Scientists found that the natural peptide LL‑37, which your body makes more of when you have enough vitamin D, can stick to the coronavirus spike protein and two other viral proteins, blocking the virus from attaching to cells in lab tests. This suggests that boosting LL‑37 might help fight COVID‑19, but the work is still early and done only in test‑tube experiments.

The role of vitamin D in Coronavirus Disease 2019 (COVID-19) outcomes remains debated, but emerging evidence suggests it may enhance recovery by strengthening immune responses. Vitamin D upregulates LL-37, an antimicrobial peptide with broad antiviral activity, including potential benefits against SARS-CoV-2. LL-37's interactions with viral proteins, however, remain incompletely understood. We investigated LL-37's interactions with the SARS-CoV-2 Spike glycoprotein and the accessory proteins ORF7a and ORF8 using surface plasmon resonance and negative-stain electron microscopy. These approaches were employed to assess LL-37's binding capabilities and potential impact on viral infectivity. LL-37 bound multiple domains of the Spike protein and inhibited its interaction with the human angiotensin-converting enzyme 2 (hACE2) receptor <i>in vitro</i>. Up to seven LL-37 molecules were observed surrounding Spike, forming a halo-like structure that may block receptor engagement. LL-37 also bound to ORF7a and ORF8, potentially impairing their ability to disrupt host cell processes. Notably, LL-37's interaction with ORF7a may prevent degradation of SNAP29, restoring autophagy and promoting viral clearance. LL-37 disrupts key viral-host interactions by binding to Spike, ORF7a, and ORF8, thereby reducing SARS-CoV-2 infectivity. These findings highlight LL-37's potential as a therapeutic agent in COVID-19 and provide mechanistic insight into its antiviral actions.