Protective effect of Brucella outer membrane complex-bearing liposomes against experimental murine brucellosis

Liposomes of stable multilamellar type, which previously demonstrated great efficiency in antibiotic transport, were used in this study as transport vehicles of antigenic extracts of Brucella melitensis (HS: complex of lipopolysaccharide/phospholipids/outer membrane proteins). The incorporation of HS into positively charged liposomes produced a protective effect against experimental murine brucellosis when they were administered 1 day before or 2 days after infection, as the number of colony-forming units in the spleen was reduced in relation to the untreated control group (P < 0.01). On the other hand, the use of HS-free or bound in liposomes with negative net charge did not produce a significant effect. Moreover, the incorporation of HS into cationic liposomes eliminated the toxicity of the lipopolysaccharide.