EPITOPIC SPECIFICITY OF A SYNTHETIC DISACCHARIDE, RECURRING LINK OF CAPSULE POLYSACCHARIDE CHAIN OF SEROTYPE 3 STREPTOCCUS PNEUMONIAE

Abstract

Aim. Study epitopic specificity of synthetic disaccharide, recurring link of serotype 3 S. pneumoniae, conjugated with bovine serum albumin (BSA). Materials and methods. Conjugate of the synthetic disaccharide with BSA was obtained by squarate method. Antigenic activity of the conjugate was studied in competitive EIA. Titers of IgG against capsule polysaccharide of serotype 3 S. pneumoniae were determined in EIA by using sera of mice immunized twice with disaccharide conjugate sorbed onto aluminum hydroxide. Results. Disaccharide conjugate used as a well-covering antigen (4 ^g/well) in EIA was characterized by a high degree of specificity and interacted only with IgG against serotype 3 S. pneumoniae in antimicrobial sera of animals without reacting with antibodies (ABs) against other pneumococcus serotypes (6B, 10A, 19A, 19F, 23F). Disaccharide conjugated with BSA was determined in competitive EIA to inhibit bonding ofABs to disaccharide by 78.8%, bacterial capsule polysaccharide by 56.9%, BSA did not inhibit the sera activity. The study of sera of mice immunized by serotype 3 S. pneumoniae disaccharide conjugate in EIA, where capsule polysaccharide was used as a plate-sorbed antigen, has established the presence of IgG against capsule polysaccharide at a titer of 1:1600. Conclusion. The disaccharide that is a single recurring link of serotype 3 S. pneumoniae contains a key epitope of capsule polysaccharide. The synthetic disaccharide could be used as a component of multivalent conjugated pneumococcal vaccines and for development of diagnostic test-systems.

Keywords

• synthetic disaccharide
• conjugate
• serotype 3 s. pneumoniae
• antibodies
• eia inhibition