Microgramma vacciniifolia Frond Lectin: In Vitro Anti-leishmanial Activity and Immunomodulatory Effects Against Internalized Amastigote Forms of Leishmania amazonensis

Purpose

The treatment of leishmaniasis, an anthropozoonosis caused by Leishmania protozoa, is limited by factors, such as adverse effects, toxicity, and excessive cost, which has highlighted the importance of novel drugs. In this context, natural products have been considered as sources of antileishmanial agents. This study investigated the leishmanicidal activity of Microgramma vacciniifolia frond lectin (MvFL) on promastigotes and amastigotes of Leishmania amazonensis.

Methods

The effects of MvFL on promastigote proliferation and macrophage infection by amastigotes were evaluated and mean inhibitory concentrations (IC₅₀) were calculated. As a safety assessment, the hemolytic capacity of MvFL (6.25–200 µg/mL) against mouse and human erythrocytes was determined. Additionally, the ability of MvFL (6.25–100 µg/mL) to modulate lysosomal and phagocytic activities and the nitric oxide (NO) production by murine peritoneal macrophages was also investigated.

Results

After 24 h, MvFL inhibited the proliferation of L. amazonensis promastigotes, with an IC₅₀ of 88 µg/mL; however, hemolytic activity was not observed. MvFL also reduced macrophage infection by amastigotes with an IC₅₀ of 52 µg/mL. Furthermore, treatment with MvFL reduced the number of amastigotes internalized by infected murine peritoneal macrophages by up to 68.9% within 48 h. At a concentration of 25 µg/mL, MvFL stimulated lysosomal activity of macrophages within 72 h, but did not alter phagocytic activity or induce NO production at any of the tested concentrations.

Conclusion

MvFL exerts antileishmanial activity and further studies are needed to assess its therapeutic potential in in vivo experimental models of leishmaniasis.