Abstract
An adult male howler monkey was kept in captivity for approximately 6 months for rehabilitation purposes. Multiple physical exam and laboratory tests were performed during this period, and no signs compatible with focal epithelial hyperplasia (FEH) were observed. About 10 days after the reintroduction, the animal was found on the ground, in agony. The gross exam revealed dog bites in multiple sites, associated with extensive hemorrhages. In the oral cavity, the lower lip mucosa and the antero-lateral-medial aspects of the tongue, showed multiple, 2–5 mm in diameter, soft, whitish, circumscribed mucosal raised plaques, either isolated or coalescent. Other findings were pulmonary edema, presence of Enterobius sp. and focal ulcerative colitis. Samples of the lower lip and all organs were fixed in 10% buffered formalin and embedded in paraffin, sectioned at 4–6 µm and stained with hematoxylin and eosin (H&E). Immunohistochemistry was performed for the detection of the viral capsid antigen (code no. B580, diluted 1:8,000, Dako) and for the detection of HPV antigens (clone 4C4/F10/H7/83, code NCL-HPV-4C4, diluted 1:40, Novocastra). In situ hybridization with a wide spectrum biotinylated probe of HPV types 6, 11, 16, 18, 30, 31, 33, 35, 45, 51 and 52 (code K0012, Dako) was performed on the formalin-fixed, paraffin-embedded tissue section. Major histopathologic findings of the lower lip included moderate acanthosis, with elongation and fusion of the epithelial cones, and koilocytosis. The immunohistochemistry test of the generic papillomavirus antigen (PV) showed strong nuclear positivity in the koilocytes. On the other hand, the specific reactions for detection of HPV 6, HPV 11 and HPV 18 were negative. There was no cross-hybridization with the HPV probe. The gross and microscopic characteristics found in this howler monkey are compatible to those previously described in humans and chimpanzees with FEH. It was shown by immunohistochemistry that the agent involved in this case is a PV with positive reactions to the viral capsid antigens (L1) only in the cells with koilocytosis on the upper stratum spinosum, which indicates a productive infection by PV. The negative result to in situ hybridization for the HPV wide-spectrum DNA probe is very interesting and eliminates the possibility of the PV of this howler monkey being related to any of these HPV types. It is emphasized that this PV is probably not related either to HPV 13 or 32, as they have a partial homology with types 6, 11, 16 and 18. These data suggest that the PV identified in this case is a mucosotropic virus specific of the howler monkey oral cavity. Further studies should be carried out so as to provide a better understanding and to characterize the epidemiology of FEH cases in neotropical primates.
Acknowledgment
This research was supported by FAPESP, grant nos. 95/3621-6 and 97/4815-4.
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