The subject matter of the invention is a method for detoxification of lipopolysaccharide (LPS) or of lipid A of a gram-negative bacterium, in which the LPS or the lipid A is mixed with a cationic lipid and, optionally, a co-lipid, so as to form a complex in which the LPS or the lipid A is associated with the cationic lipid. According to conventional methods of preparation, the cationic lipid with the co-lipid, if the latter is present, develop(s) a structure in the form of complexes, in the form of liposomes. During the preparation of the lipid complexes, the addition of the LPS or of the lipid A results in the association of the latter with the cationic lipid, in which association the LPS or the lipid A happens to be substantially detoxified. The LPS or the lipid A detoxified in this form can then be used as a vaccine antigen or as an adjuvant.
