How Do Mutations Occur During Therapy?
Soon after antiretroviral therapy is started, the amount of virus in the body is reduced dramatically. Unfortunately, no combination completely stops HIV from reproducing. There’s always a small population of virus that continues to reproduce. Therapy reduces the amount of all HIV quasispecies in the body. The amount of wild-type virus is dramatically reduced, as is the number of variants. Because wild-type virus is usually the most sensitive to antiretrovirals, HIV variants in the body may have a survival advantage. In the presence of therapy, variants can become the dominant strain of HIV, even though there is much less virus in the body. Over time, variants accumulate additional mutations. Some of these mutations will harm the virus, while others will further limit a drug’s ability to block reproduction. Once the virus has accumulated enough mutations, the drugs lose their ability to bind to it and prevent it from reproducing. As the drugs become weaker, the amount of drug-resistant
