Definition of MHC-restricted CTL epitopes from non-variable number of tandem repeat sequence of MUC1

MUC1 Story: Great Expectations, Disappointments and the Renaissance

In the course of studying human mucin MUC1, the attitude towards this molecule has been changing time and again. Initially, the list of presumable functions of MUC1 was restricted to protecting and lubricating epithelium. To date, it is assumed to play an important role in cell signaling as well as in all stages of oncogenesis, from malignant cell transformation to tumor dissemination. The story of MUC1 is full of hopes and disappointments. However, the scientific interest to MUC1 has never waned, and the more profoundly it has been investigated, the clearer its hidden potential turned to be disclosed. The therapeutic potential of mucin MUC1 has already been noted by various scientific groups at the early stages of research. Over forty years ago, the first insights into MUC1 functions became a strong ground for considering this molecule as potential target for anticancer therapy. Therefore, this direction of research has always been of particular interest and practical importance. More than 200 papers on MUC1 were published in 2016; the majority of them are dedicated to MUC1-related anticancer diagnostics and therapeutics. Here we review the history of MUC1 studies from the very first attempts to reveal its functions to the ongoing renaissance.

Comparative Immunogenicity of a Cytotoxic T Cell Epitope Delivered by Penetratin and TAT Cell Penetrating Peptides

Cell penetrating peptides (CPP), including the TAT peptide from the human immunodeficiency virus transactivator of transcription (HIV-TAT) protein and penetratin from Drosophila Antennapedia homeodomain protein, translocate various cargos including peptides and proteins across cellular barriers. This mode of delivery has been harnessed by our group and others to deliver antigenic proteins or peptides into the cytoplasm of antigen processing cells (APC) such as monocyte-derived dendritic cells (MoDC). Antigens or T cell epitopes delivered by CPP into APC in vivo generate antigen-specific cytotoxic T cell and helper T cell responses in mice. Furthermore, mice immunised with these peptides or proteins are protected from a tumour challenge. The functional properties of CPP are dependent on the various cargos being delivered and the target cell type. Despite several studies demonstrating superior immunogenicity of TAT and Antp-based immunogens, none has compared the immunogenicity of antigens delivered by TAT and Antp CPP. In the current study we demonstrate that a cytotoxic T cell epitope from the mucin 1 (MUC1) tumour associated antigen, when delivered by TAT or Antp, generates identical immune responses in mice resulting in specific MUC1 T cell responses as measured by in vivo CTL assays, IFNγ ELISpot assays and prophylactic tumour protection.

Mannan adjuvants intranasally administered inactivated influenza virus in mice rendering low doses inductive of strong serum IgG and IgA in the lung

BACKGROUND

H1N1 influenza viruses mutate rapidly, rendering vaccines developed in any given year relatively ineffective in subsequent years. Thus it is necessary to generate new vaccines every year, but this is time-consuming and resource-intensive. Should a highly virulent influenza strain capable of human-to-human transmission emerge, these factors will severely limit the number of people that can be effectively immunised against that strain in time to prevent a pandemic. An adjuvant and mode of administration capable of rendering ordinarily unprotective vaccine doses protective would thus be highly advantageous.

METHODS

The carbohydrate mannan was conjugated to whole inactivated H1N1 influenza virus at a range of ratios, and mixed with it at a range of ratios, and various doses of the resulting preparations were administered to mice via the intranasal (IN) route. Serum immunity was assessed via antigen-specific IgG ELISA and the haemagglutination-inhibition (HI) assay, and mucosal immunity was assessed via IgA ELISA of bronchio-alveolar lavages.

RESULTS

IN-administered inactivated H1N1 mixed with mannan induced higher serum IgG and respiratory-tract IgA than inactivated H1N1 conjugated to mannan, and HIN1 alone. Adjuvantation was mannan-dose-dependent, with 100 μg of mannan adjuvanting 1 μg of H1N1 more effectively than 10 or 50 μg of mannan. Serum samples from mice immunised with 1 μg H1N1 adjuvanted with 10 μg mannan did not inhibit agglutination of red blood cells (RBCs) at a dilution factor of 10 in the HI assay, but samples resulting from adjuvantation with 50 and 100 μg mannan inhibited agglutination at dilution factors of ≥ 40. Both serum IgG1 and IgG2a were induced by IN mannan-adjuvanted H1N1 vaccination, suggesting the induction of humoral and cellular immunity.

CONCLUSIONS

Mixing 100 μg of mannan with 1 μg of inactivated H1N1 adjuvanted the vaccine in mice, such that IN immunisation induced higher serum IgG and respiratory tract IgA than immunisation with virus alone. The serum from mice thus immunised inhibited H1N1-mediated RBC agglutination strongly in vitro. If mannan similarly adjuvants low doses of influenza vaccine in humans, it could potentially be used for vaccine 'dose-sparing' in the event that a vaccine shortage arises from an epidemic involving a highly virulent human-to-human transmissable influenza strain.

Cancer associated aberrant protein O-glycosylation can modify antigen processing and immune response

Aberrant glycosylation of mucins and other extracellular proteins is an important event in carcinogenesis and the resulting cancer associated glycans have been suggested as targets in cancer immunotherapy. We assessed the role of O-linked GalNAc glycosylation on antigen uptake, processing, and presentation on MHC class I and II molecules. The effect of GalNAc O-glycosylation was monitored with a model system based on ovalbumin (OVA)-MUC1 fusion peptides (+/- glycosylation) loaded onto dendritic cells co-cultured with IL-2 secreting OVA peptide-specific T cell hybridomas. To evaluate the in vivo response to a cancer related tumor antigen, Balb/c or B6.Cg(CB)-Tg(HLA-A/H2-D)2Enge/J (HLA-A2 transgenic) mice were immunized with a non-glycosylated or GalNAc-glycosylated MUC1 derived peptide followed by comparison of T cell proliferation, IFN-γ release, and antibody induction. GalNAc-glycosylation promoted presentation of OVA-MUC1 fusion peptides by MHC class II molecules and the MUC1 antigen elicited specific Ab production and T cell proliferation in both Balb/c and HLA-A2 transgenic mice. In contrast, GalNAc-glycosylation inhibited the presentation of OVA-MUC1 fusion peptides by MHC class I and abolished MUC1 specific CD8+ T cell responses in HLA-A2 transgenic mice. GalNAc glycosylation of MUC1 antigen therefore facilitates uptake, MHC class II presentation, and antibody response but might block the antigen presentation to CD8+ T cells.

The Tat-conjugated N-terminal region of mucin antigen 1 (MUC1) induces protective immunity against MUC1-expressing tumours

Mucin antigen 1 (MUC1) is overexpressed on various human adenocarcinomas and haematological malignancies and has long been used as a target antigen for cancer immunotherapy. Most of the preclinical and clinical studies using MUC1 have used the tandem repeat region of MUC1, which could be presented by only a limited set of major histocompatibility complex haplotypes. Here, we evaluated N-terminal region (2-147 amino acids) of MUC1 (MUC1-N) for dendritic cell (DC)-based cancer immunotherapy. We used Esherichia coli-derived MUC1-N that was fused to the protein transduction domain of human immunodeficiency virus Tat protein for three reasons. First, mature DCs do not phagocytose soluble protein antigens. Secondly, tumour cells express underglycosylated MUC1, which can generate epitopes repertoire that differs from normal cells, which express hyperglycosylated MUC1. Finally, aberrantly glycosylated MUC1 has been known to impair DC function. In our study, Tat-MUC1-N-loaded DCs induced type 1 T cell responses as well as cytotoxic T lymphocytes efficiently. Furthermore, they could break tolerance in the transgenic breast tumour mouse model, where MUC1-positive breast cancers grow spontaneously. Compared with DCs pulsed with unconjugated MUC1-N, DCs loaded with Tat-conjugated MUC1-N could delay tumour growth more effectively in the transgenic tumour model as well as in the tumour injection model. These results suggest that the recombinant N-terminal part of MUC1, which may provide a diverse epitope repertoire, could be utilized as an effective tumour antigen for DC-based cancer immunotherapy.

Mucin immunohistochemistry in the diagnosis and mapping of extramammary Paget's disease

Extramammary Paget's disease (EMPD) is a rare skin cancer of the genital region in which cancer cells with enlarged nuclei and pale cytoplasm are scattered singly in the affected epidermis. These cancer cells, called Paget cells, contain mucin, which is never found in normal epidermis. The oligosaccharide side chains of Paget cell mucin end with sialic acid. Sialic acid is easily detected by zirconyl haematoxylin or alcian blue. The other sugars in the oligosaccharide chains can be detected by the periodic acid-Shiff reaction. Rarely, the diagnosis of EMPD is complicated by the absence of mucin from the Paget cells. We have examined such an atypical case. The oligosaccharide side chains, including the sialic acids, are absent. In both this case and a typical case, the Paget cells contain epithelial membrane antigen mucin (MUC1) core protein and usually contain gastric surface-type mucin (MUC5AC) core protein, which can be stained by antibodies. Since neither core protein is found in normal epidermis, epithelial membrane antigen core protein may be the most reliable diagnostic marker for extramammary Paget's disease. In both the atypical case and the typical case of Paget's disease, some cells that look like keratinocytes contain mucin core proteins. These may be incipient Paget cells. We suggest that using th epithelial membrane antigen core protein as a marker for the true extent of extramammary Paget's disease could facilitate complete excision and reduce the rate of recurrence.

Pre-clinical safety evaluation of heat shock protein 65–MUC1 peptide fusion protein

With a goal of developing a medication for the treatment of MUC1 expressing human cancers, a recombinant heat shock protein 65-MUC1 fusion protein (HSP65-MUC1) between BCG derived heat shock protein 65 (HSP65) and MUC1 derived peptide (MUC1) was developed. To move the HSP65-MUC1 into a phase I clinical trial, a comprehensive non-clinical safety evaluation was conducted. The evaluation comprised of single-dose toxicity and repeat-dose toxicity studies both in mice and rhesus monkeys. The data from the study indicates that the treatment with HSP65-MUC1 is not associated with obvious toxicity in the tested animals. The changes in clinical chemistry and hematology in both the mice and monkeys were considered to be mild because there were no indications of overt toxicity after administering HSP65-MUC1. The data provided here contributed to the approval of initiating a phase I clinical trial with HSP65-MUC1 for the treatment of patients with MUC1-positive breast cancer in China.

Pilot phase III immunotherapy study in early-stage breast cancer patients using oxidized mannan-MUC1 [ISRCTN71711835]

Introduction

Mucin 1 (MUC1) is a high molecular weight glycoprotein overexpressed on adenocarcinoma cells and is a target for immunotherapy protocols. To date, clinical trials against MUC1 have included advanced cancer patients. Herein, we report a trial using early stage breast cancer patients and injection of oxidized mannan-MUC1.

Method

In a randomized, double-blind study, 31 patients with stage II breast cancer and with no evidence of disease received subcutaneous injections of either placebo or oxidized mannan-MUC1, to immunize against MUC1 and prevent cancer reoccurrence/metastases. Twenty-eight patients received the full course of injections of either oxidized mannan-MUC1 or placebo. Survival and immunological assays were assessed.

Results

After more than 5.5 years had elapsed since the last patient began treatment (8.5 years from the start of treatment of the first patient), the recurrence rate in patients receiving the placebo was 27% (4/15; the expected rate of recurrence in stage II breast cancer); those receiving immunotherapy had no recurrences (0/16), and this finding was statistically significant (P = 0.0292). Of the patients receiving oxidized mannan-MUC1, nine out of 13 had measurable antibodies to MUC1 and four out of 10 had MUC1-specific T cell responses; none of the placebo-treated patients exhibited an immune response to MUC1.

Conclusion

The results suggest that, in early breast cancer, MUC1 immunotherapy is beneficial, and that a larger phase III study should be undertaken.

Analyses of recombinant vaccinia and fowlpox vaccine vectors expressing transgenes for two human tumor antigens and three human costimulatory molecules

PURPOSE

The poor immunogenicity of tumor antigens and the antigenic heterogeneity of tumors call for vaccine strategies to enhance T-cell responses to multiple antigens. Two antigens expressed noncoordinately on most human carcinomas are carcinoembryonic antigen (CEA) and MUC-1. We report here the construction and characterization of two viral vector vaccines to address these issues.

EXPERIMENTAL DESIGN

The two viral vectors analyzed are the replication-competent recombinant vaccinia virus (rV-) and the avipox vector, fowlpox (rF-), which is replication incompetent in mammalian cells. Each vector encodes the transgenes for three human costimulatory molecules (B7-1, ICAM-1, and LFA-3, designated TRICOM) and the CEA and MUC-1 transgenes (which also contain agonist epitopes). The vectors are designated rV-CEA/MUC/TRICOM and rF-CEA/MUC/TRICOM.

RESULTS

Each of the vectors is shown to be capable of faithfully expressing all five transgenes in human dendritic cells (DC). DCs infected with either vector are shown to activate both CEA- and MUC-1-specific T-cell lines to the same level as DCs infected with CEA-TRICOM or MUC-1-TRICOM vectors. Thus, no evidence of antigenic competition between CEA and MUC-1 was observed. Human DCs infected with rV-CEA/MUC/TRICOM or rF-CEA/MUC/TRICOM are also shown to be capable of generating both MUC-1- and CEA-specific T-cell lines; these T-cell lines are in turn shown to be capable of lysing targets pulsed with MUC-1 or CEA peptides as well as human tumor cells endogenously expressing MUC-1 and/or CEA.

CONCLUSION

These studies provide the rationale for the clinical evaluation of these multigene vectors in patients with a range of carcinomas expressing MUC-1 and/or CEA.

A human cytotoxic T-lymphocyte epitope and its agonist epitope from the nonvariable number of tandem repeat sequence of MUC-1

PURPOSE

MUC-1/DF-3 remains an attractive target for vaccine therapy. It is overexpressed in the majority of human carcinomas and multiple myeloma. Clinical trials using MUC-1-based vaccines have demonstrated safety, clinical responses, and the induction of T-cell responses directed against MUC-1. Previous studies in experimental models and in clinical trials have demonstrated that altering the amino acid sequence of a "self" epitope can lead to the generation of an enhancer agonist epitope capable of eliciting stronger T-cell responses than the native epitope can.

EXPERIMENTAL DESIGN AND RESULTS

We describe here the identification of six novel class I HLA-A2 epitopes of MUC-1 that reside outside of the variable number of tandem repeat region. Each is shown to have the ability to activate human T cells as measured by IFN-gamma production. One epitope (ATWGQDVTSV, at amino acid position 92-101 and designated P-92), which demonstrated the highest level of binding to HLA-A2 and which induced the highest level of IFN-gamma in human T cells, was further studied for the generation of potential enhancer agonist epitopes. Of four potential agonists identified, one epitope (ALWGQDVTSV, designated P-93L) was identified as an enhancer agonist. Compared with the native P-92 peptide, the P-93L agonist (a). bound HLA-A2 at lower peptide concentrations, (b). demonstrated a higher avidity for HLA-A2 in dissociation assays, (c). when used with antigen-presenting cells, induced the production of more IFN-gamma by T cells than with the use of the native peptide, and (d). was capable of more efficiently generating MUC-1-specific human T-cell lines from normal volunteers and pancreatic cancer patients. Most importantly, the T-cell lines generated using the agonist epitope were more efficient than those generated with the native epitope in the lysis of targets pulsed with the native epitope and in the lysis of HLA-A2 human tumor cells expressing MUC-1.

CONCLUSIONS

In addition to the identification of novel MUC-1 epitopes outside the variable number of tandem repeat region, the studies reported here describe the first agonist epitope of MUC-1. The employment of this agonist epitope in peptide-, protein-, and vector-based vaccines may well aid in the development of effective vaccines for a range of human cancers.

Candidate epitope identification using peptide property models: application to cancer immunotherapy

Peptides derived from pathogens or tumors are selectively presented by the major histocompatibility complex proteins (MHC) to the T lymphocytes. Antigenic peptide-MHC complexes on the cell surface are specifically recognized by T cells and, in conjunction with co-factor interactions, can activate the T cells to initiate the necessary immune response against the target cells. Peptides that are capable of binding to multiple MHC molecules are potential T cell epitopes for diverse human populations that may be useful in vaccine design. Bioinformatical approaches to predict MHC binding peptides can facilitate the resource-consuming effort of T cell epitope identification. We describe a new method for predicting MHC binding based on peptide property models constructed using biophysical parameters of the constituent amino acids and a training set of known binders. The models can be applied to development of anti-tumor vaccines by scanning proteins over-expressed in cancer cells for peptides that bind to a variety of MHC molecules. The complete algorithm is described and illustrated in the context of identifying candidate T cell epitopes for melanomas and breast cancers. We analyzed MART-1, S-100, MBP, and CD63 for melanoma and p53, MUC1, cyclin B1, HER-2/neu, and CEA for breast cancer. In general, proteins over-expressed in cancer cells may be identified using DNA microarray expression profiling. Comparisons of model predictions with available experimental data were assessed. The candidate epitopes identified by such a computational approach must be evaluated experimentally but the approach can provide an efficient and focused strategy for anti-cancer immunotherapy development.

Human CTLs to Wild-Type and Enhanced Epitopes of a Novel Prostate and Breast Tumor-Associated Protein, TARP, Lyse Human Breast Cancer Cells

Vaccine therapy for prostate and breast cancer may have potential for treating these major causes of death in males and females, respectively. Critical to the development of tumor-specific vaccines is finding and characterizing novel antigens to be recognized by CD8(+) T cells. To define new CD8(+) T-cell tumor antigens, we determined two wild-type HLA-A2 epitopes from a recently found tumor-associated protein, TARP (T-cell receptor gamma alternate reading frame protein), expressed in prostate and breast cancer cells. We were also able to engineer epitope-enhanced peptides by sequence modifications. Both wild-type and enhanced epitopes induced peptide-specific CD8(+) T-cell responses in A2K(b) transgenic mice. In vitro restimulation of human CD8(+) T cells from a prostate cancer patient resulted in CD8(+) T cells reactive to the peptide epitopes that could lyse HLA-A2(+) human breast cancer cells (MCF-7) expressing TARP. Epitope-specific human CD8(+) T cells were also enumerated in patients' peripheral blood by tetramer staining. Our data suggest that HLA-A2-binding TARP epitopes and enhanced epitopes discovered in this study could be incorporated into a potential vaccine for both breast and prostate cancer.

An anti-MUC1-antibody-interleukin-2 fusion protein that activates resting NK cells to lysis of MUC1-positive tumour cells

MUC1 mucin is aberrantly glycosylated and overexpressed in a number of epithelial malignancies and is therefore a promising tumour-associated antigen for target-directed immunotherapy of a panel of malignant diseases. In MUC1-positive tumours, MHC class I expression is frequently downregulated and MUC1-specific cytotoxic T cells (CTLs) are either not available or in a state of anergy allowing tumour growth without limitation by CTL control. To activate lymphocytes and natural killer (NK) cells, we here generated an anti-MUC1-scFv-IL2 fusion protein (C595scFv-Fc-IL2) that contains the C595 single-chain antibody for MUC1 binding, the human IgG1 CH2CH3 domain for protein dimerisation, and interleukin-2 (IL2) for activation of immunological effector cells. The fusion protein binds to MUC1-derived peptides and to MUC1-positive tumour cells with the same specificity as does the C595 monoclonal antibody. Bound to MUC1, the C595scFv-Fc-IL2 fusion protein stimulates proliferation of human activated lymphocytes in vitro. Upon binding to MUC1-positive MCF7 breast carcinoma cells, moreover, the fusion protein activates resting NK cells to tumour cell lysis. These properties make the C595scFv-Fc-IL2 fusion protein a suitable candidate for the immunotherapy of MUC1-positive tumours.

Effective immunotherapy of cancer in MUC1-transgenic mice using clonal cytotoxic T lymphocytes directed against an immunodominant MUC1 epitope

The tumor-associated autoantigen MUCI is intensively studied as a potential target for antigen-specific immunotherapy of cancer. Previous reports concerning experiments in preclinical murine tumor models have provided evidence supporting the feasibility of this approach. However, such studies have not been performed with clonal cytotoxic T lymphocyte populations displaying a highly defined MUC1 specificity. The authors demonstrate that the immunodominant MUC1-specific cytotoxic T lymphocyte response in C57BL/6 mice is directed against an H-2Kb-restricted epitope, MUC1(19-27), which is derived from the N-terminal signal sequence of the MUC1 protein. Processing of this epitope was independent of transporter of antigen presentation and proteasome function. Importantly, successful immunotherapy of MUC1-overexpressing tumors in MUC1-transgenic mice was not accompanied by damage to normal somatic MUC1-positive tissues, even when this involved the infusion of large numbers of clonal cytotoxic T lymphocyte that recognized the immunodominant MUC1 epitope. Although the risk for autoimmune pathology is limited, data indicate that immune tolerance in MUC1-positive subjects restricts the breadth of the MUC1-specific cytotoxic T lymphocyte repertoire that is available for recruitment to immunotherapeutic antitumor responses.

MUC1, the renaissance molecule

MUC1 is a large, heavily glycosylated mucin expressed on the apical surfaces of most simple, secretory epithelia including the mammary gland, gastrointestinal, respiratory, urinary and reproductive tracts. Although MUC1 was thought to be an epithelial-specific protein, it is now known to be expressed on a variety of hematopoietic cells as well. Mucins function in protection and lubrication of epithelial surfaces. Transmembrane mucins, which contain cytoplasmic tail domains, appear to have additional functions through their abilities to interact with many proteins involved in signal transduction and cell adhesion. The goal of this review is to highlight recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry.

Breast cancer in mice: effect of murine MUC-1 immunization on tumor incidence in C3H/HeOuj mice

Mucin-1 (MUC-1), which is overexpressed in more than 90% of human breast cancers, is a potential target for immunotherapy. To develop a mouse model appropriate for the immunotherapy of human cancer, mouse mucin-1 (muc-1) fusion protein, containing ten tandem repeats, was made and used to immunize C3H/HeOuj mice, which supposedly have a high incidence of breast cancer. C3H/HeOuj mice were injected eight times with 5 microg oxidized mannan muc-1-glutathione-S-transferase (MMFP) with or without cyclophosphamide, which is used to increase cellular immunity. At 80 age weeks, only 12.1% (4 of 33) mice of the untreated C3H/HeOuj mice had mammary tumors. The reason for the low incidence of breast cancer in these mice is not known, but all the mammary tumors were MUC-1+ breast adenocarcinomas and were transplantable to C3H/HeOuj mice. The incidence was 11.4% (4 of 35) in mice injected with MMFP: 38.2% (13 of 34) in mice given cyclophosphamide; and 14.3% (2 of 14) in mice treated with glutathione-S-transferase. That is, cyclophosphamide increased the incidence of mammary tumors, and metastases were found in only these mice. Fewer tumors (6 of 34 or 17.6% compared with 13 of 34 or 38.2% with cyclophosphamide only) occurred in the group immunized with MMFP and cyclophosphamide. Mice immunized with MMFP had high levels of muc-1 antibodies and cellular immune responses (the frequency of the precursor of the cytotoxic Tlymphocyte cell was 1 of 40,000 to 1 of 100,000), which were not found in control groups. The occurrence of muc-1 immunity, particularly the presence of large amounts of anti-mucin-1 antibodies, had no effect on tumor incidence. Thus, the immunization with murine muc-1 reduced the tumor incidence in only cyclophosphamide-treated mice and led to strong muc-1 antibody production and to cellular responses. These findings have implications for human tumor immunotherapy in which strong antibody and weak cellular responses are to be expected and, indeed, have been found.

Mice with spontaneous pancreatic cancer naturally develop MUC-1-specific CTLs that eradicate tumors when adoptively transferred

Pancreatic cancer is a highly aggressive, treatment refractory cancer and is the fourth leading cause of death in the United States. In humans, 90% of pancreatic adenocarcinomas overexpress altered forms of a tumor-specific Ag, mucin 1 (MUC1; an epithelial mucin glycoprotein), which is a potential target for immunotherapy. We have established a clinically relevant animal model for pancreatic cancer by developing a double transgenic mouse model (called MET) that expresses human MUC1 as self molecule and develops spontaneous tumors of the pancreas. These mice exhibit acinar cell dysplasia at birth, which progresses to microadenomas and acinar cell carcinomas. The tumors express large amounts of underglycosylated MUC1 similar to humans. Tumor-bearing MET mice develop low affinity MUC1-specific CTLs that have no effect on the spontaneously occurring pancreatic tumors in vivo. However, adoptive transfer of these CTLs was able to completely eradicate MUC1-expressing injectable tumors in MUC1 transgenic mice, and these mice developed long-term immunity. These CTLs were MHC class I restricted and recognized peptide epitopes in the immunodominant tandem repeat region of MUC1. The MET mice appropriately mimic the human condition and are an excellent model with which to elucidate the native immune responses that develop during tumor progression and to develop effective antitumor vaccine strategies.

The immune response of mice and cynomolgus monkeys to macaque mucin 1-mannan

Mice immunised with human epithelial mucin MUC1 coupled to oxidised mannan produce MUC1 specific MHC Class 1 restricted CD8(+) cytotoxic T cells and are completely protected from the development of MUC1(+) tumours; such therapy may be applicable to humans. In this light we describe pre-clinical studies in cynomolgus monkeys (Macaca fascicularis), to test the efficacy of mannan-MUC1 in higher primates. Monkey MUC1 genomic clones were isolated from a macaque library, peptides and fusion protein synthesised and mice and monkeys immunised with macaque MUC1-mannan. In mice CTL responses were induced (as has been found with human MUC1 mannan conjugates), but in contrast monkeys produced a humoral response, with no T cell proliferative, cytotoxic responses or CTLp found. In spite of the presence of anti-MUC1 auto-antibodies, there was no toxicity or induction of autoimmunity.