Synthetic and immunological studies of Salmonella Enteritidis O-antigen tetrasaccharides as potential anti-Salmonella vaccines

Abstract

The conjugate of a synthetic Salmonella Enteritidis tetrasaccharide with bacteriophage Qβ induced powerful anti-glycan IgG responses for complete protection from lethal challenges of bacteria.

Syntheses of Salmonella Paratyphi A Associated Oligosaccharide Antigens and Development towards Anti‐Paratyphoid Fever Vaccines

“…In addition, tetrasaccharide 35 ( Figure 4) from Salmonella Enteritidis (S. Enteritidis), which contains at yvelose moiety on the same trisaccharide backbone,w as conjugated with BSA. [18] With Qb-glycan 1 construct in hand, its immunogenicity was first evaluated in mice. Groups of 5m ice were immunized three times with Qb-glycan 1 (1 mgo r4mgo fc arbohydrate per injection) on days 0, 14 and 28.…”

“…Evaluation of IgG subtypes raised against4mgo fQ b-glycan 1 showedt hat all major IgG subclasses (IgG1,I gG2b, IgG2c and IgG3) wereinduced against glycan 1,while IgM antibody levels were insignificant in comparison ( Figure S3). To assesst he structural selectivity and specificity of antibodies induced by Qb-glycan 1,t he binding of the post-immunization sera with BSA conjugates of pentasaccharide 2,t etrasaccharide 3 as well as S. Enteritidis OPS tetrasaccharide 35 [18] were analysed ( Figure 6). Antiserum binding to the S. Enteritidis tetrasaccharide 35 was much weaker,s uggesting the paratose and/or the backbone O-acetyl moieties are likely part of the immunodominant epitopes.…”

“…NaHCO 3 (100 mL) and water (100 mL) in succession, dried (Na 2 SO 4 ), and concentrated. The crude product was purified over SiO 2 using hexane-EtOAc (8:1) as eluant to give pure compound 17 (1.03 g) and a-glycosylated product (18) (19):T oasolution of compound 13 (5.1 g, 8.07 mmol) and compound 5 (3 g, 6.72 mmol) in anhydrous CH 2 Cl 2 (100 mL) was added MS 4 (4 g) and the reaction mixture was stirred at room temperature for 1h and then cooled to À40 8C under argon. To the cooled reaction mixture was added NIS (1.9 g, 84.7 mmol) followed by TfOH (70 ml, 0.12 mmol) and then allowed to stir at À40 8Cf or 15 min.…”

“…Procedure for flow cytometry:T he flow cytometry assay was performed using procedures similar to those described previously. [18] Briefly,asingle colony of S. Paratyphi As train ATCC 9150 was used to inoculate an overnight HS broth culture (37 8C, 220 rpm). The next day,t he bacterial suspension was diluted to an OD 600 of 0.8 and cooled on ice.…”

“…With their well-defineds tructures, synthetic oligosaccharide antigensa re attractive alternatives for vaccined evelopment. While the oligosaccharidea ntigens from severalo ther Salmonella strains have been prepared chemically before, [15][16][17][18] S. Paratyphi Ag lycans have not been synthesized.H erein, we report the first synthesis of S. Paratyphi Aa ssociated oligosaccharides 1-3 ( Figure 2). As the tetrasaccharide 1 represents at ypical repeating unit for S. Paratyphi A, it was evaluated in vaccine studies by conjugatingi tw ith ap owerful virus like particlebased carrier,t hat is, the bacteriophageQ b,w hich elicited strong anti-glycan IgG antibodyr esponses.…”