EXPRESSION OF LACZ FROM THE HTRA, NIRB AND GROE PROMOTERS IN A SALMONELLA VACCINE STRAIN - INFLUENCE OF GROWTH IN MAMMALIAN-CELLS

Attenuated Salmonella strains are currently being evaluated as live ve ctors for the delivery of heterologous antigens to the mammalian mucos al and systemic immune systems. An approach to improving the stability of heterologous antigen expression during vaccination is to drive exp ression of the foreign protein from promoters, e.g, nirB, that become activated when Salmonella enter the host. Salmonella strains were cons tructed that harboured similar multicopy plasmids encoding the lacZ ge ne. In each strain, lacZ expression was driven from either the nirB, h trA or groE promoters. Expression of LacZ increased in all vaccine str ains as they were shifted from conditions of low to high temperature. In addition, expression of lacZ driven from the htrA and nirB promoter s significantly increased when the Salmonella entered eukaryotic cells , including macrophages. Expression of lacZ from the groE promoter was significantly elevated in macrophages but not in cells derived from e pithelia. These promoters may be useful for optimising heterologous an tigen expression within immune cells of the host.