Beta thalassemia is a type of hemoglobinopathies that results in lower production of blood carrying protein, the haemoglobin. Firstly Lack of haemoglobin results in interruption of normal oxygen supply to body cells. Secondly, the normal shape of red blood cells also changes. Consequently, it leads to anaemia.
Beta thalassemia has two major categorized: first one is thalassaemia major or Cooley’s anaemia and second is thalassaemia intermedia which is a minor type. The first one is more severe and its symptoms involve anaemia, pale skin and severe growth complications as well as jaundice. Also, spleen enlargement and bones and joints issues may occur. The spleen degrades abnormal red blood cells. Their disruption releases iron in blood which leads to cardiac problems.
Gene therapy is the most advanced way of treating genetic disorders. It involves the replacement of defected gene with the normal functional gene. This normal gene will code for the proteins, required for normal cell functioning. The transfer of normal gene in cells requires a third party or gene carrier termed as ‘vector’.
Vectors are responsible for carrying and transferring the gene in host cells. Viruses and plasmids both acts as vectors for gene therapy. On the other hand, physical techniques such as electroporation for direct gene transfer damages the fragile cells. Genetically engineered Retroviridae family of viruses has its wide application for gene therapy.
Genetic Basis Of Beta Thalassemia
As we know, the genetic disorders are passed on to next progeny, so is thalasaemia. Mutation in HBB gene occurs that codes for beta globin blood protein of haemoglobin. Haemoglobin molecules consists of two beta and two alpha globin protein. Lack of any normal globin protein results in low level of haemoglobin in blood cell. Mutation in any of the four globin genes results in differently severe symptoms.
Trials For Gene Therapy Of Thalassemia
Gene therapy experiments were planned in 2005, to treat thalassemia by application of viral vectors. This vectors codes for a mutated adult beta globin gene in cells. The patient having major thalassaemia was treated by gene therapy. The viral genome was carrying the normal gene. Later, this gene was introduced in bone marrow cells of patient through gene-containing virus. The boy received gene therapy in early June of the year 2007. After the therapy the haemoglobin level of the patient was between 9 – 10g per dl. Almost one third of haemoglobin was therapeutic Hemoglobin.
Similarly in June 2007, doctors performed another successful gene therapy for thalassaemia. A stable level of haemoglobin was in between 8.5 to 9g/dl approximately two year after the therapy. The transfused cells contributed almost 2-3 % of the circulating nucleated bone marrow cells. Moreover, the patient was free to any further transfusion after 5 years of therapy.
Companies Working On Gene Therapy
There are many medical organizations working at global level to find out curative treatment strategy against genetic disorders such as thalassemia. For instance, Bluebirdbio, an international company, is also working on gene therapy with the aim to treat thalassemia as well as many other genetic disorders. Similarly, many other companies are working on gene therapy treatment methodology such as:
- American Society Of Gene Therapy
- Cooley’s Anaemia Foundation
- Global Genes
- North Of England Bone Marrow And Thalassemia Association
- UK Thalassemia Society
- National Bone Marrow Donor Programme Etc.
The recent successful gene therapy for treatment of thalassemia has built confidence of researchers and medical community. However, prohibitive cost and limitation of gene therapy are challenges in making the gene therapy a suitable treatment method for thalassemia. For bone marrow stem cells transformation, vector safety is another issue of concern that there are no chances of oncogenes/cancerous gene’s activation in patient.