A Rare Recent Case of Retrovirus Integration: An Infectious Gibbon Ape Leukemia Virus Is Colonizing a Rodent’s Genome n New Guinea

Retroviruses are viruses that multiply by incorporating their genes into the genome of a host cell. If the infected cell is a germ cell, the retrovirus can then be passed on to the next generation as an “endogenous” retrovirus (ERV) and spread as part of the host genome in that host species. In vertebrates, ERVs are ubiquitous and sometimes make up 10 per cent of the host genome. However, most retrovirus integrations are very old, already degraded and therefore inactive – their initial impact on host health has been minimized by millions of years of evolution. A research team led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) has now discovered a recent case of retrovirus colonization in a rodent from New Guinea, the white-bellied mosaic-tailed rat. In a paper in PNAS, the authors describe this new model of virus integration. The observations on this process will help to improve our understanding how retroviruses rewrite host genomes. The article, published on February 1, 2024, is titled “A Recent Gibbon Ape Leukemia Virus Germline Integration in a Rodent from New Guinea.”

Retroviruses, such as the pathogen responsible for AIDS (HIV-1), integrate into the genome of the host cells they infect during their life cycle. When this happens in the germline (egg cells or cells that produce sperm) of the host, the retrovirus can actually become a gene of the host itself. This process is apparently common, as up to 10 percent of the genomes of most vertebrates consist of the remnants of such ancient infections. One of the best studied models of this process is the koala retrovirus (KoRV), which is currently colonizing the koala genome. “What happens to the virus and the host during this process of genome colonization we do not know, as most such events occurred millions of years ago and we only see the leftover ‘fossils’ of the retrovirus,” says Prof. Alex Greenwood, Head of the Leibniz-IZW Department of Wildlife Diseases. “Nor do we know what the host suffered health-wise during the infection process. The koala retrovirus (KoRV) is one of the few models of this process that occurs in real time and where we can observe the effects of genome colonization on the host animal.”
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