1. Center for Sickle Cell Disease, Department of Medicine, Howard University, 520 W Street, NW, Washington, DC 20059, USA. .
2. Center for Sickle Cell Disease, Department of Medicine, Howard University, 520 W Street, NW, Washington, DC 20059, USA
3. Division of Emerging & Transfusion Transmitted Diseases, Center for Biologics Evaluation & Research, Food & Drug Administration, Bethesda, MD, USA