The adjuvant effect of Ubenimex (UBX), an anti-cancer immunomodulator, on a DNA AIDS vaccine. UBX was formulated into a preparation containing DNA plasmids encoding env and rev genes of HIV-1 strain IIIB, and was inoculated intramuscularly into BALB/c mice. The sera obtained with this mixture had 23–25 times higher specific IgG titres than those obtained without the use of the adjuvant. UBX also elicited both a stronger HIV-1-specific DTH reaction, as measured by the footpad swelling test, and stronger cytotoxic T lymphocyte activity, as assayed by the 51Cr-release method, compared with responses using DNA alone. The cytokine secretion profile of restimulated immune lymphoid cells showed that UBX raised IL-2 and interferon-gamma levels and decreased IL-4 production.