Skin lesions in leprosy patients showed 260-fold higher beta-defensin-3 and 39-fold higher cathelicidin gene expression compared to healthy individuals, with household contacts also showing elevated levels.
260× higher HBD-3Leprosy skin lesions showed 260-fold greater beta-defensin-3 gene expression than healthy skin, with household contacts also elevated at nearly 8-fold
What the researchers found
HBD-3 gene expression in leprosy skin lesions had a median value of 260.61 compared to 1.00 in healthy skin (p < 0.0001) — a roughly 260-fold increase. Cathelicidin expression in lesions was 38.72 versus 1.00 in healthy skin (p < 0.0001).
Critically, household contacts who did not have leprosy also showed elevated antimicrobial peptide levels: HBD-3 at 7.93 and cathelicidin at 9.8, both substantially higher than healthy individuals. Normal (non-lesional) skin in leprosy patients showed intermediate levels (HBD-3: 1.91; cathelicidin: 0.48). These findings suggest a gradient of antimicrobial peptide response from healthy individuals through exposed contacts to active disease, potentially reflecting both infection response and protective immunity.
Why it matters
Leprosy still affects over 200,000 new patients annually worldwide, and understanding the skin's natural immune defense against the bacterium is crucial for developing better prevention and treatment strategies. The finding that household contacts have elevated antimicrobial peptides suggests these molecules may provide some natural protection against developing the disease, even after exposure.
How the study worked
This was an analytic observational study conducted at Dr Mohammad Hoesin General Hospital in Palembang, Indonesia from January 2021 to June 2022. Researchers collected 72 skin samples from four groups of 18 subjects each: leprosy lesional skin, leprosy non-lesional skin, household contact skin, and healthy individual skin. Gene expression of HBD-3 and cathelicidin was measured and compared across groups using Kruskal-Wallis and Mann-Whitney statistical tests.
What this study cannot tell us
The study had a relatively small sample size of 18 subjects per group, limiting generalizability. It was conducted at a single hospital in Indonesia. Gene expression was measured at a single time point, so it's unclear how antimicrobial peptide levels change over the course of disease. The study measured mRNA expression rather than peptide protein levels, which don't always correlate. The household contacts' elevated levels could reflect subclinical infection rather than protective immunity.
How to read the evidence
This is an observational human study with a cross-sectional design and modest sample size (n=72 total samples). While it provides direct human data with highly significant statistical results, it cannot establish causality or determine whether elevated peptides are protective or reactive.
When this study was published
Published in 2023, this study reflects current research on antimicrobial peptide roles in neglected tropical diseases. The findings are relevant to ongoing efforts to understand natural immunity to leprosy.
The bigger picture
This study adds to evidence that antimicrobial peptides — particularly defensins and cathelicidin (LL-37) — are critical frontline defenders in infectious disease. The elevated levels in household contacts who remain disease-free is particularly intriguing, as it suggests these peptides may be part of a natural resistance mechanism. This has implications beyond leprosy: if antimicrobial peptide levels can be boosted in exposed populations, it could potentially serve as a preventive strategy for various skin-invading infections.
Questions still open
- Are elevated antimicrobial peptide levels in household contacts protective against developing leprosy, or are they markers of subclinical infection?
- Could boosting defensin-3 or cathelicidin production in the skin serve as a preventive strategy for leprosy-exposed populations?
- Do patients who develop leprosy despite high antimicrobial peptide levels have bacteria that are resistant to these peptides?
Common questions
What are beta-defensin-3 and cathelicidin, and why are they important in leprosy?
Why did household contacts show elevated antimicrobial peptide levels?
Read the original research
Gene Expression of Human Beta-Defensin-3 and Cathelicidin in the Skin of Leprosy Patients, Household Contacts, and Healthy Individuals from Indonesia.
Clinical, cosmetic and investigational dermatology, 16, 1485-1492
Citation
Argentina, Fifa; Suwarsa, Oki; Gunawan, Hendra; Berbudi, Afiat. (2023). Gene Expression of Human Beta-Defensin-3 and Cathelicidin in the Skin of Leprosy Patients, Household Contacts, and Healthy Individuals from Indonesia.. Clinical, cosmetic and investigational dermatology, 16, 1485-1492. https://doi.org/10.2147/CCID.S405932