New genomic find offers hope for Koala survival

A newly discovered genomic immunity to an AIDs like retrovirus plaguing Australia’s koala population offers hope in the effort to save the beloved but endangered marsupial.

Researchers from The University of Queensland and UMass Chan Medical School discovered that koalas from a population north of the Brisbane River have evolved a unique genomic immunity to the killer retrovirus threatening their species.

Professor Keith Chappell, a virologist with the AIBN, said the team were hopeful that this finding could lead to targeted breeding programs that could reduce rates of chlamydia and other health issues linked to koala retrovirus.
 

“What we found is that there is a single genetic switch that has been activated in about 30 percent of the koala population in the Sunshine Coast hinterland, suppressing the retrovirus,” Chappell said.

“This is in contrast to what we found in the population on the Gold Coast, where this adaptation is almost completely absent.”

Koala retrovirus suppresses the koala’s immune system and makes them more vulnerable to other infections like chlamydia that has ravaged populations in Queensland and New South Wales.

It has also been linked to lymphomas that have claimed the lives of many captive Koalas.
 

This work, led by research fellow Dr Michaela Blyton, shows that the Sunshine Coast hinterland koalas have developed ‘adaptive genomic immunity’ to the retrovirus in their DNA, similar to how an immune system can adapt after exposure to pathogens.

“Because this ‘genomic immunity’ can be inherited, the discovery suggests koalas with the trait could be used in breeding programs to reduce the susceptibility of other populations to the retrovirus, like on the Gold Coast,” said Dr Blyton.

The researchers were also thrilled to discover the adaptation is apparently spreading through the northern koala population, though evolutionary timescales mean it will take many generations to spread across the entire sub-population on its own.

Professor Chappell said retroviruses can alter the genetic code of a host species, and about 8 per cent of human DNA is from infections over hundreds of millions of years.

“In contrast, the koala retrovirus only entered the marsupial’s genome in the past few thousand years, which is really recent in evolutionary terms.

“Out of all the species on the planet, this is the only one where we can see a genetic response to a retrovirus in real time, rather than looking at responses to things that got into the genome millions of years ago.”

This allows the researchers to study exactly how these iconic critters are responding - it's actually a pretty amazing situation.

This information doesn’t just help the koala though, these insights allow researchers us to peer back into distant past and look at the evolutionary history of humans, and see how we're able to cope with a new virus invading our fundamental genome.

At the University of Massachusetts, Professor William Theurkauf had spent decades studying fruit flies and looking at how animals respond to genome invaders from the distant past. 

The trans-Pacific collaboration came about when he came across the koala research from UQ and saw clear parallels and a promising opportunity.

The researchers are quick to caution that while there are many other more acute threats to koalas than the retrovirus, koalas with this adaptive immunity to the retrovirus could provide more resilient animals to repopulate areas where koala numbers have been decimated by disease.

They say the breakthrough has opened the door to new or enhanced breeding programs and more research looking at other positive adaptations in Koalas across Australia, contingent on future funding.

AIBN’s multidisciplinary approach provides researchers with a broad range of expertise and cutting-edge facilities, enabling groundbreaking research like this. Professor Chappell is known for his role in developing The University of Queensland's patented molecular clamp technology.

The research was published in Cell.