Still considered a dangerous idea by many biologists and governments alike, gene modification of embryos has only recently been given the greenlight in the UK, while in China the practice it was never forbidden.

He Jiankui, a researcher from Shenzhen, announced in an interview with AP news agency that he had recently helped the first twin girls with modified DNA be born. According to the scientist, the girls' embryos were part of an experiment to induce HIV resistance in human DNA by switching off the CCR5 protein, which normally allows the virus to infect cells in a human body.

The researcher said that he had found several couples with males infected with HIV and healthy females willing to participate in the experiment through Baihualin, an AIDS advocacy group. He Jiankui assured that all the participants had been warned about possible adverse effects of the procedure, but nonetheless agreed to take part.

The head of Baihualin, going by the pseudonym "Bai Hua," explained to AP that in China, people infected with HIV may face difficulties in keeping their jobs or receiving medical assistance, and thus the possibility of sparing their children from such a fate could be lucrative for people facing the disease.

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According to test results obtained by the news agency, different embryos received different types of gene editing. Some received both copies of the gene responsible for CCR5 protein production edited, while others received only one copy edited, which, according to the limited research, might grant an individual greater resistance against the virus after becoming infected, but wouldn't prevent the infection itself.

Not all of the altered embryos were implanted for future pregnancies — parents were given the choice to reject implantation and only provide base material for the experiment, sperm and an egg. At the same time, according to AP, all the implantations have been suspended for now, as researchers want to study the recently born twin girls and determine whether gene editing is safe, let alone switching off a protein in the human body.

A University of Pennsylvania gene editing expert, Dr Kiran Musunuru, slammed the Chinese researcher's experiment as "not morally or ethically defensible" and "unconscionable." He noted in an interview with AP that the lack of CCR5 protein may have several adverse effects on a person, such as an increased chance of being infected by viruses such as the West Nile virus, and even dying from the flu. He believes that there are safer methods to prevent and fight HIV infection than gene therapy.

The head of Scripps Research Translational Institute in California, Dr Eric Topol, echoed the sentiment by saying in an interview with the news agency that the process of gene editing embryos is "far too premature" calling modifying the basic operating instructions of a human being a "big deal."

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At the same time, George Church, a geneticist at Harvard University, told AP that the experiment was "justifiable" given the "growing public health threat" that HIV poses.

Gene editing of the human embryo is a controversial topic for both the scientific community and governments. Recently, a UK ethics body, the Nuffield Council on Bioethics, officially permitted editing embryonic DNA if it serves the child's best interests. However, some scientists warn that such intrusions into human DNA could affect both the child and his or her future offspring in unexpected ways.