A novel inhibitory strategy of <i>Leishmania major</i> using <i>Kluyveromyces lactis</i> and <i>Saccharomyces cerevisiae</i> killer toxins

Leishmaniasis is a globally prevalent parasitic disease that has drawn significant attention. Killer yeasts offer a novel biological control method, presenting a potential alternative for treating leishmaniasis. This study evaluates the antileishmanial activity of <i>Kluyveromyces lactis</i> and <i>Saccharomyces cerevisiae</i> killer toxins against <i>Leishmania major</i>. Killer yeasts were isolated using the Well method. The genes encoding K2 and K.L killer toxins were identified by PCR, and the toxins were purified via SDS-PAGE. Antileishmanial and cytotoxic effects on <i>L. major</i> promastigotes and amastigotes were evaluated using the MTT assay. The first killer isolate was identified as <i>Saccharomyces cerevisiae</i> ZBAM (GenBank accession: OQ376749.1) and the second as <i>Kluyveromyces lactis</i> ZBAM (GenBank accession: OQ401036.1). IC50 values of K2 and K.L toxins against <i>L. major</i> promastigotes were significantly lower than Glucantime and Amphotericin B. The EC50 values at 24 hours for Glucantime, K2, and K.L were 11.83 ± 0.02 μg/ml, 2.35 ± 0.01 μg/ml, and 3.23 ± 0.03 μg/ml, respectively. The EC50 values for K2 and K.L against <i>L. major</i> amastigotes were also lower than Glucantime. This is the first report of the antileishmanial effects of K2 and K.L toxins against <i>L. major</i>, suggesting these yeasts as promising candidates for biological leishmaniasis treatment.