Insights into the Role of Innate Immunity in Cervicovaginal Papillomavirus Infection from Studies Using Gene-Deficient Mice.

We demonstrate that female C57BL/6J mice are susceptible to a transient lower genital tract infection with MmuPV1 mouse papillomavirus and display focal histopathological abnormalities resembling those of human papillomavirus (HPV) infection. We took advantage of strains of genetically deficient mice to study in vivo the role of innate immune signaling in the control of papillomavirus. At 4 months, we sacrificed MmuPV1-infected mice and measured viral 757/3139 spliced transcripts by TaqMan reverse transcription-PCR (RT-PCR), localization of infection by RNAscope in situ hybridization, and histopathological abnormities by hematoxylin and eosin (H&E) staining. Among mice deficient in receptors for pathogen-associated molecular patterns, MyD88-/- and STING-/- mice had 1,350 and 80 copies of spliced transcripts/µg RNA, respectively, while no viral expression was detected in MAVS-/- and Ripk2-/- mice. Mice deficient in an adaptor molecule, STAT1-/-, for interferon signaling had 46,000 copies/µg RNA. Among mice with targeted deficiencies in the inflammatory response, interleukin-1 receptor knockout (IL-1R-/-) and caspase-1-/- mice had 350 and 30 copies/µg RNA, respectively. Among mice deficient in chemokine receptors, CCR6-/- mice had 120 copies/µg RNA, while CXCR2-/- and CXCR3-/- mice were negative. RNAscope confirmed focal infection in MyD88-/-, STAT1-/-, and CCR6-/- mice but was negative for other gene-deficient mice. Histological abnormalities were seen only in the latter mice. Our findings and the literature support a working model of innate immunity to papillomaviruses involving the activation of a MyD88-dependent pathway and IL-1 receptor signaling, control of viral replication by interferon-stimulated genes, and clearance of virus-transformed dysplastic cells by the action of the CCR6/CCL20 axis.IMPORTANCE Papillomaviruses infect stratified squamous epithelia, and the viral life cycle is linked to epithelial differentiation. Additionally, changes occur in viral and host gene expression, and immune cells are activated to modulate the infectious process. In vitro studies with keratinocytes cannot fully model the complex viral and host responses and do not reflect the contribution of local and migrating immune cells. We show that female C57BL/6J mice are susceptible to a transient papillomavirus cervicovaginal infection, and mice deficient in select genes involved in innate immune responses are susceptible to persistent infection with variable manifestations of histopathological abnormalities. The results of our studies support a working model of innate immunity to papillomaviruses, and the model provides a framework for more in-depth studies. A better understanding of mechanisms of early viral clearance and the development of approaches to induce clearance will be important for cancer prevention and the treatment of HPV-related diseases.

Infectivity of murine papillomavirus in the surgical byproducts of treated tail warts.

OBJECTIVES/HYPOTHESIS: Human papillomavirus (HPV) is a highly stable DNA virus that causes disease in human organ systems, including the larynx and oropharynx. The treatment of HPV-associated diseases with scalpels, lasers, and other surgical instruments has the potential to release infectious particles, placing healthcare workers at risk. The objectives of this study were to create a reproducible in vivo animal model of papillomavirus infectivity and to compare the infectivity of byproducts of surgically treated mouse papillomavirus (MmuPV1) warts. STUDY DESIGN: Animal study. METHODS: Nude laboratory mice (Mus musculus) with established MmuPV1 tail warts were treated with scalpel excision, potassium titanyl phosphate (KTP) laser ablation, and coblator treatment. Uninfected nude mice were challenged with surgical byproducts, including ablated and heated tissue, and surgical smoke products. The incidence and time course of the appearance of warts was recorded. RESULTS: There was rapid transmission of virus in mice challenged with scalpel-treated warts, with 50% penetrance of infection at day 13 and 100% at day 32. For KTP-treated warts, there was the slower development of infection (50% by day 35) but 100% penetrance by day 52. Coblator-treated tissue reached 50% penetrance at day 59 and a maximum of 73% penetrance. Smoke plume captured during treatment with the KTP laser and coblator was highly infectious, as was the material captured in a laser filter. CONCLUSIONS: MmuPV1 remains infectious in all modes of surgically treated tissue, and the smoke plume is capable of transmitting infection. Healthcare workers should use appropriate precautions to lower their risk of infection when treating papillomavirus-associated diseases. LEVEL OF EVIDENCE: NA Laryngoscope, 130:712-717, 2020.