The AIDS virus has hideouts deep in the immune system that today’s drugs can’t reach. Now scientists finally have discovered how HIV builds one of those fortresses � and they’re exploring whether a drug already used to fight a parasite in developing countries just might hold a key to break in.

Researchers have long struggled unsuccessfully to attack what they call reservoirs of dormant HIV, and the new work is in very early stages.

But University of Rochester scientists say it may be fairly straightforward to attack one of these reservoirs, blood cells called macrophages that HIV hijacks and turns into viral hideaways.

The new discovery shows the exact steps that HIV takes to do that � and found that some existing drugs, including a long-used treatment for leishmaniasis called miltefosine, can block the main step and thus cause these cells to self-destruct.

“It’s a very smart virus,” said lead researcher Dr. Baek Kim. “They have to have a very good fence to protect their house for a long time. ... Get rid of the fence, and now their house is gone.”