Secretory IgA: Designed for Anti-Microbial Defense

Association between salivary s-IgA concentration and dental caries: A systematic review and meta-analysis

OBJECTIVE

To determine the levels of s-IgA in saliva of caries patients and healthy controls, and to evaluate whether there is a correlation between it and caries by systematic review and meta-analysis.

METHODS

 Eight databases were searched initially in April 2020 and repeated in August 2020. Two independent evaluators screened the literature and extracted the data according to the inclusion and exclusion criteria. I2 test was commonly reflected the heterogeneity. Subgroup analysis and meta-regression analysis explore the sources of heterogeneity. Sensitivity analysis, funnel diagram, Begg's rank correlation and Egger's linear regression were used to determine the possibility of publication bias.

RESULTS

A total of 30 case-control studies were included, with a total sample size of 1545 patients, including 918 caries patients and 627 healthy controls. Salivary s-IgA levels in caries patients were significantly lower than those in healthy controls. In addition, the results of subgroup analysis showed that the significant decrease of salivary s-IgA level was correlated with children patients, mixed dentition and Asian people. The funnel diagram included in the study was symmetrically distributed, and the sensitivity analysis confirmed the robustness of the results.  Conclusion: Salivary s-IgA levels in caries patients were significantly lower than in healthy controls. It has also been demonstrated that salivary s-IgA may be used as an alternative measure to identify subjects at risk of caries susceptibility, suggesting that salivary s-IgA may be a protective factor for dental caries.

The Application of Mucoadhesive Chitosan Nanoparticles in Nasal Drug Delivery

Mucosal delivery of antigens can induce both humoral and cellular immune responses. Particularly, the nasal cavity is a strongly inductive site for mucosal immunity among several administration routes, as it is generally the first point of contact for inhaled antigens. However, the delivery of antigens to the nasal cavity has some disadvantages such as rapid clearance and disposition of inhaled materials. For these reasons, remarkable efforts have been made to develop antigen delivery systems which suit the nasal route. The use of nanoparticles as delivery vehicles enables protection of the antigen from degradation and sustains the release of the loaded antigen, eventually resulting in improved vaccine and/or drug efficacy. Chitosan, which exhibits low toxicity, biodegradability, good cost performance, and strong mucoadhesive properties, is a useful material for nanoparticles. The present review provides an overview of the mucosal immune response induced by nanoparticles, recent advances in the use of nanoparticles, and nasal delivery systems with chitosan nanoparticles.

Presence of salivary IgA anti-citrullinated protein antibodies associate with higher disease activity in patients with rheumatoid arthritis

Background

Circulating IgA anti-citrullinated protein antibodies (ACPA) associate with more active disease, but a previous study implied that salivary IgA ACPA is related to a less severe disease. Therefore, we aimed to characterize the IgA ACPA response in the saliva and serum in relation to clinical picture and risk factors among patients with rheumatoid arthritis (RA).

Methods

RA patients (n = 196) and healthy blood donors (n = 101), included in the cross-sectional study “Secretory ACPA in Rheumatoid Arthritis” (SARA), were analyzed for ACPA of IgA isotype, and for subclasses IgA1 and IgA2 ACPA in paired saliva and serum samples using modified enzyme-linked immunosorbent assays (ELISA) targeting reactivity to a cyclic citrullinated peptide (anti-CCP). Cutoff levels for positive tests were set at the 99th percentile for blood donors. Antibody levels were related to clinical characteristics, radiographic damage, smoking habits, and carriage of HLA-DRB1/shared epitope (SE).

Results

IgA ACPA in the saliva was found in 12% of RA patients, IgA1 occurred in 10%, and IgA2 in 9%. In serum, IgA ACPA was found in 45% of the patients, IgA1 in 44%, and IgA2 in 39%. Levels of IgA ACPA in the saliva correlated significantly with serum levels of IgA (r = 0.455). The presence of salivary IgA ACPA was associated with a higher erythrocyte sedimentation rate (ESR), 28-joint disease activity score, tender joint count, and patient global assessment at the time of sampling. None of the antibodies was associated with smoking, SE, or radiographic damage.

Conclusion

Salivary IgA ACPAs were detected in a subset of RA patients in association with higher disease activity. This suggests that mucosal ACPA responses in the oral cavity may contribute to disease-promoting processes in RA.

Impact of Diabetes on the Gut and Salivary IgA Microbiomes

Mucosal surfaces like those present in the lung, gut, and mouth interface with distinct external environments. These mucosal gateways are not only portals of entry for potential pathogens but also homes to microbial communities that impact host health. Secretory immunoglobulin A (SIgA) is the single most abundant acquired immune component secreted onto mucosal surfaces and, via the process of immune exclusion, shapes the architecture of these microbiomes. Not all microorganisms at mucosal surfaces are targeted by SIgA; therefore, a better understanding of the SIgA-coated fraction may identify the microbial constituents that stimulate host immune responses in the context of health and disease. Chronic diseases like type 2 diabetes are associated with altered microbial communities (dysbiosis) that in turn affect immune-mediated homeostasis. 16S rRNA gene sequencing of SIgA-coated/uncoated bacteria (IgA-Biome) was conducted on stool and saliva samples of normoglycemic participants and individuals with prediabetes or diabetes (n = 8/group). These analyses demonstrated shifts in relative abundance in the IgA-Biome profiles between normoglycemic, prediabetic, or diabetic samples distinct from that of the overall microbiome. Differences in IgA-Biome alpha diversity were apparent for both stool and saliva, while overarching bacterial community differences (beta diversity) were also observed in saliva. These data suggest that IgA-Biome analyses can be used to identify novel microbial signatures associated with diabetes and support the need for further studies exploring these communities. Ultimately, an understanding of the IgA-Biome may promote the development of novel strategies to restructure the microbiome as a means of preventing or treating diseases associated with dysbiosis at mucosal surfaces.

Pathogenesis-directed therapy of 2019 novel coronavirus disease

The 2019 novel coronavirus disease (COVID-19) now is considered a global public health emergency. One of the unprecedented challenges is defining the optimal therapy for those patients with severe pneumonia and systemic manifestations of COVID-19. The optimal therapy should be largely based on the pathogenesis of infections caused by this novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the onset of COVID-19, there have been many prepublications and publications reviewing the therapy of COVID-19 as well as many prepublications and publications reviewing the pathogenesis of SARS-CoV-2. However, there have been no comprehensive reviews that link COVID-19 therapies to the pathogenic mechanisms of SARS-CoV-2. To link COVID-19 therapies to pathogenic mechanisms of SARS-CoV-2, we performed a comprehensive search through MEDLINE, PubMed, medRxiv, EMBASE, Scopus, Google Scholar, and Web of Science using the following keywords: COVID-19, SARS-CoV-2, novel 2019 coronavirus, pathology, pathologic, pathogenesis, pathophysiology, coronavirus pneumonia, coronavirus infection, coronavirus pulmonary infection, coronavirus cardiovascular infection, coronavirus gastroenteritis, coronavirus autopsy findings, viral sepsis, endotheliitis, thrombosis, coagulation abnormalities, immunology, humeral immunity, cellular immunity, inflammation, cytokine storm, superantigen, therapy, treatment, therapeutics, immune-based therapeutics, antiviral agents, respiratory therapy, oxygen therapy, anticoagulation therapy, adjuvant therapy, and preventative therapy. Opinions expressed in this review also are based on personal experience as clinicians, authors, peer reviewers, and editors. This narrative review linking COVID-19 therapies with pathogenic mechanisms of SARS-CoV-2 has resulted in six major therapeutic goals for COVID-19 therapy based on the pathogenic mechanisms of SARS-CoV-2. These goals are listed below: 1. The first goal is identifying COVID-19 patients that require both testing and therapy. This is best accomplished with a COVID-19 molecular test from symptomatic patients as well as determining the oxygen saturation in such patients with a pulse oximeter. Whether a symptomatic respiratory illness is COVID-19, influenza, or another respiratory pathogen, an oxygen saturation less than 90% means that the patient requires medical assistance. 2. The second goal is to correct the hypoxia. This goal generally requires hospitalization for oxygen therapy; other respiratory-directed therapies such as prone positioning or mechanical ventilation are often used in the attempt to correct hypoxemia due to COVID-19. 3. The third goal is to reduce the viral load of SARS-CoV-2. Ideally, there would be an oral antiviral agent available such as seen with the use of oseltamivir phosphate for influenza. This oral antiviral agent should be taken early in the course of SARS-CoV-2 infection. Such an oral agent is not available yet. Currently, two options are available for reducing the viral load of SARS-CoV-2. These are post-Covid-19 plasma with a high neutralizing antibody titer against SARS-CoV-2 or intravenous remdesivir; both options require hospitalization. 4. The fourth goal is to identify and address the hyperinflammation phase often seen in hospitalized COVID-19 patients. Currently, fever with an elevated C-reactive protein is useful for diagnosing this hyperinflammation syndrome. Low-dose dexamethasone therapy currently is the best therapeutic approach. 5. The fifth goal is to identify and address the hypercoagulability phase seen in many hospitalized COVID-19 patients. Patients who would benefit from anticoagulation therapy can be identified by a marked increase in d-dimer and prothrombin time with a decrease in fibrinogen. To correct this disseminated intravascular coagulation-like phase, anticoagulation therapy with low molecular weight heparin is preferred. Anticoagulation therapy with unfractionated heparin is preferred in COVID-19 patients with acute kidney injuries. 6. The last goal is prophylaxis for persons who are not yet infected. Potential supplements include vitamin D and zinc. Although the data for such supplements is not extremely strong, it can be argued that almost 50% of the population worldwide has a vitamin D deficiency. Correcting this deficiency would be beneficial regardless of any impact of COVID-19. Similarly, zinc is an important supplement that is important in one's diet regardless of any effect on SARS-CoV-2. As emerging therapies are found to be more effective against the SARS-CoV-2 pathogenic mechanisms identified, they can be substituted for those therapies presented in this review.

No Impact of Long-Term Fingolimod Treatment on Fecal Secretory Immunoglobulin A Levels in Patients With Multiple Sclerosis

Background

Fingolimod (FTY) is a sphingosine 1 phosphate (S1P) agonist with significant effects on immune cell distribution used as an effective disease modifying therapy in multiple sclerosis (MS) patients. Animal studies have demonstrated that a dysregulation of egress of murine secretory Immunglobulin A (sIgA)+ plasmablasts from Peyer’s patches in FTY-treated mice reduced fecal sIgA levels. Alterations in intestinal levels of sIgA could modify the gut microbiome and homeostasis in humans. We analyzed the effect of FTY on the fecal and salivary sIgA levels as marker of the humoral immune system in the gut.

Methods

Twenty five people with confirmed MS diagnosis according to 2010 revised McDonald’s criteria and on long-term continuous treatment at the MS Center in Dresden, Germany were enrolled in this exploratory cross-sectional study. Fecal and salivary sIgA were analyzed after at least 12 months of treatment with FTY or Glatiramer acetate (GA).

Results

Fifteen MS patients on FTY and 10 on GA participated in this study. The mean fecal sIgA concentration of both groups was not decreased compared to reference values and did not demonstrate significant differences between them (FTY 3323.13 μg/g +/− 2094.72; GA 2040.65 μg/g +/− 1709.07). A similar pattern was seen in the salivary sIgA and serum immunoglobulins levels.

Conclusion

In this pilot study, we could not confirm the decrease of fecal sIgA after a long-term treatment with FTY. Further longitudinal studies should evaluate the effects of MS treatments on the gut immune system in more detail.

The structures of secretory and dimeric immunoglobulin A

Secretory (S) Immunoglobulin (Ig) A is the predominant mucosal antibody, which binds pathogens and commensal microbes. SIgA is a polymeric antibody, typically containing two copies of IgA that assemble with one joining-chain (JC) to form dimeric (d) IgA that is bound by the polymeric Ig-receptor ectodomain, called secretory component (SC). Here, we report the cryo-electron microscopy structures of murine SIgA and dIgA. Structures reveal two IgAs conjoined through four heavy-chain tailpieces and the JC that together form a β-sandwich-like fold. The two IgAs are bent and tilted with respect to each other, forming distinct concave and convex surfaces. In SIgA, SC is bound to one face, asymmetrically contacting both IgAs and JC. The bent and tilted arrangement of complex components limits the possible positions of both sets of antigen-binding fragments (Fabs) and preserves steric accessibility to receptor-binding sites, likely influencing antigen binding and effector functions.

Mucosal IgA Prevents Commensal Candida albicans Dysbiosis in the Oral Cavity

The fungus Candida albicans colonizes the oral mucosal surface of 30–70% of healthy individuals. Due to local or systemic immunosuppression, this commensal fungus is able to proliferate resulting in oral disease, called oropharyngeal candidiasis (OPC). However, in healthy individuals C. albicans causes no harm. Unlike humans mice do not host C. albicans in their mycobiome. Thus, oral fungal challenge generates an acute immune response in a naive host. Therefore, we utilized C. albicans clinical isolates which are able to persist in the oral cavity without causing disease to analyze adaptive responses to oral fungal commensalism. We performed RNA sequencing to determine the transcriptional host response landscape during C. albicans colonization. Pathway analysis revealed an upregulation of adaptive host responses due to C. albicans oral persistence, including the upregulation of the immune network for IgA production. Fungal colonization increased cross-specific IgA levels in the saliva and the tongue, and IgA⁺ cells migrated to foci of fungal colonization. Binding of IgA prevented fungal epithelial adhesion and invasion resulting in a dampened proinflammatory epithelial response. Besides CD19⁺ CD138⁻ B cells, plasmablasts, and plasma cells were enriched in the tongue of mice colonized with C. albicans suggesting a potential role of B lymphocytes during oral fungal colonization. B cell deficiency increased the oral fungal load without causing severe OPC. Thus, in the oral cavity B lymphocytes contribute to control commensal C. albicans carriage by secreting IgA at foci of colonization thereby preventing fungal dysbiosis.

Structure, Function, and Therapeutic Use of IgM Antibodies

Natural immunoglobulin M (IgM) antibodies are pentameric or hexameric macro-immunoglobulins and have been highly conserved during evolution. IgMs are initially expressed during B cell ontogeny and are the first antibodies secreted following exposure to foreign antigens. The IgM multimer has either 10 (pentamer) or 12 (hexamer) antigen binding domains consisting of paired µ heavy chains with four constant domains, each with a single variable domain, paired with a corresponding light chain. Although the antigen binding affinities of natural IgM antibodies are typically lower than IgG, their polyvalency allows for high avidity binding and efficient engagement of complement to induce complement-dependent cell lysis. The high avidity of IgM antibodies renders them particularly efficient at binding antigens present at low levels, and non-protein antigens, for example, carbohydrates or lipids present on microbial surfaces. Pentameric IgM antibodies also contain a joining (J) chain that stabilizes the pentameric structure and enables binding to several receptors. One such receptor, the polymeric immunoglobulin receptor (pIgR), is responsible for transcytosis from the vasculature to the mucosal surfaces of the lung and gastrointestinal tract. Several naturally occurring IgM antibodies have been explored as therapeutics in clinical trials, and a new class of molecules, engineered IgM antibodies with enhanced binding and/or additional functional properties are being evaluated in humans. Here, we review the considerable progress that has been made regarding the understanding of biology, structure, function, manufacturing, and therapeutic potential of IgM antibodies since their discovery more than 80 years ago.

IgA as a potential candidate for enteric monoclonal antibody therapeutics with improved gastrointestinal stability

Mucosal surfaces of the gastrointestinal tract play an important role in immune homeostasis and defense and may be compromised by enteric disorders or infection. Therapeutic intervention using monoclonal antibody (mAb) offers the potential for treatment with minimal off-target effects as well as the possibility of limited systemic exposure when administered orally. Critically, to achieve efficacy at luminal surfaces, mAb must remain stable and functionally active in the gastrointestinal environment. To better understand the impact of isotype, class, and molecular structure on the intestinal stability of recombinant antibodies, we used an in vitro simulated intestinal fluid (SIF) assay to evaluate a panel of antibody candidates for enteric mAb-based therapeutics. Recombinant IgG1 was the least stable following SIF incubation, while the stability of IgA generally increased upon polymerization, with subtle differences between subclasses. Notably, patterns of variability within and between mAbs suggest that variable regions contribute to mAb stability and potentially mediate mAb susceptibility to proteases. Despite relatively rapid degradation in SIF, mAbs targeting Enterotoxigenic Escherichia coli (ETEC) displayed functional activity following SIF treatment, with SIgA1 showing improved function compared to SIgA2. The results of this study have implications for the design of enteric therapeutics and subsequent selection of lead candidates based upon in vitro intestinal stability assessments.

Genomic Variability and Post-translational Protein Processing Enhance the Immune Evasion of Mycoplasma hyopneumoniae and Its Interaction With the Porcine Immune System

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp) is a geographically widespread and economically devastating pathogen that colonizes ciliated epithelium; the infection of Mhp can damnify the mucociliary functions as well as leading to Mycoplasma pneumonia of swine (MPS). MPS is a chronic respiratory infectious disease with high infectivity, and the mortality can be increased by secondary infections as the host immunity gets down-regulated during Mhp infection. The host immune responses are regarded as the main driving force for the disease development, while MPS is prone to attack repeatedly in farms even with vaccination or other treatments. As one of the smallest microorganisms with limited genome scale and metabolic pathways, Mhp can use several mechanisms to achieve immune evasion effect and derive enough nutrients from its host, indicating that there is a strong interaction between Mhp and porcine organism. In this review, we summarized the immune evasion mechanisms from genomic variability and post-translational protein processing. Besides, Mhp can induce the immune cells apoptosis by reactive oxygen species production, excessive nitric oxide (NO) release and caspase activation, and stimulate the release of cytokines to regulate inflammation. This article seeks to provide some new points to reveal the complicated interaction between the pathogen and host immune system with Mhp as a typical example, further providing some new strategies for the vaccine development against Mhp infection.

Quorum Sensing, Biofilm, and Intestinal Mucosal Barrier: Involvement the Role of Probiotic

The intestine is a particularly dynamic environment in which the host constantly interacts with trillions of symbiotic bacteria called the microbiota. Using quorum sensing (QS) communication, bacteria can coordinate their social behavior and influence host cell activities in a non-invasive manner. Nowadays, a large amount of research has greatly spurred the understanding of how bacterial QS communication regulates bacterial cooperative behaviors due to coexistence and host-microbe interactions. In this review, we discuss bacterial QS in the gut and its role in biofilm formation. As a biological barrier, the mucosal immune system can effectively prevent pathogenic microorganisms and other immunogenic components from entering the internal environment of the host. We focus on the relationship between biofilm and intestinal mucosal immunity, and how probiotic bacteria may regulate them. This review is to provide a theoretical basis for the development of new techniques including probiotics targeting the intestinal barrier function, thereby improving gut health.

When Therapeutic IgA Antibodies Might Come of Age

BACKGROUND

Extensive efforts have been made in optimizing monoclonal immunoglobulin (Ig)G antibodies for use in clinical practice. Accumulating evidence suggests that IgA or anti-FcαRI could also represent an exciting avenue toward novel therapeutic strategies.

SUMMARY

Here, we underline that IgA is more effective in recruiting neutrophils for tumor cell killing and is potently active against several pathogens, including rotavirus, poliovirus, influenza virus, and SARS-CoV-2. IgA could also be used to modulate excessive immune responses in inflammatory diseases. Furthermore, secretory IgA is emerging as a major regulator of gut microbiota, which impacts intestinal homeostasis and global health as well. As such, IgA could be used to promote a healthy microbiota in a therapeutic setting. Key messages: IgA combines multifaceted functions that can be desirable for immunotherapy.

The Link between Oral and Gut Microbiota in Inflammatory Bowel Disease and a Synopsis of Potential Salivary Biomarkers

The objective of this review is to provide recent evidence for the oral–gut axis connection and to discuss gastrointestinal (GI) immune response, inflammatory bowel disease (IBD) pathogenesis, and potential salivary biomarkers for determining GI health. IBD affects an estimated 1.3% of the US adult population. While genetic predisposition and environment play a role, abnormal immune activity and microbiota dysbiosis within the gastrointestinal tract are also linked in IBD pathogenesis. It has been inferred that a reduced overall richness of bacterial species as well as colonization of opportunistic bacteria induce systemic inflammation in the GI tract. Currently, there is supporting evidence that both oral and gut microbiota may be related to the development of IBD. Despite this, there are currently no curative therapies for IBD, and diagnosis requires samples of blood, stool, and invasive diagnostic imaging techniques. Considering the relative ease of collection, emerging evidence of association with non-oral diseases may imply that saliva microbiome research may have the potential for gut diagnostic or prognostic value. This review demonstrates a link between saliva and intestinal profiles in IBD patients, suggesting that saliva sampling has the potential to serve as a non-invasive biomarker for gut diseases such as IBD in the oral–gut axis.

Secretory anti-citrullinated protein antibodies in serum associate with lung involvement in early rheumatoid arthritis

Objective

A ‘mucosal connection’ in RA presently attracts increasing attention. We recently described the occurrence of secretory antibodies to citrullinated protein (SC-ACPA) in sera from patients with recent-onset RA. The current study was performed to evaluate possible associations between serum levels of secretory ACPA and signs of lung involvement in patients with early, untreated RA.

Methods

One hundred and forty-two RA patients were included as part of the ‘LUng Investigation in newly diagnosed RA’ study. One hundred and six patients were examined with high-resolution CT (HRCT) and 20 patients underwent bronchoscopy, where bronchial biopsies and bronchoalveolar lavage fluid (BALF) samples were obtained. SC-ACPA in serum and BALF were detected by an enzyme-linked immunoassay. Antibody levels were related to smoking history, pulmonary function, HRCT, BALF cell counts and findings in bronchial biopsies.

Results

SC-ACPA occurred in 16% of the serum samples and in 35% of the BALF samples. SC-ACPA levels in serum correlated with SC-ACPA levels in BALF (σ = 0.50, P = 0.027) and were higher among patients with HRCT parenchymal lung abnormalities (P = 0.022) or bronchiectasis (P = 0.042). Also, ever smoking was more frequent among serum SC-ACPA-positive patients (91% vs 67%, P = 0.023), and the SC-ACPA levels correlated with the number of pack-years (σ=0.20, P = 0.020).

Conclusion

In early, untreated RA, serum levels of SC-ACPA reflect lung involvement in terms of local ACPA levels, smoking and lung abnormalities on HRCT. These findings strengthen the link between mucosal ACPA responses and the lungs in RA.

The effect of lactose and a prototype Lactobacillus acidophilus fermentation product on digestibility, nitrogen balance, and intestinal function of weaned pigs

The objective of this study was to determine the effects of lactose (LA) and a prototype Lactobacillus acidophilus fermentation product (FP) on growth performance, diet digestibility, nitrogen (N) balance, and intestinal function of weaned pigs. Twenty-eight newly weaned pigs [approximately 21 d of age; initial body weight (BW) = 5.20 ± 0.15 kg] were housed in metabolism crates and assigned to one of four treatments (n = seven pigs per treatment) corresponding to a 2 × 2 factorial design: with (LA+; 15% inclusion) or without (LA-) LA and with (FP+) or without (FP-) the prototype FP (1 g of FP per kilogram of diet; Diamond V, Cedar Rapids, IA). Feed and water were provided ad libitum. At day 5, pigs were orally given lactulose and mannitol to assess small intestinal permeability. Fecal samples were collected on days 5-9 to determine the apparent total tract digestibility (ATTD) of dry matter (DM), gross energy (GE), and N. Total urine output and fecal samples were collected on days 10-13 to determine N retention. On day 15, all pigs were euthanized to collect intestinal lumen and tissue samples. Data were analyzed for the main effects of LA and FP and their interaction using the MIXED procedure of SAS. Lactose improved average daily feed intake (ADFI; P = 0.017), the ATTD of DM (P = 0.014), the ATTD of GE (P = 0.028), and N retention (P = 0.043) and tended to increase the butyric acid concentration in the colon (P = 0.062). The FP tended to increase the digestibility of N (P = 0.090). Neither LA nor the FP affected intestinal barrier function or inflammation markers. The interaction between LA and FP affected intestinal morphology: in the jejunum, pigs fed LA+FP- had increased villus height compared with those fed LA+FP+ and LA-FP-, whereas LA+FP+ was intermediate (interaction P = 0.034). At the terminal ileum, pigs fed LA-FP+ and LA+FP- had increased villus height and villus: crypt compared with those fed LA-FP-, whereas LA+FP+ was intermediate (interaction P = 0.007 and P = 0.007, respectively). In conclusion, the addition of LA brings important nutritional attributes to nursery diets by improving feed intake, digestibility of DM and GE, and the N retention of weaned pigs; however, the functional capacity of LA to improve markers of intestinal function is limited. On the other hand, the FP showed only a mild increase in the digestibility of N but a limited capacity to improve markers of intestinal function.

Behçet's Disease Under Microbiotic Surveillance? A Combined Analysis of Two Cohorts of Behçet's Disease Patients

Background: In Behçet's disease (BD), an auto-inflammatory vasculitis, an unbalanced gut microbiota can contribute to pro-inflammatory reactions. In separate studies, distinct pro- and anti-inflammatory bacteria associated with BD have been identified.

Methods: To establish disease-associated determinants, we performed gut microbiome profiling in BD patients from the Netherlands (n = 19) and Italy (n = 13), matched healthy controls (HC) from the Netherlands (n = 17) and Italy (n = 15) and oral microbiome profiling in Dutch BD patients (n = 18) and HC (n = 15) by 16S rRNA gene sequencing. In addition, we used fecal IgA-SEQ analysis to identify specific IgA coated bacterial taxa in Dutch BD patients (n = 13) and HC (n = 8).

Results: In BD stool samples alpha-diversity was conserved, whereas beta-diversity analysis showed no clustering based on disease, but a significant segregation by country of origin. Yet, a significant decrease of unclassified Barnesiellaceae and Lachnospira genera was associated with BD patients compared to HC. Subdivided by country, the Italian cohort displays a significant decrease of unclassified Barnesiellaceae and Lachnospira genera, in the Dutch cohort this decrease is only a trend. Increased IgA-coating of Bifidobacterium spp., Dorea spp. and Ruminococcus bromii species was found in stool from BD patients. Moreover, oral Dutch BD microbiome displayed increased abundance of Spirochaetaceae and Dethiosulfovibrionaceae families.

Conclusions: BD patients show decreased fecal abundance of Barnesiellaceae and Lachnospira and increased oral abundance of Spirochaetaceae and Dethiosulfovibrionaceae. In addition, increased fecal IgA coating of Bifidobacterium, Ruminococcus bromii and Dorea may reflect retention of anti-inflammatory species and neutralization of pathosymbionts in BD, respectively. Additional studies are warranted to relate intestinal microbes with the significance of ethnicity, diet, medication and response with distinct pro- and inflammatory pathways in BD patients.

Immunoglobulin A Targeting on the N-Terminal Moiety of Viral Phosphoprotein Prevents Measles Virus from Evading Interferon-β Signaling

Immunoglobulin A (IgA) can inhibit intracellular viral replication during its transport across the epithelial cells. We find a monoclonal IgA antibody 7F1-IgA against the N-terminal moiety of the phosphoprotein (PNT) of measles virus (MV), which inhibits the intracellular replication of MV in Caco-2 cells but not in interferon-deficient Vero-pIgR cells. Transcytosis of 7F1-IgA across the MV-infected Caco-2 cells enhances the production of interferon-β (IFN-β) and the expression of IFN-stimulated genes, rendering Caco-2 cells with higher antiviral immunity. 7F1-IgA specifically interacts with MV phosphoprotein inside the MV-infected Caco-2 cell and prevents MV phosphoprotein from inhibiting the phosphorylation of JAK1 and STAT1. The intraepithelial interaction between 7F1-IgA and the viral phosphoprotein results in an earlier and stronger phosphorylation of JAK1 and STAT1 and, consequently, a more efficient nuclear translocation of STAT1 for the activation of the type I interferon pathway. Thus, IgA against phosphoprotein prevents a virus from evading type I IFN signaling and confers host epithelial cells efficient innate antiviral immunity, which potentiates a new antiviral target and an antiviral strategy.

Host defense mechanisms against Mycobacterium tuberculosis

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), remains the leading cause of death worldwide from a single infectious pathogen. Mtb is a paradigmatic intracellular pathogen that primarily invades the lungs after host inhalation of bacteria-containing droplets via the airway. However, the majority of Mtb-exposed individuals can spontaneously control the infection by virtue of a robust immune defense system. The mucosal barriers of the respiratory tract shape the first-line defense against Mtb through various mucosal immune responses. After arriving at the alveoli, the surviving mycobacteria further encounter a set of host innate immune cells that exert multiple cellular bactericidal functions. Adaptive immunity, predominantly mediated by a range of different T cell and B cell subsets, is subsequently activated and participates in host anti-mycobacterial defense. During Mtb infection, host bactericidal immune responses are exquisitely adjusted and balanced by multifaceted mechanisms, including genetic and epigenetic regulation, metabolic regulation and neuroendocrine regulation, which are indispensable for maintaining host immune efficiency and avoiding excessive tissue injury. A better understanding of the integrated and equilibrated host immune defense system against Mtb will contribute to the development of rational TB treatment regimens especially novel host-directed therapeutics.

Immunological Methods for Treatment of Vulvovaginal Infections in the Preconception Period

Traditional therapy and extensive use of medications and intravaginal autolymphocyte therapy show different results of the treatment of vulvovaginal infections. The purpose of the article was to explore safe and highly effective methods to treat vulvovaginal infections and diseases of the pelvic organs.

The standard clinical and laboratory screening of 70 patients of reproductive age was carried out to diagnose the diseases of the reproductive tract. The screening included the description of quantitative and qualitative characteristics of vaginal discharge, examining the mucous covering of the vulva and vagina, microscopic examination of Gram-stained vaginal swabs, endocervical cultures, and diagnosis of sexually transmitted infections using polymerase chain reaction. Intravaginal autolymphocyte therapy was used together with traditionally-accepted treatment schemes (etiotropic antibacterial and antifungal therapy) in the treatment of the main group (40 patients). Traditional treatment methods depending on the etiology of the development of infection were used in the control group (30 patients). The IgM, IgA, and IgG levels were also observed because of the possibility of causing embryo rejection. This study shows that in case of relapsing vulvovaginitis and mixed infections accompanied by disorders of the immune system at different levels, the use of intravaginal autolymphocyte therapy in a comprehensive therapy can be assessed as advisable and pathogenetically substantiated.

Antibody response against Pseudomonas aeruginosa and its relationship with immune mediators in the upper and lower airways of cystic fibrosis patients

BACKGROUND

The upper airways (UAW) are a niche and a reservoir of Pseudomonas aeruginosa strains that cause chronic infection of the lower airways (LAW) in cystic fibrosis (CF). Here, we assessed the role of anti-P. aeruginosa immunoglobulin A (IgA) and IgG antibodies in upper and lower airway infections in cystic fibrosis patients.

METHODS

Nasal lavage fluid and induced sputum samples of 40 CF patients were microbiologically cultured. We searched for correlations between anti-P. aeruginosa IgA and IgG levels, measured by enzyme-linked immunosorbent assay (optical density), and unspecific immune mediators in both specimens.

RESULTS

Anti-P. aeruginosa IgA (median optical density: 0.953 vs 0.298) and IgG (0.120 vs 0.059) were significantly higher in nasal lavage than in sputum, but not significantly different between patients with and without chronic P. aeruginosa infection in UAW. Matrix metallopeptidase-9 (MMP-9) in nasal lavage and neutrophil elastase (NE) in sputum were predictors of IgA in nasal lavage and IgA in sputum, respectively. IgA was a predictor of myeloperoxidase (MPO) in nasal lavage. Tissue inhibitor of metalloproteinases-1 (TIMP-1) was a predictor of IgG in sputum. IgG, TIMP-1, and NE in sputum were predictors of IgG in nasal lavage.

CONCLUSION

The anti-P. aeruginosa IgA response was more prominent in CF patients' UAW, indicating a lower degree of inflammatory responses. Proteases may play a role in the anti-P. aeruginosa humoral response in the upper and LAW, and anti-P. aeruginosa IgG may be involved in the crosstalk between upper and lower airways in cystic fibrosis patients.

Influence of Maternal Milk on the Neonatal Intestinal Microbiome

The intestinal microbiome plays an important role in maintaining health throughout life. The microbiota develops progressively after birth and is influenced by many factors, including the mode of delivery, antibiotics, and diet. Maternal milk is critically important to the development of the neonatal intestinal microbiota. Different bioactive components of milk, such as human milk oligosaccharides, lactoferrin, and secretory immunoglobulins, modify the composition of the neonatal microbiota. In this article, we review the role of each of these maternal milk-derived bioactive factors on the microbiota and how this modulation of intestinal bacteria shapes health, and disease.

Induction of systemic immunity through nasal-associated lymphoid tissue (NALT) of mice intranasally immunized with Brucella abortus malate dehydrogenase-loaded chitosan nanoparticles

Infection with Brucella abortus causes contagious zoonosis, brucellosis, and leads to abortion in animals and chronic illness in humans. Chitosan nanoparticles (CNs), biocompatible and nontoxic polymers, acts as a mucosal adjuvant. In our previous study, B. abortus malate dehydrogenase (Mdh) was loaded in CNs, and it induced high production of pro-inflammatory cytokines in THP-1 cells and systemic IgA in BALB/C mice. In this study, the time-series gene expression analysis of nasal-associated lymphoid tissue (NALT) was performed to identify the mechanism by which Mdh affect the target site of nasal immunization. We showed that intranasal immunization of CNs-Mdh reduced cell viability of epithelial cells and muscle cells at first 1 h, then induced cellular movement of immune cells such as granulocytes, neutrophils and lymphocytes at 6h, and activated IL-6 signaling pathway at 12h within NALT. These activation of immune cells also promoted signaling pathway for high-mobility group box 1 protein (HMGB1), followed by the maturation of DCs required for mucosal immunity. The CNs also triggered the response to other organism and inflammatory response, showing it is immune-enhancing adjuvant. The ELISA showed that significant production of specific IgA was detected in the fecal excretions and genital secretions from the CNs-Mdh-immunized group after 2 weeks-post immunization. Collectively, these results suggest that B. abortus Mdh-loaded CNs triggers activation of HMGB1, IL-6 and DCs maturation signaling within NALT and induce production of systemic IgG and IgA.

Maternal psychological distress before birth influences gut immunity in mid-infancy

BACKGROUND

Maternal pre-postnatal psychosocial distress increases the risk for childhood allergic disease. This may occur through a host immunity pathway that involves intestinal secretory immunoglobulin A (sIgA). Experimental animal models show changes in the gut microbiome and immunity of offspring when exposed to direct or prenatal maternal stress, but little is known in humans.

OBJECTIVE

We determined the association between maternal depression and stress symptom trajectories and infant fecal sIgA concentrations.

METHODS

1043 term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort were studied. Trajectories of maternal perceived stress and depression were based on scored scales administered in pregnancy and postpartum. sIgA was quantified in infant stool (mean age 3.7 months) with Immundiagnostik ELISA. Linear regression and logistic regression were employed to test associations.

RESULTS

Very low fecal sIgA concentrations were more common in infants of mothers in the antepartum and persistent depression trajectories (6% and 2% of women, respectively). Independent of breastfeeding status at fecal sampling, infant antibiotic exposure or other covariates, the antepartum depressive symptom trajectory was associated with reduced mean infant sIgA concentrations (β=-0.07, P < .01) and a two fold risk for lowest quartile concentrations (OR, 1.86; 95% CI: 1.02, 3.40). This lowering of sIgA yielded a large effect size in older infants (4-8 months)-breastfed and not. No associations were seen with postpartum depressive symptoms (7% of women) or with any of the perceived stress trajectories.

CONCLUSION AND CLINICAL RELEVANCE

Despite improved mood postpartum and independent of breastfeeding status, mothers experiencing antepartum depressive symptoms delivered offspring who exhibited lower fecal sIgA concentrations especially in later infancy. The implications of lowered sIgA concentrations in infant stool are altered microbe-sIgA interactions, greater risk for C difficile colonization and atopic disease in later years.

Skin-Associated B Cells in Health and Inflammation

Traditionally, the skin was believed to be devoid of B cells, and studies of the skin immune system have largely focused on other types of leukocytes. Exciting recent data show that B cells localize to the healthy skin of humans and other mammalian species with likely homeostatic functions in host defense, regulation of microbial communities, and wound healing. Distinct skin-associated B cell subsets drive or suppress cutaneous inflammatory responses with important clinical implications. Localized functions of skin-associated B cell subsets during inflammation comprise Ab production, interactions with skin T cells, tertiary lymphoid tissue formation, and production of proinflammatory cytokines but also include immunosuppression by providing IL-10. In this review, we delve into the intriguing new roles of skin-associated B cells in homeostasis and inflammation.

Anti-IL-5 in Mild Asthma Alters Rhinovirus-induced Macrophage, B-Cell, and Neutrophil Responses (MATERIAL). A Placebo-controlled, Double-Blind Study

RATIONALE

Eosinophils drive pathophysiology in stable and exacerbating eosinophilic asthma, and therefore treatment is focused on the reduction of eosinophil numbers. Mepolizumab, a humanized monoclonal antibody that neutralizes IL-5 and efficiently attenuates eosinophils, proved clinically effective in severe eosinophilic asthma but not in mild asthma.

OBJECTIVES

To study the effect of mepolizumab on virus-induced immune responses in mild asthma.

METHODS

Patients with mild asthma, steroid-naive and randomized for eosinophil numbers, received 750 mg mepolizumab intravenously in a placebo-controlled double-blind trial, 2 weeks after which patients were challenged with rhinovirus (RV) 16. FEV₁, FVC, fractional exhaled nitric oxide, symptom scores (asthma control score), viral load (PCR), eosinophil numbers, humoral (luminex, ELISA), and cellular (flow cytometry) immune parameters in blood, BAL fluid, and sputum, before and after mepolizumab and RV16, were assessed.

MEASUREMENTS AND MAIN RESULTS

Mepolizumab attenuated baseline blood eosinophils and their activation, attenuated trendwise sputum eosinophils, and enhanced circulating natural killer cells. Mepolizumab did not affect FEV₁, FVC, and fractional exhaled nitric oxide, neither at baseline nor after RV16. On RV16 challenge mepolizumab did not prevent eosinophil activation but did enhance local B lymphocytes and macrophages and reduce neutrophils and their activation. Mepolizumab also enhanced secretory IgA and reduced tryptase in BAL fluid. Finally, mepolizumab affected particularly RV16-induced macrophage inflammatory protein-3a, vascular endothelial growth factor-A, and IL-1RA production in BAL fluid.

CONCLUSIONS

Mepolizumab failed to prevent activation of remaining eosinophils and changed RV16-induced immune responses in mild asthma. Although these latter effects likely are caused by attenuated eosinophil numbers, we cannot exclude a role for basophils. Clinical trial registered with www.clinicaltrials.gov (NCT 01520051).

Growing, evolving and sticking in a flowing environment: understanding IgA interactions with bacteria in the gut

Immunology research in the last 50 years has made huge progress in understanding the mechanisms of anti-bacterial defense of deep, normally sterile, tissues such as blood, spleen and peripheral lymph nodes. In the intestine, with its dense commensal microbiota, it seems rare that this knowledge can be simply translated. Here we put forward the idea that perhaps it is not always the theory of immunology that is lacking to explain mucosal immunity, but rather that we have overlooked crucial parts of the mucosal immunological language required for its translation: namely intestinal and bacterial physiology. We will try to explain this in the context of intestinal secretory antibodies (mainly secretory IgA), which have been described to prevent, to alter, to not affect, or to promote colonization of the intestine and gut-draining lymphoid tissues, and where effector mechanisms have remained elusive. In fact, these apparently contradictory outcomes can be generated by combining the basic premises of bacterial agglutination with an understanding of bacterial growth (i.e. secretory IgA-driven enchained growth), fluid handling and bacterial competition in the gut lumen.

The antibody/microbiota interface in health and disease

The human intestine is densely colonized with commensal microbes that stimulate the immune system. While secretory Immunoglobulin (Ig) A is known to play a crucial role in gut microbiota compartmentalization, secretory IgM, and systemic IgG have recently been highlighted in host-microbiota interactions as well. In this review, we discuss important aspects of secretory IgA biology, but rather than focusing on mechanistic aspects of IgA impact on microbiota, we stress the current knowledge of systemic antibody responses to whole gut microbiota, in particular their generation, specificities, and function. We also provide a comprehensive picture of secretory IgM biology. Finally, therapeutic and diagnostic implications of these novel findings for the treatment of various diseases are outlined.

Role of gut microbiota in liver disease

The gut microbiome is the natural intestinal inhabitant that has been recognized recently as a major player in the maintenance of human health and the pathophysiology of many diseases. Those commensals produce metabolites that have various effects on host biological functions. Therefore, alterations in the normal composition or diversity of microbiome have been implicated in various diseases, including liver cirrhosis and nonalcoholic fatty liver disease. Moreover, accumulating evidence suggests that progression of dysbiosis can be associated with worsening of liver disease. Here, we review the possible roles for gut microbiota in the development, progression, and complication of liver disease.

The Role of IgA in the Pathogenesis of IgA Nephropathy

Immunoglobulin A (IgA) is the most abundant antibody isotype produced in humans, predominantly present in the mucosal areas where its main functions are the neutralization of toxins, prevention of microbial invasion across the mucosal epithelial barrier, and simultaneous maintenance of a physiologically indispensable symbiotic relationship with commensal bacteria. The process of IgA biosynthesis, interaction with receptors, and clearance can be disrupted in certain pathologies, like IgA nephropathy, which is the most common form of glomerulonephritis worldwide. This review summarizes the latest findings in the complex characteristics of the molecular structure and biological functions of IgA antibodies, offering an in-depth overview of recent advances in the understanding of biochemical, immunologic, and genetic factors important in the pathogenesis of IgA nephropathy.

Dietary leucine supplementation improves intestinal health of mice through intestinal SIgA secretion

AIMS

Leucine supplementation promotes intestinal health, but the mechanism is largely unknown. This study aimed to elucidate the mechanisms underlying the beneficial effects of leucine on intestinal homeostasis.

METHODS AND RESULTS

Female ICR mice (6-week-old) were randomly assigned into three groups: (i) mice received a basal diet; (ii) mice received a dietary 0·5% crystalline l-leucine supplementation; and (iii) mice received a dietary 1·0% crystalline l-leucine supplementation. Our results showed that leucine supplementation stimulated the secretion of SIgA in mice ileum and expression of cytokines related to SIgA production. Moreover, leucine supplementation improved the expression of mTOR and p70S6K1 expression. Further study showed that leucine supplementation markedly decreased microbiota richness and induced a shift in the Firmicutes : Bacteroidetes ratio in favour of Firmicutes.

CONCLUSIONS

Therefore, our data suggested that leucine supplementation could enhance intestinal health through the regulation of mTOR pathway and promoting SIgA secretion in the mouse intestine, which might be associated with intestinal microbiota.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study found that dietary leucine supplementation of mice could improve intestinal health by enhancing intestinal SIgA secretion via a nonexclusive mechanism, which might include T cell-dependent pathway, T cell-independent pathway and gut microbiota.

Ehrlichia chaffeensis Outer Membrane Protein 1-Specific Human Antibody-Mediated Immunity Is Defined by Intracellular TRIM21-Dependent Innate Immune Activation and Extracellular Neutralization

Antibodies are essential for immunity against Ehrlichia chaffeensis, and protective mechanisms involve blocking of ehrlichial attachment or complement and Fcγ-receptor-dependent destruction. In this study, we determined that major outer membrane protein 1 (OMP-19) hypervariable region 1 (HVR1)-specific human monoclonal antibodies (huMAbs) are protective through conventional extracellular neutralization and, more significantly, through a novel intracellular TRIM21-mediated mechanism.

Antibodies are essential for immunity against Ehrlichia chaffeensis, and protective mechanisms involve blocking of ehrlichial attachment or complement and Fcγ-receptor-dependent destruction. In this study, we determined that major outer membrane protein 1 (OMP-19) hypervariable region 1 (HVR1)-specific human monoclonal antibodies (huMAbs) are protective through conventional extracellular neutralization and, more significantly, through a novel intracellular TRIM21-mediated mechanism. Addition of OMP-1-specific huMAb EHRL-15 (IgG1) prevented infection by blocking attachment/entry, a mechanism previously reported; conversely, OMP-1-specific huMAb EHRL-4 (IgG3) engaged intracellular TRIM21 and initiated an immediate innate immune response and rapid intracellular degradation of ehrlichiae. EHRL-4-TRIM21-mediated inhibition was significantly impaired in TRIM21 knockout THP-1 cells. EHRL-4 interacted with cytosolic Fc receptor TRIM21, observed by confocal microscopy and confirmed by co-immunoprecipitation. E. chaffeensis-EHRL-4-TRIM21 complexes caused significant upregulation of proinflammatory cytokine/chemokine transcripts and resulted in rapid (<30 min) nuclear accumulation of NF-κB and TRIM21 and ehrlichial destruction. We investigated the role of TRIM21 in the autophagic clearance of ehrlichiae in the presence of EHRL-4. Colocalization between EHRL-4-opsonized ehrlichiae, polyubiquitinated TRIM21, autophagy regulators (ULK1 and beclin 1) and effectors (LC3 and p62), and lysosome-associated membrane protein 2 (LAMP2) was observed. Moreover, autophagic flux defined by conversion of LC3I to LC3II and accumulation and degradation of p62 was detected, and EHRL-4-mediated degradation of E. chaffeensis was abrogated by the autophagy inhibitor 3-methyladenine. Our results demonstrate that huMAbs are capable of inhibiting E. chaffeensis infection by distinct effector mechanisms: extracellularly by neutralization and intracellularly by engaging TRIM21, which mediates a rapid innate immune response that mobilizes the core autophagy components, triggering localized selective autophagic degradation of ehrlichiae.

Secretory IgA accumulated in the airspaces of idiopathic pulmonary fibrosis and promoted VEGF, TGF-β and IL-8 production by A549 cells

Secretory IgA (SIgA) is a well-known mucosal-surface molecule in first-line defense against extrinsic pathogens and antigens. Its immunomodulatory and pathological roles have also been emphasized, but it is unclear whether it plays a pathological role in lung diseases. In the present study, we aimed to determine the distribution of IgA in idiopathic pulmonary fibrosis (IPF) lungs and whether IgA affects the functions of airway epithelial cells. We performed immunohistochemical analysis of lung sections from patients with IPF and found that mucus accumulated in the airspaces adjacent to the hyperplastic epithelia contained abundant SIgA. This was not true in the lungs of non-IPF subjects. An in-vitro assay revealed that SIgA bound to the surface of A549 cells and significantly promoted production of vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β and interleukin (IL)-8, important cytokines in the pathogenesis of IPF. Among the known receptors for IgA, A549 cells expressed high levels of transferrin receptor (TfR)/CD71. Transfection experiments with siRNA targeted against TfR/CD71 followed by stimulation with SIgA suggested that TfR/CD71 may be at least partially involved in the SIgA-induced cytokine production by A549 cells. These phenomena were specific for SIgA, distinct from IgG. SIgA may modulate the progression of IPF by enhancing synthesis of VEGF, TGF-β and IL-8.

Rational Design and In Vivo Characterization of Vaccine Adjuvants

Many different adjuvants are currently being developed for subunit vaccines against a number of pathogens and diseases. Rational design is increasingly used to develop novel vaccine adjuvants, which requires extensive knowledge of, for example, the desired immune responses, target antigen-presenting cell subsets, their localization, and expression of relevant pattern-recognition receptors. The adjuvant mechanism of action and efficacy are usually evaluated in animal models, where mice are by far the most used. In this review, we present methods for assessing adjuvant efficacy and function in animal models: (1) whole-body biodistribution evaluated by using fluorescently and radioactively labeled vaccine components; (2) association and activation of immune cell subsets at the injection site, in the draining lymph node, and the spleen; (4) adaptive immune responses, such as cytotoxic T-lymphocytes, various T-helper cell subsets, and antibody responses, which may be quantitatively evaluated using ELISA, ELISPOT, and immunoplex assays and qualitatively evaluated using flow cytometric and single cell sequencing assays; and (5) effector responses, for example, antigen-specific cytotoxic potential of CD8+ T cells and antibody neutralization assays. While the vaccine-induced immune responses in mice often correlate with the responses induced in humans, there are instances where immune responses detected in mice are not translated to the human situation. We discuss some examples of correlation and discrepancy between mouse and human immune responses and how to understand them.

Upper Respiratory Tract Infection and Mucosal Immunity in Young Ice Hockey Players During the Pretournament Training Period

Orysiak, J, Witek, K, Malczewska-Lenczowska, J, Zembron-Lacny, A, Pokrywka, A, and Sitkowski, D. Upper respiratory tract infection and mucosal immunity in young ice hockey players during the pretournament training period. J Strength Cond Res 33(11): 3129-3135, 2019-The aim of this study was to determine the effects of 17 days of training during preparation for the Ice Hockey Under 18 World Championship of the Polish ice hockey national team on the mucosal immune function and monitor upper respiratory tract infection (URTI) incidence before, during, and after the competition. Twelve male ice hockey players (age, 17.7 ± 0.5 years) were recruited for this study. The first saliva and blood collection took place at the beginning of the training camp (without training at the training camp), the second one was collected on the 9th day of the training camp immediately after the intensification of training, and the third collection was performed on the 13th day of training (4 days before leaving for the World Championship) in the tapering phase. To assess the mucosal immune function, concentrations of secretory immunoglobulin A (sIgA), sIgA1, and sIgA2 were analyzed in saliva. Cortisol concentration and creatine kinase activity were determined in blood, as indicators of stress and muscle damage, respectively. The Wisconsin Upper Respiratory Symptom Survey-21 questionnaire was used to assess URTI symptoms. A significant increase in the sIgA1 and sIgA2 concentrations was observed in the third collection compared with the second time point (114.45 ± 33.00 vs. 77.49 ± 27.29 and 88.97 ± 25.33 vs. 71.65 ± 32.44 U, respectively). There were no statistically significant correlations between the URTI incidence and saliva variables. In conclusion, the tapering period positively affects the mucosal immune function, especially sIgA1 and sIgA2 concentrations, with no significant change in the frequency of URTI in young ice hockey players.

Depletion of dietary aryl hydrocarbon receptor ligands alters microbiota composition and function

The intestinal microbiota is critical for maintaining homeostasis. Dysbiosis, an imbalance in the microbial community, contributes to the susceptibility of several diseases. Many factors are known to influence gut microbial composition, including diet. We have previously shown that fecal immunoglobulin (Ig) A levels are decreased in mice fed a diet free of aryl hydrocarbon receptor (AhR) ligands. Here, we hypothesize this IgA decrease is secondary to diet-induced dysbiosis. We assigned mice to a conventional diet, an AhR ligand-free diet, or an AhR ligand-free diet supplemented with the dietary AhR ligand indole-3-carbinol (I3C). We observed a global alteration of fecal microbiota upon dietary AhR ligand deprivation. Compared to mice on the conventional diet, family Erysipelotrichaceae was enriched in the feces of mice on the AhR ligand-free diet but returned to normal levels upon dietary supplementation with I3C. Faecalibaculum rodentium, an Erysipelotrichaceae species, depleted its growth media of AhR ligands. Cultured fecal bacteria from mice on the AhR ligand-free diet, but not the other two diets, were able to alter IgA levels in vitro, as was F. rodentium alone. Our data point to the critical role of AhR dietary ligands in shaping the composition and proper functioning of gut microbiota.

Immune Activation in Functional Gastrointestinal Disorders

There is growing appreciation that functional gastrointestinal disorders (FGIDs) such as functional dyspepsia and irritable bowel syndrome are heterogeneous conditions linked by subtle inflammation within the gastrointestinal (GI) tract. The literature suggests that while the symptoms of these diseases may manifest with similar clinical presentations, there are significant differences in triggers and disease severity among patients classified into the same subtype. It is hypothesized that the subtle inflammation observed in these patients is related to an imbalance in GI homeostasis. Disruption of the delicate homeostatic balance within the GI tract can result from any number or combination of factors, including dysbiosis, loss of barrier integrity, genetic predisposition, or immune responses to dietary or luminal antigens. This article discusses the interplay between the immune system, microbiota, and luminal environment in FGIDs. In addition, the article proposes emerging immune pathways, including those involving T-helper type 17 response and innate lymphoid cells, as potential regulators of the subtle inflammation characteristic of FGIDs that warrant investigation in future studies.

Mucosa-Environment Interactions in the Pathogenesis of Rheumatoid Arthritis

Mucosal surfaces play a central role in the pathogenesis of rheumatoid arthritis (RA). Several risk factors, such as cigarette smoking, environmental pollution, and periodontitis interact with the host at the mucosal level, triggering immune system activation. Moreover, the alteration of microbiota homeostasis is gaining increased attention for its involvement in the disease pathogenesis, modulating the immune cell response at a local and subsequently at a systemic level. Currently, the onset of the clinical manifest arthritis is thought to be the last step of a series of pathogenic events lasting years. The positivity for anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF), in absence of symptoms, characterizes a preclinical phase of RA-namely systemic autoimmune phase- which is at high risk for disease progression. Several immune abnormalities, such as local ACPA production, increased T cell polarization towards a pro-inflammatory phenotype, and innate immune cell activation can be documented in at-risk subjects. Many of these abnormalities are direct consequences of the interaction between the environment and the host, which takes place at the mucosal level. The purpose of this review is to describe the humoral and cellular immune abnormalities detected in subjects at risk of RA, highlighting their origin from the mucosa-environment interaction.

How to assess the effectiveness of nasal influenza vaccines? Role and measurement of sIgA in mucosal secretions

Secretory IgAs (sIgA) constitute the principal isotype of antibodies present in nasal and mucosal secretions. They are secreted by plasma cells adjacent to the mucosal epithelial cells, the site where infection occurs, and are the main humoral mediator of mucosal immunity. Mucosally delivered vaccines, such as live attenuated influenza vaccine (LAIV), are able to mimic natural infection without causing disease or virus transmission and mainly elicit a local immune response. The measurement of sIgA concentrations in nasal swab/wash and saliva samples is therefore a valuable tool for evaluating their role in the effectiveness of such vaccines. Here, we describe two standardized assays (enzyme‐linked immunosorbent assay and microneutralization) available for the quantification of sIgA and discuss the advantages and limitations of their use.

Infectious episodes during pregnancy, at particular mucosal sites, increase specific IgA1 or IgA2 subtype levels in human colostrum

Background

Colostrum is the primary source of maternal immunoglobulin A (IgA) for the newborn. IgA participates in protection and regulation mechanisms of the immune response at the neonate’s mucosa. Several studies have evaluated infectious diseases and vaccine protocols effects during pregnancy on maternal milk IgA levels, with the aim to understand lactation protecting effect on newborn. However, most of their results demonstrated that there were no differences in the total IgA levels. In humans, IgA has two subclasses (IgA1 and IgA2), they have an anatomical distribution among mucosal compartments, their levels vary after antigen stimulation and are also seen to describe differential affinities in colostrum. Although there are differences between IgA subclasses in several compartments, these studies have excluded specific colostrum IgA1 and IgA2 determination.

Methods

We analyzed data from 900 women in Mexico City. With Pearson correlation, we compared the number of infectious episodes during their pregnancy that was associated with mucosal compartments (skin, respiratory and gastrointestinal tracts) and colostrum IgA subclasses.

Results

We show a correlation between increased colostrum IgA1 levels and the number of infectious episodes at respiratory tract and the skin. In contrast, infections at the gastrointestinal tract correlated with increased IgA2 amounts.

Conclusions

Infections present during pregnancy at certain mucosal site increase specific IgA subclasses levels in human colostrum. These results will help in understanding infections and immunizations effects on maternal IgA at the mammary gland, and their impact on the development and protection of the newborn.

Electronic supplementary material

The online version of this article (10.1186/s40748-019-0104-x) contains supplementary material, which is available to authorized users.

Follow up on atopy and the gastrointestinal tract - a review of a common association 2018

Primary atopic disorders can be classified as heritable genetic disorders presenting with deregulated pathogenic allergic effector responses irrespective of sensitization. In the last decade, there are parallel rises in the burden of atopic and gastrointestinal (GI) diseases. Areas covered: There is increasing recognition of an association between atopy and GI disease through immune dysregulation, the microbiome and shared genetic pathways. Since the first article on atopy and the GI tract in 2014 in this journal, many more studies have shed light on the shared pathways in these diseases, particularly in the field of eosinophilic GI disease, functional GI disorders, and inflammatory bowel disease. Expert opinion: Understanding the links with common mechanisms in atopy and GI diseases that may lead to better targeting of treatment through manipulation of immune mechanisms, the microbiome, genetics, food allergens and specific GI diseases such as inflammatory bowel disease, functional GI disorders.

Cathepsin L promotes secretory IgA response by participating in antigen presentation pathways during Mycoplasma Hyopneumoniae infection

Cathepsin L (CTSL) has been proved to help contain leishmaniasis and mycoplasma infection in mice by supporting cellular immune responses, but the regulatory functions of CTSL on mucosal immune responses haven't been tested and remain undefined. Here, we investigated the effects of CTSL on SIgA responses and invariant chain (Ii) degradations in the co-cultured swine dendritic cells (DCs) and B cells system in vitro. When the cells system were transfected with vector CTSL-GFP or incubated with recombinant CTSL (rCTSL) before they were infected with Mycoplasma hyopneumoniae (M.hp), SIgA significantly increased and Ii chain was degraded into smaller intermediates, while SIgA decreased when CTSL was knockdown or inhibited with E64. To confirm the SIgA responses promoted by CTSL contribute to the resistance to mycoplasma pneumonia, pigs injected with rCTSL before they were challenged with M.hp, showed milder clinical symptoms and histopathological damage of lungs, less mycoplasma burden together with higher secretion of SIgA, percentages of CD4+ T cells and level of MHC II molecules comparing with the group without rCTSL. Collectively, these results suggested that rCTSL could provide effective protection for piglets against mycoplasma pneumonia by enhancing M.hp-specific mucosal immune responses through its role in antigen presentation by processing the invariant chain.

Yeast-secreted, dried and food-admixed monomeric IgA prevents gastrointestinal infection in a piglet model

A scalably manufacturable oral antibody technology that can interfere with gastrointestinal (GI) targets is needed. Contrary to the complex native secretory IgA, we achieve this using a single-gene encoded monomeric-IgA-like antibody, composed of camelid VHH fused to IgA Fc (mVHH-IgA). This can be produced in soybean seeds or secreted from Pichia pastoris yeast, freeze-or spray-dried, and when delivered in food prevents enterotoxigenic Escherichia coli (F4-ETEC) infection in piglets.

A built-in adjuvant-engineered mucosal vaccine against dysbiotic periodontal diseases

Periodontitis is associated with a dysbiotic shift in the oral microbiome. Vaccine approaches to prevent microbial shifts from healthy to diseased state in oral biofilms would provide a fundamental therapeutic strategy against periodontitis. Since dental plaque formation is a polymicrobial and multilayered process, vaccines targeting single bacterial species would have limited efficacy in clinical applications. In this study, we developed a divalent mucosal vaccine consisting of a mixture of FlaB-tFomA and Hgp44-FlaB fusion proteins targeting virulence factors of inflammophilic bacteria Fusobacterium nucleatum and Porphyromonas gingivalis, respectively. Introduction of peptide linkers between FlaB and antigen improved the stability and immunogenicity of engineered vaccine antigens. The intranasal immunization of divalent vaccine induced protective immune responses inhibiting alveolar bone loss elicited by F. nucleatum and P. gingivalis infection. The built-in flagellin adjuvant fused to protective antigens enhanced antigen-specific antibody responses and class switch recombination. The divalent vaccine antisera recognized natural forms of surface antigens and reacted with diverse clinical isolates of Fusobacterium subspecies and P. gingivalis. The antisera inhibited F. nucleatum-mediated biofilm formation, co-aggregation of P. gingivalis and Treponema denticola, and P. gingivalis-host cell interactions. Taken together, the built-in adjuvant-engineered mucosal vaccine provides a technological platform for multivalent periodontitis vaccines targeting dysbiotic microbiome.

Plant-derived secretory component forms secretory IgA with shiga toxin 1-specific dimeric IgA produced by mouse cells and whole plants

A key module, secretory component (SC), was efficiently expressed in Arabidopsis thaliana. The plant-based SC and immunoglobulin A of animal or plant origin formed secretory IgA that maintains antigen-binding activity. Plant expression systems are suitable for scalable and cost-effective production of biologics. Secretory immunoglobulin A (SIgA) will be useful as a therapeutic antibody against mucosal pathogens. SIgA is equipped with a secretory component (SC), which assists the performance of SIgA on the mucosal surface. Here we produced SC using a plant expression system and formed SIgA with dimeric IgAs produced by mouse cells as well as by whole plants. To increase the expression level, an endoplasmic reticulum retention signal peptide, KDEL (Lys-Asp-Glu-Leu), was added to mouse SC (SC-KDEL). The SC-KDEL cDNA was inserted into a binary vector with a translational enhancer and an efficient terminator. The SC-KDEL transgenic Arabidopsis thaliana produced SC-KDEL at the level of 2.7% of total leaf proteins. In vitro reaction of the plant-derived SC-KDEL with mouse dimeric monoclonal IgAs resulted in the formation of SIgA. When reacted with Shiga toxin 1 (Stx1)-specific ones, the antigen-binding activity was maintained. When an A. thaliana plant expressing SC-KDEL was crossed with one expressing dimeric IgA specific for Stx1, the plant-based SIgA exhibited antigen-binding activity. Leaf extracts of the crossbred transgenic plants neutralized Stx1 cytotoxicity against Stx1-sensitive cells. These results suggest that transgenic plants expressing SC-KDEL will provide a versatile means of SIgA production.