Meningococcal disease can result in meningitis, septicemia, or both and is usually associated with fever and a characteristic nonblanching rash. Prevention with vaccines is an important part of the management of meningococcal disease because, even with antibiotic intervention, the disease is associated with high morbidity and mortality rates.1–3 Neisseria meningitidis, Haemophilus influenzae type b (Hib), and Streptococcus pneumoniae are the 3 main pathogens that cause bacterial meningitis. In the past 15 years, the introduction of effective polysaccharide-protein conjugate vaccines has significantly decreased the incidence of invasive disease caused by Hib and is expected to decrease the incidence of invasive disease caused by S. pneumoniae among vaccinated individuals.4–10 These developments leave N. meningitidis as a particularly important vaccine target in the 21st century.
N. meningitidis is enveloped in a polysaccharide capsule and is divided into 12 meningococcal serogroups on the basis of the chemical composition of the capsular polysaccharide.11 N. meningitidis is classified into serotypes and serosubtypes, which are based on the antigenic differences of the outer membrane proteins (OMPs) PorB (class 2 or 3 OMP) and PorA (class 1 OMP).12–15 The lipopolysaccharide in the outer membrane is used to classify strains into immunotypes. N. meningitidis nomenclature follows a classification scheme similar to the O:K:H typing scheme used for Escherichia coli and Salmonella, namely, serogroup:serotype:serosubtype:immunotype (eg, B:2a:P1.2:L3).12,14,16 The nomenclature of N. meningitidis is historically based on differences in monoclonal antibody recognition of the capsular polysaccharide, PorB, PorA, and lipopolysaccharide (Table 1).
Five N. meningitidis serogroups, ie, A, B, C, Y, and W135, are the principle pathogenic serogroups.17 There are significant geographic differences in the distribution of specific serogroups of meningococcal disease. For example, surveillance by the Centers for Disease Control and Prevention indicated that serogroups C (28%), Y (34%), and B (33%) were the most prevalent in the United States from 1995 to 1998 (Centers for Disease Control and Prevention, personal communication), whereas serogroup A (86%) was the most prevalent in Niamey, Niger, from 1981 to 1996.18 Serogroup B meningococcus (MenB) is prevalent in Europe, and New Zealand has been experiencing a MenB epidemic since 1991.19 Surveillance of serogroup distribution shows that prevalence can change with time. Serogroup Y accounted for only 2% of cases in the United States from 1988 to 1991, but this value increased to approximately 30% from 1995 to 1998.20–22 Serogroup distribution is important for understanding the potential effectiveness of capsular polysaccharide and capsular polysaccharide conjugate vaccines, and serosubtype distribution is important to the applicability of outer membrane vesicle (OMV) vaccines.
Plain Capsular Polysaccharide Vaccines.
With purified capsular polysaccharide as an antigen, vaccines against serogroup A meningococcus (MenA) and serogroup C meningococcus (MenC) were developed in the 1960s.23–25 A tetravalent polysaccharide vaccine against serogroups A, C, Y, and W-135 has been developed and is available worldwide.17,26,27 However, clinical studies have demonstrated that the antibody response to capsular polysaccharide vaccines is not long-lived, particularly among young children.28–34 In addition, although the clinical significance is not known, it has been shown that multiple doses of a capsular polysaccharide vaccine may result in hyporesponsiveness among infants, toddlers, and young adults.35–39
Data suggest that the hyporesponsiveness of the capsular polysaccharide vaccines may be attributable to the T cell-independent nature of the immune response to these vaccines.40,41 It has been hypothesized that T cell-independent stimulation of memory B cells in response to repeat doses of plain polysaccharide vaccine may result in terminal differentiation of B cells.37 Terminal differentiation of B cells would result in a depleted pool of B cells available for activation by subsequent vaccine doses, with reduced antibody titer.
Because of the relative ineffectiveness of the capsular polysaccharide vaccines among children <2 years of age and the limited duration of protection, routine vaccination with these polysaccharide vaccines is not recommended by the Advisory Committee on Immunization Practices (ACIP).42,43 However, capsular polysaccharide meningococcal vaccines are recommended for use in control of meningococcal outbreaks and for routine vaccination for individuals at high risk of infection, including individuals with complement deficiencies, asplenic individuals, and laboratory personnel exposed to N. meningitidis. In 2000, the ACIP recommended that entering college students be informed of the risk of meningococcal disease and the availability of the polysaccharide vaccine, after 4 epidemiologic studies reported that college freshmen, particularly those living in dormitories, were at modestly increased risk for meningococcal disease, compared with other individuals of the same age.44–46 With the prospect of new meningococcal conjugate vaccines becoming available in the near future, the ACIP is now reviewing this recommendation.
Capsular Polysaccharide-Protein Conjugate Vaccines.
Conjugating a polysaccharide to a protein can render the polysaccharide a T cell-dependent antigen.47 The first successful examples of polysaccharide-protein conjugate vaccines were conjugate vaccines against Hib.5,48–55 Hib conjugate vaccines were developed by conjugating oligosaccharides derived from the Hib capsular polysaccharide (polyribosylribitol phosphate) with carrier proteins, including diphtheria cross-reactive material (CRM)197 protein (a nontoxic mutant of diphtheria toxin), MenB OMP complex, and tetanus toxoid protein.6,54,55 The routine use of Hib conjugate vaccines has dramatically reduced the incidence of Hib disease in many countries.6,7
With the use of this conjugate vaccine technology, meningococcal vaccines were developed.56–58 Conjugation of the N. meningitidis capsular polysaccharide to a carrier protein allows the vaccine to induce a stronger immune response among infants, compared with plain polysaccharide vaccines, to prime immunologic memory, and to elicit booster responses to subsequent doses.36,37,58–71 These vaccines were first licensed in the United Kingdom on the basis of their ability to induce serum bactericidal activity, as a correlate of efficacy.72–74 MenC conjugate vaccines have also been shown to reduce nasopharyngeal carriage of N. meningitidis.75,76
A reduction in the incidence of bacterial meningitis caused by MenC infection was observed in the United Kingdom after a MenC conjugate vaccine campaign (using 3 different vaccines) that was initiated in November 1999 in response to an increase in MenC disease in that country.77 Since the initiation of the campaign, MenC vaccine has been offered to all infants on a 3-dose schedule (at 2, 3, and 4 months of age), administered at the same time as other primary immunizations, with no booster.26 A catch-up campaign targeted all children >4 months and <18 years of age. Individuals <1 year of age received 2 doses of vaccine, and those ≥1 year of age received 1 dose.26 Within 1 year after campaign initiation, an 85% reduction in the number of confirmed cases of invasive MenC disease was observed.77 A MenC CRM197 protein-conjugated vaccine was also found to be effective in a mass-immunization campaign in Quebec, Canada, that was implemented in response to a MenC epidemic that occurred there in 2001.78
It was demonstrated that serum bactericidal activity was induced after MenC-CRM197 protein conjugate vaccine administration to infants, toddlers, 3-5-year-old children, adolescents, and adults (Fig. 1). 59,79 These bactericidal assays were performed with exogenous human complement.80 Capsular polysaccharide-protein conjugate meningococcal vaccines are more immunogenic than plain capsular polysaccharide vaccines among infants, toddlers, children, and adolescents, who represent important populations at risk for meningococcal disease. Therefore, the introduction of meningococcal conjugate vaccines for routine immunization has the potential to reduce dramatically the meningococcal disease burden in affected countries. A MenC conjugate vaccine is available in Europe, and meningococcal conjugate vaccines for MenC and serogroup A/C/Y/W meningococci should be available soon in the United States. MenB, however, provides unique challenges for vaccine development.
MENB VACCINE DEVELOPMENT
MenB disease is endemic in North America and Europe and is especially prevalent, compared with other serogroups, in the Netherlands, Germany, and Denmark.2,81 Epidemics have occurred in Iceland, Norway, Belgium, the United States, Cuba, Brazil, and Chile.82–90 A MenB epidemic has been occurring in New Zealand since 1991, with some of the highest rates of MenB disease ever recorded in an industrialized country.19 Because the incidence of MenB disease is highest among children <1 year of age, the development of a MenB vaccine that is effective among young children has been of particular concern. For several reasons, however, conventional methods of vaccine development in the past 25 years have failed to produce a vaccine with a broad range of protection against circulating MenB strains.
CAPSULAR POLYSACCHARIDE-BASED VACCINE DEVELOPMENT
MenB plain capsular polysaccharide vaccines are poorly immunogenic among human subjects (both children and adults).91 In addition, the MenB capsular polysaccharide structure (α2-8-N-acetylneuraminic acid) is homologous to that of a nerve cell adhesion molecule that is present in developing neural tissue and in small amounts in adult tissues.92 A MenB capsular polysaccharide conjugate vaccine has been developed in an attempt to overcome this obstacle; however, it appears to lack immunogenicity.93 Several other conventional noncapsular approaches to MenB vaccine development have also been attempted.
NON-CAPSULAR POLYSACCHARIDE-BASED VACCINE DEVELOPMENT
Spheres of bacterial outer membrane or OMVs that contain OMPs, lipopolysaccharides, and periplasmic proteins are constantly released by N. meningitidis and other Gram-negative bacteria. OMVs prepared from meningococcal bacterial cells through detergent extraction can be used as vaccine antigens. MenB OMV vaccines have been used successfully for outbreak control; however, their success is limited to clonal outbreaks of MenB disease, because the immunogenicity of the OMV vaccines is directed primarily at PorA, which is highly variable among MenB strains.
Two MenB OMV vaccines were developed and successfully used in the late 1980s and early 1990s, in response to meningococcal outbreaks in Norway and Cuba. The first vaccine was developed by the Finlay Institute in Cuba (B:4:P1.19,15), and the second, with a different PorA, was developed by the National Institute of Public Health in Norway (B:15:P1.7,16).82,83 Efficacy studies of these vaccines were conducted during epidemics that occurred in Norway, Cuba, Brazil, and Chile.82,84–87 The vaccines were found to be immunogenic among adults and older children (70–80% efficacy within 1 year), but immunogenicity was markedly reduced among young children and infants (Table 2). In Norway, 87% efficacy was observed among adults 10 months after immunization with 2 doses, administered 6 weeks apart, although efficacy was reduced to 57% by 29 months after immunization.83,94,95
The specificity of MenB OMV vaccines was demonstrated in a study that assessed bactericidal antibody responses with the Norwegian OMV vaccine against the H4476 strain (the strain from which the vaccine was developed) and 2 distinct serosubtypes of MenB. Infants, adults, and children were given 3 injections of the Norwegian OMV vaccine, at intervals of 2 months. Ninety-eight percent of immunized infants, 98% of children, and 96% of adults exhibited a ≥4-fold antibody response against the H4476 strain.96 However, only 2% of infants, 24% of children, and 46% of adults exhibited a ≥4-fold bactericidal response against a Cuban strain (CU385), and only 12% of infants, 35% of children, and 60% of adults exhibited a bactericidal response against a strain from Chile (CH539). These results demonstrate the effects of PorA specificity among MenB serosubtypes on the immunogenicity of MenB OMV vaccines. The amino acid variability of PorA is restricted to 2 of 8 exposed loops in the predicted structure.97,98 These 2 loops account for most of the antibody response to OMV vaccines, which is why protection elicited by OMV vaccines is generally limited to the strain from which the vaccine was developed.96
MenB OMV vaccines can be useful during epidemics, when disease is caused by a single circulating serosubtype and an appropriately matched MenB OMV vaccine has been developed. Because MenB epidemics can last for more than a decade, the development of a matched vaccine may be feasible in such settings. An OMV vaccine derived from the Norwegian strain is currently undergoing evaluation under a provisional licensure in New Zealand, where a MenB epidemic has been ongoing since 1991.99 However, the OMV-based approach is not useful for routine vaccination in many areas where MenB disease is endemic and is likely to be caused by a heterogeneous population of strains expressing different PorA variants. In the United States, for example, a MenB OMV vaccine would need to be developed from 16 serosubtypes of N. meningitidis B to cover 80% of endemic MenB disease.100
In an attempt to develop a more broadly protective OMV vaccine, a hexavalent PorA OMV vaccine was developed at the National Institute for Public Health and the Environment.101 Two vaccine strains were constructed, through recombinant DNA technology, to express 3 PorA proteins each, representing the majority of circulating serosubtypes in the Netherlands and other countries in Europe.81,101 The vaccine is composed of 2 OMV preparations, 1 from each of these strains. Phase I and II studies have demonstrated that this vaccine is safe and immunogenic.102,103 This vaccine may prove to be useful for preventing MenB disease in areas where these serosubtypes are endemic.
Other noncapsular approaches to MenB vaccine development include the use of OMPs, such as transferrin-binding protein B, neisserial surface protein A, and H.8, and the use of antigens from a commensal species of Neisseria, ie, Neisseria lactamica. Transferrin-binding protein is a meningococcal surface-exposed lipoprotein that plays a role in scavenging iron from the environment.26 Transferrin-binding protein B is a subunit of this protein. Bactericidal antibodies were produced in animals immunized with recombinant transferrin-binding protein B,104 but a recombinant transferrin-binding protein B vaccine failed to elicit high titers of bactericidal antibodies in animal models.105 Efforts to improve the vaccine are ongoing.106
Neisserial surface protein A is a highly conserved meningococcal membrane protein of unknown function. Immunization of animals with recombinant neisserial surface protein A elicited bactericidal antibodies,107,108 but these antibodies were bactericidal against only 50% of genetically diverse MenB strains.109 H.8 is a surface-exposed OMP that was evaluated as a putative antigen.110 Antibodies against this protein failed to show bactericidal activity.111 N lactamica is a commensal species of Neisseria that is associated with natural immunity against meningococcal disease.112 This finding led to the hypothesis that N lactamica antigens may be useful in the development of vaccines against MenB. Development of a MenB vaccine with the use of N lactamica is ongoing.113
Various methods have been used for the development of an effective vaccine against endemic MenB disease. Although some vaccines have proved to be effective in epidemic situations and others provide some inconsistent protection against MenB strains, it is clear that a novel approach to vaccine development is necessary. The sequencing of the genome of one strain of MenB (strain MC58) has yielded a unique, genome-based approach to vaccine development.
GENOME-DERIVED VACCINE DEVELOPMENT
Conventional methods of vaccine development use proteins purified from components of organisms to identify candidate antigens. The genome-based approach to vaccine development uses the genomic sequence of an organism to identify sequences of proteins that are candidate antigens; this approach has been called reverse vaccinology.114 This approach has the potential to identify a broadly protective vaccine with improved immunogenicity, because it can access targets that might have been missed with the conventional methods for purification of bacterial components. The MenB genome-sequencing project identified 2158 open reading frames in the genome of MenB strain MC58.115 Potentially conserved amino acid sequences were identified through comparison with sequences from the genome of a MenA strain.115 Six hundred proteins that were thought to be conserved were cloned, and 350 were expressed in E coli, purified, and used to immunize mice. Twenty-nine were found to induce antibodies with bactericidal activity against MenB, a property that correlates with protective immunity. Several genome-derived antigens have been further evaluated as potential vaccine candidates, including surface-expressed proteins such as adhesion proteins and lipoproteins. Some of these genome-derived antigens are now undergoing evaluation in clinical trials.
Meningococcal disease is a major cause of morbidity and death worldwide, particularly among young children. Because it is associated with a high fatality rate even with early antibiotic intervention, the identification of a vaccine that could be used for routine prevention is a major research target. Vaccines against MenA and MenC were developed with the use of purified capsular polysaccharides from the bacterial capsule. These polysaccharide vaccines were found to elicit serum bactericidal activity among adults but not among children <2 years of age. MenC conjugate vaccines have been shown to be more immunogenic than plain polysaccharide vaccines and have been effective in reducing MenC disease in the United Kingdom and Canada. However, a vaccine against MenB that is immunogenic across a broad range of serosubtypes has not yet been developed.
To date, conventional approaches have failed to identify broadly immunogenic MenB vaccines. The capsule polysaccharide of MenB is poorly immunogenic. An OMV-based approach to vaccine development has been successful in the control of clonal outbreaks of MenB but is unlikely to produce a broadly protective vaccine because the immunodominant antigen, PorA, is hypervariable among MenB strains. Several major membrane proteins identified with conventional bacterial purification methods have been investigated, but none appear to be useful for vaccine development. Therefore, novel approaches to vaccine development for MenB are being investigated.
A genome-based vaccine approach has been initiated, with information available through the MenB genome-sequencing project. Conserved candidate proteins that elicit bactericidal activity in a mouse model have been identified. Additional study of these candidate proteins in clinical trials is ongoing, in an attempt to develop a broadly protective vaccine. Coupled with the advances in understanding of the molecular basis of the immune response and the development of new adjuvants, these new technologies offer promising new vaccine candidates for even the most challenging pathogens.
1. Greenwood BM, Bradley AK, Smith AW, Wall RA. Mortality from meningococcal disease during an epidemic in the Gambia, West Africa. Trans R Soc Trop Med Hyg. 1987;81:536–538.
2. Cartwright K, Noah N, Peltola H. Meningococcal disease in Europe: epidemiology, mortality, and prevention with conjugate vaccines: report of a European advisory board meeting, Vienna, Austria, October 6–8, 2000. Vaccine. 2001;19:4347–4356.
3. Fellick JM, Thomson AP. Long-term outcomes of childhood meningitis. Hosp Med. 2002;63:274–277.
4. Deleted in proof.
5. Robbins JB, Schneerson R, Szu SC, et al. Prevention of invasive bacterial diseases by immunization with polysaccharide-protein conjugates. Curr Top Microbiol Immunol. 1989;146:169–180.
6. Booy R, Hodgson S, Carpenter L, et al. Efficacy of Haemophilus influenzae type b conjugate vaccine PRP-T. Lancet. 1994;344:362–366.
7. Barbour ML, Mayon-White RT, Coles C, Crook DW, Moxon ER. The impact of conjugate vaccine on carriage of Haemophilus influenzae type b. J Infect Dis. 1995;171:93–98.
8. Shinefield HR, Black S. Efficacy of pneumococcal conjugate vaccines in large scale field trials. Pediatr Infect Dis J. 2000;19:394–397.
9. White CJ, Stinson D, Staehle B, et al. Measles, mumps, rubella, and varicella combination vaccine: safety and immunogenicity alone and in combination with other vaccines given to children. Clin Infect Dis. 1997;24:925–931.
10. O'Brien KL, Santosham M. Potential impact of conjugate pneumococcal vaccines on pediatric pneumococcal diseases. Am J Epidemiol. 2004;159:634–644.
11. Davis BD, Dulbecco R, Eisen HN, Ginsberg HS. The Neisseriae. In: Gotschlich EC, ed. Microbiology. 3rd ed. New York, NY: Harper; 1980:635–644.
12. Frasch CE, Zollinger WD, Poolman JT. Serotype antigens of Neisseria meningitidis and a proposed scheme for designation of serotypes. Rev Infect Dis. 1985;7:504–510.
13. Aaberge I, Helland O, Oster P, et al. Immunogenicity and reactogenicity of meningococcal group B OMV vaccine and meningococcal group C conjugate vaccine given in combination. In: Caugant D, Wedege E, eds. Abstracts of the Thirteenth International Pathogenic Neisseria Conference, Oslo, Norway; September 1–6. Oslo, Norway: Norwegian Institute of Public Health; 2002:62.
14. Abdillahi H, Poolman JT. Definition of meningococcal class 1 OMP subtyping antigens by monoclonal antibodies. FEMS Microbiol Immunol. 1988;1:139–144.
15. Poolman JT, van der Ley P, Tommassen J. Surface structures and secreted products of meningococci. In: Cartwight K, ed. Meningococcal Disease. New York, NY: John Wiley and Sons; 1995:21–34.
16. Kauffmann F. On the classification and nomenclature of the genus Salmonella. Acta Pathol Microbiol Scand [B] Microbiol Immunol. 1971;79:421–422.
17. Rosenstein N, Perkins B, Stephens D, Popovic T, Hughes J. Meningococcal disease. N Engl J Med. 2001;344:1378–1388.
18. Campagne G, Schuchat A, Djibo S, Ousseini A, Cisse L, Chippaux JP. Epidemiology of bacterial meningitis in Niamey, Niger, 1981–96. Bull World Health Organ. 1999;77:499–508.
19. Baker MG, Martin DR, Kieft CE, Lennon D. A 10-year serogroup B meningococcal disease epidemic in New Zealand: descriptive epidemiology, 1991–2000. J Paediatr Child Health. 2001;37:S13–S19.
20. Rosenstein NE, Perkins BA, Stephens DS, et al. The changing epidemiology of meningococcal disease in the United States, 1992–1996. J Infect Dis. 1999;180:1894–1901.
21. Jackson LA, Wenger JD. Laboratory-based surveillance for meningococcal disease in selected areas, United States, 1989–1991. MMWR CDC Surveill Summ. 1993;42:21–30.
22. Racoosin JA, Whitney CG, Conover CS, Diaz PS. Serogroup Y meningococcal disease in Chicago, 1991–1997. JAMA. 1998;280:2094–2098.
23. Gotschlich EC, Goldschneider I, Artenstein MS. Human immunity to the meningococcus. IV. Immunogenicity of group A and group C meningococcal polysaccharides in human volunteers. J Exp Med. 1969;129:1367–1384.
24. Gotschlich EC, Liu TY, Artenstein MS. Human immunity to the meningococcus. III. Preparation and immunochemical properties of the group A, group B, and group C meningococcal polysaccharides. J Exp Med. 1969;129:1349–1365.
25. Kabat EA, Bezer AE. The effect of variation in molecular weight on the antigenicity of dextran in man. Arch Biochem Biophys. 1958;78:306–318.
26. Jodar L, Feavers I, Salisbury D, Granoff D. Development of vaccines against meningococcal disease. Lancet. 2002;359:1499–1508.
27. Lepow ML, Beeler J, Randolph M, Samuelson JS, Hankins WA. Reactogenicity and immunogenicity of a quadrivalent combined meningococcal polysaccharide vaccine in children. J Infect Dis. 1986;154:1033–1036.
28. Zangwill KM, Stout RW, Carlone GM, et al. Duration of antibody response after meningococcal polysaccharide vaccination in US Air Force personnel. J Infect Dis. 1994;169:847–852.
29. Gold R, Lepow ML, Goldschneider I, Gotschlich EC. Immune response of human infants to polysaccharide vaccines of group A and C Neisseria meningitidis. J Infect Dis. 1977;136(suppl):S31–S35.
30. Goldschneider I, Lepow ML, Gotschlich EC. Immunogenicity of the group A and group C meningococcal polysaccharides in children. J Infect Dis. 1972;125:509–519.
31. Reingold A, Broome CV, Hightower A, et al. Age-specific differences in duration of clinical protection after vaccination with meningococcal polysaccharide A vaccine. Lancet. 1985;2:114–118.
32. Gold R, Lepow ML, Goldschneider I, Draper TF, Gotschlich EC. Kinetics of antibody production to group A and group C meningococcal polysaccharide vaccines administered during the first six years of life: prospects for routine immunization of infants and children. J Infect Dis. 1979;140:690–697.
33. Käyhty H, Karanko V, Peltola H, Sarna S, Mäkelä H. Serum antibodies to capsular polysaccharide vaccine of group A Neisseria meningitidis followed for three years in infants and children. J Infect Dis. 1980;142:861–868.
34. Lepow ML, Goldschneider I, Gold R, Randolph M, Gotschlich EC. Persistence of antibody following immunization of children with groups A and C meningococcal polysaccharide vaccines. Pediatrics. 1977;60:673–680.
35. MacDonald NE, Halperin SA, Law BJ, Danzig LE, Granoff DM. Can meningococcal C conjugate vaccine overcome immune hyporesponsiveness induced by previous administration of plain polysaccharide vaccine? JAMA. 2000;283:1826–1827.
36. Richmond P, Kaczmarski E, Borrow R, et al. Meningococcal C polysaccharide vaccine induces immunologic hyporesponsiveness in adults that is overcome by meningococcal C conjugate vaccine. J Infect Dis. 2000;181:761–764.
37. MacDonald NE, Halperin SA, Law BJ, Forrest B, Danzig LE, Granoff DM. Induction of immunologic memory by conjugated versus plain meningococcal C polysaccharide vaccine in toddlers: a randomized controlled trial. JAMA. 1998;280:1685–1689.
38. Granoff DM, Gupta RK, Belshe RB, Anderson EL. Induction of immunologic refractoriness in adults by meningococcal C polysaccharide vaccination. J Infect Dis. 1998;178:870–874.
39. Artenstein MS, Brandt BL. Immunologic hyporesponsiveness in man to group C meningococcal polysaccharide. J Immunol. 1975;115:5–7.
40. Muller E, Apicella MA. T-cell modulation of the murine antibody response to Neisseria meningitidis group A capsular polysaccharide. Infect Immun. 1988;56:259–266.
41. Taylor CE, Bright R. T-cell modulation of the antibody response to bacterial polysaccharide antigens. Infect Immun. 1989;57:180–185.
42. Centers for Disease Control and Prevention. Control and prevention of serogroup C meningococcal disease: evaluation and management of suspected outbreaks: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 1997;46:13–21.
43. Centers for Disease Control and Prevention. Prevention and control of meningococcal disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2000;49:1–10.
44. Centers for Disease Control and Prevention. Meningococcal disease and college students: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2000;49:13–20.
45. Harrison L, Dwyer D, Maples C, Billmann L. Risk of meningococcal infection in college students. JAMA. 1999;281:1906–1910.
46. Bruce M, Rosenstein N, Capparella J, Shutt K, Perkins BA, Collins M. Risk factors for meningococcal disease in college students. JAMA. 2001;286:688–693.
47. Lesinski GB, Westerink MA. Novel vaccine strategies to T-independent antigens. J Microbiol Methods. 2001;47:135–149.
48. Eskola J, Käyhty H, Takala A, et al. A randomized, prospective field trial of a conjugate vaccine in the protection of infants and young children against invasive Haemophilus influenzae type b disease. N Engl J Med. 1990;323:1381–1387.
49. Frasch CE, Hiner EE, Gross TP. Haemophilus b disease after vaccination with Haemophilus b polysaccharide or conjugate vaccine. Am J Dis Child. 1991;145:1379–1382.
50. Black SB, Shinefield HR, Fireman B, Hiatt R. Safety, immunogenicity, and efficacy in infancy of oligosaccharide conjugate Haemophilus influenzae type b vaccine in a United States population: possible implications for optimal use. J Infect Dis. 1992;165(suppl 1):S139–S143.
51. Granoff DM, Holmes SJ, Osterholm MT, et al. Induction of immunologic memory in infants primed with Haemophilus influenzae type b conjugate vaccines. J Infect Dis. 1993;168:663–671.
52. Heath PT. Haemophilus influenzae type b conjugate vaccines: a review of efficacy data. Pediatr Infect Dis J. 1998;17:S117–S122.
53. Murphy TV, Pastor P, Medley F, Osterholm MT, Granoff DM. Decreased Haemophilus colonization in children vaccinated with Haemophilus influenzae type b conjugate vaccine. J Pediatr. 1993;122:517–523.
54. Santosham M, Wolff M, Reid R, et al. The efficacy in Navajo infants of a conjugate vaccine consisting of Haemophilus influenzae type b polysaccharide and Neisseria meningitidis outer-membrane protein complex. N Engl J Med. 1991;324:1767–1772.
55. Shinefield HR, Black S. Postlicensure surveillance for Haemophilus influenzae type b invasive disease after use of Haemophilus influenzae type b oligosaccharide CRM197 conjugate vaccine in a large defined United States population: a four-year eight-month follow-up. Pediatr Infect Dis J. 1995;14:978–981.
56. Beuvery EC, Miedema F, van Delft R, Haverkamp J. Preparation and immunochemical characterization of meningococcal group C polysaccharide-tetanus toxoid conjugates as a new generation of vaccines. Infect Immun. 1983;40:39–45.
57. Costantino P, Viti S, Podda A, Velmonte MA, Nencioni L, Rappuoli R. Development and phase 1 clinical testing of a conjugate vaccine against meningococcus A and C. Vaccine. 1992;10:691–698.
58. Rennels M, King J Jr, Ryall R, et al. Dose escalation, safety, and immunogenicity study of a tetravalent meningococcal polysaccharide diphtheria conjugate vaccine in toddlers. Pediatr Infect Dis J. 2002;21:978–979.
59. MacLennan JM, Shackley F, Heath PT, et al. Safety, immunogenicity, and induction of immunologic memory by a serogroup C meningococcal conjugate vaccine in infants: a randomized controlled trial. JAMA. 2000;283:2795–2801.
60. Lepow M, Perkins B, Hughes P, Poolman J. Meningococcal vaccines. In: Plotkin S, Orenstein W, eds. Vaccines. 3rd ed. Philadelphia, PA: WB Saunders; 1999:711–727.
61. Twumasi PA Jr, Kumah S, Leach A, et al. A trial of a group A plus group C meningococcal polysaccharide-protein conjugate vaccine in African infants. J Infect Dis. 1995;171:632–638.
62. Fairley CK, Begg N, Borrow R, Fox AJ, Jones DM, Cartwright K. Conjugate meningococcal serogroup A and C vaccine: reactogenicity and immunogenicity in United Kingdom infants. J Infect Dis. 1996;174:1360–1363.
63. Borrow R, Goldblatt D, Andrews N, et al. Antibody persistence and immunological memory at age 4 years after meningococcal group C conjugate vaccination in children in the United Kingdom. J Infect Dis. 2002;186:1353–1357.
64. Leach A, Twumasi PA, Kumah S, et al. Induction of immunologic memory in Gambian children by vaccination in infancy with a group A plus group C meningococcal polysaccharide-protein conjugate vaccine. J Infect Dis. 1997;175:200–204.
65. MacDonald NE, Halperin S, Law B, Danzig L, Granoff D. Safety and immunogenicity of meningococcal C conjugated (MenC) vaccine in toddlers previously immunized with meningococcal polysaccharide (MenPS) vaccine. Pediatr Res. 1999;45:167A. Abstract 976.
66. MacLennan J, Obaro S, Deeks J, et al. Immunologic memory 5 years after meningococcal A/C conjugate vaccination in infancy. J Infect Dis. 2001;183:97–104.
67. McVernon J, MacLennan J, Buttery J, Oster P, Danzig L, Moxon ER. Safety and immunogenicity of meningococcus serogroup C conjugate vaccine administered as a primary or booster vaccination to healthy four-year-old children. Pediatr Infect Dis J. 2002;21:747–753.
68. Rennels M, Edwards K, Keyserling H, et al. Safety and immunogenicity of four doses of Neisseria meningitidis group C vaccine conjugated to CRM197 in United States infants. Pediatr Infect Dis J. 2001;20:153–159.
69. Richmond P, Borrow R, Miller E, et al. Meningococcal serogroup C conjugate vaccine is immunogenic in infancy and primes for memory. J Infect Dis. 1999;179:1569–1572.
70. Richmond P, Borrow R, Goldblatt D, et al. Ability of 3 different meningococcal C conjugate vaccines to induce immunologic memory after a single dose in UK toddlers. J Infect Dis. 2001;183:160–163.
71. Richmond P, Borrow R, Findlow J, et al. Evaluation of de-O-acetylated meningococcal C polysaccharide-tetanus toxoid conjugate vaccine in infancy: reactogenicity, immunogenicity, immunologic priming, and bactericidal activity against O-acetylated and de-O-acetylated serogroup C strains. Infect Immun. 2001;69:2378–2382.
72. Goldschneider I, Gotschlich EC, Artenstein MS. Human immunity to the meningococcus, I: the role of humoral antibodies. J Exp Med. 1969;129:1307–1326.
73. Goldschneider I, Gotschlich EC, Artenstein MS. Human immunity to the meningococcus, II: development of natural immunity. J Exp Med. 1969;129:1327–1348.
74. Borrow R, Andrews N, Goldblatt D, Miller E. Serological basis for use of meningococcal serogroup C conjugate vaccines in the United Kingdom: reevaluation of correlates of protection. Infect Immun. 2001;69:1568–1573.
75. Maiden MC, Stuart JM. Carriage of serogroup C meningococci 1 year after meningococcal C conjugate polysaccharide vaccination. Lancet. 2002;359:1829–1831.
76. Ramsay ME, Andrews NJ, Trotter CL, Kaczmarski EB, Miller E. Herd immunity from meningococcal serogroup C conjugate vaccination in England: database analysis. BMJ. 2003;326:365–366.
77. Ramsay M, Andrews N, Kaczmarski E, Miller E. Efficacy of meningococcal serogroup C conjugate vaccine in teenagers and toddlers in England. Lancet. 2001;357:195–196.
78. De Wals P, Deceuninck G, Boulianne N, Serres G. Impact of a mass immunization campaign against serogroup C meningococcal disease in 2001–2002, Province of Quebec, Canada. Int J Infect Dis. 2004;8(suppl 1):S190.
79. Choo S, Zuckerman J, Goilav C, Hatzmann E, Everard J, Finn A. Immunogenicity and reactogenicity of a group C meningococcal conjugate vaccine compared with a group A+C meningococcal polysaccharide vaccine in adolescents in a randomised observer-blind controlled trial. Vaccine. 2000;18:2686–2692.
80. Santos G, Deck R, Donnelly J, Blackwelder WC, Granoff D. Importance of complement source in measuring meningococcal bactericidal titers. Clin Diagn Lab Immunol. 2001;8:616–623.
81. Connolly M, Noah N. Is group C meningococcal disease increasing in Europe? A report of surveillance of meningococcal infection in Europe 1993–6: European Meningitis Surveillance Group. Epidemiol Infect. 1999;122:41–49.
82. Sierra GV, Campa HC, Varcacel NM, et al. Vaccine against group B Neisseria meningitidis: protection trial and mass vaccination results in Cuba. NIPH Ann. 1991;14:195–210.
83. Bjune G, Høiby EA, Grønnesby JK, et al. Effect of outer membrane vesicle vaccine against group B meningococcal disease in Norway. Lancet. 1991;338:1093–1096.
84. Zollinger WD, Boslego J, Moran E, et al. Meningococcal serogroup B vaccine protection trial and follow-up studies in Chile. NIPH Ann. 1991;14:211–213.
85. Boslego J, Garcia J, Cruz C, et al. Efficacy, safety, and immunogenicity of a meningococcal group B (15:P1. 3) outer membrane protein vaccine in Iquique, Chile. Vaccine. 1995;13:821–829.
86. De Moraes J, Perkins BA, Camargo MC, et al. Protective efficacy of a serogroup B meningococcal vaccine in Sao Paulo, Brazil. Lancet. 1992;340:1074–1078.
87. Milagres LG, Ramos SR, Sacchi CT, et al. Immune response of Brazilian children to a Neisseria meningitidis serogroup B outer membrane protein vaccine: comparison with efficacy. Infect Immun. 1994;62:4419–4424.
88. Diermayer M, Hedberg K, Hoesly F, et al. Epidemic serogroup B meningococcal disease in Oregon: the evolving epidemiology of the ET-5 strain. JAMA. 1999;281:1493–1497.
89. Van Looveren M, Vandamme P, Hauchecorne M, et al. Molecular epidemiology of recent Belgian isolates of Neisseria meningitidis serogroup B. J Clin Microbiol. 1998;36:2828–2834.
90. Peltola H, Jonsdottir K, Lystad A, Sievers CJ, Kallings I. Meningococcal disease in Scandinavia. Br Med J (Clin Res Ed). 1982;284:1618–1621.
91. Wyle FA, Artenstein MS, Brandt BL, et al. Immunologic response of man to group B meningococcal polysaccharide vaccines. J Infect Dis. 1972;126:514–521.
92. Finne J, Leinonen M, Mäkelä PH. Antigenic similarities between brain components and bacteria causing meningitis: implications for vaccine development and pathogenesis. Lancet. 1983;2:355–357.
93. Bruge J, Bouveret-Le Cam N, Danve B, Rougon G, Schulz D. Clinical evaluation of a group B meningococcal N-propionylated polysaccharide conjugate vaccine in adult, male volunteers. Vaccine. 2004;22:1087–1096.
94. Bjune G, Grønnesby JK, Høiby EA, Closs O, Nøkleby H. Results of an efficacy trial with an outer membrane vesicle vaccine against systemic serogroup B meningococcal disease in Norway. NIPH Ann. 1991;14:125–132.
95. Holst J, Feiring B, Fuglesang JE, et al. Serum bactericidal activity correlates with the vaccine efficacy of outer membrane vesicle vaccines against Neisseria meningitidis serogroup B disease. Vaccine. 2003;21:734–737.
96. Tappero JW, Lagos R, Ballesteros AM, et al. Immunogenicity of 2 serogroup B outer-membrane protein meningococcal vaccines: a randomized controlled trial in Chile. JAMA. 1999;281:1520–1527.
97. McClary RD, Finelli DS, Croker B, Davis GL. Portal hypertension secondary to a spontaneous splenic arteriovenous fistula: case report and review of the literature. Am J Gastroenterol. 1986;81:572–575.
98. Maiden MC, Suker J, McKenna AJ, Bygraves JA, Feavers M. Comparison of the class 1 outer membrane proteins of eight serological reference strains of Neisseria meningitidis. Mol Microbiol. 1991;5:727–736.
99. Holst J, Aaberge IS, Oster P, et al. A ‘tailor made’ vaccine trialled as part of public health response to group B meningococcal epidemic in New Zealand. Eurosurveill Wkly. 2003;7:6–9.
100. Tondella ML, Popovic T, Rosenstein NE, et al. Distribution of Neisseria meningitidis serogroup B serosubtypes and serotypes circulating in the United States. J Clin Microbiol. 2000;38:3323–3328.
101. Peeters CC, Rümke HC, Sundermann LC, et al. Phase I clinical trial with a hexavalent PorA containing meningococcal outer membrane vesicle vaccine. Vaccine. 1996;14:1009–1015.
102. Cartwright K, Morris R, Rumke H, et al. Immunogenicity and reactogenicity in UK infants of a novel meningococcal vesicle vaccine containing multiple class 1 (PorA) outer membrane proteins. Vaccine. 1999;17:2612–2619.
103. de Kleijn ED, de Groot R, Labadie J, et al. Immunogenicity and safety of a hexavalent meningococcal outer-membrane-vesicle vaccine in children of 2–3 and 7–8 years of age. Vaccine. 2000;18:1456–1466.
104. Danve B, Lissolo L, Mignon M, et al. Transferrin-binding proteins isolated from Neisseria meningitidis elicit protective and bactericidal antibodies in laboratory animals. Vaccine. 1993;11:1214–1220.
105. Danve B, Lissolo L, Guinet F, et al. Safety and immunogenicity of a Neisseria meningitidis group B transferrin binding protein vaccine in adults. In: Nassif X, Quentin-Millet MJ, Taha M-K, eds. Abstracts of the Eleventh International Pathogenic Neisseria Conference, November 1 to 6, Nice. Paris, France: EDK; 1998:53.
106. West D, Reddin K, Matheson M, et al. Recombinant Neisseria meningitidis transferrin binding protein A protects against experimental meningococcal infection. Infect Immun. 2001;69:1561–1567.
107. Martin D, Cadieux N, Hamel J, Brodeur B. Highly conserved Neisseria meningitidis surface protein confers protection against experimental infection. J Exp Med. 1997;185:1173–1183.
108. Cadieux N, Plante M, Rioux CR, Hamel J, Brodeur BR, Martin D. Bactericidal and cross-protective activities of a monoclonal antibody directed against Neisseria meningitidis NspA outer membrane protein. Infect Immun. 1999;67:4955–4959.
109. Moe G, Tan S, Granoff D. Differences in surface expression of NspA among Neisseria meningitidis group B strains. Infect Immun. 1999;67:5664–5675.
110. Bhattacharjee AK, Moran EE, Ray JS, Zollinger WD. Purification and characterization of H.8 antigen from group B Neisseria meningitidis. Infect Immun. 1988;56:773–778.
111. Bhattacharjee AK, Moran EE, Zollinger WD. Antibodies to meningococcal H.8 (Lip) antigen fail to show bactericidal activity. Can J Microbiol. 1990;36:117–122.
112. Oliver K, Reddin K, Bracegirdle P, et al. Neisseria lactamica protects against experimental meningococcal infection. Infect Immun. 2002;70:3621–3626.
113. Mukhopadhyay TK, Halliwell D, O'Dwyer C, et al. Rapid characterisation of outer membrane proteins in Neisseria lactamica by surface enhanced laser desorption and ionization-time of flight mass spectroscopy for use in a meningococcal vaccine. Biotechnol Appl Biochem. 2004;Aug 18.
114. Rappuoli R. Reverse vaccinology, a genome-based approach to vaccine development. Vaccine. 2001;19:2688–2691.
115. Pizza M, Scarlato V, Masignani V, et al. Identification of vaccine candidates against serogroup B meningococcus by whole-genome sequencing. Science. 2000;287:1816–1820.
© 2004 Lippincott Williams & Wilkins, Inc.