A therapeutic human anti-idiotypic antibody mimics CD55 in three distinct regions

Immunogenicity and prediction of epitopic region of antigen Ag I/II and glucosyltransferase from Streptococcus mutans

The levels of Streptococcus (S.) mutans infections in saliva were evaluated and a comparison for specific antibody levels among children with different levels of S. mutans infection was made. The promising epitopic regions of antigen AgI/II (PAc) and glucosyltransferase (GTF) for potential vaccine targets related to S. mutans adherence were screened. A total of 94 children aged 3-4 years were randomly selected, including 53 caries-negative and 41 caries-positive children. The values of S. mutans and those of salivary total secretory immunoglobulin A (sIgA), anti-PAc and anti-Glucan binding domain (anti-GLU) were compared to determine the correlation among them. It was found the level of s-IgA against specific antigens did not increase with increasing severity of S. mutans infection, and the complete amino acid sequence of PAc and GTFB was analyzed using the DNAStar Protean system for developing specific anti-caries vaccines related to S. mutans adherence. A significantly positive correlation between the amount of S. mutans and children decayed, missing, and filled teeth index was observed. No significant difference was detected in specific sIgA against PAc or GLU between any two groups. No significant correlation was found between such specific sIgA and caries index. A total of 16 peptides from PAc as well as 13 peptides from GTFB were chosen for further investigation. S. mutans colonization contributed to early children caries as an important etiological factor. The level of sIgA against specific antigens did not increase with increasing severity of S. mutans infection in children. The epitopes of PAc and GTF have been screened to develop the peptide-based or protein-based anti-caries vaccines.

The promise of the anti-idiotype concept

A basic tenet of antibody-based immunity is their specificity to antigenic determinates from foreign pathogen products to abnormal cellular components such as in cancer. However, an antibody has the potential to bind to more than one determinate, be it an antigen or another antibody. These observations led to the idiotype network theory (INT) to explain immune regulation, which has wax and waned in enthusiasm over the years. A truer measure of the impact of the INT is in terms of the ideas that now form the mainstay of immunological research and whose roots are spawned from the promise of the anti-idiotype concept. Among the applications of the INT is understanding the structural implications of the antibody-mediated network that has the potential for innovation in terms of rational design of reagents with biological, chemical, and pharmaceutical applications that underlies concepts of reverse immunology which is highlighted herein.

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.

The ability of human bispecific anti-idiotype antibody to elicit humoral and cellular immune responses in mice

Our goal is to compare the immunogenicity and the extent of immunologic reactivity between bispecific and mono anti-idiotype vaccines. We previously obtained two human anti-Id antibody fragments fuse5-G22, fuse5-I50 by phage display technology which were mimics of the antigens from nasopharyngeal carcinoma cell line (HNE2). In this study, we developed and characterized a bispecific anti-Id antibody vaccine G22-I50 and its parent monovalent antibody vaccines G22 and I50. The efficacy of G22-I50, G22, and I50 as tumor vaccines was evaluated in Balb/c mice with three injections of these vaccines adjuvanted with Freund's adjuvant. Mice immunized with G22-I50 exhibited comparable levels of antibody titers and stronger binding inhibition capabilities. Spleen cells from G22-I50-immunized mice gave a significant proliferative response and higher expression level of IFN-gamma and IL-2.These results suggested that bispecific anti-Id antibody vaccine was able to induce more powerful humoral and cell-mediated immune responses, which might make it to be a potential vaccine candidate for the therapy of nasopharyngeal carcinoma.

Antibodies designed as effective cancer vaccines

Antigen/antibody complexes can efficiently target antigen presenting cells to allow stimulation of the cellular immune response. Due to the difficulty of manufacture and their inherent instability complexes have proved inefficient cancer vaccines. However, anti-idiotypic antibodies mimicking antigens have been shown to stimulate both antibody and T cell responses. The latter are due to T cell mimotopes expressed within the complementarity-determining regions (CDRs) of antibodies that are efficiently presented to dendritic cells in vivo. Based on this observation we have designed a DNA vaccine platform called ImmunoBody, where cytotoxic T lymphocyte (CTL) and helper T cell epitopes replace CDR regions within the framework of a human IgG1 antibody. The ImmunoBody expression system has a number of design features which allow for rapid production of a wide range of vaccines. The CDR regions of the heavy and light chain have been engineered to contain unique restriction endonuclease sites, which can be easily opened, and oligonucleotides encoding the T cell epitopes inserted. The variable and constant regions of the ImmunoBody are also flanked by restriction sites, which permit easy exchange of other IgG subtypes. Here we show a range of T cell epitopes can be inserted into the ImmunoBody vector and upon immunization these T cell epitopes are efficiently processed and presented to stimulate high frequency helper and CTL responses capable of anti-tumor activity.

Immunogenicity and efficacy of a DNA vaccine encoding a human anti-idiotype single chain antibody against nasopharyngeal carcinoma

G22, an anti-idiotype single chain antibody screened from human nasopharyngeal carcinoma phage anti-idiotype antibody library, has been already identified by He et al. G22 DNA vaccine was produced by cloning G22 gene and inserting the cloned gene into pcDNA3.1. To investigate the immunogenicity of pcDNA3.1-G22, C57BL/6 mice were immunized with the vaccine, pcDNA3.1 and PBS individually and the antibody response, T cell phenocyte at the 15th, 22th, 29th, 36th day after the last immunity were detected. In the tumor protection experiment, the immunized mice were then challenged with CMT-93-G22 cells or CMT-93-mock cells. The tumor size and the survival time of the animals were compared between these groups. The results showed that DNA vaccine pcDNA3.1-G22 could raise G22-specific humoral and cellular immune responses. Furthermore, pcDNA3.1-G22 could prolong the survival time and lessen the tumor size of the CMT-93-G22-bearing mice but had no protection effect on the mice attacked by CMT-93-mock cells. These results were expected to lay foundation for further studies on the clinical application of pcDNA3.1-G22 DNA vaccine.

Monoclonal antibodies for cancer immunotherapy

Monoclonal antibodies are effective treatments for many malignant diseases. However, the ability of antibodies to initiate tumour-antigen-specific immune responses has received less attention than have other mechanisms of antibody action. We describe the rationale and evidence for the development of antibodies that can stimulate host tumour-antigen-specific immune responses. Such responses can be induced through the induction of antibody-dependent cellular cytotoxicity, promotion of antibody-targeted cross-presentation of tumour antigens, or by triggering of the idiotypic network. Future treatment modifications or combinations might be able to prolong, amplify, and shape these immune responses to increase the clinical benefits of antibody therapy for human cancer.

T-cell responses in osteosarcoma patients vaccinated with an anti-idiotypic antibody, 105AD7, mimicking CD55

We assessed T-cell responses in young osteosarcoma patients vaccinated with 105AD7, 1-6 months after having received chemotherapy. 105AD7 is a human anti-idiotypic antibody mimicking CD55, a glycoprotein that protects from attack by complement and which is overexpressed on osteosarcoma cells. Seven out of 21 investigated patients made a IFN-gamma T-cell response against the vaccine, 105AD7 as assessed by ELISPOT. Cytokine secretion was analysed using Luminex assays and revealed TNF-alpha and GM-CSF responses not only to the vaccine but also towards the native antigen, CD55, in 5 / 14 (36%) of investigated patients. Importantly, the Luminex assay was found to be more sensitive than the more established T-cell assays (ELISPOT and proliferation assay), since responses towards the native antigen were recorded in this assay. Clinical responses and induction of immune responses to both the anti-idiotype and the native CD55 antigen support the use of CD55 as a target in cancer treatment.

A Neoadjuvant/Adjuvant Randomized Trial of Colorectal Cancer Patients Vaccinated with an Anti-Idiotypic Antibody, 105AD7, Mimicking CD55

PURPOSE

To assess the tolerability and effectiveness of 105AD7 vaccination in colorectal cancer patients. 105AD7 is a human anti-idiotypic antibody mimicking CD55, a glycoprotein, which is more than expressed on colorectal cancer cells and protects them from attack by complement.

EXPERIMENTAL DESIGN

Colorectal cancer patients (n = 67) eligible for primary surgery were randomized to receive the anti-idiotypic antibody 105AD7+/-Bacillus Calmette-Guerin/alum or to no treatment (control group). The immunizations were given i.d./i.m. before surgery and continued for a period of 2 years. The patients were monitored in enzyme-linked immunospot (ELISPOT; gamma-IFN), proliferation assay, and Luminex cytokine assays.

RESULTS

No serious adverse events were recorded. Of the 32 investigated immunized patients, 14 (44%) were considered to be responders in the ELISPOT assay. Induced proliferative responses were noted in 17 of 40 (43%) monitored patients. There was no correlation between the ELISPOT and proliferation assays. Luminex analyses revealed tumor necrosis factor-alpha and granulocyte macrophage colony-stimulating factor responses not only to the vaccine but also toward the native antigen CD55 in 9 of 13 (69%) patients.

CONCLUSIONS

Immune responses to vaccination were induced in a majority of monitored patients measured by ELISPOT and proliferation assay. The lack of correlation between the ELISPOT and proliferation assays may reflect the fact that the two methods measure different T-cell responses and highlights the importance of multiple readouts in evaluating a potential cancer vaccine. Responses to both the anti-idiotype and the CD55 antigen were measurable, adding support to the use of CD55 as a target in cancer treatment.

Anti-idiotype antibody induced cellular immunity in mice transgenic for human carcinoembryonic antigen

In the present study, we have analysed the detailed cellular immune mechanisms involved in tumour rejection in carcinoembryonic antigen (CEA) transgenic mice after immunization with dendritic cells (DC) pulsed with an anti-idiotype (Id) antibody, 3H1, which mimics CEA. 3H1-pulsed DC vaccinations resulted in induction of CEA specific cytotoxic T lymphocyte (CTL) responses in vitro and the rejection of CEA-transfected MC-38 murine colon carcinoma cells, C15, in vivo (Saha et al.,Cancer Res 2004; 64: 4995-5003). These CTL mediated major histocompatibility complex (MHC) class I-restricted tumour cell lysis, production of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), and expression of Fas ligand (FasL) and TNF-related apoptosis-inducing ligand (TRAIL) in response to C15 cells. CTL used perforin-, FasL-, and TRAIL-mediated death pathways to lyse C15 cells, although perforin-mediated killing was the predominant lytic mechanism in vitro. The cytokines IFN-gamma and TNF-alpha synergistically enhanced surface expression of Fas, TRAIL receptor, MHC class I and class II on C15 cells that increased the sensitivity of tumour cells to CTL lysis. CTL activity generated in 3H1-pulsed DC immunized mice was directed against an epitope defined by the idio-peptide LCD-2, derived from 3H1. In vivo lymphocyte depletion experiments demonstrated that induction of CTL response and antitumour immunity was dependent on both CD4+ and CD8+ T cells. The analysis of splenocytes of immunized mice that had rejected C15 tumour growth revealed up-regulated surface expression of memory phenotype Ly-6C and CD44 on both CD4+ and CD8+ T cells. The adoptive transfer experiments also suggested the role of both CD4+ and CD8+ T cells in this model system. Furthermore, mice that had rejected C15 tumour growth, developed tumour-specific immunological memory.

Development of cancer vaccines to activate cytotoxic T lymphocytes

Cancer vaccines have been shown to stimulate cytotoxic T lymphocyte (CTL) responses in a variety of cancer patients. However, the response is often of low frequency and moderate avidity, and does not result in objective clinical responses. This is related to the target antigens, which are usually over-expressed self-antigens that elicit tolerogenic and regulatory immune responses, resulting in deletion or inactivation of high-avidity T cells. Although moderate-avidity T cells can be efficient killers, tumours are often poor targets as they express a variety of molecules to protect them from cell-mediated immunity. Adoptive transfer of large numbers of high-avidity T cells has been shown to induce regression of bulky disease, proving that immune responses can effectively eradicate tumours. New approaches that target activated dendritic cells in vivo, resulting in cross-presentation of CTL epitopes and release of cytokines that suppress regulatory T cells, have resulted in the production of T cells with sufficient avidity to kill tumour target cells. These approaches in combination with regimes, such as cytokine therapy, chemotherapy or radiotherapy, that modulate effector costimulatory expression on tumour targets may result in more effective second-generation cancer vaccines.

Functional Idiotopes: Tumor Antigen–Directed Expression of CD8+ T-Cell Epitopes Nested in Unique NH2-terminal VH Sequence of Antiidiotypic Antibodies?

Antiidiotypic antibodies have been and are being used for cancer immunotherapy based on the rationale that Ab2 carrying an "internal image" of the corresponding tumor antigen can induce tumor antigen-specific antibodies (i.e., Ab3 and inhibit tumor growth). Recent evidence indicates that Ab2 also induces cellular responses by CD4+ and CD8+ T cells. This finding has raised the question of where the short peptides, which express CD8+ T-cell-defined epitopes, are located and their relationship with the tumor antigen. We found that two of the four known Ab2 associated with tumor antigen, with known amino acid sequence, express unique NH2-terminal V(H) sequences which precede the framework regions. Both the unique and the shared NH2-terminal V(H) sequences are nested MHC class I antigen-binding peptides. These peptides were highly homologous with peptides from corresponding tumor antigen (carcinoembryonic antigen, CD55, and human high molecular weight melanoma-associated antigen) but differed from the tumor antigen peptides by the presence of the side chain known to mediate stronger forces of interaction with other atoms. The presence of candidate CTL epitopes in NH2-terminal V(H) of Ab2 homologous with tumor antigen may be important for the development of novel immunotherapeutic strategies for cancer.

Immune responses to the 105AD7 human anti-idiotypic vaccine after intensive chemotherapy, for osteosarcoma

105AD7 is a human monoclonal antibody that mimics the complement regulatory protein, CD55, overexpressed by many solid tumours including osteosarcoma. This study was designed to assess the toxicity and efficacy of this vaccine in a young age group of patients within 1–6 months of myleosuppressive chemotherapy. Out of 28, 20 (71%, 95% CI 51–87%) patients showed a significant T-cell proliferation response in vitro to the 105AD7 protein but not to human IgG. Furthermore, 13 out of 22 (59%, 95% CI 36–79%) patients showed antigen-specific γIFN secretion (range 20–370 U/ml). Nine out of 28 (32%, 95% CI 16–52%) patients made weak antibody responses to CD55. This study showed that 105AD7 was well tolerated in younger patients with osteosarcoma. In addition, two patients with possible clinical responses were given compassionate permission to continue immunisation quarterly for 2 years. They both remain alive and disease free 5.8 and 6.5 years from original diagnosis of osteosarcoma and showed no adverse effects of repeated immunisation. In conclusion, the majority of patients showed measurable T helper responses when vaccination was commenced within a 6-month window of intensive chemotherapy with no clinically significant toxicity. Future clinical trials incorporating immune stimulation strategies should include early introduction of vaccines during the highest risk period for relapse.

Monoclonal Anti-idiotype Antibody 6G6.C4 Fused to GM-CSF Is Capable of Breaking Tolerance to Carcinoembryonic Antigen (CEA) in CEA–Transgenic Mice

Internal image anti-idiotypic antibodies are capable of mimicking tumor-associated antigens and thus may serve as surrogate for vaccination strategies in cancer patients. The monoclonal antibody (mAb) 6G6.C4 mimics an epitope specific for the human carcinoembryonic antigen (CEA) and generates a CEA-specific response (Ab3) in various experimental animals. In humans, however, 6G6.C4 only yields a very limited humoral anti-CEA reaction presumably due to tolerance against the CEA autoantigen. In this study, we investigated the CEA-specific Ab3 response in mice transgenic for the human CEA and tested whether the antigen tolerance could be overcome by fusing a recombinant single-chain variable fragment of 6G6.C4 (scFv6G6.C4) to the murine granulocyte macrophage colony-stimulating factor (GM-CSF). Like mAb 6G6.C4, the fusion protein (scFv6G6.C4/GM-CSF) retained binding to the CEA-specific idiotype mAb T84.66. Also, scFv6G6.C4/GM-CSF was biologically active as measured by proliferation of the GM-CSF-dependent murine FDC-P1 cells in vitro. After immunization with the scFv6G6.C4/GM-CSF fusion protein, CEA-transgenic animals showed significantly enhanced Ab3 antibody responses to scFv6G6.C4 (P=0.005) and to CEA (P=0.012) compared with the scFV6G6.C4 alone. Sera from mice immunized with the fusion protein specifically recognized CEA in Western blot analyses with no cross-reaction to CEA-related antigens. Finally, the Ab3 antisera detected single CEA-expressing tumor cells in suspension as shown by flow cytometry. Taken together, these data show in a model antigenically related to the human system that vaccination with scFv6G6.C4/GM-CSF improves vaccination against an endogenous tumor-associated antigen resulting in a highly specific humoral Ab3 response in vivo that is capable of bind single circulating CEA-positive tumor cells.

Human CD4 mimicry by anti-idiotypic monoclonal antibody 16D7 is based on a conformational epitope

The mouse anti-idiotypic mAb (mAb2) 16D7 recognizes the paratope (combining site-associated epitope) of the syngeneic anti-human CD4 mAb HP2/6 (mAb1), a down-modulator of T cell function. 16D7 mimics CD4 in xenogeneic settings in humans and can thus be used to target CD4+ T cells for therapeutic purposes. To define the minimum structural requirement for CD4 mimicry, 16D7 isolated L and H chains were tested for their ability to inhibit mAb1 binding to either CD4 Ag or to mAb2. 16D7 L only specifically inhibited these interactions. Alignment of 16D7 L variable region sequence with that of CD4 defined peptides L2, L3 and L7 with at least 68% of similarity and 30% of identity to exposed regions of CD4. Furthermore, peptides L1, L4, L5, L6 and L8 were selected from a set of 10-mer overlapping peptides (covering the FW and CDR regions of 16D7 L) because of their reactivity with mAb1. Only the synthesized L2 reacted with HP2/6 in slot dot assay and inhibited mAb2-mAb1 interaction. Immunization of BALB/c mice with 16D7, 16D7-F(ab')2, 16D7 L and L2, resulted in the production of CD4-specific Ab3 only in mice immunized with 16D7 and its F(ab')2 fragments. The lack of CD4 reactivity with sera elicited with 16D7 L and L2 was not due to their lack of immunogenicity since both sera reacted with the corresponding immunogen and the former also inhibited the binding of mAb1 to 16D7. The results suggest that CD4 mimicry by 16D7 is based on a conformational epitope and L2 is only one of the HP2/6-specific contact points of 16D7.

Mouse Complement Receptor-Related Gene y/p65-Neutralized Tumor Vaccine Induces Antitumor Activity In Vivo

Two mouse tumor cell lines, Meth A (BALB/c mouse-derived fibrosarcoma) and MM46 (C3H/He mouse-derived mammary tumor), were shown to express high levels of complement receptor-related gene y/p65 (Crry/p65), a membrane-bound complement-regulatory protein. Inhibiting the complement-regulatory activity of Crry/p65 with mAb 5D5 induced high levels of C3 deposition on in vivo tumor-derived Meth A and MM46 cells. To determine the effect of Crry/p65 blockade and increased C3 deposition on in vivo tumor growth, Meth A and MM46 cells were treated with 5D5 mAb and injected into BALB/c and C3H/He mice, respectively. Pretreating MM46 cells with 5D5 mAb significantly suppressed their tumorigenicity when injected s.c. Pretreatment with 5D5 mAb had a modest effect on Meth A s.c. tumor growth. Because complement is involved in the induction of an immune response, we investigated the effect of Crry/p65 blockade and increased C3 deposition on the immunogenicity of the tumor cells in a vaccination protocol. Vaccination of mice with irradiated Meth A cells pretreated with 5D5 mAb protected mice from subsequent challenge. In contrast, vaccination with irradiated Meth A cells without pretreatment was not protective. Survival was correlated with a high titer IgM response and specific CTL activity. These data demonstrate that the functional inhibition of Crry/p65 on tumor cells affects tumor growth and immunogenicity, and that the complement deposition resulting from this inhibition can act in concert with antitumor effector mechanisms to elicit potent antitumor immunity in vivo.

Peptide mapping of a novel discontinuous epitope of the major surface adhesin from Streptococcus mutans

Guy's 13 is a mouse monoclonal antibody that specifically recognizes the major cell-surface adhesion protein SA I/II of Streptococcus mutans, one of the major causative agents of dental caries. Passive immunization with Guy's 13 prevents bacterial colonization in humans. To help elucidate the mechanism of prevention of colonization conferred by this antibody, the SA I/II epitope recognized by Guy's 13 was investigated. It was previously established that the epitope is conformational, being assembled from two non-contiguous regions of SA I/II. In the current study, using recombinant fragments of SA I/II and, ultimately, synthetic peptides, the discontinuous epitope was localized to residues 170-218 and 956-969. This work describes the mapping of a novel discontinuous epitope that requires an interaction between each determinant in order for epitope assembly and recognition by antibody to take place. Guy's 13 binds to the assembled epitope but not to these individual epitope fragments. The assembled epitope results from the interaction between the individual antigenic determinants and can be formed by mixing together determinants present on separate polypeptide chains. The data are consistent with one of the epitope fragments adopting a polyproline II-like helical conformation.

Expression of complement regulatory proteins [membrane cofactor protein (CD46), decay accelerating factor (CD55), and protectin (CD59)] in endometrial stressed cells

In the female reproductive tract, the complement system represents a defense mechanism that can act directly against pathogens and cells, and mediates inflammatory response. Endometrial cells are protected from autologous complement attack by membrane-bound complement regulatory proteins (CRPs) that prevent complement activation: membrane cofactor protein (CD46), decay accelerating factor (CD55), and protectin (CD59). In this work we show that all CRPs were overexpressed after LPS exposure. Maximal stimulatory effect was detected after 6h, and was declining after 12h, reaching control levels in 24h. CD59 was the protein showing the more prominent effect. There seems to be a slight increase of CRP expression in the endometrium of sterile patients that have anti-endometrial antibodies (AEA) in their serum. Our results suggest that under stress, the high expression of CRPs (CD46, CD55, and CD59) could protect endometrial injured cells against complement mediated lysis. The survival of these cells with some biochemical modifications would enable autoimmune response.

Anti-idiotype antibody vaccine therapy for cancer

The use of anti-idiotype (Id) antibodies as vaccines to stimulate antitumour immunity is one of several promising immunologic approaches to the therapy of cancer. Extensive studies in animal tumour models have demonstrated the efficacy of anti-Id vaccines in preventing tumour growth and curing mice with established tumours. A number of monoclonal anti-Id antibodies that mimic distinct human tumour-associated antigens (TAAs) have been developed and tested in the clinic, and demonstrate encouraging results. In general, the antigen mimicry by anti-Id antibodies has reflected structural homology in the majority of the cases, and amino acid sequence homology in a few of them. The greatest challenge of immunotherapy by means of anti-Id vaccines is to identify the optimal anti-Id antibody that will function as a true surrogate antigen for a TAA system, and ideally will generate both humoral and cellular immune responses. Although several clinical studies have shown enhanced survival of patients receiving anti-Id vaccines, the efficacy of these vaccines will depend on the results of several randomised Phase III clinical trials that are currently planned or ongoing.

Antibody-based vaccines for the treatment of melanoma

Malignant melanoma remains a difficult clinical problem. Chemotherapy is not effective and immunotherapy has long been contemplated as the preferred approach to this disease. Extensive passive and active immunotherapy trials have been conducted. Active vaccination with whole cells or defined antigens, administered with a panoply of techniques to increase immunogenicity, has yielded inconsistent results. The development of antibody-based vaccines has allowed vaccination without the need for tumor tissue material or purified antigens. The idiotype network theory originally proposed by Lindemann and by Jerne provided the basis for the development of anti-idiotype (anti-Id) antibody vaccines, which mimic the internal image of the epitope targeted for immunization. Preclinical and phase I clinical data are available for various malignancies. In melanoma, some of the anti-Id vaccines have targeted gangliosides. One of these vaccines, TriGem, has been successful in generating a robust and specific humoral immunity in melanoma patients. Phase II data suggest this anti-Id vaccine has clinical activity.

Idiotype and antigen-specific T cell responses in mice on immunization with antigen, antibody, and anti-idiotypic antibody

Idiotypic determinants of immunoglobulin molecules can evoke both CD4(+) and CD8(+) T responses and exist not only as the integral components of a bona fide antigen binding receptor but also as distinct molecular entities in the processed forms on the cell surface of B lymphocytes. The present work provides experimental evidence for the concept that regulation of memory B cell populations can be achieved through the presentation of idiotypic and anti-idiotypic determinants to helper and cytotoxic cell. The potential of B cells to present antigens to helper and cytotoxic T cells through class II and class I MHC suggests a mechanism by which both B and T cell homeostasis can be maintained. We provide evidence for the generation of idiotype- and antigen-specific Th and Tc cells upon immunization of syngenic mice with antigen or idiotypic antibody (Ab1) or anti-idiotypic antibody (Ab2). The selective activation and proliferation of the antigen-specific Th and Tc cells mediated by idiotypic stimulation observed in these experiments suggests a B-cell-driven mechanism for the maintenance of antigen-specific T cell memory in the absence of antigenic stimulation, under certain conditions.