Transgenic mice may hold key to AIDS dementia

Scientists at the Johns Hopkins School of Medicine ar hoping a colony of genetically altered mice will point the way toward new drugs that can prevent the brain deterioration that strikes about one-third of all AIDS patients.

The mice, which number in the thousands, carry genetic material from AIDS viruses that infected the brain of a person who died a few years ago. The experiment is part of a growing field, called transgenics, in which scientists endow animals with human traits for studies that could lead to treatments or cures.


Over the past decade, transgenic animals have been created at several institutions to study a host of diseases ranging from cancer to cystic fibrosis. In this case, the mice carry segments of the genetic code DNA that can do no damage because the animals are incapable of developing acquired immune deficiency syndrome.

Nonetheless, the scientists believe that subtle changes in mouse cells will yield important clues about AIDS dementia, such as which parts of the brain the virus infects, and what can be done to slow its destructive course.


For example, the research team recently began to treat the mice with an experimental drug, procystine, that is also being tried elsewhere in humans.

In such studies, individual mice are sacrificed at various stages of the experiments -- and their brains analyzed -- to give scientists a unique view of the genetic changes that occur when the nervous system is infected with the AIDS virus.

"We can't look at patients' brains at each stage of the infection," Dr. Janice Clements, a molecular biologist leading the experiments at Hopkins, said yesterday. "But we can do that with the animal model."

The scientists want to know if experimental drugs prevent the genetic material from "switching on" and causing the AIDS virus to multiply.

The experiment, described in today's issue of the journal Science, was launched three years ago when scientists created five breeder mice that spawned thousands of offspring -- each endowed with the same piece of the human immunodeficiency virus, which causes AIDS in humans.