Detection of IgG Anti-Giardia duodenalis Antibodies in Sera by Indirect Immunofluorescence and Western Blotting Assays

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.

A Thermostable Oral SARS-CoV-2 Vaccine Induces Mucosal and Protective Immunity

An ideal protective vaccine against SARS-CoV-2 should not only be effective in preventing disease, but also in preventing virus transmission. It should also be well accepted by the population and have a simple logistic chain. To fulfill these criteria, we developed a thermostable, orally administered vaccine that can induce a robust mucosal neutralizing immune response. We used our platform based on retrovirus-derived enveloped virus-like particles (eVLPs) harnessed with variable surface proteins (VSPs) from the intestinal parasite Giardia lamblia, affording them resistance to degradation and the triggering of robust mucosal cellular and antibody immune responses after oral administration. We made eVLPs expressing various forms of the SARS-CoV-2 Spike protein (S), with or without membrane protein (M) expression. We found that prime-boost administration of VSP-decorated eVLPs expressing a pre-fusion stabilized form of S and M triggers robust mucosal responses against SARS-CoV-2 in mice and hamsters, which translate into complete protection from a viral challenge. Moreover, they dramatically boosted the IgA mucosal response of intramuscularly injected vaccines. We conclude that our thermostable orally administered eVLP vaccine could be a valuable addition to the current arsenal against SARS-CoV-2, in a stand-alone prime-boost vaccination strategy or as a boost for existing vaccines.

Giardia duodenalis and Its Secreted PPIB Trigger Inflammasome Activation and Pyroptosis in Macrophages through TLR4-Induced ROS Signaling and A20-Mediated NLRP3 Deubiquitination

The extracellular protozoan parasite Giardia duodenalis is a well-known and important causative agent of diarrhea on a global scale. Macrophage pyroptosis has been recognized as an important innate immune effector mechanism against intracellular pathogens. Yet, the effects of noninvasive Giardia infection on macrophage pyroptosis and the associated molecular triggers and regulators remain poorly defined. Here we initially observed that NLRP3 inflammasome-mediated pyroptosis was activated in Giardia-treated macrophages, and inhibition of ROS, NLRP3, or caspase-1 could block GSDMD cleavage, IL-1β, IL-18 and LDH release, and the cell viability reduction. We also confirmed that Giardia-induced NLRP3 inflammasome activation was involved in its K63 deubiquitination. Thus, six candidate deubiquitinases were screened, among which A20 was identified as an effective regulator. We then screened TLRs on macrophage membranes and found that upon stimulation TLR4 was tightly correlated to ROS enhancement, A20-mediated NLRP3 deubiquitination, and pyroptotic signaling. In addition, several Giardia-secreted proteins were predicted as trigger factors via secretome analysis, of which peptidyl-prolyl cis-trans isomerase B (PPIB) independently induced macrophage pyroptosis. This was similar to the findings from the trophozoite treatment, and also led to the TLR4-mediated activation of NLRP3 through K63 deubiquitination by A20. Collectively, the results of this study have significant implications for expanding our understanding of host defense mechanisms after infection with G. duodenalis.

Regulatory role of the intestinal microbiota in the immune response against Giardia

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.

Extracellular vesicles secreted by Giardia duodenalis regulate host cell innate immunity via TLR2 and NLRP3 inflammasome signaling pathways

Giardia duodenalis, also known as G. intestinalis or G. lamblia, is the major cause of giardiasis leading to diarrheal disease with 280 million people infections annually worldwide. Extracellular vesicles (EVs) have emerged as a ubiquitous mechanism participating in cells communications. The aim of this study is to explore the roles of G. duodenalis EVs (GEVs) in host-pathogen interactions using primary mouse peritoneal macrophages as a model. Multiple methods of electron microscopy, nanoparticle tracking analysis, proteomic assays, flow cytometry, immunofluorescence, qPCR, western blot, ELISA, inhibition assays, were used to characterize GEVs, and explore its effects on the host cell innate immunity as well as the underlying mechanism using primary mouse peritoneal macrophages. Results showed that GEVs displayed typical cup-shaped structure with 150 nm in diameter. GEVs could be captured by macrophages and triggered immune response by increasing the production of inflammatory cytokines Il1β, Il6, Il10, Il12, Il17, Ifng, Tnf, Il18, Ccl20 and Cxcl2. Furthermore, activation of TLR2 and NLRP3 inflammasome signaling pathways involved in this process. In addition, CA-074 methyl ester (an inhibitor of cathepsin B) or zVAD-fmk (an inhibitor of pan-caspase) pretreatment entirely diminished these effects triggered by GEVs exposure. Taken together, these findings demonstrated that GEVs could be internalized into mouse peritoneal macrophages and regulate host cell innate immunity via TLR2 and NLRP3 inflammasome signaling pathways.

G. duodenalis, one of the most common cause of diarrheal diseases, is widely existed in the contaminated water and threatening the public health especially in developing countries. Along with the increasing resistance to anti-G. duodenalis drugs occurs, new targets against giardiasis are of urgently needed. The innate immune system is the first defense line of organism to resist multiple pathogens invasion through recognizing pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), termed Toll-like receptors (TLRs) on the surface of cell membrane and nucleotide oligomerization domain (Nod)-like receptors (NLRs) inside immune cells. Recently, extracellular vesicles have emerged as a ubiquitous mechanism participating in cells communications. In this study, EVs secreted by extracellular protozoan G. duodenalis were obtained and displayed typical cup-shaped structure with 150 nm in diameter. Moreover, GEVs could enter into primary mouse peritoneal macrophages and regulate host cell innate immunity by up-regulation of various inflammatory cytokines expression. Furthermore, TLR2 and NLRP3 inflammasome signaling pathways involved in this process. This study demonstrated that GEVs could be internalized into primary mouse peritoneal macrophages, regulate host cell innate immunity via TLR2 and NLRP3 inflammasome signaling pathways, and may provide new targets against giardiasis.

Seroprevalence of antibodies against Chlamydia trachomatis and enteropathogens and distance to the nearest water source among young children in the Amhara Region of Ethiopia

The transmission of trachoma, caused by repeat infections with Chlamydia trachomatis, and many enteropathogens are linked to water quantity. We hypothesized that children living further from a water source would have higher exposure to C. trachomatis and enteric pathogens as determined by antibody responses. We used a multiplex bead assay to measure IgG antibody responses to C. trachomatis, Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, Campylobacter jejuni, enterotoxigenic Escherichia coli (ETEC) and Vibrio cholerae in eluted dried blood spots collected from 2267 children ages 0-9 years in 40 communities in rural Ethiopia in 2016. Linear distance from the child's house to the nearest water source was calculated. We derived seroprevalence cutoffs using external negative control populations, if available, or by fitting finite mixture models. We used targeted maximum likelihood estimation to estimate differences in seroprevalence according to distance to the nearest water source. Seroprevalence among 1-9-year-olds was 43% for C. trachomatis, 28% for S. enterica, 70% for E. histolytica, 54% for G. intestinalis, 96% for C. jejuni, 76% for ETEC and 94% for C. parvum. Seroprevalence increased with age for all pathogens. Median distance to the nearest water source was 473 meters (IQR 268, 719). Children living furthest from a water source had a 12% (95% CI: 2.6, 21.6) higher seroprevalence of S. enterica and a 12.7% (95% CI: 2.9, 22.6) higher seroprevalence of G. intestinalis compared to children living nearest. Seroprevalence for C. trachomatis and enteropathogens was high, with marked increases for most enteropathogens in the first two years of life. Children living further from a water source had higher seroprevalence of S. enterica and G. intestinalis indicating that improving access to water in the Ethiopia's Amhara region may reduce exposure to these enteropathogens in young children.

Giardia intestinalis and Fructose Malabsorption: A Frequent Association

Nowadays, scientific studies are emerging on the possible etiological role of intestinal parasites in functional digestive disorders. Our study was carried out with healthy individuals (control group; n = 82) and symptomatic patients with lactose or fructose malabsorption, including positive (malabsorbers; n = 213) and negative (absorbers; n = 56) breath test, being analyzed for the presence of intestinal parasites. A high parasitic prevalence was observed in malabsorbers (41.8%), exclusively due to single-cell eukaryotes but not helminths. Giardia intestinalis was the predominant parasite in cases of abnormal absorption (26.5%), significantly associated with fructose malabsorption and doubling the probability of developing this pathology. Within controls, Blastocystis sp. (13.4%) was almost the only parasite, being the second among patients (12.6%), and Cryptosporidium parvum, the last species of clinical relevance, was detected exclusively in two malabsorbers (0.9%). The consumption of ecological food and professions with direct contact with humans arose as risk factors of parasitism. A diagnosis of carbohydrate malabsorption in adulthood is the starting point, making the search for the primary cause necessary. Accurate parasitological diagnosis should be considered another tool in the clinical routine for patients with recurrent symptoms, since their condition may be reversible with adequate therapeutic intervention.

Mouse macrophages capture and kill Giardia lamblia by means of releasing extracellular trap

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 Ca²⁺ 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.

EPIDEMIOLOGY OF CLOSTRIDIUM DIFFICILE INFECTION IN HOSPITALISED PEDIATRIC PATIENTS IN GEORGIA

Clostridium difficile, a Gram-positive spore-forming bacillus, is the most common identifiable etiologic agent of antibiotic-associated diarrhea. The incidence of Clostridium difficile infections among hospitalized children has been increasing across the world. The aim of our study was to evaluate occurrence of Clostridium difficile and some other gastrointestinal pathogens among hospitalized pediatric patients in Georgia, as far as currently statistical data on the topic is very limited in the country. One of the objectives of the study was to test and pilot the real-time Polymerase Chain Reaction diagnostic systems for rapid and simultaneous identification of number of pathogens with a particular emphasis on diarrheal disease diagnostics as these are one of the primary public health priorities in Georgia and worldwide. Cross-Sectional study has been performed on 211 samples collected from 192 pediatric patients. Two pediatric hospitals were involved in the study: M. Iashvili Children's Central Hospital and Tbilisi Children's Clinical Hospital for Infectious Diseases. Laboratory investigations were done in the Clinic NeoLab, Tbilisi, Georgia. Study materials collected for testing were stool samples. Samples were tested by EIA kits (CerTest biotec, Zaragoza, Spain) for presence of A/B toxin according to the manufacturer's instructions. EIA test positive samples were analyzed by home-made multiplex real-time polymerase chain reaction (NeoPCR Diagnostics, NeoLab, Tbilisi, Gerogia) for confirmation of the infection and for simultaneous identification of additional gastrointestinal pathogens including Entamoeba histolitica, Giardia lamblia, Cryptsporidium parvum, Adenovirus, Rotavirus, Norovirus and Astrovirus. All samples were also tested for the presence of the above listed pathogenic agents using the same type EIA kits as for Clostridium difficile described above (CerTestbiotec, Zaragoza, Spain) for presence of the corresponding pathogen. The average age of the study participants was 3.5 years, 56.7% were male and 43.3% were female patients. Presence of Clostridium difficile have been documented in 21 samples out of 211 (10%). Besides the Clostridium difficile, other enteric pathogens have been revealed with the following frequencies: Rotavirus in 12 cases (5.7%), Adenovirus in 11 (5.2%), Giardia lamblia in 10 (4.7%), Astrovirus in 3 (1.4%), Cryptsporidium parvum in 3 (1.4%), Entamoeba histolitica in 2 (0.9%), Norovirus in 2 (0.9%). 49 samples were from out-patient cases (2 samples were positive for Clostridium difficile) and 162 samples were from in-patient cases (19 samples were positive for Clostridium difficile). Clostridium difficile is the frequent pathogenic agent causing diarrheal disease among hospitalized pediatric patients. Development of Clostridium difficile related diarrhea is associated with the antibiotic treatment of pediatric patients hospitalized due to different clinical diagnosis. Targeted early detection of these pathogens is important for the optimal management of diarrheal infection in pediatric patient which will lead to the better clinical outcome and reduction of morbidity rate among hospitalized pediatric patients.

Host-Parasite Interactions in Individuals with Type 1 and 2 Diabetes Result in Higher Frequency of Ascaris lumbricoides and Giardia lamblia in Type 2 Diabetic Individuals

Host-parasite interactions in diabetic patients might influence diabetes complications and intestinal parasitosis. The aim was to investigate the occurrence of enteroparasites in individuals with diabetes types 1 and 2. A descriptive study was designed to estimate frequencies of parasites and to compare them in individuals with diabetes types 1 and 2 from two Health Centers and one hospital in the Federal District of Brazil. Patients were allocated to the study by convenience. Three fecal samples of 156 diabetic individuals (120 type 1 and 36 type 2) were analyzed using two parasitological methods. Enteroparasites or commensals frequency in diabetics was 64%. Diabetics infected with up to six species of intestinal parasites or commensals were found. Frequencies of Ascaris lumbricoides and Giardia lamblia were higher in individuals with type 2 diabetes. The lower frequency of A. lumbricoides found in type 1 diabetes may be related to a strong Th2 response to parasites. Autoimmune response developed in type 1 diabetic individuals characterized by the production of Th1 cytokines could explain low frequency of G. lamblia. High frequency of parasites found in type 2 diabetes emphasizes the importance of periodic parasitological examinations in these individuals.

Stool antigen immunodetection for diagnosis of Giardia duodenalis infection in human subjects with HIV and cancer

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.

Characterization of BIP protein of G. lamblia as a potential immunogen in a mouse infection model

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.

Use of Translation Blocking Morpholinos for Gene Knockdown in Giardia lamblia

Giardia lamblia, a major parasite, is an emerging model organism due to its compact genomic arrangement and composition. The most popular reverse genetic technique, RNAi, is ineffective in Giardia. In contrast, protein depletion by translation blocking morpholinos is suitable for most gene targets and provides up to 80% depletion of the target protein. The method is fast, reliable, and specific. After antisense morpholino oligomer delivery into Giardia trophozoites by electroporation, the cells can be used for many subsequent analyses 8-48 h after treatment. In this chapter, suitable gene tags, plasmids, and techniques necessary for proper morpholino targeting are described.

Specific histone modifications play critical roles in the control of encystation and antigenic variation in the early-branching eukaryote Giardia lamblia

During evolution, parasitic microorganisms have faced the challenges of adapting to different environments to colonize a variety of hosts. Giardia lamblia, a common cause of intestinal disease, has developed fascinating strategies to adapt both outside and inside its host's intestine, such as trophozoite differentiation into cyst and the switching of its major surface antigens. How gene expression is regulated during these adaptive processes remains undefined. Giardia lacks some typical eukaryotic features, like canonical transcription factors, linker histone H1, and complex promoter regions; suggesting that post-transcriptional and translational control of gene expression is essential for parasite survival. However, epigenetic factors may also play critical roles at the transcriptional level. Here, we describe the most common post-translational histone modifications; characterize enzymes involved in these reactions, and analyze their association with the Giardia's differentiation processes. We present evidence that NAD⁺-dependent and NAD⁺-independent histone deacetylases regulate encystation; however, a unique NAD⁺-independent histone deacetylase modulate antigenic switching. The rates of acetylation of H4K8 and H4K16 are critical for encystation, whereas a decrease in acetylation of H4K8 and methylation of H3K9 occur preferentially during antigenic variation. These results show the complexity of the mechanisms regulating gene expression in this minimalistic protozoan parasite.

IMMUNE-MOLECULAR IDENTIFICATION OF GIARDIA INTESTINALIS IN DIARRHOEAL CHILDREN: COMPARISON OF THREE DIAGNOSTIC METHODS

Giardiasis is a major health problem in both developed and developing world. A variety of methods for diagnosis of Giardia duodenalis cysts or trophozoites is available but still has certain limitations. 100 sample from diarrhoeal children who attending outpatient clinic in Abu El Rish hospital, .Kasr Al Ainy, Faculty of Medicine, Cairo University, Egypt. Giardiasis was diagnosed by direct wet mount, microscopy after formal- ethyl acetate concentration, Ridascreen ELISA assay and n-PCR targeting beta giardin (bg) gene. Using ELISA as reference standard, the methods' sensitivities, specificities, positive (PPV) and negative (NPV) predictive values and positive (LR+) and negative (LR-) likelihood ratios with 95% confidence interval (95% CI) were analyzed.The diagnostic methods were evaluated to determine their impact on the posttest probability using Fagan's nomogram. All the studied methods led to a LR+ higher than 10 indicating ability to ruling in giardiasis. n-PCR recorded LR- equal 0.00 and the probability of giardiasis would be 0% if the test was negative. The methods were also ranked on basis of Multiattribute utility theory and Analytical hierarchy process with ELISA ranked better than n-PCR.

Vaccination with Bivalent DNA Vaccine of α1-Giardin and CWP2 Delivered by Attenuated Salmonella typhimurium Reduces Trophozoites and Cysts in the Feces of Mice Infected with Giardia lamblia

Background

Giardia lamblia is one of the most common infectious protozoans in human that may cause diarrhea in travelers. Searching for antigens that induced effectively protective immunity has become a key point in the development of vaccine against giardiasis.

Methodology/Principal Findings

Mice vaccinated with G. lamblia trophozozite-specific α1-giardin DNA vaccine delivered orally by attenuated Salmonella typhimurium SL7027 elicited 74.2% trophozoite reduction, but only 28% reduction in cyst shedding compared with PBS buffer control. Oral vaccination with Salmonella-delivered cyst-specific CWP2 DNA produced 89% reduction in cysts shedding in feces of vaccinated mice. Significantly, the mice vaccinated with Salmonella-delivered bivalent α1-giardin and CWP2 DNA vaccines produced significant reduction in both trophozoite (79%) and cyst (93%) in feces of vaccinated mice. This parasite reduction is associated with the strong local mucosal IgA secretion and the IgG2a-dominant systemic immune responses in vaccinated mice.

Conclusions

The results demonstrate that bivalent vaccines targeting α1-giardin and CWP2 can protect mice against the colonization of Giardia trophozoite and block the transformation of cyst in host at the same time, and can be used to prevent Giardia infection and block the transmission of giardiasis.

Comparative Evaluation of Three Methods (Microscopic Examination, Direct Fluorescent Antibody Assay, and Immunochromatographic Method) for the Diagnosis of Giardia intestinalis From Stool Specimens

OBJECTIVE

The aim of this study was to compare direct microscopic examination, direct fluorescent antibody assay (DFA), and the immunochromatographic method (IK) and identify the best suitable method for the diagnosis of Giardia intestinalis.

METHODS

In this study, 25 stool samples that had been diagnosed as being infected with G. intestinalis using the native-Lugol and/or formol-ethyl acetate concentration method and 25 non-parasite-infected samples (the control group) were examined. After microscopic examination of stools, they were kept at -20°C for examination using DFA and IK. Stool samples were studied using DFA (CeLLabs, Crypto/Giardia-Cel IF) and IK (RIDA QUICK, Cryptosporidium/Giardia Combi Dipstick), as per the manufacturers' instructions.

RESULTS

In our study, using the DFA method, parasites were detected in all 25 stool samples in which G. intestinalis was diagnosed by direct microscopic examination. Using the IK method, a particular band indicative of the parasite was detected in 24 samples. No parasites were detected in all 25 samples in the control group.

CONCLUSION

Thus, when direct microscopic examination is taken as reference, the senstivity and specificity of DFA for the diagnosis of G. intestinalis were found to be 100% each, while those of IK were found to be 96% and 100%, respectively.

[Ethological competence of Perm Territory dwellers in the assurance of personal infection safety]

The authors attempted to analyze preventive measures against infectious and parasitic diseases, which were used domestically by the Perm Territory population, their conjugacy with the stereotypes of attitude towards domestic animals, as well as behavioral features of compliance andcompetence in the assurance of infection safety. The found gaps in the assurance of personal infection safety (drinking unboiled water, unprotected sex, disregard of helminth prevention in domestic animals, and unwillingness to go in for sports) are coherent with the epidemiological situation in the Perm Territory and to our clinical and laboratory study of the patients of the Perm Territory Children's Clinical Hospital in 2011. Enzyme immunoassay (EIA) was used to examine 10075 patients for helminths and protozoa; parasitic diseases were detected in 2047 (20.3%) persons. The diagnostic titer of antibodies to Toxocara antigens was revealed in 677 (11.8%) children of 5700 patients examined for toxocariasis; that for Opisthorchis antigens was in 595 (37.7%) of 1578 examined for Opisthorchis infestation. The diagnostic titers for echinococcosis was found in 9 (0.75%) of 1198 patients; later on the diagnosis of hydatid disease was verified by epidemiological, clinical, and laboratory studies. Despite the inadequate informative value of EIA for the diagnosis of giardiasis, high antibody titers to Lamblia antigens were detected in 766 (47.9%) of 1599 children.

Giardia duodenalis arginine deiminase modulates the phenotype and cytokine secretion of human dendritic cells by depletion of arginine and formation of ammonia

Depletion of arginine is a recognized strategy that pathogens use to evade immune effector mechanisms. Depletion depends on microbial enzymes such as arginases, which are considered virulence factors. The effect is mostly interpreted as being a consequence of successful competition with host enzymes for the substrate. However, both arginases and arginine deiminases (ADI) have been associated with pathogen virulence. Both deplete arginine, but their reaction products differ. An ADI has been implicated in the virulence of Giardia duodenalis, an intestinal parasite that infects humans and animals, causing significant morbidity. Dendritic cells (DC) play a critical role in host defense and also in a murine G. duodenalis infection model. The functional properties of these innate immune cells depend on the milieu in which they are activated. Here, the dependence of the response of these cells on arginine was studied by using Giardia ADI and lipopolysaccharide-stimulated human monocyte-derived DC. Arginine depletion by ADI significantly increased tumor necrosis factor alpha and decreased interleukin-10 (IL-10) and IL-12p40 secretion. It also reduced the upregulation of surface CD83 and CD86 molecules, which are involved in cell-cell interactions. Arginine depletion also reduced the phosphorylation of S6 kinase in DC, suggesting the involvement of the mammalian target of rapamycin signaling pathway. The changes were due to arginine depletion and the formation of reaction products, in particular, ammonium ions. Comparison of NH(4)(+) and urea revealed distinct immunomodulatory activities of these products of deiminases and arginases, respectively. The data suggest that a better understanding of the role of arginine-depleting pathogen enzymes for immune evasion will have to take enzyme class and reaction products into consideration.

The profile of snoRNA-derived microRNAs that regulate expression of variant surface proteins in Giardia lamblia

In the current investigation, we analysed all the known small nucleolar RNAs (snoRNAs) in the deeply branching protozoan parasite Giardia lamblia for potential microRNAs (miRNAs) that might be derived from them. Two putative miRNAs have since been identified by Northern blot, primer extension, 3' RACE and co-immunoprecipitation with Giardia Argonaute (GlAgo), and designated miR6 and miR10. Giardia Dicer (GlDcr) is capable of processing the snoRNAs into the corresponding miRNAs in vitro. Potential miR6 and miR10 binding sites in Giardia genome were predicted bio-informatically. A miR6 binding site was found at the 3' untranslated regions (UTR) of 44 variant surface protein (vsp) genes, whereas a miR10 binding site was identified at the 3' end of 159 vsp open-reading frames. Thirty-three of these vsp genes turned out to contain binding sites for both miR6 and miR10. A reporter mRNA tagged with the 3' end of vsp1267, which contains the target sites for both miRNAs, was translationally repressed by both miRNAs in Giardia. Episomal expression of an N-terminal c-myc tagged VSP1267 was found significantly repressed by introducing either miR6 or miR10 into the cells and the repressive effects were additive. When the 2'-O-methyl antisense oligos (ASOs) of either miR6 or miR10 was introduced, however, there was an enhancement of tagged VSP1267 expression suggesting an inhibition of the repressive effects of endogenous miR6 or miR10 by the ASOs. Of the total 220 vsp genes in Giardia, we have now found 178 of them carrying putative binding sites for all the miRNAs that have been currently identified, suggesting that miRNAs are likely the regulators of VSP expression in Giardia.

[Research progress on the mechanisms of antigenic variation in Giardia lamblia]

The intestinal protozoan parasite Giardia lamblia is one of the most common causes of diarrhoea and undergoes antigenic variation. In pathogenic microorganisms, antigenic variation is often described as a mechanism to evade the host immune system, resulting in chronic and/or recurrent infections. In the recent years, significant advances in the knowledge of the antigen switching process have been achieved. Here we review the principal knowledge on the mechanisms that regulate this process, including genomic organization, post-transcriptional gene silencing, expressional modifications, and processing and turnover of VSPs.

[ELISA and spontaneous sedimentation technique for the diagnosis of Giardia lamblia infection in stool samples of Peruvian children]

OBJECTIVE

To compare a commercial coproantigen ELISA kit and the technique of spontaneous sedimentation in tube (TSET) for the diagnosis of Giardia lamblia in fecal specimens from children in a Peruvian endemic area.

MATERIAL AND METHODS

174 fecal samples were analyzed by TSET and 2nd Generation Giardia ELISA kit.

RESULTS

51 samples were positive by ELISA and 49 by TSET.

CONCLUSIONS

The ELISA was highly sensitive and specific, simple and fast. However, the very good agreement, high precision, low cost and ability to detect other intestinal parasites makes use of TSET recommended for laboratory diagnosis in endemic areas of Peru.

Α1-giardin based live heterologous vaccine protects against Giardia lamblia infection in a murine model

Giardia lamblia is a leading protozoan cause of diarrheal disease worldwide, yet preventive medical strategies are not available. A crude veterinary vaccine has been licensed for cats and dogs, but no defined human vaccine is available. We tested the vaccine potential of three conserved antigens previously identified in human and murine giardiasis, α1-giardin, α-enolase, and ornithine carbamoyl transferase, in a murine model of G. lamblia infection. Live recombinant attenuated Salmonella enterica Serovar Typhimurium vaccine strains were constructed that stably expressed each antigen, maintained colonization capacity, and sustained total attenuation in the host. Oral administration of the vaccine strains induced antigen-specific serum IgG, particularly IgG(2A), and mucosal IgA for α1-giardin and α-enolase, but not for ornithine carbamoyl transferase. Immunization with the α1-giardin vaccine induced significant protection against subsequent G. lamblia challenge, which was further enhanced by boosting with cholera toxin or sublingual α1-giardin administration. The α-enolase vaccine afforded no protection. Analysis of α1-giardin from divergent assemblage A and B isolates of G. lamblia revealed >97% amino acid sequence conservation and immunological cross-reactivity, further supporting the potential utility of this antigen in vaccine development. Together. These results indicate that α1-giardin is a suitable candidate antigen for a vaccine against giardiasis.

[Protozoal antigen positivity in diarrheal patients admitted to emergency service: a point prevalence study]

Intestinal parasites are the important etiological agents of water and food related diarrhea cases which are frequently seen during summer/early autumn seasons in developing countries. This point prevalence study was aimed to determine the protozoal antigen positivity rate in diarrhea cases admitted to the emergency service in one single day. A total of 198 diarrheal patients (90 male, 108 female; age range: 1-82 years, mean age: 29 years) who were admitted to the emergency service of Ankara Training and Research Hospital were included in the study. Macroscopic and direct microscopic examinations were performed for the stool samples of patients, and the samples which yielded pathological microscopic findings (e.g. presence of leukocytes, erythrocytes, and trophozoits) were investigated in terms of Entamoeba histolytica adhesin antigen, Giardia intestinalis cyst antigen and Cryptosporidium oocyst antigen by commercial ELISA kits (Techlab, USA). Macroscopic examination of the stool samples revealed that 60 (30%) of them had blood and mucous, 137 (69%) were watery and one sample had normal appearance. Pathologic results were obtained for 96 (48.5%) of the samples by microscopic examination: 36 (37.5%) revealed erythrocytes, 90 (93.7%) had leukocytes and 3 (1.5%) had G.intestinalis trophozoites. Since Shigella spp. were cultured in two of these 96 samples, these two cases were omitted from the study and 94 samples were investigated by ELISA assays. G.intestinalis was detected in 13 (13.8%) and E.histolytica in 2 (2.1%) samples while Cryptosporidium antigen was not detected in any of the samples by the ELISA assays. It was concluded that ELISA antigen assays were rapid and cost-effective methods for the determination of the causative agent in cases of diarrhea.

Rapid detection and enumeration of Giardia lamblia cysts in water samples by immunomagnetic separation and flow cytometric analysis

Giardia lamblia is an important waterborne pathogen and is among the most common intestinal parasites of humans worldwide. Its fecal-oral transmission leads to the presence of cysts of this pathogen in the environment, and so far, quantitative rapid screening methods are not available for various matrices, such as surface waters, wastewater, or food. Thus, it is necessary to establish methods that enable reliable rapid detection of a single cyst in 10 to 100 liters of drinking water. Conventional detection relies on cyst concentration, isolation, and confirmation by immunofluorescence microscopy (IFM), resulting in low recoveries and high detection limits. Many different immunomagnetic separation (IMS) procedures have been developed for separation and cyst purification, so far with variable but high losses of cysts. A method was developed that requires less than 100 min and consists of filtration, resuspension, IMS, and flow cytometric (FCM) detection. MACS MicroBeads were used for IMS, and a reliable flow cytometric detection approach was established employing 3 different parameters for discrimination from background signals, i.e., green and red fluorescence (resulting from the distinct pattern emitted by the fluorescein dye) and sideward scatter for size discrimination. With spiked samples, recoveries exceeding 90% were obtained, and false-positive results were never encountered for negative samples. Additionally, the method was applicable to naturally occurring cysts in wastewater and has the potential to be automated.

A La autoantigen homologue is required for the internal ribosome entry site mediated translation of giardiavirus

Translation of Giardiavirus (GLV) mRNA is initiated at an internal ribosome entry site (IRES) in the viral transcript. The IRES localizes to a downstream portion of 5′ untranslated region (UTR) and a part of the early downstream coding region of the transcript. Recent studies indicated that the IRES does not require a pre-initiation complex to initiate translation but may directly recruit the small ribosome subunit with the help of a number of trans-activating protein factors. A La autoantigen homologue in the viral host Giardia lamblia, GlLa, was proposed as one of the potential trans-activating factors based on its specific binding to GLV-IRES in vitro. In this study, we further elucidated the functional role of GlLa in GLV-IRES mediated translation in Giardia by knocking down GlLa with antisense morpholino oligo, which resulted in a reduction of GLV-IRES activity by 40%. An over-expression of GlLa in Giardia moderately stimulated GLV-IRES activity by 20%. A yeast inhibitory RNA (IRNA), known to bind mammalian and yeast La autoantigen and inhibit Poliovirus and Hepatitis C virus IRES activities in vitro and in vivo, was also found to bind to GlLa protein in vitro and inhibited GLV-IRES function in vivo. The C-terminal domain of La autoantigen interferes with the dimerization of La and inhibits its function. An over-expression of the C-terminal domain (200–348aa) of GlLa in Giardia showed a dominant-negative effect on GLV-IRES activity, suggesting a potential inhibition of GlLa dimerization. HA tagged GlLa protein was detected mainly in the cytoplasm of Giardia, thus supporting a primary role of GlLa in translation initiation in Giardiavirus.

The effects of nitric oxide on the immune response during giardiasis

Nitric oxide (NO) is a free radical synthesized from L-arginine by different isoforms NO-synthases. NO possesses multiple and complex biological functions. NO is an important mediator of homeostasis, and changes in its generation or actions can contribute or not to pathological states. The knowledge of effects of NO has been not only important to our understanding of immune response, but also to new tools for research and treatment of various diseases. Knowing the importance of NO as inflammatory mediator in diverse infectious diseases, we decided to develop a revision that shows the participation/effect of this mediator in immune response induced against Giardia spp. Several studies already demonstrated the participation of NO with microbicidal and microbiostatic activity in giardiasis. On the other hand, some works report that Giardia spp. inhibit NO production by consuming the intermediate metabolite arginine. In fact, studies in vitro showed that G. lamblia infection of human intestinal epithelial cells had reduced NO production. This occurs due to limited offer of the crucial substrate arginine (essential aminoacid for NO production), consequently reducing NO production. Therefore, the balance between giardial arginine consumption and epithelial NO production could contribute to the variability of the duration and severity of infections by this ubiquitous parasite.

Giardia duodenalis: the double-edged sword of immune responses in giardiasis

Giardiasis is one of the most common intestinal protozoan infections worldwide. The etiological agent, Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis), is a flagellated, binucleated protozoan parasite which infects a wide array of mammalian hosts (Adam, 2001). The symptoms of giardiasis include abdominal cramps, nausea, and acute or chronic diarrhea, with malabsorption and failure of children to thrive occurring in both sub-clinical and symptomatic disease (Thompson et al., 1993). Infections are transmitted by cysts which are excreted in the feces of infected humans and animals. Human giardiasis is distributed worldwide, with rates of detection between 2-5% in the developed world and 20-30% in the developing nations (Farthing, 1994). There is significant variation in the outcome of Giardia infections. Most infections are self-limiting, although re-infection is common in endemic areas and chronic infections also occur. Moreover, some individuals suffer from severe cramps, nausea and diarrhea while others escape these overt symptoms. This review will describe recent advances in parasite genetics and host immunity that are helping to shed light on this variability.

Giardia lamblia: interleukin 6 and tumor necrosis factor-alpha release from mast cells induced through an Ig-independent pathway

Giardia lamblia is a common cause of both acute and chronic diarrheal disease in humans worldwide. It has been shown that mast cells, IL-6 and TNF-alpha are substantially involved in the early control of G. lamblia infection in mice. However, no studies have yet been reported concerning the interaction between mast cell and Giardia, as well as the mast cells mediators generated in response to Giardia infection. In this study we demonstrated the direct activation of mast cells by G. lamblia live trophozoites or trophozoite-derived antigens followed by an increase in tryptase expression and a significant release of the preformed mediator histamine. In addition, parasite derived antigens increased TNF-alpha and de novo synthesized cytokine IL-6, at the mRNA and protein level. These results strongly suggest that mast cells might be an important source not only of IL-6 but also of TNF-alpha during Giardia infection, playing an important role in the outcome of the infection.

Involvement of lectin pathway activation in the complement killing of Giardia intestinalis

Giardia intestinalis (syn. G. lamblia, G. duodenalis) is a flagellated unicellular eukaryotic microorganism that commonly causes diarrheal disease throughout the world. In humans, the clinical effects of Giardia infection range from the asymptomatic carrier state to a severe malabsorption syndrome possibly due to different virulence of the Giardia strain, the number of cysts ingested, the age of the host, and the state of the host immune system at the time of infection. The question about how G. intestinalis is controlled by the organism remains unanswered. Here, we investigated the role of the complement system and in particular, the lectin pathway during Giardia infections. We present the first evidence that G. intestinalis activate the complement lectin pathway and in doing so participate in eradication of the parasite. We detected rapid binding of mannan-binding lectin, H-ficolin and L-ficolin to the surface of G. intestinalis trophozoites and normal human serum depleted of these molecules failed to kill the parasites. Our finding provides insight into the role of lectin pathway in the control of G. intestinalis and about the nature of surface components of parasite.

Rapid and sensitive detection of Giardia lamblia using a piezoelectric cantilever biosensor in finished and source waters

The current method for detecting the waterborne parasite Giardia lamblia is tedious and requires a preconcentration step. We show for the first time a piezoelectric-excited millimeter-sized cantilever (PEMC) biosensor immobilized with a monoclonal antibody against G. lamblia that exhibits selective and sensitive detection of G. lamblia cysts in several water matrixes (buffer, tap, and river water) at a detection limit of 1-10 cysts/mL without a preconcentration step. The PEMC sensor is a resonance-based device that functions at a high-order mode near 1 MHz. The antibody-immobilized sensor was exposed to 1-10,000 G. lamblia cysts/mL samples in a flow arrangement. When the cysts bind to the antibody on the sensor, the resonant frequency of the cantilever sensor decreases and is recorded continuously. Positive confirmation of sensor detection responses was obtained by environmental scanning electron microscope of sensor surface after detection experiments. Higher sample flow rates (0.5-5.0 mL/min) gave higher sensor detection response. Detecting as few as 10 cysts per mL was achieved in all three water matrixes tested, and significant sensor response was obtained in 15 min. We also show the feasibility of analyzing at a low concentration of 1 cyst/mL in a one liter sample at a high flow rate of 5 mL/min.

Copro-antigen detection versus direct methods for the diagnosis of Giardia lamblia in patients from the National Liver Institute

In this study a commercially available immunoenzymatic assay to detect G. lamblia specific copro-antigen was evaluated. A total of 90 stool samples were tested. Diagnosis of giardiasis by ELISA for copro-Ag detection was positive in 46 (51.1%) patients whereas by direct stool analysis after formol ether concentration G. lamblia was detected in 38 (42.2%) patients only. ELISA technique for detection of Giardia copro-antigen had a sensitivity of 97.3% and a specificity of 82.6% with PPV of 80.4% and a NPV of 97.7%.

Treatment of giardiasis in common marmosets (Callithrix jacchus) with tinidazole

Giardia intestinalis is a common protozoan parasite that can infect many laboratory animal primates, although its role as a contributor to the induction of gastrointestinal disease remains unclear. This study sought to investigate the prevalence of Giardia in a colony of common marmosets by using a Giardia antigen-capture assay and to address the possible eradication of this infection by using tinidazole, an antiprotozoal similar to metronidazole but requiring fewer doses. Among 31 colony marmosets, 13 (42%) were positive for Giardia. Two doses of oral tinidazole eliminated the infection in all animals. Repeat testing of the 13 Giardia-positive monkeys 1 y later showed that 11 remained negative and that treated animals had a significant increase in weight at 1 y. Giardia antigen is common in common marmoset feces, and treatment using oral tinidazole is possible and highly effective.

Detection of pathogen based on the catalytic growth of gold nanocrystals

A homogenous detection of pathogen (Giardia lamblia cysts) based on the catalytic growth of gold nanoparticles (AuNPs) has been studied. In this study, centrifugal filters were employed as tools to concentrate and separate the pathogen cells, and moreover amplify the detection signal. The catalytic growth of gold nanoparticles was verified to be positively related to gold seeds concentration. On this basis, homogenous detection of the pathogenic bacteria in liquid phase was established by means of conjugating antibody to gold seeds. Under the given experimental condition, detection limit of G. lamblia cysts was determined as low as 1.088 x 10(3) cells ml(-1). The additional nonspecific binding tests were also conducted to verify the detection specificity. This sensing platform has been proved to be a sensitive, reliable and simple method for large-scale pathogen detection, and provide valuable insight for the development of gold nanocrystals based colorimetric biosensors.

Antibody response in children infected with Giardia intestinalis before and after treatment with Secnidazole

We examined 364 school children for intestinal parasites in a sub-urban zone of Caracas, Venezuela. Giardia intestinalis was the most prevalent parasite in stool samples from 34 children. Levels of IgA and IgG antibodies to G. intestinalis were assessed by enzyme-linked immunosorbent assay and Western blot before and after treatment with secnidazole. All patients were cured with a reduction of IgA antibody levels in 26 of 34 children and a reduction in IgG-specific antibody levels in 18 of 34 children. Serum of infected patients reacted with proteins of 14 kD to 137 kD. Some patients did not show a change in IgA serum reactivity for parasite proteins by Western blot after treatment. Seventeen children showed reduction of the reactivity or disappearance of protein reactivity (mainly the 14-kD, 122-kD, and 137-kD proteins). Antibody response was not related to clinical status, but quantitative and qualitative serum antibody response against G. intestinalis infection could be used to assess levels of new protein markers that decrease or disappear with successful chemotherapy.

[Antigen detection methods in diagnosis of amebiasis, giardiasis and cryptosporidiosis]

Amebiasis is a significant health problem in developing countries. Humans are infected by two morphologically identical species of Entamoeba. Entamoeba histolytica causes amebic colitis and liver abscess, and Entamoeba dispar is noninvasive. Giardia intestinalis infection is seen worldwide and in all age groups. But giardiasis is especially prevalent in countries with poor sanitation and unsafe water, where it's responsible for most cases of childhood diarrhea. Cryptosporidium parvum, a protozoon, is an obligate intracellular parasite which can cause fatal diarrheal disease in immunocompromised individuals. Generally, the diagnosis of human intestinal protozoa depends on microscopic detection. Microscopic detection is inexpensive, but it is very labor-intensive and requires a skilled microscopist. Antigen detection methods (direct fluorescent antibody, enzyme immunoassay, and rapid, dipstick-like tests) can be performed quickly and do not require an experienced and skilled microscopist. Recently, commercially available diagnostic kits for the intestinal parasites E. histolytica, G.intestinalis and Cryptosporidium spp. use the laboratory diagnosis. In this review, we aimed to discuss the diagnosis of these three intestinal parasites using the antigen tests.

A single-step immunochromatographic lateral-flow assay for detection of Giardia lamblia and Cryptosporidium parvum antigens in human fecal samples

RIDA Quick immunochromatographic lateral-flow assay was evaluated for diagnosis of giardiasis and cryptosporidiosis as compared to the "gold standard" stool examination. Of the 300 specimens were examined by microscopy of direct wet films, concentrated sediments, modified trichrome and modified Ziehl-Neelsen stained slides, 35 samples of Giardia, ten Cryptosporidium, 35 of other parasites, and 20 negative controls were selected for RIDA Quick test examination. All the samples that gave discrepancy results were retested by the centrifugation prior to preparation for the permanent stained smear. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of RIDA quick test for Giardia were 91.6%, 98.4%, 97% & 95.4% respectively, while that of the microscopic stool examination were 94.5%, 100%, 100% & 96.9%. The sensitivity, specificity, PPV and NPV of RIDA quick test for Cryptosporidium was 91.6%, 100%, 100% & 98.8% respectively, while that of the microscopic stool examination were 83.3%, 100%, 100% & 97.7%.

Comparison of the local immune response against Giardia lamblia cyst wall protein 2 induced by recombinant Lactococcus lactis and Streptococcus gordonii

Lactococcus lactis and Streptococcus gordonii are lactic acid bacteria (LAB) currently being advocated for use as live antigen delivery vehicles to mucosal sites. Since both vehicles differ in their capability to persist within the small intestine and in their mode of antigen delivery, we sought to compare them to determine which one was superior. In this study, we compared the efficacy of recombinant L. lactis and S. gordonii to stimulate intestinal immune responses against Giardia lamblia cyst wall protein-2 in BALB/c mice. Oral administration of either vector significantly increased the number of CD4(+) T helper and B-cells in the mesenteric lymph nodes (MLN) and Peyer's patches (PP) of immunized animals. Delivery of recombinant CWP2 (rCWP2) by L. lactis stimulated a balanced IFN-gamma/IL-4 response (MLN and PP cells) and a CWP2-specific intestinal IgA antibody response. Alternatively, delivery of rCWP2 by S. gordonii stimulated a higher frequency of IFN-gamma secreting MLN and PP cells, as well as doubling the amount of CWP2-specific intestinal IgA. In challenge studies, L. lactis and S. gordonii reduced cyst output by 71 and 90%, respectively. When compared to each other, S. gordonii-immunized animals shed 65% fewer cysts than their L. lactis-immunized counterparts. Based on these findings, we concluded that S. gordonii was superior to L. lactis as an intestinal vaccine delivery vehicle.

[Informative value of methods for laboratory diagnosis of Giardia infection]

The author assesses the informative value of two methods of laboratory diagnosis of L. intestinalis: serological assay using indirect immunofluorescence versus fecal Giardia antigen test using the immunochromatographic RIDA Quick Giardia test system. The results of these procedures were compared with those of fecal microscopy. The serological approach to diagnosing Giardia infection was found to be of low informative value. There is evidence suggesting the high specificity and sensitivity of detection of Giardia antibody in the feces, which allows it to be recommended in parasitological laboratory. It has been established that fecal prestorage in the Turdyev preservative can reduce the sensitivity of the RIDA Quick Giardia test system at the low concentration of parasitic cysts in the material being examined.

Enhanced microfiltration devices configured with hydrodynamic trapping and a rain drop bypass filtering architecture for microbial cells detection

Ultra-fine (<1 microm) microfilters are required to effectively trap microbial cells. We designed microfilters featuring a rain drop bypass architecture, which significantly reduces the likelihood of clogging at the cost of limited cell loss. The new rain drop bypass architecture configuration has a substantially lower pressure drop and allows a better efficiency in trapping protozoan cells (Cryptosporidium parvum and Giardia lamblia) in comparison to our previous generation of a microfilter device. A modified version displaying sub-micron filter gaps was adapted to trap and detect bacterial cells (Escherichia coli), through a method of cells labeling, which aims to amplify the fluorescence signal emission and therefore the sensitivity of detection.

Effect of organochlorine (DDT) exposure on experimental giardiasis

This work studied the effect of sub-chronic DDT exposure on the course of experimental giardiasis and efficacy of its treatment. A total of 160 mice were divided into six groups: G1: 30 mice received DDT and infected with Giardia lamblia. G2: 30 mice received DDT, infected and treated with tinidazole (TNZ). G3: 30 mice infected with Giardia. G4: 30 mice infected and treated with TNZ. G5: 30 mice received DDT only. G6: 10 mice served as normal control. Mice were sacrificed at 7, 14, 21 & 28 days P.I. All groups were subjected to cyst count/2 hours collected stool, trophozoite count in intestine, histopathological examination of small intestinal section and avidin biotin peroxidase technique for local IgA staining. Also, IFN-gamma was measured in sera. DDT caused early shedding of many cysts and increase in trophozoite counts for a long time, decreased intra epithelial lymphocytes, low levels of IgA & IFN-gamma and severe histopathological changes in intestinal sections in G1 as compared to G3. Also, DDT reduced the efficacy of TNZ treatment in G2 as compared to G4. The results strongly support the immunomodulating effect of DDT on experimental giardiasis that might be responsible for persistence of infection, resistance to treatment and re-infection in DDT exposed persons.

Prevalence and associated risk factors for Giardia lamblia infection among children hospitalized for diarrhea in Goiânia, Goiás State, Brazil

The objective of this study was to determine the prevalence and to identify risk factors associated with Giardia lamblia infection in diarrheic children hospitalized for diarrhea in Goiânia, State of Goiás, Brazil. A cross-sectional study was conducted and a comprehensive questionnaire was administered to the child's primary custodian. Fixed effects logistic regression was used to determine the association between infection status for G. lamblia and host, sociodemographic, environmental and zoonotic risk factors. A total of 445 fecal samples were collected and processed by the DFA methodology, and G. lamblia cysts were present in the feces of 44 diarrheic children (9.9%). A variety of factors were found to be associated with giardiasis in these population: age of children (OR, 1.18; 90% CI, 1.0 - 1.36; p = 0.052), number of children in the household (OR 1.45; 90% CI, 1.13 - 1.86; p = 0.015), number of cats in the household (OR, 1.26; 90% CI, 1.03 -1.53; p = 0.059), food hygiene (OR, 2.9; 90% CI, 1.34 - 6.43; p = 0.024), day-care centers attendance (OR, 2.3; 90% CI, 1.20 - 4.36; p = 0.034), living on a rural farm within the past six months prior hospitalization (OR, 5.4; CI 90%, 1.5 - 20.1; p = 0.03) and the number of household adults (OR, 0.59; 90% CI, 0.42 - 0.83; p = 0.012). Such factors appropriately managed may help to reduce the annual incidence of this protozoal infection in the studied population.

Mucosal delivery of a transmission-blocking DNA vaccine encoding Giardia lamblia CWP2 by Salmonella typhimurium bactofection vehicle

In this study, we investigated the use of Salmonella typhimurium (STM1 strain) as a bactofection vehicle to deliver a transmission-blocking DNA vaccine (TBDV) plasmid to the intestinal immune system. The gene encoding the full length cyst wall protein-2 (CWP2) from Giardia lamblia was subcloned into the pCDNA3 mammalian expression vector and stably introduced into S. typhimurium STM1. Eight-week-old female BALB/c mice were orally immunized every 2 weeks, for a total of three immunizations. Vaccinated and control mice were sacrificed 1 week following the last injection. Administration of the DNA vaccine led to the production of CWP2-specific cellular immune responses characterized by a mixed Th1/Th2 response. Using ELISA, antigen-specific IgA and IgG antibodies were detected in intestinal secretions. Moreover, analysis of sera demonstrated that the DNA immunization also stimulated the production of CWP2-specific IgG antibodies that were mainly of the IgG2a isotype. Finally, challenge infection with live Giardia muris cysts revealed that mice receiving the CWP2-encoding DNA vaccine were able to reduce cyst shedding by approximately 60% compared to control mice. These results demonstrate, for the first time, the development of parasite transmission-blocking immunity at the intestinal level following the administration of a mucosal DNA vaccine delivered by S. typhimurium STM1.

Cell loss in integrated microfluidic device

Cell loss during sample transporting from macro-components to micro-components in integrated microfluidic devices can considerably deteriorate cell detection sensitivity. This intrinsic cell loss was studied and effectively minimized through (a) increasing the tubing diameter connecting the sample storage and the micro-device, (b) applying a hydrodynamic focusing approach for sample delivering to reduce cells contacting and adhesion on the walls of micro-channel and chip inlet; (c) optimizing the filter design with a zigzag arrangement of pillars (13 microm in chamber depth and 0.8 microm in gap) to prolong the effective filter length, and iv) the use of diamond shaped pillar instead of normally used rectangular shape to reduce the gap length between any two given pillar (i.e. pressure drop) at the filter region. Cell trapping and immunofluorescent detection of 12 Giardia lamblia and 12 Cryptosporidium parvum cells in 150 microl solution and 50 MCF-7 breast cancer cells in 150 microl solution was completed within 15 min with trapping efficiencies improved from 79+/-11%, 50.8+/-5.5% and 41.3+/-3.6% without hydrodynamic focusing, respectively, to 90.8+/-5.8%, 89.8+/-16.6% and 77.0+/-9.2% with hydrodynamic focusing.

Tumour necrosis factor alpha contributes to protection against Giardia lamblia infection in mice

Giardia lamblia is a ubiquitous parasite that causes diarrhoea. Effective control of Giardia infections in mice has been shown to involve IgA, T cells, mast cells and IL-6. We now show that Tumour necrosis factor alpha (TNFalpha) also plays an important role in the early control of giardiasis. Mice treated with neutralizing anti-TNFalpha antibodies or genetically deficient in TNFalpha were infected with the G. lamblia clone GS/(M)-H7. In both cases, mice lacking TNFalpha had much higher parasite numbers than controls during the first 2 weeks of infections. However, anti-parasite IgA levels, mast cell responses, and IL-4 and IL-6 mRNA levels do not appear significantly altered in the absence of TNFalpha. In addition, we show that mice infected with G. lamblia exhibit increased intestinal permeability, similar to human Giardia infection, and that this increase occurs in both wild-type and TNFalpha deficient mice. We conclude that TNFalpha is essential for host resistance to G. lamblia infection, and that it does not exert its effects through mechanisms previously implicated in control of this parasite.

Effect of propolis versus metronidazole and their combined use in treatment of acute experimental giardiasis

Propolis, a honey bee product, gained popularity in alternative medicine. Its prophylactic and therapeutic effects were experimentally evaluated. One hundred and fifty immunocompetent mice were orally infected by 5 x 10(5) axenically cultivated Giardia lamblia trophozoites. The trophozoite count in intestine, interferon-gamma serum level, histopathological examination of duodenal and jejunal sections were assessed for evaluation of propolis and metronidazole (MTZ) effect after 6 & 12 days post infection (p.i). Also, T-lymphocyte profile in blood was investigated 12 days p.i using flow cytometry (FCM). Propolis as prophylaxis showed a significant decrease in intensity of infection, together with a significant increase in IF-gamma serum level and increase in CD4+: CD8+T-cell ratio. In treatment it gave a highly significant decrease in trophozoite count than that obtained by MTZ 6 days after infection but the efficacy was almost equal after 12 days. The mice treated with propolis alone showed a reversed CD4+: CD8+ T-lymphocyte ratio, such strong immune enhancing effect resulted in an undesirable increase in inflammatory response at intestinal level. The combined therapy showed a stronger efficacy in reducing the parasite count than that gained by each drug alone. Their combined use caused an immunological balance as shown by the T-lymphocyte profile that saved the intestinal homeostasis and histological architecture.