Propagation of human papillomavirus 16 using a novel adenovirus and cre/loxp mechanism

Abstract

Problem: Human papillomavirus type 16 (HPV16) infection is a major risk factor for the development of squamous cell cancers of the cervix and of the head and neck. A major barrier to understanding the progression from initial infection to cancer has been the lack of in vitro models that allow infection, replication, and persistence of the viral genome as an episome in differentiated epithelial cells. Methods: To overcome this barrier, we designed an adenoviral delivery vector that contained a full HPV16 genome flanked by LoxP homologous recombination sites plus a fluorescent reporter that was expressed only after the HPV genome was excised by Cre recombinase. Results: This system delivered circular HPV16 genomes to cervical epithelial cells and well-differentiated human airway epithelia. Following delivery, the HPV16 genome replicated and persisted as an episome in cervical keratinocytes. These cells developed an immortalized phenotype and a dysplastic epithelial appearance. Moreover, induction of differentiation led to the expression of late genes and production of infectious HPV16 virions. Conclusion: This work provides a novel means of introducing biologically active HPV genomes into epithelial cells, which are normally difficult to transfect. These methods will allow the study of HPV genome replication and gene expression in the earliest stages of HPV genome establishment and may provide a means with which to study non-oncogenic HPV viral types. Significance: Understanding the papillomavirus life cycle may aid in developing novel treatments for HPV-related head and neck diseases. Support: None reported.