HIV-1 Gag protein is a polyprotein which, during viral maturation, is cleaved to release matrix p17, core p24 and nucleopcapsid proteins. Capsid protein p24 forms the conical core that encapsulates the genomic RNA-nucleocapsid complex in the virion. The core is constituted by capsid protein hexamer subunits and is disassembled soon after virion entry. The p24 antigen contains epitopes that prime helper CD4 T-cells, which have been demonstrated to be protective and it can elicit lymphocyte proliferation.