Seroprevalence of meningococcal serogroup C bactericidal antibodies in the Portuguese population, a decade after vaccine introduction in the National Immunisation Programme

Background

The incidence of invasive meningococcal disease due to serogroup C (MenC) decreased in Portugal since the introduction of the conjugate vaccine (MCC) in the free market in 2001 and in the National Immunisation Plan in 2006. Considering the potential waning of the antibody response reported in the literature, the different vaccination schemes that were used in our country over the past decade, and that Neisseria meningitidis serogroup C continues to circulate, the Portuguese population may currently be at increased risk of infection. In the absence of national data, we evaluated the seroprotection level of the Portuguese population against MenC, in order to identify the protected fraction of the population and ponder on the necessity of a booster dose of the MCC vaccine.

Methods

We measured serum bactericidal antibody levels against MenC in a representative sample of the population (n = 1500) aged 2–64 years who participated in the 2015/2016 National Serological Survey.

Results

A total of 31.1% (466/1500, 95%CI: 29–33%) of the individuals studied were protected against MenC. The geometric mean titre was 6.5. The proportion of seroprotected was particularly low in children aged 2–4 years (<16%) who received a single dose of the vaccine at 12 months of age (vaccination strategy since 2012). The proportion of seroprotected was higher (44.7% to 53.5%) in adolescent and young adults (15–24 years of age), resulting from vaccination during the catch-up campaign at 5–15 years of age. The highest protection rates were observed when the vaccine was administered during adolescence.

Conclusion

The small fraction of population seroprotected, combined with the already known waning effect of the antibody response over time, may indicate that the Portuguese population will become progressively more exposed to the risk of infection. Taking in consideration our results, we recommend to change the current vaccination strategy and introduce a booster dose of the MCC vaccine during adolescence.

An Update on Meningococcal Vaccination

Neisseria meningitidis bacterial infection can cause severe life-threatening meningitis. Individuals who survive may be left with profound sequelae. In epidemic regions such as the meningitis belt of Africa, the case rate is drastically higher than in nonepidemic regions and is due to distinct outbreak serogroups. Two highly effective conjugate meningococcal vaccine against serogroups A, C, W and Y are licensed and indicated for prevention in childhood vaccination schedules and for travelers to outbreak regions. In the US, meningococcus serogroup B is the main cause of outbreaks, in areas with crowding such as college dorms. It has taken over 40 years to develop a meningitis type B vaccine and now there are 2 brands available for children and teens. All college-bound individuals should complete schedules of both conjugate ACWY serotypes and meningitis B vaccine series. This paper reviews details on who to vaccinate and how to use the currently available meningococcal meningitis vaccines.

Effectiveness of a Serogroup B and C Meningococcal Vaccine Developed in Cuba

INTRODUCTION Serogroup B meningococcal outer membrane vesicle vaccines have been effective against vaccine-type strains, but their effectiveness against heterologous strains has been controversial. The Cuban VA-MENGOC-BC vaccine is of this type, but also includes meningococcus C capsular polysaccharide. OBJECTIVES Assess the effectiveness of VA-MENGOC-BC in reducing meningococcal disease caused by homologous or heterologous serogroup B strains and its serological effectiveness against meningococcus C. METHODS A review of studies of VA-MENGOC-BC's application in Cuba, Brazil, Uruguay and Colombia was carried out to examine the vaccine's effectiveness in reducing meningococcal disease during serogroup B outbreaks. Serological effectiveness against serogroup C determined in these studies (indicated by bactericidal antibody titers before and after vaccination) was also analyzed. RESULTS VA-MENGOC-BC's effectiveness against homologous serogroup B strains has consistently been greater than 80% in all age groups. Effectiveness in heterologous contexts was also above 80% in individuals aged >4 years. Lower effectiveness in heterologous contexts was found in Brazilian children aged <2 years, although still >50%. Effectiveness increased when assessed based on mortality rates, as well as in cases of clinically severe meningococcal disease. The carrier-state pattern was modified after vaccination with reduction of hypervirulent lineages. Some 60% of infants (aged <1 year) attained protective bactericidal antibody titers against serogroup C. Higher protection rates were achieved in older children. CONCLUSIONS In addition to prevention of meningococcal disease caused by homologous serogroup B strains, VA-MENGOC-BC should be considered for heterologous contexts. It is protective against serogroup C in all age groups. KEYWORDS Neisseria meningitidis, meningococcal disease, meningococcal vaccines, serogroup B meningococcus, serogroup C meningococcus, immunogenicity, bacterial outer membrane proteins, heterologous effects of vaccines, acellular vaccines, Cuba.

Spatiotemporal Analysis of Serogroup C Meningococcal Meningitis Spread in Niger and Nigeria and Implications for Epidemic Response

BACKGROUND

After the re-emergence of serogroup C meningococcal meningitis (MM) in Nigeria and Niger, we aimed to re-evaluate the vaccination policy used to respond to outbreaks of MM in the African meningitis belt by investigating alternative strategies using a lower incidence threshold and information about neighboring districts.

METHODS

We used data on suspected and laboratory-confirmed cases in Niger and Nigeria from 2013 to 2017. We calculated global and local Moran's I-statistics to identify spatial clustering of districts with high MM incidence. We used a Pinner model to estimate the impact of vaccination campaigns occurring between 2015 and 2017 and to evaluate the impact of 3 alternative district-level vaccination strategies, compared with that currently used.

RESULTS

We found significant clustering of high incidence districts in every year, with local clusters around Tambuwal, Nigeria in 2013 and 2014, Niamey, Niger in 2016, and in Sokoto and Zamfara States in Nigeria in 2017.We estimate that the vaccination campaigns implemented in 2015, 2016, and 2017 prevented 6% of MM cases. Using the current strategy but with high coverage (85%) and timely distribution (4 weeks), these campaigns could have prevented 10% of cases. This strategy required the fewest doses of vaccine to prevent a case. None of the alternative strategies we evaluated were more efficient, but they would have prevented the occurrence of more cases overall.

CONCLUSIONS

Although we observed significant spatial clustering in MM in Nigeria and Niger between 2013 and 2017, there is no strong evidence to support a change in methods for epidemic response in terms of lowering the intervention threshold or targeting neighboring districts for reactive vaccination.

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

Background

Meningococcal infection starts with colonisation of the upper respiratory tract. Mucosal immunity is important for protection against acquisition and subsequent meningococcal carriage. In this study, we assessed salivary antibody levels against meningococcal serogroup A (MenA), W (MenW) and Y (MenY) after vaccination with a quadrivalent MenACWY conjugated vaccine. We also compared salivary meningococcal serogroup C (MenC) antibody levels after monovalent MenC and quadrivalent MenACWY conjugated vaccination.

Methods

Healthy participants, who had received MenC conjugate vaccine between 14 months and 3 years of age, received a (booster) MenC or MenACWY vaccination at age 10–15 years. MenA-, MenC-, MenW- and MenY-polysaccharide (PS) specific IgG and IgA levels in saliva and serum and PS specific secretory component levels in saliva were measured using the fluorescent-bead-based multiplex immunoassay.

Results

MenACYW vaccination increased salivary PS-specific IgA (2-fold) and IgG levels(>10-fold) for MenA, MenY, and MenW. After one year, salivary IgA levels had returned to baseline levels. Both vaccines induced an increase in salivary MenC-PS specific IgA (>3-fold) and IgG (>100-fold), with higher levels after MenC as compared to MenACWY vaccination. The antibody decay rate of MenC in saliva between one month and one year was similar for both vaccines. The overall correlation between serum and saliva IgA levels was low (R = 0.39, R = 0.58, R = 0.31, and R = 0.36 for MenA, MenC, MenW and MenY, respectively). Serogroup-PS specific IgG levels between serum and saliva correlated better (R ranged from 0.51 to 0.88).

Conclusions

Both primary (MenA, MenY, and MenW) and booster (MenC) parenteral meningococcal conjugate vaccination induced high salivary antibody levels. The strong correlation for MenC, MenW and MenY between saliva and serum IgG levels indicates that saliva might be used as a reliable tool to measure vaccine responses after both primary and booster meningococcal vaccination.

Brazilian meningococcal C conjugate vaccine: physicochemical, immunological, and thermal stability characteristics

High temperature is known to cause some instability in polysaccharide-protein conjugated vaccines and studies under stress conditions may be useful in determining whether short-term accidental exposure to undesired conditions can compromise product quality. In this study, we examined the structural stability of three industrial batches of Brazilian Meningococcal C conjugate bulk (MPCT) incubated at 4, 37, and 55 °C for 5 weeks. The effect of exposure to the storage temperatures was monitored by HPLC-SEC, CZE, CD and NMR techniques. The immunological significance of any physicochemical changes observed in MPCT was determined by SBA and ELISA assays of serum from immunized mice. Fluorescence emission spectra at 4 and 37 °C were similar among all samples and compatible with the native fold of the carrier protein. Fluorescence spectra of MPCT stored at 55 °C decreased in intensity and had a significant red-shift, indicating conformational changes. Far-UV CD spectra revealed a trend toward loss of structural conformation as storage temperature was increased to 55 °C. The NMR data showed modified signal intensity of the aromatic and aliphatic residues, mainly for samples incubated at 55 °C, suggesting a partial loss of tertiary structure. About 50% free saccharide content was found in bulks stored at 55 °C, but no difference was observed in the IgG or SBA titers. The present study showed physicochemical methods alone are insufficient to predict the biological activity of a MPCT conjugate vaccine without extensive validation against immunological data. However, they provide a sensitive means of detecting changes induced in a vaccine exposed to adverse environmental condition.

[Analysis for protection rate and antibody levels of epidemic cerebrospinal meningitis among children aged between 3-23 months in Liuzhou, in 2012]

Objective: To understand the level of bactericidal antibodies against Neisseria meningitidis and their rate of protection in children aged between 3 and 23 months, in Liuzhou, in 2012. Methods: Convenience sampling was performed in Liujiang, Rong'an and Sanjiang Counties from May through August, 2012. The inclusion criteria for 603 subjects were: Children aged between 3 and 23 months; no history of meningococcal meningitis; no vaccination against Neisseria meningitidis serogroup C; more than 30 days from the last vaccination against Neisseria meningitidis serogroup A. Demographic information and immunization history of the subjects were obtained using questionnaires. Venous blood samples (2.0 ml each) were collected and levels of Neisseria meningitides antibodies determined using a Serum Bactericidal Assay (SBA). The geometric mean titer (GMT) of serum bacterial antibodies was positive when it was greater than or equal to 1∶2 and protective when greater than 1∶8. Chi-square and Fisher's exact tests were used to compare differences in the positive and protective rates of serum antibodies of Neisseria meningitidis serogroup A and Neisseria meningitidis serogroup C, among children with different demographic characteristics. Kruskal-Wallis H test was used to compare differences in the GMT of serum antibodies of Neisseria meningitidis serogroup A and Neisseria meningitidis serogroup C, among children with different demographic characteristics. Results: Of 603 subjects, 325 (53.9%) were female and 278 (46.1%) were male; 276 (45.8%), 143 (23.7%) and 184 (30.5%) subjects were administered, respectively, no treatment, 1 dose vaccine and 2 doses vaccine. The GMT of serum antibodies against group A Neisseria meningitidis was 1∶1.11, the positive rate was 7.6% (46) and the protective rate was 2.0% (12). The GMT of antibodies in children receiving 1 vaccine dose was 1∶1.16 and the protective rate was 3.5% (5), both values higher than those in children receiving 2 vaccine doses (GMT: 1∶1.2, protective rate: 3.5% (5)). However, these differences were not statistically significant (GMT: H=0.64, P=0.728; protective rate: Fisher's exact test, P= 0.080). The GMT of antibodies in children receiving 1 and 2 doses of meningococcal polysaccharide vaccines were 1∶1.12 and 1∶2.30, respectively (≤180 d). The GMT of serum antibodies for group C meningococcal vaccine was 1∶1.18 and its positive and protective rates were 14.6% (88) and 2.2% (13), respectively. Conclusion: Children aged between 3 and 23 months are susceptible to Neisseria meningitidis groups A and C. The immune effectiveness of group A meningococcal polysaccharide vaccine is relatively poor in this age group and their antibody levels decreased rapidly.

Long-term persistence of protective antibodies in Dutch adolescents following a meningococcal serogroup C tetanus booster vaccination

INTRODUCTION

Due to waning immunity, infant vaccination with meningococcal serogroup C conjugated (MenCC) vaccines is insufficient to maintain long-term individual protection. Adolescent booster vaccination is thought to offer direct protection against invasive meningococcal disease (IMD) but also to reduce meningococcal carriage and transmission and in this way establish herd protection in the population. Previously, we studied antibody levels after adolescent MenCC booster vaccination. In the present study, the adolescent vaccinees were revisited after three years to determine antibody persistence and to predict long-term protection.

METHODS

Meningococcal serogroup C tetanus toxoid conjugated (MenC-TT) vaccine was administered to 10-, 12- and 15-year old participants who had been primed nine years earlier with a single dose of MenC-TT vaccine. Blood samples were collected before, 1month, 1year and 3years after the adolescent booster vaccination. Functional antibody levels were measured with serum bactericidal assay using rabbit complement (rSBA). Meningococcal serogroup C polysaccharide and tetanus toxoid specific antibody levels were measured using fluorescent-bead-based multiplex immunoassay. Long-term protection was estimated using longitudinal multilevel antibody decay modeling.

RESULTS

Of the original 268 participants, 201 (75%) were revisited after 3years. All participants still had an rSBA titer above the protective threshold of ⩾8 and 98% ⩾128. The 15-year-olds showed the highest antibody titers. Using a bi-exponential decay model, the median time to fall below the protection threshold (rSBA titer <8) was 16.3years, 45.9years and around 270years following the booster for the 10-, 12- and 15-year-olds, respectively.

CONCLUSIONS

After a first steep decline in antibody levels in the first year after the booster, antibody levels slowly declined between one and three years post-booster. A routine MenC-TT booster vaccination for adolescents in the Netherlands will likely provide long-term individual protection and potentially reduce the risk of resurgence of MenC disease in the general population.

Community-Based Outbreak of Neisseria meningitidis Serogroup C Infection in Men who Have Sex with Men, New York City, New York, USA, 2010-2013

Questions about how to protect this at-risk population deserve careful consideration.

In September 2012, the New York City Department of Health and Mental Hygiene identified an outbreak of Neisseria meningitidis serogroup C invasive meningococcal disease among men who have sex with men (MSM). Twenty-two case-patients and 7 deaths were identified during August 2010−February 2013. During this period, 7 cases in non-MSM were diagnosed. The slow-moving outbreak was linked to the use of websites and mobile phone applications that connect men with male sexual partners, which complicated the epidemiologic investigation and prevention efforts. We describe the outbreak and steps taken to interrupt transmission, including an innovative and wide-ranging outreach campaign that involved direct, internet-based, and media-based communications; free vaccination events; and engagement of community and government partners. We conclude by discussing the challenges of managing an outbreak affecting a discrete community of MSM and the benefits of using social networking technology to reach this at-risk population.

Different Dynamics for IgG and IgA Memory B Cells in Adolescents following a Meningococcal Serogroup C Tetanus Toxoid Conjugate Booster Vaccination Nine Years after Priming: A Role for Priming Age?

Background

Antibody levels wane rapidly after Meningococcal serogroup C conjugate (MenCC) vaccination in young children, rendering the need for an adolescent booster dose. It is not clear whether circulating memory B cells are associated with persistence of MenC-specific antibody levels.

Methods

Measurement of MenC-specific IgG and IgA memory B cells and levels of serum and salivary MenC-specific IgG and IgA in healthy 10-, 12- and 15-year-olds prior to and one month and one year after a MenCC booster vaccination. All participants had received a primary MenCC vaccination nine years earlier.

Results

The number of circulating MenC-specific IgG memory B cells prior to booster was low and not predictive for MenC-specific IgG responses in serum or saliva post-booster, whereas the number of MenC-specific IgA memory B cells pre-booster positively correlated with MenC-specific IgA levels in saliva post-booster (R = 0.5, P<0.05). The booster induced a clear increase in the number of MenC-specific IgG and IgA memory B cells. The number of MenC-PS-specific IgG memory B cells at 1 month post-booster was highest in the 12-year-olds. The number of MenC-specific memory B cells at one month post-booster showed no correlation with the rate of MenC-specific antibody decay throughout the first year post-booster.

Conclusions

Circulating MenC-specific IgA memory B cells correlate with IgA responses in saliva, whereas circulating MenC-specific IgG memory B cells are not predictive for MenC-specific IgG responses in serum or saliva. Our results are suggestive for age-dependent differences in pre-existing memory against MenC.

Safety and immunogenocity of a novel combined Haemophilus influenzae type b-Neisseria meningitidis serogroups A and C-tetanus-toxoid conjugate vaccine in healthy Chinese children aged 6 months to 5 years old

A novel combined Haemophilus influenzae type b-Neisseria meningitidis serogroups A and C-tetanus-toxoid conjugate vaccine (Hib-MenAC vaccine) has been developed to protect children against diseases caused by Hib, MenA, and MenC. This study investigated the safety and immunogenicity of the Hib-MenAC vaccine administered in 2-dose series to children aged 6-23 months and in a single dose to children aged 2-5 y. A randomized, positive-controlled, non-inferiority clinical trial was conducted for 1200 healthy participants in each age group. Within each age group, participants were randomly allocated to the Hib-MenAC group or the control group at a ratio of 1:1. Adverse reactions were recorded within 28 d after each dose. Blood samples were obtained to assess immunogenicity on day 0 and at 28 d after a complete vaccination course. For the investigational vaccine, the incidence of total adverse reactions in vaccinees aged 6-23 months was 46.8% and that in vaccinees aged 2-5 y was 29.8%. Most adverse reactions were mild or moderate. One non-fatal serious adverse event occurred in the Hib-MenAC group, but was unrelated to vaccination. The seroconversion rate to the 3 components reached 94.0%, and the proportion of vaccinees with rSBA titers ≥ 1:8 and PRP ≥ 0.15 g/mL reached 97.0% in both age groups. The safety and immunogenicity of the Hib-MenAC vaccine were non-inferior when compared to the licensed vaccines. It was concluded that the novel vaccine would be expected to protect children against all of the targeted diseases.

Subsets of memory CD4+ T cell and bactericidal antibody response to Neisseria meningitidis serogroup C after immunization of HIV-infected children and adolescents

Meningococcal disease is endemic in Brazil, with periodic outbreaks and case fatality rates reach as high as 18 to 20% of cases. Conjugate vaccines against meningococci are immunogenic in healthy children. However, we have previously shown a poor bactericidal antibody response to a Men C conjugate vaccine in Brazilian HIV-infected children and adolescents after a single vaccine administration. The goal of the present work was to investigate associations between bactericidal antibody response induced by MenC vaccine and the frequency and activation profile (expression of CD38, HLA-DR and CCR5 molecules) of total CD4+ memory T cell sub-populations in HIV-1-infected children and adolescents. Responders to vaccination against MenC had a predominance (about 44%) of CD4+ TINTERMEDIATE subset followed by TTRANSITIONAL memory subset (23 to 26%). Importantly, CD4+ TINT frequency was positively associated with bactericidal antibody response induced by vaccination. The positive correlation persisted despite the observation that the frequency TINT CD38+HLA-DR+ was higher in responders. In contrast, CD4+ TCENTRAL MEMORY (TCM) subset negatively correlated with bactericidal antibodies. In conclusion, these data indicate that less differentiated CD+ T cells, like TCM may be constantly differentiating into intermediate and later differentiated CD4+ T cell subsets. These include CD4 TINT subset which showed a positive association with bactericidal antibodies.

[Comparison on the levels of human serum antibody against Neisseria meningitidis serogroup C measured using serum bactericidal assay and ELISA]

OBJECTIVE

To analyze the levels of human serum antibody against Neisseria meningitidis serogroup C measured by serum bactericidal assay (SBA) and ELISA.

METHODS

SBA and a modified ELISA were applied to measure the serum bactericidal titer and the specific concentration of immunoglobulin G (IgG) against meningococcal serogroup C in sera samples. Seventy-five sera were from healthy adults without undertaking vaccination while another 429 and 388 pre- and post-vaccinated sera were from 143 infants and 194 young children immunized with conjugate vaccine or polysaccharide vaccine, respectively. Correlation between serum bactericidal titer and the concentration of specific IgG against meningococcal serogroup C was analyzed.

RESULTS

The concentration of meningococcal serogroup C specific IgG in healthy adults showed a strong correlation (r=0.814 33, P<0.001) with serum bactericidal titer through linear regression analysis. Weak correlation was observed between SBA titers and IgG concentration in pre vaccinated sera of infants and children (conjugate/polysaccharide vaccine) (infants: r=0.140 64, P>0.100/r=0.2899, P<0.05; children: r=0.540 40, P<0.05/r=0.194 36, P<0.05). After immunization with 2-dose conjugate vaccine in infants and 1-dose in children, a strong correlation between the two panels of results was observed (r=0.809 38, P<0.001 and r=0.837 23, P<0.001 respectively). However after immunization with polysaccharide vaccine, the correlation between serum bactericidal titer and concentration of specific IgG was weak (r<0.50000).

CONCLUSION

Among healthy adults and post vaccinated infants or young children immunized with conjugate vaccine, the concentration of specific IgG was comparable to the serum bactericidal titer against meningococcal serogroup C. However, it was not unfavorable to use ELISA as the principal means of measuring serum antibody responses to polysaccharide vaccine for infants under 1 year old.

Evaluation of meningococcal serogroup C conjugate vaccine programs in Canadian children: interim analysis

BACKGROUND

To assess antibody titers afforded by meningococcal C- (MenC) tetanus toxoid conjugate vaccine at 12 months of age in three different immunization schedules.

METHODS

This prospective study included three similar cohorts of healthy infants from 1-dose, 2-dose and 3-dose MenC infant immunization programs. Infants were enrolled at 12 months of age and given the final scheduled dose of MenC-tetanus toxoid conjugate vaccine with sera collected prior to and 1 month after the vaccination. Serum bactericidal activity (SBA) titers ≥ 1:8 were considered protective.

RESULTS

Before the 12 month dose, participants had significantly different protective titers according to the number of prior doses received: 100% (95% CI 97.6-100%) of infants who had 2 prior doses (at 2 and 4 months) were protected compared to 84.0% (76.7-89.3%) of participants with one dose (at 2 months) and 27.6% (21.0-35.4%) of unvaccinated infants. All subjects were protected after the 12 month MenC dose, but titers were higher with prior priming.

CONCLUSIONS

Two MenC doses given in infancy afford optimal protection during the first year of life; however, substantial protection was seen after one dose at 2 months.

Age-related immunity to meningococcal serogroup C vaccination: an increase in the persistence of IgG2 correlates with a decrease in the avidity of IgG

BACKGROUND

All children and adolescents between 1 and 19 years of age in The Netherlands received a single meningococcal serogroup C conjugate (MenCC) vaccine in 2002. During follow-up 4-5 years later, the persistence of MenC polysaccharide-specific IgG was found to be dependent on age of vaccination with higher IgG levels in the oldest immunized age categories.

METHODS AND FINDINGS

Two cross-sectional population-based serum banks, collected in 1995/1996 and in 2006/2007, were used for this study. We measured MenC polysaccharide-specific IgM, the IgG1 and IgG2 subclasses and determined the avidity of the IgG antibodies. We report that the age-related persistence of IgG after immunization with the MenCC vaccine seemed to result from an increase of IgG2 levels with age, while IgG1 levels remained stable throughout the different age-cohorts. Furthermore, an age-related increase in IgM levels was observed, correlating with the persistence of IgG antibodies with age. It is noteworthy that the increase in IgG2 correlated with a reduced IgG-avidity with age.

CONCLUSION

These date indicate that the classical characteristics of a T-cell-dependent antibody response as elicited by protein based vaccines might not be completely applicable when conjugate vaccines are administered to older children and adolescents up to 18 years of age. The response elicited by the MenCC vaccine seemed to be more a mixture of both T cell dependent and T cell independent responses in terms of humoral immunological characteristics.

Immunity against Neisseria meningitidis serogroup C in the Dutch population before and after introduction of the meningococcal c conjugate vaccine

Background

In 2002 a Meningococcal serogroup C (MenC) conjugate vaccine, with tetanus toxoid as carrier protein, was introduced in the Netherlands as a single-dose at 14 months of age. A catch-up campaign was performed targeting all individuals aged 14 months to 18 years. We determined the MenC-specific immunity before and after introduction of the MenC conjugate (MenCC) vaccine.

Methods and Findings

Two cross-sectional population-based serum banks, collected in 1995/1996 (n = 8539) and in 2006/2007 (n = 6386), were used for this study. The main outcome measurements were the levels of MenC polysaccharide(PS)-specific IgG and serum bactericidal antibodies (SBA) after routine immunization, 4–5 years after catch-up immunization or by natural immunity. There was an increasing persistence of PS-specific IgG and SBA with age in the catch-up immunized cohorts 4–5 years after their MenCC immunization (MenC PS-specific IgG, 0.25 µg/ml (95%CI: 0.19–0.31 µg/ml) at age 6 years, gradually increasing to 2.34 µg/ml,(95%CI: 1.70–3.32 µg/ml) at age 21–22 years). A comparable pattern was found for antibodies against the carrier protein in children immunized above 9 years of age. In case of vaccination before the age of 5 years, PS-specific IgG was rapidly lost. For all age-cohorts together, SBA seroprevalence (≥8) increased from 19.7% to 43.0% in the pre- and post-MenC introduction eras, respectively. In non-immunized adults the SBA seroprevalence was not significantly different between the pre- and post-MenC introduction periods, whereas PS-specific IgG was significantly lower in the post-MenC vaccination (GMT, age ≥25 years, 0.10 µg/ml) era compared to the pre-vaccination (GMT, age ≥25 years, 0.43 µg/ml) era.

Conclusion

MenCC vaccination administered above 5 years of age induced high IgG levels compared to natural exposure, increasing with age. In children below 14 months of age and non-immunized cohorts lower IgG levels were observed compared to the pre-vaccination era, whereas functional levels remained similar in adults. Whether the lower IgG poses individuals at increased risk for MenC disease should be carefully monitored. Large-scale introduction of a MenCC vaccine has led to improved protection in adolescents, but in infants a single-dose schedule may not provide sufficient protection on the long-term and therefore a booster-dose early in adolescence should be considered.

The influence of IS1301 in the capsule biosynthesis locus on meningococcal carriage and disease

Previously we have shown that insertion of IS1301 in the sia/ctr intergenic region (IGR) of serogroup C Neisseria meningitidis (MenC) isolates from Spain confers increased resistance against complement-mediated killing. Here we investigate the significance of IS1301 in the same location in N. meningitidis isolates from the UK. PCR and sequencing was used to screen a collection of more than 1500 meningococcal carriage and disease isolates from the UK for the presence of IS1301 in the IGR. IS1301 was not identified in the IGR among vaccine failure strains but was frequently found in serogroup B isolates (MenB) from clonal complex 269 (cc269). Almost all IS1301 insertions in cc269 were associated with novel polymorphisms, and did not change capsule expression or resistance to human complement. After excluding sequence types (STs) distant from the central genotype within cc269, there was no significant difference for the presence of IS1301 in the IGR of carriage isolates compared to disease isolates. Isolates with insertion of IS1301 in the IGR are not responsible for MenC disease in UK vaccine failures. Novel polymorphisms associated with IS1301 in the IGR of UK MenB isolates do not lead to the resistance phenotype seen for IS1301 in the IGR of MenC isolates.

[Testing of antibodies against serogroup C Neisseria meningitidis by serum bactericidal assay in healthy population, Liaoning province]

OBJECTIVE

To test the serum antibodies from healthy population by Serum Bactericidal Assay (SBA), in order to evaluate the level of protective antibodies against serogroup C Neisseria meningitidis in Liaoning province.

METHODS

240 serum samples were selected from eight age-group randomly. Serogroup C vaccine candidate strain (C11) and the prevail serogroup C strain (053442) were used for SBA.

RESULTS

48.33% of 240 serum samples were positive (titer > or = 1:2) to C11 vaccine strain. Protective rate of SBA was 35.83% (titer > or = 1:8), in which, > or = 6 years old were 13.33%, 7-19 years old was 61.67%, 20-39 years old were 46.67% and > or = 40 years old were 63.33%. Rate of SBA to 053442 was lower than that to C11 in the group over 15 years old by statistic analysis.

CONCLUSION

Population under 6 years old showed lower SBA capacities. With the implemention of Expanded Program on Immunization, children under 3 years old should be considered how to give them meningococcal vaccine in order to improve the titer of antibodies against Neisseria meningitidis serogroup C.

[Study on immunogenicity of group A and group C meningococcal conjugate vaccine with coupling group B meningococcal outer membrane protein]

OBJECTIVE

To evaluate the Immunogenicity of Group A and Group C Meningococcal conjugate Vaccine with coupling Group B Meningococcal Outer Membrane Protein (Men B-OMP).

METHODS

458 healthy children aged 3-5 months, 6-23 months, 2-6 years and 7-24 years were given the Groups A and C conjugate Vaccine with MenB-OMP or other vaccine as control group to measure the pre-and post-vaccination Men A and C and B by Serum Bactericidal Assay (SBA) in the double-blind randomized controlled trial.

RESULTS

97.65%-100% were 4 times or greater increase in SBA titer for the healthy children given the Groups A and C conjugate Vaccine with MenB-OMP, The geometric mean titer of SBA were 1:194-1:420, which significantly higber than controls.

CONCLUSION

The Group A and C conjugate Vaccine with MenB-OMP was safe and well immunogenic.

Investigation of serum bactericidal activity in childhood and adolescence 3-6 years after vaccination with a single dose of serogroup C meningococcal conjugate vaccine

Serogroup C meningococcal conjugate vaccines were introduced in Greece in 2001, and although no cases of serogroup C meningococcal disease were recorded in 2004, a steady increase was observed since 2005. In this study, serum bactericidal activity was assessed in sera of 269 vaccinated children at a mean time of about 5 years after vaccination. Non-protective antibody titers were observed in most children vaccinated at age <6 years (85.9%), followed by those between 6 and 10 years (62.2%). This percentage was considerably lower in adolescents vaccinated at an age >10 years (37.8%) (p<0.01). Geometric mean concentrations of serum IgG antibodies against serogroup C showed a similar variation. The results indicate that serum bactericidal antibody titers significantly correlate with age of vaccination; most children do not have protective antibody titers few years after immunization in infancy and childhood whereas most adolescents maintain sustained protection.

[Study on the bactericidal antibody against Neisseria meningitidis serogroup C strains after immunization with a divalent polysaccharide (A plus C) vaccine]

OBJECTIVE

To optimize the serum bactericidal assay (SBA), detect and analyze the bactericidal antibody level against Neisseria meningitidis serogroup C strains after divalent polysaccharide (A plus C) vaccine immunization.

METHODS

Two Neisseria meningitidis serogroup C strains, vaccine candidate strain (C11) and epidemic strain (053442), were selected as targets. The national Neisseria meningitidis standardized serum was used as reference serum. Pel-Freez infant rabbit complements was available. The optimized SBA method was used to detect bactericidal antibody against strain C11 and 053442 for 122 pairs of sera before and after immunization with a divalent polysaccharide (A and C) vaccine.

RESULTS

The strain C11 and 053442 both could be used as targeted strain for SBA. The optimized concentration of targeted strain was achieved when a whole-cell suspension of 0.35 A at 600 nm was diluted 4 x 10(4) times. Before immunization, SBA geometric mean titers (GMT) of 122 sera against strain C11 and 053442 were 1:1.75 and 1:2.63 respectively, and the protective rates were 9.8% and 17.2% respectively. After immunization, the GMTs and the protective rates of 122 sera both rose significantly (P<0.01), the GMTs against strain C11 and 053442 were 1:483.73 and 1:412.57 respectively. The protective rates against strain C11 and 053442 were 100% and 95.9% respectively.

CONCLUSION

Immunization with a divalent polysaccharide (A and C) vaccine could elevate remarkably the population SBA titer against Neisseria meningitidis serogroup C strains of different subtypes, but the surveillance of vaccine effect against different targeted strains remains necessary.

Seroprotection against serogroup C meningococcal disease in adolescents in the United Kingdom: observational study

OBJECTIVE

To determine the persistence of bactericidal antibody titres following immunisation with serogroup C meningococcal glycoconjugate vaccine at age 6-15 years in order to examine changes in persistence of antibodies with age.

DESIGN

Observational study.

SETTING

Secondary and tertiary educational institutions in the United Kingdom.

PARTICIPANTS

Healthy adolescents aged 11-20 years previously immunised between 6 and 15 years of age with one of the three serogroup C meningococcal vaccines.

INTERVENTION

Serum obtained by venepuncture.

MAIN OUTCOME MEASURES

Percentage of participants with (rabbit complement) serum bactericidal antibody titres of at least 1:8; geometric mean titres of serogroup C meningococcal serum bactericidal antibody.

RESULTS

Five years after immunisation, 84.1% (95% confidence interval 81.6% to 86.3%) of 987 participants had a bactericidal antibody titre of at least 1:8. Geometric mean titres of bactericidal antibody were significantly lower in 11-13 year olds (147, 95% confidence interval 115 to 188) than in 14-16 year olds (300, 237 to 380) and 17-20 year olds (360, 252 to 515) (P<0.0001 for both comparisons). Within these age bands, no significant difference in geometric mean titres of bactericidal antibody between recipients of the different serogroup C meningococcal vaccines was seen. More than 70% of participants had received a vaccine from one manufacturer; in this cohort, geometric mean titres were higher in those immunised at aged 10 years or above than in those immunised before the age of 10.

CONCLUSIONS

Higher concentrations of bactericidal antibody are seen five years after immunisation with serogroup C meningococcal vaccine at age 10 years or above than in younger age groups, possibly owing to immunological maturation. This provides support for adolescent immunisation programmes to generate sustained protection against serogroup C meningococcal disease not only for the vaccine recipients but also, through the maintenance of herd immunity, for younger children.

Meningococcal B vaccine: new drug. The only vaccine against some serogroup B meningococci

(1) Invasive infections due to serogroup B meningococci can be life-threatening. Antibiotics are not always effective. Vaccines available in France do not protect against serogroup B meningococci. (2) In the French region of Normandy, a vaccine manufactured by the Norwegian National Institute of Public Health and directed against serogroup B meningococci. (2) In the French region of Normandy, a vaccine manufactured by the Norwegian National Institute of Public Health and directed against a meningococcal strain related to the strain circulating in this region has been used since summer 2006 to protect children over one year of age and adolescents. (3) A review of the 16 available immunogenicity studies shows that immunogenicity is similar in children and adults when the vaccine is administered in two doses, six weeks apart. The manufacturing process was modified in 1995, and the new vaccine could be less immunogenic: three doses provided results similar to those obtained with two doses of the older vaccine. This implies that, in epidemic situations, the maximum protection conferred by the vaccine would be reached 3 to 4 months after beginning vaccination. (4) A double-blind placebo-controlled trial conducted between 1988 and 1991 included 171 800 adolescents aged 14 to 16 years who received two doses of the meningitis B vaccine, or placebo injections. During 29 months of follow-up, 12 invasive infections due to serogroup B meningococci occurred in the vaccine group, versus 24 cases in the placebo group. The protection rate was 57% but the confidence interval was very wide (21% to 78%). A correlation was established between the bactericidal antibody titre and clinical protection. (5) In this trial, the adverse events studied in 877 adolescents were infrequent: less than 4% of local adverse events, and about the same proportion of systemic adverse events (headache, nausea, fatigue, malaise), led to taking time off school. (6) Too few data are available for infants. And it is difficult to extrapolate to other countries the results obtained in Norway 10 years ago with a vaccine that was manufactured differently and may be more immunogenic. (7) In practice, vaccination with the Norwegian vaccine is justified in areas where an epidemic strain closely related to the vaccine strain is circulating, even though only about 60% of vaccinees are protected after three doses.

Immune response to conjugated meningococcal C vaccine in pediatric oncology patients

BACKGROUND

Following outbreaks of meningococcal disease in Quebec in 1991-1993 and 2000-2001, a mass vaccination campaign was performed. In 2001-2002, children aged 2 months to 20 years were immunized with the Meningococcal CRM197 vaccine (Menjugate). We examined the response of pediatric oncology patients during or following maintenance chemotherapy and post-bone-marrow transplantation to Meningococcal C vaccine.

PROCEDURE

This was an open label descriptive study of a cohort of patients from the oncology clinic at the Montreal Children's Hospital. A positive vaccine response was defined as a fourfold increase in specific IgG from baseline and a bactericidal assay using human complement (hBCA) titer >1:4.

RESULTS

Of the 25 patients with ALL, 13 had a serologic response (average 60-fold increase). The serologic responders had a higher mean B cell count (0.262) compared to non-responders 0.068 x 10.9/L [t(23) = 2.843 (P < 0.05)]. Eleven of the 12 non-responders and 4 of the responders were on maintenance chemotherapy. In addition, two of the five patients post-bone-marrow transplant, responded. Fifteen of the 34 patients (44%) had an adequate hBCA response (mean titer 61). The group included 14/18 serologic responders with hBCA response (P < 0.001) and 16/17 non-serologic responders with no hBCA response (P < 0.001).

CONCLUSIONS

Meningococcal C-conjugate vaccine produced variable responses in children with common cancers. Proximity to chemotherapy and total B cell number may help predict likelihood of response.

Meningococcal disease: a review on available vaccines and vaccines in development

Meningococcal disease continue to have a major public health impact in many countries. Five major groups of Neisseria meningitidis (A, B, C, Y and W135) are responsible for most meningococcal diseases. Plain polysaccharides vaccines for Neisseria meningitidis groups A, C, Y and W-135 have been in use for approximately 20 years, both to prevent invasive disease in high-risk population and to control disease outbreaks. However, these conventional meningococcal vaccines induce a relatively short-lasting T-cell independent immune response, are not effective in children under two years of age and can induce hyporesponsiveness. New meningococcal group C conjugate vaccines have since been developed, which offer solid advantages over the currently licensed plain polysaccharide vaccines. Tetravalent serogroup A, C, Y and W135 meningococcal vaccines are under development and one has already been licensed. There is still no universal vaccine available against the serogroup B, which is a major cause of invasive disease. This report summarises the different approaches to the development of vaccines against the pathogenic meningococci.

Age-specific seroprevalence of serogroup C meningococcal serum bactericidal antibody activity and serogroup A, C, W135 and Y-specific IgG concentrations in the Turkish population during 2005

Like many other developing countries; there is no accurate information about the antibody levels against Neisseria meningitidis in Turkey. We collected serum samples from four health centers located in different geographic regions and stratified according to age in order to obtain a baseline seroprevalence of protective antibodies to meningococcal serogroup C and provide data on seroprevalence of IgG antibodies to serogroups A, C, W135 and Y. Sera were tested for serum bactericidal antibodies (SBA) to serogroup C meningococci using rabbit serum as the complement source and by a bead based assay for serogroup A, C, W135 and Y-specific IgG. It was observed that 30% and 12% of individuals within the study population had SBA titers of > or =8 and > or =128, respectively. Overall; at least 70% of the population are susceptible (SBA titer <8) to meningococcal serogroup C disease. The rate of susceptibility was highest in infants aged 7-12 months and young children (1-4 years). Regardless of age, for serogroup A, C, W135 and Y, 60.5%, 27.2%, 12.3% and 19.2% of subjects, respectively, had serogroup-specific IgG concentrations > or =2 microg/mL. These data highlight that a large proportion of the Turkish population are susceptible to serogroups C, W135 and Y and should be considered, along with serogroup-specific disease incidence data, in future decisions on possible meningococcal vaccination programmes.

Serum bactericidal antibody response to serogroup C polysaccharide meningococcal vaccination in children with primary antibody deficiencies

Primary antibody deficiencies are characterized by decreased serum levels of immunoglobulin isotypes and increased susceptibility to infection by various microorganisms including encapsulated bacteria. This study was performed in order to evaluate bactericidal antibody response of these patients to polysaccharide meningococcal vaccine. Twenty-four antibody deficient children of mean age 11.2+/-3.5 years, and 15 sex and age-matched healthy volunteers were enrolled. All subjects received meningococcal polysaccharide vaccine A+C; blood samples were collected before vaccination and 3 weeks after vaccination. Following vaccination, the serum bactericidal antibody (SBA) geometric mean titre was significantly increased compared to the prevaccination level in the patient group (8.98 versus 1.63, P<0.001) and the control group (12.13 versus 1.26, P<0.001). All controls had a protective SBA response (SBA titre of >or=8 post-vaccination or rise of >or=4-fold from pre- to post-vaccination), whereas only 16 of 24 patients (66.6%) had a protective response (P=0.014). The non-responder patients included 5 cases with common variable immunodeficiency, two cases with hyper IgM syndrome, and one case with IgG subclass deficiency. This study indicates that some patients with primary antibody deficiencies can produce protective post-vaccination titres similar to the normal population, despite the common perception that patients with primary antibody deficiencies respond poorly to vaccination. This supports the use of polysaccharide-containing vaccines in these patients.

PorA variable antigenic regions VR1, VR2, and VR3 of Neisseria meningitidis serogroups B and C isolated in Brazil from 1999 to 2004

The high genetic diversity found among the PorA regions VR1 and VR2 of 101 Neisseria meningitidis isolates from patients with meningococcal disease and healthy carriers in Brazil contrasts with the stability found in the PorA VR3 of these isolates. The presence of VR3 epitope variant 35 or 36 on the surfaces of 87% of the strains analyzed suggests that these antigens should be considered for inclusion in new formulations of vaccines against serogroup B meningococci in Brazil.

Characterization of serogroup C meningococci isolated from 14 provinces of China during 1966-2005 using comparative genomic hybridization

Neisseria meningitidis is a major cause of bacterial meningitis and septicemia worldwide. In China, serogroup A strains were responsible for over 95% of the cases, while serogroup C strains were only recovered from a few sporadic cases. However, a sudden increase in the number of cases due to serogroup C strains occurred during 2003-2005 in Anhui Province, China. Many cases were found in other provinces at the same time. Multilocus sequence typing (MLST) results indicated that the unique sequence type 4821 clone meningococci, a new hyper-virulent lineage, was responsible for the serogroup C meningitis outbreaks. We have completed the project of sequencing the whole genome of the Chinese N. meningitidis serogroup C representative isolate 053442. We fabricated a whole-genome microarray of N. meningitidis isolate 053442 and analyzed the genome composition differences among 81 serogroup C isolates which were isolated from 14 provinces of China during 1966-2005. The comparative genomic hybridization (CGH) result shows that the genome compositions of nearly all serogroup C isolates are similar to that of 053442. The products of many absent open reading frames (ORFs) are conserved hypothetical proteins. The results will provide a valuable resource from which one can analyze the genome composition and genetic background of serogroup C meningococci in China.

Seroprevalence of bactericidal and anti-outer membrane vesicle antibodies to Neisseria meningitidis group B in England

Outer membrane vesicle (OMV) and recombinant protein-based vaccines targeted against multiple strains of group B meningococci are under development. The serum bactericidal antibody (SBA) assay has been designated the surrogate of protection, but the exact cutoff has not been determined. We measured the SBA titers in 2,415 serum samples and the anti-OMV IgG antibody concentrations in 2,672 serum samples representative of the English population to establish a baseline of natural immunity. SBA and anti-OMV IgG antibody titers are high in infants in the first 3 months of life, declining thereafter, presumably as maternal immunity wanes. About 6% of the subjects in the 1- to 11-year-old age group had SBA titers >or=4. During the teenage years, there was a marked increase in the percentage of subjects with SBA titers >or=4, rising to over 50% in 19-year-olds, with about 20% of older adults achieving this titer. The peak in SBA and anti-OMV IgG titers coincided with the peak in meningococcal carriage. Simple mathematical models confirm that the relationship between observed seroprevalence and carriage by age is consistent with carriage inducing SBA and that following an episode of carriage, SBA levels may remain elevated for many months. With the exception of children aged 3 to 11 months, there was no clear relationship between disease incidence and seroprevalence.

Protective meningococcal capsular polysaccharide epitopes and the role of O acetylation

Previous studies with group C meningococcal polysaccharide-tetanus toxoid (GCMP-TT) conjugates had suggested that the GCMP O-acetyl group masked the protective epitope for group C meningococci through steric hindrance or altered conformations. For this report, we confirmed this phenomenon and performed comparative studies with group Y meningococcal polysaccharide (GYMP)-TT to determine whether it might extend to other serogroups. The de-O-acetylated (dOA) polysaccharides (PSs) resulted in higher serum bactericidal activities (SBA) towards the O-acetylated (OA) meningococcal strains from the respective serogroups. High-resolution H-nuclear magnetic resonance spectroscopy at 500 MHz and competitive inhibition serum bactericidal assays were used to characterize the nature of the protective epitope. In head-to-head comparisons with OA PSs as SBA inhibitors, the dOA PSs provided 10 to 1,000 times better inhibition for GCMP in human and mouse antisera and 6 to 13 times better inhibition for GYMP in mouse antisera, using OA strains in all assays. In addition, the SBA for OA strains was highly correlated with dOA PS-specific immunoglobulin G (r=0.72 to 0.98) for both GCMP and GYMP. The results suggest that there may be a generalized role for the O-acetyl group to provide an epitope of misdirected immunogenicity for meningococcal PS capsules, enabling escape from immune surveillance. In addition to greater chemical consistency, the dOA forms of GCMP and GYMP conjugate vaccines endow greater immunologic competence to the PSs, rendering them capable of eliciting higher levels of functional antibodies toward the protective epitopes.

A randomized study comparing the safety and immunogenicity of a conjugate vaccine combination containing meningococcal group C and pneumococcal capsular polysaccharide—CRM197 with a meningococcal group C conjugate vaccine in healthy infants: Challenge phase

BACKGROUND

A combination nonavalent pneumococcal-group C meningococcal conjugate vaccine (Pnc9-MenC) was previously found to be safe and immunogenic when administered to infants at 2, 3 and 4 months. This study describes the persistence of immunity at 12 months of age and the immunologic response to a challenge dose of either meningococcal polysaccharide vaccine (Meningivac A+C; MnA+C), or MenC.

METHODS

A phase II, randomized, controlled trial of healthy infants. Subjects were given Pnc9-MenC or MenC vaccine at 2, 3 and 4 months of age and then challenged with either MenC or MnA+C. Group C meningococcal immunogenicity was measured by serum bactericidal assay (SBA) and an enzyme-linked immunosorbent assay (ELISA) adapted to measure antibody avidity pre- and post-challenge.

RESULTS

The MenC vaccine was more immunogenic than the Pnc9-MenC vaccine in persistence of serogroup C meningococcal polysaccharide antibodies at 12 months of age. Post-challenge at 13 months there were significant differences between the four groups in the induction of serogroup C meningococcal polysaccharide antibodies. The responses to MenC/MenC were significantly higher than in the other groups (p<0.001) and the responses to Pnc9-MenC/MnA+C were significantly lower than in the other groups (p<0.001). There was no difference between the four groups in the proportions with geometric mean concentrations (GMC) greater than 2 microg/ml (p=0.18) or with SBA titres greater than or equal to the protective level of 1:8 (p=0.89). The SBA geometric mean ratio (GMR) between pre- and post-challenge was higher in the groups challenged with MenC than those challenged with MnA+C. Antibody avidity increased over time.

CONCLUSION

We have shown that Pnc9-MenC primes effectively for immunological memory. At 13 months of age the highest immune responses were seen in the subjects primed and challenged with MenC alone. However, all groups achieved the threshold levels required for protection.

Immunogenicity, reactogenicity, and immune memory after primary vaccination with a novel Haemophilus influenzae-Neisseria meningitidis serogroup C conjugate vaccine

We evaluated two formulations of a new combined Haemophilus influenzae type b (Hib)-meningococcal serogroup C (MenC)-tetanus toxoid (TT) conjugated vaccine and two formulations of a new MenC-TT vaccine (trials 711202/001 and 711202/008; clinical trial register numbers NCT00135486 and NCT00135564 [www.ClinicalTrials.gov]). A total of 520 healthy infants were randomized to receive primary vaccination (at 2, 3, and 4 months) with either MenC-TT plus diphtheria-tetanus-acellular pertussis (DTPa)-hepatitis B virus (HBV)-inactivated poliovirus (IPV)/Hib, Hib-MenC-TT plus DTPa-HBV-IPV, or MenC-CRM(197) plus DTPa-HBV-IPV/Hib (control). At 12 to 15 months, subjects received a polysaccharide challenge with meningococcal polysaccharide C plus a DTPa-HBV-IPV/Hib booster. Immune responses were assessed 1 month after dose 2, 1 month after dose 3, and prior to and 1 month after the booster. After primary vaccination, there was no difference between groups in seroprotection rates as measured by titers of serum bactericidal antibody (SBA) to MenC (> or = 1:8) or concentrations of anti-polyribosyl ribitol phosphate (PRP) antibody (> or = 0.15 microg/ml). Prior to the booster, there was no difference between groups in SBA seroprotection rates, whereas anti-PRP seroprotection rates were significantly higher after priming with Hib-MenC-TT. Booster doses induced large increases in SBA and anti-PRP antibodies in primed groups, indicating successful priming with induction of immune memory. Reactogenicity and safety were similar in all groups during the primary and booster phases. A novel combined Hib-MenC-TT conjugate vaccine induced MenC and Hib responses comparable to those induced by licensed monovalent vaccines. A Hib-MenC-TT conjugate vaccine provides vaccination against two major pathogens in a single injection and is a suitable candidate for use in primary or booster vaccination schedules.

Meningococcal group C disease in Greece during 1993-2006: the impact of an unofficial single-dose vaccination scheme adopted by most paediatricians

The aim of this study was to evaluate the impact of the meningococcal C conjugate vaccine on the epidemiology of meningococcal C disease in Greece. Data from the National Reference Laboratory for Meningococcal Disease and a questionnaire distributed to Greek paediatricians were assessed. Since the introduction of the vaccine in 2001, 72% of Greek paediatricians have administered it as one single dose to patients aged > or =12 months. This vaccination scheme has probably contributed to a dramatic decrease in the number of meningococcal C infections, which reached zero in 2004.

Avidity of the immunoglobulin G response to a Neisseria meningitidis group C polysaccharide conjugate vaccine as measured by inhibition and chaotropic enzyme-linked immunosorbent assays

Antibody avidity, the strength of the multivalent interaction between antibodies and their antigens, is an important characteristic of protective immune responses. We have developed an inhibition enzyme-linked immunosorbent assay (ELISA) to measure antibody avidity for the capsular polysaccharide (PS) of Neisseria meningitidis group C (MnC) and determined the avidity constants (K(D)s) for 100 sera from children immunized with an MnC PS conjugate vaccine. The avidity constants were compared to the avidity indices (AI) obtained for the same sera using a chaotropic ELISA protocol. After the primary immunization series, the geometric mean (GM) K(D) was 674 nM and did not change in the months following immunization. However, the GM avidity did increase after the booster dose (GM K(D), 414 nM 1 month after booster immunization). In contrast, the GM AI increased from an initial value of 118 after the primary immunization series to 147 6 months after the completion of the primary immunization series and then further increased to 178 after booster immunization. At the individual subject level, the avidity constant and AI correlated after the primary immunization series and after booster immunization but not prior to boosting. This work suggests that the AI, as measured by the chaotropic ELISA, in contrast to the K(D), reflects changes that render antibody populations less susceptible to disruption by chaotropic agents without directly affecting the strength of the binding interactions.

Immunogenicity and reactogenicity of primary immunization with a novel combined Haemophilus influenzae Type b and Neisseria meningitidis Serogroup C-tetanus toxoid conjugate vaccine coadministered with a Diphtheria-tetanus-acellular Pertussis-hepatitis B-inactivated poliovirus vaccine at 2, 4 and 6 months

BACKGROUND

This phase II study evaluated the immunogenicity and reactogenicity of primary vaccination with a novel Hib-MenC conjugate vaccine (GlaxoSmithKline [GSK] Biologicals) coadministered with DTPa-HBV-IPV (GSK Biologicals) at 2, 4 and 6 months.

METHODS

Healthy infants were randomized to receive Hib-MenC coadministered with DTPa-HBV-IPV (N = 117) or MenC-CRM (Wyeth) coadministered with DTPa-HBV-IPV/Hib (GSK Biologicals; N = 120) at 2, 4 and 6 months. Antibody concentrations were measured before vaccination and after doses 2 and 3. Solicited local and general symptoms, unsolicited symptoms and serious adverse events (SAEs) were recorded.

RESULTS

All subjects in the Hib-MenC group had seroprotective titers of anti-PRP antibodies (>or=0.15 microg/mL) and SBA-MenC titers (>or=1:8) 1 month after the third dose. These responses were noninferior to those seen in the control group, in which a 99.1% seroprotection rate was observed for both Hib and MenC. At that time, anti-PRP and SBA-MenC GMTs were significantly higher in the Hib-MenC group (12.8 microg/mL and 2467.1 microg/mL, respectively) than in the control group (3.8 microg/mL and 1833.7 microg/mL). High seroprotection rates were already observed after the second dose of Hib-MenC; 96.4% and 100% of subjects were seroprotected to Hib and MenC, respectively. Immune responses to coadministered antigens were unimpaired; seroprotection/vaccine response rates >or=96.5% were recorded postdose 3 in the Hib-MenC group. No differences in reactogenicity were seen between the 2 study groups.

CONCLUSIONS

Coadministration of a Hib-MenC conjugate vaccine with DTPa-HBV-IPV is well tolerated and immunogenic, and does not impair the immune response to any of the coadministered antigens.

Clinical and Immunologic Risk Factors for Meningococcal C Conjugate Vaccine Failure in the United Kingdom

BACKGROUND

The meningococcal serogroup C conjugate (MCC) vaccine was introduced into the United Kingdom with licensure based on immunogenicity data not efficacy data.

METHODS

All subjects with laboratory-confirmed meningococcal serogroup C (MenC) disease from January 2000 to December 2003 in England and Wales were followed up. A vaccine failure was defined as a laboratory-confirmed case of MenC disease occurring > or =10 days after the subject's last scheduled dose of MCC vaccine. Total immunoglobulins, serum bactericidal antibody (SBA) titers, MCC anticapsular antibody levels, and avidity indices (AIs) were measured in acute and convalescent serum samples from subjects with vaccine failure and unvaccinated subjects with MenC disease.

RESULTS

Of 465 subjects with confirmed MenC disease identified among those eligible for vaccination, information on vaccination history was obtained for 462 (99.4%); of these, 53 were subjects with vaccine failure. SBA titers in convalescent serum samples and AIs in acute serum samples were significantly higher in subjects with vaccine failure than in unvaccinated subjects, (6.1-fold higher for SBA titers [P=.03] and 3.2-fold higher for AIs [P=.001]).

CONCLUSIONS

The antibody response in the subjects with vaccine failure was consistent with an anamnestic response, suggesting that MenC disease occurred despite the MCC vaccine priming for immune memory. Persistence of antibodies may be a more appropriate correlate of long-term protection for MCC vaccines than the ability to generate a booster response on exposure.

Overcoming the need for a cold chain with conjugated meningococcal Group C vaccine: A controlled, randomized, double-blind study in toddlers on the safety and immunogenicity of Menjugate, stored at room temperature for 6 months

Millions of vaccine doses are wasted each year due to a lapse in recommended storage conditions. Maintaining the cold chain for vaccines is both expensive and difficult, especially in developing countries. The present study investigated the safety and immunogenicity of a single dose of the conjugated meningococcal Group C vaccine, Menjugate, stored for 6 months at room temperature (25+/-2 degrees C, N=250) or at 2-8 degrees C (N=250) when administered to 12-23 months toddlers. In the two respective groups, 87 and 88% of toddlers reached bactericidal antibodies titers of at least 1:8. The immunogenicity of Menjugate stored at room temperature was not inferior to that stored at 2-8 degrees C. The safety profile and immunogenicity of the vaccine was not influenced by the storage condition.

CRM197-conjugated serogroup C meningococcal capsular polysaccharide, but not the native polysaccharide, induces persistent antigen-specific memory B cells

Neisseria meningitidis is one of the leading causes of bacterial meningitis and septicemia in children. Vaccines containing the purified polysaccharide capsule from the organism, a T cell-independent antigen, have been available for decades but do not appear to provide protection in infancy or immunologic memory as measured by antibody responses. By contrast, T cell-dependent serogroup C protein-polysaccharide conjugate vaccines protect against serogroup C meningococcal disease from infancy onward and prime for immunologic memory. We compared the magnitude and kinetics of plasma cell and memory B-cell responses to a meningococcal plain polysaccharide vaccine and a serogroup C glycoconjugate vaccine in adolescents previously primed with the conjugate vaccine. Plasma cell kinetics were similar for both vaccines, though the magnitude of the response was greater for the glycoconjugate. In contrast to the glycoconjugate vaccine, the plain polysaccharide vaccine did not induce a persistent immunoglobulin G (IgG) memory B-cell response. This is the first study to directly show that serogroup C meningococcal glycoconjugate vaccines induce persistent production of memory B cells and that plain polysaccharide vaccines do not, supporting the use of the conjugate vaccine for sustained population protection. Detection of peripheral blood memory B-cell responses after vaccination may be a useful signature of successful induction of immunologic memory during novel vaccine evaluation.

Population-based seroprevalence of Neisseria meningitidis serogroup C capsular antibody before the introduction of conjugate vaccine, in Australia

Neisseria meningitidis serogroup C (NMC) conjugate vaccine was introduced, in Australia, in 2003. Our aims were to determine pre-immunisation IgG NMC seroprevalence and evaluate an enzyme-linked immunosorbent assay (ELISA), previously validated against the serum bactericidal assay (SBA). 2409 sera, collected in 2002, from subjects aged 2-34 years, were tested. The geometric mean concentration (GMC) of NMC anticapsular IgG was 0.38 U/mL in subjects under 19 years and it increased to 0.67 U/mL for those aged 30-34 years. Variation in GMC correlated with reported NMC disease incidence and was higher in males than females (0.52 U/mL versus 0.41 U/mL; p=0.005). The ELISA appears suitable for serosurveillance but the IgG level that correlates with protection needs further investigation. Serosurveys will be repeated to monitor the impact of vaccination.

A conjugate vaccine composed of a heat shock protein 60 T-cell epitope peptide (p458) and Neisseria meningitidis type B capsular polysaccharide

Neisseria meningitidis type B is a major world-health problem. The Meningococcus type B capsular polysaccharide (MnB) is very poorly immunogenic and no vaccine to the antigen exists. Here, we conjugated the MnB to a T-cell carrier peptide (p458) derived from the self-60kDa heat shock protein molecule. The conjugate vaccine was effective in inducing long-lasting IgG antibodies to the MnB antigen in mice. The vaccine was also immunogenic when injected in PBS. Thus, the p458 carrier peptide can induce T-cell help for the switch to IgG Ab to the MnB antigen.

Universal childhood immunisation with pneumococcal vaccine and meningococcal serogroup C vaccine introduced in Germany

In July 2006, vaccination against meningococcal C and pneumococcal disease was added to the routine childhood immunisation programme in Germany

New rapid diagnostic tests for Neisseria meningitidis serogroups A, W135, C, and Y

BACKGROUND

Outbreaks of meningococcal meningitis (meningitis caused by Neisseria meningitidis) are a major public health concern in the African "meningitis belt," which includes 21 countries from Senegal to Ethiopia. Of the several species that can cause meningitis, N. meningitidis is the most important cause of epidemics in this region. In choosing the appropriate vaccine, accurate N. meningitidis serogroup determination is key. To this end, we developed and evaluated two duplex rapid diagnostic tests (RDTs) for detecting N. meningitidis polysaccharide (PS) antigens of several important serogroups.

METHODS AND FINDINGS

Mouse monoclonal IgG antibodies against N. meningitidis PS A, W135/Y, Y, and C were used to develop two immunochromatography duplex RDTs, RDT1 (to detect serogroups A and W135/Y) and RDT2 (to detect serogroups C and Y). Standards for Reporting of Diagnostic Accuracy criteria were used to determine diagnostic accuracy of RDTs on reference strains and cerebrospinal fluid (CSF) samples using culture and PCR, respectively, as reference tests. The cutoffs were 10(5) cfu/ml for reference strains and 1 ng/ml for PS. Sensitivities and specificities were 100% for reference strains, and 93.8%-100% for CSF serogroups A, W135, and Y in CSF. For CSF serogroup A, the positive and negative likelihood ratios (+/- 95% confidence intervals [CIs]) were 31.867 (16.1-63.1) and 0.065 (0.04-0.104), respectively, and the diagnostic odds ratio (+/- 95% CI) was 492.9 (207.2-1,172.5). For CSF serogroups W135 and Y, the positive likelihood ratio was 159.6 (51.7-493.3) Both RDTs were equally reliable at 25 degrees C and 45 degrees C.

CONCLUSIONS

These RDTs are important new bedside diagnostic tools for surveillance of meningococcus serogroups A and W135, the two serogroups that are responsible for major epidemics in Africa.