title: Development of non-antibiotic-resistant, chromosomally based, constitutive and inducible expression systems for aroA-attenuated Salmonella enterica Serovar Typhimurium.
abstract: Live-vaccine delivery systems expressing two model antigens from Mycoplasma hyopneumoniae, F2(P97) (Adh) and NrdF, were constructed using Salmonella enterica serovar Typhimurium aroA (STM-1), and immunogenicity in mice was evaluated. Recombinant plasmid-based expression (PBE) and chromosomally based expression (CBE) systems were constructed. The PBE system was formed by cloning both antigen genes into pJLA507 to create an operon downstream of temperature-inducible promoters. Constitutive CBE was achieved using a promoter-trapping technique whereby the promoterless operon was stably integrated into the chromosome of STM-1, and the expression of antigens was assessed. The chromosomal position of the operon was mapped in four clones. Inducible CBE was obtained by using the in vivo-induced sspA promoter and recombining the expression construct into aroD. Dual expression of the antigens was detected in all systems, with PBE producing much larger quantities of both antigens. The stability of antigen expression after in vivo passage was 100% for all CBE strains recovered. PBE and CBE strains were selected for comparison in a vaccination trial. The vaccine strains were delivered orally into mice, and significant systemic immunoglobulin M (IgM) and IgG responses against both antigens were detected among all CBE groups. No significant immune response was detected using PBE strains. Expression of recombinant antigens in S. enterica serovar Typhimurium aroA from chromosomally located strong promoters without the use of antibiotic resistance markers is a reliable and effective method of inducing a significant immune response.
authors.affiliation: School of Biological Sciences, University of Wollongong, NSW, 2522, Australia.
authors.forename: Jake N
authors.initials: JN
authors.lastname: Matic
authors.forename: Tamsin D
authors.initials: TD
authors.lastname: Terry
authors.forename: David
authors.initials: D
authors.lastname: Van Bockel
authors.forename: Tracy
authors.initials: T
authors.lastname: Maddocks
authors.forename: David
authors.initials: D
authors.lastname: Tinworth
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
authors.forename: Steven P
authors.initials: SP
authors.lastname: Djordjevic
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Walker
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001428:Bacterial Vaccines / Q000235:genetics* / Q000276:immunology*; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D005260:Female; D020869:Gene Expression Profiling; D023061:Gene Order; D005822:Genetic Vectors; D007075:Immunoglobulin M / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D045705:Mycoplasma hyopneumoniae / Q000235:genetics / Q000276:immunology*; D010957:Plasmids; D012486:Salmonella typhimurium / Q000235:genetics* / Q000276:immunology; D014436:Typhoid-Paratyphoid Vaccines / Q000235:genetics / Q000276:immunology; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D007075:Immunoglobulin M; D014436:Typhoid-Paratyphoid Vaccines; D014613:Vaccines, Attenuated; C087350:aroA Salmonella vaccine