Displaying and delivering viral membrane antigens via WW domain-activated extracellular vesicles

Cell-Free Expression of Nipah Virus Transmembrane Proteins for Proteoliposome Vaccine Design

Membrane proteins expressed on the surface of enveloped viruses are potent antigens in a vaccine, yet are difficult to produce and present due to their instability without a lipid scaffold. Current vaccination strategies that incorporate viral membrane proteins, such as live attenuated viruses, inactivated viruses, or extracellular vesicles, have limitations including lengthy production time, poor immunogenicity, extensive processing steps, and/or poor stability. Cell-free protein synthesis of viral membrane proteins offers a rapid, one-step method to assemble vaccine nanoparticles via cotranslational folding of membrane proteins into nanoscale liposomes. Here, we develop a vaccine candidate for the deadly Nipah virus (NiV), a highly lethal virus listed by the World Health Organization as a priority pathogen, by cell-free expressing two full-length Nipah virus membrane proteins. We demonstrate that both NiV fusion protein (NiV F) and NiV glycoprotein (NiV G) can be expressed and cotranslationally integrated into liposomes and that they fold into their native conformation. We find that the removal of a signal peptide sequence and the alteration of liposome lipid composition improve viral membrane protein incorporation. Furthermore, a lipid adjuvant, monophosphoryl lipid A (MPLA), can be readily added to liposomes without disrupting protein-vesicle loading or protein folding conformations. Finally, we demonstrate that our generated liposomal formulations lead to enhanced humoral responses in mice compared to empty and single-protein controls. This work establishes a platform to quickly assemble and present membrane antigens as multivalent vaccines that will enable a rapid response to the broad range of emerging pathogenic threats.

Advancements in the conservation of the conformational epitope of membrane protein immunogens

Generating antibodies targeting native membrane proteins presents various challenges because these proteins are often embedded in the lipid bilayer, possess various extracellular and intracellular domains, and undergo post-translational modifications. These properties of MPs make it challenging to preserve their stable native conformations for immunization or antibody generation outside of the membranes. In addition, MPs are often hydrophobic due to their membrane-spanning regions, making them difficult to solubilize and purify in their native form. Therefore, employing purified MPs for immunogen preparation may result in denaturation or the loss of native structure, rendering them inadequate for producing antibodies recognizing native conformations. Despite these obstacles, various new approaches have emerged to address these problems. We outline recent advancements in designing and preparing immunogens to produce antibodies targeting MPs. Strategies outlined here are relevant for producing antibodies for research, diagnostics, and therapies and designing immunogens for vaccination purposes.

Inverted HA-EV immunization elicits stalk-specific influenza immunity and cross-protection in mice

Enhancing protective immunity in the respiratory tract is crucial to combat influenza infection and transmission. Developing mucosal universal influenza vaccines requires effective delivery platforms to overcome the respiratory mucosal barrier and stimulate appropriate innate immune reactions, thereby bridging adaptive immune responses with minimal necessary inflammation. Meanwhile, the vaccine platforms must be biocompatible. This study employed cell-derived extracellular vesicles (EVs) as a mucosal universal influenza vaccine platform. By conjugating influenza hemagglutinin (HA) onto EV surfaces through HA-receptor interaction, we achieved an upside-down (inverted) influenza HA configuration that exposed the conserved HA stalk region while partially hiding the globular head domain. Intranasal immunization with the resulting EVs induced robust HA stalk- and virus-specific serum antibody and mucosal immune responses in mice, protecting against heterologous virus infection. Notably, EVs derived from the lung epithelial cell line A549 induced superior cross-reactive antibodies and enhanced protection upon intranasal immunization. EVs conjugating multivalent HA elicited broadly cross-reactive antibody and cellular responses against different influenza strains. Our results demonstrated that EVs conjugating multiple inverted HAs represented an effective strategy for developing a mucosal universal influenza vaccine.

Efficient and Rapid Enrichment of Extracellular Vesicles Using DNA Nanotechnology-Enabled Synthetic Nano-Glue

Swift and efficient enrichment and isolation of extracellular vesicles (EVs) are crucial for enhancing precise disease diagnostics and therapeutic strategies, as well as elucidating the complex biological roles of EVs. Conventional methods of isolating EVs are often marred by lengthy and laborious processes. In this study, we introduce an innovative approach to enrich and isolate EVs by leveraging the capabilities of DNA nanotechnology. We have developed a novel multivalent cholesterol-modified paranemic crossover DNA (PX-DNA-chol) construct, which is a four-stranded DNA structure containing adjacent double helices intertwined with their local helix axes parallel and serves as an effective synthetic nano-glue. This construct promotes the rapid coalescence of nanoscale EVs into clusters of micrometer scale, thereby streamlining their enrichment. Utilizing a conventional low-speed centrifuge, this intriguing methodology achieves a rapid concentration of EVs within minutes, bypassing the laborious and high-speed centrifugation steps typically required. The quality of EVs isolated by our technique is comparable to that obtained through ultracentrifugation methods. Given these advancements, our PX-DNA-chol-facilitated EVs enrichment protocol is poised to advance the field of EVs research, providing a robust and accessible tool for in-depth studies of EVs.

Extracellular vesicle surface display of αPD-L1 and αCD3 antibodies via engineered late domain-based scaffold to activate T-cell anti-tumor immunity

Extracellular vesicles (EVs) are emerging as promising carriers for the delivery of therapeutic biologics. Genetic engineering represents a robust strategy for loading proteins of interest into EVs. Identification of EV-enriched proteins facilitates protein cargo loading efficiency. Many EV-enriched proteins are sorted into EVs via an endosomal sorting complex required for transport (ESCRT)-dependent pathway. In parallel, viruses hijack this EV biosynthesis machinery via conserved late domain motifs to promote egress from host cells. Inspired by the similarity of biogenesis between EVs and viruses, we developed a synthetic, Late domain-based EV scaffold protein that enables the display of a set of single chain variable fragments (scFvs) on the EV surface. We named this scaffold the Late domain-based exosomal antibody surface display platform (LEAP). We applied the LEAP scaffold to reprogramme HEK293T cell-derived EVs to elicit T-cell anti-tumor immunity by simultaneously displaying αPD-L1 and αCD3 scFvs on the EV surface (denoted as αPD-L1×αCD3 bispecific T-cell engaging exosomes, BiTExos). We demonstrated that αPD-L1×αCD3 BiTExos actively redirected T cells to bind to PD-L1+ tumor cells, promoting T-cell activation, proliferation and tumoricidal cytokine production. Furthermore, the αPD-L1×αCD3 BiTExos promoted T-cell infiltration into the tumor microenvironment to mitigate the tumor burden in vivo. Our study suggested that the LEAP scaffold may serve as a platform for EV surface display and could be applied for a broad range of EV-based biomedical applications.

The Discovery of Extracellular Vesicles and Their Emergence as a Next-Generation Therapy

From their humble discovery as cellular debris to cementing their natural capacity to transfer functional molecules between cells, the long-winded journey of extracellular vesicles (EVs) now stands at the precipice as a next-generation cell-free therapeutic tool to revolutionize modern-day medicine. This perspective provides a snapshot of the discovery of EVs to their emergence as a vibrant field of biology and the renaissance they usher in the field of biomedical sciences as therapeutic agents for cardiovascular pathologies. Rapid development of bioengineered EVs is providing innovative opportunities to overcome biological challenges of natural EVs such as potency, cargo loading and enhanced secretion, targeting and circulation half-life, localized and sustained delivery strategies, approaches to enhance systemic circulation, uptake and lysosomal escape, and logistical hurdles encompassing scalability, cost, and time. A multidisciplinary collaboration beyond the field of biology now extends to chemistry, physics, biomaterials, and nanotechnology, allowing rapid development of designer therapeutic EVs that are now entering late-stage human clinical trials.

Rapid and in-depth proteomic profiling of small extracellular vesicles for ultralow samples

The integration of robust single-pot, solid-phase-enhanced sample preparation with powerful liquid chromatography-tandem mass spectrometry (LC-MS/MS) is routinely used to define the extracellular vesicle (EV) proteome landscape and underlying biology. However, EV proteome studies are often limited by sample availability, requiring upscaling cell cultures or larger volumes of biofluids to generate sufficient materials. Here, we have refined data independent acquisition (DIA)-based MS analysis of EV proteome by optimizing both protein enzymatic digestion and chromatography gradient length (ranging from 15 to 44 min). Our short 15 min gradient length can reproducibly quantify 1168 (from as little as 500 pg of EV peptides) to 3882 proteins groups (from 50 ng peptides), including robust quantification of 22 core EV marker proteins. Compared to data-dependent acquisition, DIA achieved significantly greater EV proteome coverage and quantification of low abundant protein species. Moreover, we have achieved optimal magnetic bead-based sample preparation tailored to low quantities of EVs (0.5 to 1 µg protein) to obtain sufficient peptides for MS quantification of 1908-2340 protein groups. We demonstrate the power and robustness of our pipeline in obtaining sufficient EV proteomes granularity of different cell sources to ascertain known EV biology. This underscores the capacity of our optimised workflow to capture precise and comprehensive proteome of EVs, especially from ultra-low sample quantities (sub-nanogram), an important challenge in the field where obtaining in-depth proteome information is essential.

Significance of VLPs in Vlp-circRNA vaccines: a vaccine candidate or delivery vehicle?

Circular RNAs (circRNAs) are a class of single-stranded RNAs with a closed loop lacking 5' and 3' ends. These circRNAs are translatable and, therefore, have a potential in developing vaccine. CircRNA vaccines have been shown to be more stable, safe, easy to manufacture and scale-up production when compared to mRNA vaccines. However, these vaccines also suffer from several drawbacks such as low circularization efficiency for longer RNA precursor and usage of lipid nano particles (LNPs) in their delivery. LNPs have been shown to require large amounts of RNA due to their indirect delivery from endosome to cytosol. Besides, individual components of LNPs provide reactogenicity. Usage of virus like particles (VLPs) can improve the increased production and targeted delivery of circRNA vaccines and show no reactogenicity. Moreover, VLPs has also been used to produce vaccines against several diseases such as hepatitis C virus (HCV) etc. In this article, we will discuss about the methods used to enhance synthesis or circularization efficiency of circRNA. Moreover, we will also discuss about the significance of VLPs as the delivery vehicle for circRNA and their possible usage as the dual vaccine.

Trick-or-Trap: Extracellular Vesicles and Viral Transmission

Extracellular vesicles (EVs) are lipid membrane-enclosed particles produced by most cells, playing important roles in various biological processes. They have been shown to be involved in antiviral mechanisms such as transporting antiviral molecules, transmitting viral resistance, and participating in antigen presentation. While viral transmission was traditionally thought to occur through independent viral particles, the process of viral infection is complex, with multiple barriers and challenges that viruses must overcome for successful infection. As a result, viruses exploit the intercellular communication pathways of EVs to facilitate cluster transmission, increasing their chances of infecting target cells. Viral vesicle transmission offers two significant advantages. Firstly, it enables the collective transmission of viral genomes, increasing the chances of infection and promoting interactions between viruses in subsequent generations. Secondly, the use of vesicles as vehicles for viral transmission provides protection to viral particles against environmental factors, while also expanding the cell tropism allowing viruses to reach cells in a receptor-independent manner. Understanding the role of EVs in viral transmission is crucial for comprehending virus evolution and developing innovative antiviral strategies, therapeutic interventions, and vaccine approaches.