Protein conjugates of synthetic saccharides elicit higher levels of serum IgG lipopolysaccharide antibodies in mice than do those of the O-specific polysaccharide fromShigella dysenteriaetype 1

Abstract

Our development of vaccines to prevent shigellosis is based on the hypothesis that a critical ( The average molar ratios of the saccharides to HSA ranged from 4 to 24. Serum IgG anti-LPS, elicited in mice by O-SP-HSA or synthetic tetra-, octa-, dodeca-, and hexadecasaccharide fragments, was measured by ELISA. Outbred 6-week-old female mice were injected s.c. three times at biweekly intervals with 2.5 g of saccharide as a conjugate and were bled 7 days after the second and third injections. Excepting the tetramer, conjugates of the octamer, dodecamer and hexadecamer elicited IgG LPS antibodies after the second injection, a statistically significant rise (booster) after the third injection, and higher levels than those vaccinated with O-SP-HSA (P ‫؍‬ 0.0001). The highest geometric mean levels of IgG anti-LPS were elicited by the hexadecamer with 9 chains or 9 moles of saccharide͞HSA (15.5 ELISA units) followed by the octamer with 20 chains (11.1 ELISA units) and the dodecamer with 10 chains (9.52 ELISA units). Clinical evaluation of these synthetic saccharides bound to a medically useful carrier is planned.

Effect of the nonreducing end of Shigella dysenteriae type 1 O-specific oligosaccharides on their immunogenicity as conjugates in mice

“…Rha repeating unit bound at their reducing end to a carrier protein by single point attachment (12). We showed that the synthetic oligosaccharide-protein conjugates induced higher antibody levels than the conjugates of the native O-SP.…”

“…We have mapped the effects of the oligosaccharide length and the number of saccharide chains per protein (density) on the immunogenicity of conjugates. A maximal O-SP antibody response was observed with conjugates of four repeating units and Ϸ10 chains per human serum albumin (12).…”

Synthesis, characterization, and immunogenicity in mice of Shigella sonnei O-specific oligosaccharide-core-protein conjugates

“…Evaluation of such conjugates in children showed age-related antibody responses and protection (7). A significant improvement in the immunogenicity of S. dysenteriae type 1 conjugates was achieved by using synthetic oligosaccharides (OS) of defined lengths bound by their reducing ends to a protein at defined densities (8). Synthesis of S. sonnei O-SP oligosaccharides has not been possible to date.…”

Saccharide/protein conjugate vaccines for Bordetella species: Preparation of saccharide, development of new conjugation procedures, and physico-chemical and immunological characterization of the conjugates

“…The choice of conjugation methods is restricted by the pH and temperature sensitivities of both vaccine components. The types of chemical linkages between the O-SP and the protein as well as the saccharide chain length and the chain density on the protein were shown to influence the serum antibody responses to both vaccine components [35,36,37,38,39,40]. Here we studied two conjugation methods of O-SP either by their Kdo or their glucosamine residues.…”