Drug addicts are more likely to have an old virus in their genome

One study showed that drug addicts are more likely to have an older virus that may affect dopamine production.

Scientists have studied a type of ancient retrovirus called HERV-K HML-2 (HK2). A retrovirus is a form of bug that transcribes its RNA into the DNA of a host cell to multiply. Retroviruses can either spread exogenously between individuals, such as HIV, or endogenously from parents to offspring, but it was not previously believed that they were harmful in humans.

We already know that our set of genetic instructions called the human genome contains fragments of old retroviruses from the germline or cell line of our primate ancestors. This happened because retroviruses continued to reintegrate our genomes.

HK2 is believed to be the remaining ancient retrovirus that proliferated the human germ line 250,000 years ago (considered relatively recent by the standards of evolutionary biology). The authors of the study published in the journal Proceedings of the National Academy of Sciences believe that a rare type of HK2 called RASGRF2 might be related to addiction.

An illustration of the hepatitis C virus. Scientists studied those who contracted the disease intravenously. Getty Images

"By showing strong genetic links to addiction, we advocate for de-stigmatizing addiction and intensification of pharmacological support for drug addicts," said Dr. Aris Katzourakis, professor of evolution and genomics at University of Oxford. Newsweek.

Researchers from the University of Oxford, UK, and the National Kapodistrian University of Athens, have shown that this type of HK2 can manipulate neighboring genes, including that which plays a role in the release of dopamine in the brain. Dopamine is a neurotransmitter associated with rewarding experiences and is therefore involved in addiction.

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"Some endogenous retroviruses have been tentatively linked to human pathologies, but despite intense research efforts for more than 20 years, it has been difficult to distinguish the cause of the effect," Katzourakis said. .

"We show the strongest evidence provided to date that an endogenous retrovirus is linked to harmful effects in humans, showing a link between an integrated retrovirus and addictive behavior."

Read more: How to know if you are addicted to video games and how to get help

To conduct their study, Greek researchers recruited 202 HIV-positive participants and found that RASGRF2 was 2.5 times more common in intravenous patients than in those infected by other means. And in a separate part of the UK study, 184 patients with hepatitis C were 3.6 times more likely to have RASGRF2 in their genes if they had suffered from chronic addiction than the others.

In the beginning, when researchers found a link between injecting drug users and RASGRF2, they thought it could be a coincidence.

"However, we followed this study in a second completely independent cohort and also found the association there, and we also performed laboratory experiments on a cell line that also confirmed our outcome," he said. Katzourakis.

"We have identified a plausible path for how the virus influences the behavior of the host," said Katzourakis. "This particular integration lies within a gene called RASGRF2, which is involved in the response to dopamine. This influences reward behavior and we believe that by altering the expression of RASGRF2, what the virus does in a cell line, it influences the reward seeking behavior of the individual.

But the results have not proven that viruses can change our behavior or make us more addicted, he said.

"We do not know if HERV-K HML-2 is" alive "and extends to humans nowadays, but we have strong evidence that unusual proviruses can be pathogenic," he said.

"The next important question is whether the unusual proviruses echo the" old "epidemic, or whether rarer viruses are being generated in today's human populations."