Vaccination with cytotoxic T lymphocyte epitope-containing peptide protects against a tumor induced by human papillomavirus type 16-transformed cells

Prognostic value of intratumoral interferon gamma messenger RNA expression in invasive cervical carcinomas

BACKGROUND

The production of the cytokine interferon gamma (IFN gamma) by activated peripheral blood mononuclear cells may be reduced in patients with invasive cervical carcinoma. This study was designed to assess the prognostic value of intratumoral IFN gamma messenger RNA (mRNA) levels in such patients.

METHODS

Biopsy specimens of primary cervical lesions were obtained from 27 patients with invasive squamous cell carcinoma before they received any therapy. Two prognostic groups were considered: 1) a group of 14 patients who had no apparent disease recurrence and who were alive 2 years after diagnosis (good-prognosis group) and 2) a group of 13 patients who had disease recurrence or died during the 2-year follow-up (poor-prognosis group). A competitive reverse transcription-polymerase chain reaction assay was used to measure levels of IFN gamma and beta actin mRNA. The expression of human leukocyte antigen (HLA) class II proteins (which is stimulated by IFN gamma) in tumor cells was studied by immunostaining.

RESULTS

Tumor specimens from all 14 patients in the good-prognosis group contained more than 10(3) IFN gamma mRNA copies per 5 x 10(5) beta actin mRNA copies, whereas tumor specimens from only six of the 13 patients in the poor-prognosis group contained this level of IFN gamma mRNA (two-sided P = .006). No clear relationship was observed between levels of IFN gamma mRNA and T-cell or natural killer cell infiltration in tumors; however, a statistically significant association was observed between HLA class II expression on tumor cells and IFN gamma mRNA levels (two-sided P = .01).

CONCLUSIONS

A subgroup of poor-prognosis cervical carcinoma patients who have low levels of intratumoral IFN gamma mRNA was identified.

Chimeric papillomavirus virus-like particles elicit antitumor immunity against the E7 oncoprotein in an HPV16 tumor model

Papillomavirus-like particles (VLPs) are a promising prophylactic vaccine candidate to prevent human papillomavirus (HPV) infections and associated epithelial neoplasia. However, they are unlikely to have therapeutic effects because the virion capsid proteins are not detected in the proliferating cells of the infected epithelia or in cervical carcinomas. To increase the number of viral antigen targets for cell-mediated immune responses in a VLP-based vaccine, we have generated stable chimeric VLPs consisting of the L1 major capsid protein plus the entire E7 (11 kDa) or E2 (43 kDa) nonstructural papillomavirus protein fused to the L2 minor capsid protein. The chimeric VLPs are indistinguishable from the parental VLPs in their morphology and in their ability to agglutinate erythrocytes and elicit high titers of neutralizing antibodies. Protection from tumor challenge was tested in C57BL/6 mice by using the tumor cell line TC-1, which expresses HPV16 E7, but not the virion structural proteins. Injection of HPV16 L1/L2-HPV16 E7 chimeric VLPs, but not HPV16 L1/L2 VLPs, protected the mice from tumor challenge, even in the absence of adjuvant. The chimeric VLPs also induced protection against tumor challenge in major histocompatibility class II-deficient mice, but not in beta2-microglobulin or perforin knockout mice implying that protection was mediated by class I-restricted cytotoxic lymphocytes. These findings raise the possibility that VLPs may generally be efficient vehicles for generating cell-mediated immune responses and that, specifically, chimeric VLPs containing papillomavirus nonstructural proteins may increase the therapeutic potential of VLP-based prophylactic vaccines in humans.

Prospects for human papillomavirus vaccine development: emerging HPV vaccines

This review concentrates on recent advances in human papillomavirus vaccine development. Strategies for prophylactic HPV subunit vaccines utilizing recombinantly synthesized, immunogenic virus-like particles are discussed. Therapeutic strategies focusing on the induction of cell-mediated immunity and gene manipulation for the treatment of established HPV-associated disease are also reviewed.

High structural side chain specificity required at the second position of immunogenic peptides to obtain stable MHC/peptide complexes

Peptides binding to HLA-A11 contain a hydrophobic or a small polar amino acid at position 2 and a lysine at the carboxy terminus. Synthetic peptides carrying natural and unnatural amino acids in position 2 were used to determine the requirements for formation of stable HLA-A11/peptide complexes. By kinetic analysis we demonstrate that a stereospecific interaction between the side chain residue in position 2 and a subsite of pocket B is required to obtain stable HLA/peptide complexes. This specific interaction is mediated by a methyl group or by an ethyl group bound to the asymmetric Cbeta atom with the correct configuration. Experiments performed with different peptide sequences suggest that the presence of adequate anchor residues may be sufficient to produce stable HLA/peptide complexes.

Papillomavirus virus-like particles can deliver defined CTL epitopes to the MHC class I pathway

To evaluate an antigen delivery system in which exogenous antigen can target the major histocompatibility complex (MHC) class I pathway, a single human papillomavirus (HPV) 16 E7 cytotoxic T lymphocyte (CTL) epitope and a single HIV gp160 CTL epitope were separately fused to the C-terminus of bovine papillomavirus 1 (BPV1) L1 sequence to form hybrid BPV1L1 VLPs. Mice immunized with these hybrid VLPs mounted strong CTL responses against the relevant target cells in the absence of any adjuvants. In addition, the CTL responses induced by immunization with BPV1L1/HPV16E7CTL VLPs protected mice against challenge with E7-transformed tumor cells. Furthermore, a high titer-specific antibody response against BPV1L1 VLPs was also induced, and this antiserum could inhibit papillomavirus-induced agglutination of mouse erythrocytes, suggesting that the antibody may recognize conformational determinates relevant to virus neutralization. These data demonstrate that hybrid BPV1L1 VLPs can be used as carriers to target antigenic epitopes to both the MHC class I and class II pathways, providing a promising strategy for the design of vaccines to prevent virus infection, with the potential to elicit therapeutic virus-specific CTL responses.

Protective anti-tumor immunity induced by vaccination with recombinant adenoviruses encoding multiple tumor-associated cytotoxic T lymphocyte epitopes in a string-of-beads fashion

Vaccines harboring genes that encode functional oncoproteins are intrinsically hazardous, as their application may lead to introduction of these genes into normal cells and thereby to tumorigenesis. On the other hand, oncoproteins are especially attractive targets for immunotherapy of cancer, as their expression is generally required for tumor growth, making the arisal of tumor variants lacking these antigens unlikely. Using murine tumor models, we investigated the efficacy of polyepitope recombinant adenovirus (rAd) vaccines, which encode only the immunogenic T cell epitopes derived from several oncogenes, for the induction of protective anti-tumor immunity. We chose to employ rAd, as these are safe vectors that do not induce the side effects associated with, for example, vaccinia virus vaccines. A single polyepitope rAd was shown to give rise to presentation of both H-2 and human leukocyte antigen-restricted cytotoxic T lymphocyte (CTL) epitopes. Moreover, vaccination with a rAd encoding H-2-restricted CTL epitopes, derived from human adenovirus type 5 early region 1 and human papilloma virus type 16-induced tumors, elicited strong tumor-reactive CTL and protected the vaccinated animals against an otherwise lethal challenge with either of these tumors. The protection induced was superior compared with that obtained by vaccination with irradiated tumor cells. Thus, vaccination with polyepitope rAd is a powerful approach for the induction of protective anti-tumor immunity that allows simultaneous immunization against multiple tumor-associated T cell epitopes, restricted by various major histocompatibility complex haplotypes.

Genetically modified bone marrow-derived dendritic cells expressing tumor-associated viral or "self" antigens induce antitumor immunity in vivo

The clinical application of synthetic tumor peptide-based vaccines is currently limited to patients with specified major histocompatibility complex (MHC) class I alleles. Such logistic limitations may be overcome using tumor gene-based approaches. Here we describe the effective generation of dendritic cells (DC) expressing tumor peptide-MHC complexes as a result of particle-mediated transfer of genes encoding tumor-associated antigens (TAA). Bone marrow-derived DC were transfected with plasmid DNA encoding the tumor-associated viral antigen E7 derived from human papilloma virus (HPV) 16. When applied as a vaccine, these genetically modified DC induced antigen-specific CD8+ cytotoxic T lymphocytes (CTL) in vivo and promoted the rejection of a subsequent, normally lethal challenge with an HPV 16-transformed tumor cell line. Of greatest interest, immunization of mice with syngeneic DC genetically modified to enhance their presentation of a constitutive "self" epitope derived from the tumor-suppressor gene product p53 caused a significant reduction in the in vivo growth of a chemically induced p53-positive sarcoma. These results suggest that cancer vaccines consisting of DC genetically modified to express TAA of viral or "self" origin effectively induce antitumor immunity in vivo.

Hierarchy of Epstein-Barr virus-specific cytotoxic T-cell responses in individuals carrying different subtypes of an HLA allele: implications for epitope-based antiviral vaccines

Major histocompatibility complex class I-restricted Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) in healthy virus carriers constitute a primary effector arm of the immune system in controlling the proliferation of virus-infected B cells in vivo. These CTLs generally recognize target epitopes included within the latent antigens of the virus. For example, CTLs from HLA B44+ healthy virus carriers often recognize peptide EENLLDFVRF [corrected] from EBV nuclear antigen 6. However, the strength of this response directly correlates with the HLA B44 subtype expressed by the individual donor. Indeed, HLA B*4405+ virus carriers consistently show a very high frequency of CTL precursors for the EENLLDFVRF [corrected] epitope, while a much weaker response is seen in HLA B*4403+ and HLA B*4402+ individuals. This disparity is not due to an intrinsic difference in the CTLs generated by individuals carrying different subtypes of HLA B44. In fact, virus-specific CTLs recognize EENLLDFVRF [corrected] peptide-sensitized HLA B*4405+ target cells more efficiently than B*4402+ or B*4403+ target cells irrespective of the HLA B44 subtype expressed by the donors from whom these effectors were isolated. This effect is evident whether the CTL epitope is endogenously processed or exogenously presented. In addition, a comparison of the intracellular transport kinetics of different B44 subtypes revealed that the B*4405 allele is rapidly assembled and arrives in the trans-Golgi compartment at a faster rate than B*4402 or B*4403. Based on these results, we propose that HLA class I alleles that are capable of binding peptides more efficiently from the intracellular pool, and are rapidly assembled and transported, may confer a protective advantage against viral infection.

Identification of HLA-A*0201-restricted CTL epitopes encoded by the tumor-specific MAGE-2 gene product

MAGE-2 is expressed in many tumors, including melanoma, laryngeal tumors, lung tumors and sarcomas, but not in healthy tissue, with the exception of testis. Thus, MAGE-2-derived peptides that bind to HLA class I molecules and elicit cytotoxic T lymphocyte (CTL) responses could be of significant therapeutic importance. In this study, we show that several MAGE-2-derived peptides bind with high affinity to HLA-A*0201. Three of them form complexes with HLA-A*0201 that are stable at 37 degrees C and are immunogenic in HLA-A*0201Kb transgenic mice. Moreover, CTLs against 2 of them (M2 112-120, and M2 157-166) specifically recognize cells that express both the MAGE-2 protein and HLA-A*0201Kb. These 2 peptides are processed and presented in the context of HLA-A*0201. Therefore, these peptides are candidate components in peptide-based vaccines for the treatment and prevention of several types of MAGE-2-expressing cancers.

Priming of cytotoxic T lymphocytes by five heat-aggregated antigens in vivo: conditions, efficiency, and relation to antibody responses

Mice were immunized i.p. with soluble or heat-denatured protein antigens [ovalbumin, beta-galactosidase, or recombinant E7 protein of human papilloma virus type 16 (HBV)]. Heat-denatured (100 degrees C) preparations of these proteins were able to induce cytotoxic T lymphocytes (CTL) that recognize cells expressing the respective genes, whereas native protein was either inefficient or required up to 30-fold higher doses. If the heat-treated proteins were separated into aggregated and soluble fractions by ultracentrifugation, only the aggregated fractions were able to induce specific CTL; this is probably because of the easier access to one of the major histocompatibility complex class I loading pathways for exogenous antigen. Addition of the adjuvant aluminium hydroxide (alum) to aggregated proteins abolished their ability to induce CTL; thus, a condition leading to a strong antibody response appeared to inhibit CTL induction. Interestingly, immunization with heat-denatured ovalbumin plus alum increased the IgM/IgG1 ratio compared to immunization with native ovalbumin and alum. Immunization of B6 mice transgenic for an HLA-A2/H-2K(b) hybrid gene with heat-denatured, recombinant HPV 16-E7 protein induced D(b)-restricted CTL specific for the peptide 49-57 of E7, indicating that this epitope is immunodominant over any A2-restricted E7 epitope in these mice. A whole influenza virus preparation heated to 100 degrees C or even autoclaved was still able to induce virus-specific CTL and BALB/c spleen cells heated to 100 degrees C could still cross-prime minor H-specific CTL in B6 mice, although with lower efficiency than fresh spleen cells. Thus, aggregated proteins can be considered as components for future vaccines.

Tumor eradication by wild-type p53-specific cytotoxic T lymphocytes

The tumor suppressor protein p53 is overexpressed in close to 50% of all human malignancies. The p53 protein is therefore an attractive target for immunotherapy. Cytotoxic T lymphocytes (CTLs) recognizing a murine wild-type p53 peptide, presented by the major histocompatibility complex class I molecule H-2Kb, were generated by immunizing p53 gene deficient (p53 -/-) C57BL/6 mice with syngeneic p53-overexpressing tumor cells. Adoptive transfer of these CTLs into tumor-bearing p53 +/+ nude mice caused complete and permanent tumor eradication. Importantly, this occurred in the absence of any demonstrable damage to normal tissue. When transferred into p53 +/+ immunocompetent C57BL/6 mice, the CTLs persisted for weeks in the absence of immunopathology and were capable of preventing tumor outgrowth. Wild-type p53-specific CTLs can apparently discriminate between p53-overexpressing tumor cells and normal tissue, indicating that widely expressed autologous molecules such as p53 can serve as a target for CTL-mediated immunotherapy of tumors.

Presentation of the HPV16E7 protein by skin grafts is insufficient to allow graft rejection in an E7-primed animal

The E7 transforming protein of Human Papillomavirus type 16 (HPV16) is expressed in the skin of a line of FVB mice transgenic for the E6 and E7 open reading frames of HPV16 driven from the alpha A crystallin promoter (FVB alpha AcryHPV16E6E7). We have transferred skin from FVB alpha AcryHPV16E6E7 mice to naive or E7-primed syngeneic FVB recipients to assess whether the E7 protein of HPV16 can function as a minor transplantation antigen (MTA) and promote skin graft rejection. FVB mice did not reject E7 expressing tail or flank skin grafts. E7 immunized FVB x C57BL/6J mice recipients of FVB alpha-AcryHPV16E6E7 x C57BL/6J skin generated humoral and DTH responses to E7 in vivo and E7-specific CTL precursors in the spleen, but failed to reject E7 expressing tail skin grafts by 100 days posttransfer. Thus although HPV16 E7 + ve mesenchymal and endodermal tumors can be eliminated by an E7-specific immune response, the same protein is unable to act as a MTA and promote graft rejection when expressed in skin cells. Lack of rejection of grafts expressing MTAs such as E7 may be relevant to the immunology of epithelial tumors expressing tumor-specific antigens and to our understanding of the immunology of diseases of the skin.

A peptide encoding a B-cell epitope from the N-terminus of the capsid protein L2 of bovine papillomavirus-4 prevents disease

The first 200 N-terminus amino acids of the L2 capsid protein of BPV-4 (designated L2a) are an effective prophylactic vaccine against BPV-4 infection. Vaccination with L2a induces the production of virus neutralizing antibodies, and when L2a antibodies are removed from immune sera, the sera lose their neutralization activity. L2a encodes three dominant B-cell epitopes, defined as epitope 1 (amino acids 101-120), epitope 2 (aa 131-151), and epitope 3 (aa 151-170). To investigate whether any of these epitopes are responsible individually or in combination for protection against viral challenge, synthetic peptides, corresponding to the three epitopes (peptides 11, 14, and 16, respectively) and conjugated to keyhole limpet hemocyanin (KLH) were tested in vaccination challenge experiments. Calves vaccinated with the three peptides together showed no evidence of papillomavirus infection; those vaccinated with peptide 14 alone developed only early lesions which did not progress to proper papillomas and regressed rapidly; those vaccinated with peptide 11 or peptide 16 alone were not protected and proceeded to develop papillomas. Therefore the three B-cell epitopes are not conventionally "neutralizing" when presented individually, but in combination they form a complex neutralization domain, and, in particular, epitope 2, represented by peptide 14, encodes a domain responsible for disease prevention.

Chimeric papillomavirus-like particles

We have constructed chimeric papillomavirus-like particles (CVLPs) by replacing the 34-carboxy-terminal amino acids of the HPV 16 L1 protein with various parts of the HPV 16 E7 protein. Chimeric proteins were expressed by recombinant baculoviruses and analyzed by electron microscopy for their ability to assemble into virus capsids. We were able to produce CVLPs in high efficiencies with inserts of up to 60 amino acids. CVLPs are able to induce a neutralizing antibody response, assayed by inhibition of hemagglutination of mouse erythrocytes. CVLPs are interacting with the putative receptor for papillomaviruses as they were shown to hemagglutinate mouse red blood cells and bind to and penetrate cells in vitro. As CVLPs follow a similar intracellular pathway as observed earlier for BPV VLPs, we speculate that CVLPs can be used to deliver peptides into mammalian cells in vitro and in vivo, possibly reaching the pathway for MHC class I presentation.

Dendritic cells infected with poxviruses encoding MART-1/Melan A sensitize T lymphocytes in vitro

Dendritic cells (DC) are potent professional antigen-presenting cells that can activate naive T lymphocytes and initiate cellular immune responses. As adjuvants, DC may be useful in enhancing the immunogenicity of tumor antigens and mediating tumor regression. Endogenous expression of antigen by DC offers the potential advantage of allowing prolonged constitutive presentation of endogenously processed epitopes and exploitation of multiple restriction elements for the presentation of the same antigen. In this report, we show that human DC are (a) capable of infection by recombinant poxviruses encoding melanoma-associated antigen (MAA) genes and (b) capable of efficiently processing and presenting these MAA to cytotoxic T cells. In 6/6 HLA A*0201-expressing melanoma patients tested, the virally driven expression of MART-1/Melan A MAA by DC was sufficient to generate CD8+ T lymphocytes that could recognize naturally processed epitopes on tumor cells. In most cases, specific anti-MART-1 reactivity could be detected after a single stimulation. Analysis of epitope dominance revealed that the amino acid sequence recognized by these cytotoxic T lymphocytes (CTL) corresponded to the MART-1(27-35) residues previously shown to be most commonly recognized by cytotoxic T lymphocytes expanded from metastatic melanoma lesions. These data show that the virally driven expression of MAA by DC can be exploited for the efficient induction of clinically relevant cytotoxic T-cell responses. This has clinical implications for active immunization therapy, and currently vaccine trials have been proposed for patients with metastatic melanoma.

Immunological ignorance of an E7-encoded cytolytic T-lymphocyte epitope in transgenic mice expressing the E7 and E6 oncogenes of human papillomavirus type 16

Certain human papillomaviruses (HPV) have been implicated in the etiology of cervical malignancies, and the E7 and E6 gene products of HPV type 16 are frequently expressed in these lesions. However, cytolytic T-lymphocyte (CTL)-mediated responses to HPV are rarely detectable in patients with cervical cancer. To examine whether the T-cell response is deficient during the HPV-induced transformation, we produced lines of transgenic (Tg) mice that expressed the E6 and E7 oncogenes in keratinized epithelia. The mice developed severe hypertrophy of all keratinized epithelia, but no malignancies were observed. Although epithelial cells from Tg mice could present at least an E7-encoded CTL epitope (E7 49-57), CTLs from these mice were neither primed to nor made tolerant of this epitope. No quantitative or qualitative differences were seen in the CTL responses of the Tg mice compared to those of their littermates following immunization with the peptide E7 49-57. Immunization of Tg mice with the E7 49-57 peptide protected them against a subcutaneous challenge with tumor cells expressing a transfected E7 gene, yet the skin was unaffected, although the cultured skin epithelial cells from Tg mice expressed E7. Our results suggest that the Tg mice were immunologically ignorant of HPV oncoproteins with respect to a CTL response and that a similar type of ignorance may explain why HPV-associated cervical cancer cells can escape immunological destruction.

Modulation of antigen processing and presentation by persistent virus infections and in tumors

Cell-mediated immunity is effective against cells harboring active virus replication and is critical for the elimination of ongoing infections, opposing tumor progression, and reducing or preventing the reactivation of persistent viruses and tumor metastasis. The capacity of persistent viruses and tumor cells to maintain a long-term relationship with their host presupposes mechanisms for circumventing antiviral or antitumor defenses. By suppressing the expression of molecules associated with antigen processing and presentation, abrogation of the major immune mechanism that deals with the elimination of infected and transformed cells is achieved. This is accomplished in tumors predominantly by transcriptional downregulation of genes encoding class I major histocompatibility complex antigens, peptide transporter molecules, and the proteasome-associated low molecular mass protease subunits, and in cells expressing viral proteins by interfering with peptide transport and the assembly/transport of class I complexes. In addition, virus-infected cells and selected tumor cells express mainly nonimmunogenic or antagonistic peptide epitopes. This review describes mechanisms used by viruses and in transformed cells for interference with antigen processing and presentation and addresses their significance for in vivo viral persistence and tumor progression.

E7 oncoprotein of human papillomavirus type 16 expressed constitutively in the epidermis has no effect on E7-specific B- or Th-repertoires or on the immune response induced or sustained after immunization with E7 protein

A line of FVB (H-2q) mice transgenic for the E6/E7 open reading frames of Human Papillomavirus type 16 driven from the alpha-A crystallin promoter expresses E7 mRNA in lens and skin epithelium. E7 protein is detectable in adult skin, coinciding with the development of inflammatory skin disease, which progresses to papillomata and squamous carcinomata in some mice. By examining the outcome of parenteral immunization with E7 protein, we sought to determine whether endogenous expression of E7 in skin had induced a preexisting immune outcome, i.e., specific immunity or tolerance, or whether the mice remain naive ("ignorant") to E7. Our data show that the antibody response to defined E7 B-epitopes, the proliferative response to Th epitopes, and the delayed-type hypersensitivity (DTH) response to whole E7 did not differ between groups of young and old E6/E7 transgenic mice (likely having different degrees of lifetime exposure to E7 protein) or between E6/E7-transgenic and nontransgenic parental strain control mice. Although an E7-specific CTL response could not be induced in the H-2q background of these mice, incorporation of a Db allele into the genome allowed comparison of Db-restricted CTL responses in E6/E7 transgenic and nontransgenic mice. Experiments indicated that the E7-immunization-induced CTL response did not differ significantly between E6/E7 transgenic and nontransgenic mice. We interpret these results to indicate that in spite of expression of E7 protein in adult skin, E6/E7 transgenic mice remain immunologically naive (ignorant) of E7 epitopes presented by immunization.

Cell mediated immunity induced in mice by HPV 16 L1 virus-like particles

Recombinant human papillomavirus (HPV) type 16 L1 virus-like particles (VLPs) expressed in the baculovirus system were used to investigate the cellular immune response to human papillomavirus type 16. The cell-mediated immune response was evaluated through immunization of mice with HPV 16 L1 virus-like particles using a lymphoproliferation assay and cytokine production and cytometric analysis of lymphocyte subsets. A significant proliferative response was observed which was associated with secretion of both interferon-gamma and interleukin-2. FACS analysis of splenic lymphocytes revealed that CD8+ T-cells were increased in the immunized mice. These results demonstrate that HPV 16 L1 VLPs induce a T-cell response characterized by a Th1 profile and confirm that the HPV 16 VLP is a reasonable candidate for vaccine development.

Identification of potential HLA-A *0201 restricted CTL epitopes derived from the epithelial cell adhesion molecule (Ep-CAM) and the carcinoembryonic antigen (CEA)

The altered expression pattern of the Epithelial Cell Adhesion Molecule (Ep-CAM) and the Carcinoembryonic Antigen (CEA) on tumor cells of epithelial origin as compared to normal epithelia may permit T cells to preferentially recognize and lyse these tumor cells. The binding affinity for human leucocyte antigen A2.1 (HLA-A*0201) and the capacity to form stable peptide-major histocompatibility complex (MHC) interactions with this molecule were tested for 410 Ep-CAM-derived sequences, including an overlapping set of 9 amino-acid-long peptides, and 73 CEA-derived peptides fulfilling the HLA-A*0201 motif. Peptides with a high binding affinity and a low peptide-MHC dissociation rate were subsequently tested for their immunogenicity in HLA-A*0201Kb transgenic mice. One Ep-CAM-derived peptide and 1 CEA-derived peptide were able to reproducibly induce peptide-specific cytotoxic T cells (CTL) in these mice. This indicates that EpCAM and CEA are potential target antigens for CTL-mediated immunotherapy of epithelial cancers.

Bone marrow-derived dendritic cells serve as potent adjuvants for peptide-based antitumor vaccines

Dendritic cells (DCs) are considered the most effective antigen-presenting cells (APCs) for primary immune responses. Since presentation of antigens to the immune system by appropriate professional APCs is critical to elicit a strong immune reaction and DCs seem to be quantitatively and functionally defective in the tumor host, DCs hold great promise to improve cancer vaccines. Even though they are found in lymphoid organs, skin and mucosa, the difficulty of generating large numbers of DCs has been a major limitation for their use in vaccine studies. A simple method for obtaining DCs from mouse bone marrow cells cultured in the presence of GM-CSF + interleukin 4 is now available. In four different tumor models, mice injected with DCs grown in GM-CSF plus interleukin 4 and prepulsed with a cytotoxic T lymphocyte-recognized tumor peptide epitope developed a specific cytotoxic T lymphocyte response and were protected against a subsequent tumor challenge with tumor cells expressing the relevant tumor antigen. Moreover, treatment of day 5-14 tumors with peptide-pulsed DCs resulted in sustained tumor regression in five different tumor models. These results suggest that presentation of tumor antigens to the immune system by professional APCs is a promising method to circumvent tumor-mediated immunosuppression and is the basis for ongoing clinical trials of cancer immunotherapy with tumor peptide-pulsed DCs.

The current status of therapeutic HPV vaccine

Cervical carcinoma is the second most common cause of cancer-related deaths in women worldwide. Recurrences occur in 15% of the patients after optimal treatment of low-risk early-stage disease. Treatment results of recurrent disease are relatively poor and for this reason new therapeutic strategies are warranted. Viral infection with human papillomavirus seems to have an essential part in the aetiology of cervical carcinoma. Evidence for the assumption that cervical carcinoma, among other malignancies such as melanomas, renal malignancies and Kaposi sarcoma, are immunogenic is provided by the fact that these malignancies grow more rapidly in the presence of systemic immunosuppression. Spontaneous regression for these tumour types is also described and immunohistochemical studies show extensive infiltrates in the tumour, consisting of immunocompetent cells. It is thus postulated that cellular immunity, and mainly the T-cell system plays an important role in the antitumour defence in cervical carcinoma. This review describes the rationale for the use of immunotherapy as treatment for cervical carcinoma as well as the results of recent developments in tumour immunology and its implications for the clinical use of immunotherapeutical approaches.

Minimal phenotype panels. A method for achieving maximum population coverage with a minimum of HLA antigens

Vaccination with peptides that induce a specific immune response is a potential prophylactic or therapeutic strategy against viral infections and tumors. Because of the extensive polymorphism of the HLA loci, synthetic peptide vaccines must consist of a cocktail of peptides that bind specifically to different HLA molecules. Such cocktails should be optimized for the target population as each population has its specific HLA gene frequencies. To achieve maximum population coverage with a minimum number of peptides, information is needed on the ranking of the most frequent HLA phenotypes. We introduce the minimal phenotype panel, which is the smallest combination of HLA antigens selected so that the proportion of individuals in a population that express at least one of the antigens in the panel exceeds a desired minimum value. We developed a method for assembling minimal phenotype panels based on known HLA class I gene frequencies. We give an example based on a set of 2446 well-defined HLA-typed, random, healthy, unrelated, Dutch Caucasoid individuals. In addition, we discuss the possibility of assembling minimal phenotype panels based on two-locus haplotypes, which enables the assembly of phenotype panels from the antigens of both loci.

Generation of tumor-specific cytolytic T lymphocytes from peripheral blood of cervical cancer patients by in vitro stimulation with a synthetic human papillomavirus type 16 E7 epitope

OBJECTIVE

Approximately 90% of squamous carcinomas of the cervix harbor the human papillomavirus and type 16 has been detected in nearly 50% of cases. Recent studies in mice have shown that the human papillomavirus type 16 E7 oncoprotein contains peptide epitopes that are processed and presented in association with a major histocompatibility antigen for recognition by cytolytic T lymphocytes. We investigated whether an epitope from human papillomavirus type 16 E7 could be used to generate specific human cytolytic T lymphocytes in patients with cervical carcinoma.

STUDY DESIGN

After radiation therapy, three patients with antigen HLA-A2 and with locally advanced cervical cancer underwent leukapheresis. Epitope-specific cytolytic T lymphocytes were generated from the peripheral blood mononuclear cells by in vitro stimulation with autologous peripheral blood mononuclear cells pulsed with a human papillomavirus type 16 E7, HLA-A2-restricted, synthetic peptide, E7(11-20) (YMLDLQPETT).

RESULTS

In two patients cytolytic T lymphocytes were capable of E7(11-20)-specific, HLA-A2-restricted cytolysis of the peptide-pulsed, HLA-matched, T2 target cell line. Cytolytic T lymphocytes from one of these patients also demonstrated specific cytolysis against the HLA-A2+, HPV-16+ CaSki cervical cancer cell line but did not lyse either HLA-A2+, HPV-16- MS-751 cells or HLA-A2-, HPV-16- HT-3 cells.

CONCLUSIONS

These experiments demonstrate that novel cytolytic T lymphocytes that recognize a human papillomavirus type 16 E7 epitope can be generated by using the peripheral blood mononuclear cells from irradiated patients with cervical cancer. In addition, because CaSki cells were specifically lysed by the cytolytic T lymphocytes, these data indicate that the peptide E7(11-20) is endogenously processed and presented on the cell surface of the CaSki cells. The demonstration of epitope-specific lysis of cytolytic T lymphocytes of HPV-16+ cervical cancer cells supports further efforts to develop human papillomavirus peptide-based vaccines or antigen-specific adoptive immunotherapy for the prevention and treatment of cervical carcinoma.

Identification of potential CTL epitopes of bovine RSV using allele-specific peptide motifs from bovine MHC class I molecules

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in young infants and housed calves. Depletion of CD8+ lymphocytes from calves inhibited their ability to clear the virus from the nasopharynx and lungs. To study these cells further, a cytotoxic T lymphocyte (CTL) assay was established. CTL could be demonstrated in the peripheral blood of gnotobiotic calves 7-10 days post infection (p.i.) with RSV and in lungs 10 days p.i. This response was both MHC-restricted and virus-specific. Following separation of the lung lymphocytes by magnetic activated cell sorting, it was shown that the cytolytic activity was mediated by cells of the CD8+ phenotype. To identify epitopes recognised by bovine CTL, the consensus motifs from MHC class I alleles found in the herd at Compton were identified. cDNA libraries were constructed and screened for full length class I sequences. The isolated cDNA clones were then transfected into mouse P815 cells and the expressed product immunoprecipitated and matched with a serological specificity. The bovine MHC class I molecules were isolated from lysed transfected cells by affinity chromatography, using a monoclonal antibody specific for bovine MHC class I, and bound peptides were separated by reverse-phase HPLC. Analysis of the protein sequences of bovine RSV for the defined motifs has identified potential CTL epitopes.

Construction and characterisation of a recombinant vaccinia virus expressing human papillomavirus proteins for immunotherapy of cervical cancer

The presence and consistent expression of the genes encoding the human papillomavirus (HPV) E6 and E7 proteins in the great majority of cervical tumours presents the opportunity for an immunotherapeutic approach for control of the disease. This report describes the construction and characterisation of a recombinant vaccinia virus designed to express modified forms of the E6 and E7 proteins from HPV16 and HPV18, the viruses most commonly associated with cervical cancer. The recombinant virus (designated TA-HPV) was based on the Wyeth vaccine strain of vaccinia, and was shown to express the desired gene products. Studies in mice indicated that the recombinant virus was less neurovirulent than the parental virus and was capable of inducing an HPV-specific CTL response. This pre-clinical evaluation has provided a basis for the initiation of human trials in cervical cancer patients.

Immunotherapy of cancer by peptide-based vaccines for the induction of tumor-specific T cell immunity

Recent progress in defining the molecular nature of antigens and in finding ways to manipulate T cell-mediated immune responses may provide new modalities for cancer treatment. In this report, we review preclinical studies as well as the first clinical trials with vaccination strategies aiming at the induction of anti-tumor immunity. In particular, we focus on the development of a vaccine against human papillomavirus-induced cervical carcinoma.

Synthetic peptides entrapped in microparticles can elicit cytotoxic T cell activity

Peptides from Plasmodium berghei circumsporozoite protein (CS) and influenza A virus nucleoprotein (NP) were entrapped in microparticles prepared from poly (lactide-co-glycolide) polymers, and the microparticles were administered parenterally to mice. After immunization with single or multiple doses, splenocytes were tested for a cytotoxic T cell (CTL) response and high levels of CTL activity were detected. The CTL induced were CD8+, MHC class I restricted, and could recognize virus infected cells. Peptide entrapped in microparticles of mean size < 500 nm were better inducers of CTL than larger microparticles (mean > 2 microns and above). Microparticles could also be used to deliver lipid modified peptides (lipopeptides) and elicited higher levels of cytolytic activity than either free peptide in microparticles or lipopeptide alone. Microparticles provide a novel way of inducing a CTL response using synthetic peptides.

Susceptibility to human papillomavirus-associated cervical intra-epithelial neoplasia is determined by specific HLA DR-DQ alleles

Human papillomaviruses (HPV) play a causative role in the aetiology of cervical intra-epithelial neoplasia (CIN) and cervical cancer. Human leukocyte antigens (HLA) are important in the regulation of immune response to foreign antigens. The role of genetic variation at the HLA class II loci (DR and DQ) in CIN (HPV 16, 18, 31 and 33 typed) was investigated by PCR DNA amplification and oligonucleotide probe typing of cervical smears from British Caucasian patients (n = 176) and controls (n = 416). The alleles of the DQB1*03, DRB1*04 and DRB1*11 loci were strongly associated with susceptibility to CIN. Specifically, the haplotypes DRB1*0401-DQB1*0301 and DRB1*1101-DQB1*0301 were significant and indicated susceptibility. The DQB1*03 locus was more contributory to this association than the DRB1 loci. A weak protective effect was shown for the haplotype DRB1*0101-DQB1*0501. Positive correlation was also observed for HPV-positive CIN, suggesting that specific HLA class II alleles may be important in determining the immune response to HPV antigens and the risk for CIN after HPV infection. Our results should help in the rational design of vaccines against HPV.

Induction of rat CD4+ proliferative and mouse CD8+ cytotoxic T-cell lines specific for human papillomavirus type 16 antigens

Infection by human papillomavirus type 16 (HPV16) has been associated with cervical dysplasia and carcinoma. To detect a possible cellular immune response against HPV16, we investigated the induction of T cells specific for antigens encoded by the virus. Two CD4+ T-cell lines with a specific proliferative response were isolated from the spleens of rats vaccinated using vaccinia virus vectors expressing E6 or E7 and challenged with syngeneic HPV-transformed cells. Two CD8+ T-cell lines with a specific cytotoxic activity were obtained from mice immunized using a syngeneic squamous cell tumour cell line transfected with the full-length HPV16 DNA. These results demonstrate that both CD8-mediated cytotoxic responses and CD4-mediated delayed-type hypersensitivity responses are involved in immunologic reactions to HPV antigens.

A single residue exchange within a viral CTL epitope alters proteasome-mediated degradation resulting in lack of antigen presentation

CTL epitope (KSPWFTTL) encoded by AKV/MCF type of murine leukemia virus (MuLV) differs from the sequence in Friend/Moloney/Rauscher (FMR) type in one residue (RSPWFTTL). CTL experiments indicated defective processing of the FMR peptide in tumor cells. Proteasome-mediated digestion of AKV/MCF-type 26-mer peptides resulted in the early generation and higher levels of epitope-containing fragments than digestion of FMR-type peptides, explained by prominent cleavage next to R in the FMR sequence. The fragments were identified as 10- and 11-mer peptides and were efficiently translocated by TAP. The naturally presented AKV/MCF peptide is the 8-mer, indicating ER peptide trimming. In conclusion, a single residue exchange can cause CTL epitope destruction by specific proteasomal cleavage.

Peptide vaccination can lead to enhanced tumor growth through specific T-cell tolerance induction

Vaccination with synthetic peptides representing cytotoxic T lymphocyte (CTL) epitopes can lead to a protective CTL-mediated immunity against tumors or viruses. We now report that vaccination with a CTL epitope derived from the human adenovirus type 5 E1A-region (Ad5E1A234-243), which can serve as a target for tumor-eradicating CTL, enhances rather than inhibits the growth of Ad5E1A-expressing tumors. This adverse effect of peptide vaccination was rapidly evoked, required low doses of peptide (10 micrograms), and was achieved by a mode of peptide delivery that induces protective T-cell-mediated immunity in other models. Ad5E1A-specific CTL activity could no longer be isolated from mice after injection of Ad5E1A-peptide, indicating that tolerization of Ad5E1A-specific CTL activity causes the enhanced tumor outgrowth. In contrast to peptide vaccination, immunization with adenovirus, expressing Ad5E1A, induced Ad5E1A-specific immunity and prevented the outgrowth of Ad5E1A-expressing tumors. These results show that immunization with synthetic peptides can lead to the elimination of anti-tumor CTL responses. These findings are important for the design of safe peptide-based vaccines against tumors, allogeneic organ transplants, and T-cell-mediated autoimmune diseases.

Induction of a cytolytic T-cell response in mice with a recombinant adenovirus coding for tumor antigen P815A

We investigated the efficacy of a recombinant adenovirus in inducing a cytolytic T-lymphocyte (CTL) response in mice against tumor antigen P815A, which is present on mouse mastocytoma P815. The recombinant adenoviral vector (Adeno.PIA) contained the sequence coding for the antigenic nonapeptide which binds to the H-2.Ld molecule to form antigen P815A. We verified that murine cells infected in vitro with Adeno. PIA were lysed by an anti-P815A CTL clone. Mice then received a single intradermal injection of Adeno. PIA, and after a few weeks their spleen cells were stimulated in vitro with tumor cells expressing antigen P815A. An anti-P815A CTL response was observed with the spleen lymphocytes of nearly all the mice, providing the lymphocytes were re-stimulated in vitro with cells expressing both P815A and co-stimulatory molecule B7.1. When the stimulatory cells did not express B7.1, a specific CTL response was observed in only 45% of the mice, and it was less intense. The Adeno. P1A viral vector was unable to raise an anti-P815A response in mice that had been previously infected with a recombinant adenovirus carrying the beta-galactosidase gene or with a defective adenovirus. We conclude that adenoviral vectors may be very useful for the priming of cytolytic T-cell responses directed against human tumor antigens. Other modes of immunization may be necessary to boost the responses induced with adenoviral vectors.

Use of combinatorial peptide libraries to construct functional mimics of tumor epitopes recognized by MHC class I-restricted cytolytic T lymphocytes

Identification of cytolytic T lymphocyte (CTL) epitopes presented by major histocompatibility complex (MHC) class I molecules on tumor cells is critical for the design of active immunotherapy. We describe the use of combinatorial peptide libraries with defined amino acids in two MHC anchor positions to search for epitopes that are recognized by H-2Db- and Kb-restricted CTL specific for the mouse lymphoma EL4. An iterative strategy was used for screening libraries in which 16 amino acids were divided into 3 groups and 3 subgroups: alpha (AL, VT, FY); beta (GS, P, DE); gamma (KR, H, NQ). The proportions of each group and subgroup at individual peptide positions were changed in the library synthesis, and the effect of these changes on CTL activity was measured in a sensitive RMA-S cell assay. A single H-2Db epitope mimic was deduced from the original library that contained > 2 x 10(8) potential peptides and was at least 9 logs more potent than the original library. Immunization of syngeneic mice with this peptide elicited CTL that lysed EL4 cells as well as RMA-S cells pulsed with peptides isolated from Db molecules of EL4 cells, indicating functional similarity between the mimicking peptide and the naturally processed CTL epitope. Furthermore, adoptive transfer of such a CTL line had a therapeutic effect in mice with EL4 established as an ascites tumor. Two H-2Kb-restricted epitope mimics of the same tumor were also identified. Our method represents a novel approach for the construction of MHC class I-restricted targets that can serve as immunogens for active immunotherapy of cancer.

In vivo CTL immunity can be elicited by in vitro reconstituted MHC/peptide complex

The use of peptides as a vaccine is a potentially powerful immunization strategy. We explored the possibility of inducing an efficient cytotoxic T lymphocyte (CTL) mediated immune response in mice, using in vitro reconstituted major histocompatibility complex (MHC) class I/peptide complexes as the immunogen. Recombinant derived H-2Kb and beta 2-microglobulin (beta 2m) were properly folded into an MHC class I complex using the vesicular stomatitis virus (VSV)-8mer from the natural nucleocapsid proteinN52-59 (RGYVYQGL), an immunodominant Kb epitope in C57BL/6 (B6) mice. After immunizing mice with the H-2Kb class I/VSV peptide complex and a subsequent in vitro stimulation with the VSV peptide alone, a specific CTL response was demonstrated. The method was also applicable to other peptides, for example, the Sendai virus (SV) peptideN324-332 (FAPGNYPAL). The CTL response was mediated by CD3+/CD8+ T cells and was shown to be allele specific, as only peptide loaded target cells expressing the H-2Kb allele could be recognized. It is of interest that extremely small amounts of injected MHC class I/peptide complex (i.e. 500 pg) could generate a measurable CTL response. The MHC class I/peptide complex had to be intact and properly folded to elicit an immune response, suggesting that the complex protected the peptide for internalization by antigen presenting cells (APCs) or for delivering to the proper site for peptide exchange on the cell surface of APCs. The described immunizing method can be routinely used to prime a CTL response by employing in vitro folded MHC class I/peptide complexes, without the use of adjuvants. It appears to be efficient, sensitive and specific. By using the recombinant protein system, unlimited amounts of MHC class I/peptide complex can be produced for immunization. Moreover, this protocol permits different in vitro combinations of allelic MHC class I molecules and peptide variants.

A recombinant vaccinia virus encoding human papillomavirus types 16 and 18, E6 and E7 proteins as immunotherapy for cervical cancer

BACKGROUND

Human papillomavirus (HPV) infection, especially with type 16 or 18, is associated with cervical cancer. Two HPV proteins, E6 and E7, are consistently expressed in tumour cells. The objectives of the study were to examine the clinical and environmental safety and immunogenicity in the first clinical trial of a live recombinant vaccinia virus expressing the E6 and E7 proteins of HPV 16 and 18 (TA-HPV).

METHODS

The study was an open label phase I/II trial in eight patients with late stage cervical cancer. The patients were vaccinated with a single dose of TA-HPV and kept in strict isolation to monitor local and systemic side-effects, environmental spread, and anti-E6/E7 immune responses.

FINDINGS

Vaccination resulted in no significant clinical side-effects and there was no environmental contamination by live TA-HPV. Each patient mounted an antivaccinia antibody response and three of the eight patients developed an HPV-specific antibody response that could be ascribed to the vaccination. HPV-specific cytotoxic T lymphocytes, the effector mechanism most likely to be of therapeutic benefit, were detected in one of three evaluable patients.

INTERPRETATION

Further studies to investigate the use ot TA-HPV for immunotherapy of cervical cancer are warranted.

New peptide and protein drugs

A view is presented on a number of recent developments, the present state and the perspectives, especially from a pharmacotherapeutic viewpoint, for peptide and protein drugs. The expanding use and the increasing experience create new pharmacotherapeutic modalities. Peptide and protein drugs comprise among others proteins isolated from human sources, and peptides and proteins made by biotechnology including monoclonal antibodies, recombinant human hormones, cytokines and growth factors. In the field of vaccine development also innovation is taking place. Optimal application schemes of these drugs may not have been reached and (clinical) pharmacists should contribute to the optimization. Since recombinant technology has abolished scarcity for a number of these drugs--especially 'physiological' substances--special ethical problems regarding an unlimited application or expansion of the indications may arise.

Efficient tumor eradication by adoptively transferred cytotoxic T-cell clones in allogeneic hosts

Tumor-specific cytotoxic T cells (CTLs) can play an important role against cancer as illustrated by the observation that adoptive transfer of tumor-specific CTLs can mediate potent anti-tumor effects. Although such CTLs can be detected at the tumor site, relatively little is known about the mechanisms by which they enter the tumor. In this study, the role of major histocompatibility complex (MHC) class 1 molecules on vascular endothelium in the tumor in entry of, and tumor eradication by, tumor-specific CTL was investigated. Two H-2Db-restricted CTL clones recognizing peptide VNIRNCCYI on human adenovirus type 5 early region 1-(Ad5E1)-induced tumors were used to test whether CTLs were able to cross the vascular endothelium lacking the restricting MHC molecule. One CTL clone recognizes peptide VNIRNCCYI in the context of both H-2Db and H-2Dbm14 molecules. The other CTL clone recognizes this peptide only in the context of H-2Db. Adoptive transfer of these CTLs leads to eradication of Ad5E 1-induced, H-2Db-expressing tumors in B6(H-2Db+) and Bm14(H-2Db-) nude mice. Our data show that presentation of tumor-derived peptides by MHC molecules on endothelial cells of blood vessels in a tumor do not play a major role in eradication of tumors by adoptively transferred CTL in combination with interleukin-2. Moreover, our data show that successful adoptive CTL immunotherapy is possible across allogeneic barriers, without inducing severe side effects, provided the tumor expresses the MHC class 1-peptide complex recognized by the CTLs.

p53 as a target for cancer vaccines: recombinant canarypox virus vectors expressing p53 protect mice against lethal tumor cell challenge

The p53 protein is an attractive target for immunotherapy, because mutations in the p53 gene are the most common genetic alterations found in human tumors. These mutations result in high levels of p53 protein in the tumor cell, whereas the expression level of wild-type p53 in nonmalignant tissue is usually much lower. Several canarypox virus recombinants expressing human or murine p53 in wild-type or mutant form were constructed. Immunization with these viruses protected BALB/c mice from a challenge with an isogenic and highly tumorigenic mouse fibroblast tumor cell line expressing high levels of mutant p53. The tumor protection was equally effective regardless of whether wild-type or mutant p53 was used for the immunization, indicating that the immunologic response was not dependent on any particular p53 mutation and that immunization with this live virus vaccine works effectively against mutant p53 protein expressed in a tumor cell. In tumors escaping immunologic rejection, the expression of the p53 protein was commonly down-regulated.

A short peptide eluted from the H-2Kb molecule of a polyomavirus-positive tumor corresponds to polyomavirus large T antigen peptide at amino acids 578 to 585 and induces polyomavirus-specific immunity

A short peptide in complex with the H-2Kb molecule on PyRMA, a polyomavirus transfectant of the mouse lymphoma cell line RMA, was identified as a polyomavirus tumor-specific transplantation antigen. The peptide was obtained by affinity chromatography, acidic extraction, and reverse-phase high-pressure liquid chromatography (HPLC). In one HPLC fraction, a peptide sequence in which 5 of 8 amino acids, GKxGLxxA, corresponded to residues 578 to 585 of polyomavirus large T antigen was identified. In tumor rejection assays, we therefore tested three related synthetic peptides, corresponding to the octapeptide LT 578-585, GKTGLAAA; the nonapeptide LT 578-586, GKTGLAAAL; and the decapeptide LT 578-587, GKTGLAAALI. The octapeptide was found to give the most effective immunization against the outgrowth of the polyomavirus DNA-positive PyRMA tumor. However, none of the three peptides immunized against the original polyoma-virus-negative RMA line.

Immunisation of mice using Salmonella typhimurium expressing human papillomavirus type 16 E7 epitopes inserted into hepatitis B virus core antigen

Live vaccines based on BRD509, an attenuated S. typhimurium (aroA, aroD) strain, were constructed that directed the expression of hepatitis B core antigen particles (HBcAg) (BRD969) or HBcAg harbouring human papillomavirus type 16 E7 protein sequences (BRD974), under the control of the in vivo inducible nirB promoter. These strains were used to orally or intravenously immunise different inbred mouse strains and humoral, secretory and cellular anti-E7 and anti-HBcAg responses were monitored. Both BRD969 and BRD974 induced anti-HBcAg humoral IgG responses following oral or intravenous immunisation of B10 mice, although responses were higher in BRD969 immunised animals. IgG subclass analysis revealed a predominantly IgG2a response in these animals. BRD974, but not BRD969, induced anti-E7 humoral IgG responses. Anti-HBcAg (BRD969 and BRD974) and anti-E7 (BRD974) IgA responses were detected in the intestines of orally immunised mice. Anti-Salmonella but not anti-HBcAg or anti-E7 T helper cell responses were detected in mice immunised with BRD509, BRD969 and BRD974. Thus Salmonella vaccine strains can be used to efficiently deliver HBcAg and E7 epitopes to the mucosal and systemic immune systems.