The effects of triterpene glycosides and phospholipids from marine invertebrates in the composition of tubular immunostimulating complexes on the immunogenicity of human serum albumin

To study the adjuvant activity and to optimize tubular immunostimulating complexes (TI complexes) with respect to the soluble antigen, an investigation was performed on cucumariosides and their fractions, i.e., individual triterpene glycosides that were obtained from the holothurian Cucumaria japonica, as well as on phospholipids from the sea urchin Strongylocentrotus intermedius and the starfish Distolasterias nippon included in the composition of TI complexes in order to assess their effects on the immunogenicity of human serum albumin (HSA). Generally, TI complexes showed a moderate adjuvant activity with respect to HSA; this activity can be adjusted by substitution of a cucumarioside and/or a polar lipid in the composition of the TI complex. TI complexes based on monogalactosyldyacylglycerol (MGDG) from the sea alga Ulva lactuca and cucumariosides A2-2 and A4-4 maximally stimulated anti-HSA antibody production in mice. Substitution of MGDG for phosphatidylcholine (PC) from the starfish D. nippon with an increased (compared with other investigated phospholipids) ratio of n-3/n-6 polyunsaturated fatty acids did not result in a change in the immunostimulating activity of the TI complex. However, the use of other phospholipids led to a decrease in the adjuvant activity of the TI complex, compared with that of the TI complex based on PC from D. nippon and cucumarioside A2-2. The greatest fluctuations in the contents of cytokines IL-6, IL-12, IFN-γ and GM-CSF depending on the composition of the TI complexes indicate the possibility of regulation of the T-cell immune response. The values of hematological parameters were normal.