Optimal therapeutic strategy using antigen-containing liposomes selectively delivered to antigen-presenting cells

Rational Design of Lipid-Based Vectors for Advanced Therapeutic Vaccines

Recent advancements in vaccine delivery systems have seen the utilization of various materials, including lipids, polymers, peptides, metals, and inorganic substances, for constructing non-viral vectors. Among these, lipid-based nanoparticles, composed of natural, synthetic, or physiological lipid/phospholipid materials, offer significant advantages such as biocompatibility, biodegradability, and safety, making them ideal for vaccine delivery. These lipid-based vectors can protect encapsulated antigens and/or mRNA from degradation, precisely tune chemical and physical properties to mimic viruses, facilitate targeted delivery to specific immune cells, and enable efficient endosomal escape for robust immune activation. Notably, lipid-based vaccines, exemplified by those developed by BioNTech/Pfizer and Moderna against COVID-19, have gained approval for human use. This review highlights rational design strategies for vaccine delivery, emphasizing lymphoid organ targeting and effective endosomal escape. It also discusses the importance of rational formulation design and structure-activity relationships, along with reviewing components and potential applications of lipid-based vectors. Additionally, it addresses current challenges and future prospects in translating lipid-based vaccine therapies for cancer and infectious diseases into clinical practice.

Identification of Neoantigens in Cancer Cells as Targets for Immunotherapy

The clinical benefits of immune checkpoint blockage (ICB) therapy have been widely reported. In patients with cancer, researchers have demonstrated the clinical potential of antitumor cytotoxic T cells that can be reinvigorated or enhanced by ICB. Compared to self-antigens, neoantigens derived from tumor somatic mutations are believed to be ideal immune targets in tumors. Candidate tumor neoantigens can be identified through immunogenomic or immunopeptidomic approaches. Identification of neoantigens has revealed several points of the clinical relevance. For instance, tumor mutation burden (TMB) may be an indicator of immunotherapy. In various cancers, mutation rates accompanying neoantigen loads may be indicative of immunotherapy. Furthermore, mismatch repair-deficient tumors can be eradicated by T cells in ICB treatment. Hence, immunotherapies using vaccines or adoptive T-cell transfer targeting neoantigens are potential innovative strategies. However, significant efforts are required to identify the optimal epitopes. In this review, we summarize the recent progress in the identification of neoantigens and discussed preclinical and clinical studies based on neoantigens. We also discuss the issues remaining to be addressed before clinical applications of these new therapeutic strategies can be materialized.

Using nanoparticles for in situ vaccination against cancer: mechanisms and immunotherapy benefits

Immunotherapy to treat cancer is now an established clinical approach. Immunotherapy can be applied systemically, as done with checkpoint blockade antibodies, but it can also be injected directly into identified tumors, in a strategy of in situ vaccination (ISV). ISV is designed to stimulate a strong local antitumor immune response involving both innate and adaptive immune cells, and through this generate a systemic antitumor immune response against metastatic tumors. A variety of ISVs have been utilized to generate an immunostimulatory tumor microenvironment (TME). These include attenuated microorganisms, recombinant proteins, small molecules, physical disruptors of TME (alternating magnetic and focused ultrasound heating, photothermal therapy, and radiotherapy), and more recently nanoparticles (NPs). NPs are attractive and unique since they can load multiple drugs or other reagents to influence immune and cancer cell functions in the TME, affording a unique opportunity to stimulate antitumor immunity. Here, we describe the NP-ISV therapeutic mechanisms, review chemically synthesized NPs (i.e., liposomes, polymeric, chitosan-based, inorganic NPs, etc.), biologically derived NPs (virus and bacteria-based NPs), and energy-activated NP-ISVs in the context of their use as local ISV. Data suggests that NP-ISVs can enhance outcomes of immunotherapeutic regimens including those utilizing tumor hyperthermia and checkpoint blockade therapies.

Optimal therapeutic strategy using antigen-containing liposomes selectively delivered to antigen-presenting cells

Recent immunotherapies have shown clinical success. In particular, vaccines based on particulate antigen (Ag) are expected to be implemented based on their efficacy. In the current study, we describe a strategy entailing Ag-encapsulating PEG-modified liposomes (PGL-Ag) as antigen protein delivery devices and show that the success of the liposome depends on the antigen-presenting cell (APC) capacity; after administration of PGL-Ag, dendritic cells (DCs) in particular take up the Ag and subsequently prime T cells. For the generation of antitumor T cell responses in the lymphoid tissues, the function of encapsulated Ag-capturing DCs in vivo could be a biomarker. We next designed a prime-boost strategy to enhance the antitumor effects of the PGL-Ag. In the tumor sites, we show that Ag retention in nanoparticle-capturing DCs promotes a robust antitumor response. Thus, this efficient particulate Ag-based host antigen-presenting cell delivery strategy provides a bridge between innate and adaptive immune response and offers a novel therapeutic option against tumor cells.