Opportunities and challenges for human papillomavirus vaccination in cancer

Turning the corner on therapeutic cancer vaccines

Recent advances in several areas are rekindling interest and enabling progress in the development of therapeutic cancer vaccines. These advances have been made in target selection, vaccine technology, and methods for reversing the immunosuppressive mechanisms exploited by cancers. Studies testing different tumor antigens have revealed target properties that yield high tumor versus normal cell specificity and adequate immunogenicity to affect clinical efficacy. A few tumor-associated antigens, normal host proteins that are abnormally expressed in cancer cells, have been demonstrated to serve as good targets for immunotherapies, although many do not possess the needed specificity or immunogenicity. Neoantigens, which arise from mutated proteins in cancer cells, are truly cancer-specific and can be highly immunogenic, though the vast majority are unique to each patient's cancer and thus require development of personalized therapies. Lessons from previous cancer vaccine expeditions are teaching us the type and magnitude of immune responses needed, as well as vaccine technologies that can achieve these responses. For example, we are learning which vaccine approaches elicit the potent, balanced, and durable CD4 plus CD8 T cell expansion necessary for clinical efficacy. Exploration of interactions between the immune system and cancer has elucidated the adaptations that enable cancer cells to suppress and evade immune attack. This has led to breakthroughs in the development of new drugs, and, subsequently, to opportunities to combine these with cancer vaccines and dramatically increase patient responses. Here we review this recent progress, highlighting key steps that are bringing the promise of therapeutic cancer vaccines within reach.

Hallmarks of HPV carcinogenesis: The role of E6, E7 and E5 oncoproteins in cellular malignancy

Human papillomavirus (HPV) is the most common sexually transmitted infectious agent worldwide, being also responsible for 5% of all human cancers. The integration and hypermethylation mechanisms of the HPV viral genome promote the unbalanced expression of the E6, E7 and E5 oncoproteins, which are crucial factors for the carcinogenic cascade in HPV-induced cancers. This review highlights the action of E6, E7 and E5 over key regulatory targets, promoting all known hallmarks of cancer. Both well-characterized and novel targets of these HPV oncoproteins are described, detailing their mechanisms of action. Finally, this review approaches the possibility of targeting E6, E7 and E5 for therapeutic applications in the context of cancer.

Impact of naturally occurring variation in the human papillomavirus 52 capsid proteins on recognition by type-specific neutralising antibodies

We investigated the impact of naturally occurring variation within the major (L1) and minor (L2) capsid proteins on the antigenicity of human papillomavirus (HPV) type 52 (HPV52). L1L2 pseudoviruses (PsVs) representing HPV52 lineage and sublineage variants A1, A2, B1, B2, C and D were created and tested against serum from naturally infected individuals, preclinical antisera raised against HPV52 A1 and D virus-like particles (VLPs) and neutralising monoclonal antibodies (MAbs) raised against HPV52 A1 VLP. HPV52 lineage D PsV displayed a median 3.1 (inter-quartile range 2.0-5.6) fold lower sensitivity to antibodies elicited following natural infection with, where data were available, HPV52 lineage A. HPV52 lineage variation had a greater impact on neutralisation sensitivity to pre-clinical antisera and MAbs. Chimeric HPV52 A1 and D PsV were created which identified variant residues in the FG (Q281K) and HI (K354T, S357D) loops as being primarily responsible for the reported differential sensitivities. Homology models of the HPV52 L1 pentamer were generated which permitted mapping these residues to a small cluster on the outer rim of the surface exposed pentameric L1 protein. These data contribute to our understanding of HPV L1 variant antigenicity and may have implications for seroprevalence or vaccine immunity studies based upon HPV52 antigens.

Bioproduction of a Therapeutic Vaccine Against Human Papillomavirus in Tomato Hairy Root Cultures

Human papillomavirus (HPV) tumor disease is a critical public health problem worldwide, especially in the developing countries. The recognized pathogenic function of E5, E6, and E7 oncoproteins offers the opportunity to devise therapeutic vaccines based on engineered recombinant proteins. The potential of plants to manufacture engineered compounds for pharmaceutical purposes, from small to complex protein molecules, allows the expression of HPV antigens and, possibly, the regulation of immune functions to develop very specific therapies as a reinforcement to available nonspecific therapies and preventive vaccination also in developed countries. Among plant-based expression formats, hairy root cultures are a robust platform combining the benefits of eukaryotic plant-based bioreactors, with those typical of cell cultures. In this work, to devise an experimental therapeutic vaccine against HPV, hairy root cultures were used to express a harmless form of the HPV type 16 E7 protein (E7*) fused to SAPKQ, a noncytotoxic form of the saporin protein from Saponaria officinalis, that we had shown to improve E7-specific cell-mediated responses as a fusion E7*-SAPKQ DNA vaccine. Hairy root clones expressing the E7*-SAPKQ candidate vaccine were obtained upon infection of leaf explants of Solanum lycopersicum using a recombinant plant expression vector. Yield was approximately 35.5 μg/g of fresh weight. Mouse immunization with vaccine-containing crude extracts was performed together with immunological and biological tests to investigate immune responses and anticancer activity, respectively. Animals were primed with either E7*-SAPKQ DNA-based vaccine or E7*-SAPKQ root extract-based vaccine and boosted with the same (homologous schedule) or with the other vaccine preparation (heterologous schedule) in the context of TC-1 experimental mouse model of HPV-associated tumor. All the formulations exhibited an immunological response associated to anticancer activity. In particular, DNA as prime and hairy root extract as boost demonstrated the highest efficacy. This work, based on the development of low-cost technologies, highlights the suitability of hairy root cultures as possible biofactories of therapeutic HPV vaccines and underlines the importance of the synergic combination of treatment modalities for future developments in this field.

Would immunization be the same without cross-reactivity?

"Cross-reactivity" (the observed immune response against pathogen types not specifically targeted by the vaccine antigen composition) and "cross-protection" (clinical protection against related non-vaccine microorganism types) are vaccinology concepts that are attracting renewed interest in the context of disease prevention. National health authorities are collecting mounting evidence of the importance of cross-reactivity. For some vaccines, this has been substantiated by cross-protection data from clinical studies and/or post-licensure data, where their introduction into immunization programmes has shown beneficial impacts on disease caused by related non-vaccine microorganisms. This knowledge has influenced the way new vaccines are designed, developed, and evaluated in real-life settings. Some of the new vaccines are now designed with the specific aim of having a greater breadth of protection. Ideal vaccine antigens therefore include epitopes with conserved homology across related pathogen types, because it is not always possible to include the antigens of all the individual types of a given pathogen species. The use of novel adjuvants with greater immunostimulatory properties can also contribute to improved overall vaccine cross-reactivity, as could the use of antigen delivery platforms. The growing body of evidence allows us to better understand the full impact of vaccines - beyond vaccine-type disease - which should be taken into consideration when assessing the full value of vaccination programmes.

The 5th virus-like particle and nano-particle vaccines (VLPNPV) conference

Virus-like particles (VLPs) and nano-particles (NPs) are promising vaccine platforms that have led to the successful development of commercially available vaccines. The 5th international virus-like particle and nano-particle vaccines conference was held in Bern, Switzerland, from the 25th to the 27th of September in 2018. Topics included novel vaccine production techniques, methods to enhance vaccine immunogenicity, and preclinical/clinical efficacy evaluation of vaccine candidates. Here, we report on a selection of updates that were presented including the production of vaccines in plants, novel adjuvants to enhance vaccine immunogenicity, novel techniques of conjugating vaccine platforms with target antigens and the use of VLP-based vaccines for cancer and inflammatory diseases.

Antiviral activities of Janus-type nucleosides and their related oxime-intermediates

Herpes simplex virus (HSV) infection has been recognized as the most common mucosal disease in humans, manifesting as a life-threatening infection especially for patients with compromised immunity. When combined with the emergence of resistance due to the long-term use of classical antiviral agents, these threats make novel therapeutics for HSV a clinically necessity. We therefore designed and synthesized a series of Janus-type nucleosides by combining the natural genetic alphabets into a singular nucleoside structural unit. We also synthesized a series of new compounds and systematically evaluated their antiviral activity and structure-antiviral activity relationship. The results indicated that both nucleosides and their related intermediates exhibited high anti-HSV-1 activity. Compounds HY17 and HY19, in particular, possessed excellent anti-HSV-1 activity with IC₅₀ values of 0.05 and 0.04 µg/mL, respectively. They also showed broad-spectrum antiviral activity against a multitude of diverse viruses, such as HSV-2, influenza virus A (H3N2), CVB3, HBV, HCV, and HPV. These results suggest that once their mechanisms are fully elucidated, these compounds will prove to be promising candidates as antiviral agents.

The Role of MicroRNAs in the Metastatic Process of High-Risk HPV-Induced Cancers

High-risk human papillomavirus (HPV)-driven cancers represent a major health concern worldwide. Despite the constant effort to develop and promote vaccination against HPVs, there is still a high percentage of non-vaccinated population. Furthermore, secondary prevention programs are not ubiquitous worldwide and not widely followed. Metastatic disease is the cause of the great majority of cancer-associated deaths, making it essential to determine its underlying mechanisms and to identify actionable anti-metastatic targets. Within certain types of cancer (e.g., head and neck), HPV-positive tumors show different dissemination patterns when compared with their HPV-negative counterparts, implicating HPV-related factors in the metastatic process. Among the many groups of biomolecules dysregulated by HPV, microRNAs have recently emerged as key regulators of carcinogenesis, able to control complex processes like cancer metastization. In this review, we present recent data on the role of microRNAs in the metastization of HPV-related cancers and on their possible clinical relevance as biomarkers of metastatic disease and/or as therapeutic targets.

TCR Repertoire as a Novel Indicator for Immune Monitoring and Prognosis Assessment of Patients With Cervical Cancer

There is increasing evidence that deep sequencing-based T cell repertoire can sever as a biomarker of immune response in cancer patients; however, the characteristics of T cell repertoire including diversity and similarity, as well as its prognostic significance in patients with cervical cancer (CC) remain unknown. In this study, we applied a high throughput T cell receptor (TCR) sequencing method to characterize the T cell repertoires of peripheral blood samples from 25 CC patients, 30 cervical intraepithelial neoplasia (CIN) patients and 20 healthy women for understanding the immune alterations during the cervix carcinogenesis. In addition, we also explored the signatures of TCR repertoires in the cervical tumor tissues and paired sentinel lymph nodes from 16 CC patients and their potential value in predicting the prognosis of patients. Our results revealed that the diversity of circulating TCR repertoire gradually decreased during the cervix carcinogenesis and progression, but the circulating TCR repertoires in CC patients were more similar to CIN patients than healthy women. Interestingly, several clonotypes uniquely detected in CC patients tended to share similar CDR3 motifs, which differed from those observed in CIN patients. In addition, the TCR repertoire diversity in sentinel lymphatic nodes from CC patients was higher than in tumor tissues. More importantly, less clonotypes in TCR repertoire of sentinel lymphatic node was associated with the poor prognosis of the patients. Overall, our findings suggested that TCR repertoire might be a potential indicator of immune monitoring and a biomarker for predicting the prognosis of CC patients. Although functional studies of T cell populations are clearly required, this study have expanded our understanding of T cell immunity during the development of CC and provided an experimental basis for further studies on its pathogenesis and immunotherapy.

Human papillomaviruses 16 and 58 are distributed widely among women living in Shanghai, China, with high-grade, squamous intraepithelial lesions

The distribution of human papillomaviruses (HPVs) must be understood for the control and prevention of cervical cancer. Community-based Papanicolaou and HPV DNA tests were performed on 41 578 women. The prevalences of HPV genotypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68 were assessed. In total, 10% women were infected/co-infected by these HPVs. The infection rate increased from 7.1% in women aged ⩽30 years to 10.4% in those aged 50–60 years, and then decreased slightly to 9.9% in those aged >60 years. The HPV 16 and 58 positivity rates were significantly higher among women with high-grade squamous intraepithelial lesions (HSILs) than among those with cervicitis/negativity for intraepithelial lesion or malignancy (NILM) or low-grade SILs (LSILs). The HPV 18, 52 and 68 infection rates were significantly lower in women with HSILs than in those with NILM or LSILs. The proportion of women infected by multiple HPV strains was higher among those with HSILs. The proportions of the five most common genotypes, HPV 16, 18, 33, 52 and 58, increased with the number of co-infecting strains. HPV 16 and 58 were the high-risk HPVs in the Shanghai community and should be the focus in HPV screening and vaccination.

Mechanisms of persistence by small DNA tumor viruses

Virus infection contributes to nearly 15% of human cancers worldwide. Many of the oncogenic viruses tend to cause cancer in immunosuppressed individuals, but maintain asymptomatic, persistent infection for decades in the general population. In this review, we discuss the tactics employed by two small DNA tumor viruses, Human papillomavirus (HPV) and Merkel cell polyomavirus (MCPyV), to establish persistent infection. We will also highlight recent key findings as well as outstanding questions regarding the mechanisms by which HPV and MCPyV evade host immune control to promote their survival. Since persistent infection enables virus-induced tumorigenesis, identifying the mechanisms by which small DNA tumor viruses achieve latent infection may inform new approaches for preventing and treating their respective human cancers.

Trial watch: Peptide-based vaccines in anticancer therapy

Peptide-based anticancer vaccination aims at stimulating an immune response against one or multiple tumor-associated antigens (TAAs) following immunization with purified, recombinant or synthetically engineered epitopes. Despite high expectations, the peptide-based vaccines that have been explored in the clinic so far had limited therapeutic activity, largely due to cancer cell-intrinsic alterations that minimize antigenicity and/or changes in the tumor microenvironment that foster immunosuppression. Several strategies have been developed to overcome such limitations, including the use of immunostimulatory adjuvants, the co-treatment with cytotoxic anticancer therapies that enable the coordinated release of damage-associated molecular patterns, and the concomitant blockade of immune checkpoints. Personalized peptide-based vaccines are also being explored for therapeutic activity in the clinic. Here, we review recent preclinical and clinical progress in the use of peptide-based vaccines as anticancer therapeutics.Abbreviations: CMP: carbohydrate-mimetic peptide; CMV: cytomegalovirus; DC: dendritic cell; FDA: Food and Drug Administration; HPV: human papillomavirus; MDS: myelodysplastic syndrome; MHP: melanoma helper vaccine; NSCLC: non-small cell lung carcinoma; ODD: orphan drug designation; PPV: personalized peptide vaccination; SLP: synthetic long peptide; TAA: tumor-associated antigen; TNA: tumor neoantigen

Ubiquitin-specific protease 7 sustains DNA damage response and promotes cervical carcinogenesis

Central to the recognition, signaling, and repair of DNA double-strand breaks (DSBs) are the MRE11-RAD50-NBS1 (MRN) complex and mediator of DNA damage checkpoint protein 1 (MDC1), the interplay of which is essential for initiation and amplification of the DNA damage response (DDR). The intrinsic rule governing the regulation of the function of this molecular machinery remains to be investigated. We report here that the ubiquitin-specific protease USP7 was physically associated with the MRN-MDC1 complex and that the MRN-MDC1 complex acted as a platform for USP7 to efficiently deubiquitinate and stabilize MDC1, thereby sustaining the DDR. Accordingly, depletion of USP7 impaired the engagement of the MRN-MDC1 complex and the consequent recruitment of the downstream factors p53-binding protein 1 (53BP1) and breast cancer protein 1 (BRCA1) at DNA lesions. Significantly, USP7 was overexpressed in cervical cancer, and the level of its expression positively correlated with that of MDC1 and worse survival rates for patients with cervical cancer. We demonstrate that USP7-mediated MDC1 stabilization promoted cervical cancer cell survival and conferred cellular resistance to genotoxic insults. Together, our study reveals a role for USP7 in regulating the function of the MRN-MDC1 complex and activity of the DDR, supporting the pursuit of USP7 as a potential therapeutic target for MDC1-proficient cancers.

Listeria monocytogenes as a Vector for Cancer Immunotherapy: Current Understanding and Progress

Listeria monocytogenes, a Gram-positive facultative anaerobic bacterium, is becoming a popular vector for cancer immunotherapy. Indeed, multiple vaccines have been developed utilizing modified Listeria as a tool for generating immune responses against a variety of cancers. Moreover, over a dozen clinical trials testing Listeria cancer vaccines are currently underway, which will help to understand the utility of Listeria vaccines in cancer immunotherapy. This review aims to summarize current views on how Listeria-based vaccines induce potent antitumor immunity and the current state of Listeria-based cancer vaccines in clinical trials.

Engineering virus resistance via CRISPR-Cas systems

In prokaryotes, CRISPR/Cas adaptive immunity systems target and destroy nucleic acids derived from invading bacteriophages and other foreign genetic elements. In eukaryotes, the native function of these systems has been exploited to combat viruses in mammals and plants. Rewired CRISPR/Cas9 and CRISPR/Cas13 systems have been used to confer resistance against DNA and RNA viruses, respectively. Here, we discuss recent approaches employing CRISPR/Cas systems to combat viruses in eukaryotes, highlight key challenges, and provide future perspectives. Moreover, we discuss the application of CRISPR/Cas systems in genome-wide screens to identify key host factors for virus infection to enhance our understanding of basic virus biology and to identify and study virus-host interactions.