Generation of recombinant canine interleukin-15 and evaluation of its effects on the proliferation and function of canine NK cells

Are owned dogs or stray dogs more prepared to diseases? A comparative study of immune system gene expression of perforin and granzymes

Stray dogs are inevitably exposed to more infections than owned dogs living indoor. However, no studies have investigated whether the immune system gene expression differs between owned dogs kept in better care conditions and stray dogs living outside. To investigate this, blood samples were taken from 90 dogs (45 owned and 45 stray dogs) that were checked and confirmed as healthy. By using qPCR, the amples were analyzed for the expression of the perforin, granzyme A and granzyme B genes, which are associated with the activation of apoptotic pathways in the immune system. We found that the perforin and granzyme A gene expression levels were higher in stray dogs although the differences were not statistically significant. On the other hand, a 2.81 times higher and a notable difference (P < 0.001) was found in the expression level of granzyme B gene in stray dogs. These results indicate that the immune system in stray dogs might be more prepared for diseases than that of the owned dogs and the granzyme B gene plays a more dominant role in the immune response than granzyme A and perforin.

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 and immunological effects of recombinant canine IL-15 in dogs

Interleukin-15 (IL-15) is a pleiotropic cytokine that plays pivotal roles in innate and adaptive immunity. It is also a promising cytokine for treating cancer. Despite growing interest in its use as an immunotherapeutic, its safety and immunological effects in dogs have not been reported. In this study, healthy dogs were given recombinant canine IL-15 (rcIL-15) intravenously at a daily dose of 20 μg/kg for 8 days and monitored for 32 days to determine the safety and immunological effects of rcIL-15. The repeated administration of rcIL-15 was well tolerated, did not cause any serious side effects, and promoted the selective proliferation and activation of canine anti-cancer effector cells, including CD3⁺CD8⁺ cytotoxic T lymphocytes, CD3⁺CD5^dimCD21^-, and non-B/non-T NK cell populations, without stimulating T_reg lymphocytes. The rcIL-15 injections also stimulated the expression of molecules and transcription factors associated with the activation and effector functions of NK cells, including CD16, NKG2D, NKp30, NKp44, NKp46, perforin, granzyme B, Ly49, T-bet, and Eomes. These results suggest that rcIL-15 might be a valuable therapeutic adjuvant to improve immunity against cancer in dogs.

Characterization and Potential Applications of Dog Natural Killer Cells in Cancer Immunotherapy

Natural killer (NK) cells of the innate immune system are a key focus of research within the field of immuno-oncology based on their ability to recognize and eliminate malignant cells without prior sensitization or priming. However, barriers have arisen in the effective translation of NK cells to the clinic, in part because of critical species differences between mice and humans. Companion animals, especially dogs, are valuable species for overcoming many of these barriers, as dogs develop spontaneous tumors in the setting of an intact immune system, and the genetic and epigenetic factors that underlie oncogenesis appear to be similar between dogs and humans. Here, we summarize the current state of knowledge for dog NK cells, including cell surface marker phenotype, key NK genes and genetic regulation, similarities and differences of dog NK cells to other mammals, especially human and mouse, expression of canonical inhibitory and activating receptors, ex vivo expansion techniques, and current and future clinical applications. While dog NK cells are not as well described as those in humans and mice, the knowledge of the field is increasing and clinical applications in dogs can potentially advance the field of human NK biology and therapy. Better characterization is needed to truly understand the similarities and differences of dog NK cells with mouse and human. This will allow for the canine model to speed clinical translation of NK immunotherapy studies and overcome key barriers in the optimization of NK cancer immunotherapy, including trafficking, longevity, and maximal in vivo support.

Canine non-B, non-T NK lymphocytes have a potential antibody-dependent cellular cytotoxicity function against antibody-coated tumor cells

Background

The antibody-dependent cellular cytotoxicity (ADCC) is a cell-mediated immune defense mechanism in which effector immune cells actively lyse antibody-coated target cells. The ADCC of tumor cells is employed in the treatment of various cancers overexpressing unique antigens, and only natural killer (NK) cells are known to be major effectors of antibody mediated ADCC activity. Canine NK cells are still defined as non-B, non-T large granular lymphocytes because of the lack of information regarding the NK cell-restricted specific marker in dogs, and it has never been demonstrated that canine NK cells have ADCC ability against tumor cells. In the present study, we investigated whether canine non-B, non-T NK cells have ADCC ability against target antibody-coated tumor cells, using cetuximab and trastuzumab, the only human antibodies reported binding to canine cancer cells.

Results

Activated canine non-B, non-T NK cells (CD3⁻CD21⁻CD5⁻TCRαβ⁻TCRγδ⁻) for 13~17 days ex vivo showed ADCC ability against trastuzumab- or cetuximab-coated target tumor cells expressing various levels of human epidermal growth factor receptor 2 (HER-2) and epidermal growth factor receptor (EGFR). Trastuzumab and cetuximab induced significant ADCC responses of canine NK cells even in CMT-U334 and CF41.Mg cells expressing low levels of HER-2 and/or EGFR, as well as in SKBR3 and DU145 cells overexpressing HER-2 and/or EGFR. The trastuzumab-mediated ADCC activity of NK cells was significantly enhanced by treatment with rcIL-21.

Conclusions

The results of this study suggest that canine non-B, non-T NK lymphocytes have a potential ADCC function and that combinational strategies of monoclonal antibodies with either cytokines, which activate NK cells in vivo, or adoptive transfer of NK cells may be a feasible method for amplifying the efficacy of immunotherapy against malignant cancers even with very low expression of target molecules in dogs.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2068-5) contains supplementary material, which is available to authorized users.

Roles of aberrant hemichannel activities due to mutant connexin26 in the pathogenesis of KID syndrome

Germline missense mutations in GJB2 encoding connexin (Cx) 26 have been found in keratitis, ichthyosis and deafness (KID) syndrome. We explored the effects of three mouse Cx26 mutants (Cx26-G12R, -G45E and -D50N) corresponding to KID syndrome-causative human mutants on hemichannel activities leading to cell death and the expression of immune response-associated genes. We analyzed the 3D images of cells expressing wild-type (WT) or mutant Cx26 molecules to demonstrate clearly the intracellular localization of Cx26 mutants and hemichannel formation. High extracellular Ca²⁺ conditions lead to the closure of gap junction hemichannels in Cx26-G12R or Cx26-G45E expressing cells, resulting in prohibition of the Cx26 mutant-induced cell death. Fluorescent dye uptake assays revealed that cells with Cx26-D50N had aberrantly high hemichannel activities, which were abolished by a hemichannel blocker, carbenoxolone and 18α-Glycyrrhetinic acid. These results further support the idea that abnormal hemichannel activities play important roles in the pathogenesis of KID syndrome. Furthermore, we revealed that the expressions of IL15, CCL5, IL1A, IL23R and TLR5 are down-regulated in keratinocytes expressing Cx26-D50N, suggesting that immune deficiency in KID syndrome expressing Cx26-D50N might be associated not only with skin barrier defects, but also with the down-regulated expression of immune response-related genes.

Comparison of Phenotypic and Functional Characteristics Between Canine Non-B, Non-T Natural Killer Lymphocytes and CD3+CD5dimCD21- Cytotoxic Large Granular Lymphocytes

Natural killer (NK) cells play a pivotal role in the immune response against infections and malignant transformation, and adopted transfer of NK cells is thought to be a promising therapeutic approach for cancer patients. Previous reports describing the phenotypic features of canine NK cells have produced inconsistent results. Canine NK cells are still defined as non-B and non-T (CD3⁻CD21⁻) large granular lymphocytes. However, a few reports have demonstrated that canine NK cells share the phenotypic characteristics of T lymphocytes, and that CD3⁺CD5^dimCD21⁻ lymphocytes are putative canine NK cells. Based on our previous reports, we hypothesized that phenotypic modulation could occur between these two populations during activation. In this study, we investigated the phenotypic and functional differences between CD3⁺CD5^dimCD21⁻ (cytotoxic large granular lymphocytes) and CD3⁻CD5⁻CD21⁻ NK lymphocytes before and after culture of peripheral blood mononuclear cells isolated from normal dogs. The results of this study show that CD3⁺CD5^dimCD21⁻ lymphocytes can be differentiated into non-B, non-T NK (CD3⁻CD5⁻CD21⁻TCRαβ⁻TCRγδ⁻GranzymeB⁺) lymphocytes through phenotypic modulation in response to cytokine stimulation. In vitro studies of purified CD3⁺CD5^dimCD21⁻ cells showed that CD3⁻CD5⁻CD21⁻ cells are derived from CD3⁺CD5^dimCD21⁻ cells through phenotypic modulation. CD3⁺CD5^dimCD21⁻ cells share more NK cell functional characteristics compared with CD3⁻CD5⁻CD21⁻ cells, including the expression of T-box transcription factors (Eomes, T-bet), the production of granzyme B and interferon-γ, and the expression of NK cell-related molecular receptors such as NKG2D and NKp30. In conclusion, the results of this study suggest that CD3⁺CD5^dimCD21⁻ and CD3⁻CD5⁻CD21⁻ cells both contain a subset of putative NK cells, and the difference between the two populations may be due to the degree of maturation.

Immunotherapy for Dogs: Running Behind Humans

A number of excellent reviews on the potential of canine cancer immunotherapy are available, but many extrapolate from observations in humans when in fact only very few immunotherapies have been developed for canines that have shown efficacy in well-designed studies. Pharmaceutical and biotech companies are aware that the market for more expensive immunotherapies in canines is limited resulting in limited funding for clinical trials. However, dogs and other pets deserve access to this new form of cancer therapy. The purpose of this brief review is to summarize the current status of available immunotherapies for dogs and their near-term prospects, provided we can effectively translate discoveries and progress in humans to canines.

Effects of three IL-15 variants on NCI-H446 cell proliferation and expression of cell cycle regulatory molecules

Interleukin 15 (IL-15) is a cytokine exhibiting antitumor characteristic similar to that of IL-2. However, in human tissues and cells, IL-15 expression and secretion is very limited, suggesting IL-15 functions mainly intracellularly. In the present study, we assessed the effects of transfecting NCI-H446 small cell lung cancer cells with genes encoding three IL-15 variants: prototypical IL-15, mature IL-15 peptide, and modified IL-15 in which the IL-2 signal peptide is substituted for the native signal peptide. NCI-H446 cells transfected with empty plasmid served as the control group. We found that IL-15 transfection effectively inhibited NCI-H446 cell proliferation and arrested cell cycle progression, with the modified IL-15 carrying the IL-2 signal peptide exerting the greatest effect. Consistent with those findings, expression each of the three IL-15 variants reduced growth of NCI-H446 xenograph tumors, and the modified IL-15 again showed the greatest effect. In addition, IL-15 expression led to down-regulation of the positive cell cycle regulators cyclin E and CDK2 and up-regulation of the negative cycle regulators p21 and Rb. These findings suggest IL-15 acts as a tumor suppressor that inhibits tumor cell proliferation by inducing cell cycle arrest.

NCR1 Expression Identifies Canine Natural Killer Cell Subsets with Phenotypic Similarity to Human Natural Killer Cells

Canines spontaneously develop many cancers similar to humans - including osteosarcoma, leukemia, and lymphoma - offering the opportunity to study immune therapies in a genetically heterogeneous and immunocompetent environment. However, a lack of antibodies recognizing canine NK cell markers has resulted in suboptimal characterization and unknown purity of NK cell products, hindering the development of canine models of NK cell adoptive immunotherapy. To this end, we generated a novel antibody to canine NCR1 (NKp46), the putative species-wide marker of NK cells, enabling purification of NK cells for further characterization. We demonstrate that CD3^-/NKp46⁺ cells in healthy and osteosarcoma-bearing canines have phenotypic similarity to human CD3^-/NKp46⁺ NK cells, expressing mRNA for CD16 and the natural cytotoxicity receptors NKp30, NKp44, and NKp80. Functionally, we demonstrate with the calcein release assay that canine CD3^-/NKp46⁺ cells kill canine tumor cell lines without prior sensitization and secrete IFN-γ, TNF-α, IL-8, IL-10, and granulocyte-macrophage colony-stimulating factor as measured by Luminex. Similar to human NK cells, CD3^-/NKp46⁺ cells expand rapidly on feeder cells expressing 4-1BBL and membrane-bound IL-21 (median = 20,283-fold in 21 days). Furthermore, we identify a minor Null population (CD3^-/CD21^-/CD14^-/NKp46^-) with reduced cytotoxicity against osteosarcoma cells, but similar cytokine secretion as CD3^-/NKp46⁺ cells. Null cells in canines and humans have reduced expression of NKG2D, NKp44, and CD16 compared to NKp46⁺ NK cells and can be induced to express NKp46 with further expansion on feeder cells. In conclusion, we have identified and characterized canine NK cells, including an NKp46^- subset of canine and human NK cells, using a novel anti-canine NKp46 antibody, and report robust ex vivo expansion of canine NK cells sufficient for adoptive immunotherapy.

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.