HIV, the virus that causes AIDS, is an extremely active virus. Scientists have learned that it copies itself in the body billions of times a day. And during that replication process, the virus undergoes subtle changes. In some patients, these mutations can cause many of the individual viruses to become resistant to the anti-retroviral medications used to prevent and treat AIDS.
Now researchers from Duke University in Durham, North Carolina, think they have created a very sensitive test for finding drug-resistant HIV. Dr. Charles Hicks is involved in the research. He says it's important for doctors to know when patients have drug-resistant viruses in their bodies.
"What we've learned unfortunately is that even when resistance is present in lower amounts, it can be very important in the drugs' ability to work and not work, and that can change the way in which we choose our treatments for patients."
There are tests to determine if a patient has medication-resistant HIV, but, Hicks notes, they are not very sensitive. "Currently our standard test says if the virus that you're looking for is one out of five in all the viruses in the patient, we can find it reliably. But the new test allows us to go down to a much lower, finer detail perhaps down to one in 1,000, certainly down to one in 100, which obviously is a huge improvement over one in five."
Hicks says it's important to know as soon as possible if a patient develops drug-resistant HIV. Those who do, slowly get sicker, but doctors can change the medications they prescribe to prevent that from happening.
In addition, Hicks says, patients with drug-resistant forms of the virus can pass those stronger viruses on to other people. He says this is a problem primarily in the United States and Europe, where HIV patients have been treated with anti-retrovirals for close to a decade. He sees that clearly in his research. "In North Carolina, where we've been studying the prevalence of resistance in people who are getting infected now, we find that more than ten percent of people who are getting newly infected in 2006 and 2007 are getting infected with viruses that already have some degree of resistance."
Hicks and his fellow researchers hope to refine their test further, and expect it will be available for more widespread clinical use in several years. He says that's important, because as more people around the world start taking anti-retroviral medications, scientists will need tools to detect and delay the spread of drug-resistant forms of the virus.