Food gel-based systems for efficient delivery of bioactive ingredients: design to application.

Food gels derived from natural biopolymers are valuable materials with significant scientific merit in the food industry because of their biocompatibility, safety, and environmental friendliness compared to synthetic gels. These gels serve as crucial delivery systems for bioactive ingredients. This review focuses on the selection, formulation, characterization, and behavior in gastrointestinal of hydrogels, oleogels, and bigels as delivery systems for bioactive ingredients. These three gel delivery systems exhibit certain differences in composition and can achieve the delivery of different bioactive ingredients. Hydrogels are suitable for delivering hydrophilic ingredients. Oleogels are an excellent choice for delivering lipophilic ingredients. Bigels contain both aqueous and oil phases, whose gelation makes their structure more stable, demonstrating the advantages of the above two types of gels. Besides, the formation and properties of the gel system are confirmed using different characterization methods. Furthermore, the changing behavior (e.g., swelling, disintegration, collapse, erosion) of the gel structure in the gastrointestinal is also analyzed, providing an opportunity to formulate soft substances that offer better protection or controlled release of bioactive components. This can further improve the transmissibility and utilization of bioactive substances, which is of great significance.

Iron delivery systems for controlled release of iron and enhancement of iron absorption and bioavailability.

Iron deficiency is a global nutritional problem, and adding iron salts directly to food will have certain side effects on the human body. Therefore, there is growing interest in food-grade iron delivery systems. This review provides an overview of iron delivery systems, with emphasis on the controlled release of iron during gastrointestinal digestion, as well as the enhancement of iron absorption and bioavailability. Iron-bearing proteins are easily degraded by digestive enzymes and absorbed through receptor-mediated endocytosis. Instead, protein aggregates are slowly degraded in the stomach, which delays iron release and serves as a potential iron supplement. Amino acids, peptides and polysaccharides can bind iron through iron binding sites, but the formed compounds are prone to dissociation in the stomach. Moreover, peptides and polysaccharides can deliver iron by mediating the formation of ferric oxyhydroxide which is absorbed through endocytosis or bivalent transporter 1. In addition, liposomes are unstable during gastric digestion and iron is released in large quantities. Complexes formed by polysaccharides and proteins, and microcapsules formed by polysaccharides can delay the release of iron in the gastric environment and prolong iron release in the intestinal environment. This review is conducive to the development of iron functional ingredients and dietary supplements.

Prevention and potential repair of colitis: Beneficial effects and regulatory mechanisms of food-derived anti-inflammatory peptides.

Intestinal inflammatory diseases are increasingly prevalent worldwide, and their pathogenesis is still not fully understood. As of late, studies have discovered that food-derived peptides have specific anti-inflammatory activity and can play a positive role in intestinal health. At the same time, it has broad application prospects in the prevention and treatment of colitis because of its wide source, fast absorption, and high safety. This article reviews the structure-activity and quantity-effect relationships of food-derived peptides for their anti-inflammatory effects. It then discusses their mechanism of action in inhibiting colitis from four aspects. Food-derived anti-inflammatory peptides can delay the progression of the disease by stimulating innate immunity, inhibiting inflammation, and promoting wound healing. Further experiments showed that food-derived anti-inflammatory peptides could prevent and treat colitis through four mechanisms: (a) regulation of inflammatory cytokines; (b) regulation of inflammatory pathways; (c) regulation of intestinal epithelial barrier; (d) regulation of intestinal flora balance. However, due to the treatment of colitis having limitations, there is an urgent to develop food-derived anti-inflammatory peptides as a treatment or adjunctive treatment for colitis. This review highlights the positive effects of food-derived peptides on colitis and anticipates the appearance of mitigating peptides for the therapy of colitis.

Construction of benzyl isothiocyanate-loaded fish skin gelatin-luteolin compound emulsion delivery system, and its digestion and absorption characteristics.

BACKGROUND: Fish skin gelatin (FSG) and luteolin (LUT) were used as composite emulsifiers, and benzyl isothiocyanate (BITC) was used as a model of nutrient delivery to construct a stable emulsion. The storage stability of the FSG-LUT emulsion and its effect on BITC release were investigated both in vitro and ex vivo. RESULTS: LUT can quench FSG fluorophores statically and form a stable complex through hydrogen bonding and hydrophobic interactions. The FSG-LUT emulsion storage stability and embedding rate were higher than those of the FSG emulsion. The FSG-LUT emulsion microstructure was resistant to oral and gastric digestion, and the BITC retention rate and bioaccessibility were much higher than those of the FSG emulsion. Lastly, the ex vivo everted gut sac of rat intestine study demonstrated that BITC showed the highest absorption in the ileum, and the FSG-LUT emulsion absorbed BITC and sustained a controlled release in a specific position. CONCLUSION: LUT could form stable complexes with FSG, which improved the stability and bioavailability of BITC in the FSG-LUT emulsion delivery system, and promoted further intestinal BITC absorption. © 2022 Society of Chemical Industry.

Contribution of κ-/ι-carrageenan on the gelling properties of shrimp myofibrillar protein and their interaction mechanism exploration.

BACKGROUND: The contribution and mechanism of κ-/ι-carrageenan (CG) with different hydration characteristics on the gelling properties of shrimp myofibrillar protein (MP) gelation was studied. RESULTS: The gel strength, water-holding capacity and viscoelastic properties of MP gels were significantly enhanced by 1.0% κ-/ι-CG (P < 0.05), but the microstructure showed that excessive carrageenan caused fragmentation of the gel network and a corresponding decrease in gel properties. Compared to MP-ιCG, MP-κCG showed larger breaking force and shorter breaking distance, thus enhancing the hardness and brittleness of the gel, which might be ascribed to a reinforced network skeleton and a tighter binding of κCG-myosin. However, MP-ιCG stabilized more moisture in the gel network, thereby improving the tenderness of the gel, which might be related to the electrostatic repulsion observed between the sulfate groups of ιCG and the myosin observed by molecular docking. In addition, the ß-sheet content and intermolecular interactions might be positively correlated with gel properties. CONCLUSION: In this study, a composite gel system was constructed based on the interaction of MP and CG. The quality differences of two kinds of CG-MP gels were clarified, which will provide guidance for the application of different kinds of carrageenan and the development of recombinant meat products with specific quality. © 2022 Society of Chemical Industry.

Physicochemical and functional properties of egg white peptide powders under different storage conditions.

This study aims to evaluate the effects of different storage conditions (temperature and relative humidity) on the physicochemical and functional properties of egg white peptide powders (EWPPs). The samples (EWPPs) were stored for 28 d under four conditions (4 °C, 50% RH; 4 °C, 75% RH; 25 °C, 50% RH; 25 °C, 75% RH). Results showed that storage temperature and relative humidity had a significant effect on the physicochemical and functional properties of EWPPs. The contents of antioxidant amino acids such as histidine, tyrosine, tryptophan, and lysine were reduced significantly under different storage conditions, which resulted in the decrease of the antioxidant activity of EWPPs. Circular dichroism spectroscopy analysis indicated that the secondary structure of EWPPs changed from the regular structure to the irregular coiled structure during the storage. Additionally, the hydrophobic groups of the EWPPs originally embedded inside the molecules were exposed to the surface of the molecules during the storage, which led to an aggregation of EWPPs molecule and a decrease in solubility of EWPPs. The aggregation of EWPPs molecules resulted in a decrease in emulsification, emulsification stability, foaming ability and foaming stability of the EWPPs. Therefore, different storage conditions do have an impact on the physicochemical and functional properties of EWPPs. Lower temperature and humidity storing conditions were beneficial to retain the functional property of the EWPPs.

Effects of different metal ions on the physicochemical properties and microstructure of egg white gel.

BACKGROUND: To ameliorate egg white gel's salinity and undesirable texture characteristics during curing, different metal ions (K+ , Mg2+ , Ca2+ , Zn2+ ) were used to replace sodium chloride (NaCl) to simulate salted eggs partially. The effects of these ions on the physicochemical properties, microstructure, and gel characteristics of egg white protein were studied. RESULTS: Low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) analysis showed that adding K+ , Mg2+ , Ca2+ , and Zn2+ could decrease immobile water content and increase free water content in egg white gel. Circular dichroism/fluorescence spectrophotometry (CD/FL) analysis showed that substitutive addition of K+ , Mg2+ , Ca2+, and Zn2+ changed the conformational structure of the protein, which was not conducive to the formation of the three-dimensional mesh gel structure. Differential scanning calorimetry (DSC) results show that the addition of four metal ions could reduce the thermal denaturation temperature of egg white gel. Scanning electron microscopy (SEM) showed that the gel structure of egg white in the zinc chloride (ZnCl2 ) group was rougher and more chaotic, the crosslinking degree was worse, so it was not suitable for low sodium salted egg preparations. The gel strength of the calcium chloride (CaCl2 ) group was significantly higher than other groups (P < 0.05), while the gel strength of the potassium chloride (KCl) group was similar to the NaCl group (P > 0.05). CONCLUSION: CaCl2 and KCl could be used as partial NaCl substitutes to study the addition level and ratio further and improve salted egg white quality. © 2021 Society of Chemical Industry.

Influence of fish skin gelatin-sodium alginate complex stabilized emulsion on benzyl isothiocyanate stability and digestibility in vitro and in vivo.

BACKGROUND: An emulsion delivery system for benzyl isothiocyanate (BITC) was prepared using fish skin gelatin (FSG) and sodium alginate (Alg). The effects of the FSG-Alg complex on the emulsion stability and BITC release pattern from the emulsion were investigated in vitro and in vivo. RESULTS: The storage stability and embedding rate of the 10 g kg-1 FSG and 2.5 g kg-1 Alg (FSG-Alg) emulsion were the highest among all samples. The FSG-Alg complex provided BITC a better protection during in vitro digestion. The microstructure of the FSG-Alg emulsions was more stable during in vitro digestion, and the bioaccessibility and retention rate of BITC were much higher compared to those of the FSG emulsion. The results of the ex vivo everted gut sac of rat intestine study showed that the FSG-Alg emulsion significantly increased the BITC absorption rate in the duodenum. CONCLUSION: The FSG-Alg emulsion delivery system is a highly stable system for the delivery of BITC that improves the bioaccessibility of BITC and promotes its absorption in the duodenum. © 2022 Society of Chemical Industry.

Gastrointestinal fate of food allergens and its relationship with allergenicity.

Food allergens are closely related to their gastrointestinal digestion fate, but the changes in food allergens during digestion and related mechanisms are quite complicated. This review presents in detail digestion models for predicting allergenicity, the fates of food allergens in oral, gastric and duodenal digestion, and the applications of digestomics in mapping IgE-binding epitopes of digestion-resistant peptides. Moreover, this review highlights the structure-activity relationships of food allergens during gastrointestinal digestion. Digestion-labile allergens may share common structural characteristics, such as high flexibility, rendering them easier to be hydrolyzed into small fragments with decreased or eliminated allergenicity. In contrast, the presence of disulfide bonds, tightly wound α-helical structures, or hydrophobic domains in food allergens helps them resist gastrointestinal digestion, stabilizing IgE-binding epitopes, thus maintaining their sensitization. In rare cases, digestion leads to increased allergenicity due to exposure of new epitopes. Finally, the action of the food matrix and processing on the digestion and allergenicity of food allergens as well as the underlying mechanisms was overviewed. The food matrix can directly act on the allergen by forming complexes or new epitopes to affect its gastrointestinal digestibility and thereby alter its allergenicity or indirectly affect the allergenicity by competing for enzymatic cleavage or influencing gastrointestinal pH and microbial flora. Several processing techniques attenuate the allergenicity of food proteins by altering their conformation to improve susceptibility to degradation by digestive enzymes. Given the complexity of food components, the food itself rather than a single allergen should be used to obtain more accurate data for allergenicity assessment. PRACTICAL APPLICATION: The review article will help to understand the relationship between food protein digestion and allergenicity, and may provide fundamental information for evaluating and reducing the allergenicity of food proteins.

Characterization of a synergistic antioxidant synthetic peptide from sea cucumber and pine nut.

We compared antioxidant activity of the synthetic peptide Val-Leu-Leu-Tyr-Gln-Asp-His-Cys-His (VLLYQDHCH), sea cucumber peptide Val-Leu-Leu-Tyr (VLLY) and pine seed peptide Gln-Asp-His-Cys-His (QDHCH). The structure-activity relationship was analyzed based on radical scavenging ability and Raman, circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). Based on RP-HPLC, the contents of peptides in simulated gastrointestinal tract and digestive juices in rat intestinal sac were determined, and their absorption stability were explored. These results showed that the DPPH clearance rate of VLLYQDHCH was 45.90% higher than the sum of VLLY and QDHCH at 3 mmol/L. The α-helix, ß-sheet and random coil of VLLYQDHCH increased, ß-turn decreased, and the active hydrogen site shifted. After simulated digestion and absorption, the retention rate of VLLYQDHCH was 80.86 ± 0.88% in simulated stomach and 45.75 ± 0.97% in simulated intestine. There was no significant difference in the absorption rates of the three peptides (P > 0.05). This research provided a new idea for the development of safe and green food-derived animal-plant protein antioxidant peptides.

Superhydrophobic and Antioxidative Film Based on Edible Materials for Food Packaging.

Significant wastage of the food deterioration in the food preserving process and residual liquid in a container has become a major concern for scientists and the whole society. In this study, an edible multifunctional film integrated superhydrophobicity and antioxidant ability is constructed by chitosan, tea polyphenol, carnauba wax material that is food and drug administration (FDA)-approved for food packaging. The formed edible packaging materials that exhibit great antioxidant property and extremely low water-absorbing quality, was thus proven to display excellent fresh beef preservation effect during storage of 14 days. Importantly, the formed edible multifunctional interface was also demonstrated to perform excellent superhydrophobicity due to the carnauba wax and exhibited large contact angles for various liquid foods, which could effectively reduce the liquid residue. Moreover, the formed edible multifunctional packaging materials showed good thermostability and biocompatibility, which has the potential to be applied as a functional packaging material.

The mechanism of pulsed electric field (PEF) targeting location on the spatial conformation of pine nut peptide.

In this study, the pine nut peptides, Lys-Asp-His-Cyc-His (KDHCH), was used as the molecule dynamics (MD) simulations subject, which has been proved that the antioxidant activity was improved after pulse electric field (PEF) treatment and the secondary structure was changed as the circular dichroism (CD) results showed. In the present study, we applied the MD simulation to discover the mechanism of the antioxidant activity improvement. The MD results showed that with the PEF treatment of 15 kV/cm, the oxygen atoms of KDHCH changed a lot, especially the atoms No.32 and No.63, of which the distance difference value was -3.02 nm, compared with the 0 kV/cm PEF treatment. The result showed an approach trend between residues Lys-and His-and the α-C atom of Lys, Cys-and His-all got closer after the PEF treatment, which means the structure became tight after the PEF treatment. However, the results of 45 kV/cm PEF treatment presented more effects on the change of KDHCH. The calculations of oxygen atoms show an approach trend between residues Lys, Asp-and His. The α-C atom of Lys, Cys-and His-all got closer after the PEF treatment, which means the structure became tight after the PEF treatment and proved the results of the calculations of the oxygen atoms. The structures of PEF treated and untreated peptide samples were measured by 1D and 2D nuclear magnetic resonance (NMR) in order to verify the results of the molecular dynamics simulations. The 8.37-8.40 ppm (-NH- in chain) and 8.84-8.88 ppm (-NH- in chain) appeared left shift, while at the 8.45-8.47 ppm (-NH- in chain) occurred a right shift. The 7.82 ppm (-NH- in imidazole ring) on His-shifted left after PEF treatment, which reached 7.84 ppm by the 1D-1H NMR spectroscopy. Moreover, the long-range connectivity between -NHα (8.78 ppm) on 2H-ASP and -CHα (2.72 ppm) on 1H-LYS; -SH (2.50 ppm) on 4H-CYS and -OH (3.53 ppm) on 5H-HIS all appeared in spectra of the PEF treatment sample. This study will also be helpful to further mechanism exploration.

Polyoxometalate-antioxidant peptide assembly materials with NIR-triggered photothermal behaviour and enhanced antibacterial activity.

Herein, a novel photothermal agent based on polyoxometalate clusters and food-borne antioxidant peptides was exploited to overcome the inherent problems of poor photothermal stability of polyoxometalate photothermal materials, which commonly appear in the current stage of development, and the inevitable simultaneous inflammatory responses during the therapeutic process.

Analysis of α-helix unfolding in the pine nut peptide Lys-Cys-His-Lys-Pro induced by pulsed electric field.

BACKGROUND: A variety of analytical techniques were applied to explore the effects of pulsed electric field (PEF) on α-helix structural changes in the novel antioxidant peptide Lys-Cys-His-Lys-Pro (KCHKP, 611.76 Da). RESULTS: The relative α-helix content of the KCHKP peptide was significantly altered from 100% to 89.91 ± 0.97% when the electric pulse frequency was 1800 Hz and the field intensity was 10 kV cm-1 . Moreover, the 1,1-diphenyl-2-pycryl-hydrazyl (DPPH) and 2,2-azinobis diammonium salt (ABTS) radical-scavenging activities of PEF-treated KCHKP were increased from 56.31% ± 0.74% to 84.33% ± 1.23% and from 40.56% ± 0.78% to 51.33% ± 0.27%, respectively. CONCLUSION: PEF treatment increased peptide linkage stretch vibration and altered hydrogen bonding of KCHKP. The stability of the α-helix structure was influenced by hydrogen bonds within the peptide linkage of KCHKP induced by PEF and was related to changes in antioxidant activity. © 2017 Society of Chemical Industry.

In vitro antioxidant activities of the novel pentapeptides Ser-His-Glu-Cys-Asn and Leu-Pro-Phe-Ala-Met and the relationship between activity and peptide secondary structure.

BACKGROUND: Using high-performance liquid chromatography/tandem mass spectrometry, two novel antioxidant pentapeptides [Ser-His-Glu-Cys-Asn (SHECN) and Leu-Pro-Phe-Ala-Met (LPFAM)] were identified from 1-3-kDa soybean protein hydrolysates (SPH). The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was used to evaluate cytotoxicity in HepG2 cells. Antioxidant activity was measured using in vitro assays, including the cellular antioxidant activity assay (CAA), 2,2-diphenyl-1-picrylhydrazyl or 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) inhibition, and oxygen radical absorbance capacity (ORAC) assays. Finally, the secondary structure was determined using circular dichroism (CD). RESULTS: The results revealed that two novel peptides were nontoxic and possessed antioxidant activity. SHECN had significantly higher antioxidant activity than LPFAM (P < 0.05). The CAA value of SHECN was 776.22 µmol QE 100 g-1 . SHECN also showed significant DPPH inhibition (70.18 ± 4.06%) and ABTS inhibition (88.16 ± 0.76%). It had normalized ORAC values of 0.3000 ± 0.0070 µmol GE mg-1 and 0.0900 ± 0.0020 µmol TE mg-1 , respectively. The results of the CD analysis demonstrated that, compared to LPFAM, which had much lower antioxidant activity, SHECN had a high ß-sheet content and reduced α-helix content. CONCLUSION: The results indicated that SHECN possessed high antioxidant activity. A higher ß-sheet content and lower content levels of α-helix appear to be correlated with antioxidant activity. © 2016 Society of Chemical Industry.

Effects on functional groups and zeta potential of SAP1<MW<3kDa treated by pulsed electric field technology.

BACKGROUND: SAP1

Water dynamics of Ser-His-Glu-Cys-Asn powder and effects of moisture absorption on its chemical properties.

BACKGROUND: This study has elucidated moisture dynamics in the soybean peptide, Ser-His-Glu-Cys-Asn (SHECN) powder by using dynamic vapor sorption (DVS) and nuclear magnetic resonance (NMR). We also tried to investigate the effects of moisture absorption on the biological activity and chemical properties of SHECN with some effective methods such as mid-infrared (MIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). RESULTS: DVS results showed that the moisture absorption of SHECN could reach a maximum of 33%, and the SHECN powder after synthesis actually existed in a trihydrate state of SHECN.3H2 O. Low-field NMR revealed that three water proportions including strong combined water, binding water and bulk water were involved in SHECN moisture absorption and absored water dominantly existed in the form of combined water. Magnetic resonance imaging (MRI) and MIR spectroscopy results indicated that moisture absorption could change the morphology and structure of SHECN. After moisture absorption at 50% and 75% relative humidity, 19 volatiles were identified by GC-MS analysis. Additionally, this study showed that a part of reductive groups in SHECN was oxidized and its antioxidant ability declined significantly (P < 0.05) after moisture absorption. CONCLUSION: Water absorbed into SHECN powder can significantly change its microstructure and cause its activity to decrease. We must prevent SHECN from absorbing moisture during storage because the water can accelerate the oxidation of samples and promote microbial reactions. © 2016 Society of Chemical Industry.

Characterization of sea cucumber (stichopus japonicus) ovum hydrolysates: calcium chelation, solubility and absorption into intestinal epithelial cells.

BACKGROUND: Sea cucumber (Stichopus japonicus) ovum hydrolysates (SCOHs) chelated with calcium were produced to investigate the characteristics of calcium binding and solubility, as well as to study any effects on calcium absorption by human intestinal epithelial cells. RESULTS: The results of the present study show that the calcium-binding capacity of SCOHs depended greatly on the type of proteases. The maximum level of Ca binding (0.38 mmol L-1 ) occurred when trypsin was used, with a peptide yield of 85.7%. Investigation of the possible chelating modes between SCOHs and calcium ions indicated that calcium ions bound to SCOHs primarily via interactions with carboxyl oxygen and amino nitrogen atoms of Glu and Asp and also that the phosphoserine residues might be also responsible for SCOH-calcium chelation. Moreover, SCOH-calcium complexes maintained the solubility of calcium under simulated gastrointestinal digestion, regardless of the presence of dietary components such as oxalate. Furthermore, SCOH-Ca led to higher peak intracellular [Ca2+ ]i in both Caco-2 cells (338.3 nmol L-1 versus 269.6 nmol L-1 ) and HT-29 cells (373.9 nmol L-1 versus 271.7 nmol L-1 ) than casein phosphopeptide-Ca. CONCLUSION: Carboxyl oxygen and amino nitrogen atoms in the SCOHs could bind calcium ions, forming SCOH-calcium complexes. These complexes improved calcium solubility under simulated gastrointestinal digestion and also promoted calcium absorption in Caco-2 and HT-29 cells. © 2017 Society of Chemical Industry.

Analysis of DPPH inhibition and structure change of corn peptides treated by pulsed electric field technology.

In this study, the effects on antioxidant activity and structure change of corn peptides (CPS) with 10 to 30 kDa molecular weight (MW) treated by pulsed electric field (PEF) technology were investigated. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) inhibition was used to evaluate the antioxidant activity of CPS. Response surface methodology (RSM) was used to investigate the effects of PEF treatment parameters on antioxidant activity of CPS. The optimal conditions were as follows: concentration of CPS 10 mg mL(-1), electric field intensity 15 kV cm(-1), and pulse frequency 2,000 Hz. Under the optimized conditions, the DPPH inhibition of CPS increased 32.1 %, compared to the sample untreated. And mid-infrared spectroscopy (MIR) was used for analyzing the structure change of CPS. The results showed that PEF technology could obviously increase the DPPH inhibition of CPS under the optimized conditions (P < 0.05).

Marrow mesenchymal stromal cells reduce methicillin-resistant Staphylococcus aureus infection in rat models.

BACKGROUND AIMS: Staphylococci account for a large proportion of hospital-acquired infections, especially among patients with indwelling devices. These infections are often caused by biofilm-producing strains, which are difficult to eradicate and may eventually cause bacteremia and metastatic infections. Recent evidence suggests that mesenchymal stem cells can enhance bacterial clearance in vivo. METHODS: In this study, a rat model with carboxymethyl cellulose pouch infection was used to analyze the efficacy of bone marrow-derived mesenchymal stromal cells (BMSCs) against the methicillin-resistant Staphylococcus aureus. RESULTS: The results showed that the administration of BMSCs effectively reduced the number of bacterial colonies and the expression of many cytokines and chemokines (such as interleukin [IL]-6, IL-1ß, IL-10 and CCL5). Unlike the fibroblast control groups, the pouch tissues from the BMSC-treated rats showed the formation of granulations, suggesting that the healing of the wound was in progress. CONCLUSIONS: The results indicate that the treatment of BMSCs can reduce methicillin-resistant S aureus infection in vivo, thereby reducing the inflammatory response.