Why are some drug-resistance mutations called “Major” and others called “Minor”?
So many mutations have been associated with decreased HIV-1 susceptibility by the criteria described above that it has become common to sub-classify mutations associated with each of the different drug classes. The most common sub-classifications have divided mutations into “Major” vs “Minor” or “Primary” vs “Secondary” categories. Specific criteria for these sub-classifications have never been established and existing classification schemes have been developed on an ad hoc basis. This is not surprising considering that there is not even always a consensus on what constitutes a drug resistance mutation. The following characteristics of a drug-resistance mutation have influenced its classification: (i) Effect on in vitro drug susceptibility – mutations that by themselves reduce susceptibility to one or more drugs are generally classified as “Major”. In contrast, mutations with little or no demonstrated effect on susceptibility are usually classified as accessory or “Minor”. The term acc
