Introduction Transfusion of platelet concentrates (PCs) is an essential medical approach to treat or prevent bleeding in patients with impaired platelet function or after injury. Nevertheless, the standard storage of PCs at room-temperature (RT) is associated with an increased risk of bacterial contamination as well as reduced platelet functionality. We previously showed that cold-stored PCs have better functionality compared to RT-stored PCs but reduced in vivo circulation time due to cold-induced apoptosis. To investigate cold-stored PCs hemostatic functionality upon apoptosis inhibition, we established an ex vivo model simulating physiological blood flow to evaluate the contribution of cold-stored PCs to thrombus formation.

Background: This study aims to evaluate the role of parvovirus B19 (B19V) in the pathogenesis of myocarditis in a paediatric population, including post-mortem samples from two children. Methods: From 2004 to 2023, endomyocardial biopsies (EMBs) from children under 16 years of age were analyzed using histology, immunohistochemistry, and molecular pathology. A total of 306 children with acute and 1060 children with chronic lymphocytic myocarditis were identified. Results: B19V infection was more frequent in acute myocarditis than in chronic myocarditis (43% vs. 14%), with higher viral loads in acute cases regardless of age. The most prominent cardiac CD3+ T cell infiltration was noted in children < 2 years, correlating with high cardiac B19V loads. In two male infants who died from B19V infection, B19V DNA was localized in the endothelial cells of multiple organs using in situ hybridization. Virus replication was found in the endothelial cells of small cardiac arterioles and venules but not in capillaries. B19V DNA/mRNA was also detected in immune cells, especially in the spleen and lymph nodes, revealing virus replication in B lymphocytes. Conclusions: B19V can induce severe lymphocytic myocarditis, especially in young children. The simultaneous histopathological and molecular assessment of EMBs is important for early diagnosis of viral myocarditis, preventing severe disease, and ensuring appropriate therapy.

Introduction Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin. Heparin/PF4/IgG complexes have been reported to activate platelets, neutrophils, and possibly endothelial cells, resulting in thrombocytopenia, hypercoagulability and thromboembolic complications. While the impact of anti-PF4/heparin antibodies on blood cell activation has been extensively studied, the role of endothelial cells in HIT-associated thrombosis remains underexplored. In particular, the interactions between HIT-induced procoagulancy and endothelial cells under flow conditions is not completely elucidated. In this report, we investigated how HIT antibodies induce thrombosis in an endothelialized microfluidic system.

Background: Functional platelet activation assays are required for the diagnosis of heparin -induced thrombocytopenia (HIT). Due to their sophisticated methodology, they are only available in reference centers. Objectives: To evaluate the diagnostic accuracy of the flow cytometry-based heparinactivated procoagulant platelet (HAPP) assay in the laboratory diagnosis of HIT. Methods: Procoagulant platelets (PCP), defined by the expression of phosphatidylserine and CD62-P, were evaluated by flow cytometry in platelet -rich plasma from healthy donors after incubation with patient sera in the absence and presence of heparin. A sample was considered positive in HAPP assay, if the following 3 criteria were met: 1) the percentage of PCPs was >= 10.3% after incubation with 0.2 IU/mL heparin, 2) the fold increase in presence of 0.2 IU/mL heparin compared with buffer was >= 1.5, and 3) 100 IU/mL of heparin resulted in >= 50% inhibition of PCP. HAPP assay was validated in a prospective cohort (n = 202) of consecutive specimens submitted to our laboratory for serologic diagnosis of HIT. Heparin -induced platelet activation (HIPA) assay was used as the reference standard. Results: HIT -positive sera induced PCPs in the presence of 0.2 IU/mL heparin, which was inhibited with 100 IU/mL of heparin. In the prospective validation cohort, there were 15 HIPA+ and 187 HIPA- sera. HAPP was positive in 20 samples in this cohort. Using optimized cut-offs, HAPP assay had a sensitivity of 93.3% and specificity of 96.8%. Conclusion: HAPP assay is promising as a simple and reliable functional assay for HIT; however, further studies are needed to confirm our results in larger cohorts.

Introduction: Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin. Antibodies against platelet factor 4 (PF4) or a heparin/PF4 complex have been reported to activate platelets, neutrophils and possibly endothelial cells, resulting in thrombocytopenia, hypercoagulability and thromboembolic complications. While the impact of anti-PF4/heparin antibodies on platelet, neutrophil and monocyte activation has been extensively studied, the role of endothelial cells in HIT-associated thrombosis remains underexplored. In particular, the interactions between HIT-induced procoagulancy and endothelial cells under dynamic conditions is not completely analyzed. In this report, we investigated how HIT antibodies induce thrombosis in an endothelialized microfluidic system. Methods: Fibrinogen microfluidic channels were coated with confluent monolayer of human umbilical vein endothelial cells (HUVECs). Cells were primed with low-dose TNF-α to induce a sub-thrombotic endothelial activation, prior to perfusion of whole blood. Recalcified unstimulated or Thrombin Receptor Activator Peptide 6 (TRAP-6) activated whole blood was perfused at a venous flow rate. HIT-thrombosis model was established and tested with monoclonal anti-PF4/heparin antibodies in whole blood. In brief, whole blood was pre-incubated with unfractionated heparin (UFH, 0.2 IU/mL and 100 IU/mL). Next, anti-PF4/heparin antibodies were introduced to the whole blood mixture and incubated for 30 minutes. Whole blood was recalcified and perfused over resting or primed endothelial cells at a venous shear stress. Thrombus formation was recorded over time. Results: The endothelialized microfluidic model successfully captures sub-thrombotic conditions under venous shear. Activated platelets induced a procoagulant shift and three-dimensional thrombi. We applied our thrombosis model to investigate thrombus formation induced by a HIT mimicking monoclonal antibody. We show that the heparin-dependent platelet activation predicts the thrombotic response in the microfluidic system: HIT antibodies in absence of heparin did not exert a pro-thrombotic effect on activated endothelial cells. Co-incubation with 0.2 IU/mL UFH induced thrombosis, embolization of thrombus material and channel occlusion only when endothelial cells were primed with TNF-α. The pro-thrombotic effect of HIT antibodies was fully reversed at the super-therapeutic dose of 100 IU/mL UFH. Conclusions: HIT antibodies induce thrombosis and embolization in a system emulating physiological environment. For the first time, we present a comprehensive thrombosis model that incorporates the established thrombogenicity of HIT-mimicking antibodies. We show that our thrombosis model incorporates both endothelial- and blood-based control of thrombosis. Primed endothelial cells and antibody-induced procoagulancy trigger thrombosis in a concerted fashion, allowing investigation of the underlying mechanisms and possible preclinical evaluation of potential inhibitors of HIT-thrombosis. Figure 1, upper panel: Maximal thrombus surface area coverage of TNF-α primed endothelial cells, perfused with unstimulated, TRAP-6 activated or HIT-like IgG/heparin challenged whole blood. HIT-like IgG did not increase thrombus formation in absence of heparin. Addition of low-dose heparin exerted a strong pro-thrombotic effect, that was fully reversible with a super-therapeutic concentration of heparin. Lower panel: representative images of thrombi formed by HIT-like IgG in absence and under low or high-dose heparin. Platelets: green, Calcein-AM. Scale bar: 200 µm.

Introduction Platelet concentrates are routinely used to prevent bleeding in patients with impaired platelet function or after injury. Hemostatic function of platelet concentrates has been investigated intensively under steady state settings but until now no standard and robust protocols are available for platelet function testing under shear stress. Our aim is to establish an ex vivo model to evaluate the contribution of platelet concentrates in thrombus formation.

Introduction: Platelet concentrates (PCs) are used to treat or prevent bleeding in patients with impaired platelet function or after injury. However, the standard storage of PCs at room-temperature (RT) increases the risk of bacterial contamination and is associated with reduced platelet functionality due to storage lesions. Our group reported that cold-stored PCs have better functionality compared to RT-stored PCs but reduced in vivo circulation time due to cold-induced apoptosis. In order to investigate cold-stored PCs hemostatic functionality with and without apoptosis inhibition, we established an ex vivo model simulating physiological conditions of blood flow to evaluate the contribution of cold-stored PCs in thrombus formation. Methods: Apheresis-derived PCs were stored for 1, 4, 7 and 10 days under agitation at 4°C or RT either with or without the apoptosis inhibitor G04 (RhoA GTPase inhibitor). Next, PCs were stained with CD41 antibody, recalcified and incubated with TRAP6 (thrombin receptor-activating peptide 6) to initiate thrombus formation. Platelet-depleted whole blood samples from healthy donors were spiked-in with PCs and administered to the microfluidic channels of the ex vivo system (Bioflux), under physiological shear pressure. After five minutes of perfusion the resulting thrombi were imaged and analyzed. Ability to form thrombi was further assessed by thromboelastography and impedance aggregometry. Results: Platelets from 24h storage PCs showed stable thrombus formation upon activation with TRAP6. Unstimulated platelets did not form any thrombi during the entire period of perfusion. To evaluate the effect of cold storage on platelet functions we analyzed the extent of thrombus formation of PCs stored at RT and 4°C upon CD41 staining. Our results indicate that cold-stored platelets form larger clots under flow conditions and maintain higher functionality compared to PCs stored at RT. Moreover, incubation of cold-stored PCs with the apoptosis inhibitor G04 improved ex vivo thrombus formation compared to PCs stored without the inhibitor, without inducing any adverse effects (Figure 1). Conclusion: The results indicate that our ex vivo assay, which simulates PC transfusion in thrombocytopenic patients, is suitable to test the hemostatic functions of PCs under physiological flow conditions. We demonstrated that PCs stored at 4°C show better thrombus formation ability upon stimulation by agonists compared to RT-stored PCs and that the ability to form clots under shear stress is still preserved after incubation with the apoptosis inhibitor. To conclude, cold-storage of PCs in combination with apoptosis inhibition is a promising stragedy to reduce the risk of bacterial contamination and prolong in vivo survival time while preserving platelet's hemostatic functionality.

Heparin-induced thrombocytopenia (HIT) is a severe immune-mediated prothrombotic disorder caused by antibodies (Ab) reactive to complexes of platelet factor 4 and heparin. Platelets (PLT) and their interaction with different immune cells contribute to prothrombotic conditions in HIT. However, the exact mechanisms and the role of different PLT subpopulations in this prothrombotic environment remain poorly understood. In this study, we observed that HIT patient Ab induce a new PLT population that is characterized by increased P-selectin expression and phosphatidylserine (PS) externalization. Formation of this procoagulant PLT subpopulation was dependent on engagement of PLT Fc-γ-RIIA by HIT Ab and resulted in a significant increase of thrombin generation on the PLT surface. Using an ex vivo thrombosis model and multi-parameter assessment of thrombus formation, we observed that HIT Ab-induced procoagulant PLT propagated formation of large PLT aggregates, leukocyte recruitment and most importantly, fibrin network generation. These prothrombotic conditions were prevented via the upregulation of PLT intracellular cAMP with Iloprost, a clinically approved prostacyclin analogue. Additionally, the functional relevance of P-selectin and PS was dissected. While inhibition of P-selectin did not affect thrombus formation, the specific blockade of PS prevented HIT Ab-mediated thrombin generation and most importantly procoagulant PLT-mediated thrombus formation ex vivo. Taken together, our findings indicate that procoagulant PLT are critical mediators of prothrombotic conditions in HIT. Specific PS targeting could be a promising therapeutic approach to prevent thromboembolic events in HIT patients.

Introduction Transfusion of platelet concentrates (PCs) is an essential medical strategy to treat bleeding or to prevent it. However, the standard storage at room temperature enhances the risk of bacterial contamination. We reported that cold-stored PCs had better functionality but reduced survival due to cold-induced apoptosis. In this study, we investigated the impact of apoptosis inhibition on platelet functions and half-life during cold storage.

Introduction Human malaria infections with Plasmodium falciparum are commonly accompanied by a reduction of platelet counts and thrombocytopenia. Usually, platelet counts drop within 10 to 15 days after the initial infection and do not fully recover up until the malaria infection is cleared. Previously, a variety of mechanisms for thrombocytopenia in Malaria have been proposed, including the removal of activated platelets from circulation or anti-Platelet Factor 4 (PF4) antibody-mediated platelet clearance. However, these mechanisms have commonly been studied in natural malaria infection and thus the observation periods are restricted to the symptomatic phase of the disease. Here, we report platelet phenotypes of a cohort of P. falciparum infected vaccine trial participants, covering the initial phase of infection and thrombocytopenia up to two weeks after challenge with malaria parasites.

Introduction Heparin-induced thrombocytopenia (HIT) is caused by anti- PF4/Heparin IgG antibodies, which activates platelets and leads to thrombocytopenia and thrombosis. The diagnosis of HIT can only be confirmed by using functional assays such as the Heparin-Induced Platelet Activation assay (HIPA assay). However, functional assays are technically demanding and routinely available only in specialized laboratories. The aim of the current study was to establish a flow cytometer-based method to detect procoagulant platelets using platelet-rich plasma (PRP) for the diagnosis of HIT.

Extracorporeal circulation (ECC) is frequently used in intensive care patients with impaired lung or cardiac function. Despite being a life-saving therapeutic option, ECC is associated with increased risk for both bleeding and thrombosis. The management of bleeding and thromboembolic events in ECC patients is still challenging partly due to the lack of information on the pathophysiological changes in hemostasis and platelet function during the procedure. Using a combination of an ex vivo model for shear stress and a sensitive and easy-to-use laboratory method, we analyzed platelet responsiveness during ECC. After shear stress simulation in an ex vivo closed-loop ECC model, we found a significantly decreased response of α-granules after activation with adenosine diphosphate and thrombin receptor activating peptide (TRAP-6) and CD63 expression after activation with TRAP-6. Mepacrine uptake was also significantly reduced in the ex vivo shear stress model.In the same line, platelets from patients under ECC with venovenous systems and venoarterial systems showed impaired CD62P degranulation after stimulation with ADP and TRAP-6 compared with healthy control on day 1, 6, and 10 after implantation of ECC. However, no correlation between platelet degranulation and the occurrence of bleeding or thromboembolic events was observed.The used whole blood flow cytometry with immediate fixation after drawing introduces a sensitive and easy-to-use method to determine platelet activation status and our data confirm that increased shear stress conditions under ECC can cause impaired degranulation of platelet.

Cold storage of platelets has been suggested as an alternative approach to reduce the risk of bacterial contamination and to improve the cell quality as well as functionality compared to room temperature storage. However, cold-stored platelets (CSP) are rapidly cleared from the circulation. Among several possible mechanisms, apoptosis has been recently proposed to be responsible for the short half-life of refrigerated platelets. In the present study, we investigated the impact of apoptosis inhibition on the hemostatic functions and survival of CSP. We found that blocking the transduction of the apoptotic signal induced by glycoprotein Ib (GPIb)-α clustering or the activation of caspase 9 does not impair CSP functionality. In fact, the inhibition of GPIb-α clustering mediated-apoptotic signal by a RhoA inhibitor better conserved δ granule release, platelet aggregation, adhesion and the ability to form stable clots, compared to untreated CSP. In contrast, upregulation of the protein kinase A caused a drastic impairment of platelet functions and whole blood clot stability. More importantly, we observed a significant improvement of the half-life of CSP upon inhibition of the intracellular signal induced by GPIb-α clustering. In conclusion, our study provides novel insights on the in vitro hemostatic functions and half-life of CSP upon inhibition of the intracellular cold-induced apoptotic pathway. Our data suggest that the combination of cold storage and apoptosis inhibition might be a promising strategy to prolong the storage time without impairing hemostatic functions or survival of refrigerated platelets.

Background: The diagnosis of platelet function is often difficult and the required laboratory tests can only be performed in specialized centers. Light transmission aggregometry (LTA) is the gold standard method to evaluate platelet function, but it requires a large volume of blood. On the other hand, immunofluorescence microscopy (IFM) and flow cytometry (FC) can be performed with a very small amount of blood. We present here the application of these three methods in the diagnosis of two cases with platelet dysfunction.

Life-threatening thrombotic events at unusual sites have been reported after vector-based vaccinations against severe acute respiratory syndrome coronavirus 2. This phenomenon is now termed vaccine-induced immune thrombotic thrombocytopenia (VITT). The pathophysiology of VITT is similar to that of heparin-induced thrombocytopenia (HIT) and is associated with platelet-activating antibodies (Abs) against platelet factor 4 (PF4). Therefore, current guidelines suggest nonheparin anticoagulants to treat VITT patients. In this study, we investigated the interactions of heparin, danaparoid, fondaparinux, and argatroban with VITT-Ab/PF4 complexes using an ex vivo model for thrombus formation as well as in vitro assays to analyze Ab binding and platelet activation. We found that immunoglobulin Gs (IgGs) from VITT patients induce increased adherent platelets/thrombus formation in comparison with IgGs from healthy controls. In this ex vivo flow-based model, the procoagulant activity of VITT IgGs was effectively inhibited with danaparoid and argatroban but also by heparin. Interestingly, heparin and danaparoid not only inhibited IgG binding to PF4 but were also able to effectively dissociate the preformed PF4/IgG complexes. Fondaparinux reduced the in vitro generation of procoagulant platelets and thrombus formation; however, it did not affect platelet aggregation. In contrast, argatroban showed no effect on procoagulant platelets and aggregation but significantly inhibited VITT-mediated thrombus formation. Taken together, our data indicate that negatively charged anticoagulants can disrupt VITT-Ab/PF4 interactions, which might serve as an approach to reduce Ab-mediated complications in VITT. Our results should be confirmed, however, in a clinical setting before a recommendation regarding the selection of anticoagulants in VITT patients could be made.

Coronavirus disease-2019 (COVID-19) is associated with increased thromboembolic complications. Long-term alteration in the coagulation system after acute COVID-19 infection is still a subject of research. Furthermore, the effect of sera from convalescent subjects on platelets is not known. In this study, we investigated platelet phenotype, coagulation, and fibrinolysis in COVID-19 convalescent plasma (CCP) donors and analyzed convalescent sera-induced effects on platelets. We investigated CCP donors who had a history of mild COVID-19 infection and donors who did not have COVID-19 were used as controls. We analyzed phosphatidylserine (PS) externalization, CD62p expression, and glycoprotein VI (GPVI) shedding both in platelet-rich plasma (PRP) and after incubation of washed healthy platelets with donors' sera using flow cytometry. Coagulation and fibrinolysis systems were assessed with thromboelastometry. Forty-seven CCP donors (22 males, 25 females; mean age (±SD): 41.4 ± 13.7 years) with a history of mild COVID-19 infection were included. Median duration after acute COVID-19 infection was 97 days (range, 34-401). We did not find an increased PS externalization, CD62p expression, or GPVI shedding in platelets from CCP donors. Sera from CCP donors did not induce PS externalization or GPVI shedding in healthy platelets. Sera-induced CD62p expression was slightly, albeit statistically significantly, lower in CCP donors than in plasma donors without a history of COVID-19. One patient showed increased maximum clot firmness and prolonged lysis time in thromboelastometry. Our findings suggest that procoagulant platelet phenotype is not present after mild COVID-19. Furthermore, CCP sera do not affect the activation status of platelets.

Both qualitative and quantitative platelet abnormalities are common in patients with coronavirus disease 2019 (COVID-19) and they correlate with clinical severity and mortality. Activated platelets contribute to the prothrombotic state in COVID-19 patients. Several groups have shown immune-mediated activation of platelets in critically ill COVID-19 patients. Vaccine-induced immune thrombotic thrombocytopenia is an autoimmune condition characterized by thrombocytopenia and life-threatening thrombotic events in the arterial and venous circulation. Although the initial trigger has yet to be determined, activation of platelets by immune complexes through Fc gamma RIIA results in platelet consumption and thrombosis. A better understanding of platelet activation in COVID-19 as well as in vaccine-induced thrombotic complications will have therapeutic implications. In this review, we focused on the role of immune-mediated platelet activation in thrombotic complications during COVID-19 infection and vaccine-induced immune thrombotic thrombocytopenia.

Transfusion of platelet concentrates (PCs) is an essential medical approach to stop bleeding or to prevent it. PCs are usually stored at room temperature, which enhances the risk of post-transfusion bacterial infection. Therefore, cold storage has been proposed as alternative storage condition. Recently, we reported that cold storage better conserves platelet functionality but induces a fast clearance due to increased apoptosis (Marini I. et al., Haematologica 2019). We designed a study to dissect the molecular pathways of cold-induced apoptosis. The impact of RhoA GTPase, PKA and caspase 9 on apoptosis, on functionality and survival of cold-stored platelets (CSPs) was investigated after 1, 4, 7 and 10 days of storage. We found that CSPs show pronounced apoptotic phenotype starting from day 4. The inhibition of RhoA, activation of PKA and inhibition of the autocatalytic cleavage of caspase 9 prevented the apoptotic signal during cold storage. Investigating platelet responsiveness we observed that the inhibition of both RhoA and caspase 9 did not affect the alpha granule release, in response to TRAP. In contrast, the activation of PKA caused a significant reduction of the alpha granule secretion, probably because of the PKA-mediated phosphorylation of vasodilator-stimulated phosphoprotein (VASP) (Fold increase [FI] of mean fluorescence intensity [MFI] CD62: day 4, p=0.02; day 7, p=0.06). Moreover, upon inhibition of RhoA, which blocks the glycoprotein Ib (GPIb) clustering, we detected enhance delta granule release after TRAP stimulation (FI MFI CD63: day 7, p=0.04; day 10, p=0.01). Contrarily, PKA activation and caspase 9 inhibition significantly impaired the delta granule secretion (FI MFI CD63: day 7, p=0.03; day 10, p=0.0005; and day 7, p=0.02; day 10, p=0.04, respectively). Furthermore, the inhibition of RhoA better maintained CSP aggregation after 10 days, in response to TRAP (% Maximal aggregation: p=0.02). While the presence of the PKA agonist significantly impaired the aggregation ability (% Maximal aggregation: day 4, p<0.0001; day 7, p=0.01). Interestingly, even if RhoA controls cytoskeleton reorganization during platelet activation, its inhibition did not affect CSP adhesion, probably because other members of the Rho GTPase family, like Rac1 and Cdc2, compensate the lack of RhoA functionality. Next, to deeper investigate the hemostatic functions of CSPs we performed a thromboelastography assay using platelets-depleted whole blood spiked in with CSPs. This experimental setting mimics CSP transfusion in thrombocytopenic patients. We found that both RhoA and caspase 9 treated-CSPs maintain the ability to form stable clots. In contrast, after incubation with the PKA agonist, reduced percentage of maximum clot firmness (day 4, p=0.02) and increased percentage of maximum lysis (day 4, p=0:02) were detected, indicating impairment of the thrombus formation. Since inhibition of RhoA showed the best cell functionality in our study and in accordance with the principles of the 3Rs of animal experimental technics, we analyzed whether the survival of CSPs could be improved preventing GPIb clustering. Interestingly, using a NOD/SCID muse model, higher percentage of circulating CSPs was detected after RhoA inhibition compared to buffer (day 7; 5 hours post injection, p=0.016). Taking together our results suggest that the prevention of cold-induced apoptosis in PCs is a suitable strategy to reduce the fast clearance of platelets and maintain cell hemostatic functions. In particular, inhibition of the apoptotic signaling at a very early stage, by blocking the clustering of GPIb, is the most promising approach considering the improved cell functionality. Therefore, the combination of cold storage and apoptosis inhibition has not only the advantage to prolog the storage time but it might also give a better patient outcome in specific clinical settings like active bleeding after trauma injury.

AbstractThromboembolic events are frequently reported in patients infected with the SARS-CoV-2 virus. The exact mechanisms of COVID-19-associated hypercoagulopathy, however, remain elusive. Recently, we observed that platelets (PLTs) from patients with severe COVID-19 infection express high levels of procoagulant markers, which were found to be associated with increased risk for thrombosis. In the current study, we investigated the time course as well as the mechanisms leading to procoagulant PLTs in COVID-19. Our study demonstrates the presence of PLT-reactive IgG antibodies that induce marked changes in PLTs in terms of increased inner-mitochondrial transmembrane potential (Δψ) depolarization, phosphatidylserine (PS) externalization, and P-selectin expression. The IgG-induced procoagulant PLTs and increased thrombus formation were mediated by ligation of PLT Fc-γ RIIA (FcγRIIA). In addition, contents of calcium and cyclic-adenosine-monophosphate (cAMP) in PLTs were identified to play a central role in antibody-induced procoagulant PLT formation. Most importantly, antibody-induced procoagulant events, as well as increased thrombus formation in severe COVID-19, were inhibited by Iloprost, a clinically approved therapeutic agent that increases the intracellular cAMP levels in PLTs. Our data indicate that upregulation of cAMP could be a potential therapeutic target to prevent antibody-mediated coagulopathy in COVID-19 disease.

Chorea-Acanthocytosis (ChAc) is a devastating, little understood, and currently untreatable neurodegenerative disease caused by VPS13A mutations. Based on our recent demonstration that accumulation of activated Lyn tyrosine kinase is a key pathophysiological event in human ChAc cells, we took advantage of Vps13a −/− mice, which phenocopied human ChAc. Using proteomic approach, we found accumulation of active Lyn, γ-synuclein and phospho-tau proteins in Vps13a −/− basal ganglia secondary to impaired autophagy leading to neuroinflammation. Mice double knockout Vps13a −/− Lyn −/− showed normalization of red cell morphology and improvement of autophagy in basal ganglia. We then in vivo tested pharmacologic inhibitors of Lyn: dasatinib and nilotinib. Dasatinib failed to cross the mouse brain blood barrier (BBB), but the more specific Lyn kinase inhibitor nilotinib, crosses the BBB. Nilotinib ameliorates both Vps13a −/− hematological and neurological phenotypes, improving autophagy and preventing neuroinflammation. Our data support the proposal to repurpose nilotinib as new therapeutic option for ChAc patients.