Red Cell Half Life Determination in Patients With and Without Sickle Cell Disease

Background:

Sickle cell disease (SCD) is an inherited blood disorder. It results from a single genetic change (mutation) in red blood cells (RBCs). RBCs are the cells that carry oxygen to the body. In people with SCD, some RBCs are abnormal and die early. This leaves a shortage of healthy RBCs. Researchers want to learn more about how long RBCs live in the human body.

Objective:

To study how long RBCs live in people with and without SCD.

Eligibility:

People age 18 and older who either have SCD, had SCD but were cured with a bone marrow transplant, have the sickle cell trait (SCT), or are a healthy volunteer without SCD or SCT

Design:

Participants will be screened with a medical history and physical exam. They will give a blood sample.

Participants will have a small amount of blood drawn from a vein. In the laboratory, the blood will be mixed with a vitamin called biotin. Biotin sticks to the outside of RBCs without changing their function, shape, or overall lifetime. This process is known as biotin labeling of RBCs. The biotin labeled RBCs will be returned to the participant via vein injection.

Participants will give frequent blood samples. Their RBCs will be studied to see how many biotin labeled RBCs remain over time. This shows how long the RBCs live. Participants will give blood samples until no biotin labeled RBCs can be detected.

During the study visits, participants will report any major changes to their health.

Participation lasts for up to 6 months.

Study Description:

This study will use biotin-labeling of red blood cells (RBCs) to determine the mean potential lifespan (MPL) of RBCs in patients with sickle cell disease (SCD) compared to patients who have successfully undergone curative bone marrow transplantation (BMT, allogeneic or autologous), participants with sickle cell trait, and healthy donors without SCD. Previous studies have corroborated the MPL of healthy donor RBCs to be approximately 115 days while RBCs from patients with SCD have a much more variable but consistently shorter MPL of approximately 32 days. Allogeneic BMT is a curative therapy for the treatment of severe SCD with stable, mixed donor recipient chimerism after BMT sufficient to reverse the sickle cell phenotype by virtue of improved donor red cell survival compared to the ineffective erythropoiesis of SCD. We predict that the hematologic variables associated with red cell survival among patients with SCD vs. participants with SCT and healthy donors can be used to determine the necessary amount of corrected hemoglobin required to overcome the red cell pathology of SCD. Data generated will be used to determine the utility of performing a population study of RBC lifespan in gene therapy treated patients to ultimately target the percentage of transferred globin gene needed to reverse SCD. The data generated will refine our understanding of the degree of correction necessary to reverse the phenotype of SCD.

Objectives:

Primary Objective: To determine and compare red blood cell survival in patients with SCD, patients with SCD who have undergone BMT, participants with SCT, and healthy donors, and validate the association of red cell survival with known markers of increased red cell survival.

Secondary Objectives: To evaluate correlation of markers of hemolysis (reticulocyte count), number of alpha globin genes, and fetal hemoglobin with RBC survival.

Endpoints:

Primary Endpoint: Red blood cell survival

Secondary Endpoints: Relationship of red blood cell survival to hematologic parameters. Antibody detection to biotin.

Eligibility Criteria:
INCLUSION CRITERIA:

* Age 18 or greater with a confirmed diagnosis of homozygous SCD (HbSS, HbSC, HbSB0), sickle cell trait (HbAS), or healthy volunteer (HbA)
* Normal renal function: creatinine \<1.5 mg/dL
* Negative direct antiglobulin test (DAT)
* Ability to give informed consent to participate in the protocol

EXCLUSION CRITERIA:

* Any uncontrolled chronic illness other than sickle cell disease
* Active viral, bacterial, fungal, or parasitic infection
* Consumption of biotin supplements or raw eggs within 30 days
* Blood loss within the previous 8 weeks \>540mL
* Pregnancy
* Pre-existing, naturally occurring antibodies against biotin