Evidence of an oncogenic gammaherpesvirus in domestic dogs

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

Currently, it is estimated that 15% of human neoplasms globally are caused by infectious agents, with new evidence emerging continuously. Multiple agents have been implicated in various forms of neoplasia, with viruses as the most frequent. In recent years, investigation on viral mechanisms underlying tumoral transformation in cancer development and progression are in the spotlight, both in human and veterinary oncology. Oncogenic viruses in veterinary medicine are of primary importance not only as original pathogens of pets, but also in the view of pets as models of human malignancies. Hence, this work will provide an overview of the main oncogenic viruses of companion animals, with brief notes of comparative medicine.

Epidemiology and pathological progression of erythematous lip lesions in captive sun bears (Helarctos malayanus)

This study investigates the occurrence of erythematous lip lesions in a captive sun bear population in Cambodia, including the progression of cheilitis to squamous cell carcinoma, and the presence of Ursid gammaherpesvirus 1. Visual assessment conducted in 2015 and 2016 recorded the prevalence and severity of lesions. Opportunistic sampling for disease testing was conducted on a subset of 39 sun bears, with histopathological examination of lip and tongue biopsies and PCR testing of oral swabs and tissue biopsies collected during health examinations. Lip lesions were similarly prevalent in 2015 (66.0%) and 2016 (68.3%). Degradation of lip lesion severity was seen between 2015 and 2016, and the odds of having lip lesions, having more severe lip lesions, and having lip lesion degradation over time, all increased with age. Cheilitis was found in all lip lesion biopsies, with histological confirmation of squamous cell carcinoma in 64.5% of cases. Single biopsies frequently showed progression from dysplasia to neoplasia. Eighteen of 31 sun bears (58.1%) had at least one sample positive for Ursid gammaherpesvirus 1. The virus was detected in sun bears with and without lip lesions, however due to case selection being strongly biased towards those showing lip lesions it was not possible to test for association between Ursid gammaherpesvirus 1 and lip squamous cell carcinoma. Given gammaherpesviruses can play a role in cancer development under certain conditions in other species, we believe further investigation into Ursid gammaherpesvirus 1 as one of a number of possible co-factors in the progression of lip lesions to squamous cell carcinoma is warranted. This study highlights the progressively neoplastic nature of this lip lesion syndrome in sun bears which has consequences for captive and re-release management. Similarly, the detection of Ursid gammaherpesvirus 1 should be considered in pre-release risk analyses, at least until data is available on the prevalence of the virus in wild sun bears.

Canine lymphoma and vector-borne diseases: Molecular and serological evaluation of a possible complicity

Lymphoma is the most common haematological malignancy in dogs and its aetiology is largely unknown. The presence of canine vector-borne agents (CVBD) in lymphoma tissues has been described and its causative effects questioned. We intended to evaluate the presence and extent of Leishmania infantum, Ehrlichia canis, Anaplasma phagocytophilum and Bartonella henselae infection in dogs with lymphoma. Sixty-one dogs, living in the Lisbon metropolitan area, with a diagnosis of lymphoma were enrolled. Immunofluorescence assays were used to detect serum IgG's. The presence of DNA from CVBD agents in tumour tissue was assessed by PCR. All dogs tested negative for B. henselae, A. phagocytophilum and E. canis by both serology and PCR. Regarding L. infantum, 8.2% (n = 5) of the dogs had a positive serologic result. L. infantum DNA was detected in two samples of diffuse large B-cell lymphoma (DLBCL). These results show an increased, but not significant, seropositivity (8.2% vs 7.9%) and molecular detection (3.3% vs 1.2%) for L. infantum in dogs with lymphoma, when compared to the reported canine population in the same geographical area. We could not identify an association between lymphoma and E. canis, A. phagocytophilum, B. henselae or Leishmania infantum infection in the studied population. Nevertheless, further studies, following dogs trough their CVBD disease evolution, are worthwhile and may help clarify a possible role of CVBD agents in lymphomagenesis.

Ibex-Associated Malignant Catarrhal Fever in Duikers (Cephalophus Spp)

Eight duikers, representing 3 different species cohoused in a single zoological collection, died in a 10-month period. Black, red-flanked, and yellow-backed duikers were affected, appearing clinically with a combination of anorexia, diarrhea, ataxia, tremors, and/or stupor, followed by death within 72 hours of onset of clinical signs. Consistent gross findings were pulmonary ecchymoses (8/8), generalized lymphadenomegaly (6/8), ascites (5/8), and pleural effusion (4/8). Dense lymphocyte infiltrates and arteritis affected numerous tissues in most animals. Ibex-associated malignant catarrhal fever (MCF) viral DNA was detected in all cases by polymerase chain reaction and in situ hybridization. Identical ibex-MCF virus sequence was detected in spleen of a clinically healthy ibex (Capra ibex) housed in a separate enclosure 35 meters away from the duikers.

Lack of Association Between Epstein-Barr Virus and Mammary Tumours in Dogs

INTRODUCTION

Epstein-Barr virus (EBV) is a γ-herpesvirus associated with various neoplasms in humans and is a probable aetiological agent in breast cancer; however, a causal relationship has not yet been established. Because of the epidemiological and clinicopathological similarities between breast cancer and canine mammary tumours, dogs have been proposed as a valid model for breast cancer.

MATERIAL AND METHODS

A total of 47 canine mammary gland tumour tissues were processed by routine histopathological technique with haematoxylin-eosin staining and classified according to the type of neoplasm. DNA was extracted from paraffin-embedded tissues and the EBNA-1 gene and the BamHI-W region specific for EBV were evaluated by nested PCR.

RESULTS

The histopathological evaluation revealed 2 benign neoplasms, and many carcinomas: 2 in situ, 9 simple, 3 solid, 10 complex, and 21 mixed. One sample was positive for the EBNA-1 gene, while all were negative for the BamHI-W region.

CONCLUSION

No association was found between EBV and mammary tumours in dogs. However, here we report for the first time the presence of an EBV gene sequence in a canine mammary tumour. It is likely that detection of EBV might be affected by the quality and quantity of DNA extracted from paraffin-embedded tissues. Additional studies are necessary to establish any association of EBV with mammary gland cancer in humans and in dogs, which could eventually lead to better public health prevention and control.

Presencia del marcador lmp-1 del virus epstein barr en linfomas de caninos

Epstein Barr virus (EBV) is a humans’ high prevalent virus associated with lymphoid B cells tumors development. In canines, few reports have been published regarding the presence of the virus in dogs but its role in this species remain unclear.  The aim of this study was to determine the presence of LMP-1 protein of EBV in 20 canine lymphomas tissues which were previously diagnosed in a period of time between 2004 -2014.  Lymphomas were reclassified in accordance with the new histopathological classifications for lymphomas and were stained by IHQ with anti-CD79a, anti-CD3 and anti-LMP1; specific antibodies for B lymphocytes, T lymphocytes and EBV biomarker respectively.  As a result, it was found that the most common lymphoma was T-zone lymphoma in 75% of the cases of the study. The distribution of the cases regarding the immunostaining were: 18 positive cases with anti- CD3, 2 positive cases with anti-CD79a and 6 positive cases with anti-LMP-1.  Positive cases of LMP1 as a biomarker of the presence of EBV corresponded to the 30% of the cases of the study. Chi-square test showed statistical significance between the presence of the virus and the presence of lymphomas, which suggests not only that the virus is circulating in the canine population but also that could have implications in the development of the disease. Regarding demographic parameters, only the Golden Retriever breed showed a relationship with the presence of lymphoma, but not with the presence of the virus.

Role of Feline Immunodeficiency Virus in Lymphomagenesis--Going Alone or Colluding?

Feline immunodeficiency virus (FIV) is a naturally occurring lentivirus of domestic and nondomestic feline species. Infection in domestic cats leads to immune dysfunction via mechanisms similar to those caused by human immunodeficiency virus (HIV) and, as such, is a valuable natural animal model for acquired immunodeficiency syndrome (AIDS) in humans. An association between FIV and an increased incidence of neoplasia has long been recognized, with frequencies of up to 20% in FIV-positive cats recorded in some studies. This is similar to the rate of neoplasia seen in HIV-positive individuals, and in both species neoplasia typically requires several years to arise. The most frequently reported type of neoplasia associated with FIV infection is lymphoma. Here we review the possible mechanisms involved in FIV lymphomagenesis, including the possible involvement of coinfections, notably those with gamma-herpesviruses.

No Evidence of Herpesvirus Infection in West Highland White Terriers With Canine Idiopathic Pulmonary Fibrosis

In humans, horses, and rodents, an association between pulmonary fibrotic disorders and gammaherpesvirus infection has been suggested. In dogs, canine idiopathic pulmonary fibrosis (CIPF), a progressive fibrotic lung disease of unknown origin and poorly understood pathophysiology, has been reported to occur in West Highland white terriers (WHWTs). The present study investigated the potential association between CIPF and herpesvirus infection. A PCR assay, using a mixture of degenerate and deoxyinosine-substituted primers targeting highly conserved regions of the DNA polymerase gene (DPOL) of herpesviruses, was applied on both lung and blood samples from WHWTs affected with CIPF and controls. Herpesvirus DPOL sequence could not be amplified from any of 46 lung samples (28 affected WHWTs and 18 control dogs of various breeds) and 38 blood samples (19 CIPF WHWTs and 19 control age-matched WHWTs) included. An association between CIPF and herpesvirus infection is therefore unlikely. Investigation of other causes of the disease is warranted.

Man's best friend: what can pet dogs teach us about non-Hodgkin's lymphoma?

Animal models are essential for understanding lymphoma biology and testing new treatments prior to human studies. Spontaneously arising lymphomas in pet dogs represent an underutilized resource that could be used to complement current mouse lymphoma models, which do not adequately represent all aspects of the human disease. Canine lymphoma resembles human lymphoma in many important ways, including characteristic translocations and molecular abnormalities and similar therapeutic responses to chemotherapy, radiation, and newer targeted therapies (e.g. ibrutinib). Given the large number of pet dogs and high incidence of lymphoma, particularly in susceptible breeds, dogs represent a largely untapped resource for advancing the understanding and treatment of human lymphoma. This review highlights similarities in molecular biology, diagnosis, treatment, and outcomes between human and canine lymphoma. It also describes resources that are currently available to study canine lymphoma, advantages to be gained by exploiting the genetic breed structure in dogs, and current and future challenges and opportunities to take full advantage of this resource for lymphoma studies.

Gammaherpesviruses and canine lymphoma: no evidence for direct involvement in commonly occurring lymphomas

Lymphoma is the most common haematopoietic malignancy in dogs, but little is known about the aetiology of this heterogeneous group of cancers. In humans, the Epstein–Barr virus (EBV) is associated with several lymphoma subtypes. Recently, it was suggested that EBV or an EBV-like virus is circulating in dogs. We therefore investigated whether EBV, or a novel herpesvirus, is associated with canine lymphoma using both serological and molecular techniques. In an assay designed to detect antibodies to EBV viral capsid antigens, 41 % of dogs were positive. Dogs with cancers, including lymphoma, were more frequently positive than controls, but no particular association with B-cell lymphoma was noted. EBV-specific RNA and DNA sequences were not detected in lymphoma tissue by in situ hybridization or PCR, and herpesvirus genomes were not detected using multiple degenerate PCR assays with the ability to detect novel herpesviruses. We therefore found no evidence that herpesviruses are directly involved in common types of canine lymphoma although cannot exclude the presence of an EBV-like virus in the canine population.

Canine lymphoma as a comparative model for human non-Hodgkin lymphoma: recent progress and applications

The term "lymphoma" describes a heterogeneous group of disorders involving monoclonal proliferation of malignant lymphocytes. As a group, lymphomas are among the most common tumors of dogs. Yet our enumeration and understanding of the many subtypes of lymphoma have been relatively slow, perhaps in part because for many years lymphoma was treated as a singular entity rather than a group of distinct diseases. The recognition that the full spectrum of lymphoid malignancies seen in humans also occurs in dogs, and that these tumors retain not only morphologic similarities and biological behavior but also synonymous driver molecular abnormalities, sets an ideal stage for dual-purpose research that can accelerate progress for these diseases in both species. Specifically, dogs represent exceptional models for defining causality, understanding progression, and developing new treatments for lymphoma in comparatively brief windows of time. Unique advantages of canine models include (1) spontaneous disease occurring without an isogenic background or genetic engineering; (2) chronology of disease adapted to lifespan, (3) shared environment and societal status that allows dogs to be treated as "patients," while at the same time being able to ethically explore translational innovations that are not possible in human subjects; and (4) organization of dogs into breeds with relatively homogeneous genetic backgrounds and distinct predisposition for lymphomas. Here, we will review recent studies describing intrinsic and extrinsic factors that contribute to the pathogenesis of canine and human lymphomas, as well as newly developed tools that will enhance the fidelity of these models to improve diagnosis and develop new treatments.

Comparative RNA-Seq and microarray analysis of gene expression changes in B-cell lymphomas of Canis familiaris

Comparative oncology is a developing research discipline that is being used to assist our understanding of human neoplastic diseases. Companion canines are a preferred animal oncology model due to spontaneous tumor development and similarity to human disease at the pathophysiological level. We use a paired RNA sequencing (RNA-Seq)/microarray analysis of a set of four normal canine lymph nodes and ten canine lymphoma fine needle aspirates to identify technical biases and variation between the technologies and convergence on biological disease pathways. Surrogate Variable Analysis (SVA) provides a formal multivariate analysis of the combined RNA-Seq/microarray data set. Applying SVA to the data allows us to decompose variation into contributions associated with transcript abundance, differences between the technology, and latent variation within each technology. A substantial and highly statistically significant component of the variation reflects transcript abundance, and RNA-Seq appeared more sensitive for detection of transcripts expressed at low levels. Latent random variation among RNA-Seq samples is also distinct in character from that impacting microarray samples. In particular, we observed variation between RNA-Seq samples that reflects transcript GC content. Platform-independent variable decomposition without a priori knowledge of the sources of variation using SVA represents a generalizable method for accomplishing cross-platform data analysis. We identified genes differentially expressed between normal lymph nodes of disease free dogs and a subset of the diseased dogs diagnosed with B-cell lymphoma using each technology. There is statistically significant overlap between the RNA-Seq and microarray sets of differentially expressed genes. Analysis of overlapping genes in the context of biological systems suggests elevated expression and activity of PI3K signaling in B-cell lymphoma biopsies compared with normal biopsies, consistent with literature describing successful use of drugs targeting this pathway in lymphomas.

Expression of EBV-encoded oncogenes and EBV-like virions in multiple canine tumors

Epstein-Barr virus (EBV) is a ubiquitous human oncovirus. Previous studies by us and others have indicated that pet dogs frequently encounter EBV or EBV-related viral infection. In this study, we explored whether EBV is involved in canine malignancies in dogs. EBV-specific BamHI W sequence was detected by polymerase chain reaction (PCR) in 10 of 12 canine tumor specimens, including 8 of 10 oral tumors. Using reverse transcription-PCR, gene expressions of latent membrane protein 1 (LMP 1) and BamHI H rightward reading frame 1 (BHRF1) were identified in 8 and 7 of 12 specimens, respectively. A novel LMP1 variant, T0905, was predominant in 5 canine tumor specimens and found to exist in EBV positive human BC-2 cells. Another LMP1 variant, T0902, was similar to human tumor variant JB7. The BHRF1 sequence identified from these canine tumors was identical to that of the B95-8 viral strain. LMP1 protein and EBV-encoded RNA (EBER) were detected by immunohistochemistry and fluorescent in situ hybridization, respectively, in several tumors, particularly in tumor nests of oral amelanotic melanomas. Furthermore, EBV-like virions adopting a herpesvirus egress pathway were detected in a canthal fibroblastic osteosarcoma and an oral amelanotic melanoma. In conclusion, we report the expressions of BHRF1 transcript (a viral anti-apoptotic protein), LMP1 (a viral oncoprotein) transcript and protein, EBER (a viral oncogenic RNA), and EBV-like virions in multiple canine tumors. The identity of BHRF1 and the resemblance of LMP1 variants between canine and human tumors indicate either a close evolutionary relationship between canine and human EBV, or the possibility of zoonotic transmission.

Acute virulent infection with feline immunodeficiency virus (FIV) results in lymphomagenesis via an indirect mechanism

Four cats (24%) experimentally infected with FIV unexpectedly developed neoplastic changes within four months of inoculation. While FIV has previously been associated with neoplasia, the rapidity and high attack rate seen here is highly unusual. PCR for antigen receptor rearrangements (PARR) detected clonally rearranged T cells in two animals diagnosed with B cell follicular lymphoma by classical means. All cats were negative for feline leukemia virus; gamma-herpesvirus DNA was not amplified using degenerate primers. FIV proviral load in neoplastic tissue was two orders of magnitude lower than in the periphery, lower in neoplastic vs non-neoplastic lymph node, and clonal integration was not detected. We hypothesize that neoplasia was secondary to FIV immune dysregulation, and show that PARR can augment our capacity to phenotype these tumors and distinguish follicular hyperplasia from lymphoma. Age of exposure and relative virulence of the inoculum likely contributed to this unusual presentation of FIV infection.