Intramuscular immunization with plasmid coexpressing tumour antigen and Flt-3L results in potent tumour regression

A nonviral pHEMA+chitosan nanosphere-mediated high-efficiency gene delivery system

The transport of DNA into eukaryotic cells is minimal because of the cell membrane barrier, and this limits the application of DNA vaccines, gene silencing, and gene therapy. Several available transfection reagents and techniques have been used to circumvent this problem. Alternatively, nonviral nanoscale vectors have been shown to bypass the eukaryotic cell membrane. In the present work, we developed a unique nanomaterial, pHEMA+chitosan nanospheres (PCNSs), which consisted of poly(2-hydroxyethyl methacrylate) nanospheres surrounded by a chitosan cationic shell, and we used this for encapsulation of a respiratory syncytial virus (RSV)-F gene construct (a model for a DNA vaccine). The new nanomaterial was capable of transfecting various eukaryotic cell lines without the use of a commercial transfection reagent. Using transmission electron microscopy, (TEM), fluorescence activated cell sorting (FACS), and immunofluorescence, we clearly demonstrated that the positively charged PCNSs were able to bind to the negatively charged cell membrane and were taken up by endocytosis, in Cos-7 cells. Using quantitative polymerase chain reaction (qPCR), we also evaluated the efficiency of transfection achieved with PCNSs and without the use of a liposomal-based transfection mediator, in Cos-7, HEp-2, and Vero cells. To assess the transfection efficiency of the PCNSs in vivo, these novel nanomaterials containing RSV-F gene were injected intramuscularly into BALB/c mice, resulting in high copy number of the transgene. In this study, we report, for the first time, the application of the PCNSs as a nanovehicle for gene delivery in vitro and in vivo.

Treatment with mANT2 shRNA enhances antitumor therapeutic effects induced by MUC1 DNA vaccination

In this study, we developed a combination therapy (pcDNA3/hMUC1+mANT2 shRNA) to enhance the efficiency of MUC1 DNA vaccination by combining it with mANT2 short hairpin RNA (shRNA) treatment in immunocompetent mice. mANT2 shRNA treatment alone increased the apoptosis of BMF cells (B16F1 murine melanoma cell line coexpressing an MUC1 and Fluc gene) and rendered BMF tumor cells more susceptible to lysis by MUC1-associated CD8(+) T cells. Furthermore, combined therapy enhanced MUC1 associated T-cell immune response and antitumor effects, and resulted in a higher cure rate than either treatment alone (pcDNA3/hMUC1 or mANT2 shRNA therapy alone). Human MUC1 (hMUC1)-loaded CD11c(+) cells in the draining lymph nodes of BMF-bearing mice treated with the combined treatment were found to be most effective at generating hMUC1-associated CD8(+)IFNγ(+) T cells. Furthermore, the in vitro killing activities of hMUC1-associated cytotoxic T cells (CTLs) in the combined therapy were greater than in the respective monotherapies. Cured animals treated with the combined treatment rejected a rechallenge by BMF cells, but not a rechallenge by B16F1-Fluc cells at 14 days after treatment, and showed MUC1 antigen-associated immune responses. These results suggest that combined therapy enhances antitumor activity, and that it offers an effective antitumor strategy for treating melanoma.

DNA vaccination strategies for anti-tumour effective gene therapy protocols

After more than 15 years of experimentation, DNA vaccines have become a promising perspective for tumour diseases, and animal models are widely used to study the biological features of human cancer progression and to test the efficacy of vaccination protocols. In recent years, immunisation with naked plasmid DNA encoding tumour-associated antigens or tumour-specific antigens has revealed a number of advantages: antigen-specific DNA vaccination stimulates both cellular and humoral immune responses; multiple or multi-gene vectors encoding several antigens/determinants and immune-modulatory molecules can be delivered as single administration; DNA vaccination does not induce autoimmune disease in normal animals; DNA vaccines based on plasmid vectors can be produced and tested rapidly and economically. However, DNA vaccines have shown low immunogenicity when tested in human clinical trials, and compared with traditional vaccines, they induce weak immune responses. Therefore, the improvement of vaccine efficacy has become a critical goal in the development of effective DNA vaccination protocols for anti-tumour therapy. Several strategies are taken into account for improving the DNA vaccination efficacy, such as antigen optimisation, use of adjuvants and delivery systems like electroporation, co-expression of cytokines and co-stimulatory molecules in the same vector, different vaccination protocols. In this review we discuss how the combination of these approaches may contribute to the development of more effective DNA vaccination protocols for the therapy of lymphoma in a mouse model.

Induction of antigen-specific CTL and antibody responses in mice by a novel recombinant tandem repeat DNA vaccine targeting at mucin 1 of pancreatic cancer

PURPOSE

Tandem repeat (TR) is the key epitope of mucin 1 (MUC1) for inducing cytotoxic T lymphocytes (CTL) to kill the tumor cells specifically. This study aimed to construct a new recombinant DNA vaccine based on single TR and to investigate the induced immune responses in mice.

MATERIALS AND METHODS

After the synthesis of a recombinant human TR(rhTR)and the construction of the recombinant plasmid pcDNA3.1-TR/Myc-his (+) A (pTR plasmid), C57BL/6 (H-2(b)) mice were immunized with it (TR group, n = 15). Mice inoculated with the empty vector (EV group, n = 15) and normal saline (NS group, n = 15) were used as vector and blank control, respectively. Cytotoxic assay was carried out to measure the CTL activity. And indirect enzyme-linked immunosorbent assay (ELISA) was used to detect anti-TR-specific antibodies.

RESULTS

TR group resulted in more efficient induction of CTL-specific cytolysis against TR polypeptide than both EV and NS groups (both P < 0.01). Vaccine-immunized mice had a higher equivalent concentration of anti-TR-specific antibodies (2,324 ± 238 μg/ml) than either of EV group (1,896 ± 533 μg/ml, P < 0.01) or NS group (1,736 ± 142 μg/ml, P < 0.01).

CONCLUSION

The novel recombinant TR DNA vaccine targeting at MUC1 of pancreatic cancer was constructed successfully, effectively expressing TR polypeptide in the transfected mammalian cells and inducing TR-specific CTL and antibody response.

Immunotherapy for head and neck cancer

Head and neck cancer represents a challenging disease. Despite recent treatment advances, which have improved functional outcomes, the long-term survival of head and neck cancer patients has remained unchanged for the past 25 years. One of the goals of adjuvant cancer therapy is to eradicate local regional microscopic and micrometastatic disease with minimal toxicity to surrounding normal cells. In this respect, antigen-specific immunotherapy is an attractive therapeutic approach. With the advances in molecular genetics and fundamental immunology, antigen-specific immunotherapy is being actively explored using DNA, bacterial vector, viral vector, peptide, protein, dendritic cell, and tumor-cell based vaccines. Early phase clinical trials have demonstrated the safety and feasibility of these novel therapies and the emphasis is now shifting towards the development of strategies, which can increase the potency of these vaccines. As the field of immunotherapy matures and as our understanding of the complex interaction between tumor and host develops, we get closer to realizing the potential of immunotherapy as an adjunctive method to control head and neck cancer and improve long-term survival in this patient population.

Coexpression of Flt3 ligand and GM-CSF genes modulates immune responses induced by HER2/neu DNA vaccine

DNA vaccine and dendritic cells (DCs)-based vaccine have emerged as promising strategies for cancer immunotherapy. Fms-like tyrosine kinase 3-ligand (Flt3L) and granulocyte-macrophage-colony-stimulating factor (GM-CSF) have been exploited for the expansion of DC. It was reported previously that combination of plasmid encoding GM-CSF with HER2/neu DNA vaccine induced predominantly CD4(+) T-cell-mediated antitumor immune response. In this study, we investigated the modulation of immune responses by murine Flt3L and GM-CSF, which acted as genetic adjuvants in the forms of bicistronic (pFLAG) and monocistronic (pFL and pGM) plasmids for HER2/neu DNA vaccine (pN-neu). Coexpression of Flt3L and GM-CSF significantly enhanced maturation and antigen-presentation abilities of splenic DC. Increased numbers of infiltrating DC at the immunization site, higher interferon-gamma production, and enhanced cytolytic activities by splenocytes were prominent in mice vaccinated with pN-neu in conjunction with pFLAG. Importantly, a potent CD8(+) T-cell-mediated antitumor immunity against bladder tumors naturally overexpressing HER2/neu was induced in the vaccinated mice. Collectively, our results indicate that murine Flt3L and GM-CSF genes coexpressed by a bicistronic plasmid modulate the class of immune responses and may be superior to those codelivered by two separate monocistronic plasmids as the genetic adjuvants for HER2/neu DNA vaccine.

Enhancing DNA vaccine potency by modifying the properties of antigen-presenting cells

DNA vaccines represent a potentially promising approach for antigen-specific immunotherapy. Advances in our knowledge of the adaptive immune system have indicated that professional antigen-presenting cells, especially dendritic cells (DCs), play a key role in the generation of antigen-specific immune responses. Thus, the modification of the properties of DCs represents an important strategy for enhancing the potency of DNA vaccines. This review discusses strategies to increase the number of antigen-expressing DCs, enhance antigen expression, processing and presentation in DCs, promote the activation and function of DCs, and improve DC and T-cell interaction, in order to optimize DNA vaccine-elicited immune responses. Continuing progress in our understanding of DC and T-cell biology serves as a foundation for further improvement of DNA vaccine potency, which may lead to future clinical applications of DNA vaccines for the control of infectious diseases and malignancies.

Nanosized bioceramic particles could function as efficient gene delivery vehicles with target specificity for the spleen

We have compared the ability of several nanosized bioceramic particles including negatively charged silica (SiO(2)), neutrally charged hydroxyapatite (HA) and positively charged zirconia (ZrO(2)) nanoparticles as non-viral vectors for efficient in vivo gene delivery. A mixture of highly monodispersed aqueous suspension of HA or SiO(2) nanoparticles, coated with protamine sulfate (PS), complexed efficiently with plasmid DNA and significantly enhanced transgene expression in vitro. In comparison, ZrO(2) nanoparticles gave poor transfection efficiency under similar conditions tested. It was also determined that, under the same conditions, PS-SiO(2)-DNA, but not PS-HA-DNA-nanoplexes, were able to mediate efficient transgene expression in vitro in the presence of 50% serum. Intraperitoneal injections of PS-SiO(2)-luciferase DNA nanoplexes targeted the highest level of transgene expression in the spleen of recipient mice that lasted for more than 48 h. Injection of PS-SiO(2)-pNGVL-hFLex-MUC-1 nanoplexes was able to mediate the production of Flt-3L in the sera of recipient mice. Simultaneously, the production of Flt-3L was accompanied by the stimulation of IL-2 and interferon-gamma (IFN-gamma). Most importantly, the injection of PS-SiO(2)-pNGVL-hFLex-MUC-1 nanoplexes could mount potent anti-tumour specific immune responses that led to the subsequent regression of parental tumor cells containing the muc-1 determinant.

Human sodium iodide symporter gene adjunctive radiotherapy to enhance the preventive effect of hMUC1 DNA vaccine

We demonstrate the use of combination therapy to overcome the limitations of cancer DNA vaccines by adding radioiodine gene therapy in an animal cancer model. We established a stable cell line (CT26/hMUC1-hNIS-Fluc: CMNF) expressing the hMUC1, hNIS and Fluc genes using a retro- and lentivirus system. The survival rates (%) of CMNF cells were determined using clonogenic assays after (131)I treatment. After i.m. immunization to 4 groups of Balb/c mice (pcDNA3.1, pcDNA3.1+(131)I, pcDNA3-hMUC1+PBS and pcDNA3-hMUC1+(131)I groups) with pcDNA3-hMUC1 or pcDNA3.1 once a week for 2 weeks, 1 x 10(5) CMNF cells were injected s.c. into the right thighs of mice in each group. Twenty-one days after tumor transplantation, (131)I was administered i.p. to the pcDNA3.1+(131)I and pcDNA3-hMUC1+ (131)I groups. Tumor progression was monitored in the 4 groups by bioluminescent and scintigraphic imaging and by taking caliper measurements. Tumor masses were extracted and weighted at 39 days post-tumor challenge. We confirmed that CMNF cells highly express hMUC1, hNIS and Fluc by FACS, (125)I uptake, and luciferase assay. The survival rates of CMNF were markedly reduced to (14.6 +/- 1.5)% after (131)I treatment compared with the survival rates of parental cells (p < 0.001). Tumor growth inhibition was significant only in the pcDNA3-hMUC1+ (131)I group at 39 days post challenge. Tumor masses in pcDNA3-hMUC1+ (131)I group were smaller than those of the other groups. This study shows that the weak preventive effects of cancer DNA vaccine can be overcome by radioiodine gene therapy utilizing sodium iodide symporter.

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.

Enhancing efficacy of HIV gag DNA vaccine by local delivery of GM-CSF in murine and macaque models

Controlled release of granulocyte-macrophage colony-stimulating factor (GM-CSF) protein by albumin-heparin microparticles administered via intramuscular vaccination in conjunction with HIV DNA vaccines stimulated HIV Gag-specific immune responses. In the murine model, Gag-specific cytotoxic T lymphocyte (CTL) and T helper (Th) responses were significantly enhanced by administration of murine GM-CSF microparticles. This effect was comparable to a GM-CSF encoded plasmid. In three of four rhesus monkeys, enhancement of Gag-specific antibody (Ab), Th, and CTL responses was observed 1 month after the first immunization with coadministration of human GM-CSF microparticles and HIV Gag plasmid. The second, third, and fourth booster immunizations, however, did not increase the Gag-specific immune responses. Subsequent application of Gag protein in complete Freund's adjuvant (CFA) significantly enhanced Ab and Th, but not CTL. However, Gag-specific CTL response was triggered by cytokine and Gag p55-encapsulated microparticles in all animals. The strategy of priming immune responses by coadministration of cytokine microparticles and DNA vaccines, followed by boosting with cytokine and antigen protein-encapsulated microparticles, may prove effective in improving an HIV DNA vaccine design.