1.1. Background on Sickle Cell Disease
Sickle cell disease is a disease that is most prevalent in people of African descent along with people of Mediterranean and Middle Eastern origin. This disease is known to affect about 70, 000 Americans and about 2 million people carry the trait (meaning that, they carry a single gene mutation).
Sickle Cell Disease is an autosomal recessive genetic disease that occurs due to a mutation in the β-globin gene of hemoglobin. Autosomal meaning that it is not linked to a sex chromosome, so either parent can pass on the gene to their child. This mutation is a result of a single substitution of amino acids, Glutamic for Valine at position 6 of a β globin chain. The presence of this mutation causes hemoglobin to have fewer negative charges which in turn affects hemoglobin by increasing the hydrophobic contact points on the β chain. This leads to the aggregation of hemoglobin molecules and assembling of hemoglobin polymers. The formation of long fibrils distorts the cell membrane and result in the sickle shaped cell.
This disease includes various symptoms such as shortness of breath dizziness, headache, coldness in the hands and feet, chest pain. It also leads to complications such as infections, acute chest syndrome, pulmonary arterial hypertension, delayed growth and puberty in children, stroke, multiple organ failure, gallstones, and eye damage. Treatments thus far include bone marrow transplant, hydroxyurea.
Bone marrow transplant is an avenue that is been explored in the treatment of Sickle Cell Disease. The main goal in the treatment with bone marrow transplant was to replace the defective red blood cells in the recipient. The first successful bone marrow transplant was done in 2003 by Dr Krishnamurti of Children's Hospital in Pittsburgh of the University Of Pittsburg Medical Center (UPMC). He used a reduced intensity regimen to treat his patients. Reduced-intensity conditioning is a bridge between myeloablative and non-myeloablative conditioning. Myeloablative conditioning being the complete destruction of a recipient’s bone marrow while Non-myeloablative conditioning is a reduced form of myeloablative conditioning in the sense that a lower dose of chemotherapy and radiation therapy is used. The process starts with a high dose chemotherapy treatment and then a low dose chemotherapy treatment.
The idea behind Dr Krishnamurti’s treatment was that since the main target was the red blood cell, there was no need to completely destroy the patient’s own bone marrow. He deduced that a reduced- intensity conditioning would be suitable to let the donor cell successfully be engrafted...