Archive for November, 2018

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First genetically enhanced human babies? Maybe

Tuesday, 27 November, 2018

A researcher in China claims to have used CRISPR to perform gene-editing on human embryos, two of which have been brought to term. If true (a big if), this would likely be the first case of germline genetic engineering (of nuclear DNA at least). But without any peer-reviewed publication, all we have are the unverified claims of a researcher. Even with peer-reviewed publications, this could still be a case of fraud and would require additional verification. So there’s a reason to be very skeptical.

As repercussions for this, the researcher has been suspended from his university, giving a statement that the experiment did not have ethical approval.

So what was the first gene to be edited? Apparently it was a deletion of the C-C motif chemokine receptor 5 (CCR5). This receptor is a protein on the surface of white blood cells, which the human immunodeficiency virus (HIV) uses to infect the immune system. A small percentage of people naturally have 32 DNA base pairs deleted from the CCR5 gene (this mutations is called CCR5Δ32), which renders them immune to (most) HIV infections and also some poxviruses (like smallpox). However, this only protects against the the R5 strains of HIV,  whereas the X4 strains can use another pathway (via CXCR4) to get into white blood cells. There have been documented cases of people with the CCRΔ32 mutation being infected with HIV, so it’s not total immunity to HIV.

This modification is not without side-effects either, as it may increase susceptibility to fatal influenza infections. In addition, only one of the two children had both copies of CCR5 (allegedly) deleted, whereas the other only one copy was deleted.

This is a sensible choice for a first genetic engineering target in one sense, in that it’s an easy modification to do (a deletion) and it’s something that already exists naturally so we know what the effects will be. It’s a perfect low-hanging fruit for genetic enhancement in this sense, but it’s still not a particularly beneficial target for genetic engineering because HIV is essentially a completely treatable infection in most developed nations. The reports suggest that at least one of the parents of these children had well-managed HIV, giving a further justification for this particular choice. However, if the father was the one with HIV, there are already ways to avoid transmission though IVF.

Given the risks of a new technology like CRISPR, a target should not only be one that is feasible to do and where potential side-effects are known, but also a target that is not already treatable with other technologies.

In addition, it’s not totally clear that this is a form of gene therapy or genetic enhancement. We traditionally think of vaccines to prevent diseases as a part of therapy (as we do anything that prevents, alleviates or cures a medical condition), and this is essentially a genetic version of a vaccine against HIV so likely isn’t an example of enhancement. But the line is pretty blurry anyway, and it’s possible deletion of CCR5 may improve cognitive function. So it may well be that the first case of germline genetic engineering of nuclear DNA in humans was a case of enhancement.

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