In mice, the natural antimicrobial peptide similar to human LL‑37 (called CRAMP) ramps up in skin cells and immune cells when they’re infected with the parasite that causes leishmaniasis, and this rise appears to help protect the animals from the infection.

Leishmaniasis is a serious global challenge with neither efficacious prophylactic vaccine nor effective and safe therapeutic measures. Cathelicidins, members of antimicrobial peptides family, are small proteins of innate immunity system, which represent a protective barrier against a number of potential pathogens in living organisms. The murine cathelicidin or cathelin-related antimicrobial peptide (CRAMP) is expressed by a variety of cells or tissues, and highly resembles to human cathelicidin (LL-37). It is naturally expressed at a low concentration in adolescent age, but extensively increases during cutaneous infections. Despite its important role, it has less been investigated in parasitic infections. Among all cells, macrophages and skin cells are the two important cells that directly have a relationship with <i>Leishmania major</i> parasites. The present study aimed to show whether cathelicidins protect their hosts following cutaneous leishmaniasis due to <i>L. major</i> parasites. Both <i>in vitro</i> and <i>in vivo</i> models of <i>L. major</i> infection were established by exposing of J744 cell line (murine macrophages) and BALB/c mice with the stationary phase of <i>L. major</i> promastigotes for 24&#xa0;h and 7&#xa0;days. The findings revealed that both macrophages and skin cells significantly (<i>p&#x2009;</i>&lt;&#x2009;0.05) expressed a high level of CRAMP gene and peptide after challenging with <i>L. major</i> parasites. Thus, our data suggest a protective role for cathelicidins against infections caused by <i>L. major</i> parasites. This experimental model could be considered as a novel potential vaccine candidate for planning future control strategy against human leishmaniasis.