N-Terminal Fatty Acids of NEFMUT Are Required for the CD8+ T-Cell Immunogenicity of In Vivo Engineered Extracellular Vesicles

Engineered exosomes from different sources for cancer-targeted therapy

Exosome is a subgroup of extracellular vesicles, which has been serving as an efficient therapeutic tool for various diseases. Engineered exosomes are the sort of exosomes modified with surface decoration and internal therapeutic molecules. After appropriate modification, engineered exosomes are able to deliver antitumor drugs to tumor sites efficiently and precisely with fewer treatment-related adverse effects. However, there still exist many challenges for the clinical translation of engineered exosomes. For instance, what sources and modification strategies could endow exosomes with the most efficient antitumor activity is still poorly understood. Additionally, how to choose appropriately engineered exosomes in different antitumor therapies is another unresolved problem. In this review, we summarized the characteristics of engineered exosomes, especially the spatial and temporal properties. Additionally, we concluded the recent advances in engineered exosomes in the cancer fields, including the sources, isolation technologies, modification strategies, and labeling and imaging methods of engineered exosomes. Furthermore, the applications of engineered exosomes in different antitumor therapies were summarized, such as photodynamic therapy, gene therapy, and immunotherapy. Consequently, the above provides the cancer researchers in this community with the latest ideas on engineered exosome modification and new direction of new drug development, which is prospective to accelerate the clinical translation of engineered exosomes for cancer-targeted therapy.

Nanoparticle-Based Delivery Systems for Vaccines

Vaccination is still the most cost-effective way to combat infectious illnesses. Conventional vaccinations may have low immunogenicity and, in most situations, only provide partial protection. A new class of nanoparticle-based vaccinations has shown considerable promise in addressing the majority of the shortcomings of traditional and subunit vaccines. This is due to recent breakthroughs in chemical and biological engineering, which allow for the exact regulation of nanoparticle size, shape, functionality, and surface characteristics, resulting in improved antigen presentation and robust immunogenicity. A blend of physicochemical, immunological, and toxicological experiments can be used to accurately characterize nanovaccines. This narrative review will provide an overview of the current scenario of the nanovaccine.

Virus-Induced CD8+ T-Cell Immunity and Its Exploitation to Contain the SARS-CoV-2 Pandemic

The current battle against Severe Acute Respiratory Syndrome (SARS)-Coronavirus-2 benefits from the worldwide distribution of different vaccine formulations. All anti-SARS-CoV-2 vaccines in use are conceived to induce anti-Spike neutralizing antibodies. However, this strategy still has unresolved issues, the most relevant of which are: (i) the resistance to neutralizing antibodies of emerging SARS-CoV-2 variants and (ii) the waning of neutralizing antibodies. On the other hand, both pre-clinical evidence and clinical evidence support the idea that the immunity sustained by antigen-specific CD8⁺ T lymphocytes can complement and also surrogate the antiviral humoral immunity. As a distinctive feature, anti-SARS-CoV-2 CD8⁺ T-driven immunity maintains its efficacy even in the presence of viral protein mutations. In addition, on the basis of data obtained in survivors of the SARS-CoV epidemic, this immunity is expected to last for several years. In this review, both the mechanisms and role of CD8⁺ T-cell immunity in viral infections, particularly those induced by SARS-CoV and SARS-CoV-2, are analyzed. Moreover, a CD8⁺ T-cell-based vaccine platform relying on in vivo engineered extracellular vesicles is described. When applied to SARS-CoV-2, this strategy was proven to induce a strong immunogenicity, holding great promise for its translation into the clinic.

Exosome-Based Vaccines: History, Current State, and Clinical Trials

Extracellular vesicles (EVs) are released by most cell types as part of an intracellular communication system in crucial processes such as inflammation, cell proliferation, and immune response. However, EVs have also been implicated in the pathogenesis of several diseases, such as cancer and numerous infectious diseases. An important feature of EVs is their ability to deliver a wide range of molecules to nearby targets or over long distances, which allows the mediation of different biological functions. This delivery mechanism can be utilized for the development of therapeutic strategies, such as vaccination. Here, we have highlighted several studies from a historical perspective, with respect to current investigations on EV-based vaccines. For example, vaccines based on exosomes derived from dendritic cells proved to be simpler in terms of management and cost-effectiveness than dendritic cell vaccines. Recent evidence suggests that EVs derived from cancer cells can be leveraged for therapeutics to induce strong anti-tumor immune responses. Moreover, EV-based vaccines have shown exciting and promising results against different types of infectious diseases. We have also summarized the results obtained from completed clinical trials conducted on the usage of exosome-based vaccines in the treatment of cancer, and more recently, coronavirus disease.

The C-Terminal Domain of Nefmut Is Dispensable for the CD8+ T Cell Immunogenicity of In Vivo Engineered Extracellular Vesicles

Intramuscular injection of DNA vectors expressing the extracellular vesicle (EV)-anchoring protein Nef^mut fused at its C-terminus to viral and tumor antigens elicit a potent, effective, and anti-tolerogenic CD8⁺ T cell immunity against the heterologous antigen. The immune response is induced through the production of EVs incorporating Nef^mut-derivatives released by muscle cells. In the perspective of a possible translation into the clinic of the Nef^mut-based vaccine platform, we aimed at increasing its safety profile by identifying the minimal part of Nef^mut retaining the EV-anchoring protein property. We found that a C-terminal deletion of 29-amino acids did not affect the ability of Nef^mut to associate with EVs. The EV-anchoring function was also preserved when antigens from both HPV16 (i.e., E6 and E7) and SARS-CoV-2 (i.e., S1 and S2) were fused to its C-terminus. Most important, the Nef^mut C-terminal deletion did not affect levels, quality, and diffusion at distal sites of the antigen-specific CD8⁺ T immunity. We concluded that the C-terminal Nef^mut truncation does not influence stability, EV-anchoring, and CD8⁺ T cell immunogenicity of the fused antigen. Hence, the C-terminal deleted Nef^mut may represent a safer alternative to the full-length isoform for vaccines in humans.

Simultaneous CD8+ T-Cell Immune Response against SARS-Cov-2 S, M, and N Induced by Endogenously Engineered Extracellular Vesicles in Both Spleen and Lungs

Most advanced vaccines against severe acute respiratory syndrome coronavirus (SARS-CoV)-2 are designed to induce antibodies against spike (S) protein. Differently, we developed an original strategy to induce CD8+ T cytotoxic lymphocyte (CTL) immunity based on in vivo engineering of extracellular vesicles (EVs). This is a new vaccination approach based on intramuscular injection of DNA expression vectors coding for a biologically inactive HIV-1 Nef protein (Nefmut) with an unusually high efficiency of incorporation into EVs, even when foreign polypeptides are fused to its C-terminus. Nanovesicles containing Nefmut-fused antigens released by muscle cells can freely circulate into the body and are internalized by antigen-presenting cells. Therefore, EV-associated antigens can be cross-presented to prime antigen-specific CD8+ T-cells. To apply this technology to a strategy of anti-SARS-CoV-2 vaccine, we designed DNA vectors expressing the products of fusion between Nefmut and different viral antigens, namely N- and C-terminal moieties of S (referred to as S1 and S2), M, and N. We provided evidence that all fusion products are efficiently uploaded in EVs. When the respective DNA vectors were injected in mice, a strong antigen-specific CD8+ T cell immunity became detectable in spleens and, most important, in lung airways. Co-injection of DNA vectors expressing the diverse SARS-CoV-2 antigens resulted in additive immune responses in both spleen and lungs. Hence, DNA vectors expressing Nefmut-based fusion proteins can be proposed for new anti-SARS-CoV-2 vaccine strategies.