Cyclic defensin peptide RTD-1 activates interferon antiviral pathways and blocks SARS-CoV-2 infection in human cells
Rhesus theta defensin-1 (RTD-1), a cyclic antimicrobial peptide, activates interferon and antiviral gene expression via JAK-STAT1 signaling and IFNAR receptor, inhibiting VSV and SARS-CoV-2 infection in multiple human cell types.
Quick Facts
What This Study Found
RTD-1 in human monocytes: ↑interferon and antiviral gene expression (RNA-seq). Mechanism: JAK-dependent STAT1 Y701 phosphorylation, IFNAR-dependent, NF-κB-independent. Antiviral: ↓VSV infection (THP-1), ↓SARS-CoV-2 spike pseudovirus (Vero E6), ↓authentic SARS-CoV-2 (Calu-3).
Key Numbers
How They Did This
RNA-seq of RTD-1-treated human monocytes and THP-1 cells. STAT1 phosphorylation. ISRE reporter assays with JAK inhibitor and IFNAR blockade. Viral infection inhibition assays (VSV, SARS-CoV-2 pseudovirus, authentic SARS-CoV-2).
Why This Research Matters
RTD-1 is unique: it is both anti-inflammatory (inhibits NF-κB) AND antiviral (activates interferon). This dual activity could be valuable for treating viral infections where inflammation itself is damaging, like COVID-19.
The Bigger Picture
Cyclic antimicrobial peptides with dual anti-inflammatory and antiviral properties could address the central challenge of viral diseases: controlling the pathogen while preventing the inflammatory damage that drives severe disease.
What This Study Doesn't Tell Us
In vitro studies. RTD-1 is from rhesus macaques (not human). Human theta defensins are pseudogenes. Bioavailability and delivery challenges. Antiviral potency not quantified.
Questions This Raises
- ?Could synthetic RTD-1 analogues be developed as antiviral drugs?
- ?Does the dual anti-inflammatory + antiviral mechanism work in vivo?
- ?Could RTD-1 treat COVID-19 where inflammation drives disease severity?
Trust & Context
- Key Stat:
- Anti-inflammatory + antiviral dual action RTD-1 uniquely combines NF-κB inhibition (anti-inflammatory) with JAK-STAT1 interferon activation (antiviral)—ideal for viral diseases where inflammation causes damage
- Evidence Grade:
- In vitro mechanistic study with RNA-seq, signaling analysis, and multiple viral models. Strong mechanism.
- Study Age:
- Published in 2025.
- Original Title:
- The macrocyclic peptide rhesus theta defensin 1 activates interferon and antiviral pathways in human monocytes.
- Published In:
- Journal of leukocyte biology, 117(12) (2025)
- Authors:
- Tongaonkar, Prasad(2), Trinh, Katie K, Henley, Jill E, Sell, Philip J, Thakker, Vyoma, Ouellette, André J, Selsted, Michael E
- Database ID:
- RPEP-13821
Evidence Hierarchy
Frequently Asked Questions
Can a natural peptide fight COVID-19?
This study shows RTD-1—a cyclic antimicrobial peptide—blocks SARS-CoV-2 infection in human cells by activating the body's interferon antiviral defense. It does this while also reducing inflammation (a key driver of severe COVID-19), making it uniquely suited for viral diseases where the immune response itself causes damage.
What makes RTD-1 special among antimicrobial peptides?
Most AMPs either kill pathogens directly or modulate immunity—but rarely both. RTD-1 is unique because it simultaneously activates antiviral interferon pathways (boosting viral defense) while inhibiting NF-κB inflammatory pathways (reducing tissue damage). This dual action could be transformative for treating viral infections.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-13821APA
Tongaonkar, Prasad; Trinh, Katie K; Henley, Jill E; Sell, Philip J; Thakker, Vyoma; Ouellette, André J; Selsted, Michael E. (2025). The macrocyclic peptide rhesus theta defensin 1 activates interferon and antiviral pathways in human monocytes.. Journal of leukocyte biology, 117(12). https://doi.org/10.1093/jleuko/qiaf150
MLA
Tongaonkar, Prasad, et al. "The macrocyclic peptide rhesus theta defensin 1 activates interferon and antiviral pathways in human monocytes.." Journal of leukocyte biology, 2025. https://doi.org/10.1093/jleuko/qiaf150
RethinkPeptides
RethinkPeptides Research Database. "The macrocyclic peptide rhesus theta defensin 1 activates in..." RPEP-13821. Retrieved from https://rethinkpeptides.com/research/tongaonkar-2025-the-macrocyclic-peptide-rhesus
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.