Restoration of immune responses in tumor-bearing mice by ONO-4007, an antitumor lipid A derivative

ONO-4007, a synthetic lipid A derivative, has been found to exhibit potent antitumor activity in several animal models. In the present study, we examined the effects of ONO-4007 on delayed-type hypersensitivity (DTH) reaction and antibody production in Meth A sarcoma-bearing BALB/c mice. The DTH reaction to sheep red blood cells (SRBC) and the IgG production against keyhole limpet hemocyanin (KLH), were depressed in tumor-bearing mice as well as in normal mice given Mitomycin C (MMC). However, ONO-4007 restored these immune responses to normal levels. In addition, in vitro studies showed that ONO-4007 induced the production of tumor necrosis factor-alpha (TNF-alpha) in splenic adherent cells of tumor-bearing mice more than those in normal mice. Though ONO-4007 alone had little effect on the induction of IL-2 production in spleen cells, it augmented the Concanavalin A (Con A)-stimulated IL-2 production. Moreover, ONO-4007 had a mitogenic effect on spleen cells. These results suggest that ONO-4007 may improve immunocompetence in tumor-bearing hosts and contribute to the induction of antitumor immunity and prevention of bacterial infections.