Human anti-idiotypic antibodies can be good immunogens as they target FC receptors on antigen-presenting cells allowing efficient stimulation of both helper and cytotoxic T-cell responses

MYH9 Key Amino Acid Residues Identified by the Anti-Idiotypic Antibody to Porcine Reproductive and Respiratory Syndrome Virus Glycoprotein 5 Involve in the Virus Internalization by Porcine Alveolar Macrophages

MYH9 has been identified as an indispensable cellular protein for porcine reproductive and respiratory syndrome virus (PRRSV) entry into permissive cells using the monoclonal anti-idiotypic antibody (Mab2-5G2) recognizing an antibody that specifically interacts with PRRSV glycoprotein 5 (GP5). More recently, we found that Mab2-5G2 interacted with the MYH9 C-terminal domain, designated PRA, which is required for PRRSV internalization. In this study, we demonstrate that blocking of MYH9 with Mab2-5G2 significantly diminished PRRSV internalization by porcine alveolar macrophage (PAM) via interruption of direct interaction between GP5 and MYH9, and thus remarkably inhibited subsequent infection of PAMs by PRRSV-2 isolates. Moreover, the three-dimensional structure of the Mab2-5G2 Fab-PRA complex determined via homology modeling predicted potential docking sites required for PRRSV internalization. Further analysis of Mab2-5G2-binding sites within PRA highlighted that the amino acids E1670, K1673, E1679, and I1683 in PRA are the key Mab2-5G2-binding residues. Notably, recombinant PRA protein blocked the interaction between PRRSV GP5 and cellular MYH9 by preventing translocation of MYH9 from the cytoplasm to the cell membrane, an essential step for PRRSV virion internalization. Meanwhile, porcine cell line permissive for PRRSV bearing point mutation of E1670A in MYH9 demonstrated reduced susceptibility for PRRSV infection. In conclusion, this work increases understanding of both PRRSV pathogenesis and the mechanistic role played by MYH9 in PRRSV infection.

Autoantigen complementarity and its contributions to hallmarks of autoimmune disease

The question considered is, "What causes the autoimmune response to begin and what causes it to worsen into autoimmune disease?" The theory of autoantigen complementarity posits that the initiating immunogen causing disease is a protein complementary (antisense) to the self-antigen, rather than a response to the native protein. The resulting primary antibody elicits an anti-antibody response or anti-idiotype, consequently producing a disease-inciting autoantibody. Yet, not everyone who developes self-reactive autoantibodies will manifest autoimmune disease. What is apparent is that manifestation of disease is governed by the acquisition of multiple immune-compromising traits that increase susceptibility and drive disease. Taking into account current cellular, molecular, and genetic information, six traits, or 'hallmarks', of autoimmune disease were proposed: (1) Autoreactive cells evade deletion, (2) Presence of asymptomatic autoantibodies, (3) Hyperactivity of Fc-FcR pathway, (4) Susceptibility to environmental impact, (5) Antigenic modifications of self-proteins, (6) Microbial Infections. Presented here is a discussion on how components delineated in the theory of autoantigen complementarity potentially promote the acquisition of multiple 'hallmarks' of disease.

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.

Modulation of tumor immunity by therapeutic monoclonal antibodies

The surveillance of tumors by the immune system of cancer patients and its impact on disease progression and patient survival have been largely documented over the last years. In parallel, the use of therapeutic monoclonal antibodies (mAbs) in oncology has gained a widespread recognition as it has made it possible to increase patient survival and to ameliorate the quality of life in a number of cancers. However, the clinical responses observed following mAb treatment remain largely heterogeneous and their duration is still highly unpredictable. Recently, the concept that the injection of therapeutic antibodies not only triggers early anti-tumor events such as receptor blockade, cytostasis, apoptosis, complement-dependent cytotoxicity and/or antibody-dependent cytotoxicity but also allows the host immune system to fight tumor cells through the development of a long-lasting adaptive immunity has emerged. In the present review, we will examine the arguments that support this concept by detailing the cellular and molecular events likely to underlie the induction of an efficient anti-tumor adaptive immune response by mAbs. We will also discuss the consequences of this induction on the way therapeutic antibodies can be used and inserted in a more global immunotherapeutic approach aiming at strengthening the adaptive anti-tumor immune response developed by cancer patients.

Foot-and-mouth disease virus exhibits an altered tropism in the presence of specific immunoglobulins, enabling productive infection and killing of dendritic cells

Foot-and-mouth disease virus (FMDV) causes an acute vesicular disease of farm animals. The development of successful control strategies is limited by an incomplete understanding of the immune response to FMDV. Dendritic cells (DC) mediate the induction of immunity to pathogens, but their role in FMDV infection of cattle is uncharacterized. Bovine monocyte-derived DC (moDC) were exposed to integrin-binding and cell culture-adapted strains of FMDV in vitro. MoDC were not largely susceptible to infection by integrin-binding FMDV but were susceptible to culture-adapted virus. Binding specific antibodies to integrin-binding FMDV at neutralizing or subneutralizing IgG concentrations significantly enhanced infection via CD32 (FcγR). Monocytes also expressed CD32 but were nonsusceptible to FMDV immune complex (IC) infection, indicating a requirement for additional factors involved in cellular susceptibility. Infection of moDC by the FMDV IC was productive and associated with high levels of cell death. Infected moDC were unable to efficiently stimulate FMDV-specific CD4(+) memory T cells, but exposing moDC to IC containing inactivated FMDV resulted in significantly increased T cell stimulation. Thus, neutralized FMDV concurrently loses its ability to infect susceptible cells while gaining the capacity to infect immune cells. This represents a change in the tropism of FMDV that could occur after the onset of the antibody response. We propose that IC could dynamically influence the anti-FMDV immune response and that this may explain why the early immune response to FMDV has evolved toward T cell independence in vivo. Moreover, we propose that DC targeting could prove useful in the development of effective vaccines against FMDV.

DNA vaccination with T-cell epitopes encoded within Ab molecules induces high-avidity anti-tumor CD8+ T cells

Stimulation of high-avidity CTL responses is essential for effective anti-tumor and anti-viral vaccines. In this study we have demonstrated that a DNA vaccine incorporating CTL epitopes within an Ab molecule results in high-avidity T-cell responses to both foreign and self epitopes. The avidity and frequency was superior to peptide, peptide-pulsed DC vaccines or a DNA vaccine incorporating the epitope within the native Ag. The DNA Ab vaccine was superior to an identical protein vaccine that can only cross-present, indicating a role for direct presentation by the DNA vaccine. However, the avidity of CTL responses was significantly reduced in Fc receptor gamma knockout mice or if the Fc region was removed suggesting that cross presentation of Ag via Fc receptor was also important in the induction of high-avidity CTL. These results suggest that generation of high-avidity CTL responses by the DNA vaccine is related to its ability to both directly present and cross-present the epitope. High-avidity responses were capable of efficient anti-tumor activity in vitro and in vivo. This study demonstrates a vaccine strategy to generate high-avidity CTL responses that can be used in anti-tumor and anti-viral vaccine settings.

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.

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.

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.

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.

Cancer vaccines entering Phase III clinical trials

The last 10 years have seen a growth in the number of tumour antigens identified from immune responses raised in patients. The discovery that tumours can be recognised by the immune system stimulated a great deal of work characterising the molecular mechanisms underlying immune recognition. This in turn has led to an impressive array of immunological approaches to the generation of cancer vaccines; these range from molecularly defined T cell epitopes, antibody-based vaccines, cytokine therapies, immune modulators and DNA vaccines, to whole cell vaccines and, more recently, combinations of these methods. Many of these approaches have entered Phase I/II trials and have shown interesting clinical results. Moreover, they have extended our knowledge of the immune system and our understanding of the mechanisms required to design a successful cancer vaccine. This review outlines some of the approaches that have led to some of these vaccines entering Phase III clinical trials, discusses their modes of action and reports on their current status in trial.

A novel CEA vaccine stimulates T cell proliferation, γIFN secretion and CEA specific CTL responses

Carcinoembryonic antigen (CEA) is a cell surface protein over-expressed by a wide range of tumours. The mouse anti-idiotypic antibody, 708, mimics CEA and can induce both antibody and T cell responses that specifically recognise this antigen. Sequence analysis of 708 revealed homology with a previously identified HLA-A3 T cell epitope in CEA but not to other closely related molecules. 708 was chimerised to a human IgG1 to allow Fc targeting of APCs and was deimmunised to remove unwanted T cell epitopes. The chimerised and deimmunised, but not the mouse 708, could stimulate CTL, proliferation and gammaIFN responses in vitro in normal (HLA-A3, DR1) individuals. Furthermore, the CTLs killed tumour cells expressing CEA suggesting that this deimmunised antibody could be a useful vaccine for solid tumours.

Identification of an HLA-A*0201 cytotoxic T lymphocyte epitope specific to the endothelial antigen Tie-2

Tie-2 stabilises pericyte-endothelial interactions during angiogenesis and is highly expressed on endothelium during several diseases, including arthritis, age-related macular degeneration and cancer. A vaccine that targets endothelium overexpressing Tie-2 may result in vessel damage and stimulate an inflammatory cascade resulting in disease regression. We have identified a region unique to Tie-2 (amino acids 1-196) that is homologous in humans and mice. Using computer algorithms, several HLA-A*0201 epitopes that are identical in mice and humans were predicted within this region; however, binding assays showed that the majority of these epitopes were of low affinity. Modification of the anchor residues of 4 epitopes enhanced HLA binding. These epitopes were incorporated by site-directed mutagenesis into a Tie-2 DNA construct. Immunisation of HLA*0201 transgenic mice with one of the modified Tie-2 constructs stimulated CTLs that recognised both wild-type and modified peptide-pulsed target cells. In contrast, no CTLs were generated in mice immunised with wild-type Tie-2 construct, demonstrating that the modified epitope was necessary in the generation of CTLs. Moreover, CTLs from mice immunised with the modified construct killed HLA-A*0201 endothelial cells overexpressing Tie-2. Our study demonstrates that it is possible to break tolerance to the endothelial antigen Tie-2, suggesting that it may be feasible to design a vaccine to activate CTLs to kill endothelial cells overexpressing Tie-2.

Preparation of humanized ovarian carcinoma anti-idiotypic minibody

Murine anti-idiotypic monoclonal antibody (MAb) 6B11 mimicking the tumor-associated antigen OC166-9 is used as a vaccine for the induction of an anti-tumoral immunity in experiments of in vitro and in vivo animal model with ovarian carcinoma. In this article, we have humanized 6B11 anti-idiotypic minibody using overlap polymerase chain reaction (PCR) and DNA recombinant technique, prokaryotic expression vector was produced by genetic fusion of 6B11V(L)-V(H) to human IgG1 hinge and CH3 region. Transformed E. coli BL21(DE3) were propagated and induced by isopropyl-beta D-thiogalactopyranoside (IPTG). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that a protein band with molecular weight of 50kD appeared as the expected size after transformation. Molecular weight of 100 kDa may be examined by electrophoresis in nondenaturing systems. The fusion protein was analyzed with enzyme-linked immunosorbant assay (ELISA), inhibition ELISA tests and Western blot, respectively. The humanized anti-idiotype minibody showed capacity of bivalent binding to ovarian cancer MAb COC166-9 and goat anti-human immunoglobulin IgG1. It is useful reagents for clinical use.

Cancer vaccination progress

The application of 'new' and 'recognized' tumour antigens in vaccination strategies that target CD8(+) and CD4(+) T-cell responses, and the mechanisms by which these and other effector cells are activated or respond, were discussed at the second 'Progress in Vaccination Against Cancer' meeting, held at the Nottingham Trent Djanogly Conference Centre, Nottingham, UK, from 18-20 July 2002.

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.

Production and characterisation of monoclonal anti-idiotype antibody to Vibrio anguillarum

Seven monoclonal anti-idiotype antibodies (mab2) were raised against mouse monoclonal antibody (mab1) 4A6. Identification of subclass showed that 1H5, 1D1, 2B12 and 2F12 belonged to IgG2b, 2H12 and 1H12 to IgG2a and lE10 to IgG3. The titres of these mab2 ascitic fluids ranged from 1 x 10(-4)-1 x 10(-6). The capacity of the mab2 to inhibit the binding between the corresponding rabbit antiserum and Vibrio anguillarum was investigated with the competitive inhibition ELISA. The results showed that mab2 1D1, 1E10, 1H5 and 1H12 were able to inhibit this binding. Another experiment demonstrated that mab2 1D1, 1E10 and 1H5 might induce Balb/c mice to produce Ab3 and these Ab3 competed the same antigen epitopes with Ab1. These results indicate that mab2 1D1, 1E10 and 1H5 are likely to represent an internal image of V. anguillarum and may thus be described as Ab2-beta anti-idiotype antibodies. In protection experiments, Japanese flounders vaccinated with mab21D1, 1E10 and 1H5 showed significantly enhanced survival from challenge with V. anguillarum. Thus. mab21D1, 1E10 and 1H5 may have use as idiotype vaccines for fish in aquaculture.