Novel approaches to Neisseria meningitidis vaccine design

A range of vaccines is available for preventing life-threatening diseases caused by infection with Neisseria meningitidis (meningococcus, Men). Capsule polysaccharide (CPS)-conjugate vaccines are successful prophylactics for serogroup MenA, MenC, MenW and MenY infections, and outer membrane vesicle (OMV) vaccines have been used successfully for controlling clonal serogroup MenB infections. MenB vaccines based on recombinant proteins identified by reverse vaccinology (Bexsero™) and proteomics (Trumenba™) approaches have recently been licensed and Bexsero™ has been introduced into the UK infant immunisation programme. In this review, we chart the development of these licensed vaccines. In addition, we discuss the plethora of novel vaccinology approaches that have been applied to the meningococcus with varying success in pre-clinical studies, but which provide technological platforms for application to other pathogens. These strategies include modifying CPS, lipooligosaccharide and OMV; the use of recombinant proteins; structural vaccinology approaches of designing synthetic peptide/mimetope vaccines, DNA vaccines and engineered proteins; epitope presentation on biological and synthetic particles; through vaccination with live-attenuated pathogen(s), or with heterologous bacteria expressing vaccine antigens, or to competitive occupation of the nasopharyngeal niche by commensal bacterial spp. After close to a century of vaccine research, it is possible that meningococcal disease may be added, shortly, to the list of diseases to have been eradicated worldwide by rigorous vaccination campaigns.

[Effectiveness of an immunization campaign with group A and C meningococcal polysaccharide vaccine in controlling an outbreak of group C meningococcal disease]

OBJECTIVE

To assess the safety, immunogenicity and efficacy of group A and C meningococcal polysaccharide vaccine (A/C MPV) in response to an outbreak of group C meningococcal disease.

METHODS

A vaccination campaign with A/C MPV was prompted 6 weeks after the use of group A MPV in Laibin city, Guangxi, where an outbreak of group C meningococcal meningitis occurred in 2002. Vaccinees were observed for local and systemic reactions after the vaccination and followed up for the meningococcal disease for 5 years. Blood samples were collected from 71 people in the epidemic and 43 in the non-epidemic areas before and 1 month after the vaccination and examined by ELISA to detect IgG antibodies to group A and C polysaccharides.

RESULTS

The vaccination coverage was 97%. No significant adverse reactions were observed. The positive rates of group C antibodies after vaccination was between 97.67% and 100% among the populations in the epidemic and non-epidemic areas, as well as among those negative and positive for group C antibodies prior to the vaccination. The geometric mean anti-C concentrations ranged 30.81 microg/ml to 37.44 microg/ml, showing no significant difference between groups. The incidence rate of meningococcal disease in students with timely immunization (218.58/100,000) dropped by 69.02%, when compared to that in those with delayed immunization (705.72/100,000). No clinical cases were identified during the follow-up period of 15,760 person-years.

CONCLUSION

The vaccination campaign with the Chinese group A/C MPV seemed successful in controlling the group C meningococcal outbreak. The vaccine was shown to be safe even administered after the group A vaccine only 6 weeks apart. It could induce high levels of antibodies in vulnerable population and significantly increase antibody levels in seropositive individuals, thus providing a protection of at least 5 years.

Emergence of Vaccine-Related Pneumococcal Serotypes as a Cause of Bacteremia

BACKGROUND

The heptavalent pneumococcal conjugate vaccine (PCV7) has decreased the incidence of invasive pneumococcal disease among children in the United States. In the postlicensure period, the impact of non-PCV7 serotypes against pediatric pneumococcal bacteremia is unknown.

METHODS

Episodes of bacteremia due to Streptococcus pneumoniae and other respiratory pathogens (ORP), namely Neisseria meningitidis, Haemophilus influenzae, and Moraxella catarrhalis, were identified in children <18 years old at the Children's Hospital of Philadelphia from January 1999 to May 2005. For pneumococci, serotype distribution and antibiotic resistance were compared.

RESULTS

A total of 188 episodes of pneumococcal bacteremia and 55 episodes of ORP bacteremia were identified. By comparing data from 1999-2000 with data from 2001 to May 2005, we found that the incidence of pneumococcal bacteremia decreased by 57%. The incidence of bacteremia caused by ORPs was unchanged; 1.43 episodes (95% confidence interval [CI], 0.84-2.29 episodes) to 1.25 (95% CI, 0.88-1.71) per 10,000 emergency department visits. Vaccine serotypes caused 85% of episodes of bacteremia in 1999-2000, compared with 34% of episodes of bacteremia in 2001 to May 2005 (P<.01). The percentage of isolates nonsusceptible to penicillin increased from 25% to 39% (P<.05). The percentage of episodes of pneumococcal bacteremia caused by vaccine-related serotypes--those of the same serogroup but not of the same serotype as PCV7--increased from 6% of episodes in the prelicensure period to 35% of episodes in the postlicensure period (P<.01). Rates of serotype pneumococcal bacteremia caused by nonvaccine serotypes were not statistically different between the 2 periods.

CONCLUSIONS

The overall incidence of pneumococcal bacteremia decreased by 57% after the introduction of PCV7. During the postlicensure period, there were significant decreases in the incidence of pneumococcal bacteremia caused by vaccine serotypes; however, rates of penicillin resistance and bacteremia due to vaccine-related serotypes increased.

Crossover vaccination with quadrivalent meningococcal vaccine (against A/C/Y/W-135) following recent application of bivalent meningococcal vaccine (against A/C): assessment of safety and side effect profile

BACKGROUND

Until May 2000, bivalent A/C meningococcal vaccine was the only available vaccine in Singapore for hajj travelers to Saudi Arabia. Recent worldwide reports of serogroup W-135 meningococcal meningitis associated with hajj returnees necessitated switching to quadrivalent A/C/Y/W-135 vaccine and crossover vaccination of travelers to Saudi Arabia. No safety data are available for quadrivalent vaccine following recent vaccination with bivalent vaccine. We assessed the safety and side effect profile of bivalent, quadrivalent, and quadrivalent meningococcal vaccine after recent vaccination with bivalent vaccine.

METHODS

A postvaccination telephone questionnaire survey was performed for all travelers who received either bivalent (B), quadrivalent (Q), or quadrivalent with recent (as defined by less than 6 months before) bivalent meningococcal vaccine (BQ) between 22 May and 8 June 2000 in preparation for the umrah (minor pilgrimage). Patients were asked about local reactions (pain, erythema, swelling at injection site graded in mild, moderate, and severe) and systemic reactions (fever, headache, graded in mild and severe).

RESULTS

Of 546 persons vaccinated, 323 were interviewed. Median time interval between interview and vaccination was 10 days. Of those interviewed, 64 patients received bivalent (B), 213 quadrivalent (Q), and 46 quadrivalent after recent bivalent vaccine (BQ). The median interval time between previous bivalent and quadrivalent vaccine was 5 weeks. There was no statistically significant difference in the prevalence of side effects between the three groups. Mild pain at injection site was recorded in B as 21.8%, Q as 23%, BQ as 21.7%; low grade fever in B as 7.8%, Q as 9.8%, and BQ as 15.2%.

CONCLUSIONS

Bivalent and quadrivalent meningococcal vaccine are well tolerated. Crossover vaccination of quadrivalent meningococcal vaccine after recent vaccination with bivalent vaccine does not increase the prevalence of adverse reactions and is therefore safe.