Sulfolipo-cyclodextrin in squalane-in-water as a novel and safe vaccine adjuvant

Previously, we described synergistic adjuvanticity of combinations of synth etic sulfolipo(SL)-derivatives of polysaccharide (SL-polysaccharides) and s qualane-in-water emulsions (squalane/W). In this paper, effects of type of polysaccharide and nature of oil on adjuvanticity, reactogenicity and stabi lity are described. SL-derivatives of the following polysaccharides were sy nthesised: synthetic polysucroses with weight-average molecular weight (MW) of 400,000 (Ficoll400), 70,000 (Ficoll70) and 39,000 Da (Ficoll39), polyfr uctose of 5,000 Da (inulin), linear polyglucose of 1,200 Da (maltodextrin) and cyclic polyglucose of 1,135 Da (beta-cyclodextrin). The number of sulph ate groups per monosaccharide of the different SL-polysaccharides varied be tween 0.15 and 0.23 and the number of lipid groups per monosaccharide betwe en 1.15 and 1.29. Adjuvant formulations were prepared by incorporating thes e SL-polysaccharides into oil-in-water emulsions of either squalane, hexade cane, soya oil or mineral oil. Adjuvanticity of the formulations obtained f or humoral responses to inactivated pseudorabies virus (PRV) and inactivate d influenza virus strains A/Swine (A/Swine) and MRC-11 (MRC-11) in pigs and MRC-11 and ovalbumin (OVA) in mice depended on the type of oil (squalane = mineral oil > hexadecane = soya oil) but not on the type of polysaccharide backbone of the SL-derivative. Reactogenicity assessed by local swelling i n mice decreased with decreasing MW (SL-Ficoll400 = Ficoll70 = Ficoll39 > S L-inulin = SL-maltodextrin > SL-cyclodextrin) when combined with squalane a nd decreased with the type of oil in the following order: squalane>mineral oil>hexadecane>soya oil when combined with SL-Ficoll400. Stability of the S L-polysaccharide/squalane/W emulsions at elevated temperature increased wit h decreasing MW of the SL-polysaccharide (SL-Ficoll400 < SL-Ficoll70 = SL-F icoll39 < SL-inulin = SL-maltodextrin = SL-cyclodextrin). SL-cyclodextrin/s qualane/W remained stable for >2.5 years at 4 degrees C, >18 weeks at 37 de grees C and >10 days at 60 degrees C. We concluded that reactogenicity and stability but not adjuvanticity of SL-polysaccharide/squalane/W formulation s depended an the MW of SL-polysaccharide and that SL-cyclodextrin/squalane /W is a promising non-mineral oil adjuvant as it combines strong adjuvantic ity (i.e. better than the mineral oil-based adjuvant presently applied) wit h low reactogenicity and good stability. (C) 1998 Elsevier Science Ltd. All rights reserved.