Coupling to the surface of liposomes alters the immunogenicity of hepatitis C virus-derived peptides and confers sterile immunity

Research Progress on Liposome Pulmonary Delivery of Mycobacterium tuberculosis Nucleic Acid Vaccine and Its Mechanism of Action

Traditional vaccines have played an important role in the prevention and treatment of infectious diseases, but they still have problems such as low immunogenicity, poor stability, and difficulty in inducing lasting immune responses. In recent years, the nucleic acid vaccine has emerged as a relatively cheap and safe new vaccine. Compared with traditional vaccines, nucleic acid vaccine has some unique advantages, such as easy production and storage, scalability, and consistency between batches. However, the direct administration of naked nucleic acid vaccine is not ideal, and safer and more effective vaccine delivery systems are needed. With the rapid development of nanocarrier technology, the combination of gene therapy and nanodelivery systems has broadened the therapeutic application of molecular biology and the medical application of biological nanomaterials. Nanoparticles can be used as potential drug-delivery vehicles for the treatment of hereditary and infectious diseases. In addition, due to the advantages of lung immunity, such as rapid onset of action, good efficacy, and reduced adverse reactions, pulmonary delivery of nucleic acid vaccine has become a hot spot in the field of research. In recent years, lipid nanocarriers have become safe, efficient, and ideal materials for vaccine delivery due to their unique physical and chemical properties, which can effectively reduce the toxic side effects of drugs and achieve the effect of slow release and controlled release, and there have been a large number of studies using lipid nanocarriers to efficiently deliver target components into the body. Based on the delivery of tuberculosis (TB) nucleic acid vaccine by lipid carrier, this article systematically reviews the advantages and mechanism of liposomes as a nucleic acid vaccine delivery carrier, so as to lay a solid foundation for the faster and more effective development of new anti-TB vaccine delivery systems in the future.

Polymersome-based protein drug delivery - quo vadis?

Protein-based therapeutics are an attractive alternative to established therapeutic approaches and represent one of the fastest growing families of drugs. While many of these proteins can be delivered using established formulations, the intrinsic sensitivity of proteins to denaturation sometimes calls for a protective carrier to allow administration. Historically, lipid-based self-assembled structures, notably liposomes, have performed this function. After the discovery of polymersome-based targeted drug-delivery systems, which offer manifold advantages over lipid-based structures, the scientific community expected that such systems would take the therapeutic world by storm. However, no polymersome formulations have been commercialised. In this review article, we discuss key obstacles for the sluggish translation of polymersome-based protein nanocarriers into approved pharmaceuticals, which include limitations imparted by the use of non-degradable polymers, the intricacies of polymersome production methods, and the complexity of the in vivo journey of polymersomes across various biological barriers. Considering this complex subject from a polymer chemist's point of view, we highlight key areas that are worthy to explore in order to advance polymersomes to a level at which clinical trials become worthwhile and translation into pharmaceutical and nanomedical applications is realistic.

Nano-Microparticle Platforms in Developing Next-Generation Vaccines

The first vaccines ever made were based on live-attenuated or inactivated pathogens, either whole cells or fragments. Although these vaccines required the co-administration of antigens with adjuvants to induce a strong humoral response, they could only elicit a poor CD8⁺ T-cell response. In contrast, next-generation nano/microparticle-based vaccines offer several advantages over traditional ones because they can induce a more potent CD8⁺ T-cell response and, at the same time, are ideal carriers for proteins, adjuvants, and nucleic acids. The fact that these nanocarriers can be loaded with molecules able to modulate the immune response by inducing different effector functions and regulatory activities makes them ideal tools for inverse vaccination, whose goal is to shut down the immune response in autoimmune diseases. Poly (lactic-co-glycolic acid) (PLGA) and liposomes are biocompatible materials approved by the Food and Drug Administration (FDA) for clinical use and are, therefore, suitable for nanoparticle-based vaccines. Recently, another candidate platform for innovative vaccines based on extracellular vesicles (EVs) has been shown to efficiently co-deliver antigens and adjuvants. This review will discuss the potential use of PLGA-NPs, liposomes, and EVs as carriers of peptides, adjuvants, mRNA, and DNA for the development of next-generation vaccines against endemic and emerging viruses in light of the recent COVID-19 pandemic.

The Multirole of Liposomes in Therapy and Prevention of Infectious Diseases

Liposomes are closed bilayer structures spontaneously formed by hydrated phospholipids that are widely used as efficient delivery systems for drugs or antigens, due to their capability to encapsulate bioactive hydrophilic, amphipathic, and lipophilic molecules into inner water phase or within lipid leaflets. The efficacy of liposomes as drug or antigen carriers has been improved in the last years to ameliorate pharmacokinetics and capacity to release their cargo in selected target organs or cells. Moreover, different formulations and variations in liposome composition have been often proposed to include immunostimulatory molecules, ligands for specific receptors, or stimuli responsive compounds. Intriguingly, independent research has unveiled the capacity of several phospholipids to play critical roles as intracellular messengers in modulating both innate and adaptive immune responses through various mechanisms, including (i) activation of different antimicrobial enzymatic pathways, (ii) driving the fusion–fission events between endosomes with direct consequences to phagosome maturation and/or to antigen presentation pathway, and (iii) modulation of the inflammatory response. These features can be exploited by including selected bioactive phospholipids in the bilayer scaffold of liposomes. This would represent an important step forward since drug or antigen carrying liposomes could be engineered to simultaneously activate different signal transduction pathways and target specific cells or tissues to induce antigen-specific T and/or B cell response. This lipid-based host-directed strategy can provide a focused antimicrobial innate and adaptive immune response against specific pathogens and offer a novel prophylactic or therapeutic option against chronic, recurrent, or drug-resistant infections.

Platform technologies for modern vaccine manufacturing

Improved understanding of antigenic components and their interaction with the immune system, as supported by computational tools, permits a sophisticated approach to modern vaccine design. Vaccine platforms provide an effective tool by which strategically designed peptide and protein antigens are modularized to enhance their immunogenicity. These modular vaccine platforms can overcome issues faced by traditional vaccine manufacturing and have the potential to generate safe vaccines, rapidly and at a low cost. This review introduces two promising platforms based on virus-like particle and liposome, and discusses the methodologies and challenges.

Targeting cryptic epitope with modified antigen coupled to the surface of liposomes induces strong antitumor CD8 T-cell immune responses in vivo

Active cancer immunotherapy, such as cancer vaccine, is based on the fundamental knowledge that tumor-associated antigens (TAAs) are presented on MHC molecules for recognition by specific T cells. However, most TAAs are self-antigens and are also expressed on normal tissues, including the thymus. This fact raises the issue of the tolerance of the TAA-specific T-cell repertoire and consequently the inability to trigger a strong and efficient antitumor immune response. In the present study, we used antigens chemically coupled to the surface of liposomes to target telomerase reverse transcriptase (TERT), a widely expressed self/tumor antigen. Taking advantage of the high homology between mouse and human TERT, we investigated immunogenicity and antitumor efficiency of the liposomal TERT peptides in HLA-A^*0201 transgenic HHD mice. Using the heteroclitical peptide-modifying approach with antigen-coupled liposomes, we identified a novel cryptic epitope with low affinity for HLA^*0201 molecules derived from TERT. The heteroclitical variant derived from this novel low affinity peptide exhibited strong affinity for HLA^*0201 molecules. However, it induced only weak CD8 T-cell immune responses in HHD mice when emulsified in IFA. By contrast, when coupled to the surface of the liposomes, it induced powerful CD8 T-cell immune responses which cross-reacted against the original cryptic epitope. The induced CD8 T cells also recognized endogenously TERT-expressing tumor cells and inhibited their growth in HHD mice. These data suggest that heteroclitical antigen derived from low affinity epitope of tumor antigens coupled to the surface of liposome may have a role as an effective cancer vaccine candidate.

Liposomes as vaccine delivery systems: a review of the recent advances

Liposomes and liposome-derived nanovesicles such as archaeosomes and virosomes have become important carrier systems in vaccine development and the interest for liposome-based vaccines has markedly increased. A key advantage of liposomes, archaeosomes and virosomes in general, and liposome-based vaccine delivery systems in particular, is their versatility and plasticity. Liposome composition and preparation can be chosen to achieve desired features such as selection of lipid, charge, size, size distribution, entrapment and location of antigens or adjuvants. Depending on the chemical properties, water-soluble antigens (proteins, peptides, nucleic acids, carbohydrates, haptens) are entrapped within the aqueous inner space of liposomes, whereas lipophilic compounds (lipopeptides, antigens, adjuvants, linker molecules) are intercalated into the lipid bilayer and antigens or adjuvants can be attached to the liposome surface either by adsorption or stable chemical linking. Coformulations containing different types of antigens or adjuvants can be combined with the parameters mentioned to tailor liposomal vaccines for individual applications. Special emphasis is given in this review to cationic adjuvant liposome vaccine formulations. Examples of vaccines made with CAF01, an adjuvant composed of the synthetic immune-stimulating mycobacterial cordfactor glycolipid trehalose dibehenate as immunomodulator and the cationic membrane forming molecule dimethyl dioctadecylammonium are presented. Other vaccines such as cationic liposome-DNA complexes (CLDCs) and other adjuvants like muramyl dipeptide, monophosphoryl lipid A and listeriolysin O are mentioned as well. The field of liposomes and liposome-based vaccines is vast. Therefore, this review concentrates on recent and relevant studies emphasizing current reports dealing with the most studied antigens and adjuvants, and pertinent examples of vaccines. Studies on liposome-based veterinary vaccines and experimental therapeutic cancer vaccines are also summarized.