A high-throughput screen of 584 natural products identified 21 compounds that stimulate the body's production of antimicrobial defensin peptides, with wortmannin validated as a lead compound in chickens.
21 of 584 compounds hitFrom 584 natural products screened, 21 stimulated defensin peptide production above the Z-score threshold, with wortmannin emerging as the lead compound after in vivo validation in chickens.
What the researchers found
From a library of 584 natural products screened using a luciferase reporter system driven by the avian β-defensin 9 (AvBD9) promoter, 21 compounds with a minimum Z-score of 2.0 were identified as defensin inducers.
Secondary screening in chicken macrophages and jejunal (gut) tissue explants confirmed most compounds induced defensin expression dose-dependently. The lead compound wortmannin, when given orally to chickens, enhanced AvBD9 gene expression in the duodenum and also induced most other chicken host defense peptide genes. Wortmannin synergized with butyrate to further amplify defensin production, and this combination significantly augmented the antibacterial activity of chicken monocytes.
Why it matters
Antibiotic resistance is one of the greatest threats to global health, and poultry production is a major contributor to antibiotic overuse. Rather than developing new antibiotics that bacteria can evolve resistance to, this approach boosts the animal's own immune defense peptides — a strategy that is inherently harder for bacteria to evade because defensins attack through multiple mechanisms simultaneously. If this approach translates to practice, it could reduce antibiotic use in agriculture while maintaining animal health.
How the study worked
Researchers constructed a stable macrophage cell line expressing a luciferase reporter driven by a 2-kb AvBD9 gene promoter using lentiviral transduction and puromycin selection. This reporter line was used for high-throughput screening of 584 natural products, with hits defined as compounds achieving a Z-score ≥ 2.0. Validated hits underwent secondary screening in chicken HTC macrophages and jejunal explants for dose-dependent defensin induction. The lead compound wortmannin was tested in vivo via oral administration to chickens, measuring defensin gene expression in gut tissue. Synergy experiments combined wortmannin with butyrate, and antibacterial activity was assessed using chicken monocyte killing assays.
What this study cannot tell us
The study was conducted primarily in chicken systems (macrophage cell lines, gut explants, and live chickens), and results may not directly translate to human defensin biology. Wortmannin is a known PI3K inhibitor with multiple cellular effects, which could cause unintended side effects at therapeutic doses. The in vivo validation used oral administration but did not assess disease protection outcomes or safety in long-term feeding trials. The screen focused on defensin induction and did not evaluate whether the induced peptides effectively prevented actual infections in treated animals.
How to read the evidence
This is a preclinical drug discovery study with a well-designed screening pipeline progressing from cell-based assays through tissue explants to in vivo validation in chickens. While the methodology is rigorous for early-stage research, no disease protection outcomes were measured and the work remains entirely in avian systems.
When this study was published
Published in 2018, this study is about 8 years old. The concept of boosting endogenous antimicrobial peptide production as an antibiotic alternative has continued to gain traction, though wortmannin itself has not advanced to commercial application due to its broad pharmacological activity.
The bigger picture
This study exemplifies the 'host-directed therapy' paradigm — instead of directly killing pathogens, you enhance the host's own immune defenses. Antimicrobial peptides like defensins are ancient immune weapons that have remained effective for hundreds of millions of years of evolution because they attack bacteria through multiple mechanisms, making resistance development extremely difficult. Finding natural compounds that stimulate defensin production could transform not only animal agriculture but potentially human medicine as well.
Questions still open
- Can these defensin-inducing natural compounds reduce disease incidence and antibiotic use in commercial poultry production?
- Do any of these 21 compounds also induce human defensin production, potentially offering antibiotic alternatives for human medicine?
- What is the safety profile of long-term wortmannin or butyrate supplementation in food animals?
Common questions
How could boosting the body's own antimicrobial peptides replace antibiotics?
Could this approach work for humans, not just chickens?
Read the original research
High Throughput Screening for Natural Host Defense Peptide-Inducing Compounds as Novel Alternatives to Antibiotics.
Frontiers in cellular and infection microbiology, 8, 191
Citation
Lyu, Wentao; Deng, Zhuo; Sunkara, Lakshmi T; Becker, Sage; Robinson, Kelsy; Matts, Robert; Zhang, Guolong. (2018). High Throughput Screening for Natural Host Defense Peptide-Inducing Compounds as Novel Alternatives to Antibiotics.. Frontiers in cellular and infection microbiology, 8, 191. https://doi.org/10.3389/fcimb.2018.00191