A novel non-mineral oil-based adjuvant. I. Efficacy of a synthetic sulfolipopolysaccharide in a squalane-in-water emulsion in laboratory animals.

Sulfolipopolysaccharides (SLPs) were synthesized by reaction of the synthetic polysucrose polymer Ficoll-400 with chlorosulfonic acid and lauroyl chloride in anhydrous medium. Hydrophobic derivatives were obtained by addition of a small number of sulfate and a large number of lipid groups. Gel-permeation high-performance liquid chromatography (g.p.-h.p.l.c.) exhibited a wide range in molecular weight of both Ficoll-400 and SLP polymers. The calculated weight-average molecular weight (Mw) of Ficoll-400 and SLP using polystyrene polymers as references was 187,000 and 380,000 respectively, exhibiting a twofold increase in molecular weight upon derivatization. Adjuvanticity of hydrophobic SLPs with 0.2 sulfate and 1.5 lipid groups per sucrose monomer, a squalane-in-water emulsion (S/W), SLP incorporated into S/W (SLP/S/W), and a mineral oil-based emulsion (O/W) was investigated in combination with different antigens in mice and guinea-pigs. Antibody responses in serum against ovalbumin (OVA), dinitrophenylated bovine serum albumin (DNP-BSA), inactivated influenza virus strain MRC-11 (MRC-11), a mixture of three influenza virus strains (iFlu3) and inactivated pseudorabies virus (iPRV) were measured by either haemagglutination (HA), haemagglutination inhibition (HI) or serum neutralization (SN). Vaccines were prepared by simply mixing one volume of antigen with one volume of adjuvant solution. Antibody titres after one or two injections with these antigens were enhanced significantly by SLP/S/W, SLP, S/W and O/W and in most studies, SLP/S/W was demonstrated to be more effective than either the two constituent components or the O/W adjuvant.(ABSTRACT TRUNCATED AT 250 WORDS)