Oral Papillomavirus Infection in a Pygmy Chimpanzee ( <i>Pan Paniscus</i> )

Abstract

Papillomaviruses cause a variety of benign lesions in many vertebrate species. 19 The papillomas can become florid and difficult to treat and sometimes progress to malignancies. Papillomavirus-associated lesions have been reported sporadically in nonhuman primates, and recently several distinct types of these viruses have been cloned and characterized. Focal epithelial hyperplasia was reported in the oral cavity of a common chimpanzee (Pan troglodytes), and papillomavirus-like particles were observed in the lesion by transmission electron microscopy. A similar disease that occurs in humans is associated with a specific human papillomavirus (HPV-13). Oral papillomas occur in humans and are associated with several papillomavirus types that more often infect the human lower genital tractFlorid oral papillomatosis was observed on the lingual, buccal, and gingival mucosa of a pygmy chimpanzee (Pan paniscus) that was imported from Antwerp, Belgium, and maintained in quarantine at the San Diego Zoo, San Diego, California. The lesions were sessile to papillary and ranged in size from 5 to 20 mm in diameter (Fig. 1). Three tumors were biopsied. Half of each tumor was fixed in neutral buffered 10% formalin for histopathology and immunohistochemistry and the remainder was frozen and stored at -70 C. Microscopically, lesions ranged from focal sessile areas of oral mucosal hyperplasia to typical papillomas. The papillomas consisted of marked epithelial proliferation in a normal pattern of differentiation supported on thin fibrovascular stalks (Fig. 2). The layer of cells between the strata spinosum and corneum was thick and lacked granules. The thickening appeared to be exacerbated because these cells had swollen cytoplasm that stained poorly (Fig. 3). Nuclei were oval and vesiculated but not pyknotic. A small, clear halo surrounded the nuclei. Nuclei were retained throughout the stratum corneum (parakeratosis), which was moderately thickened. Papillomavirus group-specific structural antigens were detected within nuclei of widely scattered or small clusters of cells in the upper stratum spinosum (Fig. 4) using the avidinbiotin complex technique. Serial sections of the same paraffin blocks were treated with a mixture of biotinylated probes for human papillomavirus (HPV) types 6 and 11, 16 and 18, and 31, 33, and 35 using the ViraType® in situ HPV tissue hybridization kit Papillomavirus DNA was not detected by in situ hybridization within nuclei of infected cells in the