Biology and evolution of the endogenous koala retrovirus
R. Tarlintona,*, J. Meersb and P. Youngc,*
a School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, LE12 5DR (United Kingdom), e-mail:
b School of Veterinary Sciences, University of Queensland, Brisbane, 4074 (Australia)
c School of Molecular & Microbial Sciences, University of Queensland, Brisbane, 4074 (Australia),
Although endogenous retroviruses are ubiquitous features of all mammalian genomes, the process of initial germ line invasion and subsequent inactivation from a pathogenic element has not yet been observed in a wild species. Koala retrovirus (KoRV) provides a unique opportunity to study this process of endogenisation in action as it still appears to be spreading through the koala population. Ongoing expression of the endogenous sequence and consequent high levels of viraemia have been linked to neoplasia and immunosuppression in koalas. This apparently recent invader of the koala genome shares a remarkably close sequence relationship with the pathogenic exogenous Gibbon ape leukaemia virus (GALV), and comparative analyses of KoRV and GALV are helping to shed light on how retroviruses in general adapt to a relatively benign or at least less pathogenic existence within a new host genome.