In-vitro effect of human cathelicidin antimicrobial peptide LL-37 on dengue virus type 2.
Alagarasu. K K; Patil. P S PS; Shil. P P; Seervi. M M; Kakade. M B MB; Tillu. H H; Salunke. A A
Key Findings
- Pretreating dengue virus with 10‑15 µM LL‑37 cuts infection rates and viral RNA/NS1 levels dramatically.
- The same concentration of a scrambled LL‑37 peptide has no effect, confirming the activity is specific.
- Adding LL‑37 to cells before infection or 24 h after infection does not reduce viral load.
- Computer modeling suggests LL‑37 binds to the virus’s envelope protein, blocking entry.
Practical Outcomes
- The study shows LL‑37 has antiviral potential against dengue in a petri dish, but the required concentrations and the need to treat the virus before it enters cells make it impractical for direct human use right now. Biohackers might view this as a proof‑of‑concept that could inspire future prophylactic formulations (e.g., topical sprays), but more animal and clinical research is needed before any real‑world protocol can be recommended.
Summary
In lab tests, the natural peptide LL‑37 can stop dengue virus from infecting cells, but only when the virus is mixed with a fairly high amount of the peptide before it meets the cells. It doesn’t work if you add it to cells first or after the infection has started, and a scrambled version of the peptide does nothing.
Abstract
Human Cathelicidin antimicrobial peptide LL-37 is known to have antiviral activity against many viruses. In the present study, we investigated the in-vitro effect of LL-37 on dengue virus type 2 (DENV-2) infection and replication in Vero E6 cells. To study the effect of pretreatment of virus or cells with LL-37, the virus was pretreated with different concentrations of LL-37 (2.5μM-15μM) or scrambled (Scr) LL-37(5μM-15μM) and used for infection or the cells were first treated with LL-37 and infected. To study the effect of LL-37 post infection (PI), the cells were infected first followed by addition of LL-37 to the culture medium 24h after infection. In all conditions, after the incubation, the culture supernatant was assessed for viral RNA copy number by real time RT-PCR, infectious virus particles by focus forming unit assay (FFU) and non structural protein 1 (NS1) antigen levels by ELISA. Percentage of infection was assessed using immunoflourescence assay (IFA). The results revealed that pretreatment of virus with 10-15μM LL-37 significantly reduced its infectivity as compared to virus control (P<0.0001). Moreover, pretreatment of virus with 10-15μM LL-37 significantly reduced the levels of viral genomic RNA and NS1 antigen (P<0.0001). Treatment of virus with 10-15μM LL-37 resulted in two to three log reduction of mean log<sub>10</sub> FFU/ml as compared to virus control (P<0.0001). Treatment of the virus with scrambled LL-37 had no effect on percentage of infection and viral load as compared to virus control cultures (P>0.05). Pretreatment of cells before infection or addition of LL-37 to the culture 24h PI had no effect on viral load. Molecular docking studies revealed possible binding of LL-37 to both the units of DENV envelope (E) protein dimer. Together, the in-vitro experiments and in-silico analyses suggest that LL-37 inhibits DENV-2 at the stage of entry into the cells by binding to the E protein. The results might have implications for prophylaxis against DENV infections and need further in-vivo studies.
Study Information
pubmed
2017
2017-04-09T00:00:00.000Z
10.1016/j.peptides.2017.04.002
71
31