Recurrent Variable Region Gene Usage and Somatic Mutation in the Human Antibody Response to the Capsular Polysaccharide ofStreptococcus pneumoniaeType 23F

Abstract

Combinatorial cloning and expression library analysis were used to isolate human antibody Fab fragments specific for the capsular polysaccharide of Streptococcus pneumoniae serotype 23F. Thirty 23F-specific Fabs were isolated from seven vaccinated donors, and the sequences of the heavy (H)-and light (L)-chain variable regions were determined. All individuals utilized either the V A23 L chain, the V L6 L chain, or both chains in forming the 23F-specific combining site. V A23 L chains paired primarily with VH3-23 H chains. V L6 L chains were more promiscuous in heavy-chain usage between individuals. Both H and L chains were mutated, primarily in the complementarity-determining regions, compared to their closest germ line counterpart, suggesting a recall response that has undergone affinity maturation. H-chain isotypes were reflective of those found in the serum. Shared somatic modifications demonstrated that immunoglobulin G2 (IgG2) and IgA antibodies arose from the same somatically matured B cell. Our results indicate that the response to the serotype 23F pneumococcal capsular polysaccharide is oligoclonal within the individual, with one or two paratope families accounting for the majority of expressed antibody. We also determined that, in spite of the combinatorial diversity available to the immune system, the 23F-specific response is highly restricted at the population level, with the same two L-chain-determined paratope families recurring in all individuals. Lastly, analysis of the isolated Fabs indicate all have undergone extensive somatic mutation, as well as class switch, maturational events that presumably require the participation of T cells.Streptococcus pneumoniae is a significant human pathogen causing pneumonia, bacteremia, meningitis, and otitis media. The pathogenic pneumococci are surrounded by a complex capsule composed of polymeric sugars, C polysaccharide, peptidoglycan, and surface proteins. The pneumococcal capsular polysaccharides (PPS), are heterogeneous in structure, with at least 90 different serotypes occurring within the species S. pneumoniae. PPS epitopes are immunogenic in adults and elicit antibodies that protect against infection. A vaccine containing capsular polysaccharides from 23 pneumococcal serotypes (23-valent) is available and is currently recommended for persons over 65 years of age and for other adults considered to be at increased risk of developing pneumococcal disease. Purified capsular polysaccharides do not, however, induce a protective antibody response in infants, who comprise one of the primary populations at risk. Consequently, a 7-valent polysaccharide-protein conjugate vaccine has been developed and shown to be efficacious in infants and has recently been licensed for use in this age group. Capsular polysaccharides are defined as TI-2 (T-cell-independent) antigens based on their repetitive structure and lack of immunogenicity in xid mice and human infants. The serum response to these polysaccharides in adults is oligoclonal and restricted in isotype, with immunog...

The human antibody repertoire specific for rabies virus glycoprotein as selected from immune libraries

“…2-7). While previous observations also suggest that VH-VL pairings in antibodies obtained by combinatorial cloning are extremely similar to those observed in the corresponding naturally occurring antibodies [22,23], procedures such as 'chain-shuffling' can be used to identify optimal light-chain partners [24]. Comparison of our antibody panel to clones CRJA and CR57 that were isolated using conventional B cell immortalization, however, shows that antibodies within our panel have affinities that are comparable (Fig.…”

Recognition of Human Cytomegalovirus by Human Primary Immunoglobulins Identifies an Innate Foundation to an Adaptive Immune Response

“…There is evidence that other pathogens, in addition to HCMV, have exerted selective pressure to maintain the IGHV3-30 and IGKV3-11 gene elements. Thus, the IGHV3-30 gene is also used frequently to encode Abs that bind to the carbohydrates of Streptococcus pneumoniae type 23F (11). Indeed, there is evidence that human Abs to type 23F pneumococcal polysaccharide are frequently derived from unmutated, primary Igs that are very closely related to those we have shown bind gB/AD-2S1 and that, like them, utilize IGHV3-30, IGHJ4*02, and IGKV3-11, as well as, in some instances, IGKJ1*01 (11).…”

“…Thus, the IGHV3-30 gene is also used frequently to encode Abs that bind to the carbohydrates of Streptococcus pneumoniae type 23F (11). Indeed, there is evidence that human Abs to type 23F pneumococcal polysaccharide are frequently derived from unmutated, primary Igs that are very closely related to those we have shown bind gB/AD-2S1 and that, like them, utilize IGHV3-30, IGHJ4*02, and IGKV3-11, as well as, in some instances, IGKJ1*01 (11). The only differences between these unmutated, primary Igs and the gH(M):gL(J1) Ig we described in this study would be those encoded by the differences in the D H segments and N nucleotide additions.…”

Biology and Treatment of Chronic Lymphocytic Leukemia

“…[71][72][73] Second, susceptibility to autoreactivity and autoimmunity is frequently linked within families, which would be consistent with the apparent propensity of family members of B-CLL patients to develop clonal amplifications. 47,48 Third, the structures of the B-CLL BCRs in certain instances are very reminiscent of antibodies that react with capsular polysaccharides of microorganisms, 8,74,75 e.g., Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitides. Fourth, immune cross-reactivity between polysaccharide/carbohydrate antigens and autoantigens is not infrequent 76 and anti-polysaccharide antibodies can be converted into autoantibodies (anti-dsDNA) by very minimal (1 amino acid) change in the Ig V region structure.…”