Boosting innate immunity: development and validation of a cell-based screening assay to identify LL-37 inducers

Innate Immun. 2014 May;20(4):364-76. doi: 10.1177/1753425913493338. Epub 2013 Jul 24.


Innate immunity, the front line of our defence against pathogens, relies, to a great extent, on the production of antimicrobial peptides (AMPs). These peptides exhibit antimicrobial activity and immunomodulatory properties. In humans, AMPs include the defensins (α- and β-families) and the cathelicidin, LL-37. Bacterial resistance against antibiotics is a growing concern, and novel antimicrobial strategies are needed urgently. Hence, the concept of strengthening immune defences against infectious microbes by inducing AMP expression may represent novel or complementary pharmaceutical interventions in the treatment or prevention of infections. We have developed and validated a robust cell-based reporter assay for LL-37 expression, which serves as a marker for a healthy epithelial barrier. This reporter assay can be a powerful tool for high-throughput screenings. We first employed our assay to screen a panel of histone deacetylase inhibitors and derivatives, and then the Prestwick Chemical Library of Food and Drug Administration-approved compounds. After hit confirmation and independent validation in the parental cell line we identified five novel inducers of LL-37. This reporter assay will help to identify novel drug candidates for the treatment and prevention of infections. Importantly, the pattern of hits obtained may suggest cellular pathways and key mediators involved in the regulation of AMP expression.

Keywords: CAMP gene; Antimicrobial peptides; HT-29 cell line; chemical library screening; luciferase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / metabolism*
  • Butyrates / chemistry
  • Butyrates / pharmacology*
  • Drug Discovery / methods*
  • Epithelial Cells / drug effects*
  • Epithelial Cells / immunology
  • Epithelial Cells / microbiology
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / immunology
  • Genes, Reporter / genetics
  • HT29 Cells
  • High-Throughput Screening Assays
  • Humans
  • Immunity, Innate / drug effects
  • Phenylbutyrates / chemistry
  • Phenylbutyrates / pharmacology*
  • Small Molecule Libraries / chemistry
  • United States
  • United States Food and Drug Administration


  • Antimicrobial Cationic Peptides
  • Butyrates
  • Phenylbutyrates
  • Small Molecule Libraries
  • ropocamptide