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A promising therapy for patients with B-cell lymphoma is based on vaccination with idiotype monoclonal antibodies (mAbs). Since idiotypes are different in each tumor, a personalized vaccine has to be produced for each patient. Expression of immunoglobulins with appropriate post-translational modifications for human use often requires the use of stable mammalian cells that can be scaled-up to reach the desired level of production. We have used a noncytopathic self-amplifying RNA vector derived from Semliki Forest virus (ncSFV) to generate BHK cell lines expressing murine follicular lymphoma-derived idiotype A20 mAb. ncSFV/BHK cell lines expressed approximately 2 mg/L/24 h of A20 mAb with proper quaternary structure and a glycosylation pattern similar to that of A20 mAb produced by hybridoma cells. A20 mAb purified from the supernatant of a ncSFV cell line, or from the hybridoma, was conjugated to keyhole limpet hemocyanin and used to immunize Balb/c mice by administration of four weekly doses of 25 µg of mAb. Both idiotype mAbs were able to induce a similar antitumor protection and longer survival compared to non-immunized mice. These results indicate that the ncSFV RNA vector could represent a quick and efficient system to produce patient-specific idiotypes with potential application as lymphoma vaccines.

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Immunoglobulin G can inhibit antibody response. The mechanism of immunosuppression by immunoglobulins remains unknown. Recently, we found a new factor of immunoregulation referred to as regulatory rheumatoid factor (regRF). RegRF prevents autoimmunity and reduces experimental autoimmune reactions. RegRF comprises a population of anti-idiotypic antibodies that have a unique paratope specific to the antigen-binding sites of the antibodies, and a shared paratope specific to neoepitopes of IgG Fc fragments. Given the specificity of regRF, we can anticipate that IgG would be able to induce regRF production, and consequently that the immunosuppressive effect of IgG may be mediated by regRF. We found that IgG induces regRF production in a culture of B lymphocytes obtained from the red bone marrow of intact rats. IgG does not expose neoepitopes recognized by the shared paratope of regRF, and does not acquire them in culture. Therefore, the stimulation of regRF production induced by IgG is not a result of the interaction between the shared paratope of regRF and the neoepitopes of IgG. Fc fragments of IgG are unable to stimulate regRF production. Fab fragments inhibit spontaneous regRF production. F(ab´)2 fragments stimulate regRF production in lymphocyte culture. We theorize that IgG activates regRF-producing lymphocytes through idiotype-anti-idiotype interactions.

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Nimotuzumab is a humanized monoclonal antibody against the Epidermal Growth Factor Receptor with a long history of therapeutic use, recognizing an epitope different from the ones targeted by other antibodies against the same antigen. It is also distinguished by much less toxicity resulting in a better safety profile, which has been attributed to its lower affinity compared to these other antibodies. Nevertheless, the ideal affinity window for optimizing the balance between anti-tumor activity and toxic effects has not been determined. In the current work, the paratope of the phage-displayed nimotuzumab Fab fragment was evolved in vitro to obtain affinity-matured variants. Soft-randomization of heavy chain variable region CDRs and phage selection resulted in mutated variants with improved binding ability. Two recombinant antibodies were constructed using these variable regions, which kept the original fine epitope specificity and showed moderate affinity increases against the target (3-4-fold). Such differences were translated into a greatly enhanced inhibitory capacity upon ligand-induced receptor phosphorylation on tumor cells. The new antibodies, named K4 and K5, are valuable tools to explore the role of affinity in nimotuzumab biological properties, and could be used for applications requiring a fine-tuning of the balance between binding to tumor cells and healthy tissues.

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Barcodes of natural auto-antibody (NAAb) profiles based on staining intensity of isotypes binding numbers of self-(tissue) antigen fragments were suggested as parameters for immune diversity, and related to genetic background and health status in man, rodents and poultry. Here, hens, eggs and hatchlings from chicken lines divergently selected and bred for high (H line) or low (L line) total natural antibodies (NAb) levels in plasma binding keyhole limpet hemocyanin (KLH) at 16 weeks of age were tested for their NAAb repertoire binding chicken liver homogenate (CLH) fragments using quantitative Western immunoblotting. The aims of this study were 1. to detect line differences between the H and L line adult hens, eggs and hatchlings for the IgM and IgG isotypes binding CLH fragments, 2. study the presence of NAAb of both isotypes in yolk and albumen, as well as in hatchlings to detect a maternal NAAb transfer route via the egg to the hatchling, and 3. study whether new self-antigen binding isotypes and idiotypes are present in the hatchling. NAAb binding CLH fragments were found in plasma of adult hens (both IgM and IgG), in yolk (IgG only), and hatchlings (mostly IgG, but low levels of IgM). Auto-profiles of IgM showed homogeneity, while IgG profiles were heterogenic between individual hens and individual hatchlings. Significant higher levels as indicated by staining intensity and number of stained CLH fragments were found in plasma of hens genetically selected for high levels of NAb binding KLH. Lines could be clustered based on their auto-profiles indicating that profiles of self-binding IgM and IgG antibodies are genetically based. Visual comparison, clustering and correlation of hens and their hatchlings showed similarities for the IgG, but not the IgM isotype, indicating maternal transfer of IgG NAAb via the yolk. The IgM profile in the hatchlings on the other hand might represent neonatal self-binding antibody formation. As a consequence, hatchlings initially depend for self-binding antibodies on maternal IgG provision during early life.

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BACKGROUND: Respiratory syncytial virus (RSV) infection causes significant morbidity in hematopoietic cell transplant (HCT) recipients. However, antibody responses that correlate with recovery from RSV disease are not fully understood. METHODS: In this study, antibody repertoire in paired serum and nasal wash samples from acutely RSV-A-infected HCT recipients who recovered early (<14 days of RSV shedding) were compared with late-recovered patients (≥14 days of shedding) using gene fragment phage display libraries and surface plasmon resonance. RESULTS: Anti-F serum responses were similar between these 2 groups for antibody repertoires, neutralization titers, anti-F binding antibodies (prefusion and postfusion proteins), antibody avidity, and binding to specific antigenic sites. In contrast, nasal washes from early-recovered individuals demonstrated higher binding to F peptide containing p27. While the serum RSV G antibody repertoires in the 2 groups were similar, the strongest difference between early-recovered and late-recovered patients was observed in the titers of nasal wash antibodies, especially binding to the central conserved domain. Most importantly, a significantly higher antibody affinity to RSV G was observed in nasal washes from early-recovered individuals compared with late-recovered HCT recipients. CONCLUSIONS: These findings highlight the importance of mucosal antibodies in resolution of RSV-A infection in the upper respiratory tract.

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Broadly neutralizing antibodies (bNAbs) targeting the HIV-1 envelope glycoprotein (Env) have promising utility in prevention and treatment of HIV-1 infection, and several are currently undergoing clinical trials. Due to the high sequence diversity and mutation rate of HIV-1, viral isolates are often resistant to specific bNAbs. Currently, resistant isolates are commonly identified by time-consuming and expensive in vitro neutralization assays. Here, we report machine learning classifiers that accurately predict resistance of HIV-1 isolates to 33 bNAbs. Notably, our classifiers achieved an overall prediction accuracy of 96% for 212 clinical isolates from patients enrolled in four different clinical trials. Moreover, use of gradient boosting machine - a tree-based machine learning method - enabled us to identify critical features, which had high accordance with epitope residues that distinguished between antibody resistance and sensitivity. The availability of an in silico antibody resistance predictor should facilitate informed decisions of antibody usage and sequence-based monitoring of viral escape in clinical settings.

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The promise of idiotype-based therapeutics has been disappointing forcing a new look at the concept and its potential to generate an effective approach for immunotherapy. Here, the idiotype network theory is revisited with regard to the development of efficacious anti-idiotype vaccines. The experience of polyclonal anti-Idiotype reagents in animal models as well as an understanding of the immune response in humans lends to the proposition that polyclonal anti-Idiotype vaccines will be more effective compared to monoclonal-based anti-Idiotype vaccines. This novel strategy can be adapted in Biotech-standard production of therapeutic antibodies.

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An unbalance between Abs that recognize an autoantigen (idiotypes; IDs) and Igs that bind such Abs (anti-IDs) is considered a functional event in autoimmune disorders. We investigated the presence of an ID/anti-ID network in celiac disease (CD), a condition in which antitissue transglutaminase 2 (TG2) Abs are suspected to contribute to CD pathogenesis. To characterize the ID side, we reproduced by in vitro yeast display the intestine-resident Abs from CD and control patients. These TG2-specific IDs were used to identify potential anti-IDs in the serum. We observed elevated titers of anti-IDs in asymptomatic patients with predisposition to CD and demonstrated that anti-ID depletion from the serum restores a detectable humoral response against TG2. Our study provides an alternative approach to quantify CD-related autoantibodies in cases that would be defined "negative serology" with current diagnostic applications. Therefore, we suggest that developments of this technology could be designed for perspective routine tests.

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The mechanisms for dominant T15 idiotype selection are not well understood, yet the significance of idiotypic regulation has been suggested. We proposed that to become dominant V regions of a given subset of B-1a cell must establish a functional idiotypic network with complementary T cells. Features required for the cells involved in immune network and steps preceding the establishment of clonal dominance are suggested.

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Idiotypes (Ids) are unique epitopes of Ab V regions and can trigger anti-Id immune responses, but immunization with several nonadjuvanted isologous IgG mAbs has induced tolerance to their Ids. We immunized non-lupus-prone mice with 11 allotype "a" of IgG2a (IgG2aa) and 4 IgG2c nonadjuvanted, isologous mAbs purified from serum-free medium. Of five IgG2aa mAbs with specificity for nucleosomes, the repeating histone-DNA subunit of chromatin, four elicited an IgG1 anti-mAb response and one mAb was nonimmunogenic. In contrast, none of six IgG2aa mAbs with unknown specificity triggered anti-mAb responses. The data suggested a link between immunogenicity and specificity for nucleosomes. One anti-nucleosome IgG2aa mAb, termed 3F7.A10, copurified with self-histones and was a potent immunogen for BALB/c mice. The response against IgG2aa 3F7.A10 was CD4+ Th cell-dependent, dominated by the IgG1 subclass, and Id specific. Ultracentrifugation converted the purified 3F7.A10 mAb into a weak immunogen, suggesting that the mAb had formed immunogenicity-enhancing immune complexes (ICs) with nucleosomal Ags during cell culture. BALB/c mice injected with viable MHC-incompatible 3F7.A10 hybridoma cells grown in serum-free medium mounted strong anti-Id responses. TLR9-deficient mice responded significantly weaker to Id-3F7.A10 than did TLR9-sufficient mice, suggesting that the cognate BCR efficiently internalizes the Id in an IC with nucleosomes. Passive transfer of IgG2aa 3F7.A10 to BALB/c mice with high titers of IgG1 anti-3F7.A10 led to glomerular deposits of IgG1/IgG2a complexes. The immunogenicity of Id-3F7.A10 raises the possibility that diverse Ids of nucleosome-specific Abs form ICs with nucleosomes released from dying cells and elicit spontaneous formation of anti-Id Abs in vivo.

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As implied by the idiotypic network theory, the interaction between the functional epitope of a microbicidal molecule (X) and its specific cell-wall receptor (RX) on sensitive microorganisms may be imaged by the bond between the idiotype (Id) of a neutralizing monoclonal antibody (anti-X Ab) and its anti-idiotype (anti-Id) X-like Ab (anti-anti-X Ab). Consequently, anti-X Ab Id may mimic RX acting as a vaccine (idiotypic vaccination) for the elicitation of protective anti-Id Abs with antibiotic activity (antibiobodies).

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Does maternal IgG found in placental tissue provide the fetus with more than just humoral immunity? To address this question, the IgGs from twelve placentas were studied and four of these samples were examined using mass spectrometry which revealed an IgG1k idiotype. A special dodecapeptide portion of the 3rd framework region of the VH chain sequence was identified as an idiotypic determinant in these placental- IgG1k (p-IgG1k) and referred to as peptideX2 and found to have biological activity. Antiserum to peptideX2 was made and then used with Western Immunoblotting to show that this unique H chain (containing peptideX2) appears to be present in all p-IgG tested and in all subjects tested. It appears that the placenta contains not only conventional polyclonal maternal IgGs but also an idiotypic population of maternal IgG1k which binds to TLR2>TLR4 via the epitope "peptideX2″ and promotes IL-6, TNFα, and IL-10 production and may play a role in maternal-fetal tolerance.

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The clonal B-cell immunoglobulin idiotype found on the surface of lymphomas was the first targeted tumor-specific antigen, and combinations of idiotype with classical and novel adjuvants were shown to stimulate robust humoral and cellular responses, though clinical efficacy was more variable. Cellular and in situ vaccination to help target a wider array of tumor-specific antigens have also been able to stimulate tumor-specific cellular responses, though their clinical success has also been limited. Our growing understanding of the role of regulatory cells and the immunosuppressive tumor microenvironment, along with a wide variety of immunomodulatory agents developed as of late, offer promising adjuvants to potentiate the immune responses elicited by these vaccine protocols and to achieve durable remissions.

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Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are two severe autoimmune bullous diseases of the mucosae and/or skin associated with autoantibodies directed against desmoglein (Dsg) 3 and/or Dsg1. These two desmosomal cadherins, typifying stratified epithelia, are components of cell adhesion complexes called desmosomes and represent extra-desmosomal adhesion receptors. We herein review the advances in our understanding of the immune response underlying pemphigus, including human leucocyte antigen (HLA) class II-associated genetic susceptibility, characteristics of pathogenic anti-Dsg antibodies, antigenic mapping studies as well as findings about Dsg-specific B and T cells. The pathogenicity of anti-Dsg autoantibodies has been convincingly demonstrated. Disease activity and clinical phenotype correlate with anti-Dsg antibody titers and profile while passive transfer of anti-Dsg IgG from pemphigus patients' results in pemphigus-like lesions in neonatal and adult mice. Finally, adoptive transfer of splenocytes from Dsg3-knockout mice immunized with murine Dsg3 into immunodeficient mice phenotypically recapitulates PV. Although the exact pathogenic mechanisms leading to blister formation have not been fully elucidated, intracellular signaling following antibody binding has been found to be necessary for inducing cell-cell dissociation, at least for PV. These new insights not only highlight the key role of Dsgs in maintenance of tissue homeostasis but are expected to progressively change pemphigus management, paving the way for novel targeted immunologic and pharmacologic therapies.

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Anti-idiotype antibodies against a therapeutic antibody are key reagents for the development of immunogenicity and pharmacokinetic (PK) assays during pre-clinical and clinical development. Here we have used a combination of phage and ribosome display to isolate a panel of monoclonal anti-idiotype antibodies with sub-nanomolar affinity and high specificity to a human anti-IgE monoclonal antibody. Anti-idiotype antibodies were enriched from scFv libraries using phage display, and a biochemical epitope competition assay was used to identify anti-idiotypes which neutralized IgE binding, which was essential for the intended use of the anti-idiotypes as positive controls in neutralizing anti-drug antibody (Nab) assays. The phage display-derived anti-idiotype antibodies were rapidly affinity-matured using a random point mutagenesis approach in ribosome display. Ten anti-idiotype antibodies with improved neutralizing activity relative to the parent antibodies displayed sub-nanomolar affinity for the anti-IgE antibody, representing up to 20-fold improvements in affinity from just two rounds of affinity-based selection. The optimized anti-idiotype antibodies retained the specificity of the parent antibodies, and importantly, were fit for purpose for use in PK and anti-drug antibody (ADA) assays. The approach we describe here for generation of anti-idiotype antibodies to an anti-IgE antibody is generically applicable for the rapid isolation and affinity maturation of anti-idiotype antibodies to any antibody-based drug candidate.

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BACKGROUND: The pre-symptomatic stage of Rheumatoid arthritis (RA) is associated with pro-inflammatory cytokines and autoantibodies. High levels and epitope spread by Rheumatoid factors (RhF) and autoantibodies to citrullinated proteins signify progression towards disease expression. In established RA, the persistence of high autoantibody levels reflects production by both long-lived plasma cells and short-lived plasmablasts. Neither the relative contributions to pathogenesis by autoantibodies from either source, nor the factors responsible for deciding the fate of autoantigen specific 'parent' B-cells, is understood. Phenotypic markers identifying subsets of autoreactive B-cells are therefore of interest in understanding the origin and perpetuation of the autoimmune response in RA. One such phenotypic marker is the rat monoclonal antibody, 9G4, which recognises an idiotope on immunoglobuins derived from the inherently autoreactive VH-gene, VH4-34. We therefore investigated whether the 9G4 idiotope was expressed on autoantibodies in patients with RA. METHODOLOGY/PRINCIPAL FINDINGS: Sera from 19 patients with established RA and those with <1year history of untreated polyarthritis either resolving into RA (n = 42) or non-RA diagnosis (n = 31) were included. Autoantibodies to cyclic citrullinated peptides (CCP), RhF and co-expression of the 9G4 idiotope were measured by ELISA. 9G4 recognised a population of anti-CCP antibodies in the majority of sera from patients with established disease and also in samples from patients with early disaese. 9G4+RhF levels were generally lower and not associated with positivity for, or levels of 9G4+CCP. CONCLUSIONS/SIGNIFICANCE: The persistence of 9G4+ immunoglobulins, of any isotype, in serum is rare. We describe here the novel finding of 9G4 expression on anti-CCP antibodies in patients from the earliest symptoms of RA through to established disease. Our results suggest that 9G4 expression on anti-CCP autoantibodies was not due to polyclonal expansion of VH4-34-encoded immunoglobulins. These studies may therefore provide a new focus for investigation into the evolution of the autoimmune response in RA patients.

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The introduction of rituximab for B cell lymphoma in the late 1990s inaugurated a new era of cancer therapy showcasing mAbs. mAbs are in principle an amalgamation of two characteristics of a perfect anticancer drug. First, rituximab is a therapy targeted to the tumor cell, but it carries fewer side effects than does chemotherapy. Second, with its ability to directly engage the host immune system, it could potentially elicit longer lasting anticancer immunity, although this remains to be proven. This review highlights the fundamental scientific discoveries that allowed the development of clinically successful anti-CD20 mAbs. Since the approval of rituximab, a considerable amount of work has been undertaken by different groups trying to understand the workings and limitations of anti-CD20s. All of these efforts will be critical in designing new mAbs to CD20 and other targets and, ultimately, of anticancer mAbs that will improve on, or even replace, chemotherapy.

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