scholarly journals Insights in ChAdOx1 nCov-19 Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT)

Blood ◽  
2021 ◽  
Author(s):  
Andreas Greinacher ◽  
Kathleen Selleng ◽  
Raghavendra Palankar ◽  
Jan Wesche ◽  
Stefan Handtke ◽  
...  
Keyword(s):  
Complex Formation ◽  
High Titer ◽  
Super Resolution ◽  
Virus Production ◽  
Thromboembolic Complication ◽  
Cerebral Vein ◽  
High Avidity ◽  
Dependent Manner ◽  
Platelet Factor ◽  
Systemic Dissemination

SARS-CoV-2 vaccine ChAdOx1 nCov-19 (AstraZeneca) causes a thromboembolic complication termed vaccine-induced immune thrombotic thrombocytopenia (VITT). Using biophysical techniques, mouse models and analysis of VITT patient samples we identified determinants of this vaccine-induced adverse reaction. Super-resolution microscopy visualized vaccine components forming antigenic complexes with platelet factor 4 (PF4) on platelet surfaces to which anti-PF4 antibodies obtained from VITT patients bound. PF4/vaccine complex formation was charge-driven and increased by addition of DNA. Proteomics identified substantial amounts of virus production-derived T-REx HEK293 proteins in the EDTA-containing vaccine. Injected vaccine increased vascular leakage in mice leading to systemic dissemination of vaccine components known to stimulate immune responses. Together, PF4/vaccine complex formation and the vaccine-stimulated proinflammatory milieu trigger a pronounced B cell response that results in the formation of high-avidity anti-PF4 antibodies in VITT patients. The resulting high-titer anti-PF4 antibodies potently activated platelets in the presence of PF4 or DNA and polyphosphate polyanions. Anti-PF4 VITT patient antibodies also stimulated neutrophils to release NETs in a platelet PF4-dependent manner. Biomarkers of procoagulant NETs were elevated in VITT patient serum, and NETs were visualized in abundance by immunohistochemistry in cerebral vein thrombi obtained from VITT patients. Together, vaccine-induced PF4/adenovirus aggregates and proinflammatory reactions stimulate pathologic anti-PF4 antibody production that drive thrombosis in VITT. The data support a two-step mechanism underlying VITT that resembles the pathogenesis of (autoimmune) heparin-induced thrombocytopenia.

scholarly journals Towards Understanding ChAdOx1 nCov-19 Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT)

2021 ◽  
Author(s):  
Andreas Greinacher ◽  
Kathleen Selleng ◽  
Jan Wesche ◽  
Stefan Handtke ◽  
Raghavendra Palankar ◽  
...  
Keyword(s):  
High Titer ◽  
Super Resolution ◽  
Dnase Activity ◽  
Cerebral Vein ◽  
Platelet Factor ◽  
Inflammatory Reactions ◽  
Vein Thrombosis ◽  
Human Proteins ◽  
Antibody Interactions ◽  
Super Resolution Microscopy

Abstract BackgroundSARS-CoV-2 vaccine ChAdOx1 nCov-19 rarely causes vaccine-induced immune thrombotic thrombocytopenia (VITT) that—like autoimmune heparin-induced thrombocytopenia—is mediated by platelet-activating anti-platelet factor 4 (PF4) antibodies.MethodsWe investigated vaccine, PF4, and VITT patient-derived anti-PF4 antibody interactions using dynamic light scattering, 3D-super-resolution microscopy, and electron microscopy. Mass spectrometry was used to analyze vaccine composition. We investigated the mechanism for early post-vaccine inflammatory reactions as potential co-stimulant for anti-PF4 immune response. Finally, we evaluated VITT antibodies for inducing release of procoagulant DNA-containing neutrophil extracellular traps (NETs), and measured DNase activity in VITT patient serum.ResultsBiophysical analyses showed formation of complexes between PF4 and vaccine constituents, including virus proteins that were recognized by VITT antibodies. EDTA, a vaccine constituent, increased microvascular leakage in mice allowing for circulation of virus- and virus-producing cell culture-derived proteins. Antibodies in normal sera cross-reacted with human proteins in the vaccine and likely contribute to commonly observed acute ChAdOx1 nCov-19 post-vaccination inflammatory reactions. Polyphosphates and DNA enhanced PF4-dependent platelet activation by VITT antibodies. In the presence of platelets, PF4 enhanced VITT antibody-driven procoagulant NETs formation, while DNase activity was reduced in VITT sera, with granulocyte-rich cerebral vein thrombosis observed in a VITT patient.ConclusionsChAdOx1 nCoV-19 vaccine constituents (i) form antigenic complexes with PF4, (ii) EDTA increases microvascular permeability, and (iii) vaccine components cause acute inflammatory reactions. Antigen formation in a proinflammatory milieu offers an explanation for anti-PF4 antibody production. High-titer anti-PF4 antibodies activate platelets and induce neutrophil activation and NETs formation, fueling the VITT prothrombotic response.

scholarly journals The neurorepellent, Slit2, prevents macrophage lipid loading by inhibiting CD36-dependent binding and internalization of oxidized low-density lipoprotein

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bushra Yusuf ◽  
Ilya Mukovozov ◽  
Sajedabanu Patel ◽  
Yi-Wei Huang ◽  
Guang Ying Liu ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Super Resolution ◽  
Low Density ◽  
Dependent Manner ◽  
Oxidized Low Density Lipoprotein ◽  
Cortical Actin ◽  
Cytoskeletal Remodeling ◽  
Atherosclerotic Lesions ◽  
Modified Lipoproteins

AbstractAtherosclerosis is characterized by retention of modified lipoproteins, especially oxidized low density lipoprotein (oxLDL) within the sub-endothelial space of affected blood vessels. Recruited monocyte-derived and tissue-resident macrophages subsequently ingest oxLDL by binding and internalizing oxLDL via scavenger receptors, particularly CD36. The secreted neurorepellent, Slit2, acting through its transmembrane receptor, Roundabout-1 (Robo-1), was previously shown to inhibit recruitment of monocytes into nascent atherosclerotic lesions. The effects of Slit2 on oxLDL uptake by macrophages have not been explored. We report here that Slit2 inhibits uptake of oxLDL by human and murine macrophages, and the resulting formation of foam cells, in a Rac1-dependent and CD36-dependent manner. Exposure of macrophages to Slit2 prevented binding of oxLDL to the surface of cells. Using super-resolution microscopy, we observed that exposure of macrophages to Slit2 induced profound cytoskeletal remodeling with formation of a thick ring of cortical actin within which clusters of CD36 could not aggregate, thereby attenuating binding of oxLDL to the surface of cells. By inhibiting recruitment of monocytes into early atherosclerotic lesions, and the subsequent binding and internalization of oxLDL by macrophages, Slit2 could represent a potent new tool to combat individual steps that collectively result in progression of atherosclerosis.

scholarly journals Hyperphosphorylation of the retinoblastoma gene product is determined by domains outside the simian virus 40 large-T-antigen-binding regions.

1990 ◽  
Vol 10 (12) ◽  
pp. 6586-6595 ◽  
Author(s):  
P A Hamel ◽  
B L Cohen ◽  
L M Sorce ◽  
B L Gallie ◽  
R A Phillips
Keyword(s):  
Cell Cycle ◽  
Complex Formation ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Phosphorylation Sites ◽  
Dependent Manner ◽  
Large T Antigen ◽  
T Complex ◽  
Cycle Dependent

With the murine retinoblastoma (RB) cDNA, a series of RB mutants were expressed in COS-1 cells and the pRB products were assessed for their ability (i) to bind to large T antigen (large T), (ii) to become modified by phosphorylation, and (iii) to localize in the nucleus. All point mutations and deletions introduced into regions previously defined as contributing to binding to large T abolished pRB-large T complex formation and prevented hyperphosphorylation of the RB protein. In contrast, a series of deletions 5' to these sites did not interfere with binding to large T. While some of the 5' deletion mutants were clearly phosphorylated in a cell cycle-dependent manner, one, delta Pvu, failed to be phosphorylated depsite binding to large T. pRB with mutations created at three putative p34cdc2 phosphorylation sites in the N-terminal region behaved similarly to wild-type pRB, whereas the construct delta P5-6-7-8, mutated at four serine residues C terminal to the large T-binding site, failed to become hyperphosphorylated despite retaining the ability to bind large T. All of the mutants described were also found to localize in the nucleus. These results demonstrate that the domains in pRB responsible for binding to large T are distinct from those recognized by the relevant pRB-specific kinase(s) and/or those which contain cell cycle-dependent phosphorylation sites. Furthermore, these data are consistent with a model in which cell cycle-dependent phosphorylation of pRB requires complex formation with other cellular proteins.

Expression of human adenosine deaminase in murine hematopoietic cells

1988 ◽  
Vol 8 (12) ◽  
pp. 5116-5125
Author(s):  
J W Belmont ◽  
G R MacGregor ◽  
K Wager-Smith ◽  
F A Fletcher ◽  
K A Moore ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Adenosine Deaminase ◽  
High Titer ◽  
Virus Production ◽  
Marrow Transplant ◽  
Mouse Bone Marrow ◽  
Regulation Of Expression ◽  
Murine Bone Marrow

Multiple replication-defective retrovirus vectors were tested for their ability to transfer and express human adenosine deaminase in vitro and in vivo in a mouse bone marrow transplantation model. High-titer virus production was obtained from vectors by using both a retrovirus long terminal repeat promoter and internal transcriptional units with human c-fos and herpes virus thymidine kinase promoters. After infection of primary murine bone marrow with one of these vectors, human adenosine deaminase was detected in 60 to 85% of spleen colony-forming units and in the blood of 14 of 14 syngeneic marrow transplant recipients. This system offers the opportunity to assess methods for increasing efficiency of gene transfer, for regulation of expression of foreign genes in hematopoietic progenitors, and for long-term measurement of the stability of expression in these cells.

Effect of SR121566A, a Potent GP IIb-IIIa Antagonist, on the HIT Serum/heparin-Induced Platelet Mediated Activation of Human Endothelial Cells

1998 ◽  
Vol 80 (08) ◽  
pp. 326-331 ◽  
Author(s):  
Pierre Savi ◽  
Walter Jeske ◽  
Jeanine Walenga ◽  
Jean-Marc Herbert
Keyword(s):  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Umbilical Vein ◽  
Common Adverse Effect ◽  
Surface Protein ◽  
Heparin Therapy ◽  
Serotonin Release ◽  
Dependent Manner ◽  
Platelet Factor

SummaryHeparin-induced thrombocytopenia (HIT) is a common adverse effect of heparin therapy that carries a risk of serious thrombotic events. This condition is caused by platelet aggregation, which is mediated by anti-heparin/platelet factor 4 antibodies. Sera from patients with HIT in the presence of platelets, induced the expression of E-selectin, VCAM, ICAM-1 and tissue factor and the release of IL1β, IL6, TNFα and PAI-1 by human umbilical vein endothelial cells (HUVECs) in vitro and initiated platelet adhesion to activated HUVECs. These effects which occurred in a time-dependent manner were significant in the first 1-2 h of incubation and reached a maximum after 6 to 9 h. The GP IIb-IIIa receptor antagonist SR121566A which has been shown to block platelet aggregation induced by a wide variety of agonists including HIT serum/heparin, reduced in a dose-dependent manner the HIT serum/heparin-induced, platelet mediated expression and release of the above mentioned proteins. The IC50 for inhibition of HIT serum/ heparin-induced platelet dependent HUVEC activation by SR121566A was approximately 10-20 nM. ADP, but not serotonin release, also appeared to be involved as apyrase and ATPγS blocked platelet-dependent, HIT serum/heparin-induced cell surface protein expression and cytokine release by HUVECs. Increased platelet adherence to HIT serum/heparin-activated HUVECs was inhibited by SR121566A and, to a lesser extent, by apyrase and ATPγS, showing that platelet activation and release was at the origin of the HIT serum/heparin-induced expression of these proteins by HUVECs.Thus, sera from patients with HIT induced the expression of adhesive and coagulation proteins and the release of cytokines by HUVECs through the activation of platelets which occurred in a GP IIb-IIIa-dependent manner, a process that could be selectively blocked by SR121566A.

scholarly journals LRRK2 mediates tubulation and vesicle sorting from membrane damaged lysosomes

2020 ◽  
Author(s):  
Luis Bonet-Ponce ◽  
Alexandra Beilina ◽  
Chad D. Williamson ◽  
Eric Lindberg ◽  
Jillian H. Kluss ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Super Resolution ◽  
Adaptor Protein ◽  
Dependent Manner ◽  
Leucine Rich Repeat ◽  
Biological Functions ◽  
New Process ◽  
Sporadic Parkinson’S Disease

ABSTRACTMutations in the leucine rich repeat kinase 2 (LRRK2) gene are a cause of familial and sporadic Parkinson’s disease (PD). Nonetheless, the biological functions of LRRK2 remain incompletely understood. Here, we observed that LRRK2 is recruited to lysosomes that have a ruptured membrane. Using unbiased proteomics, we observed that LRRK2 is able to recruit the motor adaptor protein JIP4 to permeabilized lysosomes in a kinase-dependent manner through the phosphorylation of RAB35 and RAB10. Super-resolution live cell imaging microscopy and FIB-SEM revealed that once at the lysosomal membrane, JIP4 promotes the formation of LAMP1-negative lysosomal tubules that release membranous content from ruptured lysosomes. Released vesicular structures are able to interact with other lysosomes. Thus, we described a new process that uses lysosomal tubulation to release vesicular structures from permeabilized lysosomes. LRRK2 orchestrates this process that we name LYTL (LYsosomal Tubulation/sorting driven by LRRK2) that, given the central role of the lysosome in PD, is likely to be disease relevant.

scholarly journals Arachidonic acid promotes the binding of 5-lipoxygenase on nanodiscs containing 5-lipoxygenase activating protein in the absence of calcium-ions

2020 ◽  
Author(s):  
Ramakrishnan B. Kumar ◽  
Pasi Purhonen ◽  
Hans Hebert ◽  
Caroline Jegerschöld
Keyword(s):  
Arachidonic Acid ◽  
Complex Formation ◽  
Calcium Ions ◽  
Dependent Manner ◽  
Present Communication ◽  
Nuclear Membranes ◽  
His Tag ◽  
C Terminus ◽  
Transmission Electron

AbstractAmong the first steps in inflammation is the conversion of arachidonic acid (AA) stored in the cell membranes into leukotrienes. This occurs mainly in leukocytes and depends on the interaction of two proteins: 5-lipoxygenase (5LO), stored away from the nuclear membranes until use and 5-lipoxygenase activating protein (FLAP), a transmembrane, homotrimeric protein, constitutively present in nuclear membrane. We could earlier visualize the binding of 5LO to nanodiscs in the presence of Ca2+-ions by the use of transmission electron microscopy (TEM) on samples negatively stained by sodium phosphotungstate. In the absence of Ca2+-ions 5LO did not bind to the membrane. In the present communication, FLAP reconstituted in the nanodiscs which could be purified if the His-tag was located on the FLAP C-terminus but not the N-terminus. Our aim was to find out if 1) 5LO would bind in a Ca2+-dependent manner also when FLAP is present? 2) Would the substrate (AA) have effects on 5LO binding to FLAP-nanodiscs? TEM was used to assess the complex formation between 5LO and FLAP-nanodiscs along with, sucrose gradient purification, gel-electrophoresis and mass spectroscopy. It was found that presence of AA by itself induces complex formation in the absence of added calcium. This finding corroborates that AA is necessary for the complex formation and that a Ca2+-flush is mainly needed for the recruitment of 5LO to the membrane. Our results also showed that the addition of Ca2+-ions promoted binding of 5LO on the FLAP-nanodiscs as was also the case for nanodiscs without FLAP incorporated. In the absence of added substances no 5LO-FLAP complex was formed. Another finding is that the formation of a 5LO-FLAP complex appears to induce fragmentation of 5LO in vitro.

scholarly journals Retinoic Acid Induces Aggregation of the Acute Promyelocytic Leukemia Cell Line NB-4 by Utilization of LFA-1 and ICAM-2

Blood ◽  
1997 ◽  
Vol 90 (7) ◽  
pp. 2747-2756 ◽  
Author(s):  
Richard S. Larson ◽  
David C. Brown ◽  
Larry A. Sklar
Keyword(s):  
Retinoic Acid ◽  
Acute Promyelocytic Leukemia ◽  
Promyelocytic Leukemia ◽  
Leukemia Cell Line ◽  
High Avidity ◽  
Dependent Manner ◽  
Adhesive Properties ◽  
Dose Dependent ◽  
Β2 Integrins ◽  
Retinoic Acid Syndrome

All-trans retinoic acid (tRA) is a potent differentiation agent that is effective therapy for acute promyelocytic leukemia (APL). However, 5% to 25% of patients develop retinoic acid syndrome, a potentially life-threatening complication in which the pathogenesis relates to adhesive alterations of APL cells. Therefore, we investigated the relationship between tRA-induced differentiation and the adhesive properties of APL cells. After confirming differentiation-related morphological changes of NB-4 cells in response to tRA, we showed that homotypic aggregation of NB-4 cells grown in tRA for 72 hours is dose-dependent with a median effective dose of approximately 50 nmol/L. Maximal aggregation occurred at mean and peak therapeutic serum concentrations (100 and 1,000 nmol/L, respectively). Aggregation also increased with the length of tRA exposure over 168 hours. Aggregation was inhibited by neutralizing antibodies against LFA-1 and ICAM-2. Notably, antibodies directed against VLA-4, other β2 integrins (Mac-1 and p150), or other potential LFA-1 counterstructures that were expressed on the cell surface (ICAM-1 and ICAM-3) did not block aggregation. Aggregation occurred with similar kinetics regardless of the presence of phorbol ester or the “activating” monoclonal antibody (MoAb) KIM 185, suggesting that the avidity of LFA-1 is not modulated on NB-4 cells in a manner similar to other leukocytes. Consistent with the prompt clinical effectiveness of methyl prednisolone sodium succinate (MPSS) in retinoic acid syndrome, MPSS rapidly inhibited homotypic aggregation in a dose-dependent manner. Thus, tRA alters the adhesive properties of APL cells by inducing the expression of high-avidity β2 integrins, aggregation is inhibited by LFA-1 and ICAM-2 MoAb, and tRA effects are rapidly reversible by MPSS. Taken together, our findings provide a clinically relevant system for study of LFA-1/ICAM-2 interaction and suggest a mechanism in part for retinoic acid syndrome and the effectiveness of MPSS in ameliorating retinoic acid syndrome.

Abstract 524: Identification of Roles for the Rho-Specific Guanine Nucleotide Dissociation Inhibitor (RhoGDI) Ly-Gdi in Platelet Function

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Anh T Ngo ◽  
Marisa L Thierheimer ◽  
Özgün Babur ◽  
Anne D Rocheleau ◽  
Xiaolin Nan ◽  
...  
Keyword(s):  
Platelet Function ◽  
Rho Gtpases ◽  
Cell Biology ◽  
Rho Gtpase ◽  
Thrombus Formation ◽  
Super Resolution ◽  
Dependent Manner ◽  
Guanine Nucleotide ◽  
Morphological Alterations ◽  
Guanine Nucleotide Dissociation Inhibitor

Introduction: Upon activation, platelets undergo specific morphological alterations critical to hemostatic plug and thrombus formation via actin cytoskeletal reorganizations driven by the Rho GTPases Rac1, Cdc42 and RhoA. Here we investigate roles for Rho-specific guanine nucleotide dissociation inhibitor proteins (RhoGDIs) in regulating platelet function. Methods and Hypothesis: Through an approach combining pharmacology, cell biology and systems biology methods we assessed the hypothesis that RhoGDI proteins regulate Rho GTPase-driven platelet functions downstream of platelet integrin and glycoprotein receptors. Results: We find that platelets express two RhoGDI family members, RhoGDI and Ly-GDI. Antibody interference and platelet spreading experiments suggest a specific role for Ly-GDI in platelet function. Intracellular staining and super resolution microscopy assays find that Ly-GDI displays an asymmetric, polarized localization that largely overlaps with Rac1 and Cdc42 as well as microtubules and protein kinase C (PKC) in platelets adherent to fibrinogen. Signaling studies based on interactome and pathways analyses also support a regulatory role for Ly-GDI in platelets, as Ly-GDI is phosphorylated at PKC substrate motifs in a PKC-dependent manner in response to the platelet collagen receptor glycoprotein (GP)VI-specific agonist collagen-related peptide. Notably, inhibition of PKC diffuses the polarized organization of Ly-GDI in spread platelets relative to its colocalization with Rac1 and Cdc42. Conclusion: In conclusion, our results support roles for Ly-GDI as a localized regulator of Rho GTPases in platelets and link PKC and Rho GTPase signaling systems to platelet function.

scholarly journals kat: a high-efficiency retroviral transduction system for primary human T lymphocytes

Blood ◽  
1994 ◽  
Vol 83 (1) ◽  
pp. 43-50 ◽  
Author(s):  
MH Finer ◽  
TJ Dull ◽  
L Qin ◽  
D Farson ◽  
MR Roberts
Keyword(s):  
T Lymphocytes ◽  
High Efficiency ◽  
High Titer ◽  
Virus Production ◽  
Retroviral Vectors ◽  
Expression Vectors ◽  
Retroviral Transduction ◽  
Human T Lymphocytes ◽  
293 Cells ◽  
Viral Titers

Abstract We describe a novel retroviral packaging system in which high titer amphotropic retrovirus was produced without the need to generate stable producer clones. kat expression vectors, which produce high levels of retroviral vector transcripts and retroviral packaging functions, were transfected into 293 cells followed by virus harvest 48 hours posttransfection. Viral titers as high as 3.8 proviral copies/cell/mL of frozen supernatant in 3T3 cells were obtained, 10- to 50-fold greater than transient viral titers reported using 3T3-based retroviral packaging lines. Cocultivation of primary human CD8+ T lymphocytes after transient transfection of 293 cells with kat plasmids resulted in transduction efficiencies of 10% to 40%, 5- to 10-fold greater compared to cocultivation with a high titer PA317 producer clone and significantly greater than previously reported results for transduction of primary human T lymphocytes with retroviral vectors. Virus produced using the kat system was shown to be free of detectable replication competent retrovirus by an extended provirus mobilization assay, demonstrating that this system is as safe as currently available stable packaging lines. The kat virus production system should be of general use for the rapid production of high titer viral supernatants, as well as for high-efficiency transduction hematopoietic cell types refractory to retroviral transduction.

Sign in / Sign up

Export Citation Format

Share Document