Autologous neu DNA vaccine can be as effective as xenogenic neu DNA vaccine by altering administration route

MMP-7 derived peptides with MHC class-I binding motifs from canine mammary tumor tissue elicit strong antigen-specific T-cell responses in BALB/c mice

Matrix Metalloproteinases (MMPs)-induced altered proteolysis of extracellular matrix proteins and basement membrane holds the key for tumor progression and metastasis. Matrix metalloproteinases-7 (Matrilysin), the smallest member of the MMP family also performs quite alike; thus serves as a potential candidate for anti-tumor immunotherapy. Conversely, being an endogenous tumor-associated antigen (TAA), targeting MMP-7 for immunization is challenging. But MMP-7-based xenovaccine can surmount the obstacle of poor immunogenicity and immunological tolerance, often encountered in TAA-based conventional vaccine for anti-tumor immunotherapy. This paves the way for investigating the potential of MMP-7-derived major histocompatibility complex (MHC)-binding peptides to elicit precise epitope-specific T-cell responses towards their possible inclusion in anti-tumor vaccine formulations. Perhaps it also ushers the path of achieving multiple epitope-based broad and universal cellular immunity. In current experiment, an immunoinformatics approach has been employed to identify the putative canine matrix matelloproteinases-7 (cMMP-7)-derived peptides with MHC class-I-binding motifs which can elicit potent antigen-specific immune responses in BALB/c mice. Immunization with the cMMP-7 DNA vaccine induced a strong CD8⁺ cytotoxic T lymphocytes (CTLs) and Th1- type response, with high level of gamma interferon (IFN-γ) production in BALB/c mice. The two identified putative MHC-I-binding nonameric peptides (Peptide_32-40 and Peptide_175-183) from cMMP-7 induced significant lymphocyte proliferation along with the production of IFN-γ from CD8⁺ T-cells in mice immunized with cMMP-7 DNA vaccine. The current observation has depicted the immunogenic potential of the two cMMP-7-derived nonapeptides for their possible exploitation in xenovaccine-mediated anti-tumor immunotherapy in mouse model.

DNA vaccine elicits an efficient antitumor response by targeting the mutant Kras in a transgenic mouse lung cancer model

Mutant Kras (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) is observed in more than 20% of non-small-cell lung cancers; however, no effective Kras target therapy is available at present. The Kras DNA vaccine may represent as a novel immunotherapeutic agent in lung cancer. In this study, we investigated the antitumor efficacy of the Kras DNA vaccine in a genetically engineered inducible mouse lung tumor model driven by Kras(G12D). Lung tumors were induced by doxycycline, and the therapeutic effects of Kras DNA vaccine were evaluated with delivery of Kras(G12D) plasmids. Mutant Kras(G12D) DNA vaccine significantly decreased the tumor nodules. A dominant-negative mutant Kras(G12D)N17, devoid of oncogenic activity, achieved similar therapeutic effects. The T-helper 1 immune response was enhanced in mice treated with Kras DNA vaccine. Splenocytes from mice receiving Kras DNA vaccine presented an antigen-specific response by treatment with peptides of Kras but not Hras or OVA. The number of tumor-infiltrating CD8(+) T cells increased after Kras vaccination. In contrast, Kras DNA vaccine was not effective in the lung tumor in transgenic mice, which was induced by mutant L858R epidermal growth factor receptor. Overall, these results indicate that Kras DNA vaccine produces an effective antitumor response in transgenic mice, and may be useful in treating lung cancer-carrying Ras mutation.

Clitocybe nuda Activates Dendritic Cells and Acts as a DNA Vaccine Adjuvant

This work represents the first evaluation of the effects of water extract of C. nuda (WE-CN), an edible mushroom, on murine bone marrow-derived dendritic cells (BMDCs) and the potential pathway through which the effects are mediated. Our experimental results show that WE-CN could induce phenotypic maturation of DCs, as shown by the increased expression of MHC and costimulatory molecules. In addition, it also induced the proinflammatory cytokines expression on DCs and enhanced both the proliferation and IFN- γ secretion of allogenic T cells. Therefore, since WE-CN did not induce maturation of DCs generated from mice with mutated TLR-4 or TLR-2, suggesting that TLR4 and TLR2 might function as membrane receptors for WE-CN. Moreover, the mechanism of action of WE-CN may be mediated by increased phosphorylation of ERK, p38, and JNK mitogen-activated protein kinase (MAPK) and increased NF- κ B p65 activity, which are important signaling molecules downstream of TLR-4 and TLR-2. Finally, coimmunization of mice with WE-CN and a HER-2/neu DNA vaccine induced a HER-2/neu-specific Th1 response that resulted in significant inhibition of HER-2/neu overexpressing mouse bladder tumor (MBT-2) growth. These data suggest that WE-CN induces DC maturation through TLR-4 and/or TLR-2 and that WE-CN can be used as an adjuvant in cancer vaccine immunotherapy.

Biolistic DNA delivery to mice with the low pressure gene gun

Biolistic DNA delivery is an approach to deliver plasmid to culture cells, plants, or animals. Plasmid DNA is usually transferred through bombardment of DNA-coated particles by highly pressurized gas in various kinds of delivery vehicles. The low pressure gene gun can deliver plasmid at lower pressure. Here, we describe methods of biolistic DNA delivery to mice using the low pressure gene gun.

Xenogeneic human p53 DNA vaccination by electroporation breaks immune tolerance to control murine tumors expressing mouse p53

The pivotal role of p53 as a tumor suppressor protein is illustrated by the fact that this protein is found mutated in more than 50% of human cancers. In most cases, mutations in p53 greatly increase the otherwise short half-life of this protein in normal tissue and cause it to accumulate in the cytoplasm of tumors. The overexpression of mutated p53 in tumor cells makes p53 a potentially desirable target for the development of cancer immunotherapy. However, p53 protein represents an endogenous tumor-associated antigen (TAA). Immunization against a self-antigen is challenging because an antigen-specific immune response likely generates only low affinity antigen-specific CD8⁺ T-cells. This represents a bottleneck of tumor immunotherapy when targeting endogenous TAAs expressed by tumors. The objective of the current study is to develop a safe cancer immunotherapy using a naked DNA vaccine. The vaccine employs a xenogeneic p53 gene to break immune tolerance resulting in a potent therapeutic antitumor effect against tumors expressing mutated p53. Our study assessed the therapeutic antitumor effect after immunization with DNA encoding human p53 (hp53) or mouse p53 (mp53). Mice immunized with xenogeneic full length hp53 DNA plasmid intramuscularly followed by electroporation were protected against challenge with murine colon cancer MC38 while those immunized with mp53 DNA were not. In a therapeutic model, established MC38 tumors were also well controlled by treatment with hp53 DNA therapy in tumor bearing mice compared to mp53 DNA. Mice vaccinated with hp53 DNA plasmid also exhibited an increase in mp53-specific CD8⁺ T-cell precursors compared to vaccination with mp53 DNA. Antibody depletion experiments also demonstrated that CD8⁺ T-cells play crucial roles in the antitumor effects. This study showed intramuscular vaccination with xenogeneic p53 DNA vaccine followed by electroporation is capable of inducing potent antitumor effects against tumors expressing mutated p53 through CD8⁺ T cells.

A novel adjuvant Ling Zhi-8 enhances the efficacy of DNA cancer vaccine by activating dendritic cells

DNA vaccine has been suggested to use in cancer therapy, but the efficacy remains to be improved. The immunostimulatory effect of a fungal immunomodulatory protein Ling Zhi-8 (LZ-8) isolated from Ganoderma lucidum has been reported. In this study, we tested the adjuvanticity of LZ-8 for HER-2/neu DNA vaccine against p185(neu) expressing tumor MBT-2 in mice. We found that recombinant LZ-8 stimulated mouse bone marrow-derived dendritic cells (DCs) via TLR4 and its stimulatory effect was not due to any microbe contaminant. In addition, LZ-8 enhanced the ability of DCs to induce antigen-specific T cell activation in vitro and in a subunit vaccine model in vivo. Surprisingly, LZ-8 cotreatment strongly improved the therapeutic effect of DNA vaccine against MBT-2 tumor in mice. This increase in antitumor activity was attributed to the enhancement of vaccine-induced Th1 and CTL responses. Consistent with the results from DCs, the promoting effect of LZ-8 on DNA vaccine was diminished when the MBT-2 tumor cells were grown in TLR4 mutant mice. Thus, we concluded that LZ-8 may be a promising adjuvant to enhance the efficacy of DNA vaccine by activating DCs via TLR4.

Promoting effect of Antrodia camphorata as an immunomodulating adjuvant on the antitumor efficacy of HER-2/neu DNA vaccine

It is well known that DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. Antrodia camphorata (AC) is a unique basidiomycete fungus of the Polyporaceae family that only grows on the aromatic tree Cinnamomum kanehirai Hayata (Lauraceae) endemic to Taiwan. Importantly, AC has been shown to be highly beneficial in the treatment and prevention of cancer. The goal of this study was to investigate whether AC is able to augment the antitumor immune properties of a HER-2/neu DNA vaccine in a mouse model in which p185neu is overexpressed in MBT-2 tumor cells. Compared with the mice that received the HER-2/neu DNA vaccine alone, co-treatment with AC suppressed tumor growth and extended the survival rate. This increase in the antitumor efficacy was attributed to the enhancement of the Th1-like cellular immune response by the HER-2/neu DNA vaccine-AC combination. Evidence for this came from the marked increase in the IFN-gamma mRNA expression in CD4+ T cells in the draining inguinal lymph nodes, an increase in the number of functional HER-2/neu-specific CTLs, and the increased tumor infiltration of both CD4+ and CD8+ T cells, depletion of which abolishes the antitumor effect of the HER-2/neu DNA vaccine-AC therapy. Our results further indicate that the treatment of mice with AC enhanced DC activation and production of Th1-activating cytokines (e.g. IL-12, and IFN-alpha) in the draining lymph nodes, which were sufficient to directly stimulate T cell proliferation and higher IFN-gamma production in response to ErbB2. Overall, these results clearly demonstrate that AC represents a promising immunomodulatory adjuvant that could enhance the therapeutic potency of HER-2/neu DNA vaccines in cancer therapy.

An HDAC inhibitor enhances the antitumor activity of a CMV promoter-driven DNA vaccine

The cytomegalovirus (CMV) promoter is considered to be one of the strongest promoters for driving the in vivo expression of genes encoded by DNA vaccines. However, the efficacy of DNA vaccines has so far been disappointing (particularly in humans), and this might be explained in part by histone deacetylase (HDAC)-mediated chromatin condensation. Hence, we sought to investigate whether increasing the expression of DNA vaccine antigens with the HDAC inhibitor OSU-HDAC42 would enhance the efficacy of DNA vaccines in vivo. A luciferase assay was used to determine the effects of OSU-HDAC42 on CMV promoter-driven DNA plasmids in vitro and in vivo. Three HDAC inhibitors were able to activate expression from the CMV promoter in NIH3T3 cells and MBT-2 bladder cancer cells. The expression of luciferase was significantly enhanced by co-administration of pCMV-luciferase and OSU-HDAC42 in mice. To explore whether OSU-HDAC42 could enhance the specific antitumor activity of a neu DNA vaccine driven by the CMV promoter, we evaluated therapeutic effects and immune responses in a mouse tumor natively overexpressing HER2/neu. Mice receiving OSU-HDAC42 in combination with the CMV-promoter neu DNA vaccine exhibited stronger antitumor effects than mice given the DNA vaccine only. In addition, a correlation between the antitumor effects and the specific cellular immune responses was observed in the mice receiving the DNA vaccine and OSU-HDAC42.

Xenogeneic immunization with human tyrosine hydroxylase DNA vaccines suppresses growth of established neuroblastoma

Neuroblastoma (NB) is a challenging malignancy of the sympathetic nervous tissue characterized by a very poor prognosis. One important marker for NB is the expression of tyrosine hydroxylase (TH), the first-step enzyme of catecholamine biosynthesis. We could show stable and high TH gene expression in 67 NB samples independent of the clinical stage. Based on this observation, we addressed the question of whether xenogeneic TH DNA vaccination is effective in inducing an anti-NB immune response. For this purpose, we generated three DNA vaccines based on pCMV-F3Ub and pBUD-CE4.1 plasmids encoding for human (h)THcDNA (A), hTH minigene (B), and hTHcDNA in combination with the proinflammatory cytokine interleukin 12 (C), and tested prophylactic and therapeutic efficacy to suppress primary tumor growth and spontaneous metastasis. Here we report that xenogeneic TH DNA vaccination was effective in eradicating established primary tumors and inhibiting metastasis. Interestingly, this effect could not be enhanced by adding the Th1 cytokine interleukin 12. However, increased IFN-gamma production and NB cytotoxicity of effector cells harvested from vaccinated mice suggested the participation of tumor-specific CTLs in the immune response. The depletion of CD8(+)T cells completely abrogated the hTH vaccine-mediated anti-NB immune response. Furthermore, rechallenging of surviving mice resulted in reduced primary tumor growth, indicating the induction of a memory immune response. In conclusion, xenogeneic immunization with TH-derived DNA vaccines is effective against NB, and may open a new venue for a novel and effective immunotherapeutic strategy against this challenging childhood tumor.

Mannose addition by yeast Pichia Pastoris on recombinant HER-2 protein inhibits recognition by the monoclonal antibody herceptin

We report here the generation of a full-length, highly glycosylated HER-2 oncoprotein using yeast strain, Pichia Pastoris. Upon treatment of secreted HER-2 with alpha-mannosidase, reactivity with the monoclonal antibody Herceptin is significantly increased. This phenomenon is due to glycosylation via mannose of the full-length HER-2 protein that extends over the antigenic epitope, which is recognized by Herceptin. The extensive glycosylation of HER-2 in Pichia Pastoris significantly increases its recognition and uptake by dendritic cells, which could be associated with increased vaccine performance.

Delivery of noncarrier naked DNA vaccine into the skin by supersonic flow induces a polarized T helper type 1 immune response to cancer

BACKGROUND

DNA vaccine is a new and powerful approach to generate immunological responses against infectious disease and cancer. The T helper type (Th)1 immune response is usually required for generating effective anti-tumor responses. A microparticulate bombardment system can induce an immune response using very low amounts of DNA. Using nozzle aerodynamics, a low pressure gene gun has been developed to decrease the noise associated with high pressure gene guns. Particles are propelled by supersonic flow through this novel nozzle. To test whether this gun could inoculate a DNA vaccine that stimulates an anti-tumor Th1 immune response, we examined the effect of direct delivery of naked DNA (i.e. without any carrier) on the anti-tumor immune response of mice.

METHODS

The luciferase reporter plasmid DNA was delivered using a low-pressure biolistic device and expressed in C3H/HeN, BALB/c, and C57BL/6 mice.

RESULTS

Plasmid DNA expression was mainly in the epidermis. Noncarrier naked neu DNA vaccine and gold particle-coated neu DNA vaccine (at 1 microg per mouse) had similar anti-tumor effects in C3H mice. However, cytokine profile examination showed the Th1-bias of the response induced by naked DNA vaccine and the Th2-bias of the response induced by coated DNA vaccine.

CONCLUSIONS

A shift in the immune response to favour enhanced tumor rejection can be achieved by skin delivery of naked DNA vaccine.

The opposing effects of lipopolysaccharide on the antitumor therapeutic efficacy of DNA vaccine

DNA vaccine represents a novel method to elicit immunity against infectious disease. Lipopolysaccharide (LPS) copurified with plasmid DNA may affect therapeutic efficacy and immunological response. We aimed to study the effect of LPS on the therapeutic efficacy of HER-2/neu DNA vaccine in a mouse tumor animal model. Plasmid DNA purified from commercial EndoFree plasmid purification kits functioned as a better therapeutic DNA vaccine than that purified from Non-EndoFree purification kit, which contains >or=0.5 microg LPS per 100 mg DNA plasmid. To further investigate the effect of LPS on the therapeutic efficacy of DNA vaccine, increasing amount of LPS was added to endotoxin-free plasmid DNA, and inoculated on mice with established tumors. One mug of LPS significantly attenuated the therapeutic effect of neu DNA vaccine and increased Th2 immune responses bias with interleukin-4 cytokine production. In contrast, high amount (100 microg) of LPS enhanced the therapeutic efficacy of neu DNA vaccine with an increase of cytotoxic T lymphocyte response and Th1 immune response. The effect of LPS on DNA vaccine was diminished when the tumor was grown in toll-like receptor 4 (TLR4)-mutant C3H/HeJ mice. Our results indicate that variation in the LPS doses exerts opposing effects on the therapeutic efficacy of DNA vaccine, and the observed effect is TLR4 dependent.