Expression of an F1/V fusion protein in attenuatedSalmonella typhimuriumand protection of mice against plague

Oral Vaccination withSalmonellaSimultaneously ExpressingYersinia pestisF1 and V Antigens Protects against Bubonic and Pneumonic Plague

“…In addition to having F1-Ag and V-Ag coexpressed or administered in their recombinant form, previous studies have shown that constructing a live vaccine that expresses both F1-and V-Ags as an F1/V fusion protein, achieves protection against Y. pestis bubonic challenge (19). However, plasmid stability is problematic, thus questioning the practicality of this vaccine.…”

“…We next questioned whether both F1-and V-Ags can be simultaneously expressed by Salmonella vaccine vector. Previous attempts (19) to successfully express both of these protective Ags were preempted with difficulties such as antibiotic marker leakage and maintaining vaccine strain stability of F1-and V-Ag fusion plasmids. In the present study, we designed and constructed a single Salmonella vaccine expressing both F1-and V-Ags to mimic the native expression of these Y. pestis Ags to similar structures in Salmonella.…”

“…Previous studies have shown that V-Ag expressed by attenuated Salmonella enterica serovar Typhimurium (S. Typhimurium) (18) or as a F1-and V-Ag fusion protein (19) can stimulate Ab responses to V-Ag and confer protection against the wild-type Y. pestis challenge. However, the plasmids used for expressing these passenger Ags are dependent on antibiotic selection, which may lessen their stability in vivo.…”

“…To achieve sufficient protective Ab titers, up to five doses need to be administered (18). To avoid plasmid segregation, mice must be dosed with the antibiotics to force selection, which achieves partial success (19). Alternatively, when F1-and V-Ags are expressed as a fusion protein in Salmonella (19) and administered parenterally, Ag stabilization again is problematic, but protection can be achieved.…”

“…To avoid plasmid segregation, mice must be dosed with the antibiotics to force selection, which achieves partial success (19). Alternatively, when F1-and V-Ags are expressed as a fusion protein in Salmonella (19) and administered parenterally, Ag stabilization again is problematic, but protection can be achieved. In this present study, to avoid immunizing with two different Salmonella vaccines, one expressing F1-Ag and another V-Ag, we investigated whether both protective Ags could be expressed simultaneously using a balanced-lethal vaccine vector ⌬aroA, ⌬asd S. Typhimurium mutant, thus, avoiding dependency upon antibiotic selection for passenger Ag expression.…”