HLA-typing: From PGD to Saviour
In may 2005, the first donor baby in Belgium was born as a result of treatment in the CRG at UZ Brussel. The treatment involved a method which makes it possible to determine the HLA-type of an embryo. A donor baby or 'Saviour baby' is a baby from whom haemopoetic cells (HSC) can be extracted from the umbilical chord, in order to try to heal an older brother of sister, who is suffering from a hereditory disease.
What is HLA-typing?
UZ Brussel has hitherto seen 81 couples for consultation both from Belgium and from overseas, who requested PGD-HLA diagnostic treatment. 230 treatments have been performed since and 23 healthy genetically compatible babies were born. |
HLA-typing of embryos (HLA stands for human leukocyte antigens) is a specific form of PGD (see pre-implantation genetic diagnosis and aneuploïd screening). Recently a method enabling the HLA-typing of embryos was developed as part of the PGD program. This technique makes it possible to select embryos which are not only disease free, but which are also HLA-identical to an already existing sibling.
HLA-molecules play a crucial role in our immune system: they ensure that our bodies recognize their own cells as indeed their own. They are found on the membranes of all cells and determine our tissue or HLA-type, which differs from person to person. A certain tissue type is inherited by both parents. The chance that someone outside the family has the same tissue type is 1 in 40,000. In organ transplantation, it is vitally important that the tissues match as closely as possible, otherwise the body will reject the organ.
The preceeding cell to the cells of the immune system is the Stemcell (HSC). These are found in the bone marrow. They have the ability to become one of many different kinds of cells, for example, red blood cells, platelets, or white blood cells. In cell diseases (such as Leukaemia or Anaemia) the patient has a reasonable chance of recovery following HSC transplantation, or bone marrow transplant. This is only possible from a HLA-compatible donor.
Because the HLA-genes are inherited 50% from each parent, the chance of being HLA-compatible with a brother or sister is 25%. If a bone marrow transplant is to be performed on a child with Leukaemia or anaemia, a suitable donor will first be sought in the family. If none of the brothers or sisters are compatible, it could be possible to make a new child with the correct HLA-type. If the condition id due to a genetic defect, the HLA-typing can be combined with investigations to identify the faulty gene, in order to avoid the new child having the same disease.
The chances of a suitable embryo being made are 19%.
During the birth of the baby, blood from the umbilical chord is collected. This contains HSC and can later be administered via a drip, to the sick child in order to save its life.
Conditions
A couple would have to meet a number of conditions before PGD-HLA can be attempted:
HSC-transplantation must be seen to be the best treatment for the sick child (on the advice of the paediatric haemotologist);
the child must still be young, because the number of cells that can be obtained from the umbilical chord is restricted, plus the number of cells administered is calculated per kilogram of body weight;
the molecular analysis for the HLA-type must be possible. Some genetic defects are not yet detectable;
there must be time, because the treatment, PGD and pregnancy are all going to take several months;
the mother must be under the age of 38. Her age is always a deciding factor in the quality of the eggs and embryos;
the parents must WANT another child. This is very important to avoid the new baby as being regarded as merely instrumental in the process of healing an already existing child. The couple will therefore be assessed by a psychologist in the CRG prior to the commencement of treatment.
Ethical questions
Ethical questions arise when dealing with PGD for HLA typing. Is the selection of a specific embryo acceptable? Are we not merely using a new baby as a medical instrument in order to heal an existing child of disease? How is the donor child, who after all has no say in the matter, going to feel when he later discovers the motivation for his existence?
The Comittee for Medical ethics at UZ Brussel deals with these questions and others like them.
Lawfully speaking, PGD/HLA is permissable if implemented for medical reasons, with no hidden motivations. Because HLA typing does not offer any benefits to the new child itself, only to a third party, namely a sick brother or sister, PGD/HLA is not forbidden.
The Comittee for Medical ethics at UZ Brussel finds the procedure morally acceptable for the following reasons;
The procedure to be performed on the child-to-be (specifically, the removal of HSC cells) may also be performed upon a child which already exists.
An IVF treatment with PGD HLA to achieve pregnancy with a genetically compatible embryo is more desirable than for example, a termination of a pregnancy following a pre-natal genetic diagnosis which indicates that the baby would be incompatible.
The 'creation' of a donor child does not give reason for a lack of respect for his autonomy or intrinsic value.
Every request for fertility treatment with PGD/HLA diagnosis and the treatment itself is evaluated and monitored by a multi-disciplinary team, existing not only of scientists and clinicians (specialists in the fields of genetics, reproductive medicine and bone marrow transplantation), but also of ethical, juristic and psychological experts.