HIV-1 Gag is produced in vast quantities during an infection and is capable of forming virus-like particles in the absence of other viral components. Gag p24, the major capsid protein of the HIV-1 virion, has been used in clinical trials as one of the components of the HIV-1 vaccine because of the high degree of sequence conservation between different isolates.

It is also well known that HIV infection causes CTL escape mutants of p24, which results in a loss of binding of CTL epitopes either to MHC class I molecules or to the T-cell receptor on CD8⁺ T cells. Mutations in CTL epitopes and escape from CTL recognition are not unique to HIV and have also been reported for other viruses. However, the effect of impaired antigen processing and presentation of HIV-1 antigens on the generation of CTL escape mutants has not been fully elucidated.