Surface glycoprotein of Borna disease virus mediates virus spread from cell to cell.

Borna disease virus (BDV) is a non-segmented negative-stranded RNA virus that maintains a strictly neurotropic and persistent infection in affected end hosts. The primary target cells for BDV infection are brain cells, e.g. neurons and astrocytes. The exact mechanism of how infection is propagated between these cells and especially the role of the viral glycoprotein (GP) for cell-cell transmission, however, are still incompletely understood. Here, we use different cell culture systems, including rat primary astrocytes and mixed cultures of rat brain cells, to show that BDV primarily spreads through cell-cell contacts. We employ a highly stable and efficient peptidomimetic inhibitor to inhibit the furin-mediated processing of GP and demonstrate that cleaved and fusion-active GP is strictly necessary for the cell-to-cell spread of BDV. Together, our quantitative observations clarify the role of Borna disease virus-glycoprotein for viral dissemination and highlight the regulation of GP expression as a potential mechanism to limit viral spread and maintain persistence. These findings furthermore indicate that targeting host cell proteases might be a promising approach to inhibit viral GP activation and spread of infection.

ORAL SQUAMOUS CELL CARCINOMA IN AN AGED CAPTIVE WHITE RHINOCEROS (CERATOTHERIUM SIMUM).

A 48-yr-old captive white rhinoceros ( Ceratotherium simum ) was euthanized due to old age, pododermatitis, and progressive laminitis of the middle toe of the left fore- and hindlimbs. Severe chronic necrotizing periodontitis and dental loss was diagnosed, although food intake prior to death had not decreased. In addition, extensive ulceration of the tongue was noted. Histologically, squamous cell carcinoma of the tongue was diagnosed with chronic severe ulcerative glossitis. Metastatic lesions were not detected. Clinicians should monitor the oral health of aging rhinoceros due to the occult nature of these lesions.