The human antimicrobial peptide LL-37 can stop HIV-1 from multiplying in immune cells in lab dishes. It works against several strains of the virus and doesn't need to change the usual HIV entry points on the cells. This suggests LL-37 might help protect tissues that naturally make it, like the lining of the mouth or gut.

The antimicrobial peptide LL-37 is the only cathelicidin that has been described in humans. LL-37 exerts chemotactic, immunomodulatory and angiogenic effects; activities that are mediated through binding to the formyl peptide receptor like (FPRL)-1 receptor. Agonistic ligation of FPRL-1 can also induce down-regulation of HIV-1 chemokine receptors and reduce susceptibility to HIV-1 infection in vitro. Therefore, we have evaluated the capacity of LL-37 to inhibit HIV-1 infection in vitro. Here we demonstrate that LL-37 inhibits HIV-1 replication in PBMC, including primary CD4(+) T cells. This inhibition was readily reproduced using various HIV-1 isolates without detectable changes in the target cell expression of HIV-1 chemokine receptors. Accordingly, the HIV-1 inhibitory effect was shown to be independent of FPRL-1 signalling. Given the epithelial expression of LL-37, it may contribute to the local protection against HIV-1 infection.