Sucrose fatty acid sulphate esters as novel vaccine adjuvants: effect of the chemical composition.

Adjuvant activity of novel, synthetic sucrose derivatives towards a recombinant glycoprotein was determined in large, non-rodent animal species. Compared to antigen alone, up to 3000-fold higher virus neutralizing antibody titres (VNTs) and 10-fold higher cellular responses against classical swine fever virus were observed in pigs after two immunizations with the sucrose derivatives combined with a squalane-in-water emulsion. The chemical composition of the derivative was crucial and sucrose esters containing one sulphate and seven dodecanoic (C12) or decanoic (C10) esters exerted the highest adjuvanticity. Derivatives without sulphate, with fewer fatty acid esters or with shorter or longer alkyl esters were less effective. Strong adjuvant activity of these formulations was the result of synergistic collaboration between the sucrose ester and the squalane emulsion, as factor of increase in VNT by the individual components was between 4 and 34. Enhanced humoral and cell-mediated immune responses lasted for at least 24 weeks. We concluded that combinations of hydrophobic, negatively-charged sucrose fatty acid sulphate esters plus submicron emulsions of squalane-in-water are strong adjuvants for humoral and cell-mediated immunity and that these formulations are promising adjuvants for future vaccines containing poor immunogens.