Demonstration of Trophozoites of G. Lamblia in Ileal Mucosal Biopsy Specimens May Reveal Giardiasis in Patients With Significantly Inflamed Parasite-free Duodenal Mucosa

Trophozoite fitness dictates the intestinal epithelial cell response to Giardia intestinalis infection

Giardia intestinalis is a non-invasive, protozoan parasite infecting the upper small intestine of most mammals. Symptomatic infections cause the diarrhoeal disease giardiasis in humans and animals, but at least half of the infections are asymptomatic. However, the molecular underpinnings of these different outcomes of the infection are still poorly defined. Here, we studied the early transcriptional response to G. intestinalis trophozoites, the disease-causing life-cycle stage, in human enteroid-derived, 2-dimensional intestinal epithelial cell (IEC) monolayers. Trophozoites preconditioned in media that maximise parasite fitness triggered only neglectable inflammatory transcription in the IECs during the first hours of co-incubation. By sharp contrast, "non-fit" or lysed trophozoites induced a vigorous IEC transcriptional response, including high up-regulation of many inflammatory cytokines and chemokines. Furthermore, "fit" trophozoites could even suppress the stimulatory effect of lysed trophozoites in mixed infections, suggesting active G. intestinalis suppression of the IEC response. By dual-species RNA-sequencing, we defined the IEC and G. intestinalis gene expression programs associated with these differential outcomes of the infection. Taken together, our results inform on how G. intestinalis infection can lead to such highly variable effects on the host, and pinpoints trophozoite fitness as a key determinant of the IEC response to this common parasite.

Giardia duodenalis: Biology and Pathogenesis

Giardia duodenalis captured the attention of Leeuwenhoek in 1681 while he was examining his own diarrheal stool, but, ironically, it did not really gain attention as a human pathogen until the 1960s, when outbreaks were reported. Key technological advances, including in vitro cultivation, genomic and proteomic databases, and advances in microscopic and molecular approaches, have led to an understanding that this is a eukaryotic organism with a reduced genome rather than a truly premitochondriate eukaryote. This has included the discovery of mitosomes (vestiges of mitochondria), a transport system with many of the features of the Golgi apparatus, and even evidence for a sexual or parasexual cycle. Cell biology approaches have led to a better understanding of how Giardia survives with two nuclei and how it goes through its life cycle as a noninvasive organism in the hostile environment of the lumen of the host intestine. Studies of its immunology and pathogenesis have moved past the general understanding of the importance of the antibody response in controlling infection to determining the key role of the Th17 response. This work has led to understanding of the requirement for a balanced host immune response that avoids the extremes of an excessive response with collateral damage or one that is unable to clear the organism. This understanding is especially important in view of the remarkable ranges of early manifestations, which range from asymptomatic to persistent diarrhea and weight loss, and longer-term sequelae that include growth stunting in children who had no obvious symptoms and a high frequency of postinfectious irritable bowel syndrome (IBS).

Infectious diseases of the upper gastrointestinal tract

A broad spectrum of pathogens produce gastrointestinal disease. The ongoing spread of human immunodeficiency virus/acquired immune deficiency syndrome, the increased use of immunosuppressive therapy and the persistence of overcrowding and suboptimal sanitation in underdeveloped areas facilitate both disease transmission from environmental and foodborne sources and person-to-person transmission. Clinicians increasingly rely on endoscopic biopsy sample interpretation to diagnose gastrointestinal infections. Thus, pathologists must be aware of diagnostic features of a variety of microbial pathogens. Detection with molecular techniques also allows for correlation between infectious agents and their histopathological features, which has expanded our knowledge of the inflammatory changes produced by infectious agents. This review covers infectious disorders of the upper gastrointestinal tract encountered in surgical pathology. Clinical, endoscopic and pathological features are presented. The review emphasises morphological features of viruses, bacteria, fungi and parasites that may be found in tissue samples, and the inflammatory patterns that they produce. Differential diagnoses and useful ancillary techniques are discussed.

Giardia Is Often Overlooked on Histopathologic Examination: A High-Volume, Single-Institution Experience

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.

Gastrointestinal findings in 26 adults with common variable immunodeficiency: The fickle nature of the disease manifests in gastrointestinal biopsies

BACKGROUND/AIMS

The aim of the present study was to demonstrate the histopathological findings in gastrointestinal (GI) biopsies in adults with common variable immunodeficiency (CVID).

MATERIALS AND METHODS

A total of 172 GI biopsies of 26 patients with CVID obtained over a 16-year period were reevaluated. Findings were analyzed using descriptive analyzes and χ2 test.

RESULTS

Female-to-male ratio was 1.36. The median age at diagnosis was 36±13.94 (16-72) years. Chronic esophagitis was noted in 3 patients. The absence of plasma cells in the stomach, duodenum, and colon was observed in 16, 14, and 9 patients, respectively. Divergent results for the presence of plasma cells in concurrent stomach and duodenum samples were found in 11 (44%) patients. Nodular lymphoid hyperplasia (NLH) was notable in the duodenum (56%). The mean number of eosinophils in one high-power field was significantly higher in duodenal biopsies with NLH (27.21 vs. 14.37, p=0.002). Active inflammation was more prominent in the colon (91%) than in the stomach (65%) and duodenum (60%). Helicobacter pylori infection was found in 57.6%, including a case with persistent infection by the coccoid form. Celiac-like villous blunting and increased intraepithelial lymphocytes were seen in 40% and 24%, respectively. In addition, 23% had giardiasis associated with acute duodenitis and duodenal NLH (p<0.05).

CONCLUSION

CVID gastroenteropathy is a challenging entity, and due to the heterogeneity in the presence and distribution of plasma cells throughout the GI tract and diverse disease course, multiple concurrent biopsies may be needed for tissue diagnosis. Duodenal CVID may present with villous alterations and giardiasis, and NLH appears to be an important clue in the duodenum. The association between duodenal NLH and eosinophil infiltration deserves further investigation.

Prolonged Duodenal Mucosal Lymphocyte Alterations in Patients With and Without Postinfectious Functional Gastrointestinal Disorders After Giardia Infection

Background

Persisting low-grade inflammation is suggested to play a role in postinfectious functional gastrointestinal disorders (PI-FGIDs). The present study examined alterations in duodenal mucosal lymphocytes during and after Giardia gastroenteritis in patients who did, or did not, develop PI-FGIDs.

Methods

Duodenal mucosal intraepithelial lymphocytes (IELs) and lamina propria CD3, CD4, CD8, and CD20 lymphocytes were quantified in 28 patients with chronic giardiasis (CG), 66 patients with persistent abdominal symptoms after acute Giardia infection (PI-FGID), 19 recovered controls (RCs), and 16 healthy volunteers (HCs). Associations with illness duration, abdominal symptoms, and histology grade were assessed.

Results

Duodenal CD4 IELs were significantly elevated in CG, then decreased, followed by an upward trend after 1 year in both the PI-FGID and RC groups. Duodenal lamina propria crypt CD4 T cells were decreased in CG, and stayed low for about 14 months before normalizing in both the PI-FGID and RC groups. Lamina propria CD20 cells were persistently elevated in all 3 Giardia-exposed groups. Biopsies with microscopic inflammation showed increased lamina propria CD20 levels.

Conclusions

Duodenal mucosal lymphocyte alterations were prolonged after Giardia infection, but similar in patients who developed PI-FGID and recovered asymptomatic controls.

Secreted Giardia intestinalis cysteine proteases disrupt intestinal epithelial cell junctional complexes and degrade chemokines

Giardiasis is a common diarrheal disease caused by the protozoan parasite Giardia intestinalis. Cysteine proteases (CPs) are acknowledged as virulence factors in Giardia but their specific role in the molecular pathogenesis of disease is not known. Herein, we aimed to characterize the three main secreted CPs (CP14019, CP16160 and CP16779), which were identified by mass spectrometry in the medium during interaction with intestinal epithelial cells (IECs) in vitro. First, the CPs were epitope-tagged and localized to the endoplasmic reticulum and cytoplasmic vesicle-like structures. Second, we showed that recombinant CPs, expressed in Pichia pastoris, are more active in acidic environment (pH 5.5-6) and we determined the kinetic parameters using fluorogenic substrates. Third, excretory-secretory proteins (ESPs) from Giardia trophozoites affect the localization of apical junctional complex (AJC) proteins and recombinant CPs cleave or re-localize the AJC proteins (claudin-1 and -4, occludin, JAM-1, β-catenin and E-cadherin) of IECs. Finally, we showed that the ESPs and recombinant CPs can degrade several chemokines, including CXCL1, CXCL2, CXCL3, IL-8, CCL2, and CCL20, which are up-regulated in IECs during Giardia-host cell interactions. This is the first study that characterizes the role of specific CPs secreted from Giardia and our results collectively indicate their roles in the disruption of the intestinal epithelial barrier and modulating immune responses during Giardia infections.

Inflammatory and infectious manifestations of immunodeficiency in the gastrointestinal tract

Immune compromise may result from genetic abnormalities, HIV/AIDS, or consequences of therapy for neoplastic and autoimmune diseases. Many immunocompromised patients develop severe gastrointestinal symptoms, particularly diarrhea, accompanied by non-specific or mild endoscopic abnormalities; mucosal biopsy with pathologic interpretation has a major role in the diagnosis and management of these patients. Immunocompromised individuals are at risk for all the diseases that affect those with a healthy immune system, but they are also prone to other illnesses that rarely affect immunocompetent patients. This review discusses the gastrointestinal manifestations of primary and acquired immunodeficiency, chemotherapy-related injury, and infections that show a predilection for immunocompromised patients. Key histologic features and relevant differential diagnoses are emphasized.

Cytology Preparations of Formalin Fixative Aid Detection of Giardia in Duodenal Biopsy Samples

Giardiasis is the most common intestinal parasitic infection in the United States. The organism elicits no, or minimal, inflammatory changes in duodenal biopsy samples, so it can be easily overlooked. We performed this study to determine whether Giardia could be isolated from the formalin fixative of biopsy samples, and to evaluate the value of fluid analysis in the assessment for potential infection. We prospectively evaluated duodenal biopsy samples from 92 patients with a clinical suspicion of giardiasis or symptoms compatible with that diagnosis (ie, diarrhea, bloating, or abdominal pain) Biopsy samples were routinely processed and stained with hematoxylin and eosin. Histologic diagnoses included giardiasis (5 cases, 4%), normal findings (64 cases, 70%), peptic injury/active duodenitis (12 cases, 13%), and intraepithelial lymphocytosis with villous blunting (10 cases, 12%). Fifteen cases (13%) showed detached degenerated epithelial cells or mucus droplets in the intervillous space that resembled Giardia. Cytology slides were prepared from formalin in the biopsy container using the standard Cytospin protocol and reviewed by a cytopathologist blinded to the biopsy findings. Cytologic evaluation revealed Giardia spp. in all 5 biopsy-proven cases, and identified an additional case that was not detected by biopsy analysis. Organisms were significantly more numerous (mean: 400 trophozoites; range, 120 to 810) and showed better morphologic features in cytology preparations compared with tissue sections (mean: 129 trophozoites; range, 37 to 253 organisms; P=0.05). Our findings suggest that cytology preparations from formalin fixative can resolve diagnostically challenging cases and even enhance Giardia detection in some cases.

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.