Sorbitol‐Induced Synchronisation of <scp> <i>Babesia duncani</i> </scp> and Assessment of Linoleic Acid Effect on Parasite‐Derived Vesicles

Human babesiosis is an emerging infectious disease caused by a bloodborne single-celled parasite belonging to the genus Babesia. Cases of human babesiosis are commonly reported in the United States, Western Europe and Asia. In the United States, the two major causative agents are Babesia microti and Babesia duncani. Transmitted to humans through tick bites, the parasite infects host red blood cells (RBCs). It induces flu-like symptoms and has evolved mechanisms to manipulate the immune system, enabling its persistence. One key mechanism is the secretion of extracellular vesicles (EVs) which carry bioactive molecules, including proteins, lipids and genetic material that modulate pathogen-host interactions and disease development. The inhibition of the secretion of these vesicles may lead to disease control. One potential inhibitor of extracellular vesicle secretion is linoleic acid (LA), a polyunsaturated lipid that has demonstrated inhibitory properties in other parasites. To study the effects of development stage-dependent stimuli on B. duncani, we employed a B. duncani in vitro continuous culture system and evaluated the use of sorbitol for synchronising parasite development. Microscopy techniques showed successful sorbitol-induced synchronisation. Using nanoparticle tracking analysis and scanning electron microscopy, we assessed the effects of LA on parasite morphology and EV characteristics. Our studies indicate that exposure of Babesia parasites to LA did not cause significant observable changes in RBC morphology or reduce EV concentrations under the tested conditions.