Immunization with mimotopes prevents growth of carcinoembryonic antigen positive tumors in BALB/c mice

Anti-angiogenic peptides application in cancer therapy; a review

Cancer is a disease advanced via surplus angiogenesis. The development of new anti-angiogenic therapeutic agents with more efficacy and fewer side effects is still quite necessary. Conventional therapies saving the life of many cancer patients but due to drug resistance and lack of specificity utilizing these methods is faced with limits. Recently, new therapeutic agents have been developed and used to treat cancers such as scaffold proteins, monoclonal antibodies, tyrosine kinase inhibitors, and peptides. In antiangiogenic drug development, anti-angiogenic peptides design is a significant aim. Peptides have developed as substantial therapeutics that are being carefully investigated in angiogenesis-dependent diseases because of their high penetrating rate into the cancer cells, high specificity, and low toxicity. In this review, we focus on anti-angiogenic peptides in the field of cancer therapy that are designed, screened, or derived from nanobodies, mimotopes, phage displays, and natural resources.

Phage Display-Based Nanotechnology Applications in Cancer Immunotherapy

Phage display is a nanotechnology with limitless potential, first developed in 1985 and still awaiting to reach its peak. Awarded in 2018 with the Nobel Prize for Chemistry, the method allows the isolation of high-affinity ligands for diverse substrates, ranging from recombinant proteins to cells, organs, even whole organisms. Personalized therapeutic approaches, particularly in oncology, depend on the identification of new, unique, and functional targets that phage display, through its various declinations, can certainly provide. A fast-evolving branch in cancer research, immunotherapy is now experiencing a second youth after being overlooked for years; indeed, many reports support the concept of immunotherapy as the only non-surgical cure for cancer, at least in some settings. In this review, we describe literature reports on the application of peptide phage display to cancer immunotherapy. In particular, we discuss three main outcomes of this procedure: (i) phage display-derived peptides that mimic cancer antigens (mimotopes) and (ii) antigen-carrying phage particles, both as prophylactic and/or therapeutic vaccines, and (iii) phage display-derived peptides as small-molecule effectors of immune cell functions. Preclinical studies demonstrate the efficacy and vast potential of these nanosized tools, and their clinical application is on the way.

Overview of Current Immunotherapies Targeting Mutated KRAS Cancers

The occurrence of somatic substitution mutations of the KRAS proto-oncogene is highly prevalent in certain cancer types, which often leads to constant activation of proliferative pathways and subsequent neoplastic transformation. It is often seen as a gateway mutation in carcinogenesis and has been commonly deemed as a predictive biomarker for poor prognosis and relapse when conventional chemotherapeutics are employed. Additionally, its mutational status also renders EGFR targeted therapies ineffective owing to its downstream location. Efforts to discover new approaches targeting this menacing culprit have been ongoing for years without much success, and with incidences of KRAS positive cancer patients being on the rise, researchers are now turning towards immunotherapies as the way forward. In this scoping review, recent immunotherapeutic developments and advances in both preclinical and clinical studies targeting K-ras directly or indirectly via its downstream signal transduction machinery will be discussed. Additionally, some of the challenges and limitations of various K-ras targeting immunotherapeutic approaches such as vaccines, adoptive T cell therapies, and checkpoint inhibitors against KRAS positive cancers will be deliberated.

Pre-treatment carcinoembryonic antigen and outcome of patients with rectal cancer receiving neo-adjuvant chemo-radiation and surgical resection: a systematic review and meta-analysis

Neo-adjuvant chemo-radiation is the standard of care for patients with locally advanced rectal carcinoma. The aim of the present paper is to evaluate the relationship of the baseline serologic concentration of the carcinoembryonic antigen with the outcome. Data sources included MEDLINE and Web of Science databases. A systematic search of the databases by a predefined criterion has been conducted. Chemo-radiation followed by surgical resection of rectal tumors was the intervention of interest. From selected studies, the relationships between carcinoembryonic antigen and pathologic complete response, disease-free survival and overall survival were assessed. Carcinoembryonic antigen correlated significantly and inversely with the rate of pathologic complete responses (OR 2.00). Similar to this relationship, a low baseline carcinoembryonic antigen concentration was associated with a better disease-free survival (OR 1.88) and a better overall survival (OR 1.85). Heterogeneity of studies and publication bias were considerable in evaluating the relationship of baseline carcinoembryonic antigen and pathologic complete response. Baseline carcinoembryonic antigen should be regarded as a predictor of outcome of patients undergoing neo-adjuvant chemo-radiation. A calibration of the cutoff value from 5 to 3 ng/ml appears more appropriate to this patient population and should be evaluated in prospective trials.

Proof of concept study with an HER-2 mimotope anticancer vaccine deduced from a novel AAV-mimotope library platform

Background: Anticancer vaccines could represent a valuable complementary strategy to established therapies, especially in settings of early stage and minimal residual disease. HER-2 is an important target for immunotherapy and addressed by the monoclonal antibody trastuzumab. We have previously generated HER-2 mimotope peptides from phage display libraries. The synthesized peptides were coupled to carriers and applied for epitope-specific induction of trastuzumab-like IgG. For simplification and to avoid methodological limitations of synthesis and coupling chemistry, we herewith present a novel and optimized approach by using adeno-associated viruses (AAV) as effective and high-density mimotope-display system, which can be directly used for vaccination. Methods: An AAV capsid display library was constructed by genetically incorporating random peptides in a plasmid encoding the wild-type AAV2 capsid protein. AAV clones, expressing peptides specifically reactive to trastuzumab, were employed to immunize BALB/c mice. Antibody titers against human HER-2 were determined, and the isotype composition and functional properties of these were tested. Finally, prophylactically immunized mice were challenged with human HER-2 transfected mouse D2F2/E2 cells. Results: HER-2 mimotope AAV-vaccines induced antibodies specific to human HER-2. Two clones were selected for immunization of mice, which were subsequently grafted D2F2/E2 cells. Both mimotope AAV clones delayed the growth of tumors significantly, as compared to controls. Conclusion: In this study, a novel mimotope AAV-based platform was created allowing the isolation of mimotopes, which can be directly used as anticancer vaccines. The example of trastuzumab AAV-mimotopes demonstrates that this vaccine strategy could help to establish active immunotherapy for breast-cancer patients.

Cancer immunotherapy by a recombinant phage vaccine displaying EGFR mimotope: an in vivo study

To date, several small molecule inhibitors and monoclonal-antibodies (like ICR-62) have been used to treat tumors over-expressing epidermal growth factor receptor (EGFR). However, the limitations associated with these conventional applications accentuate the necessity of alternative approaches. Mimotopes as compelling molecular tools could rationally be employed to circumvent these drawbacks. In the present study, an M13 phage displaying ICR-62 binding peptide mimotope is exploited as a vaccine candidate. It exhibited high affinity towards ICR62 and polyclonal anti-P-BSA antibodies. Following the mice immunization, phage-based mimotope vaccine induced humoral immunity. Elicited anti-EGFR mimotope antibodies were detected using ELISA method. Moreover, the phage vaccine was tested on the Lewis lung carcinoma mice model to investigate the prophylactic and therapeutic effects. The tumor volume was measured and recorded in different animal groups to evaluate the anti-tumor effects of the vaccine. Our data indicate that the reported phage-based mimotope could potentially elicit specific antibodies resulting in low titers of EGFR-specific antibodies and reduced tumor growth. However, in vivo experiments of prophylactic or therapeutic vaccination showed no specific advantage. Furthermore, phage-mimotope vaccine might be a promising approach in the field of cancer immunotherapy.

Cancer-associated CD43 glycoforms as target of immunotherapy

CD43 is a sialoglycosylated membrane protein that is involved in cell proliferation and differentiation. CD43 glycoforms that are recognized by the UN1 monoclonal antibody (mAb) were expressed in lymphoblastoid T-cell lines and solid tumors, such as breast, colon, gastric, and squamous cell lung carcinomas, while unexpressed in the normal counterparts. The cancer association of UN1/CD43 epitope suggested the possibility to use the UN1 mAb for tumor diagnosis and therapy. In this study, we show that the UN1 mAb was endowed with antitumor activity in vivo because its passive transfer inhibited the growth of UN1-positive HPB-ALL lymphoblastoid T cells in mice. Furthermore, we demonstrate that tumor inhibition was due to UN1 mAb-dependent natural killer-mediated cytotoxicity. By screening a phage-displayed random peptide library, we identified the phagotope 2/165 as a mimotope of the UN1 antigen, as it harbored a peptide sequence that was specifically recognized by the UN1 mAb and inhibited the binding of the UN1 mAb to UN1-positive tumor cells. On the basis of sequence homology with the extracellular region of CD43 (amino acids 64 to 83), the 2/165 peptide sequence was likely mimicking the protein core of the UN1/CD43 epitope. When used as vaccine in mice, the 2/165 phagotope raised antibodies against the UN1/CD43 antigen, indicating that the 2/165 phagotope mimicked the UN1 antigen structure, and could represent a novel immunogen for cancer immunotherapy. These findings support the feasibility of using monoclonal antibodies to identify cancer-associated mimotopes for immunotherapy.

Cancer vaccines targeting carcinoembryonic antigen: state-of-the-art and future promise

Concurrent with the US FDA's approval of the first therapeutic cancer vaccine, and supported by mounting clinical evidence indicating that targeting carcinoembryonic antigen (CEA) can safely overcome pre-existing tolerance, a multitude of novel CEA cancer vaccines are now in various stages of development. Since cancer-driven immune suppression often limits the efficacy of vaccines, numerous strategies are being examined in both preclinical and clinical settings to overcome immunosuppressive elements, including the combined use of vaccines with certain chemotherapies, immune checkpoint inhibitors, small-molecule targeted therapies and radiation. This review discusses the current state and future direction of therapeutic cancer vaccines targeting CEA, based on advances achieved over the last 5 years.

Soluble carcinoembryonic antigen activates endothelial cells and tumor angiogenesis

Carcinoembryonic antigen (CEA, CD66e, CEACAM-5) is a cell-surface-bound glycoprotein overexpressed and released by many solid tumors that has an autocrine function in cancer cell survival and differentiation. Soluble CEA released by tumors is present in the circulation of patients with cancer, where it is used as a marker for cancer progression, but whether this form of CEA exerts any effects in the tumor microenvironment is unknown. Here, we present evidence that soluble CEA is sufficient to induce proangiogenic endothelial cell behaviors, including adhesion, spreading, proliferation, and migration in vitro and tumor microvascularization in vivo. CEA-induced activation of endothelial cells was dependent on integrin β-3 signals that activate the focal-adhesion kinase and c-Src kinase and their downstream MAP-ERK kinase/extracellular signal regulated kinase and phosphoinositide 3-kinase/Akt effector pathways. Notably, while interference with VEGF signaling had no effect on CEA-induced endothelial cell activation, downregulation with the CEA receptor in endothelial cells attenuated CEA-induced signaling and tumor angiogenesis. Corroborating these results clinically, we found that tumor microvascularization was higher in patients with colorectal cancer exhibiting higher serum levels of soluble CEA. Together, our results elucidate a novel function for soluble CEA in tumor angiogenesis.

Mimotope peptides selected from phage display combinatorial library by serum antibodies of pigs experimentally infected with Taenia solium as leads to developing diagnostic antigens for human neurocysticercosis

Neurocysticercosis is caused by penetration of the tapeworm Taenia solium larvae into the central nervous system resulting in a diverse range of neurologic complications including epilepsy in endemic areas that globalization spreads worldwide. Sensitive and specific immunodiagnosis is needed for the early detection and elimination of the parasite, but the lack of standardized, readily obtainable antigens is a challenge. Here, we used the phage display for resolving the problem. The rationale of the strategy rests on the concept that the screening of combinatorial libraries with polyclonal serum to pathogens reveals families of peptides mimicking the pathogen most immunodominant epitopes indispensable for the successful diagnosis. The screening of a 7mer library with serum IgG of four pigs experimentally infected with parasite followed by computer aided segregation of the selected sequences resulted in the discovery of four clusters of homologous sequences of which one presented a family of ten mimotopes selected by three infected pig serum IgGs; the common motif sequence LSPF carried by the family was considered to be the core of an immunodominant epitope of the parasite critical for the binding with the antibody that selected the mimotopes. The immunoassay testing permitted to select a mimotope whose synthetic peptide free of the phage with the amino acid sequence Leu-Ser-Fen-Pro-Ser-Val-Val that distinguished well a panel of 21 cerebrospinal fluids of neurocysticercosis patients from the fluids of individuals with neurological complications of other etiology. This peptide is proposed as a lead for developing a novel molecularly defined diagnostic antigen(s) for the neurocysticercosis.

The roles of mast cells in anticancer immunity

The tumor microenvironment (TME), which is composed of stromal cells such as endothelial cells, fibroblasts, and immune cells, provides a supportive niche promoting the growth and invasion of tumors. The TME also raises an immunosuppressive barrier to effective antitumor immune responses and is therefore emerging as a target for cancer immunotherapies. Mast cells (MCs) accumulate in the TME at early stages, and their presence in the TME is associated with poor prognosis in many aggressive human cancers. Some well-established roles of MCs in cancer are promoting angiogenesis and tumor invasion into surrounding tissues. Several mouse models of inducible and spontaneous cancer show that MCs are among the first immune cells to accumulate within and shape the TME. Although MCs and other suppressive myeloid cells are associated with poor prognosis in human cancers, high densities of intratumoral T effector (T(eff)) cells are associated with a favorable prognosis. The latter finding has stimulated interest in developing therapies to increase intratumoral T cell density. However, cellular and molecular mechanisms promoting high densities of intratumoral T(eff) cells within the TME are poorly understood. New evidence suggests that MCs are essential for shaping the immune-suppressive TME and impairing both antitumor T(eff) cell responses and intratumoral T cell accumulation. These roles for MCs warrant further elucidation in order to improve antitumor immunity. Here, we will summarize clinical studies of the prognostic significance of MCs within the TME in human cancers, as well as studies in mouse models of cancer that reveal how MCs are recruited to the TME and how MCs facilitate tumor growth. Also, we will summarize our recent studies indicating that MCs impair generation of protective antitumor T cell responses and accumulation of intratumoral T(eff) cells. We will also highlight some approaches to target MCs in the TME in order to unleash antitumor cytotoxicity.

Cancer vaccines inducing antibody production: more pros than cons

To date, passive immunotherapy with monoclonal antibodies is a well-established option in clinical oncology. By contrast, anticancer vaccines are less advanced, with the exception of successfully applied prophylactic vaccines against oncogenic virus infections. The creation of therapeutic vaccines is still a great challenge mostly due to the self-nature of tumor antigens. Therapeutic vaccines may be based on patient-specific material including pulsed effector cells, or tumor-associated antigens and derivatives thereof, such as peptides, mimotopes and nucleic acids. The latter represents a more universal approach, which would set an ideal economic framework resulting in broad patient access. In this article we focus on cancer vaccines for antibody production, in particular mimotope vaccines. The collected evidence suggests that they will open up new treatment options in minimal residual disease and early stage disease.

Specificity of mimotope-induced anti-high molecular weight-melanoma associated antigen (HMW-MAA) antibodies does not ensure biological activity

Vaccines based on peptide mimics (mimotopes) of conformational tumor antigen epitopes have been investigated for a variety of human tumors including breast cancer, tumors expressing the carcinoembryonic antigen, B cell lymphoma, neuroblastoma, and melanoma. In our previous work, we designed a vaccine based on a mimotope of the high molecular weight-melanoma associated antigen (HMW-MAA) that elicited HMW-MAA-specific antibodies (Abs) with anti-tumor activity in vitro and in vivo. In this study, we aimed to identify mimotopes of additional distinct HMW-MAA epitopes, since they could be used to construct a polymimotope melanoma vaccine. For this purpose, random peptide phage libraries were screened with the anti-HMW-MAA monoclonal antibodies (mAbs) VT80.12 and VF1-TP43 yielding one peptide ligand for each mAb. Both peptides inhibited the binding of the corresponding mAb to the HMW-MAA. Furthermore, when coupled to the carrier protein keyhole limpet hemocyanin (KLH), both HMW-MAA mimotopes elicited peptide-specific Abs in rabbits or BALB/c mice, but only the mimotope isolated with the mAb VT80.12 elicited HMW-MAA-specific Abs and only in mice. However, the latter Abs had no detectable effect on HMW-MAA expressing human melanoma cells in vitro. These results describe limitations related to the phage display technique and emphasize the need to characterize the functional properties of the mAb utilized to isolate mimotopes of the corresponding epitopes.

Phylogenetic discordance of human and canine carcinoembryonic antigen (CEA, CEACAM) families, but striking identity of the CEA receptors will impact comparative oncology studies

Comparative oncology aims at speeding up developments for both, human and companion animal cancer patients. Following this line, carcinoembryonic antigen (CEA, CEACAM5) could be a therapeutic target not only for human but also for canine (Canis lupus familiaris; dog) patients. CEACAM5 interacts with CEA-receptor (CEAR) in the cytoplasm of human cancer cells. Our aim was, therefore, to phylogenetically verify the antigenic relationship of CEACAM molecules and CEAR in human and canine cancer.

Anti-human CEACAM5 antibody Col-1, previously being applied for cancer diagnosis in dogs, immunohistochemically reacted to 23 out of 30 canine mammary cancer samples. In immunoblot analyses Col-1 specifically detected human CEACAM5 at 180 kDa in human colon cancer cells HT29, and the canine antigen at 60, 120, or 180 kDa in CF33 and CF41 mammary carcinoma cells as well as in spontaneous mammary tumors. While according to phylogenicity canine CEACAM1 molecules should be most closely related to human CEACAM5, Col-1 did not react with canine CEACAM1, -23, -24, -25, -28 or -30 transfected to canine TLM-1 cells. By flow cytometry the Col-1 target molecule was localized intracellularly in canine CF33 and CF41 cells, in contrast to membranous and cytoplasmic expression of human CEACAM5 in HT29. Col-1 incubation had neither effect on canine nor human cancer cell proliferation. Yet, Col-1 treatment decreased AKT-phosphorylation in canine CF33 cells possibly suggestive of anti-apoptotic function, whereas Col-1 increased AKT-phosphorylation in human HT29 cells. We report further a 99% amino acid similarity of human and canine CEA receptor (CEAR) within the phylogenetic tree. CEAR could be detected in four canine cancer cell lines by immunoblot and intracellularly in 10 out of 10 mammary cancer specimens from dog by immunohistochemistry. Whether the specific canine Col-1 target molecule may as functional analogue to human CEACAM5 act as ligand to canine CEAR, remains to be defined. This study demonstrates the limitations of comparative oncology due to the complex functional evolution of the different CEACAM molecules in humans versus dogs. In contrast, CEAR may be a comprehensive interspecies target for novel cancer therapeutics.

Mimotope vaccination--from allergy to cancer

BACKGROUND

Mimotopes are peptides mimicking protein, carbohydrates or lipid epitopes and can be generated by phage display technology. When selected by antibodies, they represent exclusively B-cell epitopes and are devoid of antigen/allergen-specific T-cell epitopes. Coupled to carriers or presented in a multiple antigenic peptide form mimotopes achieve immunogenicity and induce epitope-specific antibody responses upon vaccination.

OBJECTIVE/METHODS

In allergy IgG antibodies may block IgE binding to allergens, whereas other IgG antibody specificities enhance this and support the anaphylactic reaction. In cancer, inhibitory antibody specificities prevent growth signals derived from overexpressed oncogenes, whereas growth-promoting specificities enhance signalling and proliferation. Therefore, the mimotope concept is applicable to both fields for epitope-specific vaccination and analysis of conformational B-cell epitopes for the allergen/antigen.

RESULTS/CONCLUSIONS

Mimotope technology is a relatively young theme in allergology and oncology. Still, proof of concept studies testing allergen and tumour mimotope vaccines suggest that mimotopes are ready for clinical trials.

Systematic amino acid substitutions improved efficiency of GD2-peptide mimotope vaccination against neuroblastoma

The likelihood of identifying peptides of sufficient quality for the development of effective cancer vaccines by screening of phage display libraries is low. Here, we introduce the sequential application of systematic amino acid substitution by SPOT synthesis. After the substitution of two amino acids within the sequence of a phage display-derived mimotope of disialoganglioside GD2 (mimotope MA), the novel mimotope C3 showed improved GD2 mimicry in vitro. Peptide vaccination with the C3 mimotope induced an 18-fold increased anti-GD2 serum response associated with reduction of primary tumour growth and spontaneous metastasis in contrast to MA mimotope controls in a syngeneic neuroblastoma model. In summary, SPOT provides an ideal optimisation tool for the development of phage display-derived cancer vaccines.

Characterisation of an engineered trastuzumab IgE antibody and effector cell mechanisms targeting HER2/neu-positive tumour cells

Trastuzumab (Herceptin), a humanized IgG1 antibody raised against the human epidermal growth factor receptor 2 (HER2/neu), is the main antibody in clinical use against breast cancer. Pre-clinical evidence and clinical studies indicate that trastuzumab employs several anti-tumour mechanisms that most likely contribute to enhanced survival of patients with HER2/neu-positive breast carcinomas. New strategies are aimed at improving antibody-based therapeutics like trastuzumab, e.g. by enhancing antibody-mediated effector function mechanisms. Based on our previous findings that a chimaeric ovarian tumour antigen-specific IgE antibody showed greater efficacy in tumour cell killing, compared to the corresponding IgG1 antibody, we have produced an IgE homologue of trastuzumab. Trastuzumab IgE was engineered with the same light- and heavy-chain variable-regions as trastuzumab, but with an epsilon in place of the gamma-1 heavy-chain constant region. We describe the physical characterisation and ligand binding properties of the trastuzumab IgE and elucidate its potential anti-tumour activities in functional assays. Both trastuzumab and trastuzumab IgE can activate monocytic cells to kill tumour cells, but they operate by different mechanisms: trastuzumab functions in antibody-dependent cell-mediated phagocytosis (ADCP), whereas trastuzumab IgE functions in antibody-dependent cell-mediated cytotoxicity (ADCC). Trastuzumab IgE, incubated with mast cells and HER2/neu-expressing tumour cells, triggers mast cell degranulation, recruiting against cancer cells a potent immune response, characteristic of allergic reactions. Finally, in viability assays both antibodies mediate comparable levels of tumour cell growth arrest. These functional characteristics of trastuzumab IgE, some distinct from those of trastuzumab, indicate its potential to complement or improve upon the existing clinical benefits of trastuzumab.

Reduction of human melanoma tumor growth in severe combined immunodeficient mice by passive transfer of antibodies induced by a high molecular weight melanoma-associated antigen mimotope vaccine

PURPOSE

The high molecular weight melanoma-associated antigen (HMW-MAA) is an attractive target for immunotherapy of malignant melanoma. We have recently generated a vaccine based on the HMW-MAA mimotope 225D9.2+ that was able to induce anti-HMW-MAA antibodies with antitumor activity in vitro. Here, we investigated the antitumor activity of these antibodies in a human melanoma xenotransplant severe combined immunodeficient (SCID) mouse model.

EXPERIMENTAL DESIGN

Tumors were established by injecting the human melanoma 518A2 cells into C.B.17 SCID/SCID mice. In tumor prevention experiments, 200 microg purified total IgG antibodies were injected intravenously the same day or on day 5 in therapeutic experiments. Antibody administration was repeated every fourth day and tumor volumes were measured. Antibody specificity and tumor infiltration by macrophages were investigated by immunohistochemistry.

RESULTS

Within 35 days after cell inoculation, antibody treatment reduced tumor growth up to 40% in the therapeutic and up to 62% in the tumor prevention experiments compared with the control mice. In tumors of all groups, a similar distribution of the HMW-MAA and no differences in infiltration of macrophages were detected by immunohistochemistry.

CONCLUSIONS

Here, we showed that antibodies induced by the 225D9.2+ mimotope effectively inhibited melanoma tumor growth. Additional mechanisms besides antibody-dependent cell cytotoxicity like disruption of interactions of melanoma cells mediated by extracellular matrix components seem to be involved in tumor growth inhibition. Based on our findings, we suggest that active immunization with this mimotope might be a promising strategy for treatment of melanoma.

Overview of mimotopes and related strategies in tumor vaccine development

Tumor vaccine has been studied extensively as an alternative or adjuvant therapy in the treatment of malignant tumors in the hope of prolonging the overall survival rates of cancer patients. The efficacy largely relies on the specificity of the target. In the last decade, many antibody epitopes, called mimotopes, have been revealed as candidates through phage-display technology. These mimotopes do not necessarily consist of amino acid sequences that are identical to the native antigen but they do mimic their structure. Tumor vaccines based on these mimotopes have been proposed as an important developing strategy. Some peptide mimotopes have produced encouraging clinical outcomes. Although most studies are still in the preclinical phase, these findings will possibly pave the way for the development of novel mimotope-based tumor vaccines.

A mimotope gene encoding the major IgE epitope of allergen Phl p 5 for epitope-specific immunization

A gene vaccine based on a mammalian expression vector containing the sequence of a peptide mimotope of Phl p 5 was constructed. To test whether mimotope gene vaccines can induce allergen-specific antibody responses via molecular mimicry, BALB/c mice were immunized using the mimotope construct with or without a tetanus toxin T-helper epitope. Moreover, intradermal injection was compared to epidermal application via gene gun immunization. Immunization with both mimotope gene constructs elicited allergen-specific antibody responses. As expected, gene gun bombardment induced a Th2-biased immune response, typically associated with IgG1 and IgE antibody production. In contrast, intradermal injection of the vaccine triggered IgG2a antibody expression without any detectable IgE levels, thus biasing the immune response towards Th1. In an RBL assay, mimotope-specific IgG antibodies were able to prevent cross-linking of allergen-specific IgE by Phl p 5. A construct coding for the complete Phl p 5 induced T-cell activation, IFN-gamma and IL-4 production. In contrast, the mimotope-DNA construct being devoid of allergen-specific T-cell epitopes had no capacity to activate allergen-specific T cells. Taken together, our data show that it is feasible to induce blocking IgG antibodies with a mimotope-DNA construct when applied intradermally. Thus the mimotope-DNA strategy has two advantages: (1) the avoidance of IgE induction and (2) the avoidance of triggering allergen-specific T-lymphocytes. We therefore suggest that mimotope gene vaccines are potential candidates for epitope-specific immunotherapy of type I allergy.

AllergoOncology: the role of IgE-mediated allergy in cancer

Epidemiological studies have suggested inverse associations between allergic diseases and malignancies. As a proof of concept for the capability of immunoglobulin E (IgE) to destruct tumor cells, several experimental strategies have evolved to specifically target this antibody class towards relevant tumor antigens. It could be demonstrated that IgE antibodies specific to overexpressed tumor antigens have been superior to any other immunoglobulin class with respect to antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP) reactions. In an alternative approach, IgE nonspecifically attached to tumor cells proved to be a powerful adjuvant establishing tumor-specific immune memory. Active Th2 immunity could also be achieved by applying an oral immunization regimen using mimotopes, i.e. epitope mimics of tumor antigens. The induced IgE antibodies could be cross-linked by live tumor cells leading to tumoricidic mediator release. Thus, IgE antibodies may not only act in natural tumor surveillance, but could possibly also be exploited for tumor control in active and passive immunotherapy settings. Thereby, eosinophils, mast cells and macrophages can be armed with the cytophilic IgE and become potent anti-tumor effectors, able to trace viable tumor cells in the tissues. It is strongly suggested that the evolving new field AllergoOncology will give new insights into the role of IgE-mediated allergy in malignancies, possibly opening new avenues for tumor therapy.