Serum-derived bovine immunoglobulin/protein isolate binds to various opportunistic microbes along with associated virulence factors

Abstract

The gut microbiome consists of a complex population of bacteria, fungi, and viruses that aid the host in various physiological functions. When the microbiota is imbalanced, known as dysbiosis, symbiotic microbes can become opportunistic and excrete virulence factors that decrease intestinal barrier function, causing chronic inflammation that leads to disease. Therefore, maintaining gut microbiome balance is critical to overall health. Endogenous immunoglobulins play a positive role in gut homeostasis and immunoglobulin supplements can assist the body with microbiome maintenance. Serum-derived bovine immunoglobulin/protein isolate (SBI), a spray-dried protein powder enriched in immunoglobulins (IgG, IgA, IgM), is clinically proven to help manage loose and frequent stools associated with gastrointestinal enteropathies. A previous study used an in vitro cell culture model to show that SBI binds and neutralizes pattern-associated molecular patterns by steric/immune exclusion mechanisms. The goal of our study is to expand the list of antigens to which SBI binds. We hypothesize the IgG in SBI binds additional opportunistic microbes found in the gut and their associated virulence factors. Heliobacter pylori ( H. pylori), Shigella dysenteriae, Escherichia coli ( E. coli), and Candida albicans ( C. albicans) are common microbes associated with human gastroenteropathies. Therefore, we initially tested the binding of SBI to H. pylori lysate, H. pylori cytotoxicity-associated immunodominant antigen (CagA), Shiga toxin type-1 (Stx1), E. coli cytolethal distending toxin (CDT), C. albicans lysate, and C. albicans agglutinin-like protein 3 (Als3) by a dot blot method. SBI demonstrated binding to all antigens except the H. pylori lysate. To validate specificity of IgG, further binding studies were completed using a modified ELISA. The absorbance of IgG bound to immobilized antigens increased proportionally to SBI concentration (CagA R2=0.98, Stx1 R2=0.97, CDT subunit A R2=0.99, CDT subunit C R2=0.99, C. albicans lysate R2=0.99, and Als3 R2=0.99). Control experiments verified effective blocking, non-specific binding, and functionality (denatured SBI), as no significant absorbance was measured for any antigen tested. Together, the dot blot and modified ELISA showed the IgG in SBI was found to bind to a variety of opportunistic microbes and their associated virulence factors, including CagA, Stx1, CDT subunit A, CDT subunit C, C. albicans lysate, and Als3. Future work will examine if IgG binding can promote gut microbiome balance. Proliant Health and Biologicals This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.