Mpox multi-antigen mRNA vaccine candidates by a simplified manufacturing strategy afford efficient protection against lethal orthopoxvirus challenge.

Current unprecedented mpox outbreaks in non-endemic regions represent a global public health concern. Although two live-attenuated vaccinia virus (VACV)-based vaccines have been urgently approved for people at high risk for mpox, a safer and more effective vaccine that can be available for the general public is desperately needed. By utilizing a simplified manufacturing strategy of mixing DNA plasmids before transcription, we developed two multi-antigen mRNA vaccine candidates, which encode four (M1, A29, B6, A35, termed as Rmix4) or six (M1, H3, A29, E8, B6, A35, termed as Rmix6) mpox virus antigens. We demonstrated that those mpox multi-antigen mRNA vaccine candidates elicited similar potent cross-neutralizing immune responses against VACV, and compared to Rmix4, Rmix6 elicited significantly stronger cellular immune responses. Moreover, immunization with both vaccine candidates protected mice from the lethal VACV challenge. Investigation of B-cell receptor (BCR) repertoire elicited by mpox individual antigen demonstrated that the M1 antigen efficiently induced neutralizing antibody responses, and all neutralizing antibodies among the top 20 frequent antibodies appeared to target the same conformational epitope as 7D11, revealing potential vulnerability to viral immune evasion. Our findings suggest that Rmix4 and Rmix6 from a simplified manufacturing process are promising candidates to combat mpox.

In situ self-assembly of amphiphilic dextran micelles and superparamagnetic iron oxide nanoparticle-loading as magnetic resonance imaging contrast agents.

Polymeric micelles have long been considered as promising nanocarrier for hydrophobic drugs and imaging probes, due to their nanoscale particle size, biocompatibility and ability to loading reasonable amount of cargoes. Herein, a facile method for dextran micelles preparation was developed and their performance as carriers of superparamagnetic iron oxide (SPIO) nanocrystals was evaluated. Amphiphilic dextran (Dex-g-OA) was synthesized via the Schiff base reactions between oxidized dextran and oleylamine, and self-assembled in situ into nano-size micelles in the reaction systems. The self-assembling behaviors of the amphiphilic dextran were identified using fluorescence resonance energy transfer technique by detection the energy transfer signal between the fluorophore pairs, Cy5 and Cy5.5. Hydrophobic SPIO nanoparticles (Fe3O4 NPs) were successfully loaded into the dextran micelles via the in situ self-assembly process, leading to a series of Fe3O4 NPs-loaded micelle nanocomposites (Fe3O4@Dex-g-OA) with good biocompatibility, superparamagnetism and strongly enhanced T 2 relaxivity. At the magnetic field of 0.5 T, the Fe3O4@Dex-g-OA nanocomposite with particle size of 116.2 ± 53.7 nm presented a higher T 2 relaxivity of 327.9 mM Fe - 1 ·s-1. The prepared magnetic nanocomposites hold the promise to be used as contrast agents in magnetic resonance imaging.

Dextran hydrogels via disulfide-containing Schiff base formation: Synthesis, stimuli-sensitive degradation and release behaviors.

Dextran hydrogels (Dex-SS) containing both disulfide and Schiff base bonds were developed via facile method based on the dextran oxidation and subsequent formation of Schiff base linkages between polyaldehyde dextran and cystamine, denoted as the disulfide-containing Schiff base reactions. Results of rheology, swelling and 13C CP/MAS NMR study indicated that cross-linking degree of Dex-SS hydrogels depended strongly on the molar ratio of -CHO/-NH2. Acidic and reductive (GSH) environment sensitive degradation behaviors of Dex-SS hydrogels were then evidenced by SEM, rheology study and Ellman's assay. Moreover, doxorubicin (DOX) was loaded into the hydrogel matrix and pH/GSH-responsive release behaviors were demonstrated. Cytocompatibility of Dex-SS hydrogel and effective cell uptake of released DOX was finally proved by transwell assay with HepG2 cells. Take advantages of the abundance of vicinal hydroxyl on a variety of polysaccharides, the disulfide-containing Schiff base reactions is considered as versatile method to develop stimuli-sensitive hydrogels for local drug delivery.

[Human umbilical cord mesenchymal stem cell-derived exosomes alleviate pulmonary fibrosis in mice by inhibiting epithelial-mesenchymal transition].

OBJECTIVE: To study the anti- fibrotic effect of human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-EXOs) and explore the mechanism. METHODS: Twenty-four C57 BL/6 mice were divided into 4 groups (n=6), including the control group treated with intratracheal injection of saline (3 mg/kg); lung fibrosis model group with intratracheal injection of 1.5 mg/mL bleomycin solution (prepared with saline, 3 mg/kg); EXOs1 group with intratracheal injection of 1.5 mg/mL bleomycin solution (3 mg/kg) and hUCMSC-EXOs (100 µg/250 µL, given by tail vein injection on the next day after modeling); and EXOs2 group with intratracheal injection of 1.5 mg/mL bleomycin solution (3 mg/kg) and hUCMSC-EXOs (100 µg/250 µL, given by tail vein injection on the 10th day after modeling). At 21 days after modeling, pulmonary index, lung tissue pathology and collagen deposition in the mice were assessed using HE staining and Masson staining. The expression level of TGF-ß1 was detected using ELISA, and vimentin, E-cadherin and phosphorylated Smad2/3 (p-Smad2/3) were detected using immunohistochemical staining. CCK8 assay was used to evaluate the effect of hUCMSCEXOs on the viability of A549 cells, and Western blotting was used to detect the expression levels of p-Smad2/3, vimentin, and E-cadherin in the cells. RESULTS: Compared with those in the model group, the mice treated with hUCMSC-EXOs showed significantly reduced the pulmonary index (P < 0.05), collagen deposition, lung tissue pathologies, lowered expressions of TGF-ß1 (P < 0.05), vimentin, and p-Smad2/3 and increased expression of E-cadherin. hUCMSC-EXOs given on the second day produced more pronounced effect than that given on the 11th day (P < 0.05). CCK8 assay results showed that hUCMSC-EXOs had no toxic effects on A549 cells (P > 0.05). Western blotting results showed that hUCMSC-EXOs treatment significantly increased the expression of E-cadherin and decreased the expressions of p-Smad2/3 and vimentin in the cells. CONCLUSIONS: hUCMSC-EXOs can alleviate pulmonary fibrosis in mice by inhibiting epithelialmesenchymal transition activated by the TGF-ß1/Smad2/3 signaling pathway, and the inhibitory effect is more obvious when it is administered on the second day after modeling.

Application of mesenchymal stem cell exosomes and their drug-loading systems in acute liver failure.

Stem cell exosomes are nanoscale membrane vesicles released from stem cells of various origins that can regulate signal transduction pathways between liver cells, and their functions in intercellular communication have been recognized. Due to their natural substance transport properties and excellent biocompatibility, exosomes can also be used as drug carriers to release a variety of substances, which has great prospects in the treatment of critical and incurable diseases. Different types of stem cell exosomes have been used to study liver diseases. Due to current difficulties in the treatment of acute liver failure (ALF), this review will outline the potential of stem cell exosomes for ALF treatment. Specifically, we reviewed the pathogenesis of acute liver failure and the latest progress in the use of stem cell exosomes in the treatment of ALF, including the role of exosomes in inhibiting the ALF inflammatory response and regulating signal transduction pathways, the advantages of stem cell exosomes and their use as a drug-loading system, and their pre-clinical application in the treatment of ALF. Finally, the clinical research status of stem cell therapy for ALF and the current challenges of exosome clinical transformation are summarized.

Pretreatment of exosomes derived from hUCMSCs with TNF-α ameliorates acute liver failure by inhibiting the activation of NLRP3 in macrophage.

AIMS: The management of acute liver failure (ALF) is a major challenge worldwide. The current study aimed to determine the therapeutic potential of TNF-α pretreatment of umbilical cord mesenchymal stem cell-derived exosomes (T-Exo) in ALF. MAIN METHODS: Here, we enriched T-Exo and untreated exosomes (Exo), them were measured by nanoparticle tracking analysis (NTA) for particle size detection and identified surface marker by Western blot and flow cytometry. Then the cell proliferation was detected by CCK-8 and the effect of T-Exo on the expression levels of pro-inflammatory cytokines was tested by ELISA. ALF mouse models were induced by LPS and D-GalN. H&E staining, immunohistochemistry, and Western blot were used to detect the effect of T-Exo on the levels of NLRP3 and other inflammation-related pathway proteins. qPCR was used to detect the expression level of microRNA-299-3p in T-Exo and its transfer to macrophages. Laser confocal microscopy was used to detect colocalization of exosomes,Golgi and NLRP3 in macrophages. KEY FINDINGS: Our study shows that T-Exo can reduce serum ALT, AST and proinflammatory cytokines level and inhibit activation of NLRP3 inflammation-associated pathway proteins. T-Exo treatment reduces pathological liver damage caused by ALF. Anti-inflammatory-related miRNA-299-3p is up-regulated in TNF-α-stimulated MSCs and selectively packaged into exosomes for role in exosomal treatment. And conducted preliminary exploration and hypothesis on the specific mechanism of this effect. SIGNIFICANCE: These in vitro and in vivo studies indicate that T-Exo attenuates inflammatory damage caused by ALF and promotes liver tissue repair by inhibiting the activation of the NLRP3 pathway.

Exosomes derived from human umbilical cord mesenchymal stem cells alleviate acute liver failure by reducing the activity of the NLRP3 inflammasome in macrophages.

Human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-EXOs) play an important role in the regulation of the immune system and inflammatory responses; however, their role in acute liver failure (ALF) and related pathological conditions is unclear. In this study, we found that hUCMSC-EXOs can reduce the expression of the NLRP3 inflammasome and downstream inflammatory factors in acute liver failure. Western blot and ELISA results showed that hUCMSC-EXOs decreased the expression of NLRP3, caspase-1, IL-1ß and IL-6 in LPS-stimulated RAW 264.7 macrophages. In vivo, the hUCMSC-EXOs repaired damaged liver tissue and decreased the expression of the NLRP3 inflammasome and the levels of ALT and AST in a mouse ALF model. The results of this study provide a new strategy for the application of human umbilical cord mesenchymal stem cell-derived exosomes in the treatment of ALF.