title: Absent bactericidal activity of mouse serum against invasive African nontyphoidal Salmonella results from impaired complement function but not a lack of antibody.
abstract: Nontyphoidal strains of Salmonella are a major cause of fatal bacteremia in Africa. Developing a vaccine requires an improved understanding of the relevant mechanisms of protective immunity, and the mouse model of Salmonella infection is useful for studying immunity to Salmonella in vivo. It is important to appreciate the similarities and differences between immunity to Salmonella in mice and men. Ab is important for protection against nontyphoidal Salmonella in both species, and we have previously found an important role for Ab in cell-free complement-mediated bactericidal activity against Salmonella in Africans. It is unclear whether this modality of immunity is relevant in the mouse model. C57BL/6, BALB/c, and C3H mice immunized with heat-killed Salmonella Typhimurium strains D23580 (African invasive strain) and SL1344 and live-attenuated strain SL3261 produced a Salmonella-specific Ab response. Sera from these mice deposited reduced levels of C3 on Salmonella compared with human sera and were unable to kill both wild-type and galE(-) rough mutant of D23580, indicating absent cell-free killing via classical and alternative complement pathways. Supplementing immune mouse sera with human complement enabled killing of Salmonella, whereas addition of human anti-Salmonella Ab to immune mouse sera had no effect. These findings indicate that mouse serum cannot effect [corrected] cell-free complement-dependent killing of Salmonella, because of the reduced mouse complement ability to kill these bacteria compared with human complement. This difference in Ab-dependent immunity to Salmonella in mice and men must be considered when applying findings from the mouse model of Salmonella disease and vaccination response to man.
authors.affiliation: Medical Research Council Centre for Immune Regulation and Clinical Immunology Service, Institute of Biomedical Research, School of Immunity and Infection, College of Medicine and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Siggins
authors.forename: Adam F
authors.initials: AF
authors.lastname: Cunningham
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Marshall
authors.forename: Jayne L
authors.initials: JL
authors.lastname: Chamberlain
authors.forename: Ian R
authors.initials: IR
authors.lastname: Henderson
authors.forename: Calman A
authors.initials: CA
authors.lastname: MacLennan
mesh_terms: D000328:Adult; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis* / Q000097:blood*; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology; D016470:Bacteremia / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D001770:Blood Bactericidal Activity / Q000276:immunology*; D002675:Child, Preschool; D003171:Complement Pathway, Classical / Q000276:immunology; D003165:Complement System Proteins / Q000172:deficiency* / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008295:Malawi / Q000453:epidemiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011817:Rabbits; D012480:Salmonella Infections / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D012486:Salmonella typhimurium / Q000145:classification / Q000276:immunology* / Q000472:pathogenicity*
chemical_list: D000907:Antibodies, Bacterial; D003165:Complement System Proteins