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Immunisation against bacterial meningitis
Journal of lnfection (1981)3, Supplement 1, 71-79
Immunisation against bacterial meningitis E. Coen Beuvery
Rijksinstituut voor de Volksgezondheid (R.I.V.), P.O.'Box 1, 3720 BA Bilthoven, The Netherlands Summary The vaccine potential of different surface antigens of encapsulated bacteria is considered. It is concluded that only the capsular polysaccharides provide good protection. Polysaccharides are, however, thymus-independent antigens and the antibody response is strongly influenced by the age of the recipient and his naturally acquired immunity. For a long-lasting immunity the induction of mainly IgG antibodies is essential. Such a response can easily be induced by conjugates in which the polysaccharides have been attached to thymus-dependent carriers.
Introduction Suppurative infections of the meninges are mainly caused by five species of bacteria: Neisseria meningitidis (meningococci), Streptococcus pneumoniae (pneumococci), Haemophilus influenzae, Escherichia coli and group B streptococci. These species of bacteria are encapsulated and the capsules are composed of polysaccharides. Based upon the antigenic structure of the polysaccharides the species are subdivided into serogroups and serotypes. The increasing isolation of sulphonamide-resistant meningococci since the 1960s, the more recent emergence of multiple antibiotic-resistant pneumococci and H. influenzae strains and the risk of brain damage after infection emphasises the need to develop vaccines for the prevention of bacterial meningitis. About 80 per cent of infections are caused by 21 different serogroups and serotypes. A polyvalent polysaccharide vaccine for the prevention of bacterial meningitis should for this reason contain at least the 21 different polysaccharides associated with these organisms (Table I). Table I Bacterial meningitis: serogroups and types of the main pathogens Species
Neisseria meningitidis Streptococcus pneumoniae Haemophilus influenzae Escherichia coli Group B streptococci
0163-4453/81/011071 + 09 $01.00/0
Serogroup and types (number) A, B and C (3) 1, 2, 3, 4, 6A, 7F, 8, 9N, 12F, 23F, 25, and 18C (14)
b(1)
K1(1) Ia, III(2)
©1981 The British Society for the Study of Infection
72
E.C. Beuvery Host defence against encapsulated bacteria
The classical studies of Goldschneider and co-workers (1969a, b) established that antibodies are essential for immunity to meningococcal infection. Recently, unusually severe, chronic or recurrent meningococcal infections have been recorded in association with deficiences in components of the terminal complement sequence (Nicholson and Lepow, 1979; Vogler, Newman, Stroud and Johnston, 1979). These data provide clear evidence that complement-dependant bacteriolysis is the major protective mechanism against meningococcal infection in man. The host defence mechanisms against the other species are similar. Naturally acquired bactericidal antibodies against meningococci are directed towards both capsular and non-capsular antigens (Goldschneider, Gotschlich and Artenstein, 1969a, b.) These antibodies are acquired during carriage and, possibly, subclinical infection caused by both encapsulated and non-encapsulated meningococci (Goldschneider, Gotschlich and Artenstein, 1969 a, b; Reller, MacGregor and Beaty, 1973) or by contact with bacteria possessing identical or almost identical polysaccharides (Robbins, Schneerson, Liu, Schiffer, Schiffman, Myerowitz, McCracken, Orskov and Orskov, 1974). For some years there has been a tendency to use purifed antigens instead of whole cells for vaccine production. In this context the vaccine potential of four meningococcal surface antigens will be considered. These antigens are polysaccharides, pili, outer membrane proteins and lipopolysaccharides. (1) Polysaccharide is the surface structure in direct contact with the host. All purified polysaccharides from encapsulated bacteria are immunogenic in man, except meningococcal group B polysaccharide and the structurally related Esch. coli K1 polysaccharide (Wyle, Artenstein, Brandt, Tramont, Kasper, Altieri, Berman and Lowenthal, 1972; Kasper, Wink° elhake, Brandt and Artenstein, 1973). Polysaccharide vaccines produce few adverse reactions (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978) and meningococcal group A and group C polysaccharide vaccines have proved their effectiveness during epidemics (Taunay, Galvao, Morais, Gotschlich and Feldman, 1974; Peltola et al., 1977). Polysaccharides can also be effectively combined and used as polyvalent vaccine (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978). (2) Pili are almost certainly responsible for the attachment of encapsulated meningococci to host tissue and antibodies against antigen associated with pili may prevent attachment (Craven and Frasch, 1978). However no serotyping system based upon the specificity of the pili has been develop.ed. No data are available concerning eventual induction of local immunity. (3) Outer membrane proteins are the antigens carrying serotype specificity. Although there are more than 18 different meningococcal serotypes (Zollinger and Mandrell, 1977), one (serotype 2) is responsible for 50
Immunisation against bacterial meningitis
73
per cent of infections caused by groups B, C, W135 and Y (Frasch and Friedman, 1977). However, a vaccine composed of antigen from this serotype induced only a poor antibody response in human volunteers (Frasch and Robbins, 1978; Frasch, 1979). (4) Lipopolysaccharides have endotoxin activity and are unsuitable for use as vaccine. Antibodies to lipopolysaccharides are bactericidal (Tramont, Sadoff and Artenstein, 1974) and, therefore, lipopolysaccharides devoid of lipid A might have vaccine potential. However, lipopolysaccharides from meningococcal strains cultivated in vitro lack the O-polysaccharide chain (Jennings, Bhattacharjee, Kenne, Kenny and Calver, 1980) which is present in lipopolysaccharides from Enterobacteriaceae. Lipopolysaccharides lacking this chain are less able to induce binding antibodies. Based upon these data, it must be concluded that, currently, only the polysaccharides provide good vaccine potential. Polysaccharide vaccines
Polysaccharides are polymers of units composed of a limited number of different sugar residues (Robbins, 1978). This polymeric structure gives them immunological specificity; unlike protein vaccines such as tetanus toxoid, they are thymus-independent (TI) antigens. In addition no bone marrow derived (B)-memory cells for polysaccharide antigens are induced during the primary or secondary response. After both injections only IgM antibodies are induced; the secondary response is identical to the primary one. All polysaccharides from encapsulated bacteria behave similarly in this respect. The time course of antibody response after primary and secondary immunisation polysaccharide is shown in Fig. 1. Although these data were obtained in mice (Baker, Stashak, Ams_baugh and Prescott, 1971), the course of antibody response in very young children to a number of polysaccharides, such as those derived from meningococcal group C, H. influenzae type b and pneumococcal type 6, resembles this picture. The antibody response in man to polysaccharide vaccines depends on
g
0
I
2
3
4
5
First dose Time
ff
0
I 2 Second dose
:3
4
5
(weeks)
Fig. 1. Time course of IgM (--) antibodies in mice after a first and a second dose of
polysaccharide antigen.
74
E.C.
Beuvery
several factors including naturally acquired immunity (Beuvery, submitted for publication), the age of the recipient (Gold and Lepow, 1976; Borgono, McLean, Vella, Woodhour, Canepa, Davidson and Hilleman, 1978), the molecular size of the polysaccharide (Gotschlich, Rey, Triau and Sparks, 1972; Peltola, K~iyhty, Kuronen, Haque, Sarna and M~ikel~i, 1978) and the presence of side groups in the polysaccharide chain (Glode, Lewin, Sutton, Lee, Gotschlich and Robbins, 1979). This review will consider only the first two factors. Gold and colleagues (1975, 1977) found that natural immunity to meningococcal group A polysaccharide in American children was induced earlier than that to group C polysaccharide. At the age of 18 months more than 90 per cent of children had detectable antibody levels towards group A polysaccharide, whereas this percentage was only reached in the case of group C polysaccharide after six to eight years of life. The results of vaccination with group A and group C polysaccharide vaccines also showed differences in this respect. At the age of three months primary vaccination with group A polysaccharide vaccine did not result in a detectable antibody response. In one year old children the mean antibody level induced was only about three per cent of that observed in adults (Gold, Lepow, Goldschneider, Draper and Gotschlich, 1975; Gold, Lepow, Goldschneider and Gotschlich, 1977). In children aged six to eight years this level was about 25 per cent of that found in adults (Lepow, Goldschneider, Gold, Randolph and Gotschlich, 1977). Studies with group C polysaccharide vaccine showed that all three month old infants responded to the vaccine but that the peak response was about one per cent of that induced in adults. In children aged two years the mean antibody level was found equal to about one-tenth that of the adult level (Gold, Lepow, Goldschneider, Draper and Gotschlich, 1975; Gold Lepow, Goldschneider and Gotschlich, 1977). The antibody levels induced by vaccine in the various age groups, similarly to those acquired naturally, were positively correlated with age. These workers also reported that a second dose of group A polysaccharide vaccine in children below the age of one year resulted in a booster reaction but that a second dose of group C polysaccharide vaccine gave rise to suppression of the response. In older children and adults a second dose of both polysaccharide vaccines produced antibody levels identical to that following first dose. Similar results have been reported with pneumococcal and H. influenzae type b polysaccharide vaccines (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978). The persistence of antibodies induced by the various polysaccharide vaccines is rather variable. The persistence of antibodies to group A polysaccharide in six to eight years old children was better than those against group C polysaccharide in the same age group (Lepow, Goldschneider, Gold, Randolph and Gotschlich, 1977). However, Heidelberger, Dilapi, Siegal and Walter (1950) reported prolonged persistence o~f antibodies induced in adults by various pneumococcal polysaccharides.
Immunisation against bacterial meningitis
75
In a current study we have determined quantitatively IgM, IgG and IgA antibody levels to meningococcal group A and group C polysaccharides. A group of 66 adult volunteers received combined polysaccharide vaccine and antibody levels were determined in serum samples obtained two weeks thereafter. The results are shown in Table II. Both polysaccharide vaccines induced antibodies in the three main immunoglobulin classes. However IgG and IgA antibodies are not observed in very young children or mice. The synthesis of these antibodies is probably dependant on the triggering of polysaccharide specific memory B-cells (Braley-Mullen, 1975, 1976, 1977, 1980). The presence of these memory cells may relate to previous contact with encapsulated bacteria possessing identical or almost identical polysaccharides. In these bacteria the polysaccharides are attached to outer membrane antigens forming complexes which are recognised by thymus-derived (T)-lymphocytes. These lymphocytes are responsible for the induction of the memory B-cells (Braley-Mullen, 1977). Table II Geometric means of group A polysaccharide and group C polysaccharide antibody levels in serum samples from 66 individuals obtained two weeks after vaccination with the combined polysaccharide vaccine Antibody level (geometric mean: /~g antibody protein/ml)
Group A PS antibodies Group C PS antibodies
IgM
IgG
IgA
total
2.46 (49)* 1.62 (41)
1-67 (33)* 1.95 (49)
0-90 (18)* 0.39 (10)
5.03 (100)* 3.96 (100)
* ( ) per cent total antibody.
The persistence of polysaccharide antigen induced antibodies was also studied. In Fig. 2, three salient examples are given of the time courses of IgM and IgG antibody responses after vaccination with polysaccharide vaccine. I
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Fig. 2. Time course of IgM ( - - ) and IgG (- - -) antibodies in three adults after immunisation with polysaccharide vaccine.
E . C . Beuvery
76
Patient one produced mainly IgM antibodies whereas in patient three the antibody response was predominantly of IgG class. Patient two demonstrated an intermediate response. The patterns suggest that IgM antibodies disappear faster than IgG antibodies and that the rate of decline of both IgM and IgG antibodies may be related to the ratio between the levels of IgM and IgG antibodies in the serum sample obtained 14 days after administration of the vaccine. A greater value of this ratio may result in a more rapid decline. It is concluded that, as IgG antibodies are induced by triggering of memory B-cells, the persistence of antibodies is related to the possession of these memory cells. If long lasting immunity is to be produced, administration of vaccine must result in the production of mainly IgG antibody and memory B-cells. New developments in the preparation, of polysaccharide vaccines
Further studies have examined the influence of modified polysaccharides on the antibody response of mice. Polysaccharide antigen was conjugated to tetanus toxoid as a thymus-dependent (TD) carrier. The pure polysaccharide or the conjugate were administered to mice and the response to the polysaccharide was determined. Figure 3 presents the course of IgM and IgG antibody response. Up to day 17 no IgG antibody was detected in the serum of mice injected with the pure polysaccharide. In this group the maximal IgM antibody level was found at five days and decreased rapidly thereafter. The course of IgM antibody production after injection with the conjugate was
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0.5
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Fig. 3. Time course oflgM (O) and IgG (&) antibodies against polysaccharide in mice after immunization with pure capsular polysaccharide (- - -) and with conjugated polysaccharide
(
).
Immunisation against bacterial meningitis
77
similar to that induced by the pure polysaccharide up to day seven. Thereafter secondary IgM antibody production became evident which attained its maximum at between day 10-14. Moreover, in the conjugate immunised group, IgG antibodies were detected, the level of which rose rapidly after day 10. On this evidence that additional IgM and IgG of ailtibodies are synthesised after injecting polysaccharide attached to a TD-antigen, it can be concluded that T-lymphocytes are concerned in the antibody response to the polysaccharide. In another experiment, the induction of memory B-cells for the polysaccharide was studied. A group of mice was injected with the conjugate. After 24 weeks one half of the group was injected with the pure polysaccharide and the other half with a second dose of conjugate. The results of the determination of antibodies produced against the polysaccharide are shown in Fig. 4. Up to 24 weeks after the first dose both IgM and IgG antibodies were detected. The second injection with both polysaccharide and conjugate resulted in the synthesis of IgM and IgG antibodies. During the secondary response the IgM/IgG antibody ratio altered in favour of the IgG antibody level. Moreover, the induction period of IgG antibodies seemed to be shorter than that after the first injection. From the IgG response induced by the pure polysaccharide, it can be concluded that the conjugate induced memory B-cells for the polysaccharide. A similar response is seen in adult men after vaccination with polysaccharide vaccines. Before polysaccharide-protein conjugates can be applied as vaccines for human use several aspects, including safety, influence of adjuvants and the role of memory T-cells for the carrier, require further investigation.
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~ Sec. imm. Time (weeks) Fig. 4. Time course of IgM (0) and IgO ( A ) antibodies against capsular polysaccharide in mice after a primary immunisation with conjugate and after secondary immunisation with pure capsular polysaccharide ( - - -) or with conjugated po]ysaccharide ( ).
78
E . C . Beuvery References
Baker, P. J., Stashak, P. W., Amsbaugh, D. F. and Prescott, B. (1971). Characterization of the antibody response to type III pneumococcal polysaccharide at the cellular level. I. Dose-response studies and the effect of prior immunization on the magnitude of the antibody response. Immunology, 20, 469. Borgono, J. M., McLean, A. A., Vella, P. P., Woodhour, A. F., Canepa, I., Davidson, W. L. and HiUeman, M. R. (1978). Vaccination and revaccination with polyvalent pneumococcal polysaccharide vaccines in adults and infants. Proceedings Society Experimental Biology and Medicine, 157, 148. Braley-Mullen, H. (1975). Secondary IgG responses to type Ill pneumococcal polysaccharide. I. Kinetics and antigen requirements. Journal of Immunology, 115, 1194. Braley-MuUen, H. (1976). Secondary lgG responses to type Ili pneumococcal polysaccharide. I1. Different cellular requirements for induction and elicitation. Journal of Immunology, 116, 904. Braley-Mullen, H. (1977). Secondary lgG responses to type 111 pneumococcal polysaccharide. 11I. T-cell requirement for development of B memory cells. European Journal of Immunology, 7, 775. Braley-Mullen, H. (1980). Antigen requirements for priming of lgG producing B memory cells specific for type II1 pneumococcal polysaccharide. Immunology, 40, 521. Craven, D. E. and Frasch, C. E. In Immunobiology ofNeisseria gonorrhoeae (Brooks, G. F., Gotschlich, E.C., Holmes, K.K., Sawyr, W.D. and Young, F. E., Eds). American Society for Microbiology, Washington D.C. (1978), pp. 250-252. Frasch, 'C. E. (1979). Non-capsular surface antigens of Neisseria meningitidis. Seminars in Infectious Disease, 2, 304. Frasch, C. E. and Friedman, G. L. (1977). Identification d'un serotype meningococcique des groups B, C, Y e t 135W. Medicine Tropicale (Marseille), 37, 155. Frasch, C. E. and Robbins, J. D. (1978). Protection against group B meningococcal disease. 111. Immunogenicity of serotype 2 vaccines and specificity of protection in a guinea pig model. Journal of Experimental Medicine, 147, 629; Glode, M. P., Lewin, E. B., Sutton, A., Lee, C. T., Gotschlich, E. C. and Robbins, J. B. (1979). Comparative immunogenicity of vaccines prepared from capsular polysaccharides of group C Neisseria meningitidis O-acetyl-positive and O-acetyl-negative variants and Escherichia coli K92 in adult volunteers. Journal oflnfectious Diseases, 139, 52. Gold, R., Lepow, M. L,, Goldschneider, I., Draper, T. L. and Gotschlich, E. C. (1975). Clinical evaluation of group A and group C meningococcal polysaccharide vaccines in infants. Journal Clinical Investigation, 56, 1536. Gold, R. and Lepow, M. L. (1976). Present status of polysaccharide vaccines in the prevention of meningococcal disease. Advances in Pediatrics, 23, 71. Gold, R., Lepow, M. L., Goldschneider, I. and Gotschlich, E. C. (1977). Immune response of human infants to polysaccharide vaccines of groups A and C Neisseria meningitidis. Journal of lnfectious Disease, 136, (supp.), 31. Goldschneider, I., Gotschlich, E. C. and Artenstein, M. S. (1969a). Human immunity to the meningococcus. I. The role of humoral antibodies. Journal of Experimental Medicine, 129, 1307. Goldschneider, I., Gotschlich, E. C. and Artenstein, M. S. (1969b). Human immunity to the meningococcus. 11. Development of natural immunity. Journal of Experimental Medicine, 129, 1327. Gotschlich, E. C., Rey, M., Triau, R. and Sparks, J. (1972). Quantitative determination of the human immune response to immunization with meningococcal vaccines. Journal Clinical Investigation, 51, 89. Gotschlich, E. C., Austrian, R., Cvjetanovic, B. and Robbins, J. B. (1978). Prospects for the prevention of bacterial meningitis with polysaccharide vaccines. Bulletin World Health Organization, 56, 509.
lmmunisation against bacterial meningitis
79
Heidelberger, M., Dilapi, M. M., Siegal, M. and Walter, A. W. (1950). Persistence of antibodies in human subjects injected with pneumococcal polysaccharides. Journal of Immunology, 65, 535. Jennings, H. J., Bhattacharjee, A. K., Kenne, L., Kenny, C. P. and Calver, G. (1980). The R-type lipopolysaccharides of Neisseria meningitidis. Canadian Journal of Biochemistry, 58, 128. Kasper, D. C., Winkelhake, J. L., Brandt, B. L. and Artenstein, M. S. (1973). Antigenic specificity of bacterial antibodies in antisera to Neisseria meningitidis. Journal oflnfectious Diseases, 127, 378. Lepow, M. L., Goldschneider, I., Gold, R., Randolph, M. and Gotschlich, E. C. (I977). Persistence of antibody following immunization of children with groups A and C meningococcal polysaccharide vaccines. Pediatrics, 60, 673. Nicholson, A. and Lepow, I. H. (1979). Host defense against Neisseria meningitidis requires a complement-dependent bactericidal activity. Science, 205, 298. Peltola, H., Makel~t, P. H., Kayhty, H., Jousimies, H., Herva, E., H~dlstr0m, K., Sivonen, A., Renkonen, O. V., Pettay, O., Karanko, V., Ahvonen, P. and Sarna, S. (1977). Clinical efficacy of meningococcus group A capsular polysaccharide vaccine in children three months to five years of age. New England Journal of Medicine, 297, 686. Peltola, H., Kayhty, H., Kuronen, T., Haque, N., Sarna, S. and M~kel~, P. H. (1978). Meningococcus group A vaccine in children three months to five years of age. Adverse reactions and immunogenicity related to endotoxin content and molecular weight of the polysaccharide. Journal of Pediatrics, 92, 818. Relier, L. B., MacGregor, R. R. and Beaty, H. N. (1973). Bacterial antibody after colonization with Neisseria meningitidis. Journal of lnjectious Diseases, 127, 56. Robbins, J. B., Schneerson, R., Liu, T-Y., Schiffer, M. S., Schiffman, G., Myerowitz, R. L., McCracken Jr., G. H., Orskov, I. and Orskov, F. In The Immune System and Infectious Diseases (Neter, E. and Milgrom, F., Eds). Karger, Basel (1974), pp. 218-241. Taunay, A. E., Galvao, P. A., Morais, J. S., Gotschlich, E. C. and Feldman, R. A. (1974). Disease prevention by meningococcal serogroup C polysaccharide vaccine in preschool children: results after eleven months in Sao Paulo, Brazil. Pediatric Research, 8, 429. Tramont, E. C., Sadoff, J. C. and Artenstein, M. S. (1974). Cross-reactivity of Neisseria gonorrhoeae andNeisseria meningitidis and the nature of antigens involved in the bactericidal reaction. Journal of Infectious Diseases, 130, 240. Vogler, L. B., Newman, S. L., Stroud, R. M. and Johnston, R. B. (1979). Recurrent meningococcal meningitis with absence of the sixth component of complement: An evaluation of underlying immunologic mechanisms. Pediatrics, 64, 465. Wyle, F. A., Artenstein, M. S., Brandt, B. L., Tramont, E. C., Kasper, D. L., Altieri, P. L., Berman, S. L. and Lowenthal, J. P. (1972). Immunologic response of man to group B meningococcal polysaccharide vaccines. Journal of Infectious Disease, 126, 514. Zollinger, W.D. and Mandrell, R E. (1977). Outer-membrane protein and lipopolysaccharide serotyping of Neisseria meningitidis by inhibition of a solid-phase radioimmunoassay. Infection and Immunity, 18, 424.
Immunisation against bacterial meningitis E. Coen Beuvery
Rijksinstituut voor de Volksgezondheid (R.I.V.), P.O.'Box 1, 3720 BA Bilthoven, The Netherlands Summary The vaccine potential of different surface antigens of encapsulated bacteria is considered. It is concluded that only the capsular polysaccharides provide good protection. Polysaccharides are, however, thymus-independent antigens and the antibody response is strongly influenced by the age of the recipient and his naturally acquired immunity. For a long-lasting immunity the induction of mainly IgG antibodies is essential. Such a response can easily be induced by conjugates in which the polysaccharides have been attached to thymus-dependent carriers.
Introduction Suppurative infections of the meninges are mainly caused by five species of bacteria: Neisseria meningitidis (meningococci), Streptococcus pneumoniae (pneumococci), Haemophilus influenzae, Escherichia coli and group B streptococci. These species of bacteria are encapsulated and the capsules are composed of polysaccharides. Based upon the antigenic structure of the polysaccharides the species are subdivided into serogroups and serotypes. The increasing isolation of sulphonamide-resistant meningococci since the 1960s, the more recent emergence of multiple antibiotic-resistant pneumococci and H. influenzae strains and the risk of brain damage after infection emphasises the need to develop vaccines for the prevention of bacterial meningitis. About 80 per cent of infections are caused by 21 different serogroups and serotypes. A polyvalent polysaccharide vaccine for the prevention of bacterial meningitis should for this reason contain at least the 21 different polysaccharides associated with these organisms (Table I). Table I Bacterial meningitis: serogroups and types of the main pathogens Species
Neisseria meningitidis Streptococcus pneumoniae Haemophilus influenzae Escherichia coli Group B streptococci
0163-4453/81/011071 + 09 $01.00/0
Serogroup and types (number) A, B and C (3) 1, 2, 3, 4, 6A, 7F, 8, 9N, 12F, 23F, 25, and 18C (14)
b(1)
K1(1) Ia, III(2)
©1981 The British Society for the Study of Infection
72
E.C. Beuvery Host defence against encapsulated bacteria
The classical studies of Goldschneider and co-workers (1969a, b) established that antibodies are essential for immunity to meningococcal infection. Recently, unusually severe, chronic or recurrent meningococcal infections have been recorded in association with deficiences in components of the terminal complement sequence (Nicholson and Lepow, 1979; Vogler, Newman, Stroud and Johnston, 1979). These data provide clear evidence that complement-dependant bacteriolysis is the major protective mechanism against meningococcal infection in man. The host defence mechanisms against the other species are similar. Naturally acquired bactericidal antibodies against meningococci are directed towards both capsular and non-capsular antigens (Goldschneider, Gotschlich and Artenstein, 1969a, b.) These antibodies are acquired during carriage and, possibly, subclinical infection caused by both encapsulated and non-encapsulated meningococci (Goldschneider, Gotschlich and Artenstein, 1969 a, b; Reller, MacGregor and Beaty, 1973) or by contact with bacteria possessing identical or almost identical polysaccharides (Robbins, Schneerson, Liu, Schiffer, Schiffman, Myerowitz, McCracken, Orskov and Orskov, 1974). For some years there has been a tendency to use purifed antigens instead of whole cells for vaccine production. In this context the vaccine potential of four meningococcal surface antigens will be considered. These antigens are polysaccharides, pili, outer membrane proteins and lipopolysaccharides. (1) Polysaccharide is the surface structure in direct contact with the host. All purified polysaccharides from encapsulated bacteria are immunogenic in man, except meningococcal group B polysaccharide and the structurally related Esch. coli K1 polysaccharide (Wyle, Artenstein, Brandt, Tramont, Kasper, Altieri, Berman and Lowenthal, 1972; Kasper, Wink° elhake, Brandt and Artenstein, 1973). Polysaccharide vaccines produce few adverse reactions (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978) and meningococcal group A and group C polysaccharide vaccines have proved their effectiveness during epidemics (Taunay, Galvao, Morais, Gotschlich and Feldman, 1974; Peltola et al., 1977). Polysaccharides can also be effectively combined and used as polyvalent vaccine (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978). (2) Pili are almost certainly responsible for the attachment of encapsulated meningococci to host tissue and antibodies against antigen associated with pili may prevent attachment (Craven and Frasch, 1978). However no serotyping system based upon the specificity of the pili has been develop.ed. No data are available concerning eventual induction of local immunity. (3) Outer membrane proteins are the antigens carrying serotype specificity. Although there are more than 18 different meningococcal serotypes (Zollinger and Mandrell, 1977), one (serotype 2) is responsible for 50
Immunisation against bacterial meningitis
73
per cent of infections caused by groups B, C, W135 and Y (Frasch and Friedman, 1977). However, a vaccine composed of antigen from this serotype induced only a poor antibody response in human volunteers (Frasch and Robbins, 1978; Frasch, 1979). (4) Lipopolysaccharides have endotoxin activity and are unsuitable for use as vaccine. Antibodies to lipopolysaccharides are bactericidal (Tramont, Sadoff and Artenstein, 1974) and, therefore, lipopolysaccharides devoid of lipid A might have vaccine potential. However, lipopolysaccharides from meningococcal strains cultivated in vitro lack the O-polysaccharide chain (Jennings, Bhattacharjee, Kenne, Kenny and Calver, 1980) which is present in lipopolysaccharides from Enterobacteriaceae. Lipopolysaccharides lacking this chain are less able to induce binding antibodies. Based upon these data, it must be concluded that, currently, only the polysaccharides provide good vaccine potential. Polysaccharide vaccines
Polysaccharides are polymers of units composed of a limited number of different sugar residues (Robbins, 1978). This polymeric structure gives them immunological specificity; unlike protein vaccines such as tetanus toxoid, they are thymus-independent (TI) antigens. In addition no bone marrow derived (B)-memory cells for polysaccharide antigens are induced during the primary or secondary response. After both injections only IgM antibodies are induced; the secondary response is identical to the primary one. All polysaccharides from encapsulated bacteria behave similarly in this respect. The time course of antibody response after primary and secondary immunisation polysaccharide is shown in Fig. 1. Although these data were obtained in mice (Baker, Stashak, Ams_baugh and Prescott, 1971), the course of antibody response in very young children to a number of polysaccharides, such as those derived from meningococcal group C, H. influenzae type b and pneumococcal type 6, resembles this picture. The antibody response in man to polysaccharide vaccines depends on
g
0
I
2
3
4
5
First dose Time
ff
0
I 2 Second dose
:3
4
5
(weeks)
Fig. 1. Time course of IgM (--) antibodies in mice after a first and a second dose of
polysaccharide antigen.
74
E.C.
Beuvery
several factors including naturally acquired immunity (Beuvery, submitted for publication), the age of the recipient (Gold and Lepow, 1976; Borgono, McLean, Vella, Woodhour, Canepa, Davidson and Hilleman, 1978), the molecular size of the polysaccharide (Gotschlich, Rey, Triau and Sparks, 1972; Peltola, K~iyhty, Kuronen, Haque, Sarna and M~ikel~i, 1978) and the presence of side groups in the polysaccharide chain (Glode, Lewin, Sutton, Lee, Gotschlich and Robbins, 1979). This review will consider only the first two factors. Gold and colleagues (1975, 1977) found that natural immunity to meningococcal group A polysaccharide in American children was induced earlier than that to group C polysaccharide. At the age of 18 months more than 90 per cent of children had detectable antibody levels towards group A polysaccharide, whereas this percentage was only reached in the case of group C polysaccharide after six to eight years of life. The results of vaccination with group A and group C polysaccharide vaccines also showed differences in this respect. At the age of three months primary vaccination with group A polysaccharide vaccine did not result in a detectable antibody response. In one year old children the mean antibody level induced was only about three per cent of that observed in adults (Gold, Lepow, Goldschneider, Draper and Gotschlich, 1975; Gold, Lepow, Goldschneider and Gotschlich, 1977). In children aged six to eight years this level was about 25 per cent of that found in adults (Lepow, Goldschneider, Gold, Randolph and Gotschlich, 1977). Studies with group C polysaccharide vaccine showed that all three month old infants responded to the vaccine but that the peak response was about one per cent of that induced in adults. In children aged two years the mean antibody level was found equal to about one-tenth that of the adult level (Gold, Lepow, Goldschneider, Draper and Gotschlich, 1975; Gold Lepow, Goldschneider and Gotschlich, 1977). The antibody levels induced by vaccine in the various age groups, similarly to those acquired naturally, were positively correlated with age. These workers also reported that a second dose of group A polysaccharide vaccine in children below the age of one year resulted in a booster reaction but that a second dose of group C polysaccharide vaccine gave rise to suppression of the response. In older children and adults a second dose of both polysaccharide vaccines produced antibody levels identical to that following first dose. Similar results have been reported with pneumococcal and H. influenzae type b polysaccharide vaccines (Gotschlich, Austrian, Cvjetanovic and Robbins, 1978). The persistence of antibodies induced by the various polysaccharide vaccines is rather variable. The persistence of antibodies to group A polysaccharide in six to eight years old children was better than those against group C polysaccharide in the same age group (Lepow, Goldschneider, Gold, Randolph and Gotschlich, 1977). However, Heidelberger, Dilapi, Siegal and Walter (1950) reported prolonged persistence o~f antibodies induced in adults by various pneumococcal polysaccharides.
Immunisation against bacterial meningitis
75
In a current study we have determined quantitatively IgM, IgG and IgA antibody levels to meningococcal group A and group C polysaccharides. A group of 66 adult volunteers received combined polysaccharide vaccine and antibody levels were determined in serum samples obtained two weeks thereafter. The results are shown in Table II. Both polysaccharide vaccines induced antibodies in the three main immunoglobulin classes. However IgG and IgA antibodies are not observed in very young children or mice. The synthesis of these antibodies is probably dependant on the triggering of polysaccharide specific memory B-cells (Braley-Mullen, 1975, 1976, 1977, 1980). The presence of these memory cells may relate to previous contact with encapsulated bacteria possessing identical or almost identical polysaccharides. In these bacteria the polysaccharides are attached to outer membrane antigens forming complexes which are recognised by thymus-derived (T)-lymphocytes. These lymphocytes are responsible for the induction of the memory B-cells (Braley-Mullen, 1977). Table II Geometric means of group A polysaccharide and group C polysaccharide antibody levels in serum samples from 66 individuals obtained two weeks after vaccination with the combined polysaccharide vaccine Antibody level (geometric mean: /~g antibody protein/ml)
Group A PS antibodies Group C PS antibodies
IgM
IgG
IgA
total
2.46 (49)* 1.62 (41)
1-67 (33)* 1.95 (49)
0-90 (18)* 0.39 (10)
5.03 (100)* 3.96 (100)
* ( ) per cent total antibody.
The persistence of polysaccharide antigen induced antibodies was also studied. In Fig. 2, three salient examples are given of the time courses of IgM and IgG antibody responses after vaccination with polysaccharide vaccine. I
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I
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80
120
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f
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r
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I
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I 160
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I
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Fig. 2. Time course of IgM ( - - ) and IgG (- - -) antibodies in three adults after immunisation with polysaccharide vaccine.
E . C . Beuvery
76
Patient one produced mainly IgM antibodies whereas in patient three the antibody response was predominantly of IgG class. Patient two demonstrated an intermediate response. The patterns suggest that IgM antibodies disappear faster than IgG antibodies and that the rate of decline of both IgM and IgG antibodies may be related to the ratio between the levels of IgM and IgG antibodies in the serum sample obtained 14 days after administration of the vaccine. A greater value of this ratio may result in a more rapid decline. It is concluded that, as IgG antibodies are induced by triggering of memory B-cells, the persistence of antibodies is related to the possession of these memory cells. If long lasting immunity is to be produced, administration of vaccine must result in the production of mainly IgG antibody and memory B-cells. New developments in the preparation, of polysaccharide vaccines
Further studies have examined the influence of modified polysaccharides on the antibody response of mice. Polysaccharide antigen was conjugated to tetanus toxoid as a thymus-dependent (TD) carrier. The pure polysaccharide or the conjugate were administered to mice and the response to the polysaccharide was determined. Figure 3 presents the course of IgM and IgG antibody response. Up to day 17 no IgG antibody was detected in the serum of mice injected with the pure polysaccharide. In this group the maximal IgM antibody level was found at five days and decreased rapidly thereafter. The course of IgM antibody production after injection with the conjugate was
1.0
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01
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3
5
/
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7
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Fig. 3. Time course oflgM (O) and IgG (&) antibodies against polysaccharide in mice after immunization with pure capsular polysaccharide (- - -) and with conjugated polysaccharide
(
).
Immunisation against bacterial meningitis
77
similar to that induced by the pure polysaccharide up to day seven. Thereafter secondary IgM antibody production became evident which attained its maximum at between day 10-14. Moreover, in the conjugate immunised group, IgG antibodies were detected, the level of which rose rapidly after day 10. On this evidence that additional IgM and IgG of ailtibodies are synthesised after injecting polysaccharide attached to a TD-antigen, it can be concluded that T-lymphocytes are concerned in the antibody response to the polysaccharide. In another experiment, the induction of memory B-cells for the polysaccharide was studied. A group of mice was injected with the conjugate. After 24 weeks one half of the group was injected with the pure polysaccharide and the other half with a second dose of conjugate. The results of the determination of antibodies produced against the polysaccharide are shown in Fig. 4. Up to 24 weeks after the first dose both IgM and IgG antibodies were detected. The second injection with both polysaccharide and conjugate resulted in the synthesis of IgM and IgG antibodies. During the secondary response the IgM/IgG antibody ratio altered in favour of the IgG antibody level. Moreover, the induction period of IgG antibodies seemed to be shorter than that after the first injection. From the IgG response induced by the pure polysaccharide, it can be concluded that the conjugate induced memory B-cells for the polysaccharide. A similar response is seen in adult men after vaccination with polysaccharide vaccines. Before polysaccharide-protein conjugates can be applied as vaccines for human use several aspects, including safety, influence of adjuvants and the role of memory T-cells for the carrier, require further investigation.
,.o/
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/
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4
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8
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/i;/-'.
I
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20
20
~ Sec. imm. Time (weeks) Fig. 4. Time course of IgM (0) and IgO ( A ) antibodies against capsular polysaccharide in mice after a primary immunisation with conjugate and after secondary immunisation with pure capsular polysaccharide ( - - -) or with conjugated po]ysaccharide ( ).
78
E . C . Beuvery References
Baker, P. J., Stashak, P. W., Amsbaugh, D. F. and Prescott, B. (1971). Characterization of the antibody response to type III pneumococcal polysaccharide at the cellular level. I. Dose-response studies and the effect of prior immunization on the magnitude of the antibody response. Immunology, 20, 469. Borgono, J. M., McLean, A. A., Vella, P. P., Woodhour, A. F., Canepa, I., Davidson, W. L. and HiUeman, M. R. (1978). Vaccination and revaccination with polyvalent pneumococcal polysaccharide vaccines in adults and infants. Proceedings Society Experimental Biology and Medicine, 157, 148. Braley-Mullen, H. (1975). Secondary IgG responses to type Ill pneumococcal polysaccharide. I. Kinetics and antigen requirements. Journal of Immunology, 115, 1194. Braley-MuUen, H. (1976). Secondary lgG responses to type Ili pneumococcal polysaccharide. I1. Different cellular requirements for induction and elicitation. Journal of Immunology, 116, 904. Braley-Mullen, H. (1977). Secondary lgG responses to type 111 pneumococcal polysaccharide. 11I. T-cell requirement for development of B memory cells. European Journal of Immunology, 7, 775. Braley-Mullen, H. (1980). Antigen requirements for priming of lgG producing B memory cells specific for type II1 pneumococcal polysaccharide. Immunology, 40, 521. Craven, D. E. and Frasch, C. E. In Immunobiology ofNeisseria gonorrhoeae (Brooks, G. F., Gotschlich, E.C., Holmes, K.K., Sawyr, W.D. and Young, F. E., Eds). American Society for Microbiology, Washington D.C. (1978), pp. 250-252. Frasch, 'C. E. (1979). Non-capsular surface antigens of Neisseria meningitidis. Seminars in Infectious Disease, 2, 304. Frasch, C. E. and Friedman, G. L. (1977). Identification d'un serotype meningococcique des groups B, C, Y e t 135W. Medicine Tropicale (Marseille), 37, 155. Frasch, C. E. and Robbins, J. D. (1978). Protection against group B meningococcal disease. 111. Immunogenicity of serotype 2 vaccines and specificity of protection in a guinea pig model. Journal of Experimental Medicine, 147, 629; Glode, M. P., Lewin, E. B., Sutton, A., Lee, C. T., Gotschlich, E. C. and Robbins, J. B. (1979). Comparative immunogenicity of vaccines prepared from capsular polysaccharides of group C Neisseria meningitidis O-acetyl-positive and O-acetyl-negative variants and Escherichia coli K92 in adult volunteers. Journal oflnfectious Diseases, 139, 52. Gold, R., Lepow, M. L,, Goldschneider, I., Draper, T. L. and Gotschlich, E. C. (1975). Clinical evaluation of group A and group C meningococcal polysaccharide vaccines in infants. Journal Clinical Investigation, 56, 1536. Gold, R. and Lepow, M. L. (1976). Present status of polysaccharide vaccines in the prevention of meningococcal disease. Advances in Pediatrics, 23, 71. Gold, R., Lepow, M. L., Goldschneider, I. and Gotschlich, E. C. (1977). Immune response of human infants to polysaccharide vaccines of groups A and C Neisseria meningitidis. Journal of lnfectious Disease, 136, (supp.), 31. Goldschneider, I., Gotschlich, E. C. and Artenstein, M. S. (1969a). Human immunity to the meningococcus. I. The role of humoral antibodies. Journal of Experimental Medicine, 129, 1307. Goldschneider, I., Gotschlich, E. C. and Artenstein, M. S. (1969b). Human immunity to the meningococcus. 11. Development of natural immunity. Journal of Experimental Medicine, 129, 1327. Gotschlich, E. C., Rey, M., Triau, R. and Sparks, J. (1972). Quantitative determination of the human immune response to immunization with meningococcal vaccines. Journal Clinical Investigation, 51, 89. Gotschlich, E. C., Austrian, R., Cvjetanovic, B. and Robbins, J. B. (1978). Prospects for the prevention of bacterial meningitis with polysaccharide vaccines. Bulletin World Health Organization, 56, 509.
lmmunisation against bacterial meningitis
79
Heidelberger, M., Dilapi, M. M., Siegal, M. and Walter, A. W. (1950). Persistence of antibodies in human subjects injected with pneumococcal polysaccharides. Journal of Immunology, 65, 535. Jennings, H. J., Bhattacharjee, A. K., Kenne, L., Kenny, C. P. and Calver, G. (1980). The R-type lipopolysaccharides of Neisseria meningitidis. Canadian Journal of Biochemistry, 58, 128. Kasper, D. C., Winkelhake, J. L., Brandt, B. L. and Artenstein, M. S. (1973). Antigenic specificity of bacterial antibodies in antisera to Neisseria meningitidis. Journal oflnfectious Diseases, 127, 378. Lepow, M. L., Goldschneider, I., Gold, R., Randolph, M. and Gotschlich, E. C. (I977). Persistence of antibody following immunization of children with groups A and C meningococcal polysaccharide vaccines. Pediatrics, 60, 673. Nicholson, A. and Lepow, I. H. (1979). Host defense against Neisseria meningitidis requires a complement-dependent bactericidal activity. Science, 205, 298. Peltola, H., Makel~t, P. H., Kayhty, H., Jousimies, H., Herva, E., H~dlstr0m, K., Sivonen, A., Renkonen, O. V., Pettay, O., Karanko, V., Ahvonen, P. and Sarna, S. (1977). Clinical efficacy of meningococcus group A capsular polysaccharide vaccine in children three months to five years of age. New England Journal of Medicine, 297, 686. Peltola, H., Kayhty, H., Kuronen, T., Haque, N., Sarna, S. and M~kel~, P. H. (1978). Meningococcus group A vaccine in children three months to five years of age. Adverse reactions and immunogenicity related to endotoxin content and molecular weight of the polysaccharide. Journal of Pediatrics, 92, 818. Relier, L. B., MacGregor, R. R. and Beaty, H. N. (1973). Bacterial antibody after colonization with Neisseria meningitidis. Journal of lnjectious Diseases, 127, 56. Robbins, J. B., Schneerson, R., Liu, T-Y., Schiffer, M. S., Schiffman, G., Myerowitz, R. L., McCracken Jr., G. H., Orskov, I. and Orskov, F. In The Immune System and Infectious Diseases (Neter, E. and Milgrom, F., Eds). Karger, Basel (1974), pp. 218-241. Taunay, A. E., Galvao, P. A., Morais, J. S., Gotschlich, E. C. and Feldman, R. A. (1974). Disease prevention by meningococcal serogroup C polysaccharide vaccine in preschool children: results after eleven months in Sao Paulo, Brazil. Pediatric Research, 8, 429. Tramont, E. C., Sadoff, J. C. and Artenstein, M. S. (1974). Cross-reactivity of Neisseria gonorrhoeae andNeisseria meningitidis and the nature of antigens involved in the bactericidal reaction. Journal of Infectious Diseases, 130, 240. Vogler, L. B., Newman, S. L., Stroud, R. M. and Johnston, R. B. (1979). Recurrent meningococcal meningitis with absence of the sixth component of complement: An evaluation of underlying immunologic mechanisms. Pediatrics, 64, 465. Wyle, F. A., Artenstein, M. S., Brandt, B. L., Tramont, E. C., Kasper, D. L., Altieri, P. L., Berman, S. L. and Lowenthal, J. P. (1972). Immunologic response of man to group B meningococcal polysaccharide vaccines. Journal of Infectious Disease, 126, 514. Zollinger, W.D. and Mandrell, R E. (1977). Outer-membrane protein and lipopolysaccharide serotyping of Neisseria meningitidis by inhibition of a solid-phase radioimmunoassay. Infection and Immunity, 18, 424.