Greg Simmons School of Veterinary Science University of Queensland Retrovirus replication

Reverse transcription and integration

•RNA viruses Viral RNA cDNA Host cells •Copy RNA into cDNA using RT (Provirus) chromosome Reverse Integrase •Viral DNA(provirus) inserted transcriptase into host cells chromosome using IN •If provirus integrated into germ line cells virus is “endogenous” •Provirus is then passed on to offspring Mendellian inheritencethrough

Methodology:

Blood or tissue samples collected from wild

DNA extraction

DNA assayed with PCR, nested PCR, and/or q PCR

PCR based on conserved region of pol

Amplicon sequenced confirm KoRV sequence

Sensitive and specific

Some q PCR positive samples not able to be sequenced (low proviral copy number?)

KoRV prevalence in wild populations in

In total 708 koalas tested Location No Tested No +ve % +ve North Queensland 27 27 100 South-East Queensland 250 250 100 100% prevalence in Qld (277) and Eastern New South Wales 43 43 100 NSW (100) Western New South Wales 57 57 100 Victorian mainland-Strezleckis 26 *18 69.2 Victorian mainland - 20 *11 55.0 66% in -mainland (89) Victorian mainland - other 43 *36 81.8 Raymond Victoria 29 10 34.5 Snake Island Victoria 12 6 50.0 28% in Victoria- (80) Victoria 28 6 21.4 Victoria 11 0 0 15% in Kangaroo island (162) Kangaroo Island 162 24 14.8

* An additional 18 animals (20% of 89) from Victoria mainland are “doubtful”, probably positive Majority of koalas tested from mainland Australia KoRV positive 95% (442/466) Proviral copy number

Gel from conventional KoRV PCR. All bands are KoRV positive. Note difference in band intensity, indicating differences in proviral copy number Proviral copy no./genomic unit (cell) for selected groups of KoRV positive koalas. (DNA taken from ear punch biopsies)

1A – Qld koalas + ve conventional PCR 1B – Victorian koalas +ve conventional PCR 2 – Victorian koals +ve nested PCR 3 – Vicrorian koals +ve q PCR only Significance of proviral load?

No direct evidence yet

However , anecdotal evidence suggests southern populations much healthier

Appear to have much lower prevalence of chlamydiosis and other disease

This is true even on Kangaroo island where population is highly in bred Transmission ?

Tick feeding medium KoRV infected plasma collected following feeding by Endogenous KoRV – inherited from a wild KoRV fed ticks Exogenous KoRV? Possibly arthropod vector

Can be spread in vitro by paralysis ticks using artificial feeding apparatus

Other retroviruses spread by biting arthropods

RT q PCR to detect KoRV RNA

Conclusions  KoRV widespread throughout wild koalas  So far only KoRV free koalas detected are in Victoria and South Australia  Marked difference in KoRV proviral load between Qld and Victorian koalas  Suggests endogenous vs exogenous virus in different regions  This may be significant in regards to virulence of the virus

Acknowledgements  Jo Meers, Paul Young, Jeff McKee  Jon Hanger and Jo Loader, Australian Wildlife hospital  Allan McKinnon and staff Moggil Koala Hospital  Steve Phillips  Bill Ellis  Kath Handasyde  Suzie Zendt  Damien Phillips