Thesis Defense: Effects of Cyclic Adenosine Monophosphate Independent Cyclic Adenosine Monophosphate Receptor Protein in Recombinant Attenuated Salmonella Vaccines

Time and Date

9:30am -11:30am, Jul 19, 2012


The Biodesign Institute

Address: 727 E. Tyler St. Tempe AZ 85287


Shihuan Shao
Thesis Defense

BDA AL1-10/14

Chair: Roy Curtiss III
Committee: Rajeev Misra, Jorge Reyes del Valle


Salmonella enterica is a gastrointestinal (GI) pathogen which can cause systemic diseases. It can invade the host through GI tract and induce powerful immune responses, thus is considered as a promising candidate of oral live vaccine vectors. Scientists have been making great efforts to get a properly attenuated Salmonella vaccine strain for a long time, but could not achieve a balance between attenuation and immunogenicity. So the regulated delayed attenuation/lysis Salmonella vaccine vectors were proposed as a design to seek the balance. The research work was progressing steadily, but more improvements needed to be made. As one of the possible improvements, the cyclic adenosine monophosphate (cAMP)-independent cAMP receptor protein (Crp) is expected to protect the crucial regulator, araC PBAD, in this design from interference of glucose, and enhance the colonization and immunogenicity of the vaccine strains.

In this study, the cAMP-independent crp, crp70, with or without araC PBAD promoter, was introduced into existing Salmonella vaccine strains. Then the growth rate, resistance to catabolite repression, colonization, immunogenicity and protection of these new strains were compared with wild-type crp or araC PBAD crp strains via western blot, enzyme-linked immunosorbent assay (ELISA) and animal study, so as to evaluate the effects of crp70 on the vaccine strains.

The performances of the crp70 strains in some aspects were closed to or even exceeded the crp strains, but generally they didn’t exhibit the expected advantages to their wild-type parents. Crp70 rescued the expression of araC PBAD fur from catabolite repression. The strain harboring araC PBAD crp70 was severely affected by its slow growth, and its colonization and immunogenicity was much weaker than the other ones. The Pcrp crp70 strain showed relatively good ability in colonization and immune stimulation. Both strains could provide certain level of protection against the c