PURPOSE: To prepare an anti-retrovirus vaccine having a cleavage type gag protein and not including a RNA, and to obtain the subject particle giving the cDNA of a RNA having the ability packaging the retrovirus and useful for treating AIDS, etc.

CONSTITUTION: A cell is infected with a virus vector recombined with the cDNA of the gag gene or pol gene of a virus belonging to the genus Retrovirus and not containing the cDNA of a RNA having a packaging ability, and subsequently cultured to obtain the objective retrovirus-like particle having at least a cleavage type gag protein, not including the RNA and giving anti-retrovirus vaccines useful for the prevention, therapy, etc., of intractable diseases such as AIDS, adult T cell leukemia, cancers and rheumatisms, whose etiologies have been confirmed or estimated to be due to the retroviruses, and furthermore giving the cDNA of a RNA having the ability packaging the retrovirus.