Swiss Serum and Vaccine Institute Berne

Stanley J Cryz

Emil P Furer

Didier Favre

Jean-Francois Viret

The present invention relates to live attenuated gram-negative vaccine carrier strains which are useful for expression and delivery of heterologous O-antigens (O-PS) from gram-negative pathogens. Said strains are deficient in the expression of homologous O-PS due to a defined genetic modification, preferably a deletion, and, thus, capable of efficiently expressing a desired heterologous O-PS in such a way that it is covalently coupled either to homologous or heterologous LPS core lipid A. The present invention furthermore relates to live vaccine carrier strains containing a heterologous gene or a set of heterologous genes encoding O-PS. Preferably, said strains additionally contain genes necessary for the synthesis of complete smooth heterologous LPS. The present invention also relates to live vaccines comprising said strains, preferably for immunization against gram-negative enteric pathogens.

Live vaccines against gram-negative pathogens, expressing heterologous O-antigens

The present invention relates to a method of producing an E. coli vaccine and to the vaccine produced thereby. The method involves purifying lipopolysaccharide from E. coli expressing complete O-polysaccharide sidechains;isolating the O-polysaccharide region of the lipopolysaccharide molecule by hydrolysis in dilute acetic acid and purifying it essentially free of lipid A; and covalently coupling lipid A-free O-polysaccharide via at least one hydroxyl or carboxyl group of the polysaccharide to a carrier protein. Polyvalent vaccines are prepared by combining two or more monovalent vaccines for different serotypes prepared according to the present invention. The present also relates to conjugates used in the vaccines. The conjugates of the present invention are the O-polysaccharide region of an E. coli lipoplysaccharide molecule covalently coupled to a carrier protein.

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Neuenegg, Switzerland

Stanley J Cryz