Arthropod EVs mediate dengue virus transmission through interaction with a tetraspanin domain containing glycoprotein Tsp29Fb

Fibrinogen-like 2 in tumor-associated macrophage-derived extracellular vesicles shapes an immunosuppressive microenvironment in colorectal liver metastases by promoting tumor stemness and neutrophil extracellular traps formation

Investigating the mechanisms underlying the development of an immunosuppressive microenvironment within colorectal liver metastases (CRLM) is important for identifying synergistic targets for immunotherapy. The regulatory role of tumor-associated macrophage-derived extracellular vesicles (TAM-EVs) in the immune microenvironment of CRLM has not yet been fully explored. Here, we found that TAM-EVs shaped the immunosuppressive microenvironment at the invasive front in murine CRLM models, thus dampening anti-PD-1 immunotherapy. This environment is characterized by an increased tumor stemness potential and abundant neutrophil extracellular traps (NETs) formation. Mechanistically, TAM-EVs-derived fibrinogen-like 2 (FGL2) interacts with the FCGR2B receptor in tumor cells, which further activates a p-STAT3/IL-1β positive feedback loop to increase the stemness potential of cancer cells, whereas IL-1β mediates the communication between cancer cells and neutrophils. The use of an anti-IL-1β monoclonal antibody can reduce NETs production and synergize with anti-PD-1 immunotherapy, which offers clinical translational significance for CRLM therapy. The FGL2/p-STAT3/IL-1β loop correlates with an immunosuppressive microenvironment and poor prognosis in human patients with CRLM. Our results revealed the potential of enhancing the efficacy of immunotherapy via the targeted clearance of NETs using anti-IL-1β monoclonal antibodies, which have significant clinical translational value in the treatment of CRLM.

Extracellular vesicles in arbovirus infections: from basic biology to potential clinical applications

Arthropod-borne viruses, or arboviruses, are currently considered a global health threat responsible for potentially severe human diseases. The increased population density, changes in land use and climate change are some of the factors that are contributing to the spread of these infections over the last years. The pathogenesis of these diseases and the mechanisms of interaction with the host, especially those leading to the development of severe forms, are yet to be fully understood. In recent years extracellular vesicles (EVs) have emerged as important players in the inter-cellular and host-pathogen interaction arising a lot of interest also in the field of vector-borne viruses. In this context, EVs seem to play a dual role, by either promoting, thus facilitating, or preventing infection. Many studies are showing how viruses can hijack the vesiculation machinery to escape the host immune response and exploit EVs to sustain their replication and propagation, even though EVs shed by immune cells seem essential to promote antiviral responses. In this manuscript we reviewed the current knowledge regarding the association between EVs and vector-borne viruses, paying particular attention to their possible role in disease transmission and dissemination, as well as to their potential as novel tools for clinical applications, spanning from biomarkers of clinical utility to novel therapeutic options.

Characterization of size distribution and markers for mosquito extracellular vesicles

Extracellular vesicles (EVs) are non-replicative, cell-derived membranous structures secreted by potentially all eukaryotic cells, playing a crucial role in intercellular communication. The study of EVs requires approaches and tools, which have predominantly been developed for mammalian models. Here, we undertook a multimodal characterization of mosquito EVs to provide a technical and knowledge foundation for their study. First, using a cell line model from Aedes aegypti and applying multiple analytical technologies (i.e., NTA, TEM, cryo-EM, and AFM), we observed that mosquito EVs range from 20 to 500 nm in diameter and that a majority are smaller than 100 nm. Second, we showed that smaller EVs are secreted in mosquito saliva. Third, we evaluated the capacity of differential centrifugation and size exclusion chromatography to separate mosquito EVs, revealing the strengths and weaknesses of each technology. Finally, we identified a mosquito homolog of CD63 as an extravesicular marker and the mosquito syntenin as a putative luminal marker. Overall, our results promote the development of tools and approaches for the study of mosquito EVs.

Fluorescence Reduction Neutralization Test: A Novel, Rapid, and Efficient Method for Characterizing the Neutralizing Activity of Antibodies Against Dengue Virus

Dengue virus (DENV) is a major public health threat in the tropical and subtropical regions of the world. Climate change resulting from global warming is further expanding DENV-endemic areas, adversely affecting public life and health. Despite this, no specific drug against DENV has been developed so far. Vaccines and neutralizing antibodies are the chief preventive and therapeutic tools for managing pathogenic infections. The present study describes the development of a novel fluorescence reduction neutralization test (FRNT) for evaluating the neutralizing activity of antibodies against DENV. This FRNT allows rapid antibody screening. In addition, we calculated the FRNT50 to indicate the neutralizing ability of the antibodies. In contrast to the conventional plaque reduction neutralization assay, the FRNT has a shorter experimental cycle, a simpler operation, and greater objectivity, which can greatly accelerate the research and development process of vaccines and antibodies against DENV.

Zika virus modulates arthropod histone methylation for its survival in mosquito cells

Zika virus (ZIKV) is a mosquito-borne human pathogen that causes mild febrile illness in adults and severe neurological complications and microcephaly in newborns. Studies have reported that ZIKV modulates methylation of human and viral RNA critical for its replication in vertebrate cells. In this study, we show that ZIKV modulates mosquito S-adenosyl methionine (SAMe)-synthase, an enzyme involved in the production of SAMe (methyl donor), and histone methylation for its survival in mosquito cells. Reverse transcription quantitative PCR followed by immunoblotting analysis showed increased amounts of SAMe synthase at both RNA and protein levels, respectively, in C6/36 mosquito cells infected with ZIKV at day 1 post infection (p.i.). Increased levels of SAMe was noted upon ZIKV infection at day 1 p.i in mosquito cells. In addition, increased EZH2 histone methyl transferase-like gene transcripts and methylated histone (H3K27me3) levels were evident in mosquito cells upon ZIKV infection. Exogenous addition of SAMe to mosquito cells showed increased ZIKV loads and EZH2 histone methyl transferase-like gene transcript levels. Furthermore, treatment of mosquito cells with EZH2 inhibitor resulted in reduced histone methylation and ZIKV loads. Collectively, our study provides novel information in understanding the importance of SAMe and histone methylation in the survival of ZIKV in its arthropod vector.

A game of hide-and-seek: how extracellular vesicles evade the immune system

Extracellular vesicles (EVs) are heterogeneously sized, cell-derived nanoparticles operating as proficient mediators of intercellular communication. They are produced by normal as well as diseased cells and carry a variety of cargo. While the molecular details of EV biology have been worked out over the past two decades, one question that continues to intrigue many is how are EVs able to evade the phagocytic immune cells while also being effectively internalized by the target cell or tissue. While some of the components that facilitate this process have started to be identified, many mechanisms are yet to be dissected. This review summarises some of the key mechanisms that cancer cell-derived and viral infected cell-derived EVs utilize to evade the immune system. It will discuss the diverse cloaking mechanisms, in the form of membrane proteins and cargo content that these EVs utilize to enhance pathogenesis. Further, it will highlight the different strategies that have been used to design EVs to escape the immune system, thereby increasing their circulation time with no major toxic effects in vivo. An understanding of the potential EV components that allow better immune evasion can be used to bioengineer EVs with better circulation times for therapeutic purposes.

Role of extracellular vesicles in the pathogenesis of mosquito-borne flaviviruses that impact public health

Mosquito-borne flaviviruses represent a public health challenge due to the high-rate endemic infections, severe clinical outcomes, and the potential risk of emerging global outbreaks. Flavivirus disease pathogenesis converges on cellular factors from vectors and hosts, and their interactions are still unclear. Exosomes and microparticles are extracellular vesicles released from cells that mediate the intercellular communication necessary for maintaining homeostasis; however, they have been shown to be involved in disease establishment and progression. This review focuses on the roles of extracellular vesicles in the pathogenesis of mosquito-borne flavivirus diseases: how they contribute to viral cycle completion, cell-to-cell transmission, and cellular responses such as inflammation, immune suppression, and evasion, as well as their potential use as biomarkers or therapeutics (antiviral or vaccines). We highlight the current findings concerning the functionality of extracellular vesicles in different models of dengue virus, Zika virus, yellow fever virus, Japanese encephalitis virus, and West Nile virus infections and diseases. The available evidence suggests that extracellular vesicles mediate diverse functions between hosts, constituting novel effectors for understanding the pathogenic mechanisms of flaviviral diseases.

Extracellular vesicles promote the infection and pathogenicity of Japanese encephalitis virus

Japanese encephalitis virus (JEV) is a neurotropic zoonotic pathogen that poses a serious threat to public health. Currently, there is no specific therapeutic agent available for JEV infection, primarily due to the complexity of its infection mechanism and pathogenesis. Extracellular vesicles (EVs) have been known to play an important role in viral infection, but their specific functions in JEV infection remain unknown. Here, ultracentrifugation in combination with density gradient centrifugation was conducted to purify EVs from JEV-infected cells. The purified EVs were found to be infectious, with virions observed inside the EVs. Furthermore, our study showed the formation process of virion-containing EVs both in vitro and in vivo, which involved the fusion of multivesicular bodies with the cell membrane, leading to the release of virion-containing intraluminal vesicles into the extracellular space. Further studies revealed that EVs played a crucial role in JEV propagation by facilitating viral entry and assembly-release. Furthermore, EVs assisted JEV in evading the neutralizing antibodies and promoted viral capability to cross the blood-brain and placental barriers. Moreover, in vivo experiments demonstrated that EVs were beneficial for JEV infection and pathogenicity. Taken together, our findings highlight the significant contribution of EVs in JEV infection and provide valuable insights into JEV pathogenesis.

Extracellular Vesicles from Mesenchymal Stem Cells: Potential as Therapeutics in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by the accumulation of triglycerides within hepatocytes, which can progress to more severe conditions, such as metabolic dysfunction-associated steatohepatitis (MASH), which may include progressive fibrosis, leading to cirrhosis, cancer, and death. This goal of this review is to highlight recent research showing the potential of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in reducing the key pathogenic pathways of MASLD or MASH. Methods: Relevant published studies were identified using PubMed with one or more of the following search terms: MASLD, MASH, NAFLD, NASH, exosome, extracellular vesicle (EV), therapy, and/or mesenchymal stem cells (MSC). The primary literature were subsequently downloaded and summarized. Results: Using in vitro or in vivo models, MSC-EVs have been found to counteract oxidative stress, a significant contributor to liver injury in MASH, and to suppress disease progression, including steatosis, inflammation, and, in a few instances, fibrosis. Some of these outcomes have been attributed to specific EV cargo components including microRNAs and proteins. Thus, MSC-EVs enriched with these types of molecules may have improved the therapeutic efficacy for MASLD/MASH and represent a novel approach to potentially halt or reverse the disease process. Conclusions: MSC-EVs are attractive therapeutic agents for treating MASLD/MASH. Further studies are necessary to validate the clinical applicability and efficacy of MSC-EVs in human MASH patients, focusing on optimizing delivery strategies and identifying the pathogenic pathways that are targeted by specific EV components.

Neutral sphingomyelinase 2: A promising drug target for CNS disease

Neutral sphingomyelinase 2 (nSMase2), encoded by the SMPD3 gene, is a pivotal enzyme in sphingolipid metabolism, hydrolyzing sphingomyelin to produce ceramide, a bioactive lipid involved in apoptosis, inflammation, membrane structure, and extracellular vesicle (EV) biogenesis. nSMase2 is abundantly expressed in the central nervous system (CNS), particularly in neurons, and its dysregulation is implicated in pathologies such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), prion diseases, and neuroviral diseases. In this review, we discuss the critical role of nSMase2 in the CNS and its involvement in neurological as well as non-neurological diseases. We explore the enzyme's functions in sphingolipid metabolism, its regulatory mechanisms, and the implications of its dysregulation in disease pathogenesis. The chapter highlights the therapeutic potential of pharmacologically targeting nSMase2 with small molecule inhibitors and emphasizes the need for further research to optimize inhibitor specificity and efficacy for clinical applications. By understanding the multifaceted roles of nSMase2, we aim to provide insights into novel therapeutic strategies for treating complex diseases associated with its dysregulation.

The role of small extracellular vesicles in spreading and inhibiting arthropod-borne diseases

Arthropod-borne diseases (ABDs) refer to a group of viral pathogens that affect a wide range of vertebrate hosts, including humans and non-human primates. In addition to being transmitted by mosquitoes and ticks, arthropods can also spread pathogens that cause severe human diseases. On the other hand, extracellular vesicles (EVs) can serve as cross-placental drug delivery vehicles (DDVs) to the fetus and even as antigen-presenting cells (APCs). To this end, the current review aimed to examine the role of small EVs (sEVs) in the transmission and inhibition of arthropod-borne viruses, also known as arboviruses. First, a deeper understanding of the mechanistic aspects of how these vesicles function during insect-pathogen interactions is required. Next, scalability and yield optimization must be addressed while introducing EV-based therapeutics on an industrial scale in order to implement them effectively. Finally,it is recommended to consider that sEV-mediated transfer plays a crucial role in the spread of ABDs. This is because it transfers pathogenic agents between cells within vectors, resulting in subsequent transmission to hosts. Consequently, sEVs provide potential targets for the development of novel therapies that inhibit pathogen replication or reduce arthropod vector populations. Future research in this area should emphasize how these vesicles function within host-vector systems, using advanced imaging techniques - such as high-resolution microscopy (HRM) - and cost-effective methods, in order to produce sufficient quantities for large-scale implementation.

The Yin and the Yang of extracellular vesicles during viral infections

The role of extracellular vesicles (EVs) as key players in the intercellular communication is a subject of growing interest in all areas of physiology and pathophysiology, and the field of viral infections is no exception to the rule. In this review, we focus on the current state of knowledge and remaining gaps regarding the entanglement of viruses and EVs during infections. These two entities share many similarities, mainly due to their intricated biogenesis pathways that are in constant interaction. EVs can promote the replication and dissemination of viruses within the organism, through the dysregulation of their cargo and the modulation of the innate and adaptive immune response that occurs upon infection, but they can also promote the mitigation of viral infections. Here, we examine how viruses hijack EV biogenesis pathways and describe the consequences of dysregulated EV secretion during viral infections, beneficial or not for viruses, revealing the duality of their possible effects.

Small extracellular vesicles from the human endothelial cell line EA.hy 926 exert a self-cell activation and modulate DENV-2 genome replication and infection in naïve endothelial cells

Extracellular vesicles (EVs) play crucial roles in cell signaling and communication, transporting molecules that convey a message to target cells. During infectious diseases, EVs can also carry viral molecules that may contribute to viral spread, as previously reported for dengue virus (DENV). EVs from infected endothelial cells (EC) may harbor viral segments and various sets of molecules that could contribute to endothelial dysfunction during severe dengue. However, the effect of these EVs on non-infected EC (NIC) remain unknown. We characterized the EVs produced by the human EC line EA.hy 926 infected with DENV-2 and assessed their functional impact on polarized NIC. Results showed that infection induced an increased in the quantity of produced EVs, which differentially carried proteins mainly involved in proteosome activity, along with a peptide of the NS5 viral protein. Additionally, all types of Y-RNAs were found, accompanied by a set of differentially loaded microRNAs (miRs) that could regulate DENV genome. Pre-treatment of polarized NIC with small EVs (sEVs) from infected EC before DENV-2 infection caused EC activation, a decrease in viral genome replication, and a protective effect against barrier disruption during the first 24h post-infection, suggesting that sEVs could be important in the pathology or resolution of DENV and a promising therapeutic tool for infectious diseases.

Overview of extracellular vesicles in pathogens with special focus on human extracellular protozoan parasites

Extracellular vesicles (EVs) are lipid-bilayered membrane-delimited particles secreted by almost any cell type, involved in different functions according to the cell of origin and its state. From these, cell to cell communication, pathogen-host interactions and modulation of the immune response have been widely studied. Moreover, these vesicles could be employed for diagnostic and therapeutic purposes, including infections produced by pathogens of diverse types; regarding parasites, the secretion, characterisation, and roles of EVs have been studied in particular cases. Moreover, the heterogeneity of EVs presents challenges at every stage of studies, which motivates research in this area. In this review, we summarise some aspects related to the secretion and roles of EVs from several groups of pathogens, with special focus on the most recent research regarding EVs secreted by extracellular protozoan parasites.

Progress on the Regulation of the Host Immune Response by Parasite-Derived Exosomes

Exosomes are membrane-bound structures released by cells into the external environment that carry a significant amount of important cargo, such as proteins, DNA, RNA, and lipids. They play a crucial role in intercellular communication. Parasites have complex life cycles and can release exosomes at different stages. Exosomes released by parasitic pathogens or infected cells contain parasitic nucleic acids, antigenic molecules, virulence factors, drug-resistant proteins, proteases, lipids, etc. These components can regulate host gene expression across species or modulate signaling pathways, thereby dampening or activating host immune responses, causing pathological damage, and participating in disease progression. This review focuses on the means by which parasitic exosomes modulate host immune responses, elaborates on the pathogenic mechanisms of parasites, clarifies the interactions between parasites and hosts, and provides a theoretical basis and research directions for the prevention and treatment of parasitic diseases.

Aged breast matrix bound vesicles promote breast cancer invasiveness

Aging is one of the inherent risk factors for breast cancer. Although the influence of age-related cellular alterations on breast cancer development has been extensively explored, little is known about the alterations in the aging breast tissue microenvironment, specifically the extracellular matrix (ECM). Here, for the first time in literature, we have identified tissue resident matrix bound vesicles (MBVs) within the healthy mouse breast ECM, investigated and compared their characteristics in young and aged healthy breast tissues, and studied the effects of these MBVs on normal (KTB21) and cancerous (MDA-MB-231) human mammary epithelial cells with respect to the tissue age that they are extracted from. Using vesicle labeling technology, we were able to visualize cellular uptake of the MBVs directly from the native decellularized tissue sections, showing that these MBVs have regulatory roles in the tissue microenvironment. We mimicked the ECM by embedding the MBVs in collagen gels, and showed that MBVs could be taken up by the cells. The miRNA and cytokine profiling showed that MBVs shifted towards a more tumorigenic and invasive phenotype with age, as evidenced by the more pronounced presence of cancer-associated cytokines, and higher expression levels of oncomiRs miR-10b, miR-30e, and miR-210 in MBVs isolated from aged mice. When treated with MBVs or these upregulated factors, KTB21 and MDA-MB-231 cells showed significantly higher motility and invasion compared to untreated controls. Treatment of cells with a cocktail of miRNAs (miR-10b, miR-30e, and miR-210) or with the agonist of adiponectin (AdipoRon), which both were enriched in the aged MBVs, recapitulated the effect of aged MBVs on cells. This study shows for the first time that the MBVs have a regulatory role in the tissue microenvironment and that the MBV contents change towards cancer-promoting upon aging. Studying the effects of MBVs and their cargos on cellular behavior could lead to a better understanding of the critical roles of MBVs played in breast cancer progression and metastasis.

Dissemination of the Flavivirus Subgenomic Replicon Genome and Viral Proteins by Extracellular Vesicles

Extracellular vesicles (EVs) such as exosomes have been shown to play physiological roles in cell-to-cell communication by delivering various proteins and nucleic acids. In addition, several studies revealed that the EVs derived from the cells that are infected with certain viruses could transfer the full-length viral genomes, resulting in EVs-mediated virus propagation. However, the possibility cannot be excluded that the prepared EVs were contaminated with infectious viral particles. In this study, the cells that harbor subgenomic replicon derived from the Japanese encephalitis virus and dengue virus without producing any replication-competent viruses were employed as the EV donor. It was demonstrated that the EVs in the culture supernatants of those cells were able to transfer the replicon genome to other cells of various types. It was also shown that the EVs were incorporated by the recipient cells primarily through macropinocytosis after interaction with CD33 and Tim-1/Tim-4 on HeLa and K562 cells, respectively. Since the methods used in this study are free from contamination with infectious viral particles, it is unequivocally indicated that the flavivirus genome can be transferred by EVs from cell to cell, suggesting that this pathway, in addition to the classical receptor-mediated infection, may play some roles in the viral propagation and pathogenesis.

Extracellular Vesicles in Flaviviridae Pathogenesis: Their Roles in Viral Transmission, Immune Evasion, and Inflammation

The members of the Flaviviridae family are becoming an emerging threat for public health, causing an increasing number of infections each year and requiring effective treatment. The consequences of these infections can be severe and include liver inflammation with subsequent carcinogenesis, endothelial damage with hemorrhage, neuroinflammation, and, in some cases, death. The mechanisms of Flaviviridae pathogenesis are being actively investigated, but there are still many gaps in their understanding. Extracellular vesicles may play important roles in these mechanisms, and, therefore, this topic deserves detailed research. Recent data have revealed the involvement of extracellular vesicles in steps of Flaviviridae pathogenesis such as transmission, immune evasion, and inflammation, which is critical for disease establishment. This review covers recent papers on the roles of extracellular vesicles in the pathogenesis of Flaviviridae and includes examples of clinical applications of the accumulated data.

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.

Zika Virus-Infected Monocyte Exosomes Mediate Cell-to-Cell Viral Transmission

Zika fever is a reemerging arthropod-borne viral disease; however, Zika virus (ZIKV) can be transmitted by other, non-vector means. Severe Zika fever is characterized by neurological disorders, autoimmunity, or congenital Zika syndrome. Monocytes are primary ZIKV targets in humans and, in response to infection, release extracellular vesicles like exosomes. Exosomes mediate intercellular communication and are involved in the virus's ability to circumvent the immune response, promoting pathological processes. This study aimed to evaluate the role of monocyte exosomes in cell-to-cell viral transmission. We isolated exosomes from ZIKV-infected monocytes (Mø exo ZIKV) by differential ultracentrifugation and identified them by nanoparticle tracking analysis; transmission electron microscopy; and CD63, CD81, TSG101, and Alix detection by cytofluorometry. Purified exosome isolates were obtained by uncoupling from paramagnetic beads or by treatment with UV radiation and RNase A. We found that Mø exo ZIKV carry viral RNA and E/NS1 proteins and that their interaction with naïve cells favors viral transmission, infection, and cell differentiation/activation. These data suggest that Mø exo ZIKV are an efficient alternative pathway for ZIKV infection. Knowledge of these mechanisms contributes to understanding the pathogenesis of severe disease and to the development of new vaccines and therapies.

A tangled threesome: understanding arbovirus infection in Aedes spp. and the effect of the mosquito microbiota

Arboviral infections transmitted by Aedes spp. mosquitoes are a major threat to human health, particularly in tropical regions but are expanding to temperate regions. The ability of Aedes aegypti and Aedes albopictus to transmit multiple arboviruses involves a complex relationship between mosquitoes and the virus, with recent discoveries shedding light on it. Furthermore, this relationship is not solely between mosquitoes and arboviruses, but also involves the mosquito microbiome. Here, we aimed to construct a comprehensive review of the latest information about the arbovirus infection process in A. aegypti and A. albopictus, the source of mosquito microbiota, and its interaction with the arbovirus infection process, in terms of its implications for vectorial competence. First, we summarized studies showing a new mechanism for arbovirus infection at the cellular level, recently described innate immunological pathways, and the mechanism of adaptive response in mosquitoes. Second, we addressed the general sources of the Aedes mosquito microbiota (bacteria, fungi, and viruses) during their life cycle, and the geographical reports of the most common microbiota in adults mosquitoes. How the microbiota interacts directly or indirectly with arbovirus transmission, thereby modifying vectorial competence. We highlight the complexity of this tripartite relationship, influenced by intrinsic and extrinsic conditions at different geographical scales, with many gaps to fill and promising directions for developing strategies to control arbovirus transmission and to gain a better understanding of vectorial competence. The interactions between mosquitoes, arboviruses and their associated microbiota are yet to be investigated in depth.

Extracellular vesicles recovered from plasma of severe dengue patients induce CD4+ T cell suppression through PD-L1/PD-1 interaction

IMPORTANCE

Severe dengue manifestations caused by the dengue virus are a global health problem. Studies suggest that severe dengue disease depends on uncontrolled immune cell activation, and excessive inflammation adds to the pathogenesis of severe dengue disease. Therefore, it is important to understand the process that triggers the uncontrolled activation of the immune cells. The change in immune response in mild to severe dengue may be due to direct virus-to-cell interaction or it could be a contact-independent process through the extracellular vesicles (EVs) released from infected cells. The importance of circulating EVs in the context of dengue virus infection and pathogenesis remains unexplored. Therefore, understanding the possible biological function of circulating EVs may help to delineate the role of EVs in the progression of disease. Our present study highlights that EVs from plasma of severe dengue patients can have immunosuppressive properties on CD4+ T cells which may contribute to T cell suppression and may contribute to dengue disease progression.

Viral Components Trafficking with(in) Extracellular Vesicles

The global public health burden exerted by viruses partially stems from viruses' ability to subdue host cells into creating an environment that promotes their multiplication (i.e., pro-viral). It has been discovered that viruses alter cell physiology by transferring viral material through extracellular vesicles (EVs), which serve as vehicles for intercellular communication. Here, we aim to provide a conceptual framework of all possible EV-virus associations and their resulting functions in infection output. First, we describe the different viral materials potentially associated with EVs by reporting that EVs can harbor entire virions, viral proteins and viral nucleic acids. We also delineate the different mechanisms underlying the internalization of these viral components into EVs. Second, we describe the potential fate of EV-associated viral material cargo by detailing how EV can circulate and target a naive cell once secreted. Finally, we itemize the different pro-viral strategies resulting from EV associations as the Trojan horse strategy, an alternative mode of viral transmission, an expansion of viral cellular tropism, a pre-emptive alteration of host cell physiology and an immunity decoy. With this conceptual overview, we aim to stimulate research on EV-virus interactions.

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.

Exosomes mediate the antibody-resistant intercellular transmission of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic enteric coronavirus that causes severe enteritis and lethal watery diarrhea in suckling piglets, leading to tremendous economic losses. Exosomes have been reported to participate in intercellular communication by the transportation of a variety of biological materials, including RNAs, lipids, and proteins. However, PEDV transmission routes have not yet been fully elucidated, and whether exosomes function in PEDV transmission remains unclear. In this study, we extracted and purified exosomes from PEDV-infected Vero cells using a stringent isolation method with a combination of chemical precipitation, ultracentrifugation, and incubation with CD63-labeled magnetic beads. We found that exosomes from PEDV-infected Vero cells contain viral genomic RNA and viral nucleocapsid protein. Furthermore, we demonstrated that the purified exosomes from PEDV-infected cells are capable of transmitting the virus to both PEDV-susceptible and non-susceptible cells. Importantly, exosome-mediated PEDV infection was resistant to neutralization by PEDV-specific neutralizing antibodies that potently neutralized free PEDV. Our study reveals a potential immune evasion mechanism utilized by PEDV and provides new insight into the transmission and infection of this important pathogen.

Rotavirus Particle Disassembly and Assembly In Vivo and In Vitro

Rotaviruses (RVs) are non-enveloped multilayered dsRNA viruses that are major etiologic agents of diarrheal disease in humans and in the young in a large number of animal species. The viral particle is composed of three different protein layers that enclose the segmented dsRNA genome and the transcriptional complexes. Each layer defines a unique subparticle that is associated with a different phase of the replication cycle. Thus, while single- and double-layered particles are associated with the intracellular processes of selective packaging, genome replication, and transcription, the viral machinery necessary for entry is located in the third layer. This modular nature of its particle allows rotaviruses to control its replication cycle by the disassembly and assembly of its structural proteins. In this review, we examine the significant advances in structural, molecular, and cellular RV biology that have contributed during the last few years to illuminating the intricate details of the RV particle disassembly and assembly processes.

Bombyx mori Tetraspanin A (BmTsp.A) is a facilitator in BmNPV invasion by regulating apoptosis

BmTsp.A (Bombyx mori Tetraspanin A) is one of the four transmembrane proteins which are capable to regulate multiple aspects of the immune response and are involved in various stages of viral invasion of the hosts. This study focused on the sequence features, analysis of expression pattern, as well as the effect of BmTsp.A on BmNPV (Bombyx mori nucleopolyhedrovirus) infection in the apoptotic pathway. BmTsp.A features the typical tetraspanins family, including four transmembrane domains and a major large extracellular loop domain. It is highly expressed specifically in the malpighian tubes, and its expression is increased by BmNPV induction for 48 h and 72 h. Overexpression and RNAi (RNA interference) mediated by siRNA reveal that BmTsp.A can promote the infection and replication of the virus. In addition, the overexpression of BmTsp.A regulates BmNPV-induced apoptosis, leading to changes in the expression of apoptosis-related genes and thus affecting viral proliferation. When subjected to stimulation by BmNPV infection, on the one hand, BmTsp.A inhibits Bmp53 through a Caspase-dependent pathway, which consequently promotes the expression of Bmbuffy, thereby activating BmICE to inhibit apoptosis and causing the promotion of viral proliferation. On the other hand, BmTsp.A inhibits the expression of BmPTEN and BmPkc through the phosphatidylinositol 3 kinase (PI3K)/protein kinaseB(AKT) signaling pathway, thus affecting the regulation of apoptosis. To summarize, our results demonstrate that BmTsp.A promotes viral infection and replication by inhibiting apoptosis, which is fundamental for understanding the pathogenesis of BmNPV and the immune defense mechanism of silkworm.

Aged Breast Matrix Bound Vesicles Promote Breast Cancer Invasiveness

Aging is one of the inherent risk factors for breast cancer. Although the influence of age-related cellular alterations on breast cancer development has been extensively explored, little is known about the alterations in the aging breast tissue microenvironment, specifically the extracellular matrix (ECM). Here, for the first time in literature, we have identified tissue resident matrix bound vesicles (MBVs) within the healthy mouse breast ECM, investigated and compared their characteristics in young and aged healthy breast tissues, and studied the effects of these MBVs on normal (KTB21) and cancerous (MDA-MB-231) human mammary epithelial cells with respect to the tissue age that they are extracted from. Using vesicle labeling technology, we were able to visualize cellular uptake of the MBVs directly from the native decellularized tissue sections, showing that these MBVs have regulatory roles in the tissue microenvironment. We mimicked the ECM by embedding the MBVs in collagen gels, and showed that MBVs could be taken up by the cells. The miRNA and cytokine profiling showed that MBVs shifted towards a more tumorigenic and invasive phenotype with age, as evidenced by the more pronounced presence of cancer-associated cytokines, and higher expression levels of oncomiRs miR-10b, miR-30e, and miR-210 in MBVs isolated from aged mice. When treated with MBVs or these upregulated factors, KTB21 and MDA-MB-231 cells showed significantly higher motility and invasion compared to untreated controls. Treatment of cells with a cocktail of miRNAs (miR-10b, miR-30e, and miR-210) or with the agonist of adiponectin (AdipoRon), which both were enriched in the aged MBVs, recapitulated the effect of aged MBVs on cells. This study shows for the first time that the MBVs have a regulatory role in the tissue microenvironment and that the MBV contents change towards cancer-promoting upon aging. Studying the effects of MBVs and their cargos on cellular behavior could lead to a better understanding of the critical roles of MBVs played in breast cancer progression and metastasis.

Extracellular vesicles from Zika virus-infected cells display viral E protein that binds ZIKV-neutralizing antibodies to prevent infection enhancement

Mosquito-borne flaviviruses including Zika virus (ZIKV) represent a public health problem in some parts of the world. Although ZIKV infection is predominantly asymptomatic or associated with mild symptoms, it can lead to neurological complications. ZIKV infection can also cause antibody-dependent enhancement (ADE) of infection with similar viruses, warranting further studies of virion assembly and the function of envelope (E) protein-specific antibodies. Although extracellular vesicles (EVs) from flavivirus-infected cells have been reported to transmit infection, this interpretation is challenged by difficulties in separating EVs from flavivirions due to their similar biochemical composition and biophysical properties. In the present study, a rigorous EV-virion separation method combining sequential ultracentrifugation and affinity capture was developed to study EVs from ZIKV-infected cells. We find that these EVs do not transmit infection, but EVs display abundant E proteins which have an antigenic landscape similar to that of virions carrying E. ZIKV E-coated EVs attenuate antibody-dependent enhancement mediated by ZIKV E-specific and DENV-cross-reactive antibodies in both cell culture and mouse models. We thus report an alternative route for Flavivirus E protein secretion. These results suggest that modulation of E protein release via virions and EVs may present a new approach to regulating flavivirus-host interactions.

The anti-immune dengue subgenomic flaviviral RNA is present in vesicles in mosquito saliva and is associated with increased infectivity

Mosquito transmission of dengue viruses to humans starts with infection of skin resident cells at the biting site. There is great interest in identifying transmission-enhancing factors in mosquito saliva in order to counteract them. Here we report the discovery of high levels of the anti-immune subgenomic flaviviral RNA (sfRNA) in dengue virus 2-infected mosquito saliva. We established that sfRNA is present in saliva using three different methods: northern blot, RT-qPCR and RNA sequencing. We next show that salivary sfRNA is protected in detergent-sensitive compartments, likely extracellular vesicles. In support of this hypothesis, we visualized viral RNAs in vesicles in mosquito saliva and noted a marked enrichment of signal from 3'UTR sequences, which is consistent with the presence of sfRNA. Furthermore, we show that incubation with mosquito saliva containing higher sfRNA levels results in higher virus infectivity in a human hepatoma cell line and human primary dermal fibroblasts. Transfection of 3'UTR RNA prior to DENV2 infection inhibited type I and III interferon induction and signaling, and enhanced viral replication. Therefore, we posit that sfRNA present in salivary extracellular vesicles is delivered to cells at the biting site to inhibit innate immunity and enhance dengue virus transmission.

Exosomes: from biology to immunotherapy in infectious diseases

Exosomes are extracellular vesicles derived from the endosomal compartment, which are released by all kinds of eukaryotic and prokaryotic organisms. These vesicles contain a variety of biomolecules that differ both in quantity and type depending on the origin and cellular state. Exosomes are internalized by recipient cells, delivering their content and thus contributing to cell-cell communication in health and disease. During infections exosomes may exert a dual role, on one hand, they can transmit pathogen-related molecules mediating further infection and damage, and on the other hand, they can protect the host by activating the immune response and reducing pathogen spread. Selective packaging of pathogenic components may mediate these effects. Recently, quantitative analysis of samples by omics technologies has allowed a deep characterization of the proteins, lipids, RNA, and metabolite cargoes of exosomes. Knowledge about the content of these vesicles may facilitate their therapeutic application. Furthermore, as exosomes have been detected in almost all biological fluids, pathogenic or host-derived components can be identified in liquid biopsies, making them suitable for diagnosis and prognosis. This review attempts to organize the recent findings on exosome composition and function during viral, bacterial, fungal, and protozoan infections, and their contribution to host defense or to pathogen spread. Moreover, we summarize the current perspectives and future directions regarding the potential application of exosomes for prophylactic and therapeutic purposes.

Exosomal transmission of viruses, a two-edged biological sword

As a common belief, most viruses can egress from the host cells as single particles and transmit to uninfected cells. Emerging data have revealed en bloc viral transmission as lipid bilayer-cloaked particles via extracellular vesicles especially exosomes (Exo). The supporting membrane can be originated from multivesicular bodies during intra-luminal vesicle formation and autophagic response. Exo are nano-sized particles, ranging from 40-200 nm, with the ability to harbor several types of signaling molecules from donor to acceptor cells in a paracrine manner, resulting in the modulation of specific signaling reactions in target cells. The phenomenon of Exo biogenesis consists of multiple and complex biological steps with the participation of diverse constituents and molecular pathways. Due to similarities between Exo biogenesis and virus replication and the existence of shared pathways, it is thought that viruses can hijack the Exo biogenesis machinery to spread and evade immune cells. To this end, Exo can transmit complete virions (as single units or aggregates), separate viral components, and naked genetic materials. The current review article aims to scrutinize challenges and opportunities related to the exosomal delivery of viruses in terms of viral infections and public health. Video Abstract.

The role of autophagy in viral infections

Autophagy is an evolutionarily conserved catabolic cellular process that exerts antiviral functions during a viral invasion. However, co-evolution and co-adaptation between viruses and autophagy have armed viruses with multiple strategies to subvert the autophagic machinery and counteract cellular antiviral responses. Specifically, the host cell quickly initiates the autophagy to degrade virus particles or virus components upon a viral infection, while cooperating with anti-viral interferon response to inhibit the virus replication. Degraded virus-derived antigens can be presented to T lymphocytes to orchestrate the adaptive immune response. Nevertheless, some viruses have evolved the ability to inhibit autophagy in order to evade degradation and immune responses. Others induce autophagy, but then hijack autophagosomes as a replication site, or hijack the secretion autophagy pathway to promote maturation and egress of virus particles, thereby increasing replication and transmission efficiency. Interestingly, different viruses have unique strategies to counteract different types of selective autophagy, such as exploiting autophagy to regulate organelle degradation, metabolic processes, and immune responses. In short, this review focuses on the interaction between autophagy and viruses, explaining how autophagy serves multiple roles in viral infection, with either proviral or antiviral functions.

Extracellular Vesicles and Viruses: Two Intertwined Entities

Viruses share many attributes in common with extracellular vesicles (EVs). The cellular machinery that is used for EV production, packaging of substrates and secretion is also commonly manipulated by viruses for replication, assembly and egress. Viruses can increase EV production or manipulate EVs to spread their own genetic material or proteins, while EVs can play a key role in regulating viral infections by transporting immunomodulatory molecules and viral antigens to initiate antiviral immune responses. Ultimately, the interactions between EVs and viruses are highly interconnected, which has led to interesting discoveries in their associated roles in the progression of different diseases, as well as the new promise of combinational therapeutics. In this review, we summarize the relationships between viruses and EVs and discuss major developments from the past five years in the engineering of virus-EV therapies.

Isolation of Exosomes or Extracellular Vesicles from West Nile Virus-Infected N2a Cells, Primary Cortical Neurons, and Brain Tissues

Several flaviviruses compromise the blood-brain barrier integrity, infect the central nervous system, and elicit neuroinvasion to successfully cause neuropathogenesis in the vertebrate host. Therefore, understanding the pathway(s) and mechanism(s) to block the transmission and/or dissemination of flaviviruses and perhaps other neuroinvasive viruses is considered as an important area of research. Moreover, studies that address mechanism(s) of neuroinvasion by flaviviruses are limited. In this chapter, we discuss detailed methods to isolate exosomes or extracellular vesicles (EVs) from mouse and human N2a cells, primary cultures of murine cortical neurons, and mouse brain tissue. Two different methods including differential ultracentrifugation and density gradient exosome (DG-Exo) isolation are described for the preparation of exosomes/EVs from N2a cells and cortical neurons. In addition, we discuss the detailed DG-Exo method for the isolation of exosomes from murine brain tissue. Studies on neuronal exosomes will perhaps enhance our understanding of the mechanism of neuroinvasion by these deadly viruses.

Plasma-derived exosomal miRNA as potential biomarker for diagnosis and prognosis of vector-borne diseases: A review

Early disease diagnosis is critical for better management and treatment outcome of patients. Therefore, diagnostic methods should ideally be accurate, consistent, easy to perform at low cost and preferably non-invasive. In recent years, various biomarkers have been studied for the detection of cardiovascular diseases, cerebrovascular diseases, infectious diseases, diabetes mellitus and malignancies. Exosomal microRNA (miRNA) are small non-coding RNA molecules that influence gene expression after transcription. Previous studies have shown that these types of miRNAs can potentially be used as biomarkers for cancers of the breast and colon, as well as diffuse large B-cell lymphoma. It may also be used to indicate viral and bacterial infections, such as the human immunodeficiency virus (HIV), tuberculosis and hepatitis. However, its use in the diagnosis of vector-borne diseases is rather limited. Therefore, this review aims to introduce several miRNAs derived from exosomal plasma that may potentially serve as a disease biomarker due to the body's immune response, with special focus on the early detection of vector-borne diseases.

Characterization and Involvement of Exosomes Originating from Chikungunya Virus-Infected Epithelial Cells in the Transmission of Infectious Viral Elements

The Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that affects the world's popula-tion with chikungunya disease. Adaptation of the viral life cycle to their host cells' environment is a key step for establishing their infection and pathogenesis. Recently, the accumulating evidence advocates a principal role of extracellular vesicles (EVs), including exosomes, in both the infection and pathogenesis of infectious diseases. However, the participation of exosomes in CHIKV infec-tion and transmission is not well clarified. Here, we demonstrated that the CHIKV RNA and pro-teins were captured in exosomes, which were released by viral-infected epithelial cells. A viral genomic element in the isolated exosomes was infectious to naïve mammalian epithelial cells. The assay of particle size distribution and transmission electron microscopy (TEM) revealed CHIKV-derived exosomes with a size range from 50 to 250 nm. Treatments with RNase A, Triton X-100, and immunoglobulin G antibodies from CHIKV-positive patient plasma indicated that in-fectious viral elements are encompassed inside the exosomes. Interestingly, our viral plaque for-mation also exhibited that infectious viral elements might be securely transmitted to neighboring cells by a secreted exosomal pathway. Taken together, our recent findings emphasize the evidence for a complementary means of CHIKV infection and suggest the role of exosome-mediated CHIKV transmission.

Key role of exportin 6 in exosome-mediated viral transmission from insect vectors to plants

Exosomes play a key role in virus exocytosis and transmission. The exportin family is usually responsible for cargo nucleocytoplasmic trafficking, and they are frequently found in exosomes. However, the function of exportins sorted in exosomes remains unknown. Here, we successfully isolated "cup holder"-like exosomes from the saliva of ∼30,000 small brown planthoppers, which are vectors of rice stripe virus (RSV). RSV virions were packed in comparatively large exosomes. Four viral genomic RNAs at a certain ratio were identified in the saliva exosomes. The virions contained in the saliva exosomes were capable of replicating and causing disease in rice plants. Interference with each phase of the insect exosome system affected the transmission of RSV from the insect vectors to rice plants. Fragmented exportin 6 was coimmunoprecipitated with viral nucleocapsid protein in saliva and sorted to exosomes via interactions with the cargo sorting protein VPS37a. When the expression of exportin 6 was knocked down, the amounts of RSV secreted in saliva and rice plants were reduced by 60% and 74%, respectively. These results showed that exportin 6 acted as a vehicle for transporting RSV into exosomes to overcome the barrier of insect salivary glands for horizontal transmission. Exportin 6 would represent an ideal target that could be manipulated to control the outbreak of insect-borne viruses in the future.

Antimicrobial Effect of Extracellular Vesicles Derived From Human Oral Mucosal Epithelial Cells on Candida albicans

Candida albicans (C. albicans) is a commensal microorganism that colonizes the mucosal surfaces of healthy individuals. Changes in the host or environment can lead to overgrowth of C. albicans and infection of the host. Extracellular vesicles (EVs) are released by almost all cell types and play an increasingly recognized role in fighting microbial infection. The aim of the present study was to assess whether EVs derived from human oral mucosal epithelial (Leuk-1) cells can suppress the growth and invasion of C. albicans. The in vitro efficacy of Leuk-1-EVs against C. albicans was assessed by optical microscopy, laser scanning confocal microscopy, scanning electron microscopy, and transmission electron microscopy. The germ tube formation rate, the percentage of hyphae and the microcolony optical density were also used to analyze the growth of C. albicans in a coculture model with Leuk-1 cells and EVs or after inhibition of the secretion of EVs. A mouse model of oral candidiasis was established and submucosal injection of Leuk-1-EVs in the tongue was performed. Macroscopic observation, H&E staining, PAS staining, and scanning electron microscopy were used to assess antifungal effects of Leuk-1-EVs in vivo. The in vitro results showed that the growth of C. albicans was inhibited and that the morphology and ultrastructure were changed following Leuk-1-EVs treatment. The in vivo results exhibited that white lesions of the tongue, C. albicans infection, and oral mucosal inflammation of the infected mice were significantly alleviated after Leuk-1-EVs treatment. We thus reveal an antifungal capability of EVs derived from oral epithelial cells against C. albicans that is mediated by direct damage effects and potential synergy between EVs and human oral mucosal epithelial cells. This finding offers an intriguing, previously overlooked method of antifungal defense against C. albicans.

Zika virus impacts extracellular vesicle composition and cellular gene expression in macaque early gestation trophoblasts

Zika virus (ZIKV) infection at the maternal-placental interface is associated with adverse pregnancy outcomes including fetal demise and pregnancy loss. To determine how infection impacts placental trophoblasts, we utilized rhesus macaque trophoblast stem cells (TSC) that can be differentiated into early gestation syncytiotrophoblasts (ST) and extravillous trophoblasts (EVT). TSCs and STs, but not EVTs, were highly permissive to productive infection with ZIKV strain DAK AR 41524. The impact of ZIKV on the cellular transcriptome showed that infection of TSCs and STs increased expression of immune related genes, including those involved in type I and type III interferon responses. ZIKV exposure altered extracellular vesicle (EV) mRNA, miRNA and protein cargo, including ZIKV proteins, regardless of productive infection. These findings suggest that early gestation macaque TSCs and STs are permissive to ZIKV infection, and that EV analysis may provide a foundation for identifying non-invasive biomarkers of placental infection in a highly translational model.

An Experimental Murine Model to Study Acquisition Dynamics of Tick-Borne Langat Virus in Ixodes scapularis

Ixodes scapularis ticks acquire several pathogens from reservoir animals and transmit them to humans. Development of an animal model to study acquisition/transmission dynamics of these pathogens into and from ticks, respectively, is challenging due to the fact that in nature ticks feed for a longer duration and on multiple vertebrate hosts. To understand the complex nature of pathogen acquisition/transmission, it is essential to set up a successful tick blood feeding method on a suitable vertebrate host. In this study, we provide evidence that murine model can be successfully used to study acquisition dynamics of Langat virus (LGTV), a member of tick-borne flaviviruses. Mice were inoculated intraperitoneally with LGTV that showed detectable viral loads in blood, skin, and other tissues including the brain. Both larval and nymphal ticks that were allowed to feed on the murine host successfully acquired LGTV loads. Also, we found that after molting, LGTV was transstadially transmitted from larval to nymphal stage. In addition, we noted that LGTV down-regulated IsSMase expression in all groups of ticks possibly for its survival in its vector host. Taken together, we provide evidence for the use of murine model to not only study acquisition dynamics of LGTV but also to study changes in tick gene expression during acquisition of arboviruses into ticks.

Tick Saliva and Salivary Glands: What Do We Know So Far on Their Role in Arthropod Blood Feeding and Pathogen Transmission

Ticks are blood-sucking arthropods that have developed myriad of strategies to get a blood meal from the vertebrate host. They first attach to the host skin, select a bite site for a blood meal, create a feeding niche at the bite site, secrete plethora of molecules in its saliva and then starts feeding. On the other side, host defenses will try to counter-attack and stop tick feeding at the bite site. In this constant battle between ticks and the host, arthropods successfully pacify the host and completes a blood meal and then replete after full engorgement. In this review, we discuss some of the known and emerging roles for arthropod components such as cement, salivary proteins, lipocalins, HSP70s, OATPs, and extracellular vesicles/exosomes in facilitating successful blood feeding from ticks. In addition, we discuss how tick-borne pathogens modulate(s) these components to infect the vertebrate host. Understanding the biology of arthropod blood feeding and molecular interactions at the tick-host interface during pathogen transmission is very important. This information would eventually lead us in the identification of candidates for the development of transmission-blocking vaccines to prevent diseases caused by medically important vector-borne pathogens.

Semen Extracellular Vesicles Mediate Vertical Transmission of Subgroup J Avian Leukosis Virus

Subgroup J avian leukosis virus (ALV-J) is a highly oncogenic retrovirus that has been devastating the global poultry industry since the late 1990s. The major infection model of ALV-J is vertical transmission, which is responsible for the congenital infection of progeny from generation to generation. Increasing evidence has suggested that extracellular vesicles (EVs) derived from virus-infected cells or biological fluids have been thought to be vehicles of transmission for viruses. However, the role of EVs in infection and transmission of ALV-J remains obscure. In the present study, semen extracellular vesicles (SE) were isolated and purified from ALV-J-infected rooster seminal plasma (SE-ALV-J), which was shown to contain ALV-J genomic RNA and partial viral proteins, as determined by RNA sequencing, reverse transcription-quantitative PCR and Western blotting. Furthermore, SE-ALV-J was proved to be able to transmit ALV-J infection to host cells and establish productive infection. More importantly, artificial insemination experiments showed that SE-ALV-J transmitted ALV-J infection to SPF hens, and subsequently mediated vertical transmission of ALV-J from the SPF hens to the progeny chicks. Taken together, the results of the present study suggested that ALV-J utilized host semen extracellular vesicles as a novel means for vertical transmission, enhancing our understanding on mechanisms underlying ALV-J transmission.

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SE-ALV-J- contains ALV-J genomic RNA and partial viral proteins.

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SE-ALV-J could transmit ALV-J infection to host cells and establish productive infection.

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SE-ALV-J mediates vertical transmission of ALV-J in animal model.

Alterations in arthropod and neuronal exosomes reduce virus transmission and replication in recipient cells

Aim

Targeting the modes of pathogen shedding/transmission via exosomes or extracellular vesicles has been envisioned as the best approach to control vector-borne diseases. This study is focused on altering exosomes stability to affect the pathogen transmission from infected to naïve recipient cells.

Methods

In this study, neuronal or arthropod exosomes were treated at different temperatures or with different salts or pH conditions to analyze their ability and efficiency in the transmission of tick-borne Langat virus (LGTV) from infected to naïve recipient cells.

Results

Quantitative real-time PCR (qRT-PCR) and immunoblotting analyses revealed that treatment of neuronal or tick exosomes at warmer temperatures of 37 °C or 23 °C, respectively, or with sulfate salts such as Magnesium or Ammonium sulfates or with highly alkaline pH of 9 or 11.5, dramatically reduced transmission of LGTV via infectious exosomes (human or tick cells-derived) to human neuronal (SH-SY5Y) cells or skin keratinocytes (HaCaT cells), respectively.

Conclusion

Overall, this study suggests that exosome-mediated viral transmission of vector-borne pathogens to the vertebrate host or the viral dissemination and replication within or between the mammalian host can be reduced by altering the ability of exosomes with basic changes in temperatures, salts or pH conditions.

Deciphering the Role of Extracellular Vesicles Derived from ZIKV-Infected hcMEC/D3 Cells on the Blood-Brain Barrier System

To date, no vaccines or antivirals are available against Zika virus (ZIKV). In addition, the mechanisms underlying ZIKV-associated pathogenesis of the central nervous system (CNS) are largely unexplored. Getting more insight into the cellular pathways that ZIKV recruits to facilitate infection of susceptible cells will be crucial for establishing an effective treatment strategy. In general, cells secrete a number of vesicles, known as extracellular vesicles (EVs), in response to viral infections. These EVs serve as intercellular communicators. Here, we investigated the role of EVs derived from ZIKV-infected human brain microvascular endothelial cells on the blood–brain barrier (BBB) system. We demonstrated that ZIKV-infected EVs (IEVs) can incorporate viral components, including ZIKV RNA, NS1, and E-protein, and further transfer them to several types of CNS cells. Using label-free impedance-based biosensing, we observed that ZIKV and IEVs can temporally disturb the monolayer integrity of BBB-mimicking cells, possibly by inducing structural rearrangements of the adherent protein VE-cadherin (immunofluorescence staining). Finally, differences in the lipidomic profile between EVs and their parental cells possibly suggest a preferential sorting mechanism of specific lipid species into the vesicles. To conclude, these data suggest that IEVs could be postulated as vehicles (Trojan horse) for ZIKV transmission via the BBB.

Viral Membrane Fusion Proteins and RNA Sorting Mechanisms for the Molecular Delivery by Exosomes

The advancement of precision medicine critically depends on the robustness and specificity of the carriers used for the targeted delivery of effector molecules in the human body. Numerous nanocarriers have been explored in vivo, to ensure the precise delivery of molecular cargos via tissue-specific targeting, including the endocrine part of the pancreas, thyroid, and adrenal glands. However, even after reaching the target organ, the cargo-carrying vehicle needs to enter the cell and then escape lysosomal destruction. Most artificial nanocarriers suffer from intrinsic limitations that prevent them from completing the specific delivery of the cargo. In this respect, extracellular vesicles (EVs) seem to be the natural tool for payload delivery due to their versatility and low toxicity. However, EV-mediated delivery is not selective and is usually short-ranged. By inserting the viral membrane fusion proteins into exosomes, it is possible to increase the efficiency of membrane recognition and also ease the process of membrane fusion. This review describes the molecular details of the viral-assisted interaction between the target cell and EVs. We also discuss the question of the usability of viral fusion proteins in developing extracellular vesicle-based nanocarriers with a higher efficacy of payload delivery. Finally, this review specifically highlights the role of Gag and RNA binding proteins in RNA sorting into EVs.

Origin and Characterization of Extracellular Vesicles Present in the Spider Venom of Ornithoctonus hainana

Extracellular vesicles (EVs), including exosomes and microvesicles, are membranous vesicles released from nearly all cellular types. They contain various bioactive molecules, and their molecular composition varies depending on their cellular origin. As research into venomous animals has progressed, EVs have been discovered in the venom of snakes and parasitic wasps. Although vesicle secretion in spider venom glands has been observed, these secretory vesicles’ origin and biological properties are unknown. In this study, the origin of the EVs from Ornithoctonus hainana venom was observed using transmission electron microscopy (TEM). The Ornithoctonus hainana venom extracellular vesicles (HN-EVs) were isolated and purified by density gradient centrifugation. HN-EVs possess classic membranous vesicles with a size distribution ranging from 50 to 150 nm and express the arthropod EV marker Tsp29Fb. The LC-MS/MS analysis identified a total of 150 proteins, which were divided into three groups according to their potential function: conservative vesicle transport-related proteins, virulence-related proteins, and other proteins of unknown function. Functionally, HN-EVs have hyaluronidase activity and inhibit the proliferation of human umbilical vein endothelial cells (HUVECs) by affecting the cytoskeleton and cell cycle. Overall, this study investigates the biological characteristics of HN-EVs for the first time and sheds new light on the envenomation process of spider venom.

Morphological Diversity and Dynamics of Dengue Virus Affecting Antigenicity

The four serotypes of the mature dengue virus can display different morphologies, including the compact spherical, the bumpy spherical and the non-spherical clubshape morphologies. In addition, the maturation process of dengue virus is inefficient and therefore some partially immature dengue virus particles have been observed and they are infectious. All these viral particles have different antigenicity profiles and thus may affect the type of the elicited antibodies during an immune response. Understanding the molecular determinants and environmental conditions (e.g., temperature) in inducing morphological changes in the virus and how potent antibodies interact with these particles is important for designing effective therapeutics or vaccines. Several techniques, including cryoEM, site-directed mutagenesis, hydrogen-deuterium exchange mass spectrometry, time-resolve fluorescence resonance energy transfer, and molecular dynamic simulation, have been performed to investigate the structural changes. This review describes all known morphological variants of DENV discovered thus far, their surface protein dynamics and the key residues or interactions that play important roles in the structural changes.