Development of anticancer and antiviral vaccines based on self-assembled nanoparticles

Abstract

Vaccination can activate the immune system to develop long-lasting immunity against specific antigens derived from pathogens, and is considered one of the most effective strategies for preventing infectious diseases in individuals as well as public health. In addition to prophylactic vaccines to prevent infectious diseases in advance, therapeutic vaccines to treat diseases that have already occurred are also being developed recently. In chapter 1, the basic introduction to vaccination and advantages and limitations of peptide-based vaccines are described, and self-assembled nanomaterial-based delivery systems are introduced as one of the strategies to overcome the aforementioned limitations.In chapter 2, I described the development of self-assembled nanoparticle based vaccines made of nontoxic, biocompatible lipid components for cancer treatment. Cancer immunotherapy is a treatment that uses the patient’s own immune system to treat cancer, and so is known to have fewer side effects than conventional anticancer therapy and can induce persistent antitumor effects. In particular, cancer vaccines have the advantage of inducing tumor antigen-specific immune responses as well as memory responses, so that long-term sustained antitumor effects can be expected. Despite these advantages of the cancer vaccines, the occurrence of immune evasion and suppression is believed to cause resistance against the vaccines. Immune checkpoint inhibitors, which have recently been in the spotlight as cancer immunotherapy, have been approved for clinical application in several solid cancers in that they can restore immune suppression in the tumor microenvironment. However, there are limitations in that the therapy responsiveness differs depending on the type of cancer and patients, and therapeutic effect is limited when appropriate immune responses do not exist. Therefore, there is a need for combination approach that can increase low responsiveness of the immune checkpoint blockade therapy. To overcome these limitations, combination therapy of cancer vaccine and immune checkpoint inhibitor was conducted, and a strategy to increase the therapeutic efficacy of combination therapy was proposed in this study. In particular, cancer nanovaccine based on lipid nanoparticle that can simultaneously deliver tumor antigenic peptide and adjuvant was developed. The resulting nanovaccine not only induced tumor antigen-specific T cell responses, but also showed highly potent antitumor efficacy in both prophylactic and therapeutic E.G7 tumor models. In addition, cancer nanovaccine can increase the therapeutic responsiveness to immune checkpoint inhibitors by increasing CD8$^+$ T cells infiltration and PD-L1 expression in the tumor tissue, thereby transforming immunologically cold tumor into hot tumor. The possibility of combined use of cancer nanovaccine and immune checkpoint inhibitor was also verified. In order to further increase the therapeutic effect of cancer nanovaccine, combination with anti-PD-1 antibody was performed, and the treatment efficacy was different depending on the treatment sequence and timing of each modality. Sequential administration and combination of the nanovaccine and anti-PD1 antibody could result in an effective antitumor effect and inhibition of tumor relapse. Thus, a new combination treatment regimen, consisting of cancer nanovaccine and immune checkpoint blockade immunotherapy, based on treatment sequence and timing was proposed. These findings further suggest the need to evaluate these new combination treatment regimens in other immunotherapy modalities.In chapter 3, I described the development of self-assembled protein-based nanobarrel vaccine capable of preventing influenza infectious disease. Although naturally occurring, self-assembled protein nanoarchitectures have been utilized as antigen-delivery carriers, the inability of such carriers to elicit immunogenicity requires additional use of strong adjuvants. Here, I report an immunogenic Brucella outer membrane protein BP26-derived nanoarchitecture displaying the influenza extracellular domain of matrix protein-2 (M2e) as an antiviral vaccine platform. Genetic engineering of a monomeric BP26 containing tandem repeats of M2e resulted in a hollow barrel-shaped nanoarchitecture (BP26-M2e nanobarrel). Immunization with BP26-M2e nanobarrels induced a strong M2e-specific humoral immune response in vivo that was much greater than that of a physical mixture of soluble M2e and BP26, with or without the use of an alum adjuvant. An anti-M2e antibody generated by BP26-M2e nanobarrel-immunized mice specifically bound to influenza virus-infected cells. Furthermore, in viral challenge tests, BP26-M2e nanobarrels effectively protected mice from influenza virus infection-associated death, even without the use of a conventional adjuvant. These findings suggest that the BP26-based nanobarrel developed here represents a versatile vaccine platform that can be used against various viral infections.