Virginie Renoux

Mechanisms of cell entry by human papillomaviruses: an overview

As the primary etiological agents of cervical cancer, human papillomaviruses (HPVs) must deliver their genetic material into the nucleus of the target cell. The viral capsid has evolved to fulfil various roles that are critical to establish viral infection. The particle interacts with the cell surface via interaction of the major capsid protein, L1, with heparan sulfate proteoglycans. Moreover, accumulating evidence suggests the involvement of a secondary receptor and a possible role for the minor capsid protein, L2, in cell surface interactions.The entry of HPV in vitro is initiated by binding to a cell surface receptor in contrast to the in vivo situation where the basement membrane has recently been identified as the primary site of virus binding. Binding of HPV triggers conformational changes, which affect both capsid proteins L1 and L2, and such changes are a prerequisite for interaction with the elusive uptake receptor. Most HPV types that have been examined, appear to enter the cell via a clathrin-dependent endocytic mechanism, although many data are inconclusive and inconsistent. Furthermore, the productive entry of HPV is a process that occurs slowly and asynchronously and it is characterised by an unusually extended residence on the cell surface.Despite the significant advances and the emergence of a general picture of the infectious HPV entry pathway, many details remain to be clarified. The impressive technological progress in HPV virion analysis achieved over the past decade, in addition to the improvements in general methodologies for studying viral infections, provide reasons to be optimistic about further advancement of this field.This mini review is intended to provide a concise overview of the literature in HPV virion/host cell interactions and the consequences for endocytosis.

Natural killer cells: role in local tumor growth and metastasis

Historically, the name of natural killer (NK) cells came from their natural ability to kill tumor cells in vitro. From the 1970s to date, accumulating data highlighted the importance of NK cells in host immune response against cancer and in therapy-induced antitumor response. The recognition and the lysis of tumor cells by NK cells are regulated by a complex balance of inhibitory and activating signals. This review summarizes NK cell mechanisms to kill cancer cells, their role in host immune responses against tumor growth or metastasis, and their implications in antitumor immunotherapies via cytokines, antibodies, or in combination with other therapies. The regulatory role of NK cells in autoimmunity is also discussed.

Proinflammatory Cytokines Induce Bronchial Hyperplasia and Squamous Metaplasia in Smokers: Implications for chronic obstructive pulmonary disease therapy.

Tracheobronchial squamous metaplasia is common in smokers, and is associated with both airway obstruction in chronic obstructive pulmonary disease (COPD) and increased risk of lung cancer. Although this reversible epithelial replacement is almost always observed in association with chronic inflammation, the role of inflammatory mediators in the pathogenesis of squamous metaplasia remains unclear. In the present study, we investigated the implication of cigarette smoke-mediated proinflammatory cytokine up-regulation in the development and treatment of tracheobronchial epithelial hyperplasia and squamous metaplasia. Using immunohistological techniques, we showed a higher epithelial expression of TNF-α, IL-1β, and IL-6, as well as an activation of NF-κB and activator protein-1/mitogen-activated protein kinase signaling pathways in the respiratory tract of smoking patients, compared with the normal ciliated epithelium of nonsmoking patients. In addition, we demonstrated that these signaling pathways strongly influence the proliferation and differentiation state of in vitro-generated normal human airway epithelial basal cells. Finally, we exposed mice to cigarette smoke for 16 weeks, and demonstrated that anti-TNF-α (etanercept), anti-IL-1β (anakinra), and/or anti-IL-6R (tocilizumab) therapies significantly reduced epithelial hyperplasia and the development of squamous metaplasia. These data highlight the importance of soluble inflammatory mediators in the pathogenesis of tracheobronchial squamous metaplasia. Therefore, the administration of proinflammatory cytokine antagonists may have clinical applications in the management of patients with COPD.

Human papillomavirus entry into NK cells requires CD16 expression and triggers cytotoxic activity and cytokine secretion

Human papillomavirus (HPV) infections account for more than 50% of infection‐linked cancers in women worldwide. The immune system controls, at least partially, viral infection and around 90% of HPV‐infected women clear the virus within two years. However, it remains unclear which immune cells are implicated in this process and no study has evaluated the direct interaction between HPVs and NK cells, a key player in host resistance to viruses and tumors. We demonstrated an NK‐cell infiltration in HPV‐associated preneoplastic cervical lesions. Since HPVs cannot grow in vitro, virus‐like particles (VLPs) were used as a model for studying the NK‐cell response against the virus. Interestingly, NK cells displayed higher cytotoxic activity and cytokine production (TNF‐α and IFN‐γ) in the presence of HPV‐VLPs. Using flow cytometry and microscopy, we observed that NK‐cell stimulation was linked to rapid VLP entry into these cells by macropinocytosis. Using CD16+ and CD16− NK‐cell lines and a CD16‐blocking antibody, we demonstrated that CD16 is necessary for HPV–VLP internalization, as well as for degranulation and cytokine production. Thus, we show for the first time that NK cells interact with HPVs and can participate in the immune response against HPV‐induced lesions.

Natural killer and dendritic cells collaborate in the immune response induced by the vaccine against uterine cervical cancer

Virus‐like particles (VLPs) of human papillomavirus (HPV) are used as a vaccine against HPV‐induced cancer, and recently we have shown that these VLPs are able to activate natural killer (NK) cells. Since NK cells collaborate with dendritic cells (DCs) to induce an immune response against viral infections and tumors, we studied the impact of this crosstalk in the context of HPV vaccination. NK cells in the presence of HPV‐VLPs enhanced DC‐maturation as shown by an upregulation of CD86 and HLA‐DR and an increased production of IL‐12p70, but not of the immunosuppressive cytokine IL‐10. This activation was bidirectional. Indeed, in the presence of HPV‐VLPs, DCs further activated NK cells by inducing the upregulation of cell surface activation markers (CD69 and HLA‐DR). The function of NK cells was also improved as shown by an increase in IFN‐γ secretion and cytotoxic activity against an HPV+ cell line. This crosstalk between NK cells and DCs needed CD40 interaction and IL‐12p70 secretion, whereas NKG2D was not implicated. Our results provide insight into how VLPs interact with innate immune cells and how NK cells and DCs play a role in the immune response induced by this vaccine agent.

Local Applications of GM-CSF Induce the Recruitment of Immune Cells in Cervical Low-Grade Squamous Intraepithelial Lesions

Citation Hubert P, Doyen J, Capelle X, Arafa M, Renoux V, Bisig B, Seidel L, Evrard B, Bousarghin L, Gerday C, Boniver J, Foidart J‐M, Delvenne P, Jacobs N. Local applications of GM‐CSF induce the recruitment of immune cells in cervical low‐grade squamous intraepithelial lesions. Am J Reprod Immunol 2010; 64: 126–136

Human papillomavirus oncoproteins induce a reorganization of epithelial-associated γδ T cells promoting tumor formation

Significance Of all tumor-infiltrating leukocytes, T cells bearing γδ T-cell receptors have been associated with the most favorable prognosis. However, we show here, in a mouse model of carcinogenesis induced by human papillomavirus (HPV) oncoproteins, that γδ T cells promoted the development of HPV-induced lesions. Indeed, HPV-oncoprotein expression induced an infiltration of γδ T cells producing IL-17A, a proangiogenic cytokine, and decreased density of antitumor Vγ5+ γδ T subsets. Supporting the clinical relevance of our observations, IL-17A+ γδ T cells were detected in human cervical cancer, where HPV oncoproteins are highly expressed, but not in less advanced cervical lesions. These results support the notion that viral oncoproteins can induce a switch from antitumoral to protumoral γδ T subsets in solid tumors. It has been shown that γδ T cells protect against the formation of squamous cell carcinoma (SCC) in several models. However, the role of γδ T cells in human papillomavirus (HPV)-associated uterine cervical SCC, the third-leading cause of death by cancer in women, is unknown. Here, we investigated the impact of γδ T cells in a transgenic mouse model of carcinogenesis induced by HPV16 oncoproteins. Surprisingly, γδ T cells promoted the development of HPV16 oncoprotein-induced lesions. HPV16 oncoproteins induced a decrease in epidermal Skint1 expression and the associated antitumor Vγ5+ γδ T cells, which were replaced by γδ T-cell subsets (mainly Vγ6+ γδlowCCR2+CCR6−) actively producing IL-17A. Consistent with a proangiogenic role, γδ T cells promoted the formation of blood vessels in the dermis underlying the HPV-induced lesions. In human cervical biopsies, IL-17A+ γδ T cells could only be observed at the cancer stage (SCC), where HPV oncoproteins are highly expressed, supporting the clinical relevance of our observations in mice. Overall, our results suggest that HPV16 oncoproteins induce a reorganization of the local epithelial-associated γδ T-cell subpopulations, thereby promoting angiogenesis and cancer development.