VH Families Research Articles

Analysis of SIVmac Envelope-Specific Antibodies Selected Through Phage Display.

We have constructed a single chain fragment variable (scFv) phage display library from a simian immunodeficiency virus (SIV)-infected rhesus macaque that developed unusually high-titer neutralizing antibody responses against tier-3, neutralization-resistant SIVmac239. The library was screened using trimeric (gp140) and monomeric (gp120) forms of the SIVmac239 envelope (Env) glycoprotein. We also cloned variable-heavy and variable-light (VH-VL) antibody fragments from seven previously described rhesus macaque B-cell lines (BLCLs) that produce SIV gp120-specific monoclonal antibodies (mAbs). Thirty-two gp140-specific mAbs were selected along with 20 gp120-specific ones. gp120-specific mAbs were only from the VH4 family, while gp41-specific mAbs were primarily from VH1, followed by VH4 and VH3. Rhesus macaque BLCL-derived mAbs belonged primarily to the VH4 family of antibodies followed by VH3 and a smaller number of VH1s. A preferential VH combination with Vλ light chain was observed with phage display-selected SIV Env-specific mAbs (gp120 and gp140), but not with BLCL-derived antibodies or the unpanned library. None of the tested antibodies had detectable neutralizing activity against tier-3 SIVmac239. The majority of gp120-specifc mAbs potently neutralized tier-1 SIVmac316 with 50% inhibitory concentration (IC50) values below 1 μg/ml. For gp140-specific antibodies, which were all specific for the gp41-subunit, 2 out of 11 tested neutralized SIVmac316 (IC50 of 7 and 5 μg/ml, respectively). These data suggest an order of preferential VH segment usage for SIV-specific antibodies in rhesus macaques. These antibodies will be useful in assessing the contribution of non-neutralizing antibodies to inhibition of SIV infection in vitro and in vivo.

Multiple Antibody Lineages in One Donor Target the Glycan-V3 Supersite of the HIV-1 Envelope Glycoprotein and Display a Preference for Quaternary Binding.

Broadly neutralizing antibodies targeting the HIV-1 glycan-V3 region with single lineages from individual donors have been described previously. Here we describe three lineages from a single donor, each of which targets glycan-V3. Unlike previously described glycan-V3 antibodies, these mature antibodies bind preferentially to the native Env trimer and weakly to the gp120 monomer. These data extend our knowledge of the immune response recognition of the N332 supersite region and suggest that the mode of epitope recognition is more complex than previously anticipated.

P-D7 Structural mimicry of the antigen binding modes of rhesus macaque and human anti-gp120 V3 antibodies

Background: Nonhuman primates (NHPs), such as rhesus macaques, are currently the best preclinical models for studying HIV vaccines. The details of how NHP Abs can mimic human Abs will be useful in evaluating NHP Ab responses to HIV vaccine candidates. The extensive knowledge of the antigen binding modes of anti-V3 Abs allows a structural comparison of NHP and human Ab binding modes. Methods: We have crystallized and determined the epitope complex structures of rhesus macaque anti-V3 monoclonal Abs (mAbs) 2.10A (encoded by a VH5 family gene and derived from an animal infected with SHIV SF162P4) and P2A10 and P2E3 (encoded by VH3 family genes and from an animal infected with SHIV SF162P3N). These structures were compared to the Ab-epitope interactions of human anti-V3 mAbs encoded by the equivalent human genes. Results: Human anti-V3 mAbs preferentially use VH5, VH1 and VH3 family genes with the antigen binding sites resembling either a cradle or ladle, respectively, as previously described. Similarly, rhesus macaque mAb 2.10A utilizes the cradle-binding mode while mAbs P2A10 and P2E3 use the ladle-binding mode. Additionally, the amino acids encoded by both human and macaque VH3 and VH5 family germline genes are critical for shaping the antigen binding sites. Thus, key elements in the antigen-Ab interactions are preserved between human and rhesus macaque mAbs. Conclusions: The antigen binding modes of human and rhesus macaque mAbs targeting HIV-1 gp120 V3 epitopes were found to be structurally extremely similar at the atomic level.

Molecular Characterization of Murine Monoclonal Antibody Variable Regions Specific for Hepatitis B Surface Antigen.

Hepatitis B virus (HBV) surface antigen (HBsAg) induces a vigorous neutralizing antibody response, which causes effective protection against HBV infection. Little is known about the profile of variable region genes of immunoglobuline heavy (VH) and light (VL) chains rearranged in anti-HBs antibodies, and also the possible association of this profile with specificity pattern of these antibodies to mutant forms of HBsAg. The present study determined the nucleotide sequence of VH and VL genes of mouse monoclonal antibodies (MAbs) generated against HBsAg. Hybridoma clones secreting anti-HBsAg MAbs were developed from hyperimmunized Balb/c mice. VH and VL gene sequences of all MAbs were determined by amplifying the genes using a panel of VH and VL family specific primers by reverse transcription polymerase chain reaction. The reactivity pattern of anti-HBs MAbs with different mutant forms of HBsAg was evaluated by enzyme-linked immunosorbent assay, and then the profile of antigen specificity and its association to VH/VL family expression was analyzed. Twenty-three murine hybridomas producing anti-HBs MAbs were generated. Nucleotide sequence analysis revealed that heavy chains of these MAbs were encoded by IGHV genes from the HV1 (52%), HV6 (22%), HV5 (17%), and HV3 (9%) families in combination with IGHJ2 (57%), HJ1 (26%), and HJ4 (17%). Besides, 56% of MAbs used IGHD1 genes in their VDJ rearrangements. Concerning the IGKV gene, 26% and 22% of clones used KV4 and KV10 gene families, while the rest of the clones used KV8, KV6, KV1, KV12, and KV14 gene families. Besides, the IGKJ2 gene was the most represented KJ gene (43%). No association was found between the specificity pattern of MAbs to mutant forms of HBsAg with their preferential V, D, and J genes usage for most of MAbs. The data suggest that heavy chains of anti-HBs MAbs preferentially use genes derived from the IGHV1, IGHV6, IGHJ2, and IGHD1 families. In contrast to heavy chains, which predominantly use four families of IGHV genes, light chains use more diverse IGKV gene families.

98: Determination of VH Family Usage in B-Cell Malignancies via the IgH PCR Clonality Assay

The immunoglobulin heavy chain (IgH) component of antibodies contains a variable region composed of variable (VH), diversity (D) and joining (JH) gene segments. The combinatorial rearrangement of these gene segments enables immune cells to produce a huge variety of antibodies. The human VH gene segments comprise seven families: VH1-VH7. Several types of B cell malignancies exhibit preferential VH family usage. For example, pediatric acute lymphoblastic leukemia frequently uses the …

A comprehensive analysis of immunoglobulin heavy chain genes in the Bactrian camel (Camelus bactrianus)

Heavy chain only antibodies (HCAbs) repre- sent a rare type of antibody that is devoid of light chains and the CH1 domain that have been reported in cartilaginous fish and camelids. By analyzing transcript data and genome sequences, we conducted a comprehen- sive analysis of Bactrian camel immunoglobulin heavy chain genes. Based on the transcript data, one μ gene, five γ genes, one α gene and one e gene were found. Additionally, the variable region of HCAbs (VHH) and the conventional antibodies (VH) sequences associated with the γ3, γ1a/b and μ genes were amplified. Based on these genome sequences, seven DH, six JH, μ, γ2a, γ2c, α, and e genes and a portion of a γ3 gene were observed. Different Kozak sequences within different VH families were found in our analysis, and the variability index differed between the VHH3 and VH3 families. Phyloge- netic analysis of the constant regions of the camelid immunoglobulin genes indicates that these genes appeared before the evolutionary divergence of Bactrian camels and dromedaries.

Postranslationally Modified Proteins in the Central Nervous System (CNS) Are the Dominant Antigenic Target/Stimulus of the B-Cell Receptor (BCR) in Primary CNS Lymphomas (PCNSL) Providing Strong Evidence for the Role of Chronic Autoantigenic Stimulation As an Early Step in the Pathogenesis of Aggressive B-Cell Lymphomas

Background: Sequence analyses of variable immunoglobulin gene fragments of PCNSL from immunocompetent patients have shown a VH4-34 restriction raising speculations on a selection/stimulation of a functional BCR by an autoantigen in the central nervous system. The present study focused on the search for these hypothetic autoantigens presumably driving the malignant transformation of B-cells into PCNSL cells by chronic BCR stimulation in immunocompetent patients.Methods: BCRs were expressed as recombinant Fabs based on corresponding pairs of functional variable region heavy and light chain genes, which had been amplified from isolated genomic DNA of snap-frozen lymphoma specimens and checked for binding to proteins expressed on macroarrays of human cDNA expression libraries.Results: Recombinant BCR expression was attempted in 21 and successful in twelve PCNSL cases. The VH4-34 family was overrepresented, but was found in less than a quarter of the PCNSL patients (4/21). Screening of the recombinant BCRs on protein arrays revealed that 8 of 12 recombinant PCNSL-BCRs reacted with SAMD14 and the SAM domain of neurabin-1, two proteins with high homology and preferential expression in the CNS. Subsequent proteomic analysis of cryoconserved lymphoma specimens showed that SAMD14 and the SAM domain of neurabin-1 were alternatively N-glycosylated in patients with a PCNSL-BCR specific for SAMD14 and neurabin-1, but not in the remaining PCNSL patients with BCR specificities other than for SAMD14/neurabin-1. Compared to SAMD14 and neurabin-1 from healthy controls, Asn 339 of SAMD14 and Asn 1277 of neurabin-1 were shown to carry additionally glycosylated Asn residues. Of interest, both additional glycosylation sites belonged to atypical, non-canonical Asn-Leu-Glu-Gln (N-L-E-Q) sites instead of the Asn-X-Ser/Thre consensus sequence (N-X-S/T; where X can be any amino acid except proline), which is reported to constitute 97% of N-glycosylation sites under physiologic circumstances. These atypical N-hyperglycosylations were shown for every case with sufficient biopsy material for this proteomic analysis and a PCNSL-BCR specific for SAMD14 and neurabin-1 in their PCNSL and CNS, and to a lesser degree in their peripheral blood mononuclear cells and patient-derived EBV-transformed lymphoblastoid cell lines (LCLs). Of the recombinant BCRs of all cases with sufficient material to test for hyperglycosylation, only the BCRs of the 6 cases with hyperglycosylated SAMD14/neurabin-1 reacted against SAMD14/neurabin-1. Of note, glycosylation status of 2/8 cases with recombinant SAMD14/neurabin-1 reactive BCRs could not be analyzed due to insufficient cryomaterial left after variable region gene PCRs. No hyperglycosylation of SAMD14 and neurabin-1 was found in the peripheral blood of 400 healthy controls, 100 newborns and 50 nursery residents. Moreover, antibodies against SAMD14 and neurabin-1 were detected in the sera and cerebrospinal fluids of an independent second cohort of patients with PCNSL (8/22), but not in sera of patients with secondary CNS manifestations of systemic DLBCL (0/17) or of healthy controls (0/92).Conclusion: Our results strongly suggest that the atypical (NLEQ) glycosylation of the highly homologous SAMD14 and the SAM domain of neurabin-1 maintains a chronic autoimmunogenic stimulation in the CNS, ultimately leading to the malignant transformation of B-cells with a BCR specific for these atypically N-hyperglycosylated proteins into an aggressive B-cell lymphoma in the CNS in a majority of patients with PCNSL. The fact that the VH4-34 family represents only a minority of VH families recognizing SAMD14/neurabin-1 underlines the extraordinary autoimmunogenicity of these posttranslationally modified proteins in a broad range of individuals. Our results provide the first and strongest experimental evidence for the role of chronic autoantigenic stimulation as a first step in the pathogenesis of aggressive B-cell lymphomas.Supported by Deutsche Forschungsgemeinschaft DFG, Deutsche José Carreras Leukämie Stiftung, Wilhelm-Sander-Stiftung, Deutsche Krebshilfe e.V. DisclosuresNo relevant conflicts of interest to declare.

Directed evolution of human heavy chain variable domain (VH) using in vivo protein fitness filter.

Human immunoglobulin heavy chain variable domains (VH) are promising scaffolds for antigen binding. However, VH is an unstable and aggregation-prone protein, hindering its use for therapeutic purposes. To evolve the VH domain, we performed in vivo protein solubility selection that linked antibiotic resistance to the protein folding quality control mechanism of the twin-arginine translocation pathway of E. coli. After screening a human germ-line VH library, 95% of the VH proteins obtained were identified as VH3 family members; one VH protein, MG2x1, stood out among separate clones expressing individual VH variants. With further screening of combinatorial framework mutation library of MG2x1, we found a consistent bias toward substitution with tryptophan at the position of 50 and 58 in VH. Comparison of the crystal structures of the VH variants revealed that those substitutions with bulky side chain amino acids filled the cavity in the VH interface between heavy and light chains of the Fab arrangement along with the increased number of hydrogen bonds, decreased solvation energy, and increased negative charge. Accordingly, the engineered VH acquires an increased level of thermodynamic stability, reversible folding, and soluble expression. The library built with the VH variant as a scaffold was qualified as most of VH clones selected randomly were expressed as soluble form in E. coli regardless length of the combinatorial CDR. Furthermore, a non-aggregation feature of the selected VH conferred a free of humoral response in mice, even when administered together with adjuvant. As a result, this selection provides an alternative directed evolution pathway for unstable proteins, which are distinct from conventional methods based on the phage display.

Diversity of the murine antibody response targeting influenza A(H1N1pdm09) hemagglutinin

We infected mice with the 2009 influenza A pandemic virus (H1N1pdm09), boosted with an inactivated vaccine, and cloned immunoglobulins (Igs) from HA-specific B cells. Based on the redundancy in germline gene utilization, we inferred that between 72–130 unique IgH VDJ and 35 different IgL VJ combinations comprised the anti-HA recall response. The IgH VH1 and IgL VK14 variable gene families were employed most frequently. A representative panel of antibodies were cloned and expressed to confirm reactivity with H1N1pdm09 HA. The majority of the recombinant antibodies were of high avidity and capable of inhibiting H1N1pdm09 hemagglutination. Three of these antibodies were subtype-specific cross-reactive, binding to the HA of A/South Carolina/1/1918(H1N1), and one further reacted with A/swine/Iowa/15/1930(H1N1). These results help to define the genetic diversity of the influenza anti-HA antibody repertoire profile induced following infection and vaccination, which may facilitate the development of influenza vaccines that are more protective and broadly neutralizing.Importance: Protection against influenza viruses is mediated mainly by antibodies, and in most cases this antibody response is narrow, only providing protection against closely related viruses. In spite of this limited range of protection, recent findings indicate that individuals immune to one influenza virus may contain antibodies (generally a minority of the overall response) that are more broadly reactive. These findings have raised the possibility that influenza vaccines could induce a more broadly protective response, reducing the need for frequent vaccine strain changes. However, interpretation of these observations is hampered by the lack of quantitative characterization of the antibody repertoire. In this study, we used single-cell cloning of influenza HA-specific B cells to assess the diversity and nature of the antibody response to influenza hemagglutinin in mice. Our findings help to put bounds on the diversity of the anti-hemagglutinin antibody response, as well as characterizing the cross-reactivity, affinity, and molecular nature of the antibody response.

Clonal heterogeneity of thymic B cells from early-onset myasthenia gravis patients with antibodies against the acetylcholine receptor

Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR–MG) is considered as a prototypic autoimmune disease. The thymus is important in the pathophysiology of the disease since thymus hyperplasia is a characteristic of early-onset AChR–MG and patients often improve after thymectomy. We hypothesized that thymic B cell and antibody repertoires of AChR–MG patients differ intrinsically from those of control individuals. Using immortalization with Epstein–Barr Virus and Toll-like receptor 9 activation, we isolated and characterized monoclonal B cell lines from 5 MG patients and 8 controls. Only 2 of 570 immortalized B cell clones from MG patients produced antibodies against the AChR (both clones were from the same patient), suggesting that AChR-specific B cells are not enriched in the thymus. Surprisingly, many B cell lines from both AChR–MG and control thymus samples displayed reactivity against striated muscle proteins. Striational antibodies were produced by 15% of B cell clones from AChR–MG versus 6% in control thymus. The IgVH gene sequence analysis showed remarkable similarities, concerning VH family gene distribution, mutation frequency and CDR3 composition, between B cells of AChR–MG patients and controls. MG patients showed clear evidence of clonal B cell expansion in contrast to controls. In this latter aspect, MG resembles multiple sclerosis and clinically isolated syndrome, but differs from systemic lupus erythematosus.Our results support an antigen driven immune response in the MG thymus, but the paucity of AChR-specific B cells, in combination with the observed polyclonal expansions suggest a more diverse immune response than expected.

Decreased Mutation Frequencies among Immunoglobulin G Variable Region Genes during Viremic HIV-1 Infection

Background/objectiveHIV-1 infection is complicated by high rates of opportunistic infections against which specific antibodies contribute to immune defense. Antibody function depends on somatic hypermutation (SHM) of variable regions of immunoglobulin heavy chain genes (VH-D-J). We characterized the frequency of SHM in expressed IgG mRNA immunoglobulin transcripts from control and HIV-1-infected patients.DesignWe compared utilization of genes in the most prominent VH family (VH3) and mutation frequencies and patterns of cDNA from VH3-IgG genes from 10 seronegative control subjects and 21 patients with HIV-1 infection (6 without and 15 patients with detectable plasma viremia).MethodsUnique IgG VH3 family cDNA sequences (n = 1,565) were PCR amplified, cloned, and sequenced from blood. Sequences were analyzed using online (Vbase) and in-house immunoglobulin alignment resources.ResultsMutation frequencies in the antigen-binding hypervariable complementarity determining regions (CDR1/2) of IgG class-switched B cells were lower among viremic HIV-1-infected patients vs. controls for nucleotides (CDR1/2: 10±5% vs. 13.5±6%, p = 0.03) and amino acids (CDR: 20%±10 vs. 25%±12, p = 0.02) and in structural framework regions. Mutation patterns were similar among groups. The most common VH3 gene, VH3-23, was utilized less frequently among viremic HIV-1-infected patients (p = 0.03), and overall, mutation frequencies were decreased in nearly all VH3 genes compared with controls.ConclusionsB cells from HIV-1-infected patients show decreased mutation frequencies, especially in antigen-binding VH3 CDR genes, and selective defects in gene utilization. Similar mutation patterns suggest defects in the quantity, but not quality, of mutator activity. Lower levels of SHM in IgG class-switched B cells from HIV-1-infected patients may contribute to the increased risk of opportunistic infections and impaired humoral responses to preventative vaccines.

Development of the expressed immunoglobulin &Mgr; chain repertoire during maturation of mice B cells

In the bone marrow and spleen, the developing B cell populations undergo both negative and positive selections to shape their B cell receptor repertoire. To gain insight into the shift of the immunoglobulin heavy (IgH) chain repertoire during B cell development, we undertook large scale Ig μ chain repertoire analysis of pre-B, immature B and spleen B cell populations. We found that the majority of VH gene segments, VH families, JH and D gene segments, were observed to have significantly different usage frequencies when three B cell populations were compared, but the usage profile of the VH, D, and JH genes between different B cell populations showed high correlations. In both productive and nonproductive rearrangements, the length of CDRH3 shortened signifi- cantly on average when B cells entered the periphery. However, the CDRH3 length distribution of nonproductive rearrangements did not follow a Gaussian distribution, but decreased successively in the order 3n-2, 3n-1 and 3n, suggesting a direct correlation between mRNA stability and CDRH3 length patterns of nonproductive rearrange- ments. Further analysis of the individual components comprising CDRH3 of productive rearrangements indi- cated that the decrease in CDRH3 length was largely due to the reduction of N addition at the 5' and 3' junctions. Moreover, with development, the amino acid content of CDRH3 progressed toward fewer positively charged and nonpolar residues but more polar residues. All these data indicated that the expressed Ig μ chain repertoire, especially the repertoire of CDRH3, was fine-tuned when B cells passed through several checkpoints of selection during the process of maturation.

Clonotypic Analysis Of Immunoglobulin Heavy Chain (IgH) Sequences In Patients With Waldenström's Macroglobulinemia. Correlation With MYD88 L265P Somatic Mutation Status, Clinical Features and Outcome

Background and aimWaldenström's Macroglobulinemia (WM) cells express a unique clonotypic rearrangement of heavy chain immunoglobulin (IgH) genes in each individual patient. Recent studies demonstrate high frequency of the MYD88 L265P somatic mutation in patients with WM, implying a new pathway for the pathogenesis of this disease. In this study we characterized clonal IgH genes rearrangements, IGHV gene use, somatic hypemutations (SHM) and presence of the ΜΥD88 L265P mutation in a cohort of WM patients and we investigated any eventual correlation with patients' clinical features. Patients and methods36 patients with WM were studied (median age 64y, 19 males and 17 females, symptomatic 72%, asymptomatic 28%) of whom 45%, 39% and 16% were stage IPSSWM 1, 2 and 3, respectively. Median time to treatment initiation was 13 months and median overall survival was 61 months. DNA was extracted from patients' bone marrow/blood samples and clonal IgH VDJ rearrangements were amplified by PCR using the Biomed-2 Concerted Action protocol. Monoclonal VDJ rearranged PCR fragments were sequenced and analyzed using the IMGT database (www.imgt.org). Thirty-one patients' DNA samples were also analyzed for the presence of the ΜΥD88 L265P mutation by using a mutation specific PCR assay. ResultsThe most frequent clonal rearrangements observed in our patients were in the IGVH3 family (73% of cases); the IGVH3-23 gene and the IGVH3-74 gene were used in 24.4% and 18,9% of cases, respectively. Somatic hypermutation (>2%) was seen in all but three cases (92%). Mean percentage of mutations in all cases, IGVH3 family, IGVH3-23 and IGVH3-74 genes was 7,5%, 8%, 9,4% and 7,5%, respectively. Sixty-two percent of the patients were positive for the ΜΥD88 L265P mutation and notably all three unmutated WM cases were negative for this MYD88 point mutation. No correlation between VH or DH gene usage, CDR3 length, and mutational status with clinical parameters, time to treatment initiation, or survival was found. ConclusionsWM IgH genes repertoire, as expected, differs from that observed in normal B-cells and other B-cell diseases such as MZL, MCL and B-CLL/SLL. In addition to the known hyper-representation of the IGVH3-23 gene, another member of the VH3 family, the IGVH3-74 gene is also over-represented in WM. The high IGVH mutation rate supports a derivation of WM cells from postgerminal center memory B cells in the majority (92%) of WM patients. However, the identification of a minority of WM patients (3 of 36) with unmutated IGHV gene segments, negative for the ΜΥD88 L265P mutation, supports the hypothesis that they represent a subgroup of WM not arising from post-germinal B cells with a different disease pathogenesis. Disclosures:No relevant conflicts of interest to declare.

Deep sequencing and Circos analyses of antibody libraries reveal antigen-driven selection of Ig VH genes during HIV-1 infection

The vast diversity of antibody repertoires is largely attributed to heavy chain (VH) recombination of variable (V), diversity (D) and joining (J) gene segments. We used 454 sequencing information of the variable domains of the antibody heavy chain repertoires from neonates, normal adults and an HIV-1-infected individual, to analyze, with Circos software, the VDJ pairing patterns at birth, adulthood and a time-dependent response to HIV-1 infection. Our comparative analyses of the Ig VDJ repertoires from these libraries indicated that, from birth to adulthood, VDJ recombination patterns remain the same with some slight changes, whereas some VH families are selected and preferentially expressed after long-term infection with HIV-1. We also demonstrated that the immune system responds to HIV-1 chronic infection by selectively expanding certain HV families in an attempt to combat infection. Our findings may have implications for understanding immune responses in pathology as well as for development of new therapeutics and vaccines.

Phenotypic analysis of B cell subsets in HLA*B44 positive identical twins discordant for common variable immunodeficiency and recurrent sino-pulmonary infection (P3331)

Abstract Depressed serum immunoglobulin levels (sIgs) and recurrent sinopulmonary infections mark Common Variable Immune Deficiency (CVID). Many family members of CVID patients also suffer recurrent sinopulmonary infection (RESPI) but have normal sIg. We identified HLAB44 positive identical female twins who suffer sinopulmonary infections and are discordant for CVID and RESPI. Flow cytometry subsets showed equivalent numbers of immature B cells (BC) in both twins, but lower numbers of transitional and mature BC in the CVID twin. Deep sequencing of the immunoglobulin (Ig) repertoires expressed by the transitional and mature BC showed a significant divergence in the utilization of VH1 and VH4 family gene segments, with CVID favoring VH4 and RESPI VH1. RESPI twin used JH6 more frequently, whereas CVID twin used JH3. The amino acid composition of CDR-H3 repertoire was compared with a control; the twin and control tyrosine usage in transitional BC was similar (~15%) but greatly diverged in mature BC (control 15%, RESPI 25%, CVID < 10%). Whole genome sequencing revealed homozygosity for a rare CD21 S639N polymorphism and heterozygosity for CD19 L174V. These findings suggest that in addition to an acquired block in BC development at the transitional stage, the CVID twin produces an Ig repertoire that is markedly depleted of tyrosine. This may explain why the function of the Ig repertoire in CVID is more impaired than what might be expected by sIgs levels.

Molecular characterization of immunoglobulin (Ig) genes reveals that plasmablasts generated during heterologous secondary dengue infections and circulating memory B cells after recovery are of distinct origin

Event Abstract Back to Event Molecular characterization of immunoglobulin (Ig) genes reveals that plasmablasts generated during heterologous secondary dengue infections and circulating memory B cells after recovery are of distinct origin Ramapraba Appanna1, Xu Mei Hui1, Toh Ying Xiu1, Thavamalar Balakrishnan1, Srinivasan Kandhadayar Gopalan1, Francesca Zolezzi1, Michael Poidinger1, Leo Yee Sin2, Wang Cheng-I1 and Katja Fink1* 1 Singapore Immunology Network, Singapore 2 Tan Tock Seng Hospital, Department of Infectious Diseases, Singapore Memory B cells generated after exposure to dengue viral (DENV) infection are a central component in shaping immune memory. However, re-exposure to dengue virus of a different serotype is often associated with an increased disease pathogenesis. During repeated infection, the rapid activation of memory B cells leads to the generation of massive amounts of cross-reactive antibodies. In the acute phase of a secondary infection, this B cell memory pool probably outcompetes the newly generated virus specific B cells. To characterize the specificity of plasmablasts and memory B cells generated during and after acute infection, we performed single cell RT-PCR for sequence analysis of Ig variable regions. Surprisingly, we found that memory B cells isolated one month after disease were of different genetic composition than acute phase plasmablasts. Our data reveal preferential usage of the Ig heavy chain variable region gene VH1 in DENV binding plasmablasts. In contrast, VH3 family repertoires were noted in specific long lasting circulating memory cells isolated over a month after infection. The antibodies isolated from these memory B cells had a broad reactivity, with only 30% being specific to DENV envelope (E) protein, whereas 70-80% plasmablasts were specific to E protein. Whether VH gene usage differs in primary and secondary infected patients and reflects a specific antigen/epitope selection is currently under investigation. This study can help to understand immune mechanism of protection for potential application in vaccination. Keywords: Dengue, memory B cell, plasmablast, immunoglobulin, repertoire Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Host-pathogen interactions Citation: Appanna R, Mei Hui X, Ying Xiu T, Balakrishnan T, Kandhadayar Gopalan S, Zolezzi F, Poidinger M, Yee Sin L, Cheng-I W and Fink K (2013). Molecular characterization of immunoglobulin (Ig) genes reveals that plasmablasts generated during heterologous secondary dengue infections and circulating memory B cells after recovery are of distinct origin. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00905 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Jun 2013; Published Online: 22 Aug 2013. * Correspondence: Dr. Katja Fink, Singapore Immunology Network, SINGAPORE, Singapore, katjafink3@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ramapraba Appanna Xu Mei Hui Toh Ying Xiu Thavamalar Balakrishnan Srinivasan Kandhadayar Gopalan Francesca Zolezzi Michael Poidinger Leo Yee Sin Wang Cheng-I Katja Fink Google Ramapraba Appanna Xu Mei Hui Toh Ying Xiu Thavamalar Balakrishnan Srinivasan Kandhadayar Gopalan Francesca Zolezzi Michael Poidinger Leo Yee Sin Wang Cheng-I Katja Fink Google Scholar Ramapraba Appanna Xu Mei Hui Toh Ying Xiu Thavamalar Balakrishnan Srinivasan Kandhadayar Gopalan Francesca Zolezzi Michael Poidinger Leo Yee Sin Wang Cheng-I Katja Fink PubMed Ramapraba Appanna Xu Mei Hui Toh Ying Xiu Thavamalar Balakrishnan Srinivasan Kandhadayar Gopalan Francesca Zolezzi Michael Poidinger Leo Yee Sin Wang Cheng-I Katja Fink Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Antibody-dependent cellular cytotoxicity-mediating antibodies from an HIV-1 vaccine efficacy trial preferentially use the VH1 gene family

Background The ALVAC-HIV/AIDSVAX-B/E RV144 vaccine efficacy trial showed an estimated efficacy of 31%. The immune correlates analysis raised the hypothesis that the observed protection in RV144 may be partially due to AntibodyDependent Cellular Cytotoxicity (ADCC)-mediating antibodies in the presence of low levels of Env IgA antibodies. In this study we analyzed the Ig VH family usage of vaccine-induced ADCC mAbs isolated from memory B cells of vaccinees. Methods From a total of 321,945 memory B-cells of 6 vaccinees we obtained 23 mAbs that mediated ADCC using IgG+ memory B-cell cultures (n=9) and Env-specific flow cytometric single memory B-cell sorting (n=14). ADCC activity was measured using both E.CM243 gp120-coated and E. CM235-infected target cells in a flow-based assay. Results ADCC-mediating mAbs displayed a disproportionate usage of VH1 family genes (17/23; 74%), in particular the VH1-2 gene segment (10/17; 59%), as recently observed for CD4bs broadly neutralizing antibodies (HAAD bNAbs). In contrast, only 17.1% of 111 heavy chains isolated from cultures that did not mediate ADCC used the VH1 gene. VH1 ADCC-mediating mAbs showed a high degree of V(D)J amino acid similarity to both the VH (68-84%) and VL (70-87%) HAAD motifs. V(D)J rearrangements displayed modest levels of affinity maturation (0.5-5.1% for heavy chains and 0.4-4.3% for light chains). While none of the VH1 ADCC-mediating mAbs was capable of mediating HIV-1 neutralization, the strength of their ADCC activity correlated with the levels of heavy chain somatic mutations (p=0.02). We produced the reverted unmutated ancestor antibodies of two VH1 ADCC-mediating mAbs: one bound to B.MN Env and both reacted against autoantigens. Conclusion ADCC-mediating antibodies induced by the ALVAC-HIV/ AIDSVAX-B/E vaccine underwent limited affinity maturation, and preferentially used VH1 gene segments which share the HAAD motif with CD4bs bNAbs. These observations raise the hypothesis that HIV-1 Env preferentially selects VH1 family usage for distinct subsets of antibodies with different functions.

Antibody-Dependent Cellular Cytotoxicity-Mediating Antibodies from an HIV-1 Vaccine Efficacy Trial Target Multiple Epitopes and Preferentially Use the VH1 Gene Family

The ALVAC-HIV/AIDSVAX-B/E RV144 vaccine trial showed an estimated efficacy of 31%. RV144 secondary immune correlate analysis demonstrated that the combination of low plasma anti-HIV-1 Env IgA antibodies and high levels of antibody-dependent cellular cytotoxicity (ADCC) inversely correlate with infection risk. One hypothesis is that the observed protection in RV144 is partially due to ADCC-mediating antibodies. We found that the majority (73 to 90%) of a representative group of vaccinees displayed plasma ADCC activity, usually (96.2%) blocked by competition with the C1 region-specific A32 Fab fragment. Using memory B-cell cultures and antigen-specific B-cell sorting, we isolated 23 ADCC-mediating nonclonally related antibodies from 6 vaccine recipients. These antibodies targeted A32-blockable conformational epitopes (n = 19), a non-A32-blockable conformational epitope (n = 1), and the gp120 Env variable loops (n = 3). Fourteen antibodies mediated cross-clade target cell killing. ADCC-mediating antibodies displayed modest levels of V-heavy (VH) chain somatic mutation (0.5 to 1.5%) and also displayed a disproportionate usage of VH1 family genes (74%), a phenomenon recently described for CD4-binding site broadly neutralizing antibodies (bNAbs). Maximal ADCC activity of VH1 antibodies correlated with mutation frequency. The polyclonality and low mutation frequency of these VH1 antibodies reveal fundamental differences in the regulation and maturation of these ADCC-mediating responses compared to VH1 bNAbs.

Different Pattern of Immunoglobulin Gene Usage by HIV-1 Compared to Non-HIV-1 Antibodies Derived from the Same Infected Subject

A biased usage of immunoglobulin (Ig) genes is observed in human anti-HIV-1 monoclonal antibodies (mAbs) resulting probably from compensation to reduced usage of the VH3 family genes, while the other alternative suggests that this bias usage is due to antigen requirements. If the antigen structure is responsible for the preferential usage of particular Ig genes, it may have certain implications for HIV vaccine development by the targeting of particular Ig gene-encoded B cell receptors to induce neutralizing anti-HIV-1 antibodies. To address this issue, we have produced HIV-1 specific and non-HIV-1 mAbs from an infected individual and analyzed the Ig gene usage. Green-fluorescence labeled virus-like particles (VLP) expressing HIV-1 envelope (Env) proteins of JRFL and BaL and control VLPs (without Env) were used to select single B cells for the production of 68 recombinant mAbs. Ten of these mAbs were HIV-1 Env specific with neutralizing activity against V3 and the CD4 binding site, as well as non-neutralizing mAbs to gp41. The remaining 58 mAbs were non-HIV-1 Env mAbs with undefined specificities. Analysis revealed that biased usage of Ig genes was restricted only to anti-HIV-1 but not to non-HIV-1 mAbs. The VH1 family genes were dominantly used, followed by VH3, VH4, and VH5 among anti-HIV-1 mAbs, while non-HIV-1 specific mAbs preferentially used VH3 family genes, followed by VH4, VH1 and VH5 families in a pattern identical to Abs derived from healthy individuals. This observation suggests that the biased usage of Ig genes by anti-HIV-1 mAbs is driven by structural requirements of the virus antigens rather than by compensation to any depletion of VH3 B cells due to autoreactive mechanisms, according to the gp120 superantigen hypothesis.

Molecular characterization of antigen-specific B1 and B2 B-cells populations in Cryptococcus neoformans infection in mice (43.1)

Abstract We examined B1 and B2 B-cell repertoires in Cryptococcus neoformans infection in mice. Flow-cytometry based antigen-specific staining for B-cell populations generated in response to pulmonary infection was performed using labeled un-encapsulated and encapsulated C. neoformans strains. FACS sorting and single-cell nested PCR was employed to characterize the IgH repertoire. An increase in total peritoneal B1a, B1b and B2 cell numbers was observed as early as day 3 post-infection. Frequencies of both acapsular and capsular antigen-specific cells were increased in the B1a subpopulation (18%, 5%) in infected compared to naïve mice (11%, 2%). The heavy chains of antigen-specific B2 and B1b cells recognizing acapsular and capsular cryptococcus belonged predominantly to the VH1 family. Interestingly, increased VH11 (22%) and VH12 (33%) usage was observed in antigen-specific B1a cells recognizing acapsular and encapsulated cryptococcus, respectively, compared to the conventional B1a population. Although all acapsular (VH11+) and capsular (VH12+) B1a cells used the same VH11.2.53 and VH12.1.78 genes, 60% and 80% rearrangements were unique, respectively. VH genes in both cases were essentially germline, however 40% of acapsular specific B1a cells had 4 or more N-nucleotide additions compared to capsular specific B1a cells (20%). These results indicate that naturally occurring phosphatidyl choline reactive B1a cells have broad specificities and can bind to encapsulated cryptococcus.