Immunologic memory response induced by a meningococcal serogroup C conjugate vaccine using the P64k recombinant protein as carrier.
ABSTRACT In this study, we used an adoptive lymphocyte transfer experiment to evaluate the ability of the P64k recombinant protein to recruit T-helper activity and induce immunologic memory response to the polysaccharide moiety in a meningococcal serogroup C conjugate vaccine. Adoptive transfer of splenocytes from mice immunized with the glycoconjugate conferred antipolysaccharide immunologic memory to naive recipient mice. The observed anamnestic immune response was characterized by more rapid kinetics, isotype switching from IgM to IgG and higher antipolysaccharide antibody titers compared with those reached in groups transferred with splenocytes from plain polysaccharide or phosphate-immunized mice. The memory response generated was also long lasting. Sera from mice transferred with cells from conjugate-immunized mice were the only protective in the infant rat passive protection assay, and also showed higher bactericidal titers. We demonstrated that priming the mice immune system with the glycoconjugate using the P64k protein as carrier induced a memory response to the polysaccharide, promoting a switch of the T-cell-independent response to a T-cell dependent one.
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ABSTRACT: A carrier effect is obtained typically when a hapten-protein conjugate is injected into an animal which has previously been primed with the same hapten conjugated to another carrier protein. Under these circumstances the anti-hapten secondary response is usually less than that which would have been obtained had the animal been injected with a conjugate prepared with the same carrier as that originally used for priming. Attempts have been made to account for the phenomenon in terms of the local environment hypothesis, which assumes that the receptor on immunologically competent cells recognises the hapten jointly with the area on the complete antigen which surrounds it. Alternatively the phenomenon can be accounted for by the hypothesis of cooperation, which assumes that the antigen is recognised by two receptors, one directed to the hapten and the other to a determinant on the carrier protein.Methods are described which enable carrier effects to be studied quantitatively in mice. They involve a cell transfer system in which cell suspensions prepared from large numbers of donors are distributed among irradiated syngeneic recipients. In these recipients the transferred cells can be made to perform a secondary response by appropriate antigenic stimulation. The response is monitored by binding tests in which the capacity of serum to bind highly radioactive haptens or proteins is measured. The haptens employed in this system are NIP (4-hydroxy-5-iodo-3-nitro-phenacetyl-) and DNP (2,4-dinitrophenyl-) and the proteins comprise chicken γ-globulin, bovine serum albumin, human serum albumin, ovalbumin, bovine γ-globulin, keyhole limpet hemocyanin and mouse γ-globulin.A carrier effect was regularly obtained when the proteins were tested against one another as carriers, for priming and for the secondary response. The effect could best be measured by comparing the relative potencies in the secondary response of the homologous conjugate (i. e. one with the carrier which had originally been used for priming) with heterologous conjugates (i. e. ones with new carriers). In this way the intrinsic potency of the individual protein could also be measured and allowance made for it in calculating the magnitude of the carrier effect. An average carrier effect of one thousand-fold relative potency was obtained. Priming by NIP-ovalbumin or NIP-chicken γ-globulin with secondary stimulation by NIP-bovine serum albumin (or the corresponding DNP conjugates) could be identified as the combination best suited to further study.Support for the cooperation hypothesis, particularly for that version of the hypothesis which postulates that recognition of carrier determinants allows an antigen-concentrating mechanism to operate, could be found in the parallel slopes of the dose-response curves obtained with homologous and heterologous conjugates. On the other hand the local environment hypothesis failed to pass either of the tests to which it was subjected. One, the weaker, was to compare haptens with and without spacer groups inserted between themselves and the carrier protein, in the expectation that spacers might reduce the local environment contribution: no difference could in fact be detected. The other, the stronger, was to attempt to inhibit the response with an excess of carrier protein even though the anti-hapten antibody had no detectable affinity for the carrier: such inhibition could regularly be obtained.European Journal of Immunology 02/1971; 1(1):10-7. · 4.97 Impact Factor
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ABSTRACT: The safety, immunogenicity, and immunologic priming of 2 dosages (2 microgram or 10 microgram) of a meningococcal C oligosaccharide-CRM197 conjugate vaccine was evaluated in 114 infants vaccinated at ages 2, 3, and 4 months. Antibody persistence and response to boosting with 10 microgram of meningococcal C polysaccharide were assessed. The meningococcal conjugate vaccine produced fewer local reactions than concurrent routine immunizations. Total serogroup C-specific immunoglobulin geometric mean concentration (GMC) increased from 0.3 microgram/mL before vaccination to 13.1 microgram/mL at age 5 months. Serum bactericidal antibody (SBA) geometric mean titers (GMTs) rose from <1:4 to 1:1057 at 5 months and fell by 14 months to 1:19. Following boosting, anti-C-specific immunoglobulin GMC rose to 15.9 microgram/mL and SBA GMT to 1:495. Antibody responses in the 10-microgram dose cohort were significantly higher at 5 months (P<.01) than in the 2-microgram dose cohort but were lower after polysaccharide boosting (P=.02). This meningococcal conjugate vaccine was well tolerated and immunogenic and induced immunologic memory in infants.The Journal of Infectious Diseases 06/1999; 179(6):1569-72. · 5.85 Impact Factor
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ABSTRACT: The chemical conjugation of bacterial polysaccharide to carrier proteins has proved to be an efficient tool to improve the immunological response against these bacterial antigens. In this study, we characterized the antibody response generated in a non-human primate model against the meningococcal capsular polysaccharide serogroup C (CCPS) conjugated to the P64k protein. Similar to licensed vaccines the CCPS conjugate is able to generate a good memory immune response with antibody titers threefold higher than the free CCPS. Three different ELISA protocols were used to measure the antibody response and the importance of the coating antigen was demonstrated. The ELISA using the derivatized CCPS showed the best results and had a high correlation with the bactericidal activity. The antibodies elicited showed a high protective capacity when assayed in the infant rat protection model.FEMS Immunology & Medical Microbiology 03/2005; 43(2):133-40. · 2.68 Impact Factor