Australian Researchers Stumble on Deadly Gene

CANBERRA, Australia, January 17, 2001 (ENS) - Australian scientists developing a biological contraceptive to halt mouse and rat plagues have unearthed a deadly new gene with profound implications for biological warfare.

Researchers made the discovery at the Cooperative Research Centre (CRC) for the Biological Control of Pest Animals Canberra.

A mouse plague in South Australia and Victoria in 1993 is estimated to have cost at least A$55 million (US$30.5 million) in grain losses. (Photo courtesy CSIRO)

In this particular experiment, scientists modified a mousepox virus to include the gene for a substance called interleukin-4, which affects the immune system. The aim was to boost the level of the animal's immune response to block reproduction - a process known as immuno-contraception.

Ultimately, the goal was to suppress the plagues of mice and rats which spread human diseases and destroy billions of dollars worth of grain.

Mouse plagues occur in Australia's grain growing regions on average every three years, causing massive disruption to communities and losses to farmers. Mouse plagues are increasing in frequency due to changes in farming practices.

The country's Grains Research and Development Corporation estimates that between 100,000 and 500,000 hectares of grain crops are affected each year. A plague in South Australia and Victoria in 1993 is estimated to have cost at least A$55 million (US$30.5 million) in grain losses.

Scientists found that by introducing the extra gene, they suppressed part of the mouse's immune system which deals with viruses - the cell-mediated response. As a result, lab mice normally resistant to the virus died.

Furthermore, the gene diminished the efficacy of vaccines used to protect mice by about half.

Mousepox virus does not infect humans or pose any threat to them, but the scientists are concerned that in the wrong hands, the technique could be used to strengthen biological weapons based on viruses which do affect humans.

They are calling for the global Biological Weapons Convention to be strengthened as a result of the discovery.

Formally known as the Biological and Toxin Weapons Convention, the agreement prohibits the development, production and stockpiling of biological and toxin weapons. It entered into force in 1975 and has been signed by 162 countries.

"The concern is not so much about the modified mousepox virus, but about the implications of this research, said Dr. Annabelle Duncan, of the Commonwealth Scientific Industrial Research Organization (CSIRO).

Duncan is chief of CSIRO Molecular Science and former deputy head of a United Nations team that investigated the development of biowarfare agents in Iraq following the Gulf War.

"Could a similar experiment be conducted on a human disease-causing organism with similar results? If so, could this be exploited by an unscrupulous nation or a bioterrorist to develop biological weapons?

"The answer to the first question is that we simply do not know. There is no way of extrapolating from these results to another virus and another host animal. All we can say is that it is theoretically possible.

CRC director Dr Bob Seamark. (Photo courtesy CRC)

CRC director Dr Bob Seamark stressed the experiments were undertaken with "completely humanitarian motives."

"Our aim is to counter the enormous damage and human suffering which rodents cause by devouring a major part of the global grain harvest, especially in developing countries and in Australia," said Seamark.

"In the course of science you sometimes make unexpected discoveries - penicillin is one example.

"In this case, we've found that certain changes to a mouse virus can render it more lethal and harder to immunize against.

"The best protection against any misuse of this technique was to issue a worldwide warning. We also want researchers to use this new knowledge to help design better vaccines."

The CRC is a research collaboration of the Australian National University, CSIRO, the University of Adelaide, the University of Sydney, the University of Western Australia, the Western Australia Department of Conservation and Land Management and the Western Australia Agriculture Protection Board.

A report on the discovery will be published in the Journal of Virology's February issue.