Drug resistance

HIV can change itself, or mutate, so that anti-HIV drugs do not work as well. This is called drug resistance, and it’s one of the most common reasons why HIV therapy fails. Drug-resistant HIV then needs higher levels of the same drugs to stop it from reproducing. In general, when four or more times as much drug is needed to suppress the virus in a test tube, the virus is considered resistant to that drug.

Increasing doses of drugs to overcome resistance is not possible because higher doses lead to increased risk of side effects. So when resistance occurs, people often need to change to a new anti-HIV drug combination.

How does HIV become resistant?
Resistance is usually due to changes in viral genes, called mutations. Because HIV mutates easily and reproduces very rapidly, a person may have many different HIV strains in his or her body.

Drug resistance information is from Project Inform. For more information, the full paper is at: http://www.projectinform.org/fs/GenoPheno.html

Can someone be infected with a drug-resistant strain of HIV?

Yes. It’s called transmitted drug resistance. In simple terms, transmitted drug resistance is when one person who is HIV-Positive and has developed resistance to some of the HIV drugs he’s been taking transmits that drug-resistant strain to someone who was HIV-Negative. When that person sero-converts (becomes HIV-Positive) he/she will have the same drug-resistant strain that the person who infected him has. What this means in terms of treatment is that this newly-infected person may have fewer treatment options as a result.

What if someone already has HIV- can they get transmitted drug resistance?

Yes, this is called HIV Superinfection. Click here to read about Superinfection.