Disparity in Functional Activity between Serum Anticapsular Antibodies Induced in Adults by Immunization with an Investigational Group A and C Neisseria meningitidis-Diphtheria Toxoid Conjugate Vaccine and by a Polysaccharide Vaccine
Disparity in Functional Activity between
Serum Anticapsular Antibodies Induced in Adults by Immunization with an
Investigational Group A and C Neisseria meningitidis-Diphtheria Toxoid
Conjugate Vaccine and by a Polysaccharide Vaccine
Shannon L. Harris,1 Adam Finn,2 and Dan M.
Granoff1*
Children's Hospital, Oakland Research Institute, Oakland, California 94069,1
Institute of Child Health, Bristol, United Kingdom2
Received 23 December 2002/ Returned for modification 19 February 2003/
Accepted 11 March 2003
Polysaccharide-protein conjugate vaccines elicit higher
concentrationsof serum anticapsular antibody in infants and children
thando unconjugated polysaccharide vaccines. The conjugate-inducedantibodies also have higher avidity and complement-mediated
bactericidal activity. Similar vaccine-related differences inthe
magnitude or functional activity of antibody are observed
infrequently in immunized adults. We compared the antibody responses
of adults immunized with an investigational group A and C meningococcalconjugate vaccine to those elicited by an unconjugated meningococcalpolysaccharide vaccine. Although there were no significant differencesbetween the respective geometric mean bactericidal titers of
the two vaccine groups, it took, on average, three- to fourfold
higher concentrations of polysaccharide-induced serum anticapsular
antibody to achieve 50% complement-mediated bacteriolysis than
conjugate-induced antibody (P < 0.001 for groups A and C).At
limiting doses, the polysaccharide-induced anticapsular antibodies
also were less effective in conferring passive protection against
meningococcal bacteremia in infant rats challenged with a groupC
strain (P < 0.04). The avidity index of the group C antibodies
was higher in the conjugate vaccine group than in the polysaccharide
vaccine group (P < 0.005). The disparities in the functional
activity of the anticapsular antibodies elicited in adults bythe two
vaccines imply fundamental differences in the respectiveB-cell
populations stimulated.
* Corresponding author. Mailing address: 5700 Martin Luther
King, Jr. Way, Oakland, CA 94609. Phone: (510) 450-7640. Fax: (510) 450-7915.
E-mail: dgranoff@chori.org.
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