Andrea Silvana Ropolo

Giardia lamblia, a eukaryotic intestinal parasite, produces small extracellular vesicles (sEVs) as a conserved evolutionary mechanism. This study investigates the functional role of sEVs in modulating drug response traits among G. lamblia parasites. Here, we showed that sEVs derived from metronidazole (MTZ)–resistant clones modify the expression of enzymes involved in MTZ metabolism and the production of reactive oxygen species (ROS) in recipient wild type parasites. The transfer efficiency and phenotypic impact vary depending on the genetic background of the isolates, highlighting a genotype‐specific mechanism. Our findings reveal that sEVs act as mediators of phenotypic adaptation in G. lamblia, enhancing parasite survival under drug‐induced stress. This study highlights the significance of sEVs in drug‐sensitive dynamics and lays the groundwork for investigating therapeutic interventions that target EV‐mediated sensitivity in giardiasis.

Giardia lamblia , a eukaryotic intestinal parasite, produces small extracellular vesicles (sEVs) as a conserved evolutionary mechanism. This study investigates the functional role of sEVs in transferring drug-resistance traits among parasites. sEVs derived from metronidazole (MTZ)-resistant clones are shown to modify the expression of enzymes involved in MTZ metabolism and the production of reactive oxygen species (ROS) in recipient wild-type parasites. These changes significantly alter the drug sensitivity of recipient parasites. The transfer efficiency and phenotypic impact vary depending on the genetic background of the isolates, highlighting a genotype-specific mechanism. Our findings reveal that sEVs act as mediators of phenotypic adaptation in G. lamblia , enhancing parasite survival under drug-induced stress. This study underscores the importance of sEVs in drug-resistance dynamics and provides a basis for exploring therapeutic interventions targeting EV-mediated resistance in giardiasis. Highlights In brief: Small extracellular vesicles (sEVs) from Giardia lamblia mediate genotype-specific MTZ resistance transfer. Small extracellular vesicles from drug-resistant clones (RsEVs) alter enzyme expression and reactive oxygen species (ROS) production in recipient trophozoites. The genetic background of G. lamblia isolates influences the effectiveness of resistance transfer. Findings provide insights into resistance mechanisms and potential targets for new giardiasis therapies.

Introduction: Post-translational modifications of proteins provide cellular physiology with a broad range of adaptability to the external environment flexibly and rapidly. In the case of the protozoan parasite Giardia lamblia, the study of these modifications has gained relevance in recent years, mainly focusing on methylation and deacetylation of proteins. This study investigates the significance of acetylation in this protozoan parasite.Methods: This study explores the role of acetylation in G. lamblia through a combination of immunofluorescence assays, manipulation of acetyltransferase enzymes, and the use of garcinol, an acetylation inhibitor, during the growth phase.Results: The acetylation of histone marks H3K9 and H3K27 occurs during growth and is followed by deacetylation during encystation. Transfections modifying acetyltransferase activity induced a latent cellular state, underscoring the importance of protein acetylation for parasite survival. Garcinol treatment during growth caused significant morphological changes, including plasma membrane blebbing and apoptotic-like bodies. Immunofluorescence revealed these bodies contained α-tubulin/acetylated α-tubulin and reactive oxygen species. Flow cytometry and Annexin V staining indicated early apoptosis within 24 hours of treatment. Additionally, garcinol led to the deacetylation of H3K9 and H3K27, with redistribution of tubulin and acetylated tubulin from microtubules to the cytosol. Significantly, garcinol prevented parasite recrudescence after treatment withdrawal.Discussion: These results demonstrate that acetylation is essential for trophozoite survival and highlight the natural histone acetyltransferase inhibitor garcinol as a potential candidate for drug development against giardiasis, considering its giardicidal activity.

The genetically related assemblages of the intestinal protozoa parasite Giardia lamblia are morphologically indistinguishable and are often derived from specific hosts. The Giardia assemblages are separated by large genetic distances, which might account for their relevant biological and pathogenic differences. In this work, we analyzed the RNAs cargo released into exosomal-like vesicles (ElVs) by the assemblages A and B, which differentially infect humans, and the assemblage E, which infects hoofed animals. The RNA sequencing analysis revealed that the ElVs of each assemblage contained distinct small RNA (sRNA) biotypes, suggesting a preference for specific packaging in each assemblage. These sRNAs were classified into three categories, ribosomal-small RNAs (rsRNAs), messenger-small RNAs (msRNAs), and transfer-small RNAs (tsRNAs), which may play a regulatory role in parasite communication and contribute to host-specificity and pathogenesis. Uptake experiments showed, for the first time, that ElVs were successfully internalized by the parasite trophozoites. Furthermore, we observed that the sRNAs contained inside these ElVs were first located below the plasma membrane but then distributed along the cytoplasm. Overall, the study provides new insights into the molecular mechanisms underlying the host-specificity and pathogenesis of G. lamblia and highlights the potential role of sRNAs in parasite communication and regulation.

The manner in which membrane-associated proteins interact with the membrane defines their subcellular fate and function. This interaction relies on the characteristics of the proteins, their journey after synthesis, and their interaction with other proteins or enzymes. Understanding these properties may help to define the function of a protein and also the role of an organelle. In the case of microorganisms like protozoa parasites, it may help to understand singular features that will eventually lead to the design of parasite-specific drugs. The protozoa parasite Giardia lamblia is an example of a widespread parasite that has been infecting humans and animals from ancestral times, adjusting itself to the changes of the environment inside and outside the host. Several membrane-associated proteins have been posted in the genome database GiardiaDB, although only a few of them have been characterized. This review discusses the data regarding membrane-associated proteins in relationship with lipids and specific organelles and their implication in the discovery of anti-giardial therapies.

In eukaryotes, histone lysine methylation is associated with either active or repressed chromatin states, depending on the status of methylation. Even when the amino‐terminus of Giardia lamblia histones diverges from other organisms, these regions contain lysine residues that are potential targets for methylation. When we examined the role of the histone methyltransferase 1 (HMT1) in the regulation of the encystation process by giardial histone methyltransferase 1 (GlHMT1) overexpression or downregulation, we observed an increase or a decrease in cyst production, respectively, compared to wild‐type trophozoites. A time‐lapse analysis of encystation showed that overexpression of GlHMT1 induced an earlier and faster process than in wild‐type cells together with an upregulation of mRNA expression of cyst wall proteins. Subcellular localization studies indicated that GlHMT1‐hemaglutinin was mainly associated with the nuclear and perinuclear region in both growing and encysting parasites, in agreement with bioinformatics analyses showing that GlHMT‐1 possesses nuclear localization signals in addition to the classical SU(var)3‐9, Enhancer‐of‐Zeste, Trithorax (SET), and post‐SET domains. Altogether, these findings suggest that the function of HMT1 is critical for the success and timing of the encystation process, and reinforce the idea that epigenetic marks are critical for cyst formation in G. lamblia.