ABSTRACT
Fear of childbirth (FoC) occurs in 7. 5% of pregnant women and has been associated with adverse feto-maternal outcomes. Eye Movement Desensitization and Reprocessing (EMDR) therapy has proven to be effective in the treatment of posttraumatic stress disorder (PTSD) and anxiety; however, its effectiveness regarding FoC has not yet been established. The aim was to determine the safety and effectiveness of EMDR therapy for pregnant women with FoC. This single-blind RCT (the OptiMUM-study, www.trialregister.nl, NTR5122) was conducted in the Netherlands. FoC was defined as a score ≥85 on the Wijma Delivery Expectations Questionnaire (WDEQ-A). Pregnant women with FoC and a gestational age between 8 and 20 weeks were randomly assigned to EMDR therapy or care-as-usual (CAU). The severity of FoC was assessed using the WDEQ-A. Safety was indexed as worsening of FoC symptoms, dropout, serious adverse events, or increased suicide risk. We used linear mixed model analyses to compare groups. A total of 141 women were randomized (EMDR n = 70; CAU n = 71). No differences between groups were found regarding safety. Both groups showed a very large (EMDR d = 1.36) or large (CAU d = 0.89) reduction of FoC symptoms with a mean decrease of 25.6 (EMDR) and 17.4 (CAU) points in WDEQ-A sum score. No significant difference between both groups was found (p = 0.83). At posttreatment, 72.4% (EMDR) vs. 59.6% (CAU) no longer met the criteria for FoC. In conclusion, the results are supportive of EMDR therapy as a safe and effective treatment of FoC during pregnancy, albeit without significant beneficial effects of EMDR therapy over and above those of CAU. Therefore, the current study results do not justify implementation of EMDR therapy as an additional treatment in this particular setting.
ABSTRACT
The presence of donor-specific anti-HLA antibodies (DSAs) is associated with increased risk of graft failure after kidney transplant. We hypothesized that DSAs against HLA class I, class II, or both classes indicate a different risk for graft loss between deceased and living donor transplant. In this study, we investigated the impact of pretransplant DSAs, by using single antigen bead assays, on long-term graft survival in 3237 deceased and 1487 living donor kidney transplants with a negative complement-dependent crossmatch. In living donor transplants, we found a limited effect on graft survival of DSAs against class I or II antigens after transplant. Class I and II DSAs combined resulted in decreased 10-year graft survival (84% to 75%). In contrast, after deceased donor transplant, patients with class I or class II DSAs had a 10-year graft survival of 59% and 60%, respectively, both significantly lower than the survival for patients without DSAs (76%). The combination of class I and II DSAs resulted in a 10-year survival of 54% in deceased donor transplants. In conclusion, class I and II DSAs are a clear risk factor for graft loss in deceased donor transplants, while in living donor transplants, class I and II DSAs seem to be associated with an increased risk for graft failure, but this could not be assessed due to their low prevalence.
Subject(s)
Donor Selection , Graft Rejection/mortality , HLA Antigens/immunology , Isoantibodies/adverse effects , Kidney Failure, Chronic/surgery , Kidney Transplantation/mortality , Living Donors , Adult , Cadaver , Female , Follow-Up Studies , Graft Rejection/etiology , Graft Rejection/pathology , Graft Survival , Humans , Kidney Transplantation/adverse effects , Male , Middle Aged , Postoperative Complications , Prognosis , Retrospective Studies , Risk Factors , Survival RateABSTRACT
Background: Approximately 3% of women develop posttraumatic stress disorder (PTSD) after giving birth, and 7.5% of pregnant women show a pathological fear of childbirth (FoC). FoC or childbirth-related PTSD during (a subsequent) pregnancy can lead to a request for an elective caesarean section as well as adverse obstetrical and neonatal outcomes. For PTSD in general, and several subtypes of specific phobia, eye movement desensitization and reprocessing (EMDR) therapy has been proven effective, but little is known about the effects of applying EMDR during pregnancy. Objective: To describe the protocol of the OptiMUM-study. The main aim of the study is to determine whether EMDR therapy is an effective and safe treatment for pregnant women with childbirth-related PTSD or FoC. In addition, the cost-effectiveness of this approach will be analysed. Method: The single-blind OptiMUM-study consists of two two-armed randomized controlled trials (RCTs) with overlapping design. In several hospitals and community midwifery practices in Amsterdam, the Netherlands, all eligible pregnant women with a gestational age between eight and 20 weeks will be administered the Wijma delivery expectations questionnaire (WDEQ) to asses FoC. Multiparous women will also receive the PTSD checklist for DSM-5 (PCL-5) to screen for possible PTSD. The clinician administered PTSD scale (CAPS-5) will be used for assessing PTSD according to DSM-5 in women scoring above the PCL-5 cut-off value. Fifty women with childbirth-related PTSD and 120 women with FoC will be randomly allocated to either EMDR therapy carried out by a psychologist or care-as-usual. Women currently undergoing psychological treatment or women younger than 18 years will not be included. Primary outcome measures are severity of childbirth-related PTSD or FoC symptoms. Secondary outcomes are percentage of PTSD diagnoses, percentage caesarean sections, subjective childbirth experience, obstetrical and neonatal complications, and health care costs. Results: The results are meant to provide more insight about the safety and possible effectiveness of EMDR therapy during pregnancy for women with PTSD or FoC. Conclusion: This study is the first RCT studying efficacy and safety of EMDR in pregnant women with PTSD after childbirth or Fear of Childbirth.
ABSTRACT
Solid-phase multiplex-bead assays are widely used in transplantation to detect anti-human leukocyte antigen (HLA) antibodies. These assays enable high resolution detection of low levels of HLA antibodies. However, multiplex-bead assays are costly and yield variable measurements that limit the comparison of results between laboratories. In the context of a Dutch national Consortium study we aimed to determine the inter-assay and inter-machine variability of multiplex-bead assays, and we assessed how to reduce the assay reagents costs. Fifteen sera containing a variety of HLA antibodies were used yielding in total 7092 median fluorescence intensities (MFI) values. The inter-assay and inter-machine mean absolute relative differences (MARD) of the screening assay were 12% and 13%, respectively. The single antigen bead (SAB) inter-assay MARD was comparable, but showed a higher lot-to-lot variability. Reduction of screening assay reagents to 50% or 40% of manufacturers' recommendations resulted in MFI values comparable to 100% of the reagents, with an MARD of 12% or 14%, respectively. The MARD of the 50% and 40% SAB assay reagent reductions were 11% and 22%, respectively. From this study, we conclude that the reagents can be reliably reduced at least to 50% of manufacturers' recommendations with virtually no differences in HLA antibody assignments.
Subject(s)
Automation, Laboratory/economics , HLA Antigens/immunology , Immunoassay/economics , Isoantibodies/blood , Reagent Kits, Diagnostic/economics , Alleles , Automation, Laboratory/standards , HLA Antigens/blood , Histocompatibility Testing , Humans , Immune Sera/chemistry , Immunoassay/standards , Kidney Transplantation , Observer Variation , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
We evaluated the efficacy and safety of rituximab as induction therapy in renal transplant patients. In a double-blind, placebo-controlled study, 280 adult renal transplant patients were randomized between a single dose of rituximab (375 mg/m(2)) or placebo during transplant surgery. Patients were stratified according to panel-reactive antibody (PRA) value and rank number of transplantation. Maintenance immunosuppression consisted of tacrolimus, mycophenolate mofetil and steroids. The primary endpoint was the incidence of biopsy proven acute rejection (BPAR) within 6 months after transplantation. The incidence of BPAR was comparable between rituximab-treated (23/138, 16.7%) and placebo-treated patients (30/142, 21.2%, p = 0.25). Immunologically high-risk patients (PRA >6% or re-transplant) not receiving rituximab had a significantly higher incidence of rejection (13/34, 38.2%) compared to other treatment groups (rituximab-treated immunologically high-risk patients, and rituximab- or placebo-treated immunologically low-risk (PRA ≤ 6% or first transplant) patients (17.9%, 16.4% and 15.7%, p = 0.004). Neutropenia (<1.5 × 10(9) /L) occurred more frequently in rituximab-treated patients (24.3% vs. 2.2%, p < 0.001). After 24 months, the cumulative incidence of infections and malignancies was comparable. A single dose of rituximab as induction therapy did not reduce the overall incidence of BPAR, but might be beneficial in immunologically high-risk patients. Treatment with rituximab was safe.
Subject(s)
Antibodies, Monoclonal, Murine-Derived/therapeutic use , Graft Rejection/epidemiology , Graft Rejection/prevention & control , Immunosuppressive Agents/therapeutic use , Kidney Transplantation , Adult , B-Lymphocytes/pathology , Biopsy , Double-Blind Method , Female , Graft Rejection/pathology , Humans , Incidence , Kidney/pathology , Male , Middle Aged , Remission Induction , Rituximab , Treatment OutcomeABSTRACT
Traditionally, antirejection therapy in organ transplantation has mainly been directed at T cells. During recent years, the role of B cells in acute rejection has attracted more attention. In the Radboud University Medical Center (Nijmegen, The Netherlands) we performed a randomized, placebo controlled study to assess the efficacy and safety of rituximab as induction therapy after renal transplantation. In parallel we investigated the effects of rituximab on the numbers and function of B and T cells. An overview of the results, which have largely been published in peer reviewed papers, is presented below.
Subject(s)
Antibodies, Monoclonal, Murine-Derived/therapeutic use , Graft Rejection/prevention & control , Immunosuppression Therapy/methods , Immunosuppressive Agents/therapeutic use , Kidney Transplantation , B-Lymphocytes/cytology , B-Lymphocytes/immunology , Graft Rejection/drug therapy , Graft Rejection/immunology , Humans , Lymphocyte Activation/immunology , Lymphocyte Count , Placebos , Rituximab , T-Lymphocytes/cytology , T-Lymphocytes/immunologyABSTRACT
Kidney transplantation is the best treatment option for patients with end-stage renal failure. At present, approximately 800 Dutch patients are registered on the active waiting list of Eurotransplant. The waiting time in the Netherlands for a kidney from a deceased donor is on average between 3 and 4 years. During this period, patients are fully dependent on dialysis, which replaces only partly the renal function, whereas the quality of life is limited. Mortality among patients on the waiting list is high. In order to increase the number of kidney donors, several initiatives have been undertaken by the Dutch Kidney Foundation including national calls for donor registration and providing information on organ donation and kidney transplantation. The aim of the national PROCARE consortium is to develop improved matching algorithms that will lead to a prolonged survival of transplanted donor kidneys and a reduced HLA immunization. The latter will positively affect the waiting time for a retransplantation. The present algorithm for allocation is among others based on matching for HLA antigens, which were originally defined by antibodies using serological typing techniques. However, several studies suggest that this algorithm needs adaptation and that other immune parameters which are currently not included may assist in improving graft survival rates. We will employ a multicenter-based evaluation on 5429 patients transplanted between 1995 and 2005 in the Netherlands. The association between key clinical endpoints and selected laboratory defined parameters will be examined, including Luminex-defined HLA antibody specificities, T and B cell epitopes recognized on the mismatched HLA antigens, non-HLA antibodies, and also polymorphisms in complement and Fc receptors functionally associated with effector functions of anti-graft antibodies. From these data, key parameters determining the success of kidney transplantation will be identified which will lead to the identification of additional parameters to be included in future matching algorithms aiming to extend survival of transplanted kidneys and to diminish HLA immunization. Computer simulation studies will reveal the number of patients having a direct benefit from improved matching, the effect on shortening of the waiting list, and the decrease in waiting time.
Subject(s)
Histocompatibility Testing/methods , Kidney Failure, Chronic/surgery , Kidney Transplantation/mortality , Tissue and Organ Procurement/methods , Waiting Lists , Epitopes, B-Lymphocyte/immunology , Epitopes, T-Lymphocyte/immunology , Graft Rejection/immunology , Graft Survival/immunology , HLA Antigens/immunology , Humans , Kidney/immunology , Kidney/surgery , Quality of Life , Renal DialysisABSTRACT
BACKGROUND: Although numerous studies investigate sensory regeneration and reinnervation of the hind paw of the rat after nerve damage, no comprehensive overview of its normal innervation is present in literature. The Evans Blue extravasation technique is a well-known technique to study patterns of skin innervation. This technique has been performed differently by various groups but was never used to study the entire skin innervation in rats' hind paw including all three branches of the sciatic nerve and the saphenous nerve in detail. NEW METHOD: In this paper, we have used the Evans Blue extravasation technique to chart the skin areas innervated by the sural, peroneal, tibial and/or saphenous nerves, which together innervate the entire hind paw of the rat, and use a new technique to analyze the distribution, overlap and variability of the results. The technique is based on analysis of whole hind paws using Optical Surface Mapping (OSM) in combination with the Computer Assisted Surgical Anatomy Mapping (CASAM) technology. RESULTS: While the plantar hind paw is mainly innervated by the tibial nerve, the dorsal hind paw is supplied by the sural, peroneal and the saphenous nerve. COMPARISON WITH EXISTING METHODS: Although our results basically concur with the general nerve-specific innervation of the rat hind paw, they show considerable detail in their areas of overlap as well as in the amount of variability between animals. CONCLUSION: These results will be invaluable to study and evaluate patterns of innervation and reinnervation of intact and damaged nerve fibers.
Subject(s)
Evans Blue , Hindlimb/innervation , Image Processing, Computer-Assisted/methods , Neuroanatomical Tract-Tracing Techniques/methods , Neuronal Tract-Tracers , Optical Imaging/methods , Animals , Electric Stimulation , Female , Hindlimb/anatomy & histology , Male , Peroneal Nerve/anatomy & histology , Rats, Inbred Lew , Reproducibility of Results , Sciatic Nerve/anatomy & histology , Skin/anatomy & histology , Skin/injuries , Sural Nerve/anatomy & histology , Surgery, Computer-Assisted/methods , Tibial Nerve/anatomy & histologyABSTRACT
We previously demonstrated the ability of CD3-specific antibodies (Abs) to induce tolerance of fully mismatched pancreatic islets when administered at the time of effector T-cell priming (day +7). When administered on day -1, CD3 Abs only displayed an immunosuppressive effect with no permanent acceptance. Here we show that rejection correlates with progressive migration of CD4(+) and CD8(+) T cells into the graft. In contrast, the day +7 CD3 Ab tolerogenic effect is associated with absence of de novo accumulation of CD8(+) T cells within the allograft while CD4(+) T-cell migration is not altered. Furthermore, the increased proportion in T-regulatory cells, observed both in the draining lymph nodes and in the transplanted islets, was more pronounced after the delayed (day +7) than the early (day -1) CD3 Ab course. Last, tolerance-promoting (day +7), but not immunosuppressive (day -1) CD3 Ab treatment was associated with an elevated in situ Foxp3/α-1,2-mannosidase gene expression ratio, identified as a biomarker predicting tolerance in renal transplant patients. In conclusion, intragraft-enhanced regulation over effector function after the delayed but not the early CD3 antibody therapy discriminates between the tolerance-promoting and immunosuppressive effect of CD3 Ab treatment and further highlights the importance of the therapeutic window.
Subject(s)
Autoantibodies/immunology , CD3 Complex/immunology , Islets of Langerhans Transplantation , Models, Animal , Animals , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Mice , Mice, Inbred Strains , Real-Time Polymerase Chain Reaction , Transplantation, HomologousABSTRACT
Despite remarkable progress in organ transplantation through the development of a wealth of immunosuppressive drugs highly effective at controlling acute rejection, two major problems still remain, the loss of transplants due to chronic rejection and the growing number of sensitized recipients due to previous transplants, transfusions or pregnancies. Induction of immune tolerance appears to be the only way to curb this complex situation. Here we describe that a therapy, already successfully used to restore immune tolerance to self-antigens in overt autoimmunity, is effective at promoting transplant tolerance. We demonstrate that a short low-dose course with CD3 antibodies started after transplantation, at the time of effector T cell priming to alloantigens, induces permanent acceptance of fully mismatched islet allografts. Mechanistic studies revealed that antigen-specific regulatory and effector T cells are differentially affected by the treatment. CD3 antibody treatment preferentially induces apoptosis of activated alloreactive T cells which is mandatory for tolerance induction. In contrast, regulatory T cells are relatively spared from CD3 antibody-induced depletion and can transfer antigen-specific tolerance thus arguing for their prominent role in sustaining long-term graft survival.
Subject(s)
Antibodies, Monoclonal/pharmacology , CD3 Complex/pharmacology , Immune Tolerance/immunology , Islets of Langerhans/immunology , Transplantation Tolerance/immunology , Animals , Antibodies, Monoclonal/immunology , CD3 Complex/immunology , Cell Transplantation/methods , Disease Models, Animal , Graft Rejection , Graft Survival , Immune Tolerance/drug effects , Isoantigens/immunology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Random Allocation , Real-Time Polymerase Chain Reaction , Risk Factors , Sensitivity and Specificity , Time Factors , Transplantation Immunology/physiology , Transplantation Tolerance/physiologySubject(s)
Emphysema/diagnostic imaging , Kidney Transplantation/adverse effects , Pyelonephritis/diagnostic imaging , Anti-Bacterial Agents/therapeutic use , Emphysema/epidemiology , Emphysema/etiology , Emphysema/therapy , Female , Fever/etiology , Humans , Middle Aged , Nephrectomy , Pyelonephritis/epidemiology , Pyelonephritis/etiology , Pyelonephritis/therapy , Radiography , Rare DiseasesABSTRACT
Recently two major outbreaks of mumps have occurred: in the UK more than 56,000 cases were notified between 2004 and 2005, and in the United States, 6,584 cases were reported in 2006. Most patients were young healthy adults, in whom mumps normally has a benign course. Little is known about mumps in the immunocompromised patient. Here, we report a case of a 56-year renal transplant recipient who developed acute irreversible transplant failure due to interstitial nephritis caused by mumps. RNA of the mumps virus was detected in the urine as well as in a renal biopsy. In view of the ongoing presence of the mumps virus in the population, one should be aware of the possible occurrence of this infection in immunocompromised patients.
Subject(s)
Kidney Transplantation/adverse effects , Mumps/etiology , Biopsy , Graft Rejection , Humans , Immunocompromised Host , Kidney/virology , Male , Middle Aged , Mumps/complications , Nephritis, Interstitial/etiology , Postoperative Complications , RNA, Viral/metabolismABSTRACT
The molecular defect of a new Bernard-Soulier patient, originating from Morocco and presenting thrombocytopenia with large platelets and an absence of ristocetin-induced platelet agglutination, has been identified and reproduced in transfected heterologous cells. Gene sequencing revealed insertion of a guanine in the domain coding for the transmembrane region of the glycoprotein (GP) Ib beta subunit. This mutation causes a translational frame shift, which creates putative novel transmembrane and cytoplasmic 37 and 125 amino acids domains, respectively. A 34 kDa immunoreactive GPIb beta band, instead of the normal 26 kDa subunit, was detected by Western blotting in lysates from the patient's platelets and from transfected cells and in immunoprecipitates of metabolically labeled cells. The abnormal subunit did not associate with GPIb alpha and was mainly intracellular, although a significant fraction could reach the cell surface. Cells expressing the mutant GPIb-IX complex adhered to a von Willebrand factor matrix but were unable to change shape, unlike cells expressing the wild-type receptor. These results strongly suggest a novel role of the GPIb beta subunit and its transmembrane-intracellular region in GPIb-VWF-dependent signaling, in addition to a role in correct assembly and cell surface targeting of the GPIb-V-IX complex.
Subject(s)
Bernard-Soulier Syndrome/genetics , Platelet Glycoprotein GPIb-IX Complex/genetics , Signal Transduction , Amino Acid Sequence , Animals , Bernard-Soulier Syndrome/blood , Bernard-Soulier Syndrome/complications , Blood Platelets/pathology , CHO Cells , Cell Membrane , Cell Shape , Child, Preschool , Cricetinae , Cytoplasm , Female , Frameshift Mutation , Humans , Peptide Fragments , Signal Transduction/genetics , Thrombocytopenia/etiology , Transfection , von Willebrand Factor/metabolismABSTRACT
The multisubunit leucine-rich glycoprotein (GP) Ib-IX-V complex mediates von Willebrand factor-dependent platelet adhesion at sites of blood-vessel injury. Molecular defects of this receptor are reported to cause the Bernard-Soulier haemorrhagic disorder. To gain insight into the mechanisms controlling expression of normal and defective receptors, we performed pulse-chase metabolic studies and detailed analysis of intracellular processing in GPIb-IX-transfected Chinese-hamster ovary cells. In the native complex, after early subunit association, sugars N-linked to the three subunits are trimmed and sialylated in the Golgi compartment and GPIbalpha undergoes extensive O-glycosylation. Surface biotinylation during chase demonstrated that only fully processed complexes reach the cell surface. Tunicamycin treatment revealed that early N-glycosylation is not required for O-glycosylation of GPIbalpha and surface expression of the complex. Biosynthetic studies were then performed on a Bernard-Soulier variant based on previous description of abnormal GPIbalpha size and decreased surface expression. The mutant complex associated normally, but displayed defective processing of its N-linked sugars and abnormal O-glycosylation of GPIbalpha. Confocal immunofluorescence microscopy revealed that the mutant complexes could reach the cell surface but also accumulated intracellularly, while use of compartment specific markers showed strong co-localization in the endoplasmic reticulum (ER) and ER-to-Golgi intermediate compartments ('ERGIC') and only slight labelling of the cis-Golgi. Blockade before the Golgi was confirmed by brefeldin A treatment, which restored O-glycosylation and processing of N-linked sugars. The present study has shown that transfer from the ER to the Golgi represents an important step for controlling post-translational processing and surface expression of normal GPIb-IX-V complex.
Subject(s)
Platelet Glycoprotein GPIb-IX Complex/biosynthesis , Platelet Glycoprotein GPIb-IX Complex/metabolism , Protein Processing, Post-Translational , Animals , CHO Cells , Carbohydrate Metabolism , Cell Membrane/metabolism , Cricetinae , Cytoplasm/metabolism , Endoplasmic Reticulum/metabolism , Glycosylation , Golgi Apparatus/metabolism , Kinetics , Leucine/genetics , Microscopy, Confocal , Mutation , Platelet Glycoprotein GPIb-IX Complex/genetics , Protein Subunits , Protein TransportABSTRACT
GPIbbeta is disulfide-linked to GPIbalpha to form GPIb, a platelet receptor for von Willebrand factor (vWF). GPIb is in turn non covalently linked to GPIX and GPV to form the GPIb/V/IX complex. Apart from its contribution to controlling surface expression of the complex, the exact function of GPIbbeta is not well established due to a lack of suitable ligands or antibodies. The present report describes a monoclonal antibody (RAM.1) that labeled the 26 kDa GPIbbeta subunit on western blots and coprecipitated the three subunits of the GPIb/IX complex from lysates of platelets and transfected CHO and K562 cells. RAM.1 bound to GPIbbeta deleted of its intracellular domain whereas Gi27, directed against intracellular GPIbbeta, did not. Using synthetic peptides, the RAM.1 epitope was mapped to a putative cysteine loop within the COOH-terminal leucine-rich flanking region. In functional assays, RAM.1 had no effect on platelet aggregation induced by ADP, collagen or thrombin, but inhibited ristocetin induced platelet agglutination and botrocetin induced vWF binding. RAM.1 inhibited adhesion of GPIb/V/IX transfected K562 cells to a vWF matrix under flow, increased their rolling velocity and decreased the resistance of cells to detachment at high shear. This study suggests a role of GPIbbeta in modulating the adhesive properties of GPIb/V/IX and describes a useful tool to analyze the exact functions of GPIbbeta.
Subject(s)
Antibodies, Monoclonal/pharmacology , Platelet Adhesiveness/drug effects , Platelet Glycoprotein GPIb-IX Complex/immunology , von Willebrand Factor/pharmacology , Animals , Antibodies, Monoclonal/isolation & purification , Blood Platelets/chemistry , Blood Platelets/drug effects , Blood Platelets/immunology , Drug Interactions , Epitopes/chemistry , Epitopes/immunology , Humans , Male , Mice , Platelet Aggregation/drug effects , Platelet Aggregation Inhibitors/pharmacology , Platelet Glycoprotein GPIb-IX Complex/physiology , Protein Binding/drug effects , Protein Structure, Tertiary , Rats , Species Specificity , von Willebrand Factor/antagonists & inhibitors , von Willebrand Factor/metabolismABSTRACT
The mechanisms governing the biosynthesis and surface expression of platelet adhesive receptors on parent megakaryocytes are as yet poorly understood. In particular, the assembly and processing of the multisubunit glycoprotein (GP) Ib-IX-V complex, a receptor for von Willebrand factor (vWf) is not fully understood. In the present work, these questions were addressed by reproducing a natural mutation of GPIbalpha found in a variant case of Bernard-Soulier syndrome (Nancy I), due to the deletion of leucine 179 in the seventh leucine-rich repeat of the polypeptide. Wild type and mutated GPIbalpha were transfected into CHO cells expressing GPlbbeta and GPIX. Flow cytometry showed surface expression of the three subunits of both GPIb-IX complexes, but GPlbalphadeltaLeu was present at lower levels (20-40%) and was recognized only by a sub class of monoclonal antibodies which epitopes were not modified by the mutation. These properties reproduce the defect found in the patient's platelets, demonstrating the causative nature of the mutation and validate the use of the CHO cells model. Biochemical studies were performed in an attempt to elucidate the mechanism of the conformational change of GPIbalphadeltaLeu. They unexpectedly revealed a major glycosylation deficiency of the mutated GPIbalpha leading to a 40% decrease in molecular weight. The other two subunits of the complex were however normal and present at the plasma membrane. The deletion led to complete functional deficiency with lack of vWf binding of CHOalphadeltaLeu transfected cells in the presence of botrocetin and defective adhesion to a vWf coated surface under static conditions. Finally, in contrast to normal CHOalphabetaIX cells, which displayed rolling and deceleration when perfused over a vWf surface, CHOalphadeltaLeubetaIX cells were unable to roll over or attach to a vWf substratum. These results show that the integrity of the leucine-rich region of GPIbalpha is essential for normal processing and function of the GPIb-IX complex. In addition, these results obtained in a cellular system supported the suspected role of the macroglycopeptide region of GPIbalpha in maintaining a suitable conformation of this multisubunit receptor to perform its adhesive function.
Subject(s)
Bernard-Soulier Syndrome/genetics , Mutation , Platelet Glycoprotein GPIb-IX Complex/chemistry , Protein Processing, Post-Translational , Adolescent , Animals , Binding Sites , CHO Cells , Cricetinae , Cricetulus , Glycosylation/drug effects , Humans , Leucine/chemistry , Male , Molecular Weight , Peptide Fragments/chemistry , Peptide Fragments/metabolism , Platelet Adhesiveness , Platelet Glycoprotein GPIb-IX Complex/genetics , Platelet Glycoprotein GPIb-IX Complex/physiology , Protein Binding , Protein Conformation , Protein Processing, Post-Translational/drug effects , Protein Structure, Tertiary , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/metabolism , Sequence Deletion , Structure-Activity Relationship , Tunicamycin/pharmacology , von Willebrand Factor/metabolismABSTRACT
Leucine-rich repeats are conserved structural motifs present in the four components of the human platelet glycoprotein Ib/IX/V complex receptor for the adhesive protein von Willebrand factor. The absence or abnormality of this complex is responsible for Bernard-Soulier disease, an autosomal recessive bleeding disorder. We report a deletion of leucine 179, located in a highly conserved position of the seventh leucine-rich repeat of GPIb alpha, found in a variant form of Bernard-Soulier disease (Bernard-Soulier Nancy I). Three affected siblings of a family were characterized by absence of ristocetin-induced platelet agglutination, although ADP aggregation was normal. Flow cytometry studies showed detectable amounts of all four members of the GPIb/IX/V complex on the surface of the patients' platelets. Western blotting revealed normal levels of GPIX, decreased levels of GPIb beta and GPV, and < 1% of GPIb alpha. RT-PCR studies showed the presence of mRNA coding for GPIb alpha, GPIb beta, GPIX and GPV. Sequencing showed a three-base deletion which results in the absence of a leucine residue, highly conserved across the seven leucine-rich repeats of GPIb alpha and also within the other members of the leucine-rich glycoprotein family. The absence of the leucine 179 in a patient's GPIb alpha is believed to cause a conformational change in the protein which would account for the lack of binding of most of the MoAbs tested and would be responsible for the absence of von Willebrand factor binding. These results point to the leucine-rich region of GPIb alpha as being required for the correct exposure of the von Willebrand binding site as well as for the correct assembly and stability of the GPIb/IX/V complex on the platelet surface.