International Society of Blood Transfusion survey of experiences of blood banks and transfusion services during the COVID-19 pandemic.

BACKGROUND AND OBJECTIVES: The coronavirus disease 2019 (COVID-19) pandemic has impacted blood systems worldwide. Challenges included maintaining blood supplies and initiating the collection and use of COVID-19 convalescent plasma (CCP). Sharing information on the challenges can help improve blood collection and utilization. MATERIALS AND METHODS: A survey questionnaire was distributed to International Society of Blood Transfusion members in 95 countries. We recorded respondents' demographic information, impacts on the blood supply, CCP collection and use, transfusion demands and operational challenges. RESULTS: Eighty-two responses from 42 countries, including 24 low- and middle-income countries, were analysed. Participants worked in national (26.8%) and regional (26.8%) blood establishments and hospital-based (42.7%) institutions. CCP collection and transfusion were reported by 63% and 36.6% of respondents, respectively. Decreases in blood donations occurred in 70.6% of collecting facilities. Despite safety measures and recruitment strategies, donor fear and refusal of institutions to host blood drives were major contributing factors. Almost half of respondents working at transfusion medicine services were from large hospitals with over 10,000 red cell transfusions per year, and 76.8% of those hospitals experienced blood shortages. Practices varied in accepting donors for blood or CCP donations after a history of COVID-19 infection, CCP transfusion, or vaccination. Operational challenges included loss of staff, increased workloads and delays in reagent supplies. Almost half of the institutions modified their disaster plans during the pandemic. CONCLUSION: The challenges faced by blood systems during the COVID-19 pandemic highlight the need for guidance, harmonization, and strengthening of the preparedness and the capacity of blood systems against future infectious threats.

Psychological impact of the COVID-19 pandemic on young professionals in blood banks and transfusion services: A global cross-sectional survey.

BACKGROUND AND OBJECTIVES: The COVID-19 pandemic brought about changes to daily life as measures to contain the spread of the virus increased across the world. The aim of this survey was to assess the psychological impact of the pandemic on young professionals (YPs) in transfusion medicine. MATERIALS AND METHODS: A cross-sectional web-based survey was distributed electronically to ISBT members inviting YPs (≤40 years) to participate. Statistical analysis was performed using SPSS software. RESULTS: Two hundred and fifty-nine YPs completed the survey, including 107 clinicians/physicians and/or nurses. Almost half of the YPs (52.5%) indicated increased stress levels and 15.4% indicated symptoms of depression. YPs highlighted the loss of social engagement (59.1%) and increased pressure from information seen on media (35.5%) as factors negatively impacting their psychological wellbeing. Further, 20.8% expressed increased economic stress resulting from concerns about job security. Almost half of the YPs indicated that their organization provided moderate/occasional holistic support to them and their families. Sixty percent and 74.4% of YPs reported increased workload and staff absence due to COVID-19 infection, respectively. Only half of clinicians/physicians and/or nurses indicated that they often had sufficient personal protective equipment. The majority of these (76.6%) had family/household members living with them, and 61% indicated that they were significantly worried about infecting them because of the nature of their work. CONCLUSION: COVID-19 had a major impact on the well-being of YPs working in transfusion medicine. Measures are required to ensure that YPs are protected and mentally supported while undertaking their duties in current and future pandemics.

Endocannabinoids control platelet activation and limit aggregate formation under flow.

BACKGROUND: The endocannabinoid system has previously been implicated in the regulation of neurons and inflammatory cells. Additionally, it has been reported that endocannabinoid receptors are present on circulating platelets, but there has been conflicting evidence on their contribution to platelet function. OBJECTIVES: Our aim was to examine the role of endocannabinoids in platelet function in vitro and in vivo. METHODS AND RESULTS: We studied the effects of the well-characterized endogenous endocannabinoid anandamide on platelet aggregation in suspension, α-granule release, calcium mobilization, Syk phosphorylation, as well as platelet spreading and aggregate formation under flow. Anandamide inhibits platelet aggregation and α-granule release by collagen, collagen-derived peptide CRP-XL, ADP, arachidonic acid and thromboxane A2 analogue U46619. However, activation via thrombin receptor PAR-1 stays largely unaffected. Calcium mobilization is significantly impaired when platelets are stimulated with collagen or CRP-XL, but remains normal in the presence of the other agonists. In line with this finding, we found that anandamide prevents collagen-induced Syk phosphorylation. Furthermore, anandamide-treated platelets exhibit reduced spreading on immobilized fibrinogen, have a decreased capacity for binding fibrinogen in solution and show perturbed platelet aggregate formation under flow over collagen. Finally, we investigated the influence of Cannabis sativa consumption by human volunteers on platelet activation. Similar to our in vitro findings with anandamide, ex vivo collagen-induced platelet aggregation and aggregate formation on immobilized collagen under flow were impaired in whole blood of donors that had consumed Cannabis sativa. CONCLUSIONS: Endocannabinoid receptor agonists reduce platelet activation and aggregate formation both in vitro and ex vivo after Cannabis sativa consumption. Further elucidation of this novel regulatory mechanism for platelet function may prove beneficial in the search for new antithrombotic therapies.

A novel FcγRIIa Q27W gene variant is associated with common variable immune deficiency through defective FcγRIIa downstream signaling.

We identified a novel Q27W FcγRIIa variant that was found more frequently in common variable immunodeficiency (CVID) or CVID-like children. We analyzed the possible functional consequence of the Q27W FcγRIIa mutation in human cells. We used peripheral blood mononuclear cells from Q27W FcγRIIa patients and healthy controls, and cultured cells that overexpress the Q27W and common FcγRIIa variants. The Q27W FcγRIIa mutation does not disrupt FcγRIIa surface expression in peripheral blood mononuclear cells. Mononuclear cells express multiple FcγR, precluding careful analysis of Q27W FcγRIIa functional deviation. For functional analysis of FcγRIIa function, we therefore overexpressed the Q27W FcγRIIa and common FcγRIIa variant in IIA1.6 cells that are normally deficient in FcγR. We show that FcγRIIa triggering-induced signaling is obstructed, as measured by both decrease in calcium flux and defective MAPK phosphorylation. In conclusion, we here describe a novel Q27W FcγRIIa variant that causes delayed downstream signaling. This variant may contribute to CVID.

Limited promiscuity of HLA-DRB1 presented peptides derived of blood coagulation factor VIII.

The formation of inhibitory antibodies directed against coagulation factor VIII (FVIII) is a severe complication in the treatment of hemophilia A patients. The induction of anti-FVIII antibodies is a CD4(+) T cell-dependent process. Activation of FVIII-specific CD4(+) T cells is dependent on the presentation of FVIII-derived peptides on MHC class II by antigen-presenting cells. Previously, we have shown that FVIII-pulsed human monocyte-derived dendritic cells can present peptides from several FVIII domains. In this study we show that FVIII peptides are presented on immature as well as mature dendritic cells. In immature dendritic cells half of the FVIII-loaded MHC class II molecules are retained within the cell, whereas in LPS-matured dendritic cells the majority of MHC class II/peptide complexes is present on the plasma membrane. Time-course studies revealed that presentation of FVIII-derived peptides was optimal between 12 and 24 hours after maturation but persisted for at least 96 hours. We also show that macrophages are able to internalize FVIII as efficiently as dendritic cells, however FVIII was presented on MHC class II with a lower efficiency and with different epitopes compared to dendritic cells. In total, 48 FVIII core-peptides were identified using a DCs derived of 8 different donors. Five HLA-promiscuous FVIII peptide regions were found - these were presented by at least 4 out of 8 donors. The remaining 42 peptide core regions in FVIII were presented by DCs derived from a single (30 peptides) or two to three donors (12 peptides). Overall, our findings show that a broad repertoire of FVIII peptides can be presented on HLA-DR.

Modification of an exposed loop in the C1 domain reduces immune responses to factor VIII in hemophilia A mice.

Development of neutralizing Abs to blood coagulation factor VIII (FVIII) provides a major complication in hemophilia care. In this study we explored whether modulation of the uptake of FVIII by APCs can reduce its intrinsic immunogenicity. Endocytosis of FVIII by professional APCs is significantly blocked by mAb KM33, directed toward the C1 domain of FVIII. We created a C1 domain variant (FVIII-R2090A/K2092A/F2093A), which showed only minimal binding to KM33 and retained its activity as measured by chromogenic assay. FVIII-R2090A/K2092A/F2093A displayed a strongly reduced internalization by human monocyte-derived dendritic cells and macrophages, as well as murine BM-derived dendritic cells. We subsequently investigated the ability of this variant to induce an immune response in FVIII-deficient mice. We show that mice treated with FVIII-R2090A/K2092A/F2093A have significantly lower anti-FVIII Ab titers and FVIII-specific CD4(+) T-cell responses compared with mice treated with wild-type FVIII. These data show that alanine substitutions at positions 2090, 2092, and 2093 reduce the immunogenicity of FVIII. According to our findings we hypothesize that FVIII variants displaying a reduced uptake by APCs provide a novel therapeutic approach to reduce inhibitor development in hemophilia A.

The macrophage mannose receptor promotes uptake of ADAMTS13 by dendritic cells.

ADAMTS13 is a plasma metalloproteinase that regulates platelet adhesion and aggregation by cleaving ultra-large VWF multimers on the surfaces of endothelial cells. Autoantibodies directed against ADAMTS13 prohibit the processing of VWF multimers, initiating a rare and life-threatening disorder called acquired thrombotic thrombocytopenic purpura. The formation of autoantibodies depends on the activation of CD4(+) T cells. This process requires immune recognition, endocytosis, and subsequent processing of ADAMTS13 into peptides that are presented on MHC class II molecules to CD4(+) T cells by dendritic cells (DCs). In the present study, we investigated endocytosis of recombinant ADAMTS13 by immature monocyte-derived DCs using flow cytometry and confocal microscopy. After incubation of fluorescently labeled ADAMTS13 with DCs, significant uptake of ADAMTS13 was observed. Endocytosis of ADAMTS13 was completely blocked by the addition of EGTA and mannan. ADAMTS13 endocytosis was decreased in the presence of a blocking mAb directed toward the macrophage mannose receptor (MR). Furthermore, siRNA silencing of MR reduced the uptake of ADAMTS13 by DCs. In addition, in vitro binding studies confirmed the interaction of ADAMTS13 with the carbohydrate recognition domains of MR. The results of the present study indicate that sugar moieties on ADAMTS13 interact with MR, thereby promoting its endocytosis by APCs.

Requirements for immune recognition and processing of factor VIII by antigen-presenting cells.

Generation of inhibitory antibodies upon repeated FVIII infusion represents a major complication in hemophilia care. Professional antigen presenting cells (APCs) are crucial for orchestration of humoral immune responses. APCs are capable of internalizing soluble as well as particulate antigens through various mechanisms resulting in loading of antigen-derived peptides on MHC class I or II for presentation to T cells. This review highlights how FVIII is recognized and processed by APCs. The significance and contribution of candidate receptors involved in FVIII uptake by APC are discussed. Recent findings defining the repertoire of FVIII peptides presented on MHC class II are addressed. Studies in murine models of hemophilia A suggest that modulation of APC function can reduce inhibitor formation. Based on this we anticipate that modulation of FVIII uptake by APCs may yield novel therapeutic approaches for treatment or prevention of inhibitor formation in patients with hemophilia A.

Uptake of blood coagulation factor VIII by dendritic cells is mediated via its C1 domain.

BACKGROUND: The uptake and processing of blood coagulation factor VIII (FVIII) by antigen-presenting cells and the subsequent presentation of FVIII-derived peptides to CD4(+) T cells direct the immune response to FVIII in patients with hemophilia A. Multiple receptors including mannose receptor and low-density lipoprotein receptor-related protein-1 (LRP1) have been implicated in FVIII uptake. OBJECTIVE: This work studies the involvement of receptor candidates in FVIII uptake by dendritic cells (DCs). Furthermore, we explore FVIII residues that mediate endocytosis. METHODS: FVIII uptake was performed with human monocyte-derived and murine bone marrow-derived DCs. To investigate FVIII endocytosis, competition assays with soluble receptor ligands, binding studies with recombinant receptor fragments, and small-interfering RNA-induced gene silencing were performed. In addition, FVIII-targeting monoclonal antibodies KM33 and VK34 were used. To confirm in vitro results, hemophilic E17 knockout mice were pretreated with antibodies prior to FVIII injections and anti-FVIII titers were determined. RESULTS: Upon treatment of DCs with mannan or LRP ligand α2-macroglobulin, we observed only a minor decrease in FVIII internalization. In addition, small interfering RNA-mediated knockdown of LRP, mannose receptor, or DC-SIGN expression in monocyte-derived dendritic cells did not prevent FVIII uptake. Binding studies using Fc chimeras revealed that LRP, DC-SIGN, and mannose receptor can bind to FVIII; however, we did not observe a critical role for these receptors in FVIII uptake. Previous studies have shown that human antibodies targeting the C1 (KM33) and A2 (VK34) domains of FVIII interfere with binding to endocytic receptors. Preincubation of FVIII with VK34 did not influence FVIII uptake; however, KM33 completely inhibited FVIII endocytosis by both monocyte-derived dendritic cells and bone marrow-derived dendritic cells. Accordingly, anti-FVIII antibody titers were greatly reduced following the preadministration of KM33 in vivo. CONCLUSION: Together, our observations emphasize the physiological significance of KM33-targeted residues within the C1 domain in the uptake of FVIII by DCs in vitro and in vivo.

HLA-DR-presented peptide repertoires derived from human monocyte-derived dendritic cells pulsed with blood coagulation factor VIII.

Activation of T-helper cells is dependent upon the appropriate presentation of antigen-derived peptides on MHC class II molecules expressed on antigen presenting cells. In the current study we explored the repertoire of peptides presented on MHC class II molecules on human monocyte derived dendritic cells (moDCs) from four HLA-typed healthy donors. MHC class II-bound peptides could be routinely recovered from small cultures containing 5 × 10(6) cells. A fraction of the identified peptides were derived from proteins localized in the plasma membrane, endosomes, and lysosomes, but the majority of peptides that were presented on MHC class II originate from other organelles. Subsequently, we studied the antigen-specific peptide repertoire after endocytosis of a soluble antigen. Blood coagulation factor VIII (FVIII) was chosen as the antigen since our current knowledge on MHC class II presented peptides derived from this immunogenic therapeutic protein is limited. Analysis of the total repertoire of MHC class II-associated peptides revealed that per individual sample 20-50 FVIII-derived peptides were presented on FVIII-pulsed moDCs. Repertoires of FVIII-derived peptides eluted from moDCs derived from a panel of four HLA typed donors revealed that some MHC class II-presented FVIII peptides were presented by multiple donors, whereas the presentation of other FVIII peptides was donor-specific. In total 32 different core peptides were presented on FVIII-pulsed moDCs from four HLA-typed donors. Together our findings provide an unbiased approach to identify peptides that are presented by MHC class II on antigen-loaded moDCs from individual donors.

Proinflammatory activation pattern of human umbilical vein endothelial cells induced by IL-1ß, TNF-α, and LPS.

Endothelial cells play a critical role in inflammation by responding to several endogenous and exogenous proinflammatory stimuli. The three most studied factors that provide inflammatory signals to endothelial cells are lipopolysaccharide (LPS), tumor necrosis factor (TNF)-α, and interleukin (IL)-1ß; however, their effects on endothelial cells were thoroughly compared at the level of gene expression only. Therefore, our aim was to assess the differences in the signaling pathways, adhesion molecules, and cytokines induced by proinflammatory factors in human umbilical vein endothelial cells (HUVEC). In this study, we demonstrated that signaling of LPS was less effective than that of IL-1ß, and was significantly slower than that ofTNF-α and IL-1ß, which can be partially explained by the special localization of Toll-like receptor 4 (TLR4). We showed that TLR4 is mainly localized in Golgi apparatus in HUVEC. The proinflammatory capacity of TNF-α was similar to that of IL-1ß in inducing NF-κB nuclear translocation, while IL-1ß was the strongest activator of MAPK pathways. Moreover, expression of E-selectin, IL-6, and IL-8 was induced most efficiently by IL-1ß, while LPS and TNF-α had less effect, whereas we did not find such a difference in ICAM-1 and MCP-1 expression. Due to the higher induction of E-selectin and IL-8, IL-1ß might have more important role in neutrophil recruitment than LPS and TNF-α. By above-mentioned parameters we identified a signaling and expression pattern for the three proinflammatory molecules. This pattern illustrates how complex a proinflammatory process can be, and may enable us to predict and compare the pathomechanism of various inflammatory diseases.

Protein kinase inhibitor-induced endothelial cell cytotoxicity and its prediction based on calculated molecular descriptors.

Protein kinase inhibitors (PKIs) as potent signal transduction therapeutic compounds represent a very rapidly expanding group of anticancer drugs. These agents may be toxic for endothelial cells, however, very few experimental data exist on the cytotoxicity of PKIs. The aim of this study was to set up an appropriate test system for endothelial cells and to assess the structure-related cytotoxic effects of a selected library of PKIs. The inhibitor library contains several lead molecules with different basic structures and a set of modified derivatives of the lead compounds. The toxicity of PKIs did not correlate directly with the structural features of the molecules. However, we successfully built up a model based on 15 calculated molecular descriptors, which is capable of predicting cytotoxicity with acceptable probability. Our results show that the cytotoxic effects of PKIs should be taken into account for optimal drug development to overcome endothelial cell-related side effects.

Molecular and cellular aspects of protein misfolding and disease.

Proteins are essential elements for life. They are building blocks of all organisms and the operators of cellular functions. Humans produce a repertoire of at least 30,000 different proteins, each with a different role. Each protein has its own unique sequence and shape (native conformation) to fulfill its specific function. The appearance of incorrectly shaped (misfolded) proteins occurs on exposure to environmental changes. Protein misfolding and the subsequent aggregation is associated with various, often highly debilitating, diseases for which no sufficient cure is available yet. In the first part of this review we summarize the structural composition of proteins and the current knowledge of underlying forces that lead proteins to lose their native structure. In the second and third parts we describe the molecular and cellular mechanisms that are associated with protein misfolding in disease. Finally, in the last part we portray recent efforts to develop treatments for protein misfolding diseases.

Activation of human platelets by misfolded proteins.

OBJECTIVE: Protein misfolding diseases result from the deposition of insoluble protein aggregates that often contain fibrils called amyloid. Amyloids are found in Alzheimer disease, atherosclerosis, diabetes mellitus, and systemic amyloidosis, which are diseases where platelet activation might be implicated. METHODS AND RESULTS: We induced amyloid properties in 6 unrelated proteins and found that all induced platelet aggregation in contrast to fresh controls. Amyloid-induced platelet aggregation was independent of thromboxane A2 formation and ADP secretion but enhanced by feedback stimulation through these pathways. Treatments that raised cAMP (iloprost), sequestered Ca2+ (BAPTA-AM) or prevented amyloid-platelet interaction (sRAGE, tissue-type plasminogen activator [tPA]) induced almost complete inhibition. Modulation of the function of CD36 (CD36-/- mice), p38(MAPK) (SB203580), COX-1 (indomethacin), and glycoprotein Ib alpha (Nk-protease, 6D1 antibody) induced approximately 50% inhibition. Interference with fibrinogen binding (RGDS) revealed a major contribution of alphaIIb beta3-independent aggregation (agglutination). CONCLUSIONS: Protein misfolding resulting in the appearance of amyloid induces platelet aggregation. Amyloid activates platelets through 2 pathways: one is through CD36, p38(MAPK), thromboxane A2-mediated induction of aggregation; the other is through glycoprotein Ib alpha-mediated aggregation and agglutination. The platelet stimulating properties of amyloid might explain the enhanced platelet activation observed in many diseases accompanied by the appearance of misfolded proteins with amyloid.

Proinflammatory changes in human umbilical cord vein endothelial cells can be induced neither by native nor by modified CRP.

The role of C-reactive protein (CRP) in atherosclerosis is controversial. It is not clear, either, if the presumed endothelium-activating effect of CRP resides in native CRP (nCRP) or in a conformational isoform of CRP known as modified CRP (mCRP). In the present study we evaluated and compared the effect of nCRP, recombinant modified CRP (rmCRP) and urea-modified CRP (umCRP) on human umbilical vein endothelial cells (HUVECs). CRP preparations were carefully analyzed by biochemical, immunological and cell biological methods in order to avoid endotoxin or sodium azide contamination as well as inappropriate conformational changes, which together had possibly been the main reason for the previously published controversial results. Neither nCRP nor mCRP showed significant cytotoxicity up to 100 microg ml(-1) at 24 h but high concentrations of CRPs induced cell death at 48 h. rmCRP but not nCRP nor umCRP showed membrane binding to HUVEC by confocal microscopy. However, none of the CRP forms induced intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin expression or IL-8 production. Monocyte chemotactic protein-1 production was weakly inhibited by high concentration of both nCRP and rmCRP, analyzed by sandwich ELISA. Neither nCRP nor mCRP could induce pro-inflammatory changes in the phenotype of HUVECs. Therefore, our present findings do not support the notion that different isoforms of CRP alone have significant effects on inflammation of the vessel wall via an interaction with endothelial cells (ECs), although one cannot exclude the possibility that there may be significant differences among various types of ECs in the response to CRP.