Cellular Prion Protein Expression in the Brain Tissue from Brucella ceti -Infected Striped Dolphins ( Stenella coeruleoalba ).

Brucella ceti , a zoonotic pathogen of major concern to cetacean health and conservation, is responsible for severe meningo-encephalitic/myelitic lesions in striped dolphins ( Stenella coeruleoalba ), often leading to their stranding and death. This study investigated, for the first time, the cellular prion protein (PrP c ) expression in the brain tissue from B. ceti -infected, neurobrucellosis-affected striped dolphins. Seven B. ceti -infected, neurobrucellosis-affected striped dolphins, found stranded along the Italian coastline (6) and in the Canary Islands (1), were investigated, along with five B. ceti -uninfected striped dolphins from the coast of Italy, carrying no brain lesions, which served as negative controls. Western Blot (WB) and immunohistochemistry (IHC) with an anti-PrP murine monoclonal antibody were carried out on the brain parenchyma of these dolphins. While PrP c IHC yielded inconclusive results, a clear-cut PrP c expression of different intensity was found by means of WB analyses in the brain tissue of all the seven herein investigated, B. ceti -infected and neurobrucellosis-affected cetacean specimens, with two dolphins stranded along the Italian coastline and one dolphin beached in Canary Islands also exhibiting a statistically significant increase in cerebral PrP c expression as compared to the five Brucella spp.-negative control specimens. The significantly increased PrP c expression found in three out of seven B. ceti -infected, neurobrucellosis-affected striped dolphins does not allow us to draw any firm conclusion(s) about the putative role of PrP c as a host cell receptor for B. ceti . Should this be the case, an upregulation of PrP c mRNA in the brain tissue of neurobrucellosis-affected striped dolphins could be hypothesized during the different stages of B. ceti infection, as previously shown in murine bone marrow cells challenged with Escherichia coli . Noteworthy, the inflammatory infiltrates seen in the brain and in the cervico-thoracic spinal cord segments from the herein investigated, B. ceti -infected and neurobrucellosis-affected striped dolphins were densely populated by macrophage/histiocyte cells, often harboring Brucella spp. antigen in their cytoplasm, similarly to what was reported in macrophages from mice experimentally challenged with B. abortus . Notwithstanding the above, much more work is needed in order to properly assess the role of PrP c , if any, as a host cell receptor for B. ceti in striped dolphins.