Blood group A enhances SARS-CoV-2 infection.

Among the risk factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), ABO(H) blood group antigens are among the most recognized predictors of infection. However, the mechanisms by which ABO(H) antigens influence susceptibility to COVID-19 remain incompletely understood. The receptor-binding domain (RBD) of SARS-CoV-2, which facilitates host cell engagement, bears significant similarity to galectins, an ancient family of carbohydrate-binding proteins. Because ABO(H) blood group antigens are carbohydrates, we compared the glycan-binding specificity of SARS-CoV-2 RBD with that of galectins. Similar to the binding profile of several galectins, the RBDs of SARS-CoV-2, including Delta and Omicron variants, exhibited specificity for blood group A. Not only did each RBD recognize blood group A in a glycan array format, but each SARS-CoV-2 virus also displayed a preferential ability to infect blood group A-expressing cells. Preincubation of blood group A cells with a blood group-binding galectin specifically inhibited the blood group A enhancement of SARS-CoV-2 infection, whereas similar incubation with a galectin that does not recognize blood group antigens failed to impact SARS-CoV-2 infection. These results demonstrated that SARS-CoV-2 can engage blood group A, providing a direct link between ABO(H) blood group expression and SARS-CoV-2 infection.

Patients taking benralizumab, dupilumab, or mepolizumab have lower postvaccination SARS-CoV-2 immunity.

BACKGROUND: Biologic therapies inhibiting the IL-4 or IL-5 pathways are very effective in the treatment of asthma and other related conditions. However, the cytokines IL-4 and IL-5 also play a role in the generation of adaptive immune responses. Although these biologics do not cause overt immunosuppression, their effect in primary severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunization has not been studied completely. OBJECTIVE: Our aim was to evaluate the antibody and cellular immunity after SARS-CoV-2 mRNA vaccination in patients on biologics (PoBs). METHODS: Patients with severe asthma or atopic dermatitis who were taking benralizumab, dupilumab, or mepolizumab and had received the initial dose of the 2-dose adult SARS-CoV-2 mRNA vaccine were enrolled in a prospective, observational study. As our control group, we used a cohort of immunologically healthy subjects (with no significant immunosuppression) who were not taking biologics (NBs). We used a multiplexed immunoassay to measure antibody levels, neutralization assays to assess antibody function, and flow cytometry to quantitate Spike-specific lymphocytes. RESULTS: We analyzed blood from 57 patients in the PoB group and 46 control subjects from the NB group. The patients in the PoB group had lower levels of SARS-CoV-2 antibodies, pseudovirus neutralization, live virus neutralization, and frequencies of Spike-specific B and CD8 T cells at 6 months after vaccination. In subgroup analyses, patients with asthma who were taking biologics had significantly lower pseudovirus neutralization than did subjects with asthma who were not taking biologics. CONCLUSION: The patients in the PoB group had reduced SARS-CoV-2-specific antibody titers, neutralizing activity, and virus-specific B- and CD8 T-cell counts. These results have implications when considering development of a more individualized immunization strategy in patients who receive biologic medications blocking IL-4 or IL-5 pathways.

Enhanced IgG immune response to COVID-19 vaccination in patients with sickle cell disease.

Patients with sickle cell disease (SCD) are considered to be immunocompromised, yet data on the antibody response to SARS-CoV-2 vaccination in SCD is limited. We investigated anti-SARS-CoV-2 IgG titres and overall neutralizing activity in 201 adults with SCD and demographically matched non-SCD controls. Unexpectedly, patients with SCD generate a more robust and durable COVID-19 vaccine IgG response compared to matched controls, though the neutralizing activity remained similar across both cohorts. These findings suggest that patients with SCD achieve a similar antibody response following COVID-19 vaccination compared to the general population, with implications for optimal vaccination strategies for patients with SCD.

Characterization of the inflammatory response to COVID-19 illness in pregnancy.

OBJECTIVE: Pregnant patients face greater morbidity and mortality from COVID-19 related illness than their non-pregnant peers. Previous research in non-pregnant patients established that poor clinical outcomes in SARS-CoV-2 positive patients admitted to the ICU were correlated with a significant increase in the proinflammatory markers interleukin (IL)-1ß, IL-6, IL-8, and IL-10. Importantly, high levels of these inflammatory markers have also been associated with adverse pregnancy outcomes, including spontaneous preterm birth, preeclampsia, and severe respiratory disease. STUDY DESIGN: This was a retrospective cohort study that compared the serum inflammatory cytokine profiles of pregnant patients with acute/post-acute SARS-CoV-2 infection to those with previous exposure. All subjects in both cohorts tested positive for SARS-CoV-2 antibodies; however, those in the acute/post-acute infection cohort had a documented positive SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) result within 30 days of serum sample collection. Serum samples were obtained during prenatal venipuncture from 13 to 39 weeks' gestation and the cohorts were matched by gestational age. The inflammatory cytokines interferon (IFN)-γ, IL-10, IL-1ß, IL-4, IL-6, IL-8, and tumor necrosis factor (TNF)-α were assayed from maternal serum using a standard ELISA assay and median cytokine concentrations were compared using the Mann-Whitney test. RESULTS AND DISCUSSION: We enrolled 50 non-Hispanic Black patients with confirmed COVID-19 infection who received prenatal care at Grady Memorial Hospital in Atlanta, Georgia. Those with acute/post-acute infection (n = 22) had significantly higher concentrations of SARS-CoV-2 antibody, IL-10, IL-1ß, and IL-8, while patients with previous exposure (n = 28) had significantly higher concentrations of IL-4. There were no significant inter-group differences in medical comorbidities. Pregnant patients with acute/post-acute SARS-CoV-2 infection had significantly higher serum concentrations of pro-inflammatory cytokines as compared to those with previous exposure, suggesting that, like in the non-pregnant population, SARS-CoV-2 infection alters the levels of circulating proinflammatory markers during pregnancy. The increased levels of cytokines may contribute to the adverse obstetric outcomes observed with COVID-19 illness.

Preimmune Recognition and Response to Microbial Metabolites.

It is now well understood that the eukaryotic host has evolved multiple mechanisms to monitor and respond to the diverse and biochemically active microbiota that thrives in a symbiotic fashion in the gut and other tissues. Generally, these mechanisms are based on traditional notions of innate and adaptive immune processes, which are mediated by recognition of, and response to, microbially derived macromolecules. Microbes themselves are metabolically active and contribute a vast array of small molecules, not present in germ-free model systems, with diverse putative and unknown biological function, and intensive work is ongoing to unravel their roles in physiological systems. Metazoans have evolved and maintain distinct gene regulatory networks to detect and respond to environmental, non-self-molecules (xenobiotics), and interestingly, recent investigation has shown that these pathways are operational in the detection and response to microbiota-derived small metabolites. These processes likely represent a general mechanism of host-microbe crosstalk, and they have clinical implications in drug and xenobiotic metabolism.

Commensal microbiota-induced redox signaling activates proliferative signals in the intestinal stem cell microenvironment.

A distinct taxon of the Drosophila microbiota, Lactobacillus plantarum, is capable of stimulating the generation of reactive oxygen species (ROS) within cells, and inducing epithelial cell proliferation. Here, we show that microbial-induced ROS generation within Drosophila larval stem cell compartments exhibits a distinct spatial distribution. Lactobacilli-induced ROS is strictly excluded from defined midgut compartments that harbor adult midgut progenitor (AMP) cells, forming a functional 'ROS sheltered zone' (RSZ). The RSZ is undiscernible in germ-free larvae, but forms following monocolonization with L. plantarumL. plantarum is a strong activator of the ROS-sensitive CncC/Nrf2 signaling pathway within enterocytes. Enterocyte-specific activation of CncC stimulated the proliferation of AMPs, which demonstrates that pro-proliferative signals are transduced from enterocytes to AMPs. Mechanistically, we show that the cytokine Upd2 is expressed in the gut following L. plantarum colonization in a CncC-dependent fashion, and may function in lactobacilli-induced AMP proliferation and intestinal tissue growth and development.

Are We Forgetting About IgA? A Re-examination of Coronavirus Disease 2019 Convalescent Plasma.

BACKGROUND: While convalescent plasma (CP) may benefit patients with COVID-19, fundamental questions remain regarding its efficacy, including the components of CP that may contribute to its therapeutic effect. Most current serological evaluation of CP relies on examination of total immunoglobulin or IgG-specific anti-SARS-CoV-2 antibody levels. However, IgA antibodies, which also circulate and are secreted along the respiratory mucosa, represent a relatively uncharacterized component of CP. STUDY DESIGN AND METHODS: Residual samples from patients and CP donors were assessed for IgM, IgG, and IgA anti-SARS-CoV-2 antibody titers against the receptor-binding domain responsible for viral entry. Symptom onset was obtained by chart review. RESULTS: Increased IgA anti-SARS-CoV-2 antibody levels correlated with clinical improvement and viral clearance in an infant with COVID-19, prompting a broader examination of IgA levels among CP donors and hospitalized patients. Significant heterogeneity in IgA levels was observed among CP donors, which correlated weakly with IgG levels or the results of a commonly employed serological test. Unlike IgG and IgM, IgA levels were also more likely to be variable in hospitalized patients and this variability persisted in some patients >14 days following symptom onset. IgA levels were also less likely to be sustained than IgG levels following subsequent CP donation. CONCLUSIONS: IgA levels can be very heterogenous among CP donors and hospitalized patients and do not necessarily correlate with commonly employed testing platforms. Examining isotype levels in CP and COVID-19 patients may allow for a tailored approach when seeking to fill specific gaps in humoral immunity.

Interactions Between Commensal Bacteria and Enteric Neurons, via FPR1 Induction of ROS, Increase Gastrointestinal Motility in Mice.

BACKGROUND & AIMS: Reduced gastrointestinal (GI) motility is a feature of disorders associated with intestinal dysbiosis and loss of beneficial microbes. It is not clear how consumption of beneficial commensal microbes, marketed as probiotics, affects the enteric nervous system (ENS). We studied the effects of the widely used probiotic and the commensal Lactobacillus rhamnosus GG (LGG) on ENS and GI motility in mice. METHODS: Conventional and germ free C57B6 mice were gavaged with LGG and intestinal tissues were collected; changes in the enteric neuronal subtypes were assessed by real-time polymerase chain reaction, immunoblots, and immunostaining. Production of reactive oxygen species (ROS) in the jejunal myenteric plexi and phosphorylation (p) of mitogen-activated protein kinase 1 (MAPK1) in the enteric ganglia were assessed by immunoblots and immunostaining. Fluorescence in situ hybridization was performed on jejunal cryosections with probes to detect formyl peptide receptor 1 (FPR1). GI motility in conventional mice was assessed after daily gavage of LGG for 1 week. RESULTS: Feeding of LGG to mice stimulated myenteric production of ROS, increased levels of phosphorylated MAPK1, and increased expression of choline acetyl transferase by neurons (P < .001). These effects were not observed in mice given N-acetyl cysteine (a ROS inhibitor) or LGGΩSpaC (an adhesion-mutant strain of LGG) or FPR1-knockout mice. Gavage of mice with LGG for 1 week significantly increased stool frequency, reduced total GI transit time, and increased contractions of ileal circular muscle strips in ex vivo experiments (P < .05). CONCLUSIONS: Using mouse models, we found that LGG-mediated signaling in the ENS requires bacterial adhesion, redox mechanisms, and FPR1. This pathway might be activated to increase GI motility in patients.

Neutrophil-Derived Reactive Oxygen Orchestrates Epithelial Cell Signaling Events during Intestinal Repair.

Recent evidence has demonstrated that reactive oxygen (eg, hydrogen peroxide) can activate host cell signaling pathways that function in repair. We show that mice deficient in their capacity to generate reactive oxygen by the NADPH oxidase 2 holoenzyme, an enzyme complex highly expressed in neutrophils and macrophages, have disrupted capacity to orchestrate signaling events that function in mucosal repair. Similar observations were made for mice after neutrophil depletion, pinpointing this cell type as the source of the reactive oxygen driving oxidation-reduction protein signaling in the epithelium. To simulate epithelial exposure to high levels of reactive oxygen produced by neutrophils and gain new insight into this oxidation-reduction signaling, epithelial cells were treated with hydrogen peroxide, biochemical experiments were conducted, and a proteome-wide screen was performed using isotope-coded affinity tags to detect proteins oxidized after exposure. This analysis implicated signaling pathways regulating focal adhesions, cell junctions, and maintenance of the cytoskeleton. These pathways are also known to act via coordinated phosphorylation events within proteins that constitute the focal adhesion complex, including focal adhesion kinase and Crk-associated substrate. We identified the Rho family small GTP-binding protein Ras-related C3 botulinum toxin substrate 1 and p21 activated kinases 2 as operational in these signaling and localization pathways. These data support the hypothesis that reactive oxygen species from neutrophils can orchestrate epithelial cell-signaling events functioning in intestinal repair.

Formyl peptide receptor 2 regulates monocyte recruitment to promote intestinal mucosal wound repair.

Mucosal wound repair is coordinated by dynamic crosstalk between endogenous and exogenous mediators and specific receptors on epithelial cells and infiltrating immune cells. One class of such receptor-ligand pairs involves formyl peptide receptors (FPRs) that have been shown to influence inflammatory response and repair. Here we explored the role of murine Fpr2/3, an ortholog of human FPR2/receptor for lipoxin A4 (ALX), in orchestrating intestinal mucosal repair. Compared with wild-type (WT) mice, Fpr2/3-/- mice exhibited delayed recovery from acute experimental colitis and perturbed repair after biopsy-induced colonic mucosal injury. Decreased numbers of infiltrating monocytes were observed in healing wounds from Fpr2/3-/- mice compared with WT animals. Bone marrow transplant experiments revealed that Fpr2/3-/- monocytes showed a competitive disadvantage when infiltrating colonic wounds. Moreover, Fpr2/3-/- monocytes were defective in chemotactic responses to the chemokine CC chemokine ligand (CCL)20, which is up-regulated during early phases of inflammation. Analysis of Fpr2/3-/- monocytes revealed altered expression of the CCL20 receptor CC chemokine receptor (CCR)6, suggesting that Fpr2/3 regulates CCL20-CCR6-mediated monocyte chemotaxis to sites of mucosal injury in the gut. These findings demonstrate an important contribution of Fpr2/3 in facilitating monocyte recruitment to sites of mucosal injury to influence wound repair.-Birkl, D., O'Leary, M. N., Quiros, M., Azcutia, V., Schaller, M., Reed, M., Nishio, H., Keeney, J., Neish, A. S., Lukacs, N. W., Parkos, C. A., Nusrat, A. Formyl peptide receptor 2 regulates monocyte recruitment to promote intestinal mucosal wound repair.

Daratumumab in multiple myeloma.

The development of effective monoclonal antibodies for the treatment of myeloma has been a long journey of clinical and drug development. Identification of the right target antigen was a critical part of the process. CD38 as a target has been considered for some time, but clinically, daratumumab, a CD38 monoclonal antibody, was the first to be tested, and it has delivered the best clinical responses as a single agent to date. Its proven safety and efficacy in combination with other antimyeloma agents have led to several US Food and Drug Administration approvals for treating myeloma. Furthermore, the results of early trials in the induction therapy setting have demonstrated a beneficial role when it is added to the existing induction regimens. This review summarizes the importance of CD38 as a target and examines the clinical development of the CD38 monoclonal antibody daratumumab and its clinical significance in combination regimens in both patients with relapsed/refractory myeloma and patients with newly diagnosed myeloma.

Serum Amyloid A1 Is an Epithelial Prorestitutive Factor.

Several proteins endogenously produced during the process of intestinal wound healing have demonstrated prorestitutive properties. The presence of serum amyloid A1 (SAA1), an acute-phase reactant, within inflamed tissues, where it exerts chemotaxis of phagocytes, is well recognized; however, a putative role in intestinal wound repair has not been described. Herein, we show that SAA1 induces intestinal epithelial cell migration, spreading, and attachment through a formyl peptide receptor 2-dependent mechanism. Induction of the prorestitutive phenotype is concentration and time dependent and is associated with epithelial reactive oxygen species production and alterations in p130 Crk-associated substrate staining. In addition, using a murine model of wound recovery, we provide evidence that SAA1 is dynamically and temporally regulated, and that the elaboration of SAA1 within the wound microenvironment correlates with the influx of SAA1/CD11b coexpressing immune cells and increases in cytokines known to induce SAA expression. Overall, the present work demonstrates an important role for SAA in epithelial wound recovery and provides evidence for a physiological role in the wound environment.

Anemia induces gut inflammation and injury in an animal model of preterm infants.

BACKGROUND: While very low birth weight (VLBW) infants often require multiple red blood cell transfusions, efforts to minimize transfusion-associated risks have resulted in more restrictive neonatal transfusion practices. However, whether restrictive transfusion strategies limit transfusions without increasing morbidity and mortality in this population remains unclear. Recent epidemiologic studies suggest that severe anemia may be an important risk factor for the development of necrotizing enterocolitis (NEC). However, the mechanism whereby anemia may lead to NEC remains unknown. STUDY DESIGN AND METHODS: The potential impact of anemia on neonatal inflammation and intestinal barrier disruption, two well-characterized predisposing features of NEC, was defined by correlation of hemoglobin values to cytokine levels in premature infants and by direct evaluation of intestinal hypoxia, inflammation and gut barrier disruption using a pre-clinical neonatal murine model of phlebotomy-induced anemia (PIA). RESULTS: Increasing severity of anemia in the preterm infant correlated with the level of IFN-gamma, a key pro-inflammatory cytokine that may predispose an infant to NEC. Gradual induction of PIA in a pre-clinical model resulted in significant hypoxia throughout the intestinal mucosa, including areas where intestinal macrophages reside. PIA-induced hypoxia significantly increased macrophage pro-inflammatory cytokine levels, while reducing tight junction protein ZO-1 expression and increasing intestinal barrier permeability. Macrophage depletion reversed the impact of anemia on intestinal ZO-1 expression and barrier function. CONCLUSIONS: Taken together, these results suggest that anemia can increase intestinal inflammation and barrier disruption likely through altered macrophage function, leading to the type of predisposing intestinal injury that may increase the risk for NEC.

Cosmc is an X-linked inflammatory bowel disease risk gene that spatially regulates gut microbiota and contributes to sex-specific risk.

Inflammatory bowel disease (IBD) results from aberrant immune stimulation against a dysbiotic mucosal but relatively preserved luminal microbiota and preferentially affects males in early onset disease. However, factors contributing to sex-specific risk and the pattern of dysbiosis are largely unexplored. Core 1 ß3GalT-specific molecular chaperone (Cosmc), which encodes an X-linked chaperone important for glycocalyx formation, was recently identified as an IBD risk factor by genome-wide association study. We deleted Cosmc in mouse intestinal epithelial cells (IECs) and found marked reduction of microbiota diversity in progression from the proximal to the distal gut mucosa, but not in the overlying lumen, as seen in IBD. This loss of diversity coincided with local emergence of a proinflammatory pathobiont and distal gut restricted pathology. Mechanistically, we found that Cosmc regulates host genes, bacterial ligands, and nutrient availability to control microbiota biogeography. Loss of one Cosmc allele in males (IEC-Cosmc-/y) resulted in a compromised mucus layer, spontaneous microbe-dependent inflammation, and enhanced experimental colitis; however, females with loss of one allele and mosaic deletion of Cosmc in 50% of crypts (IEC-Cosmc+/-) were protected from spontaneous inflammation and partially protected from experimental colitis, likely due to lateral migration of normal mucin glycocalyx from WT cells over KO crypts. These studies functionally validate Cosmc as an IBD risk factor and implicate it in regulating the spatial pattern of dysbiosis and sex bias in IBD.

Symbiotic lactobacilli stimulate gut epithelial proliferation via Nox-mediated generation of reactive oxygen species.

The resident prokaryotic microbiota of the metazoan gut elicits profound effects on the growth and development of the intestine. However, the molecular mechanisms of symbiotic prokaryotic-eukaryotic cross-talk in the gut are largely unknown. It is increasingly recognized that physiologically generated reactive oxygen species (ROS) function as signalling secondary messengers that influence cellular proliferation and differentiation in a variety of biological systems. Here, we report that commensal bacteria, particularly members of the genus Lactobacillus, can stimulate NADPH oxidase 1 (Nox1)-dependent ROS generation and consequent cellular proliferation in intestinal stem cells upon initial ingestion into the murine or Drosophila intestine. Our data identify and highlight a highly conserved mechanism that symbiotic microorganisms utilize in eukaryotic growth and development. Additionally, the work suggests that specific redox-mediated functions may be assigned to specific bacterial taxa and may contribute to the identification of microbes with probiotic potential.

Loss of Junctional Adhesion Molecule A Promotes Severe Steatohepatitis in Mice on a Diet High in Saturated Fat, Fructose, and Cholesterol.

BACKGROUND & AIMS: There is evidence from clinical studies that compromised intestinal epithelial permeability contributes to the development of nonalcoholic steatohepatitis (NASH), but the exact mechanisms are not clear. Mice with disruption of the gene (F11r) encoding junctional adhesion molecule A (JAM-A) have defects in intestinal epithelial permeability. We used these mice to study how disruption of the intestinal epithelial barrier contributes to NASH. METHODS: Male C57BL/6 (control) or F11r(-/-) mice were fed a normal diet or a diet high in saturated fat, fructose, and cholesterol (HFCD) for 8 weeks. Liver and intestinal tissues were collected and analyzed by histology, quantitative reverse-transcription polymerase chain reaction, and flow cytometry. Intestinal epithelial permeability was assessed in mice by measuring permeability to fluorescently labeled dextran. The intestinal microbiota were analyzed using 16S ribosomal RNA sequencing. We also analyzed biopsy specimens from proximal colons of 30 patients with nonalcoholic fatty liver disease (NAFLD) and 19 subjects without NAFLD (controls) undergoing surveillance colonoscopy. RESULTS: F11r(-/-) mice fed a HFCD, but not a normal diet, developed histologic and pathologic features of severe NASH including steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis, whereas control mice fed a HFCD developed only modest steatosis. Interestingly, there were no differences in body weight, ratio of liver weight:body weight, or glucose homeostasis between control and F11r(-/-) mice fed a HFCD. In these mice, liver injury was associated with significant increases in mucosal inflammation, tight junction disruption, and intestinal epithelial permeability to bacterial endotoxins, compared with control mice or F11r(-/-) mice fed a normal diet. The HFCD led to a significant increase in inflammatory microbial taxa in F11r(-/-) mice, compared with control mice. Administration of oral antibiotics or sequestration of bacterial endotoxins with sevelamer hydrochloride reduced mucosal inflammation and restored normal liver histology in F11r(-/-) mice fed a HFCD. Protein and transcript levels of JAM-A were significantly lower in the intestinal mucosa of patients with NAFLD than without NAFLD; decreased expression of JAM-A correlated with increased mucosal inflammation. CONCLUSIONS: Mice with defects in intestinal epithelial permeability develop more severe steatohepatitis after a HFCD than control mice, and colon tissues from patients with NAFLD have lower levels of JAM-A and higher levels of inflammation than subjects without NAFLD. These findings indicate that intestinal epithelial barrier function and microbial dysbiosis contribute to the development of NASH. Restoration of intestinal barrier integrity and manipulation of gut microbiota might be developed as therapeutic strategies for patients with NASH.

Timing of developmental reduction in epithelial glutathione redox potential is associated with increased epithelial proliferation in the immature murine intestine.

BackgroundThe intracellular redox potential of the glutathione (GSH)/glutathione disulfide (GSSG) couple regulates cellular processes. In vitro studies indicate that a reduced GSH/GSSG redox potential favors proliferation, whereas a more oxidized redox potential favors differentiation. Intestinal growth depends upon an appropriate balance between the two. However, how the ontogeny of intestinal epithelial cellular (IEC) GSH/GSSG redox regulates these processes in the developing intestine has not been fully characterized in vivo.MethodsOntogeny of intestinal GSH redox potential and growth were measured in neonatal mice.ResultsWe show that IEC GSH/GSSG redox potential becomes increasingly reduced (primarily driven by increased GSH concentration) over the first 3 weeks of life. Increased intracellular GSH has been shown to drive proliferation through increased poly-ADP-ribose polymerase (PARP) activity. We show that increasing IEC poly-ADP-ribose chains can be measured over the first 3 weeks of life, indicating an increase in IEC PARP activity. These changes are accompanied by increased intestinal growth and IEC proliferation as assessed by villus height/crypt depth, intestinal length, and Ki67 staining.ConclusionUnderstanding how IEC GSH/GSSG redox potential is developmentally regulated may provide insight into how premature human intestinal redox states can be manipulated to optimize intestinal growth and adaptation.

Redox control of Cas phosphorylation requires Abl kinase in regulation of intestinal epithelial cell spreading and migration.

Intestinal wounds often occur during inflammatory and ischemic disorders of the gut. To repair damage, intestinal epithelial cells must rapidly spread and migrate to cover exposed lamina propria, events that involve redox signaling. Wounds are subject to extensive redox alterations, particularly resulting from H2O2 produced in the adjacent tissue by both the epithelium and emigrating leukocytes. The mechanisms governing these processes are not fully understood, particularly at the level of protein signaling. Crk-associated substrate, or Cas, is an important signaling protein known to modulate focal adhesion and actin cytoskeletal dynamics, whose association with Crk is regulated by Abl kinase, a ubiquitously expressed tyrosine kinase. We sought to evaluate the role of Abl regulation of Cas at the level of cell spreading and migration during wound closure. As a model, we used intestinal epithelial cells exposed to H2O2 or scratch wounded to assess the Abl-Cas signaling pathway. We characterized the localization of phosphorylated Cas in mouse colonic epithelium under baseline conditions and after biopsy wounding the mucosa. Analysis of actin and focal adhesion dynamics by microscopy or biochemical analysis after manipulating Abl kinase revealed that Abl controls redox-dependent Cas phosphorylation and localization to influence cell spreading and migration. Collectively, our data shed new light on redox-sensitive protein signaling modules controlling intestinal wound healing.

Wild-type and mutant AvrA- Salmonella induce broadly similar immune pathways in the chicken ceca with key differences in signaling intermediates and inflammation.

Salmonella enterica serovar Typhimurium (ST) is a serious infectious disease throughout the world, and a major reservoir for Salmonella is chicken. Chicken infected with Salmonella do not develop clinical disease, this may be the result of important host interactions with key virulence proteins. To study this, we inoculated chicken with mutant Salmonella Typhimurium that lacked the virulence protein AvrA (AvrA(-)). AvrA is referred to as an avirulence factor, as it moderates the host immune response. The lack of the AvrA virulence gene in ST resulted in reduced weight gain, enhanced persistence and greater extraintestinal organ invasion in chickens, as compared to wild-type (WT) ST. Kinome analysis was performed on inoculated cecal tissue. The majority of the signal transduction pathways induced by AvrA(-) and WT ST were similar; however, we observed alterations in innate immune system signaling. In addition, a leukocyte migration pathway was altered by AvrA(-) ST that may allow greater gut barrier permeability and invasion by the mutant. Cytokine expression did not appear significantly altered at 7 d post-inoculation; at 14 d post-inoculation, there was an observed increase in the expression of anti-inflammatory IL-10 in the WT inoculated ceca. This study is the first to describe mutant AvrA(-) ST infection of chicken and provides further insight into the Salmonella responses observed in chicken relative to other species such as humans and cattle.

Epithelial adhesion mediated by pilin SpaC is required for Lactobacillus rhamnosus GG-induced cellular responses.

Lactobacillus rhamnosus GG is a widely used probiotic, and the strain's salutary effects on the intestine have been extensively documented. We previously reported that strain GG can modulate inflammatory signaling, as well as epithelial migration and proliferation, by activating NADPH oxidase 1-catalyzed generation of reactive oxygen species (ROS). However, how strain GG induces these responses is unknown. Here, we report that strain GG's probiotic benefits are dependent on the bacterial-epithelial interaction mediated by the SpaC pilin subunit. By comparing strain GG to an isogenic mutant that lacks SpaC (strain GGΩspaC), we establish that SpaC is necessary for strain GG to adhere to gut mucosa, that SpaC contributes to strain GG-induced epithelial generation of ROS, and that SpaC plays a role in strain GG's capacity to stimulate extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling in enterocytes. In addition, we show that SpaC is required for strain GG-mediated stimulation of cell proliferation and protection against radiologically inflicted intestinal injury. The identification of a critical surface protein required for strain GG to mediate its probiotic influence advances our understanding of the molecular basis for the symbiotic relationship between some commensal bacteria of the gut lumen and enterocytes. Further insights into this relationship are critical for the development of novel approaches to treat intestinal diseases.