A vaccine targeting telomerase enhances survival of dogs affected by B-cell lymphoma

Linear DNA amplicons as a novel cancer vaccine strategy

BACKGROUND

DNA-based vaccines represent a simple, safe and promising strategy for harnessing the immune system to fight infectious diseases as well as various forms of cancer and thus are considered an important tool in the cancer immunotherapy toolbox. Nonetheless, the manufacture of plasmid DNA vaccines has several drawbacks, including long lead times and the need to remove impurities from bacterial cultures. Here we report the development of polymerase chain reaction (PCR)-produced amplicon expression vectors as DNA vaccines and their in vivo application to elicit antigen-specific immune responses in animal cancer models.

METHODS

Plasmid DNA and amplicon expression was assessed both in vitro, by Hela cells transfection, and in vivo, by evaluating luciferase expression in wild-type mice through optical imaging. Immunogenicity induced by DNA amplicons was assessed by vaccinating wild-type mice against a tumor-associated antigen, whereas the antitumoral effect of DNA amplicons was evaluated in a murine cancer model in combination with immune-checkpoint inhibitors (ICIs).

RESULTS

Amplicons encoding tumor-associated-antigens, such as telomerase reverse transcriptase or neoantigens expressed by murine tumor cell lines, were able to elicit antigen-specific immune responses and proved to significantly impact tumor growth when administered in combination with ICIs.

CONCLUSIONS

These results strongly support the further exploration of the use of PCR-based amplicons as an innovative immunotherapeutic approach to cancer treatment.

COVID-eVax, an electroporated DNA vaccine candidate encoding the SARS-CoV-2 RBD, elicits protective responses in animal models

The COVID-19 pandemic caused by SARS-CoV-2 has made the development of safe and effective vaccines a critical priority. To date, four vaccines have been approved by European and American authorities for preventing COVID-19, but the development of additional vaccine platforms with improved supply and logistics profiles remains a pressing need. Here we report the preclinical evaluation of a novel COVID-19 vaccine candidate based on the electroporation of engineered, synthetic cDNA encoding a viral antigen in the skeletal muscle. We constructed a set of prototype DNA vaccines expressing various forms of the SARS-CoV-2 spike (S) protein and assessed their immunogenicity in animal models. Among them, COVID-eVax-a DNA plasmid encoding a secreted monomeric form of SARS-CoV-2 S protein receptor-binding domain (RBD)-induced the most potent anti-SARS-CoV-2 neutralizing antibody responses (including against the current most common variants of concern) and a robust T cell response. Upon challenge with SARS-CoV-2, immunized K18-hACE2 transgenic mice showed reduced weight loss, improved pulmonary function, and lower viral replication in the lungs and brain. COVID-eVax conferred significant protection to ferrets upon SARS-CoV-2 challenge. In summary, this study identifies COVID-eVax as an ideal COVID-19 vaccine candidate suitable for clinical development. Accordingly, a combined phase I-II trial has recently started.

Adenovirus Type 6: Subtle Structural Distinctions from Adenovirus Type 5 Result in Essential Differences in Properties and Perspectives for Gene Therapy

Adenovirus vectors are the most frequently used agents for gene therapy, including oncolytic therapy and vaccine development. It’s hard to overestimate the value of adenoviruses during the COVID-19 pandemic as to date four out of four approved viral vector-based SARS-CoV-2 vaccines are developed on adenovirus platform. The vast majority of adenoviral vectors are based on the most studied human adenovirus type 5 (HAdV-C5), however, its immunogenicity often hampers the clinical translation of HAdV-C5 vectors. The search of less seroprevalent adenovirus types led to another species C adenovirus, Adenovirus type 6 (HAdV-C6). HAdV-C6 possesses high oncolytic efficacy against multiple cancer types and remarkable ability to induce the immune response towards carrying antigens. Being genetically very close to HAdV-C5, HAdV-C6 differs from HAdV-C5 in structure of the most abundant capsid protein, hexon. This leads to the ability of HAdV-C6 to evade the uptake by Kupffer cells as well as to distinct opsonization by immunoglobulins and other blood proteins, influencing the overall biodistribution of HAdV-C6 after systemic administration. This review describes the structural features of HAdV-C6, its interaction with liver cells and blood factors, summarizes the previous experiences using HAdV-C6, and provides the rationale behind the use of HAdV-C6 for vaccine and anticancer drugs developments.

Immunotherapeutic Strategies for Canine Lymphoma: Changing the Odds Against Non-Hodgkin Lymphoma

The new era of immune-oncology has brought complexities and challenges that emphasize the need to identify new strategies and models to develop successful and cost-effective therapies. The inclusion of a canine model in the drug development of cancer immunotherapies is being widely recognized as a valid solution to overcome several hurdles associated with conventional preclinical models. Driven by the success of immunotherapies in the treatment of human non-Hodgkin lymphoma (NHL) and by the remarkable similarities of canine NHL to its human counterpart, canine NHL has been one of the main focus of comparative research. Under the present review, we summarize a general overview of the challenges and prospects of today's cancer immunotherapies and the role that comparative medicine might play in solving the limitations brought by this rapidly expanding field. The state of art of both human and canine NHL and the rationale behind the use of the canine model to bridge the translational gap between murine preclinical studies and human clinical trials are addressed. Finally, a review of currently available immunotherapies for canine NHL is described, highlighting the potential of these therapeutic options.

Safety, tolerability and immunogenicity of V934/V935 hTERT vaccination in cancer patients with selected solid tumors: a phase I study

Background

Human telomerase reverse transcriptase (hTERT) is an antigen that may represent a target for a novel anti-cancer strategy. A pilot, phase I study tested the safety and feasibility of a prime-boost immunization regimen based on V935, an adenoviral type 6 vector vaccine expressing a modified version of hTERT, administered alone or in combination with V934, a DNA plasmid that also expresses the same antigen and is delivered using the electroporation injection technique.

Methods

Treatments: Group #1 received two doses (low-dose: 0.5 × 10⁹ vg, and high-dose: 0.5 × 10¹¹ vg) of V935 followed by a 4-week observation period. Group #2 received three doses of V934-electroporation and two doses of V935 following a 4-week observation period. Doses were low-dose V934 (0.25 mg of plasmid) with low-dose V935 (0.5 × 10⁹ vg); high-dose V934 (2.5 mg of plasmid) with high-dose V935 (0.5 × 10¹¹ vg). Group #3 received five doses of V934-EP and two doses of V935: V934 was administered IM every 2 weeks for five doses. Following a 4-week observation period, V935 was administered IM every 2 weeks for two doses followed by a 4-week observation period. One (1) dose level was tested in treatment group #3: high-dose V934 (2.5 mg of plasmid), in combination with high-dose V935 (0.5 × 1011 vg). Immunogenicity was measured by ELISPOT assay and three pools of peptides encompassing the sequence of hTERT.

Results

In total, 37 patients affected by solid tumors (prostate cancer in 38%) were enrolled. The safety profile of different regimens was good and comparable across groups, with no severe adverse events, dose-limiting toxicities or treatment discontinuations. As expected, the most common adverse events were local reactions. A significant increase in ELISPOT responses against hTERT peptide pool 2 was observed (p < 0.01), while no evidence of boosting was observed for peptide pools 1 and 3. This was also evident for group #1 and #2 separately. In patients with prostate cancer, there was a significant increase in ELISPOT response against hTERT peptide pool 2 following immunization (p < 0.01), regardless of previous therapy, immunosuppressing agents, or adenoviral type 6 titers at screening.

Conclusion

Our results suggest the safety and feasibility of V934/V935 hTERT vaccination in cancer patients with solid tumors

Trial Registration Name of the registry: ClinicalTrial.gov Trial registration number: NCT00753415 Date of registration: 16 September 2008 Retrospectively registered URL of trial registry record: https://clinicaltrials.gov/ct2/results?cond=&term=NCT00753415&cntry=&state=&city=&dist=

A Role for Dogs in Advancing Cancer Immunotherapy Research

While rodent cancer models are essential for early proof-of-concept and mechanistic studies for immune therapies, these models have limitations with regards to predicting the ultimate effectiveness of new immunotherapies in humans. As a unique spontaneous, large animal model of cancer, the value of conducting studies in pet dogs with cancer has been increasingly recognized by the research community. This review will therefore summarize key aspects of the dog cancer immunotherapy model and the role that these studies may play in the overall immunotherapy drug research effort. We will focus on cancer types and settings in which the dog model is most likely to impact clinical immuno-oncology research and drug development. Immunological reagent availability is discussed, along with some unique opportunities and challenges associated with the dog immunotherapy model. Overall it is hoped that this review will increase awareness of the dog cancer immunotherapy model and stimulate additional collaborative studies to benefit both man and man's best friend.

Of Mice, Dogs, Pigs, and Men: Choosing the Appropriate Model for Immuno-Oncology Research

The immune system plays dual roles in response to cancer. The host immune system protects against tumor formation via immunosurveillance; however, recognition of the tumor by immune cells also induces sculpting mechanisms leading to a Darwinian selection of tumor cell variants with reduced immunogenicity. Cancer immunoediting is the concept used to describe the complex interplay between tumor cells and the immune system. This concept, commonly referred to as the three E's, is encompassed by 3 distinct phases of elimination, equilibrium, and escape. Despite impressive results in the clinic, cancer immunotherapy still has room for improvement as many patients remain unresponsive to therapy. Moreover, many of the preclinical results obtained in the widely used mouse models of cancer are lost in translation to human patients. To improve the success rate of immuno-oncology research and preclinical testing of immune-based anticancer therapies, using alternative animal models more closely related to humans is a promising approach. Here, we describe 2 of the major alternative model systems: canine (spontaneous) and porcine (experimental) cancer models. Although dogs display a high rate of spontaneous tumor formation, an increased number of genetically modified porcine models exist. We suggest that the optimal immuno-oncology model may depend on the stage of cancer immunoediting in question. In particular, the spontaneous canine tumor models provide a unique platform for evaluating therapies aimed at the escape phase of cancer, while genetically engineered swine allow for elucidation of tumor-immune cell interactions especially during the phases of elimination and equilibrium.

Naturally occurring cancers in pet dogs as pre-clinical models for cancer immunotherapy

Despite the significant progress in tumor prevention, early detection, diagnosis and treatment made over recent decades, cancer is still an enormous public health challenge all around the world, with the number of people affected increasing every year. A great deal of effort is therefore being devoted to the search for novel safe, effective and economically sustainable treatments for the growing population of neoplastic patients. One main obstacle to this process is the extremely low percentage of therapeutic approaches that, after successfully passing pre-clinical testing, actually demonstrate activity when finally tested in humans. This disappointing and expensive failure rate is partly due to the pre-clinical murine models used for in vivo testing, which cannot faithfully recapitulate the multifaceted nature and evolution of human malignancies. These features are better mirrored in natural disease models, i.e., companion animals affected by cancers. Herein, we discuss the relevance of spontaneous canine tumors for the evaluation of the safety and anti-tumor activity of novel therapeutic strategies before in-human trials, and present our experience in the development of a vaccine that targets chondroitin sulphate proteoglycan (CSPG)4 as an example of these comparative oncology studies.

Opportunities and challenges of active immunotherapy in dogs with B-cell lymphoma: a 5-year experience in two veterinary oncology centers

BACKGROUND

Pet dogs spontaneously develop lymphoma. An anthracycline-based multidrug chemotherapy regimen represents the treatment cornerstone; however, cure is rarely achieved. We have been treating dogs with B-cell lymphoma with an autologous vaccine (APAVAC®) and CHOP-based chemotherapy since 2011.

METHODS

To better characterize the safety and efficacy of APAVAC®, and to find the best candidates for immunotherapy, we designed a retrospective study on all dogs treated with chemo-immunotherapy to date and compared them with those dogs treated with chemotherapy only. All dogs were completely staged and re-staged at the end of treatment. The primary endpoint was the effectiveness of chemo-immunotherapy, measured as time to progression (TTP), lymphoma-specific survival (LSS), and 1-, 2-, and 3-year survival rates. The secondary objective was safety.

RESULTS

Three hundred dogs were included: 148 (49.3%) received chemotherapy and 152 (50.7%) chemo-immunotherapy. Overall, the latter survived significantly longer (median LSS, 401 vs 220; P <  0.001). Among dogs with diffuse large B-cell lymphoma, the 1-, 2- and 3-year survival rates were 20, 13 and 8% for chemotherapy, and 51, 19 and 10% for chemo-immunotherapy. The benefit of chemo-immunotherapy was particularly relevant in dogs with concurrent high serum LDH, stage V, substage a disease and not previously treated with steroids (median LSS, 480 vs 85 days; P <  0.001). Among dogs with nodal marginal zone lymphoma, those having at least 3 of the aforementioned characteristics significantly benefited from chemo-immunotherapy (median LSS, 680 vs 160 days, P <  0.001). The 1-, 2- and 3-year survival rates were 30, 16 and 10% for chemotherapy, and 55, 28 and 10% for chemo-immunotherapy. Among dogs with follicular lymphoma, lack of immunotherapy administration was the only variable significantly associated with increased risk of tumor-related death. Chemo-immunotherapy was remarkably well tolerated, with no local or systemic adverse events.

CONCLUSIONS

Overall, the addition of immunotherapy to a traditional CHOP protocol is associated with improved outcome in dogs with B-cell lymphoma, regardless of histotype and evaluated prognostic factors. Moreover, the identikit of the best candidate for immune-therapy was delineated for the most common histotypes. The study also confirms the excellent tolerability of the vaccine.

Poly-specific neoantigen-targeted cancer vaccines delay patient derived tumor growth

BACKGROUND

Personalized cancer vaccines based on neoantigens have reached the clinical trial stage in melanoma. Different vaccination protocols showed efficacy in preclinical models without a clear indication of the quality and the number of neoantigens required for an effective cancer vaccine.

METHODS

In an effort to develop potent and efficacious neoantigen-based vaccines, we have developed different neoantigen minigene (NAM) vaccine vectors to determine the rules for a successful neoantigen cancer vaccine (NCV) delivered by plasmid DNA and electroporation. Immune responses were analyzed at the level of single neoantigen by flow cytometry and correlated with tumor growth. Adoptive T cell transfer, from HLA-2.1.1 mice, was used to demonstrate the efficacy of the NCV pipeline against human-derived tumors.

RESULTS

In agreement with previous bodies of evidence, immunogenicity was driven by predicted affinity. A strong poly-functional and poly-specific immune response was observed with high affinity neoantigens. However, only a high poly-specific vaccine vector was able to completely protect mice from subsequent tumor challenge. More importantly, this pipeline - from the selection of neoantigens to vaccine design - applied to a new model of patient derived tumor xenograft resulted in therapeutic treatment.

CONCLUSIONS

These results suggest a feasible strategy for a neoantigen cancer vaccine that is simple and applicable for clinical developments.

Tel-eVax: a genetic vaccine targeting telomerase for treatment of canine lymphoma

BACKGROUND

we have recently shown that Tel-eVax, a genetic vaccine targeting dog telomerase (dTERT) and based on Adenovirus (Ad)/DNA Electro-Gene-Transfer (DNA-EGT) technology can induce strong immune response and increase overall survival (OS) of dogs affected by multicentric Diffuse Large B cell Lymphoma (DLBCL) when combined to COP therapy in a double-arm study. Here, we have utilized a clinically validated device for veterinary electroporation called Vet-ePorator™, based on Cliniporator™ technology currently utilized and approved in Europe for electrochemotherapy applications and adapted to electrogenetransfer (EGT).

METHODS

17 dogs affected by DLBCL were vaccinated using two Ad vector injections (Prime phase) followed by DNA-EGT (Boost phase) by means of a Vet-ePorator™ device and treated in the same time with a 27-week Madison Wisconsin CHOP protocol. The immune response was measured by ELISA assays using pool of peptides.

RESULTS

No significant adverse effects were observed. The OS of vaccine/CHOP animals was 64.5 weeks, in line with the previous study. Dogs developed antibodies against the immunizing antigen.

CONCLUSIONS

Tel-eVax in combination with CHOP is safe and immunogenic in lymphoma canine patients. These data confirm the therapeutic efficacy of dTERT vaccine and hold promise for the treatment of dogs affected by other cancer types. More importantly, our findings may translate to human clinical trials and represent new strategies for cancer treatment.

Evaluation of frequency and intensity of asymptomatic anisocytosis in the Japanese dog breeds Shiba, Akita, and Hokkaido

Microcytosis is observed in healthy Japanese breed dogs. The aim of the study was to evaluate the frequency and intensity of asymptomatic anisocytosis using a three-grade scale in Japanese dog breeds with special emphasis on the following indices: mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, and red blood cell distribution width. The retrospective study included analyses of blood morphology and blood smear for clinically healthy Japanese dog breeds Shiba, Akita, and Hokkaido aged from 6 months to 14 years, performed as a part of preventative care. A total of 74 dogs of both sexes were qualified for the study. The group included both neutered and non-neutered animals (Akita – 17 females, 12 males, Shiba – 24 females, 18 males, Hokkaido – 2 females, 1 male). The blood smear revealed significant anisocytosis in 60.8% and mild anisocytosis in 28.4% of the tested dogs – 89.2% in total. Microcytosis was reported for 25.7% of the tested Japanese breed dogs. Reduced mean cell haemoglobin and mean cell haemoglobin concentration were diagnosed in 75.7% and 40.5% of dogs, respectively. Red blood cell distribution width as an anisocytosis indicator exceeded the norm in 12% of the tested dogs. Compared to mixed breed dogs, the Japanese breeds had a reduced mean cell volume, mean cell haemoglobin concentration and significant anisocytosis in the blood smear as well as a higher red blood cell distribution width indicator. Veterinarians should consider these differences when interpreting the results of morphological blood tests.

Checkpoint molecule expression by B and T cell lymphomas in dogs

Immunotherapies targeting checkpoint molecule programmed cell death 1 (PD-1) protein were shown to be effective for treatment of non-Hodgkin lymphoma in people, but little is known about the expression of PD-1 or its ligand PD-L1 by canine lymphoma. Therefore, flow cytometry was used to analyse expression of PD-1 and PD-L1 in canine lymphoma, using fine-needle aspirates of lymph nodes from 34 dogs with B cell lymphoma (BCL), 6 dogs with T cell lymphoma (TCL) and 11 dogs that had relapsed. Furthermore, fine-needle aspirates were obtained from 17 healthy dogs for comparison. Lastly, the impact of chemotherapy resistance on expression of PD-1 and PD-L1 was assessed in vitro. These studies revealed increased expression of PD-L1 by malignant B cells compared to normal B cells. In the case of TCL, tumour cells and normal T cells both showed low to negative expression of PD-1 and PD-L1. In addition, tumour infiltrating lymphocytes from both BCL and TCL had increased expression of both PD-1 and PD-L1 expression compared to B and T cells from lymph nodes of healthy animals. In vitro, chemotherapy-resistant BCL and TCL cell lines exhibited increases in both PD-1 and PD-L1 expression, compared to non-chemotherapy selected tumour cells. These findings indicate that canine lymphomas exhibit upregulated checkpoint molecule expression, though the impact of checkpoint molecule expression on tumour biological behaviour remains unclear.

Molecular cloning of canine Wilms' tumor 1 for immunohistochemical analysis in canine tissues

Wilms’ tumor 1 (WT1) expression has been investigated in various human cancers as a target molecule for cancer immunotherapy. However, few studies have focused on WT1 expression in dogs. Firstly, cDNA of canine WT1 (cWT1) was molecularly cloned from normal canine kidney. The cross-reactivity of the anti-human WT1 monoclonal antibody (6F-H2) with cWT1 was confirmed via Western blotting using cells overexpressing cWT1. Immunohistochemical staining revealed that cWT1 expression was detected in all canine lymphoma tissues and in some normal canine tissues, including the kidney and lymph node. cWT1 is a potential immunotherapy target against canine cancers.

Electroporation in veterinary oncology

Cancer treatments in veterinary medicine continue to evolve beyond the established standard therapies of surgery, chemotherapy and radiation therapy. New technologies in cancer therapy include a targeted mechanism to open the cell membrane based on electroporation, driving therapeutic agents, such as chemotherapy (electro-chemotherapy), for local control of cancer, or delivery of gene-based products (electro-gene therapy), directly into the cancer cell to achieve systemic control. This review examines electrochemotherapy and electro-gene therapy in veterinary medicine and considers future directions and applications.

Progress in Adaptive Immunotherapy for Cancer in Companion Animals: Success on the Path to a Cure

Harnessing the ability of the immune system to eradicate cancer has been a long-held goal of oncology. Work from the last two decades has finally brought immunotherapy into the forefront for cancer treatment, with demonstrable clinical success for aggressive tumors where other therapies had failed. In this review, we will discuss a range of therapies that are in different stages of clinical or preclinical development for companion animals with cancer, and which share the common objective of eliciting adaptive, anti-tumor immune responses. Even though challenges remain, manipulating the immune system holds significant promise to create durable responses and improve outcomes in companion animals with cancer. Furthermore, what we learn from this process will inform and accelerate development of comparable therapies for human cancer patients.

Cancer immunotherapy in veterinary medicine: Current options and new developments

Excitement in the field of tumor immunotherapy is being driven by several remarkable breakthroughs in recent years. This review will cover recent advances in cancer immunotherapy, including the use of T cell checkpoint inhibitors, engineered T cells, cancer vaccines, and anti-B cell and T cell antibodies. Inhibition of T cell checkpoint molecules such as PD-1 and CTLA-4 using monoclonal antibodies has achieved notable success against advanced tumors in humans, including melanoma, renal cell carcinoma, and non-small cell lung cancer. Therapy with engineered T cells has also demonstrated remarkable tumor control and regression in human trials. Autologous cancer vaccines have recently demonstrated impressive prolongation of disease-free intervals and survival times in dogs with lymphoma. In addition, caninized monoclonal antibodies targeting CD20 and CD52 just recently received either full (CD20) or conditional (CD52) licensing by the United States Department of Agriculture for clinical use in the treatment of canine B-cell and T-cell lymphomas, respectively. Thus, immunotherapy for cancer is rapidly moving to the forefront of cancer treatment options in veterinary medicine as well as human medicine.

Novel metronomic chemotherapy and cancer vaccine combinatorial strategy for hepatocellular carcinoma in a mouse model

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer and represents the third and the fifth leading cause of cancer-related death worldwide in men and women, respectively. Hepatitis B virus (HBV) and hepatitis C virus (HCV) chronic infections account for pathogenesis of more than 80 % of primary HCC. HCC prognosis greatly varies according to stage at beginning of treatment, but the overall 5-year survival rate is approximately 5-6 %. Given the limited number of effective therapeutic strategies available, immunotherapies and therapeutic cancer vaccines may help in improving the clinical outcome for HCC patients. However, the few clinical trials conducted to date have shown contrasting results, indicating the need for improvements. In the present study, a novel combinatorial strategy, based on metronomic chemotherapy plus vaccine, is evaluated in a mouse model. The chemotherapy is a multi-drug cocktail including taxanes and alkylating agents, which is administered in a metronomic-like fashion. The vaccine is a multi-peptide cocktail including HCV as well as universal tumor antigen TERT epitopes. The combinatorial strategy designed and evaluated in the present study induces an enhanced specific T cell response, when compared to vaccine alone, which correlates to a reduced Treg frequency. Such results are highly promising and may pave way to relevant improvements in immunotherapeutic strategies for HCC and beyond.

On the potential of oncolytic virotherapy for the treatment of canine cancers

Over 6 million dogs are diagnosed with cancer in the USA each year. Treatment options for many of these patients are limited. It is important that the veterinary and scientific communities begin to explore novel treatment protocols for dogs with cancer. Oncolytic viral therapy is a promising treatment option that may prove to be relatively inexpensive and effective against several types of cancer. The efficacy of oncolytic virus therapies has been clearly demonstrated in murine cancer models, but the positive outcomes observed in mice are not always seen in human cancer patients. These therapies should be thoroughly evaluated in dogs with spontaneously arising cancers to provide needed information about the potential effectiveness of virus treatment for human cancers and to promote the health of our companion animals. This article provides a review of the results of oncolytic virus treatment of canine cancers.

Enhanced therapeutic effect of APAVAC immunotherapy in combination with dose-intense chemotherapy in dogs with advanced indolent B-cell lymphoma

The aim of this non-randomized controlled trial was to compare time to progression (TTP), lymphoma-specific survival (LSS), and safety of an autologous vaccine (consisting of hydroxyapatite ceramic powder and Heat Shock Proteins purified from the dogs' tumors, HSPPCs-HA) plus chemotherapy versus chemotherapy alone in dogs with newly diagnosed, clinically advanced, histologically confirmed, multicentric indolent B-cell lymphoma. The vaccine was prepared from dogs' resected lymph nodes and administered as an intradermal injection. Forty-five client-owned dogs were enrolled: 20 dogs were treated with dose-intense chemotherapy, and 25 received concurrent immunotherapy. Both treatment arms were well tolerated, with no exacerbated toxicity in dogs also receiving the vaccine. TTP was significantly longer for dogs treated with chemo-immunotherapy versus those receiving chemotherapy only (median, 209 versus 85 days, respectively, P=0.015). LSS was not significantly different between groups: dogs treated with chemo-immunotherapy had a median survival of 349 days, and those treated with chemotherapy only had a median survival of 200 days (P=0.173). Among vaccinated dogs, those mounting an immune response had a significantly longer TTP and LSS than those with no detectable response (P=0.012 and P=0.003, respectively). Collectively these results demonstrate that vaccination with HSPPCs-HA may produce clinical benefits with no increased toxicity, thereby providing a strategy for enhancing chemotherapy in dogs with advanced indolent lymphoma.

The importance of comparative oncology in translational medicine

Human cancer is so complex that in vivo preclinical models are needed if effective therapies are to be developed. Naturally occurring cancers in companion animals are therefore a great resource, as shown by the remarkable growth that comparative oncology has seen over the last 30 years. Cancer has become a leading cause of death in companion animals now that more pets are living long enough to develop the disease. Furthermore, more owners are seeking advanced and novel therapies for their pets as they are very much considered family members. Living in the same environments, pets and humans are often afflicted by the same types of cancer which show similar behavior and, in some species, express the same antigen molecules. The treatment of pet tumors using novel therapies is of compelling translational significance.

Tapping the Potential of DNA Delivery with Electroporation for Cancer Immunotherapy

Cancer is a worldwide leading cause of death, and current conventional therapies are limited. The search for alternative preventive or therapeutic solutions is critical if we are going to improve outcomes for patients. The potential for DNA vaccines in the treatment and prevention of cancer has gained great momentum since initial findings almost 2 decades ago that revealed that genetically engineered DNA can elicit an immune response. The combination of adjuvants and an effective delivery method such as electroporation is overcoming past setbacks for naked plasmid DNA (pDNA) as a potential preventive or therapeutic approach to cancer in large animals and humans. In this chapter, we aim to focus on the novel advances in recent years for DNA cancer vaccines, current preclinical data, and the importance of adjuvants and electroporation with emphasis on prostate, melanoma, and cervical cancer.

Clinical trials of immunogene therapy for spontaneous tumors in companion animals

Despite the important progress obtained in the treatment of some pets' malignancies, new treatments need to be developed. Being critical in cancer control and progression, the immune system's appropriate modulation may provide effective therapeutic options. In this review we summarize the outcomes of published immunogene therapy veterinary clinical trials reported by many research centers. A variety of tumors such as canine melanoma, soft tissue sarcomas, osteosarcoma and lymphoma, feline fibrosarcoma, and equine melanoma were subjected to different treatment approaches. Both viral and mainly nonviral vectors were used to deliver gene products as cytokines, xenogeneic tumor associated antigens, specific ligands, and proapoptotic regulatory factors. In some cases autologous, allogenic, or xenogeneic transgenic cytokine producing cells were assayed. In general terms, minor or no adverse collateral effects appeared during this kind of therapies and treated patients usually displayed a better course of the disease (longer survival, delayed or suppressed recurrence or metastatic spread, and improvement of the quality of life). This suggests the utility of these methodologies as standard adjuvant treatments. The encouraging outcomes obtained in companion animals support their ready application in veterinary clinical oncology and serve as preclinical proof of concept and safety assay for future human gene therapy trials.

Oncolytic virotherapy of canine and feline cancer

Cancer is the leading cause of disease-related death in companion animals such as dogs and cats. Despite recent progress in the diagnosis and treatment of advanced canine and feline cancer, overall patient treatment outcome has not been substantially improved. Virotherapy using oncolytic viruses is one promising new strategy for cancer therapy. Oncolytic viruses (OVs) preferentially infect and lyse cancer cells, without causing excessive damage to surrounding healthy tissue, and initiate tumor-specific immunity. The current review describes the use of different oncolytic viruses for cancer therapy and their application to canine and feline cancer.

Trial Watch: DNA vaccines for cancer therapy

During the past 2 decades, the possibility that preparations capable of eliciting tumor-specific immune responses would mediate robust therapeutic effects in cancer patients has received renovated interest. In this context, several approaches to vaccinate cancer patients against their own malignancies have been conceived, including the administration of DNA constructs coding for one or more tumor-associated antigens (TAAs). Such DNA-based vaccines conceptually differ from other types of gene therapy in that they are not devised to directly kill cancer cells or sensitize them to the cytotoxic activity of a drug, but rather to elicit a tumor-specific immune response. In spite of an intense wave of preclinical development, the introduction of this immunotherapeutic paradigm into the clinical practice is facing difficulties. Indeed, while most DNA-based anticancer vaccines are well tolerated by cancer patients, they often fail to generate therapeutically relevant clinical responses. In this Trial Watch, we discuss the latest advances on the use of DNA-based vaccines in cancer therapy, discussing the literature that has been produced around this topic during the last 13 months as well as clinical studies that have been launched in the same time frame to assess the actual therapeutic potential of this intervention.

Safety and efficacy of a genetic vaccine targeting telomerase plus chemotherapy for the therapy of canine B-cell lymphoma

Client-owned pet dogs represent exceptional translational models for advancement of cancer research because they reflect the complex heterogeneity observed in human cancer. We have recently shown that a genetic vaccine targeting dog telomerase reverse transcriptase (dTERT) and based on adenovirus DNA electro-gene-transfer (Ad/DNA-EGT) technology can induce strong cell-mediated immune responses against this tumor antigen and increase overall survival of dogs affected by B-cell lymphosarcoma (LSA) in comparison with historical controls when combined with a cyclophosphamide, vincristine, and prednisone (COP) chemotherapy regimen. Here, we have conducted a double-arm clinical trial with an extended number of LSA patients, measured the antigen-specific immune response, and evaluated potential toxic effects of the immunotherapy along with a follow-up of patients survival for 3.5 years. The immune response was measured by enzyme-linked immunospot assay. The expression of dTERT was quantified by quantitative polymerase chain reaction. Changes in hematological parameters, local/systemic toxicity or organic dysfunction and fever were monitored over time during the treatment. dTERT-specific cell-mediated immune responses were induced in almost all treated animals. No adverse effects were observed in any dog patient that underwent treatment. The overall survival time of vaccine/COP-treated dogs was significantly increased over the COP-only cohort (>76.1 vs. 29.3 weeks, respectively, p<0.0001). There was a significant association between dTERT expression levels in LSA cells and overall survival among vaccinated patients. In conclusion, Ad/DNA-EGT-based cancer vaccine against dTERT in combination with COP chemotherapy is safe and significantly prolongs the survival of LSA canine patients. These data confirm the therapeutic efficacy of dTERT vaccine and support the evaluation of this approach for other cancer types as well as the translation of this approach to human clinical trials.

Recent progress in canine tumor vaccination: potential applications for human tumor vaccines

Tumor vaccination holds great promise for the treatment of cancer and research concerning tumor vaccination in dogs is of great interest for veterinary as well as human medicine. Indeed, cancer is the leading cause of death in adult dogs and companion animals are acknowledged as excellent preclinical models for human oncology. The license of the veterinary melanoma vaccine (Oncept™) and Provenge® for the treatment of prostate cancer in men established tumor vaccination as a valid treatment modality for cancer. Although the results with this and other vaccines are promising, there are still some hurdles to overcome. In this article, preclinical and clinical trials with tumor vaccines in dogs are discussed, as well as the surplus value of canine cancer patients for human medicine.

Phase 1 studies of the safety and immunogenicity of electroporated HER2/CEA DNA vaccine followed by adenoviral boost immunization in patients with solid tumors

BACKGROUND

DNA electroporation has been demonstrated in preclinical models to be a promising strategy to improve cancer immunity, especially when combined with other genetic vaccines in heterologous prime-boost protocols. We report the results of 2 multicenter phase 1 trials involving adult cancer patients (n=33) with stage II-IV disease.

METHODS

Patients were vaccinated with V930 alone, a DNA vaccine containing equal amounts of plasmids expressing the extracellular and trans-membrane domains of human HER2, and a plasmid expressing CEA fused to the B subunit of Escherichia coli heat labile toxin (Study 1), or a heterologous prime-boost vaccination approach with V930 followed by V932, a dicistronic adenovirus subtype-6 viral vector vaccine coding for the same antigens (Study 2).

RESULTS

The use of the V930 vaccination with electroporation alone or in combination with V932 was well-tolerated without any serious adverse events. In both studies, the most common vaccine-related side effects were injection site reactions and arthralgias. No measurable cell-mediated immune response (CMI) to CEA or HER2 was detected in patients by ELISPOT; however, a significant increase of both cell-mediated immunity and antibody titer against the bacterial heat labile toxin were observed upon vaccination.

CONCLUSION

V930 vaccination alone or in combination with V932 was well tolerated without any vaccine-related serious adverse effects, and was able to induce measurable immune responses against bacterial antigen. However, the prime-boost strategy did not appear to augment any detectable CMI responses against either CEA or HER2.

TRIAL REGISTRATION

Study 1 - ClinicalTrials.gov, NCT00250419; Study 2 - ClinicalTrials.gov, NCT00647114.

Kinesin spindle protein SiRNA slows tumor progression

The kinesin spindle protein (KSP), a member of the kinesin superfamily of microtubule-based motors, plays a critical role in mitosis as it mediates centrosome separation and bipolar spindle assembly and maintenance. Inhibition of KSP function leads to cell cycle arrest at mitosis with the formation of monoastral microtubule arrays, and ultimately, to cell death. Several KSP inhibitors are currently being studied in clinical trials and provide new opportunities for the development of novel anticancer therapeutics. RNA interference (RNAi) may represent a powerful strategy to interfere with key molecular pathways involved in cancer. In this study, we have established an efficient method for intratumoral delivery of siRNA. We evaluated short interfering RNA (siRNA) duplexes targeting luciferase as surrogate marker or KSP sequence. To examine the potential feasibility of RNAi therapy, the siRNA was transfected into pre-established lesions by means of intratumor electro-transfer of RNA therapeutics (IERT). This technology allowed cell permeation of the nucleic acids and to efficiently knock down gene expression, albeit transiently. The KSP-specific siRNA drastically reduced outgrowth of subcutaneous melanoma and ovarian cancer lesions. Our results show that intratumoral electro-transfer of siRNA is feasible and KSP-specific siRNA may provide a novel strategy for therapeutic intervention.

Electro-gene-transfer as a new tool for cancer immunotherapy in animals

The concept of vaccines based on the direct inoculation of plasmid DNA gained initial proof-of-concept in small rodent species. Further development was hampered by the difficulty to confirm immunogenicity and efficacy in large animal species and, most importantly, in human clinical trials. These negative findings led to the search of complementary technologies which, in combination with intradermal or intramuscular plasmid DNA injection would result in more robust delivery, decreased interindividual variability, clear evidence of clinical efficacy and which would eventually lead to market approval of new vaccine products. The use of high-pressure, needleless devices as an enhancing tool for plasmid DNA delivery led to recent approval by USDA of Oncept™, a therapeutic cancer vaccine directed against tyrosinase for the therapy of melanoma in dogs. An alternative approach to improve plasmid DNA delivery is electro-gene-transfer (EGT). In this article, we briefly review the principles of DNA-EGT and the evidences for efficacy of a telomerase reverse transcriptase vaccine in a dog clinical trial, and provide perspectives for the use of this technology for broader applications in pet animals.

The dog as a possible animal model for human non-Hodgkin lymphoma: a review

Lymphoma represents the most frequent hematopoietic cancer in dogs, and it shows significant overlap with the human disease. Several environmental factors have been associated with canine lymphoma, suggesting that they may contribute to lymphomagenesis. Canine lymphoma often presents in advanced stage (III-V) at diagnosis and, most commonly, has an aggressive clinical course requiring prompt treatment, which relies on the use of polychemotherapy. In this review, we will summarize the state-of-the-art of canine lymphoma epidemiology, pathobiology, diagnostic work-up and therapy, and will highlight the links to the corresponding human disease, providing evidence for the use of dog as an animal model of spontaneous disease.

Genetic cancer vaccines: current status and perspectives

INTRODUCTION

The recent approval of the first therapeutic cancer vaccine by the US Regulatory Agency represents a breakthrough event in the history of cancer treatment. The past scepticism towards this type of therapeutic intervention is now replaced by great expectations. The field is now moving towards the development of alternative vaccination technologies, which are capable of generating stronger, more durable and efficient immune responses against specific tumour-associated antigens (TAAs) in combination with cheaper and more standardised manufacturing.

AREAS COVERED

In this context, genetic vaccines are emerging among the most promising methodologies. Several evidences point to combinations of different genetic immunisation modalities (heterologous prime/boost) as a powerful approach to induce superior immune responses and achieve greater clinical efficacy. In this review, we provide an overview of the current status of development of genetic cancer vaccines with particular emphasis on adenoviral vector prime/DNA boost vaccination schedules.

EXPERT OPINION

We believe that therapeutic genetic cancer vaccines have the strong potential to become an established therapeutic modality for cancer in next coming years, in a manner similar to what have now become monoclonal antibodies.

Adoptive T-cell therapy improves treatment of canine non-Hodgkin lymphoma post chemotherapy

Clinical observations reveal that an augmented pace of T-cell recovery after chemotherapy correlates with improved tumor-free survival, suggesting the add-back of T cells after chemotherapy may improve outcomes. To evaluate adoptive immunotherapy treatment for B-lineage non-Hodgkin lymphoma (NHL), we expanded T cells from client-owned canines diagnosed with NHL on artificial antigen presenting cells (aAPC) in the presence of human interleukin (IL)-2 and IL-21. Graded doses of autologous T cells were infused after CHOP chemotherapy and persisted for 49 days, homed to tumor, and significantly improved survival. Serum thymidine kinase changes predicted T-cell engraftment, while anti-tumor effects correlated with neutrophil-to-lymphocyte ratios and granzyme B expression in manufactured T cells. Therefore, chemotherapy can be used to modulate infused T-cell responses to enhance anti-tumor effects. The companion canine model has translational implications for human immunotherapy which can be readily exploited since clinical-grade canine and human T cells are propagated using identical approaches.

Genetic immunization with plasmid DNA mediated by electrotransfer

The concept of DNA immunization was first advanced in the early 1990s, but was not developed because of an initial lack of efficiency. Recent technical advances in plasmid design and gene delivery techniques have allowed renewed interest in the idea. Particularly, a better understanding of genetic immunization has led to construction of optimized plasmids and the use of efficient molecular adjuvants. The field also took great advantage of new delivery techniques such as electrotransfer. This is a simple physical technique consisting of injecting plasmid DNA into a target tissue and applying an electric field, allowing up to a thousandfold more expression of the transgene than naked DNA. DNA immunization mediated by electrotransfer is now effective in a variety of preclinical models against infectious or acquired diseases such as cancer or autoimmune diseases, and is making its way through the clinics in several ongoing phase I human clinical trials. This review will briefly describe genetic immunization mediated by electrotransfer and the main fields of application.

Emerging cancer vaccines: the promise of genetic vectors

Therapeutic vaccination against cancer is an important approach which, when combined with other therapies, can improve long-term control of cancer. In fact, the induction of adaptive immune responses against Tumor Associated Antigens (TAAs) as well as innate immunity are important factors for tumor stabilization/eradication. A variety of immunization technologies have been explored in last decades and are currently under active evaluation, such as cell-based, protein, peptide and heat-shock protein-based cancer vaccines. Genetic vaccines are emerging as promising methodologies to elicit immune responses against a wide variety of antigens, including TAAs. Amongst these, Adenovirus (Ad)-based vectors show excellent immunogenicity profile and have achieved immunological proof of concept in humans. In vivo electroporation of plasmid DNA (DNA-EP) is also a desirable vaccine technology for cancer vaccines, as it is repeatable several times, a parameter required for the long-term maintenance of anti-tumor immunity. Recent findings show that combinations of different modalities of immunization (heterologous prime/boost) are able to induce superior immune reactions as compared to single-modality vaccines. In this review, we will discuss the challenges and requirements of emerging cancer vaccines, particularly focusing on the genetic cancer vaccines currently under active development and the promise shown by Ad and DNA-EP heterologous prime-boost.