Phase IIa safety and immunogenicity of a therapeutic vaccine, TA-GW, in persons with genital warts

An Update on Human Papilloma Virus Vaccines: History, Types, Protection, and Efficacy

Human papillomavirus (HPV) is the most common sexually transmitted agent worldwide. Early prevention with HPV vaccination is a safe and effective method against this disease. HPV vaccines provided more protection against several oncogenic HPV strains. Three prophylactic HPV vaccines have been approved to target high-risk HPV types and protect against HPV-related disorders. These existing vaccines are based on the recombinant DNA technology and purified L1 protein that is assembled to form HPV empty shells. The prophylactic vaccines are highly immunogenic and can induce production of specific neutralizing antibodies. However, therapeutic vaccines are different from these prophylactic vaccines. They induced cell-mediated immunity against transformed cells, instead of neutralizing antibodies. The second generation of prophylactic HPV vaccines, made from alternative viral components using cost-effective production strategies, is undergoing clinical evaluation. The purpose of this review is to provide a complete and up-to-date review of the types of HPV vaccines and the efficiency of each of them for readers.

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.

Progress in L2-Based Prophylactic Vaccine Development for Protection against Diverse Human Papillomavirus Genotypes and Associated Diseases

The human papillomaviruses (HPVs) are a family of small DNA tumor viruses including over 200 genotypes classified by phylogeny into several genera. Different genera of HPVs cause ano-genital and oropharyngeal cancers, skin cancers, as well as benign diseases including skin and genital warts. Licensed vaccines composed of L1 virus-like particles (VLPs) confer protection generally restricted to the ≤9 HPV types targeted. Here, we examine approaches aimed at broadening the protection against diverse HPV types by targeting conserved epitopes of the minor capsid protein, L2. Compared to L1 VLP, L2 is less immunogenic. However, with appropriate presentation to the immune system, L2 can elicit durable, broadly cross-neutralizing antibody responses and protection against skin and genital challenge with diverse HPV types. Such approaches to enhance the strength and breadth of the humoral response include the display of L2 peptides on VLPs or viral capsids, bacteria, thioredoxin and other platforms for multimerization. Neither L2 nor L1 vaccinations elicit a therapeutic response. However, fusion of L2 with early viral antigens has the potential to elicit both prophylactic and therapeutic immunity. This review of cross-protective HPV vaccines based on L2 is timely as several candidates have recently entered early-phase clinical trials.

Human papillomavirus first and second generation vaccines-current status and future directions

It has been more than 10 years that the first prophylactic papillomavirus vaccine became available, although distribution has been mainly limited to the more affluent countries. The first two vaccines have been a great success, hundreds of millions of women and a much smaller number of men have been vaccinated ever since. In a few countries with high vaccination coverage, in particular Australia but also parts of Great Britain and others, clinical impact of vaccination programs is already visible and there are indications for herd immunity as well. Vaccine efficacy is higher than originally estimated and the vaccines have an excellent safety profile. Gardasil9 is a second generation HPV virus-like particle vaccine that was licensed in 2015 and there are more to come in the near future. Currently, burning questions in respect to HPV vaccination are the duration of protection - especially in regard to cross-protection - reduction of the three-dose regimen and its impact on cross-protection; and duration of response, as well as protection against oropharyngeal HPV infections. Furthermore, researchers are seeking to overcome limitations of the VLP vaccines, namely low thermal stability, cost, invasive administration, limited coverage of non-vaccine HPV types, and lack of therapeutic efficacy. In this review we summarize the current status of licensed VLP vaccines and address questions related to second and third generation 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.

Developments in L2-based human papillomavirus (HPV) vaccines

Infections with sexually transmitted high-risk Human Papillomavirus (hrHPV), of which there are at least 15 genotypes, are responsible for a tremendous disease burden by causing cervical, and subsets of other ano-genital and oro-pharyngeal carcinomas, together representing 5% of all cancer cases worldwide. HPV subunit vaccines consisting of virus-like particles (VLP) self-assembled from major capsid protein L1 plus adjuvant have been licensed. Prophylactic vaccinations with the 2-valent (HPV16/18), 4-valent (HPV6/11/16/18), or 9-valent (HPV6/11/16/18/31/33/45/52/58) vaccine induce high-titer neutralizing antibodies restricted to the vaccine types that cause up to 90% of cervical carcinomas, a subset of other ano-genital and oro-pharyngeal cancers and 90% of benign ano-genital warts (condylomata). The complexity of manufacturing multivalent L1-VLP vaccines limits the number of included VLP types and thus the vaccines' spectrum of protection, leaving a panel of oncogenic mucosal HPV unaddressed. In addition, current vaccines do not protect against cutaneous HPV types causing benign skin warts, or against beta-papillomavirus (betaPV) types implicated in the development of non-melanoma skin cancer (NMSC) in immunosuppressed patients. In contrast with L1-VLP, the minor capsid protein L2 contains type-common epitopes that induce low-titer yet broadly cross-neutralizing antibodies to heterologous PV types and provide cross-protection in animal challenge models. Efforts to increase the low immunogenicity of L2 (poly)-peptides and thereby to develop broader-spectrum HPV vaccines are the focus of this review.

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.

Evaluating the efficacy of therapeutic HIV vaccines through analytical treatment interruptions

INTRODUCTION

The development of an effective therapeutic HIV vaccine that induces immunologic control of viral replication, thereby eliminating or reducing the need for antiretroviral therapy (ART), would be of great value. Besides the obvious challenges of developing a therapeutic vaccine that would generate effective, sustained anti-HIV immunity in infected individuals is the issue of how to best assess the efficacy of vaccine candidates.

DISCUSSION

This review discusses the various outcome measures assessed in therapeutic HIV vaccine clinical trials involving individuals receiving suppressive ART, with a particular focus on the role of analytical treatment interruption (ATI) as a way to assess the virologic control induced by an immunotherapy. This strategy is critical given that there are otherwise no readily available measures to determine the ability of a vaccine-induced immune response to effectively control HIV replication. The various outcome measures that have been used to assess vaccine efficacy in published therapeutic HIV vaccine clinical trials will also be discussed. Outcome measures have included the kinetics of viral rebound, the new viral set point and changes in the size of the viral reservoir. Clinically relevant outcomes such as the CD4 decline, the time to resume therapy or the time to meet the criterion to resume therapy, the proportion of participants who resume therapy and/or the development of clinical symptoms such as acute retroviral syndrome are also measures of vaccine efficacy.

CONCLUSIONS

Given the lack of consistency between therapeutic HIV vaccine trials in how efficacy is assessed, comparing vaccines has been difficult. It would, therefore, be beneficial to determine the most clinically relevant measure for use in future studies. Other recommendations for future clinical trials also include studying compartments in addition to blood and replacing ATIs with single-copy assays in situations in which the use of an ATI is not ideal.

Phylogenetic considerations in designing a broadly protective multimeric L2 vaccine

While the oncogenic human papillomavirus (HPV) types with the greatest medical impact are clustered within the α9 and α7 species, a significant fraction of cervical cancers are caused by α5, α6, and α11 viruses. Benign genital warts are caused principally by the α10 viruses HPV6 and HPV11. In an effort to achieve broad protection against both cervical cancer- and genital wart-associated types, we produced at high levels in bacteria a multimeric protein (α11-88x8) fusing eight polypeptides corresponding to a protective domain comprising L2 residues ∼11 to 88 derived from HPV6 (α10), HPV16 (α9), HPV18 (α7), HPV31 (α9), HPV39 (α7), HPV51 (α5), HPV56 (α6), and HPV73 (α11) and a truncated derivative with the last three units deleted (α11-88x5). Mice were immunized three times with α11-88x8 or α11-88x5 adjuvanted with alum or the licensed HPV vaccines and challenged intravaginally with HPV6, HPV16, HPV26, HPV31, HPV33, HPV35, HPV45, HPV51, HPV56, HPV58, or HPV59 pseudovirions. The α11-88x5 and α11-88x8 vaccines induced similarly robust protection against each HPV type tested and indistinguishable HPV16-neutralizing antibody titers. Passive transfer of α11-88x8 antisera was protective. Further, rabbit antisera to α11-88x8 and α11-88x5 similarly neutralized native HPV18 virions. These findings suggest that immunologic competition between units is not a significant issue and that it is not necessary to include a unit of L2 derived from each species to achieve broader protection against diverse medically significant HPV types than is achieved with the licensed HPV vaccines.

The contribution of NT-gp96 as an adjuvant for increasing HPV16 E7-specific immunity in C57BL /6 mouse model

To control cervical cancer, efficient vaccination against human papillomavirus (HPV) is highly required. Despite the advantages and safety of the protein vaccines, additional strategies to enhance their immunogenicity are needed. E7 is a transforming protein which represents a perfect target antigen for vaccines or immunotherapies. Heat shock proteins (HSPs) facilitate cellular immune responses to antigenic peptides or proteins bound to them. Regarding to previous studies, vaccination with purified HSP/antigen complexes efficiently elicit antigen-specific immune responses in mice model. The N-terminal of glycoprotein 96 (NT-gp96) has adjuvant effect and can induce effective cumulative immune response against clinical disorders, especially cancers. In this study, the recombinant HPV16 E7 and E7 linked to NT-gp96 (E7-NT-gp96) proteins were generated in prokaryotic expression system. Mice were vaccinated twice with this recombinant proteins and the immunogenicity of the fusion protein was determined. The preventive efficacy of E7-NT-gp96 fusion protein was also evaluated and compared to E7 protein after challenging with cancerous TC-1 cell line. In vitro re-stimulated splenocytes of mice vaccinated with rE7-NT-gp96 protein induced higher IFN-γ response in comparison with E7 protein immunization. Moreover, immunization with E7-NT-gp96 protein displayed low but stable humoral responses at post-challenge time. The data showed that vaccination with fused E7-NT-gp96 protein delayed the tumour occurrence and growth as compared to protein E7 alone. These results suggest that fused adjuvant-free E7-NT-gp96 protein vaccination could direct the immune responses towards Th1 immunity. Furthermore, the linkage of NT-gp96 to E7 could enhance protective anti-tumour immunity.

New Approaches to Immunotherapy for HPV Associated Cancers

Cervical cancer is the second most common cancer of women worldwide and is the first cancer shown to be entirely induced by a virus, the human papillomavirus (HPV, major oncogenic genotypes HPV-16 and -18). Two recently developed prophylactic cervical cancer vaccines, using virus-like particles (VLP) technology, have the potential to prevent a large proportion of cervical cancer associated with HPV infection and to ensure long-term protection. However, prophylactic HPV vaccines do not have therapeutic effects against pre-existing HPV infections and do not prevent their progression to HPV-associated malignancy. In animal models, therapeutic vaccines for persisting HPV infection can eliminate transplantable tumors expressing HPV antigens, but are of limited efficacy in inducing rejection of skin grafts expressing the same antigens. In humans, clinical trials have reported successful immunotherapy of HPV lesions, providing hope and further interest. This review discusses possible new approaches to immunotherapy for HPV associated cancer, based on recent advances in our knowledge of the immunobiology of HPV infection, of epithelial immunology and of immunoregulation, with a brief overview on previous and current HPV vaccine clinical trials.

[Prophylactic and therapeutic vaccines against human papilloma virus]

Infection with human papilloma virus (HPV) has been identified as the cause of recurrent papillomatosis and of a subgroup of squamous cell carcinomas of the head and neck. A change in prevalence of these lesions, especially for oropharyngeal carcinoma, can be expected as a consequence of the introduction of prophylactic HPV vaccines for young women, targeting the most frequent high- and low-risk HPV subtypes. Vaccination for the major low-risk HPV types has proven to be highly effective against genital warts and activity against papillomatosis can be expected. The possibilities of prophylactic HPV vaccination as well as new developments and the rationale for therapeutic vaccines are discussed on the basis of the current literature.

Immunotherapy for cervical cancer: Research status and clinical potential

The high-risk types of human papillomavirus (HPV) have been found to be associated with most cervical cancers and play an essential role in the pathogenesis of the disease. Despite recent advances in preventive HPV vaccine development, such preventive vaccines are unlikely to reduce the prevalence of HPV infections within the next few years, due to their cost and limited availability in developing countries. Furthermore, preventive HPV vaccines may not be capable of treating established HPV infections and HPV-associated lesions, which account for high morbidity and mortality worldwide. Thus, it is important to develop therapeutic HPV vaccines for the control of existing HPV infection and associated malignancies. Therapeutic vaccines are quite different from preventive vaccines in that they require the generation of cell-mediated immunity, particularly T cell-mediated immunity, instead of the generation of neutralizing antibodies. The HPV-encoded early proteins, the E6 and E7 oncoproteins, form ideal targets for therapeutic HPV vaccines, since they are consistently expressed in HPV-associated cervical cancer and its precursor lesions and thus play crucial roles in the generation and maintenance of HPV-associated disease. Our review covers the various therapeutic HPV vaccines for cervical cancer, including live vector-based, peptide or protein-based, nucleic acid-based, and cell-based vaccines targeting the HPV E6 and/or E7 antigens. Furthermore, we review the studies using therapeutic HPV vaccines in combination with other therapeutic modalities and review the latest clinical trials on therapeutic HPV vaccines.

Developing vaccines against minor capsid antigen L2 to prevent papillomavirus infection

A subset of human papillomavirus (HPV) genotypes is responsible for approximately 5% of all cancer deaths globally, and uterine cervical carcinoma accounts for the majority of these cases. The impact of HPV is greatest for women who do not have access to effective secondary preventive measures, and consequently over 80% of cervical cancer deaths worldwide occur in developing nations. The understanding that persistent infection by this 'oncogenic' subset of HPV genotypes is necessary for the development of cervical carcinoma has driven the development of preventive vaccines. Two preventive vaccines comprising recombinant HPV L1 virus-like particles (VLPs) have been licensed. However, the current cost of these vaccines precludes sustained global delivery, and they target only two of the approximately 15 known oncogenic HPV types, although approximately 70% of cervical cancer cases are attributed to these two types and there is evidence for some degree of cross-protection against other closely related types. A possible approach to broader immunity at lower cost is to consider vaccination against L2. L2 vaccines can be produced inexpensively and they also have the promise of conferring much broader cross-type protective immunity than that observed with L1 VLP immunization. However, L2 vaccine development lags behind L1 VLP vaccines and several technical hurdles remain.

[Experimental vaccines for sexually transmitted infections]

INTRODUCTION

Sexually transmitted infections (STIs) are major global public health problems. Present strategies for prevention have limitations. Vaccines are an attractive addition to the current prevention armamentarium because they provide durable protection and do not require repetitive adherence to be effective. Challenges for vaccination include induction and long-term maintenance of mucosal immune responses in the female genital tract.

VACCINES

A REALISTIC GOAL? For the time being, US Centers for Disease Control and Prevention have recommended only hepatitis and HPV immunization to be routinely offered. Final, III stage trials are underway on other prophylactic vaccines for human papillomavirus and genital herpes. Though vaccines against Chlamydia trachomatis and Neisseria gonorrhoeae are in early stages of development they do offer the hope of preventing pelvic inflammations. The high incidence of HIV-infection for which a vaccine would not be readily available, "cries out" for an effective vaccine.

VACCINES FOR HPV INFECTIONS

According to a recent meta-analysis of worldwide prevalence data, vaccinating with HPV-16/18 VLP against HPV-16 and HPV-18 could prevent over 70% of invasive cervical cancer worldwide. The latest release of data from the phase III trial of a quadrivalent recombinant non-infectious vaccine HPV-6/11/16/18 L1 VLP, including HPV types 6, 11, 16, 18 have given complete protection against HPV-16/18-related cervical intraepithelial neoplasias 1, 2/3, and adenocarcinoma in situ and cancer through 2 years of post-vaccination follow up.

CONCLUSION

Despite the fact that the development of vaccines for STI prevention was rather slow in the past, the ideal vaccine would decrease transmission of the infection between partners and would prevent complications of disease. Moreover, in future decades, increasingly successful universal vaccination of newborns and children will substantially reduce the need for vaccination of persons with specific risk factors, including sexual risk.

Antigen-specific immunotherapy of cervical and ovarian cancer

We contrast the efforts to treat ovarian cancer and cervical cancer through vaccination because of their different pathobiology. A plethora of approaches have been developed for therapeutic vaccination against cancer, many of which target defined tumor-associated antigens (TAAs). Persistent infection with oncogenic human papillomavirus (HPV) types causes cervical cancer. Furthermore, cervical cancer patients frequently mount both humoral and T-cell immune responses to the HPV E6 and E7 oncoproteins, whose expression is required for the transformed phenotype. Numerous vaccine studies target these viral TAAs, including recent trials that may enhance clearance of pre-malignant disease. By contrast, little is known about the etiology of epithelial ovarian cancer. Although it is clear that p53 mutation or loss is a critical early event in the development of epithelial ovarian cancer, no precursor lesion has been described for the most common serous histotype, and even the location of its origin is debated. These issues have complicated the selection of appropriate ovarian TAAs and the design of vaccines. Here we focus on mesothelin as a promising ovarian TAA, because it is overexpressed and immunogenic at high frequency in patients, is displayed on the cell surface, and potentially contributes to ovarian cancer biology.

Therapeutic human papillomavirus vaccines: current clinical trials and future directions

BACKGROUND

Cervical cancer is the second largest cause of cancer deaths in women worldwide. It is now evident that persistent infection with high-risk human papillomavirus (HPV) is necessary for the development and maintenance of cervical cancer. Thus, effective vaccination against HPV represents an opportunity to restrain cervical cancer and other important cancers. The FDA recently approved the HPV vaccine Gardasil for the preventive control of HPV, using HPV virus-like particles (VLP) to generate neutralizing antibodies against major capsid protein, L1. However, prophylactic HPV vaccines do not have therapeutic effects against pre-existing HPV infections and HPV-associated lesions. Furthermore, due to the considerable burden of HPV infections worldwide, it would take decades for preventive vaccines to affect the prevalence of cervical cancer. Thus, in order to speed up the control of cervical cancer and treat current infections, the continued development of therapeutic vaccines against HPV is critical. Therapeutic HPV vaccines can potentially eliminate pre-existing lesions and malignant tumors by generating cellular immunity against HPV-infected cells that express early viral proteins such as E6 and E7.

OBJECTIVE

This review discusses the future directions of therapeutic HPV vaccine approaches for the treatment of established HPV-associated malignancies, with emphasis on current progress of HPV vaccine clinical trials.

METHODS

Relevant literature is discussed.

RESULTS/CONCLUSION

Though their development has been challenging, many therapeutic HPV vaccines have been shown to induce HPV-specific antitumor immune responses in preclinical animal models and several promising strategies have been applied in clinical trials. With continued progress in the field of vaccine development, HPV therapeutic vaccines may provide a potentially promising approach for the control of lethal HPV-associated malignancies.

Cellular binding partners of the human papillomavirus E6 protein

The high-risk strains of human papillomavirus (HR-HPV) are known to be causative agents of cervical cancer and have recently also been implicated in cancers of the oropharynx. E6 is a potent oncogene of HR-HPVs, and its role in the progression to malignancy has been and continues to be explored. E6 is known to interact with and subsequently inactivate numerous cellular proteins pivotal in the mediation of apoptosis, transcription of tumor suppressor genes, maintenance of epithelial organization, and control of cell proliferation. Binding of E6 to these proteins cumulatively contributes to the oncogenic potential of HPV. This paper provides an overview of these cellular protein partners of HR-E6, the motifs known to mediate oncoprotein binding, and the agents that have the potential to interfere with E6 expression and activity and thus prevent the subsequent progression to oncogenesis.

Vaccination of Healthy Volunteers with Human Papillomavirus Type 16 L2E7E6 Fusion Protein Induces Serum Antibody that Neutralizes across Papillomavirus Species

Oncogenic human papillomavirus (HPV) infection is a necessary cause of cervical cancer. Therefore, vaccination to prevent or eliminate HPV infection could reduce the incidence of cervical cancer. A fusion protein comprising HPV16 L2, E6, and E7 is a candidate combination preventive and therapeutic HPV vaccine. The L1- and L2-specific and neutralizing serum antibody titers and peripheral blood mononucleocyte antigen-specific proliferative responses generated by vaccination thrice at monthly intervals with HPV16 L2E7E6 were compared in two studies: a phase I randomized double-blind placebo controlled dose escalation trial in 40 healthy volunteers and a phase II trial of HPV16 L2E7E6 at the maximum dose in 29 women with high-grade anogenital intraepithelial neoplasia (AGIN). Vaccination of healthy volunteers induced L2-specific serum antibodies that were detected 1 month after the final vaccination (P(binomial) < 0.001). There was a significant trend to seroconversion for HPV16 and HPV18 neutralizing antibodies with increasing vaccine dose (P = 0.006 and P = 0.03, respectively). Seroconversion for HPV18 neutralizing antibodies showed a significant positive trend with increasing dose (P = 0.03) and was associated with seroconversion for HPV16 neutralizing antibodies (P(exact) = 0.04). The antigen-specific proliferative response of vaccinated healthy volunteers also showed a significant trend with increasing vaccine dose (P = 0.04). However, AGIN patients responded less effectively to vaccination than healthy patients for induction of HPV16 L2-specific antibody (P < 0.001) and proliferative responses (P < 0.001). Vaccination of healthy volunteers thrice with 533-mug HPV16 L2E7E6 at monthly intervals induced L2-specific serum antibodies that neutralized across papillomavirus species. Responses in AGIN patients were infrequent.

[Anti human-papillomavirus vaccines: concepts, aims and trials]

PURPOSE

Human Papillomaviruses (HPV) are epitheliotropic for stratified malpighian epithelia such as those of the cervix. Among them, oncogenic viruses are detectable in 99.7% of cervical cancers. A great priority is to develop a vaccine either against primary infection (preventive vaccine) allowing protection against HPV infection or therapeutic vaccine in order to kill previously infected or transformed keratinocytes.

CURRENT KNOWLEDGE AND KEY POINTS

Preventive vaccines against HPV contain virus like particles (VLP) 16 and 18 and induce a high titer of blood anti-VLP antibodies. They were recently tested in humans and have shown true efficiency for the prevention of cervical cancer. The therapeutic vaccines are therefore currently being developed in order to increase anti-HPV natural CD4+ and CD8+ T-cell immunity in women infected during their sexual activity.

FUTURE PROSPECTS

The perspective of the prophylactic vaccines is to decrease both genital HPV infection and cervical cancer. The impact of preventive vaccine must be carefully analyzed in order to prevent collateral side effects. The therapeutic vaccines have also a future in women already infected by HPV and might have an efficiency similar to surgery in the treatment of cervical intraepithelial neoplasia.

Novel methods to treat and prevent human papillomavirus infection

The human papillomavirus (HPV), a ubiquitous sexually transmitted virus, is the causative agent for cervical dysplasia and carcinoma worldwide. Current treatment methods primarily utilize ablative and excisional procedures to remove dysplastic, HPV-infected cervical tissue. However, these procedures require intensive cytopathological surveillance and carry inherent risks of bleeding, infection and possible future pregnancy complications. Development of an effective vaccine against HPV would dramatically reduce the need for costly cytological and histological surveillance. HPV represents an ideal candidate for vaccine development, and current research efforts in the realm of prophylactic and therapeutic vaccine design show great promise. A host of various vaccine techniques are currently being developed and tested and, if effective, will have a significant impact on the incidence of cervical dysplasia and carcinoma.

Human papillomavirus infection: An old disease, a new vaccine

Human papillomavirus (HPV) infection is common and causes a wide spectrum of disease. With recent advances in the development of prophylactic HPV vaccines, it is likely that these will be licensed for use in the near future. This review focuses on the science behind HPV vaccines, published clinical trial results for both prophylactic and therapeutic HPV vaccines, important issues relevant to implementation and cost-effectiveness models of HPV vaccination programs. It may be that an HPV vaccine that protects against the complications of HPV infection such as cervical cancer will be one of the most significant public health initiatives of this decade.

Assessment of knowledge and attitudes of young uninsured women toward human papillomavirus vaccination and clinical trials

STUDY OBJECTIVE

To assess knowledge and attitudes of young uninsured women toward human papillomavirus (HPV) vaccination and clinical trials.

DESIGN

Cross-sectional study.

SETTING

Clinic-based sample in Brazil.

PARTICIPANTS

A consecutive sample of 204 women aged 16 to 23 years, attending a public outpatient gynecological clinic.

INTERVENTIONS

A questionnaire administered by in-person interview.

MAIN OUTCOME MEASURES

Data on knowledge and attitudes towards HPV vaccination.

RESULTS

Overall, 72% of the respondents would enroll in a HPV vaccine trial, despite the fact that 69% of women were ignorant of what HPV may cause, and only 10% acknowledged that HPV might lead to cervical cancer. The need of a placebo arm (31%) and three vaccinations injections (26%) were the trial design characteristics most cited for deterring participation. Factors promoting participation were "careful/detailed consultations by the same physician" (92%), "access to more information on women's health" (84%), and "office visits on time" (79%); whereas "clinic too far from home" (36%), "fear of adverse events" (29%), and "gynecologic examination discomfort" (25%) were the most commonly reported reasons for not enrolling in a trial. Being sexually active, more than three lifetime sexual partners and perception of high risk for cervical cancer were predictors of participation in a HPV vaccine trial.

CONCLUSIONS

Knowledge of HPV infection and cervical cancer is low in this urban, young population. Thus, when planning HPV vaccine trials, it is important to consider implementing educational programs to provide knowledge of the benefits of a preventive vaccine and information on the etiology of and risk factors for cervical cancer.

Human papillomavirus type 16 E5 protein as a therapeutic target

Cervical cancer is a progressive disease with an onset of one to two decades on average. During the productive replication stage, the Human papillomavirus (HPV) genome is maintained episomally in the infected cervical epithelium and early gene products, including E5, are expressed. Therefore, E5 has a potential to contribute to the HPV-associated carcinogenic process. In invasive malignancies, the HPV genomes are commonly integrated into the host genome, and E6 and E7 genes remain intact. However, the E5 is lost or, if present, under-expressed as compared with the E6 and E7 proteins. This suggests that E5 may play a critical role in the genesis of cervical cancer but less of a role in its persistence or progression. In the initiation of neoplasia and the premalignant stage, there are fewer malignant cells than in the invasive malignancies. Moreover, cells in the invasive malignant stage are found to have a very low level of MHC class I and II, which could hamper the presentation of the antigen and lead to a decreased immune response. Since the E5 protein is likely to play a role during the early tumorigenesis stage, a therapeutic vaccine to target and eliminate the E5-expressing cells may be a good strategy to prevent premalignant lesions from progressing toward invasive cervical cancers. This paper provides an overview of HPV-induced cervical carcinogenesis and strategies for designing prophylactic and therapeutic vaccines to prevent and cure the cervical cancer. In particular, focus will be on the rationale of targeting the E5 protein to develop therapeutic vaccines.

Vaccines against human papillomavirus and cervical cancer: promises and challenges

Cervical cancer and precancerous lesions of the genital tract are major threats to the health of women worldwide. The introduction of screening tests to detect cervical cancer precursor lesions has reduced cervical cancer rates in the developed world, but not in developing countries. Human papillomavirus (HPV) is the primary etiologic agent of cervical cancer and dysplasia. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by HPV vaccines. Two vaccine strategies have been developed. First, prevention of HPV infection through induction of capsid-specific neutralizing antibodies has been studied in clinical trials. However, because the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, a second approach of developing therapeutic vaccines by targeting nonstructural early viral antigens has also been developed. Because two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are coexpressed in the majority of HPV-containing carcinomas, most therapeutic vaccines target one or both of these gene products. A variety of approaches is being tested in therapeutic vaccine clinical trials, whereby E6 and/or E7 are administered in live vectors, as peptides or protein, in nucleic acid form, or in cell-based vaccines. The paradigm of preventing HPV infection through vaccination has been tested, and two vaccines are currently in phase III clinical trials. However, current therapeutic vaccine trials are less mature with respect to disease clearance. A number of approaches have shown significant therapeutic benefit in preclinical papillomavirus models and await testing in patient populations to determine the most effective curative strategy.

Immunotherapy for gynaecological malignancies

Gynaecological malignancies, excluding breast cancer, cause approximately 25,000 deaths yearly among women in the US. Therefore, novel approaches for the prevention or treatment of these diseases are urgently required. In the case of cervical cancer, human papillomavirus (HPV) xenoantigens are readily recognised by the immune system, and their targeting has shown great promise in preclinical models of therapeutic vaccination and in clinical studies of preventative vaccination. A growing body of evidence indicates that ovarian cancer is also immunogenic and can thus be targeted through immunotherapy. This review outlines the principles and problems of immunotherapy for cervical and ovarian cancer, including the authors' personal assessment.

Human papillomavirus vaccines and adolescents

PURPOSE OF REVIEW

This review will describe human papillomavirus (HPV) vaccines in development, summarize data regarding safety and efficacy of these vaccines, and discuss key issues related to HPV vaccine implementation.

RECENT FINDINGS

Evidence from epidemiologic and genetic studies has confirmed that HPV infection is a necessary cause of cervical cancer and contributes to the development of other cancers. HPV infection also may cause nonmalignant conditions such as external genital warts and recurrent respiratory papillomatosis. Over the past decade, several vaccines that target common HPV types have entered clinical trials. These vaccines are classified as prophylactic or therapeutic. The goal of prophylactic vaccines is to prevent primary or persistent HPV infections, and thus prevent cervical cancer and/or genital warts. Recent evidence indicates that prophylactic vaccines are well tolerated, highly immunogenic and effective in preventing persistent HPV infection and cervical intraepithelial neoplasia (CIN). Questions remain, however, concerning vaccine efficacy against HPV-related diseases other than cervical cancer, the duration of protection, vaccine acceptability and feasibility of vaccine delivery in the developing world. The goal of therapeutic vaccines is to prevent progression of HPV infection, induce regression of CIN or condylomata, or eradicate residual cervical cancer. Although therapeutic vaccines appear to induce both humoral and cell-mediated immunity, they have not consistently demonstrated clinical efficacy.

SUMMARY

HPV vaccines in development have the potential to reduce the substantial morbidity and mortality associated with cervical cancer and other HPV-associated diseases. Large-scale efficacy studies that are planned or underway will provide additional information about vaccine tolerance and efficacy.

Progress in vaccines for sexually transmitted diseases

The development pipeline for vaccines to control sexually transmitted infections holds greater promise than ever before. Preclinical studies are encouraging in the development of chlamydia and gonococcal vaccines, and for the first time, recent clinical trials have shown the feasibility of creating vaccines to control genital herpes and cervical human papillomavirus infections. Behavioral research suggests that these vaccines will likely find acceptance among health care providers and consumers.

[Vaccination against human papillomaviruses]

Human papillomaviruses (HPV) have an epithelial tropism and numerous oncogenic HPV are responsible for uterine cervical cancer. Here we analyse the published studies concerning both prophylactic and therapeutic vaccines against HPV.

Therapy for genital human papillomavirus-related disease

Genital human papillomavirus (HPV) infection is very common, and often sub-clinical and usually resolves without any treatment. Genital warts are caused by HPV 6/11 infection and are one of the commonest clinically recognised disease manifestations of genital HPV. Subjects with genital warts usually perceive them as cosmetically disfiguring, often leading to adverse psychological symptoms, and most subjects with genital warts will present requesting treatment. A wide variety of treatments are available including both provider- and patient-applied therapies. Various individual subject and disease factors mediate appropriate therapy choice. Some of the treatments that are used for genital warts can also be used for some cases of intraepithelial neoplasia caused by high-oncogenic risk HPVs occurring at vulval, anal or penile sites. Specific treatment considerations apply to genital warts in pregnancy and laryngeal papillomatosis and these are also discussed.

Vaccination Against Cervical Cancer: Hopes and Realities

Globally, carcinomas of the anogenital tract, in particular cervical cancer, remain some of the most common cancers in women, cervical cancer represents the second most frequent gynecological malignancy and the third leading cause of cancer-related death in women worldwide. The causal relationship between human papilomavirus (HPV) infection and anogenital cancer has prompted substantial interest in the development of both preventive and therapeutic vaccines against high-risk HPV types. In the past decade, several groups have shown encouraging results using experimental vaccination systems in animal models and these results have led to several current prophylactic and therapeutic vaccine clinical trials in humans. Prophylactic vaccination focuses on the induction of high titer neutralizing antibodies that are potentially protective against incident and persistent HPV infection. Two major phase II clinical trials conducted by pharmaceutical companies have demonstrated that their vaccines have 100% efficacy in preventing persistent viral DNA and its associated cellular abnormalities; however, whether they induce long-lasting protective immunity is yet to be determined. At least one US FDA approved prophylactic vaccine targeting the two most common high-risk HPVs is expected to be on the market within the next 2-3 years. Nevertheless, significant reductions in the frequency and onset of cytologic screening and incidences of HPV-related lesions are not expected to become apparent for decades due to the fact that there will be women who are already infected with HPV, the long latency period between infection and development of high-grade lesions, and lesions associated with other high-risk HPV types not being included in the vaccines. Therapeutic vaccines aim to control HPV-associated malignancies by stimulating cellular immune responses that target established HPV infections via viral proteins. Progress in the field of HPV immunotherapy has remained elusive, with clinical trials being limited to small numbers of patients. Potential treatment of precancerous lesions is unique to HPV-associated infection and cancer because of cytologic monitoring and HPV typing. Unlike more common surgical treatments for cervical lesions, active immunotherapy has the potential to address HPV persistence as the cause of lesion development in addition to leaving the patient with long-term immunity that can be reactivated if and when the patient becomes reinfected.

Emerging human papillomavirus vaccines

Human papillomavirus (HPV) infections are a leading cause of virus-associated cancers of the anogenital, oropharyneal and cutaneous epithelium. The most prevalent of these is cervical cancer, which is responsible for approximately 500,000 deaths annually worldwide. A group of about 15 serologically unrelated 'high-risk' HPV types are responsible for almost all HPV-associated cancers. Prevention of papillomavirus infection can be achieved by induction of capsid-specific neutralising antibodies in preclinical animal papillomavirus models and in recent human clinical trials. High titres of conformationally-dependent, type-specific HPV-neutralising antibodies are triggered by HPV virus-like particle (VLP) vaccines. Overcoming the problems of type-specificity of the responses to these VLP vaccines is a potentially important area of current HPV vaccine research, with an emphasis on induction of more broadly cross-protective neutralising responses. Viral oncogenes E6 and E7 are continuously present in HPV-associated cancers and are prime targets for HPV therapeutic vaccines. A variety of approaches are being tested in therapeutic vaccine clinical trials and in various preclinical animal papillomavirus models for efficacy. Approaches include genetic vaccines, recombinant virus vaccines, dendritic cell-based strategies, immunomodulatory strategies and various combination strategies to maximise cell-mediated immunity to papillomavirus proteins present in HPV infections and cancers. The success of preventive HPV VLP vaccines in clinical trials is clear. However, current therapeutic vaccine trials are less effective with respect to disease clearance. Nevertheless, a series of combination approaches have shown significant therapeutic enhancement in preclinical papillomavirus models and await testing in patient populations to determine the most effective strategy. There is much encouragement that HPV vaccines will be the most effective approach to prevention and cure of infections caused by this group of viruses, which re-present a significant human pathogen.

[Up to date in sexually transmitted infections: epidemiology, diagnostic approaches and treatments]

In the last years, there have been important advances in sexually transmitted infections such as genome sequencing of Treponema pallidum, Chlamydia trachomatis or Mycoplasma genitalium; the new taxonomic position of Calymmatobacterium granulomatis; commercial diagnostic systems based on nucleic acid amplification; the emergence of quinolone resistance in Neisseria gonorrhoeae; new therapeutic approaches in vulvovaginal candidiasis that include boric acid; the demonstration that valacyclovir reduces the risk of transmission of genital herpes or the availability of immune-response modifier in the treatment of genital warts, and that are questions in the goal of this review. Viral hepatitis and HIV were no reviewed by space reasons.

Preventative and therapeutic vaccines for cervical cancer

"High-risk" genotypes of the human papillomavirus (HPV), most commonly HPV genotype 16, are the primary etiologic agents of cervical cancer. Indeed HPV DNA is detected in 99% of cervical carcinomas. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by the induction of the appropriate viral-antigen-specific immune responses. Transmission of papillomavirus may be prevented by the generation of antibodies to capsid proteins L1 and L2 that neutralize viral infection. HPV L1 virus-like particles (VLPs) show great promise as prophylactic HPV vaccines in ongoing clinical trials but L2-based preventative vaccines have yet to be tested in patients. Since the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, therapeutic vaccines generally target the nonstructural early viral antigens. Two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are co-expressed in the majority of HPV-containing carcinomas. Although other early viral antigens show promise for vaccination against papillomas, therapeutic vaccines targeting E6 and E7 may provide the best opportunity to control HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 are administered in live vectors, as peptides or proteins, 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 this new generation of HPV preventative and therapeutic vaccines function in patients as demonstrated in animal models, oncogenic HPV infection and its associated malignancies could be controlled by vaccination. Importantly, recent advances in HPV detection and continued improvements in screening further enhance our opportunities to systematically eradicate HPV-associated malignancy.

Progress on new vaccine strategies against chronic viral infections

Among the most cost-effective strategies for preventing viral infections, vaccines have proven effective primarily against viruses causing acute, self-limited infections. For these it has been sufficient for the vaccine to mimic the natural virus. However, viruses causing chronic infection do not elicit an immune response sufficient to clear the infection and, as a result, vaccines for these viruses must elicit more effective responses--quantitative and qualitative--than does the natural virus. Here we examine the immunologic and virologic basis for vaccines against three such viruses, HIV, hepatitis C virus, and human papillomavirus, and review progress in clinical trials to date. We also explore novel strategies for increasing the immunogenicity and efficacy of vaccines.

Vaccination to prevent and treat cervical cancer

Human papillomaviruses (HPVs) are the primary etiologic agents of cervical cancer. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by HPV vaccines. Transmission of papillomavirus may be prevented by the generation of antibodies to capsid proteins L1 and L2 that neutralize viral infection. However, because the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, therapeutic vaccines generally target nonstructural early viral antigens. Two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are coexpressed in the majority of HPV-containing carcinomas. Thus, therapeutic vaccines targeting E6 and E7 may provide the best option for controlling HPV-associated malignancies. Various candidate therapeutic HPV vaccines are currently being tested whereby E6 and/or E7 are administered in live vectors, as peptides or protein, in nucleic acid form, as components of chimeric virus-like particles, or in cell-based vaccines. Encouraging results from experimental vaccination systems in animal models have led to several prophylactic and therapeutic vaccine clinical trials. If these preventive and therapeutic HPV vaccines prove successful in patients, as they have in animal models, then oncogenic HPV infection and its associated malignancies may be controllable by vaccination.

Progress on new vaccine strategies against chronic viral infections

Among the most cost-effective strategies for preventing viral infections, vaccines have proven effective primarily against viruses causing acute, self-limited infections. For these it has been sufficient for the vaccine to mimic the natural virus. However, viruses causing chronic infection do not elicit an immune response sufficient to clear the infection and, as a result, vaccines for these viruses must elicit more effective responses--quantitative and qualitative--than does the natural virus. Here we examine the immunologic and virologic basis for vaccines against three such viruses, HIV, hepatitis C virus, and human papillomavirus, and review progress in clinical trials to date. We also explore novel strategies for increasing the immunogenicity and efficacy of vaccines.

Therapeutic vaccines for chronic infections

Therapeutic vaccines aim to prevent severe complications of a chronic infection by reinforcing host defenses when some immune control, albeit insufficient, can already be demonstrated and when a conventional antimicrobial therapy either is not available or has limited efficacy. We focus on the rationale and challenges behind this still controversial strategy and provide examples from three major chronic infectious diseases- human immunodeficiency virus, hepatitis B virus, and human papillomavirus-for which the efficacy of therapeutic vaccines is currently being evaluated.

Human papillomavirus infections: diagnosis, treatment, and hope for a vaccine

HPV infections are common, with millions of Americans infected. Common gynecologic manifestations of HPV infection include genital warts and cervical neoplasia. The CDC recently issued guidelines for the treatment of genital warts. Gynecologists should be familiar with these therapies and their potential short-comings. A recently reported clinical trial has raised hopes that HPV and its sequelae may be prevented by vaccination.

Papillomavirus vaccines in clinical trials

Cervical cancer remains a leading cause of death for women in the developing world, and the treatment of preneoplastic cervical lesions is a considerable public-health burden in the developed world. There is unambiguous evidence that human papillomaviruses (HPVs) trigger the development of cervical and other anogenital malignancies, and that continued expression of HPV antigens in the tumours drives the neoplastic progression. The viral cause of cervical cancer is also its Achilles heel. Prophylactic vaccines to prevent HPV infection and therapeutic vaccines targeted at the HPV tumour antigens are in clinical trials. A firm grasp of the molecular pathogenesis of HPVs and the natural history of genital HPV infections, combined with greater understanding of how to trigger effective immune responses, offers hope for the elimination of HPV-associated diseases.

Vaccines for viral diseases with dermatologic manifestations

Vaccines against infectious diseases have been available since the 1800s, when an immunization strategy against smallpox developed by Jenner gained wide acceptance. Until recently, the only vaccination strategies available involved the use of protein-based, whole killed, and attenuated live virus vaccines. These strategies have led to the development of effective vaccines against a variety of diseases with primary or prominent cutaneous manifestations. Effective and safe vaccines now used worldwide include those directed against measles and rubella (now commonly used together with a mumps vaccine as the trivalent MMR), chickenpox, and hepatitis B. The eradication of naturally occurring smallpox remains one of the greatest successes in the history of modern medicine, but stockpiles of live smallpox exist in the United States and Russia. Renewed interest in the smallpox vaccine reflects concerns about a possible bioterrorist threat using this virus. Yellow fever is a hemorrhagic virus endemic to tropical areas of South America and Africa. An effective vaccine for this virus has existed since 1937, and it is used widely in endemic areas of South America, and to a lesser extent in Africa. This vaccine is recommended once every 10 years for people who are traveling to endemic areas. Advances in immunology have led to a greater understanding of immune system function in viral diseases. Progress in genetics and molecular biology has allowed researchers to design vaccines with novel mechanisms of action (eg, DNA, vector, and VLP vaccines). Vaccines have also been designed to specifically target particular viral components, allowing for stimulation of various arms of the immune system as desired. Ongoing research shows promise in prophylactic and therapeutic vaccination for viral infections with cutaneous manifestations. Further studies are necessary before vaccines for HSV, HPV, and HIV become commercially available.

Vaccine candidates in STD

Sexually transmitted diseases (STDs) are caused by organisms that infect the mucosal surfaces of the genitourinary tract. In spite of its public health importance, current STD vaccine research lags behind work against pathogens that target another mucosal region, the respiratory tract. In the latter case, live-attenuated viral vaccines, killed whole-cell bacterial vaccines, subunit/protein bacterial vaccines, and bacterial polysaccharide vaccines have been enormously successful. To move STD vaccine research forward, complex issues must be resolved. Those include selection of an appropriate antigen (e.g. scientific feasibility and intellectual property rights), the manufacture of the vaccine (e.g. delivery systems, formulation processes, and production steps), and the appropriate public health approach (e.g. medical indications and marketing aspects). Particular scientific problems have delayed STD vaccine development, like incomplete attenuation (human herpes simplex virus type 2), accentuated immunopathology (Chlamydia trachomatis), poor immunogenicity (Treponema pallidum), and broad antigenic heterogeneity (Neisseria gonorrhoeae). Nevertheless, efforts continue with the use of protein antigens: for example, the haemolysin toxoid of Haemophilus ducreyi; the major outer membrane protein(s) of N. gonorrhoeae and C. trachomatis; the glycoprotein D of human herpes simplex virus type 2; and the proteins E6 and E7 of human papilloma virus. It may be predicted that eventual STD vaccines (administered either for prophylaxis or for therapy) will use approaches that include (1) live-attenuated viruses, (2) subunit proteins or inactivated whole organisms given with mucosal adjuvants or with cellular immune response adjuvants, and (3) DNA plasmids expressing the vaccine antigen.

Clinical Trials in Cervical Intraepithelial Neoplasia: Balancing the Need for Efficacy Data with Patient Safety

OBJECTIVE.: Trial designs for novel nonsurgical, nonablative therapies for cervical intraepithelial neoplasia grades 2 and 3 (CIN 2,3) must ensure patient safety while providing sufficient time to show clinical effects. We propose an observation period based on literature and current practice. MATERIALS AND METHODS.: We reviewed 3 types of literature regarding observation of untreated CIN 2,3: 1) the management of CIN in pregnancy, perhaps the best existing model of observation; 2) the natural history of untreated CIN 2,3; and 3) the optimal means of protecting patient safety during longer-term follow-up of untreated CIN 2,3 lesions. RESULTS.: Data from both the pregnant and nonpregnant patient populations indicate that delaying treatment of CIN for periods of several weeks to several months is rarely associated with clinically significant disease progression. Screening and follow-up criteria that promote patient safety have been suggested and seem adaptable to clinical trials. CONCLUSIONS.: Careful screening and follow-up of patients with CIN 2,3 allows an observation period of at least 6 months after nonsurgical, nonablative therapy in clinical trials.

Therapeutic vaccination against chronic viral infections

Chronic viral infections such as those caused by hepatitis B virus, human papilloma virus, herpes simplex virus, and HIV, in theory, present logical targets of active specific immunotherapy. Indeed, immunological mechanisms are involved in several aspects of their pathogenesis and natural course, such as virus persistence, destruction of infected cells and control of viral replication. Therapeutic vaccination could therefore be an adequate replacement for, or adjunct to, existing therapies. Almost all approaches to therapeutic vaccination have been evaluated in those four disease areas. Despite encouraging results in animals none of these attempts has, so far, been completely successful in the human setting. However, with a better understanding of the immunological mechanisms involved in the control of disease successful therapeutic vaccines, used alone or in combination with other therapies, are an achievable goal.