Pre-clinical safety and efficacy of TA-CIN, a recombinant HPV16 L2E6E7 fusion protein vaccine, in homologous and heterologous prime-boost regimens

A safe and potentiated multi-type HPV L2-E7 nanoparticle vaccine with combined prophylactic and therapeutic activity

Persistent infection with high-risk human papillomavirus (HPV) is widely recognized as the primary cause of cervical and other malignant cancers. There are six licensed prophylactic vaccines available against HPV, but none of them shows any significant therapeutic effect on pre-existing infections or lesions. Thus, a prophylactic vaccine also endowed with therapeutic activity would afford protection regardless of the vaccine recipients HPV-infection status. Here, we describe the refinement and further potentiation of a dual-purpose HPV nanoparticle vaccine (hereafter referred to as cPANHPVAX) relying on eight different HPV L2 peptide epitopes and on the E7 oncoantigens from HPV16 and 18. cPANHPVAX not only induces anti-HPV16 E7 cytotoxic T-cell responses in C57BL/6 mice, but also anti-HPV18 E7 T-cell responses in transgenic mice with the A2.DR1 haplotype. These cytotoxic responses add up to a potent, broad-coverage humoral (HPV-neutralizing) response. cPANHPVAX safety was further improved by deletion of the pRb-binding domains of E7. Our dual-purpose vaccine holds great potential for clinical translation as an immune-treatment capable of targeting active infections as well as established HPV-related malignancies, thus benefiting both uninfected and infected individuals.

J. Ertl H. Preclinical Immunogenicity and Efficacy Studies for Therapeutic Vaccines for Human Papillomavirus-Type-16-Associated Cancer

The objective of this study was to conduct preclinical immunogenicity and efficacy studies with several therapeutic vaccines for human papillomavirus (HPV)-16-associated cancers expressing the early antigens E5, E6, and E7 with or without E2. The viral oncoproteins were either expressed by themselves as fusion proteins or the fusion proteins were inserted genetically into herpes simplex virus (HSV)-1 glycoprotein D (gD) which, upon binding to the herpes virus entry mediator (HVEM), inhibits an early T cell checkpoint mediated by the B and T cell mediator (BTLA). This, in turn, lowers the threshold for T cell activation and augments and broadens CD8+ T cell responses to the antigens. The fusion antigens were expressed by chimpanzee adenovirus (AdC) vectors. Expression of the HPV antigens within gD was essential for vaccine immunogenicity and efficacy against challenge with TC-1 cells, which express E7 and E6 of HPV-16 but neither E5 nor E2. Unexpectedly, inclusion of E2 increased both CD8+ T cell responses to the other oncoproteins of HPV-16 and the effectiveness of the vaccines to cause the regression of sizable TC-1 tumors.

Skin-Grafting and Dendritic Cell "Boosted" Humanized Mouse Models Allow the Pre-Clinical Evaluation of Therapeutic Cancer Vaccines

Vaccines have been hailed as one of the most remarkable medical advancements in human history, and their potential for treating cancer by generating or expanding anti-tumor T cells has garnered significant interest in recent years. However, the limited efficacy of therapeutic cancer vaccines in clinical trials can be partially attributed to the inadequacy of current preclinical mouse models in recapitulating the complexities of the human immune system. In this study, we developed two innovative humanized mouse models to assess the immunogenicity and therapeutic effectiveness of vaccines targeting human papillomavirus (HPV16) antigens and delivering tumor antigens to human CD141+ dendritic cells (DCs). Both models were based on the transference of human peripheral blood mononuclear cells (PBMCs) into immunocompromised HLA-A*02-NSG mice (NSG-A2), where the use of fresh PBMCs boosted the engraftment of human cells up to 80%. The dynamics of immune cells in the PBMC-hu-NSG-A2 mice demonstrated that T cells constituted the vast majority of engrafted cells, which progressively expanded over time and retained their responsiveness to ex vivo stimulation. Using the PBMC-hu-NSG-A2 system, we generated a hyperplastic skin graft model expressing the HPV16-E7 oncogene. Remarkably, human cells populated the skin grafts, and upon vaccination with a DNA vaccine encoding an HPV16-E6/E7 protein, rapid rejection targeted to the E7-expressing skin was detected, underscoring the capacity of the model to mount a vaccine-specific response. To overcome the decline in DC numbers observed over time in PBMC-hu-NSG-A2 animals, we augmented the abundance of CD141+ DCs, the specific targets of our tailored nanoemulsions (TNEs), by transferring additional autologous PBMCs pre-treated in vitro with the growth factor Flt3-L. The Flt3-L treatment bolstered CD141+ DC numbers, leading to potent antigen-specific CD4+ and CD8+ T cell responses in vivo, which caused the regression of pre-established triple-negative breast cancer and melanoma tumors following CD141+ DC-targeting TNE vaccination. Notably, using HLA-A*02-matching PBMCs for humanizing NSG-A2 mice resulted in a delayed onset of graft-versus-host disease and enhanced the efficacy of the TNE vaccination compared with the parental NSG strain. In conclusion, we successfully established two humanized mouse models that exhibited strong antigen-specific responses and demonstrated tumor regression following vaccination. These models serve as valuable platforms for assessing the efficacy of therapeutic cancer vaccines targeting HPV16-dysplastic skin and diverse tumor antigens specifically delivered to CD141+ DCs.

Exploring the Molecular Pathogenesis, Pathogen Association, and Therapeutic Strategies against HPV Infection

The human papillomavirus (HPV), commonly documented as the cause of warts, has gained much interest recently due to its possible links to several types of cancer. HPV infection is discussed in this review from multiple angles, including its virology, epidemiology, etiology, immunology, clinical symptoms, and treatment. Recent breakthroughs in molecular biology have led to the development of new methods for detecting and treating HPV in tissue. There is no cure for HPV, and although vaccines are available to prevent infection with the most common HPV viruses, their utilization is limited. Destruction and excision are the primary treatment modalities. This review sheds light on the epidemiology, molecular pathogenesis, the association of several other pathogens with HPV, the latest treatment strategies available to treat the same, and an overview of the progress made and the obstacles still to be overcome in the fight against HPV infection.

Albumin and interferon-β fusion protein serves as an effective vaccine adjuvant to enhance antigen-specific CD8+ T cell-mediated antitumor immunity

BACKGROUND

Type I interferons (IFN) promote dendritic cells maturation and subsequently enhance generation of antigen-specific CD8 +T cell for the control of tumor. Using type I interferons as an adjuvant to vaccination could prove to be a potent strategy. However, type I interferons have a short half-life. Albumin linked to a protein will prolong the half-life of the linked protein.

METHODS

In this study, we explored the fusion of albumin to IFNβ (Alb-IFNβ) for its functional activity both in vitro and in vivo. We determined the half-life of Alb-IFNβ following treatment in the serum, tumor, and tumor draining lymph nodes in both wild type and FcRn knockout mice. We characterized the ability of Alb-IFNβ to enhance antigen-specific CD8+ T cells using ovalbumin (OVA) or human papillomavirus (HPV) E7 long peptides. Next, we evaluated the therapeutic antitumor effect of coadministration of AlbIFNβ with antigenic peptides against HPVE7 expressing tumor and the treatment's ability to generate HPVE7 antigen specific CD8+ T cells. The contribution of the antitumor effect by lymphocytes was also examined by an antibody depletion experiment. The ability of Alb-IFNβ to serve as an adjuvant was tested using clinical grade therapeutic protein-based HPV vaccine, TACIN.

RESULTS

Alb-IFNβ retains biological function and does not alter the biological activity of IFNβ. In addition, Alb-IFNβ extends half-life of IFNβ in serum, lymph nodes and tumor. The coadministration of Alb-IFNβ with OVA or HPVE7 antigenic peptides enhances antigen-specific CD8 +T cell immunity, and in a TC-1 tumor model results in a significant therapeutic antitumor effect. We found that CD8 +T cells and dendritic cells, but not CD4 +T cells, are important for the observed antitumor therapeutic effect mediated by Alb-IFNβ. Finally, Alb-IFNβ served as a potent adjuvant for TA-CIN for the treatment of HPV antigen expressing tumors.

CONCLUSIONS

Overall, Alb-IFNβ serves as a potent adjuvant for enhancement of strong antigen-specific CD8 +T cell antitumor immunity, reduction of tumor burden, and increase in overall survival. Alb-IFNβ potentially can serve as an innovative adjuvant for the development of vaccines for the control of infectious disease and cancer.

Heterologous administration of HPV16 E7 epitope-loaded nanocomplexes inhibits tumor growth in mouse model

The nanostructured complexes can result in enhanced vaccine efficacy by facilitating the distribution and uptake of antigens by antigen-presenting cells (APCs), thereby stimulating immune responses. Here, we hypothesized that either directly coating of nanoadjuvants including aluminum phosphate (AlPO₄) and adenovirus (Ad) with a modified HPV16 E7 MHC-I specific epitope, RAHYNIVTF_49-57, or mixing the CpG oligodeoxynucleotide (CpG-ODN) with the cationic epitope to form nanocomlexes, and their combinational therapy would enhance their anti-tumor effects in a TC-1 mouse model. The positively-charged HPV16 E7 epitope was attracted to the oppositely-charged adjuvants by electrostatic interaction to generate epitope/adjuvant nanocomplexes. We showed that coating the nanosized adjuvants with the cationic epitope increased the particles' surface charge without significant change in their size. We then tested the cellular immunogenicity and therapeutic efficacy of nanocomplexes by measuring IL-10 and IFN-γ production, the expression of CD107a as a marker of CTL response, and tumor growth inhibition. The nanocomplexes were administered either in homologous or heterologous prime-boost regimens, and heterologous immunizations including Ad/Pep-CpG/Pep, CpG/Pep-Ad/Pep, Ad/Pep-Alum/Pep, and Alum/Pep-Ad/Pep induced significantly higher levels of IL-10, IFN-γ, and CD107a-expressing CD8 T cells compared with homologous administrations. Furthermore, the tumor growth was significantly suppressed in mice receiving nanostructured complexes in the heterologous immunizations. Our study highlights the potential of the heterologous prime-boost administration of the epitope-coated nanostructures as an effective immunization strategy.

Designing a therapeutic and prophylactic candidate vaccine against human papillomavirus through vaccinomics approaches

OBJECTIVE

Human papillomavirus (HPV) is the main cause of cervical cancer, the 4^th prominent cause of death in women globally. Previous vaccine development projects have led to several approved prophylactic vaccines available commercially, all of which are made using major capsid-based (L1). Administration of minor capsid protein (L2) gave rise to the second generation investigational prophylactic HPV vaccines, none of which are approved yet due to low immunogenicity provided by the L2 capsid protein. On the other hand, post-translation proteins, E6 and E7, have been utilized to develop experimental therapeutic vaccines. Here, in silico designing of a therapeutic and prophylactic vaccine against HPV16 is performed.

METHODS

In this study, several immunoinformatic and computational tools were administered to identify and design a vaccine construct with dual prophylactic and therapeutic applications consisting of several epitope regions on L2, E6, and E7 proteins of HPV16.

RESULTS

Immunodominant epitope regions (aa 12-23 and 78-78 of L2 protein, aa 11-27 of E6 protein, and aa 70-89 of E7 protein) were employed, which offered adequate immunogenicity to induce immune responses. Resuscitation-promoting factors (RpfB and RpfE) of Mycobacterium tuberculosis were integrated in two separate constructs as TLR4 agonists to act as vaccine adjuvants. Following physiochemical and structural evaluations carried out by various bioinformatics tools, the designed constructs were modeled and validated, resulting in two 3D structures. Molecular docking and molecular dynamic simulations suggested stable ligand-receptor interactions between the designed construct and TLR4.

CONCLUSION

Ultimately, this study led to suggest the designed construct as a potential vaccine candidate with both prophylactic and therapeutic applications against HPV by promoting Th1, Th2, CTL, and B cell immune responses, which should be further confirmed in experimental studies.

Cervical Cancer Immunotherapy: Facts and Hopes

It is a sad fact that despite being almost completely preventable through human papillomavirus (HPV) vaccination and screening, cervical cancer remains the fourth most common cancer to affect women worldwide. Persistent high-risk HPV (hrHPV) infection is the primary etiologic factor for cervical cancer. Upward of 70% of cases are driven by HPV types 16 and 18, with a dozen other hrHPVs associated with the remainder of cases. Current standard-of-care treatments include radiotherapy, chemotherapy, and/or surgical resection. However, they have significant side effects and limited efficacy against advanced disease. There are a few treatment options for recurrent or metastatic cases. Immunotherapy offers new hope, as demonstrated by the recent approval of programmed cell death protein 1-blocking antibody for recurrent or metastatic disease. This might be augmented by combination with antigen-specific immunotherapy approaches, such as vaccines or adoptive cell transfer, to enhance the host cellular immune response targeting HPV-positive cancer cells. As cervical cancer progresses, it can foster an immunosuppressive microenvironment and counteract host anticancer immunity. Thus, approaches to reverse suppressive immune environments and bolster effector T-cell functioning are likely to enhance the success of such cervical cancer immunotherapy. The success of nonspecific immunostimulants like imiquimod against genital warts also suggest the possibility of utilizing these immunotherapeutic strategies in cervical cancer prevention to treat precursor lesions (cervical intraepithelial neoplasia) and persistent hrHPV infections against which the licensed prophylactic HPV vaccines have no efficacy. Here, we review the progress and challenges in the development of immunotherapeutic approaches for the prevention and treatment of cervical cancer.

RG1-VLP and Other L2-Based, Broad-Spectrum HPV Vaccine Candidates

Licensed human papillomavirus (HPV) vaccines contain virus-like particles (VLPs) self-assembled from L1 major-capsid proteins that are remarkably effective prophylactic immunogens. However, the induced type-restricted immune response limits coverage to the included vaccine types, and costly multiplex formulations, restrictive storage and distribution conditions drive the need for next generation HPV vaccines. Vaccine candidates based upon the minor structural protein L2 are particularly promising because conserved N-terminal epitopes induce broadly cross-type neutralizing and protective antibodies. Several strategies to increase the immunological potency of such epitopes are being investigated, including concatemeric multimers, fusion to toll-like receptors ligands or T cell epitopes, as well as immunodominant presentation by different nanoparticle or VLP structures. Several promising L2-based vaccine candidates have reached or will soon enter first-in-man clinical studies. RG1-VLP present the HPV16L2 amino-acid 17–36 conserved neutralization epitope “RG1” repetitively and closely spaced on an immunodominant surface loop of HPV16 L1-VLP and small animal immunizations provide cross-protection against challenge with all medically-significant high-risk and several low-risk HPV types. With a successful current good manufacturing practice (cGMP) campaign and this promising breadth of activity, even encompassing cross-neutralization of several cutaneous HPV types, RG1-VLP are ready for a first-in-human clinical study. This review aims to provide a general overview of these candidates with a special focus on the RG1-VLP vaccine and its road to the clinic.

Vaccination Strategies for the Control and Treatment of HPV Infection and HPV-Associated Cancer

Human papillomavirus (HPV) is the most common sexually transmitted infection, currently affecting close to 80 million Americans. Importantly, HPV infection is recognized as the etiologic factor for numerous cancers, including cervical, vulval, vaginal, penile, anal, and a subset of oropharyngeal cancers. The prevalence of HPV infection and its associated diseases are a significant problem, affecting millions of individuals worldwide. Likewise, the incidence of HPV infection poses a significant burden on individuals and the broader healthcare system. Between 2011 and 2015, there were an estimated 42,700 new cases of HPV-associated cancers each year in the United States alone. Similarly, the global burden of HPV is high, with around 630,000 new cases of HPV-associated cancer occurring each year. In the last decade, a total of three preventive major capsid protein (L1) virus-like particle-based HPV vaccines have been licensed and brought to market as a means to prevent the spread of HPV infection. These prophylactic vaccines have been demonstrated to be safe and efficacious in preventing HPV infection. The most recent iteration of the preventive HPV vaccine, a nanovalent, L1-VLP vaccine, protects against a total of nine HPV types (seven high-risk and two low-risk HPV types), including the high-risk types HPV16 and HPV18, which are responsible for causing the majority of HPV-associated cancers. Although current prophylactic HPV vaccines have demonstrated huge success in preventing infection, existing barriers to vaccine acquisition have limited their widespread use, especially in low- and middle-income countries, where the burden of HPV-associated diseases is highest. Prophylactic vaccines are unable to provide protection to individuals with existing HPV infections or HPV-associated diseases. Instead, therapeutic HPV vaccines capable of generating T cell-mediated immunity against HPV infection and associated diseases are needed to ameliorate the burden of disease in individuals with existing HPV infection. To generate a cell-mediated immune response against HPV, most therapeutic vaccines target HPV oncoproteins E6 and E7. Several types of therapeutic HPV vaccine candidates have been developed including live-vector, protein, peptide, dendritic cell, and DNA-based vaccines. This chapter will review the commercially available prophylactic HPV vaccines and discuss the recent progress in the development of therapeutic HPV vaccines.

Heterologous vaccine regimen: Stakeholder acceptance and implementation considerations

Heterologous vaccine regimens deliver antigens through different vaccine components or vector types at sequential time points. Clinical development shows promising results and several candidates may be progressing to licensure in the coming years. This study aimed at exploring future acceptance and uptake of such regimens (also called heterologous prime-boost) and to identify implementation-associated benefits and challenges. Survey tools were developed based on findings from a previous literature search shared with the study team, and exploratory interviews with global stakeholders. An online survey and key informant interviews in six countries were conducted with stakeholders at national and sub-national level, including policy-makers, regulators and implementers. The interview guide and the online survey covered: (a) awareness of, and knowledge about, heterologous vaccine regimens; (b) rating of regimen-associated perceived benefits and challenges; (c) anticipation of possible challenges in relation to four hypothetical introduction scenarios; (d) potential acceptance benefits and challenges at the policy, health facility and recipient level. Sixty-two interviews were conducted at national level. The online survey was completed by 50 participants. Across the four introduction scenarios, respondents considered the highest potential for the introduction of heterologous regimens for immunoprophylaxis was among adolescents/adults for diseases against which no vaccines are currently available. Most reservations were related to logistics, record keeping, and recipient compliance. Adding a new heterologous vaccine regimen to the routine immunization calendar for children was considered feasible if it could generate an increased and longer-term immune response. Introduction in preparation of or following a disease outbreak was considered less favourably, with respondents stressing the difficulty of logistics in emergency situations, and the potential lag in the onset of protection. The recent approval of the first heterologous vaccine regimen for the prevention of Ebola Virus Disease will soon bring new light to the topic.

PD-1 blockade synergizes with intratumoral vaccination of a therapeutic HPV protein vaccine and elicits regression of tumor in a preclinical model

INTRODUCTION

The human papillomavirus (HPV) encoded oncoproteins E6 and E7 are constitutively expressed in HPV-associated cancers, making them logical therapeutic targets. Intramuscular immunization of patients with HPV16 L2E7E6 fusion protein vaccine (TA-CIN) is well tolerated and induces HPV-specific cellular immune responses. Efficacy of PD-1 immune checkpoint blockade correlates with the level of tumor-infiltrating CD8 + T cells, yet most patients lack significant tumor infiltration of immune cells making immune checkpoint blockade suboptimal. We hypothesized that intratumoral vaccination with TA-CIN could increase the number of tumor-infiltrating CD8 + T cells, synergize with PD-1 blockade and result in better control of tumors compared with either PD-1 blockade or vaccination alone.

METHODS

We examined the immunogenicity and antitumor effects of intratumoral vaccination with TA-CIN alone or in combination with PD-1 blockade in the TC-1 syngeneic murine tumor model expressing HPV16 E6/E7.

RESULTS

Intratumoral vaccination with TA-CIN induced stronger antigen-specific CD8 + T cell responses and antitumor effects. Intratumoral TA-CIN vaccination generated a systemic immune response that was able to control distal TC-1 tumors. Furthermore, intratumoral TA-CIN vaccination induced tumor infiltration of antigen-specific CD8 + T cells. Knockout of Batf3 abolished antigen-specific CD8 + T cell responses and antitumor effects of intratumoral TA-CIN vaccination. Finally, PD-1 blockade synergizes with intratumoral TA-CIN vaccination resulting in significantly enhanced antigen-specific CD8 + T cell responses and complete regression of tumors, whereas either alone failed to control established TC-1 tumor.

CONCLUSIONS

Our results provide rationale for future clinical testing of intratumoral TA-CIN vaccination in combination with PD-1 blockade for the control of HPV16-associated tumors.

Combined prophylactic and therapeutic immune responses against human papillomaviruses induced by a thioredoxin-based L2-E7 nanoparticle vaccine

Global burden of cervical cancer, the most common cause of mortality caused by human papillomavirus (HPV), is expected to increase during the next decade, mainly because current alternatives for HPV vaccination and cervical cancer screening programs are costly to be established in low-and-middle income countries. Recently, we described the development of the broadly protective, thermostable vaccine antigen Trx-8mer-OVX313 based on the insertion of eight different minor capsid protein L2 neutralization epitopes into a thioredoxin scaffold from the hyperthermophilic archaeon Pyrococcus furiosus and conversion of the resulting antigen into a nanoparticle format (median radius ~9 nm) upon fusion with the heptamerizing OVX313 module. Here we evaluated whether the engineered thioredoxin scaffold, in addition to humoral immune responses, can induce CD8⁺ T-cell responses upon incorporation of MHC-I-restricted epitopes. By systematically examining the contribution of individual antigen modules, we demonstrated that B-cell and T-cell epitopes can be combined into a single antigen construct without compromising either immunogenicity. While CD8⁺ T-cell epitopes had no influence on B-cell responses, the L2 polytope (8mer) and OVX313-mediated heptamerization of the final antigen significantly increased CD8⁺ T-cell responses. In a proof-of-concept experiment, we found that vaccinated mice remained tumor-free even after two consecutive tumor challenges, while unvaccinated mice developed tumors. A cost-effective, broadly protective vaccine with both prophylactic and therapeutic properties represents a promising option to overcome the challenges associated with prevention and treatment of HPV-caused diseases.

Currently, there are three licensed prophylactic vaccines available against HPV, but none of them shows a therapeutic effect on pre-existing infections. Thus, a prophylactic vaccine also endowed with a therapeutic activity presents application potentials to individuals regardless of their HPV-infection status. Such a dual-purpose vaccine would be particularly valuable for post-exposure prophylaxis and shields population from recurrent HPV infections. Here, we constructed a combined vaccine relying on L2- and E7-specific epitopes grafted onto the surface of a hyper-stable thioredoxin scaffold. The resulting antigen was converted into a nanoparticle format with the use of a heptamerization domain. Our data document that the modular design of the antigen allows combination of B-cell and T-cell epitopes in one antigen without compromising either’s immunogenicity. The antigen retains its ability to provide broad protection against different HPV types but also presents strong therapeutic effects in a mouse tumor model. Therefore, the vaccine is potentially capable of resolving productive infection as well as HPV-related malignancies, and thus benefitting both uninfected and already infected individuals. Moreover, our vaccine utilizes E. coli as protein producer and distribution does not require cold-chain, which reduces costs making it applicable to less-affluent countries.

HPV16-E7 Protein T Cell Epitope Prediction and Global Therapeutic Peptide Vaccine Design Based on Human Leukocyte Antigen Frequency: An In-Silico Study

Cervical cancer is the second most common leading cause of women's death due to cancer worldwide, about 528,000 patients’ cases and 266,000 deaths per year, related to human papillomavirus (HPV). Peptide-based vaccines being safe, stable, and easy to produce have demonstrated great potential to develop therapeutic HPV vaccine. In this study, the major histocompatibility complex (MHC) class I, class II T cell epitopes of HPV16-E7 were predicted. Therefore, we designed a plan to find the most effective peptides to prompt appropriate immune responses. For this purpose, retrieving protein sequences, conserved region identification, phylogenic tree construction, T cell epitope prediction, epitope-predicted population coverage calculation, and molecular docking were performed consecutively and most effective immune response prompting peptides were selected. Based on different tools index, six CD8+ T cells and six CD4+ epitopes were chosen. This combination of 12 epitopes created a putative global vaccine with a 95.06% population coverage. These identified peptides can be employed further for peptide analysis and can be used as a peptide or poly-epitope candidates for therapeutic vaccine studies to treat HPV-associated cancers.

Therapeutic Vaccines for HPV-Associated Malignancies

Human papillomavirus (HPV)-related malignancies are responsible for almost all cases of cervical cancer in women, and over 50% of all cases of head and neck carcinoma. Worldwide, HPV-positive malignancies account for 4.5% of the global cancer burden, or over 600,000 cases per year. HPV infection is a pressing public health issue, as more than 80% of all individuals have been exposed to HPV by age 50, representing an important target for vaccine development to reduce the incidence of cancer and the economic cost of HPV-related health issues. The approval of Gardasil^® as a prophylactic vaccine for high-risk HPV 16 and 18 and low-risk HPV6 and 11 for people aged 11-26 in 2006, and of Cervarix^® in 2009, revolutionized the field and has since reduced HPV infection in young populations. Unfortunately, prophylactic vaccination does not induce immunity in those with established HPV infections or HPV-induced neoplasms, and there are currently no therapeutic HPV vaccines approved by the US Food and Drug Administration. This comprehensive review will detail the progress made in the development of therapeutic vaccines against high-risk HPV types, and potential combinations with other immunotherapeutic agents for more efficient and rational designs of combination treatments for HPV-associated malignancies.

Therapeutic Vaccines Against Human Papilloma Viruses: Achievements and Prospects

Human papillomaviruses of high carcinogenic risk (HR HPVs) are major etiological agents of malignant diseases of the cervix, vulva, penis, anal canal, larynx, head, and neck. Prophylactic vaccination against HPV, which mainly covers girls and women under 25, does not prevent vertical and horizontal HPV transmission in infants and children and does not have a therapeutic effect. As a result, a significant proportion of the population is not protected from the HPV infection and development of HPV-associated neoplastic transformation and cancer, which indicates the need for development and introduction of therapeutic HPV vaccines. Unlike prophylactic vaccines aimed at the formation of virus-neutralizing antibodies, therapeutic vaccines elicit cellular immune response leading to the elimination of infected and malignant cells expressing viral proteins. The ideal targets for vaccine immunotherapy are highly conserved HR HPV oncoproteins E6 and E7 expressed in precancerous and tumor tissues. Here, we describe expression of these proteins during different stages of HPV infection, their antigenic and immunogenic properties, and T-cell epitopes, the response to which correlates with natural regression of HPV-induced neoplastic changes. The review describes patterns of E6 and E7 oncoproteins presentation to the immune system as components of candidate vaccines along with the results of the most promising preclinical trials and animal models used in these trials. Special attention is paid to vaccine candidates which have shown efficacy in clinical trials in patients with HPV-associated neoplastic changes.

Demarcated thresholds of tumor-specific CD8 T cells elicited by MCMV-based vaccine vectors provide robust correlates of protection

BACKGROUND

The capacity of cytomegalovirus (CMV) to elicit long-lasting strong T cell responses, and the ability to engineer the genome of this DNA virus positions CMV-based vaccine vectors highly suitable as a cancer vaccine platform. Defined immune thresholds for tumor protection and the factors affecting such thresholds have not well been investigated in cancer immunotherapy. We here determined using CMV as a vaccine platform whether critical thresholds of vaccine-specific T cell responses can be established that relate to tumor protection, and which factors control such thresholds.

METHODS

We generated CMV-based vaccine vectors expressing the E7 epitope and tested these in preclinical models of HPV16-induced cancer. Vaccination was applied via different doses and routes (intraperitoneal (IP), subcutaneous (SC) and intranasal (IN)). The magnitude, kinetics and phenotype of the circulating tumor-specific CD8⁺ T cell response were determined. Mice were subsequently challenged with tumor cells, and the tumor protection was monitored.

RESULTS

Immunization with CMV-based vaccines via the IP or SC route eliciting vaccine-induced CD8⁺ T cell responses of > 0.3% of the total circulating CD8 T cell population fully protects mice against lethal tumor challenge. However, low dose inoculations via the IP or SC route or IN vaccination elicited vaccine-induced CD8⁺ T cell responses that did not reach protective thresholds for tumor protection. In addition, whereas weak pre-existing immunity did not alter the protective thresholds of the vaccine-specific T cell response following subsequent immunization with CMV-based vaccine vectors, strong pre-existing immunity inhibited the development of vaccine-induced T cells and their control on tumor progression.

CONCLUSIONS

This study highlight the effectiveness of CMV-based vaccine vectors, and shows that demarcated thresholds of vaccine-specific T cells could be defined that correlate to tumor protection. Together, these results may hold importance for cancer vaccine development to achieve high efficacy in vaccine recipients.

Therapeutic vaccines for high-risk HPV-associated diseases

Cancer is the second leading cause of death worldwide, and it is estimated that Human papillomavirus (HPV) related cancers account for 5% of all human cancers. Current HPV vaccines are extremely effective at preventing infection and neoplastic disease; however, they are prophylactic and do not clear established infections. Therapeutic vaccines which trigger cell-mediated immune responses for the treatment of established infections and malignancies are therefore required. The E6 and E7 early genes are ideal targets for vaccine therapy due to their role in disruption of the cell cycle and their constitutive expression in premalignant and malignant tissues. Several strategies have been investigated for the development of therapeutic vaccines, including live-vector, nucleic acid, peptide, protein-based and cell-based vaccines as well as combinatorial approaches, with several vaccine candidates progressing to clinical trials. With the current understanding of the HPV life cycle, molecular mechanisms of infection, carcinogenesis, tumour biology, the tumour microenvironment and immune response mechanisms, an approved HPV therapeutic vaccine seems to be a goal not far from being achieved. In this article, the status of therapeutic HPV vaccines in clinical trials are reviewed, and the potential for plant-based vaccine production platforms described.

The current state of therapeutic and T cell-based vaccines against human papillomaviruses

Human papillomavirus (HPV) is known to be a necessary factor for many gynecologic malignancies and is also associated with a subset of head and neck malignancies. This knowledge has created the opportunity to control these HPV-associated cancers through vaccination. However, despite the availability of prophylactic HPV vaccines, HPV infections remain extremely common worldwide. In addition, while prophylactic HPV vaccines have been effective in preventing infection, they are ineffective at clearing pre-existing HPV infections. Thus, there is an urgent need for therapeutic and T cell-based vaccines to treat existing HPV infections and HPV-associated lesions and cancers. Unlike prophylactic vaccines, which generate neutralizing antibodies, therapeutic, and T cell-based vaccines enhance cell-mediated immunity against HPV antigens. Our review will cover various therapeutic and T cell-based vaccines in development for the treatment of HPV-associated diseases. Furthermore, we review the strategies to enhance the efficacy of therapeutic vaccines and the latest clinical trials on therapeutic and T cell-based HPV vaccines.

Development of HPV Vaccines for HPV-associated Head and Neck Squamous Cell Carcinoma

High-risk genotypes of the human papillomavirus (HPV), particularly HPV type 16, are found in a distinct subset of head and neck squamous cell carcinomas (HNSCC). Thus, these HPV-associated HNSCC may be prevented or treated by vaccines designed to induce appropriate HPV virus-specific immune responses. Infection by HPV may be prevented by neutralizing antibodies specific for the viral capsid proteins. In clinical trials, vaccines comprised of HPV virus-like particles (VLPs) have shown great promise as prophylactic HPV vaccines. However, given that capsid proteins are not expressed at detectable levels by infected basal keratinocytes, vaccines with therapeutic potential must target other non-structural viral antigens. Two HPV oncogenic proteins, E6 and E7, are important in the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Therefore, therapeutic vaccines targeting these proteins may have potential to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 is administered in live vectors, in peptides or protein, in nucleic acid form, as components of chimeric VLPs, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. Should they fulfill their promise, these vaccines may prevent HPV infection or control its potentially life-threatening consequences in humans.

Perspectives for therapeutic HPV vaccine development

Background

Human papillomavirus (HPV) infections and associated diseases remain a serious burden worldwide. It is now clear that HPV serves as the etiological factor and biologic carcinogen for HPV-associated lesions and cancers. Although preventative HPV vaccines are available, these vaccines do not induce strong therapeutic effects against established HPV infections and lesions. These concerns create a critical need for the development of therapeutic strategies, such as vaccines, to treat these existing infections and diseases.

Main Body

Unlike preventative vaccines, therapeutic vaccines aim to generate cell-mediated immunity. HPV oncoproteins E6 and E7 are responsible for the malignant progression of HPV-associated diseases and are consistently expressed in HPV-associated diseases and cancer lesions; therefore, they serve as ideal targets for the development of therapeutic HPV vaccines. In this review we revisit therapeutic HPV vaccines that utilize this knowledge to treat HPV-associated lesions and cancers, with a focus on the findings of recent therapeutic HPV vaccine clinical trials.

Conclusion

Great progress has been made to develop and improve novel therapeutic HPV vaccines to treat existing HPV infections and diseases; however, there is still much work to be done. We believe that therapeutic HPV vaccines have the potential to become a widely available and successful therapy to treat HPV and HPV-associated diseases in the near future.

Immunotherapy for human papillomavirus-associated disease and cervical cancer: review of clinical and translational research

Cervical cancer is the fourth most lethal women's cancer worldwide. Current treatments against cervical cancer include surgery, radiotherapy, chemotherapy, and anti-angiogenic agents. However, despite the various treatments utilized for the treatment of cervical cancer, its disease burden remains a global issue. Persistent infection of human papillomavirus (HPV) has been identified as an essential step of pathogenesis of cervical cancer and many other cancers, and nation-wide HPV screening as well as preventative HPV vaccination program have been introduced globally. However, even though the commercially available prophylactic HPV vaccines, Gardasil (Merck) and Cervarix (GlaxoSmithKline), are effective in blocking the entry of HPV into the epithelium of cervix through generation of HPV-specific neutralizing antibodies, they cannot eliminate the pre-existing HPV infection. For these reason, other immunotherapeutic options against HPV-associated diseases, including therapeutic vaccines, have been continuously explored. Therapeutic HPV vaccines enhance cell-mediated immunity targeting HPV E6 and E7 antigens by modulating primarily dendritic cells and cytotoxic T lymphocyte. Our review will cover various therapeutic vaccines in development for the treatment of HPV-associated lesions and cancers. Furthermore, we will discuss the potential of immune checkpoint inhibitors that have recently been adopted and tested for their treatment efficacy against HPV-induced cervical cancer.

A Multi-Component Prime-Boost Vaccination Regimen with a Consensus MOMP Antigen Enhances Chlamydia trachomatis Clearance

BACKGROUND

A vaccine for Chlamydia trachomatis is of urgent medical need. We explored bioinformatic approaches to generate an immunogen against C. trachomatis that would induce cross-serovar T-cell responses as (i) CD4(+) T cells have been shown in animal models and human studies to be important in chlamydial protection and (ii) antibody responses may be restrictive and serovar specific.

METHODS

A consensus antigen based on over 1,500 major outer membrane protein (MOMP) sequences provided high epitope coverage against the most prevalent C. trachomatis strains in silico. Having designed the T-cell immunogen, we assessed it for immunogenicity in prime-boost regimens. This consensus MOMP transgene was delivered using plasmid DNA, Human Adenovirus 5 (HuAd5) or modified vaccinia Ankara (MVA) vectors with or without MF59(®) adjuvanted recombinant MOMP protein.

RESULTS

Different regimens induced distinct immune profiles. The DNA-HuAd5-MVA-Protein vaccine regimen induced a cellular response with a Th1-biased serum antibody response, alongside high serum and vaginal MOMP-specific antibodies. This regimen significantly enhanced clearance against intravaginal C. trachomatis serovar D infection in both BALB/c and B6C3F1 mouse strains. This enhanced clearance was shown to be CD4(+) T-cell dependent. Future studies will need to confirm the specificity and precise mechanisms of protection.

CONCLUSION

A C. trachomatis vaccine needs to induce a robust cellular response with broad cross-serovar coverage and a heterologous prime-boost regimen may be an approach to achieve this.

Progress and prospects for L2-based human papillomavirus vaccines

Human papillomavirus (HPV) is a worldwide public health problem, particularly in resource-limited countries. Fifteen high-risk genital HPV types are sexually transmitted and cause 5% of all cancers worldwide, primarily cervical, anogenital and oropharyngeal carcinomas. Skin HPV types are generally associated with benign disease, but a subset is linked to non-melanoma skin cancer. Licensed HPV vaccines based on virus-like particles (VLPs) derived from L1 major capsid antigen of key high risk HPVs are effective at preventing these infections but do not cover cutaneous types and are not therapeutic. Vaccines targeting L2 minor capsid antigen, some using capsid display, adjuvant and fusions with early HPV antigens or Toll-like receptor agonists, are in development to fill these gaps. Progress and challenges with L2-based vaccines are summarized.

Current state in the development of candidate therapeutic HPV vaccines

The identification of human papillomavirus (HPV) as an etiological factor for HPV-associated malignancies creates the opportunity to control these cancers through vaccination. Currently, available preventive HPV vaccines have not yet demonstrated strong evidences for therapeutic effects against established HPV infections and lesions. Furthermore, HPV infections remain extremely common. Thus, there is urgent need for therapeutic vaccines to treat existing HPV infections and HPV-associated diseases. Therapeutic vaccines differ from preventive vaccines in that they are aimed at generating cell-mediated immunity rather than neutralizing antibodies. The HPV-encoded early proteins, especially oncoproteins E6 and E7, form ideal targets for therapeutic HPV vaccines since they are consistently expressed in HPV-associated malignancies and precancerous lesions, playing crucial roles in the generation and maintenance of HPV-associated disease. Our review will cover various therapeutic vaccines in development for the treatment of HPV-associated lesions and cancers. Furthermore, we review strategies to enhance vaccine efficacy and the latest clinical trials on therapeutic HPV vaccines.

Design, Immune Responses and Anti-Tumor Potential of an HPV16 E6E7 Multi-Epitope Vaccine

Cervical cancer is a common type of cancer among women worldwide and infection with high-risk human papillomavirus (HPVs) types represents the major risk factor for the etiopathogenesis of the disease. HPV-16 is the most frequently identified HPV type in cervical lesions and expression of E6 and E7 oncoproteins is required for the uncontrolled cellular proliferation. In the present study we report the design and experimental testing of a recombinant multi-epitope protein containing immunogenic epitopes of HPV-16 E6 and E7. Tumor preventive assays, based on the engraftment of TC-1 cells in mice, showed that the E6E7 multi-epitope protein induced a full preventive anti-tumor protection in wild-type mice, as well as in mice deficient in expression of CD4+ T cells and TLR4 receptor. Nonetheless, no anti-tumor protection was observed in mice deficient in CD8+ T cells. Also, the vaccine promoted high activation of E6/E7-specific T cells and in a therapeutic-approach, E6E7 protein conferred full anti-tumor protection in mice. These results show a potential use of this E6E7 multi-epitope antigen as a new and promising antigen for the development of a therapeutic vaccine against tumors induced by HPV.

Safety and Efficacy Data on Vaccines and Immunization to Human Papillomavirus

Since the discovery of the causal association between human papillomavirus (HPV) and cervical cancer, efforts to develop an effective prophylactic vaccine to prevent high-risk HPV infections have been at the forefront of modern medical research. HPV causes 530,000 cervical cancer cases worldwide, which is the second most common cause of cancer deaths in women; a worldwide collaboration among epidemiologists, molecular biologists, vaccinologists, virologists, and clinicians helped lead to the development of two highly effective prophylactive HPV vaccines. The first, Gardasil, is a quadrivalent vaccine made up of recombinant HPV L1 capsid proteins from the two high-risk HPV types (16/18) responsible for 70% of cervical cancer cases as well as two low-risk HPV types (6/11) which are the causative agent for genital warts. The second, Cervarix, is a bivalent vaccine that was FDA approved three years after Gardasil and is also composed of L1 capsid proteins from HPV types 16/18. This review article focuses on the safety and efficacy data of both FDA-approved vaccines, as well as highlighting a few advances in future HPV vaccines that show promise in becoming additional treatment options for this worldwide disease.

A prime/boost strategy using DNA/fowlpox recombinants expressing the genetically attenuated E6 protein as a putative vaccine against HPV-16-associated cancers

BACKGROUND

Considering the high number of new cases of cervical cancer each year that are caused by human papilloma viruses (HPVs), the development of an effective vaccine for prevention and therapy of HPV-associated cancers, and in particular against the high-risk HPV-16 genotype, remains a priority. Vaccines expressing the E6 and E7 proteins that are detectable in all HPV-positive pre-cancerous and cancer cells might support the treatment of HPV-related lesions and clear already established tumors.

METHODS

In this study, DNA and fowlpox virus recombinants expressing the E6F47R mutant of the HPV-16 E6 oncoprotein were generated, and their correct expression verified by RT-PCR, Western blotting and immunofluorescence. Immunization protocols were tested in a preventive or therapeutic pre-clinical mouse model of HPV-16 tumorigenicity using heterologous (DNA/FP) or homologous (DNA/DNA and FP/FP) prime/boost regimens. The immune responses and therapeutic efficacy were evaluated by ELISA, ELISPOT assays, and challenge with TC-1* cells.

RESULTS

In the preventive protocol, while an anti-E6-specific humoral response was just detectable, a specific CD8(+) cytotoxic T-cell response was elicited in immunized mice. After the challenge, there was a delay in cancer appearance and a significant reduction of tumor volume in the two groups of E6-immunized mice, thus confirming the pivotal role of the CD8(+) T-cell response in the control of tumor growth in the absence of E6-specific antibodies. In the therapeutic protocol, in-vivo experiments resulted in a higher number of tumor-free mice after the homologous DNA/DNA or heterologous DNA/FP immunization.

CONCLUSIONS

These data establish a preliminary indication for the prevention and treatment of HPV-related tumors by the use of DNA and avipox constructs as safe and effective immunogens following a prime/boost strategy. The combined use of recombinants expressing both E6 and E7 proteins might improve the antitumor efficacy, and should represent an important approach to control HPV-associated cancers.

Sequential cisplatin therapy and vaccination with HPV16 E6E7L2 fusion protein in saponin adjuvant GPI-0100 for the treatment of a model HPV16+ cancer

Clinical studies suggest that responses to HPV16 E6E7L2 fusion protein (TA-CIN) vaccination alone are modest, and GPI-0100 is a well-tolerated, potent adjuvant. Here we sought to optimize both the immunogenicity of TA-CIN via formulation with GPI-0100 and treatment of HPV16+ cancer by vaccination after cisplatin chemotherapy. HPV16 neutralizing serum antibody titers, CD4+ T cell proliferative and E6/E7-specific CD8+ T cell responses were significantly enhanced when mice were vaccinated subcutaneously (s.c.) or intramuscularly (i.m.) with TA-CIN formulated with GPI-0100. Vaccination was tested for therapy of mice bearing syngeneic HPV16 E6/E7+ tumors (TC-1) either in the lung or subcutaneously. Mice treated with TA-CIN/GPI-0100 vaccination exhibited robust E7-specific CD8+ T cell responses, which were associated with reduced tumor burden in the lung, whereas mice receiving either component alone were similar to controls. Since vaccination alone was not sufficient for cure, mice bearing s.c. TC-1 tumor were first treated with two doses of cisplatin and then vaccinated. Vaccination with TA-CIN/GPI-0100 i.m. substantially retarded tumor growth and extended survival after cisplatin therapy. Injection of TA-CIN alone, but not GPI-0100, into the tumor (i.t.) was similarly efficacious after cisplatin therapy, but the mice eventually succumbed. However, tumor regression and extended remission was observed in 80% of the mice treated with cisplatin and then intra-tumoral TA-CIN/GPI-0100 vaccination. These mice also exhibited robust E7-specific CD8+ T cell and HPV16 neutralizing antibody responses. Thus formulation of TA-CIN with GPI-0100 and intra-tumoral delivery after cisplatin treatment elicits potent therapeutic responses in a murine model of HPV16+ cancer.

Oral vaccination against HPV E7 for treatment of cervical intraepithelial neoplasia grade 3 (CIN3) elicits E7-specific mucosal immunity in the cervix of CIN3 patients

BACKGROUND

Cervical intraepithelial neoplasia grade 3 (CIN3) is a mucosal precancerous lesion caused by high-risk human papillomavirus (HPV). Induction of immunological clearance of CIN3 by targeting HPV antigens is a promising strategy for CIN3 therapy. No successful HPV therapeutic vaccine has been developed.

METHODS

We evaluated the safety and clinical efficacy of an attenuated Lactobacillus casei expressing modified full-length HPV16 E7 protein in patients with HPV16-associated CIN3. Ten patients were vaccinated orally during dose optimization studies (1, 2, 4, or 6 capsules/day) at weeks 1, 2, 4, and 8 (Step 1). Seven additional participants were only tested using the optimized vaccine formulation (Step 2), giving a total of 10 patients who received optimized vaccination. Cervical lymphocytes (CxLs) and peripheral blood mononuclear cells (PBMCs) were collected and E7 specific interferon-γ-producing cells were counted (E7 cell-mediated immune responses: E7-CMI) by ELISPOT assay. All patients were re-evaluated 9 weeks after initial vaccine exposure using cytology and biopsy to assess pathological efficacy.

RESULTS

No patient experienced an adverse event. E7-CMI in both CxLs and PBMCs was negligible at baseline. All patients using 4-6 capsules/day showed increased E7-CMI in CxLs, whereas patients using 1-2 capsules/day did not. No patient demonstrated an increase in E7-CMI in their PBMCs. In comparison between patients of cohorts, E7-CMI at week 9 (9 wk) in patients on 4 capsules/day was significantly higher than those in patients on 1, 2, or 6 capsules/day. Most patients (70%) taking the optimized dose experienced a pathological down-grade to CIN2 at week 9 of treatment. E7-CMI in CxLs correlated directly with the pathological down-grade.

CONCLUSIONS

Oral administration of an E7-expressing Lactobacillus-based vaccine can elicit E7-specific mucosal immunity in the uterine cervical lesions. We are the first to report a correlation between mucosal E7-CMI in the cervix and clinical response after immunotherapy in human mucosal neoplasia.

Measurement of neutralizing serum antibodies of patients vaccinated with human papillomavirus L1 or L2-based immunogens using furin-cleaved HPV Pseudovirions

Antibodies specific for neutralizing epitopes in either Human papillomavirus (HPV) capsid protein L1 or L2 can mediate protection from viral challenge and thus their accurate and sensitive measurement at high throughput is likely informative for monitoring response to prophylactic vaccination. Here we compare measurement of L1 and L2-specific neutralizing antibodies in human sera using the standard Pseudovirion-Based Neutralization Assay (L1-PBNA) with the newer Furin-Cleaved Pseudovirion-Based Neutralization Assay (FC-PBNA), a modification of the L1-PBNA intended to improve sensitivity towards L2-specific neutralizing antibodies without compromising assay of L1-specific responses. For detection of L1-specific neutralizing antibodies in human sera, the FC- PBNA and L1-PBNA assays showed similar sensitivity and a high level of correlation using WHO standard sera (n = 2), and sera from patients vaccinated with Gardasil (n = 30) or an experimental human papillomavirus type 16 (HPV16) L1 VLP vaccine (n = 70). The detection of L1-specific cross-neutralizing antibodies in these sera using pseudovirions of types phylogenetically-related to those targeted by the L1 virus-like particle (VLP) vaccines was also consistent between the two assays. However, for sera from patients (n = 17) vaccinated with an L2-based immunogen (TA-CIN), the FC-PBNA was more sensitive than the L1-PBNA in detecting L2-specific neutralizing antibodies. Further, the neutralizing antibody titers measured with the FC-PBNA correlated with those determined with the L2-PBNA, another modification of the L1-PBNA that spacio-temporally separates primary and secondary receptor engagement, as well as the protective titers measured using passive transfer studies in the murine genital-challenge model. In sum, the FC-PBNA provided sensitive measurement for both L1 VLP and L2-specific neutralizing antibody in human sera. Vaccination with TA-CIN elicits weak cross-protective antibody in a subset of patients, suggesting the need for an adjuvant.

Recombinant Leishmania tarentolae encoding the HPV type 16 E7 gene in tumor mice model

Background: Cervical cancer, the third most prevalent cause of cancer in women worldwide, is associated with HPVs. The critical role of E7 protein in HPV-related malignancies has designated it as a strong contender for generating vaccines against HPV. Materials & methods: In this study, we developed a novel live vaccine using recombinant Leishmania tarentolae expressing E7-green fluorescent protein (GFP) fusion protein for the protection of mice against HPV-associated tumors. In order to transfect L. tarentolae with E7-GFP fusion construct, pLEXSY-neo2 system was applied. Followed by PCR, fluorescence imaging and fluorescence-activated cell sorting analysis, integration of E7-GFP gene into parasites genome was confirmed. A comparative study of six groups of C57BL/6 mice was performed to analyze antigen-specific humoral and cellular immune responses against E7 encoding live and DNA vaccines. Furthermore, the anti-tumor protective effect of L. tarentolae-E7-GFP was compared to other vaccination strategies, namely pcDNA-E7 as the DNA vaccine and pcDNA-E7/L. tarentolae-E7-GFP as the prime-boost regimen. Results: We found that E7-GFP expressing recombinant L. tarentolae induces significant levels of IgG2a and IFN-γ, while there is no significant IL-5 production compared with that of other strategies and control groups before and after challenge with TC-1 tumor cells. It is noteworthy that the designed live vaccine showed the best protection and minimum tumor size among all groups against TC-1-induced tumors. Conclusion: Overall, the results obtained revealed that the E7-GFP recombinant L. tarentolae could be a potential live vaccine for induction of immune responses in vivo.

Immune responses elicited by co-immunization of Plasmodium vivax and P. falciparum MSP-1 using prime-boost immunization strategies

Carboxy-terminus of merozoite surface protein-1 (MSP-1(19) ) is the major protein on the surface of the plasmodial merozoite that acts as one of the most important blood-stage vaccine candidates. The present investigation was designed to evaluate the immune responses when either two recombinant antigens (rPvMSP-1(19) + rPfMSP-1(19)) or two plasmid constructs (pcDNA3.1 hygro-PvMSP-1(19) + pcDNA3.1 hygro-PfMSP-1(19)) were administered in combination at a single site in mice by using different immunization strategies (protein/protein, DNA/DNA and DNA/protein) at weeks 0, 5 and 8. All mice were monitored for the level of MSP-1(19) -specific antibody for up to 40 weeks. The inclusion of both recombinant antigens in a vaccine mixture could not inhibit induction of antibodies to the other antigen when the two recombinant antigens were combined in immunization formulation. Interestingly, antisera from immunized mice with either recombinant antigen failed to cross-react with heterologous antigen. Moreover, the results of this study showed that co-immunization with both antigens at a single site generated a substantial PvMSP-1(19) - and PfMSP-1(19) -specific antibody responses and also IFN-γ cytokine production (Th1 response) in DNA/protein prime-boost immunization strategies. The increased humoral response to PvMSP-1(19) and PfMSP-1(19) lasted nearly a year after immunization. Therefore, the results of this study are encouraging for the development of multi-species malaria vaccine based on MSP-1(19) antigen.

Experience with synthetic vaccines for cancer and persistent virus infections in nonhuman primates and patients

Synthetic vaccines, in particular long synthetic peptides of approximately 25-50 amino acids in length, are attractive for HIV vaccine development and for induction of therapeutic immune responses in patients with (pre-)malignant disorders. In the case of preventive vaccine development against HIV, no major success has been achieved, but the possibilities are by no means exhausted. A long peptide vaccine consisting of 13 overlapping peptides, which together cover the entire length of the two oncogenic proteins E6 and E7 of high-risk human papilloma virus type 16 (HPV16), caused complete regression of all lesions and eradication of virus in 9 out of 20 women with high-grade vulvar intraepithelial neoplasia, a therapy-resistant preneoplastic disorder. The nature and strength of the vaccine-prompted T cell responses were significantly correlated with the clinical response. Synthetic peptide vaccines are attractive, because they allow rational improvement of vaccine design and detailed pharmacokinetic and pharmacodynamic studies not possible with conventional vaccines. Improvements are possible by addition or conjugation of adjuvants, notably TLR ligands, to the synthetic peptides.

Bone marrow vaccination: a novel approach to enhance antigen specific antitumor immunity

Bone marrow (BM) serves as a reservoir for a unique population of memory T cells with strong effector properties that make them ideal targets for cancer immunotherapy strategies. However, direct vaccination and priming of T cells within the BM of the host has never been investigated. This study evaluates the specific immune response induced via a new method of direct intra-bone marrow (IBM) vaccination in an animal model of human papillomavirus-associated cancer. We found that IBM vaccinations with the class I HPV-16 E7 epitope induce large numbers of activated, IFN-γ-producing E7-specific lymphocytes in the BM. In prophylactic tumor challenge experiments, direct intra-BM vaccination was found to be protective against tumor formation for 80% of the mice. In the therapeutic setting, IBM vaccination induced tumor regression in 3 of 10 vaccinated mice and delayed tumor growth in the remaining animals. Finally, adoptive transfer of BM cells from IBM vaccinated mice to naïve animals conferred complete protection against tumor growth. These data demonstrate the capacity of direct IBM vaccination to induce potent antigen-specific immunity resulting in protection from tumor growth in an animal model. Specifically targeting BM T cells with vaccines may improve responses to cancer immunotherapy and offer important clinical advantages, especially in the setting of bone marrow malignancies.

Safety and Immunogenicity of a Human Papillomavirus Peptide Vaccine (CIGB-228) in Women with High-Grade Cervical Intraepithelial Neoplasia: First-in-Human, Proof-of-Concept Trial

Objective. CIGB-228 is a novel therapeutic vaccine consisting of HLA-restricted HPV16 E7 epitope adjuvated with VSSP. This trial was designed to evaluate the toxicity, safety, immunogenicity, HPV clearance, and lesion regression. Methods. Seven women were entered. All were HLA-A2 positive, had biopsy-proven high-grade CIN, histologically positive for HPV16, and beared persistent postbiopsy lesions visible by digital colposcopy. HLA-A2 women with biopsy-proven high-grade CIN, HPV16-positive, and beared persistent postbiopsy lesions visible by digital colposcopy were vaccinated. One weekly injections of CIGB-228 vaccine was given for four weeks. Then, loop electrosurgical excision procedure (LEEP) of the transformation zone was performed. Study subjects were followed for 1 year after LEEP. Results. No toxicity beyond grade 1 was observed during and after the four vaccinations. Five of seven women had complete and partial regression. Cellular immune response was seen in all patients. HPV was cleared in three of the patients with complete response. Conclusion. CIGB-228 vaccination was well tolerated and capable to induce IFNγ-associated T-cell response in women with high-grade CIN. In several patients, lesion regression and HPV clearance were observed.

E6 and E7 fusion immunoglobulin from human papilloma virus 16 induces dendritic cell maturation and antigen specific activation of T helper 1 response

Human papilloma virus (HPV) 16 causes cervical cancer. Induction of oncogenesis by HPV 16 is primarily dependent on the function of E6 and E7 proteins, which inactivate the function of p53 and pRB, respectively. Thus, blocking the activity of the E6 and E7 proteins from HPV 16 is critical to inhibiting oncogenesis during infection. We have expressed and purified soluble HPV 16 E6 and E7 fusion immunoglobulin (Ig), which were combined with the constant region of an Ig heavy chain, in a mammalian system. To assess whether soluble E6 and E7 fusion Igs induce effective cellular immune responses, immature dendritic cells (DCs) were treated with these fusion proteins. Soluble E6 and E7 fusion Igs effectively induced maturation of DCs. Furthermore, immunization with soluble E6 and E7 fusion Igs in mice resulted in antigen-specific activation of T helper 1 (Th1) cells. This is the first comprehensive study to show the molecular basis of how soluble HPV 16 E6 or E7 fusion Igs induces Th1 responses through the maturation of DCs. In addition, we show that DC therapy using soluble HPV E6 and E7 fusion Igs may be a valuable tool for controlling the progress of cervical cancer.

Fowlpox virus recombinants expressing HPV-16 E6 and E7 oncogenes for the therapy of cervical carcinoma elicit humoral and cell-mediated responses in rabbits

Background

Around half million new cases of cervical cancer arise each year, making the development of an effective therapeutic vaccine against HPV a high priority. As the E6 and E7 oncoproteins are expressed in all HPV-16 tumour cells, vaccines expressing these proteins might clear an already established tumour and support the treatment of HPV-related precancerous lesions.

Methods

Three different immunisation regimens were tested in a pre-clinical trial in rabbits to evaluate the humoral and cell-mediated responses of a putative HPV-16 vaccine. Fowlpoxvirus (FP) recombinants separately expressing the HPV-16 E6 (FP_E6) and E7 (FP_E7) transgenes were used for priming, followed by E7 protein boosting.

Results

All of the protocols were effective in eliciting a high antibody response. This was also confirmed by interleukin-4 production, which increased after simultaneous priming with both FP_E6 and FP_E7 and after E7 protein boost. A cell-mediated immune response was also detected in most of the animals.

Conclusion

These results establish a preliminary profile for the therapy with the combined use of avipox recombinants, which may represent safer immunogens than vaccinia-based vectors in immuno-compromised individuals, as they express the transgenes in most mammalian cells in the absence of a productive replication.

Perspectives for the development of human papillomavirus vaccines and immunotherapy

Human papillomavirus (HPV) is the most common sexually transmitted infection and is responsible for 90-99% of cervical cancer (CxCa) cases. Although effective screening programs have reduced the incidence of CxCa in developed countries, they are often not well organized. Prophylactic vaccination against HPV seems to be a good strategy for the prevention of CxCa. However, because millions of women are already infected with HPV, therapeutic HPV vaccines need to be developed further to treat these women. This review discusses the actual perspectives on both HPV vaccines and immunotherapy worldwide. In addition, some of the perspectives in France are also briefly discussed.