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Efficacy of novel cancer immunization protocols could be tested in cell line-derived xenograft tumor models (CDX), which are based on the implantation of human tumor cell lines into mice for the development of different tumors by numerous means, such as subcutaneous implantation and orthotopic, venial, or peritoneal injections. However, the disadvantages of this model are the biological alteration of the derived cells or the inability of the cell lines to accurately reflect the complexity of tumor heterogeneity. Therefore, syngeneic mouse models, which offer a relatively simple grafting technique, preservation of lineage hierarchy, and the ability to generate tumors in as little as 2-8 weeks, are being used to study potential future applications in medical treatment, particularly immunotherapies. Here, we describe a B16.F10 C57Bl/6 mouse melanoma model we selected for therapeutic studies employing IL-2 and IL-12 immunization protocols. Procedure of tumor cells inoculation and melanoma development in mice is described in detail, as first and necessary set-up for successful immunization experiments., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Since conventional therapeutic approaches in cancer are highly invasive they hardly prolong patient survival for more than few months. Having the ability to stimulate both cellular and humoural immune responses, immunisation with naked plasmid DNA encoding tumour-associated antigens or tumour-specific antigens has recently reported a plethora of advantages, and the improvement of vaccine efficacy has emerged as a goal in the development of DNA vaccination as anti-tumour therapy. Nevertheless, because of their poor immunogenicity when administered as unformulated intramuscular injections, plasmid DNA vaccines need to be improved. Recent data suggest that the DNA vaccine efficacy may significantly be increased by electroporation. This review highlights the recent literature that supports electroporation as an effective strategy to improve DNA-based vaccination protocols, investigating the most relevant studies, recently developed for the applications of DNA vaccine electrotransfer against tumours in pre-clinical and clinical studies.

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.

Eradication of cancer cells is imperative for a successful treatment of tumours. In addition to the existent chemotherapy or radiation therapy, other novel immunotherapeutic strategies to fight tumours are currently under investigation. One of these is cancer vaccination, an approach aimed at inducing effective immune responses in the host against defined tumour antigens. Among several classes of cancer vaccines, the subunit vaccines based on the single and multi epitope-approach are worthy of note as they offer an exquisite specificity in targeting only tumour cells. In this review we will focus on the significant advances made in the development and use of epitope-based cancer vaccines, reporting a selection of important and recent patents on tumour antigen discovery and epitope design for immunotherapy of cancer.

The idiotypic structure present on B-cell neoplasms is a tumor-specific antigen and an attractive target for immunotherapy. Here, the tumor protective effects recruited by CDR3-based DNA vaccines in the poorly immunogenic, highly aggressive 38C13 murine B-cell lymphoma model were evaluated. The regions belonging to the idiotypic V(H) and V(L) CDR3 sequences were chosen for the design of two synthetic mini-genes and arranged in high-level expression plasmids. Syngeneic C3H/HeN mice were immunized by intramuscular electroporation with pV(H)CDR3-IL-2 and pV(L)CDR3-IL-2 naked DNAs. This approach provided protection in about 60% of animals challenged with a 2-fold lethal dose of tumor cells, as opposed to non-survivors in control groups. Furthermore, a long-term survival was induced in these mice since they were still alive and tumor-free 4 months following tumor challenge. Analysis of the humoral immunity revealed the presence of antibodies reactive with the peptides encompassing the CDR3 sequences in the sera of vaccinated mice. Moreover, immune sera specifically reacted with the parental 38C13 tumor cells in flow cytometry assays, indicating that such immunization elicited anti-idiotypic antibodies. These findings provide a basis for exploring the use of CDR3-based DNA vaccines against B-cell lymphoma.

Several reports have suggested that the mechanism of protection induced by antiidiotypic vaccination against low-grade lymphoproliferative disorders is likely to be antibody mediated. Here we test the hypothesis that DNA vaccination with the short peptide encompassing the complementary-determining region 3 hypervariable region of immunoglobulin heavy chain (VH-CDR3) may elicit a specific antibody immune response able to recognize the native antigens in the form required for therapy. As a test system, we used the VH-CDR3 sequences derived from two patients with non-Hodgkin's B lymphomas (PA, AS) and one patient with hairy cell leukemia (BA) to immunize outbred Swiss mice. This experimental model could mimic a clinical setting in which different patients present distinct HLA haplotypes. Individual tumor-specific VH-CDR3 sequences were amplified by a two-step procedure and directly cloned into multigenic plasmid vectors (pRC100 and derived) with and without mouse interleukin 2 (mIL-2). Each tumor-specific sequence was characterized by sequencing. Female Swiss mice were vaccinated i.m. with plasmids expressing the tumor-specific VH-CDR3 sequence alone (pRC101-PA), mIL-2 plus the VH-CDR3 sequence (pRC111-PA), or a different unrelated antigen (NS3 of hepatitis C virus; pRC112), the sole mIL-2 (pRC110), and the empty plasmid (pRC100). Boost injections were performed at 3 and 16 weeks from the first vaccination, and sera were drawn before each vaccination and at 6, 9, and 19 weeks. Induction of anti-VH-CDR3s antibodies in the sera and their ability to recognize native antigens on patients' tumor cells were evaluated by FACS analysis. Up to 56% (n = 25) of mice vaccinated with pRC111-PA plasmid and 20% (n = 15) of mice vaccinated with pRC101-PA developed a specific immune response that was maintained throughout 19 weeks of observation in 40% of pRC111-PA-vaccinated mice. No response was detected in sera obtained from mice vaccinated with the other plasmids (n = 45). pRC111-PA injection s.c. was less effective (13%, n = 15) than i.m. injection (53%, n = 15). Indeed, we demonstrated that antibodies elicited by naked DNA vaccination against three different patient-derived VH-CDR3 peptides (pRC111-PA or BA or AS) readily reacted with binding epitopes on the idiotypic proteins expressed on the surface of tumor cells derived from each patient; 60, 40, and 40% of, respectively, PA-, BA-, and AS-vaccinated mice developed specific antibodies. No cross-reactivity was detected among the three different CDR3s against tumor cells derived from the other two patients. The outbred mouse strategy confirmed the significant matching potential of three different VH-CDR3 peptides to be efficaciously presented through different MHCs. We conclude that individual VH-CDR3 DNA vaccination can result in a potentially effective specific immune response against non-Hodgkin's B lymphoma cells by a rapid and low-cost therapeutic approach.