Patent Evaluation: Salmonella typhi Mutants for Use in the Production of Oral Vaccines

Summary

Novelty: The production of acid-tolerant Salmonella typhi and double aro mutants is disclosed. Some forms are potentially useful for the preparation of oral vaccines against typhoid fever. They are also potentially useful as carriers of genes which express protective antigens cloned from other pathogens.

Biology: Conditions for enhancing the growth of acid-tolerant S. typhi are described. DNA techniques were used to construct defined deletions in the genes of acid-tolerant S. typhi strain ISP 1820. LD₅₀ values of S. typhi strain ISP 1820 and three mutants are recorded. A clinical trial of nine volunteers of an S. typhi candidate vaccine (strain CVD 906) is described.