Steven C. Fausch

Human Dendritic Cells Are Activated by Chimeric Human Papillomavirus Type-16 Virus-Like Particles and Induce Epitope-Specific Human T Cell Responses In Vitro

Human papillomavirus (HPV)-derived chimeric virus-like particles (VLPs) are the leading candidate vaccine for the treatment or prevention of cervical cancer in humans. Dendritic cells (DCs) are the most potent inducers of immune responses and here we show for the first time evidence for binding of chimeric HPV-16 VLPs to human peripheral blood-derived DCs. Incubation of immature human DCs with VLPs for 48 h induced a significant up-regulation of the CD80 and CD83 molecules as well as secretion of IL-12. Confocal microscopy analysis revealed that cell surface-bound chimeric VLPs were taken up by DCs. Moreover, DCs loaded with chimeric HPV-16 L1L2-E7 VLPs induced an HLA-*0201-restricted human T cell response in vitro specific for E7-derived peptides. These results clearly demonstrate that immature human DCs are fully activated by chimeric HPV-16 VLPs and subsequently are capable of inducing endogenously processed epitope-specific human T cell responses in vitro. Overall, these findings could explain the high immunogenicity and efficiency of VLPs as vaccines.

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.

Cervical cancer vaccines: emerging concepts and developments.

Certain human cancers are linked to infection by oncogenic viruses that are able to cause transformation of the normal host cell into a cancerous cell. Human papillomavirus (HPV) DNA and expression of viral transforming proteins are found in virtually all cervical cancer cells, indicating an important role of this virus in the pathogenesis of the disease. Evidence exists that the immune response to cancer cells can play a major role in determining the outcome of disease. The fact that HPV is a necessary cause for cervical cancer provides a clear opportunity to develop a therapeutic vaccine against the virus to treat patients with cervical cancer at its early and late stages. Development of a prophylactic vaccine for HPV would also reduce the incidence of cervical neoplasias by preventing virus infection. Various candidate HPV vaccines are being developed and tested in animal models and/or in human clinical trials. These HPV vaccines, both preventive and therapeutic, are the subjects of this review. J. Cell. Physiol. 186:169–182, 2001.

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.

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.

Uptake of Human Papillomavirus Virus-Like Particles by Dendritic Cells Is Mediated by Fcγ 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 FcγRIII, and immature dendritic cells (DC) become activated after incubation with HPV VLP; however, it is unclear whether FcγR on DC are involved. In mice, FcγRII and FcγRIII are homologous and bind similar ligands. In this study, we show that binding and uptake of VLP by DC from FcγRII, FcγRIII, and FcγRII/III-deficient mice are reduced by up to 50% compared with wild-type mice. Additionally, maturation of murine DC from FcγRII/III-deficient mice by VLP is also reduced, indicating that DC maturation, and thus Ag presentation, is diminished in the absence of expression of FcγR. To investigate the in vivo contribution of FcγR in the induction of cellular immunity, FcγR 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-γ ELISPOT, and cytotoxicity assays. All readouts indicated that the frequency of E7-specific CD4+ and CD8+ T cells induced in all FcγR-deficient mice after immunization with cVLP was significantly diminished. Based on these results, we propose that the low-affinity FcγR 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.

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.

Targeting Viral Antigens for the Treatment of Malignancies

Viruses implicated in the development of human cancer include hepatitis B (HBV) and hepatitis C (HCV) viruses, human papilloma virus (HPV), Epstein-Barr virus (EBV), human T-cell lymphoma virus, and human herpes virus 8. Together they contribute significantly to the total incidence of cancer worldwide. Current work in each of these virus systems seeks to understand the mechanisms of viral action and identify strategies of immune intervention to combat viral infection and subsequent transformation. It is thought that oncogenic proliferation may be instigated by the presence and expression of viral oncogenes, which may be integrated into the host genome. Critical viral genes may also interfere with host genes, resulting in the activation of cellular proto-oncogenes and/or the inactivation of anti-oncogenes and their products. Targeting such viral proteins through various vaccination strategies offers both therapeutic and prophylactic strategies against viral induced malignancies.