Anti-idiotypic DNA vaccines for lymphoma immunotherapy require the presence of both variable region genes for tumor protection

Idiotypes as immunogens: facing the challenge of inducing strong therapeutic immune responses against the variable region of immunoglobulins

Idiotype (Id)-based immunotherapy has been exploited as cancer treatment option. Conceived as therapy for malignancies bearing idiotypic antigens, it has been also extended to solid tumors because of the capacity of anti-idiotypic antibodies to mimic Id-unrelated antigens. In both these two settings, efforts are being made to overcome the poor immune responsiveness often experienced when using self immunoglobulins as immunogens. Despite bearing a unique gene combination, and thus particular epitopes, it is normally difficult to stimulate the immune response against antibody variable regions. Different strategies are currently used to strengthen Id immunogenicity, such as concomitant use of immune-stimulating molecules, design of Id-containing immunogenic recombinant proteins, specific targeting of relevant immune cells, and genetic immunization. This review focuses on the role of anti-Id vaccination in cancer management and on the current developments used to foster anti-idiotypic B and T cell responses.

Genetic immunization with CDR3-based fusion vaccine confers protection and long-term tumor-free survival in a mouse model of lymphoma

Therapeutic vaccination against idiotype is a promising strategy for immunotherapy of B-cell malignancies. We have previously shown that CDR3-based DNA immunization can induce immune response against lymphoma and explored this strategy to provide protection in a murine B-cell lymphoma model. Here we performed vaccination employing as immunogen a naked DNA fusion product. The DNA vaccine was generated following fusion of a sequence derived from tetanus toxin fragment C to the V_HCDR3_109−116 epitope. Induction of tumor-specific immunity as well as ability to inhibit growth of the aggressive 38C13 lymphoma and to prolong survival of vaccinated mice has been tested. We determined that DNA fusion vaccine induced immune response, elicited a strong protective antitumor immunity, and ensured almost complete long-term tumor-free survival of vaccinated mice. Our results show that CDR3-based DNA fusion vaccines hold promise for vaccination against lymphoma.

Current advances, problems and prospects for vaccine-based immunotherapy in follicular non-Hodgkin's lymphoma

Despite advances in chemotherapy, radiotherapy and combined modality treatment, a significant proportion of non-Hodgkin's lymphomas remain incurable. The disease usually responds well to chemotherapy or radiation, but relapses are observed within months to a few years, with frequent failure of subsequent therapies. High-dose chemotherapy with or without radiation and autologous or allogeneic hematopoietic stem cell transplantation provide higher cure rates and longer remissions in certain patients with aggressive lymphomas. However, the higher treatment-related morbidity and mortality of high-dose chemotherapy has driven a search for new and more tumor-specific treatment modalities, such as immunotherapy. Tumor antigens expressed by B-cell lymphomas, such as the "idiotype antigen", are seen as unique and specific target molecules for direct lymphoma immunotherapy. This review will delineate advances, problems and prospects for approaches to anti-B cell lymphoma immunotherapy where pre-clinical studies and proof of principle have been directly translated to patient care.

Developing idiotype vaccines for lymphoma: from preclinical studies to phase III clinical trials

Therapeutic vaccines for B-cell non-Hodgkin lymphoma (NHL) using the clonal tumour immunoglobulin idiotype (Id) have been under development for more than three decades. A major obstacle for rapid progress in the field has been that the Id vaccine is patient-specific and required the generation of a custom-made product. The manufacturing issues were recently overcome by advances in hybridoma and recombinant DNA technology which facilitated the completion of several phase I and II clinical trials. The strong immunogenicity and apparent clinical benefit observed on the early phase studies led to the initiation of three randomized phase III clinical trials that are also nearing completion. This review will focus on the development of Id vaccines before and after the introduction of rituximab for the treatment of B-cell NHL and also discuss potential strategies to enhance the efficacy of active immunotherapy in the future.

Construction of miniantibodies for the in vivo study of human autoimmune diseases in animal models

Background

Phage display antibody libraries have been made from the lymphocytes of patients suffering from autoimmune diseases in which the antibodies are known to play a role in the pathogenesis or are important for the diagnosis of the disease. In the case of Celiac Disease, the immune response is directed against the autoantigen tissue transglutaminase. However, despite numerous studies, the role of these antibodies in the pathogenesis of this disease has not been elucidated.

Results

We were able to engineer specific anti-transglutaminase antibody fragments in the form called "miniantibody". These are produced by genetic fusion of anti-tTG scFv to Human, Mouse or Rat Fc domains, making them suitable for in vivo expression. The results obtained here indicate that the miniantibody molecule is efficiently secreted, and that the reactivity to the antigen is retained even after fusion to heterologous Fc domains. Further analysis demonstrate that the molecule is secreted as homodimeric, mimicking original antibody structure. Finally, the in vivo expression in mice leads to detectable serum levels with no apparent gross immune response by the host.

Conclusion

In this work we demonstrated the usefulness of a method for the in vivo expression of miniantibodies specific to transglutaminase, corresponding to the autoimmune specificity of Celiac Disease. This can be proposed as a general method to study the pathogenic role of autoimmune antibodies in autoimmune diseases.

Anti-idiotype antibodies in cancer treatment

As a cancer immunotherapy tool, idiotypes (Ids) have been used in different ways over the last three decades, depending on the actual human tumor cell target. It all started with passive, monoclonal, anti-Id antibody treatment of B-cell lymphoma, a setting in which results were tantalizing, but logistics unsustainable. It then moved toward the development of anti-Id vaccines for the treatment of the same tumors, a setting in which we have recently provided the first formal proof of principle of clinical benefit associated with the use of a human cancer vaccine. Meanwhile, it also expanded in the direction of exploiting the antigenic mimicry of some Ids with Id-unrelated, tumor-associated antigens for the immunotherapy of a number of solid tumors, a setting in which clinical results are still far from being consolidated. All in all, over the years Id-based immunotherapy has paved the way for a number of seminal therapeutic improvements for cancer patients, including the development of most if not all Id-unrelated monoclonal antibodies that have recently revolutionized the field.

Immunization of mice with DNA coding for the variable regions of anti-idiotypic antibody generates antigen-specific response

Understanding the mechanisms of generation and maintenance of immunological memory is crucial for rational vaccine design. A hypothesis known as relay hypothesis was earlier proposed which explains the maintenance of immunological memory through interaction of idiotypic and anti-idiotypic lymphocytes. In the present study, we have shown that immunization with rinderpest virus hemagglutinin protein specific anti-idiotypic antibody (Ab(2)v(beta)) DNAs coding for heavy and light chains generates antigen-specific antibody and T cell responses as well as Ab1 specific T cell response. We further show that boosting with the recombinant Ab(2)-vbeta proteins generates B and T cell memory response specific for antigen in anti-id DNA primed mice. This study provides experimental evidence for perpetuation of immunological memory through idiotypic network interactions.

The extracellular membrane-proximal domain of human membrane IgE controls apoptotic signaling of the B cell receptor in the mature B cell line A20

Ag engagement of BCR in mature B cells can deliver specific signals, which decide cell survival or cell death. Circulating membrane IgE+ (mIgE+) cells are found in extremely low numbers. We hypothesized that engagement of an epsilonBCR in a mature isotype-switched B cell could induce apoptosis. We studied the role of the extracellular membrane-proximal domain (EMPD) of human mIgE upon BCR engagement with anti-Id Abs. Using mutants lacking the EMPD, we show that this domain is involved in controlling Ca2+ mobilization in immunoreceptors of both gamma and epsilon isotypes, as well as apoptosis in signaling originated only from the epsilonBCR. We mapped to the epsilonCH4 ectodomain the region responsible for apoptosis in EMPD-deleted receptors. Ca2+ mobilization was not related to apoptotic signaling. This apoptotic pathway was caspase independent, involved ERK1/2 phosphorylation and was partially rescued by CD40 costimulation. We therefore conclude that the EMPD of human mIgE is a key control element of apoptotic signaling delivered through engagement of epsilonBCR within the context of a mature B cell.

Current status of therapeutic vaccines for non-Hodgkin's lymphoma

PURPOSE OF REVIEW

Therapeutic vaccines targeting B cell lymphoma idiotype have reached an advanced stage of clinical development, with three multicenter randomized clinical trials ongoing. This review describes the rationale and development of this immunotherapeutic approach, the design of current phase III trials, and other active vaccination approaches likely to move forward into clinical testing for lymphomas.

RECENT FINDINGS

Several groups have achieved promising results in phase II trials of patient-specific idiotype vaccines, with very few side effects noted. Anti-idiotype antibodies, in addition to cytotoxic T cells, are now believed to be important effectors of antitumor immunity after idiotype vaccination. The manufacturing of autologous tumor idiotype proteins is being rapidly refined by the use of molecular technologies. Two trials involving more than 1000 patients are now under way, which use idiotype vaccination after induction chemotherapy; one trial completed accrual in early 2004. A third trial opened in 2004, using rituximab followed by idiotype vaccine with maintenance booster vaccines continuing throughout the period of normal B cell recovery. In accordance with the United States Food and Drug Administration, progression-free survival serves as the accepted primary efficacy endpoint in these studies.

SUMMARY

Lymphoma idiotype vaccination represents a promising immunotherapeutic approach targeting a patient-specific tumor antigen. The results of pivotal phase III trials for three first-generation idiotype vaccines will become available in the next several years. Advanced manufacturing techniques should permit application of this tailor-made treatment to large numbers of non-Hodgkin's lymphoma patients.

Electroporation as a "prime/boost" strategy for naked DNA vaccination against a tumor antigen

We have developed novel DNA fusion vaccines encoding tumor Ags fused to pathogen-derived sequences. This strategy activates linked T cell help and, using fragment C of tetanus toxin, amplification of anti-tumor Ab, CD4(+), and CD8(+) T cell responses is achievable in mice. However, there is concern that simple DNA vaccine injection may produce inadequate responses in larger humans. To overcome this, we tested electroporation as a method to increase the transfection efficiency and immune responses by these tumor vaccines in vivo in mice. Using a DNA vaccine expressing the CTL epitope AH1 from colon carcinoma CT26, we confirmed that effective priming and tumor protection in mice are highly dependent on vaccine dose and volume. However, suboptimal vaccination was rendered effective by electroporation, priming higher levels of AH1-specific CD8(+) T cells able to protect mice from tumor growth. Electroporation during priming with our optimal vaccination protocol did not improve CD8(+) T cell responses. In contrast, electroporation during boosting strikingly improved vaccine performance. The prime/boost strategy was also effective if electroporation was used at both priming and boosting. For Ab induction, DNA vaccination is generally less effective than protein. However, prime/boost with naked DNA followed by electroporation dramatically increased Ab levels. Thus, the priming qualities of DNA fusion vaccines, integrated with the improved Ag expression offered by electroporation, can be combined in a novel homologous prime/boost approach, to generate superior antitumor immune responses. Therefore, boosting may not require viral vectors, but simply a physical change in delivery, facilitating application to the cancer clinic.

BCL1 lymphoma protection induced by idiotype DNA vaccination is entirely dependent on anti-idiotypic antibodies

DNA vaccination with the idiotype (Id) of tumour B-cell membrane immunoglobulins (Ig) is a validated strategy to induce tumour protection to several mouse lymphomas. The relative contribution of anti-Id antibodies and T lymphocytes to tumour rejection is still debated. Previous studies in the BCL1 lymphoma model showed that scFv DNA immunisation induces a polyclonal antibody response restricted to conformational epitopes formed by the parental V(L)/V(H) association. We implemented a system based on this specificity to investigate the mechanism of BCL1 lymphoma protection induced by DNA immunisation. Antibody response and survival of mice immunised with the tumour Id scFv were compared with those of mice immunised simultaneously with two chimeric scFvs, containing either the tumour-derived V(L) or V(H) paired to an irrelevant V(H) or V(L) domain, respectively. Animals vaccinated with one or both chimeric constructs were not protected, despite the exposure to all putative tumour Id-derived MHC class I and class II T-cell epitopes. In addition, conformational antibodies induced by DNA vaccination caused tumour cells apoptosis and cell cycle arrest in vitro and transferred protection in vivo. Therefore, lymphoma rejection appears to be completely dependent on the induction of anti-Id antibodies.

DNA vaccination against tumors

DNA vaccines have been used to generate protective immunity against tumors in a variety of experimental models. The favorite target antigens have been those that are frequently expressed by human tumors, such as carcinoembryonic antigen (CEA), ErbB2/neu, and melanoma-associated antigens. DNA vaccines have the advantage of being simple to construct, produce and deliver. They can activate all arms of the immune system, and allow substantial flexibility in modifying the type of immune response generated through codelivery of cytokine genes. DNA vaccines can be applied by intramuscular, dermal/epidermal, oral, respiratory and other routes, and pose relatively few safety concerns. Compared to other nucleic acid vectors, they are usually devoid of viral or bacterial antigens and can be designed to deliver only the target tumor antigen(s). This is likely to be important when priming a response against weak tumor antigens. DNA vaccines have been more effective in rodents than in larger mammals or humans. However, a large number of methods that might be applied clinically have been shown to ameliorate these vaccines. This includes in vivo electroporation, and/or inclusion of various immunostimulatory molecules, xenoantigens (or their epitopes), antigen-cytokine fusion genes, agents that improve antigen uptake or presentation, and molecules that activate innate immunity mechanisms. In addition, CpG motifs carried by plasmids can overcome the negative effects of regulatory T cells. There have been few studies in humans, but recent clinical trials suggest that plasmid/virus, or plasmid/antigen-adjuvant, prime-boost strategies generate strong immune responses, and confirm the usefulness of plasmid-based vaccination.

Use of adenoviruses encoding CD40L or IL-2 against B cell lymphoma

Some B cell lymphomas lack important costimulatory properties that could prevent them from being used as cell based vaccines. Infection of A20 B lymphoma cells with a replication-defective adenovirus encoding murine (m) CD40L, but not mIL-2, produces an antigen presentation phenotype with upregulation of MHC Class I/II, induction of B7-1/2 molecules and production of MIL-12 and MIP-1alpha. Subcutaneous vaccination with irradiated Ad-mCD40L-infected- or Ad-mIL-2-infected-A20 cells generated A20-specific CD8+ T cell responses and cross reactive A20 Ig antibodies. Only vaccination with Ad-mCD40L-infected A20 cells produced a significant delay in tumor growth and long-term survival (p = 0.0039). Stronger protective immunity to A20 challenge was generated by intravenous priming with A20 cells infected with Ad-mCD40L, Ad-mIL-2 or their combination followed by a boost immunization with A20 cells activated with syngeneic fibroblasts expressing CD40L. Compared to Ad-LacZ-infected A20 priming, the combination priming was most effective followed by Ad-mCD40L and Ad-mIL-2 (p = 0.0027, p = 0.0027, p = 0.0163 respectively). Significant A20-specific CD8+ T cell-mediated cytotoxicity was only demonstrated in splenocytes from these groups of vaccinated animals. By contrast, ELISPOT assay of splenocytes from all A20 prime/boosted vaccinated groups demonstrated increases in gamma-interferon release by T cells elicited by in vitro stimulation either with A20 cells or another syngeneic 2PK-3 lymphoma, indicating the presence of cross reactive immunity. Similarly anti-A20 immunoglobulin antibodies generated after vaccination were not necessarily A20 idiotype-specific. Direct therapy of pre-established tumors was achieved with the combination of Ad-mCD40L and Ad-mIL-2 given at Days 4 and 8 at the tumor site with a significant long-term survival of 85% of tumor-bearing mice (p = 0.0001). Our study strongly supports the use of Ad-CD40L and Ad-IL-2 combination therapy for the treatment of patients with B cell lymphoma.

Enhancement of antibody responses in DNA vaccination using a vector encoding a universal T-helper cell epitope

DNA vaccination appears as a very promising approach to raise protective antibodies against a variety of proteins from pathogens or tumor cells, but is often hindered by the low immunogenicity of the genetic vectors used for the immunizations. To enhance the humoral response through improvement of the antigenic presentation of newly synthesized proteins upon vaccination, we engineered a plasmid coding for a low immunogenic protein (an scFv, i.e. the single-chain Fragment variable of a well-characterized antibody) fused to a small-size universal T-helper cell epitope derived from tetanus toxin, whose efficiency in classical protein-based immunization protocols has already been demonstrated. We found that immunization of C57Bl/6 mice using this vector greatly enhanced the production not only of specific antibodies recognizing essentially conformational epitopes on the undenatured scFv protein but also of antibodies against linear epitopes on the denatured protein. Since this T-epitope is known to be accommodated by several haplotypes of H-2 molecules in mice, as well as by various class II MHC molecules in humans, the results reported here allow us to conclude that this method could be of general interest for future applications of genetic immunization, including DNA-based vaccinations in humans.

Vaccine and antibody-directed T cell tumour immunotherapy

Clearer evidence for immune surveillance in malignancy and the identification of many new tumour-associated antigens (TAAs) have driven novel vaccine and antibody-targeted responses for therapy in cancer. The exploitation of active immunisation may be particularly favourable for TAA where tolerance is incomplete but passive immunisation may offer an additional strategy where the immune repertoire is affected by either tolerance or immune suppression. This review will consider how to utilise both active and passive types of therapy delivered by T cells in the context of the failure of tumour-specific immunity by presenting cancer patients. This article will outline the progress, problems and prospects of several different vaccine and antibody-targeted approaches for immunotherapy of cancer where proof of principle pre-clinical studies have been or will soon be translated into the clinic. Two examples of vaccination-based therapies where both T cell- and antibody-mediated anti-tumour responses are likely to be relevant and two examples of oncofoetal antigen-specific antibody-directed T cell therapies are described in the following sections: (1) therapeutic vaccination against human papillomavirus (HPV) antigens in cervical neoplasia; (2) B cell lymphoma vaccines including against immunoglobulin idiotype; (3) oncofoetal antigens as tumour targets for redirecting T cells with antibody strategies.

Active immunotherapy in follicular lymphoma

The antigen receptors expressed by follicular lymphomas represent tumor-specific antigens ("idiotypes"). In murine models, vaccination with tumor-derived idiotype in a variety of formulations can induce protective lymphoma-specific immunity. Phase II clinical trials in follicular lymphoma have also demonstrated idiotype-specific immune responses. Clinical data from these trials indicate sustained progression-free survival, disappearance of minimal residual disease, and even frank lymphoma regression in some cases. Phase III trials to prove the beneficial effects of active immunotherapy are currently being conducted. Additional research efforts focus on the most efficacious vaccination route and on the development of convenient methods to manufacture individual idiotype vaccines.

Efficient Folding of the FcεRI α-chain Membrane-proximal Domain D2 Depends on the Presence of the N-terminal Domain D1

Human high affinity receptor for IgE is a membrane glycoprotein multichain complex presenting two extracellular Ig modules in its alpha-chain (D1D2). The receptor IgE binding region is located within the membrane-proximal module D2, while the N-terminal module D1 appears to promote an optimal receptor conformation for IgE binding. To understand the structural relationship between the two modules, we dissected FcepsilonRI alpha-chain into its discrete Ig units and expressed them in mammalian cells. Unexpectedly, D2 was secreted as a disulphide-linked dimer, while D1 was monomeric. Active secretion and full glycosylation of dimeric D2 suggest a native-like conformation of the protein, justifying the escape from the endoplasmic reticulum/Golgi quality control systems. We then propose a domain-swapping model for D2, in which two interdigitated polypeptide chains assume the overall conformation of two Ig modules, as observed for rat CD2 N-terminal domain. Fusion of an unrelated Ig fold moiety at the N terminus of D2 did not interfere with its dimerisation. While D1D2 assumes a correct fold, co-expression of both isolated domains in the same cell did not restore monomeric folding of D2. Thus, D1 appears to assist the appropriate folding of FcepsilonRI alpha-chain, acting as an uncleavable intramolecular chaperone-like block towards D2.

Induction of a systemic immune response by a polyvalent melanoma-associated antigen DNA vaccine for prevention and treatment of malignant melanoma

Studies have demonstrated that active-specific immunotherapy has potential for controlling melanoma progression. We developed a polyvalent melanoma gene vaccine using a plasmid vector to deliver the immunogenic human melanoma-associated antigens (MAAs) gp100 and TRP-2. The MAA-containing plasmids were delivered individually in vivo using the hemagglutinating virus Japan (HVJ)-anionic liposome delivery system. C57BL/6 mice were immunized weekly by intramuscular (i.m.) injection or intranasal (i.n.) inoculation for 3 weeks. Although both i.m. and i.n. immunization induced Th1 (T helper) and Th2 cell responses to gp100 and TRP2, the i.m. route induced a better Th1 response. MAA-specific IgG2a, IgG1, and delayed-type hypersensitivity (DTH) responses were induced against both MAAs by i.m. immunization. We assessed the vaccine for its prophylactic and therapeutic effect against the murine B16 F10 melanoma. Animals vaccinated and subsequently challenged with a lethal dose of B16 cells were significantly (P<0.01) protected against tumor progression and had significantly (P<0.01) enhanced survival compared with treatment using control plasmid. We also developed a therapeutic model in which mice were given B16 cells and subsequently immunized with the vaccine or treated with control plasmid. In animals treated with the vaccine, tumor growth was significantly (P<0.01) controlled, and survival was prolonged compared with controls. These studies demonstrate that the polyvalent DNA vaccine induces an effective systemic Th response.

DNA fusion vaccines against B-cell tumors

DNA vaccination is currently being explored as a potential strategy for combatting cancer. However, tumor antigens are often weak and the immune system of patients may be compromised. For B-cell tumors, immunoglobulin idiotypic antigens provide defined targets but are poorly immunogenic. Fusion of a sequence derived from tetanus toxin to the genes encoding idiotypic determinants has proved highly effective in activating protective anti-tumor immunity. DNA fusion vaccines containing immuno-enhancing sequences can augment and direct immune attack on a range of target antigens. Gene-based fusion vaccines offer ease of manipulation and flexible design to activate effective attack on cancer.

Anti-idiotypic antibodies induced by genetic immunisation are directed exclusively against combined V(L)/V(H) determinants

DNA vaccines encoding the idiotype of immunoglobulins of tumour B cells were shown to induce protection in several mouse lymphoma models. The mechanism of rejection of tumour cells has not been fully understood, but there is strong evidence suggesting that engagement of the idiotype by anti-idiotypic antibodies may directly result in inhibition of tumour growth. In this study, we have investigated the structural basis of the idiotypic/anti-idiotypic interaction following immunisation with DNA vaccines. scFvs containing only one of the two tumour-derived V regions recombined to an irrelevant V region partner were generated. These constructs encoding a secretory form of the scFv were used as immunogens to induce anti-Id antibodies. The same scFvs were expressed as membrane-bound molecules on the surface of mammalian cells. Analysis of immune sera on the membrane-displayed idiotypes revealed that DNA immunisation induced a polyclonal antibody response restricted to conformational combined epitopes formed by the parental V(L)/V(H) association. Immune sera raised by scFv DNA vaccination did not show any detectable reactivity towards chimeric scFvs containing only one of the two immunising V regions, indicating that the response against combined V(L)/V(H)determinants is highly dominant. Remarkably, the same immunogen, delivered as scFv protein, induced antibodies also directed against chain-specific determinants. These findings indicate that presentation of properly folded idiotypes results in a highly specific antibody response directed exclusively to private idiotypic determinants of the V(L)/V(H) combination of the immunogen.