A novel lineage-tracing mouse model for studying early MmuPV1 infections

Abstract

Human papillomaviruses are DNA viruses that ubiquitously infect humans and have been associated with hyperproliferative lesions. The recently discovered mouse specific papillomavirus (MmuPV1) provides the opportunity to study papillomavirus infections in vivo in the context of a common laboratory mouse model (Mus musculus). To date, a major challenge in the field has been the lack of tools to identify, observe, and characterize individually the papillomavirus hosting cells and also trace the progeny of these cells over time. Here, we present the successful generation of an in vivo lineage-tracing model of MmuPV1-harboring cells and their progeny by means of genetic reporter activation. Following the validation of the system both in vitro and in vivo, we used it to provide a proof-of-concept of its utility. Using flow-cytometry analysis, we observed increased proliferation dynamics and decreased MHC-I cell surface expression in MmuPV1-treated tissues which could have implications in tissue regenerative capacity and ability to clear the virus. This model is a novel tool to study the biology of the MmuPV1 host-pathogen interactions.

Protocol for in vivo lineage tracing of the mouse-papillomavirus-type 1-infected cells in mice

“…We previously validated that the constructed MmuPV1-lox-Cre-lox plasmid can indeed lead to reporter activation, Cre-excision, and MmuPV1 genome recircularization both in vivo and in vitro . 1 However, we previously were not able to observe any wart development at the later time points of the infection with the plasmid and we were also not able to re-infect a second set of mice from the swab samples of the tail skins of the first set of mice (not shown here). These observations indicate to a possibility that the resulting virions in vivo from the generated plasmid might not be generating enough infectious viral particles.…”

“…There is a restriction to the availability of lox-Cre-lox plasmid which is a unique reagent generated for this study and is not available commercially. This plasmid can either be generated by following the instructions provided previously elsewhere 1 and briefly mentioned here or can be accessed via contacting to the lead contact listed here.…”

Inhibition of Cellular MEK/ERK Signaling Suppresses Murine Papillomavirus Type 1 Replicative Activities and Promotes Tumor Regression

“…Infection with MmuPV1 or oncogenic HPVs leads to increased expression of Ki67, a basal cell proliferation marker [55][56][57][58] and Sundberg et al showed similar staining patterns between Ki67 and K5 in MmuPV1-induced tail tumors [55]. Furthermore, MEK inhibition is known to reduce Ki67 staining in epithelial tumors [59,60].…”

The human papillomavirus late life cycle and links to keratinocyte differentiation

“…Importantly, the tractability of a murine model offers an approach to lineage tracing of MmuPV1 infected cells, including observation of late events and spatial analysis of host-pathogen interactions, which could transform our understanding of HPV late gene expression. 189 Therapeutic strategies against HPV infection would involve inhibiting the viral life cycle and, for high-risk types, targeting persistent infection by interfering with increased viral oncoproteins expression responsible for cancer progression. 190 A strategy to reveal HPV infection in the lower epithelial layers would involve induction of capsid protein synthesis as this would stimulate an immune response against infection.…”

“…However, murine epithelia generally display fewer cell layers than human epithelia 188 and MmuPV1 does not express an E5 protein, which is important for late gene expression 44,45 meaning that late events in the MmuPV1 184 life cycle may exhibit significant differences to that of HPVs. Importantly, the tractability of a murine model offers an approach to lineage tracing of MmuPV1 infected cells, including observation of late events and spatial analysis of host‐pathogen interactions, which could transform our understanding of HPV late gene expression 189 …”