Abstract: 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.

Abstract: 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.

Abstract: This invention relates to a method of isolating deletion mutants of Vibrio cholerae, wherein the deletion is predetermined by digestion with restriction endonucleases of known specificity. The deletions are inserted into the Vibrio cholerae chromosome by in vivo recombination betweem a plasmid carrying the desired deletion, with adjacent flanking sequences, and the Vibrio cholerae chromosome. The invention includes the isolation and characterization of a new Vibrio cholerae strain having a deletion in the tox gene, as defined by Acc I restriction endonuclease sites.

Abstract: Polysaccharide-protein conjugates were synthesized utilizing polysaccharide derived from hydrolyized Pseudomonas aeruginosa lipopolysacharide covalently coupled to either tetanus toxoid or P. aeruginosa toxin A, utilizing a spacer molecule and a coupling agent. Conjugates produced in such a manner possess a molecular weight of greater than 350,000, are nontoxic and non-pyrogenic, and upon immunization of animals induced protective anti-LPS antibody and antibody which neutralizes the lethal effect of tetanus toxin or toxin A. The polysaccharide-tetanus toxoid conjugate and polysaccharide-toxin A conjugate are safe and immunogenic when parenterally administered to humans.

Abstract: The present invention relates to immunogenic preparations of Klebsiella species serotype-specific capsular polysaccharides. The invention involves the treatment of Klebsiella capsular polysaccharides in dilute sodium hydroxide to detoxify co-purified toxic lipopolysaccharides and to yield immunogenic vaccine preparations safe for parenteral administration to humans. The polyvalent vaccines prepared by use of the above vaccine are effective at providing protection against infections caused by Klebsiella species bacilli.