New molecular basis associated with CD36-negative phenotype in the sub-Saharan African population

High-Throughput CD36 Phenotyping on Human Platelets Based on Sandwich ELISA and Mutant Gene Analysis

Background

CD36 deficiency is closely associated with fetal/neonatal alloimmune thrombocytopenia, platelet transfusion refractoriness, and other hemorrhage disorders, particularly in Asian and African populations. There is a clinical need for rapid and high-throughput methods of platelet CD36 (pCD36) phenotyping to improve the availability of CD36 typing of donors and assist clinical blood transfusions for patients with anti-CD36 antibodies. Such methods can also support the establishment of databases of pCD36-negative phenotypes.

Study Design and Methods

A sandwich enzyme-linked immunosorbent assay (ELISA) for CD36 phenotyping of human platelets was developed using anti-CD36 monoclonal antibodies. The reliability of the assay was evaluated by calculating the intra-assay and inter-assay coefficients of variation (CV). A total of 1,691 anticoagulant whole blood samples from healthy blood donors were randomly selected. PCD36 expression was measured using a sandwich ELISA. PCD36 deficiency was confirmed by flow cytometry (FC). Mutations underlying pCD36 deficiency were identified using polymerase chain reaction sequence-based typing (PCR-SBT).

Results

The sandwich ELISA for pCD36 phenotyping had high reliability (intra-assay CV, 2.1-4.8%; inter-assay CV, 2.3-5.2%). The sandwich ELISA was used to screen for CD36 expression on platelets isolated from 1,691 healthy blood donors. Of these, 36 samples were pCD36-negative. FC demonstrated absence of CD36 expression on monocytes in three of the 36 cases. In the present study population, the frequency of CD36 deficiency was 2.13% (36/1,691), of which 0.18% (3/1,691) was type I deficiency and 1.95% (33/1,691) was type II deficiency. In addition, we used PCR-SBT to characterize the gene mutations in exons 3-14 of the CD36 gene in 27 cases of CD36 deficiency and discovered 10 types of mutations in 13 pCD36-negative samples.

Conclusion

The present study describes the development and characterization of a highly reliable sandwich ELISA for high-throughput screening for pCD36 expression. This novel method is feasible for clinical applications and provides a useful tool for the establishment of databases of pCD36-negative phenotype donors.

Ex Vivo Activation of Red Blood Cell Senescence by Plasma from Sickle-Cell Disease Patients: Correlation between Markers and Adhesion Consequences during Acute Disease Events

BACKGROUND: Blood transfusion remains a key treatment for managing occlusive episodes and painful crises in sickle-cell disease (SCD). In that clinical context, red blood cells (RBCs) from donors and transfused to patients, may be affected by plasma components in the recipients’ blood. Senescence lesion markers appear on the red cells after transfusion, shortening the RBC lifespan in circulation. In the specific context of SCD, senescence signals can also trigger the occlusive painful events, typical of the disease. This work follows through our previous data that described a RBC senescence process, rapidly detected after challenge with SCD pathological plasmas. In this clinical context, we wanted here to further explore the characteristics and physiologic consequences of AA RBC lesions associated with senescence, as lesions caused by RBCs after transfusion may have adverse consequences for SCD patients. METHODS: Plasma samples from SCD patients, with acute symptoms (n = 20) or steady-state disease (n = 34) were co-incubated with donor AA RBCs from blood units for 24 to 48 h. Specific markers signing RBC senescence were quantified after the incubation with SCD plasma samples. The physiologic in-flow adhesion was investigated on senescent RBCs, an in vitro technic into biochips that mimic adherence of RBCs during the occlusive events of SCD. RESULTS: Senescence markers on AA RBCs, together with their in-flow adhesion to the plasma-bridging protein thrombospondin, were associated with the clinical status of the SCD patients from whom plasma was obtained. In these experiments, the highest values were obtained for SCD acute plasma samples. Adhesion of senescent RBCs into biochips, which is not reversed by a pre-treatment with recombinant Annexin V, can be reproduced with the use of chemical agents acting on RBC membrane channels that regulate either Ca²⁺ entry or modulating RBC hydration. CONCLUSION: We found that markers on red cells are correlated, and that the senescence induced by SCD plasma provokes the adhesion of RBCs to the vessel wall protein thrombospondin. In-flow adhesion of senescent red cells after plasma co-incubations can be reproduced with the use of modulators of RBC membrane channels; activating the Piezo1 Ca²⁺ mechanosensitive channel provokes RBC adhesion of normal (non-senescent) RBCs, while blocking the Ca²⁺-dependent K⁺ Gardos channel, can reverse it. Clinically modulating the RBC adhesion to vascular wall proteins might be a promising avenue for the treatment of painful occlusive events in SCD.