Identification of a ras oncogene peptide that contains both CD4(+) and CD8(+) T cell epitopes in a nested configuration and elicits both T cell subset responses by peptide or DNA immunization

In silico/In vivo analysis of high-risk papillomavirus L1 and L2 conserved sequences for development of cross-subtype prophylactic vaccine

Human papillomavirus (HPV) is the most common sexually transmitted infection in the world and the main cause of cervical cancer. Nowadays, the virus-like particles (VLPs) based on L1 proteins have been considered as the best candidate for vaccine development against HPV infections. Two commercial HPV (Gardasil and Cervarix) are available. These HPV VLP vaccines induce genotype-limited protection. The major impediments such as economic barriers especially gaps in financing obstructed the optimal delivery of vaccines in developing countries. Thus, many efforts are underway to develop the next generation of vaccines against other types of high-risk HPV. In this study, we developed DNA constructs (based on L1 and L2 genes) that were potentially immunogenic and highly conserved among the high-risk HPV types. The framework of analysis include (1) B-cell epitope mapping, (2) T-cell epitope mapping (i.e., CD4⁺ and CD8⁺ T cells), (3) allergenicity assessment, (4) tap transport and proteasomal cleavage, (5) population coverage, (6) global and template-based docking, and (7) data collection, analysis, and design of the L1 and L2 DNA constructs. Our data indicated the 8-epitope candidates for helper T-cell and CTL in L1 and L2 sequences. For the L1 and L2 constructs, combination of these peptides in a single universal vaccine could involve all world population by the rate of 95.55% and 96.33%, respectively. In vitro studies showed high expression rates of multiepitope L1 (~57.86%) and L2 (~68.42%) DNA constructs in HEK-293T cells. Moreover, in vivo studies indicated that the combination of L1 and L2 DNA constructs without any adjuvant or delivery system induced effective immune responses, and protected mice against C3 tumor cells (the percentage of tumor-free mice: ~66.67%). Thus, the designed L1 and L2 DNA constructs would represent promising applications for HPV vaccine development.

Antigen-delivery through invariant chain (CD74) boosts CD8 and CD4 T cell immunity

Eradication of tumors by the immune system relies on the efficient activation of a T-cell response. For many years, the main focus of cancer immunotherapy has been on cytotoxic CD8 T-cell. However, stimulation of CD4 helper T cells is critical for the promotion and maintenance of immune memory, thus a good vaccine should evoke a two-dimensional T-cell response. The invariant chain (Ii) is required for the MHC class II heterodimer to be correctly guided through the cell, loaded with peptide, and expressed on the surface of antigen presenting cells (APC). We previously showed that by replacing the Ii CLIP peptide by an MHC-I cancer peptide, we could efficiently load MHC-I. This prompted us to test whether longer cancer peptides could be loaded on both MHC classes and whether such peptides could be accommodated in the CLIP region of Ii. We here present data showing that expanding the CLIP replacement size leads to T-cell activation. We demonstrate by using long peptides that APCs can present peptides from the same Ii molecule on both MHC-I and -II. In addition, we present evidence that antigen presentation after Ii-loading was superior to an ER-targeted minigene construct, suggesting that ER-localization was not sufficient to obtain efficient MHC-II loading. Finally, we verified that Ii-expressing dendritic cells could prime CD4⁺ and CD8⁺ T cells from a naïve population. Taken together our study demonstrates that CLIP peptide replaced Ii constructs fulfill some of the major requirements for an efficient vector for cancer vaccination.

Designing of CD8+ and CD8+-overlapped CD4+ epitope vaccine by targeting late and early proteins of human papillomavirus

BACKGROUND AND AIM

Human papillomavirus (HPV) is an oncogenic agent that causes over 90% of cases of cervical cancer in the world. Currently available prophylactic vaccines are type specific and have less therapeutic efficiency. Therefore, we aimed to predict the potential species-specific and therapeutic epitopes from the protein sequences of HPV45 by using different immunoinformatics tools.

METHODS

Initially, we determined the antigenic potential of late (L1 and L2) and early (E1, E2, E4, E5, E6, and E7) proteins. Then, major histocompatibility complex class I-restricted CD8+ T-cell epitopes were selected based on their immunogenicity. In addition, epitope conservancy, population coverage (PC), and target receptor-binding affinity of the immunogenic epitopes were determined. Moreover, we predicted the possible CD8+, nested interferon gamma (IFN-γ)-producing CD4+, and linear B-cell epitopes. Further, antigenicity, allergenicity, immunogenicity, and system biology-based virtual pathway associated with cervical cancer were predicted to confirm the therapeutic efficiency of overlapped epitopes.

RESULTS

Twenty-seven immunogenic epitopes were found to exhibit cross-protection (≥55%) against the 15 high-risk HPV strains (16, 18, 31, 33, 35, 39, 51, 52, 56, 58, 59, 68, 69, 73, and 82). The highest PC was observed in Europe (96.30%), North America (93.98%), West Indies (90.34%), North Africa (90.14%), and East Asia (89.47%). Binding affinities of 79 docked complexes observed as global energy ranged from -10.80 to -86.71 kcal/mol. In addition, CD8+ epitope-overlapped segments in CD4+ and B-cell epitopes demonstrated that immunogenicity and IFN-γ-producing efficiency ranged from 0.0483 to 0.5941 and 0.046 to 18, respectively. Further, time core simulation revealed the overlapped epitopes involved in pRb, p53, COX-2, NF-X1, and HPV45 infection signaling pathways.

CONCLUSION

Even though the results of this study need to be confirmed by further experimental peptide sensitization studies, the findings on immunogenic and IFN-γ-producing CD8+ and overlapped epitopes provide new insights into HPV vaccine development.

K-ras mutation targeted to gastric tissue progenitor cells results in chronic inflammation, an altered microenvironment, and progression to intraepithelial neoplasia

Chronic infectious diseases, such as Helicobacter pylori infection, can promote cancer in a large part through induction of chronic inflammation. Oncogenic K-ras mutation in epithelial cells activates inflammatory pathways, which could compensate for a lack of infectious stimulus. Gastric histopathology and putative progenitor markers [doublecortin and calcium/calmodulin-dependent protein kinase-like 1 (Dcamkl1) and keratin 19 (K19)] in K19-K-ras-V12 (K19-kras) transgenic mice were assessed at 3, 6, 12, and 18 months of age, in comparison with Helicobacter felis-infected wild-type littermates. Inflammation was evaluated by reverse transcription-PCR of proinflammatory cytokines, and K19-kras mice were transplanted with green fluorescent protein (GFP)-labeled bone marrow. Both H. felis infection and K-ras mutation induced upregulation of proinflammatory cytokines, expansion of Dcamkl1(+) cells, and progression to oxyntic atrophy, metaplasia, hyperplasia, and high-grade dysplasia. K19-kras transgenic mice uniquely displayed mucous metaplasia as early as 3 months and progressed to high-grade dysplasia and invasive intramucosal carcinoma by 20 months. In bone marrow-transplanted K19-kras mice that progressed to dysplasia, a large proportion of stromal cells were GFP(+) and bone marrow-derived, but only rare GFP(+) epithelial cells were observed. GFP(+) bone marrow-derived cells included leukocytes and CD45(-) stromal cells that expressed vimentin or α smooth muscle actin and were often found surrounding clusters of Dcamkl1(+) cells at the base of gastric glands. In conclusion, the expression of mutant K-ras in K19(+) gastric epithelial cells can induce chronic inflammation and promote the development of dysplasia.

Multiple roles for CD4+ T cells in anti-tumor immune responses

Our understanding of the importance of CD4+ T cells in orchestrating immune responses has grown dramatically over the past decade. This lymphocyte family consists of diverse subsets ranging from interferon-gamma (IFN-gamma)-producing T-helper 1 (Th1) cells to transforming growth factor-beta (TGF-beta)-secreting T-regulatory cells, which have opposite roles in modulating immune responses to pathogens, tumor cells, and self-antigens. This review briefly addresses the various T-cell subsets within the CD4+ T-cell family and discusses recent research efforts aimed at elucidating the nature of the 'T-cell help' that has been shown to be essential for optimal immune function. Particular attention is paid to the role of Th cells in tumor immunotherapy. We review some of our own work in the field describing how CD4+ Th cells can enhance anti-tumor cytotoxic T-lymphocyte (CTL) responses by enhancing clonal expansion at the tumor site, preventing activation-induced cell death and functioning as antigen-presenting cells for CTLs to preferentially generate immune memory cells. These unconventional roles for Th lymphocytes, which require direct cell-to-cell communication with CTLs, are clear examples of how versatile these immunoregulatory cells are.

DNA vaccines against cancer

Significant progress made in the field of tumor immunology by the characterization of a large number of tumor antigens, and the better understanding of the mechanisms preventing immune responses to malignancies has led to the extensive study of cancer immunization approaches such as DNA vaccines encoding tumor antigens. This article reviews major aspects of DNA immunization in cancer. It gives a brief history and then discusses the proposed mechanism of action, preclinical and clinical studies, and methods of enhancing the immune responses induced by DNA vaccines.

Is genetic vaccination against allergy possible?

Genetic immunization has proven a powerful method to induce antiallergic immune responses. The underlying functional principle has been described to be based on the recruitment of allergen-specific Th1 cells, CD8+ cells and the establishment of a Th1 cytokine milieu, which prevent the development of a Th2-biased response in a protective setup and can balance an ongoing Th2-type response in a therapeutic situation. Genetic immunization with plasmid DNA offers innovative solutions to the major problems associated with protein immunization, such as crosslinking of pre-existing immunoglobulin E on mast cells/basophils or induction of de novo synthesis of immunoglobulin E by the protein immunization itself. It easily enables the routine production of hypoallergenic vaccines, which do not translate native allergens, thus avoiding potential anaphylactic side effects. DNA vaccines can also be applied as mixtures of single vaccines, making them interesting candidates for treatment based on component-resolved diagnosis, followed by an individualized therapy with the relevant allergens. In addition to the description of up-to-date allergen gene vaccine approaches, this review gives an overview of animal studies dealing with the following topics: danger signals as the inherent adjuvant properties, methods to optimize the vaccine immunogenicity, modulation of the immune response, nonparenteral applications and low-dose vaccination strategies.

Identification of Immunodominant Epitopes of α-Gliadin in HLA-DQ8 Transgenic Mice following Oral Immunization

Celiac disease, triggered by wheat gliadin and related prolamins from barley and rye, is characterized by a strong association with HLA-DQ2 and HLA-DQ8 genes. Gliadin is a mixture of many proteins that makes difficult the identification of major immunodominant epitopes. To address this issue, we expressed in Escherichia coli a recombinant alpha-gliadin (r-alpha-gliadin) showing the most conserved sequence among the fraction of alpha-gliadins. HLA-DQ8 mice, on a gluten-free diet, were intragastrically immunized with a chymotryptic digest of r-alpha-gliadin along with cholera toxin as adjuvant. Spleen and mesenteric lymph node T cell responses were analyzed for in vitro proliferative assay using a panel of synthetic peptides encompassing the entire sequence of r-alpha-gliadin. Two immunodominant epitopes corresponding to peptide p13 (aa 120-139) and p23 (aa 220-239) were identified. The response was restricted to DQ and mediated by CD4+ T cells. In vitro tissue transglutaminase deamidation of both peptides did not increase the response; furthermore, tissue transglutaminase catalyzed extensive deamidation in vitro along the entire r-alpha-gliadin molecule, but failed to elicit new immunogenic determinants. Surprisingly, the analysis of the cytokine profile showed that both deamidated and native peptides induced preferentially IFN-gamma secretion, despite the use of cholera toxin, a mucosal adjuvant that normally induces a Th2 response to bystander Ags. Taken together, these data suggest that, in this model of gluten hypersensitivity, deamidation is not a prerequisite for the initiation of gluten responses.

Cancer immunotherapy targeting Sp17: when should the laboratory findings be translated to the clinics?

Despite advances in chemotherapeutic agents, the prognosis for some cancers remains extremely poor, suggesting the need for other treatment modalities. Immunotherapy appears an ideal approach because the mechanisms of tumor cell killing induced by tumor vaccines are different from those from chemotherapy. Various investigations are ongoing to identify suitable targets for this purpose. Sperm protein 17 (Sp17) was originally identified by our group as a novel cancer-testis antigen in various malignancies, including multiple myeloma. Sp17 is a highly immunogenic protein and the observation that more than 90% of vasectomized males develop immunity against Sp17 suggests the opportunity and safety of Sp17 for tumor vaccines. Recent works by other workers suggest a low level of expression of Sp17 in some normal tissues, and investigators have questioned whether Sp17 is in fact a suitable target for immunotherapy. In this paper, we review the general principles of immunotherapy and provide evidence supporting the highly immunogenic nature of Sp17. We also address the discrepancies between the objectives of oncologists involved in treating cancer patients and their familiarity with acceptable levels of toxicity of any effective therapy and those of pure laboratory-based investigators. Finally, we present some early clinical data supporting the rationale for further investigations of Sp17 for tumor vaccines.

Determination of Thrombopoietin-Derived Peptides Recognized by Both Cellular and Humoral Immunities in Healthy Donors and Patients with Thrombocytopenia

Thrombopoietin (TPO) is a cytokine that promotes megakaryocytopoiesis and thrombopoiesis and is considered a drug suitable for patients with thrombocytopenia. However, unexpected severe thrombocytopenia has developed in some healthy individuals participating in phase I clinical trials with a pegylated recombinant human megakaryocyte growth factor (PEG-rHuMGDF) that contained the first 163 amino acids of endogenous TPO, which resulted in hampering the further development of clinical trials. Autoimmune responses to PEG-rHuMGDF, which cross-reacted with endogenous TPO, were suggested to be involved in this rare but severe adverse event, although the immunogenic epitopes have not yet been determined. To better understand the molecular basis of such autoimmune reactions, we investigated the reactivity of 18 TPO-derived peptides with HLA-A2-binding motifs to plasma and T cells, both from patients with thrombocytopenia (n=24) and from healthy donors (HDs) (n=24). Four peptides, including those possessing amino acids in receptor-binding sites, were preferentially reactive to plasma from at least 20% of the patients, whereas one peptide at position 101-109 was equally reactive to those of the patients and the HDs. Each of the five peptides had the ability to induce peptide-specific cytotoxic T lymphocytes (CTLs) in both groups, albeit with less frequency among the patients. More important, each of these five peptides had the ability to induce HLA-A2-restricted and peptide-specific CTL activity reactive to cells that produce TPO. These results may provide new insights to gain a better understanding of autoimmune reactions to TPO.

Direct Cross-Priming by Th Lymphocytes Generates Memory Cytotoxic T Cell Responses

Under optimal Ag stimulation, CTL become functional effector and memory T cells. Professional APCs (pAPC) are considered essential for the activation of CTL, due to their unique capacity to provide costimulation and present exogenous Ags through MHC class I molecules. In this study, we report a novel means by which Th lymphocytes acquire and present MHC class I determinants to naive CTL. Although previous studies have looked at T cell Ag presentation to activated T cells, this study presents the first example of Ag presentation by Th cells to naive CTL. We report that activated Th cells can function as effective pAPC for CTL. Our results show that: 1) In addition to acquisition of cell surface molecules, including MHC class I/peptide complexes, from pAPC, Th cells can acquire and present MHC class I-binding peptides through TCR-MHC class II interactions with pAPC; 2) the acquired Ag can be functionally presented to CTL; and 3) Ag presentation by Th cells induces naive CTL to proliferate and preferentially differentiate into cells that phenotypically and functionally resemble central memory T cells. These findings suggest a novel role of Th cells as pAPC for the development of memory immune responses.

DNA vaccines for non-infectious diseases: new treatments for tumour and allergy

The last decade of DNA vaccine research was characterised by a pioneer spirit and enormous enthusiasm, with a large number of publications demonstrating the usefulness of this approach. Unfortunately, DNA vaccines have not necessarily met the high clinical expectations and a number of complications need to be overcome. In the case of cancer and allergy, the requirements for achieving the objectives are very different. Vaccines against allergies need to suppress or alter an unwanted immune response, while a cancer DNA vaccine has to overcome tolerance and/or immune suppression and initiate a powerful immune response. This review addresses currently used general optimisation strategies for DNA vaccines such as modification of immunisation regimens, improving the delivery systems and using molecular adjuvants. In addition, cancer-specific approaches, such as the stimulation of innate and adaptive immunity with replicase-based DNA vaccines, and targeting non-tumour-associated antigens (TAAs) are discussed. Specifically for the optimisation of DNA vaccination against allergies, procedures such as allergen gene recoding, T helper (Th)1 modulation, and the creation of safe DNA vaccines by gene fragmentation, ubiquitination or using artificial hypoallergens are being analysed. These strategies, individually or in combination, hold the potential of making DNA vaccines useful for application in the clinic.

CD4+ T cell matters in tumor immunity

CD4+ T cells have been shown to be able to affect tumor growth through both direct and indirect means. In addition, a requirement has been demonstrated for CD4+ T cells in the regulation and induction of T cell memory, and CD4+ suppressor T cells have been identified, stressing a role for CD4+ T cells in the induction and maintenance of antitumor immune responses. A review of the involvement of CD4+ T cells at different stages of tumor immunity is provided, and based on these data we discuss how CD4+ T cell response induction could be incorporated into tumor immunotherapy strategies.

Identification of T helper cell-recognized epitopes in the chitinase of the filarial nematode Onchocerca volvulus

T helper cell-recognized epitopes were determined in chitinase of Onchocerca volvulus, a vaccine candidate protein. The proliferation of splenic T cells of mice immunized with recombinant protein was tested with a library of chitinase-peptides of 16 amino acids with termini overlapping by 12 amino acids, and a library of "designer peptides", i.e. sequences identified with three epitope-predicting algorithms. Fourteen epitope-bearing stretches were identified with the peptides of the overlapping library. Testing of the designer peptides partially confirmed these data and revealed additional epitopes. Five clusters of epitopes were identified for the creation of peptide or minigene DNA vaccines with good potency and potential range of MHC allele presentation.

Towards patient-specific tumor antigen selection for vaccination

In this review, we discuss the possibilities for combining the power of molecular analysis of the antigens expressed in a given individual tumor with the design of a tailored vaccine containing defined antigens. Step 1 is a differential gene expression analysis of tumor and corresponding normal tissue. Step 2 is the analysis of human leukocyte antigen (HLA) ligands on tumor cells. Step 3 is data mining with the aim to select those antigens that might be suitable for tumor attack by the adaptive immune system. Step 4 is the on-the-spot clinical grade production of the constituents of the patient tailored vaccine, e.g. peptides. Step 5 is then vaccination and monitoring. Although it will not be possible to cover all relevant antigens expressed in a tumor, the antigens that can be identified with our present technical possibilities might be enough for improved immunotherapy. The scope of the present review is to explore the possibilities and the formidable technical and logistical challenge for such individual patient-oriented antigen definition to be used for therapeutic immunization.

Established human papillomavirus type 16-expressing tumors are effectively eradicated following vaccination with long peptides

Peptide-based vaccines aimed at the induction of effective T cell responses against established cancers have so far only met with limited clinical success and clearly need to be improved. In a preclinical model of human papillomavirus (HPV)16-induced cervical cancer we show that prime-boost vaccinations with the HPV16-derived 35 amino-acid long peptide E7(43-77), containing both a CTL epitope and a Th epitope, resulted in the induction of far more robust E7-specific CD8(+) T cell responses than vaccinations with the minimal CTL epitope only. We demonstrate that two distinct mechanisms are responsible for this effect. First, vaccinations with the long peptide lead to the generation of E7-specific CD4(+) Th cells. The level of the induced E7-specific CD8(+) T cell response proved to be dependent on the interactions of these Th cells with professional APC. Second, we demonstrate that vaccination with the long peptide and dendritic cell-activating agents resulted in a superior induction of E7-specific CD8(+) T cells, even when T cell help was excluded. This suggests that, due to its size, the long peptide was preferably endocytosed, processed, and presented by professional APCs. Moreover, the efficacy of this superior HPV-specific T cell induction was demonstrated in therapeutic prime-boost vaccinations in which the long peptide admixed with the dendritic cell-activating adjuvant oligodeoxynucleotide-CpG resulted in the eradication of large, established HPV16-expressing tumors. Because the vaccine types used in this study are easy to prepare under good manufacturing practice conditions and are safe to administer to humans, these data provide important information for future clinical trials.