Human Papillomavirus L1L2-E7 Virus-Like Particles Partially Mature Human Dendritic Cells and Elicit E7-Specific T-Helper Responses From Patients With Cervical Intraepithelial Neoplasia or Cervical Cancer In Vitro

Design of a Synthetic Long Peptide Vaccine Targeting HPV-16 and -18 Using Immunoinformatic Methods

Human papillomavirus types 16 and 18 cause the majority of cervical cancers worldwide. Despite the availability of three prophylactic vaccines based on virus-like particles (VLP) of the major capsid protein (L1), these vaccines are unable to clear an existing infection. Such infected persons experience an increased risk of neoplastic transformation. To overcome this problem, this study proposes an alternative synthetic long peptide (SLP)-based vaccine for persons already infected, including those with precancerous lesions. This new vaccine was designed to stimulate both CD8+ and CD4+ T cells, providing a robust and long-lasting immune response. The SLP construct includes both HLA class I- and class II-restricted epitopes, identified from IEDB or predicted using NetMHCPan and NetMHCIIPan. None of the SLPs were allergenic nor toxic, based on in silico studies. Population coverage studies provided 98.18% coverage for class I epitopes and 99.81% coverage for class II peptides in the IEDB world population's allele set. Three-dimensional structure ab initio prediction using Rosetta provided good quality models, which were assessed using PROCHECK and QMEAN4. Molecular docking with toll-like receptor 2 identified potential intrinsic TLR2 agonist activity, while molecular dynamics studies of SLPs in water suggested good stability, with favorable thermodynamic properties.

Development of multiepitope therapeutic vaccines against the most prevalent high-risk human papillomaviruses

Aim: Our goal was the development of DNA- or peptide-based multiepitope vaccines targeting HPV E7, E6 and E5 oncoproteins in tumor mouse model. Materials & methods: After designing the multiepitope E7, E6 and E5 constructs from four types of high risk HPVs (16, 18, 31 & 45) using bioinformatics tools, mice vaccination was performed by different homologous and heterologous modalities in a prophylactic setting. Then, anti-tumor effects of the best prophylactic strategies were studied in a therapeutic setting. Results: In both prophylactic and therapeutic experiments, groups receiving homologous E7+E6+E5 polypeptide, and heterologous E7+E6+E5 DNA prime/polypeptide boost were successful in complete rejection of tumors. Conclusion: The designed multiepitope constructs can be considered as promising candidates to develop effective therapeutic HPV vaccines.

A comprehensive in silico analysis for identification of therapeutic epitopes in HPV16, 18, 31 and 45 oncoproteins

Human papillomaviruses (HPVs) are a group of circular double-stranded DNA viruses, showing severe tropism to mucosal tissues. A subset of HPVs, especially HPV16 and 18, are the primary etiological cause for several epithelial cell malignancies, causing about 5.2% of all cancers worldwide. Due to the high prevalence and mortality, HPV-associated cancers have remained as a significant health problem in human society, making an urgent need to develop an effective therapeutic vaccine against them. Achieving this goal is primarily dependent on the identification of efficient tumor-associated epitopes, inducing a robust cell-mediated immune response. Previous information has shown that E5, E6, and E7 early proteins are responsible for the induction and maintenance of HPV-associated cancers. Therefore, the prediction of major histocompatibility complex (MHC) class I T cell epitopes of HPV16, 18, 31 and 45 oncoproteins was targeted in this study. For this purpose, a two-step plan was designed to identify the most probable CD8+ T cell epitopes. In the first step, MHC-I and II binding, MHC-I processing, MHC-I population coverage and MHC-I immunogenicity prediction analyses, and in the second step, MHC-I and II protein-peptide docking, epitope conservation, and cross-reactivity with host antigens’ analyses were carried out successively by different tools. Finally, we introduced five probable CD8+ T cell epitopes for each oncoprotein of the HPV genotypes (60 epitopes in total), which obtained better scores by an integrated approach. These predicted epitopes are valuable candidates for in vitro or in vivo therapeutic vaccine studies against the HPV-associated cancers. Additionally, this two-step plan that each step includes several analyses to find appropriate epitopes provides a rational basis for DNA- or peptide-based vaccine development.

T cell ignorance is bliss: T cells are not tolerized by Langerhans cells presenting human papillomavirus antigens in the absence of costimulation

Human papillomavirus type 16 (HPV16) infections are intra-epithelial, and thus, HPV16 is known to interact with Langerhans cells (LCs), the resident epithelial antigen-presenting cells (APCs). The current paradigm for APC-mediated induction of T cell anergy is through delivery of T cell receptor signals via peptides on MHC molecules (signal 1), but without costimulation (signal 2). We previously demonstrated that LCs exposed to HPV16 in vitro present HPV antigens to T cells without costimulation, but it remained uncertain if such T cells would remain ignorant, become anergic, or in the case of CD4+ T cells, differentiate into Tregs. Here we demonstrate that Tregs were not induced by LCs presenting only signal 1, and through a series of in vitro immunizations show that CD8⁺ T cells receiving signal 1+2 from LCs weeks after consistently receiving signal 1 are capable of robust effector functions. Importantly, this indicates that T cells are not tolerized but instead remain ignorant to HPV, and are activated given the proper signals.

A novel therapeutic vaccine composed of a rearranged human papillomavirus type 16 E6/E7 fusion protein and Fms-like tyrosine kinase-3 ligand induces CD8+ T cell responses and antitumor effect

The development of cervical cancer is mainly caused by infection with high risk genotypes of human papillomavirus, particularly type 16 (HPV16), which accounts for more than 50% of cervical cancer. The two early viral oncogenes, E6 and E7, are continuously expressed in cervical cancer cells and are necessary to maintain the malignant cellular phenotype, thus providing ideal targets for immunotherapy of cervical cancer. In this study, a novel vaccine strategy was developed based on a rationally shuffled HPV16 E6/E7 fusion protein, the addition of Fms-like tyrosine kinase-3 ligand (Flt3L) or the N domain of calreticulin (NCRT), and the usage of a CpG adjuvant. Four recombinant proteins were constructed: m16E6E7 (mutant E6/E7 fusion protein), rm16E6E7 (rearranged mutant HPV16 E6/E7 fusion protein), Flt3L-RM16 (Flt3L fused to rm16E6E7), and NCRT-RM16 (NCRT fused to rm16E6E7). Our results suggest that Flt3L-RM16 was the most potent of these proteins in terms of inducing E6- and E7-specific CD8⁺ T cell responses. Additionally, Flt3L-RM16 significantly induced regression of established E6/E7-expressing TC-1 tumors. Higher doses of Flt3L-RM16 trended toward higher levels of antitumor activity, but these differences did not reach statistical significance. In summary, this study found that Flt3L-RM16 fusion protein is a promising therapeutic vaccine for immunotherapy of HPV16-associated cervical cancer.

Co-administration with DNA encoding papillomavirus capsid proteins enhances the antitumor effects generated by therapeutic HPV DNA vaccination

Background

DNA vaccines have emerged as attractive candidates for the control of human papillomavirus (HPV)-associated malignancies. However, DNA vaccines suffer from limited immunogenicity and thus strategies to enhance DNA vaccine potency are needed. We have previously demonstrated that for DNA vaccines encoding HPV-16 E7 antigen (CRT/E7) linkage with calreticulin (CRT) linked enhances both the E7-specific CD8⁺ T cell immune responses and antitumor effects against E7-expressing tumors. In the current study, we aim to introduce an approach to elicit potent CD4⁺ T cell help for the enhancement of antigen-specific CD8⁺ T cell immune responses generated by CRT/E7 DNA vaccination by using co-administration of a DNA vector expressing papillomavirus major and minor capsid antigens, L1 and L2.

Result

We showed that co-administration of vectors containing codon-optimized bovine papillomavirus type 1 (BPV-1) L1 and L2 in combination with DNA vaccines could elicit enhanced antigen-specific CD8⁺ in both CRT/E7 and ovalbumin (OVA) antigenic systems. We also demonstrated that co-administration of vectors expressing BPV-1 L1 and/or L2 DNA with CRT/E7 DNA led to the generation of L1/L2-specific CD4⁺ T cell immune responses and L1-specific neutralizing antibodies. Furthermore, we showed that co-administration with DNA encoding BPV1 L1 significantly enhances the therapeutic antitumor effects generated by CRT/E7 DNA vaccination. In addition, the observed enhancement of CD8⁺ T cell immune responses by DNA encoding L1 and L2 was also found to extend to HPV-16 L1/L2 system.

Conclusion

Our strategy elicits both potent neutralizing antibody and therapeutic responses and may potentially be extended to other antigenic systems beyond papillomavirus for the control of infection and/or cancer.

A novel, broad spectrum therapeutic HPV vaccine targeting the E7 proteins of HPV16, 18, 31, 45 and 52 that elicits potent E7-specific CD8T cell immunity and regression of large, established, E7-expressing TC-1 tumors

Persistent infection by high risk genotypes of human papillomavirus (HPV) is the cause of cervical cancer, which remains one of the most common cancers among women worldwide. In addition, there is a growing appreciation that high risk HPVs are associated with a number of other cancers including anogenital cancers as well as a subset of head and neck cancers. Recently, prophylactic HPV vaccines targeting the two most prevalent high risk HPVs (HPV16 and HPV18) have been deployed in large-scale vaccination campaigns. However, the extent to which these prophylactic vaccines confer protection against other high risk HPV genotypes is largely unknown and prophylactic vaccines have been shown to be ineffective against pre-existing infection. Thus there continues to be an urgent need for effective therapeutic vaccines against HPV. The E7 protein of HPV16 has been widely studied as a target for therapeutic vaccines in HPV-associated cancer settings because HPV16 is the most prevalent of the high risk HPV genotypes. However, HPV16 accounts for only about 50% of cervical cancers and there are at least 15 other high risk HPVs that are known to be oncogenic. We have developed a novel, broad-spectrum, therapeutic vaccine (Pentarix) directed at the E7 proteins from five of the most prevalent high-risk genotypes of HPV worldwide (HPV16, 18, 31, 45 and 52) that together account for more than 80% of all HPV-associated cancers. Pentarix is a recombinant protein-based vaccine that elicits strong, multi-genotype specific CD8 T cell immunity when administered to mice in combination with adjuvants comprised of agonists of the TLR3 or TLR9 family of innate immune receptors. Furthermore, large, established E7-expressing TC-1 tumors undergo rapid and complete regression after therapeutic vaccination of mice with Pentarix. Together, these data suggest that Pentarix may be of clinical value for patients with E7-positive, HPV-associated precancerous lesions or malignant disease.

Papillomavirus virus like particle-based therapeutic vaccine against human papillomavirus infection related diseases: immunological problems and future directions

Chronic infection with certain types of human papillomaviruses (HPV), especially HPV-16 and HPV-18, leads to the development of cervical cancer. Prophylactic HPV vaccines based on HPV virus like particles (VLPs) have now been developed. The commercial vaccines, Gardasil and Cervarix are clinically effective in preventing HPV infection but do not have a therapeutic effect against existing chronic HPV infections. However, papillomavirus (PV) VLPs elicit strong cytotoxic T cell (CTL) responses and PV VLPs without any adjuvant have therapeutic effects in animal PV infection model. Alum in Gardasil, Alum and 3-O-deacylated-4'-monophosphoryl lipid A (ASO4) in Cervarix may stimulate IL10 production and inhibit the Th1, CTL immune response of immunized individuals. PV VLPs also stimulate the production of IL10 by CD4(+) T cells, which prevent their CTL generation effect as a therapeutic vaccine. Neutralizing IL10 at the time of PV VLPs immunization increases cytotoxic T cell responses. PV VLPs incorporating PV early protein E2, 6 and 7, together with immune stimulator that promote strong type 1 responses, and at the same time blocking the effect of IL10 may have therapeutic effect against HPV infection related diseases and are worth further basic and clinical investigation.

Novel plant virus-based vaccine induces protective cytotoxic T-lymphocyte-mediated antiviral immunity through dendritic cell maturation

Currently used vaccines protect mainly through the production of neutralizing antibodies. However, antibodies confer little or no protection for a majority of chronic viral infections that require active involvement of cytotoxic T lymphocytes (CTLs). Virus-like particles (VLPs) have been shown to be efficient inducers of cell-mediated immune responses, but administration of an adjuvant is generally required. We recently reported the generation of a novel VLP system exploiting the self-assembly property of the papaya mosaic virus (PapMV) coat protein. We show here that uptake of PapMV-like particles by murine splenic dendritic cells (DCs) in vivo leads to their maturation, suggesting that they possess intrinsic adjuvant-like properties. DCs pulsed with PapMV-like particles displaying the lymphocytic choriomeningitis virus (LCMV) p33 immunodominant CTL epitope (PapMV-p33) efficiently process and cross-present the viral epitope to p33-specific transgenic T cells. Importantly, the CTL epitope is also properly processed and presented in vivo, since immunization of p33-specific T-cell receptor transgenic mice with PapMV-p33 induces the activation of large numbers of specific CTLs. C57BL/6 mice immunized with PapMV-p33 VLPs in the absence of adjuvant develop p33-specific effector CTLs that rapidly expand following LCMV challenge and protect vaccinated mice against LCMV infection in a dose-dependent manner. These results demonstrate the efficiency of this novel plant virus-based vaccination platform in inducing DC maturation leading to protective CTL responses.

Insect baculoviruses strongly potentiate adaptive immune responses by inducing type I IFN

Baculoviruses (BVs) are dsDNA viruses that are pathogenic for insects. They have been used worldwide as selective bioinsecticides and for producing recombinant proteins in insect cells. Surprisingly, despite their widespread use in research and industry and their dissemination in the environment, the potential effects of these insect viruses on the immune responses of mammals remain totally unknown. We show in this study that BVs have strong adjuvant properties in mice, promoting potent humoral and CD8(+) T cell adaptive responses against coadministered Ag. BVs also induce the in vivo maturation of dendritic cells and the production of inflammatory cytokines. We demonstrate that BVs play a major role in the strong immunogenicity of virus-like particles produced in the BV-insect cell expression system. The presence of even small numbers of BVs among the recombinant proteins produced in the BV expression system may therefore strengthen the immunological properties of these proteins. This adjuvant behavior of BVs is mediated primarily by IFN-alphabeta, although mechanisms independent of type I IFN signaling are also involved. This study demonstrates that nonpathogenic insect viruses may have a strong effect on the mammalian immune system.