed by serotype C Neisseria meningitidis. Its protein conjugates are current vaccines against group C meningitis. To address some concerns about traditional protein conjugate vaccines, a new type of fully synthetic vaccines composed of oligosialic acids and glycolipids was explored. In this regard, α-2,9-linked di-, tri-, tetra-, and pentasialic acids were prepared and conjugated with monophosphoryl lipid A (MPLA). Immunological studies of the conjugates in C57BL/6J mouse revealed that they alone elicited robust immune responses comparable to that induced by corresponding protein conjugates plus adjuvant, suggesting the self-adjuvanting properties of MPLA conjugates. The elicited antibodies were mainly IgG2b and IgG2c, suggesting T cell dependent immunities. The antisera had strong and specific binding to α-2,9-oligosialic acids and to group C meningococcal polysaccharide and cell, indicating the ability of antibodies to selectively target the bacteria. The antisera also mediated strong bactericidal activities. Structure–activity relationship analysis of the MPLA conjugates also revealed that the immunogenicity of oligosialic acids decreased with elongated sugar chain, but all tested MPLA conjugates elicited robust immune responses. It is concluded that tri- and tetrasialic acid–MPLA conjugates are worthy of further investigation as the first fully synthetic and self-adjuvanting vaccines against group C meningitis.

A High-Throughput Size Exclusion Chromatography Method to Determine the Molecular Size Distribution of Meningococcal Polysaccharide Vaccine.

Molecular size distribution of meningococcal polysaccharide vaccine is a readily identifiable parameter that directly correlates with the immunogenicity. In this paper, we report a size exclusion chromatography method to determine the molecular size distribution and distribution coefficient value of meningococcal polysaccharide serogroups A, C, W, and Y in meningococcal polysaccharide (ACWY) vaccines. The analyses were performed on a XK16/70 column packed with sepharose CL-4B with six different batches of Ingovax® ACWY, a meningococcal polysaccharide vaccine produced by Incepta Vaccine Ltd., Bangladesh. A quantitative rocket immunoelectrophoresis assay was employed to determine the polysaccharide contents of each serogroup. The calculated distribution coefficient values of serogroups A, C, W, and Y were found to be 0.26 ± 0.16, 0.21 ± 0.11, 0.21 ± 0.11, and 0.14 ± 0.12, respectively, and met the requirements of British Pharmacopeia. The method was proved to be robust for determining the distribution coefficient values which is an obligatory requirement for vaccine lot release.

Invasive Meningococcal Meningitis Serogroup C Outbreak in Northwest Nigeria, 2015 - Third Consecutive Outbreak of a New Strain.

BACKGROUND: In northwest Nigeria in 2013 and 2014, two sequential, localized outbreaks of meningitis were caused by a new strain of Neisseria meningitidis serogroup C (NmC). In 2015, an outbreak caused by the same novel NmC strain occurred over a wider geographical area, displaying different characteristics to the previous outbreaks. We describe cases treated by Médecins Sans Frontières (MSF) in the 2015 outbreak. METHODS: From February 10 to June 8, 2015, data on cerebrospinal meningitis (CSM) cases and deaths were recorded on standardized line-lists from case management sites supported by MSF. Cerebrospinal fluid (CSF) samples from suspected cases at the beginning of the outbreak and throughout from suspected cases from new geographical areas were tested using rapid Pastorex® latex agglutination to determine causative serogroup. A subset of CSF samples was also inoculated into Trans-Isolate medium for testing by the WHO Collaborating Centre for Reference and Research on Meningococci, Oslo. Reactive vaccination campaigns with meningococcal ACWY polysaccharide vaccine targeted affected administrative wards. RESULTS: A total of 6394 (65 confirmed and 6329 probable) cases of CSM including 321 deaths (case fatality rate: 5.0%) were recorded. The cumulative attack rate was 282 cases per 100,000 population in the wards affected. The outbreak lasted 17 weeks, affecting 1039 villages in 21 local government areas in three states (Kebbi, Sokoto, Niger). Pastorex® tests were NmC positive for 65 (58%) of 113 CSF samples. Of 31 Trans-Isolate medium samples, 26 (84%) tested positive for NmC (14 through culture and 12 through PCR); all had the same rare PorA type P1.21-15,16 as isolates from the 2013 and 2014 outbreaks. All 14 culture-positive samples yielded isolates of the same genotype (ST-10217 PorA type P1.21-15,16 and FetA type F1-7). More than 222,000 targeted individuals were vaccinated relatively early in the outbreak (administrative coverage estimates 98% and 89% in Kebbi and Sokoto, respectively). CONCLUSIONS: The outbreak was the largest caused by NmC documented in Nigeria. Reactive vaccination in both states may have helped curtail the epidemic. A vaccination campaign against NmC with a long-lasting conjugate vaccine should be considered in the region.

Simple alternative to sialic acid determination in meningococcal polysaccharides W or Y

Physicochemical methods are the primary tests used to ensure that batches of meningococcal polysaccharide (PS) antigens are manufactured consistently to those shown to be safe and effective in clinical trials. Although modern physicochemical methods of analysis providing structural information about the antigens have been developed and used, simpler assays, which can be readily validated, are still in use for polysaccharide batch release. The simple and cheap method for Neisseria meningitidis serogroup W or Y polysaccharide (MenW or MenY PS) content quantification has been developed. This colorimetric method is based on the galactose or glucose quantification in MenW or MenY PS hydrolysate, respectively. Intra- and inter-assay precision and accuracy of the novel method have been demonstrated, in comparison to the same properties of the current regulatory approved method for the same purpose — sialic acid quantification. We provided the calculation of the possible future regulatory requirement for the galactose or glucose content in MenW or MenY PS, respectively, and revealed in detail the stoichiometric calculation behind it.

Challenges and Opportunities While Developing a Group A Meningococcal Conjugate Vaccine Within a Product Development Partnership: A Manufacturer's Perspective From the Serum Institute of India.

Background. In 2002, the Meningitis Vaccine Project (MVP) chose the Serum Institute of India, Ltd (SIIL), as its manufacturing partner to establish a product development partnership (PDP) with the Meningitis Vaccine Project (MVP). MVP was a collaboration between PATH and the World Health Organization (WHO) to develop meningococcal conjugate vaccines for sub-Saharan Africa.Method. From the outset, SIIL recognized that a partnership with MVP carried some risk but also offered important opportunities for accessing new conjugate vaccine technology and know-how. Over 3 years, SIIL successfully accepted technology transfer for the group A meningococcal polysaccharide from SynCo Bio Partners and a conjugation method from the US Food and Drug Administration.Results. SIIL successfully scaled up production of a group A meningococcal conjugate vaccine that used SIIL tetanus toxoid as the carrier protein. Phase 1 studies began in India in 2005, followed by phase 2/3 studies in Africa and India. A regulatory dossier was submitted to the Indian authorities in April 2009 and WHO in September 2009. Export license was granted in December 2009, and WHO prequalification was obtained in June 2010. Vaccine was introduced at public scale in Burkina Faso that December. The group A meningococcal conjugate vaccine was named MenAfriVac, and is the first internationally qualified vaccine developed outside of big pharma.Conclusions. The project proved to be a sound investment for SIIL and is a concrete example of the potential for PDPs to provide needed products for resource-poor countries.

Technical Development of a New Meningococcal Conjugate Vaccine.

Background. Group A Neisseria meningitidis has been a major cause of bacterial meningitis in the sub-Saharan region of Africa in the meningitis belt. Neisseria meningitidis is an encapsulated pathogen, and antibodies against the capsular polysaccharide are protective. Polysaccharide–protein conjugate vaccines have proven to be highly effective against several different encapsulated bacterial pathogens. Purified polysaccharide vaccines have been used to control group A meningococcal (MenA) epidemics with minimal success.Methods. A monovalent MenA polysaccharide–tetanus toxoid conjugate was therefore developed. This vaccine was developed by scientists working with the Meningitis Vaccine Project, a partnership between PATH and the World Health Organization.Results. A high-efficiency conjugation method was developed in the Laboratory of Bacterial Polysaccharides in the Center for Biologics Evaluation and Research and transferred to the Serum Institute of India, Ltd, which then developed methods for purification of the group A polysaccharide and used its tetanus toxoid as the carrier protein to produce the now-licensed, highly effective MenAfriVac conjugate vaccine.Conclusions. Although many years of application of meningococcal polysaccharide vaccines have had minimal success in preventing meningococcal epidemics in the meningitis belt of Africa, our collaborative efforts to develop a MenA conjugate vaccine yielded a safe and highly effective vaccine.

Long-term immunogenicity and safety after a single dose of the quadrivalent meningococcal serogroups A, C, W, and Y tetanus toxoid conjugate vaccine in adolescents and adults: 5-year follow-up of an open, randomized trial

BackgroundLong-term protection against meningococcal disease is associated with persistence of post-vaccination antibodies at protective levels. We evaluated the bactericidal antibody persistence and safety of the quadrivalent meningococcal serogroups A, C, W and Y tetanus-toxoid conjugate vaccine (MenACWY-TT) and the meningococcal polysaccharide serogroups A, C, W, and Y vaccine (MenACWY-PS) up to 5 years post-vaccination.MethodsThis phase IIb, open, randomized, controlled study conducted in the Philippines and Saudi Arabia consisted of a vaccination phase and a long-term persistence phase. Healthy adolescents and adults aged 11–55 years were randomized (3:1) to receive a single dose of MenACWY-TT (ACWY-TT group) or MenACWY-PS (Men-PS group). Primary and persistence results up to 3 years post-vaccination have been previously reported. Antibody responses against meningococcal serogroups A, C, W, and Y were assessed by a serum bactericidal antibody assay using rabbit complement (rSBA, cut-off titers 1:8 and 1:128) at Year 4 and Year 5 post-vaccination. Vaccine-related serious adverse events (SAEs) and cases of meningococcal disease were assessed up to Year 5.ResultsOf the 500 vaccinated participants, 404 returned for the Year 5 study visit (Total Cohort Year 5). For the Total Cohort Year 5, 71.6–90.0 and 64.9–86.3 % of MenACWY-TT recipients had rSBA titers ≥1:8 and ≥1:128, respectively, compared to 24.8–74.3 and 21.0–68.6 % of MenACWY-PS recipients. The rSBA geometric mean titers (GMTs) remained above the pre-vaccination levels in both treatment groups. Exploratory analyses suggested that both rSBA GMTs as well as the percentages of participants with rSBA titers above the cut-offs were higher in the ACWY-TT than in the Men-PS group for serogroups A, W and Y, with no apparent difference for MenC. No SAEs related to vaccination or cases of meningococcal disease were reported up to Year 5.ConclusionThese results suggest that a single dose of MenACWY-TT could protect at least 72 % of vaccinated adolescents and adults against meningococcal disease at least 5 years post-vaccination.Trial registrationClinicalTrials.gov NCT00356369Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-1138-y) contains supplementary material, which is available to authorized users.

Molecular shape and immunogenicity of meningococcal polysaccharide group A conjugate vaccine

Neisseria meningitidis is a leading cause of severe bacterial infections in infants and young children. As a major virulence factor, meningococcal capsular polysaccharide (PS) is poorly immunogenic and generally does not induce immunological memory. Conjugation of PS with a carrier protein can significantly increase the PS-specific immunogenicity and induce immunological memory. It is well known that the molecular shape/size of the conjugate vaccine is important for its immunogenicity. However, little is known about the molecular shape/size of the meningococcal conjugate vaccine. A meningococcal PS–ovalbumin (OVA) conjugate vaccine was prepared using cystamine as linker. Four components (P1–P4) with different molecular size were fractionated from the conjugate. Small angle X-ray scattering (SAXS) analysis revealed that the conjugate vaccine exhibited a rod-like shape similar to virus-like particles. PS-specific immunogenicity of the conjugate vaccine was related to its molecular shape and increased as a function of its molecular size. Thus, the present study provides a three-dimensional shape of the conjugate vaccine and helps to identify optimal design of a potent meningococcal conjugate vaccine.

Salivary Functional Antibody Secretion Is Reduced in Older Adults: A Potential Mechanism of Increased Susceptibility to Bacterial Infection in the Elderly.

Bacterial infections in the elderly are common and associated with high morbidity and mortality, with pneumonia the second commonest cause of death. Reductions in antibodies against specific bacterial antigens in saliva and serum could contribute to infection risk in older adults, although they have yet to be examined in relation to age. IgG, IgA and IgM antibody levels in paired saliva and serum samples were measured against 12 pneumococcal, 4 meningococcal and haemophilus polysaccharide antigens and diphtheria and tetanus toxoids in healthy younger (n = 28, 21-34 years) and older (n = 44, 60-80 years) adults. Older adults had lower antibody concentrations in saliva than young adults, with the most striking differences observed for salivary antibody secretion rates. In serum, older adults registered lower concentrations for only a minority of antibodies. Young adults who had previously received a polysaccharide pneumococcal vaccination (PPV23) had higher levels of anti-pneumococcal antibodies in serum and in saliva. Only minor differences were observed in antibody levels between older adults who had/had not received PPV23, and there was no evidence of memory in saliva. Age differences were much greater in salivary antibodies than in serum; older adults had reduced salivary secretion rates of antibodies across bacterial antigens. This decline in local immunity may contribute to increased infection risk in the elderly. The poor memory from pneumococcal vaccination in serum and saliva suggests that PPV23 may be ineffective in older adults for both systemic and local protection.

Post-Vaccination Encephalomyelitis Following Meningococcal Polysaccharide Vaccine (Mencevax ACWY): A Case Report

Introduction: Post-vaccination encephalomyelitis is an inflammatory disorder of the central nervous system. It is triggered by certain vaccines. The diagnosis of post-vaccination encephalomyelitis depends on the close temporal relationship between vaccination and clinical presentation. Case Presentation: We describe a 30-year-old man with post-vaccination encephalomyelitis following Mencevax ACWY meningococcal polysaccharide vaccine. Encephalomyelitis is a very rare side effect of this vaccine. Conclusions: Post-vaccination encephalomyelitis is a very rare side effect of Mencevax ACWY.

BCR repertoire sequencing: different patterns of B-cell activation after two Meningococcal vaccines.

Next-generation sequencing was used to investigate the B cell receptor heavy chain transcript repertoire of different B cell subsets (naïve, marginal zone, IgM memory and IgG memory) at baseline, and of plasma cells 7 days following administration of serogroup ACWY meningococcal polysaccharide and protein-polysaccharide conjugate vaccines. Baseline B cell subsets could be distinguished from each other using a small number of repertoire properties (clonality, mutation from germ-line and complementarity-determining region 3 length) that were conserved between individuals. However, analyzing the complementarity-determining region 3 amino acid sequence (which is particularly important for antigen binding) of the baseline subsets showed few sequences shared between individuals. In contrast, day 7 plasma cells demonstrated nearly tenfold greater sequence sharing between individuals than the baseline subsets, consistent with the plasma cells being induced by the vaccine antigen, and sharing specificity for a more limited range of epitopes. By annotating plasma cell sequences based on IgG subclass usage and mutation, and also comparing them to the sequences of the baseline cell subsets, we were able to identify different signatures after the polysaccharide and conjugate vaccines. Plasma cells produced after conjugate vaccination were predominantly IgG1, and most related to IgG memory cells. In contrast, after polysaccharide vaccination, the plasma cells were predominantly IgG2, less mutated, and were equally likely to be related to marginal zone, IgM memory or IgG memory cells. High-throughput B cell repertoire sequencing thus provides a unique insight into patterns of B cell activation not possible from more conventional measures of immunogenicity.

Moderate PEGylation of the carrier protein improves the polysaccharide-specific immunogenicity of meningococcal group A polysaccharide conjugate vaccine

Neisseria meningitidis can cause severe and fulminant diseases such as meningitis. Meningococcal capsular polysaccharide (PS) is a key virulence determinant that is not able to induce immunological memory. Conjugation of PS to a carrier protein can significantly increase the immunogenicity of PS and induce immunological memory. Due to the classically described carrier-induced epitopic suppression (CIES) mechanisms, a strong immune response against the carrier protein could suppress the immune response to PS after coadministration of free carrier protein with the conjugate vaccine. However, it was not clear whether suppressing or enhancing the protein-specific immunogenicity could improve the PS-specific immunogenicity of the conjugate vaccine. Thus, moderate PEGylation, extensive PEGylation and oligomerization were used to regulate the immunogenicity of tetanus toxoid (TT) in the conjugate vaccine (PS-TT). Moderate PEGylation led to a 2.7-fold increase in the PS-specific IgG titers elicited by PS-TT. In contrast, extensive PEGylation and oligomerization of TT led to 1.4-fold and 1.6-fold decrease in the PS-specific IgG titers elicited by PS-TT, respectively. The PS-specific immunogenicity of PS-TT can be increased by moderate PEGylation through mild suppression of the TT-specific immunogenicity. The PS-specific immunogenicity of PS-TT was decreased through significant suppression or enhancement of the TT-specific immunogenicity. Thus, our study contributes to understand the CIES mechanisms and improve the PS-specific immunogenicity of a meningococcal PS conjugate vaccine.

Development and Evaluation of a Multiplex Microsphere Assay for Quantitation of IgG and IgA Antibodies against Neisseria meningitidis Serogroup A, C, W, and Y Polysaccharides

We developed and evaluated a rapid and simple multiplex microsphere assay for the quantification of specific IgG and IgA antibodies against meningococcal serogroup A, C, W, and Y capsular polysaccharides in serum and saliva. Meningococcal polysaccharides were conjugated to distinct magnetic carboxylated microspheres, and the performance of the assay was assessed using the CDC1992 standard meningococcal reference serum and a panel of serum and saliva samples. The standard curve was linear over an eight 3-fold dilution range in the IgG assay and a seven 3-fold dilution range in the IgA assay. No cross-reactivity was discovered, and the assay showed high specificity with ≥91% homologous inhibition and ≤11% heterologous inhibition for all serogroups and immunoglobulin classes. Lower limits of detections were ≤280 pg/ml for IgG and ≤920 pg/ml for IgA antibodies. The assay was reproducible, with a mean coefficient of variation of ≤5% for intra-assay duplicates, a mean coefficient of variation of ≤20% for interassay repeated analysis with different conjugations of microspheres, and a mean coefficient of variation within 25.8% for interoperator variation. The assay showed good correlation to the standard meningococcal polysaccharide enzyme-linked immunosorbent assay (ELISA) for detection of serum antibodies. This multiplex assay is robust and reliable and requires less sample volume, and less time and workload are needed than for ELISA, making this method highly relevant for serological and salivary investigations on the effect of meningococcal vaccines and for immunosurveillance studies.

Trends and variations in the epidemiology of meningococcal disease in Kuwait 1987-2013.

The introduction of Haemophilus influenzae type b (Hib) conjugate vaccine and conjugate pneumococcal vaccine into routine childhood vaccination in Kuwait has resulted in the emergence of Neisseria meningitidis as the leading cause of invasive bacterial infection in children. Currently, a quadrivalent ACYW-135 meningococcal polysaccharide vaccine is administered as part of routine childhood vaccination in Kuwait at the age of 2 years. Conjugate meningococcal vaccines have been shown to be more effective in preventing meningococcal infection in young children. The objective of this study was to describe the epidemiology of meningococcal disease (MD) in Kuwait and evaluate the need for conjugate vaccine in routine childhood immunization. We have reviewed the MD surveillance data from the communicable disease unit, Ministry of Health, Kuwait during the period from 1987 to 2013. The analysis included microbiologically confirmed cases of N. meningitidis in the blood and cerebrospinal fluid. There were 293 cases of confirmed MD during the study period. Two hundred and four cases (70%) were in children ≤ 14 years of age. The mean incidence rate was 0.5/100,000 persons. The dominant serogroups were W-135 and B, accounting for 80 cases (32%) each. Serogroup B accounted for 69/204 (34%) of all cases in children ≤ 14 years and serogroup A accounted for 36/89 40% of all adult cases. There were three outbreaks: 1987 (caused by serogroup A), 1989 (caused by serogroup W-135) and 2002 (caused by serogroup B). The mean case fatality rate was 13.5%. In conclusion, despite childhood routine vaccination with ACYW-135 polysaccharide vaccine, infants and young children remain at high risk for MD, which supports the introduction of conjugate meningococcal vaccine to the routine childhood vaccination schedule.

Conjugation of β-glucan markedly increase the immunogencity of meningococcal group Y polysaccharide conjugate vaccine

Meningococcal disease is a fatal illness of sudden onset caused by Neisseria meningitides. Meningococcal capsular polysaccharide (CPS) is a major virulence factor that generally does not induce immunological memory. Conjugation with a carrier protein can significantly increase the immunogenicity of CPS and induce immunological memory. However, it is highly desired to optimize the CPS-specific immunogenicity of the conjugate vaccine. Although adjuvant has been widely used to improve the immunogenicity of antigens, co-administration and conjugation of adjuvant with the conjugate vaccine has rarely been investigated. As a stimulator of humoral and cellular immunity, β-glucan can activate macrophages and trigger intracellular processes to secrete cytokines initiating inflammatory reactions. In the present study, a conjugate vaccine (CPS-TT) was generated by conjugation of tetanus toxoid (TT) with meningococcal group Y CPS. CPS-TT was further conjugated with β-glucan to generate CPS-TT-G. Immunization with CPS-TT-G led to an 8.2-fold increase in the CPS-specific IgG titers as compared with CPS-TT. Presumably, conjugation of β-glucan ensured the two components to simultaneously reach the antigen presenting cells and stimulate the immune response. In contrast, co-administration of β-glucan suppressed the CPS-specific immunogenicity of CPS-TT. Thus, conjugation of β-glucan is an effective strategy to markedly improve the CPS-specific immunogenicity of the conjugate vaccine.