phoP/phoQ-Deleted Salmonella typhi (Ty800) Is a Safe and Immunogenic Single Dose Typhoid Fever Vaccine in Volunteers
Open Access
- 1 June 1996
- journal article
- clinical trial
- Published by Oxford University Press (OUP) in The Journal of Infectious Diseases
- Vol. 173 (6) , 1408-1414
- https://doi.org/10.1093/infdis/173.6.1408
Abstract
The phoP/phoQ virulence regulatory genes of Salmonella typhi Ty2 were deleted, and the resultant strain (Ty800) was tested as a live attenuated typhoid fever vaccine in human volunteers. Groups of 2 or 3 subjects received single oral doses of 107, 108, 109, or 1010 cfu. Two volunteers who received the largest dose had self-limited side effects; no bacteremias were detected. Ten of 11 subjects had evidence of intestinal immune responses to the vaccine as measured by increases in S. typhi lipopolysaccharide-specific IgA-secreting cells in peripheral blood samples. Humoral immune responses were measured and compared with those of control vaccinees who received 4 oral doses of S. typhi Ty21a. In the most sensitive assays, 9 of 11 volunteers and 5 of 8 Ty21a control vaccinees had evidence of IgG directed against S. typhi antigens. Ty800 is safe, and single oral doses are highly immunogenic in humans.Keywords
This publication has 0 references indexed in Scilit: