Endothelial cells are integral components of all vasculature within complex organisms. As they line the blood vessel wall, endothelial cells are constantly exposed to a variety of molecular factors and shear force that can induce cellular damage and stress. However, how endothelial cells are removed or eliminate unwanted cellular contents, remains unclear. The generation of large extracellular vesicles (EVs) has emerged as a key mechanism for the removal of cellular waste from cells that are dying or stressed. Here, we used intravital microscopy of the bone marrow to directly measure the kinetics of EV formation from endothelial cells in vivo under homoeostatic and malignant conditions. These large EVs are mitochondria-rich, expose the 'eat me' signal phosphatidylserine, and can interact with immune cell populations as a potential clearance mechanism. Elevated levels of circulating EVs correlates with degradation of the bone marrow vasculature caused by acute myeloid leukaemia. Together, our study provides in vivo spatio-temporal characterization of EV formation in the murine vasculature and suggests that circulating, large endothelial cell-derived EVs can provide a snapshot of vascular damage at distal sites.
© 2024. The Author(s).

Estrogens regulate eosinophilia in asthma and other inflammatory diseases. Further, peripheral eosinophilia and tumor-associated tissue eosinophilia (TATE) predicts a better response to immune checkpoint blockade (ICB) in breast cancer. However, how and if estrogens affect eosinophil biology in tumors and how this influences ICB efficacy has not been determined. Here, we report that estrogens decrease the number of peripheral eosinophils and TATE, and this contributes to increased tumor growth in validated murine models of breast cancer and melanoma. Moreover, estrogen signaling in healthy female mice also suppressed peripheral eosinophil prevalence by decreasing the proliferation and survival of maturing eosinophils. Inhibiting estrogen receptor (ER) signaling decreased tumor growth in an eosinophil-dependent manner. Further, the efficacy of ICBs was increased when administered in combination with anti-estrogens. These findings highlight the importance of ER signaling as a regulator of eosinophil biology and TATE and highlight the potential near-term clinical application of ER modulators to increase ICB efficacy in multiple tumor types.

ABSTRACT Astrocytes play important roles in the central nervous system (CNS) during health and disease. Prior studies have shown that gut commensals derived indole derivatives as well as secondary bile acids modulate astrocyte function during the late stage of EAE (recovery phase). Here we show that administering vancomycin to mice starting during the early stage of EAE improved disease recovery, an effect that is mediated by the gut microbiota. We observed that 6 taxa within the Clostridia vadinBB60 genus were enriched in vancomycin treated mice compared to untreated EAE mice. Vancomycin-treated EAE mice also had elevated serum levels of the anti-inflammatory tryptophan derived metabolite, indole-3-lactic acid and decreased levels of deoxycholic acid, a pro-inflammatory secondary bile acid. RNA sequencing revealed altered expression of several genes belonging to the mammalian target of rapamycin (mTOR) pathway in astrocytes obtained during the late stage of EAE from vancomycin treated EAE mice. Furthermore, we observed a link between serum levels of indole derivatives and bile acids and expression of several genes belonging to the mTOR pathway. Interestingly, the mTOR signaling cascades have been implicated in several key biological processes including innate (e.g., astrocyte) immune responses as well as neuronal toxicity/degeneration. In addition, rapamycin, a specific inhibitor of mTOR, has been shown to inhibit the induction and progression of established EAE. Collectively, our findings suggest that the neuroprotective effect of vancomycin is at least partially mediated by indole derivatives and secondary bile acids modulating the expression of mTOR pathway genes in astrocytes. HIGHLIGHTS Vancomycin attenuated established EAE through regulation of the microbiota. Vancomycin induced increased serum level of indole-3-lactic acid as well as decreased serum levels of indoxyl-3-sulfate, p-cresol and deoxycholic acid. Vancomycin modulated the expression of mTOR pathway genes in astrocytes Lactobacillus reuteri (enriched in vancomycin treated mice) regulated the expression of mTOR pathway genes in astrocytes Serum levels of indole-3-lactic acid, indoxyl-3-sulfate, p-cresol and deoxycholic acid correlated with expression of mTOR pathway genes in astrocytes

A key barrier to the development of vaccines that induce broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV) and other viruses of high antigenic diversity is the design of priming immunogens that induce rare bnAb-precursor B cells. The high neutralization breadth of the HIV bnAb 10E8 makes elicitation of 10E8-class bnAbs desirable; however, the recessed epitope within gp41 makes envelope trimers poor priming immunogens and requires that 10E8-class bnAbs possess a long heavy chain complementarity determining region 3 (HCDR3) with a specific binding motif. We developed germline-targeting epitope scaffolds with affinity for 10E8-class precursors and engineered nanoparticles for multivalent display. Scaffolds exhibited epitope structural mimicry and bound bnAb-precursor human naive B cells in ex vivo screens, protein nanoparticles induced bnAb-precursor responses in stringent mouse models and rhesus macaques, and mRNA-encoded nanoparticles triggered similar responses in mice. Thus, germline-targeting epitope scaffold nanoparticles can elicit rare bnAb-precursor B cells with predefined binding specificities and HCDR3 features.
© 2024. The Author(s).

Stimulator of interferon genes (STING)-dependent signaling is requisite for effective anti-microbial and anti-tumor activity. STING signaling is commonly defective in cancer cells, which enables tumor cells to evade the immunosurveillance system. We evaluate here whether intrinsic STING signaling in such tumor cells could be reconstituted by creating recombinant herpes simplex viruses (rHSVs) that express components of the STING signaling pathway. We observe that rHSVs expressing STING and/or cGAS replicate inefficiently yet retain in vivo anti-tumor activity, independent of oncolytic activity requisite on the trans-activation of extrinsic STING signaling in phagocytes by engulfed microbial dsDNA species. Accordingly, the in vivo effects of virotherapy could be simulated by nanoparticles incorporating non-coding dsDNA species, which comparably elicit the trans-activation of phagocytes and augment the efficacy of established cancer treatments including checkpoint inhibition and radiation therapy. Our results help elucidate mechanisms of virotherapeutic anti-tumor activity as well as provide alternate strategies to treat cancer.
Published by Elsevier Inc.