VACCINES FOR THE PREVENTION OF ENCAPSULATED BACTERIAL DISEASES: CURRENT STATUS, PROBLEMS AND PROSPECTS FOR THE FUTURE JOHN
B. ROBBINS
Bureau of Biologics, 8800 Rockville
INTRODUCTIOY It
is an honor for me and my colleagues to participate in this colloquium acknowledging the scientific accomplishments and the special contribution of Professor Michael Heideiberger to the vaccine program of the Bureau of Biologics. When, as a medical student I first became interested in infectious diseases and immunology, the late Dr. Chandler A. Stetson urged me to read Lectures in fmmun~ehemi.~tr~ by Michael Heidelberger (Heideiberger, 1956). These accounts of the introduction of quantitative chemical and physical measurements to the study of immunity was my introduction to the accomplishments of this remarkable man. His discoveries and continued attention to unanswered questions of the structure of carbohydrates and the immune response they elicit in humans remain stimulating to scientists in many disciplines. Recent FDA activities have been concerned with the regulation of new bacterial poiysaccharide vaccines. Many of our decisions were aided by publications and conversations with this gifted and giving individual. For example, the establishment of reference anticapsular pofysaccharide antisera for pneumococcal, meningococcal and Haemophilus irtj7uenzae radioimmunoassay required quantitation of human precipitating antibody described by Professor Heideiberger (Heidelberger & MacPherson, 1943). Professor Heideiberger is an author of at least one of the references for each of the 14 pneumococcal polysaccharides cited in the FDA brochure describing minimum requirements for the currently licensed vaccine (Federal Register). One cannot approach the subject of standardization ofcapsular polysaccharides without ret&ring to him or his associates’ work. The first references in the FDA’s General Bibliography for Pneumococcai Vaccine Licensure is The Sofubfe Specif;c Substance of Penumococcus by Heideiberger and Avery in the Journal 01‘ Experimental Medicine (Heideiberger & Avery, 1923, 1924; Heidelbcrger, Avery CL Goebei, 1929). More recently, we used reference by Heidelberger and Nimmich (1976) to point out the potential for pneumococcal capsular poiysaccharide vaccine to prevent septicemia caused by Kfebsieflu species (Heideiberger & Nimmich, 1972, 1976). The only published structural study of 839
Pike,
Bethesda.
MD 20011. U.S.A
pneumococcus type 25 is dated 1977 and has as an author Dr. Heideiberger (Das, Heidelberger & Brown, 1976). Dr. Heidelberger’s discovery of the pyruvate content of pneumococcal type-4 poiysaccharide was published in 1972 (Heidelberger. Gotschlich & Higginbotham, 1972). One of Professor Heideiberger’s contributions was the development of a multivalent pneumococcal capsular polysaccharide vaccine. This effort, together with those of Drs. MacLeod, Hodges, dilapi, Siegel and Walters, resulted in the awarding of a license to the E. R. Squibb Company in 1945 (MacLeod et ui., 1945). The increasing development and use of antibiotics resulted in this company withdrawing their license without prejudice in 1947. Thereafter, largely through the persistence and broad scientific avenues taken by Dr. Robert Austrian and his associates. the need for preventation of pneumococcal disease was reconsidered (Austrian & Gold, 1964; Mufson et ul.. 1974; Austrian, 1975) and resulted in the production. study, standardization and recent iicensure of a I4 talent pneumococcal polysaccharide vaccine (Smit ef al., 1977). This effort was aided by the simultaneous, rapid development of a meningococcal vaccine composed of Group A and Group C capsular polysaccharides (Gotschiich et af., 1969; Artenstein t-‘f al.. 1970; Wong et al., 1977). PREVENTION RATHER THAN TREATMENT FOR CONTROL OF ENCAPSULATED BACTERIAL DISEASE
The view that we have achieved effective control of encapsulated bacterial diseases has been challenged. Encapsulated bacterial diseases, including those caused by pneumococci, meningococci, ~u~~rn~~ph~fu.~ injluenzae type b, Group B streptococci, Escherichiu coli, Salmonella typhosa, Klehsiella penumoniae and S~aph~fococ~us aureus, remain substantial public health threats. For example, the mortality and morbidity of one disease caused by these organisms, bacterial meningitis, although successfully ‘cured’ in most patients by antibiotics, is unacceptably high. The overall mortality of pneumococcal meningitis has been reported to be about 307; (Baird, Whittle & Greenwood, 1976). A long-term follow of 6000 ‘cured’ meningococcal meningitis patients revealed significant central nervous system problems in about IO”,, (WHO.
.1OHY I3
s-lo
1077). The
lnorbidity
meningitis.
measured
of ‘cured‘
type-b
H. ir~fl~vrxw
by tixcd central nervous deficit.
Ip/~o\tr ha\c comparatively structures. Sialic acids arc frcqucnt simple components of disease-us~ociatsd capsules. Thib Encapsulated gram-positive or gram-negative monosaccharide is found in 9 01‘the 3 I bacteria listed bacteria cause ;I variety of clinical diseases with in Table I. However. their presence. per \c. doe5 not septicemia as a common pathogenic factor. The explain the disease potential of these hactcrla. l-01 capsules of thesepathogens. which confer this invasive example. E. c,o/i strains with the K93 capsularproperty. share several properties: (I) they are surface polysaccharide. u linear +iallc acid homopol~mc~- uith structures in direct contact with the host; (2) all are linkages similar to those of mmlngococc;II Group5 B polymers composed mostly of monosaccharides. They and C, and E. c,o/i K I capsular polq~accll~trld~2. arc’ ma> be linear homopolymers of a single saccharide infrequently associated with dixca\e (Cilodc C/ ol.. such as meningoccal Groups A. B and C‘ and 1977: Egan . Got~chlich and LILI halt po\tulatcd that two or more monosaccharides such as pneumococcal the molecular size ofpurified capsular poly~accharide~ types 3 and 8. multi-chained branched copolymers solution was due to multi chain in aqueous composed of at least five monosaccharides and aggregation (LIU c’t N/., 1977). Their prclimlnal-k Mark additional moieties such ah pyruvic acid or as suggests that this aggregation is due to m~celle pneumococcal type 4. or contain phosphodiester formation consisting of polysaccharlde chains of bonds such as H. i~~//wnrrw type b and pneumococcal about 40.000. A glycolipid. attached by ;I pho\phatc type 6 (Table I ): (3) all purltied capsular diester joining the reducing monoaccharldc of Groups polqsacchurides are antigenic. and probably all are A. B and C meninpococcal polysaccharidc. 15 immunogenic although meningococcal Group B and composed of a phosphate and glycerol \uh\tltuteJ E c,o/i K I. a~, prepared to date. fail to induce serum with two Cl2-I4 fatt) acids 1s the molcty forming thih antibodies in most adult5 (W,y!c C/ (I/.. 1972): (4) the micellar structure. This glycol~p~d moiet! could he antlpenicity and immunogeniclty of several capsular Of tt1c capslllar~ involved in the attachment polysaccharides have been shown to be directly related polysaccharides to the intact bacteria. Detailed to their mol. wt (probably valid for all) (Martin it [I/.. analysis of these capsules irl ti/lc on the bacteria and in 1956: Kabat & Bezcr. 195X: Howard ef (I/.. 1971: solution will be required for characteriration of their Gotschlich. 1974); (5) the virulence of some virulence and immunogenic propertie\. cncapsulatcd bacteria is directly related to the amount per bacterial cell and to the mol. wt of their capsular polysaccharides (MacLeod & Krauss. 1950; Shin et P\\EI \lOC’O(‘( I r/l.. 1969: Smith & Wood. 1969: Kaijser. 1973: Glynn e/ Pneumococci cause a variety of diseases with ol., 1977). This is seemingly contradictory to the observation that immunogenicity (presumably a different frequencies in different age groups. In adult\. protective propert>) and mol. wt are directly related. pneumonia is the most common scrlous disease. while However. increasing mol. wt may confer In infants. pneumococci are the most common cause 01‘ serious and rc-occurring otitls media (Heffron. characteristics that permit both activation of immunocyte surfaces and responsiveness as well as 1939: Kamme et rrl.. 1970: Slo)c~- VI o/.. 1974). interference with effective binding and inactivation of Pneumococcal meninpitis occur\ at all ages. In sonic protective components such as complement proteins African and Asian countries. pncumococcal dlseasc is (Wood. 1941; Wood & Smith. 1949). The best a leading public health problem (Delltt & Douglas explanation by which capsular polysaccharides confer 1973; Odouri & Shah, 1973). Patients with del’ectiic invasiveness through an anti-phagocytic mechanism splenic function. ofwhich sickle cell anemia ISthe mo\t (Wood. 1941; Wood & Smith. 1949: Johnston P/ ul.. common. areespecially susceptible to \e\crc and often overwhelming pneumococcal dlscase dcsplte antl1969; Shin (‘I u/.. 1969; Roberts. 1970: Stossel 1’1al., microbial therapy (Pearson. 1977). 1973). The cell wall mucopeptide of gram-positive and the lipopolysaccharide of gram-negative bacteria can Following the Tillctt and Francis obscr\:ttion that
.IOHN
s-l7 puritied
capsular
antibody
in humans.
polysaccharides belton
type-spcclfic
disease
injected
types
with
(k-rancis,
1034:
Induced
(11(I/. showed
protection
I
in
and II capsular
krancis
&
Tillett,
H. ROBBlhS
serum
in the 1930s
CCC‘
recruits
system
Ekwurzel
(‘I
Because ofextcnsivc
pneumococcal accoi-ding
polysaccharidcs 1930;
polysaccharides.
polysaccharides
to :I serological
designated
al.. 1938: I-rlton. 103X). .4 group headed by MacLeod, Includine I’rofeaor Heldelburger. showed IOO”,,
example.
cl‘ficacq ?or
26. respectivelv.
caused
types
I. 2. 5 and
b> these
organisms
earl>
I urthel-.
these in\estipators
111 WWII
01‘ individuals
soldiers.
Thiz
c;trrlagc using
was
prorect~on elderIF
cpidcmiological National
Discascb
Institute
pi-olect~\‘c and other South
Al‘rican
bacterial
high
attack
rate
01‘ their
divided
hark.
equal
groups
pneumococc~rl
\ accine.
saline
These
placebo.
antibody inlo
~;is
;I multivalent
Austrian.
capsular
and
1977.
Smlt
c’/ r/l..
1977).
or meningococcal
did not occur. There
were no significant
in the vaccine recipients. in ;I rural
population
1077).
A prcllmlnary
chlldrcn
Mith
sickle
Guinea
shoued
control
due
to
type\
capsular
itrc S3 zcrologlcallq
poll xxcharides
1970:
C/ 01..
and
to bc solbed discax
distinct
(Kaufman
IO7 I ).
Lund.
In
other bel’orc can
be
pnc~~mococc~~I discahe (X0-90”,,) types.
Accordingly.
contain
at lcast
I4 capsular
signiticant
pneumococcal
chrce variables
arc related Isolates.
disease
;frca. Types 111 ;I
45(72)
Africa
recent
in
vaccine I’ormulationh geographic ol‘dlsease. to
the number
account
for
Ibrtunately. II)
of types to one
have been I‘ound only in
Type
Egypt. To
least
and
absorption
prepared
remaining
for their
IOO”,, coLerage
types in the laccinc will.
rhe
\arlable
is thee\aluation
cro\kreacti\it\i
01‘
with
(Krishnomurthy
monosaccharide I9A(S7).
I -rhamnose
rabbit
acti\#ities.
un-
ofsurveillance pneumococcal
to know
the
their
against It will
causing
disease.
of multiple
This
discasc
(Appelbaum
ha\c utilized
type
with
more accurateI! ih emphazi;lctl resistant
isolatch
rrom
01 (II..
(includlnr chlor-
.lohannesburg.
1977).
Our
curl-cnt
19).
(3) The time-related change in the praalencc pncumococcal type5 in disease isolates. empha\i/cd Lund
and
unexplained Barnes.
Finland.
remains
phenomenon
1977). isolates and 40s.
Types
;I
(Lund.
I’a\cinating 1970:
U.S.
t\\o
and
types
Europe
xc
Kc
among
during
\Irtually
01’ h) and
Finland
3 and 5 were prominent
in the
These
h! t;pc
cephalothtn
tetraqcline~.
I9F(
from
to serotype
methicillin.
ampicillin.
Africa
Laccines
bc
~111
immunitcd
antibiotic
clindamycin. erythromgcln. amphenicol and cotrimosia)le) South
in
it
for this liner type
those
the organisms
G.
induced
related lypcs
be important
from
pncumococcl
and I)-
to Identil!,
H vaccine prepared serologically
\acc~nc to character102
peniclllm
19A(57)
l’or thl\ cro\\-
are
the world
and especially
IO) and
II-glucose,
cross-protcctlic:
antibodies
throughout
disco\cr)
the
type
genetic basis
pneumococcal rcccnt
al-c
in
gluco\amine
polysuccharides.
the I9 group.
There
lOF(
be necessary
whether
protect
disease Isolates speciticitl
will
these
puriticd
thcsc two
197X).
whereas
to characterize
When by
betuecn
of
plus
and
pol~saccharides
galactosamlne.
and possible
and
humans
work
of whole
similarltles
phosphate.
Further
reactivit)
within
;I nd
thcsc I’our moieties
galactose.
antisera
ili.jection
relation
19Fcontamz and
I‘rom ussa)
w#hole organisms
composition
Type
;md
IO gi-oup
t:\idencc
C/ ol.,
dil‘l’ercnces
:I\;
I9U(5X)
and agglutination
intracenous
organisms
U.S..
I9 antixra
01‘ this
hyperimmunc
a close serological
1930s
pneumococcal
lG30”,,
ol’
by multiple
sub-types
disease
or capsular
IYA(57).
indicate
Thus.
approach
W,,
using Qucllung
All
I9A(57).
isolates
isolate
are classitied
antisera.
19).
art
111 Ihc
isolates
disease
19) and
studies
29 was a maJor isolate
have to double.
(2) Another data
the
At
types arc limited
may have to be adjusted
destination.
I4
to achieve
immunity.
to the distribution
Some
and Asia.
seriou\
i\ caused by about
polysaccharides
and 46(73)
sur\ey
most
an elf‘ecti\e vaccme must disease
among
pneumococcal
(‘I rrl.. 1960: Lund.
However.
capa&ir
Southern
l9F(
I9t(
most
cast
In
isolates
In children.
typing
types
arc X0”,, earlier
lOA(57)
There
with
one lqpe uill
(Rile>
available
7 qpc 6
and SH(26).
disease
another
to
t>pcs has not
6A(6)
of
XV’,, ofdiscasc
In the U.S..
important
considered.
( I)
react
For
19c‘(59).
were obtained
disease elficxy
01‘ pncumococcal
approximately
adverse effects
c’t t/l.. 1977).
thcrc arc‘ \c\craI problems
complete
6B(26).
the structural
C/ i/i.. 1976:
anemia
ccl1
(Ammann
degree of
capsular
XV’,,
The
relation
I-01. instance,
both
and 20”,, are 6B(26). type
contains
mcningococcal
results
111 Neu study
hcmoflohinopathlc~ )‘a.
Similar
poly-
Dlscase
pneumococcal
or
Incorporation
was achicvcd (Austrian
with
approximately
major
the serum
and a high
pneumococcal
protcctlon
other
\ accinc
by their
formulation
capsular-specific ~IWIW
individual
al‘kcted
were
multl\alent
that
t-act
formalinized
sekrral
miners
menmgococcal
to
not
the first
investigated.
will
adults.
vaccine-induced
later more prectse assays with purilicd
pneumonia
recruit
showed
in
has an
encapsulated
rcceiking
studies
response
accharides
within The
the
vaccines
pncumococcal
mcningitib
mine
into
Infectious studied
populalion 01‘
been thoroughly
laboratnrles
tvpcs as sinplc cntitlcs.
between these cross-reacti\c
antiserum
i-or
;I\ 6A
these types as 6 and antlscra.
immunity
uill
and
denotes
available
and
based
(21(I/.. 1960).
basis
clinical
and
system With
Danish
two types rccognired
cross-reactive
type I9 with
& Dohmc This
including
In
groups
chemical
are
(21(I/. and others.
01‘ Allerpy
will identify
The
types within (Kaulhnan
6 contains
U.S.
care hospital
cf’fects ol‘multicalent
2nd meningococcal months
the
and 6B. The
6A(6)
hacterimia
a chronic
miners.
disease
Kauffman. type-specific
and
Sharp
injected
a decreased
showed
recruit
extraordinary
these
and. hence. a lower
01‘ Austrian
and later Merck
1945).
immunity‘
to
Following
studies
Forces
(I/..
colleagues.
attendIng
1947).
(Kauflinan.
troops
pneumoniu
individuals
cf
with
vaccine.
against
Armed
attributed
unimmunizcd
Iri\iilenl
pneumonia
a ‘herd
interacting
el‘ltict
ofthcir ;I
U.S.
bho~
in the immunired
exposure
the
in
(MacLcod
recruits cl‘kct
7 against
Group
classification.
capsular
upon thiscross-reactivity
cross-reactivity,
have been designated
the
absent from recent sur\cys. C’ontinued aur\eillancc MIII be necessary 10 dctermlne uhethcr the appearance 01’ some pneumococcal types will bc ta~ored bq ~acc~nc’ usage. (3) Age-related diflrrences in the distrlbutlon 01‘ pneumococcal types and sub-types are imporkmt 111 determining the multlcalcnt \acc~nc I’ormulation.
Vaccines
Against
Encapsulated
Types 6,9, 14, 19F( 19) 23 and I8C(56) predominate in CSF and purulent otitis media isolates from otherwise healthy infants and from the blood and CSF of infants and children with absent or defective spleen function (72). Curiously. there is a direct relation between infant disease type and the low immunogenicity of these types in this age group (73). Types I, 2,3,4.8 and 12 which are more frequently associated with serious disease in adults are more immunogenic in infants (Austrian. 1977; Borgono er al.. 1978). This inverse relation between immunogenicity and virulence of pneumococcal types associated with disease is an important theoretical and practical problem for pneumococcal and other bacterial disease prevention with significant attack rates in this a& group. Pneumococcal otitis media poses a special problem for immunoprophylaxis. That otitis media constitutes a serious cause of immediate morbidity and acquired hearing loss has only recently been appreciated by the medical community. Studies are under way to evaluate vaccine-induced prevention of pneumococcal otitis media. The data suggests that with our current vaccines. infants under two years of age will not respond to those pneumococcal types most frequently associated with disease. Further, it is possible that external secretory mechanisms in addition to serum antibodies, have to be induced to prevent otitis media. The type-specific inhibition upon nasopharyngeal acquisition induced by the pneumococcal polysaccharide vaccine suggests that an immunogenic vaccine
Bacterial
in the infant age group will be protective against otitis media. Dr. Heidelberger has reported extensive crossreactivity between pneumococcal capsular polysaccharides. including vaccine types. and Klebsiella and E. coli (Avery rt cd., 1925: Heidelberger pt cd.. 1968; Heideiberger & Nimmich, 1972; Robbins et ul.. 1972: Heidelberger & Nimmich, 1976: #rskov et ul.. 1977). Both Klebsiella and E. coli are common in hospital associated infections. Cross-immunity to these organisms may be induced with pneumococcal vaccines and this possibility should be studied.
There are at least seven meningococcal capsular polysaccharides designated Groups (Table 2). Most meningococcal disease is caused by Groups A, B and C. W I35 and Group Y have been recentlv shown to comprise approximately IO”/,, of disease -isolates in some countries (WHO, 1976). Epidemiologic characteristics of meningococcal disease can be related to the Group. Group A is usually associated with acute epidemics or high levels of endemic disease (Gold & Lepow, 1976). Outbreaks and occasionally smaller epidemics have been associated with Groups B and C. The sudden emergence of severe meningococcal epidemic in Brazil, especially Sao Paulo. from 1972 to 1974 was originally caused by Group C and then by
Table ?. C‘ross-reacting antigens of pharyngeal and’or enterlc organisms Invasive
Pathogen
Cross-reacting organism
Pneumococcus Type I
to capsukrr
polywccharldes
Meningococcus Group A
ol
bacteria Cross-reacting
structure
Extracellular polysaccharidc. not characterized K7 capsular polysaccharrdc acid component Extracellular polysaccharrdc. acid component
Type 3
Group
x43
Drseases
structure r,-glucuronic n-glucuronic
J~-acetyl-p-mannosamine phosphate component ofextracellular polysaccharide ,Y-acetyl-u-mannosamine phosphate component ofextracellular polysaccharide O-acetyl + and O-acetyl - form variants of K I capsular polysaccharide. cz 2-X linked ,V-acetyl neuraminic actd K92 capsular polysaccharide, :V-acetyl neuraminic acid homopolymer with alternating J 2-8, 2-9 linkages
C
E.whrric~hia di Staphylococcus aureu. Bacillus pumilis. Bacillus sub t ilis Locrohacillus plantorum Pneumococcus
K IO0capsular polysaccharlde, +3)-/I-t,Chose (1 + 2) ribitol-S-phosphate + Polyribitol phosphate component of cell wall teichotc acrd Type 26 (VIB), 29 and 30 capsular polysaccharide ribitol phosphate component ,v-acetyl galacturonrc acid component extraccllular polysaccharide
ol
both Groups A and C. The recent epidemic of meningococcal meningitis in Finland, first observed in young army recruits and then in the general population. was due to Group A (Makela C/ ~1.. 1975). Outbreaks of’ meningococcal Group B disease habe occurred in Belgium. England and Norway (Mumford rt 01.. 1974: B@vrc t”t (II., 1977: Griffiss clt (11.. 1977: Jacobson c’t L/I.. 1977). Success in prevention 01‘ Groups A and C meningococcal meningitis in older children and adults has been achieved with capsular polysaccharidc vaccines (WHO. 1976: Peltola (‘I crl.. 1977). These vaccines are now licensed products in the U.S. and other countries and under manulhcture by at least five countries. At least four problems prcvcnt complete vaccinecontrol ofmeningococcal disease. I-lr\t it is the lesser immunogenicity of polysaccharides in infants that group with the highest attack rate (Gold & Lepow,, 1976). Data l‘rom Finland and the immunogenicity studiesconducted in the U.S. indicate that prevention ofGroup A disease can bc achieved bq two injections initiated at three months and then again at six months of age (XX). Group c‘ has not been shown to be fully protcctivc under the age 01‘two years and this correlates well with its lesser immunogenicity m this age group. Important information regarding the human infant immune response to Group A in contrast to Group C menmgococcal polysaccharidcs has been developed by Gold. LepoM and Gotschlich (89). Injection of Group A polysaccharide into infants 3 months of‘ age induced no antibody response. A slight response was elicited in individuals older than 6 months and this increased with arc (Gold (‘I o/.. 1975. 1977). Booster immunization showed inlants. who received Group A vaccine at 3. 7 or I? months. responded significantly greater than int’ants who had received only one inJectIon. This booster ellt-ct was no longer demonstrable in individuals o\er IX months. These tindings were utilized to prcvcnt Group A meningococcal disease in Finnish children (Peltola 1’1 cl/.. 1977). In contrast. Group c’ meningococcal polysaccharide induced 21significant (but probably not sufficiently high to be protective) antibody response as early as 3 months of age. With Increasing age the response increased but the mean antlbod) concentration achieved at 1 year was approximately 1’10th that ofolder children and adults. In contrast to the anamestic response induced by Group A meninpococcal polysaccharldc in infmts up to IX months. Group C exert ;I supprcstic effect ~lpon reimmunization of this age group. One approach to ;i solution to this problem of :I non-protective response to Group C‘ meningococcal polysaccharidc has been studied by Glade (‘I u/.. (1976). These workers utilized a Group C‘ meningococcal polysaccharide var’lant lacking Oacetyl (Apicella. 1974). This capsular polysaccharidc variant comprised about IO”,, of disease isolates (Apicella & Feldman. 1976). The Group C capsule was purified and was found to induce higher levels of antibodies compared to the O-acetyl positice vaccine in young adult volunteers (Glade (‘I (I/.. 1979). Antibodies induced by the O-acetyl negative variant were bactericidal for the O-acet>l positibr organisms. Further studies to characterize 11s immunogenlcity in younger individual\ arc under \\a!
A second hurdle is that vaccines for the so-called minor groups have not been tested. Because of their low disease attack rate it is unlikely that one clinical trial will be able to verify their disease efficacy. relation the direct between the However. immunogenicit? and disease efficacy of groups A and c‘ polysaccharldes suggests these Groups can be included in the multivalent vaccine if they are shown to induce serum antibodies with biologic activity, such as complement-dependent bactericidal reaction (Gotschlich (‘t t/l., 1969). Preliminary studies suggest Groups 29E. WI35 and Y are immunogenic and induce bactericidal antibodies (Farquhar c’f ul.. 1977). A third problem is that the duration of vaccineinduced immunity is not yet known (Lepow C/ r/l.. 1977). Some worker\ suggest that re-immunization may be necessary 3-3 years later. even in the adult group. to restore antibodies to their maximum level and to retard their rate of decline observed after initial immunization (94). Fourth. the Group B capsular polysaccharide (and I? cali K I ) has not proved to be an effective immunogcn (Wyle C/ al.. 1972: Kasper ~‘1 (I/.. 1973). Two approaches to this problem have provided Important new information regarding the physiology of encapsulated bacteria/host interaction. The tirst. advocated by Frasch and others. is the study ofanother surface structure. the outer membrane proteins of meningococci (E‘rasch & Gotschlich. 1974; Frdsch. tY77: Mumford ot al.. 1974: Zollinger & MandrelI. 1977). There is a polymorphic system. presumably controlled at ;I Tingle locus, of antigenially related proteins. These outer membrane proteins have been designated ~s~vv/~~x’sand have many characteristics that support their use as vaccines. (a) Using hyperimmune rabbit antisera. prepared by multiple injections of whole bacteria. serotype-specific reagents have been prepared (Frasch & Chapman. 1973). The serotyping reagent prepared with Group B strains has been shown to react with outer membrane proteins among meningococcal Groups B. c‘. I’. W I35 and 29E (Frasch & Friedman. 1977). It is interesting that Group A and 29E strains. which do not contain sialic acid. do not react with these antisera. (b) To-date. IS variants have been identified. The serotype distribution of these scrotypes among isolates from discused or healthy individuals resembles that of the capsular polysaccharides. For example. disease is associated with onI1 some serotyprs. Some scrotypcs have been associated only with carriage and some are associated with carriage and ‘or disease (Frasch. 1977). Scrotypinp prohidcs a tool for assessing the disease potential of isolates tn an outbreak or epidemic (Jacobson CI (I/.. 1977: Mumford c’t rrl.. 1974). (c) The serotype protems can be prepared in highly purified form free from significant contamination by other cellular components especially endotoxin. Injection of animals with the purified serotypc proteins elicits bactericidal antibodies and a protective effect in several animal models (Frnsch & Robbins. 1978). Further, anti-serotype protein antibodies and antipolysaccharide antibodies exert a synergystic protective effect (Frasch CI cl/.. 1976). This important finding suggests that immuniration with both the serotypc protein and capsular polysaccharide could provide ;I longer duration of immunity since the protective effect of these two antibodies may be
\:accinea Against Encapsulated Bacterial Diseases greater than their sum. Since only several serotype proteins are associated with disease among the Groups B, C, Y and W I35 stramb a serotype protein vaccine may require only several components. It should be noted that the Group C epidemic in Brazil was caused almost exclusively by serotype 2. These findings provide the impetus for studying outer membrane proteins and other surface antigens such as pili (attachment factors) of other encapsulated bacteria. Investigators have shied away from studying other surface structures because it has been assumed that capsules formed a non-penetrable covering. Antibodies to the 0 antigen of gram-negative bacteria exert a protective effect although with a lower specific activity than that of anti-capsular antibodies. Noncapsular antibodies may exert a bactericidal effect (Muschel, 1960: Osawa & Muschel, 1964). Kabat and Heidelberger showed that absorption ofhyperimmune antiserum, prepared by repeated injection of whole bacteria. with either encapsulated or unencapsulated variants of the immunizing strains. removed antibodies to non-capsular antigens indicating that the latter were available for interaction with serum antibodies in both bacterial preparations (Pittman, 1931).
Although thcrc arc 51x capsular types of H. irzfluenxr. most serious disease is caused by type b (Parke ef ul., 1977). This organism is the leading cause of bacterial meningitis in the U.S.. Sweden and Finland (Johnson & AlLin. 1971; Peltola L’I(I/.. 1977~). H. i~~flucwxc~ type b also causes other serious diseases including epiglottitis. septic arthritis and pneumonitis with empyema (Smith & Robbins, 1974). Until recently, only deaths due to H. in/lucwx~e type b have been reported. Bused upon limited surveys. it has been estimated that there are about 12.000 cases per year in the U.S. Several workers have reported that about one third of ‘cured’ patients have significant permanent CNS deficits (Sell c’t uI.. 1972; Lindberg c/ ul., 1977). One of the important observations regarding the pathogenic role of the H. in/1u(wxw type b capsule was reported by Heidelberger and Alexander (Alexander et ul.. 1944). These workers showed that the protective element in hyperimmunc rabbit therapeutic antisera could be removed by absorption with purified type b capsular polysaccharide. Efforts to-date to prevent H. ir@rnxc type b disease by inducing type by antibodies with capsular polysaccharide vaccines can be summarized: the type b capsule can be prepared in non-toxic high molecular form with trace amounts of protein. nucleic acid und endotoxin contaminants (Smith CI al.. 1975: Parke C’I(I/.. 1977). Injection of these preparations into adults induced long-lived serum antibodies with bactericidal. opsonic and mouse-prbtective activity. In.jection of children of between 18 months and 5 years resulted in ;t serum antibody response which was protective but shortlived (Robbins tz/ r/l.. 1973: Smith PI ul.. 1975). Todate, disease efficacy has been established for children after the age of IX months injected with the purified capsular polysaccharide (Peltola et rrl., 1977~). However, current prcparatlons induce only a shortlived immunity in older infants and little or no
x45
proteclion in the lounger infants. those uith the highest attack rate (Parke ct ul., 1977: Smith rt rrl.. 1975). Based upon these studies as well ilS analyses ol individuals x-linked with hypogammaglobulinemia rccciving effective passive immunotherapy with pooled immunoglobulin it has been estimated that a protective serum anti-type b level ranges about 0.2 /cg,rnl (Robbins (‘/ ul., 1973). Thus. a protective effect of a polysaccharide vaccine can be predicted. Current programs involve the study of protein-polysaccharide complexes and the use ol cross-reacting organisms. Another method proposed for induction of serum antibodies has been deliberate colonization with E.sc/rc~ric~/~itrc,o/i K 100 strains containing a capsular polysaccharide antigenically and immunogenically related to H. iyflucnxe type b (Schnecrson & Robbins. 1975). The capsular polysaccharide is composed ofequlmolar amounts of ribosc. ribitol and phosphate. “C NMR studies shorn a different. though yet not completely characterized linkage (Branefors-Hclandcr CI ul.. 1976: Egan (‘I t/l.. 1978).
It ha5 been known for many years that home serotypes are found more often among E. co/i isolates from blood, CSF and urinary tract as compared to their frequency in stools of healthy individuals (Sjostedt. 1946: @rskov ct c/l.. 1971: Mabeck c’f u/.. 1970; Clrskov V/ rrl.. 1977~). Adircct correlation was made between the presence of acidic capsular polysaccharides (K antigens) and E. co/i strains isolated from extragastrointestinal sites such as the blood. urinary tract or CSF (C)rskov c’f(I/.. 1977u).Two invasive E. co/i diseases are prominent in humans and have been associated with capsular polvsaccharides. These are childhood urinary tract inyections and neonatal septicemia and meningitis. Capsular polysaccharide (K) antigens have been shown to exert an important role in determining the disease potential of E. co/i invasive for the renal parrnchyma as contrasted to those confined to the lower urinary tract (Mabeck c,tu/.. 1970: Hanson, 1973; Glynn cjtul.. 1977; Glynn & Howard, 1970; Kaijser 1’1 (I/.. 1977). Although there are 100 K antigens observed to date. E. c,o/i isolates from urinary tract infections of children and young adults are caused almost exclusively by tive K types. The E. co/i isolated from the renal parenchyma have K antigens of higher mol. wt and higher concentration per bacterial cell than those confined to the bladder and gastrointestinal tract (Kaijser, 1973; Glynn cutul.. 1977). Reinfection may be related to the finding that serum antibodies to the K capsular polysaccharide appear infrequently and in low levels following convalesence from urinary tract infection (Hanson, 1973). In contrast. antibodies to the CJ and H antigen appear in high concentration. It has been shown that antibodies to the K polysaccharide have a higher specific protective activity than antibodies to the 0 antigen (Kaijser o/ ul., 1972: Kaijser 6i Ahlstedt, 1977). Considering their frequency. reoccurrence and potential for permanent Injury, vaccines containing the most frequently encountered E. c,o/i K antigens should be studied for prevention of E. w/i urinary tract infections.
the cast‘ 01 neonatal
For
lcast X0”,, ofthe been shown (Robbinz K I
organisms
to possess
c’/ t/l..
the K
1074).
and
Group
study
01‘ neonatal
revealed
many
observed
in
meningitis
caused
I’catures
C/
Anticap>ular
concentration (I/..
of
2 highly
ausccptibilit~
crlticial
to
assay.
antibody susceptiblllty. unusual
that E.\c,/~ic,/fitr suggesting
Study
of
There
problem
aspect 01‘ K I capsular ,E. c,oli Kl
phenomenon ohserced
I’orm \ariatlon intensltles 011
antiserum properties
i\ due
to
;I
polqsaccharide the j~-acctyl dihtributcd
has
c,o/i K
:lgkll
and
by
The
indicate
that
the
new
antlgcnic
in
immunogenic
than
position
Bacterial
positi\c
the O-acctyl
is ;I major 1964:
nieninglti\ cuusc
Baker.
is
polysaccharides to Group
( I
antigens
to be directed
to type-specitic
GI-oup
H (Lancetirld
(‘I t/l..
III.
type\ ofhpccific All
disease.
antigens
1075).
Landy.
from
poor types
prognosis la
and
has been shown III.
Another
capsular
able to show preparation
conl‘erred
;I challenge
model
long-lived.
extracted in
has been within
are at least la. lb. II and with
clinical
to
disease. with
a
due to \.ariant.
loucr
from.
the
mouse
human
assay
vacclnc
shown
to
have
against
S.
/J~&SU
induce al..
incomplete
1974:
moiety
and
higher than
among
is
anti
.S.
an equivalent
more
active
antibodies
bactericidal
0 antibodies
whole
bacterIaI are highly
immunity
various
purified
acetone-inactivated Vi
C/ c/i.. 1970). the
This than
specific
protection. of their
Hornick
c’/
C./ic~urztlii
from
IO times
preparations.
1964). Typhoid
and the duration
antigens
1954: Hornick
is 20 times more active
bvhole.
Vi
and
mol. wt than the Vi preparation
01‘ the
Citrobactcr
Muschel.
extracted
in
fed S
has been re-
polqsaccharide (Landq.
preparation
bacterial-cell
were
by this
to primates
problem
protection
dosage
induced volunteers
.5‘. /.~pl~o.\n TY-2.
/~~/~/Io.scI Vi antigen
antibodies
to be largely
using Vi capsular
(I/.. 1970). 7he VI antigen
among
sepsis
this
they
was incomplete
this protection
a
also as E.
extracts.
to human
With extracted
38 (referred
antibodies
by newer methods
ofconslderably
preparation
53%
Rcccntlq.
l9S4;
In the late 1950s.
some protection
and
O-acetyl
01‘ Vi antigen.
bacterial
strum
that
/~pho.str. Howsever.
according
activities
f~~r~clii
with a capsular
associates isolated and compositlon. immuno-
polysaccharide
C‘i/~&c~/c~
from
(Kauflinan,
1956).
and
Isolates
:V-acetyl,
antigen)
C/ r/l..
c,o/i) by acid-treatment
cell-wall
onset
acid (Vi
Vi
and the
surfaces
in some hosts.
are encapsulated
Martln
fever, the
H. and
S. /~./~~zo.suis an
mucosal
01‘
effect
01‘ differentiation
and typhoid
components.
composed
genic and protectibc similar
N/..
antigens
An carlq clinical characteri~tlcs. characterircd by sevel-c overwhelming
1954:
in\estlgatcd
There
distribution
in\ariablq
FEXEH)
mice and humans
Landy. Webster and their characterlrcd the chemical
more
are caphules and all have been associated but ha\c ;I unique
in
fever. Part
to .5‘. /~~~/Io.Yu. 0.
bacterial
pol~palacturonic
on
(Eickhoffrt
dcsignatcd
in rcactivitc
typhoid
lack
carriage
between laboratory
prepared
models
to the
polysaccharide
s
protective
bc due
ma>
the blood
variant.
specific
in animal
this
This
B Streptococcus
shown Ibur
plasma
of non-immune
in preventing
been
i\ randomly
is
antibodies
stream
capsular
classitication
upon
(I 36). However.
antibodies.
( 1.1 I’HOID
the blood
or absence
ncgati\e
O(‘O(
Ciroup
B Streptococcus
in
to measure
the protective
enters
colonies
and
due to Group
based
Studies
regarding
B. A
poly%aharide
ofdisease111new horns 1977).
Streptococci
capsular
B type III
that penetrates
of the O-acetyl
determinants
I’ I{ s1 Hk:l~l
III
this serum
I \ i .\r\;l’l(;k.\
between asymptomatic
not (;Hot
with IgG
with human
organism
I antisera.
the
acid monomer
O-acctql
streptococcal
type
data).
entcric
on thcc‘7 and CU. Prcliminaryc.xperlments
confers
mothers
population
to be immunogenic
administered
is controbcrsy
lack of purilicd
differential
co/i K
change
an
01‘ halo
I
by the presence
ncuraminic
and
or by active Immunization
dill‘erences
which
~a/(I/.. 1977).
E.
of 01
Group
variation
single
\tructur;iI
moictie\.
01‘ O-acotyl
Ibrm
with some E.
conferred
ofant+Vi
I’or precention
can be detcctcd b) dil’l~rences
agplutinatlng
H
el‘l?ct 01‘ Group
.S II. \lO \&/.I. 1 ~~/‘t/O.Y
host
polyzaccharidc
K I (Ursko\
surrc)undlng
grown It
as
tI. co/i
in In
are in profrrys.
disease
haz revealed
and mcnlngococcu\
known
in the
mothers
disease
to
may pro\ ~dc ;I new ;ikenuc for research of both
8
There
problems
antibodies
ol‘ this
ncwjborns
ih insufficient
technical
K I
B
Group
(unpublished
wjhether passively
co/i
that
determinant
unreholccd
adults
to be absent
without
has been shown
& by
er LI/., 19770).
colonited
mothers
Puritied
the protective
in
of
type III (Baker
measured
B type III
babies
almost
to becapsular
An at risk
for Group
born
due
type-specific
01‘ newborns
B streptococci.
polysaccharlde
capsular Group
Z&30”,,
antibodies.
;I\
disease (Baker
identifying
organism,
\el-otypcs I’ound in the
common
surveys.
is B
component
have been shown
who contracted
young
main
septicemia,
including
Antibodies.
has been defined
by repeated effect
acid as their
by
Group
type antigens
19761~).
disease
1975).
The
ha\e been shown
All
Group
with
prognosis
Ill.
of disease
late onset birth)
rat model (Robbinz
(Sarl‘l‘ c’r explain the development of age-related immune response to capsular polysaccharide vaccine by postulating an increasing reservoir of differentiated B cells induced by crossreacting bacteria. Serum antibodies are only one component of host resistance. Their importance is illustrated by the remarkable susceptibility to repeated and severe disease with encapsulated bacteria suffered by patients with x-linked hypogammaglobulinemia (Rosen bz Janeway, 1964). C‘omplemcnt component deficiencies, defective splenic function and as yet unknown host genetic factors predispose to encapsulated bacterial diseases (Alper rt ol.. lY70: Whisnant ct (I/., 1975; Pearson. 1977; Johnston (‘1 trl.. 1978).
There is an increasing interest in prevention of human diseases due to encapsulated bacteria. The virulence of encapsulated bacteria is related to their capsular polysaccharides. This virulence is most probably mediated by their anti-phagocytic effect. Other bacterial surface components, such as outer membrane proteins of Group B and other meningococcal groups. may be related to virulence but the mechanism of this relation has not yet been characterized. Anti-capsular antibodies mediate immunity by activation of complement. Evidence indicates that IgM and IgG antibodies are protective moieties. Information from animal models, and from unusual disease susceptibility states in humans.
Vaccines
Against
Encapsulated
indicate that in the spleen, genetic control of immunoglobulin synthesis and the complement system are required for effective resistance. Capsular polysaccharides may be prepared in highly purified form with no serious reactogenicity. Most capsular polysaccharides are immunogenic and have been effective in preventing serious diseases due to their homologous organism in individuals older than 2 years. Theoretically, it should be possible to prepare a multivalent capsular polysaccharide vaccine for all common species,
invasive
organisms.
For pathogenic
bacterial
such as pneumococci with many capsular types, immunization has not resulted in emergence of other capsular types as pathogens. A preventative immunization program with our existing vaccines cannot yet achieve the goal of elimination of all encapsulated bacterial disease because most capsular polysaccharide vaccines studied to-date do not induce effective disease prevention in infants and young children. Methods to increase the immunogenicity of our current vaccines and to develop immunigens against meningococcal Group B and E. coli Kl are needed. The mechanism by which only some of the many bacterial capsular polysaccharides confer invasiveness is not known. Some evidence indicates that both the chemical (composition) and physical (mol. wt) properties may be important variables related to virulence. Further understanding of these characteristics might provide opportunities to supersede polysaccharide-specific immunity. Incorporation of a new vaccine into current public health programs requires continued surveillance by Public Health agencies to insure its effectiveness as well as to prepare for any unpredicted adventitious reactions. Surveillance for these bacterial diseases requires serological reagents and trained personnel. It is worthwhile to mention problem of pneumococcal type identification. Other causes of vaccine failures may be due to genetic or acquired deficiencies in host resistance. The study of pneumococcal and later other capsular polysaccharides lead to the discovery of immune tolerance. DNA as the transforming principle and hence the genetic information, identification of gamma globulins as antibodies and their molecular heterogeneity. quantitative methods for the measurement 01 antibodies and complement, virulence mechanisms of human pathogens and important probes for immunologic studies. There is every hope that studies of these interesting molecules, although appearing ‘applied’ will continue to reveal important ‘basic’ scientific information. REFERENCES
Alexander H. E.. Heidelberger M. & Leidy G. (1944) The protective or cur;Ltive element in type b H. infl~rr~ac~ rabbit serum. y~lc J. Biol. Med. 16, 425-438. Alper C. A.. Abramson N., Johnston R. B. Jr.. Jandl J. H. & Rosen F S. (1970) Increased susceptibility to Infection associated with abnormalittes of complement-functions and of the third component of complement (C3). ,v,srzs LXXXIX, 184-194. Austrian R. &Gold J. (1964) Pneumococcal hacteremia with especial reference to bacteremlc pneumococcal pneumonia. Ann. inrern. Mrd 60, 759-776. Avery 0. T.. Heidelberger M. & Goebal W. F. (lY75) The soluble specific substance of Friedlander‘s bacillus. Paper II. Chemical and immunological relationship\ ol pneumococcus type II and of a strain of Friedlander’s bacillus. J. e.x-p Med. 42, 709-725. Baird D. R.. Whittle H. C. & Greenwood B. M. (1976) Mortality from pneumococcal meningitis. Ltrnc,er II, 1344-1346. Baker C. J. (1977) Summary of the workshop on perinatal infections due to group B Srr~,~~roc,oc,c,u.\.J mfwr. Di.c 136, 137. Baker C. J. & Kasper D. L. (1976~) Microcapsule of type III strams of Group B .xrrrptococ~c~\: production and morphology. Infwr. Immun. 13, I X9-lY4. Baker C. J. & Kasper D. L. (1976h) Identification of slalic acid in polysaccharide antigens of Group B .sIT(‘~,I)Io(‘o(‘L’II.,. fnfecr. Immm. 13, 284-288. Baker C. J.. Kasper D. L.. Tager 1. B., Paredcs A.. Alpert S.. McCormack W. M & Goroff D. (1977~) Ouantitntlve determination of antlhody to capsular polqs&haride in infection with Type III strains Group B S/r.c,~/~,~.oc,c.lc\.J. clirr. Inw.s/ 59, 8 l&8 18.
850
JOHN
B. ROBBINS
Baker P. J.. Morse H. C., Gross S. C.. Sta\hak I’. W. & Studies on the mechanlw of the Immunologvxl paralysis I’l-c~cotl B. ( I Y77h) Maturation 01. regulator) factor\ induced in mice by pncumococcal polyaaccharidea. J. ~nllurnc~ng magnitude of antibody response to capa~la~ Itttmrr,~. 74, 17-26. polysaccharide of type I I I .Tt,.c,ptoc.oc,c,rr.v /~rt~~/rr,torrirtc,. .I I-inland M. (1973) Excursionr Into epidemiology, wlected irzfcc,t.Di.v.136, S23. studies during the past four decades at Boston c‘itj Baltimore R. S., Kaaper D. L.. Baker C. J. Xc Goroff D. K. Hospital. J i/r/w~. ni.\ 128, 76-l 24. (1977) Antigcnic specificity of opsonophagocytlc Finland M. & Barnes M. W. (1977) Changes in occurrrncc of antlboda in rabblt antIsera to group B streptococci. J cnpsular serotqpcs of Strcptocouuspw~v~~~~~t~icrc~ at Boston /t?v?lUn. 118, 673-67X. City Hospital during selected years between I935 and 1974. Borgono J. M.. McLean A. A.. Vella P. P.. Woodhour A. I-.. J. c,/in. .4limhio/. 5, 154-l 66. Canepa 1.. Da\td\on W. L. & Hlllcman M. R. (197X) Fintand M. & Shuman H. L. (lY42) The type-specific Vaccination and revaccination with pol~ralcnt agglutinln response of children uith pneumococcal pneumococcal polysaccharide vaccine? in adults and pneumoniah. J. fmtttwt. 45, 2 15-242 infants. Proc,. Sot, cx,j. Biol. :Mrt/. 157, 14X-I 54. Francis T. (1934) Antigenic action of the hpecitic BQvre K., Holtrn E.. Vik-Mo H.. Brondbo A.. Bratlid D.. polqsaccharidr of pncumococcus Type I In man. Pwc Bjark P. & Moe P. J. ( 1977) &‘rv.c.w~o rmwirt,qit~t/i,~ SM C’Yp Bid Med. 31, 493-495 infectIons in northern Norway: an epidemic in 1976lY75 I.rancis T Jr. & Tillctt W. S. (1930) C‘utancous reaction\ in due mainly to Group B organlm\. J IU/saccharidcs. Frasch C’. E., Parka I... McNcilis R. M. & Gotschhch E. C. .w?t/. J 4 MS/I, 4Y-51. ( 1976) Protection against Group B mrningococcal disease. Dowling H. I-. (1973) The rise and I’all of pneumonia-control I. C‘omparlson of group-specific and type-specific programs. J. infwt Di.c 127, 201-206. protection in the chick embryo model. .f. KY/>.Mcri. 144. Egan W.. I_lu T.-Y.. Dorrow D., Cohen J. S., Robbins J. D.. 3 I Y-32’). Gotschlich E. c’. & Robbins J. B. (1977) Structural studies Frasch C. E. & Robbins J. D. ( 1978) ProtectIon against group on the slalic acid polymer antigen of ~.s~~/wrrc~hrtrw/i strain B meningococcal disease III Immunogenicity ofserotype BOS-I 2. Bioc~/rcwi\rr~~ 16, 3687-3697. 2 vaccines and speaticitl of protection 1n a guinea pig Egan W. M.. Tsui F. P.. Liu T.-Y.. Schneerson R. (lY78) model. J. c\f’. ,Mcc/. 147, 62%644. Structural studies of the KIOO capsular polysaccharide Glode M. P.. Robbins B., Liu T.-I’., Gotschlich E. C.. Orskoc I. 8: Orsko\ F. (1977) C‘ro\s-antigenicity and antigen of E~ch~ri~~hiu w/i. Submitted for publication. immunogcniaty between capsular polysaccharides of Exkhoff T. C.. Klein J. O., Daly A. K.. Ingall D. & Finland M. 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