Reductively aminated D-xylose-albumin conjugate as the immunogen for generation of IgG and IgE antibodies specific to D-xylitol, a haptenic allergen

Prediction of clinical efficacy of subcutaneous immunotherapy for Artemisia sieversiana pollen allergic rhinitis by serum metabolomics

BACKGROUND/PURPOSE

Specific immunotherapy is the only effective etiological treatment for allergic rhinitis, but subcutaneous immunotherapy has a slow onset and poor compliance. Predicting the clinical efficacy of subcutaneous immunotherapy in advance can reduce unnecessary medical costs and resource waste. This study aimed to identify metabolites that could predict the efficacy of subcutaneous immunotherapy on seasonal allergic rhinitis by serum metabolomics.

METHODS

Patients (n = 43) with Artemisia sieversiana pollen allergic rhinitis were enrolled and treated with subcutaneous immunotherapy for one year. Patients were divided into the ineffective group (n = 10) and effective group (n = 33) according to the therapeutic index. Serum samples were collected before treatment. Metabolomics was determined by liquid chromatography-mass spectrometry combined with gas chromatography-mass spectrometry and analyzed differential compounds and related metabolic pathways.

RESULTS

A total of 129 differential metabolites (P < 0.05) were identified and 4 metabolic pathways, namely taurine and hypotaurine metabolism, pentose and glucuronate interconversions, pentose phosphate pathway, and alanine, aspartate, and glutamate metabolism, were involved.

CONCLUSION

Some metabolites, such as hypotaurine, taurine, and l-alanine, have the potential to become predictive biomarkers for effective subcutaneous immunotherapy.

Recognition of flavin mononucleotide, Haemophilus influenzae type b and its capsular polysaccharide vaccines by antibodies specific to D-ribitol-5-phosphate

D-Ribitol-5-phosphate (Rbt-5-P) is an important metabolite in the pentose phosphate pathway and an integral part of bacterial cell wall polysaccharides, specifically as polyribosyl ribitol phosphate (PRP) in Haemophilus influenzae type b (Hib). The major objective of this study was to investigate whether an antibody specific to Rbt-5-P can recognize the PRP of Hib. D-Ribose-5-phosphate was reacted with proteins in the presence of sodium cyanoborohydride to obtain Rbt-5-P epitopes; 120 h reaction resulted in conjugation of ~30 and ~17 moles of Rbt-5-P/mole of BSA and OVA, respectively, based on decrease in amino groups, MALDI-TOF analyses, an increase in apparent molecular weight (SDS-PAGE) and glycoprotein staining. Immunization of rabbits with Rbt-5-P-BSA conjugate generated antibodies to Rbt-5-P as demonstrated by dot immunoblot and non-competitive ELISA. Homogeneous Rbt-5-P-specific antibody was purified from Rbt-5-P-BSA antiserum subjected to caprylic acid precipitation followed by hapten-affinity chromatography; its affinity constant is 7.1 × 10(8) M(-1). Rbt-5-P antibody showed 100 % specificity to Rbt-5-P, ~230 %, 10 % and 3.4 % cross-reactivity to FMN, riboflavin and FAD, respectively; the antibody showed ~4 % cross-reactivity to D-ribitol and <3 % to other sugars/sugar alcohols. Rbt-5-P-specific antibody recognized Hib conjugate vaccines containing PRP which was inhibited specifically by Rbt-5-P, and also detected Hib cell-surface capsular polysaccharides by immunofluorescence. In conclusion, Rbt-5-P-protein conjugate used as an immunogen elicited antibodies binding to an epitope also present in PRP and Hib bacteria. Rbt-5-P-specific antibody has potential applications in the detection and quantification of free/bound Rbt-5-P and FMN as well as immunological recognition of Hib bacteria and its capsular polysaccharide.

Recognition of riboflavin and the capsular polysaccharide of Haemophilus influenzae type b by antibodies generated to the haptenic epitope D-ribitol

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.

Indirect competitive immunoassay for detection of vitamin B₂ in foods and pharmaceuticals

An indirect immunoassay for the determination of vitamin B2 in food samples and vitamin tablets was developed. A carbodiimide-modified active ester method was used to synthesize the immunogen for vitamin B2. The coupling ratio of vitamin B2 to carrier protein in immunogen was 19.98:1. The titer of the polyclonal antibody was 1:64000, and the antibody showed high specificity in the presence of vitamin B2 photolytic products and other B group vitamins. The immunoassay showed detection limits (LODs) of 1.07 ng/mL in PBS, 24.6 ng/g in vitamin drink, and 0.50 mg/kg in milk powder. Recovery was 99.58-110.91% in milk powder and 70.20-100.5% in vitamin drink. Vitamin B2 samples were analyzed by high-pressure liquid chromatography (HPLC) and the immunoassay, and results showed good agreement. Finally, this method was applied to detect vitamin B2 in commercial milk powder and vitamin tablets, and the detected amount correlated well with the labeled amount.

Binding affinity of anti-xylitol antibodies to canine hepatic vessels

Xylitol is used as a sugar substitute in food products. Dogs have been reported to experience lethal liver injury after accidental ingestion of xylitol. Because liver injury may be a serious consequence of canine immune-mediated reactions, antibodies produced against xylitol may attack the liver. Therefore, in the present study, we evaluated whether binding sites for xylitol antibodies are located at the liver or not. Anti-xylitol antibodies were generated by immunization of rabbits with a xylose-bovine serum albumin conjugate. Immunohistological examination showed that binding sites for the anti-xylitol antibodies were located in the hepatic arteries and the portal veins. Western blotting analyses by using a canine liver homogenate showed 4 protein bands with different molecular weights which reacted with anti-xylitol antibodies. Therefore, binding of anti-xylitol antibodies to the vessels may be the first step in an immune-mediated pathogenic response in xylitol toxicity. Further studies are necessary to determine the effects of anti-xylitol antibodies on the liver in the pathogenesis of xylitol toxicity.

Microbial and bioconversion production of D-xylitol and its detection and application

D-Xylitol is found in low content as a natural constituent of many fruits and vegetables. It is a five-carbon sugar polyol and has been used as a food additive and sweetening agent to replace sucrose, especially for non-insulin dependent diabetics. It has multiple beneficial health effects, such as the prevention of dental caries, and acute otitis media. In industry, it has been produced by chemical reduction of D-xylose mainly from photosynthetic biomass hydrolysates. As an alternative method of chemical reduction, biosynthesis of D-xylitol has been focused on the metabolically engineered Saccharomyces cerevisiae and Candida strains. In order to detect D-xylitol in the production processes, several detection methods have been established, such as gas chromatography (GC)-based methods, high performance liquid chromatography (HPLC)-based methods, LC-MS methods, and capillary electrophoresis methods (CE). The advantages and disadvantages of these methods are compared in this review.