Archives for: April 2007
The UK Human Fertilisation and Embryology Authority (HFEA) has agreed in principle to screening and selection of embryos for couples who have the possibility of passing on a gene for breast cancer.
Previously genetic screening has only been carried out for embryos with the risk of having a gene that always causes disease, such as cystic fibrosis.
Now the HFEA are allowing screening of genes on a case by case basis that would give the individual an increased risk of disease, such as the BRCA1 gene, which raises the risk of cancer in adulthood by 60-80%.
This kind of approach can be seen as a move away from human genetic diversity and the concept of addressing the environmental influences of switching genes on or off, towards a genetic inbreeding and the kind of uniformity depicted by Huxley.
A previous entry on this column described how polyethylene glycol could be used to 'hide' the blood group antigens on a red blood cell, turning any transfused blood into something that looks like O negative to the recipient's immune system. The entry also mentioned another method using the galactosidase enzyme, which can transform group B blood into group O by removing the galactose from the blood cell surface. The problem with the enzyme-based method was that the enzymes used for converting blood (taken from green coffee beans) were relatively inefficient, and a lot of enzymes would be needed to do the job, not necessarily at a neutral pH, which could be detrimental to the blood cells.
It did not therefore seem like an April fool joke when the journal Nature Biotechnology reported on April 1st a method of transforming any blood into blood group O. The paper announces the discovery of "two bacterial glycosidase gene families that provide enzymes capable of efficient removal of A and B antigens at neutral pH with low consumption of recombinant enzymes". The researchers described how two bacteria, Elizabethkingia meningosepticum and Bacterioides fragilis, contain enzymes that can remove both A and B antigens from red blood cells. This still does not address the problem of the Rhesus antigen on the blood cells of Rhesus positive individuals, which means that to make universal donor blood that is acceptable for anyone in an emergency (O Rh negative), the blood would have to be taken from Rhesus negative donors, who are in the minority compared with Rhesus positive individuals.
Patient trials will be needed before the blood group conversion method can be used in live situations to ensure that the IgM antibodies against opposing blood group antigens are not activated.