Enhanced mucosal and systemic immunogenicity of human papillomavirus-like particles encapsidating interleukin-2 gene adjuvant

Nanoadjuvants: Promising Bioinspired and Biomimetic Approaches in Vaccine Innovation

Adjuvants are the important part of vaccine manufacturing as they elicit the vaccination effect and enhance the durability of the immune response through controlled release. In light of this, nanoadjuvants have shown unique broad spectrum advantages. As nanoparticles (NPs) based vaccines are fast-acting and better in terms of safety and usability parameters as compared to traditional vaccines, they have attracted the attention of researchers. A vaccine nanocarrier is another interesting and promising area for the development of next-generation vaccines for prophylaxis. This review looks at the various nanoadjuvants and their structure-function relationships. It compiles the state-of-art literature on numerous nanoadjuvants to help domain researchers orient their understanding and extend their endeavors in vaccines research and development.

A Survey of Preclinical Studies Evaluating Nanoparticle-Based Vaccines Against Non-Viral Sexually Transmitted Infections

A worldwide estimate of over one million STIs are acquired daily and there is a desperate need for effective preventive as well as therapeutic measures to curtail this global health burden. Vaccines have been the most effective means for the control and potential eradication of infectious diseases; however, the development of vaccines against STIs has been a daunting task requiring extensive research for the development of safe and efficacious formulations. Nanoparticle-based vaccines represent a promising platform as they offer benefits such as targeted antigen presentation and delivery, co-localized antigen-adjuvant combinations for enhanced immunogenicity, and can be designed to be biologically inert. Here we discuss promising types of nanoparticles along with outcomes from nanoparticle-based vaccine preclinical studies against non-viral STIs including chlamydia, syphilis, gonorrhea, and recommendations for future nanoparticle-based vaccines against STIs.

Nanoparticle Vaccines Against Infectious Diseases

Due to emergence of new variants of pathogenic micro-organisms the treatment and immunization of infectious diseases have become a great challenge in the past few years. In the context of vaccine development remarkable efforts have been made to develop new vaccines and also to improve the efficacy of existing vaccines against specific diseases. To date, some vaccines are developed from protein subunits or killed pathogens, whilst several vaccines are based on live-attenuated organisms, which carry the risk of regaining their pathogenicity under certain immunocompromised conditions. To avoid this, the development of risk-free effective vaccines in conjunction with adequate delivery systems are considered as an imperative need to obtain desired humoral and cell-mediated immunity against infectious diseases. In the last several years, the use of nanoparticle-based vaccines has received a great attention to improve vaccine efficacy, immunization strategies, and targeted delivery to achieve desired immune responses at the cellular level. To improve vaccine efficacy, these nanocarriers should protect the antigens from premature proteolytic degradation, facilitate antigen uptake and processing by antigen presenting cells, control release, and should be safe for human use. Nanocarriers composed of lipids, proteins, metals or polymers have already been used to attain some of these attributes. In this context, several physico-chemical properties of nanoparticles play an important role in the determination of vaccine efficacy. This review article focuses on the applications of nanocarrier-based vaccine formulations and the strategies used for the functionalization of nanoparticles to accomplish efficient delivery of vaccines in order to induce desired host immunity against infectious diseases.

Mutual enhancement of IL-2 and IL-7 on DNA vaccine immunogenicity mainly involves regulations on their receptor expression and receptor-expressing lymphocyte generation

Our previous study showed that IL-2 and IL-7 could mutually enhance the immunogenicity of canine parvovirus VP2 DNA vaccine, although the underlying mechanism remained unknown. Here, we used the OVA gene as a DNA vaccine in a mouse model to test their enhancement on DNA vaccine immunogenicity and to explore the molecular mechanism. Results showed that both IL-2 and IL-7 genes significantly increased the immunogenicity of OVA DNA vaccine in mice. Co-administration of IL-2 and IL-7 genes with OVA DNA significantly increased OVA-specific antibody titers, T cell proliferation and IFN-γ production compared with IL-2 or IL-7 alone, confirming that IL-2 and IL-7 mutually enhanced DNA vaccine immunogenicity. Mechanistically, we have shown that IL-2 significantly stimulated generation of IL-7 receptor-expressing lymphocytes, and that IL-7 significantly induced IL-2 receptor expression. These results contribute to an explanation of the mechanism of the mutual effects of IL-2 and IL-7 on enhancing DNA vaccine immunogenicity and provided a basis for further investigation on their mutual effects on adjuvant activity and immune regulation.

Improving vaccines by incorporating immunological coadjuvants

While vaccination continues to be the most successful interventionist health policy to date, infectious disease remains a significant cause of death worldwide. A primary reason that vaccination is not able to generate effective immunity is a lack of appropriate adjuvants capable of initiating the desired immune response. Adjuvant combinations can potentially overcome this problem; however, the possible permutations to consider, which include the route and kinetics of vaccination, as well as combinations of adjuvants, are practically limitless. This review aims to summarize the current understanding of adjuvants and related immunological processes and how this knowledge can and has been applied to the strategic selection of adjuvant combinations as components of vaccines against human infectious disease.

Developments in virus-like particle-based vaccines for infectious diseases and cancer

Virus-like particles hold great promise for the development of effective and affordable vaccines. Indeed, virus-like particles are suitable for presentation and efficient delivery of linear as well as conformational antigens to antigen-presenting cells. This will ultimately result in optimal B-cell activation and cross-presentation with both MHC class I and II molecules to prime CD4(+) T-helper as well as CD8(+) cytotoxic T cells. This article provides an update on the development and use of virus-like particles as vaccine approaches for infectious diseases and cancer.

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.

Enhancing efficacy and mucosa-tropic distribution of an oral HIV-PsV DNA vaccine in animal models

A strategy combined the oral delivery route and bovine papillomavirus (BPV) pseudovirus (PsV)-based human immunodeficiency virus (HIV) DNA vaccine, which has been proven to enhance the mucosal immunization compared with the systemic immunization and in general does not induce effective mucosal immune responses. In this study, the immune responses against the BPV expressing HIV gp41 epitopes (ELDKWA, NWFDIT) after oral administration in Cynomolgus monkeys (Macaca fascicularis) were assessed, and the biodistribution of plasmid DNA encapsulated in the papillomavirus-like particles (VLPs) were evaluated in murine models. Results showed that oral immunization with the HIV-PsV DNA vaccine in monkey generated p24 and gp41 epitopes-specific serum IgG. Importantly, these induced antibodies had been shown to neutralize HIV-1 primary strain. In addition, the advantage of VLPs as vehicles delivering genes had been first revealed in biodistribution results. Therefore, orally administered HIV-PsV DNA vaccine was well-tolerated, enhanced the mucosa targeting property of the plasmid DNA, and reduced the nontargeting distribution, which indicate that it would reduce stress associated with systemic vaccination.

Enhanced humoral and cellular immune responses after sublingual immunization against human papillomavirus 16 L1 protein with adjuvants

Needle-free nonparenteral vaccines offer a number of practical advantages, especially in developing countries. To address the effects of vaccine administration route, we tested mucosal and systemic immune responses against human papillomavirus 16 L1(HPV16L1) protein using intranasal, intravaginal, transdermal, sublingual (SL) and intramuscular routes. The SL route provided the most effective mucosal secretory IgA (sIgA) and serum IgG responses. After a 150 microg antigen dose via the SL route, saliva sIgA levels were 7.2- and 5.8-fold higher than those achieved via intravaginal and transdermal routes, respectively. Notably, SL administration even produced 4.6-fold higher levels of vaginal sIgA levels than did intravaginal delivery of 150 microg antigen. To enhance the immunogenicity of SL vaccines, we tested the adjuvanticity of nine molecules: three toll-like receptor agonists, three nucleotide-binding oligomerization-domain agonists, vitamin D3, poly-gamma-glutamic acid and cholera toxin subunit B (CTB). Among the molecules tested, CTB provided the most enhanced mucosal sIgA and systemic IgG induction. SL-applied CTB enhanced the production of interleukin-4 and interferon-gamma from stimulated CD4+ T cells. Moreover, interferon-gamma-producing CD8+ T cell responses were increased 1.7-fold after co-treatment with SL CTB and HPV16L1. These results suggest the potential of the SL route for delivery of HPV16L1 vaccines using CTB as an adjuvant.

Incorporation of membrane-bound, mammalian-derived immunomodulatory proteins into influenza whole virus vaccines boosts immunogenicity and protection against lethal challenge

Background

Influenza epidemics continue to cause morbidity and mortality within the human population despite widespread vaccination efforts. This, along with the ominous threat of an avian influenza pandemic (H5N1), demonstrates the need for a much improved, more sophisticated influenza vaccine. We have developed an in vitro model system for producing a membrane-bound Cytokine-bearing Influenza Vaccine (CYT-IVAC). Numerous cytokines are involved in directing both innate and adaptive immunity and it is our goal to utilize the properties of individual cytokines and other immunomodulatory proteins to create a more immunogenic vaccine.

Results

We have evaluated the immunogenicity of inactivated cytokine-bearing influenza vaccines using a mouse model of lethal influenza virus challenge. CYT-IVACs were produced by stably transfecting MDCK cell lines with mouse-derived cytokines (GM-CSF, IL-2 and IL-4) fused to the membrane-anchoring domain of the viral hemagglutinin. Influenza virus replication in these cell lines resulted in the uptake of the bioactive membrane-bound cytokines during virus budding and release. In vivo efficacy studies revealed that a single low dose of IL-2 or IL-4-bearing CYT-IVAC is superior at providing protection against lethal influenza challenge in a mouse model and provides a more balanced Th₁/Th₂ humoral immune response, similar to live virus infections.

Conclusion

We have validated the protective efficacy of CYT-IVACs in a mammalian model of influenza virus infection. This technology has broad applications in current influenza virus vaccine development and may prove particularly useful in boosting immune responses in the elderly, where current vaccines are minimally effective.

Biological gene delivery vehicles: beyond viral vectors

Gene therapy covers a broad spectrum of applications, from gene replacement and knockdown for genetic or acquired diseases such as cancer, to vaccination, each with different requirements for gene delivery. Viral vectors and synthetic liposomes have emerged as the vehicles of choice for many applications today, but both have limitations and risks, including complexity of production, limited packaging capacity, and unfavorable immunological features, which restrict gene therapy applications and hold back the potential for preventive gene therapy. While continuing to improve these vectors, it is important to investigate other options, particularly nonviral biological agents which include bacteria, bacteriophage, virus-like particles (VLPs), erythrocyte ghosts, and exosomes. Exploiting the natural properties of these biological entities for specific gene delivery applications will expand the repertoire of gene therapy vectors available for clinical use. Here, we review the prospects for nonviral biological delivery vehicles as gene therapy agents with focus on their unique evolved biological properties and respective limitations and potential applications. The potential of these nonviral biological entities to act as clinical gene therapy delivery vehicles has already been shown in clinical trials using bacteria-mediated gene transfer and with sufficient development, these entities will complement the established delivery techniques for gene therapy applications.

General strategy for decoration of enveloped viruses with functionally active lipid-modified cytokines

Viral particles preferentially incorporate extra- and intracellular constituents of host cell lipid rafts, a phenomenon central to pseudotyping. Based on this mechanism, we have developed a system for the predictable decoration of enveloped viruses with functionally active cytokines that circumvents the need to modify viral proteins themselves. Human interleukin-2 (hIL-2), hIL-4, human granulocyte-macrophage colony-stimulating factor (hGM-CSF), and murine IL-2 (mIL-2) were used as model cytokines and fused at their C terminus to the glycosylphosphatidylinositol (GPI) acceptor sequence of human Fcgamma receptor III (CD16b). We show here that genetically modified cytokines are all well expressed on 293 producer cells. However, only molecules equipped with GPI anchors but not those linked to transmembrane/intracellular regions of type I membrane proteins are efficiently targeted to lipid rafts and consequently to virus-like particles (VLP) induced by Moloney murine leukemia virus Gag-Pol. hIL-4::GPI and hGM-CSF::GPI coexpressed on VLP were found to differentiate monocytes towards dendritic cells. Apart from myeloid-committed cell types, VLP-bound cytokines also act efficiently on lymphocytes. hIL-2::GPI strongly costimulated T-cell receptor (TCR)/CD3 dependent T-cell activation in vitro and mIL-2::GPI-coactivated antigen-specific T cells in vivo. On a molar basis, the functional activity of VLP-bound hIL-2::GPI was found to be comparable to that of soluble hIL-2. VLP decorated with hIL-2::GPI and coexpressing a TCR/CD3 ligand have an IL-2-specific activity of 5 x 10(4) units/mg protein. Virus particles decorated with lipid-modified cytokines might help to improve viral strains for vaccination purposes, the propagation of factor-dependent cell types, as well as gene transfer by viral systems in the future.

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

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

Vaccine strategies for human papillomavirus-associated cancers

PURPOSE OF REVIEW

To review novel immunologic strategies for the prevention and treatment of human papillomavirus infection and associated diseases. Both animal model systems and human protocols are discussed.

RECENT FINDINGS

Many vaccine platforms for both prevention of human papillomavirus infection and treatment of associated disease have been developed. Virus-like particle constructs containing human papillomavirus capsid proteins have been shown to protect against human papillomavirus infection. Novel peptide or protein constructs containing modified E6 or E7 proteins, novel adjuvants, fusion proteins such as immunoglobulin-G-heavy chain E7, or heat shock proteins have been made as therapeutic modalities. In addition, many new recombinant vaccine vectors such as vaccinia, Listeria species, adenovirus, Semliki Forest vectors, and others have been developed as carriers of immunotherapeutic agents. Recently, chimeric virus-like particle vaccines have been developed to treat existing human papillomavirus-induced neoplasms.

SUMMARY

Immunotherapy protocols using a variety of recombinant vectors and modified human papillomavirus proteins induce in-vitro T cell responses and may lead to tumor regression. Vaccine-induced in-vitro immune reactivity and clinical vaccine effects are often not well associated. Further analysis of ongoing human immunotherapy trials is awaited.