Scientists have been abuzz with excitement ever since it became clear that CRISPR would unlock a new world of powerful gene editing techniques. Teams around the world have experimented with CRISPR-based gene editing techniques in human embryos, but no one has allowed those embryos to become living, breathing people — until now. A Chinese team claims to have used CRISPR to make two infants that are resistant to HIV infection.
The CRISPR/Cas9 system was derived from bacterial cells and allows scientists to make precise cuts in DNA. Cas9 is the enzyme that actually makes the cut, but it needs CRISPR DNA sequences as a guide to find the right location in a genome. Researchers have used CRISPR in the lab to neuter disease-carrying mosquitoes, halt HIV replication inside cells, and engineer bacteria that can eat plastic. There is no scientific consensus on the ethics of editing genes in human embryos for the purpose of reproduction, but now we may be seeing the world’s first “designer babies.”
According to He Jiankui of the Southern University of Science and Technology in Shenzhen, his team used CRISPR to edit the genes of human embryos that eventually became twin girls Lulu and Nana. The change to the twins’ CCR5 gene causes their cells to carry a mutated form of the CCR5 protein. This mutation should protect them from HIV infection.
In a video posted after the announcement, He Jiankui explains why they chose to focus on HIV first. While medication can control HIV and prevent the development of AIDS, we know some people won’t develop an infection even when exposed to the virus. HIV uses CCR5 to gain access to white blood cells, where it replicates and goes on to infect more cells. As a result, the CCR5 gene is one of the most studied in the human genome, and we’ve identified a variant that blocks HIV. Those with the mutated CCR5 gene don’t have the matching cell surface protein for HIV, so the virus particles can’t get into cells. The gene editing procedure in China replicated this mutation in day-old embryos to imbue the resulting babies with the same resistance.
The team created 16 edited embryos and implanted 11 of them in women before the twin pregnancy occurred. He Jiankui says the twins are healthy and have undergone genetic testing to ensure the modified gene was present and no other genes had been changed.
It’s important to stress that this research has not yet been published in a peer-reviewed journal. The Southern University of Science and Technology also issued a statement that it was not involved in the experiment, which took place at an outside facility. Scientists around the world are expressing a mix of skepticism and shock following the announcement. Many of them say that using CRISPR to create modified humans is reckless when the technology is still so new. If the results are confirmed, there are serious ethical questions to consider. Chinese medical authorities are pledging to investigate.