Newborn ’ s stem cells now guaranteed to save life of genetically compromised sibling
Until now , “ saviour siblings ” faced risks but a new screening technique can deliver certainty
The procedure involves donating haematopoietic stem cells harvested from the newborn baby ’ s umbilical cord to the older sibling .
After nearly two years spent far from home desperately waiting for their IVF conception and the birth of a second baby , a couple from the Maldives recently became the first in the world to deliver a so-called “ saviour sibling ” using a new technique that ensures the new child will save the life of its ill brother .
The son , who was born last November , will soon be able to cure his 12-year-old brother of beta thalassaemia major , a deadly blood condition inherited from parents who both have mutations of the HBB gene .
The procedure involves donating haematopoietic stem cells harvested from the newborn baby ’ s umbilical cord to the older sibling . These cells are known with certainty to be an accurate genetic match for the stricken sibling after high-definition direct human leukocyte antigen ( HLA ) typing was used for the first time to assess genetic similarity .
That means that the parents can be entirely certain that their new baby will cure their 12-year-old , putting an end to years of blood transfusions , pain , and despair . The family are currently recuperating at home in the Maldives and have yet to decide when the cord blood transfer will be made .
“ We could not even imagine this . It ’ s like a breakthrough , a miracle ,” Nasih Jamaal , the father , told Global Health Asia-Pacific from Kuala Lumpur , where the IVF , HLA typing , and birth took place . Thalassemia is a genetic blood condition that prevents the body from producing sufficient haemoglobin , an iron-rich protein in red blood cells that carries oxygen to all parts of the body .
Children born with beta thalassemia major , the most severe form of thalassemia and common in Asia , will have symptoms early in life that include pale skin and poor appetite . They tend to be fussy and will often suffer from infections . Over time , further symptoms will appear , including slowed growth , abdominal swelling , and jaundice .
A diagnosis is most often made between 6 and 12 years of age . Without treatment , the spleen , liver , and heart become enlarged . Bones can also become thin , brittle , and deformed . Patients will require regular blood transfusions their whole lives , and few will live beyond their early twenties .
Beta thalassaemia major can be cured by the patient receiving transplants from a genetically matched donor . Once the patient ’ s bone marrow is replaced by the introduction of fresh bone marrow or stem cells , the body will be able to produce normal blood cells , enabling the patient to live a full life .
The challenge in such procedures is that unless doctors achieve a 100 percent match between the patient and the donor , there ’ s a chance the bone marrow will be rejected following transplantation .
This is where high-definition direct HLA — an evolution over conventional typing — can make a revolutionary difference in selecting a saviour sibling embryo . This new typing , using next-generation sequencing , allows for much more accurate analysis of the human leukocyte antigen gene , which regulates the immune system , than the conventional method . It does this by looking at each of the donor ’ s various genetic sequences and identifies with complete accuracy whether they match those of the patient .
This additional certainty is an essential component of the saviour sibling programme , since the probability is that just one in 16 embryos will provide a compatible genetic match for the sick child . Geneticists need to screen each suitable embryo for the thalassaemia gene and perform other preimplantation genetic tests . This process considerably cuts down further the probability of a match .
Identifying with certainty which embryo is suitable is a necessary precondition for transplantation into the mother ’ s womb .
Another benefit of direct HLA is that it ’ s more likely to result in a successful full-term pregnancy , since fewer cells need to be taken from the embryo for analysis .
In conventional HLA , five to 10 cells from an embryo containing on average 200 cells are removed each time a test is performed . After multiple tests , the cells in the embryo are significantly reduced , leaving it less viable after transplantation . This means that a suitable match may not result in pregnancy , and the opportunity is wasted .
In contrast , direct HLA enables multiple DNA copies to be created from a single biopsy , and these copies can then be used for a wide range of tests without harming the embryo .
“ This technique means the baby will be a 100 percent match to the other sibling in order to enable a stem cell transplant to save the older sibling from certain death ,” Dr Colin Lee , medical director of Alpha IVF and Women ’ s Specialists in Kuala Lumpur , which handled the process of assisted pregnancy , genetic typing , and birth , told Global Health Asia-Pacific .
“ We ’ re delighted to be the first fertility centre in
44 APRIL 2021 GlobalHealthAsiaPacific . com