Using recombinant Lactococci as an approach to dissect the immunomodulating capacity of surface piliation in probiotic Lactobacillus rhamnosus GG

PLoS One. 2013 May 14;8(5):e64416. doi: 10.1371/journal.pone.0064416. Print 2013.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Adhesion / immunology
  • Cytokines / biosynthesis
  • DNA, Recombinant / genetics*
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Fimbriae, Bacterial / immunology
  • Fimbriae, Bacterial / physiology*
  • Genetic Engineering*
  • HEK293 Cells
  • Humans
  • Immunity, Innate
  • Immunomodulation*
  • Lacticaseibacillus rhamnosus / immunology
  • Lacticaseibacillus rhamnosus / physiology*
  • Lactococcus / genetics*
  • Mucus / microbiology
  • Probiotics / pharmacology*
  • Signal Transduction / immunology
  • Surface Properties
  • Toll-Like Receptor 2 / metabolism

Substances

  • Cytokines
  • DNA, Recombinant
  • Toll-Like Receptor 2

Grants and funding

This study, including some salary costs of the AP team, was financed by the Academy of Finland-funded Center of Excellence in Microbial Food Safety (CoE-MiFoSa) research program (141140) (http://www.aka.fi), as well as partly by budget funding from the Faculty of Veterinary Medicine (University of Helsinki; http://www.helsinki.fi/university/index.html) and by a European Research Council grant (250172). Salary funding to WMdV was through an Academy of Finland Professorship (137389). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.