Papillomas and carcinomas associated with a papillomavirus in European harvest mice (Micromys minutus)

A review of sebum in mammals in relation to skin diseases, skin function, and the skin microbiome

Diseases vary among and within species but the causes of this variation can be unclear. Immune responses are an important driver of disease variation, but mechanisms on how the body resists pathogen establishment before activation of immune responses are understudied. Skin surfaces of mammals are the first line of defense against abiotic stressors and pathogens, and skin attributes such as pH, microbiomes, and lipids influence disease outcomes. Sebaceous glands produce sebum composed of multiple types of lipids with species-specific compositions. Sebum affects skin barrier function by contributing to minimizing water loss, supporting thermoregulation, protecting against pathogens, and preventing UV-induced damage. Sebum also affects skin microbiome composition both via its antimicrobial properties, and by providing potential nutrient sources. Intra- and interspecific variation in sebum composition influences skin disease outcomes in humans and domestic mammal species but is not well-characterized in wildlife. We synthesized knowledge on sebum function in mammals in relation to skin diseases and the skin microbiome. We found that sebum composition was described for only 29 live, wild mammalian species. Sebum is important in dermatophilosis, various forms of dermatitis, demodicosis, and potentially white-nose syndrome. Sebum composition likely affects disease susceptibility, as lipid components can have antimicrobial functions against specific pathogens. It is unclear why sebum composition is species-specific, but both phylogeny and environmental effects may drive differences. Our review illustrates the role of mammal sebum function and influence on skin microbes in the context of skin diseases, providing a baseline for future studies to elucidate mechanisms of disease resistance beyond immune responses.

Rodent Papillomaviruses

Preclinical infection model systems are extremely valuable tools to aid in our understanding of Human Papillomavirus (HPV) biology, disease progression, prevention, and treatments. In this context, rodent papillomaviruses and their respective infection models are useful tools but remain underutilized resources in the field of papillomavirus biology. Two rodent papillomaviruses, MnPV1, which infects the Mastomys species of multimammate rats, and MmuPV1, which infects laboratory mice, are currently the most studied rodent PVs. Both of these viruses cause malignancy in the skin and can provide attractive infection models to study the lesser understood cutaneous papillomaviruses that have been frequently associated with HPV-related skin cancers. Of these, MmuPV1 is the first reported rodent papillomavirus that can naturally infect the laboratory strain of mice. MmuPV1 is an attractive model virus to study papillomavirus pathogenesis because of the ubiquitous availability of lab mice and the fact that this mouse species is genetically modifiable. In this review, we have summarized the knowledge we have gained about PV biology from the study of rodent papillomaviruses and point out the remaining gaps that can provide new research opportunities.

Multiple viral plaques with sebaceous differentiation associated with an unclassified papillomavirus type in a cat

CASE HISTORY AND CLINICAL FINDINGS A 15-year-old neutered male domestic short-haired cat was presented due to multiple 0.5-2 cm-diameter crusting plaques in the left preauricular region, over the bridge of nose, and in the right periocular region. The plaques did not appear to cause discomfort. HISTOPATHOLOGICAL FINDINGS Biopsy samples of four plaques were examined histologically. Three plaques consisted of well-demarcated foci of mild epidermal hyperplasia overlying markedly hyperplastic sebaceous glands. Approximately 60% of the hyperplastic cells contained a large cytoplasmic vacuole that ranged from being clear to containing prominent grey-blue fibrillar material. The fourth plaque was composed solely of epidermal hyperplasia, consistent with previous descriptions of feline viral plaques. MOLECULAR BIOLOGY Papillomavirus DNA was amplified from all four plaques using PCR. A single DNA sequence was amplified from the plaques with sebaceous differentiation. This sequence was identical to the FdPV-MY sequence previously suggested to be from a putative unclassified papillomavirus type. Felis catus papillomavirus type 2 sequences were amplified from the plaque typical of feline viral plaques. Immunohistochemistry to detect p16^CDKN2A protein (p16) showed marked immunostaining throughout the hyperplastic epidermis and adnexal structures within the plaques with sebaceous differentiation. DIAGNOSIS Multiple feline viral plaques with variable sebaceous differentiation. CLINICAL RELEVANCE Feline viral plaques with sebaceous differentiation have not been previously reported in cats. The presence of unique cell changes within these lesions, the detection of an unclassified papillomavirus type, and the p16 immunostaining within these plaques suggest that they may have been caused by the papillomavirus that contains the FdPV-MY sequence.

In vitro and Animal Models for Antiviral Therapy in Papillomavirus Infections

The need for antiviral therapies for papillomavirus infections is well recognized but the difficulties of reproducing the infectious cycle of papillomaviruses in vitro has hindered our understanding of virus-cell interactions and the regulation of viral gene expression during permissive growth. Recent advances in understanding the temporal expression and function of papillomavirus proteins has enabled consideration of a targeted approach to papillomavirus chemotherapy and in particular the inhibition of viral replication by targeting the E1 and E2 proteins. There are in vitro culture systems available for the screening of new chemotherapeutic agents, since significant advances have been made with culture systems which promote epithelial differentiation in vitro. However, to date, there are no published data which show that virions generated in vitro can infect keratinocytes and initiate another round of replication in vitro. In vivo animal models are therefore necessary to assess the efficacy of antivirals in preventing and treating viral infection, particularly for the low-risk genital viruses which are on the whole refractory to culture in vitro. Although papillomaviruses affect a wide variety of hosts in a species-specific manner, the animals most useful for modelling papillomavirus infections include the rabbit, ox, mouse, dog, horse, primate and sheep. The ideal animal model should be widely available, easy to house and handle, be large enough to allow for adequate tissue sampling, develop lesions on anatomical sites comparable with those in human diseases and these lesions should be readily accessible for monitoring and ideally should yield large amounts of infectious virus particles for use in both in vivo and in vitro studies. The relative merits of the various papillomavirus animal models available in relation to these criteria are discussed.

MmuPV1 infection and tumor development of T cell-deficient mice is prevented by passively transferred hyperimmune sera from normal congenic mice immunized with MmuPV1 virus-like particles (VLPs)

Infection by mouse papillomavirus (PV), MmuPV1, of T cell-deficient, B6.Cg-Foxn1(nu)/J nude mice revealed that four, distinct squamous papilloma phenotypes developed simultaneously after infection of experimental mice. Papillomas appeared on the muzzle, vagina, and tail at or about day 42days post-inoculation. The dorsal skin developed papillomas and hair follicle tumors (trichoblastomas) as early as 26days after infection. Passive transfer of hyperimmune sera from normal congenic mice immunized with MmuPV1 virus-like particles (VLPs) to T cell-deficient strains of mice prevented infection by virions of experimental mice. This study provides further evidence that T cell deficiency is critical for tumor formation by MmuPV1 infection.

Localization of Bovine Papillomavirus Nucleic Acid in Equine Sarcoids

Bovine papillomaviruses (BPV1/BPV2) have long been associated with equine sarcoids; deciphering their contribution has been difficult due to their ubiquitous presence on skin and in the environment, as well as the lack of decent techniques to interrogate their role in pathogenesis. We have developed and characterized an in situ hybridization (ISH) assay that uses a pool of probes complementary to portions of the E5, E6, and E7 genes. This assay is highly sensitive for direct visualization of viral transcript and nucleic acid in routinely processed histopathologic samples. We demonstrate here the visualization of BPV nucleic acid in 18 of 18 equine sarcoids, whereas no detectable viral DNA was present in 15 of 15 nonsarcoid controls by this technique. In nearly 90% (16/18) of the sarcoids, 50% or more of the fibroblastic cell nuclei distributed throughout the neoplasm had detectable hybridization. In the remaining 2 cases, fewer than half of the fibroblastic cells contained detectable hybridization, but viral nucleic acid was also detected in epithelial cells of the sebaceous glands, hair follicles and epidermis. A sensitive ISH assay is an indispensable addition to the molecular methods used to detect viral nucleic acid in tissue. We have used this technique to determine the specific cellular localization and distribution of BPV in a subset of equine sarcoids.

Immune status, strain background, and anatomic site of inoculation affect mouse papillomavirus (MmuPV1) induction of exophytic papillomas or endophytic trichoblastomas

Papillomaviruses (PVs) induce papillomas, premalignant lesions, and carcinomas in a wide variety of species. PVs are classified first based on their host and tissue tropism and then their genomic diversities. A laboratory mouse papillomavirus, MmuPV1 (formerly MusPV), was horizontally transmitted within an inbred colony of NMRI-Foxn1(nu)/Foxn1nu (nude; T cell deficient) mice of an unknown period of time. A ground-up, filtered papilloma inoculum was not capable of infecting C57BL/6J wild-type mice; however, immunocompetent, alopecic, S/RV/Cri-ba/ba (bare) mice developed small papillomas at injection sites that regressed. NMRI-Foxn1(nu) and B6.Cg-Foxn1(nu), but not NU/J-Foxn1(nu), mice were susceptible to MmuPV1 infection. B6 congenic strains, but not other congenic strains carrying the same allelic mutations, lacking B- and T-cells, but not B-cells alone, were susceptible to infection, indicating that mouse strain and T-cell deficiency are critical to tumor formation. Lesions initially observed were exophytic papillomas around the muzzle, exophytic papillomas on the tail, and condylomas of the vaginal lining which could be induced by separate scarification or simultaneous scarification of MmuPV1 at all four sites. On the dorsal skin, locally invasive, poorly differentiated tumors developed with features similar to human trichoblastomas. Transcriptome analysis revealed significant differences between the normal skin in these anatomic sites and in papillomas versus trichoblastomas. The primarily dysregulated genes involved molecular pathways associated with cancer, cellular development, cellular growth and proliferation, cell morphology, and connective tissue development and function. Although trichoepitheliomas are benign, aggressive tumors, few of the genes commonly associated with basal cell carcinoma or squamous cells carcinoma were highly dysregulated.

Characterization of Mus musculus papillomavirus 1 infection in situ reveals an unusual pattern of late gene expression and capsid protein localization

Full-length genomic DNA of the recently identified laboratory mouse papillomavirus 1 (MusPV1) was synthesized in vitro and was used to establish and characterize a mouse model of papillomavirus pathobiology. MusPV1 DNA, whether naked or encapsidated by MusPV1 or human papillomavirus 16 (HPV 16) capsids, efficiently induced the outgrowth of papillomas as early as 3 weeks after application to abraded skin on the muzzles and tails of athymic NCr nude mice. High concentrations of virions were extracted from homogenized papillomatous tissues and were serially passaged for >10 generations. Neutralization by L1 antisera confirmed that infectious transmission was capsid mediated. Unexpectedly, the skin of the murine back was much less susceptible to virion-induced papillomas than the muzzle or tail. Although reporter pseudovirions readily transduced the skin of the back, infection with native MusPV1 resulted in less viral genome amplification and gene expression on the back, including reduced expression of the L1 protein and very low expression of the L2 protein, results that imply skin region-specific control of postentry aspects of the viral life cycle. Unexpectedly, L1 protein on the back was predominantly cytoplasmic, while on the tail the abundant L1 was cytoplasmic in the lower epithelial layers and nuclear in the upper layers. Nuclear localization of L1 occurred only in cells that coexpressed the minor capsid protein, L2. The pattern of L1 protein staining in the infected epithelium suggests that L1 expression occurs earlier in the MusPV1 life cycle than in the life cycle of high-risk HPV and that virion assembly is regulated by a previously undescribed mechanism.

Cutaneous hybrid cyst in a sprague-dawley rat

This report describes a spontaneous hybrid cyst in a Sprague-Dawley (SD) rat. A 52-week-old, male SD rat had a cutaneous cyst on the left mystacial pad. Histologically, the cyst wall showed infundibular differentiation with keratohyalin granules in the granular layer and matrical differentiation comprising basaloid epithelial cells with trichohyalin granules. The cyst cavity was filled with lamellar, flaky keratin and aggregates of shadow cells. Immunohistochemically, the infundibular-type epithelium was positive for cytokeratin (CK) AE1/AE3, CK KL1 and CK14 but negative for CK15, whereas the matrical-type epithelium was negative for all four CK isoforms examined. These immunohistochemical properties of the infundibular- and matrical-type epithelia were similar to those of the infundibulum and inferior segment of normal hair follicles, respectively. Based on these findings, the cyst was diagnosed as a hybrid cyst, comprising more than one type of cyst arising from various parts of the pilosebaceous unit.

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-Foxn1(nu)/Foxn1(nu) (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.

Genomic analysis of the first laboratory-mouse papillomavirus

A papillomavirus (PV) that naturally infects laboratory mice will provide an extremely valuable tool for PV research. We describe here the isolation, cloning and molecular analysis of the first novel laboratory-mouse PV, designated MusPV. This agent, recently identified in the tissues from florid and asymmetrical papillomas on the face of nude mice (NMRI-Foxn1(nu)/Foxn1(nu)), was demonstrated to be transmissible to immunocompetent mice (Ingle et al., 2010). The MusPV genome is 7510 bp in length, is organized similarly to those of other PVs and has at least seven ORFs (E1, E2, E4, E6, E7, L1 and L2). Phylogenetic analysis indicates that MusPV belongs to the π genus together with four other rodent PVs (McPV2, MaPV1, MmiPV and RnPV1). Of the rodent PVs, MusPV appears most closely related to Mastomys coucha PV (McPV2), with 65 % genomic homogeneity and 80 % L1 amino acid similarity. Rodent PVs, except for MnPV1, do not contain any identifiable retinoblastoma protein (RB) binding sites. MusPV has one putative RB-binding site on the E6 protein but not on the E7 protein. Non-coding regions (NCRs) of PVs maintain multiple binding sites for transcription factors (TFs). The NCR of MusPV has numerous sites for TF binding, of which at least 13 TFs are common to all PVs in the π genus. MusPV provides a potentially valuable, novel mouse model to study mechanisms of infection, oncology and novel preventive and therapeutic approaches in mice that can be translated to diseases caused by human PVs.

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-Foxn1(nu)/Foxn1(nu) (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.

Papillomavirus-Associated Cutaneous Neoplasia in Mammals

For humans, strong evidence indicates that some mucosal papillomavirus (PV) types cause genital and oral neoplasia, and weaker evidence suggests that some cutaneous PVs may cause cutaneous squamous cell carcinomas (SCC). For nonhuman species, strong evidence supports a causal role of PVs in the development of feline and equine sarcoids. Likewise, PVs are believed to cause cutaneous SCCs in rabbits, western barred bandicoots, and some rodents. Furthermore, some evidence suggests that PVs may influence the development of both feline and canine cutaneous SCCs. This review discusses the evidence that PVs cause human cutaneous SCCs and the proposed mechanisms for this action. It then reviews preneoplastic and neoplastic skin diseases that are associated with PV infection in nonhuman mammals.

In situ hybridization to detect bandicoot papillomatosis carcinomatosis virus type 1 in biopsies from endangered western barred bandicoots (Perameles bougainville)

The western barred bandicoot (Perameles bougainville) is an endangered Australian marsupial species in which a papillomatosis and carcinomatosis syndrome occurs. Bandicoot papillomatosis carcinomatosis virus type 1 (BPCV1) is associated with the lesions of this progressively debilitating syndrome. Five digoxigenin-labelled DNA probes were generated for in situ hybridization (ISH) and the technique was optimized and performed on formalin-fixed paraffin-embedded (FFPE) biopsies. Staining of keratinocyte and sebocyte nuclei within lesions was achieved with all five probes. The sensitivity of ISH (76.9%) surpassed that of PCR (30.8%) for FFPE samples. The sensitivity of ISH varied from 81% (papillomas) and 70% (carcinoma in situ) to 29% (squamous cell carcinomas). The specificity of the test was confirmed using an irrelevant probe and papillomas from other species. These results strengthen the association between BPCV1 and the western barred bandicoot papillomatosis and carcinomatosis syndrome and give insight into the biology of the virus-host interaction.

Cutaneous papillomatosis and carcinomatosis in the Western barred bandicoot (Perameles bougainville)

A progressive wart-like syndrome in both captive and wild populations of the Western barred bandicoot (WBB) is hindering conservation efforts to prevent the extinction of this endangered marsupial. In this study, 42 WBBs exhibiting the papillomatosis and carcinomatosis syndrome were examined. The disease was characterized by multicentric proliferative lesions involving cutaneous and mucosal surfaces, which were seen clinically to increase in size with time. Grossly and histologically the smaller skin lesions resembled papillomas, whereas the larger lesions were most commonly observed to be squamous cell carcinomas. Large amphophilic intranuclear inclusion bodies were observed in hyperplastic conjunctival lesions of 8 WBBs under light microscopy. Conjunctival lesions from 2 WBBs examined using transmission electron microscopy contained a crystalline array of spherical electron-dense particles of 45-nm diameter, within the nucleus of conjunctival epithelial cells, consistent with a papillomavirus or polyomavirus. Conjunctival samples from 3 bandicoots that contained intranuclear inclusion bodies also demonstrated a positive immunohistochemical reaction after indirect immunohistochemistry for papillomavirus structural antigens. Ultrastructural and/or immunohistochemical evidence of an etiologic agent was not identified in the nonconjunctival lesions examined. Here we describe the gross, histopathologic, ultrastructural, and immunohistochemical findings of a papillomatosis and carcinomatosis syndrome recently identified in the WBB.

A novel virus detected in papillomas and carcinomas of the endangered western barred bandicoot (Perameles bougainville) exhibits genomic features of both the Papillomaviridae and Polyomaviridae

Conservation efforts to prevent the extinction of the endangered western barred bandicoot (Perameles bougainville) are currently hindered by a progressively debilitating cutaneous and mucocutaneous papillomatosis and carcinomatosis syndrome observed in captive and wild populations. In this study, we detected a novel virus, designated the bandicoot papillomatosis carcinomatosis virus type 1 (BPCV1), in lesional tissue from affected western barred bandicoots using multiply primed rolling-circle amplification and PCR with the cutaneotropic papillomavirus primer pairs FAP59/FAP64 and AR-L1F8/AR-L1R9. Sequencing of the BPCV1 genome revealed a novel prototype virus exhibiting genomic properties of both the Papillomaviridae and the Polyomaviridae. Papillomaviral properties included a large genome size ( approximately 7.3 kb) and the presence of open reading frames (ORFs) encoding canonical L1 and L2 structural proteins. The genomic organization in which structural and nonstructural proteins were encoded on different strands of the double-stranded genome and the presence of ORFs encoding the nonstructural proteins large T and small t antigens were, on the other hand, typical polyomaviral features. BPCV1 may represent the first member of a novel virus family, descended from a common ancestor of the papillomaviruses and polyomaviruses recognized today. Alternatively, it may represent the product of ancient recombination between members of these two virus families. The discovery of this virus could have implications for the current taxonomic classification of Papillomaviridae and Polyomaviridae and can provide further insight into the evolution of these ancient virus families.

Complete genomic characterization of a murine papillomavirus isolated from papillomatous lesions of a European harvest mouse (Micromys minutus)

The papillomaviruses form a large group of species-specific pathogens that cause epithelial proliferations in a wide spectrum of animal hosts. Previous reports demonstrated a relatively high frequency of a variety of skin lesions in captive European harvest mice. The Micromys minutus papillomavirus (MmPV) was isolated from one of these lesions found on a captive European harvest mouse in a regional zoo in Chicago. In this study we present the entire genomic sequence of MmPV. The MmPV genome is organized into the seven classical papillomaviral open reading frames. Phylogenetic analysis places MmPV together with a papillomavirus (PV) isolated from a Syrian golden Hamster (HaOPV) in the genus Pipapillomavirus. The similar clustering pattern of the MmPV–HaOPV pair and their rodent hosts support the hypothesis of papillomaviral and host co-phylogenetic descent. The availability of the complete genomic sequence of a mouse PV should allow researchers to use MmPV as a model for PV carcinogenesis.

Flow cytometric quantitation of the protective efficacy of dendritic cell based vaccines in a human papillomavirus type 16 murine challenge model

A murine model for the assessment of protective immunity to human papillomavirus (HPV) type 16, a virus that does not naturally infect mice, is described. In this system, protection was tested following intranasal challenge of mice with a recombinant vaccinia virus expressing both the selected HPV antigen and a beta-galactosidase (beta-gal) reporter. The extent of viral infectivity was determined by measuring beta-gal positive lung cells using flow cytometry. The efficacy of this model to measure protective immunity was evaluated by priming mice with the beta-gal vaccinia virus then challenging the mice with the same virus. Vaccinia primed mice had negligible numbers of beta-gal positive cells in the lung 5 days following viral challenge indicating protection, whereas around 50% of cells were infected in immunologically naive, challenged mice. The protective efficacy of two dendritic cell vaccines for HPV16 was measured in this model. Both vaccines provided some protection to subsequent viral challenge, compared with their controls. Although this protection model was applied to HPV in this study, it may also have broad application to other viruses that do not infect mice naturally.

High frequency and diversity of cutaneous appendageal tumors in organ transplant recipients

BACKGROUND

Recipients of organ transplant who are immunosuppressed are at greatly increased risk of nonmelanoma skin cancers compared with the general population, but their risk of appendageal tumors is unknown.

OBJECTIVE

Our aim was to conduct a systematic examination of cutaneous appendageal tumors arising in recipients of organ transplants compared with individuals who were immunocompetent (ICP).

METHODS

We conducted a retrospective, clinicopathologic analysis of consecutive appendageal tumors arising in 650 recipients of organ transplants and in the general population of approximately 605,000 people served by our institution.

RESULTS

Between 1993 and 1998, 231 appendageal tumors were identified in 211 individuals; 23 tumors were found in 21 of 650 patients undergoing transplant (3%), 10 in individuals with other immunosuppressive conditions, 3 in 2 patients with Muir-Torre syndrome, and 195 in 178 apparently ICP. In addition to the increased frequency of appendageal tumors among recipients of transplants, malignant tumors were overrepresented (43% of transplant tumors vs 4% in ICP; P <.0001) as were tumors of sebaceous origin (30% vs 6%; P <.0001).

CONCLUSIONS

Recipients of organ transplant who are immunosuppressed have a greatly increased risk of cutaneous appendageal tumors compared with apparently ICP. In addition, their tumors are more likely to be malignant and of sebaceous origin.

Healthy skin of many animal species harbors papillomaviruses which are closely related to their human counterparts

Papillomaviruses associated with clinical symptoms have been found in many vertebrate species. In this study, we have used an L1 gene consensus PCR test designed to detect a broad spectrum of human skin papillomaviruses to analyze swab samples from healthy skin of 111 animals belonging to 19 vertebrate species. In eight of the species, papillomavirus DNA was found with the following prevalences: chimpanzees, 9 of 11 samples positive; gorillas, 3 of 4; long-tailed macaques, 14 of 16; spider monkeys, 2 of 2; ruffed lemurs, 1 of 2; cows, 6 of 10; European elks, 4 of 4; aurochs, 1 of 1. In total, 53 new putative animal papillomavirus types were found. The results show that skin papillomaviruses can be detected in healthy skin from many different animal species and are sufficiently related genetically to their human counterparts to be identified by a human skin papillomavirus primer set (FAP59 and FAP64).

Comparison of chemical carcinogen skin tumor induction efficacy in inbred, mutant, and hybrid strains of mice: morphologic variations of induced tumors and absence of a papillomavirus cocarcinogen

Chemical carcinogen induction of skin tumors in mice was investigated to determine (i) if tumor induction efficacy was modified by single gene mutations, (ii) if the histologic types of the tumors varied with these mutations, and (iii) if a novel papillomavirus was involved as a cocarcinogen. A two-stage carcinogenesis protocol (7,12-dimethylbenz[a]anthracene followed by 12-O-tetradecanoylphorbol-13-acetate) was used to induce papillomas in 14 inbred, two hybrid, and 15 other genetic stocks of mice with inherited, single-gene mutations causing skin abnormalities. Histopathological, immunohistochemical, and Southern blot analyses were performed to determine tumor type and to detect the presence of papillomaviruses. The histologic types of tumors induced included early follicular papillomas, mixed papillomas, exophytic papillomas, hyperplastic papillomas, fibropapillomas, squamous cell carcinomas, and mast cell tumors. The efficacy of tumor induction was influenced by strain background, as seen by the clustering of mice into high-, intermediate-, and nonresponding groups. Similarly, tumor induction efficacy was affected by specific mutant genes that cause skin abnormalities. No evidence of papillomavirus structural antigens or viral genomic DNA was identified in 547 induced tumors. These observations indicate that numerous modifier genes but not papillomaviruses are involved in cutaneous chemical carcinogenesis.

Presence of human papilloma virus type 16 DNA sequences in human nonmelanoma skin cancers

The presence of human papillomaviruses (HPV) has been shown to be associated with the development and progression of invasive cancers of the genital tract, skin, and head and neck. In this study we analyzed 37 human nonmelanoma skin cancers (21 squamous cell carcinomas and 16 basal cell carcinomas) for the presence of HPV sequences. The polymerase chain reaction (PCR) was employed using primers designed to amplify DNA encoding the E6-E7 region of HPV types 6b/11, 16, and 18. HPV type 6b/11 and 18 sequences were absent from the DNA of all 37 tumors examined. However, HPV type 16 sequences were detected in four of 21 squamous cell carcinomas (SCC) (19%) and three of 16 basal cell carcinomas (BCC) (19%) as indicated on agarose gel electrophoresis by the presence of a single specific DNA band of predicted length. Furthermore, HPV type 16 sequences were absent in the DNA of normal skin from these seven skin cancer patients. The presence of HPV type 16 sequences in the seven skin tumors was confirmed by dot blot hybridization of PCR-amplified material to 32P-labeled HPV type 16, but not to HPV type 6/11 or 18-specific probes. These data indicate that HPV type 16, but not 6b/11 or 18, is associated with development of some human nonmelanoma skin cancers.

Ultraviolet radiation-induced skin tumors in a South American opossum (Monodelphis domestica)

A total of 19 male and 21 female South American opossums (Monodelphis domestica) were exposed to 250 J/m2 ultraviolet radiation from FS-40 sunlamps (280-400 nm) three times weekly for 70 weeks. The backs of the opossums were shaved as necessary to remove hair. In order to prevent photoreactivation of ultraviolet radiation-induced pyrimidine dimers by the light-dependent photolyase enzyme of the opossum, ultraviolet radiation-exposed opossums were housed under red lights (600-800 nm). The opossum photolyase requires light in the 320-450 nm range for its activity. Twenty-nine control opossums (14 males and 15 females) were irradiated by fluorescent lights with emission spectra primarily in the visible light range (320-700 nm); these control opossums were also housed under red lights, and their backs were also shaved to remove hair. No skin tumors were observed in control opossums, while ultraviolet radiation-exposed opossums developed a variety of hyperplastic and neoplastic skin lesions on the backs and on a single ear. Hyperplastic lesions included foci of epithelial hyperplasia, dermal fibroplasia, and focal proliferation of dermal melanocytes. A total of 20 ultraviolet radiation-exposed opossums (50%) developed skin tumors, and 13 opossums (32.5%) had more than a single tumor. Epithelial tumors included 25 papillomas, four keratoacanthomas, seven carcinomas in situ, three microinvasive squamous cell carcinomas, two invasive squamous cell carcinomas, and a single basal cell tumor. Ten dermal spindle cell tumors also occurred; most of these appeared to be fibrosarcomas. Two benign melanomas and one malignant melanoma were observed.

Immunohistochemical detection of papillomavirus structural antigens in animal hyperplastic and neoplastic epithelial lesions

One hundred and seventy-two hyperplastic and neoplastic epithelial lesions from 8 different mammalian and 1 avian species have been tested with an immunohistochemical technique to detect papillomavirus structural antigens. Selected lesions were diagnosed histologically as papilloma, fibropapilloma, equine sarcoid, squamous cell carcinoma, basalioma, epulis, keratoacanthoma, trichoepithelioma, pilomatrixoma, epidermal inclusion cyst, and hyperkeratotic or acanthotic epidermal lesions. Positive nuclear staining was detected in 14 out of 23 papillomas, 8 out of 32 fibropapillomas and in 1 out of 3 hyperplastic epidermal lesions. Positive samples were found in 5 of 8 mammalian species. Selected samples were also examined by transmission electron microscopy. In 4 samples papillomavirus was seen. In two other samples, negative with immunoperoxidase technique, papovavirus-like particles were observed.

Papillomavirus infection of aged Persian cats

Papillomavirus infection was confirmed in 2 Persian cats with sessile hyperkeratotic skin lesions. Skin lesions were not typical papillomas as found in other species. Papillomavirus were demonstrated in negative stain preparations of homogenized tissue and within nuclei of cells in the stratum granulosum. Papillomavirus group-specific antigens were detected within nuclei corresponding to those containing virions. Attempts to transmit this disease to other cats or propagate the virus in tissue cultures were unsuccessful. A 7.8-kilobase DNA molecule was present in low-stringency Southern blots using a bovine papillomavirus type 1 cloned DNA probe. In reverse Southern blots, the cat papillomavirus hybridized under conditions of low stringency with all papillomavirus genomes tested. Combined with limited restriction endonuclease restriction mapping, the above information indicates that the feline cutaneous papillomavirus is a unique virus type and thus expands the list of hosts known to be infected by papillomaviruses.

Enhancement of u.v.-induced skin carcinogenesis in the hairless mouse by inoculation with cell-free extracts of skin tumours

The presence of papillomaviral-like DNA has been described in ultraviolet light-induced tumours in the skin of the hairless mouse (14). Here we describe the effects of the inoculation of cell-free extracts of ultraviolet light-induced tumours into the scarified skin of normal hairless mice, prior to exposure of the mice to a cumulative carcinogenic dose of ultraviolet light. Extracts from papillomas or squamous cell carcinomas enhanced the susceptibility of the inoculated mice to ultraviolet light-induced tumorigenesis, if the extracts contained papillomaviral DNA sequences detected by cross-hybridization with Mastomys natalensis papillomaviral DNA. The recipient mice developed a greater tumour incidence, tumour yield, tumour diameter and degree of malignancy.