Immunobiology of human papillomavirus infection and vaccination - implications for second generation vaccines

Severe hematuria in a patient receiving bevacizumab and pembrolizumab for metastatic cervical cancer: a case report

BACKGROUND

Bevacizumab is a monoclonal antibody drug targeting Vascular Endothelial Growth Factor (VEGF), which binds to VEGF receptors to inhibit vascular endothelial cell proliferation and angiogenesis, thus inhibiting tumorigenesis. Pembrolizumab is a monoclonal antibody that can bind to the programmed death-1 (PD-1) receptor, which can block the binding of the PD-1 receptor to its ligands PD-L1 and PD-L2, and release PD-1 pathway-mediated suppression of immune responses. By blocking the activity of PD-1, the purpose of inhibiting tumor growth is achieved.

CASE PRESENTATION

We report a severe hematuria of bevacizumab plus pembrolizumab, in a 58-year-old woman with metastatic cervical cancer. After three cycles every three weeks of consolidation chemotherapy (carboplatin, paclitaxel, bevacizumab) and following three cycles consolidation chemotherapy (carboplatin, paclitaxel, bevacizumab, pembrolizumab), the patient presented a worsening state. Manifested as massive gross hematuria with blood clots. After stopping chemotherapy, cefoxitin, tranexamic acid and hemocoagulase atrox therapy was administered resulting in rapid clinical improvement. The patient was a cervical cancer with bladder metastasis that increases the risk of development of hematuria. Inhibition of VEGF, which has anti-apoptotic, anti-inflammatory, and pro-survival influences on endothelial cells, weakens their regenerative capacity and increases expression of proinflammatory genes leading to weakened supporting layers of blood vessels and, hence, to damaged vascular integrity. In our patient, the development of hematuria may result from the anti-VEGF effect of bevacizumab. In addition, pembrolizumab may also cause bleeding, and the mechanism of bleeding caused by pembrolizumab is currently unclear, which may be related to immune mediation.

CONCLUSION

To our knowledge, this is the first case reporting on the development of severe hematuria during bevacizumab plus pembrolizumab treatment, which should alert the clinicians in case of bleeding adverse events onset in older patients under bevacizumab plus pembrolizumab therapy.

Evaluating the quality of HPV vaccine-related information on the Portuguese Internet

Human papillomavirus (HPV) is considered the second largest human carcinogen after tobacco and is responsible for 5% of all cancers, 10% of cancers in women, and 15% of all cancers in developing countries. Among these, cervical cancer is the most prevalent. An HPV vaccine has recently been developed to provide primary protection against the viral infection. In 2014, Brazil's National Immunization Program (Programa Nacional de Imunizações, PNI) started making a quadrivalent vaccine available to the public. However, after 2014, the vaccine coverage dropped and did not reach the PNI's targets. Among other factors, this low uptake was due to the quality of information on the Internet. Using Google Trends, the main search terms used to search for vaccine-related information on the Internet were identified. The content of the identified websites was analyzed using the DISCERN instrument and their reach was determined using their page authority score. Most of the texts analyzed were not of high quality. The data that most commonly reach the lay public are from sites that lack scientific rigor. We found a weak correlation between the DISCERN and page authority scores. Based on our analysis, we inferred that the information that reaches the user is not always the most accurate and can lead to harmful decisions on vaccination. The content that reaches the user most easily is not always of sound quality. New analyses are important, especially on the impact of social networks that present even fewer criteria in publications and are more easily accessible.

Inducible expression of human papillomavirus-16 L1 capsomeres in the plastomes of Nicotiana tabacum: Transplastomic plants develop normal flowers and pollen

Human papillomavirus type-16 (HPV-16) is the major HPV type involved in causing cervical cancer among women. The disease burden is high in developing and underdeveloped countries. Previously, the constitutive expression of HPV-16 L1 protein led to male sterility in transplastomic tobacco plants. Here, the HPV-16 L1 gene was expressed in chloroplasts of Nicotiana tabacum under the control of an ethanol-inducible promoter, trans-activated by nucleus-derived signal peptide. Plants containing nuclear component were transformed with transformation vector pEXP-T7-L1 by biolistic gun. The transformation and homoplasmic status of transformed plants was verified by polymerase chain reaction and Southern blotting, respectively. Protein was induced by spraying 5% ethanol for 7 consecutive days. The correct folding of L1 protein was confirmed by antigen-capture ELISA using a conformation-specific antibody. The L1 protein accumulated up to 3 μg/g of fresh plant material. The L1 protein was further purified using affinity chromatography. All transplastomic plants developed normal flowers and produced viable seeds upon self-pollination. Pollens also showed completely normal structure under light microscope and scanning electron microscopy. These data confirm the use of the inducible expression as plant-safe approach for expressing transgenes in plants, especially those genes that cause detrimental effects on plant growth and morphology.

Natural and vaccine-induced B cell-derived systemic and mucosal humoral immunity to human papillomavirus

Introduction: Human papillomavirus (HPV) are the causative agent of mucosal neoplasia. Both cervical, anal and oropharyngeal cancers incidence is constantly increasing, making the HPV infection, a significant worldwide concern. Together, the CD8+ T cytotoxic cell-mediated response and the HPV-specific antibody response control most of the HPV infections before the development of cancers.Areas covered: We searched the MEDLINE and EMBASE databases and identified 228 eligible studies from 1987 to 2019 which examines both naturally acquired and vaccine induced humoral immunity against HPV infection in female and male subjects from worldwide origin. Herein, we synthesize current knowledge on the features of systemic and mucosal humoral immunity against HPV. We discuss the issues of the balance between the viral clearance or the escape to the host immune response, the differences between natural and vaccine-induced HPV-specific antibodies and their neutralizing capability. We also discuss the protection afforded after natural infection or following prophylactic vaccination.Expert opinion: Understanding the antibody response induced by HPV infection has led to the design of first-generation prophylactic vaccines. Now, prophylactic vaccination induces protective and long-lasting antibody response which would also strengthened the natural moderate humoral response in people previously exposed to the virus.

Efficacy of Human Papillomavirus L1 Protein Vaccines (Cervarix and Gardasil) in Reducing the Risk of Cervical Intraepithelial Neoplasia: A Meta-analysis

Human papillomavirus (HPV) can induce cervical intraepithelial neoplasia (CIN). Vaccination against HPV can play an important role in CIN prevention. This study aims to estimate the efficacy of L1 protein vaccines (Cervarix and Gardasil) in CIN 1, 2, 3 risk reduction using meta-analysis. Relevant articles were identified by two independent researchers searching international databanks. After application of inclusion/exclusion criteria and quality assessment, eligible articles were entered into the final meta-analysis. Inverse variance method and fixed effect model were used to combine the results of the primary studies. The heterogeneity between the results was assessed using Cochrane and I² indices. Of 11,530 evidence identified during the primary search, three papers were found eligible for meta-analysis, including 7213 participants in the intervention groups and 7170 healthy controls. The efficacy (95% confidence interval) of HPV 6, 11, 16, 18 monovalent and quadrivalent vaccines against CIN 1, CIN 2, and CIN 3 were estimated as of 95% (88–98), 97% (85–99), and 95% (78–99), respectively. This study showed that L1 protein vaccines Cervarix and Gardasil are highly protective vaccines playing an effective role in the prevention of HPV 6, 11, 16, 18 which are responsible for CIN 1, CIN 2, and CIN 3.

Papillomavirus infection and squamous cell carcinoma in horses

Squamous cell carcinoma (SCC) is a common disease that seriously impairs the health and welfare of affected horses and other equids. In humans, almost all cervical carcinomas, a high percentage of anogenital SCCs and a subset of SCCs of the head and neck are caused by high-risk human papillomavirus (hrHPV) infection. Since hrHPV-induced human cancers and equine SCC have similar cytological and histopathological features, it has been hypothesised that equine SCCs could also be induced by papillomaviruses. This review provides an overview of the current evidence for an aetiological association between papillomavirus infections and equine SCCs and SCC precursor lesions. SCC of apparently papillomavirus-unrelated aetiology are also discussed, as are recent advances in equine SCC prophylaxis.

Human Papillomavirus and Its Testing Assays, Cervical Cancer Screening, and Vaccination

Human papillomavirus (HPV) was found to be the causative agent for cervical cancer in the 1980s with almost 100% of cervical cancer cases testing positive for HPV. Since then, many studies have been conducted to elucidate the molecular basis of HPV, the mechanisms of carcinogenesis of the virus, and the risk factors for HPV infection. Traditionally, the Papanicolaou test was the primary screening method for cervical cancer. Because of the discovery and evolving understanding of the role of HPV in cervical dysplasia, HPV testing has been recommended as a new method for cervical cancer screening by major professional organizations including the American Cancer Society, American Society for Colposcopy and Cervical Pathology, and the American Society for Clinical Pathology. In order to detect HPV infections, many sensitive and specific HPV assays have been developed and used clinically. Different HPV assays with various principles have shown their unique advantages and limitations. In response to a clear causative relationship between high-risk HPV and cervical cancer, HPV vaccines have been developed which utilize virus-like particles to create an antibody response for the prevention of HPV infection. The vaccines have been shown in long-term follow-up studies to be effective for up to 8 years; however, how this may impact screening for vaccinated women remains uncertain. In this chapter, we will review the molecular basis of HPV, its pathogenesis, and the epidemiology of HPV infection and associated cervical cancer, discuss the methods of currently available HPV testing assays as well as recent guidelines for HPV screening, and introduce HPV vaccines as well as their impact on cervical cancer screening and treatments.

Human Papillomavirus Infection, Infertility, and Assisted Reproductive Outcomes

The human papillomavirus (HPV) is a sexually transmitted infection common among men and women across all geographic and socioeconomic subgroups worldwide. Recent evidence suggests that HPV infection may affect fertility and alter the efficacy of assisted reproductive technologies. In men, HPV infection can affect sperm parameters, specifically motility. HPV-infected sperm can transmit viral DNA to oocytes, which may be expressed in the developing blastocyst. HPV can increase trophoblastic apoptosis and reduce the endometrial implantation of trophoblastic cells, thus increasing the theoretical risk of miscarriage. Vertical transmission of HPV during pregnancy may be involved in the pathophysiology of preterm rupture of membranes and spontaneous preterm birth. In patients undergoing intrauterine insemination for idiopathic infertility, HPV infection confers a lower pregnancy rate. In contrast, the evidence regarding any detrimental impact of HPV infection on IVF outcomes is inconclusive. It has been suggested that vaccination could potentially counter HPV-related sperm impairment, trophoblastic apoptosis, and spontaneous miscarriages; however, these conclusions are based on in vitro studies rather than large-scale epidemiological studies. Improvement in the understanding of HPV sperm infection mechanisms and HPV transmission into the oocyte and developing blastocyst may help explain idiopathic causes of infertility and miscarriage.

Next generation prophylactic human papillomavirus vaccines

The two licensed bivalent and quadrivalent human papillomavirus (HPV) L1 (the major papillomavirus virion protein) virus-like particle (VLP) vaccines are regarded as safe, effective, and well established prophylactic vaccines. However, they have some inherent limitations, including a fairly high production and delivery cost, virus-type restricted protection, and no reported therapeutic activity, which might be addressed with the development of alternative dosing schedules and vaccine products. A change from a three-dose to a two-dose protocol for the licensed HPV vaccines, especially in younger adolescents (aged 9-13 years), is underway in several countries and is likely to become the future norm. Preliminary evidence suggests that recipients of HPV vaccines might derive prophylactic benefits from one dose of the bivalent vaccine. Substantial interest exists in both the academic and industrial sectors in the development of second-generation L1 VLP vaccines in terms of cost reduction-eg, by production in Escherichia coli or alternative types of yeast. However, Merck's nonavalent vaccine, produced via the Saccharomyces cerevisiae production system that is also used for their quadrivalent vaccine, is the first second-generation HPV VLP vaccine to be available on the market. By contrast, other pharmaceutical companies are developing microbial vectors that deliver L1 genes. These two approaches would add an HPV component to existing live attenuated vaccines for measles and typhoid fever. Prophylactic vaccines that are based on induction of broadly cross-neutralising antibodies to L2, the minor HPV capsid protein, are also being developed both as simple monomeric fusion proteins and as virus-like display vaccines. The strong interest in developing the next generation of vaccines, particularly by manufacturers in middle-to-high income countries, increases the likelihood that vaccine production will become decentralised with the hope that effective HPV vaccines will be made increasingly available in low-resource settings where they are most needed.

The potential of plants for the production and delivery of human papillomavirus vaccines

The available vaccines against human papillomavirus have some limitations such as low coverage due to their high cost, reduced immune coverage and the lack of therapeutic effects. Recombinant vaccines produced in plants (genetically engineered using stable or transient expression systems) offer the possibility to obtain low cost, efficacious and easy to administer vaccines. The status on the development of plant-based vaccines against human papillomavirus is analyzed and placed in perspective in this review. Some candidates have been characterized at a preclinical level with interesting outcomes. However, there is a need to perform the immunological characterization of several vaccine prototypes, especially through the oral administration route, as well as develop new candidates based on new chimeric designs intended to provide broader immunoprotection and therapeutic activity.

Research Progress in Head and Neck Squamous Cell Carcinoma: Best Abstracts of ICHNO 2015

Head and neck squamous cell carcinoma (HNSCC) is a highly heterogeneous group of tumors that develop via one of the two primary carcinogenic pathways: chemical carcinogenesis through exposure to tobacco and alcohol or virally induced tumorigenesis. HPV-negative (HPV-) and HPV-positive (HPV+) HNSCCs represent distinct disease entities, and the latter is associated with a substantially improved outcome. Differences in molecular pathogenesis account for these different outcomes; their staging classification and therapeutic regimens also are currently being re-evaluated, and re-evaluation would be significantly facilitated by robust biomarkers for patient stratification. Through the past years, with the advent of the omics era, a better understanding of the biology of HNSCC has been accompanied by the exploration of a large and rapidly expanding number of targeted agents, which might be incorporated into standard management in the future. In the era of personalized medicine, and with a view to improve the outcomes and quality of life of patients, current research efforts also are focused on the identification of specific biomarkers for treatment selection. Treatment of HNSCC is expected to change in the next decade if molecular biology continues to evolve. Herein, we highlight research progress in HNSCC presented at the fifth International Conference on Innovative Approaches in Head and Neck Oncology (ICHNO).

Expression of HPV-16 L1 capsomeres with glutathione-S-transferase as a fusion protein in tobacco plastids: an approach for a capsomere-based HPV vaccine

Human Papillomavirus (HPV) is the main cause of cervical cancer, which is the second most severe cancer of women worldwide, particularly in developing countries. Although vaccines against HPV infection are commercially available, they are neither affordable nor accessible to women in low income countries e.g. Africa. Thus, alternative cost-effective vaccine production approaches need to be developed. This study uses tobacco plants to express pentameric capsomeres of HPV that have been reported to generate elevated immune responses against HPV. A modified HPV-16 L1 (L1_2xCysM) protein has been expressed as a fusion protein with glutathione-S-transferase (GST) in tobacco chloroplasts following biolistic transformation. In total 7 transplastomic lines with healthy phenotypes were generated. Site specific integration of the GST-L1_2xCysM and aadA genes was confirmed by PCR. Southern blot analysis verified homogenous transformation of all transplastomic lines. Antigen capture ELISA with the conformation-specific antibody Ritti01, showed protein expression as well as the retention of immunogenic epitopes of L1 protein. In their morphology, GST-L1 expressing tobacco plants were identical to wild type plants and yielded fertile flowers. Taken together, these data enrich knowledge for future development of cost-effective plant-made vaccines against HPV.

Current perspectives on HPV vaccination: a focus on targeting the L2 protein

ABSTRACT: 

Thirty years ago, human papillomavirus types 16 and 18 were isolated from cervical carcinomas, and it has been almost 10 years since the introduction of the first prophylactic virus-like particle (VLP) vaccine. The VLP vaccines have already impacted the reduction of pre-malignant lesions and genital warts, and it is expected that vaccination efforts will successfully lower the incidence of cervical cancer before the end of the decade. Here we summarize the historical developments leading to the prophylactic HPV vaccines and discuss current advances of next-generation vaccines that aim to overcome certain limitations of the VLP vaccines, including their intrinsic narrow range of protection, stability and production/distribution costs.

Immunogenicity of recombinant human bocavirus-1,2 VP2 gene virus-like particles in mice

Human bocavirus (HBoV), a recently identified pathogen with a worldwide distribution is closely related to paediatric acute respiratory infection and gastroenteritis. The present study was performed to evaluate the immunogenicity of HBoV1 and HBoV2 virus-like particles (VLPs) as vaccine candidates in mice. Both HBoV1 and HBoV2 VLPs were expressed in the bacmid virus–SF9 cell system. Mice were inoculated three times at 3-week intervals with HBoV VLPs at one dose intramuscular (i.m.) or intradermal (i.d.) with or without the addition of the alum adjuvant. ELISA was used to detected antibody, and ELISPOT was used to test cellular immune responses. HBoV-specific IgG antibodies were induced and alum adjuvant improved the antibody titres and avidity, while the inoculation pathway had no influence. T helper type 1/ type 2 immune responses were balanced induced by HBoV1 VLPs but not HBoV2 VLPs. Serum IgG antibody cross-reactivity rates of the two subtypes were similar, but cross-reactions of HBoV1 immunization groups were higher. The single i.m. group had more interferon-γ-secreting splenocytes. These data indicate that HBoV VP2 VLPs have good immunogenicity with induction of strong humoral and cellular immune responses, and they may be potential candidate vaccines for HBoV infection.

Human papillomavirus vaccination: current indications and future directions

Human papillomavirus (HPV) is one of the most common sexually transmitted infections affecting both men and women worldwide. The development of the prophylactic HPV vaccines is a significant pharmaceutical innovation with potential to reduce HPV-related morbidity. However, barriers to the universal use and acceptability of the HPV vaccines continue to exist in both economically privileged and disadvantaged countries. It may be decades before the impact of preventive vaccines on HPV-related diseases caused by the considerable burden of HPV infections will be seen. Collaborative efforts must continue to promote vaccine implementation.

Susceptibility to cervical cancer: an overview

Cervical cancer is the second most common cancer in females worldwide. It is well-established that Human Papillomavirus (HPV) infections play a critical role in the development of cervical cancer. However, a large number of women infected with oncogenic HPV types will never develop cervical cancer. Thus, there are several external environment and genetic factors involved in the progression of a precancerous lesion to invasive cancer. In this review article, we addressed possible susceptible phenotypes to cervical cancer, focusing on host genome and HPV DNA variability, multiple HPV infections, co-infection with other agents, circulating HPV DNA and lifestyle.

Construction and characterisation of a recombinant fowlpox virus that expresses the human papilloma virus L1 protein

BACKGROUND

Human papilloma virus (HPV)-16 is the most prevalent high-risk mucosal genotype. Virus-like-particle (VLP)-based immunogens developed recently have proven to be successful as prophylactic HPV vaccines, but are still too expensive for developing countries. Although vaccinia viruses expressing the HPV-16 L1 protein (HPV-L1) have been studied, fowlpox-based recombinants represent efficient and safer vectors for immunocompromised hosts due to their ability to elicit a complete immune response and their natural host-range restriction to avian species.

METHODS

A new fowlpox virus recombinant encoding HPV-L1 (FPL1) was engineered and evaluated for the correct expression of HPV-L1 in vitro, using RT-PCR, immunoprecipitation, Western blotting, electron microscopy, immunofluorescence, and real-time PCR assays.

RESULTS

The FPL1 recombinant correctly expresses HPV-L1 in mammalian cells, which are non-permissive for the replication of this vector.

CONCLUSION

This FPL1 recombinant represents an appropriate immunogen for expression of HPV-L1 in human cells. The final aim is to develop a safe, immunogenic, and less expensive prophylactic vaccine against HPV.

Human papillomavirus genotype prevalence in cervical biopsies from women diagnosed with cervical intraepithelial neoplasia or cervical cancer in Fiji

BACKGROUND

There is currently limited information about human papillomavirus (HPV) genotype distribution in women in the South Pacific region. This study's objective was to determine HPV genotypes present in cervical cancer (CC) and precancers (cervical intraepithelial lesion (CIN) 3) in Fiji.

METHODS

Cross-sectional analysis evaluated archival CC and CIN3 biopsy samples from 296 women of Melanesian Fijian ethnicity (n=182, 61.5%) and Indo-Fijian ethnicity (n=114, 38.5%). HPV genotypes were evaluated using the INNO-LiPA assay in archival samples from CC (n=174) and CIN3 (n=122) among women in Fiji over a 5-year period from 2003 to 2007.

RESULTS

Overall, 99% of the specimens tested were HPV DNA-positive for high-risk genotypes, with detection rates of 100%, 97.4% and 100% in CIN3, squamous cell carcinoma (SCC) and adenosquamous carcinoma biopsies, respectively. Genotypes 16 and 18 were the most common (77%), followed by HPV 31 (4.3%). Genotype HPV 16 was the most common identified (59%) in CIN3 specimens, followed by HPV 31 (9%) and HPV 52 (6.6%). Multiple genotypes were detected in 12.5-33.3% of specimens, depending on the pathology.

CONCLUSION

These results indicated that the two most prevalent CC-associated HPV genotypes in Fiji parallel those described in other regions worldwide, with genotype variations thereafter. These data suggest that the currently available bivalent and quadrivalent HPV vaccines could potentially reduce cervical cancers in Fiji by over 80% and reduce precancers by at least 60%.

Plastid expression of a double-pentameric vaccine candidate containing human papillomavirus-16 L1 antigen fused with LTB as adjuvant: transplastomic plants show pleiotropic phenotypes

Human papillomavirus (HPV) causes cervical cancer in women worldwide, which is currently prevented by vaccines based on virus-like particles (VLPs). However, these vaccines have certain limitations in their availability to developing countries, largely due to elevated costs. Concerning the highest burden of disease in resource-poor countries, development of an improved mucosal and cost-effective vaccine is a necessity. As an alternative to VLPs, capsomeres have been shown to be highly immunogenic and can be used as vaccine candidate. Furthermore, coupling of an adjuvant like Escherichia coli heat-labile enterotoxin subunit B (LTB) to an antigen can increase its immunogenicity and reduce the costs related to separate co-administration of adjuvants. Our study demonstrates the expression of two pentameric proteins: the modified HPV-16 L1 (L1_2xCysM) and LTB as a fusion protein in tobacco chloroplasts. Homoplasmy of the transplastomic plants was confirmed by Southern blotting. Western blot analysis showed that the LTB-L1 fusion protein was properly expressed in the plastids and the recombinant protein was estimated to accumulate up to 2% of total soluble protein. Proper folding and display of conformational epitopes for both LTB and L1 in the fusion protein was confirmed by GM1-ganglioside binding assay and antigen capture ELISA, respectively. However, all transplastomic lines showed chlorosis, male sterility and growth retardation, which persisted in the ensuing four generations studied. Nevertheless, plants reached maturity and produced seeds by pollination with wild-type plants. Taken together, these results pave the way for the possible development of a low-cost adjuvant-coupled vaccine with potentially improved immunogenicity against cervical cancer.

Human papillomavirus: science and technologies for the elimination of cervical cancer

INTRODUCTION

Academic research has made a significant advancement in understanding the viral causes of cervical cancer and generating the technology for prevention, both at the primary and secondary levels. Human papillomaviruses (HPVs) have been recognized as the first necessary cause of cervical cancer, the second most common cancer in women worldwide.

AREAS COVERED

This paper reviews the epidemiological evidence of the causality of HPV in relation to cervical cancer, other genital tract cancers and some cancers of the oral cavity and oropharynx. The review also covers HPV DNA testing as a screening tool. DNA probes of high-risk HPV types in different formats have been fully validated as primary screening tests, as secondary triage tests and as a prognostic marker following treatment of high grade squamous intraepithelial lesions (HSIL). They consistently showed significant superiority over the conventional Pap smears. Biomarkers of the activation of oncogenes (HPV mRNA, p16 and other) are being tested as screening options to improve in sensitivity and specificity, with promising results. HPV vaccines against the two most common HPV types in cancer have completed their Phase III trials with excellent results in efficacy and safety. Combined strategies of HPV vaccination and HPV-based screening tests could theoretically control cervical cancer in any population in which a large coverage with both preventive options is ensured. Accessibility of developing countries to vaccination and low-cost HPV screening options are the barriers to overcome at present.

EXPERT OPINION

This paper provides a synthesis of the evidence available supporting the novel paradigm for cervical cancer prevention that has reached a large consensus within the mainstream HPV and cervical cancer prevention research communities. The available technology for prevention and its developments allows real opportunities for cervical cancer elimination in defined populations to be foreseen.

Antibodies to the envelope glycoprotein of human T cell leukemia virus type 1 robustly activate cell-mediated cytotoxic responses and directly neutralize viral infectivity at multiple steps of the entry process

Infection of human cells by human T cell leukemia virus type 1 (HTLV-1) is mediated by the viral envelope glycoproteins. The gp46 surface glycoprotein binds to cell surface receptors, including heparan sulfate proteoglycans, neuropilin 1, and glucose transporter 1, allowing the transmembrane glycoprotein to initiate fusion of the viral and cellular membranes. The envelope glycoproteins are recognized by neutralizing Abs and CTL following a protective immune response, and therefore, represent attractive components for a HTLV-1 vaccine. To begin to explore the immunological properties of potential envelope-based subunit vaccine candidates, we have used a soluble recombinant surface glycoprotein (gp46, SU) fused to the Fc region of human IgG (sRgp46-Fc) as an immunogen to vaccinate mice. The recombinant SU protein is highly immunogenic and induces high titer Ab responses, facilitating selection of hybridomas that secrete mAbs targeting SU. Many of these mAbs recognize envelope displayed on the surface of HTLV-1-infected cells and virions and several of the mAbs robustly antagonize envelope-mediated membrane fusion and neutralize pseudovirus infectivity. The most potently neutralizing mAbs recognize the N-terminal receptor-binding domain of SU, though there is considerable variation in neutralizing proficiency of the receptor-binding domain-targeted mAbs. By contrast, Abs targeting the C-terminal domain of SU tend to lack robust neutralizing activity. Importantly, we find that both neutralizing and poorly neutralizing Abs strongly stimulate neutrophil-mediated cytotoxic responses to HTLV-1-infected cells. Our data demonstrate that recombinant forms of SU possess immunological features that are of significant utility to subunit vaccine design.

Incident cervical HPV infections in young women: transition probabilities for CIN and infection clearance

BACKGROUND

We describe transition probabilities for incident human papillomavirus (HPV) 16/18/31/33/35/45/52/58/59 infections and cervical intraepithelial neoplasia (CIN) 1 lesions.

METHODS

Women ages 16 to 23 years underwent cytology and cervical swab PCR testing for HPV at approximately 6-month intervals for up to 4 years in the placebo arm of an HPV vaccine trial. The cumulative proportion of incident HPV infections with diagnosed CIN, clearing (infection undetectable), or persisting without CIN, were estimated.

RESULTS

Most incident infections cleared, without detection of CIN, ranging at 36 months from 66.9% for HPV31 to 91.1% for HPV59. There was little variation in the 36-month proportion of incident HPV16, 18, and 31 infections followed by a CIN1 lesion positive for the relevant HPV type (range 16.7%-18.6%), with lower risks for HPV59 (6.4%) and HPV33 (2.9%). Thirty-six-month transition probabilities for CIN2 ranged across types from 2.2% to 9.1%; however, the number of events was generally too small for statistically significant differences to be seen across types for this endpoint, or CIN3.

CONCLUSIONS

Some incident HPV types appear more likely to result in diagnosed CIN1 than others. The relative predominance of HPV16, vis-à-vis some other high-risk HPV types (e.g., HPV33) in prevalent CIN2/3, appears more directly associated with relatively greater frequency of incident HPV16 infections within the population, than a higher risk of infection progression to CIN2/3.

IMPACT

Nearly all incident HPV infections either manifest as detectable CIN or become undetectable within 36 months. Some HPV types (e.g., 16 and 33) appear to have similar risk of CIN2/3 despite widely varied incidence.

New adjuvants in evolving vaccine strategies

Adjuvants are becoming the key players of vaccine formulations to enhance the immunogenicity of subunit (peptides, proteins, virus-like particles (VLPs)) and DNA vaccines, as well as to reach the current new goals of preventing and/or treating chronic infectious diseases and cancers. Induction of humoral response, in particular neutralizing antibodies able to inhibit the binding of pathogens to their cellular receptors, remains a major goal of vaccines targeted to prevent acute lytic infections; induction/modulation of cellular immunity is, however, critical to fight latently/chronically infected cells as well as cancer cells. The new adjuvants, included in vaccine preparations, are currently able to modify the presentation of epitopes to the immune system with a specific T(H)1 versus T(H)2 polarization efficacy. A paradigm of the relevance of these new adjuvants is the immunological result obtained with the inclusion of monophosphoryl lipid A in the formulation of L1-based human papillomavirus (HPV)-naked VLPs. In the May issue of this journal, Garcon and colleagues describe the highly enhanced humoral and memory B cellular immunity of the AS04-adjuvanted HPV vaccine, which results in a long-lasting and broad spectrum immunity.

Transplastomic expression of a modified human papillomavirus L1 protein leading to the assembly of capsomeres in tobacco: a step towards cost-effective second-generation vaccines

Certain types of human papillomaviruses (HPV) are causatively associated with cervical carcinoma, the second most common cancer in women worldwide. Due to limitations in the availability of currently used virus-like particle (VLP)-based vaccines against HPV to women of developing countries, where most cases of cervical cancer occur, the development of a cost-effective second-generation vaccine is a necessity. Capsomeres have recently been demonstrated to be highly immunogenic and to have a number of advantages as a potential cost-effective alternative to VLP-based HPV vaccines. We have expressed a mutated HPV-16 L1 (L1_2xCysM) gene that retained the ability to assemble L1 protein to capsomeres in tobacco chloroplasts. The recombinant protein yielded up to 1.5% of total soluble protein. The assembly of capsomeres was examined and verified by cesium chloride density gradient centrifugation and sucrose sedimentation analysis. An antigen capture enzyme-linked immunosorbent assay confirmed the formation of capsomeres by using a conformation-specific monoclonal antibody which recognized the conformational epitopes. Transplastomic tobacco plants exhibited normal growth and morphology, but all such lines showed male sterility in the T₀, T₁ and T₂ generations. Taken together, these results indicate the possibility of producing a low-cost capsomere-based vaccine by plastids.

Incidence, duration, and reappearance of type-specific cervical human papillomavirus infections in young women

BACKGROUND

We describe the incidence and duration of cervical human papillomavirus (HPV) infection episodes along with the risk of infection reappearance following a period of nondetection.

METHODS

Women (1,788) ages 16 to 23 years underwent cytologic testing and PCR-based testing of cervical swab samples for HPV DNA (HPV-16/18/31/33/35/45/52/58/59) at approximately 6-month intervals for up to 4 years in the context of a phase 3 clinical trial (placebo arm). HPV type-specific incidence rates were estimated per 100 person-years. Duration of type-specific cervical infection episodes and risk of reappearance following a period of nondetection were estimated using Kaplan-Meier methods.

RESULTS

HPV-16 exhibited the highest (5.9), and HPV-35 and HPV-33 exhibited the lowest (1.0) incidence rates per 100 person-years. Mean cervical infection durations ranged from 13 months for HPV-59 to 20 months for HPV-16 and 58 (with ongoing infections censored at the time of treatment, if done). The risk of cervical infection reappearance within approximately 3 years following a period of nondetection ranged from 0% to 16% across HPV types, with a mean of 8%. Limited evidence was found for a role of false-positive HPV tests, missed infections that were above the threshold for detection, or new acquisition of infection in accounting for patterns of infection reappearance.

CONCLUSIONS

Incidence of high-risk cervical infection was observed to vary considerably more across HPV types than infection duration. A nontrivial proportion of women exhibited infection reappearance following a period of nondetection, with a potential explanation for many such events observed within this analysis being a return to detectable levels of a previously acquired infection.

IMPACT

The risk of HPV infection reappearance following a period of nondetection has not been previously reported for individual HPV types, and this study finds that a nontrivial proportion of infected women exhibit reappearances. Future studies could ascertain subject-level factors that potentially modify the risk of infection reappearance.

A prophylactic vaccine for breast cancer?

Cancer vaccines are the Holy Grail for patients and clinicians alike. The possibility that we can be vaccinated against common cancers is very appealing and the socioeconomic consequences are significant. A recent paper from Vincent Tuohy's group, published in the journal Nature Medicine, suggests a new approach for the development of a prophylactic vaccine for breast cancer. Their strategy was to induce mammary gland failure in mice by immunisation with an antibody specific to a milk protein that resulted in autoimmunity during lactation. This also showed some efficacy as a therapeutic vaccine. Can we look forward to the elimination of breast cancer?

Chloroplasts as expression platforms for plant-produced vaccines

Production of recombinant subunit vaccines from genes incorporated in the plastid genome is advantageous because of the attainable expression level due to high transgene copy number and the absence of gene silencing; biocontainment as a consequence of maternal inheritance of plastids and no transgene presence in the pollen; and expression of multiple transgenes in prokaryotic-like operons. We discuss the core technology of plastid transformation in Chlamydomonas reinhardtii, a unicellular alga, and Nicotiana tabacum (tobacco), a flowering plant species, and demonstrate the utility of the technology for the production of recombinant vaccine antigens.

Nucleic acid sequence-based amplification assay for human papillomavirus mRNA detection and typing: evidence for DNA amplification

Human papillomavirus (HPV) E6/E7 mRNA has been proposed as a more specific marker for cervical dysplasia and cancer than HPV DNA. This study evaluated the RNA specificity of nucleic acid sequence-based amplification (NASBA)-based HPV detection using HPV DNA plasmids (HPV type 16 [HPV16], HPV18, HPV31, HPV33, and HPV45) and nucleic acid extracts of several cell lines, which were systematically subjected to enzymatic treatments with DNase and RNase. HPV plasmid dilutions (10(6) to 10(0) copies/microl) and nucleic acid extracts (total DNA, RNA-free DNA, total RNA, and DNA-free RNA) of unfixed and fixed (PreServCyt and SurePath) HaCaT, HeLa, and CaSki cells were tested with the NucliSENS EasyQ HPV test. The RNA-free DNA extracts of HeLa and CaSki cells could be amplified by HPV18 and -16 NASBA, respectively. Fixation of the cells did not influence NASBA. All HPV plasmids could be detected with NASBA. Based on the plasmid dilution series, a lower detection limit of 5 x 10(3) HPV DNA copies could be determined. Our study identified viral double-stranded DNA as a possible target for NASBA-based HPV detection. The differences in diagnostic accuracy between the NASBA-based tests and conventional HPV DNA detection assays seem to be attributable not to the more specific amplification of viral mRNA but to the limited type range and the lower analytical sensitivity for HPV DNA.

Combined prophylactic and therapeutic intranasal vaccination against human papillomavirus type-16 using different adeno-associated virus serotype vectors

BACKGROUND

Cervical cancer is the second most frequent cancer among woman worldwide and is considered to be caused by infection with high-risk papilloma viruses. Genetic immunization using recombinant adeno-associated virus (rAAV) vectors has shown great promise for vaccination against human papillomavirus (HPV) infections.

METHODS

rAAV5, -8 and -9 vectors expressing an HPV16 L1/E7 fusion gene were generated and applied intranasally for combined prophylactic and therapeutic vaccination of mice.

RESULTS

The rAAV5 and the rAAV9 vectors showed efficient induction of both humoral and cellular immune responses, whereas rAAV8 failed to immunize mice by the intranasal route. The L1-specific immune response evoked by expression of the L1/E7 fusion gene, however, was lower than that evoked by expression of the L1 antigen alone. This deficiency could be compensated by application of Escherichia coli heat-labile enterotoxin or monophsphoryl lipid as adjuvant upon vaccination with rAAV5-L1/E7. Coimmunization of rAAV9-L1/E7 with rAAV5-L1 or boosting of rAAV9-L1/E7 with rAAV5-L1 strongly increased L1-specific neutralizing antibody titres to levels above those achieved by vaccination with vectors expressing L1 alone. Both vectors elicited a vibrant cytotoxic T-lymphocyte response against L1 or E7. Nasal immunization with rAAV5 or rAAV9 was superior to vaccination with HPV16-L1 virus-like particles (VLPs) or HPV16-L1/E7 CVLPs with respect to humoral and cellular immune responses. Vaccination with the rAAV vectors led to a significant protection of animals against a challenge with different HPV tumour cell lines.

CONCLUSIONS

Our results show that rAAV5 and rAAV9 vectors are promising candidates for a non-invasive nasal vaccination strategy.

Memory CD8+ T cell differentiation

In response to infection or effective vaccination, naive antigen-specific CD8+ T cells undergo a dramatic highly orchestrated activation process. Initial encounter with an appropriately activated antigen-presenting cell leads to blastogenesis and an exponential increase in antigen-specific CD8+ T cell numbers. Simultaneously, a dynamic differentiation process occurs, resulting in formation of both primary effector and long-lived memory cells. Current findings have emphasized the heterogeneity of effector and memory cell populations with the description of multiple cellular subsets based on phenotype, function, and anatomic location. Yet, only recently have we begun to dissect the underlying factors mediating the temporal control of the development of distinct effector and memory CD8+ T cell sublineages. In this review we will focus on the requirements for mounting an effective CD8+ T cell response and highlight the elements regulating the differentiation of effector and memory subsets.

Rotavirus enterotoxin NSP4 has mucosal adjuvant properties

Rotavirus nonstructural protein 4 (NSP4) is a protein with pleiotropic properties. It functions in rotavirus morphogenesis, pathogenesis, and is the first described viral enterotoxin. Since many bacterial toxins function as potent mucosal adjuvants, we evaluated whether baculovirus-expressed recombinant simian rotavirus SA11 NSP4 possesses adjuvant activity by co-administering NSP4 with keyhole limpet hemocyanin (KLH), tetanus toxoid (TT) or ovalbumin (OVA) as model antigens in mice. Following intranasal immunization, NSP4 significantly enhanced both systemic and mucosal immune responses to model immunogens, as compared to the control group, in an antigen-specific manner. Both full-length and a cleavage product of SA11 NSP4 had adjuvant activity, localizing this activity to the C-terminus of the protein. NSP4 forms from virulent and avirulent porcine rotavirus OSU strain, and SA11 NSP4 localized within a 2/6-virus-like particle (VLP) also exhibited adjuvant effects. These studies suggest that the rotavirus enterotoxin NSP4 can function as an adjuvant to enhance immune responses for a co-administered antigen.

Human papillomavirus genotypes in asymptomatic young women from public schools in Rio de Janeiro, Brazil

INTRODUCTION: The aim of this work was to survey HPV information from a random population of young women from Rio de Janeiro, Brazil. METHODS: This cross-sectional study included cervical samples from 241 female students. To determine human papillomavirus status, polymerase chain reaction amplification was performed. HPV typing was determined by restriction fragment length polymorphism analysis. Demographic data, life style, sexual and gynecological history were obtained through use of a structured questionnaire. RESULTS: The average age of the women was 19.6 years-old (SD=3.4 years). HPV prevalence was 27.4%. Nineteen different HPV genotypes were detected, including 13 high risk types. HPV 16 was the most prevalent type (6.2%), followed by 31 (4.1 %) and 66 (3.7%). Most of the oncogenic types belonged to the A9 species (28/48). The frequency of women infected by at least one oncogenic type was significantly higher than those only infected by low risk types (18.7% versus 7.5%). Cervical changes were detected in 12.5% of the sample and were significantly linked to infection with HPV types of the A9 species. Demographic variables, sexual initiation, or number of sexual partners were not associated with HPV prevalence, variety of HPV genotypes or oncogenic types. CONCLUSIONS: The relative frequency of HPV genotypes other than vaccine types in young females should be taken into account when evaluating vaccination strategies. Due to the high prevalence of HPV infection among the population studied, implementation of sex education in schools, promotion of condom use and an organized screening program to prevent cervical cancer must be encouraged for this age group.

HPV prevalence in Colombian women with cervical cancer: implications for vaccination in a developing country

Human Papillomavirus (HPV) vaccines have been considered potentially cost-effective for the reduction of cervical cancer burden in developing countries; their effectiveness in a public health setting continues to be researched. We conducted an HPV prevalence survey among Colombian women with invasive cancer. Paraffin-embedded biopsies were obtained from one high-risk and one low-middle-risk regions. GP5+/GP6+ L1 primers, RLB assays, and E7 type specific PCR were used for HPV-DNA detection. 217 cases were analyzed with 97.7% HPV detection rate. HPV-16/18 prevalence was 63.1%; HPV-18 had lower occurrence in the high-risk population (13.8% versus 9.6%) allowing for the participation of less common HPV types; HPV-45 was present mainly in women under 50 and age-specific HPV type prevalence revealed significant differences. Multiple high-risk infections appeared in 16.6% of cases and represent a chance of replacement. Age-specific HPV prevalence and multiple high-risk infections might influence vaccine impact. Both factors highlight the role of HPVs other than 16/18, which should be considered in cost-effectiveness analyses for potential vaccine impact.

Virus-like particle vaccines and adjuvants: the HPV paradigm

Complex antigen structures currently represent the most-studied approach for prophylactic as well as therapeutic vaccines. Different types of complex vaccines, including virus-like particles and virosomes, have been developed depending on the nature of the viral pathogen they are trying to replicate (enveloped vs naked) or the modality to express antigenic epitopes (i.e., the binding of envelope protein on liposomic structures). The complex structure of these vaccines provides them with some adjuvanted properties, not uniformly present for all virus-like particle types. The further inclusion of specific adjuvants in vaccine preparations can modify the presentation modality of such particles to the immune system with a specific Th1 versus Th2 polarization efficacy. A paradigm of the relevance of these new adjuvants are the immunological results obtained with the inclusion of monophosphoryl lipid A adjuvant in the formulation of L1-based human papillomavirus-naked virus-like particles to reduce a Th1 cellular immunity impairment, peculiar for alum-derived adjuvants, along with the induction of highly enhanced humoral and memory B-cellular immunity.

An HPV 16 L1-based chimeric human papilloma virus-like particles containing a string of epitopes produced in plants is able to elicit humoral and cytotoxic T-cell activity in mice

Background

Even though two prophylactic vaccines against HPV are currently licensed, infections by the virus continue to be a major health problem mainly in developing countries. The cost of the vaccines limits wide-scale application in poor countries. A promising strategy for producing affordable and efficient vaccines involves the expression of recombinant immunogens in plants. Several HPV genes have been expressed in plants, including L1, which can self-assemble into virus-like particles. A plant-based, dual prophylactic/therapeutic vaccine remains an attractive possibility.

Results

We sought to express in tomato plants chimeric HPV 16 VLPs containing L1 fused to a string of epitopes from HPV 16 E6 and E7 proteins. The L1 employed had been modified to eliminate a strong inhibitory region at the 5' end of the molecule to increase expression levels. Several tomato lines were obtained expressing either L1 alone or L1-E6/E7 from 0.05% to 0.1% of total soluble protein. Stable integration of the transgenes was verified by Southern blot. Northern and western blot revealed successful expression of the transgenes at the mRNA and protein level. The chimeric VLPs were able to assemble adequately in tomato cells. Intraperitoneal administration in mice was able to elicit both neutralizing antibodies against the viral particle and cytotoxic T-lymphocytes activity against the epitopes.

Conclusion

In this work, we report for the first time the expression in plants of a chimeric particle containing the HPV 16 L1 sequence and a string of T-cell epitopes from HPV 16 E6 and E7 fused to the C-terminus. The particles were able to induce a significant antibody and cytotoxic T-lymphocytes response. Experiments in vivo are in progress to determine whether the chimeric particles are able to induce regression of disease and resolution of viral infection in mice. Chimeric particles of the type described in this work may potentially be the basis for developing prophylactic/therapeutic vaccines. The fact that they are produced in plants, may lower production costs considerably.

An update of prophylactic human papillomavirus L1 virus-like particle vaccine clinical trial results

This review focuses on recent publications of clinical trials of two prophylactic human papillomavirus (HPV) vaccines: Gardasil (Merck & Co., Inc., Whitehouse Station, NJ USA), a quadrivalent vaccine containing L1 virus-like particles (VLPs) of types -6, 11, 16, and 18, and Cervarix (GlaxoSmithKline Biologicals, Rixensart, Belgium), a bivalent vaccine containing VLPs of types -16 and 18. In efficacy trials involving young women, both vaccines produced outstanding efficacy against primary and secondary endpoints associated with the vaccine type HPVs and were highly and consistently immunogenic. Both had excellent safety records and, as expected, the most frequent vaccine-related adverse were mild to moderate injection site sequelae. No evidence of waning protection was observed after four years for endpoints examined ranging from incident infection to cervical intraepithelial neoplasia grade 3 associated with the vaccine type HPVs. Gardasil was also highly efficacious at preventing vaginal/vulvar lesions and genital warts. However, neither vaccine demonstrated therapeutic efficacy against prevalent infections or lesions, regardless of the associated HPV type. Cervarix has shown limited cross-protection against infection with specific closely related types while preliminary results of limited cross-protection have been presented for Gardasil. As expected, more limited efficacy was noted for both vaccines when women with prevalent infection were included or endpoints associated with any HPV type were evaluated. Immunological bridging trials involving adolescent girls and boys were also recently published. For both vaccines, serum VLP antibody levels in girls were non-inferior to those generated in young women and antibody response to Gardasil was also non-inferior in boys. The results of these studies have led to the approval of Gardasil and Cervarix by national regulatory agencies in a number of countries.

Human Papillomavirus Vaccines and Vaccine Implementation

Countries are now challenged by the rapid development of vaccines aimined at the primary prevention of infections. In the years to come, several vaccines will need to be considered as potential candidates in routine immunization programs. Recently, two new vaccines against two/four types of human papillomavirus (HPV) have been commercialized. Bivalent HPV 16 and 18 (Cervarix™) and quadrivalent HPV 6, 11, 16 and 18 (Gardasil®) vaccines are now extensively used in some countries. These vaccines will prevent infection and long-running complications, such as cervical cancer, other HPV-related cancers and genital warts (for the quadrivalent vaccine). The beneficial effect of these vaccines will be largely observed in women. This article summarizes the burden of HPV preventable disease worldwide and briefly describes the impact of secondary prevention and the most relevant aspects of the current available vaccines, their efficacy and safety. Finally, some major aspects that are likely to impact the introduction of these vaccines around the world are outlined, with particular emphasis on developing countries.