Enhancement of antitumor activity of OK-432 (picibanil) by Triton X-114 phase partitioning.

OK-432 (Picibanil), a Streptococcal immunotherapeutic agent, has been used for immunotherapy of various cancers as a biological response modifier (BRM). However, OK-432 contains multiple components consisting of immunotherapeutic ones and contaminants which may weaken the effects or exert side-effects. In this study, we investigated extraction of contaminants from OK-432 using Triton X-114 (TX-114)-water phase partitioning and examined an antitumor effect of the resulting preparation. OK-432 was subjected to TX-114 partitioning to give residual precipitate designated as OK-TX-ppt. OK-TX-ppt exerted no TLR2-mediated activity, but induced interleukin (IL)-6 in human PBMC. OK-TX-ppt also induced tumor necrosis factor (TNF)-alpha, IL-10, IL-12, and interferon (IFN)-gamma in PBMC. Moreover, IFN-gamma-inducing activity of OK-TX-ppt was significantly higher and IL-10 production was lower than that of OK-432. In tumor-bearing mice model, administration of OK-TX-ppt i.p. extended the survival time of Meth-A-bearing mice compared to OK-432. OK-TX-ppt also increased the levels of IL-12 and IFN-gamma in mouse spleen cells in vitro. These results indicated that TX-114 partitioning removed some contaminants, which attenuates the antitumor effect, from OK-432 and increase the immunotherapeutic effects of OK-432.

Evidence of immunostimulating lipoprotein existing in the natural lipoteichoic acid fraction.

Lipoteichoic acid (LTA) is a cell surface glycoconjugate of gram-positive bacteria and is reported to activate the innate immune system. We previously reported that purified LTA obtained from Enterococcus hirae has no immunostimulating activity, but a subfraction (Eh-AF) in an LTA fraction possesses activity. In this study, we established a mouse monoclonal antibody neutralizing the activity of Eh-AF and investigated its inhibitory effects. Monoclonal antibody (MAbEh1) was established by the immunization of BALB/c mice with Eh-AF, followed by hybridoma screening based on its inhibitory effect for the production of interleukin-6 (IL-6) induced by Eh-AF. MAbEh1 neutralized the production of IL-6 by LTA fraction from not only E. hirae but also Staphylococcus aureus, while it failed to block that of lipopolysaccharide, suggesting that the antibody recognized a common active structure(s) in LTA fractions. Synthetic glycolipids in these LTAs did not induce cytokine production, at least in our system. Interestingly, the antibody was found to inhibit the activity of immunostimulating synthetic lipopeptides, Pam(3)CSK(4) and FSL-1. These results suggest that MAbEh1 neutralizes the activity of lipoprotein-like compounds which is responsible for the activity of the LTA fraction of E. hirae and S. aureus.