A mutation in the CCR5 gene, which makes a person almost invulnerable to the effects of HIV, turned out to be dangerous for its carriers - in the old years of life, it increases the likelihood of a person's premature death by 21%. Geneticists write about this in the journal Nature Medicine.
Over the past few years, physicians and virologists have encountered several cases where the body of some patients suppressed HIV for an unusually long time, or got rid of the virus forever or indefinitely. Examples of this are the so-called "Berlin" and "London" patients.
Their invulnerability to the effects of HIV is due to the fact that a small set of genes is present in the human genome, the work of which is critical for HIV, but not too essential for the survival of immune cells.
Mutations in these genes, for example, in the CXCR4 and CCR5 regions, are found in the DNA of a very small number of people. This makes them virtually immune to the effects of many types of HIV or unusually resistant to the virus, which was typical, for example, for the so-called "Mississippi child."
A year ago, scientists from Moscow State University conducted similar experiments using defective embryos, and the Chinese molecular biologist He Jiankui announced last fall that he was able to carry out such an "operation" on a full-fledged embryo and obtain the first "transgenic" children invulnerable to the action of the immunodeficiency virus.
These experiments with the CRISPR / Cas9 genomic editor, as noted by Nielsen, stirred up the scientific community and forced many scientists, including the Californian geneticist himself, to study all the possible pros and cons of the appearance of a mutant version of the CCR5 gene in human DNA.
To do this, American researchers analyzed data collected by British medical services as part of the Biobank project. Its creators have collected and decoded over half a million genomes of residents and immigrants from Great Britain, as well as all medical and social information about their lives.
“We are dealing with a completely complete protein that plays an important role in the functioning of the body and has a similar structure in many different species of animals. Therefore, it is reasonable to assume that its destruction is unlikely to be beneficial to you. Otherwise, evolution would have gotten rid of it long ago in the distant past,”the geneticist continues.
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Analyzing these data, Nielsen and his colleague Xinzhu Wei relied on a very simple idea. If damage to CCR5 somehow affected a person's life, then this should have been reflected in mortality statistics, the incidence of other diseases, and other data.
Scientists immediately came across several interesting things that pointed to the potential downsides of "HIV immunity." First, the number of people with two copies of a mutant version of CCR5 was unusually low compared to carriers of one such mutation or ordinary people.
As geneticists explain, this in itself indicates the danger of this mutation, since the number of its carriers would be noticeably higher with the harmless nature of this genetic "typo".
Second, a similar pattern was observed among older Britons who are immune to HIV. They died 21% more often than the rest of the Biobank project, and this gap widened with age.
What exactly causes the carriers of this mutation to die more often and earlier than other people is not yet clear. However, scientists hypothesize that damage to both copies of CCR5 makes a person immune to HIV, but more susceptible to other diseases, such as the flu or the common cold.
