Beta HPV38 oncoproteins act with a hit-and-run mechanism in ultraviolet radiation-induced skin carcinogenesis in mice.

Cutaneous beta human papillomavirus (HPV) types are suspected to be involved, together with ultraviolet (UV) radiation, in the development of non-melanoma skin cancer (NMSC). Studies in in vitro and in vivo experimental models have highlighted the transforming properties of beta HPV E6 and E7 oncoproteins. However, epidemiological findings indicate that beta HPV types may be required only at an initial stage of carcinogenesis, and may become dispensable after full establishment of NMSC. Here, we further investigate the potential role of beta HPVs in NMSC using a Cre-loxP-based transgenic (Tg) mouse model that expresses beta HPV38 E6 and E7 oncogenes in the basal layer of the skin epidermis and is highly susceptible to UV-induced carcinogenesis. Using whole-exome sequencing, we show that, in contrast to WT animals, when exposed to chronic UV irradiation K14 HPV38 E6/E7 Tg mice accumulate a large number of UV-induced DNA mutations, which increase proportionally with the severity of the skin lesions. The mutation pattern detected in the Tg skin lesions closely resembles that detected in human NMSC, with the highest mutation rate in p53 and Notch genes. Using the Cre-lox recombination system, we observed that deletion of the viral oncogenes after development of UV-induced skin lesions did not affect the tumour growth. Together, these findings support the concept that beta HPV types act only at an initial stage of carcinogenesis, by potentiating the deleterious effects of UV radiation.

Correction: E6 and E7 from Beta Hpv38 Cooperate with Ultraviolet Light in the Development of Actinic Keratosis-Like Lesions and Squamous Cell Carcinoma in Mice.

[This corrects the article DOI: 10.1371/journal.ppat.1002125.].

HPV16 RNA patterns defined by novel high-throughput RT-qPCR as triage marker in HPV-based cervical cancer precursor screening.

OBJECTIVE: Cervical cancer precursor screening by HPV testing has a low positive predictive value for advanced lesion. HPV16 RNA patterns characteristic for HPV16-transformed cells but based on laborious, cost-intensive singleplex NASBA reactions promised high value in triaging HPV16 DNA-positive women. METHODS: We developed two high-throughput reverse transcriptase quantitative (RT-q) PCR assays for the HPV16 transcripts E6*I, E1^E4 and E1C and the cellular transcript ubiquitin C and analysed RNA of 158 singly HPV16 DNA-positive cervical cell samples archived in PreservCyt buffer for the presence of transformation-associated HPV16 RNA patterns, i.e., upregulation of E6*I relative to E1^E4 and/or presence of E1C. RESULTS: HPV16 RNA pattern analyses classified 85% of 58 samples diagnosed ≤CIN1 (no cytologically and histologically detectable cervical lesion or CIN grade 1) as negative and 90% of 59 samples diagnosed as ≥CIN3 (CIN grade 3 or invasive cancer) as positive. Among 41 CIN grade 2 samples representing an intermediate lesion group, 49% were HPV16 RNA patterns-positive. Interestingly, 3 of 4 HPV16 RNA patterns-positive lesions initially diagnosed as ≤CIN1 at follow-up 5-24 months later had progressed to ≥CIN2. CONCLUSIONS: We successfully developed and validated a second generation of HPV16 RNA patterns assay by rapid RT-qPCR as triage marker for HPV16 DNA-positive women offering clinical utility to distinguish between the need for immediate colposcopy and continued observation. Limited follow-up data suggests that HPV16 RNA patterns-positivity in ≤CIN1 lesions can predict disease progression.

Pathogenic role of the eight probably/possibly carcinogenic HPV types 26, 53, 66, 67, 68, 70, 73 and 82 in cervical cancer.

Eight HPV types (HPV26, 53, 66, 67, 68, 70, 73 and 82) that are phylogenetically closely related to 12 WHO-defined high-risk (HR) HPV have been rarely but consistently identified as single HPV infections in about 3% of cervical cancer (CxCa) tissues. Due to lack of biological data, these types are referred to as probable/possible (p) HR-HPV. To analyse their biological activity in direct comparison to HR-HPV types, we selected 55 formalin-fixed, paraffin-embedded (FFPE) CxCa tissues harbouring single pHR-HPV infections (2-13 cases per type) and 266 tissues harbouring single HR-HPV (7-40 cases per type) from a worldwide, retrospective, cross-sectional study. Single HPV infection was verified by two genotyping methods. Presence of type-specific spliced E6*I mRNA transcripts and expression of cellular proteins indicative of HPV transformation were assessed in all cases. In 55 CxCa tissues with pHR-HPV, E6*I mRNA expression was 100%; high p16(INK4a) , 98%; low pRb, 96%; low CyD1, 93%; and low p53, 84%. Compared to HPV16 tissues as a reference, individual frequencies of these five markers did not differ significantly, either for any of the eight pHR-HPV and the 11 other HR types individually or for the groups of pHR and HR types without HPV16. We conclude that the eight pHR-HPV types, when present as a single infection in CxCa, are biologically active and affect the same cellular pathways as any of the fully recognized carcinogenic HR-HPV types. Therefore we have provided molecular evidence of carcinogenicity for types currently classified as probably/possibly carcinogenic. Although this evidence is crucial for HPV-type carcinogenicity classification, per se it is not sufficient for inclusion of these HPV types into population-wide primary and secondary prevention programmes. Such decisions have to include careful estimation of effectiveness and cost-benefit analyses.

Tumor prevention in HPV8 transgenic mice by HPV8-E6 DNA vaccination.

The genus beta human papillomavirus 8 (HPV8) is involved in the development of cutaneous squamous cell carcinomas (SCCs) in individuals with epidermodysplasia verruciformis. Immunosuppressed transplant recipients are prone to harbor particularly high betapapillomavirus DNA loads, which may contribute to their highly increased risk of SCC. Tumor induction in HPV8 transgenic mice correlates with increased expression of viral oncogenes E6 and E2. In an attempt to prevent skin tumor development, we evaluated an HPV8-E6-DNA vaccine, which was able to stimulate a detectable HPV8-E6-specific cell-mediated immune response in 8/15 immunized mice. When skin of HPV8 transgenic mice was grafted onto non-transgenic littermates, the grafted HPV8 transgenic tissue was not rejected and papillomas started to grow within 14 days all over the transplant of 9/9 non-vaccinated and 7/15 not successfully vaccinated mice. In contrast, no papillomas developed in 6/8 successfully vaccinated mice. In the other two of these eight mice, a large ulcerative lesion developed within the initial papilloma growth or papilloma development was highly delayed. As the vaccine completely or partially prevented papilloma development without rejecting the transplanted HPV8 positive skin, the immune system appears to attack only keratinocytes with increased levels of E6 protein, which would give rise to papillomas.

Biological activity of probable/possible high-risk human papillomavirus types in cervical cancer.

Judging the carcinogenicity of human papillomavirus (HPV) types rarely found in cervical cancer (CxCa) is hindered by lack of studies of their biological activity in cancer tissues. To asses transcriptional activity of HPV types, we have developed ultra-short amplimer, splice-site specific, E6*I mRNA RT-PCR assays for 12 high-risk (HR)-HPV (IARC Group 1) and eight probable/possible high-risk (pHR)-HPV types (IARC Group 2A/B carcinogens). Previously unreported E6*I splice sites of the six pHR-HPV types 26, 53, 67, 70, 73 and 82 were identified by cloning and sequencing. We analyzed 97 formalin-fixed paraffin-embedded (FFPE) Mongolian CxCa biopsies for presence of HPV DNA by two sensitive genotyping assays, for E6*I transcripts of all HR-/pHR-HPV types identified and for expression of HPV surrogate markers p16(INK4a), pRb and p53. E6*I of at least one HR-/pHR-HPV was expressed in 94 (98%) of cancer tissues including seven with pHR-HPV types 26, 66, 70 or 82 as single transcribed types. Fifty-eight of E6*I mRNA transcribing cases were analyzable by immunohistochemistry and displayed p16(INK4a) overexpression in 57 (98%), pRb downregulation in 56 (97%) and p53 downregulation in 36 (62%) tissues. The newly developed E6*I mRNA RT-PCR assays appeared to be highly sensitive method to analyze HPV transcription in FFPE materials. Our finding of viral oncogene transcription of pHR-HPV types 26, 66, 70 and 82 in cervical tumors, in the absence of any other transcriptionally active HR-type and with p16(INK4a) overexpression and pRb downregulation, may support a reassessment of the carcinogenicity classification of these pHR-HPV types.

Human papillomavirus type 38 E6 and E7 act as tumour promoters during chemically induced skin carcinogenesis.

Many findings support a possible involvement of a subgroup of human papillomaviruses (HPVs), called cutaneous beta HPV types, in the development of non-melanoma skin cancer. The skin of transgenic (Tg) mice expressing viral oncoproteins E6 and E7 from different cutaneous beta HPV types, including HPV38, showed an increased susceptibility to UV-induced and/or chemically induced skin carcinogenesis compared with wild-type animals. In this study, we show that beta HPV38 E6 and E7 oncoproteins act as promoter and progression factors in multi-stage skin carcinogenesis, strongly cooperating with the initiator and DNA damage agent 7,12-dimethylbenz[a]anthracene. In contrast, exposure of HPV38 E6/E7 Tg mice to the promoter 12-O-tetradecanoylphorbol-13-acetate did not significantly result in the development of skin lesions. These findings further support the role of beta HPV types in skin carcinogenesis, providing additional insight into their precise contribution to the multi-step process.

Comparative analysis of transforming properties of E6 and E7 from different beta human papillomavirus types.

The cutaneous beta human papillomavirus (beta HPV) types appear to be involved in skin carcinogenesis. However, only a few beta HPVs have been investigated so far. Here, we compared the properties of E6 and E7 oncoproteins from six uncharacterized beta HPVs (14, 22, 23, 24, 36, 49). Only HPV49 E6 and E7 immortalized primary human keratinocytes and efficiently deregulated the p53 and pRb pathways. Furthermore, HPV49 E6, similarly to E6 from the oncogenic HPV16, promoted p53 degradation.

E6 and E7 from beta HPV38 cooperate with ultraviolet light in the development of actinic keratosis-like lesions and squamous cell carcinoma in mice.

Cutaneous beta human papillomavirus (HPV) types appear to be involved in the development of non-melanoma skin cancer (NMSC); however, it is not entirely clear whether they play a direct role. We have previously shown that E6 and E7 oncoproteins from the beta HPV type 38 display transforming activities in several experimental models. To evaluate the possible contribution of HPV38 in a proliferative tissue compartment during carcinogenesis, we generated a new transgenic mouse model (Tg) where HPV38 E6 and E7 are expressed in the undifferentiated basal layer of epithelia under the control of the Keratin 14 (K14) promoter. Viral oncogene expression led to increased cellular proliferation in the epidermis of the Tg animals in comparison to the wild-type littermates. Although no spontaneous formation of tumours was observed during the lifespan of the K14 HPV38 E6/E7-Tg mice, they were highly susceptible to 7,12-dimethylbenz(a)anthracene (DMBA)/12-0-tetradecanoylphorbol-13-acetate (TPA) two-stage chemical carcinogenesis. In addition, when animals were exposed to ultraviolet light (UV) irradiation, we observed that accumulation of p21(WAF1) and cell-cycle arrest were significantly alleviated in the skin of Tg mice as compared to wild-type controls. Most importantly, chronic UV irradiation of Tg mice induced the development of actinic keratosis-like lesions, which are considered in humans as precursors of squamous cell carcinomas (SCC), and subsequently of SCC in a significant proportion of the animals. In contrast, wild-type animals subjected to identical treatments did not develop any type of skin lesions. Thus, the oncoproteins E6 and E7 from beta HPV38 significantly contribute to SCC development in the skin rendering keratinocytes more susceptible to UV-induced carcinogenesis.

NF-κ B-dependent upregulation of ICAM-1 by HPV16-E6/E7 facilitates NK cell/target cell interaction.

NK cell recognition of tumor cells is mediated by a delicate balance of signals received by MHC class I-binding inhibitory NK cell receptors and activating NK cell receptors, which mainly bind to virus-, stress- or tumor-induced ligands. In addition, adhesion molecules such as the intercellular adhesion molecule-1 (ICAM-1) and its receptors, the lymphocyte function-associated antigen-1 (LFA-1) and Mac-1, are crucial for immune synapse formation and NK cell-mediated killing. In this study, we show that expression of the adhesion molecule ICAM-1 was rapidly induced by E6 and -E7 oncoproteins of HPV16, -18, -5 and -8, but not of HPV38 and -6 in primary human keratinocytes after retroviral transduction. ICAM-1 was upregulated in E6E7-expressing keratinocytes both at mRNA and protein levels. The observed ICAM-1 upregulation in HPV16-E6E7-expressing keratinocytes was partially dependent on activation of the NF-κB pathway. Importantly, the upregulated ICAM-1 expression in HPV16-E6E7-expressing keratinocytes led to enhanced conjugate formation with NK cells. We previously showed that HPV16-positive cervical carcinomas frequently express low levels of inhibitory NK cell ligands and high levels of activating NK cell ligands. Moreover, levels of the adhesion molecule ICAM-1 are enhanced by HPV16-E6/E7. Therefore, strategies that aim at harnessing NK cells might be beneficial for the treatment of cervical carcinoma.

Synthetic double-stranded RNAs are adjuvants for the induction of T helper 1 and humoral immune responses to human papillomavirus in rhesus macaques.

Toll-like receptor (TLR) ligands are being considered as adjuvants for the induction of antigen-specific immune responses, as in the design of vaccines. Polyriboinosinic-polyribocytoidylic acid (poly I:C), a synthetic double-stranded RNA (dsRNA), is recognized by TLR3 and other intracellular receptors. Poly ICLC is a poly I:C analogue, which has been stabilized against the serum nucleases that are present in the plasma of primates. Poly I:C(12)U, another analogue, is less toxic but also less stable in vivo than poly I:C, and TLR3 is essential for its recognition. To study the effects of these compounds on the induction of protein-specific immune responses in an animal model relevant to humans, rhesus macaques were immunized subcutaneously (s.c.) with keyhole limpet hemocyanin (KLH) or human papillomavirus (HPV)16 capsomeres with or without dsRNA or a control adjuvant, the TLR9 ligand CpG-C. All dsRNA compounds served as adjuvants for KLH-specific cellular immune responses, with the highest proliferative responses being observed with 2 mg/animal poly ICLC (p = 0.002) or 6 mg/animal poly I:C(12)U (p = 0.001) when compared with immunization with KLH alone. Notably, poly ICLC -- but not CpG-C given at the same dose -- also helped to induce HPV16-specific Th1 immune responses while both adjuvants supported the induction of strong anti-HPV16 L1 antibody responses as determined by ELISA and neutralization assay. In contrast, control animals injected with HPV16 capsomeres alone did not develop substantial HPV16-specific immune responses. Injection of dsRNA led to increased numbers of cells producing the T cell-activating chemokines CXCL9 and CXCL10 as detected by in situ hybridization in draining lymph nodes 18 hours after injections, and to increased serum levels of CXCL10 (p = 0.01). This was paralleled by the reduced production of the homeostatic T cell-attracting chemokine CCL21. Thus, synthetic dsRNAs induce an innate chemokine response and act as adjuvants for virus-specific Th1 and humoral immune responses in nonhuman primates.

The HPV16 transcriptome in cervical lesions of different grades.

Infections with high-risk human papillomaviruses (HPV), mainly HPV type 16, can cause malignant transformation of the human cervical epithelium and cervical cancer (CxCa). Very little is known about the quantitative expression of HPV16 transcripts in cervical lesions of different grades. We have analysed the viral transcriptome in 80 HPV16 DNA positive cervical smears including lesions of different cytological grades, using nucleic acid sequence-based amplification (NASBA)-Luminex hybridisation assays quantifying spliced and unspliced HPV16 transcripts. Based on the quantitative analysis of single transcripts, highly significant changes in transcript levels were observed between different grades of cervical lesions. In conclusion, quantitative expression changes of HPV16 transcript markers may be involved in tumour progression. This study provides a basis for selection of candidate RNA markers for diagnostics of HPV16-related disease.

Identification of B-cell epitopes on virus-like particles of cutaneous alpha-human papillomaviruses.

Human papillomavirus (PV) (HPV) types 2, 27, and 57 are closely related and, hence, represent a promising model system to study the correlation of phylogenetic relationship and immunological distinctiveness of PVs. These HPV types cause a large fraction of cutaneous warts occurring in immunocompromised patients. Therefore, they constitute a target for the development of virus-like particle (VLP)-based vaccines. However, the immunogenic structure of HPV type 2, 27, and 57 capsids has not been studied yet. Here we provide, for the first time, a characterization of the B-cell epitopes on VLPs of cutaneous alpha-HPVs using a panel of 94 monoclonal antibodies (MAbs) generated upon immunization with capsids from HPV types 2, 27, and 57. The MAbs generated were characterized regarding their reactivities with glutathione S-transferase-L1 fusion proteins from 18 different PV types, the nature of their recognized epitopes, their isotypes, and their ability to neutralize HPV type 2, 27, 57, or 16. In total, 33 of the 94 MAbs (35%) showed type-specific reactivity. All type-specific MAbs recognize linear epitopes, most of which map to the hypervariable surface loop regions of the L1 amino acid sequence. Four of the generated MAbs neutralized pseudovirions of the inoculated HPV type efficiently. All four MAbs recognized epitopes within the BC loop, which is required and sufficient for their neutralizing activity. Our data highlight the immunological distinctiveness of individual HPV types, even in comparison to their closest relatives, and they provide a basis for the development of VLP-based vaccines against cutaneous alpha-HPVs.

Analysis of modified human papillomavirus type 16 L1 capsomeres: the ability to assemble into larger particles correlates with higher immunogenicity.

L1 capsomeres purified from Escherichia coli represent an economic alternative to the recently launched virus-like particle (VLP)-based prophylactic vaccines against infection with human papillomavirus types 16 and 18 (HPV-16 and HPV-18), which are causative agents of cervical cancer. It was recently reported that capsomeres are much less immunogenic than VLPs. Numerous modifications of the L1 protein leading to the formation of capsomeres but preventing capsid assembly have been described, such as the replacement of the cysteine residues that form capsid-stabilizing disulfide bonds or the deletion of helix 4. So far, the influence of these modifications on immunogenicity has not been thoroughly investigated. Here, we describe the purification of eight different HPV-16 L1 proteins as capsomeres from Escherichia coli. We compared them for yield, structure, and immunogenicity in mice. All L1 proteins formed almost identical pentameric structures yet differed strongly in their immunogenicity, especially regarding the humoral immune responses. Immunization of TLR4(-/-) mice and DNA immunization by the same constructs confirmed that immunogenicity was independent of different degrees of contamination with copurifying immune-stimulatory molecules from E. coli. We hypothesize that immunogenicity correlates with the intrinsic ability of the capsomeres to assemble into larger particles, as only assembly-competent L1 proteins induced high antibody responses. One of the proteins (L1DeltaN10) proved to be the most immunogenic, inducing antibody titers equivalent to those generated in response to VLPs. However, preassembly prior to injection did not increase immunogenicity. Our data suggest that certain L1 constructs can be used to produce highly immunogenic capsomeres in bacteria as economic alternatives to VLP-based formulations.

Enhancement of immunogenicity of a therapeutic cervical cancer DNA-based vaccine by co-application of sequence-optimized genetic adjuvants.

Treatment of patients with cervical cancer by conventional methods (mainly surgery, but also radiotherapy and chemotherapy) results in a significant loss in quality of life. A therapeutic DNA vaccine directed to tumor-specific antigens of the human papilloma virus (HPV) could be an attractive treatment option. We have developed a nontransforming HPV-16 E7-based DNA vaccine containing all putative T cell epitopes (HPV-16 E7SH). DNA vaccines, however, are less immunogenic than protein- or peptide-based vaccines in larger animals and humans. In this study, we have investigated an adjuvant gene support of the HPV-16 E7SH therapeutic cervical cancer vaccine. DNA encoded cytokines (IL-2, IL-12, GM-CSF, IFN-gamma) and the chemokine MIP1-alpha were co-applied either simultaneously or at different time points pre- or post-E7SH vaccination. In addition, sequence-optimized adjuvant genes were compared to wild type genes. Three combinations investigated lead to an enhanced IFN-gamma response of the induced T cells in mice. Interestingly, IFN-gamma secretion of splenocytes did not strictly correlate with tumor response in tumor regression experiments. Gene-encoded MIP-1alpha applied 5 days prior to E7SH-immunization combined with IFN-gamma or IL-12 (3 days) or IL-2 (5 days) postimmunization lead to a significantly enhanced tumor response that was clearly associated with granzyme B secretion and target cells lysis. Our results suggest that a conditioning application and combination with adjuvant genes may be a promising strategy to enhance synergistically immune responses by DNA immunization for the treatment of cervical cancer.

Cancer susceptibility of beta HPV49 E6 and E7 transgenic mice to 4-nitroquinoline 1-oxide treatment correlates with mutational signatures of tobacco exposure.

We have previously showed that a transgenic (Tg) mouse model with cytokeratin 14 promoter (K14)-driven expression of E6 and E7 from beta-3 HPV49 in the basal layer of the epidermis and of the mucosal epithelia of the digestive tract (K14 HPV49 E6/E7 Tg mice) are highly susceptible to upper digestive tract carcinogenesis upon exposure to 4-nitroquinoline 1-oxide (4NQO). Using whole-exome sequencing, we show that in K14 HPV49 E6/E7 Tg mice, development of 4NQO-induced cancers tightly correlates with the accumulation of somatic mutations in cancer-related genes. The mutational signature in 4NQO-treated mice was similar to the signature observed in humans exposed to tobacco smoking and tobacco chewing. Similar results were obtained with K14 Tg animals expressing mucosal high-risk HPV16 E6 and E7 oncogenes. Thus, beta-3 HPV49 share some functional similarities with HPV16 in Tg animals.

Activating NK cell receptor ligands are differentially expressed during progression to cervical cancer.

Human papillomavirus-induced cervical carcinomas often show impaired expression of MHC class I molecules resulting in the inability of tumor cells to directly present viral peptides to cytotoxic T lymphocytes. Loss of MHC class I expression combined with the expression of activating NK cell receptor ligands renders tumor cells potentially susceptible to NK cell attack. Thus, in this study, we analyzed the expression of activating NK cell receptor ligands, NK cell accumulation and activation status in situ in normal ectocervical tissue (NCT), cervical intraepithelial neoplasia (CIN) and squamous cervical carcinoma (CxCa). We observed that expression of the DNAM-1 ligand CD155 was frequently upregulated in CxCa, but not in CIN. The NKG2D ligand MICA was upregulated in fewer CxCa biopsies. In contrast, another NKG2D ligand ULBP2 was preferentially expressed in differentiated epithelial cells of NCT. Increased numbers of NK cells were detected in CIN as compared to NCT and CxCa. Expression of activating NK cell receptor ligands combined with loss of MHC class I was not correlated with enhanced NK cell accumulation or activation status. Furthermore, we demonstrate that cervical cancer cell lines are killed by the NK cell line, NKL, in a NKG2D- and DNAM-1-dependent manner in vitro. Since a significant number of CxCa biopsies showed low MHC class I expression combined with high expression of one or more of the tested activating NK cell receptor ligands, we conclude that CxCa might be a promising target for NK cell-based adoptive immunotherapy.

Comparison of DNA- and mRNA-transfected mouse dendritic cells as potential vaccines against the human papillomavirus type 16 associated oncoprotein E7.

BACKGROUND: Dendritic cells (DCs) mediate the generation of strong cytotoxic T-lymphocyte (CTL) responses by functioning in antigen presentation and exerting adjuvant properties. We compared several activation markers and parameters of biological activity of DNA- and mRNA-transfected DCs in vitro and in vivo. METHODS: CpG-matured, bone marrow derived C57BL/6 mouse DCs were electroporated either with enhanced green fluorescence protein (EGFP) or human papillomavirus type 16 (HPV16) E7 expression plasmids or in vitro transcribed mRNAs encoding for the codon-optimized E7 or a shuffled version thereof. Activation marker expression and antigen presentation was analysed by fluorescence-activated cell sorting. The migratory behaviour of transfected DCs were investigated by in vitro chemotaxis experiments and cytokine expression by ELISA. CTL-priming capacity of transfected DCs were determined by vaccination of mice. RESULTS: mRNA transfection produced a two- to fourfold increase of the activation markers CD40, CD80, CD86 and MHC I and MHC II molecules. Predominately antigen-expressing DCs migrated after mRNA transfection. Furthermore, mRNA-transfected DCs were capable of inducing a chemokine gradient. After maturation, electroporation and activation with soluble CD40 ligand and interferon-y, DCs displayed a T-helper cell type 2 cytokine expression pattern. Nevertheless, E7-transfected DCs were able to prime E7-specific CTL responses in vivo. The highest E7-specific CTL frequencies were found in mice immunized with mRNA-transfected DCs. The in vitro expanded CTLs exerted functional E7-specific cytotoxic activity. CONCLUSIONS: Genetically modified DCs are suitable vehicles for the induction of E7-specific CTL responses in mice and hence could help to eradicate HPV-associated lesions in humans.

Vaccination trial with HPV16 L1E7 chimeric virus-like particles in women suffering from high grade cervical intraepithelial neoplasia (CIN 2/3).

Persistent infection with human papillomaviruses (HPV) is a prerequisite for the development of cervical cancer. Vaccination with virus-like particles (VLP) has demonstrated efficacy in prophylaxis but lacks therapeutic potential. HPV16 L1E7 chimeric virus-like particles (CVLP) consist of a carboxy-terminally truncated HPV16L1 protein fused to the amino-terminal part of the HPV16 E7 protein and self-assemble by recombinant expression of the fusion protein. The CVLP are able to induce L1- and E7-specific cytotoxic T lymphocytes. We have performed a first clinical trial to gain information about the safety and to generate preliminary data on the therapeutic potential of the CVLP in humans. A randomized, double blind, placebo-controlled clinical trial has been conducted in 39 HPV16 mono-infected high grade cervical intraepithelial neoplasia (CIN) patients (CIN 2/3). Two doses (75 mug or 250 mug) of CVLP were applied. The duration of the study was 24 weeks with 2 optional visits after another 12 and 24 weeks. The vaccine showed a very good safety profile with only minor adverse events attributable to the immunization. Antibodies with high titers against HPV16 L1 and low titers against HPV16 E7 as well as cellular immune responses against both proteins were induced. Responses were equivalent for both vaccine concentrations. A trend for histological improvement to CIN 1 or normal was seen in 39% of the patients receiving the vaccine and only 25% of the placebo recipients. Fifty-six percent of the responders were also HPV16 DNA-negative by the end of the study. Therefore, we demonstrated evidence for safety and a nonsignificant trend for the clinical efficacy of the HPV16 L1E7 CVLP vaccine.

Binding of human papilloma virus L1 virus-like particles to dendritic cells is mediated through heparan sulfates and induces immune activation.

Immunization using human papilloma virus (HPV)-L1 virus-like particles (VLPs) induces a robust and effective immune response, which has recently resulted in the implementation of the HPV-L1 VLP vaccination in health programs. However, during infection, HPV can escape immune surveillance leading to latency and disease. Dendritic cells (DCs) induce effective immune responses after vaccination, but might also induce immune modulation during infection. The interaction of HPV-L1 VLPs with mucosal DCs determines the immune response. However, little is known about the receptors on mucosal DC subsets involved in HPV-L1 VLP binding. Therefore, we set out to investigate the interaction of HPV-L1 VLPs with the different mucosal DC subsets; the subepithelial DCs and Langerhans cells (LCs). We observed strong binding of HPV-L1 VLPs to both DCs and LCs. We did not observe an involvement for C-type lectins such as dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN) and langerin. The HPV-L1 VLP binding to DCs was mediated through heparan sulfates, since it was abrogated by heparinase-II treatment. The heparan sulfate proteoglycan syndecan-3 binds VLPs and is expressed on both DCs and LCs. Binding of VLPs to DCs, but not to LCs, strongly correlated with the levels of heparan sulfates and syndecan-3, suggesting that syndecan-3 is the main receptor for HPV-L1 VLPs on DCs. VLP interaction with DCs resulted in the up-regulation of co-stimulatory molecules and the production of the cytokines IL-6, IL-8, IL-10 and IL-12p40. Our results support an important role for syndecan-3 as a HPV receptor on DCs, which could be important for both vaccine development and understanding HPV pathogenesis.