The human papillomavirus (HPV) type 16 E7 oncogene is critical to carcinogenesis and highly conserved. Previous studies identified a preponderance of non-synonymous E7 variants amongst HPV16-positive cancer-free controls compared to those with cervical cancer. To investigate the function of E7 variants, we constructed full-length HPV16 E7 genes and tested variants at positions H9R, D21N, N29S, E33K, T56I, D62N, S63F, S63P, T64M, E80K, D81N, P92L, and P92S (found only in controls); D14E, N29H (CIN2), and P6L, H51N, R77S (CIN3). We determined the steady-state level of cytoplasmic and nuclear HPV16 E7 protein. All variants from the controls showed a reduced level of steady-state E7 protein, with 7/13 variants having deficient protein levels. In contrast, 2/3 variants from the CIN3 precancer group had near-normal E7 levels. We assayed the activity of representative variants in stably transfected NIH3T3 cells. The H9R, E33K, P92L, and P92S variants found in control subjects had lower transforming activity than D14E and N29H variants (CIN2); and the R77S (CIN3) had activity only slightly reduced from wildtype E7. In addition, R77S and WT E7 caused increased migration of NIH3T3 cells in a wound-healing assay as compared with H9R, E33K, P92L, and P92S (controls) and D14E (CIN2). These data provide evidence that the E7 variants found in HPV16-positive cancer-free women are partially defective for transformation and cell migration further demonstrating the importance of fully active E7 in clinical cancer development.

High incidence of epithelial malignancies in HIV-1 infection is associated with co-infection with oncogenic viruses, such as high-risk human papillomaviruses (HR HPVs), most often HPV16. A collaboration between HIV-1 and HR HPVs in the malignant transformation of epithelial cells exposed to both viruses have long been anticipated. Here, we delineated the effects on in vitro and in vivo properties of HPV16-infected cervical cancer cells of HIV-1 reverse transcriptase. Epidermoid carcinoma Ca Ski cells were made to express RT of HIV-1 clade A (RT_A) or Green Fluorescence Protein (GFP) by lentiviral transduction, subclones with one or six copies of RT_A and six copies of GFP DNA were generated. Expression by subclones of GFP was assessed by flow cytometry, and of RT_A, by Western blotting. Cells were assessed for the levels of mRNA of the RT_A, E6 and its isoforms, and cellular factors characterizing oxidative stress, and EMT by the real-time PCR. Parameters of glycolysis and mitochondrial respiration were assessed by Seahorse technology. Subclones were surveyed for the changes in cell cycle, doubling time, migration capacity, clonogenic activity and for the capacity to form tumors in nude mice. Ca Ski RT_A produced 20-55 fg of RT_A per cell. Expression of RT_A caused a proportional increase in the expression of E6*I isoform. In Ca Ski, RT_A suppressed mitochondrial respiration and oxygen consumption, and increased glycolysis. Compared to parental cells and GFP control, transcription in Ca Ski RT_A of epithelial (E-CADHERIN) state marker was increased, and of mesenchymal (VIMENTIN) decreased, indicating acquisition by cells of the hybrid epithelial/mesenchymal (E/M) phenotype. While Ca Ski GFP and Ca Ski RT_A with one gene insert had reduced migration rate, decreased clonogenic activity in vitro, and diminished capacity to form tumors in nude mice, increase in RT_A copicity/expression mitigated these effects. Altogether, expression of HIV-1 RT_A gave Ca Ski cells the plasticity required to overcome negative effects of lentiviral transduction and potentially increased their tumorigenicity.

Persistent human papillomavirus (HPV) infection is responsible for practically all cervical and a high proportion of anogenital and oropharyngeal cancers. Therapeutic HPV vaccines in clinical development show great promise in improving outcomes for patients who mount an anti-HPV T cell response, but far from all patients elicit a sufficient immunological response. This witnesses a translational gap between animal models and human patients. Here, we investigated the potential of a new assay consisting of co-culturing vaccine-transduced dendritic cells (DCs) with syngeneic healthy human peripheral blood mononuclear cells (PBMCs) to mimic a human in vivo immunization. This new promising human ex vivo PBMC assay was evaluated using an innovative therapeutic adenovirus (Adv)-based HPV vaccine encoding the E1, E2, E6, and E7 HPV16 genes. This new method allowed us to show that vaccine-transduced DCs yielded functional effector T cells and unveiled information on immunohierarchy showing E1-specific T cell immunodominance over time. We suggest that this assay can be a valuable translational tool to complement the known animal models, not only for HPV therapeutic vaccines, and supports the use of E1 as an immunotherapeutic target. Nevertheless, the findings reported here need to be validated in a larger number of donors, and preferably in patient samples.

Beginning in 2012, our understanding of human papillomavirus (HPV) subcellular trafficking has undergone a drastic paradigm shift. Work from multiple laboratories has revealed that HPV has evolved a unique means to deliver its viral genome (vDNA) to the cell nucleus, relying on a myriad of host cell proteins and processes. The major breakthrough finding from these recent endeavors was the realization of L2-dependent utilization of cellular sorting factors for the retrograde transport of vDNA away from degradative endo/lysosomal compartments to the Golgi, prior to mitosis-dependent nuclear accumulation of L2/vDNA. An overview of current models of HPV entry, subcellular trafficking, and the role of L2 during initial infection is provided below, highlighting unresolved questions and gaps in knowledge.