Identification of a Human Natural Killer Cell Lineage-Restricted Progenitor in Fetal and Adult Tissues.

Natural killer (NK) cells are cytotoxic lymphocytes and play a vital role in controlling viral infections and cancer. In contrast to B and T lymphopoiesis where cellular and regulatory pathways have been extensively characterized, the cellular stages of early human NK cell commitment remain poorly understood. Here we demonstrate that a Lin(-)CD34(+)CD38(+)CD123(-)CD45RA(+)CD7(+)CD10(+)CD127(-) population represents a NK lineage-restricted progenitor (NKP) in fetal development, umbilical cord blood, and adult tissues. The newly identified NKP has robust NK cell potential both in vitro and in vivo, generates functionally cytotoxic NK cells, and lacks the ability to produce T cells, B cells, myeloid cells, and innate lymphoid-like cells (ILCs). Our findings identify an early step to human NK cell commitment and provide new insights into the human hematopoietic hierarchy.

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

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.

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.

Altered α-defensin 5 expression in cervical squamocolumnar junction: implication in the formation of a viral/tumour-permissive microenvironment.

Human papillomavirus (HPV) infection, particularly type 16, is causally associated with cancer of the uterine cervix, which mainly develops at the squamocolumnar (SC) junction. The progression of cervical HPV infections into (pre)neoplastic lesions suggests that viral antigens are not adequately recognized by innate immunity or presented to the adaptive immune system. Members of the defensin family have recently been found to inhibit viral and bacterial pathogens, to stimulate the migration of immune cells and to play a role in anticancer responses. In the present study, we focused on the poorly characterized human α-defensin 5 (HD-5) and its possible role in these processes. We showed that HD-5 was able to prevent HPV virion entry into cervical keratinocytes and to influence adaptive immunity. Indeed, this peptide specifically induced the chemoattraction and proliferation of both activated T lymphocytes and immature dendritic cells in a CCR2/CCR6-dependent manner and stimulated the infiltration of these professional antigen-presenting cells in a (pre)neoplastic epithelium transplanted in vivo in immunodeficient mice. No chemotactic effect was observed with plasmacytoid dendritic cells, macrophages or natural killer cells. Proliferative and angiogenic effects of HD-5 were also assessed in vitro and in vivo. However there was a striking regional disparity in expression of HD-5, being prominent in ectocervical, vaginal and vulvar neoplasia, while absent, or nearly so, in the cervical SC junction. Taken together, these results suggest one possible explanation for why the SC junction is uniquely vulnerable to both high-risk HPV infection (via reduced HD-5 expression and viral entry) and progression of neoplasia (via altered cell-mediated immune responses and altered microenvironment).

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-1ß, 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-1ß (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.

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.

Impact of a mutator phenotype on motility and cell adherence in Salmonella Heidelberg.

In this study, we investigated adherence and motility of the hypermutator Salmonella enterica Heidelberg B182 bovine strain related to a 12bp deletion in mutS. This mutator phenotype was associated with increased adherence to epithelial cells and with high expression of fimA as shown by real-time RT-PCR. Motility studies showed that fliC were up-regulated in the B182 strain, while fljA and fljB were down-regulated. In order to determine if mutated mutS is implicated in this genes expression, isogenic strains, derived from a WT strain, containing the 12bp deletion in mutS (Δ12bpmutS) or an inactivated mutS (ΔmutS) were generated. Δ12bpmutS and ΔmutS strains showed a spontaneous mutation rate similar to the environmental strain B182, but exhibited lower adherence capacity and fimA expression. In contrast to the fimbriae genes, in Δ12bpmutS, fliC expression was up-regulated, but fljA and fljB expression were decreased, as in the B182 strain. Only fljB expression was increased in ΔmutS mutants. Taken together, our data suggest that mutS alteration does not influence fimbriae expression but can impact flagella genes.

Local applications of GM-CSF induce the recruitment of immune cells in cervical low-grade squamous intraepithelial lesions.

PROBLEM: Quantitative alterations of antigen-presenting cells (APC) in (pre)neoplastic lesions of the uterine cervix associated with human papillomavirus (HPV) infection suggest a diminished capacity to capture viral antigens and to induce a protective immune response. METHOD OF STUDY: To test whether a cervical application of GM-CSF could restore an immune response against HPV in women with cervical low-grade squamous intraepithelial lesions (LSIL), we performed two clinical trials with 11 healthy women and 15 patients with LSIL. RESULTS: GM-CSF applications were well tolerated in all enrolled women, and no difference in toxicity between the treated and placebo groups was observed during the follow-up (until 30 months). Interestingly, in the GM-CSF treated group, a significant increase of APC and cytotoxic T-lymphocyte infiltration was observed in the cervical biopsies with no change in regulatory T cell numbers. All the HPV16(+) patients exhibited an immune response against HPV16 after GM-CSF applications, as shown by NK and/or T cells producing IFN-gamma whereas no cellular immune response was observed before the treatment. Moreover, the anti-virus-like particles antibody titers also increased after the treatment. CONCLUSION: These encouraging results obtained from a limited number of subjects justify further study on the therapeutic effect of APC in cervical (pre)neoplastic lesions.

Induction of antibody response against hepatitis E virus (HEV) with recombinant human papillomavirus pseudoviruses expressing truncated HEV capsid proteins in mice.

A hepatitis E virus (HEV) vaccine would be valuable to reduce the morbidity and mortality associated with the infection in endemic areas. HEV pseudocapsids and epidermal delivery of HEV ORF2 DNA vaccine by gene-gun have been shown to confer protection against virus challenge in monkeys. Vectorization of a DNA vaccine by virus-like particles is a new immunization approach. We report here the successful immunization of mice with two ORF2 genes encapsidated into human papillomavirus type 31 virus-like particles. The HEV genes ORF2(112-660) and ORF2(112-608) were optimized for expression in mammalian cells and inserted in a baculovirus-derived vector for expression in insect cells. When expressed in Sf21 insect cells, ORF2(112-660) led to the production of irregular 15 nm particles that accumulated in the cytoplasm of the cells, whereas ORF2(112-608) induced the production of 18nm particles that were present in both the cell culture medium and the cell cytoplasm. Anti-HEV immune responses were higher for the 15 nm particles (HEV112-660) than that for to the 18 nm particles (HEV112-608). Delivery into mice of two HEV ORF2 genes via a papillomavirus VLP was very effective in the induction of anti-HEV antibodies. In addition, an effective immune response to human papillomavirus capsids occurred. These engineered pseudoviruses were thus demonstrated to induce immune responses to both hepatitis E virus and human papillomavirus when they were administered to mice intramuscularly.