Novel Laboratory Mouse Papillomavirus (MusPV) Infection

Most papillomaviruses (PVs) are oncogenic. There are at least 100 different human PVs and 65 nonhuman vertebrate hosts, including wild rodents, which have species–specific PV infections. Florid papillomatosis arose in a colony of NMRI-Foxn1nu/Foxn1nu (nude) mice at the Advanced Centre for Treatment Research and Education in Cancer in India. Lesions appeared at the mucocutaneous junctions of the nose and mouth. Histologically, lesions were classical papillomas with epidermal hyperplasia on thin fibrovascular stalks in a verrucous pattern. Koilocytotic cells were observed in the stratum granulosum of the papillomatous lesions. Immunohistochemically, these abnormal cells were positive for PV group-specific antigens. With transmission electron microscopy, virus particles were observed in crystalline intranuclear inclusions within keratinocytes. The presence of a mouse PV, designated MusPV, was confirmed by amplification of PV DNA with degenerative primers specific for PVs. This report is the first of a PV and its related disease in laboratory mice.