- Severe combined immunodeficiency
is also called bubble boy disease and it is a rare congenital disorder
- The patient has little or no
- Gene therapy offers hope for
children with bubble boy disease
- Gene therapy by GlaxoSmithKline
called Strimvelis approved by EU regulatory body
Gene therapy offers
hope for babies with severe combined immunodeficiency disorder (SCID). This
inherited disorder affects the development of the T-lymphocytes which are
essential for the recognition and destruction of invading cells.
The European Union regulatory panel has recommended that gene therapy for bubble baby disease
, by GlaxoSmithKline, be approved. The positive signal shown by the regulatory panel on April 1st
paves the way for a new treatment method, offering hope for many affected babies.
Immunodeficiency Disorder (SCID)
Severe combined immunodeficiency Disorder
are a group of congenital diseases that are rare and are characterized by the absence of specialized white blood cells, leading to susceptibility towards infections by bacteria, viruses and fungi.
‘Use of targeted gene therapy like Crispr/Cas 9 system improves treatment of bubble boy disease.’
In one particular form of SCID, there is a deficiency of the enzyme adenosine deaminase (ADA) with the enzyme substrate clogging the cells. The lymphoid cells which are still immature are highly susceptible to this build up of the substrate, resulting in their failure to mature. This leads to a poorly developed immune system.
The 'Bubble Boy'
David Vetter was
born on September 21st 1971 with SCID and was forced to live within a bubble in
real life to avoid contracting any infection, thus the name 'bubble boy'. David
was transferred within 30 seconds of being delivered into an insulated bubble
that was sterilized.
His parents had
an older child with the same disease who died in infancy. They refused to abort
David when he was in the womb, though doctors claimed that there was a 1 in 2
chance that he could be born with SCID.
that he might gain immunity as he grew older but he didn't. NASA designed
'bubbles entertainment centers' where David could play. To get him to play
outdoor, NASA designed special space suits that he could wear, when he was six.
David had to crawl out of the insulator bubble, through an insulated tunnel,
before getting into the suit.
When he was 11 years old, doctors decided to try bone marrow transfusion
from his unmatched tissue sister to help improve his condition. However, David dies a few months after the transfusion, when he was 12, when he developed lymphoma due to Epstein-Barr virus.
The condition of
David Vetter drew international attention and David
Center was set up in Bayer College and Hospital for
research into SCID.
Bone Marrow Transplant
The transfer of
stem cells that develop into blood cells, from the bone marrow of a tissue-matched brother or sister of the affected baby offers good scope for
the management of the disease. This provides a good supply of blood cells and
immune cells and the patient can theoretically live for a long time with
many patients have tissue-matched donors from whom they
can opt for transplants. Mismatched tissue donors result in higher risk of rejection. A bone marrow transplant is highly effective when the
procedure is performed within few months of the birth of the baby.
marrow transplant offers a certain degree of hope for patients with bubble
disease, it is dependent on tissue matching with a donor. Patients without a
tissue-matched donor have only 50% chance of survival.
In gene therapy, the genes that are not functional are replaced by genes that do. This aids in improving the condition of the babies with SCID. An article published by Booth C, Gaspar HB
and Thrasher AJ, titled "Treating Immunodeficiency through HSC Gene Therapy" and published in the Journal Trends In Molecular Medicine
(March 2016) described the salient features of using gene therapy for SCID.
- Gene therapy has been studied and used in the trial for the past 20 years.
- In earlier studies, two gammaretroviruses were used as vectors to transfer the corrected DNA.
- The use of these viral vectors was found to result in leukemia in many of the SCID patients.
- Safer vectors are now being used to deliver the targeted DNA.
- The therapy increases the life expectancy of the babies, free from the bubble environment.
EU Clearance for GlaxoSmithKline Gene Therapy
The therapy developed by GlaxoSmithKline is called Strimvelis and has been used to treat 22
babies with SCID for the past 14 years. All the babies are still alive, without the need for the bubble nor further surgeries.
the pharmaceutical giant to patent this therapy and the EU regulatory body has
provided positive opinions.
The confident strides in medical technology due to the use of gene therapy aids in saving many babies from across the world from debilitating disorders. The use of highly specific DNA targeting platforms like CRISPR/Cas 9
, TALENs and ZFNs will aid in precise treatment and care.