A phase I study to evaluate a human papillomavirus (HPV) type 18 L1 VLP vaccine

Papillomavirus virus-like particles as vehicles for the delivery of epitopes or genes

Papillomaviruses (PVs) are simple double-strand DNA viruses whose virion shells are T = 7 icosahedrons and composed of major capsid protein L1 and minor capsid protein L2.L1 alone or together with L2 can self-assemble into virus-like particles (VLPs) when expressed in eukaryotic or prokaryotic expression systems. Although the VLPs lack the virus genome DNA, their morphological and immunological characteristics are very similar to those of nature papillomaviruses. PV VLP vaccination can induce high titers of neutralizing antibodies and can effectively protect animals or humans from PV infection. Moreover, PV VLPs have been good candidates for vehicles to deliver epitopes or genes to target cells. They are widely used in the fields of vaccine development, neutralizing antibody detection, basic virologic research on papillomaviruses, and human papillomavirus (HPV) screening. Besides the structural biology and immunological basis for PV VLPs used as vehicles to deliver epitopes or genes, this review details the latest findings on chimeric papillomavirus VLPs and papillomavirus pseudoviruses, which are two important forms of PV VLPs used to transfer epitopes or genes.

Immunologic responses following administration of a vaccine targeting human papillomavirus Types 6, 11, 16, and 18

Human papillomavirus (HPV) infection causes cervical cancer and genital warts. Young women (1106) were randomized to receive one of three formulations of a quadrivalent HPV (Types 6/11/16/18) L1 virus-like particle (VLP) vaccine or one of two placebo formulations. The goal was to assess vaccine safety and immunogenicity in baseline HPV 6/11/16 or 18-naïve and previously infected subjects. All three formulations were highly immunogenic. At Month 2 (postdose 1), among women with vaccine-type antibodies at baseline, vaccine-induced anti-HPV responses were approximately 12- to 26-fold higher than those observed in baseline-naïve women, suggesting an anamnestic response. Following an initial, similar sized decline, anti-HPV responses plateaued and remained stable through end-of-study (3.0 years). No vaccine-related serious adverse experiences were reported.

Human papillomavirus genotype prevalence in cervical biopsies from women diagnosed with cervical intraepithelial neoplasia or cervical cancer in Melbourne, Australia

Multicenter international phase III clinical trials using multivalent human papillomavirus (HPV) vaccines for cervical cancer (CC) prevention are underway. As HPV immunity is type specific, defining HPV genotype prevalence in different regions to ascertain whether predominant types differ geographically is considerably important prior to vaccine implementation. This study aimed to define HPV genotypes present in CC and high-grade dysplasia among women in Melbourne, Australia. HPV genotype analysis of a cross section of women in Melbourne with cervical dysplasia/cancer was performed. A total of 493 cervical biopsies from patients being treated for moderate (n= 122) or severe (n= 180) cervical intraepithelial neoplasia (CIN II/III) or CC (n= 191) were tested for HPV genotypes using the PGMY09/11 primer system and line blot assay. HPV detection rates were 63.9%, 72.8%, and 86.9% in CIN II, CIN III, and CC biopsies, respectively. The most prevalent HPV genotypes among CC biopsies were HPV-16 (52.9%), HPV-18 (18.3%), HPV-45 (6.3%), HPV-39 (3.1%), and HPV-73 (2.6%). Multiple HPV infections, comprising two to five types, were identified in 14.4% of biopsies, being significantly fewer (5.2%) among CC biopsies (P < 0.0001). These results indicate that the two most prevalent CC-associated HPV genotypes in Australia parallel those described internationally, with type variations thereafter.

Prophylactic HPV vaccines: Reducing the burden of HPV-related diseases

HPV-associated diseases, such as cervical and other anogenital cancers, cervical and anal intraepithelial neoplasia, genital warts, and recurrent respiratory papillomatosis confer considerable morbidity and mortality, and are significant health care concerns. Successful vaccination strategies that protect against HPV infection are expected to substantially reduce HPV-related disease burden. Prophylactic HPV vaccines in late stages of clinical testing are composed of HPV L1 capsid protein that self-assemble into virus-like particles (VLPs) when expressed in recombinant systems. Proof-of-principle trials have suggested that intramuscular injections of VLPs results in strong adaptive immune responses, both B- and T-cell mediated, that are capable of neutralizing subsequent natural infections. Furthermore, phase 2 trials of a bivalent vaccine designed to protect against high-risk HPV types 16 and 18 and a quadrivalent vaccine designed to protect against HPV 16 and 18, and low-risk, genital wart-causing HPV 6 and 11 have demonstrated that VLP vaccines reduce the incidence of HPV-associated disease in vaccinated individuals. To derive the greatest public health benefit, HPV vaccines offering protection from cervical cancer and genital warts will, ideally, be administered prior to the initiation of sexual activity; therefore, educational initiatives will be essential to communicate the risks and adverse consequences of HPV infection and to foster widespread vaccine acceptance.

Harnessing the power of prevention: human papillomavirus vaccines

Human papillomavirus (HPV) infection and HPV-associated diseases pose a considerable health care burden in the United States. The morbidity and mortality associated with HPV infection and HPV-associated diseases, ranging from genital warts to cervical cancer, have prompted both the use of screening measures to monitor HPV infection and the development of numerous treatment modalities to address its clinical sequelae. Although screening programs have dramatically reduced the incidence of cervical cancer through early detection and treatment, this devastating illness, which frequently affects women of reproductive age, remains a major public health concern. Prophylactic vaccines that prevent HPV infection have proved to be safe, well tolerated, highly efficacious, and induce long-lasting immunity to HPV. Multivalent vaccines that protect against the most common disease-causing HPV types should significantly reduce the morbidity and mortality associated with HPV.

Human Papillomavirus Quadrivalent (types 6, 11, 16, 18) Recombinant Vaccine (Gardasil??)

Human papillomavirus (HPV) quadrivalent recombinant vaccine is a mixture of virus-like particles derived from the L1 capsid proteins of HPV types 6, 11, 16 and 18. It is administered intramuscularly in a three-dose regimen, with the initial injection followed by subsequent doses at months 2 and 6. The vaccine is indicated for use in the prevention of cervical cancer, vulvar and vaginal precancer and cancers, precancerous lesions and genital warts associated with HPV types 6, 11, 16 or 18 infection in adolescents and young women. The quadrivalent vaccine has demonstrated good immunogenicity in young women (16-26 years) and male and female adolescents (aged 9-15 years), inducing high and persistent anti-HPV antibody titres. In a randomised phase III trial designed to bridge efficacy in young women to adolescents (using immunogenicity as a surrogate), the quadrivalent HPV vaccine in adolescents was at least as immunogenic as that in young women. In randomised, double-blind, placebo-controlled trials in >20 000 young women (aged 16-26 years), the vaccine was highly effective in preventing cervical dysplasia of any grade and external genital lesions related to HPV types 6, 11, 16 and 18 infection. These women were followed up for an average of 2 years.black triangle The vaccine was well tolerated, with injection-site reactions and fever being the most common vaccine-related adverse events.

HPV vaccines

The ability to generate human papillomavirus virus (HPV)-like particles by the synthesis and self-assembly in vitro of the major virus capsid protein L1 has transformed our prospects for preventing cervical carcinoma in women. These particles provide vaccines that are immunogenic and safe, and data from proof-of-principle efficacy trials strongly suggest that they will protect against persistent HPV infection and cervical intraepithelial neoplasia. However, the duration of protection provided by these vaccines is not known, the antibody responses induced are HPV-type-specific and immunisation must occur pre-exposure to the virus. Second-generation vaccines could include an early antigen for protection post exposure and alternative delivery systems might be needed for the developing world. Therapeutic vaccines for low-grade intraepithelial disease are realistic but high-grade disease presents major hurdles for immunotherapies.

Vaccination as a prevention strategy for human papillomavirus-related diseases

Childhood vaccines have had an enormously beneficial impact on human health. Large-scale vaccination programs have controlled diseases associated with high morbidity and mortality such as poliomyelitis, smallpox, diphtheria, tetanus, yellow fever, pertussis, Haemophilus influenzae, Streptococcus pneumoniae, measles, mumps, and rubella. Human papillomavirus (HPV) is a significant source of morbidity and mortality throughout the world. In the United States, HPV is the most common sexually transmitted infection (STI), and sexually active adolescents are at particularly high risk for HPV acquisition. Genetic and epidemiologic studies have clearly demonstrated that HPV infection is a necessary cause of both cervical cancer and genital warts. More than 99% of cervical cancers contain at least one high-risk HPV type, and approximately 70% contain HPV types 16 or 18. Moreover, low-risk HPV types 6 or 11 are responsible for approximately 90% of genital warts and almost all cases of recurrent respiratory papillomatosis. Thus, a vaccine that could prevent HPV acquisition would have the potential to significantly reduce the incidence of both childhood and adult diseases.

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.

[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.

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.

Prophylactic quadrivalent human papillomavirus (types 6, 11, 16, and 18) L1 virus-like particle vaccine in young women: a randomised double-blind placebo-controlled multicentre phase II efficacy trial

BACKGROUND

A randomised double-blind placebo-controlled phase II study was done to assess the efficacy of a prophylactic quadrivalent vaccine targeting the human papillomavirus (HPV) types associated with 70% of cervical cancers (types 16 and 18) and with 90% of genital warts (types 6 and 11).

METHODS

277 young women (mean age 20.2 years [SD 1.7]) were randomly assigned to quadrivalent HPV (20 microg type 6, 40 microg type 11, 40 microg type 16, and 20 microg type 18) L1 virus-like-particle (VLP) vaccine and 275 (mean age 20.0 years [1.7]) to one of two placebo preparations at day 1, month 2, and month 6. For 36 months, participants underwent regular gynaecological examinations, cervicovaginal sampling for HPV DNA, testing for serum antibodies to HPV, and Pap testing. The primary endpoint was the combined incidence of infection with HPV 6, 11, 16, or 18, or cervical or external genital disease (ie, persistent HPV infection, HPV detection at the last recorded visit, cervical intraepithelial neoplasia, cervical cancer, or external genital lesions caused by the HPV types in the vaccine). Main analyses were done per protocol.

FINDINGS

Combined incidence of persistent infection or disease with HPV 6, 11, 16, or 18 fell by 90% (95% CI 71-97, p<0.0001) in those assigned vaccine compared with those assigned placebo.

INTERPRETATION

A vaccine targeting HPV types 6, 11, 16, 18 could substantially reduce the acquisition of infection and clinical disease caused by common HPV types.

Genital infection with human papillomavirus in adolescents

Human papillomavirus (HPV) infection is one of the most common sexually transmitted infections in adolescents. Such infection is associated with substantial health risks and is unpredictable in its resolution. Genital warts are the most common clinical manifestations of genital HPV infections. Most genital warts are caused by low risk HPV types (notably HPV-6 and -11). The majority of genital HPV infections are latent or subclinical. Although the outcome of a genital HPV infection is variable, the infection is usually transient and complete resolution is common. However, persistent infections with high-risk HPV types (notably HPV-16 and -18) are associated with the development of cervical intraepithelial dysplasia (CIN), which may progress to cervical cancer. Genital warts, generally diagnosed in the clinic, can be treated with imiquimod, podofilox, podophyllin, liquid nitrogen, bichloroacetic or trichloroacetic acid, or surgery. Cervical cytology screening is an ideal screening test for subclinical HPV infection with resultant CIN. Annual cervical cytology screening should begin approximately 3 years after initiation of sexual intercourse but no later than age 21 years. Because of the high rate of regression of low-grade squamous intraepithelial lesions (LSIL) in adolescents, the cytologic study should be repeated within 6 to 12 months. Colposcopy should be reserved for persistent LSIL. Patients with high-grade squamous intraepithelial lesions (HSIL) should be referred for colposcopy and biopsy. Confirmed HSIL should be treated with cryotherapy, laser therapy, or loop electrosurgical excisional procedure. The use of therapeutic vaccines is still experimental. HPV infection can be prevented, to a certain extent, by delaying the initiation of sexual activity, limiting the number of sexual partners, and using latex condoms. Several viruslike particle candidate vaccines are under development for the prevention of HPV. These vaccines have been proven safe, well tolerated, highly immunogenic, and highly efficacious. Such vaccines are urgently needed and ultimately may be an important preventive measure.