• Vaccine Name: Aro-deleted S. Typhi
• Target Pathogen: Salmonella spp.
• Target Disease: Salmonellosis
• Type: Live, attenuated vaccine
• Antigen: The antigen used was aro-deleted S. Typhi, a strain designated as CVD 908 (Tacket and Levine, 2007).
• AroD gene engineering:
  • Type: Recombinant protein preparation
  • Description: Inactivation of AroD results in attenuation, and the deletions of both AroC and AroD provide a high level of safety against restoration of pathogenicity by recombination. An aroC/aroD-deleted derivative of S. Typhi strain Ty2 (the parent strain of Ty21a) is designated the strain "CVD 908" (Tacket and Levine, 2007).
  • Detailed Gene Information: Click Here.
• AroC gene engineering:
  • Type: Recombinant protein preparation
  • Description: Inactivation of AroC results in attenuation, and the deletions of both AroC and AroD provide a high level of safety against restoration of pathogenicity by recombination. An aroC/aroD-deleted derivative of S. Typhi strain Ty2 (the parent strain of Ty21a) is designated the strain "CVD 908" (Tacket and Levine, 2007).
  • Detailed Gene Information: Click Here.
• Preparation: CVD 908 was created by deleting both aroC and aroD, preventing restoration of pathogenicity by recombination (Tacket and Levine, 2007).
• Virulence: After a single dose of the vaccine (5 × 10^4 or 5 × 10^5 cfu), vaccine bacteremia was not detected in serial blood cultures. Half of the subjects tested with this dose developed serum IgG anti–lipopolysaccharide antibodies and IgA anti-LPS antibody-secreting cells (Tacket and Levine, 2007).
• Description: The aromatic metabolites, such as aroC and aroD, force Salmonella to be nutritionally dependent on p-aminobenzoic acid and 2,3-dihydroxy, both of which are not available in mammilian tissues, preventing proliferation in the host cells (Tacket and Levine, 2007).

Human Response

• Vaccination Protocol: Each vaccine was ingested and contained 2.2 3 10^8 organisms of lyophilized vaccine. A second lower dose contained 5 3 10^7 viable organisms. Volunteers fasted for 90 minutes before and after vaccination. A placebo of sodium bicarbonate was also included (Tacket et al., 2000).
  
• Immune Response: After a single oral dose, CVD 908-htrA stimulates vigor-
  ous mucosal, humoral, and cellular immune responses at levels (Tacket et al., 2000).
• Side Effects: Two volunteers had diarrhea in the first 24 h after ingesting vaccine. Three volunteers had
  diarrhea that occurred later (Tacket et al., 2000).
• Efficacy: Recipients of the high dose of CVD 908-htrA had a mean of 189 anti-LPS IgA ASC per 10^6 PBMC. Vigorous IgM and IgG ASC responses were detected among vaccinees. ASC-producing an-ti-H antigen IgA occurred in a majority of participants (Tacket et al., 2000).
• Host human IgA response
  • Description: ASCs producing IgA anti-LPS were detected in 100% of recipients of the high-dose vaccine and in 92% of recipients of the lower-dose vaccine. ASCs producing IgA anti-H antigen occurred in 79% and 73% of high- and lower-dose vaccine recipients, respectively (Tacket and Levine, 2007).
  • Detailed Gene Information: Click Here.