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Giardia duodenalis is a waterborne zoonotic protozoan that causes gastrointestinal inflammation. Giardiasis and metabolic illnesses share features such as chronic inflammation and intestinal symptoms. Receptor for advanced glycation end products (RAGE) signaling plays a role in metabolic illnesses and intestinal inflammatory responses. The presence of protozoan viruses can influence host immunological responses triggered by protozoa. However, these effects of G. duodenalis remain unknown. In this study, mice treated with the RAGE inhibitor FPS-ZM1 showed more severe intestinal damage, including increased intestinal permeability and lesions, compared to that of the untreated group. Next, we found that G. duodenalis infection activated RAGE, leading to increased secretion of pro-inflammatory cytokines, including IL-1 β, IL-6, IL-12, TNF-α and IFN-γ in mouse intestinal epithelial cells. Notably, these pro-inflammatory responses were significantly higher in Giardiavirus (GLV)-free Giardia than those of GLV-containing Giardia, except for IFN-γ. Additionally, lactate dehydrogenase (LDH) release, GSDMD-N cleavage, and the morphological observation of pyroptosis were significantly higher in cells induced by GLV-free Giardia than those infected with GLV-carrying Giardia. Differences were also observed in the MAPK (p-JNK, p-38, p-ERK) and NF-κB pathway activation, as well as reactive oxygen species (ROS) levels, with higher activation in cells infected by GLV-free Giardia, and the ROS was involved in the regulation of p38 MAPK and JNK activation. These findings reveal the potential of RAGE as a target for developing vaccines or drugs, suggesting the differences in the regulation of host immune responses induced by GLV-free Giardia or GLV-containing Giardia, providing new insights for the prevention and treatment of giardiasis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025. Published by Elsevier B.V.)

Giardia doudenalis ( lamblia , intestinalis ) is a protozoan parasite that inhabits the lumen of the upper small intestine of vertebrates, causing chronic abdominal pains and severe diarrhea, symptoms of giardiasis, a persistent and recurrent infection. This characteristic is mainly due to the presence of membrane variant-specific surface proteins (VSPs) that give this parasite the ability to successively infect the host through antigenic variation. Using high-resolution scanning microscopy (HR-SM), we observed the presence, formation, and extension of tunneling-nanotube-like surface structures in Giardia , especially following parasite challenges with VSP antibodies. They were seen all over the parasite surface, both in vitro and in vivo , showing that G . duodenalis nanotube formation occurs in complex environments such as the gut. In addition, we also observed that some of these nanotubes displayed a periodic strangulation that produces 100 nm vesicles that seemed to be released in a process similar to that previously observed in Trypanosoma brucei. The presence of nanotube-like structures in G. duodenalis highlights yet another strategy of cellular communication utilized by these parasites, whether between themselves or with the host cell.

Giardia lamblia , the cause of giardiasis, significantly impacts patients with metabolic disorders related to insulin resistance (IR). Both giardiasis and metabolic disorders share elements such as chronic inflammation and intestinal dysbiosis, which substantially affect the metabolic and cytokine profiles of patients. This review discusses the mechanisms of virulence of G. lamblia , its influence on the immune system, and its association with metabolic disorders. The review aims to show how G. lamblia invasion acts on the immune system and the glucose and lipid metabolism. Key findings reveal that G. lamblia infection, by disrupting intestinal permeability, alters microbiota composition and immune responses, potentially impairing metabolic status. Future research should focus on elucidating the specific mechanisms by which G. lamblia influences the metabolism, exploring the long-term consequences of chronic infection, and developing targeted therapeutic strategies that include both parasitic and metabolic aspects. These insights underscore the need for a multidisciplinary approach to the treatment of giardiasis in patients with metabolic disorders.

Immunoassays are important tools in diagnosing giardiasis, though there are several controversies inherent in the existing methods. We conducted a systematic review and meta-analysis to assess the pooled diagnostic accuracy of immunoassays in detecting the gastrointestinal disease-causing parasite Giardia lamblia. Our comprehensive search, which included PubMed, Scopus, and ScienceDirect from 2000 up until 2023, resulted in 34 studies reporting the performance of 24 different immunoassays. The overall pooled sensitivity and specificity of immunoassays and subgroup analyses were determined. Notably, ImmunoCardSTAT® and RIDASCREEN® Giardia were the most used assays (n = 6 studies each). They exhibited sensitivity and specificity of 84 % and 99 % and 93 % and 99 %, respectively. Sub-group analysis on the type of immunoassays (without the case-control studies) showed that commercial ELISA had higher sensitivity (96 %) compared to a commercial immunochromatographic (88 %), which justifies the difference of sensitivity between ImmunoCardSTAT® and RIDASCREEN® Giardia. However, the applicability between these two in clinical settings, replacing the gold standard, should be considered including the time, equipment requirement, and budget. Samples from symptomatic patients showed higher sensitivity (92 %) compared to asymptomatic patients (79 %). Overall, immunoassays can be a practical replacement for the current gold standard, but more information should be gathered regarding the cost of providing more conclusive suggestions on these findings., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Giardiasis is a parasitic disease caused by Giardia lamblia ( G. lamblia ) that affects people worldwide. Still, few studies report on the immunoregulatory effects of the biomolecules of colostrum during interactions with G. lamblia . This study aimed to assess the concentrations of melatonin and cortisol hormones, the percentage of Treg cells, and the levels of cytokines IL-10 and TGF-β in colostrum from mothers who tested positive for the parasite. This cross-sectional study analyzed colostrum samples from 25 puerperal. The samples were tested using an ELISA to determine if they were seropositive for G. lamblia and the type of antibody present (IgM and IgG). Based on the results, the samples were divided into three groups: a control group (N = 10) with no reaction to either IgM or IgG, a group seropositive for IgG (IgG + /IgM - ; N = 8), and a group seropositive for IgM (IgM + /IgG - ; N = 7). The concentrations of melatonin and cortisol were measured using the ELISA method. Additionally, cytokines IL-10 and TGF-β and immunophenotyping were analyzed using flow cytometry. In the group that tested positive for IgM anti- G. lamblia , the concentration of melatonin was lower. However, in the colostrum from mothers who tested positive for IgG anti- G. lamblia , the level of this hormone had increased. The cortisol levels were similar between the groups, regardless of seropositivity. There was a higher percentage of Treg cells in the colostrum from mothers who tested positive for IgM anti- G. lamblia . TGF-β levels also increased in the colostrum of mothers who tested positive for IgM anti- G. lamblia . In the seronegative group for G. lamblia , there was a positive correlation between melatonin concentration and the percentage of Treg cells. These data suggest that the increase in regulatory cells and cytokines and the reduction in melatonin in colostrum from mothers with recent giardia infection may contribute to the evolution and manifestation of the disease.

Giardia lamblia is an important protozoan cause of diarrheal disease worldwide, delayed development and cognitive impairment in children in low- and middle-income countries, and protracted post-infectious syndromes in developed regions. G. lamblia resides in the lumen and at the epithelial surface of the proximal small intestine but is not mucosa invasive. The protozoan parasite is genetically diverse with significant genome differences across strains and assemblages. Animal models, particularly murine models, have been instrumental in defining mechanisms of host defense against G. lamblia , but mice cannot be readily infected with most human pathogenic strains. Antibiotic pretreatment can increase susceptibility, suggesting that the normal microbiota plays a role in controlling G. lamblia infection in mice, but the broader implications on susceptibility to diverse strains are not known. Here, we have used gnotobiotic mice to demonstrate that robust intestinal infection can be achieved for a broad set of human-pathogenic strains of the genetic assemblages A and B. Furthermore, gnotobiotic mice were able to eradicate infection with a similar kinetics to conventional mice after trophozoite challenge. Germ-free mice could also be effectively immunized by the mucosal route with a protective antigen, α1-giardin, in a manner dependent on CD4 T cells. These results indicate that the gnotobiotic mouse model is powerful for investigating acquired host defenses in giardiasis, as the mice are broadly susceptible to diverse G. lamblia strains yet display no apparent defects in mucosal immunity needed for controlling and eradicating this lumen-dwelling pathogen., Competing Interests: The authors declare no conflict of interest.

Introduction: Serological assays are alternative laboratory tools for the diagnosis of parasitic infections. The aim of this work was to evaluate the performance of the indirect fluorescent antibody test (IFAT) and Western blotting (WB) for the detection of IgG anti-Giardia antibodies in human sera., Methodology: Sera from individuals infected with Giardia duodenalis, other parasites or non-parasitized were selected for serological assays. Ninety-seven sera were tested by IFAT at 1:20 and 1:40 dilutions and of these, 40 samples were also analyzed by WB., Results: The sensitivity and specificity of the IFAT was 97% and 46.9% at 1:20 sera dilution, and 39.4% and 59.4% at 1:40 sera dilution. The low molecular weight polypeptides fractions of 25 kDa, 27-31 kDa and 45-55 kDa were the most frequently identified by the sera of individuals infected with G. duodenalis, along with low cross-reactivity, presenting an individual sensitivity of 42.8%, 50.0% and 57.1%, and specificity of 83.3%, 83.3% and 91.7%, respectively. The highest overall sensitivity of WB (85.7%) was based on the immunoreactivity of sera with at least one of those proteins. The concordance between the detection of G. duodenalis in feces by microscopy and the WB results was considered substantial (Kappa = 0.61)., Conclusion: Constant exposure to Giardia infection throughout a lifetime can maintain high levels of specific antibodies in serum, even without active infection. Moreover, proteins found in intestinal amoebas may hinder the serological diagnosis of giardiasis in endemic areas due to cross-reactivity, which can be partially solved using Giardia low molecular weight proteins., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Background: Giardia duodenalis is a parasitic organism that can cause giardiasis, an intestinal infection, particularly prevalent in young children, with clinical symptoms of diarrhea. We previously reported that extracellular G. duodenalis triggers intracellular nucleotide-binding oligomerization-like receptor 3 (NLRP3) inflammasome activation and regulates the host inflammatory response by secreting extracellular vesicles (EVs). However, the exact pathogen-associated molecular patterns in G. duodenalis EVs (GEVs) involved in this process and the role of the NLRP3 inflammasome in giardiasis remain to be elucidated., Methods: Recombinant eukaryotic expression plasmids of pcDNA3.1(+)-alpha-2 and alpha-7.3 giardins in GEVs were constructed, transfected into primary mouse peritoneal macrophages and screened by measuring the expression levels of the inflammasome target molecule caspase-1 p20. The preliminary identification of G. duodenalis alpha-2 and alpha-7.3 giardins was further verified by measuring the protein expression levels of key molecules of the NLRP3 inflammasome (NLRP3, pro-interleukin-1 beta [IL-1β], pro-caspase-1, and caspase-1 p20), the secretion levels of IL-1β, the level of apoptosis speck-like protein (ASC) oligomerization and the immunofluorescence localization of NLRP3 and ASC. The roles of the NLRP3 inflammasome in G. duodenalis pathogenicity were then evaluated using mice in which NLRP3 activation was blocked (NLRP3-blocked mice), and body weight, parasite burden in the duodenum and histopathological changes in the duodenum were monitored. In addition, we explored whether alpha-2 and alpha-7.3 giardins triggered IL-1β secretion in vivo through the NLRP3 inflammasome and determined the roles of these molecules in G. duodenalis pathogenicity in mice., Results: Alpha-2 and alpha-7.3 giardins triggered NLRP3 inflammasome activation in vitro. This led to caspase-1 p20 activation, upregulation of the protein expression levels of NLRP3, pro-IL-1β and pro-caspase-1, significant enhancement of IL-1β secretion, ASC speck formation in the cytoplasm and also induction of ASC oligomerization. Deletion of the NLRP3 inflammasome aggravated G. duodenalis pathogenicity in mice. Compared to wild-type mice gavaged with cysts, mice gavaged with cysts in NLRP3-blocked mice displayed increased trophozoite loads and severe duodenal villus damage, characterized by necrotic crypts with atrophy and branching. In vivo assays revealed that alpha-2 and alpha-7.3 giardins could induce IL-1β secretion through the NLRP3 inflammasome and that immunization with alpha-2 and alpha-7.3 giardins decreased G. duodenalis pathogenicity in mice., Conclusions: Overall, the results of the present study revealed that alpha-2 and alpha-7.3 giardins trigger host NLRP3 inflammasome activation and decrease G. duodenalis infection ability in mice, which are promising targets for the prevention of giardiasis., (© 2023. The Author(s).)

Background & Aims: The protozoa Giardia duodenalis is a major cause of gastrointestinal illness worldwide, but underlying pathophysiological mechanisms remain obscure, partly due to the absence of adequate cellular models. We aimed at overcoming these limitations and recapitulating the authentic series of pathogenic events in the primary human duodenal tissue by using the human organoid system., Methods: We established a compartmentalized cellular transwell system with electrophysiological and barrier properties akin to duodenal mucosa and dissected the events leading to G. duodenalis-induced barrier breakdown by functional analysis of transcriptional, electrophysiological, and tight junction components., Results: Organoid-derived cell layers of different donors showed a time- and parasite load-dependent leak flux indicated by collapse of the epithelial barrier upon G. duodenalis infection. Gene set enrichment analysis suggested major expression changes, including gene sets contributing to ion transport and tight junction structure. Solute carrier family 12 member 2 and cystic fibrosis transmembrane conductance regulator-dependent chloride secretion was reduced early after infection, while changes in the tight junction composition, localization, and structural organization occurred later as revealed by immunofluorescence analysis and freeze fracture electron microscopy. Functionally, barrier loss was linked to the adenosine 3',5'-cyclic monophosphate (cAMP)/protein kinase A-cAMP response element-binding protein signaling pathway., Conclusions: Data suggest a previously unknown sequence of events culminating in intestinal barrier dysfunction upon G. duodenalis infection during which alterations of cellular ion transport were followed by breakdown of the tight junctional complex and loss of epithelial integrity, events involving a cAMP/protein kinase A-cAMP response element-binding protein mechanism. These findings and the newly established organoid-derived model to study G. duodenalis infection may help to explore new options for intervening with disease and infection, in particular relevant for chronic cases of giardiasis., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The MORDOR trial in Niger, Malawi, and Tanzania found that biannual mass distribution of azithromycin to children younger than 5 years led to a 13.5% reduction in all-cause mortality (NCT02048007). To help elucidate the mechanism for mortality reduction, we report IgG responses to 11 malaria, bacterial, and protozoan pathogens using a multiplex bead assay in pre-specified substudy of 30 communities in the rural Niger placebo-controlled trial over a three-year period (n = 5642 blood specimens, n = 3814 children ages 1-59 months). Mass azithromycin reduces Campylobacter spp. force of infection by 29% (hazard ratio = 0.71, 95% CI: 0.56, 0.89; P = 0.004) but serological measures show no significant differences between groups for other pathogens against a backdrop of high transmission. Results align with a recent microbiome study in the communities. Given significant sequelae of Campylobacter infection among preschool aged children, our results support an important mechanism through which biannual mass distribution of azithromycin likely reduces mortality in Niger., (© 2022. The Author(s).)

Our aim was to evaluate the impact of immunosuppression on the development of giardiasis. Thirty-six gerbils (4-6 weeks old) were distributed in four groups containing nine animals each: Control (CT); Control-Infected by Giardia lamblia (CTIn), Immunosuppressed (IS), and Immunosuppressed-Infected by G. lamblia (ISIn). Animals in the IS and ISIn groups received intramuscular dexamethasone solution for 25 days. On the 11th day, the animals in the CTIn and ISIn groups were inoculated with G. lamblia. After 14 days of infection, the 25th day of the experiment, all groups were euthanized. Four hours after euthanasia, the intestinal permeability was evaluated and sections of the duodenum and spleen were harvested for morphometric and histopathological analyses. Immunosuppressed groups showed a significant increase in intestinal permeability compared to control and infected groups. Considering that the infection can become chronic in immunosuppressed groups, we should be alert to the possibilities of chronic inflammatory changes, both locally and systemically, due to the loss of the intestinal barrier. Lesions were observed in the duodenal mucosa of the gerbils of the CTIn group, with reduced villi size, crypt hyperplasia, edema, and the presence of inflammatory infiltrate in the lamina propria. In the ISIn group, we observed no inflammation, long and intact villi, and a significant increase in the area of intestinal mucins, despite the large number of trophozoites identified. Our results suggest that exacerbation of the immune response has a direct relationship with the appearance of lesions during enteritis produced by G. lamblia in the assessed model., (Copyright © 2021. Published by Elsevier Inc.)

Giardiasis represents a latent problem in public health due to the exceptionally pathogenic strategies of the parasite Giardia lamblia for evading the human immune system. Strains resistant to first-line drugs are also a challenge. Therefore, new antigiardial therapies are urgently needed. Here, we tested giardial arginine deiminase (GlADI) as a target against giardiasis. GlADI belongs to an essential pathway in Giardia for the synthesis of ATP, which is absent in humans. In silico docking with six thiol-reactive compounds was performed; four of which are approved drugs for humans. Recombinant GlADI was used in enzyme inhibition assays, and computational in silico predictions and spectroscopic studies were applied to follow the enzyme's structural disturbance and identify possible effective drugs. Inhibition by modification of cysteines was corroborated using Ellman's method. The efficacy of these drugs on parasite viability was assayed on Giardia trophozoites, along with the inhibition of the endogenous GlADI. The most potent drug against GlADI was assayed on Giardia encystment. The tested drugs inhibited the recombinant GlADI by modifying its cysteines and, potentially, by altering its 3D structure. Only rabeprazole and omeprazole decreased trophozoite survival by inhibiting endogenous GlADI, while rabeprazole also decreased the Giardia encystment rate. These findings demonstrate the potential of GlADI as a target against giardiasis.

Multiplex bead assays (MBAs) for serologic testing have become more prevalent in public health surveys, but few studies have assessed their test performance. As part of a trachoma study conducted in a rural part of Ethiopia in 2016, dried blood spots (DBS) were collected from a random sample of 393 children aged 0 to 9 years, with at least two separate 6-mm DBS collected on a filter card. Samples eluted from DBS were processed using an MBA on the Luminex platform for antibodies against 13 antigens of nine infectious organisms: Chlamydia trachomatis, Vibrio cholera, enterotoxigenic Escherichia coli, Cryptosporidium parvum, Entamoeba histolytica, Camplyobacter jejuni, Salmonella typhimurium Group B, Salmonella enteritidis Group D, and Giardia lamblia. Two separate DBS from each child were processed. The first DBS was run a single time, with the MBA set to read 100 beads per well. The second DBS was run twice, first at 100 beads per well and then at 50 beads per well. Results were expressed as the median fluorescence intensity minus background (MFI-BG), and classified as seropositive or seronegative according to external standards. Agreement between the three runs was high, with intraclass correlation coefficients of > 0.85 for the two Salmonella antibody responses and > 0.95 for the other 11 antibody responses. Agreement was also high for the dichotomous seropositivity indicators, with Cohen's kappa statistics exceeding 0.87 for each antibody assay. These results suggest that serologic testing on the Luminex platform had strong test performance characteristics for analyzing antibodies using DBS.

The proteoglycan serglycin (SG) is expressed by different innate and adaptive immune cells, e.g. mast cells, macrophages, neutrophils, and cytotoxic T lymphocytes, where SG contributes to correct granule storage and extracellular activity of inflammatory mediators. Here the serglycin-deficient (SG -/- ) mouse strain was used to investigate the impact of SG on intestinal immune responses during infection with the non-invasive protozoan parasite Giardia intestinalis . Young (≈11 weeks old) oral gavage-infected congenic SG -/- mice showed reduced weight gain as compared with the infected SG +/+ littermate mice and the PBS-challenged SG -/- and SG +/+ littermate mice. The infection caused no major morphological changes in the small intestine. However, a SG-independent increased goblet cell and granulocyte cell count was observed, which did not correlate with an increased myeloperoxidase or neutrophil elastase activity. Furthermore, infected mice showed increased serum IL-6 levels, with significantly reduced serum IL-6 levels in infected SG-deficient mice and decreased intestinal expression levels of IL-6 in the infected SG-deficient mice. In infected mice the qPCR analysis of alarmins, chemokines, cytokines, and nitric oxide synthases (NOS), showed that the SG-deficiency caused reduced intestinal expression levels of TNF-α and CXCL2, and increased IFN-γ, CXCL1, and NOS1 levels as compared with SG-competent mice. This study shows that SG plays a regulatory role in intestinal immune responses, reflected by changes in chemokine and cytokine expression levels and a delayed weight gain in young SG -/- mice infected with G. intestinalis ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Li, Peirasmaki, Svärd and Åbrink.)

Giardia duodenalis is one of the most commonly found intestinal parasites in mammalian hosts. Infections can generally be cleared by mounting an adequate protective immune response that is orchestrated through IL-17A. This study was aimed to investigate if and how the intestinal microbiome affects the protective Th17 response against Giardia by analysing and comparing the immune response following a G. muris and G. duodenalis infection in antibiotic treated and untreated mice. Depletion of the intestinal flora by antibiotic treatment had a severe effect on the infection dynamics of both Giardia species. Not only duration of infection was affected, but also the parasite burden increased significantly. Markers associated with a protective immune response, such as IL-17A and mannose binding lectin 2 were still significantly upregulated following infection in the antibiotic-treated mice, despite the lack of protection. On the other hand, the antibiotic treatment significantly decreased the level of IgA in the intestinal lumen by affecting its transporter and by reducing the number of IgA + B-cells at the Peyer's patches. Furthermore, the depletion of the gut microbiota by antibiotics also significantly lowered the intestinal motility. The combination of these factors likely results in a decreased clearance of the parasite from the intestinal tract.

Aims. Giardia: is sometimes missed by the pathologist, and we sought to determine how often this occurs at our institution-a large tertiary care center with a subspecialty gastrointestinal pathology service and what certain clinical and histologic clues can be used to flag cases with a higher likelihood of infection, targeting them for greater scrutiny., Methods and Results: We identified a set of patients who tested positive for Giardia with a stool-based test, and who also received a small bowel biopsy at a similar time-point. These biopsies were retrospectively reviewed for Giardia , finding 8 positive cases. The organism was prospectively detected in 4 cases (50%) but overlooked in the remaining 4 cases (50%). Three of the 4 cases missed cases showed only rare organisms. The detected cases tended to more frequently have prominent lymphoid aggregates (3 detected cases, 0 overlooked cases) and intraepithelial lymphocytosis (3 detected cases, 0 overlooked cases). Certain clinical and histologic clues can be used to flag cases with a higher likelihood of infection. Specifically, we found abnormalities of the mucosa (active inflammation, intraepithelial lymphocytosis, villous expansion, prominent lymphoid aggregates) in each case, and 4 of 8 cases were from immunocompromised patients. Finally, 2 of 8 cases were terminal ileum biopsies., Conclusions: Biopsies with a histologic abnormality or those from immunocompromised patients should receive greater attention. Routinely looking for Giardia at that terminal ileum is necessary.

Aims: IgA and Th17 responses are pivotal for the control of Giardia infections. Eosinophils support IgA class switching, the survival of intestinal IgA + plasma cells at steady state and can control Th17 activity in the small intestine. To see whether eosinophils regulate adaptive immune responses during giardiasis, we investigated Giardia muris infections in wild-type BALB/c and eosinophil-deficient ∆dblGATA-1 mice., Methods and Results: Infected ∆dblGATA-1 mice did not differ markedly in parasite control from wild-type mice. Confirming previous studies, naive ∆dblGATA-1 mice displayed diminished IgA + B cell frequencies in Peyer's patches. However, IgA class switching and intestinal IgA secretion in response to G muris infection were comparable in wild-type BALB/c and ∆dblGATA-1 mice. Both strains displayed similarly low intestinal Th17 responses, accompanied by a mild expansion of type 3 innate lymphoid cells (ILC3)., Conclusions: Contrasting previous reports on overt small intestinal Th17 activity in eosinophil-deficient mice, IL-17A production is kept in check in the absence of eosinophils during Giardia infection. Suboptimal homeostatic IgA responses in the absence of eosinophils are transiently fostered in infected mice and the maintenance of IgA + plasma cells appears to be restored during persisting Giardia infection., (© 2020 The Authors. Parasite Immunology published by John Wiley & Sons Ltd.)

Giardia intestinalis has been observed in human stools since the invention of the microscope. However, it was not recognized as a pathogen until experimental infections in humans in the 1950s resulted in diarrheal illness [1]. We now know that this protozoan is capable of inducing a malabsorptive diarrhea and that the parasite is a major contributor to stunting in young children [2]. However, the majority of infections with this parasite are not accompanied by overt diarrhea and several studies indicate that it actually has a protective effect against moderate-severe diarrhea [3]. There is therefore significant interest in the mechanisms responsible for the wide variation observed in the clinical outcomes of infection with Giardia. This review will highlight recent work on the interactions among the parasite, the host microbiome and the immune response as contributing to this variation., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Giardiasis is the major water-borne diarrheal disease present worldwide caused by the common intestinal parasite, Giardia duodenalis. This work aims to investigate the effect of G. duodenalis infection pathogenicity in immunosuppressed animals through histopathological examination. A total of 45 BALB/c mice were divided into four groups; G1 (negative control), G2 (healthy animals exposed to Giardia); G3 (immunosuppressed animals exposed to Giardia), and G4 (non-exposed immunosuppressed animals). Our study revealed that G3 was the most affected group with an infection rate of 100%. The animals showed general weakness, soft stool, and high death rate with severe histopathological changes in the duodenum and mild degenerative changes in hepatic tissues. In G2, the maximal lesions in both duodenum and liver were on the 11 th day. We spotted damage in the villi, edema in the central core, and submucosa, in addition to increased cellular infiltration with inflammation in lamina propria. The presence of the parasites within the villi and the lumen was clear. Most of the hepatocytes revealed hydropic and fatty changes, also dilated congested central veins and edema were observed. G3 changes were more intense than G2 with massive Giardia trophozoites between the intestinal villi, lumen, and extensive fatty liver degeneration. Immune suppression plays a significant role in the severity of injury with the Giardia parasites in duodenum and liver cells.

Aims: Giardia lamblia is a protozoan parasite that causes giardiasis, one of the most common worldwide gastrointestinal diseases. For rational development of a Giardia vaccine, increasing our understanding of the host-Giardia interaction is crucial. In this study, we analysed the immunogenicity and antigenicity of two G lamblia strain variants [GS and GS-5G8 (+)], which express different levels of the variant-specific surface protein (VSP) 5G8 and also analysed the intestinal histological changes associated with Giardia infection., Methods and Results: We evaluated the antibody responses induced by G lamblia strains in infected, reinfected and immunized C3H/HeJ mice using ELISA, flow cytometry, Western blotting and histological analysis. Our results showed that G lamblia GS-5G8 (+) was more immunogenic and antigenic than the GS strain. The antibody response against the GS-5G8 (+) strain primarily recognized 5G8 protein. Serum antibody from infected and reinfected mice exhibited specific agglutination of trophozoites in vitro. GS-5G8 (+)-infected mice showed higher CD19 + infiltrating cell levels compared to GS-infected animals., Conclusion: G lamblia strains with different expression levels of an immunogenic antigen (VSP 5G8) induce differential antibody responses. A better understanding of the immunogenic proteins of G lamblia will contribute to the rational development of an effective vaccine against this parasitic disease., (© 2020 John Wiley & Sons Ltd.)

The protozoan Giardia lamblia is the most common cause of parasitic gastrointestinal infection worldwide. The parasite developed sophisticated, yet not completely disclosed, mechanisms to escape immune system and growth in the intestine. To further understand the interaction of G. lamblia with host immune cells, we investigated the ability of parasites to modulate the canonical activation of mouse macrophages (Raw 264.7 cell line) and human monocyte-derived macrophages triggered by the TLR4 agonist, lipopolysaccharide (LPS). We observed that G. lamblia impairs LPS-evoked pro-inflammatory status in these macrophage-like cells through inhibition of cyclooxygenase-2 and inducible nitric oxide synthase expression and subsequent NO production. This effect was in part due to the activity of three G. lamblia proteases, a 135 kDa metalloprotease and two cysteine proteases with 75 and 63 kDa, that cleave the p65 RelA subunit of the nuclear factor-kappa B (NF-κB). Moreover, Tnf and Ccl4 transcription was increased in the presence of the parasite. Overall, our data indicates that G. lamblia modulates macrophages inflammatory response through impairment of the NF-κB, thus silencing a crucial signaling pathway of the host innate immune response.

Mast cells have been shown to affect the control of infections with the protozoan parasite Giardia intestinalis . Recently, we demonstrated that Giardia excretory-secretory proteins inhibited the activity of the connective tissue mast cell-specific protease chymase. To study the potential role of the chymase mouse mast cell protease (mMCP)-4 during infections with Giardia, mMCP-4 +/+ and mMCP-4 -/- littermate mice were gavage-infected with G. intestinalis trophozoites of the human assemblage B isolate GS. No significant changes in weight gain was observed in infected young (≈10 weeks old) mMCP-4 -/- and mMCP-4 +/+ littermate mice. In contrast, infections of mature adult mice (>18 weeks old) caused significant weight loss as compared to uninfected control mice. We detected a more rapid weight loss in mMCP-4 -/- mice as compared to littermate mMCP-4 +/+ mice. Submucosal mast cell and granulocyte counts in jejunum increased in the infected adult mMCP-4 -/- and mMCP-4 +/+ mice. This increase was correlated with an augmented intestinal trypsin-like and chymotrypsin-like activity, but the myeloperoxidase activity was constant. Infected mice showed a significantly lower intestinal neutrophil elastase (NE) activity, and in vitro, soluble Giardia proteins inhibited human recombinant NE. Serum levels of IL-6 were significantly increased eight and 13 days post infection (dpi), while intestinal IL-6 levels showed a trend to significant increase 8 dpi. Strikingly, the lack of mMCP-4 resulted in significantly less intestinal transcriptional upregulation of IL-6, TNF-α, IL-25, CXCL2, IL-2, IL-4, IL-5, and IL-10 in the Giardia -infected mature adult mice, suggesting that chymase may play a regulatory role in intestinal cytokine responses.

Covalent loading or directional binding of biomolecules on gold nanoparticles (AuNPs) could lead to better results than simple direct adsorption for an enhanced ELISA application. The use of Mini-Parasep solvent-free (SF) without ether or ethyl acetate for the clean and efficient concentration of protozoa cysts, it is a single-use device for in vitro diagnostic use only. In this work, we used Mini-Parasep SF for the detection of giardia cysts in comparison to direct smear and Merthiolate-Iodine Formaldehyde Concentration (MIFC) technique in addition to its use in antigen detection by AuNPs biomolecule loading using rabbit polyclonal antibodies (pAb) against purified Giardia antigen (PGA). As a result, Mini-Parasep SF was the most effective method for Giardia cyst detection and regarding optimization of Mini-Parasep antigen detection, our data showed increased sensitivity and specificity of nano-sandwich ELISA to 92% and 94% respectively and increased positive predictive value (PPV) and negative predictive value (NPV) to 88.64% and 95.91% respectively. In conclusion, this research provides that Mini-Parasep SF concentrator enhanced Giardia cyst detection and improved antigen preparation for AuNPs sandwich ELISA in giardiasis diagnosis. The advantages of this method are the short assay time and the raised accuracy of antigen detection providing concentrated samples without the risk of solvent use and being a disposable Mini-Parasep it helps in giardia antigen purification as well as raising the sensitivity and specificity of ELISA through binding AuNPs.

Background: Mast cells are involved in the host immune response controlling infection with the non-invasive intestinal protozoan parasite Giardia intestinalis. Experimental infections in rodents with G. intestinalis showed increased intestinal expression of mucosal and connective mast cell specific proteases suggesting that both mucosal and connective tissue mast cells are recruited and activated during infection. During infection Giardia excretory-secretory proteins (ESPs) with immunomodulatory capacity are released. However, studies investigating potential interactions between Giardia ESPs and the connective tissue mast cell specific serine proteases, i.e. human chymase and mouse mast cell protease (mMCP)-4 and, human and mouse tryptase (mMCP-6) remain scarce., Results: We first investigated if soluble Giardia proteins (sGPs), which over-lap extensively in protein content with ESP fractions, from the isolates GS, WB and H3, could induce mast cell activation. sGPs induced a minor activation of bone marrow derived mucosal-like mast cells, as indicated by increased IL-6 secretion and no degranulation. Furthermore, sGPs were highly resistant to degradation by human tryptase while human chymase degraded a 65 kDa sGP and, wild-type mouse ear tissue extracts degraded several protein bands in the 10 to 75 kDa range. In striking contrast, sGPs and ESPs were found to increase the enzymatic activity of human and mouse tryptase and to reduce the activity of human and mouse chymase., Conclusion: Our finding suggests that Giardia ssp. via enhancement or reduction of mast cell protease activity may modulate mast cell-driven intestinal immune responses. ESP-mediated modulation of the mast cell specific proteases may also increase degradation of tight junctions, which may be beneficial for Giardia ssp. during infection., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Infection with the intestinal parasite Giardia duodenalis is one of the most common causes of diarrheal disease in the world. Previous work has demonstrated that the cells and mechanisms of the adaptive immune system are critical for clearance of this parasite. However, the innate system has not been as well studied in the context of Giardia infection. We have previously demonstrated that Giardia infection leads to the accumulation of a population of CD11b + , F4/80 + , ARG1 + , and NOS2 + macrophages in the small intestinal lamina propria. In this report, we sought to identify the accumulation mechanism of duodenal macrophages during Giardia infection and to determine if these cells were essential to the induction of protective Giardia immunity. We show that F4/80 + , CD11b + , CD11c int , CX3CR1 + , MHC class II + , Ly6C - , ARG1 + , and NOS2 + macrophages accumulate in the small intestine during infections in mice. Consistent with this resident macrophage phenotype, macrophage accumulation does not require CCR2, and the macrophages incorporate EdU, indicating in situ proliferation rather than the recruitment of monocytes. Depletion of macrophages using anti-CSF1R did not impact parasite clearance nor development of regulatory T cell or Th17 cellular responses, suggesting that these macrophages are dispensable for protective Giardia immunity., (Copyright © 2019 The Authors.)

Giardia lamblia is a common intestinal parasitic infection that although often acutely asymptomatic, is associated with debilitating chronic intestinal and extra-intestinal sequelae. In previously healthy adults, a primary sporadic Giardia infection can lead to gut dysfunction and fatigue. These symptoms correlate with markers of inflammation that persist well after the infection is cleared. In contrast, in endemic settings, first exposure occurs in children who are frequently malnourished and also co-infected with other enteropathogens. In these children, Giardia rarely causes symptoms and associates with several decreased markers of inflammation. Mechanisms underlying these disparate and potentially enduring outcomes following Giardia infection are not presently well understood. A body of work suggests that the outcome of experimental Giardia infection is influenced by the nutritional status of the host. Here, we explore the consequences of experimental Giardia infection under conditions of protein sufficiency or deficiency on cytokine responses of ex vivo bone marrow derived dendritic cells (BMDCs) to endotoxin stimulation. We show that BMDCs from Giardia- challenged mice on a protein sufficient diet produce more IL-23 when compared to uninfected controls whereas BMDCs from Giardia challenged mice fed a protein deficient diet do not. Further, in vivo co-infection with Giardia attenuates robust IL-23 responses in endotoxin-stimulated BMDCs from protein deficient mice harboring enteroaggregative Escherichia coli. These results suggest that intestinal Giardia infection may have extra-intestinal effects on BMDC inflammatory cytokine production in a diet dependent manner, and that Giardia may influence the severity of the innate immune response to other enteropathogens. This work supports recent findings that intestinal microbial exposure may have lasting influences on systemic inflammatory responses, and may provide better understanding of potential mechanisms of post-infectious sequelae and clinical variation during Giardia and enteropathogen co-infection., Competing Interests: The authors have declared that no competing interests exist.

In this study, we evaluated serum markers of immune responses in children infected with G. duodenalis and compared them with the characterized parasite isolates. The reactivity indexes (RI) of IgG (1.503 ± 0.819) and IgA (2.308 ± 1.935) antibodies were significantly higher (P < 0.001) in infected children than in non-infected children. There were also statistically significantly higher serum levels (P < 0.05) of IFN-γ (393.10 ± 983.90 pg/mL) as well as serum (30.03 ± 10.92 μmol/L) and saliva nitric oxid derivatives (NO x ) (192.4 ± 151.2 μmol/L) in children infected with G. duodenalis compared to the group of non-parasitized children (127.4 ± 274.30 pg/mL; 25.82 ± 7.74 μmol/L and 122.5 ± 105.90 μmol/L, respectively). Regarding the characterized genetic variants of G. duodenalis and the immune response profiles, no differences were observed in terms of antibody reactivity or levels of serum cytokine and NO x among children infected with AI or AII subassemblages. The elevated levels of IFN-γ and NO x indicate that G. duodenalis intestinal infection in humans induces a cellular immune response detectable at the systemic level. Moreover, no significant differences in the antibody reactivity profile or the cytokine and NO x production in the sera of children infected with AI or AII G. duodenalis variants were observed, suggesting that subtypes of the parasite do not influence the immune response profile., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Innate lymphoid cells (ILCs) are key players during an immune response at the mucosal surfaces, such as lung, skin, and gastrointestinal tract. Giardia lamblia is an extracellular protozoan pathogen that inhabits the human small intestine. In this study, ILCs prepared from the lamina propria of mouse small intestine were incubated with G. lamblia trophozoites. Transcriptional changes in G. lamblia-exposed ILCs resulted in identification of activation of several immune pathways. Secretion of interleukin (IL)-17A, IL-17F, IL-1β, and interferon-γ was increased, whereas levels of IL-13, IL-5, and IL22, was maintained or reduced upon exposure to G. lamblia. Goup 3 ILC (ILC3) was found to be dominant amongst the ILCs, and increased significantly upon co-cultivation with G. lamblia trophozoites. Oral inoculation of G. lamblia trophozoites into mice resulted in their presence in the small intestine, of which, the highest number of parasites was detected at the 5 days-post infection. Increased ILC3 was observed amongst the ILC population at the 5 days-post infection. These findings indicate that ILC3 from the lamina propria secretes IL-17 in response to G. lamblia, leading to the intestinal pathology observed in giardiasis.

Giardia lamblia , one of the most common protozoal infections of the human intestine, is an important worldwide cause of diarrheal disease, malabsorption, malnutrition, delayed cognitive development in children, and protracted postinfectious syndromes. Despite its medical importance, no human vaccine is available against giardiasis. A crude veterinary vaccine has been developed, and experimental vaccines based on expression of multiple variant-specific surface proteins have been reported, but poorly defined vaccine components and excessive antigen variability are problematic for pharmaceutical vaccine production. To expand the repertoire of antigen candidates for vaccines, we reasoned that surface proteins may provide an enriched source of such antigens since key host effectors, such as secretory IgA, can directly bind to such antigens in the intestinal lumen and interfere with epithelial attachment. Here, we have applied a proteomics approach to identify 23 novel surface antigens of G. lamblia that show >90% amino acid sequence identity between the two human-pathogenic genetic assemblages (A and B) of the parasite. Surface localization of a representative subset of these proteins was confirmed by immunostaining. Four selected proteins, uridine phosphorylase-like protein-1, protein 21.1 (GL50803&#95;27925), α1-giardin, and α11-giardin, were subsequently produced in recombinant form and shown to be immunogenic in mice and G. lamblia -infected humans and confer protection against G. lamblia infection upon intranasal immunization in rodent models of giardiasis. These results demonstrate that identification of conserved surface antigens provides a powerful approach for overcoming a key rate-limiting step in the design and construction of an effective vaccine against giardiasis., (Copyright © 2019 American Society for Microbiology.)

Giardiasis is a re-emerging infectious disease with outbreaks reported globally specially in children and malnourished individuals leading to malabsorption, growth retardation, and severe diarrhea. Thus, in the present study, prophylactic administration of synbiotic as the functional food was used to assess its antigiardial potential in malnourished murine giardiasis. Interestingly, prior administration of synbiotic (Lactobacillus casei + inulin) even to malnourished-Giardia-infected mice led to increased body mass, small intestine mass, lactobacilli counts, and reduced severity of giardiasis as evident by decreased cyst and trophozoite counts. Synbiotic therapy further boosted the innate and acquired immune response resulting into increase in nitric oxide, antigiardial secretory IgA and IgG antibody levels along with IL-6 and IL-10 cytokines, and decreased levels of inflammatory TNF-α cytokine in both serum and intestinal fluid in malnourished-synbiotic-Giardia-infected mice compared with malnourished-Giardia-infected mice. More specifically, histopathological and scanning electron microscopy analysis of the small intestine also confirmed the modulatory potentials of synbiotic in malnourished-synbiotic-Giardia mice which had less cellular and mucosal damage compared with severely damaged, mummified, and blunted villi in malnourished-Giardia-infected mice. Taken together, this is the first experimental study to report that prior supplementation of synbiotic restored the gut morphology and improved the immune status of the malnourished-Giardia-infected mice, and could be considered as the prophylactic adjunct therapy for malnourished individuals.

Infection with Giardia produces a wide range of clinical outcomes. Acutely infected patients may have no overt symptoms or suffer from severe cramps, diarrhea, nausea and even urticaria. Recently, post-infectious irritable bowel syndrome and chronic fatigue syndrome have been identified as long-term sequelae of giardiasis. Frequently, recurrent and chronic Giardia infection is considered a major contributor to stunting in children from low and middle income countries. Perhaps the most unusual outcome of infection with Giardia is the apparent reduced risk of developing moderate-to-severe diarrhea due to other enteric infections which has been noted in several recent studies. The goal of understanding immune responses against Giardia is therefore to identify protective mechanisms which could become targets for vaccine development, but also to identify mechanisms whereby infections lead to these other diverse outcomes. Giardia induces a robust adaptive immune response in both humans and animals. It has been known for many years that there is production of large amounts of parasite-specific IgA following infection and that CD4 + T cell responses contribute to this IgA production and control of the infection. In the past decade, there have been advances in our understanding of the non-antibody effector mechanisms used by the host to fight Giardia infections, in particular the importance of the cytokine interleukin (IL)-17 in orchestrating these responses. There have also been major advances in understanding how the innate response to Giardia infection is initiated and how it contributes to the development of adaptive immunity. Finally, there here have been significant increases in our knowledge of how the resident microbial community influences the immune response and how these responses contribute to the development of some of the symptoms of giardiasis. In this article, we will focus on data generated in the last 10 years and how it has advanced our knowledge about this important parasitic disease., (© 2019 Elsevier Ltd All rights reserved.)

Cellular immune responses were tested to determine the effect of fenbendazole on the function of lymphocytes from Bolivian squirrel monkeys (Samiri boliviensis boliviensis). Giardia-infected squirrel monkeys were treated with commercially available fenbendazole (FBZ)-medicated monkey chow. Immune responses were compared between historical controls (Giardia naïve, untreated with FBZ (control animals)) and Giardia-infected, FBZ-treated squirrel monkeys (study animals). Peripheral blood lymphocytes from study monkeys had significantly lower stimulation indices compared to control animals when cultured in vitro with concanavalin A (Con A) (p<0.0001), phytohaemagglutinin (PHA) (p<0.0001) and lipopolysaccharide (LPS) (p<0.0001). PBMCs were also analyzed for IFN-γ producing cells in response to stimulation with Con A, PHA, PWM, and LPS by the cytokine ELISPOT assay. Significantly higher responses to Con A- (p<0.0001), and PHA- (p<0.001) stimulated cultures from Giardia-infected and fenbendazole treated compared to controls. Flow cytometric analysis for expression of cell surface markers revealed a significant increase in B- and NKT-lymphocytes and significant decrease in CD14+CD16+ monocytes after FBZ treatment. Also, circulating plasma cytokines IFN-γ, TNF-α, IL-12p40, IL-1β, IL-10, IL-13, IL-1ra, IL-6 and IL-4 were significantly decreased after FBZ treatment. Comparison of hematologic parameters between controls and FBZ-treated squirrel monkeys revealed significantly lower numbers of total leukocytes, neutrophils, monocytes, and eosinophils compared to controls. However, erythrocyte indices (red cell count, hemoglobin and hematocrit were significantly higher in FBZ-treated monkeys. Our findings suggest that fenbendazole treatment may alter sensitive immune and molecular measures of inflammation. Postponing the experimental use of squirrel monkeys until at least 6 weeks after FBZ treatment should be considered., Competing Interests: The authors have declared that no competing interests exist.

Giardia lamblia is one of the most prevalent parasites residing in the duodenum of human and many other mammals throughout the world which is transmitted via ingested cysts through contaminated food or water. The severity of disease may depend on multiple parasite and host factors. Commonly, children and immunologically compromised persons like AIDS patient exhibit severe diarrhea, malabsorption and weight loss, however, there are also some infected people who are asymptomatic or only exhibit mild clinical symptoms and can shed the Giardia cysts in the environment. Although many studies have indicated that the innate immune system is important for Giardia defense, however, whether the innate immune responses such extracellular traps (ETs) could be induced by G. lamblia is still unclear. In recent years, macrophage extracellular traps (METs) have been described as an effective defense mechanism against invading microorganisms. In the present study, the formation of METs triggered by G. lamblia trophozoites was investigated. The formation of METs induced by G. lamblia trophozoites of mouse macrophage was observed with Scanning Electron Microscopy (SEM). The main components DNA, H3 histone and MPO were confirmed by Sytox orange staining, DNase1 digestion, immunofluorescence staining and fluorescence confocal microscopy. Inhibitor assays suggested that G. lamblia trophozoites triggered METs formation through ERK1/2 and p38 MAPK signal pathways and was Store-operated Ca 2+ entry (SOCE) dependent. In addition, the process of METs formation triggered by G. lamblia trophozoites was also time and dose-dependent. Furthermore, the production of Reactive Oxygen Species (ROS) in macrophages stimulated with G. lamblia trophozoites significantly increased whereas no significant changes were observed about LDH activity., (Copyright © 2018. Published by Elsevier Ltd.)

Mast cells play a central role in the early clearance of the intestinal parasite Giardia lamblia. In a previous study, we reported that G. lamblia live trophozoites or trophozoite-derived total soluble extract induced direct activation (IgE-independent) of mast cells and release of IL-6 and TNF-α. To identify the Giardia molecules and the mast cell receptors involved in this activation, trophozoite-derived total soluble proteins separated into three fractions (F1-F3) were evaluated for its ability to activate mast cells in vitro. F2 activated mast cells in a greater extent than F1 and F3. Furthermore, F2 induced the release of IL-6 and TNF-α by mast cells. TLR2 and TLR4 expression increased slightly after mast cell stimulation with either F2 or total soluble extract; however, these receptors were not involved in F2 or total soluble extract-induced proinflammatory cytokine production. Proteins present in F2 as unique and high-intensity bands identified by liquid chromatography coupled with tandem mass spectrometry, include molecules with important biological activities such as enolase and arginine deiminase (ADI). Recombinant ADI and enolase were tested for their ability to activate mast cells, but only ADI induced a significant release of IL-6 and TNF-α. ADI product, citrulline but not ammonium, also induced mast cell release of TNF-α. Interestingly, recombinant ADI still stimulated the secretion of TNF-α by mast cells in a arginine-free medium, although in a lower extend that in the presence of arginine, indicating that either ADI itself can stimulate mast cells or through its metabolic product, citrulline.

Introduction/aims: The long-term humoral immune response after a natural giardiasis infection is not well understood. The aim of this study was to evaluate longitudinal serum IgA and IgG/M responses towards conserved regions of two Giardia variant-specific surface proteins (VSP) and whether these responses differ between Giardia assemblages and durations of infection., Methods: We recruited thirty Giardia-positive patients, mainly returning travellers, and eighteen healthy adults presumed to be Giardia unexposed. Blood samples were collected before treatment, and at 6 weeks, 6 months and 12 months after the infection cleared. We used a multiplex bead-based flow cytometry immunoassay to measure Giardia specific IgA and IgG/M responses targeting two recombinant antigens from G. lamblia VSP proteins 3 and 5 (VSP3 and VSP5)., Results: Serum levels of anti-VSP5 and anti-VSP3 IgA decreased rapidly to low levels after treatment but continued to be substantially higher than that of presumed unexposed controls even after 6 and 12 months. The IgG/M response decreased more gradually but remained significantly higher than presumed unexposed controls at all time points, except for anti-VSP3 at 12 months. There were no significant difference in responses for infections with assemblage A and assemblage B Giardia lamblia. Chronic infections (>8 weeks) were associated with a significantly lower anti-VSP5 IgG/M response., Conclusion: This study describes the kinetics of the humoral immune response against two Giardia VSP proteins over one year, and the considerable cross reactivity between the two human infective Giardia assemblages. Persons with chronic Giardia infection seem to have lower levels of VSP antibodies., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

The lumen-dwelling protozoan Giardia is an important parasitic cause of diarrheal disease worldwide. Infection can persist over extended periods with minimal intestinal inflammation, suggesting that Giardia may attenuate host responses to ensure its survival, although clearance eventually occurs in most cases. IL-10 is an anti-inflammatory regulator critical for intestinal homeostasis and controlling host responses to bacterial exposure, yet its potential role in coordinating antiprotozoal host defense in the intestine is not known. In this study, we found that murine infection with the natural enteric pathogen Giardia muris induced a transient IL-10 response after 2-4 wk at the primary site of infection in the upper small intestine, but parasite colonization and eradication were not affected by the absence of the cytokine in gene-targeted mice. However, IL-10 was critical for controlling infection-associated immunological sequelae in the colon because severe and persistent diarrhea and colitis were observed in IL-10-deficient mice within 1-2 wk postinfection but not in uninfected littermate controls. Inflammation was characterized by epithelial hyperplasia, neutrophil and macrophage expansion, and Th1 induction and could be prevented by blockade of IL-12/IL-23 p40 but not depletion of CD11c + dendritic cells. Furthermore, the intestinal microbiota underwent characteristic shifts in composition and was required for disease because antibiotics and loss of TLR signaling in MyD88-deficient mice protected against colitis. Together, our data suggest that transient infection by a luminal and seemingly noninflammatory pathogen can trigger sustained colitis in genetically susceptible hosts, which has broader implications for understanding postinfectious syndromes and other chronic intestinal inflammatory conditions., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Children are more susceptible to Giardia lamblia infection. Cells and hormones contained in human colostrum have an immunoprotective action against giardiasis, but the effects of advanced maternal age on these components are poorly understood. This study analyzed the colostrum of older women to determine melatonin and cortisol levels besides the participation of these hormones on the functional activity of phagocytes against G. lamblia. Colostrum samples were collected from younger (18 to 35 years old) and older (over 36 years old) lactating women. Colostrum samples were subjected to melatonin and cortisol determination, immunophenotyping, quantification of superoxide release, and assessment of phagocytic rate and microbicidal activity of phagocytes treated with hormones and in the presence of G. lamblia. Colostrum from mothers of advanced age contained higher melatonin and cortisol levels and a lower rate of cells expressing CD14 + and CD15 + . In the colostru of these older mothers, melatonin increased superoxide release by phagocytes. In both groups, superoxide release by phagocytes treated with cortisol was higher in the presence of G. lamblia. In colostrum from mothers of advanced age, mononuclear (MN) phagocytes treated with melatonin showed higher phagocytosis of G. lamblia and higher microbicidal index. In younger mothers, MN and polymorphonuclear (PMN) colostrum phagocytes exhibited higher rates of G. lamblia elimination when treated with both melatonin and cortisol. In older mothers, cortisol and melatonin regulation for the functional activity of colostrum phagocytes against G. lamblia may represent an additional defense mechanism, relevant for the protection and treatment of parasitic infections in breastfed children.

Aims: Giardiasis is one of the major causes of diarrhea worldwide and its symptoms vary in intensity, which can be attributed to different parasite assemblages. The goal of the present study was to compare the effects of infection caused by assemblages AII and BIV ofGiardia duodenalis on the response of the small intestine, microbiota, and behavioral parameters in mice., Main Methods: Swiss mice were infected with assemblages AII and BIV of G. duodenalis for 15 days. Leucometry, pain, intestinal microbiota and histological parameters of the duodenum and jejunum were evaluated in the experimental groups., Key Findings: Both assemblages modified the composition of the intestinal microbiota. Infection with assemblage AII promoted leukocytosis, reflected by increasing number of polymorphonuclear cells, intraepithelial lymphocytes and pain-related behavior, indicating that this was the more aggressive assemblage with regard to its effects on the intestinal mucosa and duodenum., Significance: The specific assemblage of the parasite is an important parameter that affects symptomatology in the host., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Giardia duodenalis is a common intestinal protozoan parasite known to modulate host immune responses, including dendritic cell (DC) function. Coinfections of intestinal pathogens are common, and thus, DCs may be concurrently exposed to antigens from multiple parasites. Here, we investigated the effects of G. duodenalis products on human monocyte-derived DC function independently and in combination with helminth antigens (Ascaris suum and Trichuris suis). All antigens individually induced an anti-inflammatory phenotype in DCs, reducing lipopolysaccharide (LPS)-induced interleukin (IL)-6, IL-12p70 and tumour necrosis factor (TNF)-α secretion. G. duodenalis and T. suis products also consistently upregulated IL-10 production. Despite a similar modulation of cytokine secretion, additive effects between Giardia and helminth products were not observed, indicating a dominant effect of a single parasite stimulus and limited interactive effects on DC function. G. duodenalis trophozoites induced rapid apoptosis in DCs, which was not observed with the helminth antigens suggesting that the modulatory effects of G. duodenalis may override that of A. suum and T. suis. Thus, G. duodenalis modulates DC activity by modulating cytokine secretion and/or inducing apoptosis, which may be a parasite-driven mechanism to dampen host immunity and establish chronic infections. The differential mechanisms of DC modulation by intestinal parasites warrant further attention., (© 2018 John Wiley & Sons Ltd.)

Toxoplasmosis is mostly associated with other intestinal parasitic infections especially Giardia due to shared mode of peroral infection. Toxoplasma and Giardia induce a strong T-helper 1- immune response. Our aim was to induce a protective immune response that results in significant impact on intestinal and extra-intestinal phases of Toxoplasma infection. This study was conducted in experimental animals and assessment of Giardia cyst extract effect on Toxoplasma infection was investigated by histopathological examination of small intestine and brain, Toxoplasma cyst count and iNOS staining of the brain, measurement of IFN-γ and TGF-β in intestinal tissues. Results showed that the brain Toxoplasma cyst number was decreased in mice infected with Toxoplasma then received Giardia cyst extract as compared to mice infected with Toxoplasma only. This effect was produced because Giardia cyst extract augmented the immune response to Toxoplasma infection as evidenced by severe inflammatory reaction in the intestinal and brain tissues, increased levels of IFN-γ and TGF-β in intestinal tissues and strong iNOS staining of the brain. In conclusion, Giardia cyst extract generated a protective response against T. gondii infection. Therefore, Giardia antigen will be a suitable candidate for further researches as an immunomodulatory agent against Toxoplasma infection., (© 2017 John Wiley & Sons Ltd.)

Giardia lamblia is one of the most common infectious protozoans in the world. Giardia rarely causes severe life-threatening diarrhea, and may even have a slight protective effect in this regard, but it is a major contributor to malnutrition and growth faltering in children in the developing world. Giardia infection also appears to be a significant risk factor for postinfectious irritable bowel and chronic fatigue syndromes. In this review we highlight recent work focused on the impact of giardiasis and the mechanisms that contribute to the various outcomes of this infection, including changes in the composition of the microbiota, activation of immune responses, and immunopathology., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This longitudinal observational study was conducted to investigate the spontaneous effect of Giardia and Cryptosporidium infections on acute phase response (APR) in reindeer calves (Rangifer tarandus tarandus) in Finnish Lapland. Serum (n=609) and faecal samples (n=366) were collected from 54 reindeer calves aged zero to 33days. The samples were analysed for Giardia, Cryptosporidium, acute phase proteins (APP) and γ-globulins. Linear regression models were used to investigate associations of early Giardia infection (before 12days of life) with the response of APPs and acquiring of passive immunity. Giardia was detected in 100% and Cryptosporidium in 23% of calves. There was a negative association between early Giardia infection and γ-globulin concentrations (p=0.032) and a positive association with serum amyloid A (SAA) concentrations (p=0.042). The results suggest a protective effect of colostrum against Giardia infection and that early infection may induce activation of APR., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Human infection with the protozoan parasite Giardia duodenalis is one the most common parasitic diseases worldwide. Higher incidence rates of giardiasis have been reported from human subjects with multiple debilitating chronic conditions, including hypogammaglobulinemia and common variable immunodeficiency (CVID). In the current study, stool specimens were collected from 199 individuals diagnosed with HIV or cancer and immunocompetent subjects. The sensitivity of microscopy-based detection on fresh stool preparations, trichrome staining and stool antigen immunodetection for the diagnosis of G. duodenalis were 36%, 45.5% and 100%, respectively when compared with a highly sensitive stool-based PCR method as the gold standard. Further multilocus molecular analyses using glutamate dehydrogenase (gdh) and triose phosphate isomerase (tpi) loci demonstrated that the AI genotype of G. duodenalis was the most prevalent, followed by the AII genotype and mixed (AI+B) infections. We concluded that stool antigen immunodetection-based immunoassays and stool-based PCR amplification had comparable sensitivity and specificity for the diagnosis of G. duodenalis infections in these populations. Stool antigen detection-based diagnostic modalities are rapid and accurate and may offer alternatives to conventional microscopy and PCR-based diagnostic methods for the diagnosis of G. duodenalis in human subjects living with HIV or cancer., (Copyright © 2017. Published by Elsevier B.V.)

The protozoan parasite Giardia duodenalis is responsible for more than 280 million cases of gastrointestinal complaints ("giardiasis") every year, worldwide. Infections are acquired orally, mostly via uptake of cysts in contaminated drinking water. After transformation into the trophozoite stage, parasites start to colonize the duodenum and upper jejunum where they attach to the intestinal epithelium and replicate vegetatively. Outcome of Giardia infections vary between individuals, from self-limiting to chronic, and asymptomatic to severely symptomatic infection, with unspecific gastrointestinal complaints. One proposed mechanism for pathogenesis is the breakdown of intestinal barrier function. This has been studied by analyzing trans-epithelial electric resistances (TEER) or by indicators of epithelial permeability using labeled sugar compounds in in vitro cell culture systems, mouse models or human biopsies and epidemiological studies. Here, we discuss the results obtained mainly with epithelial cell models to highlight contradictory findings. We relate published studies to our own findings that suggest a lack of barrier compromising activities of recent G. duodenalis isolates of assemblage A, B, and E in a Caco-2 model system. We propose that this epithelial cell model be viewed as mimicking asymptomatic infection. This view will likely lead to a more informative use of the model if emphasis is shifted from aiming to identify Giardia virulence factors to defining non-parasite factors that arguably appear to be more decisive for disease.

The protozoan parasite Giardia is a highly prevalent intestinal pathogen with a wide host range. Data obtained in mice, cattle and humans revealed the importance of IL-17A in the development of a protective immune response against Giardia. The aim of this study was to further unravel the protective effector mechanisms triggered by IL-17A following G. muris infection in mice, by an RNA-sequencing approach. C57BL/6 WT and C57BL/6 IL-17RA KO mice were orally infected with G. muris cysts. Three weeks post infection, intestinal tissue samples were collected for RNA-sequencing, with samples from uninfected C57BL/6 WT and C57BL/6 IL-17RA KO animals serving as negative controls. Differential expression analysis showed that G. muris infection evoked the transcriptional upregulation of a wide array of genes, mainly in animals with competent IL-17RA signaling. IL-17RA signaling induced the production of various antimicrobial peptides, such as angiogenin 4 and α- and β-defensins and regulated complement activation through mannose-binding lectin 2. The expression of the receptor that regulates the secretion of IgA into the intestinal lumen, the polymeric immunoglobulin receptor, was also dependent on IL-17RA signaling. Interestingly, the transcriptome data showed for the first time the involvement of the circadian clock in the host response following Giardia infection.

Giardia lamblia is a protozoan parasite that causes one of the most common gastrointestinal diseases worldwide. To eliminate the parasite from the host intestine, it is necessary the activation of B-cell and T-cell dependent mechanisms. The knowledge about Giardia antigens that can stimulate the host immune response is limited. Recently, it has been described the Binding Immunoglobulin Protein (BIP) of G. lamblia (71kDa) as a potential immunogen. Additionally, our group has identified a highly immunogenic antigen (5G8 protein) of G. lamblia with a relative molecular mass of approximately 70kDa. There is some evidence suggesting that the 5G8 protein may activate both humoral and cellular immune responses. Based on these observations and preliminary mass spectrometry analyses, we hypothesized that the antigen 5G8 could be the BIP protein. In the present study, we characterize immunochemically the BIP protein of Giardia. Flow cytometric assays and western blotting were used to determine the expression profile of BIP and 5G8 antigens in Giardia trophozoites. The differences in expression profile indicated that BIP and 5G8 are not the same molecule. ELISA and Western blotting assays revealed that BIP protein was recognized by antibodies produced during G. lamblia infection in C3H/HeN mice. MTT assays did not reveal the activation of cellular immune response induced by BIP protein in vitro. In addition, we identified the potential B-cell and T-cell epitopes of G. lamblia BIP protein. This molecule is a conserved protein among Giardia strains and other pathogens. The complete immunological characterization of this antigen will contribute to a better understanding of the host-parasite interactions in Giardia infection., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Diverse enteropathogen exposures associate with childhood malnutrition. To elucidate mechanistic pathways whereby enteric microbes interact during malnutrition, we used protein deficiency in mice to develop a new model of co-enteropathogen enteropathy. Focusing on common enteropathogens in malnourished children, Giardia lamblia and enteroaggregative Escherichia coli (EAEC), we provide new insights into intersecting pathogen-specific mechanisms that enhance malnutrition. We show for the first time that during protein malnutrition, the intestinal microbiota permits persistent Giardia colonization and simultaneously contributes to growth impairment. Despite signals of intestinal injury, such as IL1α, Giardia-infected mice lack pro-inflammatory intestinal responses, similar to endemic pediatric Giardia infections. Rather, Giardia perturbs microbial host co-metabolites of proteolysis during growth impairment, whereas host nicotinamide utilization adaptations that correspond with growth recovery increase. EAEC promotes intestinal inflammation and markers of myeloid cell activation. During co-infection, intestinal inflammatory signaling and cellular recruitment responses to EAEC are preserved together with a Giardia-mediated diminishment in myeloid cell activation. Conversely, EAEC extinguishes markers of host energy expenditure regulatory responses to Giardia, as host metabolic adaptations appear exhausted. Integrating immunologic and metabolic profiles during co-pathogen infection and malnutrition, we develop a working mechanistic model of how cumulative diet-induced and pathogen-triggered microbial perturbations result in an increasingly wasted host.

AbstractMore than 2 billion people are infected with parasites globally, and the majority have coinfections. Intestinal protozoa and helminths induce polarizing CD4 + T-helper cell 1 (Th1) mediated cytokine responses within the host. Such immune polarization may inhibit the ability of the host to mount an adequate immune response for pathogen clearance to concurrent pathogens. The current study evaluated the plasma cytokine profile in Ascaris and Giardia coinfected children compared with Giardia - and Ascaris -only infected children. Fecal samples and blood samples were collected from asymptomatic 3-year-old children living in the district of Quininde, Ecuador. Stool samples that tested positive for Giardia lamblia -only, Ascaris lumbricoides- only, or G. lamblia and A. lumbricoides coinfections were confirmed by quantitative real-time polymerase chain reaction. Plasma samples from the study subjects were used to quantitate cytokines. A total of 39 patients were evaluated. Children with coinfection had a significant decrease in Th1 cytokine production, interleukin 2 (IL-2) ( P < 0.05), IL-12 ( P < 0.05), and tumor necrosis factor alpha ( P < 0.05) compared with Giardia -only infected children. Coinfected children had an increase in IL-10/interferon gamma (IFN-γ) ratio compared with uninfected ( P < 0.05) and Ascaris alone ( P < 0.05). The increased IL-10/IFN-γ ratio in the setting of decreased Th1 cytokine response indicates Th2 polarization in the coinfected group. Reduced Th1 cytokines in children coinfected with Ascaris and Giardia may impair the host's ability to eradicate Giardia infection leading to chronic giardiasis.

Giardiasis is one of the most frequent entero-parasites worldwide; its prevalence is more common in developing countries. Giardia lamblia is considered one of the opportunistic parasites and aits clinical manifestations represent the expression of host resistance and parasite viri lence. As of chronic giardiasis cases were expected to worsen in immunosuppressed patients with development of various complications. This work assessed the histolopathological and the possible immunological effects of infection with G. lamblia in an immunosuppressed experimental animal model in comparison to immunocompetent one. Mice were divided into 4 groups;. group I: simmunocompetent (IC) mice infected with G. lamblia cysts, group II: immunosup pressed (S) mice infected with cysts, group III: uninfected immunocompetent mice and group. IV: uninfected immunosuppressed mice. From each group, small intestine was. removed for histopathological and molecular studies. Also, cyst counting in the stool of infected mice was estimated. We found that the number of G. lamblia cysts in the stool of IS mice was significantly higher than that from IC ones. Shortening of the villi was more pronounced in the IS than in IC group. Furthermore, intraepithelial lymphocytic count, goblet cell count and mast cell count were significantly decreased in the IS infected group as compared to IC ones. Expression of interleukin.6 mRNA showed high expression in IC infected mice while it was weak in IS mice. In conclusicn, the present study revealed the importance of the innate immunity presented by goblet cells, mast cells and other adaptive immunity responses; in the clearance of Giardia.

Giardia intestinalis (G.I), is an anaerobic protozoan and the aetiological agent of giardiasis, a diarrhoea present worldwide and associated with poverty. G.I has a simple life cycle alternating between cyst and trophozoite. Cysts are transmitted orally to the stomach and transform to trophozoites in the intestine by a multifactorial process. Recently, microvesicles (MVs) have been found to be released from a wide range of eukaryotic cells. We have observed a release of MVs during the life cycle of G.I., identifying MVs from active trophozoites and from trophozoites differentiating to the cyst form. The aim of the current work was to investigate the role of MVs from G.I in the pathogenesis of giardiasis. MVs from log phase were able to increase the attachment of G. intestinalis trophozoites to Caco-2 cells. Moreover, MVs from G. intestinalis could be captured by human immature dendritic cells, resulting in increased activation and allostimulation of human dendritic cells. Lipid rafts participate in the MV biogenesis and in the attachment to Caco-2 cells. Nevertheless, proteomic analysis from two types of MVs has shown slight differences at the protein levels. An understanding of biogenesis and content of MVs derived from trophozoites might have important implications in the pathogenesis of the disease., (Copyright © 2017 Elsevier GmbH. All rights reserved.)