The invention relates to a composition comprising at least one antigen, wherein the antigen is a protein or glycoprotein of a HIV-2 virus, wherein the HIV-2 virus has infectious properties with respect to human T4 lymphocytes and the essential morphological or immunological property of at least one of the retroviruses deposited at the CNCM under No. I-502, I-532, I-642, and I-643. It also relates to a process for the production of HIV-2 retrovirus antigens by lysing cells infected with the virus or lysing purified virus and recovering the antigens.