A noncovalent complex vaccine prepared with detoxified Escherichia coli J5 (Rc chemotype) lipopolysaccharide and Neisseria meningitidis group B outer membrane protein produces protective antibodies against gram-negative bacteremia

Earlier studies showed that purified IgG from sera of rabbits immunized with a boiled Escherichia coli J5 (Re chemotype) whole cell vaccine protected neutropenic rats against gram-negative bacterial sepsis, In the present study, de-O-acylated J5 lipopolysaccharide (J5 DLPS) as a noncovalent complex with Neisseria meningitidis group B outer membrane protein (GBOMP) elicited anti-J5 LPS antibodies in rabbits, IgG prepared from immune rabbit sera protected neutropenic rats against lethal challenge with Pseudomonas aeruginosa 12:4:4 (Fisher Devlin immunotype 6), Sixteen of 26 rats treated with the postimmune serum IgG were protected compared with none of 20 rats treated with the control rabbit serum IgG (P <.001), In vitro binding studies showed binding of anti-J5 IgG to several gram-negative bacteria, These results indicate that a subunit vaccine made of J5 DLPS as a noncovalent complex with GBOMP may protect against gram-negative bacteremia.