# Standardized Artemisia annua Exhibits Dual Antileishmanial Activity and Immunomodulatory Potential In Vitro

## TL;DR

Artemisia annua shows strong antiparasitic and anti-inflammatory effects against Leishmania infantum in lab tests, suggesting it could be a safe treatment for canine leishmaniasis.

## Contribution

This is the first study to demonstrate Artemisia annua's dual antileishmanial and immunomodulatory effects against Leishmania infantum in vitro.

## Key findings

- Artemisia annua extracts effectively kill Leishmania infantum parasites in both promastigote and amastigote stages.
- The extracts reduce harmful inflammation by lowering TNF-α and IL-6 in macrophages without causing toxicity.
- The therapeutic effects correlate with the artemisinin concentration in the extract.

## Abstract

Leishmaniasis, a parasitic disease transmitted by sandflies, affects both humans and animals, with dogs serving as the primary domestic reservoir of Leishmania infantum. Current treatments are often limited by relapses, adverse effects and the emergence of resistance. This study aimed to evaluate the in vitro antileishmanial and immunomodulatory effects of Artemisia annua extracts against Leishmania infantum. Extracts of Artemisia annua were tested on parasites and immune cells to assess antiparasitic efficacy, modulation of inflammatory responses, and cytotoxicity. Artemisia annua extracts exhibited strong activity against the parasite and effectively reduced harmful inflammatory responses in host immune cells, without inducing toxicity. Moreover, these dual therapeutic effects showed a clear dose-dependent relationship with artemisinin concentration within the extracts. As artemisinin increases, so does the magnitude of both therapeutic effects. These findings support artemisinin-rich Artemisia annua as a promising plant-based complementary strategy for veterinary use against Leishmania infantum infection, with preliminary indications of a favorable safety profile in vitro and potential translational value in leishmaniasis control.

Leishmaniasis is a parasitic disease caused by Leishmania spp., transmitted by sandflies, and endemic in 98 countries. Leishmania infantum, the main agent of visceral leishmaniasis in Europe, commonly infects both humans and animals, with dogs as the principal domestic reservoir. Clinical manifestations in dogs depend on the host immune response. A robust Th1 response facilitates macrophage activation and parasite control, while persistently elevated TNF-α and IL-6 can lead to chronic inflammation and tissue damage. Current treatments reduce parasite load but rarely achieve complete cure and are often associated with relapses and resistance. Artemisia annua, source of artemisinin, could be a promising alternative to canine leishmaniasis. Despite its potential, no published studies have investigated its effect specifically against Leishmania infantum as well as its possible dual action: antiparasitic and immunomodulation. We conducted in vitro evaluations of a standardized Artemisia annua extract. Leishmanicidal activity was assessed against both promastigote and amastigote stages, and cytokine modulation was evaluated in RAW 264.7 macrophages. The extract showed strong leishmanicidal activity without cytotoxicity and significantly reduced TNF-α and IL-6 levels under inflammatory conditions, and in both cases, efficiency was correlated with artemisinin content. These results support Artemisia annua as a promising safer therapeutic adjuvant candidate for canine leishmaniasis, targeting both the parasite and the host inflammatory response.