Abstract: Recombinant Bordetella pertussis strains derived from parent strain Tohama are provided. The new strains are obtained by homologous recombination using a allelic exchange vector pSS4245, which allows the replacement of sections of the bacterial chromosome without leaving any accessory mutations. The segment encoding PT subunit S1 is replaced to introduce two mutations causing inactivation of the toxic activity of PT. This strain can be further modified to express increased amounts of rPT and/or PRN. A second copy of the ptx cluster of the five PT structural genes of the ptx-ptl operon with their promoter and the ptl terminator and containing the above mutations can be inserted elsewhere on the chromosome. In addition, a second copy of the PRN gene can be inserted on the chromosome. In both cases, abandoned gene loci are selected as the insertion site to avoid the introduction of unwanted genetic alterations.

Abstract: Recombinant Bordetella pertussis strains derived from parent strain Tohama are provided. The new strains are obtained by homologous recombination using a allelic exchange vector pSS4245, which allows the replacement of sections of the bacterial chromosome without leaving any accessory mutations. The segment encoding PT subunit S1 is replaced to introduce two mutations causing inactivation of the toxic activity of PT. This strain can be further modified to express increased amounts of rPT and/or PRN. A second copy of the ptx cluster of the five PT structural genes of the ptx-ptl operon with their promoter and the ptl terminator and containing the above mutations can be inserted elsewhere on the chromosome. In addition, a second copy of the PRN gene can be inserted on the chromosome. In both cases, abandoned gene loci are selected as the insertion site to avoid the introduction of unwanted genetic alterations.

Abstract: The present invention discloses a process for extracting a cell-bound protein of bacterial origin, useful in acellular vaccines, comprising contacting a suspension of the cell-bound protein with a flocculating agent prior to heat treatment.

Abstract: Stable and effective multivalent vaccine compositions comprising Hepatitis B surface antigen (HBsAg) are described wherein the HBsAg component is stable for one week at 37.degree. C. and is highly immunogenic, for example when the vaccine is administered to infants. The compositions typically comprise HBsAg adsorbed to aluminium phosphate and other antigens, especially those suitable for use in a paediatric vaccine, adsorbed to aluminium phosphate or aluminium hydroxide. Methods for preparing the vaccines and the use of aluminium phosphate to stabilise HBsAg in a multivalent vaccine formulation are also described.

Abstract: A detoxified B. pertussis toxin or antigenic preparation is described, which is characterized by stability to reversion to toxicity upon storage at 4.degree.-8.degree. C. and at temperatures above 23.degree. C. Also provided are methods for producing detoxified pertussis toxin and vaccines containing same.