Impaired Gut Barrier: Implications for Autoimmune Disease and COVID-19 Infection

Educational Objectives

The goal of this program is to improve management of impaired gut barrier permeability. After hearing and assimilating this program, the clinician will be better able to:

1. Classify the contribution of the intestinal microbiome in gut barrier function and human health.
2. Relate the function of zonulin to development of various diseases associated with impaired gut barrier permeability.
3. Manage multisystem inflammatory syndrome in children.

Summary

Microbiome development: humans undergo embryogenesis in a sterile environment but are colonized by various microbial communities shortly after birth until a balance is created; genetics, immunogenetics, the major histocompatibility complex, diet, and breast milk influence which bacteria dominate the commensal microbiota; the ileum is the most metabolically and immunologically active section of the gastrointestinal (GI) tract, and its bacteria collectively contain 100-fold more genes than humans (who have ≈20,000 genes, per the Human Genome Project); infections (eg, influenza) or dietary changes can instantly alter the relative predominance of the bacteria

Gut barrier permeability: the epithelial cells secrete glycosylated proteins that form a mucous layer that serves as a barrier to other bacteria; the epithelial lining of the intestines contains tight junctions which physically prevent bacteria from passing through; in early development, some microbes help immune cells proliferate, divide, and differentiate (into, eg, regulatory T-cells, T-helper 17 cells); the composition of the exposed microbial community plays a very crucial role in gut barrier function; microbes are necessary for digestion and metabolism of, eg, starches; sampling microbes just enough to provide stimulation to the immune system is crucial, as an improper balance can cause food intolerances, allergies, and autoimmune diseases

Tight junction regulation: the tight junctions of epithelial cells are regulated by transcription and are normally very effective at limiting the entry of, eg, bacteria, viruses, toxins into the body and circulation; the epithelial cells produce zonulin, a protein which is secreted into the lumen and engages specific receptors in order to regulate tight junctions; insufficient signal during certain inflammatory states causes tight junctions to break down; larazotide (initially known as AT1001) antagonizes zonulin, thus blocking the effects of inflammatory factors and re-establishing tight junctions; preclinical phase I and II trial findings in celiac disease were promising; the United States Food and Drug Administration (FDA) fast-tracked larazotide for investigation because it does not induce toxicity

Zonulin and rheumatoid arthritis (RA): patients with preclinical autoimmunity have autoantibodies (eg, anti-citrullinated protein antibodies, rheumatoid factors) in the circulation but are healthy and do not have joint symptoms, yet some will develop overt disease when autoreactive lymphocyte cells settle into their joints; Tajik et al (2020) discovered higher serum zonulin levels in people with RA, compared with other inflammatory diseases, suggesting a breakdown in the intestinal tight junctions; high zonulin levels appear to be relatively specific; people identified as having preclinical autoimmunity also have higher serum levels of zonulin, and higher levels are associated with more rapid development of overt RA; biopsies revealed fewer tight junctions between epithelial cells in people with RA

Surrogate markers for gut permeability (Azzouz et al, 2019): fecal calprotectin — present in the stool of patients with systemic lupus erythematosus (SLE) and without colitis; a granule derived from neutrophils; serum soluble CD14 (sCD14) — acute-phase reactant; production by the liver is stimulated by lipopolysaccharide (LPS), suggesting leakage of microbial factors into the bloodstream; serum α1 acid glycoprotein — another suggestive (though not definitive) biomarker present in patients with SLE

Influence of bacteria: Silverman et al (2022) discovered significantly increased presence of Blautia (Ruminococcus) gnavus (RG; spore-producing anaerobic bacterium) in patients with progressive SLE, vs patients without SLE; the SLE Disease Activity Index parallels the frequency of RG; the genomes of RG colonies in patients with SLE differ from those found in healthy patients; the RG strains from patients with lupus nephritis increase intestinal permeability in mice (primarily female mice) and reproduce the gut barrier defect; the mice developed strain-specific antibodies containing double-stranded DNA; the RG strains from healthy individuals did not produce the same findings in mice

Zonulin and COVID-19 associated multisystem inflammatory syndrome of children (MIS-C)

Presentation: diagnostic criteria include age <21 yr, ≥1 day of significant fever, severe illness causing hospitalization, multisystem disease, serologic evidence of systemic inflammation (including elevations in, eg, C-reactive protein [CRP], erythrocyte sedimentation rate, fibrinogen, D-dimer, ferritin), and objective evidence of SARS-CoV-2 (through reverse transcription polymerase chain reaction or antigen exposure) without an alternative diagnosis; patients exhibit prominent GI symptoms but not pulmonary symptoms; presentation of MIS in children is dissimilar to adult presentation; symptoms include, eg, headaches, high levels of inflammatory markers, cardiac involvement, chest pain (minor), pulmonary infiltrates (minor), thrombocytopenia, neutrophilia, lymphopenia, renal involvement; death is possible

Yonker et al (2021): found that hospitalized children with MIS-C had higher levels of zonulin, LPS-binding protein, and sCD14, compared with children without MIS-C as well as with children without COVID-19; stool samples of patients with MIS-C contained evidence of anti-spike immunoglobulin A (IgA), IgG, and IgM; treatment — remdesivir was not helpful and increased CRP levels; intravenous immune globulin was ineffective; anakinra decreased CRP levels, though the children had persistent antigenemia (ie, spike protein levels were unaffected); larazotide decreased CRP and anti-spike levels and improved D-dimer levels without imparting toxic effects (as it is absorbed by the intestine and digested by proteases before reaching the biliary duct)

Readings

Azzouz D, Omarbekova A, Heguy A, et al. Lupus nephritis is linked to disease-activity associated expansions and immunity to a gut commensal. Ann Rheum Dis. 2019;78(7):947-956. doi:10.1136/annrheumdis-2018-214856; Duerkop BA, Vaishnava S, Hooper LV. Immune responses to the microbiota at the intestinal mucosal surface. Immunity. 2009;31(3):368-376. doi:10.1016/j.immuni.2009.08.009; Fasano A. Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. 2011;91(1):151-75. doi:10.1152/physrev.00003.2008; Fasano A, Not T, Wang W, et al. Zonulin, a newly discovered modulator of intestinal permeability, and its expression in coeliac disease. Lancet. 2000;355(9214):1518-9. doi:10.1016/S0140-6736(00)02169-3; Martín R, Miquel S, Ulmer J, et al. Role of commensal and probiotic bacteria in human health: a focus on inflammatory bowel disease. Microb Cell Factories. 2013;12:71. doi:10.1186/1475-2859-12-71; Nakra NA, Blumberg DA, Herrera-Guerra A, et al. Multi-system inflammatory syndrome in children (MIS-C) following SARS-CoV-2 infection: review of clinical presentation, hypothetical pathogenesis, and proposed management. Children (Basel). 2020;7(7):69. doi: 10.3390/children7070069; Silverman GJ, Deng J, Azzouz DF. Sex-dependent Lupus Blautia (Ruminococcus) gnavus strain induction of zonulin-mediated intestinal permeability and autoimmunity. Front Immunol. 2022;13:897971. doi:10.3389/fimmu.2022.897971; Tajik N, Frech M, Schulz O, et al. Targeting zonulin and intestinal epithelial barrier function to prevent onset of arthritis. Nat Commun. 2020;11(1):1995. doi:10.1038/s41467-020-15831-7; Yonker LM, Gilboa T, Ogata AF, et al. Multisystem inflammatory syndrome in children is driven by zonulin-dependent loss of gut mucosal barrier. J Clin Invest. 2021;131(14):e149633. doi:10.1172/JCI149633; Yonker LM, Swank Z, Gilboa T, et al. Zonulin antagonist, larazotide (AT1001), as an adjuvant treatment for multisystem inflammatory syndrome in children: a case series. Crit Care Explor. 2022;4(2):e0641. doi:10.1097/CCE.0000000000000641.

Disclosures

For this program, the following relevant financial relationships were disclosed and mitigated to ensure that no commercial bias has been inserted into this content: Dr. Silverman is a consultant for BMS, Genentech, GSK, Hi Bio, Inmagene, and Roche and receives grant support from BMS, Genentech, LRA, and NIH. Members of the planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Silverman was recorded at the 11th Annual Basic and Clinical Immunology for the Busy Clinician, held February 25-26, 2023, in Scottsdale, AZ, and presented by the Cleveland Clinic Foundation. For information on future CME activities from this presenter, please visit https://www.clevelandclinicmeded.com. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 1.25 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 1.25 CE contact hours.

Lecture ID:

IM702101

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.