Murine Immune Response toNeisseria meningitidisGroup C Capsular Polysaccharide: Analysis of Monoclonal Antibodies Generated in Response to a Thymus-Independent Antigen and a Thymus-Dependent Toxoid Conjugate Vaccine

Abstract

Antibody (Ab) responses to polysaccharides (PSs) such as Neisseria meningitidis group C PS (MCPS) are characterized as being thymus independent (TI) and are restricted with regard to clonotype and isotype expression. PS conjugated to proteins, e.g., MCPS coupled to tetanus toxoid (MCPS-TT), elicits a thymusdependent (TD) response. In order to understand the influence of the form of a vaccine (TI versus TD) on the Ab repertoire, we generated monoclonal antibody (MAb) panels from mice immunized and boosted with MCPS or MCPS-TT in different ways. The panels of MAbs were examined for isotype, fine specificity, affinity, and V H gene family usage. The use of MCPS-TT resulted in a shift in the isotype from immunoglobulin M (IgM) and IgG3 elicited in response to the MCPS to primarily IgG1. This isotype shift was accompanied by a change in the fine specificity of the response to the conjugate compared to that of PS. New fine specificities and increased affinity were observed in response to the TD antigen (Ag). Dot blot and Northern analyses of MCPS MAbs revealed that V H gene family usage is dominated by V H J558, used by 23 of 39 MAbs. V H 3609 was seen in three MAbs of restricted fine specificity. V H Q52, V H 7183, and V H VGAM3-8 were seen in more than one MAb across these panels, while V H 10 and V H X24 were detected only once in response to the TI-2 Ag. All MAbs in the panels utilized kappa light chains, and all functional J genes were expressed.The capsular polysaccharide (PS) constitutes the major virulence factor of many pathogenic bacteria that cause invasive diseases. Antibodies (Abs) against these PSs are protective (27,28). PSs are classified as thymus-independent-2 (TI-2) antigens (Ags) because they do not require mature T cells to elicit a humoral response in vivo. These PS Ags are immunogenic in adults but are only poorly or nonimmunogenic in infants and young children who are highly susceptible to infection caused by encapsulated bacteria (28,31,44,65).The response to capsular PS is markedly different from the response to most protein Ags (thymus-dependent [TD] Ags). The Ab response to TI-2 Ag develops late in ontogeny (25,44,50) and in mice utilizes a particular late-developing subset of B cells that is defined by the expression of Lyb5 and other cell markers (39, 60). TI Ags also generally fail to elicit a memory response or show affinity maturation. In contrast, the ability to respond to a TD Ag is present at birth and results in the formation of memory cells, and the Ab response undergoes subsequent affinity maturation upon reimmunization (61). For TI Ag, immunoglobulin G3 (IgG3) and IgM are the major isotypes expressed in mice, even after secondary immunization (45), whereas for TD Ag, the ratio of IgG to IgM increases after secondary immunization, with IgG1 being the major subclass (52,59,60).The majority of the anti-PS responses are oligoclonal and encoded by a few variable regions of the heavy chain (V H ) gene families (10). The anti-␣(133) dextran Ab, for example, expresses mainly the V H J55...

A Peptide Mimotope of Type 8 Pneumococcal Capsular Polysaccharide Induces a Protective Immune Response in Mice

“…A PROTECTIVE MIMOTOPE OF TYPE 8 PNEUMOCOCCUS 331 the present study, the IgG subclass response resembled that observed for some PS-protein conjugates (18,31,42). Similar to the response to a GXM mimotope (16) and polysaccharide on the surface of whole pneumococci (51), the PUB1-TTinduced type 8 PS response was also characterized by the appearance of IgG early in the response and a lack of significant boosting.…”

Age-Related Disparity in Functional Activities of Human Group C Serum Anticapsular Antibodies Elicited by Meningococcal Polysaccharide Vaccine

“…1. Positive controls in the assay include two murine monoclonal antibodies (MAbs), MAbs 706 and 735, with known preferential binding to OAc-negative or OAc-positive polysaccharide, respectively (14). (Antibodies were kindly provided by K. Stein, U.S. Food and Drug Administration, Bethesda, Md.…”

Pneumococcal Capsular Polysaccharide Vaccine-Mediated Protection against Serotype 3Streptococcus pneumoniaein Immunodeficient Mice

“…In contrast, the response to PPS when conjugated to a protein carrier is dominated by IgG1 in mice and humans (45,50,63,80), and this is considered representative of a T-cell-dependent (TD) response. Although the T-cell response to PPS-based conjugate vaccines has been shown to have TD features, the response can also have characteristics of a TI or an "incomplete" TD response (3,30,38,49,76). The antibody response of Wt mice to PPS3 in our study was consistent with a TD response, with IgG1 as the predominant IgG subclass.…”