Molecular diagnosis of a laboratory mouse papillomavirus (MusPV)

MusPV, a novel papillomavirus (PV) that naturally infects laboratory mice, was isolated and characterized from a colony of NMRI-Foxn1nu/Foxn1nu (nude) mice in India. Because MusPV may have been missed during routine pathogen screening of mice in colonies worldwide, a variety of detection methods are described to detect MusPV. The clinical and histologic lesions of productive MusPV infections fit PV-associated features, including papillomas, koilocytes within the stratum granulosum of the hyperplastic/acanthotic papillomatous epithelium, and the presence of intranuclear virus particles in koilocytotic cells visualized by electron microscopy. Antiserum against disrupted PV virions, isolated from another species (canine), identified conserved viral antigens in productively infected cells by immunohistochemistry. A rolling circle technique was used to amplify viral circular DNAs followed by endonuclease restriction enzyme digestion to determine the correct size of PV DNA. Consensus PV degenerative primers, My09/11, commonly used to detect many different types of PVs by polymerase chain reaction (PCR), particularly mucosotropic HPVs, also identified MusPV and all rodent PVs tested. Since there was one nucleotide mismatch between the My09/11 primer set and the MusPV template, a new primer set, MusPV–My09/11, was designed to specifically detect MusPV in latent infections and spontaneous MusPV-induced papillomas. Southern blot analysis verified the presence of full size PV DNA in infected tissues. Virus-like particles (VLPs), generated from MusPV L1 genes, provided a substrate for serological testing of naturally and experimentally infected mice. In summary, a series of diagnostic assays were developed and validated to detect MusPV infection in skin tumors and serological response in laboratory mice.