A retroviral etiology for malignant neoplasias in koalas has long been suspected. Evidence for retroviral involvement was bolstered in 2000 by the isolation of a koala retrovirus (KoRV), now termed KoRV-A. KoRV-A is an endogenous retrovirus-a retrovirus that infects germ cells-a feature that makes it a permanent resident of the koala genome. KoRV-A lacks the genetic diversity of an exogenous retrovirus, a quality associated with the ability of a retrovirus to cause neoplasias. In 2013, a second KoRV isolate, KoRV-B, was obtained from koalas with lymphomas in the Los Angeles Zoo. Unlike KoRV-A, which is present in the genomes of all koalas in the United States, KoRV-B is restricted in its distribution and is associated with host pathology (neoplastic disease). Here, our current understanding of the evolution of endogenous and exogenous KoRVs, and the relationship between them, is reviewed to build a perspective on the future impact of these viruses on koala sustainability.

中文翻译：

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考拉逆转录病毒：进化和疾病动态。

长期以来，人们一直怀疑树袋熊有恶性肿瘤的逆转录病毒病因。2000年，通过分离树袋熊逆转录病毒（KoRV）（现在称为KoRV-A），增强了逆转录病毒参与的证据。KoRV-A是一种内源性逆转录病毒，一种可感染生殖细胞的逆转录病毒，具有使其成为考拉基因组的永久居民的功能。KoRV-A缺乏外源性逆转录病毒的遗传多样性，这种质量与逆转录病毒引起肿瘤形成的能力有关。2013年，在洛杉矶动物园从患有淋巴瘤的考拉中获得了第二种KoRV分离株KoRV-B。与美国所有考拉的基因组中存在的KoRV-A不同，KoRV-B的分布受到限制，并且与宿主病理（肿瘤疾病）有关。在这里，我们目前对内源性和外源性KoRVs进化的理解，