In an animal model, a strong T-cell response to specific viral amino acids eliminated the initial SIV virus, leaving only mutated variants.

“how many base pairs by the way just to put in it had two or three changes it depends this is an RNA or DNA virus this is an RNA virus so what is HIV which is our neighbors so and it's notoriously error-prone when it copies itself but what we discovered it happened is that the monkey had made a massive t-cell response directed against eight amino acids and an amino acid is a you think of it like a string of pearls and this was eight pearls this t-cell response had wiped out the initial infective virus so that all that was present replicating in that animal now was a virus that had mutations in that area”