Human immunodeficiency virus (HIV) envelope glycoprotein (Env) is a major target for the development of vaccines and antiviral drugs because it is essential for viral entry into susceptible target cells. Over time, the viral envelope glycoprotein of human immunodeficiency virus type 1 (HIV-l) changes. Despite the availability of antiretroviral drugs, studies show that the (C2-V5) region diversifies at a rate of about 1% per year. Throughout an infection, many glycosylation sites are added to and enlarge the variable loops 1 and 2 (VI-V2) of the envelope glycoprotein. Errors in reverse transcription, a rapid viral replication cycle, and recombination all contribute to these envelope variations. However, the rate at which a mutation is fixed in a virus population depends on the selective advantage or disadvantage conferred by the mutation itself, as well as the level of viral replication capacity.