Researchers in China have reported editing the genes of human embryos to try to make them resistant to HIV infection. Their paper1 — which used CRISPR editing tools in non-viable embryos and destroyed them after three days — is only the second published claim of gene-editing in human embryos.
In April 2015, a different China-based team announced that they had modified a gene linked to a blood disease in human embryos (which were also non-viable and so could not have resulted in a live birth)2. That report — a world first — fuelled global deliberations over the ethics of modifying embryos and human reproductive cells, and led to calls for a moratorium on even such proof-of-principle research.
At the time, rumours swirled that other teams had conducted similar experiments; sources in China told Nature’s news team that a handful of papers had been submitted for publication. The latest paper, which appeared in the Journal of Assisted Reproduction and Genetics on 6 April, might be one of these. Nature’s news team has asked the paper’s corresponding author, stem-cell scientist Yong Fan, for comment, but had not heard from him by the time of this report.
In the paper, Fan, who is at Guangzhou Medical University, and his team say that they collected a total of 213 fertilized human eggs between April and September 2014. The fertilized eggs, donated by 87 patients, were unsuitable for implantation (as part of in vitro fertility therapy) because they contained an extra set of chromosomes.
Fan’s team used CRISPR–Cas9 genome editing to introduce into the embryos a mutation that cripples an immune-cell gene called CCR5. Some humans naturally carry this mutation (which is known as CCR5Δ32) and they are resistant to HIV, because the mutation stops the virus using the CCR5 protein to sneak into the T cells it tries to infect.
Genetic analysis showed that 4 of the 26 human embryos targeted were successfully modified.
-more at Nature