Design of immunogenic and effective multi-epitope DNA vaccines for melanoma

DNA vaccines as promising immuno-therapeutics against cancer: a new insight

Cancer is one of the leading causes of mortality around the world and most of our conventional treatments are not efficient enough to combat this deadly disease. Harnessing the power of the immune system to target cancer cells is one of the most appealing methods for cancer therapy. Nucleotide-based cancer vaccines, especially deoxyribonucleic acid (DNA) cancer vaccines are viable novel cancer treatments that have recently garnered significant attention. DNA cancer vaccines are made of plasmid molecules that encode tumor-associated or tumor-specific antigens (TAAs or TSAs), and possibly some other immunomodulatory adjuvants such as pro-inflammatory interleukins. Following the internalization of plasmids into cells, their genes are expressed and the tumor antigens are loaded on major histocompatibility molecules to be presented to T-cells. After the T-cells have been activated, they will look for tumor antigens and destroy the tumor cells upon encountering them. As with any other treatment, there are pros and cons associated with using these vaccines. They are relatively safe, usually well-tolerated, stable, easily mass-produced, cost-effective, and easily stored and transported. They can induce a systemic immune response effective on both the primary tumor and metastases. The main disadvantage of DNA vaccines is their poor immunogenicity. Several approaches including structural modification, combination therapy with conventional and novel cancer treatments (such as chemotherapy, radiotherapy, and immune checkpoint blockade (ICB)), and the incorporation of adjuvants into the plasmid structure have been studied to enhance the vaccine's immunogenicity and improve the clinical outcome of cancer patients. In this review, we will discuss some of the most promising optimization strategies and examine some of the important trials regarding these vaccines.

The future of cancer immunotherapy: DNA vaccines leading the way

Immuno-oncology has revolutionized cancer treatment and has opened up new opportunities for developing vaccination methods. DNA-based cancer vaccines have emerged as a promising approach to activating the bodily immune system against cancer. Plasmid DNA immunizations have shown a favorable safety profile and there occurs induction of generalized as well as tailored immune responses in preclinical and early-phase clinical experiments. However, these vaccines have notable limitations in immunogenicity and heterogeneity and these require refinements. DNA vaccine technology has been focusing on improving vaccine efficacy and delivery, with parallel developments in nanoparticle-based delivery systems and gene-editing technologies such as CRISPR/Cas9. This approach has showcased great promise in enhancing and tailoring the immune response to vaccination. Strategies to enhance the efficacy of DNA vaccines include the selection of appropriate antigens, optimizing insertion in a plasmid, and studying combinations of vaccines with conventional strategies and targeted therapies. Combination therapies have attenuated immunosuppressive activities in the tumor microenvironment and enhanced the capability of immune cells. This review provides an overview of the current framework of DNA vaccines in oncology and focuses on novel strategies, including established combination therapies and those still under development.The challenges that oncologists, scientists, and researchers need to overcome to establish DNA vaccines as an avant-garde approach to defeating cancer, are also emphasized. The clinical implications of the immunotherapeutic approaches and the need for predictive biomarkers have also been reviewed upon. We have also tried to extend the role of Neutrophil extracellular traps (NETs) to the DNA vaccines. The clinical implications of the immunotherapeutic approaches have also been reviewed upon. Ultimately, refining and optimizing DNA vaccines will enable harnessing the immune system's natural ability to recognize and eliminate cancer cells, leading the world towards a revolution in cancer cure.

Strategies in DNA vaccine for melanoma cancer

According to reports of the international agency for cancer on research, although malignant melanoma shows less prevalence than nonmelanoma skin cancers, it is the major cause of skin cancer mortality. Given that, the production of effective vaccines to control melanoma is eminently required. In this regard, DNA-based vaccines have been extensively investigated for melanoma therapy. DNA vaccines are capable of inducing both cellular and humoral branches of immune responses. These vaccines possess some valuable advantages such as lack of severe side effects and high stability compared to conventional vaccination methods. The ongoing studies are focused on novel strategies in the development of DNA vaccines encoding artificial polyepitope immunogens based on the multiple melanoma antigens, the inclusion of molecular adjuvants to increase the level of immune responses, and the improvement of delivery approaches. In this review, we have outlined the recent advances in the field of melanoma DNA vaccines and described their implications in clinical trials as a strong strategy in the prevention and control of melanoma.

Evaluation of protection induced by in vitro maturated BMDCs presenting CD8+ T cell stimulating peptides after a heterologous vaccination regimen in BALB/c model against Leishmania major

Leishmaniasis is a complex vector-borne disease mediated by Leishmania parasite and a strong and long-lasting CD4⁺ Th1 and CD8⁺-T cell immunity is required to control the infection. Thus far multivalent subunit vaccines have met this requirement more promisingly. However several full protein sequences cannot be easily arranged in one construct. Instead, new emerging immune-informatics based epitope formulations surpass this restriction. Herein, we aimed to examine the protective potential of a dendritic cell based vaccine presenting epitopes to CD8⁺ and CD4⁺-T cells in combination with DNA vaccine encoding the same epitopes against murine cutaneous leishmaniasis. Immature DCs were loaded with epitopes (selected from parasite proteome) in vitro with or without CpG oligonucleotides and were used to immunize BALB/c mice. Peptide coding DNA was used to boost the system and immunological responses were evaluated after Leishmania (L.) major infectious challenge. The pre-challenge response to included epitopes was Th1 polarized which potentially lowered the infection at early time points post-challenge but not at later weeks. Collectively, DC prime-DNA boost was found to be a promising approach for Th1 polarization however the constituent epitopes undoubtedly make a significant contribution in the protection outcome of the vaccine.

Treatment with an immature dendritic cell-targeting vaccine supplemented with IFN-α and an inhibitor of DNA methylation markedly enhances survival in a murine melanoma model

BACKGROUND

The chemokine MIP-3α (CCL20) binds to CCR6 on immature dendritic cells. DNA vaccines fusing MIP-3α to melanoma-associated antigens have shown improved efficacy and immunogenicity in the B16F10 mouse melanoma model. Here, we report that the combination of type-I interferon therapy (IFNα) with 5-Aza-2'-deoxycitidine (5Aza) profoundly enhanced the therapeutic efficacy of a MIP-3α-Gp100-Trp2 DNA vaccine.

METHODS

Beginning on day 5 post-transplantation of B16F10 melanoma, vaccine was administered intramuscularly (i.m.) by electroporation. CpG adjuvant was given 2 days later. 5Aza was given intraperitoneally at 1 mg/kg and IFNα therapy either intratumorally or i.m. as noted. Tumor sizes, tumor growth, and mouse survival were assessed. Tumor lysate gene expression levels and tumor-infiltrating lymphocytes (TILs) were assessed by qRT-PCR and flow cytometry, respectively.

RESULTS

Adding IFNα and 5Aza treatments to mice vaccinated with MIP-3α-Gp100-Trp2 leads to reduced tumor burden and increased median survival (39% over vaccine and 95% over controls). Tumor lysate expression of CCL19 and CCR7 were upregulated ten and fivefold over vaccine, respectively. Vaccine-specific and overall CD8+ TILs were increased over vaccine (sevenfold and fourfold, respectively), as well as the proportion of TILs that were CD8+ (twofold).

CONCLUSIONS

Efficient targeting of antigen to immature dendritic cells with a chemokine-fusion vaccine offers an alternative to classic and dendritic cell vaccines. Combining this approach with IFNα and 5Aza treatment significantly improved vaccine efficacy. This improved efficacy correlated with changes in chemokine gene expression and CD8+ TIL infiltration and was dependent on the presence of all therapeutic components.

Cancer DNA vaccines: current preclinical and clinical developments and future perspectives

The recent developments in immuno-oncology have opened an unprecedented avenue for the emergence of vaccine strategies. Therapeutic DNA cancer vaccines are now considered a very promising strategy to activate the immune system against cancer. In the past, several clinical trials using plasmid DNA vaccines demonstrated a good safety profile and the activation of a broad and specific immune response. However, these vaccines often demonstrated only modest therapeutic effects in clinical trials due to the immunosuppressive mechanisms developed by the tumor. To enhance the vaccine-induced immune response and the treatment efficacy, DNA vaccines could be improved by using two different strategies. The first is to increase their immunogenicity by selecting and optimizing the best antigen(s) to be inserted into the plasmid DNA. The second strategy is to combine DNA vaccines with other complementary therapies that could improve their activity by attenuating immunosuppression in the tumor microenvironment or by increasing the activity/number of immune cells. A growing number of preclinical and clinical studies are adopting these two strategies to better exploit the potential of DNA vaccination. In this review, we analyze the last 5-year preclinical studies and 10-year clinical trials using plasmid DNA vaccines for cancer therapy. We also investigate the strategies that are being developed to overcome the limitations in cancer DNA vaccination, revisiting the rationale for different combinations of therapy and the different possibilities in antigen choice. Finally, we highlight the most promising developments and critical points that need to be addressed to move towards the approval of therapeutic cancer DNA vaccines as part of the standard of cancer care in the future.

In SilicoDesigning a Novel Multi-epitope DNA Vaccine against Anti-apoptotic Proteins in Tumor Cells

Background:

Cancer therapy has been known as one of the most important challenges in the world. Various therapeutic methods such as cancer immunotherapy are used to eradicate tumor cells. Vaccines have an important role among different cancer immunotherapeutic approaches. In the field of vaccine production, bioinformatics approach is considered as a useful tool to design multi-epitope cancer vaccines, mainly for selecting immunodominant Cytotoxic T Lymphocytes (CTL) and Helper T Lymphocytes (HTL) epitopes.

Objective:

Generally, to design efficient multi-epitope cancer vaccines, Tumor-Specific Antigens (TSA) are targeted. In the context of DNA-based cancer vaccines, they contain genes that code tumor antigens and are delivered to host by different methods.

Methods:

In this study, the anti-apoptotic proteins (BCL2, BCL-X, survivin) that are over-expressed in different tumor cells were selected for CTL and HTL epitopes prediction through different servers such as RANKPEP, CTLpred, and BCPREDS.

Results:

Three regions from BCL2 and one region from BCL-X were selected as CTL epitopes and two segments from survivin were defined as HTL epitopes. In addition, β-defensin was used as a proper adjuvant to enhance vaccine efficacy. The aforesaid segments were joined together by appropriate linkers, and some important properties of designed vaccine such as antigenicity, allergenicity and physicochemical characteristics were determined by various bioinformatics servers.

Conclusion:

Based on the bioinformatics results, the physicochemical and immunological features showed that the designed vaccine construct can be used as an efficient cancer vaccine after its efficacy was confirmed by in vitro and in vivo immunological assays.

Expression and serological application of recombinant epitope-repeat protein carrying an immunodominant epitope of Newcastle disease virus nucleoprotein

Purpose

The aim of the present study was to develop a serodiagnostic test for differentiation infected from vaccinated animal (DIVA) strategy accompanying the marker vaccine lacking an immunodominant epitope (IDE) of nucleoprotein of Newcastle disease virus (NDV).

Materials and Methods

Recombinant epitope-repeat protein (rERP) gene encoding eight repeats of the IDE sequence (ETQFLDLMRAVANSMR) by tetra-glycine linker was synthesized. Recombinant baculovirus carrying the rERP gene was generated to express the rERP in insect cells. Specificity and sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) employing the rERP was evaluated.

Results

The rERP with molecular weight of 20 kDa was successfully expressed by the recombinant baculovirus in an insect-baculovirus system. The rERP was antigenically functional as demonstrated by Western blotting. An indirect ELISA employing the rERP was developed and its specificity and sensitivity was determined. The ELISA test allowed discrimination of NDV infected sera from epitope deletion virus vaccinated sera.

Conclusion

The preliminary results represent rERP ELISA as a promising DIVA diagnostic tool.

Oncolytic vaccines increase the response to PD-L1 blockade in immunogenic and poorly immunogenic tumors

Activation of immune checkpoint pathways and limited T- cell infiltration result in immunological escape of tumors. Although immune checkpoint inhibitors are currently approved for several types of cancers, the response rate is often limited by the lack of tumor specific T-cells within the malignant tissue. Therefore, new combinatorial strategies are needed to enhance the clinical benefit of immune checkpoint inhibitors. We have previously developed PeptiCRAd, an oncolytic vaccine platform capable of directing the immune response toward tumor epitopes. In this study, we evaluated whether the platform could be used to increase the response rate to checkpoint inhibitors in both highly immunogenic and poorly immunogenic tumors, such as melanoma and triple negative breast cancer (TNBC). We report here that anti-PD-L1 therapy in combination with PeptiCRAd significantly reduced the growth of melanomas and increased the response rate to checkpoint inhibition. In fact, we registered a higher rate of complete responses among mice treated with the combination. This approach promoted the presence of non-exhausted antigen-specific T-cells within the tumor in comparison to anti-PD-L1 monotherapy. Furthermore, we found that targeting both MHC-I and II restricted tumor epitopes was necessary to decrease the growth of the poorly immunogenic TNBC model 4T1 and that combination with PD-L1 blockade increased the number of responders to checkpoint inhibition. Finally, the described strategy was validated in a translational in vitro model using HLA matched human PBMCs and tumor cell lines. Consistent to our previous results, improved cytotoxicity was observed with combination of PeptiCRAd and anti-PD-L1. These results demonstrate that oncolytic virus based cancer vaccine can significantly improve the response rate to checkpoint blocking antibodies in the context of immunogenic and non-immunogenic tumors.

DEC205-DC targeted DNA vaccine against CX3CR1 protects against atherogenesis in mice

Studies disrupting the chemokine pathway CX3CL1 (fractalkine)/ CX3CR1 have shown decreased atherosclerosis in animal models but the techniques used to interrupt the pathway have not been easily translatable into human trials. DNA vaccination potentially overcomes the translational difficulties. We evaluated the effect of a DNA vaccine, targeted to CX3CR1, on atherosclerosis in a murine model and examined possible mechanisms of action. DNA vaccination against CX3CR1, enhanced by dendritic cell targeting using DEC-205 single chain variable region fragment (scFv), was performed in 8 week old ApoE-/- mice, fed a normal chow diet. High levels of anti-CX3CR1 antibodies were induced in vaccinated mice. There were no apparent adverse reactions to the vaccine. Arterial vessels of 34 week old mice were examined histologically for atherosclerotic plaque size, macrophage infiltration, smooth muscle cell infiltration and lipid deposition. Vaccinated mice had significantly reduced atherosclerotic plaque in the brachiocephalic artery. There was less macrophage infiltration but no significant change to the macrophage phenotype in the plaques. There was less lipid deposition in the lesions, but there was no effect on smooth muscle cell migration. Targeted DNA vaccination to CX3CR1 was well tolerated, induced a strong immune response and resulted in attenuated atherosclerotic lesions with reduced macrophage infiltration. DNA vaccination against chemokine pathways potentially offers a potential therapeutic option for the treatment of atherosclerosis.

Encapsulation of Hydrophilic and Hydrophobic Peptides into Hollow Mesoporous Silica Nanoparticles for Enhancement of Antitumor Immune Response

Codelivery of combinational antigenic peptides and adjuvant to antigen presenting cells is expected to amplify tumor specific T lymphocytes immune responses while minimizing the possibility of tumor escaping and reducing immune tolerance to single antigenic peptide. However, the varied hydrophobicities of these multivariant derived short antigenic peptides limit their codelivery efficiency in conventional delivery systems. Here, a facile yet effective route is presented to generate monodisperse and stable hollow mesoporous silica nanoparticles (HMSNs) for codelivering of HGP100_25-33 and TRP2_180-188 , two melanoma-derived peptides with varied hydrophobicities. The HMSNs with large pore size can improve the encapsulation efficiency of both HGP100 and TRP2 after NH₂ modification on the inner hollow core and COOH modification in the porous channels. HGP100 and TRP2 loaded HMSNs (HT@HMSNs) are further enveloped within monophosphoryl lipid A adjuvant entrapped lipid bilayer (HTM@HMLBs), for improved stability/biocompatibility and codelivery efficiency of multiple peptides, adjuvant, and enhanced antitumor immune responses. HTM@HMLBs increase uptake by dendritic cells (DCs) and stimulate DCs maturation efficiently, which further induce the activation of both tumor specific CD8⁺ and CD4⁺ T lymphocytes. Moreover, HTM@HMLBs can significantly inhibit tumor growth and lung metastasis in murine melanoma models with good safety profiles. HMSNs enveloped with lipid bilayers (HMLBs) are believed to be a promising platform for codelivery of multiple peptides, adjuvant, and enhancement of antitumor efficacy of conventional vaccinations.

Breast cancer vaccines delivered by dendritic cell-targeted lentivectors induce potent antitumor immune responses and protect mice from mammary tumor growth

Breast cancer immunotherapy is a potent treatment option, with antibody therapies such as trastuzumab increasing 2-year survival rates by 50%. However, active immunotherapy through vaccination has generally been clinically ineffective. One potential means of improving vaccine therapy is by delivering breast cancer antigens to dendritic cells (DCs) for enhanced antigen presentation. To accomplish this in vivo, we pseudotyped lentiviral vector (LV) vaccines with a modified Sindbis Virus glycoprotein so that they could deliver genes encoding the breast cancer antigen alpha-lactalbumin (Lalba) or erb-b2 receptor tyrosine kinase 2 (ERBB2 or HER2) directly to resident DCs. We hypothesized that utilizing these DC-targeting lentiviral vectors asa breast cancer vaccine could lead to an improved immune response against self-antigens found in breast cancer tumors. Indeed, single injections of the vaccine vectors were able to amplify antigen-specific CD8T cells 4-6-fold over naïve mice, similar to the best published vaccine regimens. Immunization of these mice completely inhibited tumor growth in a foreign antigen environment (LV-ERBB2 in wildtype mice), and it reduced the rate of tumor growth in a self-antigen environment (LV-Lalba in wildtype or LV-ERBB2 in MMTV-huHER2 transgenic). These results show that a single injection with targeted lentiviral vectors can be an effective immunotherapy for breast cancer. Furthermore, they could be combined with other immunotherapeutic regimens to improve outcomes for patients with breast cancer.

A novel multi-epitope vaccine from MMSA-1 and DKK1 for multiple myeloma immunotherapy

The identification of novel tumour-associated antigens is urgently needed to improve the efficacy of immunotherapy for multiple myeloma (MM). In this study, we identified a membrane protein MMSA-1 (multiple myeloma special antigen-1) that was specifically expressed in MM and exhibited significantly positive correlation with MM. We then identified HLA-A*0201-restricted MMSA-1 epitopes and tested their cytotoxic T lymphocyte (CTL) response. The MMSA-1 epitope SLSLLTIYV vaccine was shown to induce an obvious CTL response in vitro. To improve the immunotherapy, we constructed a multi-epitope peptide vaccine by combining epitopes derived from MMSA-1 and Dickkopf-1 (DKK1). The effector T cells induced by multi-epitope peptide vaccine-loaded dendritic cells lysed U266 cells more effectively than MMSA-1/DKK1 single-epitope vaccine. In myeloma-bearing severe combined immunodeficient mice, the multi-epitope vaccine improved the survival rate significantly compared with single-epitope vaccine. Consistently, multi-epitope vaccine decreased the tumour volume greatly and alleviated bone destruction. The frequencies of CD4⁺ and CD8⁺ T cells was significantly increased in mouse blood induced by the multi-epitope vaccine, indicating that it inhibits myeloma growth by changing T cell subsets and alleviating immune paralysis. This study identified a novel peptide from MMSA-1 and the multi-epitope vaccine will be used to establish appropriate individualized therapy for MM.

Analysis of Immune Epitopes of Respiratory Syncytial Virus for Designing of Vectored Vaccines Based on Influenza Virus Platform

The immunoepitope database was used for analysis of experimentally detected epitopes of the respiratory syncytial virus (RSV) proteins and for selection of the epitope combinations for subsequent designing of recombinant vectored anti-RSV vaccines based on attenuated influenza viruses. Three cassettes containing the most promising B- and T-cell RSV epitopes were selected: peptide F (243-294) supporting the formation of humoral immunity in animals; fragment M2-1 (70-101+114-146) containing two MHC I epitopes (82-90 and 127-135); and MHC II-epitope (51-66). The selected constructions contained no neoepitopes causing undesirable effects of vaccination, such as immunotolerance or autoimmunity.

Post-Genomics and Vaccine Improvement for Leishmania

Leishmaniasis is a parasitic disease that primarily affects Asia, Africa, South America, and the Mediterranean basin. Despite extensive efforts to develop an effective prophylactic vaccine, no promising vaccine is available yet. However, recent advancements in computational vaccinology on the one hand and genome sequencing approaches on the other have generated new hopes in vaccine development. Computational genome mining for new vaccine candidates is known as reverse vaccinology and is believed to further extend the current list of Leishmania vaccine candidates. Reverse vaccinology can also reduce the intrinsic risks associated with live attenuated vaccines. Individual epitopes arranged in tandem as polytopes are also a possible outcome of reverse genome mining. Here, we will briefly compare reverse vaccinology with conventional vaccinology in respect to Leishmania vaccine, and we will discuss how it influences the aforementioned topics. We will also introduce new in vivo models that will bridge the gap between human and laboratory animal models in future studies.

CD4 T-cells transduced with CD80 and 4-1BBL mRNA induce long-term CD8 T-cell responses resulting in potent antitumor effects

Therapeutic cancer vaccines are an attractive alternative to conventional therapies to treat malignant tumors, and more importantly, to prevent recurrence after primary therapy. However, the availability of professional antigen-presenting cells (APCs) has been restricted by difficulties encountered in obtaining sufficient professional APCs for clinical use. We have prepared an alternative cellular vaccine with CD4 T-cells that can be expanded easily to yield a pure and homogeneous population in vitro. To enhance their potency as a therapeutic vaccine, in vitro expanded CD4 T-cells were transfected with RNAs encoding the costimulatory ligands CD80, 4-1BBL, or both (CD80-T, 4-1BBL-T, and CD80/4-1BBL-T-cells, respectively). We observed augmented cell vitality in CD80/4-1BBL-T-cells in vitro and in vivo. Significant CD8 T-cell responses eliciting in vivo proliferation and cytotoxicity were obtained with CD80/4-1BBL-T-cell vaccination compared to CD80-T and 4-1BBL-T-cell vaccinations. In contrast, β2m-deficient CD80/4-1BBL-T-cells were not as effective as wile-type CD80/4-1BBL-T-cells in priming CD8 T-cells. Furthermore, CD80/4-1BBL-T-cell immunization resulted in curing established EG7 tumors, resulting in the generation of memory CD8 T-cell responses, and elicited therapeutic antitumor responses against B16 melanoma. These results suggest that CD4 T-cells endowed with costimulatory ligands allow the design of effective vaccination strategies against cancer.

Immunogenicity evaluation of a rationally designed polytope construct encoding HLA-A*0201 restricted epitopes derived from Leishmania major related proteins in HLA-A2/DR1 transgenic mice: steps toward polytope vaccine

Background

There are several reports demonstrating the role of CD8 T cells against Leishmania species. Therefore peptide vaccine might represent an effective approach to control the infection. We developed a rational polytope-DNA construct encoding immunogenic HLA-A2 restricted peptides and validated the processing and presentation of encoded epitopes in a preclinical mouse model humanized for the MHC-class-I and II.

Methods and Findings

HLA-A*0201 restricted epitopes from LPG-3, LmSTI-1, CPB and CPC along with H-2Kd restricted peptides, were lined-up together as a polytope string in a DNA construct. Polytope string was rationally designed by harnessing advantages of ubiquitin, spacers and HLA-DR restricted Th1 epitope. Endotoxin free pcDNA plasmid expressing the polytope was inoculated into humanized HLA-DRB1*0101/HLA-A*0201 transgenic mice intramuscularly 4 days after Cardiotoxin priming followed by 2 boosters at one week interval. Mice were sacrificed 10 days after the last booster, and splenocytes were subjected to ex-vivo and in-vitro evaluation of specific IFN-γ production and in-vitro cytotoxicity against individual peptides by ELISpot and standard chromium-51(⁵¹Cr) release assay respectively. 4 H-2Kd and 5 HLA-A*0201 restricted peptides were able to induce specific CD8 T cell responses in BALB/C and HLA-A2/DR1 mice respectively. IFN-γ and cytolytic activity together discriminated LPG-3-P1 as dominant, LmSTI-1-P3 and LmSTI-1-P6 as subdominant with both cytolytic activity and IFN-γ production, LmSTI-1-P4 and LPG-3-P5 as subdominant with only IFN-γ production potential.

Conclusions

Here we described a new DNA-polytope construct for Leishmania vaccination encompassing immunogenic HLA-A2 restricted peptides. Immunogenicity evaluation in HLA-transgenic model confirmed CD8 T cell induction with expected affinities and avidities showing almost efficient processing and presentation of the peptides in relevant preclinical model. Further evaluation will determine the efficacy of this polytope construct protecting against infectious challenge of Leishmania. Fortunately HLA transgenic mice are promising preclinical models helping to speed up immunogenicity analysis in a human related mouse model.

Identification and translational validation of novel mammaglobin-A CD8 T cell epitopes

Mammaglobin-A (MAM-A) is a secretory protein that is overexpressed in 80 % of human breast cancers. Its near-universal expression in breast cancer as well as its exquisite tissue specificity makes it an attractive target for a breast cancer prevention vaccine, and we recently initiated a phase 1 clinical trial of a MAM-A DNA vaccine. Previously, we have identified multiple MAM-A CD8 T cell epitopes using a reverse immunology candidate epitope approach based on predicted binding, but to date no attempt has been made to identify epitopes using an unbiased approach. In this study, we used human T cells primed in vitro with autologous dendritic cells expressing MAM-A to systematically identify MAM-A CD8 T cell epitopes. Using this unbiased approach, we identified three novel HLA-A2-restricted MAM-A epitopes. CD8 T cells specific for these epitopes are able to recognize and lyse human breast cancer cells in a MAM-A-specific, HLA-A2-dependent fashion. HLA-A2(+)/MAM-A(+) breast cancer patients have an increased prevalence of CD8 T cells specific for these novel MAM-A epitopes, and vaccination with a MAM-A DNA vaccine significantly increases the number of these CD8 T cells. The identification and translational validation of novel MAM-A epitopes has important implications for the ongoing clinical development of vaccine strategies targeting MAM-A. The novel MAM-A epitopes represent attractive targets for epitope-based vaccination strategies, and can also be used to monitor immune responses. Taken together these studies provide additional support for MAM-A as an important therapeutic target for the prevention and treatment of breast cancer.

Design and evaluation of a tandemly arranged outer membrane protein U (OmpU) multi-epitope as a potential vaccine antigen against Vibrio mimicus in grass carps (Ctenopharyngodon idella)

Vibrio mimicus (V. mimicus) is an extracellular pathogen that causes ascites disease in aquatic animals. In our previous studies, the outer membrane protein U (OmpU) of V. mimicus has been proven to be a protective antigen, and several mimotopes of the protein were identified. Here, a tandemly arranged multi-epitope peptide (named 6EPIS) was designed with six mimotopes and heterologously expressed. Then, the immunoprotection efficacy of recombinant 6EPIS (r6EPIS) was evaluated in grass carps (Ctenopharyngodon idella) by determining relative percentage survival (RPS), specific immunoglobulin M (IgM) antibody titer, and transcriptional levels of immune-related genes of inoculated grass carps. Fish vaccinated with r6EPIS via intraperitoneal injection exhibited 85.71% RPS over the control, when challenged with V. mimicus. The enzyme-linked immunosorbent assay titer of specific IgM antibodies against r6EPIS reached 1:12,800 on Day 28 post the primary immunization. After 28 days post immunization, the transcriptional level of total IgM mRNA was significantly higher in the r6EPIS-vaccinated fish than in those vaccinated with recombinant OmpU, inactivated bacterin and rHis tag peptide (p<0.05). In addition, the transcription levels of interleukin-1β and tumor necrosis factor-α genes in the spleen and head kidney of r6EPIS-vaccinated fish were significantly increased during the period of immunization and early phase of infection, while the transcription level of interleukin-10 gene was significantly increased from Day 3 to 7 post challenge, compared to the control level. These results show that r6EPIS was highly immunogenic and could elicit strong protective immune responses. It may be an attractive vaccine candidate against V. mimicus infection.

Intramuscular DNA vaccination protocols mediated by electric fields

Vaccination is historically one of the most important methods for preventing infectious diseases in humans and animals. New insights in the biology of the immune system allow a more rational design of vaccines, and new vaccination strategies are emerging. DNA vaccines have been proposed as a promising approach for introducing foreign antigens into the host for inducing protective immunity against infectious and cancer diseases. Nevertheless, because of their poor immunogenicity, plasmid DNA vaccination strategies need further implementations. Recent data suggest electrotransfer as a useful tool to improve DNA-based vaccination protocols, being able to stimulate both the humoral and cellular immune responses. In preclinical trials, gene electrotransfer is successfully used in prime-boost combination protocols and its tolerability and safety has been demonstrated also in Phase I clinical trials. In this chapter, we report a short comment supporting electrotransfer as an effective strategy to improve DNA-based vaccination protocols and describe the vaccination procedures by plasmid DNA in combination with electrotransfer and hyaluronidase pretreatment in use in our laboratory.

DNA prime-adenovirus boost immunization induces a vigorous and multifunctional T-cell response against hepadnaviral proteins in the mouse and woodchuck model

Induction of hepatitis B virus (HBV)-specific cytotoxic T cells by therapeutic immunization may be a strategy to treat chronic hepatitis B. In the HBV animal model, woodchucks, the application of DNA vaccine expressing woodchuck hepatitis virus (WHV) core antigen (WHcAg) in combination with antivirals led to the prolonged control of viral replication. However, it became clear that the use of more potent vaccines is required to overcome WHV persistence. Therefore, we asked whether stronger and more functional T-cell responses could be achieved using the modified vaccines and an optimized prime-boost vaccination regimen. We developed a new DNA plasmid (pCGWHc) and recombinant adenoviruses (AdVs) showing high expression levels of WHcAg. Mice vaccinated with the improved plasmid pCGWHc elicited a stronger WHcAg-specific CD8(+) T-cell response than with the previously used vaccines. Using multicolor flow cytometry and an in vivo cytotoxicity assay, we showed that immunization in a DNA prime-AdV boost regimen resulted in an even more vigorous and functional T-cell response than immunization with the new plasmid alone. Immunization of naïve woodchucks with pCGWHc plasmid or AdVs induced a significant WHcAg-specific degranulation response prior to the challenge, this response had not been previously detected. Consistently, this response led to a rapid control of infection after the challenge. Our results demonstrate that high antigen expression levels and the DNA prime-AdV boost immunization improved the T-cell response in mice and induced significant T-cell responses in woodchucks. Therefore, this new vaccination strategy may be a candidate for a therapeutic vaccine against chronic HBV infection.

DEC205-DC targeted DNA vaccines to CX3CR1 and CCL2 are potent and limit macrophage migration

Monocytes utilise a variety of chemokines to traffic to atherosclerotic plaques. CX3C chemokine ligand 1 (CX3CL1 & Fractalkine) and its receptor CX3CR1 and monocyte chemoattractant protein 1 (CCL2) have been identified as chemokines/receptors that have an important role in the migration and recruitment of monocytes during the pathogenesis of several inflammatory diseases including atherosclerosis. DNA vectors containing single chain variable region fragment (scFv) for DC-targeted receptor DEC205 were cloned with mouse CX3CR1 and CCL2 genes respectively, and vaccinated into C57/BL6 mice weekly for 3 weeks. Induced anti-CX3CR1 and anti-CCL2 in vaccinated mice was examined by ELISA and Western Blot analysis, while the cellular response was examined by ELISPOT. The inhibition of chemotaxis of J774 macrophages to Py-4-1 endothelial cells was examined by in vitro transwell migration assay using serum collected from vaccinated mice. All vaccinated mice generated anti-CX3CR1 and anti-CCL2 Ab and cellular response by 8 weeks after DNA vaccination. Macrophage migration towards TNF-α activated endothelial cells was significantly inhibited by serum containing both anti-CX3CR1 or anti-CCL2 Ab from vaccinated mice. These results demonstrate that DC-targeting of DNA vaccines to self-antigens generates functional immune responses which can inhibit specific key chemotactic targets. This suggests a potential therapeutic role for chemokine/receptor DNA vaccination in atherosclerosis, where chemotaxis has a pivotal role in the inflammatory process.