Uptake of human papillomavirus virus-like particles by dendritic cells is mediated by Fcgamma receptors and contributes to acquisition of T cell immunity.

Chimeric human papillomavirus virus-like particles (HPV cVLP) are immunogens able to elicit potent CTL responses in mice against HPV16-transformed tumors; however, the mechanism of T cell priming has remained elusive. HPV VLP bind to human MHC class II-positive APCs through interaction with FcgammaRIII, and immature dendritic cells (DC) become activated after incubation with HPV VLP; however, it is unclear whether FcgammaR on DC are involved. In mice, FcgammaRII and FcgammaRIII are homologous and bind similar ligands. In this study, we show that binding and uptake of VLP by DC from FcgammaRII, FcgammaRIII, and FcgammaRII/III-deficient mice are reduced by up to 50% compared with wild-type mice. Additionally, maturation of murine DC from FcgammaRII/III-deficient mice by VLP is also reduced, indicating that DC maturation, and thus Ag presentation, is diminished in the absence of expression of FcgammaR. To investigate the in vivo contribution of FcgammaR in the induction of cellular immunity, FcgammaR single- and double-knockout mice were immunized with HPV16 L1/L2-E7 cVLP, and the frequency of E7-specific T cells was analyzed by tetramer binding, IFN-gamma ELISPOT, and cytotoxicity assays. All readouts indicated that the frequency of E7-specific CD4(+) and CD8(+) T cells induced in all FcgammaR-deficient mice after immunization with cVLP was significantly diminished. Based on these results, we propose that the low-affinity FcgammaR contribute to the high immunogenicity of HPV VLP during T cell priming by targeting VLP to DC and inducing a maturation state of the DC that facilitates Ag presentation to and activation of naive T cells.

Human papillomavirus can escape immune recognition through Langerhans cell phosphoinositide 3-kinase activation.

Human papillomavirus (HPV) infection of cervical epithelium is linked to the generation of cervical cancer. Although most women infected with HPV clear their lesions, the long latency period from infection to resolution indicates that HPV evolved immune escape mechanisms. Dendritic cells, which are targeted by vaccination procedures, incubated with HPV virus-like particles induce an HPV-specific immune response. Langerhans cells (LC), which are located at the sites of primary infection, do not induce a response implicating the targeting of LC as an immune escape mechanism used by HPV. LC incubated with HPV virus-like particles up-regulate the phosphoinositide 3-kinase (PI3-K) pathway and down-regulate MAPK pathways. With the inhibition of PI3-K and incubation with HPV virus-like particles, LC initiate a potent HPV-specific response. PI3-K activation in LC defines a novel escape mechanism used by HPV, and PI3-K inhibition may serve as an effective clinical target to enhance HPV immunity.

Heterologous papillomavirus virus-like particles and human papillomavirus virus-like particle immune complexes activate human Langerhans cells.

Chimeric human papillomavirus virus-like particles (HPV cVLP) are currently being explored as a therapeutic vaccination strategy against cervical cancer. HPV cVLP are being explored as a result of their interaction with and activation of dendritic cells, a potent antigen-presenting cell. However Langerhans cells, another type of antigen-presenting cell, can interact with HPV cVLP especially during mucosal routes of vaccine administration. Langerhans cells are not activated by HPV cVLP, utilize a different endocytosis mechanism than DC for HPV cVLP uptake, do not initiate an immune response toward HPV cVLP derived antigens, and are potentially immunosuppressive after interaction with HPV cVLP. Taken together, these findings indicate that the overall effectiveness of HPV cVLP as a therapeutic vaccine may be reduced. Bovine papillomavirus (BPV) VLP, cotton-tail rabbit papillomavirus (CRPV) VLP, and HPV VLP immune complexes (IC), which are taken up via similar endocytosis mechanisms in DC and LC, activate both cell types. DC and LC incubated with these VLP upregulate surface activation markers and increase secretion of IL-12 p70. The activated cells are then able to initiate an immune response against chimeric VLP-derived antigens. These data indicate that other therapeutic vaccination strategies based on using chimeric BPV VLP, chimeric CRPV VLP, or chimeric HPV VLP immune complexes may be more effective in generating an immune response against HPV-induced diseases such as cervical cancer.

Peptide-based vaccines for cancer immunotherapy.

One approach in the immunotherapy of cancer patients involves vaccination with peptides derived from tumour-associated antigens specifically designed to associate with T cells in the context of major histocompatibility complex (MHC) class I or II molecules. Several clinical trials in different tumour types have been conducted utilising this vaccination strategy. The majority of trials indicate that peptide vaccination has few toxicities associated with its administration, but disparities exist between in vitro and clinical responses. However, this represents an evolving field and, thus, it is difficult to draw firm conclusions concerning the efficacy of peptide-based vaccines for cancer immunotherapy. Improvements to peptide vaccination, including the addition of various adjuvants, the utilisation of peptide-pulsed dendritic cells, multipeptide vaccinations, the addition of helper peptides and peptide delivery through the use of mini-genes, are encouraging and serve as important guides for future research.

Differential uptake and cross-presentation of human papillomavirus virus-like particles by dendritic cells and Langerhans cells.

A causal link between cervical cancer and high-risk human papillomaviruses has been established. The virus infects basal cells of the mucosa, where Langerhans cells are the resident antigen-presenting cells. Langerhans cells and dendritic cells, which are targeted by vaccination, internalize similar amounts of human papillomavirus virus-like particles (VLPs), albeit through different uptake mechanisms. VLP uptake by dendritic cells results in activation and cross-presentation of MHC class I-restricted peptides with costimulation to T cells. Conversely, VLP uptake by Langerhans cells leads to cross-presentation in the absence of costimulation. Efficient VLP cross-presentation by Langerhans cells with costimulation can be achieved by addition of CD40 ligand. The lack of a protective immune response after viral contact with Langerhans cells may explain why some women fail to mount an immune response against the virus or why the immune responses that do develop may allow the virus to persist. Because VLPs are currently being tested as a vaccine against cervical cancer, our data are very topical and have implications for optimal vaccination strategies against this disease.

Cervical cancer vaccines: recent advances in HPV research.

Carcinomas of the anogenital tract, particularly cancer of the cervix, account for almost 12% of all cancers in women, and so represent the second most frequent gynecological malignancy in the world (48). It is well established that chronic infection of cervical epithelium by human papillomaviruses (HPV) is necessary for the development of cervical cancer. In fact, HPV DNA has been demonstrated in more than 99.7% of cervical cancer biopsy specimens, with high-risk HPV16 and HPV18 sequences being most prevalent (45,73). Therefore, an effective vaccine that would mount an immune response against HPV-related proteins might contribute to the prevention or elimination of HPV expressing lesions. This review will concentrate on the most recent advances in vaccine-mediated prevention and immunotherapy of HPV-induced cervical cancer, including presentations from the 20(th) International HPV Conference held in October 2002 in Paris.

HPV protein/peptide vaccines: from animal models to clinical trials.

Human Papillomaviruses are viruses that infect the epithelial layers of the oral, rectal, vaginal, and cervical mucosa. There is a causal link between the development of cervical cancer and some other cancers and high-risk human papillomavirus infection (1, 2). Currently there is no prophylactic or therapeutic vaccine available against human papillomavirus infection and its associated lesions. In addition, there exists a high degree of species specificity associated with papillomavirus infection precluding human papillomavirus's use in animal models. Therefore, multiple researchers have utilized a variety of homologous animal papillomaviruses and animal model systems for the development of vaccine strategies against papillomaviruses. The goal of their efforts is to identify vaccine strategies that are efficacious in the animal model systems and translate these strategies into human clinical trials against human papillomavirus. The development of such a vaccine would ultimately result in a reduction in the incidence of cervical cancer and some other HPV-linked cancers and may provide therapy for individuals harboring papillomavirus lesions. This review discusses the advances in papillomavirus vaccinology using proteins/peptides, from the work completed in the animal models to the results of the early human clinical trials.

Human papillomavirus virus-like particles do not activate Langerhans cells: a possible immune escape mechanism used by human papillomaviruses.

High-risk human papillomaviruses are linked to several malignancies including cervical cancer. Because human papillomavirus-infected women do not always mount protective antiviral immunity, we explored the interaction of human papillomavirus with Langerhans cells, which would be the first APCs the virus comes into contact with during infection. We determined that dendritic cells, normally targeted by vaccination procedures and Langerhans cells, normally targeted by the natural virus equally internalize human papillomavirus virus-like particles. However, in contrast to dendritic cells, Langerhans cells are not activated by human papillomavirus virus-like particles, illustrated by the lack of: up-regulating activation markers, secreting IL-12, stimulating T cells in an MLR, inducing human papillomavirus-specific immunity, and migrating from epidermal tissue. Langerhans cells, like dendritic cells, can display all of these characteristics when stimulated by proinflammatory agents. These data may define an intriguing immune escape mechanism used by human papillomavirus and form the basis for designing optimal vaccination strategies.