Microparticles and infectious diseases

Biomarkers of sepsis-induced coagulopathy: diagnostic insights and potential therapeutic implications

Diagnosing coagulopathy in septic patients remains challenging in intensive care. Disseminated intravascular coagulation (DIC) indeed presents with complex pathophysiology, complicating timely diagnosis. Epidemiological data indicate a significant prevalence of DIC in septic patients, with mortality rates up to 60%. Despite advances, current biomarker-based diagnostic tools often fail to provide early and accurate detection. This review evaluates the utility and limitations of traditional and emerging biomarkers for diagnosing sepsis-induced coagulopathy (SIC) and DIC. We also assess the effectiveness of anticoagulant therapy guided by biomarker-based diagnostic criteria.

Innate immune response in acute critical illness: a narrative review

BACKGROUND

Activation of innate immunity is a first line of host defense during acute critical illness (ACI) that aims to contain injury and avoid tissue damages. Aberrant activation of innate immunity may also participate in the occurrence of organ failures during critical illness. This review aims to provide a narrative overview of recent advances in the field of innate immunity in critical illness, and to consider future potential therapeutic strategies.

MAIN TEXT

Understanding the underlying biological concepts supporting therapeutic strategies modulating immune response is essential in decision-making. We will develop the multiple facets of innate immune response, especially its cellular aspects, and its interaction with other defense mechanisms. We will first describe the pathophysiological mechanisms of initiation of innate immune response and its implication during ACI. We will then develop the amplification of innate immunity mediated by multiple effectors. Our review will mainly focus on myeloid and lymphoid cellular effectors, the major actors involved in innate immune-mediated organ failure. We will third discuss the interaction and integration of innate immune response in a global view of host defense, thus considering interaction with non-immune cells through immunothrombosis, immunometabolism and long-term reprogramming via trained immunity. The last part of this review will focus on the specificities of the immune response in children and the older population.

CONCLUSIONS

Recent understanding of the innate immune response integrates immunity in a highly dynamic global vision of host response. A better knowledge of the implicated mechanisms and their tissue-compartmentalization allows to characterize the individual immune profile, and one day eventually, to develop individualized bench-to-bedside immunomodulation approaches as an adjuvant resuscitation strategy.

Subphenotypes of platelet count trajectories in sepsis from multi-center ICU data

Although thrombocytopenia on admission to the ICU is associated with increased in-hospital mortality in septic patients, the role of longitudinally measured platelet counts, which are dynamically changing, is unclear. We aimed to identify patterns of dynamic platelet count trajectories and evaluate their association with outcomes and thrombocytopenia in septic patients. We tested the longitudinal platelet trajectory patterns of sepsis patients within the first four days of ICU admission in the MIMIC-IV database and their association with 28-day mortality, and independently validated our findings in the eICU-CRD database. Statistical methods used included multivariate regression, propensity score analysis, doubly robust estimation, gradient boosting model, and inverse probability weighting to ensure the robustness of our findings. A total of 22,866 septic patients were included in our study. The trajectory analysis categorizes patients into ascending (AS), stable (ST), or descending (DS) patterns. The risk of 28-day mortality was increased in the DS patients (OR = 2.464, 95%CI 1.895-3.203, p < 0.001) and ST patients (OR = 1.302, 95%CI 1.067-1.589, p = 0.009) compared to AS patients. The AS patients had lower ICU length of stay (2.36 vs. 4.32, p < 0.001) and 28-day maximum SOFA scores (5.00 vs. 6.00, p < 0.001) than the DS patients, but had more ventilator-free days within 28 days than the DS group (26.00 vs. 24.00, p < 0.001). The mediating effect of thrombocytopenia was significant (p < 0.001 for the average causal mediation effect (ACME)). Longitudinal platelet trajectory was associated with risk-adjusted 28-day mortality among patients with sepsis and was proportionally mediated through thrombocytopenia.

Involvement of extracellular vesicles in the interaction of hosts and Toxoplasma gondii

Toxoplasma gondii, the causative agent of toxoplasmosis, is widely distributed. This protozoan parasite is one of the best adapted, being able to infect innumerous species of animals and different types of cells. This chapter reviews current literature on extracellular vesicles secreted by T. gondii and by its hosts. The topics describe the life cycle and transmission (1); toxoplasmosis epidemiology (2); laboratorial diagnosis approach (3); The T. gondii interaction with extracellular vesicles and miRNAs (4); and the perspectives on T. gondii infection. Each topic emphases the host immune responses to the parasite antigens and the interaction with the extracellular vesicles and miRNAs.

Extracellular vesicles in bacterial and fungal diseases - Pathogenesis to diagnostic biomarkers

Intercellular communication among microbes plays an important role in disease exacerbation. Recent advances have described small vesicles, termed as "extracellular vesicles" (EVs), previously disregarded as "cellular dust" to be vital in the intracellular and intercellular communication in host-microbe interactions. These signals have been known to initiate host damage and transfer of a variety of cargo including proteins, lipid particles, DNA, mRNA, and miRNAs. Microbial EVs, referred to generally as "membrane vesicles" (MVs), play a key role in disease exacerbation suggesting their importance in pathogenicity. Host EVs help coordinate antimicrobial responses and prime the immune cells for pathogen attack. Hence EVs with their central role in microbe-host communication, may serve as important diagnostic biomarkers of microbial pathogenesis. In this review, we summarize current research regarding the roles of EVs as markers of microbial pathogenesis with specific focus on their interaction with host immune defence and their potential as diagnostic biomarkers in disease conditions.

Dogs with canine visceral leishmaniasis have a boost of extracellular vesicles and miR-21-5p up-expression

This retrospective cohort study analysed extracellular vesicles (EVs) and microRNAs (miRNAs) excreted in canine sera from dogs with canine visceral leishmaniasis (CanVL). A total of 56 canine sera were divided into Group I (28, from healthy dogs) and Group II (28, from the same dogs, but already with CanVL). CanVL was determined by clinical and laboratory diagnoses. Canine sera were ultra-centrifuged to recover EVs (Can-EVs). Analyses by transmission electron microscopy, nanoparticle tracking analysis (NTA), sodium dodecyl sulfate-poli-acrylammide gel eletroforesis (SDS-PAGE) and, Immunoblot confirmed the presence of (i) microvesicles/exosomes and (ii) the tetraspanins CD63 and CD9. EVs secreted by Leishmania (Leishmania) infantum-EVs were reactive against sera from dogs with CanVL (performed by ELISA and Immunoblot). NTA analyses exhibited that concentrations of Can-EVs from dogs with CanVL (7.78 × 1010 Can-EVs/mL) were higher (p < .0001) than the non-infected dogs (mean: 1.47 × 1010 Can-EVs/mL). These results suggested that concentrations of Can-EVs were able to distinguish dogs with CanVL from healthy dogs. The relative expressions of 11 miRNAs species (miR-21-5p, miR-146a-5p, miR-125b-5p, miR-144-3p, miR-194-5p, miR-346, miR-29c-3p, miR-155-5p, miR-24-3p, miR-181a-5p, and miR-9-5p) were estimated in purified miRNAs of 30 canine sera. Dogs with CanVL up-expressed miR-21-5p and miR-146a-5p when compared with healthy dogs. The other miRNA species were poorly or not expressed in canine sera. In conclusion, this study suggests that CanVL induces changes in size and concentration of Can-EVs, as well as, the up-expression of miR-21-5p and miR-146a-5p in infected dogs.

Increased circulating microparticles contribute to severe infection and adverse outcomes of COVID-19 in patients with diabetes

Patients with diabetes infected with COVID-19 have greater mortality than those without comorbidities, but the underlying mechanisms remain unknown. This study aims to identify the mechanistic interactions between diabetes and severe COVID-19. Microparticles (MPs), the cell membrane-derived vesicles released on cell activation, are largely increased in patients with diabetes. To date, many mechanisms have been postulated for increased severity of COVID-19 in patients with underlying conditions, but the contributions of excessive MPs in patients with diabetes have been overlooked. This study characterizes plasma MPs from normal human subjects and patients with type 2 diabetes in terms of amount, cell origins, surface adhesive properties, ACE2 expression, spike protein binding capacity, and their roles in SARS-CoV-2 infection. Results showed that over 90% of plasma MPs express ACE2 that binds the spike protein of SARS-CoV-2. MPs in patients with diabetes increase 13-fold in quantity and 11-fold in adhesiveness when compared with normal subjects. Perfusion of human plasma with pseudo-typed SARS-CoV-2 virus or spike protein-bound MPs into human endothelial cell-formed microvessels-on-a chip demonstrated that MPs from patients with diabetes, not normal subjects, interact with endothelium and carry SARS-CoV-2 into cells through endocytosis, providing additional virus entry pathways and enhanced infection. Results also showed a large percentage of platelet-derived tissue factor-bearing MPs in diabetic plasma, which could contribute to thrombotic complications with SARS-CoV-2 infection. This study reveals a dual role of diabetic MPs in promoting SARS-CoV-2 entry and propagating vascular inflammation. These findings provide novel mechanistic insight into the high prevalence of COVID-19 in patients with diabetes and their propensity to develop severe vascular complications.NEW & NOTEWORTHY This study provides the first evidence that over 90% of human plasma microparticles express ACE2 that binds SARS-CoV-2 S protein with high affinity. Thus, the highly elevated adhesive circulating microparticles identified in patients with diabetes not only have greater SARS-CoV-2 binding capacity but also enable additional viral entry through virus-bound microparticle-endothelium interactions and enhanced infection. These findings reveal a novel mechanistic insight into the adverse outcomes of COVID-19 in patients with diabetes.

Development of chloramphenicol wound dressing protein-based microparticles in chitosan hydrogel system for improved effectiveness of dermal wound therapy

Skin wounds have been reported to increase the number of microbial colonies susceptible to infection. Treatments using oral antibiotics have been limited due to their toxicity and hydrophobic characteristics. In this study, we developed a formulation of chloramphenicol microparticles (CPL MPs), which was modified into chitosan hydrogel to increase treatment efficiency in targeting infections and creating an optimal environment to support the healing process. CPL MPs were prepared by a cross-linker stabilized method using whey protein (WPI) biopolymer, and the CPL MPs hydrogel was designed using chitosan biopolymer. Based on the result, CPL-loaded MPs showed desired physical and encapsulation characteristics. In the in vitro study, drug release of CPL MPs in simulated wound fluid represented approximately 99.40 ± 7.01 % of the system after 24 h. The antibacterial activity of CPL-loaded MPs formulation (MIC value 12.5 μg/mL, MBC 25 μg/mL) was effective as MIC concentration increased. Furthermore, the formulation of CPL MPs into hydrogel showed a better dermatokinetic profile compared to hydrogel with pure CPL. Interestingly, the antibacterial activity of the ex vivo infection model showed that Staphylococcus aureus activity decreased by up to 99.98 % after 24 h administration of CPL MPs hydrogel when compared to pure-CPL hydrogel and blank hydrogel. These studies have confirmed that incorporating CPL MPs into hydrogel can provide a promising approach to skin infection treatment.

Procoagulant Activity of Blood and Microvesicles Is Disturbed by Pneumococcal Pneumolysin, Which Interacts with Coagulation Factors

The coagulation and contact systems are parts of the innate immune system as they prevent bleeding and dissemination of pathogens and also contribute to microbial killing by inflammatory reactions and the release of antimicrobial peptides. Here, we investigated the influence of Streptococcus pneumoniae on the coagulation and contact system. S. pneumoniae (pneumococci), but no other investigated streptococcal species, impairs coagulation of blood by autolysis and release of pneumolysin. Defective blood coagulation results from the lysis of tissue factor-producing mononuclear cells and their procoagulant microvesicles, which are the main trigger for blood coagulation during sepsis. In addition, pneumolysin binds coagulation and contact system factors, but this does not result in activation. Thus, pneumococci modulate activation of the coagulation system by releasing pneumolysin, which could potentiate lung injury during pneumonia.

Toxoplasmosis in Human and Animals Around the World. Diagnosis and Perspectives in the One Health Approach

Toxoplasmosis is a unique health disease that significantly affects the health of humans, domestic animals, wildlife and is present in ecosystems, including water, soil and food. Toxoplasma gondii is one of the best-adapted parasites in the word. This parasite is able to persist for long periods in its hosts, in different geographic regions of the word. This review summarizes the current literature of these themes, focusing on: (1) toxoplasmosis, a zoonotic infection; (2) One health approach and toxoplasmosis; (3) human toxoplasmosis; (4) animal toxoplasmosis; (5) toxoplasmosis diagnosis, as immunological, parasitological and molecular diagnosis; (6) T. gondii outbreaks caused by infected meat, milk and dairy products, as well as, vegetables and water consume; (7) studies in experimental models; (8) genetic characterization of T. gondii strains; (9) extracellular vesicles and miRNA; and (10) future perspectives on T. gondii and toxoplasmosis. The vast prevalence of toxoplasmosis in both humans and animals and the dispersion and resistence of T. gondii parasites in environment highlight the importance of the one health approach in diagnostic and control of the disease. Here the different aspects of the one health approach are presented and discussed.

Serum Exosomal microRNA Profiling in AIDS Complicated with Talaromyces marneffei Infection

Introduction

In order to find the early diagnostic markers of AIDS combined with TM infection, we detected and analyzed the serum exosomal miRNAs of AIDS patients with or without TM infection.

Materials and Methods

We profiled the expression levels of miRNAs via RNA sequencing in serum exosomes from the pooled samples of 17 AIDS patients combined without TM infection and 15 AIDS combined with TM infection patients. For external validation, we validated these results using real-time quantification polymerase chain reaction (qRT-PCR) in an independent cohort of 35 AIDS patients combined without TM infection and 33 AIDS combined with TM infection patients. Finally, bioinformatics was used to predict the target genes and pathways of meaningful miRNAs.

Results

A total of 131 serum exosomal miRNAs including 73 up-regulated and 59 down-regulated miRNAs were found to be differentially expressed (log2FC≥1 and FDR <0.01) in the two groups. A validation analysis revealed that three miRNAs (miR-192-5p, miR-194-5p and miR-1246) were upregulated in exosomes from AIDS combined with TM infection patients. ROC analyses showed that the AUC in combined diagnosis of the three miRNAs was 0.742, and the diagnostic sensitivity and specificity were 0.568 and 0.861, respectively. In the biological process analysis, all the 3 miRNAs were involved in transcription, DNA-templated and positive regulation of transcription from RNA polymerase II promoter. At the same time, the related pathways were involved in TGF-β signaling pathway, AMPK signaling pathway, Wnt signaling pathway, MAPK signaling pathway, cGMP-PKG and cAMP signaling pathway, etc.

Conclusion

miR-192-5p, miR-194-5p and miR-1246 in serum exosomes might be a potential biomarker for AIDS combined with TM infection patients, which may be involved in TGF-β signaling pathway, AMPK signaling pathway, Wnt signaling pathway, MAPK signaling pathway, cGMP-PKG and cAMP signaling pathway, etc. Further research is needed on the biological functions and mechanisms of these miRNAs.

Characterization of extracellular vesicles isolated from types I, II and III strains of Toxoplasma gondii

This study investigated the participation extracellular vesicles (EVs) in Toxoplasma gondii-host interaction. EVs of three T. gondii strains (RH, ME-49 and VEG) were purified by chromatography and ELISA. Results of "nanoparticle tracking analysis" and scanning electron microscopy showed that RH strain released more EVs than other strains. Images of transmission electron microscopy showed that in beginning of incubation (culture medium), EVs were inside of tachyzoites preparing to be released. After 24 hours, they were largely produced inside tachyzoites and were released through plasma membrane. The parasite burden of mice infected with RH strain plus EVs was increased and with early death of 1-2 days compared of those that received only parasites. EV proteins of ME-49 and VEG strains were poorly reactive to sera of infected patients in imunoblot. However, those from RH strain were reactive against sera of patients with cerebral toxoplasmosis. EVs stimulated murine splenocytes caused similar production of IFN-γ and IL-10 levels. RH strain derived EVs stimulated more TNF-α than those stimulated by other strains. T. gondii and infected hosts can express the same miRNAs (miR-155-5p, miR-125b-5p, miR-423-3p). In conclusion, T. gondii derived EVs promote host-parasite interactions, modulate host immune responses, carry virulent factors and cause an imbalance in cellular immune response.

Characterization of murine extracellular vesicles and Toxoplasma gondii infection

This study characterized extracellular vesicles (EVs) of sera from mice infected with Toxoplasma gondii or immunized with EVs derived T gondii. EVs were purified of sera from four groups (5 A/Sn mice/group). EV-IM: Mice immunized with T gondii-released EVs; ACT: mice in acute infection; CHR: mice in chronic infection; and NI: normal mice. EVs were purified by ultracentrifugation. Concentration of serum-derived EVs from NI group was smaller than EV-IM, ACT and CHR groups. Most of the EVs from ACT and CHR groups were microvesicles, and they were bigger than the NI group. The same results were shown by Transmission Electron Microscopy. The presence of exosomes was shown in immunoblotting by tetraspanin (CD63 and CD9) evidence. Splenocytes of EV-IM, CHR and NI groups were stimulated with T. gondii derived EVs. EV-IM and CHR groups up-expressed IFN-γ; TNF-α and IL-17, when compared with the NI group. IL-10 was up-expressed only in the EV-IM group. EV-IM, ACT and CHR groups expressed more miR-155-5p, miR-29c-3p and miR-125b-5p than the NI group. Host-T gondii interaction can occur, also, via EVs. miRNAs participate in the modulation of cellular immune response against T gondii. These data give subsidies to propose the differentiation between infect or noninfect hosts by concentration of EVs.

A Role for Extracellular Vesicles in SARS-CoV-2 Therapeutics and Prevention

Extracellular vesicles (EVs) are the common designation for ectosomes, microparticles and microvesicles serving dominant roles in intercellular communication. Both viable and dying cells release EVs to the extracellular environment for transfer of cell, immune and infectious materials. Defined morphologically as lipid bi-layered structures EVs show molecular, biochemical, distribution, and entry mechanisms similar to viruses within cells and tissues. In recent years their functional capacities have been harnessed to deliver biomolecules and drugs and immunological agents to specific cells and organs of interest or disease. Interest in EVs as putative vaccines or drug delivery vehicles are substantial. The vesicles have properties of receptors nanoassembly on their surface. EVs can interact with specific immunocytes that include antigen presenting cells (dendritic cells and other mononuclear phagocytes) to elicit immune responses or affect tissue and cellular homeostasis or disease. Due to potential advantages like biocompatibility, biodegradation and efficient immune activation, EVs have gained attraction for the development of treatment or a vaccine system against the severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) infection. In this review efforts to use EVs to contain SARS CoV-2 and affect the current viral pandemic are discussed. An emphasis is made on mesenchymal stem cell derived EVs' as a vaccine candidate delivery system.

Preliminary study of microparticle coagulation properties in septic patients with disseminated intravascular coagulation

Background

Sepsis typically results in enhanced coagulation system activation and microthrombus formation. Microparticle (MP) production promotes coagulation and enhances pro-coagulation. This study investigated how circulating MP levels and tissue factor-bearing MP (TF+-MP) activity caused coagulation in patients with septic disseminated intravascular coagulation (DIC).

Methods

Thirty patients with septic DIC and 30 healthy controls were studied from December 2017 to March 2019. Patient blood samples were collected at enrolment (day 1) and on days 3 and 5; DIC scores and Sequential Organ Failure Assessment (SOFA) scores were recorded. TF+-MP activity was measured using TF-dependent factor Xa generation experiments. Circulating MP concentrations were determined by MP capture assay. Clotting factor activity, antithrombin level, soluble thrombomodulin, and serum tissue factor pathway inhibitor (TFPI) concentrations were measured.

Results

Patients with septic DIC had lower circulating MP levels than healthy control patients. Circulating MP levels in patients with septic DIC were positively correlated with DIC scores and negatively correlated with coagulation factors, but TF+-MP activity did not correlate with clotting factor levels and TFPI.

Conclusions

In patients with septic DIC, circulating MP levels are important in promoting coagulation activation and increasing clotting factor consumption. TF+-MP activity may not be the main form of active TF.

MAGEA4 Coated Extracellular Vesicles Are Stable and Can Be Assembled In Vitro

Extracellular vesicles (EVs) are valued candidates for the development of new tools for medical applications. Vesicles carrying melanoma-associated antigen A (MAGEA) proteins, a subfamily of cancer-testis antigens, are particularly promising tools in the fight against cancer. Here, we have studied the biophysical and chemical properties of MAGEA4-EVs and show that they are stable under common storage conditions such as keeping at +4 °C and -80 °C for at least 3 weeks after purification. The MAGEA4-EVs can be freeze-thawed two times without losing MAGEA4 in detectable quantities. The attachment of MAGEA4 to the surface of EVs cannot be disrupted by high salt concentrations or chelators, but the vesicles are sensitive to high pH. The MAGEA4 protein can bind to the surface of EVs in vitro, using robust passive incubation. In addition, EVs can be loaded with recombinant proteins fused to the MAGEA4 open reading frame within the cells and also in vitro. The high stability of MAGEA4-EVs ensures their potential for the development of EV-based anti-cancer applications.

Emerging roles of extracellular vesicles in COVID-19, a double-edged sword?

The sudden outbreak of SARS‐CoV‐2‐infected disease (COVID‐19), initiated from Wuhan, China, has rapidly grown into a global pandemic. Emerging evidence has implicated extracellular vesicles (EVs), a key intercellular communicator, in the pathogenesis and treatment of COVID‐19. In the pathogenesis of COVID‐19, cells that express ACE2 and CD9 can transfer these viral receptors to other cells via EVs, making recipient cells more susceptible for SARS‐CoV‐2 infection. Once infected, cells release EVs packaged with viral particles that further facilitate viral spreading and immune evasion, aggravating COVID‐19 and its complications. In contrast, EVs derived from stem cells, especially mesenchymal stromal/stem cells, alleviate severe inflammation (cytokine storm) and repair damaged lung cells in COVID‐19 by delivery of anti‐inflammatory molecules. These therapeutic beneficial EVs can also be engineered into drug delivery platforms or vaccines to fight against COVID‐19. Therefore, EVs from diverse sources exhibit distinct effects in regulating viral infection, immune response, and tissue damage/repair, functioning as a double‐edged sword in COVID‐19. Here, we summarize the recent progress in understanding the pathological roles of EVs in COVID‐19. A comprehensive discussion of the therapeutic effects/potentials of EVs is also provided.

Helicobacter pylori Outer Membrane Vesicles and Extracellular Vesicles from Helicobacter pylori-Infected Cells in Gastric Disease Development

Extracellular vesicles (EVs) are cell-derived vesicles important in intercellular communication that play an essential role in host-pathogen interactions, spreading pathogen-derived as well as host-derived molecules during infection. Pathogens can induce changes in the composition of EVs derived from the infected cells and use them to manipulate their microenvironment and, for instance, modulate innate and adaptive inflammatory immune responses, both in a stimulatory or suppressive manner. Gastric cancer is one of the leading causes of cancer-related deaths worldwide and infection with Helicobacter pylori (H. pylori) is considered the main risk factor for developing this disease, which is characterized by a strong inflammatory component. EVs released by host cells infected with H. pylori contribute significantly to inflammation, and in doing so promote the development of disease. Additionally, H. pylori liberates vesicles, called outer membrane vesicles (H. pylori-OMVs), which contribute to atrophia and cell transformation in the gastric epithelium. In this review, the participation of both EVs from cells infected with H. pylori and H. pylori-OMVs associated with the development of gastric cancer will be discussed. By deciphering which functions of these external vesicles during H. pylori infection benefit the host or the pathogen, novel treatment strategies may become available to prevent disease.

Immunization with extracellular vesicles excreted by Toxoplasma gondii confers protection in murine infection, activating cellular and humoral responses

The study aim was to analyze whether microvesicles and exosomes, named extracellular vesicles (EVs), purified from Toxoplasma gondii are able to stimulate the protective immunity of experimental mice when administered, as challenge, a highly virulent strain. EVs excreted from T. gondii tachyzoites (RH strain) were purified by chromatography and used for immunization assays in inbred mouse groups (EV-IM). Chronic infected (CHR) and naive (NI) mice were used as control groups, since the immune response is well known. After immunizations, experimental groups were challenged with 100 tachyzoites. Next, parasitemias were determined by real-time PCR (qPCR), and survival levels were evaluated daily. The humoral response was analyzed by detection of IgM, IgG, IgG1 and IgG2a, and opsonization experiments. The cellular response was evaluated in situ by immunohistochemistry on IFN-γ, IL-10, TNF-α and IL-17 expression in cells of five organs (brain, heart, liver, spleen and skeletal muscles). EV immunization reduced parasitemia and increased the survival index in two mouse lineages (A/Sn and BALB/c) infected with a lethal T. gondii strain. EV-IM mice had higher IgG1 levels than IgM or IgG2a. IgGs purified from sera of EV-IM mice were able to opsonize tachyzoites (RH strain), and mice that received these parasites had lower parasitemias, and mortality was delayed 48 h, compared with the same results from those receiving parasites opsonized with IgG purified from NI mice. Brain and spleen cells from EV-IM mice more highly expressed IFN-γ, IL-10 and TNF-α. In conclusion, EV-immunization was capable of inducing immune protection, eliciting high production of IgG1, IFN-γ, IL-10 and TNF-α.

Membrane Microvesicles as Potential Vaccine Candidates

The prevention and control of infectious diseases is crucial to the maintenance and protection of social and public healthcare. The global impact of SARS-CoV-2 has demonstrated how outbreaks of emerging and re-emerging infections can lead to pandemics of significant public health and socio-economic burden. Vaccination is one of the most effective approaches to protect against infectious diseases, and to date, multiple vaccines have been successfully used to protect against and eradicate both viral and bacterial pathogens. The main criterion of vaccine efficacy is the induction of specific humoral and cellular immune responses, and it is well established that immunogenicity depends on the type of vaccine as well as the route of delivery. In addition, antigen delivery to immune organs and the site of injection can potentiate efficacy of the vaccine. In light of this, microvesicles have been suggested as potential vehicles for antigen delivery as they can carry various immunogenic molecules including proteins, nucleic acids and polysaccharides directly to target cells. In this review, we focus on the mechanisms of microvesicle biogenesis and the role of microvesicles in infectious diseases. Further, we discuss the application of microvesicles as a novel and effective vaccine delivery system.

Extracellular Vesicles: Roles in Human Viral Infections, Immune-Diagnostic, and Therapeutic Applications

Membrane-bound vesicles that are released from cells are increasingly being studied as a medium of intercellular communication, as these act to shuttle functional proteins, such as lipids, DNA, rRNA, and miRNA, between cells during essential physiological processes. Extracellular vesicles (EVs), most commonly exosomes, are consistently produced by virus-infected cells, and they play crucial roles in mediating communication between infected and uninfected cells. Notably, pathophysiological roles for EVs have been established in various viral infections, including human immune deficiency virus (HIV), coronavirus (CoV), and human adenovirus (HAdv). Retroviruses, such as HIV, modulate the production and composition of EVs, and critically, these viruses can exploit EV formation, secretion, and release pathways to promote infection, transmission, and intercellular spread. Consequently, EV production has been investigated as a potential tool for the development of improved viral infection diagnostics and therapeutics. This review will summarize our present knowledge of EV–virus relationships, focusing on their known roles in pathophysiological pathways, immunomodulatory mechanisms, and utility for biomarker discovery. This review will also discuss the potential for EVs to be exploited as diagnostic and treatment tools for viral infection.

Extracellular Vesicle-Related Thrombosis in Viral Infection

Although the outcomes of viral infectious diseases are remarkably varied, most infections cause acute diseases after a short period. Novel coronavirus disease 2019, which recently spread worldwide, is no exception. Extracellular vesicles (EVs) are small circulating membrane-enclosed entities shed from the cell surface in response to cell activation or apoptosis. EVs transport various kinds of bioactive molecules between cells, including functional RNAs, such as viral RNAs and proteins. Therefore, when EVs are at high levels, changes in cell activation, inflammation, angioplasty and transportation suggest that EVs are associated with various diseases. Clinical research on EVs includes studies on the coagulatory system. In particular, abnormal enhancement of the coagulatory system through EVs can cause thrombosis. In this review, we address the functions of EVs, thrombosis, and their involvement in viral infection.

Microparticles in the pathogenesis of TB: Novel perspectives for diagnostic and therapy management of Mycobacterium tuberculosis infection

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, usually chronic and has a progressive clinical course. Despite the availability of effective chemotherapy, TB is a leading killer of young adults worldwide and the global multi-drug resistant TB is reaching epidemic proportions. Interrupt transmission through early detection and treatment of the patients is a main element of the drug-resistant TB control strategy. However, many drugable targets in pathogens are already inhibited by current antibiotics and there is not a biomarker that indicate normal or pathogenic biological processes, or pharmacological responses to therapeutic intervention. Studies directed at evaluate key elements of host response to infection may identify biomarkers with measurable characteristics that indicate pathogenic biological processes. Cell-derived microparticles (MPs) are membrane-coated vesicles that represent subcellular elements and have been identified increasingly in a broad range of diseases and emerging as potential novel biomarker to pathological processes. In addition, MPs carry contents from their cells of origin as bioactive molecules as cytokines, enzymes, surface receptors, antigens and genetic information and may provide a means of communication between cells. Molecules-loaded MPs may interplay with the immune system and therefore can acts on inflammation, cell activation and migration. Therefore, MPs may be an important factor to immune process during Mtb infection, especially in pulmonary granulomas and influence the outcome of infection. Their characterization may facilitate an appropriate diagnosis, optimize pharmacological strategies and might be further explored as potential targets for future clinical interventions.

Similarities in the General Chemical Composition of Colon Cancer Cells and Their Microvesicles Investigated by Spectroscopic Methods-Potential Clinical Relevance

Colon cancer constitutes 33% of all cancer cases in humans and the majority of patients with metastatic colon cancer still have poor prognosis. An important role in cancer development is the communication between cancer and normal cells. This may occur, among others, through extracellular vesicles (including microvesicles) (MVs), which are being released by both types of cells. MVs may regulate a diverse range of biological processes and are considered as useful cancer biomarkers. Herein, we show that similarity in the general chemical composition between colon cancer cells and their corresponding tumor-derived microvesicles (TMVs) does exist. These results have been confirmed by spectroscopic methods for four colon cancer cell lines: HCT116, LoVo, SW480, and SW620 differing in their aggressiveness/metastatic potential. Our results show that Raman and Fourier Transform InfraRed (FTIR) analysis of the cell lines and their corresponding TMVs did not differ significantly in the characterization of their chemical composition. However, hierarchical cluster analysis of the data obtained by both of the methods revealed that only Raman spectroscopy provides results that are in line with the molecular classification of colon cancer, thus having potential clinical relevance.

Human extracellular vesicles and correlation with two clinical forms of toxoplasmosis

Aim

This study analyzed microvesicles and exosomes, called as extracellular vesicles (EVs) excreted in serum and cerebrospinal fluid (CSF) from patients with cerebral or gestational toxoplasmosis.

Methods

Clinical samples from 83 individuals were divided into four groups. Group I, 20 sera from healthy individuals and pregnant women (seronegative for toxoplasmosis); group II, 21 sera from seropositive patients for toxoplasmosis (cerebral or gestational forms); group III, 26 CSF samples from patients with cerebral toxoplasmosis/HIV co-infection (CT/HIV) (seropositive for toxoplasmosis); and group IV, 16 CSF samples from seronegative patients for toxoplasmosis, but with HIV infection and other opportunistic infections (OI/HIV). Serum and CSF samples were ultracentrifuged to recover EVs. Next, vesicle size and concentration were characterized by Nanoparticle Tracking Analysis (NTA).

Results

Concentrations of serum-derived EVs from toxoplasmosis patients (mean: 2.4 x 10¹⁰ EVs/mL) were statically higher than of non-infected individuals (mean: 5.9 x 10⁹ EVs/mL). Concentrations of CSF-derived EVs were almost similar in both groups. CT/HIV (mean: 2.9 x 10⁹ EVs/mL) and OI/HIV (mean: 4.8 x 10⁹ EVs/mL). Analyses by NTA confirmed that CSF-derived EVs and serum-derived EVs had size and shape similar to microvesicles and exosomes. The mean size of EVs was similar in serum and CSF. Thus, the concentration, and not size was able distinguish patients with toxoplasmosis than healthy individuals. Presence of exosomes was also confirmed by transmission electron microscopy and evidence of tetraspanins CD63 and CD9 in immunoblotting. Relative expressions of miR-146a-5p, miR-155-5p, miR-21-5p, miR-29c-3p and miR-125b-5p were estimated in exosomal miRNA extracted of EVs.

Serum-derived EVs from group II (cerebral and gestational toxoplasmosis) up-expressed miR-125b-5p and miR-146a-5p. CSF-derived EVs from CT/HIV patients) up-expressed miR-155-5p and miR-21-5p and were unable to express miR-29c-3p.

Conclusion

These data suggest the participation of EVs and exosomal miRNAs in unbalance of immune response as elevation of TNF-α, IL-6; and downregulation of IFN-γ in cerebral and gestational forms of toxoplasmosis.

First visualization of circulating neutrophil extracellular traps using cell fluorescence during human septic shock-induced disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a severe complication of septic shock. Polymorphonuclear neutrophils (PMNs) may play a key role in septic shock-induced DIC via the release of neutrophils extracellular traps (NETs). NETs capture invading pathogens, but also act as a pro-coagulant surface at the interface between immunity and thrombosis. During septic shock-induced DIC, neutrophil activation may result in excessive NET formation. Herein, we originally report the presence of circulating NETs in human blood during septic shock-induced DIC. To investigate NET formation during shock-induced DIC neutrophils were isolated from patients in septic shock associated with (n = 3) or without (n = 3) DIC. Neutrophils from healthy donors (n = 3) were stimulated in vitro with ionomycin as NET formation positive controls. PMNs smears were stained with mouse anti-human FITC anti-myeloperoxidase antibody and the blue-fluorescent DAPI nucleic acid stain. NETs were identified as elongated extracellular DNA fibers associated to myeloperoxidase detected by immunofluorescence. NETs were unambiguously observed in PMNs from septic shock patients with DIC but not from patients without DIC. NETs features in DIC+ patients were undistinguishable from those observed in ionomycin-induced PMNs from healthy donors. Fluorescence images of NETs were associated to extracellular cytoplasmic expansions. Our data report for the first time the direct visualization of circulating NETs in patients with septic shock-induced DIC. The in vivo relevance of previously reported indirect markers of NETosis (neutrophil side fluorescence) is confirmed.

Increasing procoagulant activity of circulating microparticles in patients living with HIV

OBJECTIVES

HIV-infected individuals are at higher risk of non-AIDS diseases associated with procoagulant status. Microparticles are elevated in disorders associated with thrombosis (e.g., cardiovascular diseases). We investigated the association between microparticle levels in untreated and treated HIV-infected subjects, and determined the association with immune status, viral replication, and duration of antiretroviral therapy.

PATIENTS AND METHODS

We included 144 HIV-infected subjects, including 123 on antiretroviral therapy (ART) and 21 before treatment initiation. A control group of 40 HIV-negative healthy adults matched for age and sex was used for comparison of microparticle levels. Treated subjects were divided into five groups depending on the period of antiretroviral exposure. Statistically significant differences were determined by Kruskal-Wallis test and Chi² test. The relation between microparticles and other parameters was assessed using Spearman's coefficient of correlation.

RESULTS

Microparticle levels were significantly higher in treated and untreated HIV-infected subjects than in non-HIV-infected controls (P<0.001). The microparticle level was similar between the groups on treatment (P=0.913). No association between the microparticle level and CD4+ count, CD4+/CD8+ ratio, number of HIV-1 RNA copies, or duration of exposure to antiretroviral treatment was observed.

CONCLUSION

Increased levels of microparticles may be due to processes independent of viral replication and CD4+ cell count, and microparticle release might persist even during viral suppression by antiretroviral treatment. Elevated microparticle levels might occur in response to other triggers.

Isolation and characterization of exosomes released from mosquito cells infected with dengue virus

Exosomes are endocytic origin small-membrane vesicles secreted to the extracellular space by most cell types. Exosomes released from virus infected-cells can mediate the cell-to-cell communication to promote or modulate viral transmission. Dengue virus (DENV) is an arbovirus transmitted by Aedes mosquitoes bite to humans. Interestingly, the role of exosomes during the DENV infection in mammalian cells has already been described. However, little is known about exosomes derived from infected mosquito cells. Thus, the exosomes released from DENV-infected C6/36 cells were isolated, purified and analyzed using an antibody against the tetraspanin CD9 from human that showed cross-reactivity with the homologs to human CD9 found in Aedes albopictus (AalCD9). The exosomes from DENV infected cells were larger than the exosomes secreted from uninfected cells, contained virus-like particles, and they were able to infect naïve C6/36 cells, suggesting that exosomes are playing a role in virus dissemination.

Neutrophil Activation During Septic Shock

In addition to their well-known role as the cellular mediators of immunity, key other roles have been identified for neutrophils during septic shock. Importantly, neutrophils indeed play a critical role in the recently described immunothrombosis concept and in septic shock-induced coagulopathy. Septic shock is one of the most severe forms of infection, characterized by an inadequate host response to the pathogenic organism. This host response involves numerous defense mechanisms with an intense cellular activation, including neutrophil activation. Neutrophils are key cells of innate immunity through complex interactions with vascular cells and their activation may participate in systemic tissue damages. Their activation also leads to the emission of neutrophil extracellular traps, which take part in both pathogen circumscription and phagocytosis, but also in coagulation activation. Neutrophils thus stand at the interface between hemostasis and immunity, called immunothrombosis.The present review will develop a cellular approach of septic shock pathophysiology focusing on neutrophils as key players of septic shock-induced vascular cell dysfunction and of the host response, associating immunity and hemostasis. We will therefore first develop the role of neutrophils in the interplay between innate and adaptive immunity, and will then highlight recent advances in our understanding of immunothrombosis septic shock-induced coagulopathy.

Extracellular vesicles as mediators of immunopathology in infectious diseases

In the last decades, extracellular vesicles have emerged as important elements in cell-cell communication and as key players in disease pathogenesis via transmission of their cargo between different cells. Various works have described different subpopulations of these membrane structures, based on their cell of origin, biogenesis, size, biophysical properties and cargo. In addition to their pathophysiological role in the development and progression of different diseases including infectious diseases, neurodegenerative disorders and cancer, extracellular vesicles are now recognized for their potential as novel therapeutic targets and intelligent drug delivery system. Here, we have reviewed the most recent data on different subtypes of extracellular vesicles, focusing on microvesicles and exosomes and their subpopulations, their involvement in immune-mediated pathogenesis of various infectious diseases and their role as potential therapeutic targets.

Immunohaemostasis: a new view on haemostasis during sepsis

Host infection by a micro-organism triggers systemic inflammation, innate immunity and complement pathways, but also haemostasis activation. The role of thrombin and fibrin generation in host defence is now recognised, and thrombin has become a partner for survival, while it was seen only as one of the "principal suspects" of multiple organ failure and death during septic shock. This review is first focused on pathophysiology. The role of contact activation system, polyphosphates and neutrophil extracellular traps has emerged, offering new potential therapeutic targets. Interestingly, newly recognised host defence peptides (HDPs), derived from thrombin and other "coagulation" factors, are potent inhibitors of bacterial growth. Inhibition of thrombin generation could promote bacterial growth, while HDPs could become novel therapeutic agents against pathogens when resistance to conventional therapies grows. In a second part, we focused on sepsis-induced coagulopathy diagnostic challenge and stratification from "adaptive" haemostasis to "noxious" disseminated intravascular coagulation (DIC) either thrombotic or haemorrhagic. Besides usual coagulation tests, we discussed cellular haemostasis assessment including neutrophil, platelet and endothelial cell activation. Then, we examined therapeutic opportunities to prevent or to reduce "excess" thrombin generation, while preserving "adaptive" haemostasis. The fail of international randomised trials involving anticoagulants during septic shock may modify the hypothesis considering the end of haemostasis as a target to improve survival. On the one hand, patients at low risk of mortality may not be treated to preserve "immunothrombosis" as a defence when, on the other hand, patients at high risk with patent excess thrombin and fibrin generation could benefit from available (antithrombin, soluble thrombomodulin) or ongoing (FXI and FXII inhibitors) therapies. We propose to better assess coagulation response during infection by an improved knowledge of pathophysiology and systematic testing including determination of DIC scores. This is one of the clues to allocate the right treatment for the right patient at the right moment.

Herpesviruses hijack host exosomes for viral pathogenesis

Herpesviruses are remarkable pathogens possessing elaborate mechanisms to seize various host cellular components for immune evasion, replication, and virion egress. As viruses are dependent upon their hosts, investigating this intricate interplay has revealed that the exosome pathway is utilised by alpha (Herpes Simplex Virus 1), beta (Human Cytomegalovirus, and Human Herpesvirus 6) and gamma (Epstein-Barr Virus, and Kaposi Sarcoma-associated Herpesvirus) herpesviruses. Virions and exosomes share similar properties and functions. For example, exosomes are small membranous nanovesicles (30-150nm) released from cells that contain proteins, DNA, and various coding and non-coding RNA species. Given exosomes can shuttle various molecular cargo from a donor to recipient cell, they serve as important vehicles facilitating cell-cell communication. Therefore, exploitation by herpesviruses impacts several aspects of infection including: i) acquisition of molecular machinery for secondary envelopment and viral assembly, ii) export of immune-related host proteins from infected cells, iii) enhancing infection in surrounding cells via transfer of viral proteins, mRNA and miRNA, and iv) regulation of viral protein expression to promote persistence. Studying the dichotomy that exists between host exosomes and herpesviruses has two benefits. Firstly, it will reveal the precise pathogenic mechanisms viruses have evolved, generating knowledge for antiviral development. Secondly, it will shed light upon fundamental exosome characteristics that remain unknown, including cargo selection, protein trafficking, and non-canonical biogenesis.

Infrared spectroscopic characterization of monocytic microvesicles (microparticles) released upon lipopolysaccharide stimulation

Microvesicles (MVs) are involved in cell-cell interactions, including disease pathogenesis. Nondestructive Fourier-transform infrared (FTIR) spectra from MVs were assessed as a technique to provide new biochemical insights into a LPS-induced monocyte model of septic shock. FTIR spectroscopy provided a quick method to investigate relative differences in biomolecular content of different MV populations that was complementary to traditional semiquantitative omics approaches, with which it is difficult to provide information on relative changes between classes (proteins, lipids, nucleic acids, carbohydrates) or protein conformations. Time-dependent changes were detected in biomolecular contents of MVs and in the monocytes from which they were released. Differences in phosphatidylcholine and phosphatidylserine contents were observed in MVs released under stimulation, and higher relative concentrations of RNA and α-helical structured proteins were present in stimulated MVs compared with MVs from resting cells. FTIR spectra of stimulated monocytes displayed changes that were consistent with those observed in the corresponding MVs they released. LPS-stimulated monocytes had reduced concentrations of nucleic acids, α-helical structured proteins, and phosphatidylcholine compared with resting monocytes but had an increase in total lipids. FTIR spectra of MV biomolecular content will be important in shedding new light on the mechanisms of MVs and the different roles they play in physiology and disease pathogenesis.-Lee, J., Wen, B., Carter, E. A., Combes, V., Grau, G. E. R., Lay, P. A. Infrared spectroscopic characterization of monocytic microvesicles (microparticles) released upon lipopolysaccharide stimulation.

Uptake of parasite-derived vesicles by astrocytes and microglial phagocytosis of infected erythrocytes may drive neuroinflammation in cerebral malaria

Astrocytes and microglia are activated during cerebral malaria (CM) and contribute to the production and release of several mediators during neuroinflammatory processes. Whether these changes are the consequence of a direct crosstalk between glial cells and the malarial parasite and how these cells participate in the pathogenesis of CM is not yet clear. We therefore examined the interaction of astrocytes and microglia with Plasmodium berghei ANKA-infected red blood cells using primary cell cultures derived from newborn C57BL/6 mice. We observed a dynamic transfer of vesicles from the parasite to astrocytes within minutes of contact, and the phagocytosis of infected red blood cells by microglia. Differential gene expression studies using the Affymetrix GeneChip^® microarray, and quantitative PCR analyses showed the increase in expression of the set of genes belonging to the immune response network in parasite activated astrocytes and microglia. Interestingly, expression of these genes was also significantly upregulated in brains of mice dying from CM compared with uninfected mice or infected mice that did not develop the neuropathology. Accumulation of parasite-derived vesicles within astrocytes, and the phagocytosis of infected red blood cells by microglia induced a subsequent increase in interferon gamma inducible protein 10 (IP10) in both the brain and plasma of infected mice at the onset of CM, confirming a role for this molecule in CM pathogenesis. Altogether, these observations point to a possible role for glial cells in the neuropathological processes leading to CM. GLIA 2016 GLIA 2017;65:75-92.

Development of a NanoBioAnalytical platform for "on-chip" qualification and quantification of platelet-derived microparticles

Blood microparticles (MPs) are small membrane vesicles (50-1000nm), derived from different cell types. They are known to play important roles in various biological processes and also recognized as potential biomarkers of various health disorders. Different methods are currently used for the detection and characterization of MPs, but none of these methods is capable to quantify and qualify total MPs at the same time, hence, there is a need to develop a new approach for simultaneous detection, characterization and quantification of microparticles. Here we show the potential of surface plasmon resonance (SPR) method coupled to atomic force microscopy (AFM) to quantify and qualify platelet-derived microparticles (PMPs), on the whole nano-to micro-meter scale. The different subpopulations of microparticles could be determined via their capture onto the surface using specific ligands. In order to verify the correlation between the capture level and the microparticles concentration in solution, two calibration standards were used: Virus-Like Particles (VLPs) and synthetic beads with a mean diameter of 53nm and 920nm respectively. The AFM analysis of the biochip surface allowed metrological analysis of captured PMPs and revealed that more than 95% of PMPs were smaller than 300nm. Our results suggest that our NanoBioAnalytical platform, combining SPR and AFM, is a suitable method for a sensitive, reproducible, label-free characterization and quantification of MPs over a wide concentration range (≈10⁷ to 10¹² particles/mL; with a limit of detection (LOD) in the lowest ng/µL range) which matches with their typical concentrations in blood.

Smart blood cell and microvesicle-based Trojan horse drug delivery: Merging expertise in blood transfusion and biomedical engineering in the field of nanomedicine

Therapeutic and diagnostic applications of nanomedicine are playing increasingly important roles in human health. Various types of synthetic nanoparticles, including liposomes, micelles, and other nanotherapeutic platforms and conjugates, are being engineered to encapsulate or carry drugs for treating diseases such as cancer, cardiovascular disorders, neurodegeneration, and inflammations. Nanocarriers are designed to increase the half-life of drugs, decrease their toxicity and, ideally, target pathological sites. Developing smart carriers with the capacity to deliver drugs specifically to the microenvironment of diseased cells with minimum systemic toxicity is the goal. Blood cells, and potentially also the liposome-like micro- and nano-vesicles they generate, may be regarded as ideally suited to perform such specific targeting with minimum immunogenic risks. Blood cell membranes are "decorated" with complex physiological receptors capable of targeting and communicating with other cells and tissues and delivering their content to the surrounding pathological microenvironment. Blood cells, such as erythrocytes, have been developed as permeable carriers to release drugs to diseased tissues or act as biofactory allowing enzymatic degradation of a pathological substrate. Interestingly, attempts are also being made to improve the targeting capacity of synthetic nanoparticles by "decorating" their surface with blood cell membrane receptor-like biochemical structures. Research is needed to further explore the benefits that blood cell-derived microvesicles, as a Trojan horse delivery systems, can bring to the arsenal of therapeutic micro- and nanotechnologies. This short review focuses on the therapeutic roles that red blood cells and platelets can play as smart drug-delivery systems, and highlights the benefits that blood transfusion expertise can bring to this exciting and novel biomedical engineering field.

Evidence-Based Clinical Use of Nanoscale Extracellular Vesicles in Nanomedicine

Recent research has demonstrated that all body fluids assessed contain substantial amounts of vesicles that range in size from 30 to 1000 nm and that are surrounded by phospholipid membranes containing different membrane microdomains such as lipid rafts and caveolae. The most prominent representatives of these so-called extracellular vesicles (EVs) are nanosized exosomes (70-150 nm), which are derivatives of the endosomal system, and microvesicles (100-1000 nm), which are produced by outward budding of the plasma membrane. Nanosized EVs are released by almost all cell types and mediate targeted intercellular communication under physiological and pathophysiological conditions. Containing cell-type-specific signatures, EVs have been proposed as biomarkers in a variety of diseases. Furthermore, according to their physical functions, EVs of selected cell types have been used as therapeutic agents in immune therapy, vaccination trials, regenerative medicine, and drug delivery. Undoubtedly, the rapidly emerging field of basic and applied EV research will significantly influence the biomedicinal landscape in the future. In this Perspective, we, a network of European scientists from clinical, academic, and industry settings collaborating through the H2020 European Cooperation in Science and Technology (COST) program European Network on Microvesicles and Exosomes in Health and Disease (ME-HAD), demonstrate the high potential of nanosized EVs for both diagnostic and therapeutic (i.e., theranostic) areas of nanomedicine.

Focus on Extracellular Vesicles: Development of Extracellular Vesicle-Based Therapeutic Systems

Many types of cells release phospholipid membrane vesicles thought to play key roles in cell-cell communication, antigen presentation, and the spread of infectious agents. Extracellular vesicles (EVs) carry various proteins, messenger RNAs (mRNAs), and microRNAs (miRNAs), like a “message in a bottle” to cells in remote locations. The encapsulated molecules are protected from multiple types of degradative enzymes in body fluids, making EVs ideal for delivering drugs. This review presents an overview of the potential roles of EVs as natural drugs and novel drug-delivery systems.

Placental Microparticles and MicroRNAs in Pregnant Women with Plasmodium falciparum or HIV Infection

Background

During pregnancy, syncytiotrophoblast vesicles contribute to maternal tolerance towards the fetus, but also to pathologies such as pre-eclampsia. The aim of the study was to address whether Plasmodium falciparum and HIV infections in pregnancy affect the secretion, microRNA content and function of trophoblast microparticles.

Methods

Microparticles were isolated and characterized from 122 peripheral plasmas of Mozambican pregnant women, malaria- and/or HIV-infected and non-infected. Expression of placenta-related microRNAs in microparticles was analysed by qPCR and the effect of circulating microparticles on dendritic cells assessed by phenotype analysis and cytokine/chemokine measurement.

Results

Concentrations of total and trophoblast microparticles detected by flow cytometry were higher in HIV-positive (P = 0.005 and P = 0.030, respectively) compared to non-infected mothers, as well as in women delivering low birthweight newborns (P = 0.032 and P = 0.021, respectively). miR-517c was overexpressed in mothers with placental malaria (P = 0.034), compared to non-infected. Microparticles from HIV-positive induced a higher expression of MHCII (P = 0.021) and lower production of MCP1 (P = 0.008) than microparticles from non-infected women.

Conclusions

In summary, alterations in total and trophoblast microparticles associated with malaria and HIV in pregnant women may have an immunopathogenic role. The potential for placental-derived vesicles and microRNAs as biomarkers of adverse outcomes during pregnancy and malaria infection should be confirmed in future studies.

An overview of the role of microparticles/microvesicles in blood components: Are they clinically beneficial or harmful?

Blood cells and tissues generate heterogeneous populations of cell-derived vesicles, ranging from approximately 50 nm to 1 µm in diameter. Under normal physiological conditions and as an essential part of an energy-dependent natural process, microparticles (MPs) are continuously shed into the circulation from membranes of all viable cells such as megakaryocytes, platelets, red blood cells, white blood cells and endothelial cells. MP shedding can also be triggered by pathological activation of inflammatory processes and activation of coagulation or complement systems, or even by shear stress in the circulation. Structurally, MPs have a bilayered phospholipid structure exposing coagulant-active phosphatidylserine and expressing various membrane receptors, and they serve as cell-to-cell shuttles for bioactive molecules such as lipids, growth factors, microRNAs, and mitochondria. It was established that ex vivo processing of blood into its components, involving centrifugation, processing by various apheresis procedures, leucoreduction, pathogen reduction, and finally storage in different media and different types of blood bags, can impact MP generation and content. This is mostly due to exposure of the collected blood to anticoagulant/storage media and due to shear stresses or activation, contact with artificial surfaces, or exposure to various leucocyte-removal filters and pathogen-reduction treatments. Such artificially generated MPs, which are added to the original pool of MPs collected from the donor, may exhibit specific functional characteristics, as MPs are not an inert element of blood components. Not surprisingly, MPs' roles and functionality are therefore increasingly seen to be fully relevant to the field of transfusion medicine, and as a parameter of blood safety that must be considered in haemovigilance programmes. Continual advancements in assessment methods of MPs and storage lesions are gradually leading to a better understanding of the impacts of blood collection on MP generation, while clinical research should clarify links of MPs with transfusion reactions and certain clinical disorders. Harmonization and consensus in sampling protocols, sample handling and processing, and assessment methods are needed to achieve consensual interpretations. This review focuses on the role of MPs as an essential laboratory tool and as a most effective player in transfusion science and medicine and in health and disease.

Extracellular vesicles from infected cells: potential for direct pathogenesis

Infections that result in natural or manmade spread of lethal biological agents are a concern and require national and focused preparedness. In this manuscript, as part of an early diagnostics and pathogen treatment strategy, we have focused on extracellular vesicles (EVs) that arise following infections. Although the field of biodefense does not currently have a rich resource in EVs literature, none the less, similar pathogens belonging to the more classical emerging and non-emerging diseases have been studied in their EV/exosomal contents and function. These exosomes are formed in late endosomes and released from the cell membrane in almost every cell type in vivo. These vesicles contain proteins, RNA, and lipids from the cells they originate from and function in development, signal transduction, cell survival, and transfer of infectious material. The current review focuses on how different forms of infection exploit the exosomal pathway and how exosomes can be exploited artificially to treat infection and disease and potentially also be used as a source of vaccine. Virally-infected cells can secrete viral as well as cellular proteins and RNA in exosomes, allowing viruses to cause latent infection and spread of miRNA to nearby cells prior to a subsequent infection. In addition to virally-infected host cells, bacteria, protozoa, and fungi can all release small vesicles that contain pathogen-associated molecular patterns, regulating the neighboring uninfected cells. Examples of exosomes from both virally and bacterially infected cells point toward a re-programming network of pathways in the recipient cells. Finally, many of these exosomes contain cytokines and miRNAs that in turn can effect gene expression in the recipient cells through the classical toll-like receptor and NFκB pathway. Therefore, although exosomes do not replicate as an independent entity, they however facilitate movement of infectious material through tissues and may be the cause of many pathologies seen in infected hosts.

Procoagulant phospholipid concentration in canine erythrocyte concentrates stored with or without prestorage leukoreduction

OBJECTIVE

To evaluate canine erythrocyte concentrates (ECs) for the presence of procoagulant phospholipid (PPL), determine whether PPL concentration changes during the course of storage of ECs, and ascertain whether prestorage leukoreduction (removal of leukocytes via gravity filtration) reduces the development of PPL.

SAMPLE

10 whole blood units (420 g each) collected from 10 random-source, clinically normal dogs (1 U/dog).

PROCEDURES

The dogs were randomized to 1 of 2 groups. Of the 10 whole blood units collected, 5 were processed through a standard method, and 5 underwent leukoreduction. Whole blood units were processed to generate ECs, from which aliquots were aseptically collected from each unit weekly for 5 weeks. Supernatants from the concentrates were evaluated for procoagulant activity, which was converted to PPL concentration, by use of an automated assay and by measurement of real-time thrombin generation.

RESULTS

Supernatants from stored canine ECs contained procoagulant activity as measured by both assays. In general, the PPL concentration gradually increased during the storage period, but leukoreduction reduced the development of increased procoagulant activity over time.

CONCLUSIONS AND CLINICAL RELEVANCE

The presence of PPL in canine ECs may be associated with procoagulant and proinflammatory effects in vivo, which could have adverse consequences for dogs treated with ECs.

Inflammation-induced endothelial cell-derived extracellular vesicles modulate the cellular status of pericytes

Emerging lines of evidence have shown that extracellular vesicles (EVs) mediate cell-to-cell communication by exporting encapsulated materials, such as microRNAs (miRNAs), to target cells. Endothelial cell-derived EVs (E-EVs) are upregulated in circulating blood in different pathological conditions; however, the characteristics and the role of these E-EVs are not yet well understood. In vitro studies were conducted to determine the role of inflammation-induced E-EVs in the cell-to-cell communication between vascular endothelial cells and pericytes/vSMCs. Stimulation with inflammatory cytokines and endotoxin immediately induced release of shedding type E-EVs from the vascular endothelial cells, and flow cytometry showed that the induction was dose dependent. MiRNA array analyses revealed that group of miRNAs were specifically increased in the inflammation-induced E-EVs. E-EVs added to the culture media of cerebrovascular pericytes were incorporated into the cells. The E-EV-supplemented cells showed highly induced mRNA and protein expression of VEGF-B, which was assumed to be a downstream target of the miRNA that was increased within the E-EVs after inflammatory stimulation. The results suggest that E-EVs mediate inflammation-induced endothelial cell-pericyte/vSMC communication, and the miRNAs encapsulated within the E-EVs may play a role in regulating target cell function. E-EVs may be new therapeutic targets for the treatment of inflammatory diseases.

Platelet microparticles: detection and assessment of their paradoxical functional roles in disease and regenerative medicine

There is increasing research on and clinical interest in the physiological role played by platelet microparticles (PMPs). PMPs are 0.1-1-μm fragments shed from plasma membranes of platelets that are undergoing activation, stress, or apoptosis. They have a phospholipid-based structure and express functional receptors from platelet membranes. As they are the most abundant microparticles in the blood and they express the procoagulant phosphatidylserine, PMPs likely complement, if not amplify, the functions of platelets in hemostasis, thrombosis, cancer, and inflammation, but also act as promoters of tissue regeneration. Their size and structure make them instrumental in platelet-cell communications as a delivery tool of platelet-borne bioactive molecules including growth factors, other signaling molecules and micro (mi)RNA. PMPs can therefore be a pathophysiological threat or benefit to the cellular environment when interacting with the blood vasculature. There is also increasing evidence that PMP generation is triggered during blood collection, separation into components, and storage, a phenomenon potentially leading to thrombotic and inflammatory side effects in transfused patients. Evaluating PMPs requires strict pre-analytical and analytical procedures to avoid artifactual generation and ensure accurate assessment of the number, size repartitioning, and functional properties. This review describes the physical and functional methods developed for analyzing and quantifying PMPs. It then presents the functional roles of PMPs as markers or triggers of diseases like thrombosis, atherosclerosis, and cancer, and discusses the possible detrimental immunological impact of their generation in blood components. Finally we review the potential function of PMPs in tissue regeneration and the prospects for their use in therapeutic strategies for human health.

Production, fate and pathogenicity of plasma microparticles in murine cerebral malaria

In patients with cerebral malaria (CM), higher levels of cell-specific microparticles (MP) correlate with the presence of neurological symptoms. MP are submicron plasma membrane-derived vesicles that express antigens of their cell of origin and phosphatidylserine (PS) on their surface, facilitating their role in coagulation, inflammation and cell adhesion. In this study, the in vivo production, fate and pathogenicity of cell-specific MP during Plasmodium berghei infection of mice were evaluated. Using annexin V, a PS ligand, and flow cytometry, analysis of platelet-free plasma from infected mice with cerebral involvement showed a peak of MP levels at the time of the neurological onset. Phenotypic analyses showed that MP from infected mice were predominantly of platelet, endothelial and erythrocytic origins. To determine the in vivo fate of MP, we adoptively transferred fluorescently labelled MP from mice with CM into healthy or infected recipient mice. MP were quickly cleared following intravenous injection, but microscopic examination revealed arrested MP lining the endothelium of brain vessels of infected, but not healthy, recipient mice. To determine the pathogenicity of MP, we transferred MP from activated endothelial cells into healthy recipient mice and this induced CM-like brain and lung pathology. This study supports a pathogenic role for MP in the aggravation of the neurological lesion and suggests a causal relationship between MP and the development of CM.

Cerebral malaria (CM) is a potentially fatal neurological syndrome characterised by unrousable coma. Since the detection of high levels of plasma microparticles (MP) in patients with CM, it has been demonstrated that inhibition of MP production confers protection from murine CM. However, the precise mechanisms of action of these MP during CM have not been completely deciphered. In this study, we used experimental models of CM to measure the production and origins of MP over the course of infection. We found low baseline circulating MP in healthy mice and these were subsequently raised at the time of the neurological syndrome. Phenotypic analyses showed that circulating MP were predominantly from activated host cells that have previously been established to participate in CM pathogenesis. We show for the first time transferred MP impairing endothelial integrity and inducing CM-like pathology in the brain and lung of healthy animals. Our study dissects what tissues these MP localise to exert their effects, as little is known about their fate following the initial release. These data suggest a causal relationship between MP and the development of CM and also warrant further investigation into the representation of MP as a marker of CM risk.

Membrane properties involved in calcium-stimulated microparticle release from the plasma membranes of S49 lymphoma cells

This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32–42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

Using annexin V-coated magnetic beads to capture active tissue factor-bearing microparticles from body fluids

Microparticles, found in all body fluids including peripheral blood, are important elements that regulate cellular interactions under both physiological and pathological conditions. They play an important role in blood clot formation and increased cell aggregation. However, little is known about the components of the microparticles and their mechanism of action. A method to quantify and assess the underlying mechanism of action of microparticles in pathologies is therefore desirable. We present a specific method to isolate cell-derived microparticles from malignant effusions using annexin V-coated magnetic microbeads. The microparticles can be detected by flow cytometry. Our results show that the microparticles can be isolated with >80% specificity when bound to annexin V-coated magnetic beads, which was originally developed for the detection of apoptotic cells. We also show that the isolated microparticles were still functionally active and can be used for further analysis. Thus, our method enables isolation as well as structural and functional characterisation of the microparticles which are produced in numerous patho-physiological situations. This should help gain a deeper insight into various disease situations, which in turn should pave the way for the development of novel drugs and specific therapy strategies.