A retrovirus discovered in Neanderthal and Denisovan genomes is more frequently found in people who inject drugs and is likely associated with addictive behavior, according to findings published in Proceedings of the National Academy of Sciences of the United States of America.
“The human genome is littered with retroviral elements as a result of ancient retroviral infections in the germ line of our primate ancestors,” Gkikas Magiorkinis, MD, MSc, PhD, assistant professor in the department of hygiene, epidemiology and medical statistics at the National and Kapodistrian University of Athens in Greece, and colleagues wrote. “Some of these retroviral invasions proliferated successfully by continuously reintegrating in their host genomes.”
Previously, Infectious Disease News reported on the discovery of hepatitis B viruses in remains that date back to the Bronze Age.
According to Magiorkinis and colleagues, pathogenic endogenous retroviruses (ERVs) are not new in the animal kingdom, but so far have not been concretely linked to harmful effects in humans.
“Most people think these ancient viruses are harmless. From time to time, people have shown overexpression of HK2” — HERV-K HML-2, the focus of the study — “in cancer, but it has been difficult to distinguish cause from effect,” Magiorkinis said in a new release.
Although proliferation of most human retroviruses (HERVs) stopped millions of years ago, HK2 may still be propagating, the researchers said.
For the study, they analyzed 202 patients with HIV-1 from Greece and 184 patients with hepatitis C virus from the United Kingdom. In the HIV-1-positive cohort, Magiorkinis and colleagues found an uncommon HK2 integration in RASGRF2 — a gene involved in dopaminergic activity in the brain — 2.5 times more frequently in patients infected via IV drug use compared with patients infected in other ways, 14% vs. 6%. Additionally, in the hepatitis C cohort, it was identified 3.6 times more frequently in patients infected via chronic drug use, 34% vs. 9.5%.
After further CRISPR testing to determine the mechanism behind HK2 integration of RASGRF2 and its responsibility for addictive behaviors, the researchers suggested that the gene may have the ability for dopaminergic manipulation.
“We know of clear biological roles for a small number of human endogenous retroviruses,” Aris Katzourakis, PhD, professor of evolution and genomics in the department of zoology at Oxford University, said in the release. “However, there has never before been strong evidence in support of a role in human biology of an endogenous retrovirus that is unfixed, in other words not shared by all individuals in the population. Our study shows for the first time that rare variants of HK2 can affect a complex human trait. The replication of this finding in the distinct Athens and Glasgow cohorts is particularly important.” – by Marley Ghizzone
Disclosure: The authors report no relevant financial disclosures.
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