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)

A novel non-mineral oil-based adjuvant. II. Efficacy of a synthetic sulfolipopolysaccharide in a squalane-in-water emulsion in pigs.

The adjuvanticity of a sulfolipopolysaccharide (SLP) incorporated into a squalane-in-water emulsion (SLP/S/W) was compared with that of a mineral oil-in-water (O/W) adjuvant currently used in commercial porcine vaccines. Groups of pigs were immunized twice with vaccines comprising either inactivated influenza virus (iFlu3 containing strains A/Swine, MRC-11 and X-79), inactivated pseudorabies virus (iPRV), live pseudorabies virus (PRV) or inactivated porcine parvovirus (iPPV) as antigen and SLP/S/W or O/W as adjuvant. Antibody titres in serum 2 or 3 weeks after the second immunization were measured by haemagglutination inhibition (HI) or serum neutralization (SN) assays. Both adjuvants significantly augmented the antibody responses against the antigens tested. Mean factors of increase obtained by SLP/S/W and O/W were: 315 and 91, respectively, for A/Swine; 478 and 137 for MRC-11; 362 and 128 for X-79; 69 and 49 for iPRV; and 23 and 7 for live PRV. Increased humoral immunity against live PRV was affirmed by reduced levels and duration of virus excreted by pigs after challenge with virulent PRV. Immunization of pigs with iPPV plus adjuvant SLP/S/W gave 36-fold higher titres than with O/W. It was concluded that SLP/S/W is more effective than O/W in stimulating humoral immunity against the viral antigens examined and that the two constituents SLP and S/W interact synergistically. Advantages of SLP/S/W over O/W include stronger adjuvanticity, better biocompatibility and lower doses of active substances.