Most notably, KoRV appears completely absent from koalas on Kangaroo Island off the coast of South Australia. They show that KoRV is present, at variable copy number, in the germline of all koalas found in Queensland, but that animals from some areas of southern Australia lack the provirus. A recent paper in Nature by Tarlington and colleagues provides evidence that koalas are in the midst of a germline invasion by the koala retrovirus (KoRV). Enter the koala - an Australian icon and a potentially endangered species. Until now, we have never had the opportunity of observing or studying such genomic colonization as it takes place.
If the infected cell is a germ cell, then that genetic association can persist for many generations, with the provirus forming part of the genome of every cell in progeny.
The unique replication cycle of retroviruses, involving the integration of viral genetic information into host-cell DNA as a provirus, allows the formation of a permanent association between the virus and the infected cell. The genomes of all higher organisms are littered with the remnants of past retroviral infections, some dating back many tens of millions of years.
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