Devil Facial Tumour Disease Cells Research Articles

Tasmanian devil cathelicidins exhibit anticancer activity against Devil Facial Tumour Disease (DFTD) cells

The Tasmanian devil (Sarcophilus harrisii) is endangered due to the spread of Devil Facial Tumour Disease (DFTD), a contagious cancer with no current treatment options. Here we test whether seven recently characterized Tasmanian devil cathelicidins are involved in cancer regulation. We measured DFTD cell viability in vitro following incubation with each of the seven peptides and describe the effect of each on gene expression in treated cells. Four cathelicidins (Saha-CATH3, 4, 5 and 6) were toxic to DFTD cells and caused general signs of cellular stress. The most toxic peptide (Saha-CATH5) also suppressed the ERBB and YAP1/TAZ signaling pathways, both of which have been identified as important drivers of cancer proliferation. Three cathelicidins induced inflammatory pathways in DFTD cells that may potentially recruit immune cells in vivo. This study suggests that devil cathelicidins have some anti-cancer and inflammatory functions and should be explored further to determine whether they have potential as treatment leads.

Extracellular vesicle proteomes of two transmissible cancers of Tasmanian devils reveal tenascin-C as a serum-based differential diagnostic biomarker.

The iconic Tasmanian devil (Sarcophilus harrisii) is endangered due to the transmissible cancer Devil Facial Tumour Disease (DFTD), of which there are two genetically independent subtypes (DFT1 and DFT2). While DFT1 and DFT2 can be differentially diagnosed using tumour biopsies, there is an urgent need to develop less-invasive biomarkers that can detect DFTD and distinguish between subtypes. Extracellular vesicles (EVs), the nano-sized membrane-enclosed vesicles present in most biofluids, represent a valuable resource for biomarker discovery. Here, we characterized the proteome of EVs from cultured DFTD cells using data-independent acquisition-mass spectrometry and an in-house spectral library of > 1500 proteins. EVs from both DFT1 and DFT2 cell lines expressed higher levels of proteins associated with focal adhesion functions. Furthermore, hallmark proteins of epithelial-mesenchymal transition were enriched in DFT2 EVs relative to DFT1 EVs. These findings were validated in EVs derived from serum samples, revealing that the mesenchymal marker tenascin-C was also enriched in EVs derived from the serum of devils infected with DFT2 relative to those infected with DFT1 and healthy controls. This first EV-based investigation of DFTD increases our understanding of the cancers' EVs and their possible involvement in DFTD progression, such as metastasis. Finally, we demonstrated the potential of EVs to differentiate between DFT1 and DFT2, highlightingtheir potential use as less-invasive liquid biopsies for the Tasmanian devil.

Post-release immune responses of Tasmanian devils vaccinated with an experimental devil facial tumour disease vaccine

Abstract Context Disease is increasingly becoming a driver of wildlife population declines and an extinction risk. Vaccines are one of the most successful health interventions in human history, but few have been tested for mitigating wildlife disease. The transmissible cancer, devil facial tumour disease (DFTD), triggered the Tasmanian devil’s (Sarcophilus harrisii) inclusion on the international endangered species list. In 2016, 33 devils from a DFTD-free insurance population were given an experimental DFTD vaccination before their wild release on the Tasmanian northern coast. Aim To determine the efficacy of the vaccination protocol and the longevity of the induced responses. Method Six trapping trips took place over the 2.5 years following release, and both vaccinated and incumbent devils had blood samples and tumour biopsies collected. Key results In all, 8 of the 33 vaccinated devils were re-trapped, and six of those developed DFTD within the monitoring period. Despite the lack of protection provided by the vaccine, we observed signs of immune activation not usually found in unvaccinated devils. First, sera collected from the eight devils showed that anti-DFTD antibodies persisted for up to 2 years post-vaccination. Second, tumour-infiltrating lymphocytes were found in three of four biopsies collected from vaccinated devils, which contrasts with the ‘immune deserts’ typical of DFTs; only 1 of the 20 incumbent devils with DFTD had a tumour biopsy exhibiting immune-cell infiltrate. Third, immunohistochemical analysis of the vaccinated devils’ tumour biopsies identified the functional immune molecules associated with antigen-presenting cells (MHC-II) and T-cells (CD3), and the immune checkpoint molecule PD-1, all being associated with anti-tumour immunity in other species. Conclusions These results correlate with our previous study on captive devils in which a prophylactic vaccine primed the devil immune system and, following DFTD challenge and tumour growth, immunotherapy induced complete tumour regressions. The field trial results presented here provide further evidence that the devil immune system can be primed to recognise DFTD cells, but additional immune manipulation could be needed for complete protection or induction of tumour regressions. Implications A protective DFTD vaccine would provide a valuable management approach for conservation of the Tasmanian devil.

Curse of the devil: molecular insights into the emergence of transmissible cancers in the Tasmanian devil (Sarcophilus harrisii).

The Tasmanian devil (Sarcophilus harrisii) is the only mammalian species known to be affected by multiple transmissible cancers. Devil facial tumours 1 and 2 (DFT1 and DFT2) are independent neoplastic cell lineages that produce large, disfiguring cancers known as devil facial tumour disease (DFTD). The long-term persistence of wild Tasmanian devils is threatened due to the ability of DFTD cells to propagate as contagious allografts and the high mortality rate of DFTD. Recent studies have demonstrated that both DFT1 and DFT2 cancers originated from founder cells of the Schwann cell lineage, an uncommon origin of malignant cancer in humans. This unprecedented finding has revealed a potential predisposition of Tasmanian devils to transmissible cancers of the Schwann cell lineage. In this review, we compare the molecular nature of human Schwann cells and nerve sheath tumours with DFT1 and DFT2 to gain insights into the emergence of transmissible cancers in the Tasmanian devil. We discuss a potential mechanism, whereby Schwann cell plasticity and frequent wounding in Tasmanian devils combine with an inherent cancer predisposition and low genetic diversity to give rise to transmissible Schwann cell cancers in devils on rare occasions.

TNF May Negatively Regulate Phagocytosis of Devil Facial Tumour Disease Cells by Activated Macrophages

ABSTRACTIntroduction: Macrophage phagocytosis of pathogens and tumour cells is an important early event in protection against infectious disease and cancer. As tumour necrosis factor α (TNF) is an important cytokine in macrophage activation, we investigated the involvement of TNF in macrophage phagocytosis of tumour cells.Methods: We used Devil Facial Tumour Disease (DFTD) cancer cells as the target tumour cells. The Tasmanian devil (Sarcophilus harrisii) population is threatened by the transmissible DFTD. Using DFTD cells provided the opportunity to determine if these cells can be phagocytosed and investigate requirement for TNF. As effector cells, bone marrow derived macrophages (BMDMs), generated from C57BL/6 wild type (B6.WT) and C57BL/6 TNF-/- (B6.TNF-/-) mice were used. Phagocytosis of DFTD cells was investigated by confocal microscopy and flow cytometry.Results: DFTD cells were consistently phagocytosed by B6.WT and B6.TNF-/- BMDMs with similar efficiency in vitro. Consequently the DFTD cells are not resistant to phagocytosis. Following activation by exposure to IFNγ and LPS or LPS alone, B6.TNF-/- BMDMs had higher phagocytic efficiency and lower nitric oxide (NO) production compared to wild-type controls. In addition, NO seems to be unlikely to be the involved in phagocytosis efficiency in IFNγ and LPS activated B6.TNF-/- macrophages and consequences thereof.Conclusion: Our results indicate that TNF is not required for IFNγ and LPS or LPS alone activation of macrophage phagocytosis. TNF may negatively regulate macrophage phagocytosis of tumour cells.

Lessons learnt from the Tasmanian devil facial tumour regarding immune function in cancer.

Genetic and genomic technologies have facilitated a greater understanding of the Tasmanian devil immune system and the origins, evolution and spread of devil facial tumour disease (DFTD). DFTD is a contagious cancer that has caused significant declines in devil populations across Tasmania. Immune responses to DFTD are rarely detected, allowing the cancer to pass between individuals and proliferate unimpeded. Early immunosenscence in devils appears to decrease anti-tumour immunity in older animals compared to younger animals, which may increase susceptibility to DFTD and explain high DFTD prevalence in this age group. Devils also have extremely low major histocompatibility complex (MHC) diversity, and multiple alleles are shared with the tumour, lowering histocompatibility barriers which may have contributed to DFTD evolution. DFTD actively evades immune attack by down-regulating cell-surface MHC I molecules, making it effectively invisible to the immune system. Altered MHC I profiles should activate natural killer (NK) cell anti-tumour responses, but these are absent in DFTD infection. Recent immunisation and immunotherapy using modified DFTD cells has induced an anti-DFTD immune response and regression of DFTD in some devils. Knowledge gained from immune responses to a transmissible cancer in devils will ultimately reveal useful insights into immunity to cancer in humans and other species.

Gomesin peptides prevent proliferation and lead to the cell death of devil facial tumour disease cells

The Tasmanian devil faces extinction due to devil facial tumour disease (DFTD), a highly transmittable clonal form of cancer without available treatment. In this study, we report the cell-autonomous antiproliferative and cytotoxic activities exhibited by the spider peptide gomesin (AgGom) and gomesin-like homologue (HiGom) in DFTD cells. Mechanistically, both peptides caused a significant reduction at G0/G1 phase, in correlation with an augmented expression of the cell cycle inhibitory proteins p53, p27, p21, necrosis, exacerbated generation of reactive oxygen species and diminished mitochondrial membrane potential, all hallmarks of cellular stress. The screening of a novel panel of AgGom-analogues revealed that, unlike changes in the hydrophobicity and electrostatic surface, the cytotoxic potential of the gomesin analogues in DFTD cells lies on specific arginine substitutions in the eight and nine positions and alanine replacement in three, five and 12 positions. In conclusion, the evidence supports gomesin as a potential antiproliferative compound against DFTD disease.

Regression of devil facial tumour disease following immunotherapy in immunised Tasmanian devils

Devil facial tumour disease (DFTD) is a transmissible cancer devastating the Tasmanian devil (Sarcophilus harrisii) population. The cancer cell is the ‘infectious’ agent transmitted as an allograft by biting. Animals usually die within a few months with no evidence of antibody or immune cell responses against the DFTD allograft. This lack of anti-tumour immunity is attributed to an absence of cell surface major histocompatibility complex (MHC)-I molecule expression. While the endangerment of the devil population precludes experimentation on large experimental groups, those examined in our study indicated that immunisation and immunotherapy with DFTD cells expressing surface MHC-I corresponded with effective anti-tumour responses. Tumour engraftment did not occur in one of the five immunised Tasmanian devils, and regression followed therapy of experimentally induced DFTD tumours in three Tasmanian devils. Regression correlated with immune cell infiltration and antibody responses against DFTD cells. These data support the concept that immunisation of devils with DFTD cancer cells can successfully induce humoral responses against DFTD and trigger immune-mediated regression of established tumours. Our findings support the feasibility of a protective DFTD vaccine and ultimately the preservation of the species.

Demonstration of immune responses against devil facial tumour disease in wild Tasmanian devils.

Devil facial tumour disease (DFTD) is a recently emerged fatal transmissible cancer decimating the wild population of Tasmanian devils (Sarcophilus harrisii). Biting transmits the cancer cells and the tumour develops in the new host as an allograft. The literature reports that immune escape mechanisms employed by DFTD inevitably result in host death. Here we present the first evidence that DFTD regression can occur and that wild devils can mount an immune response against the disease. Of the 52 devils tested, six had serum antibodies against DFTD cells and, in one case, prominent T lymphocyte infiltration in its tumour. Notably, four of the six devils with serum antibody had histories of DFTD regression. The novel demonstration of an immune response against DFTD in wild Tasmanian devils suggests that a proportion of wild devils can produce a protective immune response against naturally acquired DFTD. This has implications for tumour–host coevolution and vaccine development.

Mitogen-activated Tasmanian devil blood mononuclear cells kill devil facial tumour disease cells.

Devil facial tumour disease (DFTD) is a transmissible cancer that has brought the host species, the Tasmanian devil, to the brink of extinction. The cancer cells avoid allogeneic immune recognition by downregulating cell surface major histocompatibility complex (MHC) I expression. This should prevent CD8(+) T cell, but not natural killer (NK) cell, cytotoxicity. The reason why NK cells, normally reactive to MHC-negative cells, are not activated to kill DFTD cells has not been determined. The immune response of wild devils to DFTD, if it occurs, is uncharacterised. To investigate this, we tested 12 wild devils with DFTD, and found suggestive evidence of low levels of antibodies against DFTD cells in one devil. Eight of these devils were also analysed for cytotoxicity, however, none showed evidence for cytotoxicity against cultured DFTD cells. To establish whether mimicking activation of antitumour responses could induce cytotoxic activity against DFTD, Tasmanian devil peripheral blood mononuclear cells (PBMCs) were treated with either the mitogen Concanavalin A, the Toll-like receptor agonist polyinosinic:polycytidylic acid or recombinant Tasmanian devil IL-2. All induced the PBMC cells to kill cultured DFTD cells, suggesting that activation does not occur after encounter with DFTD cells in vivo, but can be induced. The identification of agents that activate cytotoxicity against DFTD target cells is critical for developing strategies to protect against DFTD. Such agents could function as adjuvants to induce functional immune responses capable of targeting DFTD cells and tumours in vivo.

Toll-like receptor signaling is functional in immune cells of the endangered Tasmanian devil

Devil facial tumour disease (DFTD) is a fatally transmissible cancer that threatens the Tasmanian devil population. As Tasmanian devils do not produce an immune response against DFTD cells, an effective vaccine will require a strong adjuvant. Activation of innate immune system cells through toll-like receptors (TLRs) could provide this stimulation. It is unknown whether marsupials, including Tasmanian devils, express functional TLRs. We isolated RNA from peripheral blood mononuclear cells and, with PCR, detected transcripts for TLRs 2, 3, 4, 5, 6, 7, 8, 9, 10 and 13. Stimulation of the mononuclear cells with agonists to these TLRs increased the expression of downstream TLR signaling products (IL1α, IL6, IL12A and IFNβ). Our data provide the first evidence that TLR signaling is functional in the mononuclear cells of the Tasmanian devil. Future DFTD vaccination trials will incorporate TLR agonists to enhance the immune response against DFTD.

Evidence for induction of humoral and cytotoxic immune responses against devil facial tumor disease cells in Tasmanian devils (Sarcophilus harrisii) immunized with killed cell preparations

Tasmanian devils (Sarcophilus harrisii) risk extinction from a contagious cancer, devil facial tumour disease (DFTD) in which the infectious agent is the tumor cell itself. Because devils are unable to produce an immune response against the tumor cells no devil has survived ‘infection’. To promote an immune response we immunized healthy devils with killed DFTD tumor cells in the presence of adjuvants. Immune responses, including cytotoxicity and antibody production, were detected in five of the six devils. The incorporation of adjuvants that act via toll like receptors may provide additional signals to break ‘immunological ignorance’. One of these devils was protected against a challenge with viable DFTD cells. This was a short-term protection as re-challenge one year later resulted in tumor growth. These results suggest that Tasmanian devils can generate immune responses against DFTD cells. With further optimization of immune stimulation it should be possible to protect Tasmanian devils against DFTD with an injectable vaccine.

Mouse Model of Devil Facial Tumour Disease Establishes That an Effective Immune Response Can be Generated Against the Cancer Cells.

The largest carnivorous marsupial in Australia, the Tasmanian devil (Sarcophilus harrisii) is facing extinction in the wild due to a transmissible cancer known as Devil Facial Tumour Disease (DFTD). DFTD is a clonal cell line transmitted from host to host with 100% mortality and no known immunity. While it was first considered that low genetic diversity of the population of devils enabled the allograft transmission of DFTD recent evidence reveals that genetically diverse animals succumb to the disease. The lack of an immune response against the DFTD tumor cells may be due to a lack of immunogenicity of the tumor cells. This could facilitate transmission between devils. To test immunogenicity, mice were injected with viable DFTD cells and anti-DFTD immune responses analyzed. A range of antibody isotypes against DFTD cells was detected, indicating that as DFTD cells can induce an immune response they are immunogenic. This was supported by cytokine production, when splenocytes from mice injected with DFTD cells were cultured in vitro with DFTD cells and the supernatant analyzed. There was a significant production of IFN-γ and TNF-α following the first injection with DFTD cells and a significant production of IL-6 and IL-10 following the second injection. Splenocytes from naïve or immunized mice killed DFTD cells in in vitro cytotoxicity assays. Thus, they are also targets for immunological destruction. We conclude that as an immune response can be generated against DFTD cells they would be suitable targets for a vaccine.

27. Assessment of periaxin expression in human peripheral nerve sheath tumours and related lesions

Periaxin is a newly described protein that is expressed in myelinating Schwann cells. In developing and regenerating nerves, periaxin is predominantly localised to the adaxonal surface of Schwann cells as they begin to form compact myelin. In adult nerves, peraxin is expressed by myelinating Schwann cells and localised to the abax-onal surface. Its localisation changes dynamically during ensheath-ment and myelination. Periaxin is expressed in devil facial tumour disease (DFTD), a transmissible cancer that is threatening the survival of the Tasmanian devil ( Sarcophilus harrisii) . DFTD cells express proteins characteristic of myelinating Schwann cells, including periaxin. A useful diagnostic marker for DFTD is expression of periaxin. We investigated the expression of periaxin in a variety of human peripheral nerve sheath tumours and related lesions such as schwannomas, neurofibromas, traumatic neuromas, solitary circumscribed neuromas, malignant peripheral nerve sheath tumours and granular cell tumours. Several different human tissue controls including bowel, gallbladder, smooth muscle neoplasms, naevi and melanoma were also used. The expression of periaxin was compared with a range of proteins associated with nerve tissue including S100, neurofilament, EMA and CD34. We conclude that periaxin, correlates most closely with neurofilament expression, in schwannomas, neurofibromas and normal nerve tissue controls. Periaxin does not appear to have an additional role in the diagnosis of human peripheral nerve sheath tumours and related lesions.

Does the devil facial tumour produce immunosuppressive cytokines as an immune evasion strategy?

A unique transmissible cancer known as the Devil Facial Tumour Disease (DFTD) is threatening the Tasmanian devil (Sarcophilus harrisii) with extinction. This disease is highly unusual as it is one of only two naturally occurring contagious cancers. The tumour is transmitted by biting and is able to spread between genetically diverse hosts. Why the tumours are not recognised as foreign and rejected by the host immune system in unknown. One mechanism that allows human cancers to avoid immune suppression is by producing cytokines which down-regulate the hosts immune system. Four key cytokines involved in this process are TGFβ1, VEGF-A, IL-10 and IL-6. In this study we investigated whether these cytokines could be involved in immune avoidance in DFTD. To do this we compared expression of these cytokines in tumour and control tissues using qPCR. We found no significant upregulation of any of these cytokines in tumour tissue. We therefore conclude that these cytokines do not play a role in the spread of DFTD. Further work will be needed to elucidate how DFTD cells avoid immune rejection.

Cancer from Hell: Devil Facial Tumour Disease

Event Abstract Back to Event Cancer from Hell: Devil Facial Tumour Disease Terry Pinfold1*, Gabriella Brown1, Alexandre Kriess1 and Gregory Woods1 1 Menzies Research Institute Tasmania, Australia Devil Facial Tumour Disease (DFTD) is a rare form of cancer that spreads like a contagious disease. It is a parasitic clonal cell line transmitted between hosts through biting. The disease is limited to Tasmanian devils, which are carnivorous marsupials endemic to Tasmania, an island state of Australia. It has a 100% mortality rate, has reduced the population by 80% and may cause extinction of the Tasmanian devil in the wild within the next 30 years. The lack of immunogenicity may be one possible mechanism used by DFTD cells to escape the host’s immune system. Because of the lack of molecular tools and limited access to Tasmanian devils we developed a mouse model of DFTD. The tumour cells are immunogenic as immunocompetent BALB/c and C57BL/6 mice rejected xenograft implantation of 10^6 DFTD cells while immunocompromised NOD/SCID mice accepted the xenograft and developed DFTD tumours. Evidence for the immunological basis of the rejection was demonstrated with adoptive protection by splenocytes transferred from BALB/c to NOD/SCID mice. In vitro stimulation of devil lymphocytes induced cytotoxic anti-DFTD activity. To determine if this could be effective in vivo, two NOD/SCID mice were co-injected with 5 x 10^5 DFTD cells and 5 x 10^6 stimulated devil lymphocytes. Seven weeks later the tumour growth was less than 10% compared to the control. Replication of this work with 10^4 DFTD cells plus lymphocytes failed to engraft the tumour providing insight into possible immunotherapy approaches for the disease. Keywords: Devil Facial Tumour Disease, DFTD, Infectious cancer, Tasmanian devil, Contagious cancer Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Translational immunology and immune intervention Citation: Pinfold T, Brown G, Kriess A and Woods G (2013). Cancer from Hell: Devil Facial Tumour Disease. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00604 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 12 Jun 2013; Published Online: 22 Aug 2013. * Correspondence: Mr. Terry Pinfold, Menzies Research Institute Tasmania, Hobart, Australia, tpinfold@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Terry Pinfold Gabriella Brown Alexandre Kriess Gregory Woods Google Terry Pinfold Gabriella Brown Alexandre Kriess Gregory Woods Google Scholar Terry Pinfold Gabriella Brown Alexandre Kriess Gregory Woods PubMed Terry Pinfold Gabriella Brown Alexandre Kriess Gregory Woods Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Extreme Telomere Length Dimorphism in the Tasmanian Devil and Related Marsupials Suggests Parental Control of Telomere Length

Telomeres, specialised structures that protect chromosome ends, play a critical role in preserving chromosome integrity. Telomere dynamics in the Tasmanian devil (Sarcophilus harrisii) are of particular interest in light of the emergence of devil facial tumour disease (DFTD), a transmissible malignancy that causes rapid mortality and threatens the species with extinction. We used fluorescent in situ hybridisation to investigate telomere length in DFTD cells, in healthy Tasmanian devils and in four closely related marsupial species. Here we report that animals in the Order Dasyuromorphia have chromosomes characterised by striking telomere length dimorphism between homologues. Findings in sex chromosomes suggest that telomere length dimorphism may be regulated by events in the parental germlines. Long telomeres on the Y chromosome imply that telomere lengthening occurs during spermatogenesis, whereas telomere diminution occurs during oogenesis. Although found in several somatic cell tissue types, telomere length dimorphism was not found in DFTD cancer cells, which are characterised by uniformly short telomeres. This is, to our knowledge, the first report of naturally occurring telomere length dimorphism in any species and suggests a novel strategy of telomere length control. Comparative studies in five distantly related marsupials and a monotreme indicate that telomere dimorphism evolved at least 50 million years ago.

Natural killer cell mediated cytotoxic responses in the Tasmanian devil.

The Tasmanian devil (Sarcophilus harrisii), the world's largest marsupial carnivore, is under threat of extinction following the emergence of an infectious cancer. Devil facial tumour disease (DFTD) is spread between Tasmanian devils during biting. The disease is consistently fatal and devils succumb without developing a protective immune response. The aim of this study was to determine if Tasmanian devils were capable of forming cytotoxic antitumour responses and develop antibodies against DFTD cells and foreign tumour cells. The two Tasmanian devils immunised with irradiated DFTD cells did not form cytotoxic or humoral responses against DFTD cells, even after multiple immunisations. However, following immunisation with xenogenic K562 cells, devils did produce cytotoxic responses and antibodies against this foreign tumour cell line. The cytotoxicity appeared to occur through the activity of natural killer (NK) cells in an antibody dependent manner. Classical NK cell responses, such as innate killing of DFTD and foreign cancer cells, were not observed. Cells with an NK-like phenotype comprised approximately 4 percent of peripheral blood mononuclear cells. The results of this study suggest that Tasmanian devils have NK cells with functional cytotoxic pathways. Although devil NK cells do not directly recognise DFTD cancer cells, the development of antibody dependent cell-mediated cytotoxicity presents a potential pathway to induce cytotoxic responses against the disease. These findings have positive implications for future DFTD vaccine research.

MHC gene copy number variation in Tasmanian devils: implications for the spread of a contagious cancer.

Tasmanian devils face extinction owing to the emergence of a contagious cancer. Devil facial tumour disease (DFTD) is a clonal cancer spread owing to a lack of major histocompatibility complex (MHC) barriers in Tasmanian devil populations. We present a comprehensive screen of MHC diversity in devils and identify 25 MHC types and 53 novel sequences, but conclude that overall levels of MHC diversity at the sequence level are low. The majority of MHC Class I variation can be explained by allelic copy number variation with two to seven sequence variants identified per individual. MHC sequences are divided into two distinct groups based on sequence similarity. DFTD cells and most devils have sequences from both groups. Twenty per cent of individuals have a restricted MHC repertoire and contain only group I or only group II sequences. Counterintuitively, we postulate that the immune system of individuals with a restricted MHC repertoire may recognize foreign MHC antigens on the surface of the DFTD cell. The implication of these results for management of DFTD and this endangered species are discussed.