title: Recognition of riboflavin and the capsular polysaccharide of Haemophilus influenzae type b by antibodies generated to the haptenic epitope D-ribitol.
abstract: D-Ribitol, a five-carbon sugar alcohol, is an important metabolite in the pentose phosphate pathway; it is an integral part of riboflavin (vitamin B2) and cell wall polysaccharides in most Gram-positive and a few Gram-negative bacteria. Antibodies specific to D-ribitol were generated in New Zealand white rabbits by using reductively aminated D-ribose-BSA conjugate as the immunogen. MALDI-TOF and amino group analyses of ribitol-BSA conjugate following 120 h reaction showed ~27-30 mol of ribitol conjugated per mole BSA. The presence of sugar alcohol in the conjugates was also confirmed by an increase in molecular mass and a positive periodic acid-Schiff staining in SDS-PAGE. Caprylic acid precipitation of rabbit serum followed by hapten affinity chromatography on ribitol-KLH-Sepharose CL-6B resulted in pure ribitol-specific antibodies (~45-50 μg/mL). The affinity constant of ribitol antibodies was found to be 2.9 × 10(7) M(-1) by non-competitive ELISA. Ribitol antibodies showed 100% specificity towards ribitol, ~800% cross-reactivity towards riboflavin, 10-15% cross-reactivity with sorbitol, xylitol and mannitol, and 5-7% cross-reactivity with L-arabinitol and meso-erythritol. The specificity of antibody to ribitol was further confirmed by its low cross-reactivity (0.4%) with lumichrome. Antibodies to D-ribitol recognized the purified capsular polysaccharide of Haemophilus influenzae type b, which could be specifically inhibited by ribitol. In conclusion, antibodies specific to D-ribitol have been generated and characterized, which have potential applications in the detection of free riboflavin and ribitol in biological samples, as well as identification of cell-surface macromolecules containing ribitol.
authors.affiliation: Department of Biochemistry and Nutrition, CSIR-Central Food Technological Research Institute, 'Chaluvamba Vilas', KRS Road, Mysore, 570020, Karnataka State, India.
authors.forename: G
authors.initials: G
authors.lastname: Ravi
authors.forename: Yeldur P
authors.initials: YP
authors.lastname: Venkatesh
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D002846:Chromatography, Affinity / Q000379:methods; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006241:Haptens / Q000276:immunology; D007106:Immune Sera / Q000032:analysis; D008297:Male; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D011817:Rabbits; D012255:Ribitol / Q000276:immunology*; D012256:Riboflavin / Q000276:immunology*
chemical_list: D000939:Epitopes; D006241:Haptens; D007106:Immune Sera; D011135:Polysaccharides, Bacterial; D012255:Ribitol; D012256:Riboflavin