Giardia lamblia: Laboratory Maintenance, Lifecycle Induction, and Infection of Murine Models

Giardia intestinalis reshapes mucosal immunity toward a Type 2 response that attenuates inflammatory bowel-like diseases

Diarrheal diseases are the second leading cause of death in children worldwide. Epidemiological studies show that co-infection with Giardia intestinalis decreases the severity of diarrhea. Here, we show that Giardia is highly prevalent in the stools of asymptomatic school-aged children. It orchestrates a Th2 mucosal immune response, characterized by increased antigen-specific Th2 cells, IL-25, Type 2-associated cytokines, and goblet cell hyperplasia. Giardia infection expanded IL-10-producing Th2 and GATA3+ Treg cells that promoted chronic carriage, parasite transmission, and conferred protection against Toxoplasma gondii-induced lethal ileitis and DSS-driven colitis by downregulating proinflammatory cytokines, decreasing Th1/Th17 cell frequency, and preventing collateral tissue damage. Protection was dependent on STAT6 signaling, as Giardia-infected STAT6-/- mice no longer regulated intestinal bystander inflammation. Our findings demonstrate that Giardia infection reshapes mucosal immunity toward a Type 2 response, which confers a mutualistic protection against inflammatory disease processes and identifies a critical role for protists in regulating mucosal defenses.

Traditional medicinal plants in the treatment of gastrointestinal parasites in humans: A systematic review and meta-analysis of clinical and experimental evidence

Gastrointestinal (GI) parasites cause significant morbidity and mortality worldwide. The use of conventional antiparasitic drugs is often inhibited due to limited availability, side effects or parasite resistance. Medicinal plants can be used as alternatives or adjuncts to current antiparasitic therapies. This systematic review and meta-analysis aimed to critically synthesise the literature on the efficacy of different plants and plant compounds against common human GI parasites and their toxicity profiles. Searches were conducted from inception to September 2021. Of 5393 screened articles, 162 were included in the qualitative synthesis (159 experimental studies and three randomised control trials [RCTs]), and three articles were included in meta-analyses. A total of 507 plant species belonging to 126 families were tested against different parasites, and most of these (78.4%) evaluated antiparasitic efficacy in vitro. A total of 91 plant species and 34 compounds were reported as having significant in vitro efficacy against parasites. Only a few plants (n = 57) were evaluated for their toxicity before testing their antiparasitic effects. The meta-analyses revealed strong evidence of the effectiveness of Lepidium virginicum L. against Entamoeba histolytica with a pooled mean IC50 of 198.63 μg/mL (95% CI 155.54-241.72). We present summary tables and various recommendations to direct future research.

Application of Proteomics to the Study of the Therapeutics and Pathogenicity of Giardia duodenalis

Giardia duodenalis remains a neglected tropical disease. A key feature of the sustained transmission of Giardia is the ability to form environmentally resistant cysts. For the last 38 years, proteomics has been utilised to study various aspects of the parasite across different life cycle stages. Thirty-one articles have been published in PubMed from 2012 to 2022 related to the proteomics of G. duodenalis. Currently, mass spectrometry with LC-MS/MS and MALDI-TOF/TOF has been commonly utilised in proteomic analyses of Giardia, which enables researchers to determine potential candidates for diagnostic biomarkers as well as vaccine and drug targets, in addition to allowing them to investigate the virulence of giardiasis, the pathogenicity mechanisms of G. duodenalis, and the post-translational modifications of Giardia proteins throughout encystation. Over the last decade, valuable information from proteomics analyses of G. duodenalis has been discovered in terms of the pathogenesis and virulence of Giardia, which may provide guidance for the development of better means with which to prevent and reduce the impacts of giardiasis. Nonetheless, there is room for improving proteomics analyses of G. duodenalis, since genomic sequences for additional assemblages of Giardia have uncovered previously unknown proteins associated with the Giardia proteome. Therefore, this paper aims to review the applications of proteomics for the characterisation of G. duodenalis pathogenicity and the discovery of novel vaccine as well as drug targets, in addition to proposing some general directions for future Giardia proteomic research.

Oxygen-dependent regulation of permeability in low resistance intestinal epithelial cells infected with Giardia lamblia

Intestinal epithelial cells (IECs) reside in a highly anaerobic environment that is subject to daily fluctuations in partial oxygen pressure (pO₂), depending on intestinal tissue perfusion. This condition, known as physiological hypoxia, has a major impact on the maintenance of gut homeostasis, such as effects on the integrity and function of the intestinal epithelial barrier. Giardia lamblia is a microaerophilic protozoan parasite that infects and colonizes the small intestine of its host, causing watery diarrhea. The disease, known as giardiasis, is associated with enhanced intestinal permeability and disruption or reorganization of tight junction (TJ) proteins between IECs. Given the central role of oxygen in gut homeostasis, in this study, we aimed to evaluate whether pO₂ affects intestinal permeability (flux of ions and macromolecules) and TJ protein expression in human IECs during G. lamblia infection. Using human cell lines HuTu-80 and Caco-2 as models of "loose" (low resistance) and "tight" (high resistance) intestines, respectively, we elucidated that low pO₂ drives intestinal barrier dysfunction in IECs infected with trophozoites through dephosphorylation of protein kinase C (PKC α/β II). Additionally, we demonstrated that IECs infected with trophozoites in the presence of a pharmacological PKC activator (phorbol 12-myristate 13-acetate) partially restored the barrier function, which was correlated with increased protein expression levels of zonula occludens (ZO)-2 and occludin. Collectively, these results support the emerging theory that molecular oxygen impacts gut homeostasis during Giardia infection via direct host signaling pathways. These findings further our knowledge regarding Giardia-host interactions and the pathophysiological mechanisms of human giardiasis.

Occurrence, genetic characterization, and zoonotic importance of Giardia duodenalis in various species of rodents (Mus musculus, Rattus norvegicus, and Rattus rattus)

Giardia duodenalis is a well-known flagellated parasite and the causative agent of protozoal diarrhea in animals and humans worldwide. Current study was aimed at determination of G. duodenalis prevalence, genetic variation and zoonotic significance in various species of rodents in Shiraz, southwestern Iran. In brief, 120 fecal specimens were collected from rodents (Rattus rattus, Rattus norvegicus, and Mus musculus) during May up to November 2021 and microscopically examined for Giardia cysts. Further molecular characterization of positive samples was done by nested-PCR, followed by nucleotide sequencing of the triose phosphate isomerase (tpi) gene. A total prevalence of 3.3% (4/120) was observed in rodents, with highest rate in black rats [5% (2/40)]. Regarding brown rats and house mice, only one sample was found to be positive, showing 2.5% and 2.5% prevalence, respectively. It is noteworthy that Giardia B and G assemblages were found in black rats (one case/genotype), whereas the only positive samples from brown rats and house mice were characterized as assemblage G. The major findings of the present study were the presence of both zoonotic and non-zoonotic Giardia assemblages in examined rats in Shiraz and the potential of black rats to harbor Giardia infection to humans. These concerns should be taken seriously in terms of public health. Nevertheless, the true epidemiology and assemblage distribution of Giardia is still open to question.

Real-Time PCR for Molecular Detection of Zoonotic and Non-Zoonotic Giardia spp. in Wild Rodents

Giardiasis in humans is a gastrointestinal disease transmitted by the potentially zoonotic Giardia duodenalis genotypes (assemblages) A and B. Small wild rodents such as mice and voles are discussed as potential reservoirs for G. duodenalis but are predominantly populated by the two rodent species Giardia microti and Giardia muris. Currently, the detection of zoonotic and non-zoonotic Giardia species and genotypes in these animals relies on cumbersome PCR and sequencing approaches of genetic marker genes. This hampers the risk assessment of potential zoonotic Giardia transmissions by these animals. Here, we provide a workflow based on newly developed real-time PCR schemes targeting the small ribosomal RNA multi-copy gene locus to distinguish G. muris, G. microti and G. duodenalis infections. For the identification of potentially zoonotic G. duodenalis assemblage types A and B, an established protocol targeting the single-copy gene 4E1-HP was used. The assays were specific for the distinct Giardia species or genotypes and revealed an analytical sensitivity of approximately one or below genome equivalent for the multi-copy gene and of about 10 genome equivalents for the single-copy gene. Retesting a biobank of small rodent samples confirmed the specificity. It further identified the underlying Giardia species in four out of 11 samples that could not be typed before by PCR and sequencing. The newly developed workflow has the potential to facilitate the detection of potentially zoonotic and non-zoonotic Giardia species in wild rodents.