Biology subjects

Calvert, V.

Publications and source records attributed to Calvert, V..

3 recordsLinked to original sources

bioRxiv2025

Molecular Mechanisms of Priming Innate Immunity by Small Extracellular Vesicles Released during Infection with Gram-negative Bacteria

Much still remains to understand about the underlying molecular mechanisms by which the trafficking of small extracellular vesicles (sEVs) modulates innate immune responses during infection with pathogenic Gram-negative bacteria. To address this significant gap in knowledge, we used two infection models to investigate innate immune regulation by the sEVs released from cells infected with either Yersinia pestis (Yp) or Burkholderia thailandensis (Bt), designated as EXi-Yp and EXi-Bt respectively. The EXi induced differentiation of naive human monocytes to macrophages and triggered robust pro-inflammatory cytokine release, including release of IL-6, mirroring direct bacterial infection effects. Comprehensive cell signaling analyses revealed that the EXi modulate a small set of host signaling proteins, with p38 activation being primarily responsible for the observed protective effects. EXi-induced p38 activation leads to increased IL-6 release, which in turn is responsible for decreased bacterial survival within recipient immune cells that are subsequently infected. Consistent with the in vitro results, mice administered with EXi-Yp exhibited elevated serum IL-6 levels and were protected from Yp infection. Furthermore, using our microfluidic chip platform that allows functional interrogation of EV effects under physiologically relevant conditions, we have demonstrated that EXi exchange between Yp-infected cells and naive recipient monocytes leads to differentiation of the recipient cells to macrophages. Together, our findings reveal a largely unexplored aspect of innate immunity and provide a mechanistic model in which EXi prime local and distant naive monocytes via p38-induced differentiation and IL-6 production to protect against infection with Gram-negative bacteria.

immunology↗

bioRxiv2025

Separating faces in ARMS metabarcoding improves marine biodiversity monitoring: a comparison across protocols, experimental designs, and photographic surveys

Monitoring marine biodiversity requires approaches that capture its full complexity through space and time. DNA metabarcoding coupled with Autonomous Reef Monitoring Structures (ARMS) is increasingly used for this purpose, yet most applications still pool all sessile fractions and rarely benchmark molecular ouputs against photographic observations. Here, we combined photographic analysis with cytochrome c oxidase I (COI) metabarcoding across ten north-western Mediterranean sites to test, compare, and refine ARMS-based monitoring protocols. We first optimized laboratory procedures (DNA extraction and polymerase choice) and applied the control-driven, replicate-aware VTAM pipeline to minimize false positives and ensure full traceability. We then conducted the first face-by-face comparison of - and {beta}-diversity between imaging and eDNA in which each individual ARMS face was metabarcoded separately rather than pooled. Metabarcoding detected [~]15x higher site-level richness and revealed stronger correlations with geographic distance and environmental gradients, whereas photography provided complementary information on macro-taxa and surface cover. For metabarcoding, processing each face separately yielded much higher richness and markedly stronger {beta}-diversity-distance correlations than with the NOAA pooling protocol, demonstrating that pooling inflates sampling variance resulting in a loss of the ecological signal. Grouping faces into five structural categories offered a more operational alternative while further increasing -diversity and strengthening {beta}-diversity correlations. Overall, our results show that retaining ARMS microhabitat structure is critical for maximizing metabarcoding performance. Using five structural sessile fractions per ARMS combined with a control-driven bioinformatic workflow provides a reproducible, scalable framework for long-term eDNA monitoring and early detection of biodiversity change.

ecology↗

bioRxiv2025

Pancreatic cancer-intrinsic HuR regulates the pro-tumorigenic properties of extracellular vesicles

Pancreatic ductal adenocarcinoma (PDAC) tumors contain chaotic vasculature that limits immune surveillance and promotes early events in the metastatic cascade. However, current antiangiogenic therapies have failed in PDAC, and thus, it remains important to uncover mechanisms by which cancer cells signal to endothelial cells to increase angiogenesis. Our lab has shown that the tumor-intrinsic RNA-binding protein HuR (ELAVL1) plays an important role re-shaping the tumor microenvironment (TME) by regulating the stability and translation of cytokine encoding transcripts. Herein, we demonstrate that PDAC-intrinsic HuR influences endothelial cell function in the TME via extracellular vesicle (EV) signaling, an underexplored signaling axis in tumor progression. We found that HuR knockout (KO) tumors have impaired growth in an immunocompetent mouse model, and that administering purified wildtype (WT) EVs can increase tumor growth. Further, we observed that PDAC EVs contain HuR-dependent mRNA and protein cargoes relating to endothelial cell function and angiogenesis. Treatment of endothelial cells with HuR WT EVs strongly increased the expression of genes involved in barrier function and endothelial cell development, and directly increased their migratory and tube forming functions. In an immunocompetent orthotopic mouse model of PDAC, we showed that HuR increases endothelial cell presence and sprouting, while decreasing ICAM-1 expression. Importantly, we found utilizing a genetic EV reporter, that decreased ICAM-1 within WT tumors occurs in endothelial cells that have imported PDAC EVs, suggesting that this signaling axis is directly modulating endothelial cell behavior in vivo. Collectively, our data reveal a new role of HuR in EV signaling to endothelial cells, promoting angiogenesis while restricting endothelial cell leukocyte trafficking behavior.

cancer biology↗