Gene therapy
Murine _-thalassemia models have been successfully cured with
the use of a retroviral vector (TN39) transferring the human
_-globin gene sequence and its promoter region into murine stem
cells of TI and TM mice.98,99 _-Globin gene transfer into progenitor
hematopoietic cells of humans is also being studied.100,101 However,
concerns regarding gene transfer include the need for improved efficiency
of gene delivery and mastery of vector stability, viral titers,
nononcogenic insertion, the variable expression of globin genes, and the
variable contributions of the _-thalassemia phenotype and other modifiers
to the effectiveness of gene transfer.102
One regularly transfused patient with Hb-E/_o thalassemia has
been reported who, after nonmyeloablative conditioning, received
autologous bone marrow CD34_ cells transduced with a lentiviral
vector expressing a _A-787Q globin gene, and has remained stable
without transfusion support for 2 years.103 In addition, a phase 1
study of transfusion-dependent _-thalassemia patients using the
TNS q.3.55 lentiviral vector encoding human _-globin gene after
nonmyeloablative conditioning is planned. This approach may
prevent graft rejection in patients who do not have identically
matched HLA donors and therefore are at higher risk to develop
GVHD and continuous immune suppression.104 Several other
molecular approaches for gene therapy using different mutations of
stop codons and aberrant splicing have also been described.102
Gene therapy is a promising approach to curing thalassemia but is
still in the early investigational phase trials.
In conclusion, we have tried to describe the different clinical
manifestations of thalassemia with the optimal care that is available
today. However, very different treatment approaches exist worldwide
depending on factors, such as socioeconomic conditions,
cultural traditions, and the quality of available health care. Currently,
in parts of the world where sufficient resources exist to
support optimal transfusion and chelation programs, thalassemia
patients are living longer and maintaining a good quality of life,
with a select few being cured using bone marrow transplantation.26,27