title: Using recombinant Lactococci as an approach to dissect the immunomodulating capacity of surface piliation in probiotic Lactobacillus rhamnosus GG.
abstract: Primarily arising from their well understood beneficial health effects, many lactobacilli strains are considered good candidates for use as probiotics in humans and animals. Lactobacillar probiosis can itself be best typified by the Lactobacillus rhamnosus GG strain, which, with its well-documented clinical benefits, has emerged as one of the most widely used probiotics in the food and health-supplement industries. Even so, many facets of its molecular mechanisms and limitations as a beneficial commensal bacterium still remain to be thoroughly explored and dissected. Because L. rhamnosus GG is one of only a few such strains exhibiting surface piliation (called SpaCBA), we sought to examine whether this particular type of cell-surface appendage has a discernible immunomodulating capacity and is able to trigger targeted responses in human immune-related cells. Thus, presented herein for this study, we recombinantly engineered Lactococcus lactis to produce native (and pilin-deleted) SpaCBA pili that were assembled in a structurally authentic form and anchored to the cell surface, and which had retained mucus-binding functionality. By using these recombinant lactococcal constructs, we were able to demonstrate that the SpaCBA pilus can be a contributory factor in the activation of Toll-like receptor 2-dependent signaling in HEK cells as well as in the modulation of pro- and anti-inflammatory cytokine (TNF-α, IL-6, IL-10, and IL-12) production in human monocyte-derived dendritic cells. From these data, we suggest that the recombinant-expressed and surface-anchored SpaCBA pilus, given its projected functioning in the gut environment, might be viewed as a new microbe-associated molecular pattern (MAMP)-like modulator of innate immunity. Accordingly, our study has brought some new insight to the molecular immunogenicity of the SpaCBA pilus, thus opening the way to a better understanding of its possible role in the multifaceted nature of L. rhamnosus GG probiosis within the human gut.
authors.affiliation: Department of Veterinary Biosciences, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland. ingemar.von.ossowski@helsinki.fi
authors.forename: Ingemar
authors.initials: I
authors.lastname: von Ossowski
authors.forename: Taija E
authors.initials: TE
authors.lastname: Pietilä
authors.forename: Johanna
authors.initials: J
authors.lastname: Rintahaka
authors.forename: Elina
authors.initials: E
authors.lastname: Nummenmaa
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Mäkinen
authors.forename: Justus
authors.initials: J
authors.lastname: Reunanen
authors.forename: Reetta
authors.initials: R
authors.lastname: Satokari
authors.forename: Willem M
authors.initials: WM
authors.lastname: de Vos
authors.forename: Ilkka
authors.initials: I
authors.lastname: Palva
authors.forename: Airi
authors.initials: A
authors.lastname: Palva
mesh_terms: D001422:Bacterial Adhesion / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D004274:DNA, Recombinant / Q000235:genetics*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000276:immunology / Q000502:physiology*; D005818:Genetic Engineering; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D056747:Immunomodulation; D052201:Lacticaseibacillus rhamnosus / Q000276:immunology / Q000502:physiology*; D017045:Lactococcus / Q000235:genetics*; D009093:Mucus / Q000382:microbiology; D019936:Probiotics / Q000494:pharmacology*; D015398:Signal Transduction / Q000276:immunology; D013499:Surface Properties; D051195:Toll-Like Receptor 2 / Q000378:metabolism
chemical_list: D016207:Cytokines; D004274:DNA, Recombinant; D051195:Toll-Like Receptor 2