Lactococcus lactis Delivery of Surface Layer Protein A Protects Mice from Colitis by Re-Setting Host Immune Repertoire

Inflammatory bowel disease (IBD) is characterized by gastrointestinal inflammation comprised of Crohn’s disease and ulcerative colitis. Centers for Disease Control and Prevention report that 1.3% of the population of the United States (approximately 3 million people) were affected by the disease in 2015, and the number keeps increasing over time. IBD has a multifactorial etiology, from genetic to environmental factors. Most of the IBD treatments revolve around disease management, by reducing the inflammatory signals. We previously identified the surface layer protein A (SlpA) of Lactobacillus acidophilus that possesses anti-inflammatory properties to mitigate murine colitis. Herein, we expressed SlpA in a clinically relevant, food-grade Lactococcus lactis to further investigate and characterize the protective mechanisms of the actions of SlpA. Oral administration of SlpA-expressing L. lactis (R110) mitigated the symptoms of murine colitis. Oral delivery of R110 resulted in a higher expression of IL-27 by myeloid cells, with a synchronous increase in IL-10 and cMAF in T cells. Consistent with murine studies, human dendritic cells exposed to R110 showed exquisite differential gene regulation, including IL-27 transcription, suggesting a shared mechanism between the two species, hence positioning R110 as potentially effective at treating colitis in humans.

A Computational Approach for Protein-Protein Interactions of Bacterial Surface Layer Protein with Human Erb3 and αIIB-β3 Receptors

Host microbial interactions had significant factors in maintains homeostasis and immune-related activity. One such interaction made by Lactobacillus sp. with Surface layer proteins (Slps) had been studied through a computational approach. Erb3 and αIIB-β3, which are epithelial surface layer receptors, are subjected to interact with the Slp homology model. Both cell surface receptors were subjected to interact through computational docking, followed by molecular dynamics simulations through the coarse-grain method to explore the conformational stability. Through the implementation of the molecular docking for the surface layer protein A, we have shown the surface layer protein A, protein-protein interactions are higher in cellular receptors with epidermal growth factor receptor at an -34.45 ΔG and -51.19 ΔG through molecular docking with Erb3 and αIIB-β3. This study shows the unique interaction of Slp with the epithelial surface receptors like Erb3 and αIIB-β3, which are multipurpose applications in microbial-based drug therapeutics.

Surface Layer Protein A Expressed in Clostridioides difficile DJNS06-36 Possesses an Encephalitogenic Mimotope of Myelin Basic Protein

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Recent studies suggest that migration of Th1 and Th17 cells specific for enteric bacteria from the gut to the CNS may lead to the initiation and/or exacerbation of autoimmune diseases including MS. Human leukocyte antigen (HLA)-DR15 is an MHC class II (MHCII) haplotype highly associated with the development of MS that contains the two HLA-DRB* genes, DRB1*1501 (DR2b) and DRB5*0101 (DR2a). To identify enteric bacteria which harbor antigenic epitopes that activate myelin-specific T cells and drive CNS inflammation, we screened for enteric bacteria which express cross-reactive epitopes (‘mimotopes’) of an immunodominant myelin basic protein 89–98 (MBP89-98) epitope. Based on known MHCII HLA-DR2a amino acid binding motifs and cultivation with splenic T cells isolated from MBP-T cell receptor (TCR)/DR2a transgenic (Tg) mice, we discovered that a certain variant of surface layer protein A (SLPA), which is expressed by a subtype of Clostridioides difficile, contains an amino acid sequence that activates MBP89-98-reactive T cells. Furthermore, activation of MBP-specific T cells by SLPA upon active immunization induced experimental autoimmune encephalomyelitis (EAE) in MBP-TCR/DR2a Tg mice. This study suggests that a unique strain of C. difficile possesses an encephalitogenic mimotope of MBP that activates autoreactive, myelin-specific T cells.