Transformation of the genital epithelial tract occurs early in California sea lion development

Otariid gammaherpesvirus 1 in South American fur seals (Arctocephalus australis) and a novel related herpesvirus in free-ranging South American sea lions (Otaria byronia): Prevalence and effects of age, sex, and sample type

Otariid gammaherpesvirus 1 (OtGHV1) is associated with high rates of urogenital carcinoma in free-ranging California sea lions (Zalophus californianus; CSL), and until recently was reported only in the Northern Hemisphere. The objective of this study was to survey free-ranging South American sea lions (Otaria byronia; SASL) and South American fur seals (Arctocephalus australis: SAFS) in Punta San Juan, Peru for OtGHV1 and to determine prevalence characteristics. Twenty-one percent (14/67) of urogenital swabs collected over three years (2011, 2014, 2015) from live pinnipeds of both species tested positive with a pan-herpesvirus conventional PCR. Sequencing of SAFS amplicons revealed 100% homology to OtGHV1 at the DNA polymerase, glycoprotein B, and viral bcl2-like genes. Sequencing of SASL amplicons revealed a novel related virus, herein called Otariid gammaherpesvirus 8 (OtGHV8). For comparison of sample sites, urogenital, conjunctival, and oropharyngeal swabs collected from 136 live pinnipeds of both species at Punta San Juan between 2011-2018 were then assayed using quantitative PCR for a segment of the OtGHV1/8 DNA polymerase gene using a qPCR assay now determined to cross-react between the two viruses. In total, across both species, 38.6% (51/132) of urogenital swabs, 5.6% (4/71) of conjunctival swabs, and 1.1% (1/90) of oropharyngeal swabs were positive for OtGHV1/8, with SASL only positive on urogenital swabs. Results from SASL were complicated by the finding of OtGHV8, necessitating further study to determine prevalence of OtGHV1 versus OtGHV8 using an alternate assay. Results from SAFS suggest a potential relationship between OtGHV1 in SAFS and CSL. Though necropsy surveillance in SAFS is very limited, geographic patterns of OtGHV1-associated urogenital carcinoma in CSL and the tendency of herpesviruses to cause more detrimental disease in aberrant hosts suggests that it is possible that SAFS may be the definitive host of OtGHV1, which gives further insight into the diversity and phyogeography of this clade of related gammaherpesviruses.

Bacterial dysbiosis and epithelial status of the California sea lion (Zalophus californianus) in the Gulf of California

Despite the high incidence of urogenital carcinoma (UGC) in California sea lions stranded along California, no UGC has been reported in other areas of their distribution; however, cell morphologies typical of premalignant states have been found. Risk factors for UGC include high of organochlorines and infection with a gammaherpesvirus, OtHV-1, but the importance of the bacteriome for epithelial status remains unknown. We characterized the genital bacteriome of adult female California sea lions along their distribution in the Gulf of California and examined whether the diversity and abundance of the bacteriome varied spatially, whether there were detectable differences in the bacteriome between healthy and altered epithelia, and whether the bacteriome was different in California sea lions infected with OtHV-1 or papillomavirus. We detected 2270 ASVs in the genital samples, of which 35 met the criteria for inclusion in the core bacteriome. Fusobacteriia and Clostridia were present in all samples, at high abundances, and Actinobacteria, Alphaproteobacteria, and Campylobacteria were also well-represented. Alpha diversity and abundance of the California sea lion genital bacteriome varied geographically. The abundance of bacterial ASVs varied depending on the genital epithelial status and inflammation, with differences driven by classes Fusobacteriia, Clostridia, Campylobacteria and Alphaproteobacteria. Alpha diversity and abundance were lowest in samples in which OtHV-1 was detected, and highest those with papillomavirus. Our study is the first investigation of how the bacteriome is related to epithelial status in a wild marine species prone to developing cancer.

Diffuse large B cell lymphoma and a novel gammaherpesvirus in northern elephant seals Mirounga angustirostris

Two emaciated male northern elephant seal (NES) Mirounga angustirostris pups were admitted to The Marine Mammal Center (Sausalito, California, USA) and treated for malnutrition. Complete blood counts showed a progressive moderate to marked leukocytosis characterized by a predominance of large monomorphic mononuclear cells of probable lymphoid origin, frequently with flower-shaped nuclei. Both seals were euthanized due to suspected lymphoid neoplasia. At necropsy, most lymph nodes in both pups were markedly enlarged, some with distinct white nodules, the spleens were diffusely enlarged, and the intestinal mucosae were thickened. Histopathologic features consistent with disseminated large cell lymphoma were identified to varying degrees of severity in lymph nodes, bone marrow, liver, tonsils, spleen, liver, intestines, kidneys, lower urinary tract, and several other organs. Immunohistochemical staining of neoplastic cells was most consistent with B lymphocyte origin, with most cells staining positively for Pax 5 and CD20 with admixed small CD3-positive T lymphocytes and CD204-positive macrophages. PCR and sequencing identified a novel gammaherpesvirus, herein called miroungine gammaherpesvirus 3, from affected tissues. This virus is in a clade outside of named genera that utilize hosts in the suborder Caniformia. The present study is the first description of diffuse large B cell lymphoma with leukemic manifestation and concomitant detection of a novel gammaherpesvirus in free-living NESs. Further research regarding the prevalence of this new gammaherpesvirus and its associated pathogenesis in this species is indicated.

Unlocking the Role of a Genital Herpesvirus, Otarine Herpesvirus 1, in California Sea Lion Cervical Cancer

Urogenital carcinoma in California sea lions (Zalophus californianus) is the most common cancer of marine mammals. Primary tumors occur in the cervix, vagina, penis, or prepuce and aggressively metastasize resulting in death. This cancer has been strongly associated with a sexually transmitted herpesvirus, otarine herpesvirus 1 (OtHV1), but the virus has been detected in genital tracts of sea lions without cancer and a causative link has not been established. To determine if OtHV1 has a role in causing urogenital carcinoma we sequenced the viral genome, quantified viral load from cervical tissue from sea lions with (n = 95) and without (n = 163) urogenital carcinoma, and measured viral mRNA expression using in situ mRNA hybridization (Basescope®) to quantify and identify the location of OtHV1 mRNA expression. Of the 95 sea lions diagnosed with urogenital carcinoma, 100% were qPCR positive for OtHV1, and 36% of the sea lions with a normal cervix were positive for the virus. The non-cancer OtHV1 positive cases had significantly lower viral loads in their cervix compared to the cervices from sea lions with urogenital carcinoma. The OtHV1 genome had several genes similar to the known oncogenes, and RNA in situ hybridization demonstrated high OtHV1 mRNA expression within the carcinoma lesions but not in normal cervical epithelium. The high viral loads, high mRNA expression of OtHV1 in the cervical tumors, and the presence of suspected OtHV1 oncogenes support the hypothesis that OtHV1 plays a significant role in the development of sea lion urogenital carcinoma.

Transcriptional Profiles of California Sea Lion Peripheral NK and CD+8 T Cells Reflect Ecological Regionalization and Infection by Oncogenic Viruses

The California sea lion is one of the few wild mammals prone to develop cancer, particularly urogenital carcinoma (UGC), whose prevalence is currently estimated at 25% of dead adult sea lions stranded along the California coastline. Genetic factors, viruses and organochlorines have been identified as factors that increase the risk of occurrence of this pathology. Given that no cases of UGC have as yet been reported for the species along its distribution in Mexican waters, the potential relevance of contaminants for the development of urogenital carcinoma is highlighted even more as blubber levels of organochlorines are more than two orders of magnitude lower in the Gulf of California and Mexican Pacific than in California. In vitro studies have shown that organochlorines can modulate anti-viral and tumor-surveillance activities of NK and cytotoxic T-cells of marine mammals, but little is known about the activity of these effectors in live, free-living sea lions. Here, we examine leukocyte transcriptional profiles of free-ranging adult California sea lions for eight genes (Eomes, Granzyme B, Perforin, Ly49, STAT1, Tbx21, GATA3, and FoxP3) selected for their key role in anti-viral and tumor-surveillance, and investigate patterns of transcription that could be indicative of differences in ecological variables and exposure to two oncogenic viruses: sea lion type one gammaherpesvirus (OtHV-1) and sea lion papillomavirus type 1 (ZcPV-1) and systemic inflammation. We observed regional differences in the expression of genes related to Th1 responses and immune modulation, and detected clear patterns of differential regulation of gene expression in sea lions infected by genital papillomavirus compared to those infected by genital gammaherpesvirus or for simultaneous infections, similar to what is known about herpesvirus and papillomavirus infections in humans. Our study is a first approach to profile the transcriptional patterns of key immune effectors of free-ranging California sea lions and their association with ecological regions and oncogenic viruses. The observed results add insight to our understanding of immune competence of marine mammals, and may help elucidate the marked difference in the number of cases of urogenital carcinoma in sea lions from US waters and other areas of their distribution.

Effects of polychlorinated biphenyls (PCB) on California sea lion (Zalophus californianus) lymphocyte functions upon in vitro exposure

Polychorinated biphenyl (PCB) congeners are a cause for concern due to their persistence in the environment, their lipophilic properties that cause them to bio-accumulate in top predators, and their adverse effects on mammalian health. For example, the common urogenital carcinoma reported in California sea lions (Zalophus californianus) (CSL) is associated with high tissue levels of PCBs, but the mechanisms responsible for this association are unknown. This study investigated the effect of exposure to six PCB congeners and a congener mix at low and environmentally relevant concentrations on NK cell-like and T cell activity using in vitro assays on cryopreserved lymph node mononuclear cells isolated from dead CSL. Non dioxin-like congeners 153 and 180 increased lymphocyte proliferation at 5 and 10 ppm, while congener 138 decreased proliferation by up to 43% at 15 ppm. Dioxin-like PCBs 118 and 169 did not affect lymphocyte proliferation, while the effects of congener 105 depended on the mitogen concentration; these did not correlate with their predicted toxic equivalent factors. NK cell-like activity was affected only by the highest concentration of PCBs tested; it was increased by non-dioxin-like congeners 138 and 153, and decreased by dioxin-like congener 169. The PCB congener mix suggested that the effects of PCB congeners were not simply additive. Our results concur with effects of PCBs reported for other pinniped's lymphocytes and add further experimental support to the observation that dioxin-like PCBs are not the most toxic congeners for marine mammals, contrary to effects in other species. This is the first evidence of in vitro suppression of NK cell-like cytotoxicity by a dioxin-like congener in a pinniped. More importantly, the observed results suggest that PCBs can modulate the CSL immune system, increasing exposed individuals' susceptibility to viral and oncogenic challenges.

PAROTID CARCINOMA IN A FREE-RANGING CALIFORNIA SEA LION ( ZALOPHUS CALIFORNIANUS)

A free-ranging juvenile California sea lion ( Zalophus californianus) stranded on the coast of Vancouver, British Columbia, with signs of lethargy and emaciation in April 2016. An asymmetrical skull with a prominent superficial cervical lymph node was found on initial assessment. Fine-needle aspirates and biopsies of the lymph node were consistent with neoplasia and the animal was humanely euthanized and presented for necropsy. A metastatic parotid gland adenocarcinoma was diagnosed with regional lymph node and pulmonary metastases. Local invasion of contiguous skeletal muscle, bone, ear, and tonsils was extensive and likely accounted for the unilateral craniofacial deformity. Neoplasia of nonurogenital origin in juvenile California sea lions are reported infrequently. This is the first case of a parotid carcinoma in a California sea lion.

No evidence for clonal transmission of urogenital carcinoma in California sea lions ( Zalophus californianus)

Urogenital carcinoma is a highly metastatic cancer affecting California sea lions ( Zalophus californianus). The disease has high prevalence amongst stranded animals, and is one of the most commonly observed cancers in wildlife. The genital localisation of primary tumours suggests the possibility that coital transmission of an infectious agent could underlie this disease. Otarine herpesvirus type 1 has been associated with lesions, however a causative role for this virus has not been confirmed. We investigated the possibility that urogenital carcinoma might be clonally transmissible, spread by the direct transfer of cancer cells. Analysis of sequences at the mitochondrial DNA control region in seven matched tumour and host pairs confirmed that tumour genotypes were identical to those of their matched hosts and did not show similarity with tumours from other individuals. Thus our findings suggest that urogenital carcinoma in California sea lions is not clonally transmitted, but rather arises from transformed host cells.

Melanin granules melanophages and a fully-melanized epidermis are common traits of odontocete and mysticete cetaceans

BACKGROUND

The cellular mechanisms used to counteract or limit damage caused by exposure of marine vertebrates to solar ultraviolet (UV) radiation are poorly understood. Cetaceans are vulnerable because they lack protective skin appendages and are obliged to surface continuously to breathe, thus being exposed repeatedly to UV light. Although molecular mechanisms of photoprotection of cetaceans have been studied, there is limited knowledge about their epidermal structure and photoprotective effectors.

OBJECTIVE

To describe and compare the epidermis of mysticete and odontocete cetaceans and identify potentially photoprotective traits.

ANIMALS

Twenty eight free-living individuals belonging to six cetacean species were sampled in the Mexican Central Pacific and Gulf of California. Species sampled were the bottlenose dolphin, pantropical spotted dolphin, spinner dolphin, Bryde's whale, fin whale and humpback whale.

METHODS

Histological and cytological evaluation of skin biopsy tissue collected in the field between 2014 and 2016.

RESULTS

All cetaceans had only three epidermal layers, lacking both the stratum granulosum and stratum lucidum. A relatively thick stratum corneum with a parakeratosis-like morphology was noted. Melanin was observed within keratinocytes in all epidermal layers, including the stratum corneum and apical melanin granules obscured the keratinocyte nucleus. Keratinocytes had a perinuclear halo. Keratinocyte diameter differed between cetacean suborders and amongst species. Melanophage clusters were common in most cetacean species.

CONCLUSIONS

The widespread presence of melanin and the unexpectedly high number of melanophages may constitute a unique photoprotective trait of cetaceans and could reflect primitive adaptations to their environment and to their obligate marine-bound life.

MHC class II transcription is associated with inflammatory responses in a wild marine mammal

Inflammation is one of the most important non-specific and rapid responses that a vertebrate can elicit in response to damage or a foreign insult. To date, despite increasing evidence that the innate and adaptive branches of immunity are more intricately related than previously thought, few have examined interactions between the Major Histocompatibility Complex (MHC, a polymorphic region of the vertebrate genome that is involved with antigen presentation) and inflammation, and even less is known about these interactions in an eco-immunological context. Here, we examined the effect of MHC class II DRB gene multiplicity and transcription on phytohemagglutinin (PHA)-induced inflammation during the early stages of development of California sea lions. Neither constitutive nor expressed ZacaDRB diversity was found to be associated with pup responses to PHA at any of the stages of pup development. However, for two-month-old pups, those with a specific MHC-DRB locus (ZacaDRB-A) tended to have less efficient responsive inflammation. Transcription of distinct MHC-DRB loci was also linked to PHA-induced inflammation, with patterns that varied markedly between ages, and that suggested that ongoing infectious processes could limit the capacity to respond to a secondary challenge. Life history constraints and physiological processes associated with development of California sea lions, in conjunction with their changing pathogenic environment could explain the observed effects of MHC class II transcription on PHA-induced inflammation. To our knowledge, ours is the first study to examine the importance of expressed vs. constitutive MHC loci on inflammation in a natural population.