title: Engineering and preclinical evaluation of attenuated nontyphoidal Salmonella strains serving as live oral vaccines and as reagent strains.
abstract: While nontyphoidal Salmonella (NTS) has long been recognized as a cause of self-limited gastroenteritis, it is becoming increasingly evident that multiple-antibiotic-resistant strains are also emerging as important causes of invasive bacteremia and focal infections, resulting in hospitalizations and deaths. We have constructed attenuated Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Enteritidis strains that can serve as live oral vaccines and as "reagent strains" for subunit vaccine production in a safe and economical manner. Prototype attenuated vaccine strains CVD 1921 and CVD 1941, derived from the invasive wild-type strains S. Typhimurium I77 and S. Enteritidis R11, respectively, were constructed by deleting guaBA, encoding guanine biosynthesis, and clpP, encoding a master protease regulator. The clpP mutation resulted in a hyperflagellation phenotype. An additional deletion in fliD yielded reagent strains CVD 1923 and CVD 1943, respectively, which export flagellin monomers. Oral 50% lethal dose (LD₅₀) analyses showed that the NTS vaccine strains were all highly attenuated in mice. Oral immunization with CVD 1921 or CVD 1923 protected mice against lethal challenge with wild-type S. Typhimurium I77. Immunization with CVD 1941 but not CVD 1943 protected mice against lethal infection with S. Enteritidis R11. Immune responses induced by these strains included high levels of serum IgG anti-lipopolysaccharide (LPS) and anti-flagellum antibodies, with titers increasing progressively during the immunization schedule. Since S. Typhimurium and S. Enteritidis are the most common NTS serovars associated with invasive disease, these findings can pave the way for development of a highly effective, broad-spectrum vaccine against invasive NTS.
authors.affiliation: University of Maryland School of Medicine, Center for Vaccine Development, Baltimore, MD 21201, USA. stennant@medicine.umaryland.edu
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Tennant
authors.forename: Jin-Yuan
authors.initials: JY
authors.lastname: Wang
authors.forename: James E
authors.initials: JE
authors.lastname: Galen
authors.forename: Raphael
authors.initials: R
authors.lastname: Simon
authors.forename: Marcela F
authors.initials: MF
authors.lastname: Pasetti
authors.forename: Orit
authors.initials: O
authors.lastname: Gat
authors.forename: Myron M
authors.initials: MM
authors.lastname: Levine
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001426:Bacterial Proteins / Q000235:genetics; D005260:Female; D005818:Genetic Engineering / Q000379:methods*; D006147:Guanine / Q000378:metabolism; D007115:Immunization Schedule; D007074:Immunoglobulin G / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D022562:Salmonella Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D012477:Salmonella enteritidis / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D014613:Vaccines, Attenuated / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D022562:Salmonella Vaccines; D014613:Vaccines, Attenuated; D006147:Guanine