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Differential and defective expression of Koala Retrovirus reveal complexity of
host and virus evolution

R.E Tarlinton 1, N. Sarker 2, J. Fabijan 3, T. Dottorini 1, L. Woolford 3, J. Meers 2, G.Simmons 2, H.Owen 2, J.M.Seddon 2, F. Hemmatzedah 3, D.Trott 3, N. Speight 3, R.D.Emes 1,4

1 School of Veterinary Medicine and Science, University of Nottingham, UK

2 School of Veterinary Science, University of Queensland, Australia

3 School of Animal and Veterinary Sciences, University of Adelaide, Australia

4 Advanced Data Analysis Centre, University of Nottingham, UK


Koala retrovirus (KoRV) is unique amongst endogenous (inherited) retroviruses in that its incorporation to the host genome is still active, providing an opportunity to study what drives this fundamental process in vertebrate genome evolution. RNA sequencing of KoRV from koala populations with high virus burden (Queensland) and low virus burden (South Australia) identified that South Australian animals, a population previously thought to have KoRV negative animals, harboured replication defective KoRV. This discovery provides the first evidence that a host population may maintain defective KoRV as protection from the infectious form of KoRV. This offers the intriguing prospect of being able to monitor and selectively breed for disease resistance to protect other wild koala populations from KoRV induced disease.