Extracellular Vesicles in Viral Pathogenesis: A Case of Dr. Jekyll and Mr. Hyde

Emerging mechanisms of obesity-associated immune dysfunction

Obesity is associated with a wide range of complications, including type 2 diabetes mellitus, cardiovascular disease, hypertension and nonalcoholic fatty liver disease. Obesity also increases the incidence and progression of cancers, autoimmunity and infections, as well as lowering vaccine responsiveness. A unifying concept across these differing diseases is dysregulated immunity, particularly inflammation, in response to metabolic overload. Herein, we review emerging mechanisms by which obesity drives inflammation and autoimmunity, as well as impairing tumour immunosurveillance and the response to infections. Among these mechanisms are obesity-associated changes in the hormones that regulate immune cell metabolism and function and drive inflammation. The cargo of extracellular vesicles derived from adipose tissue, which controls cytokine secretion from immune cells, is also dysregulated in obesity, in addition to impairments in fatty acid metabolism related to inflammation. Furthermore, an imbalance exists in obesity in the biosynthesis and levels of polyunsaturated fatty acid-derived oxylipins, which control a range of outcomes related to inflammation, such as immune cell chemotaxis and cytokine production. Finally, there is a need to investigate how obesity influences immunity using innovative model systems that account for the heterogeneous nature of obesity in the human population.

Extracellular vesicles as therapeutics for inflammation and infection

Extracellular vesicles (EVs) are an emergent next-generation biotechnology with broad application potential. In particular, immunomodulatory bioactivity of EVs leading to anti-inflammatory effects is well-characterized. Cell source and culture conditions are critical determinants of EV therapeutic efficacy, while augmenting EV anti-inflammatory bioactivity via diverse strategies, including RNA cargo loading and protein surface display, has proven effective. Yet, translational challenges remain. Additionally, the potential of direct antimicrobial EV functionality has only recently emerged but offers the possibility of overcoming drug-resistant bacterial and fungal infections through novel, multifactorial mechanisms. As discussed herein, these application areas are brought together by the potential for synergistic benefit from technological developments related to EV cargo loading and biomanufacturing.

Extracellular Vesicles: A Novel Mode of Viral Propagation Exploited by Enveloped and Non-Enveloped Viruses

Extracellular vesicles (EVs) are small membrane-enclosed structures that have gained much attention from researchers across varying scientific fields in the past few decades. Cells secrete diverse types of EVs into the extracellular milieu which include exosomes, microvesicles, and apoptotic bodies. These EVs play a crucial role in facilitating intracellular communication via the transport of proteins, lipids, DNA, rRNA, and miRNAs. It is well known that a number of viruses hijack several cellular pathways involved in EV biogenesis to aid in their replication, assembly, and egress. On the other hand, EVs can also trigger host antiviral immune responses by carrying immunomodulatory molecules and viral antigens on their surface. Owing to this intricate relationship between EVs and viruses, intriguing studies have identified various EV-mediated viral infections and interrogated how EVs can alter overall viral spread and longevity. This review provides a comprehensive overview on the EV-virus relationship, and details various modes of EV-mediated viral spread in the context of clinically relevant enveloped and non-enveloped viruses.

Intercellular Transport of Viral Proteins

Viruses are vehicles to exchange genetic information and proteins between cells and organisms by infecting their target cells either cell-free, or depending on cell-cell contacts. Several viruses like certain retroviruses or herpesviruses transmit by both mechanisms. However, viruses have also evolved the properties to exchange proteins between cells independent of viral particle formation. This exchange of viral proteins can be directed to target cells prior to infection to interfere with restriction factors and intrinsic immunity, thus, making the target cell prone to infection. However, also bystander cells, e.g. immune cell populations, can be targeted by viral proteins to dampen antiviral responses. Mechanistically, viruses exploit several routes of cell-cell communication to exchange viral proteins like the formation of extracellular vesicles or the formation of long-distance connections like tunneling nanotubes. Although it is known that viral nucleic acids can be transferred between cells as well, this chapter concentrates on viral proteins of human pathogenic viruses covering all Baltimore classes and summarizes our current knowledge on intercellular transport of viral proteins between cells.

Curcumin-Loaded Macrophage-Derived Exosomes Effectively Improve Wound Healing

This study aims to investigate the potential therapeutic effect of exosomes derived from macrophages loaded with curcumin (Exos-cur) on the healing of diabetic wounds. As a new type of biomaterial, Exos-cur has better stability, anti-inflammation, and antioxidation biological activity. In in vitro experiments, Exos-cur can promote the proliferation, migration, and angiogenesis of HUVECs (human umbilical vein endothelial cells) while reducing the ROS (reactive oxygen species) produced by HUVECs induced by high glucose, regulating the mitochondrial membrane potential, reducing cell oxidative damage, and inhibiting oxidative stress and inflammation. In the in vivo experiment, the Exos-cur treatment group had an increased percentage of wound closure and contraction compared with the diabetic wound control group. Hematoxylin-eosin staining (HE) and Masson staining showed that the Exos-cur treatment group had more advanced re-epithelialization, and the generated mature granulation tissue was rich in a large number of capillaries and newly deposited collagen fibers. Western blot and immunofluorescence analyses showed that Exos-cur can inhibit inflammation by activating the Nrf2/ARE pathway, upregulate the expression of wound healing-related molecules, promote angiogenesis, and accelerate wound healing in diabetic rats. These results show that Exos-cur has a good therapeutic effect on diabetic skin defects and provide experimental evidence for the potential clinical benefits of Exos-cur.

Recent updates on liposomal formulations for detection, prevention and treatment of coronavirus disease (COVID-19)

The unprecedented outbreak of severe acute respiratory syndrome-2 (SARS-CoV-2) worldwide has rendered it one of the most notorious pandemics ever documented in human history. As of November 2022, nearly 626 million cases of infection and over 6.6 million deaths have been reported globally. The scientific community has made significant progress in therapeutics and prevention for the management of coronavirus disease (COVID-19), including the development of vaccines and antiviral agents such as monoclonal antibodies and antiviral drugs. Although many advancements and a plethora of positive results have been obtained and global restrictions are being uplifted, obstacles in efficiently delivering these therapies, such as their rapid clearance, suboptimal biodistribution, and toxicity to organs, have yet to be addressed. To address these drawbacks, researchers have attempted applying nanotechnology-based formulations. Here, we summarized the recent data about COVID-19, its emergence, pathophysiology and life cycle, diagnosis, and currently-available medications. Subsequently, we discussed the progress in lipid nanocarriers, such as liposomes in infection detection and control. This review provides critical insights into the design of the latest liposomal-based formulations for tackling the barriers to detecting, preventing, and treating SARS-CoV-2.

Construction of Yeast Display Libraries for Selection of Antigen-Binding Variants of Large Extracellular Loop of CD81, a Major Surface Marker Protein of Extracellular Vesicles

Over the last two decades, yeast display methodology has served as a popular tool for discovery, humanization, stability improvement, and affinity maturation of antibodies and antibody fragments, but also for development of diverse non-antibody protein scaffolds towards the ability of antigen recognition. Yeast display is particularly well suited for multiparametric analysis of properties of derivatized proteins, allowing the evolution of most diverse protein structures into antigen binding entities with favorable expression, stability, and folding properties. Here we present the methodological basics of a novel yeast display-based approach for the functionalization of the large extracellular loop of CD81 into a de novo antigen binding unit. CD81 is intrinsically overrepresented on the surface of extracellular vesicles (EVs), naturally occurring nanoparticle units that act as cell-to-cell messengers by delivering their intracellular cargo from the source cell into a recipient cell. This amazing feature makes them of highest biotechnological interest, yet methods for their targeted delivery are still in their infancy. As a novel approach for introducing EV surface modifications enabling specific target cell recognition and internalization, we have prepared yeast display libraries of CD81 large extracellular loop mutants, which are selected towards specific antigen binding and resulting mutants conveniently clicked into the full-length EV surface protein. Resulting EVs display wild-type-like characteristics regarding the expression level and distribution of recombinant proteins and are hence promising therapeutic tools.

Extracellular vesicles in obesity and its associated inflammation

Obesity is characterized by low-grade, chronic inflammation, which promotes insulin resistance and diabetes. Obesity can lead to the development and progression of many autoimmune diseases, including inflammatory bowel disease, psoriasis, psoriatic arthritis, rheumatoid arthritis, thyroid autoimmunity, and type 1 diabetes mellitus (T1DM). These diseases result from an alteration of self-tolerance by promoting pro-inflammatory immune response by lowering numbers of regulatory T cells (T_regs), increasing Th1 and Th17 immune responses, and inflammatory cytokine production. Therefore, understanding the immunological changes that lead to this low-grade inflammatory milieu becomes crucial for the development of therapies that suppress the risk of autoimmune diseases and other immunological conditions. Cells generate extracellular vesicles (EVs) to eliminate cellular waste as well as communicating the adjacent and distant cells through exchanging the components (genetic material [DNA or RNA], lipids, and proteins) between them. Immune cells and adipocytes from individuals with obesity and a high basal metabolic index (BMI) produce also release exosomes (EXOs) and microvesicles (MVs), which are collectively called EVs. These EVs play a crucial role in the development of autoimmune diseases. The current review discusses the immunological dysregulation that leads to inflammation, inflammatory diseases associated with obesity, and the role played by EXOs and MVs in the induction and progression of this devastating conditi8on.

mRNA Trafficking in the Nervous System: A Key Mechanism of the Involvement of Activity-Regulated Cytoskeleton-Associated Protein (Arc) in Synaptic Plasticity

Synaptic activity mediates information storage and memory consolidation in the brain and requires a fast de novo synthesis of mRNAs in the nucleus and proteins in synapses. Intracellular localization of a protein can be achieved by mRNA trafficking and localized translation. Activity-regulated cytoskeleton-associated protein (Arc) is a master regulator of synaptic plasticity and plays an important role in controlling large signaling networks implicated in learning, memory consolidation, and behavior. Transcription of the Arc gene may be induced by a short behavioral event, resulting in synaptic activation. Arc mRNA is exported into the cytoplasm and can be trafficked into the dendrite of an activated synapse where it is docked and translated. The structure of Arc is similar to the viral GAG (group-specific antigen) protein, and phylogenic analysis suggests that Arc may originate from the family of Ty3/Gypsy retrotransposons. Therefore, Arc might evolve through “domestication” of retroviruses. Arc can form a capsid-like structure that encapsulates a retrovirus-like sentence in the 3′-UTR (untranslated region) of Arc mRNA. Such complex can be loaded into extracellular vesicles and transported to other neurons or muscle cells carrying not only genetic information but also regulatory signals within neuronal networks. Therefore, Arc mRNA inter- and intramolecular trafficking is essential for the modulation of synaptic activity required for memory consolidation and cognitive functions. Recent studies with single-molecule imaging in live neurons confirmed and extended the role of Arc mRNA trafficking in synaptic plasticity.

Mesenchymal Stem Cell Derived Extracellular Vesicles for Repairing the Neurovascular Unit after Ischemic Stroke

Ischemic stroke is a debilitating disease and one of the leading causes of long-term disability. During the early phase after ischemic stroke, the blood-brain barrier (BBB) exhibits increased permeability and disruption, leading to an influx of immune cells and inflammatory molecules that exacerbate the damage to the brain tissue. Mesenchymal stem cells have been investigated as a promising therapy to improve the recovery after ischemic stroke. The therapeutic effects imparted by MSCs are mostly paracrine. Recently, the role of extracellular vesicles released by these MSCs have been studied as possible carriers of information to the brain. This review focuses on the potential of MSC derived EVs to repair the components of the neurovascular unit (NVU) controlling the BBB, in order to promote overall recovery from stroke. Here, we review the techniques for increasing the effectiveness of MSC-based therapeutics, such as improved homing capabilities, bioengineering protein expression, modified culture conditions, and customizing the contents of EVs. Combining multiple techniques targeting NVU repair may provide the basis for improved future stroke treatment paradigms.

Why Cells and Viruses Cannot Survive without an ESCRT

Intracellular organelles enwrapped in membranes along with a complex network of vesicles trafficking in, out and inside the cellular environment are one of the main features of eukaryotic cells. Given their central role in cell life, compartmentalization and mechanisms allowing their maintenance despite continuous crosstalk among different organelles have been deeply investigated over the past years. Here, we review the multiple functions exerted by the endosomal sorting complex required for transport (ESCRT) machinery in driving membrane remodeling and fission, as well as in repairing physiological and pathological membrane damages. In this way, ESCRT machinery enables different fundamental cellular processes, such as cell cytokinesis, biogenesis of organelles and vesicles, maintenance of nuclear–cytoplasmic compartmentalization, endolysosomal activity. Furthermore, we discuss some examples of how viruses, as obligate intracellular parasites, have evolved to hijack the ESCRT machinery or part of it to execute/optimize their replication cycle/infection. A special emphasis is given to the herpes simplex virus type 1 (HSV-1) interaction with the ESCRT proteins, considering the peculiarities of this interplay and the need for HSV-1 to cross both the nuclear-cytoplasmic and the cytoplasmic-extracellular environment compartmentalization to egress from infected cells.