Human Papillomavirus Vaccine: History, Immunology, Current Status, and Future Prospects

Human Papillomavirus Vaccines

Objective:

TO review the pharmacology, efficacy, safety, tolerability, and pharmacoeconomics of Cervarix and Gardasil, 2 human papillomavirus (HPV) vaccines.

Data Sources:

English-language articles were obtained by MEDLINE search (1966–February 2006) using the key words human papillomavirus vaccine, Cervarix, and Gardasil. Bibliographies of selected articles were used to identify additional sources.

Study Selection and Data Extraction:

All available published articles or abstracts reporting the results of human studies of HPV vaccines were reviewed for inclusion in this article. Additional information about ongoing clinical trials was obtained from manufacturers' Web sites.

Data Synthesis:

Cervarix and Gardasil are recombinant vaccines against HPV. Cervarix targets HPV-16 and -18, which are responsible for 70% of cervical cancers. Gardasil also targets HPV-16 and -18, plus the HPV-6 and -11 types responsible for more than 80% of genital warts. Both vaccines have been effective in preventing persistent infection with targeted HPV types and in preventing cervical intraepithelial lesions, while Gardasil has also been effective in preventing vulvar and vaginal neoplasia and genital warts. Both vaccines have been well tolerated, with the most common adverse effects occurring at the injection site. Phase III trials are ongoing to further evaluate vaccine efficacy.

Conclusions:

Cervarix and Gardasil are effective for prevention of HPV infection and cervical lesions. Issues remaining to be addressed include duration of protection, efficacy for prevention of cervical cancer, optimal age for vaccination, feasibility of application to the developing world, the ideal combination of HPV subtypes, and the most efficient combination of vaccination and cervical cancer screening.

Lymph node-targeted immunotherapy mediates potent immunity resulting in regression of isolated or metastatic human papillomavirus-transformed tumors

PURPOSE

The goal of this study was to investigate the therapeutic potential of a novel immunotherapy strategy resulting in immunity to localized or metastatic human papillomavirus 16-transformed murine tumors.

EXPERIMENTAL DESIGN

Animals bearing E7-expressing tumors were coimmunized by lymph node injection with E7 49-57 antigen and TLR3-ligand (synthetic dsRNA). Immune responses were measured by flow cytometry and antitumor efficacy was evaluated by tumor size and survival. In situ cytotoxicity assays and identification of tumor-infiltrating lymphocytes and T regulatory cells were used to assess the mechanisms of treatment resistance in bulky disease. Chemotherapy with cyclophosphamide was explored to augment immunotherapy in late-stage disease.

RESULTS

In therapeutic and prophylactic settings, immunization resulted in a considerable expansion of E7 49-57 antigen-specific T lymphocytes in the range of 1/10 CD8(+) T cells. The resulting immunity was effective in suppressing disease progression and mortality in a pulmonary metastatic disease model. Therapeutic immunization resulted in control of isolated tumors up to a certain volume, and correlated with antitumor immune responses measured in blood. In situ analysis showed that within bulky tumors, T-cell function was affected by negative regulatory mechanisms linked to an increase in T regulatory cells and could be overcome by cyclophosphamide treatment in conjunction with immunization.

CONCLUSIONS

This study highlights a novel cancer immunotherapy platform with potential for translatability to the clinic and suggests its potential usefulness for controlling metastatic disease, solid tumors of limited size, or larger tumors when combined with cytotoxic agents that reduce the number of tumor-infiltrating T regulatory cells.

Induction of CD4-independent E7-specific CD8+ memory response by heat shock fusion protein

Infection with human papillomavirus type 16 (HPV16) is strongly associated with a number of disease states, of which cervical and anal cancers represent the most drastic endpoints. Induction of T-cell-mediated immunity, particularly cytotoxic T lymphocytes (CTL), is important in eradication of HPV-induced lesions. Studies have shown that heat shock protein fusion proteins are capable of inducing potent antigen-specific CTL activity in experimental animal models. In addition, E7-expressing tumors in C57BL/6 mice can be eradicated by treatment with HspE7, an Hsp fusion protein composed of Mycobacterium bovis BCG Hsp65 linked to E7 protein of HPV16. More importantly, HspE7 has also displayed significant clinical benefit in phase II clinical trials for the immunotherapy of HPV-related diseases. To delineate the mechanisms underlying the therapeutic effects of HspE7, we investigated the capability of HspE7 to induce antigen-specific protective immunity. Here, we demonstrate that HspE7 primes potent E7-specific CD8(+) T cells with cytolytic and cytokine secretion activities. These CD8(+) T cells can differentiate into memory T cells with effector functions in the absence of CD4(+) T-cell help. The HspE7-induced memory CD8(+) T cells persist for at least 17 weeks and confer protection against E7-positive murine tumor cell challenge. These results indicate that HspE7 is a promising immunotherapeutic agent for treating HPV-related disease. Moreover, the ability of HspE7 to induce memory CD8(+) T cells in the absence of CD4(+) help indicates that HspE7 fusion protein may have activity in individuals with compromised CD4(+) functions, such as those with invasive cancer and/or human immunodeficiency virus infection.

Recent advances in human papillomavirus vaccines

The human papillomavirus (HPV) is one of the most common sexually transmitted infections and the etiologic agent of cervical dysplasia and cancer. Recent research on the safety and efficacy of prophylactic vaccines against HPV has shown promising results with nearly 100% efficacy in preventing persistent infections and cervical dysplasia. Several approaches are being tested in therapeutic vaccine clinical trials whereby E6, E7, or both agents are administered in live viral vectors, as proteins, or in nucleic acid form. Cell-based therapeutic vaccines are also being tested. HPV vaccines have the potential to eradicate a major cancer and source of morbidity around the world.

Eradication of established HPV 16-expressing tumors by a single administration of a vaccine composed of a liposome-encapsulated CTL-T helper fusion peptide in a water-in-oil emulsion

Human papillomavirus (HPV)-induced cervical cancer is the second most common cancer among women worldwide with half a million new cases per year. Despite the encouraging development of a preventive vaccine for HPV, a therapeutic vaccine for cervical cancer or pre-cancerous lesions remains a high priority. The preclinical study reported here used VacciMax((R)) (VM) to deliver a peptide-based vaccine composed of an HPV 16 E7-derived cytotoxic T lymphocyte (CTL) epitope fused to the T helper epitope PADRE (FP) and combined with CpG or lipopeptide adjuvant. In the study, C57BL/6 mice received 0.5million HPV 16-expressing C3 tumor cells. Mice were inoculated post-tumor challenge with a single s.c. injection of FP-CpG-VM on either day 4, 5, 6, 9, or 14. All mice that received the FP-CpG-VM vaccine were tumor-free to day 130 when the experiment was terminated. In contrast, only a minority of mice that received a control vaccine were tumor-free on day 60. Cytotoxicity assays, ELISPOT and intracellular staining for interferon (IFN)-gamma showed the immune response was specific for the selected CTL epitope. All mice that received the FP-CpG-VM vaccine remained tumor-free when re-challenged with 6million C3 cells. Cytotoxicity assays 4 months post-challenge showed that only splenocytes from mice inoculated with the FP-CpG-VM vaccine had high lysis activity. These results indicate that VacciMax((R)) causes a rapid, robust, durable and therapeutic CTL response to HPV 16 E7 protein expressing tumors.

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.

Human Papillomavirus Infections of the Genital and Respiratory Tracts in Young Children

Human papillomavirus (HPV) causes papillomas (warts) on the skin and respiratory mucosal surfaces (laryngeal and oral papillomas) in addition to condyloma acuminata (anogenital warts). HPV has become one of the most common sexually transmitted diseases in adults. Vertical transmission from mother to infant during birth is well recognized. Laryngeal papillomas are the most common tumors of the larynx in children worldwide, and recurrent lesions are common occurrences. Anogenital warts in children are problematic in that child sexual abuse is a potential means of acquisition, but many cases are acquired perinatally. Postnatal acquisition by nonsexual means also can occur. The likelihood of sexual abuse as the mode of acquisition increases with increasing age in childhood. The virus infects primarily epithelial cells, where it can exist as a long-term latent infection that can reactivate or persist actively (even subclinically), with resultant accumulation of host chromosomal mutations. The latter accounts for the oncogenic potential of a number of HPV types, and childhood infections may lead to neoplasia later in life. Regression of papillomas over the course of months to years is the usual natural course. Numerous treatments are available, but most do not prevent persistent infection or problematic recurrences. Multivalent HPV vaccines have been developed, and early results of clinical trials appear to be very promising.