Beneficial therapeutic effects with different particulate structures of murine polyomavirus VP1-coat protein carrying self or non-self CD8 T cell epitopes against murine melanoma

Artificial viruses: A nanotechnology based approach

OBJECTIVES

The main objective of this work was to review and summarise the detailed literature available on viral nanoparticle and the strategies utilised for their manufacture along with their applications as therapeutic agents.

DATA ACQUISITION

The reported literature related to development and application of virus nanoparticles have been collected from electronic data bases like ScienceDirect, google scholar, PubMed by using key words like "viral nanoparticles", "targeted drug delivery" and "vaccines" and related combinations.

RESULT

From the detailed literature survey, virus nanoparticles were identified as carriers for the targeted delivery. Due to the presence of nanostructures in virus nanoparticles, these protect the drugs from the degradation in the gastrointestinal tract and in case of the delivery of gene medicine, they carry the nucleic acids to the target/susceptible host cells. Thus, artificial viruses are utilised for targeted delivery to specific organ in biomedical and biotechnological areas.

CONCLUSION

Thus, virus nanoparticles can be considered as viable option as drug/gene carrier in various healthcare sectors especially drug delivery and vaccine and can be explored further in future for the development of better drug delivery techniques.

Virus-like Particle (VLP) Vaccines for Cancer Immunotherapy

Cancer vaccines are increasingly being studied as a possible strategy to prevent and treat cancers. While several prophylactic vaccines for virus-caused cancers are approved and efficiently used worldwide, the development of therapeutic cancer vaccines needs to be further implemented. Virus-like particles (VLPs) are self-assembled protein structures that mimic native viruses or bacteriophages but lack the replicative material. VLP platforms are designed to display single or multiple antigens with a high-density pattern, which can trigger both cellular and humoral responses. The aim of this review is to provide a comprehensive overview of preventive VLP-based vaccines currently approved worldwide against HBV and HPV infections or under evaluation to prevent virus-caused cancers. Furthermore, preclinical and early clinical data on prophylactic and therapeutic VLP-based cancer vaccines were summarized with a focus on HER-2-positive breast cancer.

Chimeric virus-like particles presenting tumour-associated MUC1 epitope result in high titers of specific IgG antibodies in the presence of squalene oil-in-water adjuvant: towards safe cancer immunotherapy

Background

Immunotherapy is emerging as a powerful treatment approach for several types of cancers. Modulating the immune system to specifically target cancer cells while sparing healthy cells, is a very promising approach for safer therapies and increased survival of cancer patients. Tumour-associated antigens are favorable targets for cancer immunotherapy, as they are exclusively expressed by the cancer cells, minimizing the risk of an autoimmune reaction. The ability to initiate the activation of the immune system can be achieved by virus-like particles (VLPs) which are safe and potent delivery tools. VLP‐based vaccines have evolved dramatically over the last few decades and showed great potential in preventing infectious diseases. Immunogenic potency of engineered VLPs as a platform for the development of effective therapeutic cancer vaccines has been studied extensively. This study involves recombinant VLPs presenting multiple copies of tumour-specific mucin 1 (MUC1) epitope as a potentially powerful tool for future immunotherapy.

Results

In this report VLPs based on the structural protein of Norovirus (NoV VP1) were genetically modified to present multiple copies of tumour-specific MUC1 epitope on their surface. Chimeric MUC1 particles were produced in the eukaryotic Leishmania tarentolae expression system and used in combination with squalene oil-in-water emulsion MF59 adjuvant to immunize BALB/c mice. Sera from vaccinated mice demonstrated high titers of IgG and IgM antibodies which were specifically recognizing MUC1 antigen.

Conclusions

The obtained results show that immunization with recombinant chimeric NoV VP1- MUC1 VLPs result in high titers of MUC1 specific IgG antibodies and show great therapeutic potential as a platform to present tumour-associated antigens.

Graphical Abstract

Virus-like particles for vaccination against cancer

Active immunotherapy of cancer aims to treat the disease by inducing effective cellular and humoral immune responses. Virus‐like particle‐based vaccines have evolved dramatically over the last few decades, greatly reducing morbidity and mortality of several infectious diseases and expectedly preventing cervical cancer caused by human papilloma virus. In contrast to these broad successes of disease prevention, therapeutic cancer vaccines remain to demonstrate clinical benefit. Yet, several preclinical and clinical trials have revealed promising results and are paving the way for medical breakthroughs. This study reviews and discusses the recent preclinical development and clinical trials in this field.

This article is categorized under:

Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Virus like particles as a platform for cancer vaccine development

Cancers have killed millions of people in human history and are still posing a serious health problem worldwide. Therefore, there is an urgent need for developing preventive and therapeutic cancer vaccines. Among various cancer vaccine development platforms, virus-like particles (VLPs) offer several advantages. VLPs are multimeric nanostructures with morphology resembling that of native viruses and are mainly composed of surface structural proteins of viruses but are devoid of viral genetic materials rendering them neither infective nor replicative. In addition, they can be engineered to display multiple, highly ordered heterologous epitopes or peptides in order to optimize the antigenicity and immunogenicity of the displayed entities. Like native viruses, specific epitopes displayed on VLPs can be taken up, processed, and presented by antigen-presenting cells to elicit potent specific humoral and cell-mediated immune responses. Several studies also indicated that VLPs could overcome the immunosuppressive state of the tumor microenvironment and break self-tolerance to elicit strong cytotoxic lymphocyte activity, which is crucial for both virus clearance and destruction of cancerous cells. Collectively, these unique characteristics of VLPs make them optimal cancer vaccine candidates. This review discusses current progress in the development of VLP-based cancer vaccines and some potential drawbacks of VLPs in cancer vaccine development. Extracellular vesicles with close resembling to viral particles are also discussed and compared with VLPs as a platform in cancer vaccine developments.

Cell-permeable capsids as universal antigen carrier for the induction of an antigen-specific CD8+ T-cell response

Vaccine platforms that can be flexibly loaded with antigens can contribute to decrease response time to emerging infections. For many pathogens and chronic infections, induction of a robust cytotoxic T lymphocytes-mediated response is desirable to control infection. Antigen delivery into the cytoplasm of antigen presenting cells favors induction of cytotoxic T cells. By fusion of the cell-permeable translocation motif (TLM)-peptide to the capsid-forming core protein of hepatitis B virus, and by insertion of the strep-tag in the spike tip (a domain that protrudes from the surface of the capsid), cell-permeable carrier capsids were generated that can be flexibly loaded with various antigens. Loading with antigens was demonstrated by electron microscopy, density gradient centrifugation and surface plasmon resonance spectroscopy. Confocal immunofluorescence microscopy showed that cell-permeable carrier capsids mediate transfer of cargo antigen into the cytoplasm. Using cell-permeable carrier capsids loaded with ovalbumin as model antigen, activation of antigen presenting cells and ovalbumin-specific CD8⁺ T-cells, which correlates with enhanced specific killing activity, was found. This demonstrates the capacity of TLM-carrier-capsids to serve as universal antigen carrier to deliver antigens into the cytoplasm of antigen presenting cells, which leads to enhanced MHC class I-mediated presentation and induction of antigen-specific cytotoxic T lymphocytes response.

Viruses and Virus-Like Particles in Biotechnology: Fundamentals and Applications

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this chapter, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitoring, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

Production and biomedical applications of virus-like particles derived from polyomaviruses

Virus-like particles (VLPs), aggregates of capsid proteins devoid of viral genetic material, show great promise in the fields of vaccine development and gene therapy. These particles spontaneously self-assemble after heterologous expression of viral structural proteins. This review will focus on the use of virus-like particles derived from polyomavirus capsid proteins. Since their first recombinant production 27 years ago these particles have been investigated for a myriad of biomedical applications. These virus-like particles are safe, easy to produce, can be loaded with a broad range of diverse cargoes and can be tailored for specific delivery or epitope presentation. We will highlight the structural characteristics of polyomavirus-derived VLPs and give an overview of their applications in diagnostics, vaccine development and gene delivery.

Immunotherapy for polyomaviruses: opportunities and challenges

Polyomaviruses are small DNA viruses present in mammals and birds, and in 1953 the first one to be described was murine polyomavirus. It was not until 1971 that the first two human polyomaviruses (HPyVs), BK virus and JC virus, were discovered and found to be common in humans, but only associated with disease in severely immunosuppressed patients. Since 2007, seven new HPyVs have been identified: KI polyomavirus, WU polyomavirus, Merkel cell polyomavirus, HPyV6, HPyV7, trichodyplasia spinulosa polyomavirus and HPyV9. Notably, Merkel cell polyomavirus was detected in Merkel cell cancer, a tumor mainly found in elderly and immunocompromised individuals, while trichodyplasia spinulosa polyomavirus was found in trichodyplasia spinulosa, a skin disorder observed only in immunosuppressed individuals. Consequently, many polyomaviruses cause problems in immunosuppressed individuals. This review deals with these issues, and the potential of the capsid protein VP1 to form virus-like particles for use as vaccines against polyomavirus infections.

Induction of insert-specific immune response in mice by hamster polyomavirus VP1 derived virus-like particles carrying LCMV GP33 CTL epitope

Hamster polyomavirus (HaPyV) major capsid protein VP1 based chimeric virus-like particles (VLPs) carrying model GP33 CTL epitope derived from Lymphocytic choriomeningitis virus (LCMV) were generated in yeast and examined for their capability to induce CTL response in mice. Chimeric VP1-GP33 VLPs were effectively processed in antigen presenting cells in vitro and in vivo and induced antigen-specific CD8+ T cell proliferation. Mice immunized only once with VP1-GP33 VLPs without adjuvant developed an effective GP33-specific memory T cell response: 70% were fully and 30% partially protected from LCMV infection. Moreover, aggressive growth of tumors expressing GP33 was significantly delayed in these mice in vivo. Therefore, HaPyV VP1-derived VLP harboring CTL epitopes are attractive vaccine candidates for the induction of insert-specific CTL immune response.

Adjuvant combination and antigen targeting as a strategy to induce polyfunctional and high-avidity T-cell responses against poorly immunogenic tumors

Low antigen expression and an absence of coimmunostimulatory signals may be partly responsible for the low immunogenicity of many tumors. It may be possible to overcome this situation by defining a combination of adjuvants and antigens that can activate a high-avidity antitumor response. Using the poorly immunogenic B16-OVA melanoma cells as tumor model, we tested different combinations of adjuvants and antigens to treat established tumors. In the absence of exogenous antigens, repeated administration of the TLR7 ligand Imiquimod together with anti-CD40 agonistic antibodies activated only innate immunity, which was insufficient to reject intradermal tumors. Administering this adjuvant combination together with OVA as a tumor antigen induced T-cell responses that delayed tumor growth. However, administering a combination of anti-CD40 plus TLR3 and TLR7 ligands, together with antigen targeting to dendritic cells through TLR4, was sufficient to induce tumor rejection in 50% of mice. This response was associated with a greater activation of innate immunity and induction of high-avidity polyfunctional CD8(+) T-cell responses, which each contributed to tumor rejection. This therapy activated T-cell responses not only against OVA, which conferred protection against a rechallenge with B16-OVA cells, but also activated T-cell responses against other melanoma-associated antigens. Our findings support the concept that multiple adjuvant combination and antigen targeting may be a useful immunotherapeutic strategy against poorly immunogenic tumors.

Virus-like particles in vaccine development

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome, potentially yielding safer and cheaper vaccine candidates. A handful of prophylactic VLP-based vaccines is currently commercialized worldwide: GlaxoSmithKline's Engerix (hepatitis B virus) and Cervarix (human papillomavirus), and Merck and Co., Inc.'s Recombivax HB (hepatitis B virus) and Gardasil (human papillomavirus) are some examples. Other VLP-based vaccine candidates are in clinical trials or undergoing preclinical evaluation, such as, influenza virus, parvovirus, Norwalk and various chimeric VLPs. Many others are still restricted to small-scale fundamental research, despite their success in preclinical tests. This article focuses on the essential role of VLP technology in new-generation vaccines against prevalent and emergent diseases. The implications of large-scale VLP production are discussed in the context of process control, monitorization and optimization. The main up- and down-stream technical challenges are identified and discussed accordingly. Successful VLP-based vaccine blockbusters are briefly presented concomitantly with the latest results from clinical trials and the recent developments in chimeric VLP-based technology for either therapeutic or prophylactic vaccination.

Viruses and Virus-Like Particles in Biotechnology

Although viruses are simple biological systems, they are capable of evolving highly efficient techniques for infecting cells, expressing their genomes, and generating new copies of themselves. It is possible to genetically manipulate most of the different classes of known viruses in order to produce recombinant viruses that express foreign proteins. Recombinant viruses have been used in gene therapy to deliver selected genes into higher organisms, in vaccinology and immunotherapy, and as important research tools to study the structure and function of these proteins.

Virus-like particles (VLPs) are multiprotein structures that mimic the organization and conformation of authentic native viruses but lack the viral genome. They have been applied not only as prophylactic and therapeutic vaccines but also as vehicles in drug and gene delivery and, more recently, as tools in nanobiotechnology.

In this article, basic and advanced features of viruses and VLPs are presented and their major applications are discussed. The different production platforms based on animal cell technology are explained, and their main challenges and future perspectives are explored. The implications of large-scale production of viruses and VLPs are discussed in the context of process control, monitorization, and optimization. The main upstream and downstream technical challenges are identified and discussed accordingly.

Immunotherapeutic polyoma and human papilloma virus-like particles

Polyomavirus and human papillomavirus (HPV) virus-like particles (VLPs) can be obtained by producing their major capsid protein VP1 (for polyomavirus) or L1 (for HPV) free from other viral genes in, for example, a baculovirus insect system, yeast, Escherichia coli or similar systems. Polyomavirus and HPV VLPs can immunize healthy individuals, and in some cases T-cell-deficient hosts, against primary infection with the corresponding virus. Chimeric VLPs from polyomaviruses or HPVs containing fusion proteins between the VP1/L1 or VP2/VP3/L2 minor capsid proteins and selected antigens can also be produced. These VLPs can then induce B- or T-cell immune responses and be used as preventive or therapeutic vaccines against cancers induced by the corresponding virus, or a cancer bearing the selected tumor antigen.

Exuberated numbers of tumor-specific T cells result in tumor escape

Cytotoxic T cells (CTL) play a major role in tumor rejection. Expansion of CTLs, either by immunization or adoptive transfer, is a prominent goal in current immunotherapy. The antigen-specific nature of these expansion processes inevitably initiates a clonotypic attack on the tumor. By injecting an Ovalbumin-expressing melanoma into OT-I mice, in which >90% of CTLs recognize an Ovalbumin peptide, we show that an increased number of tumor-specific CTLs causes emergence of escape variants. We show that these escape variants are a result of antigen silencing via a yet undetermined epigenetic mechanism, which occurs frequently and is spontaneously reversible. We further show that an increase in the time of tumor onset in OT-I compared with C57BL/6J is a result of immune selection.

Cellular and humoral immune responses to chimeric EGFP-pseudocapsids derived from the mouse polyomavirus after their intranasal administration

Mouse polyomavirus (MPyV) VP1-pseudocapsids carrying enhanced green fluorescent protein (EGFP-VLPs) were used for intranasal immunization of mice. EGFP-VLPs induced strong anti-VP1 but not anti-EGFP antibody production. In vitro restimulation with antigen-pulsed bone marrow-derived dendritic cells (BMDCs) induced remarkable T-cell proliferative response specific for both VP1 and EGFP antigen and IL-2 and IFN-gamma production. Surprisingly, no specific cytotoxic activities against VP1 and EGFP proteins were detected. After intranasal administration of EGFP-VLPs, as well as after polyomavirus infection, a moderate reduction of CD4(+)CD25(+)Foxp3(+) T cells was observed in spleens but not in lymph nodes and peripheral blood, suggesting that both MPyV virions and pseudocapsids are able to induce changes in distribution of regulatory T cells. Treatment of EGFP-VLPs pulsed BMDCs with inhibitors of endosomal acidification proved that presentation of peptides on MHCgp class II is dependent on acidic endosomal environment. Substantial decrease of CD4-specific T-cell proliferation in the presence of proteasome inhibitor suggests that MHCgp class II might load VPL-derived peptides processed by proteasomes. Thus, polyomavirus derived VLPs appear to be promising delivery and adjuvant vehicles for therapeutic proteins.

Vaccination, immune and gene therapy based on virus-like particles against viral infections and cancer

Virus-like particles (VLPs) are self-assembling, non-replicating particles lacking the viral genome that are formed by one or several viral structural proteins. VLPs can be purified after expression in yeast cells, insect cells using baculoviruses, Escherichia coli or mammalian cells. Recently, vaccines based on VLPs have come into focus with the FDA approval of a VLP-based vaccine against human papilloma viruses. However, this application of VLPs is just one of many developments within the VLP field. Other potential applications under development besides vaccines against viruses or cancers also include gene delivery and treatment of different disorders.

Development of a vaccine marker technology: Display of B cell epitopes on the surface of recombinant polyomavirus-like pentamers and capsoids induces peptide-specific antibodies in piglets after vaccination

Highly immunogenic capsomers (pentamers) and virus-like particles (VLPs) were generated through insertion of foreign B cell epitopes into the surface-exposed loops of the VP1 protein of murine polyomavirus and via heterologous expression of the recombinant fusion proteins in E. coli. Usually, complex proteins like the keyhole limpet hemocyanin (KLH) act as standard carrier devices for the display of such immunogenic peptides after chemical linkage. Here, a comparative analysis revealed that antibody responses raised against the carrier entities, KLH or VP1 pentamers, did not significantly differ up to 18 weeks, demonstrating the highly immunogenic nature of VP1-based particulate structures. The carrier-specific antibody response was reproducibly detected in the meat juice after processing. More importantly, chimeric VP1 pentamers and VLPs carrying peptides of 12 and 14 amino acids in length, inserted into the BC2 loop, induced a strong and long-lasting humoral immune response against VP1 and the inserted foreign epitope. Remarkably, the epitope-specific antibody response was only moderately decreased when VP1 pentamers were used instead of VLPs. In conclusion, we identified polyomavirus VP1-based structures displaying surface-exposed immunodominant B cell epitopes as being an efficient carrier system for the induction of potent peptide-specific antibodies. The application of this approach in vaccine marker technology in livestock holding and the meat production chain is discussed.

Murine polyomavirus-like particles induce maturation of bone marrow-derived dendritic cells and proliferation of T cells

We analysed the effects of murine polyomavirus-like particles (PLPs) on bone marrow-derived dendritic cells (BMDCs) and T cells in vitro. BMDCs activated with PLPs up-regulated CD40, CD80, CD86 and major histocompatibility complex (MHC) class II surface markers and produced proinflammatory cytokines. Chimeric PLPs [expressing the ovalbumin (OVA)-peptides OVA(257-264) or OVA(323-339)], but not wildtype PLPs, activated OVA-specific CD8 T cells and OVA-specific CD4 T cells, respectively, indicating both MHC class I and II presentation of the peptides by antigen-presenting cells. Our results suggest that PLPs may be used as vaccine adjuvants priming dendritic cells to induce potent T cell responses.