Impact of conjugation chemistry on the immunogenicity of S. Typhimurium conjugate vaccines

Abstract

Salmonella Typhimurium is major cause of invasive nontyphoidal Salmonella disease in Africa. Conjugation of S. Typhimurium O-antigen to an appropriate carrier protein constitutes a possible strategy for the development of a vaccine against this disease, for which no vaccines are currently available. The conjugation chemistry used is one of the parameters that can affect the immunogenicity of glycoconjugate vaccines. Herein different glycoconjugates were synthesized to investigate the impact of this variable on the immunogenicity of S. Typhimurium conjugate vaccines in mice, all with CRM₁₉₇ as carrier protein. Random derivatization along the O-antigen chain was compared with site-directed activation of the terminal KDO sugar residue of the core oligosaccharide. In particular, two different random approaches were used, based on the oxidation of the polysaccharide, which differently impact the structure and conformation of the O-antigen chain. For the selective conjugation methods, linkers of two different lengths were compared. When tested in mice, all conjugates induced anti-O-antigen IgG antibodies with serum bactericidal activity. Similar anti-O-antigen antibody levels were elicited independent of the chemistry used and a higher degree of saccharide derivatization did not impact negatively on the anti-O-antigen IgG response. Bactericidal activity of serum antibodies induced by selective conjugates was similar independent of the length of the spacer used. Random conjugates elicited antibodies with greater bactericidal activity than selective ones, and an inverse correlation was found between degree of O-antigen modification and antibody functional activity.

GMMA and Glycoconjugate Approaches Compared in Mice for the Development of a Vaccine against Shigella flexneri Serotype 6

“…OAg populations of different average sizes were conjugated to CRM 197 (kindly provided by GSK Vaccines) using both a selective and a random approach. For selective conjugation, OAg was derivatized with adipic acid dihydrazide (ADH) by reductive amination of the KDO terminal sugar and linked to the amino groups on the protein after attachment of a second linker, adipic acid bis (N-hydrosuccinimide) (SIDEA), to ADH [32]. The OAg-ADH intermediates were desalted by a PD10 desalting column prepacked with a Sephadex G-25 Superfine (GE Healthcare, Marlborough, MA, USA) or HiPrep xK 16/14 desalting column 20 mL, prepacked with Sephacryl G-10 Superfine (GE Healthcare, Marlborough, MA, USA) based on OAg average size.…”

Sugar–Protein Connectivity Impacts on the Immunogenicity of Site‐Selective Salmonella O‐Antigen Glycoconjugate Vaccines

“…By these methods and others previously reported,5b,c a diverse set of site‐selective derivatizations at disulfide, lysines, tyrosines, and glutamates/aspartates of CRM 197 (Scheme ) was prepared and a survey of immunogenicity of various regioisomeric OAg‐based glycoconjugate vaccines against S. typhimurium was conducted 9d. 11…”

“…For coupling with the protein, OAg was modified at the terminal KDO sugar. After introduction of an adipic acid dihydrazide (ADH) molecule by reductive amination,11, 14 a second linker was introduced with a terminal alkyne group (Scheme ; see the Supporting Information).…”

Glycoconjugate vaccines: some observations on carrier and production methods

“…A particularly interesting feature of this study was the improvement seen if directed conjugation was used rather than allowing conjugation to occur at random, which suggests that reducing the polydispersity may improve immunogenicity. Conversely, Stefanetti et al (2014) found that random conjugation improves the bactericidal activity of antibodies produced in response to Sa. enterica serovar typhimurium O-antigen conjugated to CRM197.…”