title: Salmonella typhi vaccine strain in vitro; low infectivity in human cell line U937.
abstract: Salmonella typhi strain Ty21a has been used for live oral vaccine. The infectivity of Ty21a, in comparison with S. typhi Ty2, was evaluated using the human monocyte-macrophage cell line U937. Assays were performed by quantitative microscopy and viable count technique. Ty2 infected approximately 100% of the cells, multiplied extensively within these cells and caused cell death. The same dose of Ty21a infected only about 15% of the cells, resulting in a low number of intracellular bacilli and cell survival. The use of gentamicin in the test confirmed intracellular multiplication of Ty2 but not Ty21a. The system described may be suitable as a test system for characterization of the degree of virulence of Ty21a and other live, oral typhoid vaccines.
authors.affiliation: Division of Product Quality Control, Food and Drug Administration, Bethesda, Maryland 20892.
authors.forename: E M
authors.initials: EM
authors.lastname: Dragunsky
authors.forename: C R
authors.initials: CR
authors.lastname: Wooden
authors.forename: S A
authors.initials: SA
authors.lastname: Vargo
authors.forename: I S
authors.initials: IS
authors.lastname: Levenbook
mesh_terms: D001428:Bacterial Vaccines / Q000633:toxicity*; D002460:Cell Line; D015169:Colony Count, Microbial; D003470:Culture Media; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D010587:Phagocytosis / Q000276:immunology; D012485:Salmonella typhi / Q000254:growth & development / Q000472:pathogenicity*; D014613:Vaccines, Attenuated / Q000633:toxicity
chemical_list: D001428:Bacterial Vaccines; D003470:Culture Media; D005839:Gentamicins; D014613:Vaccines, Attenuated