Contaminants in Atlantic walruses in Svalbard Part 2: Relationships with endocrine and immune systems.

Marine mammals in the Barents Sea region have among the highest levels of contaminants recorded in the Arctic and the Atlantic walrus (Odobenus rosmarus rosmarus) is one of the most contaminated species within this region. We therefore investigated the relationships bewteen blubber concentrations of lipophilic persistent organic pollutants (POPs) and plasma concentrations of perfluoroalkyl substances (PFASs) and markers of endocrine and immune functions in adult male Atlantic walruses (n = 38) from Svalbard, Norway. To do so, we assessed plasma concentrations of five forms of thyroid hormones and transcript levels of genes related to the endocrine and immune systems as endpoints; transcript levels of seven genes in blubber and 23 genes in blood cells were studied. Results indicated that plasma total thyroxine (TT4) concentrations and ratio of TT4 and reverse triiodothyronine decreased with increasing blubber concentrations of lipophilic POPs. Blood cell transcript levels of genes involved in the function of T and B cells (FC like receptors 2 and 5, cytotoxic T-lymphocyte associated protein 4 and protein tyrosine phosphatase non-receptor type 22) were increased with plasma PFAS concentrations. These results suggest that changes in thyroid and immune systems in adult male walruses are linked to current levels of contaminant exposure.

Structural characterisation of Toll-like receptor 1 (TLR1) and Toll-like receptor 6 (TLR6) in elephant and harbor seals.

Pinnipeds are a diverse clade of semi-aquatic mammals, which act as key indicators of ecosystem health. Their transition from land to marine environments provides a complex microbial milieu, making them vulnerable to both aquatic and terrestrial pathogens, thereby contributing to pinniped population decline. Indeed, viral pathogens such as influenza A virus and phocine distemper virus (PDV) have been identified as the cause of several of these mass mortality events. Furthermore, bacterial infection with mammalian Brucella sp. and methicillin-resistant Staphylococcus aureus strains have also been observed in marine mammals, posing further risk to both co-habiting endangered species and public health. During these disease outbreaks, mortality rates have varied amongst different pinniped species. Analyses of innate immune receptors at the host-pathogen interface have previously identified variants which may drive these species-specific responses. Through a combination of both sequence- and structure-based methods, this study characterises members of the Toll-like receptor (TLR) 1 superfamily from both harbour and elephant seals, identifying variations which will help us to understand these species-specific innate immune responses, potentially aiding the development of specific vaccine-adjuvants for these species.

Immunohistochemical characterization of selected cell markers for the detection of hematopoietic cells in formalin-fixed, paraffin wax-embedded lymphoid tissues of harbor seals (Phoca vitulina) and walruses (Odobenus rosmarus rosmarus).

To facilitate a detailed investigation of pinniped lymphoid organs, 30 monoclonal antibodies (mAb) as well as eight polyclonal antibodies (pAb) of different species specificities directed against cell antigens of the hematopoietic system were tested for immunohistochemical cross-reactivity on formalin-fixed, paraffin wax-embedded tissues of harbor seals (Phoca vitulina) and a walrus (Odobenus rosmarus rosmarus). Six monoclonal and eight polyclonal antibodies showed specific immunoreactivities. Lymphocytes were immunolabeled by an anti-CD3 pAb, anti-Foxp3 mAb and anti-CD79 alpha mAb, while plasma cell subpopulations were recognized by anti-IgA pAb, anti-IgG pAb and anti-IgM pAb as well as by anti-kappa- and anti-lambda light chain pAb. Cells of the histiocytic lineage were recognized by lysozyme-, myeloid/histiocyte antigen-, and CD68-specific markers. Furthermore, dendritic cell-like cells were detected by an anti-S100 protein pAb. The MHC class II antigen was labeled on the majority of immune cells of the harbor seal and walrus using a bovine mAb. Mast cells were stained by an anti-mast cell tryptase mAb. Thus, using these antibodies from various species, it is now possible to determine phenotypical changes in lymphoid organs and detect different leukocyte subsets involved in inflammatory responses in archived tissue samples of these pinniped species.

Viral and bacterial serology of free-ranging Pacific walrus.

Serum or heparinized plasma samples were obtained between 1994 and 1996 from 20 male and 20 female adult free-ranging Pacific walrus (Odobenus rosmarus divergens) from St. Lawrence Island and Round Island, Alaska. Samples were screened for antibodies to some potentially pathogenic bacteria and viruses. No sample had detectable antibody to Brucella spp. Three of 40 (8%) had low antibody titers to Leptospira interrogans serovars. Phocine distemper virus antibodies were not detected. Serologic responses to one or more caliciviruses (San Miguel sea lion virus 12 or vesicular exanthema of swine serotypes E54, F55, G55, 1934B) were detected in 18% (seven of 40) walrus. Antibodies to one or more subtypes of influenza A virus (H10, N2, N3, N5, N6, N7) were detected in 21% (eight of 38). Periodic screening of free-ranging populations for exposure to infectious diseases has become an important component of bio-monitoring programs to facilitate understanding and detecting trends in marine mammal populations.