Saving the devil… from cancer

The Tasmanian devil

The Tasmanian devil  

Erica Rex

Due to the facial tumour disease, Tasmanian devil population falls to 50,000 from 1,50,000

They’re inky black, pointy-eared, furry and, in a fierce sort of way, cute. And in May of this year, they were added to Australia’s endangered species list. Ordinarily solitary, Tasmanian devils commune only to feast on carrion and to mate in short-lived passionate couplings during which they tear each other to ribbons. Their spine-decalcifying caterwauls — a sequence of whuffings, snarlings and growlings — have evoked satanic visions since the first European settlers arrived on the island of Tasmania more than a century ago.

The Tasmanian devil has been trapped in a purgatory of its own. Since 1996, a deadly cancer, devil facial tumour disease, has preyed on the devil. Its population plummeted to fewer than 50,000 from about 1,50,000, said Dr. Hamish McCallum, senior scientist with the Devil Facial Tumour Disease Programme at the University of Tasmania. The devils’ situation is dire. Yet as more has been learned about the disease, hope has appeared. Scientists have begun an experimental inoculation programme, and this year, Dr. Woods identified one devil able to mount an antibody response to the tumour.

The devil, Cedric, is a 3-year-old male from western Tasmania who has been living in captivity for several months. Dr. Woods inoculated Cedric and his half-brother, Clinky, who was also disease-free at the time, with irradiated — that is, dead — devil tumour cells. Although they had the same mother, Cedric and Clinky had different fathers. Dr. Woods repeated the vaccination three times. He then administered live tumour cells to both. Cedric mounted an immune response and lived. Clinky did not develop an immune response, and he succumbed to the cancer. His father’s genetics made Clinky’s immune system more like that of the devils found in eastern Tasmania.

All mammalian immune systems rely on certain cells to recognise invaders. Demarcation of “otherness” at the cellular level is carried out in a part of the mammalian genome called the major histocompatibility complex, or MHC. An animal’s ability to fight off disease depends on this group of genes. MHC is responsible for the cell markers that flag the difference between cells that are “self” and those that are “non-self.” But the tumour’s MHC is what makes it deadly to the devil. “The tumour has no foreign cell surface markers,” said Dr. Katherine Belov, a scientist in the Australasian Wildlife Genomics Group at the University of Sidney. “If tumour cells get into a devil, its own immune system should be able to see the cells as foreign. That doesn’t happen because the tumour’s cells look like devils’ own cells,” she said.

Dr. Belov likened the process to genetic matching for an organ transplant. — New York Times News Service

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