Polysaccharide-protein Conjugate Research Articles

The Potency of Maillard Conjugates Containing Whey Protein as Natural Emulsifier

There is a continued need for the advancement of natural emulsifiers to replace synthetic emulsifiers, driven by human health concerns. This study is aimed at producing protein-polysaccharide conjugates through the Maillard reaction and at evaluating its ability as an emulsifier based on its emulsifying properties. The proteins used in this study were bovine milk whey protein and soy protein isolates, while the polysaccharides were maltodextrin and pectin. The protein-polysaccharide conjugation used a Maillard reaction under dry heating conditions. The protein and polysaccharide mass ratios were 1 : 2 and 1 : 3. The results showed that the types of proteins and polysaccharides and their mass affect the surface tension of the conjugate products. Whey protein-pectin conjugates with a mass ratio of 1 : 2 and a concentration of 1% had the lowest surface tension at 43.77 dyne/cm2. This conjugate sample also showed the highest emulsifying index at 27.20 m2/g. The conjugate powder containing pectin as a polysaccharide showed better emulsifying activity than that of those containing maltodextrin. However, the smallest droplet size of the emulsion (256.5 nm) resulted from the emulsification process using whey protein-maltodextrin conjugates as an emulsifier. The FTIR and gel electrophoresis (SDS-PAGE) analysis confirmed the conjugation formation. In general, protein-polysaccharide conjugates containing whey protein could potentially act as a natural emulsifier for food.

Humoral and cellular immune responses induced by serogroup W135 meningococcal conjugate and polysaccharide vaccines

Investigating the mechanisms by which W135 meningococcal conjugate (PSW135-TT) activates adaptive immune responses in mice can provide a comprehensive understanding of the immune mechanisms of bacterial polysaccharide conjugate vaccines. We compared B-cell and T-cell immune responses immunized with W135 meningococcal capsular polysaccharides (PSW135), tetanus toxoid (TT) and PSW135-TT in mice. The results showed that PSW135-TT could induce higher PSW135-specific and TT-specific IgG antibodies with a significant enhancement after two doses. All serum antibodies immunized with PSW135- TT had strong bactericidal activity, whereas none of the serum antibodies immunized with PSW135 had bactericidal activity. Besides, IgM and IgG antibodies immunized with PSW135-TT after two doses were positively correlated with the titer of bactericidal antibodies. We also found Th cells favored Th2 humoral immune responses in PSW135-TT, PSW135, and TT-immunized mice, especially peripheral blood lymphocytes. Furthermore, PSW135-TT and TT could effectively activate bone marrow derived dendritic cells (BMDCs) and promote BMDCs to highly express major histocompatibility complex Ⅱ (MHCⅡ), CD86 and CD40 molecules in mice, whereas PSW135 couldn’t. These data verified the typical characteristics of PSW135-TT and TT as T cell dependent antigen (TD-Ag) and PSW135 as T cell independent antigen (TI-Ag), which will be very helpful for further exploration of the immune mechanism of polysaccharide-protein conjugate vaccines and improvement of the quality of bacterial polysaccharide conjugate vaccines in future.

Development of Coconut Protein Concentrate-Xanthan Gum Conjugate by Wet-Dry Heating Method for Red Palm Oil Emulsification

Protein-polysaccharide conjugation is commonly achieved by wet and dry heating methods. Therefore, this study aimed to produce red palm oil (RPO) emulsifiers by conjugating coconut protein concentrate (CPC) and xanthan gum (XG) through a combination of wet and dry heating method using a cabinet dryer. Several factors, including reaction time (3, 4, 5, 6, and 7 hours), pH (3, 5, 7, 9, and 11), and protein-polysaccharide ratio (1:3, 1:2, 1:1, 2:1, and 3:1) were evaluated for their effect on the Emulsion Activity Index (EAI) and Emulsion Stability Index (ESI). The ability of the obtaining conjugate to emulsify RPO was evaluated, and the results showed that CPC contained 67.40% protein. Reaction time, pH, and protein-XG ratio had a significant effect on EAI and ESI. Meanwhile, optimal conditions for the formation of the CPC-XG conjugate, based on EAI and ESI, were a reaction time of 5 hours, pH 9, and protein-polysaccharide ratio of 2:1. Fourier Transform Infrared (FTIR) analysis showed that the CPC-XG conjugate had a change in absorption at a wavelength number of around 1640 cm -1 , indicating the presence of a Maillard reaction product. Furthermore, the CPC-XG conjugate used in RPO emulsion has a characteristic EAI value of 23.74 m 2 /g, ESI of 271.32 minutes, a droplet size of 790 nm, and a zeta potential of -36.9 mV. These results suggest that the CPC-XG conjugate produced by the wet-dry heating method has the potential for producing stable RPO emulsions.

Polysaccharide Aldehydes and Ketones: Synthesis and Reactivity.

Polysaccharides are biodegradable, abundant, sustainable, and often benign natural polymers. The achievement of selective modification of polysaccharides is important for targeting specific properties and structures and will benefit future development of highly functional, sustainable materials. The synthesis of polysaccharides containing aldehyde or ketone moieties is a promising tool for achieving this goal because of the rich chemistry of aldehyde or ketone groups, including Schiff base formation, nucleophilic addition, and reductive amination. The obtained polysaccharide aldehydes or ketones themselves have rich potential for making useful materials, such as self-healing hydrogels, polysaccharide-protein therapeutic conjugates, or drug delivery vehicles. Herein, we review recent advances in synthesizing polysaccharides containing aldehyde or ketone moieties and briefly introduce their reactivity and corresponding applications.

Casein-alginate conjugates prepared from a transacylation reaction as novel nanocarriers of curcumin for enhanced loading capacity, pH stability, and bioaccessibility

Protein-polysaccharide conjugates are potential carriers to deliver polyphenols such as curcumin in beverages. In this study, the objective was to study properties of casein-alginate conjugates prepared using a transacylation reaction as carriers of curcumin. For encapsulation, 2 mg/mL conjugate was mixed with 0.5, 1.0, or 1.5 mg/mL curcumin at pH 13.0 for 1 h, followed by adjusting pH to 7.0, 4.6, and 3.0 and centrifugation. The treatments had an encapsulation efficiency of about 80%, and the loading capacity of 18–36% was higher than studies using other protein-polysaccharide conjugates. The encapsulation resulted from hydrophobic interactions between curcumin and casein and the capsule dispersions were stable during 30-day storage at 4 °C and with additional 0–500 mM NaCl. Nanoencapsulation did not change the antioxidant activity of curcumin and resulted in 57% bioaccessibility, much higher than <10% of pristine curcumin. This work may be significant to deliver hydrophobic bioactive compounds in functional beverages.

Streptococcus agalactiae serotype Ia capsular polysaccharide production from a Brazilian strain

The pathogen S. agalactiae, categorized as Lancefield group B streptococci (GBS), is a Gram-positive bacterium, encapsulated, anaerobic facultative bacillus, which occurs in pairs or short chains. It was responsible for more than 319,000 cases of infections in neonates. Early and late streptococci, in the course of an illness or medical condition, are infections that have high mortality and morbidity rates, with an incidence of 2.0 to 5.0 per 1000 live births in North America, Europe, and Australia. The infection of newborns usually happens through transmission from infected mothers during and after childbirth, with GBS being among the critical bacterial infections in the Brazilian epidemiological picture. S. agalactiae strains isolated from different regions of Brazil, indicate a great diversity among the isolated serotypes but with a higher incidence of serotype Ia. Publications report that, in pregnant women in Brazil, the prevalence of serotype Ia has been constant between 2002 and 2018, followed by serotypes II and IV. Serotypes Ib, III, and V also appear, but with some fluctuations in different regions of the country. The pathogen which causes invasive disease are usually surrounded by a polysaccharide capsule and is its major virulence factor, being that the key antigen in protective response triggered by polysaccharides and, more recently, protein-polysaccharide conjugate vaccines. The development of antibiotic resistance by these microorganisms to different antibiotics has been the guideline in leading therapeutic options against these infections including the use of prophylactic vaccines in pregnant women, immunosuppressed or older people. Such prophylactic alternatives can be constructed from capsular polysaccharides.Based on the experience in the production and purification of Neisseria meningitidis polysaccharides for vaccines, Bio-Manguinhos developed a process for the production, purification and characterization of S. agalactiae Ia polysaccharides. In the present study, the capsular polysaccharide from the strain isolated in clinical material of a public hospital, in Rio de Janeiro – Brazil, was obtained from simple batch cultures, with purification process achieving about 20 mg g−1 in yield for cell dry weight (CDW) and ca. of 100 % of purity. Hence, to prove that the CPS of GBS Ia can be consistently produced, purified, and characterized by NMR, HRGC-MS, and SEC-MALS – from such strain – to be used in vaccine productions against S. agalactiae.

Maillard conjugates of whey protein isolate and gum Arabic: Enhanced functional properties and unique gut microbiota regulation

Interactions between proteins and polysaccharides can be used to design food ingredients with potential functional properties. However, the effects of the products formed through different interactions on the gut microbiota remain unclear. In this study, the functional properties and gut microbiota regulation of whey protein isolate (WPI), gum Arabic (GA), their physical mixture (WPI-GA-M) and Maillard conjugates (WPI-GA-C) were investigated in vitro, aiming to understand the effects of protein-polysaccharide conjugation on gut microbiota and to promote the potential applications of conjugates in the food industry. The results showed that WPI-GA-C prepared by Maillard reaction showed improved antioxidant, emulsifying, and anti-inflammatory properties than WPI, GA and WPI-GA-M. Moreover, WPI-GA-C showed unique effects in regulating the gut microbiota by significantly increasing the relative abundances of Bacteroides eggerthii and B. ovatus and enriching the pathways of carbohydrate metabolism and other amino acids metabolism. In brief, the conjugates showed better functional properties with the potential to improve human health by promoting the growth of beneficial bacteria.

Screening of West Cameroonian edible plant-based mucilage for the production of improved protein-polysaccharide conjugates

In developing countries, blending the powders of locally utilized edible plants for mucilage extraction can be a way to address the growing demand for more viscous and soluble cost-effective hydrocolloids. This study aimed to identify mucilaginous edible plants exploited in the western region of Cameroon in order to enhance the viscosity and water solubility of their mucilages. A semi-administered questionnaire facilitated a comprehensive ethno-nutritional survey. Powders (200 μm) from mucilaginous plants available were defatted, oven dried, and used to produce crude extracts in a water bath (50 °C, 1 h, 2 cycles), with distilled water (1:10, m/v), followed by triple filtration (60 μm, 25 °C) and double centrifugation (2900 g, 20 min). The apparent viscosity of these crude extracts was recorded (spindle 2#, 600 s−1, 60 rpm) at 25 °C, and compared to a 0.2% (m/v) xanthan gum solution (in distilled water). The best plant powders were blended (5 blends) for use under an alkaline condition (pH 10, 0.025 M) for optimal liquid mucilage production and its corresponding powder named hibisanua, derived by coagulating the liquid mucilage (4 °C, 96% ethyl alcohol), oven drying (45 °C), powdering, and sieving (200 μm). Some rheological parameters were determined. FTIR and SEM analysis were carried out with the mucilage hibisanua. Out of 300 surveyed participants, 120 (40%) from 17 ethnicities use the identified plants. Thirty species were found, spanning 27 genera and 19 botanical families. Hibiscus esculentus (okra) pods, Triumfetta annua (nkui) bark, and Corchorus olitorius (lalo) leaves are commonly used in traditional food processing. However, only okra (9.23 Pa s) and nkui (5.54 Pa s) liquid mucilage viscosities were similar to xanthan, making their defatted powders interesting. The validated plant powder mixture (F2) thus comprised 10% nkui and 90% okra (w/w). Their crude extract of concentration 1.51% (w/v) showed the highest dynamic viscosity (23.05 Pa s), not significantly different (p ≥ 0.05) from the control. The resulting dry mucilage with a yield of 215.8 mg/g F2 had the highest solubility (83.05%) with a specific viscosity of 11.519 Pa s upon a desirability of 0.73. All polysaccharides’ solutions exhibited pseudoplastic characteristics and shear-thinning behaviour. A concentrated solution (1.51%) of hibisanua had a rheologic index (0.742) and viscous relaxation time (69.25 s) comparable to xanthan gum. Its structural analysis revealed functional group and morphological changes, typical of highly physical gelling pectic mucilages. These findings support the formulated plant powder approach and the use of its mucilage in the food and pharmaceutical industries.

A novel approach to determine residual aldehyde content in conjugated polysaccharides with 3-methyl-2-benzothiazolinonehydrazon (MBTH) by colorimetric method, automation, and HP-SEC

Polysaccharide activation by periodate oxidation to form aldehydes, followed by conjugation with proteins via reductive amination is a general procedure to make polysaccharide-protein conjugate vaccines. Controlling the level of residue aldehyde content after conjugation is critical to ensure vaccine product stability. Herein, to support conjugation process optimization, we developed a 3-methyl-2-benzothiazolone hydrazone (MBTH) chemistry-based colorimetric method, which can measure low-level residual aldehyde polysaccharide-protein conjugate in high throughput 96-well plate format. This mechanism of detection works in two steps. First, MBTH reacts with the aldehyde group to form azine. Then the excess MBTH was oxidized by ferric ammonium sulfate in sulfamic acid to form a reactive cation, which reacts further with azine to form formazan, a characteristic blue chromophore at 610 nm, for colorimetric detection. The method performance, including detection limit, linearity range, matrix effect, kinetics, and color stability was systematically studied. For samples with severe matrix interference, a supplemental size exclusion chromatography (SEC) method was also developed as an alternative method.

Sesame protein hydrolysate-gum Arabic Maillard conjugates for loading natural anthocyanins: Characterization, in vitro gastrointestinal digestion and storage stability

Protein-polysaccharide conjugates formed via Maillard reaction have the potential as a new type of encapsulation system. However, understanding the effects of the Maillard conjugates as carriers for anthocyanins (ANTs) is limited. The objectives of this study were to develop conjugation of sesame protein hydrolysate (SPH) and gum Arabic (GA) via a wet heating approach with variable times (1, 3, 6, and 12 h) and to investigate the ability of freshly prepared conjugates for encapsulation of Malva Sylvestris (common mallow) ANTs. Conjugate production was confirmed by the appearance of new properties, e.g., altered color, chemical interaction, and changed secondary and tertiary structures. The glycation degree of the conjugates increased to a maximum at 12 h. Conjugation with GA helped the partial unfolding of SPH, and improved its solubility and thermal stability. The ability of SPH, GA, and their conjugate as carriers were compared via the spray drying method. The encapsulation efficiency, morphology and simulated gastrointestinal conditions were investigated. The more homogeneous particles produced by the conjugate ensured greater retention and preservation of ANTs. The release of ANTs during in vitro simulated digestion was significantly slowed by encapsulation, particularly for encapsulated ANTs within the Maillard product. In storage for 90 days at 35 °C, the retention of ANTs was much higher within conjugates (93.13%) compared to nonencapsulated powder (39.76%). This research confirmed that the novel carrier prepared by the controlled Maillard reaction can be a proper wall material in the encapsulation of ANTs.

Comprehensive structural and functional characterization of a new protein-polysaccharide conjugate between grass pea protein (Lathyrus sativus) and xanthan gum produced by wet heating

The purpose of this work was to use a controlled wet-heating process to promote Maillard reaction (MR) between grass pea protein (GPPI) and xanthan gum (XG), and then analyse structural, functional and antioxidant properties of the conjugate (GPPI-XGCs). During heating, the degree of glycation of all conjugated samples was raised (up to 37.43 %) and, after heating for 24 h, the lightness of the samples decreased by 24.75 %. Circular dichroism showed changes in secondary structure with lower content of α-helix and random coil in conjugates. XRD patterns showed that MR destroyed the crystalline structure of the protein. In addition, Lys and Arg content of the produced conjugates decreased by 16.94 % and 6.17 %, respectively. Functional properties including foaming capacity and stability were increased by 45.17 % and 37.17 %, and solubility reached 98.88 %, due to the protein unfolding driven by MR. GPPI-XGCs showed significantly higher antioxidant activities with maximum ABTS-RS value of 49.57 %. This study revealed how MR can improve GPPI's properties, which can aid the food industry in producing a wide range of plant-based foods. Especially, among other characteristics, the foaming properties were significantly improved and the final product can be introduced as a promising foaming agent to be used in food formulation.

Antiproliferative activity and apoptosis‑inducing effects of Trametespolyzona polysaccharides against human breast cancer cells.

Fungal polysaccharides have garnered interest due to their biological activities in terms of anticancer properties and antioxidant activity. The present study aimed to evaluate the anticancer properties and antioxidant activity of a newly isolated white-rot fungus, Trametes polyzona CU07 from Thailand. Crude T. polyzona polysaccharides (CTPPs) were extracted from mycelia using hot water. The chemical properties, including total carbohydrates, molecular weight and protein content, and Fourier-transform infrared spectroscopy analysis, were then investigated. The antioxidant activity was determined against the radicals 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The anticancer properties were evaluated in MCF-7 breast cancer (BC) cells, whereas the 293 cell line was used as a control. The inhibitory effects of CTPPs on viability were determined by MTT assay, followed by BrdU incorporation assay to assess cell proliferation. The induction of apoptosis was determined by flow cytometry. CTPPs were considered polysaccharide-protein conjugates, which had molecular weights in the range of 0.3-22,528 kDa. They contained ~50 and 37% carbohydrate and protein, respectively, with glucose as the main monosaccharide component. Notably, CTPPs had high antioxidant activity against ABTS, and had a significant inhibitory effect on the MCF-7 cell line with a half-maximal inhibitory concentration value of 0.58 mg/ml. However, they exhibited little effect on the 293 cell line. The BrdU incorporation assay demonstrated that CTPPs inhibited proliferation by ~20% compared with that in untreated cells. CTPPs also induced early- and late-stage apoptosis of MCF-7 cells. These results indicated that the CTPPs may exhibit potential antiproliferative and antioxidant activity, and apoptosis-inducing effects against human BC cells.

Investigation of structural and physicochemical properties of microcapsules obtained from protein-polysaccharide conjugate via the Maillard reaction containing Satureja khuzestanica essential oil

In this study, some common proteins including, whey protein isolate (WPI), soy protein isolate (SPI), and gelatin (G) conjugated with maltodextrin (MD) via Maillard reaction and were then used to encapsulate Satureja khuzestanica essential oil (SKEO). The higher glycation degree was obtained at a pH of 9 and 3 h of heating at 60 °C for SPI and WPI, and 90 °C for G. The results of FTIR and intrinsic fluorescence test showed the possibility of covalent binding formation between proteins and maltodextrin. The encapsulation efficiencies were obtained about 83.84 %, 88.95 %, and 89.27 % for MD-SPI, MD-G, and MD-WPI, respectively. Moreover, the Maillard reaction-based microcapsules had higher antioxidant activity than the physical mixture of protein-polysaccharide. The addition of SKEO to microcapsules improved antimicrobial activity. The results of this study demonstrated that MD-WPI and MD-G, as encapsulating materials, can be used to enhance the physiochemical properties of microcapsules loaded with SKEO.

Prognoses of patients undergoing hemodialysis administered 23-valent pneumococcal polysaccharide versus 13-valent pneumococcal protein conjugate vaccines

IntroductionSequential vaccination with the 13-valent pneumococcal protein conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) is recommended for patients undergoing hemodialysis; however, evidence for the efficacy of these pneumococcal vaccines for patients undergoing hemodialysis is limited to a single dose. We aimed to evaluate the prognosis of patients undergoing hemodialysis who received vaccination with PPSV23 alone versus sequential vaccination with PCV13 and PPSV23. MethodsPatients undergoing hemodialysis who were vaccinated with PPSV23 alone (PPSV23 group) or PCV13 followed by PPSV23 (PCV13+PPSV23 group) between 2014 and 2016 were included; the observation period was three years from the first injection. Patients who underwent hemodialysis between 2011 and 2012 were included as controls. After propensity score matching using age, sex, dialysis vintage, diabetes history, pneumonia history, and serum albumin and creatinine levels, survival analysis was performed. ResultsThe study included 89, 71, and 319 patients in the PPSV23, PCV13+PPSV23, and control groups, respectively. After propensity score matching, the PPSV23 and control group 1 (79 patients each) and the PCV13+PPSV23 and control group 2 (61 patients each) were compared. Significant differences were observed in the survival rate between the PPSV23 group and control group 1 (p = 0.005) but not between the PCV13+PPSV23 group and control group 2. Pneumonia-related mortality in the two vaccinated groups did not differ significantly during the observation period. ConclusionsPatients who received PPSV23 had a favorable prognosis; however, no positive effect was demonstrated in the PCV13+PPSV23 group.

Individual polysaccharide quantification in polyvalent pneumococcal conjugate vaccine using rate nephelometry

The multivalent pneumococcal conjugate vaccine (PCV) contains purified polysaccharides of different serotypes conjugated to a carrier protein. Testing the final formulated product for individual serotype polysaccharide content is critical in vaccine quality control which requires an assay specific to each serotype polysaccharide present in the formulated product. Antibodies specific to the serotypes specific polysaccharide were used in rate nephelometry assay for quantifying individual serotype polysaccharides in the formulated vaccine. Generally, native polysaccharide (NP) have been used as reference standard. However, the polysaccharide antigen in the vaccine product is in the conjugate form (CRM197 linked) and hence using NP as a reference standard may not be suitable. Activated quenched polysaccharide (AQP) as a reference standard in rate nephelometry would be more appropriate. The epitope structure of AQP closely represents the polysaccharide-protein conjugate drug product (DP) after trypsin digestion. Hence, AQP was evaluated as a novel reference standard for the accurate and precise determination of individual polysaccharides in the multivalent DP. Rate nephelometry assay using AQP could be used for DP release and stability for monitoring time-dependent changes in the product and establishing the shelf life. A similar strategy could be applied to test and release monovalent or multivalent polysaccharide-protein conjugate vaccines (Meningococcal, Haemophilus influenza Type B, Typhoidal, and non-typhoidal salmonella).

High internal phase emulsion stabilized by whey protein isolate-gum Arabic Maillard conjugate: Characterization and application in 3D printing

High internal phase emulsions (HIPEs) stabilized by protein-polysaccharide are attracting considerable attention in the food industry and have been used in the emerging 3D printing. However, research on protein-polysaccharide Maillard conjugates with health-promoting effects used in HIPEs and 3D printing is limited. Developing HIPEs with enhanced stability, printability, and desirable functional properties remains a challenge. This study was aimed to investigate the potential of whey protein isolate-gum Arabic Maillard conjugates (WPI-GA-C) as emulsifiers for stabilizing HIPEs and to prepare HIPEs with improved properties for personalized functional foods and 3D printing. The effects of WPI-GA-C concentration and oil mass fraction on the properties of HIPEs were systematically characterized. The results showed that the WPI-GA-C concentration and oil mass fraction had significant effects on the particle size, processability, and textural, rheological and 3D printing properties of HIPEs. The HIPEs stabilized with 3% WPI-GA-C and 80% oil mass fraction exhibited better self-supporting properties, higher viscosity, higher storage modulus, and lower frequency dependence compared with HIPEs prepared with lower WPI-GA-C concentrations (1% and 2%) and lower oil mass fractions (74% and 77%). The prepared HIPEs could be used as food-grade 3D printing inks to print models with good dimensional printing accuracy. In conclusion, WPI-GA-C could be used to prepare stable HIPEs as potential inks for 3D printing. These results provided new insights into personalized functional food applications with protein-polysaccharide Maillard conjugate stabilized emulsions.

Early-onset group B streptococcal disease in African countries and maternal vaccination strategies.

Invasive group B streptococcal (GBS) disease is the commonest perinatally-acquired bacterial infection in newborns; the burden is higher in African countries where intrapartum antibiotic prophylaxis strategies are not feasible. In sub-Saharan Africa, almost one in four newborns with GBS early-onset disease will demise, and one in ten survivors have moderate or severe neurodevelopmental impairment. A maternal GBS vaccine to prevent invasive GBS disease in infancy is a pragmatic and cost-effective preventative strategy for Africa. Hexavalent polysaccharide protein conjugate and Alpha family surface protein vaccines are undergoing phase II clinical trials. Vaccine licensure may be facilitated by demonstrating safety and immunological correlates/thresholds suggestive of protection against invasive GBS disease. This will then be followed by phase IV effectiveness studies to assess the burden of GBS vaccine preventable disease, including the effect on all-cause neonatal infections, neonatal deaths and stillbirths.

Impact of aluminum adjuvants on the stability of pneumococcal polysaccharide-protein conjugate vaccines

Development of a vaccine drug product requires formulation optimization to ensure that the vaccine’s effectiveness is preserved upon storage throughout the shelf-life of the product. Although aluminum adjuvants have been widely used in vaccine formulations to safely and effectively potentiate an immune response, careful attention must be directed towards ensuring that the type of aluminum adjuvant does not impact the stability of the antigenic composition. PCV15 is a polysaccharide-protein conjugate vaccine comprising the pneumococcal polysaccharide (PnPs) serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F), each individually conjugated to the protein carrier CRM197. PCV15 was formulated with either amorphous aluminum hydroxyphosphate sulfate adjuvant (AAHS) or aluminum phosphate adjuvant (AP) and examined for both stability and immunogenicity. Using a collection of methods to evaluate vaccine stability, it was discovered that certain PCV15 serotypes (e.g., 6A, 19A, 19F) formulated with AAHS resulted in a reduction of immunogenicity in vivo and a reduction in recoverable dose as tested by an in vitro potency assay. The same polysaccharide-protein conjugates formulated with AP were stable regarding all measures tested. Moreover, the reduction in potency of certain serotypes correlated with chemical degradation of the polysaccharide antigen caused by the aluminum adjuvant as measured by reducing polyacrylamide gel electrophoresis (SDS-PAGE), High-Pressure Size Exclusion Chromatography coupled with UV detection (HPSEC-UV) and ELISA immunoassay. This study suggests a formulation, which includes AAHS, may negatively impact the stability of a pneumococcal polysaccharide-protein conjugate vaccine that contains phosphodiester groups. This decrease in stability would likely result in a decrease in the “active” concentration of antigen dose, and herein, it is shown that such instability directly compromised vaccine immunogenicity in an animal model. The results presented in this study help to explain critical degradation mechanisms of pneumococcal polysaccharide-protein conjugate vaccines.

Behavior of protein-polysaccharide conjugate-stabilized food emulsions under various destabilization conditions.

The sensitivity of protein-stabilized emulsions to flocculation, coalescence, and phase separation under destabilization conditions (i.e., heating, aging, pH, ionic strength, and freeze-thawing) may limit the widespread use of proteins as effective emulsifiers. Therefore, there is a great interest in modulating and improving the technological functionality of food proteins by conjugating them with polysaccharides, through the Maillard reaction. The present review article highlights the current approaches of protein-polysaccharide conjugate formation, their interfacial properties, and the behavior of protein-polysaccharide conjugate stabilized emulsions under various destabilization conditions, including long-term storage, heating and freeze-thawing treatments, acidic conditions, high ionic strength, and oxidation. Protein-polysaccharide conjugates are capable of forming a thick and cohesive macromolecular layer around oil droplets in food emulsions and stabilizing them against flocculation and coalescence under unfavorable conditions, through steric and electrostatic repulsion. The protein-polysaccharide conjugates could be therefore industrially used to design emulsion-based functional foods with high physicochemical stability.

Dual-Responsive Enzyme-Polysaccharide Conjugate as a Nanocarrier System for Enzyme Prodrug Therapy.

Biopolymer-based drug delivery systems have gained considerable attention in the field of nanomedicine. In this study, a protein-polysaccharide conjugate was synthesized by covalent conjugation of the enzyme horseradish peroxidase (HRP) with acetalated dextran (AcDex) via a thiol exchange reaction. The resulting bioconjugate shows a dual-responsive behavior in acidic and reductive environments to achieve a controlled release of drugs. The self-assembly of this amphiphilic HRP-AcDex conjugate allows the encapsulation of prodrug indole-3-acetic acid (IAA) into the hydrophobic polysaccharide core. Under slightly acidic conditions, the acetalated polysaccharide reverts to its native hydrophilic form, which triggers the disassembly of micellar nanoparticles and the release of the encapsulated prodrug. The conjugated HRP further activates the prodrug by oxidation of IAA into cytotoxic radicals, which leads to cellular apoptosis. The results indicate that the HRP-AcDex conjugate in combination with IAA has great potential to be used as a novel enzyme prodrug therapy for cancer treatment.