Evaluation of the Lon‐Deficient Salmonella Strain as an Oral Vaccine Candidate

Abstract

We evaluated the efficacy of CS2022 (the Lon protease-deficient mutant strain of Salmonella enterica serovar Typhimurium) as a candidate live oral vaccine strain against subsequent oral challenge with a virulent strain administered to BALB/c and C57BL/6 mice. CS2022 persistently resided in the spleen, mesenteric lymph nodes, Peyer's patches, and cecum of both strains of mice after a single oral inoculation with 1 x 10(8) colony-forming units. Finally, CS2022 almost disappeared from each tissue sample by week 12 in BALB/c mice, whereas CS2022 still resided in each tissue type at week 12 after inoculation of C57BL/6 mice. A significant increase in the serovar Typhimurium lipopolysaccharide-specific secretory immunoglobulin A (s-IgA), as measured for one of the mucosal immune responses, was detected in bile and intestinal samples of both strains of immunized mice at week 4 after immunization. In addition, the expression of gamma interferon mRNA in the spleens of both strains of immunized mice, especially those of C57BL/6 mice, was significantly increased at week 4 after immunization and was boosted during the following 5 days after the challenge was administered to the mice. Furthermore, peritoneal macrophages isolated from immunized mice at week 4 after immunization exhibited an increase in intracellular killing activity against both virulent and avirulent Salmonella. The present results suggested that salmonellae-specific s-IgA on the mucosal surfaces induced by immunization with CS2022 generally prevented mice from succumbing to an oral challenge with a virulent strain. Simultaneously, CS2022 promoted the protective immunity associated with macrophages in both strains of mice.

CD46 Transgenic Mouse Model of Necrotizing Fasciitis Caused by Streptococcus pyogenes Infection

“…Thus, 7-week-old mice were s.c. infected with a total of 1 ϫ 10 7 CFU of stationary-growth-phase GAS into both hind footpads (5 ϫ 10 6 CFU per footpad). After s.c. infection, the survival rates were observed every 24 h for 336 h postinfection, or the number of bacteria in the blood and tissue samples including the popliteal lymph nodes (PLN), spleen, and liver were determined by plating onto sheep blood agar (11,27). All mice were bred at the animal facility at the Kitasato Institute, and all mouse experiments were performed in accordance with institutional protocol guidelines under an approved protocol.…”

An oralSalmonellavaccine promotes the down-regulation of cell surface Toll-like receptor 4 (TLR4) and TLR2 expression in mice

“…CS2022 was able to invade murine gut-associated lymphoid tissue (GALT) and to infect it persistently after a single oral immunization Kodama et al, 2005). The level of immunity induced in this manner provided mice with extremely good protection against either oral Kodama et al, 2005) or subcutaneous ( Fig.…”

“…Salmonella enterica serovar Typhimurium SR-11 w3456 (virulent strain, resistant to tetracycline) or CS2022 (vaccine strain, lon::chloramphenicol resistance) was routinely grown in L-broth [1% Bacto tryptone (Difco, Detroit, MI), 0.5% Bacto yeast extract (Difco), 0.5% sodium chloride, 0.1% glucose, pH 7.4] or on L-agar at 37 1C Kodama et al, 2005). Listeria monocytogenes 10403S (serotype 1) was routinely grown in brain heart infusion (BHI) broth (Difco) or BHI agar (Difco) at 37 1C (Bishop & Hinrichs, 1987;Hanawa et al, 2002).…”

“…Six-week-old female BALB/c (H-2 d ) mice (Charles River Japan, Yokohama, Japan) were orally immunized with 1 Â 10 8 CFU of exponential-growth-phase salmonellae of CS2022, which were concentrated in 20-mL doses in phosphate-buffered saline (PBS), pH 7.4, containing 0.01% (w/v) gelatin (BSG), as described previously Kodama & Matsui, 2004;Kodama et al, 2005). To determine the extent of bacterial clearance, at week 6 after oral immunization both immunized and nonimmunized mice were inoculated subcutaneously (both hind footpads) with w3456 or L. monocytogenes at a dose of 1 Â 10 5 or 5 Â 10 5 CFU, respectively.…”

Enhancement of Immune Responses by an Attenuated Salmonella enterica Serovar Typhimurium Strain Secreting an Escherichia coli Heat-Labile Enterotoxin B Subunit Protein as an Adjuvant for a Live Salmonella Vaccine Candidate

“…Salmonella enterica serotype Typhimurium is the serotype most frequently associated with the diarrheal diseases and is commonly transmitted from animal to human through livestock-and domestic fowl-derived food products (34,50). S. Typhimurium induces clinical enteric fever in mouse models with symptoms similar to human symptomology after S. enterica serovar Typhi infection (16,25,50). Infections may be asymptomatic or can result in enteric and fatal systemic disease.…”