Immunoglobulin light chain variable region gene sequences for human antibodies to Haemophilus influenzae type b capsular polysaccharide are dominated by a limited number of V kappa and V lambda segments and VJ combinations

Light chain skewing in autoantibodies and B-cell receptors of the citrullinated antigen-binding B-cell response in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 1% of the world population. RA is associated with the presence of autoantibodies, of which anti-citrullinated protein antibodies (ACPA) are most prominent. ACPA are produced by citrullinated antigen-binding B cells that have presumably survived tolerance checkpoints. So far, it is unclear how and when such autoreactive B cells emerge. Light chain (LC) rearrangement and mutation rates can be informative with regard to selection steps during B-cell development. Therefore, we studied LC characteristics of ACPA-expressing B cells and secreted ACPA with the aim to better understand the development of this disease-specific, autoreactive B-cell response. Paired ACPA-IgG and ACPA-depleted IgG were isolated from serum (n = 87) and synovial fluid (SF, n = 21) of patients with established RA. We determined the LC composition for each fraction by ELISA using kappa(Igκ)- and lambda(Igλ) LC-specific antibodies. Cellular LC expression was determined using flow cytometry. In addition, we used a B-cell receptor (BCR)-specific PCR to obtain LC variable region sequences of citrullinated antigen- and tetanus toxoid (TT)-binding B cells. In serum, we observed an increased frequency of lambda LC in ACPA-IgG (1.64:1) compared to control IgG (2.03:1) and to the κ/λ ratio reported for healthy individuals (2:1). A similar trend towards higher frequencies of lambda LCs was observed for ACPA-IgG in SF (1.84:1). Additionally, the percentage of Igλ-expressing B cells was higher for citrullinated antigen-binding B cells (51%) compared to TT-specific (43%) and total CD19+CD20+ B cells (36%). Moreover, an increased Igλ percentage was observed in BCR-sequences derived from ACPA-expressing (49%) compared to TT-specific B cells (34%). Taken together, we report an enhanced frequency of lambda LCs in the secreted ACPA-IgG repertoire and, on the cellular level, in BCR sequences of ACPA-expressing B cells compared to control. This skewing in the autoreactive B-cell repertoire could reflect a process of active selection.

VDJ gene usage among B-cell receptors in ABO-incompatible kidney transplantation determined by RNA-seq Transcriptomic analysis

BACKGROUND

Studies on B-cell subtypes and V(D)J gene usage of B-cell receptors in kidney transplants are scarce. This study aimed to investigate V(D)J gene segment usage in ABO-incompatible (ABOi) kidney transplant (KT) patients compared to that in ABO-compatible (ABOc) KT patients.

METHODS

We selected 16 ABOi KT patients with accommodation (ABOiA), 6 ABOc stable KT patients (ABOcS), and 6 ABOi KT patients with biopsy-proven acute antibody-mediated rejection (ABOiR) at day 10, whose graft tissue samples had been stored in the biorepository between 2010 and 2014. Complete transcriptomes of graft tissues were sequenced and analyzed through RNA sequencing (RNA-seq). The international ImMunoGeneTics information system (IMGT®) was used for in-depth comparison of V(D)J gene segment usage.

RESULTS

The mean age of the 28 KT recipients was 43.3 ± 12.8 years, and 53.6% were male. By family, IGHV3, IGHJ4, IGLV2, and IGLJ3 gene segments were most frequently used in all groups, and their usage was not statistically different among the three patient groups. While IGKV3 was most frequently used in both the ABOiA and ABOiR groups, IGKV1 was most commonly used in the ABOcS group. In addition, while IGKJ1 was most commonly used in the ABOiA and ABOcS groups, IGKJ4 was most frequently used in the ABOiR group. According to individual gene segments, IGHV4-34 and IGHV4-30-2 were more commonly used in the ABOiR group than in the ABOiA group, and IGHV6-1 was more commonly used in the ABOcS group than in the ABOiR group. IGLV7-43 was more commonly used in the ABOcS group than in the ABOi group. However, technical variability, small sample size, and potential confounding effects of Rituximab or HLA mismatching are limitations of our study.

CONCLUSIONS

Our findings suggest that RNA-seq transcriptomic analyses can provide information on the V(D)J gene usage of B-cell receptors and the mechanisms of accommodation and immune reaction in ABOi KT.

Antigen nature and complexity influence human antibody light chain usage and specificity

Human antibodies consist of a heavy chain and one of two possible light chains, kappa (κ) or lambda (λ). Here we tested how these two possible light chains influence the overall antibody response to polysaccharide and protein antigens by measuring light chain usage in human monoclonal antibodies from antibody secreting cells obtained following vaccination with Pneumovax23. Remarkably, we found that individuals displayed restricted light chain usage to certain serotypes and that lambda antibodies have different specificities and modes of cross-reactivity than kappa antibodies. Thus, at both the monoclonal (7 kappa, no lambda) and serum levels (145μg/mL kappa, 2.82μg/mL lambda), antibodies to cell wall polysaccharide were nearly always kappa. The pneumococcal reference serum 007sp was analyzed for light chain usage to 12 pneumococcal serotypes for which it is well characterized. Similar to results at the monoclonal level, certain serotypes tended to favor one of the light chains (14 and 19A, lambda; 6A and 23F, kappa). We also explored differences in light chain usage at the serum level to a variety of antigens. We examined serum antibodies to diphtheria toxin mutant CRM197 and Epstein-Barr virus protein EBNA-1. These responses tended to be kappa dominant (average kappa-to-lambda ratios of 4.52 and 9.72 respectively). Responses to the influenza vaccine were more balanced with kappa-to-lambda ratio averages having slight strain variations: seasonal H1N1, 1.1; H3N2, 0.96; B, 0.91. We conclude that antigens with limited epitopes tend to produce antibodies with restricted light chain usage and that in most individuals, antibodies with lambda light chains have specificities different and complementary to kappa-containing antibodies.

High-resolution description of antibody heavy-chain repertoires in humans

Antibodies' protective, pathological, and therapeutic properties result from their considerable diversity. This diversity is almost limitless in potential, but actual diversity is still poorly understood. Here we use deep sequencing to characterize the diversity of the heavy-chain CDR3 region, the most important contributor to antibody binding specificity, and the constituent V, D, and J segments that comprise it. We find that, during the stepwise D-J and then V-DJ recombination events, the choice of D and J segments exert some bias on each other; however, we find the choice of the V segment is essentially independent of both. V, D, and J segments are utilized with different frequencies, resulting in a highly skewed representation of VDJ combinations in the repertoire. Nevertheless, the pattern of segment usage was almost identical between two different individuals. The pattern of V, D, and J segment usage and recombination was insufficient to explain overlap that was observed between the two individuals' CDR3 repertoires. Finally, we find that while there are a near-infinite number of heavy-chain CDR3s in principle, there are about 3–9 million in the blood of an adult human being.

[Transgenesis and humanization of murine antibodies]

The properties of monoclonal antibodies explain why they are such a successful class of therapeutic molecules. However, pionneered initial antibodies were of murine origin and triggered an immune response which limited the therapeutic potential of the antibody and generated deleterious effects. Consequently, tremendous efforts have been developped to engineer these murine Ig by introducing human sequences in vitro, or in vivo by humanization of murine antibodies, leading to chimeric immunoglobulins, and more recently generation of fully human antibodies in transgenic mice with a more or less diversified V repertoire. These approaches have led to the development of an increasing number of these chimeric or humanized monoclonal antibodies entering pharmaceutical pipelines.

Human antibodies from transgenic animals

Laboratory mice provide a ready source of diverse, high-affinity and high-specificity monoclonal antibodies (mAbs). However, development of rodent antibodies as therapeutic agents has been impaired by the inherent immunogenicity of these molecules. One technology that has been explored to generate low immunogenicity mAbs for in vivo therapy involves the use of transgenic mice expressing repertoires of human antibody gene sequences. This technology has now been exploited by over a dozen different pharmaceutical and biotechnology companies toward developing new therapeutic mAbs, and currently at least 33 different drugs in clinical testing--including several in pivotal trials--contain variable regions encoded by human sequences from transgenic mice. The emerging data from these trials provide an early glimpse of the safety and efficacy issues for these molecules. Nevertheless, actual product approval, the biggest challenge so far, is required to fully validate this technology as a drug discovery tool. In the future, it may be possible to extend this technology beyond rodents and use transgenic farm animals to directly generate and produce human sequence polyclonal sera.

Molecular analysis of monoclonal antibodies to group variant capsular polysaccharide of Neisseria meningitidis: recurrent heavy chains and alternative light chain partners

We determined the molecular sequence of monoclonal antibodies (mAbs) to serogroups B and C capsular polysaccharides (PS) of Neisseria meningitidis. N. meningitidis infections are a leading cause of bacterial septicemia and meningitis in humans. Antibodies to PS are fundamental to host defense and diagnostics. The polysaccharide capsule of group B N. meningitidis is poorly immunogenic and thus is an important model for studying pathogen-host co-evolution through understanding the molecular basis of the host immune response. We used a modified reverse-transcriptase PCR to amplify and sequence the V-genes of murine hybridomas produced against types B and C capsular PS. Databank analysis of the sequences encoding the V-genes of type C capsular PS mAb, 4-2-C, reveal that heavy chain alleles are recurrently used to encode this specificity in mice. Interestingly, a V-gene from the same germline family also encodes the V-domain of mAbs 2-2-B, which targets the antigenically distinct serogroup B capsular PS. Somatic mutation, junctional diversity and alternative light chains collectively impart the specificity for these serologically distinct epitopes. Knowledge of the specific immunoglobulin genes used to target common bacterial virulence factors may lead to insights on pathogen-host co-evolution, and the potential use of this information in pre-symptomatic diagnosis is discussed.

Protective and nonprotective human immunoglobulin M monoclonal antibodies to Cryptococcus neoformans glucuronoxylomannan manifest different specificities and gene use profiles

The features of protective murine antibodies to the Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM) have been rigorously investigated; however, the characteristics of protective human antibodies to GXM have not been defined. We produced monoclonal antibodies (MAbs) from XenoMouse mice (transgenic mice that express human immunoglobulin M [IgM], IgG2, and kappa) which were immunized with a C. neoformans serotype D strain 24067 GXM-diphtheria toxoid conjugate. This study reports the specificity and efficacy of three human IgM MAbs, G14, G15, and G19, generated from these mice. Each MAb was specific for GXM, but G14 and G19 had different specificity based on their binding to serotype A strain H99 and SB4 GXMs, to which G15 did not bind. Nucleic acid sequence analysis revealed that G15 uses V(H)3-64 in the germ line configuration. G14 and G19 use V(H)6-1, which has somatic mutations. All of the MAbs use V kappa DPK22/A27. Studies of MAb efficacy in BALB/c mice showed that administration of 0.1 mg, but not 1 or 0.01 mg, of G15 prolonged survival against lethal C. neoformans strain 24067 challenge, whereas G14 and G19 were not protective at any dose. This panel of MAbs illustrates that serotype D GXM has epitopes that elicit human antibodies that can be either protective or nonprotective. Our findings suggest that V(H) gene use may influence GXM specificity and efficacy, and they provide insights into the possible contribution that V(H) gene use may have in resistance and susceptibility to cryptococcosis.

Generation of murine monoclonal antibodies to Haemophilus influenzae type b capsular polysaccharide by in vivo immunization

Haemophilus influenzae type b (Hib) is a pathogenic gram-negative bacterium associated with human disease, especially in young children. Protective immune response to Hib results from antibodies developed against the polyribosylribitol phosphate (PRP) capsular polysaccharide of the bacterium. Several investigators in the study of immune response to Hib have produced human monoclonal antibodies to PRP. Only two previous groups have reported the generation of murine anti-PRP monoclonal antibodies using either immunizing mice with inactivated Hib bacteria or a combination of in vivo and in vitro immunization of mice with PRP conjugate antigen (PRP-D). In this present study, we generated murine anti-PRP monoclonal antibody secreting hybridomas for the first time by simple in vivo immunization with PRP conjugate antigen (PRP-T). The anti-PRP antibodies from one hybridoma clone (B10) are further characterized and potential applications are discussed.

Molecular ontogeny of the human antibody repertoire to the Haemophilus influenzae type B polysaccharide: expression of canonical variable regions and their variants in vaccinated infants

A structurally conserved antibody combining site, encoded by the IGH V3-23 and kappa A2 variable (V) region gene segments, predominates the adult immune response to the Haemophilus influenzae type b (Hib) capsular polysaccharide (PS). This site has been elevated to canonical status based upon its relative molecular uniformity and prevalence in adults. To date, no studies have examined the primary structure of Hib PS-specific antibodies in young infants, who are the primary targets of Hib vaccination. In this study we show that canonical Hib PS-specific heavy (H) and light (L) chain V regions are present in 4-month-old infants following two vaccinations with Hib PS-protein conjugates. The infant V regions contain sequence polymorphisms that resemble those found in adult antibodies, as well as polymorphisms at position 95a of the A2 L chain not previously observed in adults. In vitro studies of Fab fragments and recombinant IgG2 antibodies using these V regions identify sequence polymorphisms that impact Hib PS binding affinity and bactericidal activity. These results demonstrate the establishment of canonical V regions in early ontogeny and provide a structural explanation of how canonical antibodies in the infant can vary in their affinity and protective activity against Hib.

Structure-function relationships for human antibodies to pneumococcal capsular polysaccharide from transgenic mice with human immunoglobulin Loci

To investigate the influence of antibody structure and specificity on antibody efficacy against Streptococcus pneumoniae, human monospecific antibodies (MAbs) to serotype 3 pneumococcal capsular polysaccharide (PPS-3) were generated from transgenic mice reconstituted with human immunoglobulin loci (XenoMouse mice) vaccinated with a PPS-3-tetanus toxoid conjugate and their molecular genetic structures, epitope specificities, and protective efficacies in normal and complement-deficient mice were determined. Nucleic acid sequence analysis of three MAbs (A7, 1A2, and 7C5) revealed that they use two different V(H)3 genes (A7 and 1A2 both use V3-15) and three different V(kappa) gene segments. The MAbs were found to have similar affinities for PPS-3 but different epitope specificities and CDR3 regions. Both A7 and 7C5 had a lysine at the V(H)-D junction, whereas 1A2 had a threonine. Challenge experiments with serotype 3 S. pneumoniae in BALB/c mice revealed that both 10- and 1- micro g doses of A7 and 7C5 were protective, while only a 10- micro g dose of 1A2 was protective. Both A7 and 7C5 were also protective in mice lacking either an intact alternative (FB(-/-)) or classical (C4(-/-)) complement pathway, but 1A2 was not protective in either strain. Our data suggest that PPS-3 consists of epitopes that can elicit both highly protective and less protective antibodies and that the superior efficacies of certain antibodies may be a function of their structures and/or specificities. Further investigation of relationships between structure, specificity, and efficacy for defined MAbs to PPS may identify antibody features that might be useful surrogates for antibody (and vaccine) efficacy.

Structural determinants of the human idiotype HibId-1

The human antibody response to the capsular polysaccharide of Haemophilus influenzae type b is predominated by antibodies expressing a light-chain-associated idiotype designated HibId-1. HibId-1 is expressed by kappa light chains encoded by either the A2 or A18 variable region genes. In this report we use site-directed mutagenesis and molecular modeling to show that HibId-1 expression is determined by residues in the first and second complimentarity determining regions that are widely separated in the primary sequence, but closely juxtaposed by the tertiary folding of the mature light chain molecule. Of the known human light chains, only alleles of A2 and A18 encode these residues at these positions in their germline configuration. VIG10, a mouse monoclonal antibody of unknown specificity that expresses HibId-1, and 23F.2, an A2-utilizing Streptococcus pneumoniae 23F polysaccharide-specific human Fab fragment that lacks HibId-1, provide examples of the HibId-1 determinant both arising and being lost by somatic mutation. In addition, we show that the residues responsible for HibId-1 expression can be disassociated from those required for antigen binding.

Additive effect of neutralizing antibody and antiviral drug treatment in preventing virus escape and persistence

Poorly cytopathic or noncytopathic viruses can escape immune surveillance and establish a chronic infection. Here we exploited the strategy of combining antiviral drug treatment with the induction of a neutralizing antibody response to avoid the appearance of neutralization-resistant virus variants. Despite the fact that H25 immunoglobulin transgenic mice infected with lymphocytic choriomeningitis virus mounted an early neutralizing antibody response, the virus escaped from neutralization and persisted. After ribavirin treatment of H25 transgenic mice, the appearance of neutralization-resistant virus was prevented and virus was cleared. Thus, the combination of virus-neutralizing antibodies and chemotherapy efficiently controlled the infection, whereas each defense line alone did not. Similar additive effects may be unexpectedly efficient and beneficial in humans after infections with persistent viruses such as hepatitis C virus and hepatitis B virus and possibly human immunodeficiency virus.

Production of protective human antipneumococcal antibodies by transgenic mice with human immunoglobulin loci

Infections with Streptococcus pneumoniae remain a significant cause of morbidity and mortality. To gain insight into structure-function relationships for human antibodies to pneumococcal capsular polysaccharide (PPS), we studied the response of transgenic mice reconstituted with human immunoglobulin loci, XenoMouse, to PPS antigens in a pneumococcal vaccine. Enzyme-linked immunosorbent assays of sera from mice vaccinated with a 23-valent pneumococcal vaccine revealed that they produced serotype-specific human antibodies, with the greatest response being to the PPS of serotype 3 (PPS 3). Molecular sequence analysis of three monoclonal antibodies (MAbs) to PPS 3 generated from lymphoid cells from mice vaccinated with a 23-valent pneumococcal vaccine or a PPS 3-bovine serum albumin conjugate revealed that they all used heavy-chain immunoglobulin genes from the V(H)3 family, two expressed light chain genes from the human Vkappa1 family, and one expressed a mouse lambda light chain. The protective efficacy of the two MAbs was examined in mice. A 10-microgram dose of both, and a 1-microgram dose of one, significantly prolonged survival from a lethal serotype 3 infection in CBA/N mice. Our data show that XenoMouse mice produced protective, serotype-specific human antibodies to PPS 3, and they lend support to the proposal that these animals represent a useful model to study the human antibody response to PPS antigens.

Polysaccharide vaccines as probes of antibody repertoires in man

Antibodies specific for capsular polysaccharide epitopes mediate immunity to encapsulated bacterial pathogens, and accordingly, vaccine development has focused upon the induction of these specificities. Efficacious vaccines, consisting of either polysaccharide alone or polysaccharide coupled to protein carriers, have been developed for a number of pathogens. Their clinical importance notwithstanding, these vaccines serve as model antigens to study the genetic and somatic forces molding adaptive immunity in man. In this article we review progress aimed at delineating the structure and dynamics of the human antibody repertoire to the Haemophilus influenzae type b polysaccharide (Hib PS), a system which has been studied from infancy to old age. Collectively, the data reveal a repertoire which is encoded by a relatively large number of germline variable (V) region gene segments, but which is typically expressed within individuals as a markedly restricted, oligoclonal population. One particular V domain has attained canonical status because of its high penetrance at the population level and its predominance in individual repertoires. Although this combining site is assembled in early infancy and retains its prominence throughout life, its frequency of expression, affinity and protective function are dictated by the molecular form of the Hib PS immunogen (vaccine). The determinants of Hib PS binding affinity can include both germline and somatically-acquired V region polymorphisms. We discuss how these properties of the Hib PS repertoire could impact immunity to Hib, and we consider the implications of these findings towards understanding the evolution of immunoglobulin germline V genes.

Structural requirements of the major protective antibody to Haemophilus influenzae type b

Protective antibodies to the important childhood pathogen Haemophilus influenzae type b (Hib) are directed against the capsular polysaccharide (HibCP). Most of the antibody is encoded by a well-defined set of ("canonical") immunoglobulin genes, including the Vkappa A2 gene, and expresses an idiotypic marker (HibId-1). In comparison to noncanonical antibodies, the canonical antibody is generally of higher avidity, shows higher levels of in vitro bactericidal activity, and is more protective in infant rats. Using site-directed mutagenesis, we here characterize canonical HibCP antibodies expressed as antigen-binding fragments (Fabs) in Escherichia coli, define amino acids involved in antigen binding and idiotype expression, and propose a three-dimensional structure for the variable domains. We found that canonical Fabs, unlike a noncanonical Fab, bound effectively to HibCP in the absence of somatic mutations. Nevertheless, pronounced mutation-based affinity maturation was demonstrated in vivo. An almost perfect correlation was found between unmutated gene segments that mediated binding in vitro and those encoding canonical HibCP antibodies in vivo. Thus, the Vkappa A2a gene could be replaced by the A2c gene but not by the highly homologous sister gene, A18b, corresponding to the demonstrated usage of A2c but not of A18b in vivo. Similarly, only Jkappa1 and Jkappa3, which predominate in the response in vivo, were able to facilitate binding in vitro. These findings suggest that the restricted immunoglobulin gene usage in HibCP antibodies reflects strict structural demands ensuring relatively high affinity prior to somatic mutations-requirements met by only a limited spectrum of immunoglobulin gene combinations.

In Vivo Selection of Neutralization-Resistant Virus Variants But No Evidence of B Cell Tolerance in Lymphocytic Choriomeningitis Virus Carrier Mice Expressing a Transgenic Virus-Neutralizing Antibody

B cell tolerance is maintained by active deletion and functional anergy of self-reactive B cells depending on the time, amount, and site of the self-antigen expression. To study B cell tolerance toward a transplacentally transmitted viral Ag, we crossed transgenic mice expressing the μ heavy and the κ light chain of the lymphocytic choriomeningitis virus (LCMV)-neutralizing mAb KL25 (HL25-transgenic mice) with persistently infected LCMV carrier mice. Although HL25-transgenic LCMV carrier mice exhibited the same high virus titers as nontransgenic LCMV carrier mice, no evidence for B cell tolerance was found. In contrast, enhanced LCMV-neutralizing Ab titers were measured that, however, did not clear the virus. Instead, LCMV isolates from different tissues turned out to be neutralization resistant Ab escape variants expressing different substitutions of amino acid Asn119 of the LCMV-glycoprotein 1 that displays the neutralizing B cell epitope. Virus variants with the same mutations were also selected in vitro in the presence of the transgenic mAb KL25 confirming that substitutions of Asn119 have been selected by LCMV-neutralizing Abs. Thus, despite abundant expression of viral neo-self-antigen in HL25-transgenic LCMV carrier mice, transgenic B cells expressing LCMV-neutralizing Abs were rather stimulated than tolerized and neutralization resistant Ab escape variants were selected in vivo.

Polysaccharide binding potential of the human A2 or A18 kappa light chain homologues

Antibodies having light (L) chains encoded by the kappaII-A2 variable region gene segment predominate in the human response to the Haemophilus influenzae type b polysaccharide (Hib PS). To determine whether the closely related homologue of the A2 gene, the kappaII-A18 gene, has the potential to contribute to the repertoire, we examined Hib PS binding to a series of recombinant Fab fragments having either A2 or A18 L chains isolated from a Hib PS-vaccinated adult. The ability to bind Hib PS resided exclusively with those Fab fragments having A2 and containing an insertional arginine at the variable-joining junction. Thus, despite the sequence similarity between A2 and A18, only A2 contributes to the canonical Hib PS paratope.

The First Dose of a Haemophilus influenzae Type b Conjugate Vaccine Reactivates Memory B Cells: Evidence for Extensive Clonal Selection, Intraclonal Affinity Maturation, and Multiple Isotype Switches to IgA2

The Ab response of a healthy adult to the first dose of a Haemophilus influenzae type b capsular polysaccharide (HibCP) conjugate vaccine was studied at the level of Ig gene usage by circulating Ab-secreting cells. Forty-one IgA and 17 IgG mRNA sequences were obtained. The major part of the response was confined to IgA Ab-secreting cells, and 72% of the IgA sequences were derived from the progeny of a single rearranged B cell. These sequences could be arranged in a genealogical tree showing multiple somatic mutations and at least two intraclonal isotype switches to IgA2. Fourteen somatic mutations were shared by this clonal progeny, indicating that extreme clonal selection had occurred early in the clonal development. Taking into account the frequency of somatic mutations and the clone size, it was evident that the responding cell population must have originated from a mutated, highly selected, and expanded population of cells existing before vaccination, i.e., memory B cells. The dominating heavy and light chains of the response were combined in a Fab that bound HibCP. It was shown that the shared heavy and light chain mutations increased the affinity for HibCP considerably, indicating that the clonal selection had been driven by affinity. Pre-existing memory cells in unvaccinated adults may explain several features of Ab responses to polysaccharide vaccines and may play a role in acquiring the ability to respond to pure polysaccharides during infancy.

Haemophilus influenzae Type b Polysaccharides-Protein Conjugate Vaccine Elicits a More Diverse Antibody Repertoire in Infants Than in Adults

Conjugation of bacterial polysaccharides (PS) to protein carriers confers the ability to elicit protective serum Ab in infants, who respond poorly to plain PS. The serum Ab of young children immunized with Haemophilus influenzae type b (Hib) PS conjugate vaccine varies with age and Ag formulation. To understand these age-related changes in human anti-Hib PS immune responses we determined the variable region gene sequences encoding anti-Hib PS mAbs of infants immunized with Hib oligosaccharide-diphtheria toxin vaccine. The anti-Hib PS repertoire of children differs from that of adults. A smaller proportion of mAbs from children have high affinity for Hib PS, and the overall variable region gene repertoire of infants is more diverse than that in adults. Variable region genes encoding high affinity mAbs of infants are similar to the restricted repertoire described in adults. Low affinity anti-Hib PS mAbs of infants are encoded by a heterogeneous group of genes that are uncommonly observed in the adult repertoire. Abs with high affinity for Hib PS from infants, like most mAbs from adults, react only with Hib PS and the structurally similar PS of Escherichia coli K100, whereas low affinity mAbs of infants are polyreactive. The low affinity anti-Hib PS mAbs of infants immunized with Hib oligosaccharide-diphtheria toxin vaccine vaccine are not reflected in serum Ab. However, the differences between the variable region gene repertoires of adults and infants may account for the distinct immunologic characteristics of the anti-Hib PS responses in young children immunized with other vaccine formulations.

Role of κII-A2 Light Chain CDR-3 Junctional Residues in Human Antibody Binding to the Haemophilus influenzae Type b Polysaccharide

Abs using the κII-A2 V gene segment predominate the human Ab repertoire to the Haemophilus influenzae b (Hib) polysaccharide (PS). All A2 anti-Hib PS Abs sequenced to date possess a 10-amino acid L chain complementarity-determining region-3 (CDR-3) having an insertional arginine (Arg) at position 95a, the V-J junction. These findings suggest an essential requirement for this conserved Arg residue in determining Hib PS-binding affinity. We examined this requirement by performing chain recombination experiments in which a series of A2 L chains, differing at position 95a, were combined individually with an Fd region known to generate a Hib PS-combining site when paired with an A2-Arg(95a)-Jκ1 V region. Hib PS binding of the recombinant Fabs was evaluated quantitatively using a radioantigen-binding assay. Fabs having A2 L chains with either Arg or lysine in position 95a in combination with Jκ1 gave equivalent and strongest binding to Hib PS. Fabs having A2-Jκ1 L chains with either tyrosine, glycine, alanine, leucine, serine, or threonine in position 95a, or having an A2-Arg(95a)-Jκ3 L chain, gave intermediate binding. Fabs having A2-Jκ1 L chains with glutamate or aspartate at 95a or with no junctional residue showed little or no Hib PS binding. These results demonstrate the importance of L chain junctional residue, as well as Jκ usage and CDR-3 length, in determining Hib PS-binding affinity. Contrary to expectation, an Arg junctional residue is not essential for generating either high or intermediate affinity-binding sites.

Clonal Analysis of a Human Antibody Response. III. Nucleotide Sequences of Monoclonal IgM, IgG, and IgA to Rabies Virus Reveal Restricted Vκ Gene Utilization, Junctional VκJκ and VλJλ Diversity, and Somatic Hypermutation

In previous work, we generated four IgM, five IgG1, and one IgA1 mAbs to rabies virus using B cells from four subjects vaccinated with inactivated rabies virus, a thymus-dependent (TD) mosaic Ag, and sequenced the mAb VHDJH genes. Here, we have cloned the VκJκ and VλJλ genes to complete the primary structure of the Ag-binding site of these mAbs. While the anti-rabies virus mAb selection of Vλ genes (2e.2.2 twice, DPL11, and DPL23) reflected the representation of the Vλ genes in the human haploid genome (stochastic utilization), that of Vκ genes (O2/O12 twice, O8/O18, A3/A19, A27, and L2) did not (p = 0.0018) (nonstochastic utilization). Furthermore, the selection of both Vκ and Vλ genes by the anti-rabies virus mAbs vastly overlapped with that of 557 assorted VκJκ rearrangements, that of 253 VλJλ rearrangements in λ-type gammopathies, and that of other Abs to thymus-dependent Ags, including 23 anti-HIV mAbs and 51 rheumatoid factors, but differed from that of 43 Abs to Haemophilus influenzae type b polysaccharide, a prototypic thymus-independent (TI) Ag. The anti-rabies virus mAb VκJκ and VλJλ segments displayed variable numbers of somatic mutations, which, in mAb58 and the virus-neutralizing mAb57, entailed a significant concentration of amino acid replacements in the complementarity-determining regions (p = 0.0028 and p = 0.0023, respectively), suggesting a selection by Ag. This Ag-dependent somatic selection process was superimposed on a somatic diversification process that occurred at the stage of B cell receptor for Ag rearrangement, and that entailed V gene 3′ truncation and N nucleotide additions to yield heterogeneous CDR3s.

Molecular Analysis of Polyreactive Monoclonal Antibodies from Rheumatic Carditis: Human Anti-N-Acetylglucosamine/Anti-Myosin Antibody V Region Genes

Anti-myosin Abs are associated with inflammatory heart diseases such as rheumatic carditis and myocarditis. In this study, human cross-reactive anti-streptococcal/anti-myosin mAbs 1.C8, 1.H9, 5.G3, and 3.B6, produced from peripheral blood lymphocytes of patients with rheumatic carditis, and mAb 10.2.5, produced from a tonsil, were characterized, and the nucleotide sequences of their VH and VL genes were analyzed. Human mAbs 1.C8, 1.H9, 10.2.5, and 3.B6 reacted with human cardiac myosin while mAb 5.G3 did not. The mAbs were strongly reactive with N-acetyl-β-d-glucosamine, the dominant epitope of the group A streptococcal carbohydrate. mAb 1.H9 was moderately cytotoxic to rat heart cells in vitro in the presence of complement. The anti-myosin mAbs from rheumatic carditis were found to react with specific peptides from the light meromyosin region of the human cardiac myosin molecule. Anti-streptococcal/anti-myosin mAbs from normal individuals reacted with distinctly different light meromyosin peptides. The mAbs were encoded by VH3 gene segments V3-8, V3-23, and V3-30 and by the VH4 gene segment V4-59. The variable region genes encoding the anti-streptococcal/anti-myosin repertoire were heterogeneous and exhibited little evidence of Ag-driven somatic mutation.

Differential use of immunoglobulin light chain genes and B lymphocyte expansion at sites of disease in rheumatoid arthritis (RA) compared with circulating B lymphocytes

The presence of germinal centre-like structures and clonotypic expansion of lymphocytes in RA synovia may indicate a site-specific immune response to local antigens, rather than passively entrapped immune cells, that sustains synovial inflammation. In this study we compare the nature of immunoglobulin light chain variable region gene use in the synovium of RA patients with peripheral B cells to determine the nature of the synovial immune response. Using Vlambda and Vkappa gene fingerprinting, which relies on differences in CDR3 length, we demonstrate differences in the pattern of Vlambda and Vkappa use and clonotypic expansion of B cells between the synovium and peripheral blood of RA patients. Further, we show that some synovial rearrangements with long CDR3 are selectively expanded. These longer than usual CDR3 were generated by a number of mechanisms including N-additions. However, the observed differences were not uniform in different patients. These observations suggest that local synovial antigens drive significant numbers of T and B lymphocytes selected from an existing repertoire shaped by genetic and environmental factors. Further, the data argue against passive retention of most B cells in the synovium of RA patients.

Heterogeneity of antibodies reactive with the dominant antigen of Actinobacillus actinomycetemcomitans

The serotype b-specific carbohydrate antigen (SbAg) of Actinobacillus actinomycetemcomitans Y4 is reported to be the O antigen of lipopolysaccharide, and the highest titers of serum antibody reactive with A. actinomycetemcomitans in early-onset periodontitis (EOP) patients bind SbAg. These high titers of serum antibody reactive with SbAg are associated with a lesser extent and severity of periodontal disease. The aim of this study was to determine if a limited number of genes code for anti-SbAg antibodies as has been shown for immunoglobulin G (IgG) reactive with the type b polysaccharide from Haemophilus influenzae. Serum IgG reactive with the SbAg was prepared from 20 high-titer EOP patients by affinity chromatography. The IgG subclass concentrations were determined, and heterogeneity was analyzed by isoelectric focusing (IEF). IgG2 was the dominant subclass (83% of total IgG) in the anti-SbAg IgG fraction and represented an average of 1.33% of total serum IgG2. The IgG2 reactive with SbAg was isolated from the affinity-purified IgG fraction by affinity chromatography with protein A and subclass-specific monoclonal antibodies. On IEF gels, only 4 to 20 bands were observed in the anti-SbAg IgG fractions, indicating limited heterogeneity. N-terminal amino acid sequence analysis of eight representative anti-SbAg IgG2 preparations indicated that variable heavy and light chains consisted largely of V(H)III and V(kappa)II, respectively. However, a significant fraction of anti-SbAg may use V(H) and V(lambda) genes with blocked N termini. In short, these findings indicate that IgG reactive with SbAg is very much like the antibody reactive with H. influenzae type b polysaccharide. Similarities include IgG2 dominance, limited bands on IEF gels, supporting an oligoclonal response, and use of genes from V(H)III and V(kappa)II regions.

Population studies of the human V kappa A18 gene polymorphism in Caucasians, blacks and Eskimos. New functional alleles and evidence for evolutionary selection of a more restricted antibody repertoire

Immunoglobulin gene polymorphisms are interesting because they reflect differences in the available antibody repertoire which may affect the susceptibility to specific infections. Until recently, the human V kappa gene, A18, was known as a nonfunctional gene only. In this study, we cloned and sequenced four apparently functional alleles and determined the gene frequencies in three well-defined populations: Danish Caucasians, eastern Greenland Eskimos and Mozambican blacks. The A18b allele that was recently described in Native American Navajos by Atkinson et al. was found in all three populations with gene frequencies of 8%, 45% and 23% in Caucasians, Eskimos and blacks, respectively. Conversely, the frequencies of the nonfunctional A18a allele were 92%, 55% and 57%. Further, three new A18 alleles, c, d, and e were found exclusively in blacks, among whom they had an total frequency of 19%. These data indicate that both the A18a and A18b alleles originated before the diversification of Africans and non-Africans 90,000 years ago, whereas the A18c, A18d and A18e alleles may have a more recent origin. The functionality of the A18b allele was documented by the demonstration of properly rearranged and somatically hypermutated A18b messenger RNA present in the blood lymphocytes of individuals carrying this allele. The expression clearly exceeded that of a known functional V gene, A2, indicating that functional A18 alleles contribute significantly to the available antibody repertoire. In this context, it is surprising that the functional A18b allele apparently has been negatively selected in the Caucasian population, among whom 85% completely lack a functional gene.

VHDJH gene sequences and antigen reactivity of monoclonal antibodies produced by human B-1 cells: evidence for somatic selection

To understand whether the distinct VHDJH gene utilization by natural polyreactive Abs reflects the developmentally restricted Ig VHDJH rearrangements putatively expressed by B-1 cells, we generated 11 (8 IgM, 1 IgG3, 2 IgA1), 7 (6 IgM, 1 IgG1), and 7 (2 IgM, 3 IgG1, 2 IgG3) mAb-producing lines using B-1a (surface CD5+, CD45RAlow), B-1b (surface CD5-, CD45RAlow, CD5 mRNA+), and B-2 (surface CD5-, CD45RAhigh, CD5 mRNA-) cells, respectively, sorted from adult human peripheral blood. Most B-1a and B-1b, but no B-2, cell-derived mAbs were polyreactive; i.e., they bound different self and foreign Ags with different affinities. B-1a and B-2 mAbs preferentially utilized VH4 (p = 0.003) and VH3 (p = 0.010) genes, respectively. All three mAb populations utilized DXP, DLR, DN DH genes, and JH6, but no mAb utilized DHQ52. There were fewer unencoded nucleotide (N) additions in the VHDJH junctions of B-1b (3.00 +/- 2.52, mean +/- SD) than of B-1a (12.45 +/- 3.93, p = 1.23 x 10(-5)) or B-2 (8.29 +/- 4.75, p = 0.020) mAbs. Partly due to the fewer N additions and a paucity of D-D fusions, the B-1b mAb CDR3s were significantly shorter than the B-1a mAb CDR3s (p = 0.013), which contained a nonrandom Tyr distribution (p = 0.003). Finally, all but two B-1 cell-derived mAbs were mutated, in a fashion similar to that of the Ag-selected B-2 mAbs. Thus, in the human adult, B-1 cells that make natural polyreactive Abs may not be representative of the predominantly B-1 developmental waves of colonization of the fetal and neonatal B cell repertoires, and are somatically selected.

Human Fab fragments specific for the Haemophilus influenzae b polysaccharide isolated from a bacteriophage combinatorial library use variable region gene combinations and express an idiotype that mirrors in vivo expression

To determine whether the human antibody (Ab) repertoire to the Haemophilus influenzae type b capsular polysaccharide (Hib PS) could be studied at the molecular level with phage display technology, we constructed a phage Fab library by using peripheral blood from a vaccinated adult. Phage were selected based on Hib PS binding. Two distinct Hib PS-specific phage clones were identified whose Fab fragments used the same V(H) region paired with two different V(L) regions. The V(L) regions were derived from two independent rearrangements of the A2c gene with Jkappa1, and both contained a nontemplated arginine codon at the V-Jkappa junction. The two A2 V gene segments differed from the A2c germ line sequence in 0 and 5 bases. The V(H) region consisted of the V(H)26 gene segment having 98% identity to the germline nucleotide sequence, a D region of 9 bases, and J(H)4b1. Usage of V(H)26 in combination with A2 V regions containing a junctional arginine is a predominant configuration of naturally occurring Hib PS-specific Abs. Liquid- and solid-phase assays showed that phage-derived Fab reacted with Hib PS and expressed HibId-1, an idiotype associated with the kappaII-A2 V region. These findings extend the database of V region polymorphisms that can contribute to the Hib PS repertoire and demonstrate that Hib PS-specific Fab fragments isolated from combinatorial phage libraries use V gene combinations which mirror the natural repertoire.

A defective Vkappa A2 allele in Navajos which may play a role in increased susceptibility to haemophilus influenzae type b disease

The antibody response to H. influenzae type b (Hib) is pauciclonal, and is dominated by antibodies using the VkappaA2 gene. Navajos have a 5-10-fold increased incidence of Hib disease compared with control populations. We hypothesized that a polymorphism in one of the genes in this oligoclonal response may lead to increased disease susceptibility. Since the predominant A2+ anti-Hib antibodies have high avidity for Hib and can be unmutated, the A2 Vkappa gene was analyzed. Over half of the Navajos studied, but only one control individual, had a new allele of A2, termed A2b, with three changes from the published A2 germline sequence. One of the changes was in the recombination signal sequence, suggesting that the A2b allele might not undergo V-J rearrangement very frequently. This possibility was confirmed by analyzing the relative frequency of non-productive A2 rearrangements in A2a/b heterozygous Navajos. Many fewer A2b rearrangements were observed, showing that the A2b allele is defective in its ability to undergo rearrangement. The prevalence of this allele in Navajos may play a role in their increased susceptibility to invasive Hib disease. If so, it would underscore the importance of the germline Ig repertoire for protective antibody responses to pathogenic bacteria in unimmunized children.

B-cell superantigens: implications for selection of the human antibody repertoire

For several decades, B-cell interactions with antigens were thought to occur only through a clonal activation mechanism, in which the hypervariable regions of the immunoglobulin receptor are exclusively involved in ligand binding. However, an additional mode of interaction can occur, whereby molecules, termed B-cell superantigens, can bind human B cells bearing immunoglobulin receptors of a given variable (V)-gene family. This mechanism requires contributions from regions outside the conventional hypervariable loops and results in a B-cell response of increased magnitude. Here, Moncef Zouali reviews recent in vitro and in vivo observations on human B-cell superantigens in the context of the current consensus of B-cell development, and discusses the implications of these novel concepts with respect to pathogenesis.

Molecular and idiotypic analysis of antibodies to Cryptococcus neoformans glucuronoxylomannan

Antibodies to the Cryptococcus neoformans capsular glucuronoxylomannan (GXM) form the basis of two potential therapeutic intervention strategies, i.e., conjugate vaccines and passive antibody therapy. To better understand the molecular basis of the antibody response, the heavy- and light-chain immunoglobulin variable region (VH and VL, respectively) sequences of seven monoclonal antibodies (MAbs) to GXM were determined. Rabbit anti-idiotypic serum was made to the previously characterized murine MAb 2H1 and used to study MAb 2H1 idiotype expression in other GXM-binding MAbs and immune sera. MAb E1 originated from a C3H/HeJ mouse immunized with C. neoformans serotype A polysaccharide. MAbs 471, 1255, 339, 3C2, 386, and 302 originated from BALB/c mice immunized with polysaccharide of serotypes A, A, B, C, D, and D, respectively, conjugated to sheep erythrocytes. In the E1, VH uses V11 from the T15 gene family and JH3 and has a D segment of three amino acids, and the VL uses a VKSer-like gene family element and JK5. In MAbs 471 and 3C2, the VH uses VH7183-like gene family elements and JH2 and has D segments of seven amino acids, and the VL uses VK5.1 and JK1. In MAbs 1255 and 339, the VH uses VH10-like gene elements and JH4 and has six codon D segments, and the VL uses a VK21-like gene element and JK5. In MAbs 302 and 386, respectively, the VH uses VHGAM-like gene elements and JH2 and JH3 and has six and four codon D segments, and VL uses VK4/5-like gene elements and JK1.VH usage, MAb 2H1 idiotype expression, and fine specificity mapping define a minimum of three GXM epitopes which elicit protective antibodies. The results confirm that the antibody response is highly restricted, suggest a close relationship between molecular structure and serological properties, and provide insight into protein structural motifs important for GXM binding.

Variable region sequences of a protective human monoclonal antibody specific for the Haemophilus influenzae type b capsular polysaccharide

A hybridoma secreting a human immunoglobulin G2 kappa monoclonal antibody (MAb) specific for the capsular polysaccharide of Haemophilus influenzae type b (Hib) was isolated. This MAb, designated CA4, was bactericidal to Hib in vitro and protected infant rats from Hib bacteremia. Nucleotide sequence analysis of CA4 variable (V) region cDNA showed that the heavy (H)-chain V region was of subgroup III and was 96% identical to the VH germ line gene segment DP77 (V3-21). The light (L)-chain V region was of the kappa subgroup III and was 94% identical to the A27 (Humkv325) germ line gene, which is commonly used by rheumatoid factors and other autoantibodies. MAb CA4 did not have rheumatoid factor activity and did not react with histones, DNA, or chromatin. These findings identify an additional VHIII gene segment which can contribute to the anti-Hib capsular polysaccharide repertoire and demonstrate that a VL gene commonly encoding autoantibodies can be utilized for protective immunity.

Molecular analysis of the human immunoglobulin V lambda II gene family

The 8.12 idiotype characterizes a subpopulation of anti-DNA antibodies in patients with systemic lupus erythematosus (SLE). The idiotype is present on lambda light chains and has previously been shown to be exclusively encoded by V lambda II light chains. RFLP analysis of the V lambda II gene family has shown the family to consist of 10 to 15 members. Thus far, the sequences of seven V lambda II germline genes are reported in the literature with one of these a pseudogene. To identify the V lambda II genes that encode 8.12 positive antibodies and to further characterize the V lambda II family, germline V lambda II clones were derived from a patient with SLE. Two libraries were constructed: a genomic DNA library and a library of PCR-derived V lambda II gene products obtained using a conserved V lambda II leader region primer and a primer for the nonamer region 3' of the coding sequence. We now describe seven new germline genes, two of which are pseudogenes. Comparison of V lambda II germline genes to sequences of 8.12 positive light chains produced by EBV-transformed B cell lines show that all 8.12 positive light chains are encoded by a limited number of highly homologous members of the V lambda II family. 8.12 negative V lambda II encoded light chains also derive from a limited number of V lambda II genes, suggesting that only a subset of the apparently available V lambda II genes are commonly expressed.

Comparison of nonhuman primate antibodies against Haemophilus influenzae type b polysaccharide with human antibodies in oligoclonality and in vivo protective potency

Nonhuman primates are often used as a model for studying vaccines for humans. However, it is not always clear how closely the antibody responses in these species mimic human responses. Recent studies have characterized the human antibody response to Haemophilus influenzae type b (Hib) in great detail. In this study, we have compared the antibody response to Hib of humans with those of other primates. Studies of isoelectric points and V kappa subgroup usage show that, like humans, nonhuman primates produce oligoclonal antibodies. Also, monkey antibodies to the Hib polysaccharide are as protective as human antibodies in an in vivo model of Hib infection. Thus, we conclude that nonhuman primates produce antibodies to Hib polysaccharide that are structurally and functionally similar to human antibodies and are a good model for testing human vaccines.

Variable region sequences and idiotypic expression of a protective human immunoglobulin M antibody to capsular polysaccharides of Neisseria meningitidis group B and Escherichia coli K1

We determined the heavy (H)- and light (L)-chain variable (V) region nucleotide and translated amino acid sequences of the human immunoglobulin M(kappa) monoclonal antibody (MAb) 5E1, which is specific for the polysaccharide capsule of Escherichia coli K1 and Neisseria meningitidis group B (poly[alpha(2-->8)-N-acetylneuraminic acid]) and which is protective in animal models of infection. The 5E1 VH gene is a member of the VHIIIb family and is 97% homologous to the 9.1 germ line gene. The 5E1 VL gene is a member of the kappa I subgroup and is 98% homologous to the germ line gene, 15A, also known as KLO12. The VL and/or VH genes used by 5E1 are highly homologous to the V genes encoding antibodies to the Haemophilus influenzae type b polysaccharide and to antibodies reactive with self-antigens such as erythrocyte "i," DNA, and thyroid peroxidase. We also produced three murine anti-idiotype (Id) MAbs against 5E1. All three anti-Ids recognize a minor subset of antimeningococcal B polysaccharide antibodies present in serum from normal adults. Two of the anti-Ids define distinct Ids associated with antibodies having kappa I-15A V regions. These 15A-associated Ids are expressed by some heterologous human antimeningococcal B polysaccharide MAbs, and they also are independently expressed by two human MAbs that are specific for either the H. influenzae b polysaccharide or the i erythrocyte antigen and that utilize the kappa I-15A V region. Taken together, these data indicate that the 5E1 antibody uses V regions that recur in the human antibody repertoires to this polysaccharide and to structurally dissimilar polysaccharides and autoantigens. Thus, the poor immunogenicity of poly[alpha(2-->8)-N-acetylneuraminic acid] cannot be explained by the unavailability of certain critical VH and VL genes required for generation of antibody response.

Variable-region subgroup distribution among lambda-type immunoglobulins in normal human serum

The distribution of the major VL subgroups (V lambda I, V lambda II, V lambda III, V lambda IV, V lambda VI, and V lambda VIII) among lambda-type immunoglobulins (Igs) in normal serum was determined by a sandwich enzyme-linked immunosorbent assay (ELISA) using a panel of murine anti-human V lambda-subgroup-specific monoclonal antibodies (MoAbs) and appropriate reference standard proteins. The mean concentration of lambda I, lambda II, lambda III, lambda IV, lambda VI, and lambda VIII Igs in serum specimens obtained from 23 adults was 2158, 162, 1958, 264, 225, and 169 micrograms/mL and represented 44, 3, 40, 5, 5, and 3% of the total Ig lambda population, respectively. The low percentage of lambda II Igs in normal serum was in marked contrast to the approximately 40% incidence of this V lambda subgroup found among lambda-type Bence Jones proteins and monoclonal serum Igs obtained from patients with multiple myeloma and AL amyloidosis, or approximately 60% in Waldenström's macroglobulinemia. The non-random expression of the V lambda II subgroup in these diseases implies a relationship between V lambda-gene usage and plasma cell, as well as certain types of lymphocytic dyscrasias.

Cloning and characterisation of TPO autoantibodies using combinatorial phage display libraries

Thyroid lymphocyte RNA from a Hashimoto patient with high serum levels of autoantibodies to thyroid peroxidase (TPO) was used to construct a phage display antibody library in the phagemid vector pComb3. The library (100,000cfu) encoded IgG1 heavy chains together with kappa light chains. Selection of the phages displaying TPO antibody on TPO-coated ELISA plates yielded a phage population enriched for surface expression of TPO antibody Fabs. 3 different Fabs specific for TPO were subsequently isolated with affinities in the region of 10(9) molar-1. 2 of the Fabs recognised the same, or closely related, epitopes on TPO whereas the third Fab recognised a different epitope. These 2 epitopes were recognised by TPO autoantibodies in the serum of the lymphocyte donor and a series of 10 patient sera. Available sequence data showed that several non-self antibodies and non-thyroid autoantibodies use the same V kappa and VH germline genes as TPO autoantibodies. There appeared to be no clear relationship between gene sequence or gene family usage by TPO autoantibodies of the same or similar epitope specificity.

Structure of the VH and VL segments of polyreactive and monoreactive human natural antibodies to HIV-1 and Escherichia coli beta-galactosidase

B lymphocytes committed to the production of antibodies binding to antigens on pathogenic bacteria and viruses (natural antibodies) are common components of the normal human B cell repertoire. A major proportion of natural antibodies is capable of binding multiple antigens (polyreactive antibodies). Using B cells from three HIV-1 seronegative healthy subjects, and purified HIV-1 and beta-galactosidase from Escherichia coli as selecting antigen, we generated three natural IgM mAb to HIV-1 and a natural IgM mAb to beta-galactosidase. The three HIV-1-selected antibodies (mAb102, mAb103, and mAb104) were polyreactive. They bound with different affinities (Kd = 10(-6) to 10(-8) M) to the HIV-1 envelope gp160, the p24 core protein, and the p66 reverse transcriptase, but not to the 120 glycosylated env protein. They also bound to beta-galactosidase (Kd approximately 10(-7) M), tetanus toxoid, and various various self antigens. In contrast, the natural mAb selected for binding to beta-galactosidase (mAb207.F1) was monoreactive, in that it bound with a high affinity (Kd < 10(-8) M) to this antigen, but to none of the other antigens tested, including HIV-1. Structural analysis of the VH and VL segments revealed that the natural mAb utilized three segments of the VHIV gene family and one of the VHIII family, in conjunction with VL segments of the V lambda I, V lambda II, V lambda III, or V kappa IV subgroups. In addition, the natural mAb VH and VL segments were in unmutated or virtually unmutated (germline) configuration, including those of the monoreactive mAb207.F1 to beta-galactosidase, and were identical or closely related to those utilized by specific autoantibodies or specific antibodies to viral and/or bacterial pathogens. Thus, the present data show that both polyreactive and monoreactive natural antibodies to foreign antigen can be isolated from the normal human B cell repertoire. They also suggest that the VH and VL segments of not only polyreactive but also monoreactive natural antibodies can be encoded in unmutated or minimally mutated genes, and possibly provide the templates for the specific high affinity antibodies elicited by self or foreign antigens.

Cloning and sequencing of human immunoglobulin V lambda gene segments

To provide the building blocks for making synthetic antibody fragments we have used the polymerase chain reaction (PCR) to clone human variable (V) gene segments of lambda light chains. The PCR primers were based on the sequences of known human V lambda segments, and were used to isolate 14 new V lambda segments (including 4 pseudogenes) from a single individual. We have compiled a sequence directory from this data and other sources to include all known human V lambda segments with open reading frames and we have identified a new V lambda family (V lambda IX). Almost all of the segments (22/24) have different sequences in the complementarity-determining regions, setting a lower limit to the structural diversity of the antigen binding sites encoded by human V lambda genes in the human population.

Restricted immunoglobulin VH usage and VDJ combinations in the human response to Haemophilus influenzae type b capsular polysaccharide. Nucleotide sequences of monospecific anti-Haemophilus antibodies and polyspecific antibodies cross-reacting with self antigens

To examine the human antibody repertoire generated against a biologically significant antigen we have obtained sequences of heavy chain variable region genes (IgVH) from 15 monoclonal antibodies specific for the capsular polysaccharide of Haemophilus influenzae type b (Hib PS). All VH segments are members of the VH3 family and 9 of 15 are members of the smaller VH3b subfamily. Restriction is evident by the shared use of certain VDJ joints in independent hybridomas from different subjects. Two hybridomas generated from the same subject demonstrate identical heavy chain variable region gene sequences but differ in isotype and rearrange alternative light chain variable region genes (IgVL), suggesting that in a normal immune response, a single pre-B cell clone may use different light chain rearrangements and give rise to progeny capable of reacting with antigen. Using a polymerase chain reaction assay optimized to detect base pair differences among VH genes we demonstrate that at least a portion of expressed anti-Hib PS VH genes have undergone somatic mutation. Anti-Hib PS heavy chain genes are homologous to VH segments encoding autoantibodies and two hybridomas secrete anti-Hib PS antibody that cross-reacts with self antigens (double-stranded DNA and single-stranded DNA). Comparison of VH regions of self-reactive and monospecific anti-Hib PS Ab demonstrates no consistent structural feature correlating with fine antigen specificity. These data demonstrate significant restriction in VH usage and VDJ recombination in the anti-Hib PS response and confirm that autoantibodies may be elicited during normal immune responses.

Variable region expression in the antibody responses of infants vaccinated with Haemophilus influenzae type b polysaccharide-protein conjugates. Description of a new lambda light chain-associated idiotype and the relation between idiotype expression, avidity, and vaccine formulation. The Collaborative Vaccine Study Group

Haemophilus influenzae b polysaccharide (Hib PS)-protein conjugate vaccines differ chemically and immunologically. To determine whether anti-Hib PS variable region expression might differ according to vaccine formulation, infants were vaccinated at 2, 4, and 6 mo of age with Hib PS coupled to either meningococcal outer membrane protein complex (Hib PS-OMPC) or tetanus toxoid (Hib PS-T), or Hib PS oligomers coupled to a mutant diphtheria toxin (Oligo-CRM). Two anti-Hib PS idiotypes were measured in sera obtained after the third injection: HibId-1, expressed by anti-Hib PS antibodies having the kappa II-A2 variable region, and HibId-2, a newly defined cross-reactive idiotype associated with a subset of anti-Hib PS antibodies having lambda VII variable regions. HibId-1 was present in 33, 68, and 64% of infants given either Hib PS-OMPC, Oligo-CRM, or Hib PS-T, respectively (P < 0.001). The respective values for HibId-2 were 47, 18, and 10% (P = 0.001). Subjects who were vaccinated with Hib PS-OMPC or Hib PS-T and who produced detectable HibId-1-positive antibody, had significantly higher mean antibody avidity than subjects who did not produce HibId-1 positive antibodies. In contrast, Oligo-CRM evoked high avidity anti-Hib PS antibodies, irrespective of the idiotypic profile. These findings indicate fundamental differences in both variable region content and antibody quality elicited by different Hib PS conjugate vaccines.

The alternative binding site for protein A in the Fab fragment of immunoglobulins

Twenty-six new human or murine monoclonal immunoglobulins (IgM, IgA, murine IgG1 or human IgG3) with a known V-region sequence were tested for alternative (non-Fc) binding to Staphylococcal protein A. Seven of them did not bind at all. Four immunoglobulins (all mouse IgG1) were bound but easily eluted (at pH 6). They were probably bound via the Fc part. All eleven were classified as negative for alternative binding. Fifteen immunoglobulins were found to bind more firmly; they came off the protein A column at pH 4-3 (alternative binders). Amino acid sequences of immunoglobulins that have been typed in the present work or earlier (25 binders and 26 non-binders) were compared. The light chain, the C region of the heavy chain and the D and JH segments look irrelevant for alternative binding. The N-terminal portion (amino acids 1-94) of the H chain probably forms the ligand of protein A. A peptide making the ligand cannot be reliably localized within this stretch but binder proteins had a high homology in residues 6-29. All mouse immunoglobulins expressing VH genes of families J606 or S107 were alternative binders; those expressing other families were non-binders.

Sequence analyses of three immunoglobulin G anti-virus antibodies reveal their utilization of autoantibody-related immunoglobulin Vh genes, but not V lambda genes

Accumulated sequence analyses of the antibody repertoire have revealed that most autoantibodies and developmentally regulated antibodies share a small set of germline Ig-variable region (V) genes. The findings have prompted speculation that certain autoantibodies are of developmental importance and may be instrumental in maintaining homeostasis of the adult antibody repertoire. In order to evaluate this hypothesis critically, it is first necessary to determine the V gene usage in human antibodies against foreign substances. Unfortunately, only a few such antibodies have had their heavy and light chains characterized. To rectify the situation, we adapted the anchored polymerase chain reaction to clone and analyze rapidly the expressed V genes for three anti-virus IgG antibodies. The results show that all three heavy chain V (Vh) genes are highly homologous to the known autoantibody-related Vh genes. In contrast, two light chain V (VL) genes of the V lambda 1 subgroup are similar to a non-autoantibody-related germline V lambda 1 gene. Taken together with the reported Vh and VL sequences of several antibodies against viruses and bacteria, the data show that many antipathogen antibodies may use the same small set of Vh genes that encode autoantibodies, but diverse VL genes that are distinct from autoantibody-related VL genes. Thus, only a small portion of the potentially functional germline Vh genes are used recurrently to generate most antibodies in a normal antibody repertoire, regardless of their reactivities with either self or non-self.

The human antibody V region repertoire to the type B capsular polysaccharide of Haemophilus influenzae

The V region repertoire of the human antibody response to the type b capsular polysaccharide of Haemophilus influenzae (Hib-PS) is being defined at the molecular level using antibodies purified from serum of immunized adults. The VH of this response is restricted to the VHIII subgroup while the VL can be divided into two categories. The most common VL, expressed in > 90% of adults and usually constituting the majority of a subjects anti-Hib-PS antibody response, is restricted to the product of a single V kappa II gene known as A2 that probably lacks somatic mutations. The product of the A2 gene is invariably joined to one of several J kappa products by an inserted arginine at the V kappa-J kappa junction. In contrast to the restricted nature of the dominant VL clonotype, the second category of VL constitutes a heterogeneous group of at least seven different VL gene products that often contain somatic mutations and generally exhibit crossreactivity with a related polysaccharide from E. coli. Elucidation of anti-Hib-PS V regions at the molecular level will permit examination of structure-function relationships among these clinically important antibodies and should make the V region repertoire to Hib-PS a useful model for studying human V gene responses.