[Red blood cell alloimmunization among polytransfused patients in the National Hospital and University Center of Cotonou: about 51 cases]. / Allo-immunisation anti-érythrocytaire chez les polytransfusés au Centre National Hospitalier Universitaire de Cotonou: à propos de 51 cas.

Blood transfusion is a medical procedure used to treat patients with labile blood product. Each transfusion of globular concentrate exposes recipients to the risk of red blood cell alloimmunization. The test for red cell antibodies (RCA) ensures the immunohaematological safety of transfused patients. In Benin, this test is not performed in a systematic way or included either in the pre-transfusion or in the post-transfusion tests. The purpose of this study is to determine the presence of red cell antibodies among polytransfused patients. RCA was performed using indirect antiglobulin test on gel-filtration in 51 polytransfused patients including 26 selected in the Department of Hematology and 25 in the Department of Nephrology at the National Hospital and University Center of Cotonou. After phenotyping alloimmunized patients, tests for detecting signs of hemolysis were performed. Clinical data as well as those on transfusion were collected from transfusion registries and medical records. The prevalence of alloimmunization in our study population was 13.73%. The antibodies identified had the following characteristics: association of anti-RH1 and anti-RH3, anti LE1, association of anti-RH3 and anti-FY1. Alloantibodies were more frequent in patients who had received more than 15 packed red blood cells. Laboratory tests showed signs of hemolysis in one alloimmunized patient. There was no correlation between age, sex, clinical diagnosis and the occurrence of red blood cell alloimmunization. The test for red cell antibodies should be systematically performed in polytransfused patients in order to ensure better transfusion recipient safety in Benin.

From benchmarking to best practices: Lessons from the laboratory quality improvement programme at the military teaching hospital in Cotonou, Benin.

BACKGROUND: In 2015, the Army Teaching Hospital-University Teaching Hospital (HIA-CHU [Hôpital D'instruction des Armées de Cotonou Centre Hospitalier et Universitaire]) laboratory in Benin launched a quality improvement programme in alignment with the World Health Organization Regional Office for Africa's Stepwise Laboratory Improvement Process Towards Accreditation (SLIPTA). Among the sub-Saharan African laboratories that have used SLIPTA, few have been francophone countries, and fewer have belonged to a military health system. The purpose of this article was to outline the strategy, implementation, outcomes and military-specific challenges of the HIA-CHU laboratory quality improvement programme from 2015 to 2018. INTERVENTION: The strategy for the quality improvement programme included: external baseline SLIPTA evaluation, creation of work plan based on SLIPTA results, execution of improvement projects guided by work plan, assurance of accountability via regular meetings, training of personnel to improve personnel competencies, development of external stakeholder relationships for sustainability and external follow-up post-SLIPTA evaluation. LESSONS LEARNT: Over a period of 3 years, the HIA-CHU laboratory improved its SLIPTA score by 29% through a quality improvement process guided by work plan implementation, quality management system documentation, introduction of new proficiency testing and internal quality control programmes, and enhancement of personnel competencies in technical and quality management through training. RECOMMENDATIONS: The programme has yielded achievements, but consistent improvement efforts are necessary to address programme challenges and ensure continual increases in SLIPTA scores. Despite successes, military-specific challenges such as the high mobility of personnel have hindered programme progress. The authors recommend that further implementation research data be shared from programmes using SLIPTA in under-represented settings such as military health systems.

Prevalence of hemoglobin abnormalities in an apparently healthy population in Benin

ABSTRACT Background: Sickle cell disease is the most common monogenic disorder in humans and is a major public health concern in sub-Saharan Africa. In Benin, the prevalence of sickle cell disease is estimated to be 4.8%. Our study aimed to describe the prevalence of hemoglobin abnormalities in an apparently healthy Benin population. Methods: One thousand four hundred and eighty-three men and women, apparently in good health after medical screening, were tested for hemoglobin abnormalities by hemoglobin electrophoresis and the Emmel test. Subjects who were found to have homozygous or double heterozygous hemoglobin abnormalities, were re-sampled and a confirmation hemogram and hemoglobin electrophoresis test by capillary electrophoresis was performed. Results: Our study population was predominantly male (97.7%) with an average age of 21.3 years. 1390 subjects reported that they did not know their hemoglobin electrophoresis status. Hemoglobin electrophoresis profiles found were as follows: 1077 (72.6%) AA (normal), 238 (16.1%) AS, 161 (10.9%) AC, 3 (0.2%) SC, 4 (0.2%) CC and 0 (0%) SS. The 406 subjects with abnormal hemoglobin had balanced somatic growth, with general physical examination results showing no abnormalities. In the seven subjects with major sickle cell syndrome or hemoglobinosis (SC and CC), their values of various hemogram parameters were normal apart from the discreet presence of microcytic anemia. Conclusion: Our study highlights the need for increased routine testing of hemoglobin abnormalities and newborn screening for sickle cell disease in order to enhance early disease detection, prevention and comprehensive care.

Prevalence of hemoglobin abnormalities in an apparently healthy population in Benin.

BACKGROUND: Sickle cell disease is the most common monogenic disorder in humans and is a major public health concern in sub-Saharan Africa. In Benin, the prevalence of sickle cell disease is estimated to be 4.8%. Our study aimed to describe the prevalence of hemoglobin abnormalities in an apparently healthy Benin population. METHODS: One thousand four hundred and eighty-three men and women, apparently in good health after medical screening, were tested for hemoglobin abnormalities by hemoglobin electrophoresis and the Emmel test. Subjects who were found to have homozygous or double heterozygous hemoglobin abnormalities, were re-sampled and a confirmation hemogram and hemoglobin electrophoresis test by capillary electrophoresis was performed. RESULTS: Our study population was predominantly male (97.7%) with an average age of 21.3 years. 1390 subjects reported that they did not know their hemoglobin electrophoresis status. Hemoglobin electrophoresis profiles found were as follows: 1077 (72.6%) AA (normal), 238 (16.1%) AS, 161 (10.9%) AC, 3 (0.2%) SC, 4 (0.2%) CC and 0 (0%) SS. The 406 subjects with abnormal hemoglobin had balanced somatic growth, with general physical examination results showing no abnormalities. In the seven subjects with major sickle cell syndrome or hemoglobinosis (SC and CC), their values of various hemogram parameters were normal apart from the discreet presence of microcytic anemia. CONCLUSION: Our study highlights the need for increased routine testing of hemoglobin abnormalities and newborn screening for sickle cell disease in order to enhance early disease detection, prevention and comprehensive care.

Anomalies immuno-hématologiques et maladies auto-immunes au Centre National Hospitalier Universitaire Hubert Koutoukou Maga (CNHU/HKM) de Cotonou

Introduction : Les maladies auto-immunes (MAI) sont associées à des manifestations immuno-hématologiques de gravité variable. Objectif : Décrire les anomalies immuno-hématologiques retrouvées chez les patients atteints de MAI au CNHU-HKM de Cotonou. Matériels et méthode : Etude prospective, transversale à visée descriptive et analytique menée de novembre 2017 à février 2018 dans les services de Médecine Interne, de Rhumatologie et des Mala-dies du Sang du CNHU-HKM. Le laboratoire d'Hématologie Biologique et celui de Biochimie du même centre ont servi pour la réalisation des différentes explorations biologiques. Résultats : Quarante-quatre patients connus et suivis pour MAI ont été inclus. Parmi eux, 90,9% étaient des femmes. La moyenne d'âge était de 39,7 ans. La polyarthrite rhumatoïde (PR) et le lupus érythémateux systématique (LES) étaient les MAI les plus présentes avec des fréquences respectives de 59,1% et 29,5%. Au plan des analyses biologiques, 24 malades présentaient au moins une anoma-lie de l'hémogramme. Les principales anomalies quantitatives retrouvées étaient l'anémie et la lym-phopénie avec des fréquences respectives de 35,1% et 32,4%. Des anomalies qualitatives touchaient les hématies et les plaquettes. Sept patients sur les 44 possédaient des auto-anticorps anti-érythrocytaires. La présence de ces auto-anticorps était associée à des anomalies de l'hémogramme.Conclusion : Notre étude met en exergue la fréquence élevée des anomalies hématologiques chez les patients atteints de MAI et le rôle important du laboratoire d'hématologie dans leur prise en charge. La prise en charge de ces patients requiert une parfaite collaboration interdisciplinaire

Performance des médécins dans la démarche diagnostique des anémies dans la ville de Cotonou: évolution de 2011 à 2016

Introduction : L'anémie est un problème de santé publique. Pour une prise en charge efficace, une démarche diagnostique méthodique et rigoureuse doit être observée. Objectif : Evaluer l'évolution de la performance théorique et pratique des médecins en matière de diagnostic des anémies entre 2011 et 2016. Méthodologie : Dans la continuité d'une étude réalisée en 2011, 133 médecins ont été évalué sur leurs performances théoriques et pratiques à mener la démarche diagnostique des anémies. Les con-naissances théoriques ont été évaluées par un questionnaire. La performance pratique a été évaluée à l'aide de 60 dossiers de patients traités pour une anémie non drépanocytaire dans les formationssanitaires retenues. Les différents scores obtenus ont été comparés à ceux de 2011. Résultats : L'analyse globale des résultats montre que 48,1% des médecins enquêtés ont eu une performance insuffisante contre 87,9% en 2011 ; une performance acceptable de 50,4% contre 12,1% en 2011 pour la démarche diagnostique théorique. En ce qui concerne la performance diagnostique pratique, 53,3% des médecins avaient une performance insuffisante contre 74% en 2011 et une per-formance acceptable de 46,7% contre 26% en 2011. Les scores enregistrés en 2016 sont meilleurs à ceux retrouvés en 2011 (p=0,000%) Conclusion : Outre le renforcement de l'enseignement des anémies durant les formations médicales,une politique de formation continue est nécessaire pour remédier aux insuffisances constatées

L'expérience en cytologie hématologique au Bénin

Introduction : La maîtrise de la cytologie hématologique reste indispensable malgré l'avènement des automates. Objectif : Faire le point de la pratique de la cytologie hématologique au Bénin. Matériels et méthode : Etude transversale à visée descriptive et analytique comportant un volet ré-trospectif et un volet prospectif. Seize formations sanitaires tirées au hasard et réparties sur l'ensemble des 34 zones sanitaires que compte le pays avaient été incluses en tenant compte des différents niveaux de la pyramide sanitaire. Les données enregistrées ont été saisies avec Excel et analysées grâce au logiciel Epi info version 7.2. Résultats : Six hôpitaux sur 16 avaient un laboratoire d'Hématologie et seul le laboratoire d'Hématologie du Centre National Hospitalier Universitaire-HKM disposait de personnels spécialistes. Le nombre moyen de technicien était de 5 par centre et 60,4% d'entre eux étaient de niveau A. Le nombre moyen d'hémogrammes réalisés par mois était de 3000 pour le CNHU, 603 pour les Hôpitaux de zone et 549 pour les Centres Hospitaliers départementaux. L'étude du frottis sanguin était de réalisation systématique dans seulement 6 centres. Aucune autre activité de cytologie hématologique en dehors de l'hémogramme n'était réalisée sauf au CNHU-HKM et à l'Hôpital de zone de Tanguiéta qui réalisaient des myélogrammes et des adénogrammes. Ces deux derniers centres disposaient également d'un dispositif de télé-hémato-cytologie. Conclusion : Notre étude révèle des insuffisances en cytologie hématologique. Les solutions propo-sées passent par le recrutement et la formation de personnels qualifiés, l'équipement et l'approvisionnement des laboratoires

[Emergency treatment of sickle cell diseases in the Blood Diseases Department at the Koutoukou Maga National Teaching Hospital, Cotonou, Benin]. / Urgences drépanocytaires au Service des Maladies du Sang du Centre National Hospitalier Universitaire-Hubert Koutoukou Maga de Cotonou, Benin.

INTRODUCTION: Evolution of sickle cell disease is marked by the occurrence of acute complications, some of which are real emergencies that can give rise to life-threatening or functional cosequences. This study aims to evaluate the frequency and the evolution of emergency treatment of sickle cell disease in the Blood Diseases Department at the Koutoukou Maga National Teaching Hospital, Cotonou. METHODS: We conducted a retrospective and descriptive study of all patients hospitalized for emergency treatment of sickle cell disease from January 2014 to December 2015. We excluded patients hospitalized for chronic sickle cell disease complications. RESULTS: Out of 813 hospitalizations, two hundred and four (204) emergency treatments of sickle cell disease were registered (prevalence 25%). The average age of our patients was 24.2 years. The most represented age group was 20-30 years (45.6%). Male sex predominated (60.8%). Pupils/students was the most represented group (55.9%). Acute pain was the primary reason for hospitalization to 63.7%. Normal homozygous individuals (SS) were mostly represented (72.1%). Osteoarticular vaso-occlusive complications predominated (70.1%). Documented infectious complications were dominated by malaria (27.5%). Decompensated anemia accounted for 30.4%. Therapeutic approach was based on hydration (85.3%). The average length of stay in hospital was 5.4 days. Outcome was favorable in 96,5% of cases. Mortality accounted for 2.5%. CONCLUSION: Emergency treatments of sickle cell disease are frequent. Early diagnosis as well as early and effective management are necessary. Ongoing training programs in emergency treatments of sickle cell disease are necessary to reduce mortality.

Evaluation du statut martial des hémodialyses suivis au CNHU-HKM de Cotonou

Introduction : Le but de ce travail est d'évaluer l'état martial des hémodialysés du CNHU-HKM de Cotonou. Patient et Méthodes : Il s'agit d'une étude transversale à visée descriptive et analytique, réalisée en janvier 2017 dans l'Unité d'Hémodialyse du Centre National Hospitalier et Universitaire Hubert Koutoukou MAGA (CNHU-HKM). Ont été inclus, les patients hémodialysés chroniques, en dialyse de plus de 3 mois et âgés d'au moins 18 ans, sans pathologie intercurrente et non hospitalisés dans les 4 dernières semaines. L'évaluation de l'anémie a porté sur l'hémoglobine (g/dl), la ferritinémie (ng/ml) et le coefficient de saturation de la transferrine (CST). L'analyse des données a été faite au moyen des logiciels Excel 2013 et SPSS ver 8.0. Résultats : Au total, 190 hémodialysés ont été retenus, l'âge moyen était de 48,81±12.7 avec un sex-ratio de 1,71 et une ancienneté en dialyse de 68,25± 59,5 mois. Le taux moyen d'hémoglobine était de 8,6 ± 1,8 g/dl avec une ferritinemie moyenne de 1056,60± 1388,60 µg/l. La prévalence de l'anémie était de 91,6%. Parmi les patients, 23,7% avaient une ferritinemie entre 300 et 500 ng/dl et 66,8% avaient une ferritinemie élevée. Le CST était bas chez 69 patients soit 36,3% .Tous nos patients étaient sous EPO 4000 ui/semaine et la pluspart ont une supplémentation en fer. Discussion et Conclusion: Le pourcentage de nos patients répondant aux recommandations concernant l'anémie chez les hémodialysés est strictement inferieur aux données de la littérature. La ferritinemie de la moyenne de nos patients est supérieur aux normes, ce qui pourrait les exposer aux complications d'une surcharge ferrique

Biomonitoring of 29 trace elements in whole blood from inhabitants of Cotonou (Benin) by ICP-MS.

This study aimed to investigate the blood concentration of 29 trace elements, metals or metalloids, in a healthy population of Cotonou not directly exposed to metals in order to propose reference values. Blood samples from 70 blood donors were collected in K2 EDTA tubes for trace elements during September 2015 and a questionnaire was used to assess lifestyle exposure. Blood metal concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) equipped with a quadrupole-based reaction cell. Among the selected blood donors 51.4% were aged from 18 to 36 years and 49.6% from 37 to 65 years. Among the 29 elements analyzed As, Pb, Mn, Pd, Sb, Co, Se, Sr showed blood concentrations higher than the reference values found in the literature for non-exposed healthy European populations and their geometric means were respectively 5.81; 47.39; 19.71; 1.91; 7.50; 0.66; 163.01; 30.53µg/L. This study provides the first reference value (5th-95th percentiles) for each element in Cotonou, which enables us to carry out further investigations on environmental and occupational exposure.

The hide and seek of Plasmodium vivax in West Africa: report from a large-scale study in Beninese asymptomatic subjects.

BACKGROUND: Plasmodium vivax is considered to be absent from western Africa, where the prevalence of Duffy-negative red blood cell phenotype proves to be high. Several studies have, however, detected P. vivax infection cases in this part of Africa, raising the question of what is the actual prevalence of P. vivax in local populations. METHODS: The presence of P. vivax was investigated in a large population of healthy blood donors in Benin using microscopy, serology and molecular detection. The seroprevalence was measured with species-specific ELISA using two recombinant P. vivax proteins, namely rPvMSP1 and rPvCSP1. Specific molecular diagnosis of P. vivax infection was carried out using nested-PCR. The performances and cut-off values of both rPvCSP1 and rPvMSP1 ELISA were first assessed using sera from P. vivax-infected patients and from non-exposed subjects. RESULTS: Among 1234 Beninese blood donors, no parasites were detected when using microscopy, whereas 28.7% (354/1234) of patients exhibited had antibodies against rPvMSP1, 21.6% (266/1234) against rPvCSP1, and 15.2% (187/1234) against both. Eighty-four samples were selected for nested-PCR analyses, of which 13 were positive for P. vivax nested-PCR and all Duffy negative. CONCLUSION: The results of the present study highlight an unexpectedly high exposure of Beninese subjects to P. vivax, resulting in sub-microscopic infections. This suggests a probably underestimated and insidious parasite presence in western Africa. While the vaccination campaigns and therapeutic efforts are all focused on Plasmodium falciparum, it is also essential to consider the epidemiological impact of P. vivax.

The ears of the African elephant: unexpected high seroprevalence of Plasmodium ovale and Plasmodium malariae in healthy populations in Western Africa.

BACKGROUND: Malaria Is A Life-Threatening Pathology In Africa. Plasmodium Falciparum And Plasmodium Vivax Attract The Most Focus Because Of Their High Prevalence And Mortality. Knowledge About The Prevalence Of The Cryptic Pathogens Plasmodium Ovale And Plasmodium Malariae Is Limited. Thanks To Recombinant Tools, Their Seroprevalence Was Measured For The First Time, As Well As The Prevalence Of Mixed Infections In A Malaria-Asymptomatic Population In Benin, A Malaria-Endemic Country. METHODS: A Panel Of 1,235 Blood Donations Collected Over Ten Months In Benin Was Used For Validation Of The Recombinant Tools. Recombinant P. Falciparum, P. Malariae, P. Ovale MSP1, And P. Falciparum AMA1 Were Engineered And Validated On A Biobank With Malaria-Infected Patients (N = 144) Using A Species-Speific ELISA Test (Recelisa). Results Were Compared To An ELISA Using A Native P. Falciparum Antigen (NatELISA). RESULTS: Among Microscopically Negative African Blood Donors, 85% (1,050/1,235) Present Antibodies Directed To Native P. Falciparum, 94.4% (1,166/1,235) To rPfMSP1 And rPfAMA1, 56.8% (702/1,235) To rPoMSP1, 67.5% (834/1235) To rPmMSP1 And 45.3% Of The Malaria Seropositive Population Had Antibodies Recognizing The Three Species. CONCLUSION: A High Rate Of Antibodies Against P. Ovale And P. Malariae Was Found In Asymptomatic Blood Donors. The Proportion Of Mixed Infections Involving Three Species Was Also Unexpected. These Data Suggest That Determining Seroprevalence For These Cryptic Species Is An Appropriate Tool To Estimate Their Incidence, At The Eve Of Upcoming Anti-P. Falciparum Vaccination Campaigns.

Is a Plasmodium lactate dehydrogenase (pLDH) enzyme-linked immunosorbent (ELISA)-based assay a valid tool for detecting risky malaria blood donations in Africa?

BACKGROUND: Malaria is a leading cause of mortality in southern Benin. The main causative agent, Plasmodium falciparum, poses a threat on critical transfusions in pregnant women and children. This study's objective was to compare the performance of different malaria screening methods in blood donors in southern Benin, a malaria-endemic country. METHODS: Blood from 2,515 voluntary blood donors in Benin was collected over a period of 10 months in ethylenediaminetetraacetic acid (EDTA) tubes, which were then classified according to extraction time: long rainy season, short dry season, short rainy season, and long dry season. Microscopic examination was used to count parasites. Parasite density (PD) was expressed as the number of parasites per µL of blood. Pan Plasmodium pLDH detection was assessed by an ELISA-malaria antigen test. Using crude soluble P. falciparum antigens, an ELISA-malaria antibody test detected anti-Plasmodium antibodies. RESULTS: Among the 2,515 blood donors (2,025 males and 488 females) screened, the rate of asymptomatic Plasmodium carriage was 295/2,515 (11.72%, 95% CI: 10.5-13.1%). Males had a higher infection rate (12.4%) than did females (8.8%). Parasite density was very low: between seven and100 parasites per µL of blood was reported in 80% of donors with parasitaemia. Three Plasmodium species were diagnosed: P. falciparum in 280/295 patients (95.0%), Plasmodium malariae in 14/295 (5.0%), and Plasmodium ovale in 1/295 (0.34%). Malaria prevalence in donors was higher during the rainy seasons (13.7%) compared with the dry seasons (9.9%). The use of a highly sensitive assay enabled pan Plasmodium pLDH detection in 966/2,515 (38.4%, 95% CI: 36.5%-40.3%). Malaria antibody prevalence was 1,859/2,515 (73.9%, 95% CI: 72.16-75.6%). Donors' antigenaemia and antibody levels varied significantly (P <0.05) over the course of the four seasons. The highest antigenaemia rate 323/630 (51.3%), was observed during the short rainy season, while the highest antibody prevalence, 751/886 (84.7%), was recorded during the long dry season. CONCLUSION: Blood donations infected with Plasmodium can transmit malaria to donation recipients. Malaria diagnostic methods are currently available, but the feasibility criteria for mass screening in endemic areas become preponderant. Detection of the pLDH antigen seems to be an adequate screening tool in endemic areas, for this antigen indicates parasite presence. Routine screening of all donated blood would prevent infected blood donations and reduce P. falciparum transmission in critical patients, such as children and pregnant women. This tool would also decrease medical prophylaxis in donation recipients and contribute to lower Plasmodium resistance.

Misconceptions about sickle cell disease (SCD) among lay people in Benin.

OBJECTIVE: The aim of this study was to determine the accuracy of people's ideas in Benin about the common affliction of sickle cell disease (SCD). METHODS: A questionnaire asking for the degree of agreement with 111 statements about SCD was given in 2011 to 6 physicians (the gold standard) and 178 lay people living in Cotonou, Benin. A misconception was defined as a statistically significant (p<0.001) deviation of at least 2.5 points on the 0-10 response scale of the lay people's mean response from that of the physicians. RESULTS: Lay people tended not to be sufficiently aware that SCD is a hereditary illness, that a genetic test can detect the gene, that having it does not automatically lead to illness, that SCD may induce severe kidney, lung, heart, or cerebrovascular disorders, and that SCD cannot be cured by traditional healers. These misconceptions were greater among those who knew they had SCD or carried the gene than among those who knew they did not. CONCLUSION: Major efforts are needed to overcome the educational and cultural barriers to accurate understanding of how to prevent and treat SCD among lay people in Benin, especially among those at greatest risk.

Transfusion safety in francophone African countries: an analysis of strategies for the medical selection of blood donors.

BACKGROUND: The goal of selecting a healthy blood donor is to safeguard donors and reduce the risks of infections and immunologic complications for recipients. STUDY DESIGN AND METHODS: To evaluate the blood donor selection process, a survey was conducted in 28 blood transfusion centers located in 15 francophone African countries. Data collected included availability of blood products, risk factors for infection identified among blood donor candidates, the processing of the information collected before blood collection, the review process for the medical history of blood donor candidates, and deferral criteria for donor candidates. RESULTS: During the year 2009, participating transfusion centers identified 366,924 blood donor candidates. A mean of 13% (range, 0%-36%) of the donor candidates were excluded based solely on their medical status. The main risk factors for blood-borne infections were having multiple sex partners, sexual intercourse with occasional partners, and religious scarification. Most transfusion centers collected this information verbally instead of having a written questionnaire. The topics least addressed were the possible complications relating to the donation, religious scarifications, and history of sickle cell anemia and hemorrhage. Only three centers recorded the temperature of the blood donors. The deferral criteria least reported were sickle cell anemia, piercing, scarification, and tattoo. CONCLUSIONS: The medical selection process was not performed systemically and thoroughly enough, given the regional epidemiologic risks. It is essential to identify the risk factors specific to francophone African countries and modify the current medical history questionnaires to develop a more effective and relevant selection process.

The role of platelet/endothelial cell adhesion molecule 1 (CD31) and CD38 antigens in marrow microenvironmental retention of acute myelogenous leukemia cells.

In acute myelogenous leukemia (AML), leukemic cell-microenvironment interactions within various niches (stromal/osteoblastic or sinusoidal endothelial cell niches) have a role in leukemia cell survival and drug resistance. The AML leukemic cells express platelet/endothelial cell adhesion molecule-1 (CD31) and CD38, two adhesion molecules that could interact with microenvironmental elements, i.e., CD31 on the surface of marrow endothelial cells (CD31/CD31 and CD38/CD31 interactions) and hyaluronate (CD38/hyaluronate interactions). We report a physical association of these two antigens on the plasma membrane of myeloid leukemic cells. In this context, in vitro experiments done using interaction-blocking anti-CD31 and anti-CD38 monoclonal antibodies (CLB-HEC75 and OKT10, respectively) indicate that an excess of CD31 on the cell membrane of leukemic cells (CD31/CD38 MFI ratio >1) promotes a homotypic interaction with marrow endothelial cells, resulting in higher transendothelial migration. Conversely, an excess of CD38 (CD31/CD38 MFI ratio <1) allows leukemic cells to be entrapped within the bone marrow microenvironment through hyaluronate adhesion. The results obtained in vitro using fluorescence resonance energy transfer, co-capping, and co-immunoprecipitation experiments, and hyaluronate adhesion and transendothelial migration assays, are supported by immunophenotypic characterization of marrow leukemic cells from 78 AML patients on which CD38 expression levels were found to be positively correlated with those of CD31. Importantly, the excess of CD31 in those samples was associated with a higher peripheral WBC count. These findings indicate that bone marrow retention of AML cells depends on CD31 and CD38 coexpression levels.