A bio-nanocapsule containing envelope protein domain III of Japanese encephalitis virus protects mice against lethal Japanese encephalitis virus infection

Self-assembling protein nanocages for modular enzyme assembly by orthogonal bioconjugation

The wide variety of enzymatic pathways that can benefit from enzyme scaffolding is astronomical. While enzyme co-localization based on protein, DNA, and RNA scaffolds has been reported, we still lack scaffolds that offer well-defined and uniform three-dimensional structures for enzyme organization. Here we reported a new approach for protein co-localization using naturally occurring protein nanocages as a scaffold. Two different nanocages, the 25 nm E2 and the 34 nm heptatitis B virus, were used to demonstrate the successfully co-localization of the endoglucanase CelA and cellulose binding domain using the robust SpyTag/SpyCatcher bioconjugation chemistry. Because of the simplicity of the assembly, this strategy is useful not only for in vivo enzyme cascading but also the potential for in vivo applications as well.

Nanoparticles as Vaccines to Prevent Arbovirus Infection: A Long Road Ahead

Arthropod-borne viruses (arboviruses) are a significant public health problem worldwide. Vaccination is considered one of the most effective ways to control arbovirus diseases in the human population. Nanoparticles have been widely explored as new vaccine platforms. Although nanoparticles' potential to act as new vaccines against infectious diseases has been identified, nanotechnology's impact on developing new vaccines to prevent arboviruses is unclear. Thus, we used a comprehensive bibliographic survey to integrate data concerning the use of diverse nanoparticles as vaccines against medically important arboviruses. Our analysis showed that considerable research had been conducted to develop and evaluate nanovaccines against Chikungunya virus, Dengue virus, Zika virus, Japanese encephalitis virus, and West Nile virus. The main findings indicate that nanoparticles have great potential for use as a new vaccine system against arboviruses. Most of the studies showed an increase in neutralizing antibody production after mouse immunization. Nevertheless, even with significant advances in this field, further efforts are necessary to address the nanoparticles' potential to act as a vaccine against these arboviruses. To promote advances in the field, we proposed a roadmap to help researchers better characterize and evaluate nanovaccines against medically important arboviruses.

[DDS Nanocarriers Mimicking Early Infection Machinery of Viruses]

Viruses are natural nanocarriers that deliver various biological cargos, such as DNA, RNA, and proteins. We are developing a new nanocarrier by mimicking the early mechanism of infection by hepatitis B virus (HBV). When the HBV envelope L protein is overexpressed in yeast cells, hollow nanoparticles displaying L proteins are synthesized. This nanoparticle, namely a bio-nanocapsule (BNC), can specifically attach to, and then internalize into, human hepatic cells by implementing the early mechanism of infection by HBV. In this review, we outlined the cellular uptake mechanism of HBV/BNC linking to L protein function. The L protein contains several functional domains in the pre-S1 region, including the fusogenic domain and the heparin-binding domain. The fusogenic domain corresponding to the pre-S1(9-24) region is responsible for the low pH-dependent membrane fusion of BNC. The heparin-binding domain corresponding to the pre-S1(30-42) region has a strong affinity to heparin as compared to that of known heparin-binding peptides, such as vitronectin and gp120 in human immunodeficiency virus-1. This heparin-binding domain binds to heparan sulfate proteoglycan (HSPG) at the cell surface of human hepatic cells. These functional domains are present in any virus, thus, these viral envelope proteins are very useful in designing novel DDS nanocarriers.

CD11c-specific bio-nanocapsule enhances vaccine immunogenicity by targeting immune cells

BACKGROUND

Various nanocarriers have been used to deliver subunit vaccines specifically to dendritic cells (DCs) for the improvement of immunogenicity. However, due to their insufficient DC priming ability, these vaccines could not elicit effective innate immunity. We have recently developed a DC-targeting bio-nanocapsule (BNC) by displaying anti-CD11c IgGs via protein A-derived IgG Fc-binding Z domain on the hepatitis B virus envelope L protein particles (α-DC-ZZ-BNC).

RESULTS

After the chemical modification with antigens (Ags), the α-DC-ZZ-BNC-Ag complex could deliver Ags to DCs efficiently, leading to effective DC maturation and efficient endosomal escape of Ags, followed by Ag-specific T cell responses and IgG productions. Moreover, the α-DC-ZZ-BNC modified with Japanese encephalitis virus (JEV) envelope-derived D3 Ags could confer protection against 50-fold lethal dose of JEV injection on mice.

CONCLUSION

The α-DC-ZZ-BNC-Ag platform was shown to induce humoral and cellular immunities effectively without any adjuvant.

Bio-nanocapsules displaying various immunoglobulins as an active targeting-based drug delivery system

The bio-nanocapsule (BNC) is an approximately 30-nm particle comprising the hepatitis B virus (HBV) envelope L protein and a lipid bilayer. The L protein harbors the HBV-derived infection machinery; therefore, BNC can encapsulate payloads such as drugs, nucleic acids, and proteins and deliver them into human hepatocytes specifically in vitro and in vivo. To diversify the possible functions of BNC, we generated ZZ-BNC by replacing the domain indispensable for the human hepatotrophic property of BNC (N-terminal region of L protein) with the tandem form of the IgG Fc-binding Z domain of Staphylococcus aureus protein A. Thus, the ZZ-BNC is an active targeting-based drug delivery system (DDS) nanocarrier that depends on the specificity of the IgGs displayed. However, the Z domain limits the animal species and subtypes of IgGs that can be displayed on ZZ-BNC. In this study, we introduced into BNC an Ig κ light chain-binding B1 domain of Finegoldia magna protein L (protein-L B1 domain) and an Ig Fc-binding C2 domain of Streptococcus species protein G (protein-G C2 domain) to produce LG-BNC. The LL-BNC was constructed in a similar way using a tandem form of the protein-L B1 domain. Both LG-BNC and LL-BNC could display rat IgGs, mouse IgG1, human IgG3, and human IgM, all of which not binding to ZZ-BNC, and accumulate in target cells in an antibody specificity-dependent manner. Thus, these BNCs could display a broad spectrum of Igs, significantly improving the prospects for BNCs as active targeting-based DDS nanocarriers.

STATEMENT OF SIGNIFICANCE

We previously reported that ZZ-BNC, bio-nanocapsule deploying the IgG-binding Z domain of protein A, could display cell-specific antibody in an oriented immobilization manner, and act as an active targeting-based DDS nanocarrier. Since the Z domain can only bind to limited types of Igs, we generated BNCs deploying other Ig-binding domains: LL-BNC harboring the tandem form of Ig-binding domain of protein L, and LG-BNC harboring the Ig binding domains of protein L and protein G sequentially. Both BNCs could display a broader spectrum of Igs than does the ZZ-BNC. When these BNCs displayed anti-CD11c IgG or anti-EGFR IgG, both of which cannot bind to Z domain, they could bind to and then enter their respective target cells.

Development of a virus-mimicking nanocarrier for drug delivery systems: The bio-nanocapsule

As drug delivery systems, nanocarriers should be capable of executing the following functions: evasion of the host immune system, targeting to the diseased site, entering cells, escaping from endosomes, and releasing payloads into the cytoplasm. Since viruses perform some or all of these functions, they are considered naturally occurring nanocarriers. To achieve biomimicry of the hepatitis B virus (HBV), we generated the "bio-nanocapsule" (BNC)-which deploys the human hepatocyte-targeting domain, fusogenic domain, and polymerized-albumin receptor domain of HBV envelope L protein on its surface-by overexpressing the L protein in yeast cells. BNCs are capable of delivering various payloads to the cytoplasm of human hepatic cells specifically in vivo, which is achieved via formation of complexes with various materials (e.g., drugs, nucleic acids, and proteins) by electroporation, fusion with liposomes, or chemical modification. In this review, we describe BNC-related technology, discuss retargeting strategies for BNCs, and outline other virus-inspired nanocarriers.

Sortase A-mediated multi-functionalization of protein nanoparticles

A new strategy was developed to create multi-functionalizaton of protein nanoparticles using Sortase A-mediated ligation, resulting in modified protein nanoparticles that are both thermally responsive and catalytic active.