Opimization of Salmonella as a carrier for vaccination

• Main Author: Abd El Halim Hegazy, Wael
• Other Authors: Prof. Dr. Michael Hensel
• Format: Doctoral Thesis
• Language: English
• Published: 2011
• Subjects: Salmonella; Vaccination; TTSS; SPI2 effectors; ddc:570
• Online Access: https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-201112078591

Salmonella is a facultative intracellular bacteria which can grow and replicate within the infected host cells as well as extracellulary. The use of intracellular bacteria that have access to the host cell cytosol may allow a more specific targeting of DNA vaccine vectors to professional Antigen presenting cells (APC). The strategy of using live attenuated Salmonella to deliver plasmid-encoded antigens under the transcriptional control of eukaryotic promoters has been used successfully in vaccination. Another strategy, heterologous antigens can be expressed in Salmonella as fusions with recombinant or native proteins. This approach has been used mainly to direct the expression of the desired antigen to a particular location of the bacterial cell and increase the immunogenicity of foreign antigens by fusing them to proteins that could exert a carrier effect. Salmonella type III secretion system (TTSS)-mediated translocation can be used for efficient delivery of heterologous antigens to the cytosol of antigen-presenting cells leading to prominent both CD4 and CD8 T-cells. In this work we tried SPI2 membranal translocated effectors antigen fusions such as SseJ, SifA, SseL and SteC. Our In-vitro and in-vivo experiments prove that SseJ effector fusion is the best candidate for vaccination. In previous work it was shown that SifB promoter was the most efficient in-vivo inducible promoter. Here we show that SseJ antigen fusion protein under control of SifB is the most efficient in comparison to other effector fusions under control of other invivo inducible promoters. htrA/purD douple mutant S.typhimurium was used as attenuated carrier for vaccination, in this study we find that delta SifA mutant can stimulate in-vitro T-cell proliferation to same level.