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

Secretion of dengue virus envelope protein ectodomain from mammalian cells is dependent on domain II serotype and affects the immune response upon DNA vaccination

Dengue virus (DENV) is currently among the most important human pathogens and affects millions of people throughout the tropical and subtropical regions of the world. Although it has been a World Health Organization priority for several years, there is still no efficient vaccine available to prevent infection. The envelope glycoprotein (E), exposed on the surface on infective viral particles, is the main target of neutralizing antibodies. For this reason it has been used as the antigen of choice for vaccine development efforts. Here we show a detailed analysis of factors involved in the expression, secretion and folding of E ectodomain from all four DENV serotypes in mammalian cells, and how this affects their ability to induce neutralizing antibody responses in DNA-vaccinated mice. Proper folding of E domain II (DII) is essential for efficient E ectodomain secretion, with DIII playing a significant role in stabilizing soluble dimers. We also show that the level of protein secreted from transfected cells determines the strength and efficiency of antibody responses in the context of DNA vaccination and should be considered a pivotal feature for the development of E-based DNA vaccines against DENV.

Dengue E Protein Domain III-Based DNA Immunisation Induces Strong Antibody Responses to All Four Viral Serotypes

Dengue virus (DENV) infection is a major emerging disease widely distributed throughout the tropical and subtropical regions of the world affecting several millions of people. Despite constants efforts, no specific treatment or effective vaccine is yet available. Here we show a novel design of a DNA immunisation strategy that resulted in the induction of strong antibody responses with high neutralisation titres in mice against all four viral serotypes. The immunogenic molecule is an engineered version of the domain III (DIII) of the virus E protein fused to the dimerising CH3 domain of the IgG immunoglobulin H chain. The DIII sequences were also codon-optimised for expression in mammalian cells. While DIII alone is very poorly secreted, the codon-optimised fusion protein is rightly expressed, folded and secreted at high levels, thus inducing strong antibody responses. Mice were immunised using gene-gun technology, an efficient way of intradermal delivery of the plasmid DNA, and the vaccine was able to induce neutralising titres against all serotypes. Additionally, all sera showed reactivity to a recombinant DIII version and the recombinant E protein produced and secreted from mammalian cells in a mono-biotinylated form when tested in a conformational ELISA. Sera were also highly reactive to infective viral particles in a virus-capture ELISA and specific for each serotype as revealed by the low cross-reactive and cross-neutralising activities. The serotype specific sera did not induce antibody dependent enhancement of infection (ADE) in non-homologous virus serotypes. A tetravalent immunisation protocol in mice showed induction of neutralising antibodies against all four dengue serotypes as well.

Dengue disease is a mosquito-borne viral infection caused by Dengue virus (DENV), one of the most important human pathogens worldwide. DENV infection produces a systemic disease with a broad symptomatic spectrum ranging from mild febrile illness (Dengue Fever, DF) to severe haemorrhagic manifestations (Dengue Haemorrhagic fever and Dengue Shock Syndrome, DHF and DSS respectively). To date there is no vaccine available to prevent dengue disease. We show here a strategy of immunisation, tested in mice, that elicits a strong immune response against the four different DENV serotypes. The novelties presented in our work open the way to the development of an efficient vaccine accessible to developing countries.

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.

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.

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.

Failure of vaccination with idiotypic protein or DNA, (+/-IL-2), the depletion of regulatory T cells, or the blockade of CTLA-4 to prolong dormancy in mice with BCL1 lymphoma

Immunization of mice with the idiotype (Id) immunoglobulin from the murine B cell lymphoma, BCL1, before inoculating tumor cells can induce tumor dormancy. In this model, the tumor cells grow for a short period of time and then regress. The mice live for months or years with approximately 1 million tumor cells in their spleens. Some mice relapse due to decreases in the anti-Id antibody titers or the development of mutations in the residual tumor cells which render them refractory to negative signaling by the anti-Id antibody. In this study we determined whether we could eliminate the residual dormant cells by using a DNA vaccine against the Id or by immunomodulation of T-cell subsets in vivo. Our results demonstrate that dormancy can be maintained by further immunizations with either the BCL1 Id protein or DNA vaccine encoding its single-chain Fv fragment. We also found that a cytotoxic T-cell response was not induced by either in vivo administration of vaccine alone or by the vaccine plus interleukin-2. In addition the injection of anti-cytotoxic T-lymphocyte-associate antigen did not prolong dormancy. Finally, the in vivo administration of anti-CD25 to deplete regulatory T cells did not prolong dormancy. Dormancy in this model is dependent primarily upon anti-Id antibodies, our results suggest that other strategies to target residual dormant BCL1 cells are warranted. They also suggest that the elimination of dormant tumor may represent a greater challenge than the elimination of primary tumors.

B-cell lymphoma and myeloma protection induced by idiotype vaccination with dendritic cells is mediated entirely by T cells in mice

Immunoglobulin idiotypes (Id) of malignant B cells are tumor-specific antigens that may be targeted for immunotherapy. Id-directed immunotherapy by immunization with autologous Id has been initiated in clinical trials to control residual disease in B-cell lymphoma and multiple myeloma. The effector mechanisms responsible for destruction of B-cell tumors are a controversial issue. The authors show that vaccination with Id-pulsed dendritic cells (DCs) or with soluble Id-KLH in adjuvant induced immune responses that eliminated both B-cell lymphoma and myeloma in tumor-bearing mice; however, the two vaccination regimens resulted in distinct immune responses. Whereas soluble Id plus adjuvant induced high levels of anti-Id antibodies, the Id-pulsed DCs did not induce anti-Id or any antitumor antibodies. Immunization with Id-pulsed DCs induced a significant increase in the frequency of Id-reactive T cells. Depletion studies in DC-vaccinated mice showed that the predominant effector cells responsible for tumor rejection were of the CD8 subset. The finding that DC-based Id vaccines elicit tumor protection, which is entirely based on cell-mediated effector mechanisms, is of particular importance for plasma cell tumors because these tumors do not express Id on the surface and hence do not bind anti-Id antibodies.

Toward Personalized Immunotherapy for Non-Hodgkin Lymphoma

The idiotypic determinants of B-cell lymphomas, formed by cell-specific rearrangement of the immunoglobulin genes, are unique and are therefore a suitable target against which to direct immunotherapy. Recent advances in our understanding of the fundamental mechanisms behind an effective immune response, coupled with advances in genetic engineering techniques, have led to a renewed interest in immunotherapy. Early clinical studies have confirmed the immunogenicity of the idiotypic antigen in patients with lymphoma. This review discusses the different methods of idiotypic vaccination currently under investigation in the clinic, including protein, genetic, and cellular vaccines. Protein vaccines are the most clinically advanced, with phase III trials of idiotypic protein linked to GM-CSF currently underway. DNA vaccines are easier to produce but to date only appear to be weakly immunogenic in man. Dendritic cell vaccines have shown promise but their use may be limited by the complexity of this approach. This review also highlights other approaches not yet in the clinic but that have shown promise in the laboratory, such as viral vaccines and T-cell therapy.