Blood Cell Binding Research Articles

Genetic diversity and natural selection of apical membrane antigen-1 (ama-1) in Cameroonian Plasmodium falciparum isolates

Antigenic variation associated with genetic diversity in global Plasmodium falciparum apical membrane antigen-1 (PfAMA-1) is a major impediment to designing an effective malaria vaccine. Here, we report the first study on genetic diversity and natural selection of the Pfama-1 gene in P. falciparum isolates from Cameroon. A total of 328 P. falciparum positive samples collected during 2016 and 2019 from five localities of Cameroon were analysed. The ectodomain coding fragment of Pfama-1 gene was amplified for polymorphism profiling and natural selection analysis. A total of 108 distinct haplotypes were found in 203 P. falciparum isolates with considerable nucleotide diversity (π = 0.016) and haplotype diversity (Hd = 0.976). Most amino acid substitutions detected were scattered in ectodomain-I and few specific mutations viz P145L, K148Q, K462I, L463F, N471K, S482L, E537G, K546R and I547F were seen only in Cameroonian isolates. A tendency of natural selection towards positive diversifying selection was observed (Taj-D = 2.058). Five positively selected codon sites (P145L, S283L, Q308E/K, P330S and I547F) were identified, which overlapped with predicted B-cell epitopes and red blood cell (RBC) binding sites, suggesting their potential implication in host immune pressure and parasite-RBC binding complex modulation. The Cameroonian P. falciparum populations indicated a moderate level of genetic differentiation when compared with global sequences, with few exceptions from Vietnam and Venezuela. Our findings provide baseline data on existing Pfama-1 gene polymorphisms in Cameroonian field isolates, which will be useful information for malaria vaccine design.

CD38 x ICAM-1 Bispecific Antibody Is a Novel Approach for Treating Multiple Myeloma and Lymphoma.

The cluster of differentiation 38 (CD38) is a well-validated target for treating multiple myeloma. Although anti-CD38 mAbs have demonstrated outstanding initial responses in patients with multiple myeloma, nearly all patients eventually develop resistance and relapse. In addition, currently approved CD38 targeting therapies have failed to show monotherapy efficacy in lymphomas, where CD38 expression is present but at lower levels. To effectively target CD38 on tumor cells, we generated an antibody-dependent cellular cytotoxicity (ADCC) enhanced bispecific CD38 x intercellular cell adhesion molecule 1 (ICAM-1) antibody, VP301. This bispecific antibody targets unique epitopes on CD38 and ICAM-1 on tumor cells with reduced red blood cell binding compared with the benchmark CD38 antibody daratumumab. VP301 demonstrated potent ADCC and antibody-dependent cellular phagocytosis activities on a selected set of myeloma and lymphoma cell lines even those with low CD38 expression. In an ex vivo drug sensitivity assay, we observed responses to VP301 in multiple myeloma primary samples from relapsed/refractory patients. Moreover, VP301 demonstrated potent tumor inhibition activities in in vivo myeloma and lymphoma models. Interestingly, combination of VP301 with the immunomodulatory drug, lenalidomide, led to synergistic antitumor growth activity in an in vivo efficacy study. In conclusion, the CD38 x ICAM-1 bispecific antibody VP301 demonstrated promising efficacy and specificity toward CD38+ and ICAM-1+ tumor cells and represents a novel approach for treating multiple myeloma and lymphoma.

Investigating Tacrolimus Disposition in Paediatric Patients with a Physiologically Based Pharmacokinetic Model Incorporating CYP3A4 Ontogeny, Mechanistic Absorption and Red Blood Cell Binding.

Tacrolimus is a crucial immunosuppressant for organ transplant patients, requiring therapeutic drug monitoring due to its variable exposure after oral intake. Physiologically based pharmacokinetic (PBPK) modelling has provided insights into tacrolimus disposition in adults but has limited application in paediatrics. This study investigated age dependency in tacrolimus exposure at the levels of absorption, metabolism, and distribution. Based on the literature data, a PBPK model was developed to predict tacrolimus exposure in adults after intravenous and oral administration. This model was then extrapolated to the paediatric population, using a unique reference dataset of kidney transplant patients. Selecting adequate ontogeny profiles for hepatic and intestinal CYP3A4 appeared critical to using the model in children. The best model performance was achieved by using the Upreti ontogeny in both the liver and intestines. To mechanistically evaluate the impact of absorption on tacrolimus exposure, biorelevant in vitro solubility and dissolution data were obtained. A relatively fast and complete release of tacrolimus from its amorphous formulation was observed when mimicking adult or paediatric dissolution conditions (dose, fluid volume). In both the adult and paediatric PBPK models, the in vitro dissolution profiles could be adequately substituted by diffusion-layer-based dissolution modelling. At the level of distribution, sensitivity analysis suggested that differences in blood plasma partitioning of tacrolimus may contribute to the variability in exposure in paediatric patients.

Sequential roles for red blood cell binding proteins enable phased commitment to invasion for malaria parasites

Invasion of red blood cells (RBCs) by Plasmodium merozoites is critical to their continued survival within the host. Two major protein families, the Duffy binding-like proteins (DBPs/EBAs) and the reticulocyte binding like proteins (RBLs/RHs) have been studied extensively in P. falciparum and are hypothesized to have overlapping, but critical roles just prior to host cell entry. The zoonotic malaria parasite, P. knowlesi, has larger invasive merozoites and contains a smaller, less redundant, DBP and RBL repertoire than P. falciparum. One DBP (DBPα) and one RBL, normocyte binding protein Xa (NBPXa) are essential for invasion of human RBCs. Taking advantage of the unique biological features of P. knowlesi and iterative CRISPR-Cas9 genome editing, we determine the precise order of key invasion milestones and demonstrate distinct roles for each family. These distinct roles support a mechanism for phased commitment to invasion and can be targeted synergistically with invasion inhibitory antibodies.

Abstract 6334: VBI-002, a CD47xICAM-1 bispecific antibody for the treatment of hepatocellular carcinoma, melanoma and non-small cell lung cancers

Abstract Intercellular Cell Adhesion Molecule 1 (ICAM-1, CD54) is a type I transmembrane protein and a member of the immunoglobulin superfamily. ICAM-1 is involved in many key processes such as cell-cell interactions, signal transduction and leukocytes trans-endothelial migration. ICAM-1 is constitutively present at low levels on healthy tissues but highly expressed in some hematological cancers and solid tumors, making it an attractive tumor target. VBI-002 is a novel human IgG1 based CD47xICAM-1 bispecific antibody with excellent safety profile and potent single agent activities in xenograft models of lymphoma, multiple myeloma and some solid tumors (Cancer Res 2022;82(12_Suppl):Abstract nr 3430). The bispecific design allows VBI-002 to selectively block CD47/SIRPα binding in tumor cells with high ICAM-1 expression. In contrast to the benchmark CD47 monoclonal antibody, VBI-002 exhibits minimal red blood cell binding and does not cause hemagglutination. In non-human primate (NHP) safety study, four weekly doses of 60 mg/kg VBI-002 were well-tolerated with only mild and reversible reduction in hemoglobin and platelets. Here we further investigate the anti-tumor activities of VBI-002 in solid tumors. Gene expression analysis suggested that ICAM-1 is highly expressed in non-small cell lung cancers (NSCLC), melanoma and a subset of hepatocellular carcinoma. Flow cytometry studies confirmed the frequent co-expression of ICAM-1 and CD47 in these tumors. VBI-002 has potent ICAM-1 dependent SIRPα blocking, antibody-dependent cellular phagocytosis and antibody-dependent cellular cytotoxicity activities against cell lines of NSCLC, hepatocellular carcinoma, and melanoma. Furthermore, in vivo efficacy studies demonstrated that VBI-002 has potent single agent activities in cell line derived xenograft (CDX) models of NSCLC, hepatocellular carcinoma, and melanoma. Weekly dose of 20 mg/kg VBI-002 is sufficient to stop tumor growth or drive tumor regression in most models. Notably, VBI-002 is highly effective against NSCLC CDX models carrying Kras mutation and it synergizes with paclitaxel to provide additional anti-tumor activity. In conclusion, VBI-002 is a versatile novel CD47xICAM-1 bispecific antibody with potent single agent activity in various solid tumors and combined well with standard of care chemotherapies for added activity. Thus, VBI-002 warrants clinical evaluations as a single agent and in combination with standard of care chemotherapies. Citation Format: Oi Kwan Wong, Xinhua Wang, Leonard Post, Xiaocheng Chen. VBI-002, a CD47xICAM-1 bispecific antibody for the treatment of hepatocellular carcinoma, melanoma and non-small cell lung cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6334.

Abstract 1870: VBI-003, a CD47xEpCAM bispecific antibody as a potential treatment for colorectal and small cell lung cancers

Abstract CD47/SIRPα axis is an important checkpoint of innate immune system and is often exploited by tumor cells to evade host immune surveillance. In recent years, therapies such as anti-CD47 monoclonal antibodies (mAbs) and SIRPα fusion proteins that target this axis have garnered much attention. Although exciting clinical activities have been observed in hematological cancers, responses in solid tumors are less impressive and often require complex combination strategies. We previously described a novel CD47xEpCAM bispecific antibody, VBI-003, built on a human IgG1 backbone to harness the power of blocking CD47/SIRPα pathway while preserving the effector functions of IgG1 Fc (J ImmunoTher Cancer 2021;9:doi: 10.1136/jitc-2021-SITC2021.274). The bispecific design aims to improve selectivity so that SIRPα blocking and stable binding occur selectively on tumor cells where both CD47 and EpCAM are present. In vitro studies show that VBI-003 exhibits minimal red blood cell binding and does not cause hemagglutination, in contrast to benchmark CD47 mAb. VBI-003 has potent single agent activity in cell line derived xenograft (CDX) models of gastric and esophageal cancers. Here, we further explored the anti-tumor activities of VBI-003 in areas with great unmet needs such as small cell lung cancers (SCLC) and colorectal cancers (CRC). Gene expression analysis from public datasets reveals frequent expression of CD47 and EpCAM in SCLC and CRC tumors. Flow cytometry studies confirmed co-expression of CD47 and EpCAM on SCLC and CRC cell lines. Furthermore, in vitro assays showed that VBI-003 has potent EpCAM dependent SIRPα blocking, antibody-dependent cellular phagocytosis and antibody-dependent cellular cytotoxicity activities towards SCLC and CRC cell lines. Moreover, VBI-003 demonstrated potent single agent activity in multiple CDX models of SCLC with tumor regression and often outperformed benchmark CD47 mAb. Significant tumor growth inhibition was observed in colorectal cancer models post VBI-003 treatment, with additional activity by combination with standard of care chemotherapies. VBI-003 synergized with irinotecan and outperformed monotherapy groups in CDX models of CRC. In conclusion, VBI-003 has potent single agent activity in SCLC tumor models and combined synergistically with irinotecan in CRC models. Our data support further investigation of VBI-003 as a treatment for CD47 and EpCAM expressing SCLC and CRC. Citation Format: Oi Kwan Wong, Xinhua Wang, Xiaocheng Chen, Leonard Post. VBI-003, a CD47xEpCAM bispecific antibody as a potential treatment for colorectal and small cell lung cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1870.

Genetic diversity in the transmission-blocking vaccine candidate Plasmodium vivax gametocyte protein Pvs230 from the China–Myanmar border area and central Myanmar

BackgroundSexual stage surface antigens are potential targets of transmission-blocking vaccines (TBVs). The gametocyte and gamete surface antigen P230, a leading TBV candidate, is critical for red blood cell binding during exflagellation and subsequent oocyst development. Here, the genetic diversity of Pvs230 was studied in Plasmodium vivax parasite isolates from the China–Myanmar border (CMB) and central Myanmar.MethodsPlasmodium vivax isolates were collected in clinics from malaria-endemic areas of the CMB (143 samples) and Myanmar (23 samples). The interspecies variable part (IVP, nucleotides 1–807) and interspecies conserved part (ICP, 808–2862) of Pvs230 were amplified by PCR and sequenced. Molecular evolution studies were conducted to evaluate the genetic diversity, signature of selection, population differentiation, haplotype network, and population structure of the study parasite populations and publicly available Pvs230 sequences from six global P. vivax populations.ResultsLimited genetic diversity was observed for the CMB (π = 0.002) and Myanmar (π = 0.001) isolates. Most amino acid substitutions were located in the IVP and cysteine-rich domain of Pvs230. Evidence of positive selection was observed for IVP and purifying selection for ICP. Codon-based tests identified specific codons under natural selection in both IVP and ICP. The fixation index (FST) showed low genetic differentiation between East and Southeast Asian populations, with FST ranging from 0.018 to 0.119. The highest FST value (FST = 0.503) was detected between the Turkey and Papua New Guinea populations. A total of 92 haplotypes were identified in global isolates, with the major haplotypes 2 and 9 being the most abundant and circulating in East and Southeast Asia populations. Several detected non-synonymous substitutions were mapped in the predicted structure and B-cell epitopes of Pvs230.ConclusionsWe detected low levels of genetic diversity of Pvs230 in global P. vivax populations. Geographically specific haplotypes were identified for Pvs230. Some mutations are located within a potential B-cell epitope region and need to be considered in future TBV designs.Graphical

Progress of CD47 immune checkpoint blockade agents in anticancer therapy: a hematotoxic perspective.

CD47, a transmembrane protein, acts as a "do not eat me" signal that is overexpressed in many tumor cell types, thereby forming a signaling axis with its ligand signal regulatory protein alpha (SIRPα) and enabling the tumor cells to escape from macrophage-mediated phagocytosis. Several clinical trials with CD47 targeting agents are underway and have achieved impressive results preliminarily. However, hematotoxicity (particularly anemia) has emerged as the most common side effect that cannot be neglected. In the development of CD47 targeting agents, various methods have been used to mitigate this toxicity. In this review, we summarized five strategies used to alleviate CD47 blockade-induced hematotoxicity, as follows: change in the mode of administration; dual targeting bispecific antibodies of CD47; CD47 antibodies/SIRPα fusion proteins with negligible red blood cell binding; anti-SIRPα antibodies; and glutaminyl-peptide cyclotransferase like inhibitors. With these strategies, the development of CD47 targeting agents can be improved.

Modeling the effects of malaria on red blood cell binding at the vascular interface

Malaria is one of the largest diseases affecting tropical and subtropical regions, with more than 200 million cases and between 400,000 and 500,000 deaths annually, disproportionately afflicting the young, elderly, or immune compromised (1,2). Infamously spread by infected mosquitoes, the disease is caused by several parasitic species of Plasmodium (P. falciparum, P. malariae, P. vivax, P. ovale, and P. knowlesi). Symptoms of the disease can include chills, fever, nausea, anemia, vomiting, and flu-like symptoms, such as body aches and malaise; in extreme cases, it causes seizures, coma, and death.

A novel platform for peptide-mediated affinity capture and LC-MS/MS identification of host receptors involved in Plasmodium invasion

Successful Plasmodium falciparum invasion of red blood cells includes the orderly execution of highly specific receptor-ligand molecular interactions between the parasite's proteins and the red blood cell membrane proteins. There is a growing need for elucidating receptor-ligand pairings, which will help in understanding the parasite's biology and provide the fundamental basis for developing prophylactic or therapeutic alternatives leading to mitigating or eliminating this type of malaria.We have thus used Plasmodium falciparum RH5 - derived peptides and ghost red blood cell proteins in synthetic peptide affinity capture assays to identify important host receptors used by Plasmodium spp. in the invasion of red blood cells. LC-MS/MS analysis confirmed the extensively described interaction between PfRH5 and the basigin receptor on the red blood cell membrane.As shown here, tagged synthetic peptides displaying high binding ability to erythrocytes can be used to identify receptors present in protein extracts from ghost red blood cells via affinity capture and LC-MS/MS. SignificanceThe article describes a novel approach for identifying red blood cell receptors based on the ability of synthetic peptides having high red blood cell binding capacity to capture Plasmodium spp. receptors on proteins extracted from ghost red blood cells. Specifically, novel methods to identify Plasmodium falciparum reticulocyte binding protein homolog 5 PfRH5 and basigin interaction using a combination of affinity capture and LC-MS/MS assays is described. Identification of these host RBC receptors interacting with malarial parasite proteins is of utmost importance in studying the disease's pathogenesis and will provide crucial information in understanding the parasite's biology. In addition, data from these studies can be used to identify potential therapeutic target(s) to mitigate or eliminate this debilitating disease.

Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace – Part I adjustments to the adult systemic model

California’s Division of Occupational Safety and Health has initiated a process to update its standards for exposure to lead in workplaces. In support of this effort, the state’s Office of Environmental Health Hazard Assessment evaluated the age-specific, bio-kinetic model of lead metabolism in humans, originally published by R.W. Leggett in 1993. This model was ultimately chosen for its physiologic realism and practicality in characterizing the relationship between air lead concentrations and blood lead levels in chronically exposed worker and its practicality in making necessary adjustments. Leggett’s original model systematically under-predicts bone and blood levels in workers such that several adjustments to the parameters are needed to improve predictions for occupational exposure scenarios. The aim of this work is to incorporate new information about the bio-kinetics of lead in workers and to adjust the Leggett model to improve its predictions.The Leggett model was evaluated by comparing its predictions with information on lead concentrations in bone, blood, and urine from workers and other chronically exposed adults. Key model parameters were identified based upon a review of the relevant exposure assessment and modeling literature. Adjustments to the model parameters were made based on empirical evidence. They included reducing the level of lead in blood (BLL) where the rate of decrease in red blood cell binding begins and ends, lead accumulation rate in cortical bone, the rate of lead elimination in trabecular bone, and rate of lead transferred from diffusible plasma to urine. Regression methods and visual inspection of plotted data were used to assess the effect of adjustments on model predictions. When compared with the original, the adjusted Leggett model more accurately predicted lead concentrations observed in active and retired workers. Also, the adjusted Leggett model required less lead uptake to reach the same BLLs for BLLs less than 25 µg/dL and more time for BLLs to decline than the original Leggett model. These findings are important for defining an adequately protective occupational standard for lead exposure.

Absorption, Distribution and Excretion of [14C] Zamicastat after Single Oral and Intravenous Administration in Rats and Dogs

BackgroundZamicastat is a dopamine‐β‐hydroxylase inhibitor (1), previously showed to increase the survival rate in the monocrotaline rat model of pulmonary arterial hypertension.ObjectivesThe purpose of this study was to characterize the absorption, distribution and elimination of 14C‐zamicastat in rat and dog, after single oral (p.o.) or intravenous (i.v.) administration.MethodsWistar rats and Beagle dogs were administered with 14C‐zamicastat at 30 mg/kg orally or intravenously with 2.5 mg/kg (rat) and 0.1 mg/kg (dog). Plasma, urine and faeces samples were collected at different time‐points to measure the plasma exposure and the recovery of total radioactivity up to 168 h post‐dose. Whole body phosphor imaging (WBPI) was evaluated in rat after p.o. administration of 30 mg/kg of 14C‐zamicastat. The extent of plasma protein binding was determined by equilibrium dialysis and blood cell binding was determined, using centrifugation, on pooled male samples from each species.ResultsAfter single oral dosing of 14C‐zamicastat, more than 95% of total radioactivity was recovered at five and seven days from rats and dogs, respectively. The radioactivity peaked in plasma between 6 to 8 h and 2 to 4 h post‐dosing in rats and dogs, respectively, followed by a slow elimination over time. Zamicastat related radioactivity was mainly recovered in faeces with very low levels (less than 20% of total radioactivity) excreted in urine in both species. Following i.v. administration more than 80% of radioactivity was recovered in both species mainly via feaces excretion. The WBPI study indicates that radioactivity was distributed throughout the body with the majority of tissues achieving a tissue:blood ratio greater than 2. Elimination of radioactivity progressed over time with most tissues reaching the low limit of quantification at 168h. The highest tissue:blood ratios were noted in thyroid gland, lung and harderian gland at, respectively, 168h, 8h and 8h post‐dosing. Protein binding data indicates that zamicastat is preferentially bound to plasma proteins in a concentration independent manner, with 98% and 96% bound to rat and dog plasma proteins, respectively.ConclusionZamicastat is a highly plasma protein bound compound after oral administration and it is extensively distributed to tissues. After oral administration to rats and dogs, radioactivity was almost completely recovered with most of zamicastat‐related radioactivity excreted through faeces.

Development of AO-176, a Next-Generation Humanized Anti-CD47 Antibody with Novel Anticancer Properties and Negligible Red Blood Cell Binding.

Inhibitors of adaptive immune checkpoints have shown promise as cancer treatments. CD47 is an innate immune checkpoint receptor broadly expressed on normal tissues and overexpressed on many tumors. Binding of tumor CD47 to signal regulatory protein alpha (SIRPα) on macrophages and dendritic cells triggers a "don't eat me" signal that inhibits phagocytosis enabling escape of innate immune surveillance. Blocking CD47/SIRPα interaction promotes phagocytosis reducing tumor burden in numerous xenograft and syngeneic animal models. We have developed a next-generation humanized anti-CD47 antibody, AO-176, that not only blocks the CD47/SIRPα interaction to induce tumor cell phagocytosis, but also induces tumor cytotoxicity in hematologic and solid human tumor cell lines, but not normal noncancerous cells, by a cell autonomous mechanism (not ADCC). AO-176 also binds preferentially to tumor versus many normal cell types. In particular, AO-176 binds negligibly to RBCs in contrast to tumor cells, even at high concentrations up to 200 μg/mL and does not agglutinate RBCs up to 1 mg/mL in vitro These properties are expected not only to decrease the antigen sink, but also to minimize on-target clinical adverse effects observed following treatment with other reported RBC-binding anti-CD47 antibodies. When tested in cynomolgus monkeys, AO-176 was well tolerated with no adverse effects. Finally, we show that AO-176 demonstrates dose-dependent antitumor activity in tumor xenograft models. Taken together, the unique properties and antitumor activity of our next-generation anti-CD47 antibody, AO-176, distinguishes it from other CD47/SIRPα axis targeting agents in clinical development.

Sodium arsenite exposure impairs B cell proliferation and enhances vascular inflammation in Plasmodium berghei mouse model

Arsenic exposure has been linked to an impaired immune response and inflammation. Our study investigated the effects of sodium arsenite on host immune response and vascular inflammation during malarial infection. Mice were divided into three groups: control (C), Plasmodium berghei infection (I) and sodium arsenite exposure with Plasmodium berghei infection (As-I). The results showed that splenocyte proliferation stimulated by lipopolysaccharide (LPS) and pokeweed mitogen (PWM) was suppressed in the I group, and the suppression was more pronounced in the As-I group, suggesting that acquired immunity in infected mice was worsening following arsenic exposure. ICAM-1, an adhesion protein involved in parasite-infected red blood cell (iRBC) binding to endothelium, and HIF-1α, a hypoxia marker protein in the descending aorta, were increased in the As-I group compared to the I group. Collectively, our results suggest that arsenic may increase host susceptibility to malaria through suppression of B cell proliferation and enhancement of adhesion between iRBC and endothelium by increasing ICAM-1.

Influence of dynamic flow conditions on adsorbed plasma protein corona and surface-induced thrombus generation on antifouling brushes

The information regarding the nature of protein corona (and its changes) and cell binding on biomaterial surface under dynamic conditions is critical to dissect the mechanism of surface-induced thrombosis. In this manuscript, we investigated the nature of protein corona and blood cell binding in heparinized recalcified human plasma, platelet rich plasma and whole blood on three highly hydrophilic antifouling polymer brushes, (poly(N, N-dimethylacrylamide) (PDMA), poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly[N-(2-hydroxypropyl) methacrylamide] (PHPMA) using an in vitro blood loop model at comparable arterial and venous flow, and static conditions. A fluid dynamics model was used initially to better understand the resulting flow patterns in a vertical channel containing the substrates to arrive at the placement of the substrates within the blood loop. The protein binding on the brush modified substrates was determined using ellipsometry, fluorescence microscopy and the nature of the protein corona was investigated using mass spectrometry based proteomics. The flow elevated fouling on brush coated surface from blood. The extent of plasma protein adsorption and platelet adhesion onto PDMA brush was lower than other surfaces in both static and flow conditions. The profiles of adsorbed protein corona showed strong dependence on the test conditions (static vs. flow), and the chemistry of the polymer brushes. Specially, the PDMA brush under flow conditions was more enriched with coagulation proteins, complement proteins, vitronectin and fibronectin but was less enriched with serum albumin. Apolipoprotein B-100 and complement proteins were the most abundant proteins seen on PMPC and PHPMA surfaces under both flow and static conditions, respectively. Unlike PDMA brush, the flow conditions did not affect the composition of protein corona on PMPC and PHPMA brushes. The nature of the protein corona formed in flow conditions influenced the platelet and red blood cell binding. The dependence of shear stress on platelet adhesion from platelet rich plasma and whole blood highlights the contribution of red blood cells in enhancing platelet adhesion on the surface under high shear condition.

Molecular Links between Erythrocyte Adhesion and Vascular Dysfunction in Diabetes Mellitus, Polycythemia Vera, Retinal Vascular Occlusion

Despite clinical and epidemiological studies quantitative and qualitative abnormalities red blood cell (RBC) role in thrombosis has been ignored. Abnormal interaction of RBCs with vascular endothelium has been demonstrated in diabetes mellitus, Polycythemia vera (PV) and retinal vascular occlusion (RVO) after the first description in sickle cell anemia. The molecular basis has been identified. In diabetes mellitus, glycation of RBC band 3 caused the ligation to the receptor for advanced glycation end products (RAGE) present on endothelium. An abnormal Lu/BCAM (CD 239) expression in PV is responsible for the binding to endothelium annexin V. In RVO, RBC phosphatidylserine overexpression mediated the attachment to vascular laminin alpha-5 chain. Red blood cell binding altered the nonthrombotic properties of endothelium leading to thrombosis.

VLA-4 blockade by natalizumab inhibits sickle reticulocyte and leucocyte adhesion during simulated blood flow.

Very Late Antigen-4 (VLA-4, α4β1-integrin, ITGA4) orchestrates cell-cell and cell-endothelium adhesion. Given the proposed role of VLA-4 in sickle cell disease (SCD) pathophysiology, we evaluated the ability of the VLA-4 blocking antibody natalizumab to inhibit SCD blood cell adhesion. Natalizumab recognized surface VLA-4 on leucocytes and reticulocytes in whole blood from SCD subjects. SCD reticulocytes were positive for VLA-4, while VLA-4 staining of non-SCD reticulocytes was undetectable. Titrations with natalizumab revealed the presence of saturable levels of VLA-4 on both SCD reticulocytes and leucocytes similar to healthy subject leucocytes. Under physiological flow conditions, the adhesion of SCD whole blood cells and isolated SCD leucocytes to immobilized vascular cell adhesion molecule 1 (VCAM-1) was blocked by natalizumab in a dose-dependent manner, which correlated with cell surface receptor binding. Natalizumab also inhibited >50% of whole blood cell binding to TNF-α activated human umbilical vein endothelial cell monolayers under physiological flow at clinically relevant concentrations (10to 100μg/ml). This indicates that VLA-4 is the dominant receptor that drives SCD reticulocyte and mononuclear cell adhesion to VCAM-1 and that the VLA-4 adhesion to VCAM-1 is a significant contributor to SCD blood cell adhesion to endothelium. Thus, VLA-4 blockade may be beneficial in sickle cell disease.

Microarray analysis of PBMC after Plasmodium falciparum infection: Molecular insights into disease pathogenesis.

To find out host gene expression profiles after malarial infection. Further time-course microarray analysis of peripheral blood mononuclear cells focusing on malaria pathogenesis was performed. Up-regulation of coagulation-related genes, heat shock proteins, glycolytic enzymes, glucose transporters, and vacuolar H(+)-ATPases was found in acute febrile malaria. In early malaria, prior to detectable parasitemia, CD36 and ICAM1 were up-regulated. During acute malaria, there is correlation between IL-1β and heat shock proteins. CD163, a hemoglobin scavenger receptor, was up-regulated in acute malaria to potentially facilitate free hemoglobin up-take by leukocytes. In acute malaria, high MafB gene expression was negatively correlated with hemoglobin and platelet counts. Consistent with hemoglobin down-regulation, peripheral red blood cell counts tended to increase during acute malaria. Up-regulations of red blood cell and leukocyte binding mediators like CD36, ICAM1, thrombospondin, and thrombomodulin may contribute to the pathogenesis of cerebral malaria. Similarly, up-regulation of correlated glycolytic enzymes, glucose transporter and H(+)-ATPases may contribute to the hypoglycemia and metabolic acidosis frequently observed in serious malaria patients. Overall gender effects on gene expression profiles between male and female were not apparent, except for some hemoglobins were significantly down-regulated in male versus female, which suggesting males are prone to malaria-related anemia. Leukocyte gene expression profiles can explain the pathogenesis of malarial complication such as fever, metabolic acidosis, hypoglycemia, anemia, and coagulopathy.

Label-free Microfluidic Sensing by Detection of Interaction-triggered Change in Blood Flow Characteristics

Microfluidic devices exploit combined physical, chemical and biological phenomena that could be unique in the sub-millimeter dimensions. The blood is a non-Newtonian fluid, containing particulate and soluble elements, which penetrates the whole body carrying a wealth of biomedical information. The design of microfluidic devices capable of extracting immediately this information is the current goal of development Point-of-Care (POC) medical devices. We examined the characteristics of blood flow in specially designed microfluidic devices having different geometric structure and material composition with the aim of defining suitable conditions for sensitive detection of changes in the interactions between particulate elements of the blood and the adequately modified surfaces of the microfluidic system. As a model experiment we demonstrated the fast analysis of the AB0 blood group system, applying respective antibody reagents and capillary blood samples with different blood groups. We showed that by tuning the hydrophilicity of the surface and capillary dimensions of the microfluidic system it is possible to detect precisely the red blood cell binding to the capillary walls by monitoring the flow rate characteristics in an autonomous microfluidic system. Our proof-of-concept results point to a novel direction in blood analysis in autonomous microfluidic systems and also provide the basis for the construction of a simple quantitative device for blood group determination.

Image‐derived and arterial blood sampled input functions for quantitative PET imaging of the angiotensin II subtype 1 receptor in the kidney

The radioligand 11C-KR31173 has been introduced for positron emission tomography (PET) imaging of the angiotensin II subtype 1 receptor in the kidney in vivo. To study the biokinetics of 11C-KR31173 with a compartmental model, the input function is needed. Collection and analysis of arterial blood samples are the established approach to obtain the input function but they are not feasible in patients with renal diseases. The goal of this study was to develop a quantitative technique that can provide an accurate image-derived input function (ID-IF) to replace the conventional invasive arterial sampling and test the method in pigs with the goal of translation into human studies. The experimental animals were injected with [11C]KR31173 and scanned up to 90 min with dynamic PET. Arterial blood samples were collected for the artery derived input function (AD-IF) and used as a gold standard for ID-IF. Before PET, magnetic resonance angiography of the kidneys was obtained to provide the anatomical information required for derivation of the recovery coefficients in the abdominal aorta, a requirement for partial volume correction of the ID-IF. Different image reconstruction methods, filtered back projection (FBP) and ordered subset expectation maximization (OS-EM), were investigated for the best trade-off between bias and variance of the ID-IF. The effects of kidney uptakes on the quantitative accuracy of ID-IF were also studied. Biological variables such as red blood cell binding and radioligand metabolism were also taken into consideration. A single blood sample was used for calibration in the later phase of the input function. In the first 2 min after injection, the OS-EM based ID-IF was found to be biased, and the bias was found to be induced by the kidney uptake. No such bias was found with the FBP based image reconstruction method. However, the OS-EM based image reconstruction was found to reduce variance in the subsequent phase of the ID-IF. The combined use of FBP and OS-EM resulted in reduced bias and noise. After performing all the necessary corrections, the areas under the curves (AUCs) of the AD-IF were close to that of the AD-IF (average AUC ratio=1±0.08) during the early phase. When applied in a two-tissue-compartmental kinetic model, the average difference between the estimated model parameters from ID-IF and AD-IF was 10% which was within the error of the estimation method. The bias of radioligand concentration in the aorta from the OS-EM image reconstruction is significantly affected by radioligand uptake in the adjacent kidney and cannot be neglected for quantitative evaluation. With careful calibrations and corrections, the ID-IF derived from quantitative dynamic PET images can be used as the input function of the compartmental model to quantify the renal kinetics of 11C-KR31173 in experimental animals and the authors intend to evaluate this method in future human studies.