CRISPR Used to Edit Genes in Human Embryos

Mainstream scientists question the ethics and safety of claims by a Chinese scientist to edit embryos to impart resistance to AIDS virus.

Gene editing of human embryos is banned in the United States because of the risk of harm to other genes and the fact that edited genes can be inherited by future generations.

However, the practice isn’t banned in China, and researcher He Jiankui recently reported that a baby was born that grew from an embryo that he subjected to CRISPR gene editing during fertility treatments. The goal of the gene editing was to make the baby resistant to infection to HIV (and therefore AIDS). Previously, He was supported by physics and bioengineering professor Michael Deem, his former adviser at Rice University. 

He practiced in the lab on mouse, monkey and human embryos, disabling the CCR5 gene, which encodes a protein that allows the HIV virus to enter a cell. In the current experiment, washed sperm were placed into eggs to create embryos, and then the CRISPR gene editing tool was used. The embryo cells were evaluated 3–5 days later to confirm that editing occurred. The editing was done on embryos formed for seven different couples, who each had the choice whether to use the edited embryos.

The one pregnancy that has been achieved involved twins. According to He, tests show one baby has both CCR5 genes altered, while the other has just one affected allele. Scientists who have reviewed the data suggest that such claims cannot be made based on the tests conducted to date. They also indicate that the editing appeared to be incomplete, and one of the twins exhibits mosaicism, with different cells harboring different changes. There is concern that the scientists used this embryo given they knew about these issues before implantation. 

In addition, it is known that people without the CCR5 gene tend to have increased susceptibility to other viruses, including West Nile and influenza.

Furthermore, He did not give official notice of his work until well after it was started, and it is not clear whether the couples involved fully understood the potential risks and benefits. Documents refer to the project as an “AIDS vaccine development” program. However, both He and Deem assert that the couples clearly understood what the program entailed.

The reaction has been quite strong. It has been referred to as an experiment that is “not morally or ethically defensible” and “far too premature.” Others see it as justifiable given the threat posed by AIDS, particularly in China. Scientists involved in the development of CRISPR editing technology have stated that gene editing in human embryos should be limited to cases where an unmet medical need exists and no other treatment options exist and even suggested that a moratorium be put in place on implantation of edited embryos.


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