Intestinal function and injury in acquired immunodeficiency syndrome-related cryptosporidiosis

Herbal-based compounds: A review on treatments of cryptosporidiosis

Cryptosporidium, a monoxenous apicomplexan coccidia, is a prevalent diarrhetic and an opportunistic agent, mainly in immunocompromised individuals. As there are few chemotherapeutic compounds that have limited efficacy, we need to identify new compounds or specific parasite targets for designing more potent drugs to treat cryptosporidiosis. Herbal products with low toxicity, environmental compatibility, wide therapeutic potential, and abundant resources can be considered alternatives for treatment. The current review tried to summarize the studies on plants or herbal bioactive constituents with anti-cryptosporidial activities. Based on constituents, plants act via different mechanisms, and further investigations are needed to clarify the exact mechanisms by which they act on the developmental stages of the parasite or host-parasite relationships.

Immunity to Cryptosporidium: insights into principles of enteric responses to infection

Cryptosporidium parasites replicate within intestinal epithelial cells and are an important cause of diarrhoeal disease in young children and in patients with primary and acquired defects in T cell function. This Review of immune-mediated control of Cryptosporidium highlights advances in understanding how intestinal epithelial cells detect this infection, the induction of innate resistance and the processes required for activation of T cell responses that promote parasite control. The development of a genetic tool set to modify Cryptosporidium combined with tractable mouse models provide new opportunities to understand the principles that govern the interface between intestinal epithelial cells and the immune system that mediate resistance to enteric pathogens.

A case of septic shock due to delayed diagnosis of Cryptosporidium infection after liver transplantation

BACKGROUND

Cryptosporidium is recognized as a significant pathogen of diarrhea disease in immunocompromised hosts, and studies have shown that Cryptosporidium infection is high in solid organ transplantation (SOT) patients and often has serious consequences. Because of the lack of specificity of diarrheasymptoms cased by Cryptosporidium infection, it is rarely reported in patients undergoing liver transplantation (LT). It frequently delays diagnosis, coming with severe consequences. In clinical work, diagnosing Cryptosporidium infection in LT patients is also complex but single, and the corresponding anti-infective treatment regimen has not yet been standardized. A rare case of septic shock due to a delayed diagnosis of Cryptosporidium infection after LT and relevant literature are discussed in the passage.

CASE PRESENTATION

A patient who had received LT for two years was admitted to the hospital with diarrhea more than 20 days after eating an unclean diet. After failing treatment at a local hospital, he was admitted to Intensive Care Unit after going into septic shock. The patient presented hypovolemia due to diarrhea, which progressed to septic shock. The patient's sepsis shock was controlled after receiving multiple antibiotic combinations and fluid resuscitation. However, the persistent diarrhea, as the culprit of the patient's electrolyte disturbance, hypovolemia, and malnutrition, was unsolved. The causative agent of diarrhea, Cryptosporidium infection, was identified by colonoscopy, faecal antacid staining, and blood high-throughput sequencing (NGS). The patient was treated by reducing immunosuppression and Nitazoxanide (NTZ), which proved effective in this case.

CONCLUSION

When LT patients present with diarrhea, clinicians should consider the possibility of Cryptosporidium infection, in addition to screening for conventional pathogens. Tests such as colonoscopy, stool antacid staining and blood NGS sequencing can help diagnose and treat of Cryptosporidium infection early and avoid serious consequences of delayed diagnosis. In treating Cryptosporidium infection in LT patients, the focus should be on the patient's immunosuppressive therapy, striking a balance between anti-immunorejection and anti-infection should be sought. Based on practical experience, NTZ therapy in combination with controlled CD4 + T cells at 100-300/mm³ was highly effective against Cryptosporidium without inducing immunorejection.

Host innate immune responses and microbiome profile of neonatal calves challenged with Cryptosporidium parvum and the effect of bovine colostrum supplementation

Introduction

Calves are highly susceptible to gastrointestinal infection with Cryptosporidium parvum (C. parvum), which can result in watery diarrhea and eventually death or impaired development. With little to no effective therapeutics, understanding the host's microbiota and pathogen interaction at the mucosal immune system has been critical to identify and test novel control strategies.

Methods

Herein, we used an experimental model of C. parvum challenge in neonatal calves to describe the clinical signs and histological and proteomic profiling of the mucosal innate immunity and microbiota shifts by metagenomics in the ileum and colon during cryptosporidiosis. Also, we investigated the impact of supplemental colostrum feeding on C. parvum infection.

Results

We showed that C. parvum challenged calves experienced clinical signs including pyrexia and diarrhea 5 days post challenge. These calves showed ulcerative neutrophil ileitis with a proteomic signature driven by inflammatory effectors, including reactive oxygen species and myeloperoxidases. Colitis was also noticed with an aggravated mucin barrier depletion and incompletely filled goblet cells. The C. parvum challenged calves also displayed a pronounced dysbiosis with a high prevalence of Clostridium species (spp.) and number of exotoxins, adherence factors, and secretion systems related to Clostridium spp. and other enteropathogens, including Campylobacter spp., Escherichia sp., Shigella spp., and Listeria spp. Daily supplementation with a high-quality bovine colostrum product mitigated some of the clinical signs and modulated the gut immune response and concomitant microbiota to a pattern more similar to that of healthy unchallenged calves.

Discussion

C. parvum infection in neonatal calves provoked severe diarrheic neutrophilic enterocolitis, perhaps augmented due to the lack of fully developed innate gut defenses. Colostrum supplementation showed limited effect mitigating diarrhea but demonstrated some clinical alleviation and specific modulatory influence on host gut immune responses and concomitant microbiota.

Immune Impairment Associated with Vitamin A Deficiency: Insights from Clinical Studies and Animal Model Research

Vitamin A (VA) is critical for many biological processes, including embryonic development, hormone production and function, the maintenance and modulation of immunity, and the homeostasis of epithelium and mucosa. Specifically, VA affects cell integrity, cytokine production, innate immune cell activation, antigen presentation, and lymphocyte trafficking to mucosal surfaces. VA also has been reported to influence the gut microbiota composition and diversity. Consequently, VA deficiency (VAD) results in the imbalanced production of inflammatory and immunomodulatory cytokines, intestinal inflammation, weakened mucosal barrier functions, reduced reactive oxygen species (ROS) and disruption of the gut microbiome. Although VAD is primarily known to cause xerophthalmia, its role in the impairment of anti-infectious defense mechanisms is less defined. Infectious diseases lead to temporary anorexia and lower dietary intake; furthermore, they adversely affect VA status by interfering with VA absorption, utilization and excretion. Thus, there is a tri-directional relationship between VAD, immune response and infections, as VAD affects immune response and predisposes the host to infection, and infection decreases the intestinal absorption of the VA, thereby contributing to secondary VAD development. This has been demonstrated using nutritional and clinical studies, radiotracer studies and knockout animal models. An in-depth understanding of the relationship between VAD, immune response, gut microbiota and infections is critical for optimizing vaccine efficacy and the development of effective immunization programs for countries with high prevalence of VAD. Therefore, in this review, we have comprehensively summarized the existing knowledge regarding VAD impacts on immune responses to infections and post vaccination. We have detailed pathological conditions associated with clinical and subclinical VAD, gut microbiome adaptation to VAD and VAD effects on the immune responses to infection and vaccines.

Whole transcriptome analysis of HCT-8 cells infected by Cryptosporidium parvum

BACKGROUND

Cryptosporidium species are zoonotic protozoans that are important causes of diarrhoeal disease in both humans and animals. Non-coding RNAs (ncRNAs) play an important role in the innate immune defense against Cryptosporidium infection, but the underlying molecular mechanisms in the interaction between human ileocecal adenocarcinoma (HCT-8) cells and Cryptosporidium species have not been entirely revealed.

METHODS

The expression profiles of messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) in the early phase of infection of HCT-8 cells with Cryptosporidium parvum and at 3 and 12 h post infection were analyzed using the RNA-sequencing technique. The biological functions of differentially expressed RNAs (dif-RNAs) were discovered through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The targeting relationships between three ncRNAs and mRNAs were analyzed using bioinformatics methods, followed by building a competing endogenous RNA (ceRNA) regulatory network centered on miRNAs.

RESULTS

After strictly filtering the raw data, our analysis revealed 393 dif-lncRNAs, 69 dif-miRNAs and 115 dif-mRNAs at 3 hpi, and 450 dif-lncRNAs, 129 dif-miRNAs, 117 dif-mRNAs and one dif-circRNA at 12 hpi. Of these, 94 dif-lncRNAs, 24 dif-miRNAs and 22 dif-mRNAs were detected at both post-infection time points. Eleven dif-lncRNAs, seven dif-miRNAs, eight dif-mRNAs and one circRNA were randomly selected and confirmed using the quantitative real-time PCR. Bioinformatics analyses showed that the dif-mRNAs were significantly enriched in nutritional absorption, metabolic processes and metabolism-related pathways, while the dif-lncRNAs were mainly involved in the pathways related to the infection and pathogenicity of C. parvum (e.g. tight junction protein) and immune-related pathways (e.g. cell adhesion molecules). In contrast, dif-miRNAs and dif-circRNA were significantly enriched in apoptosis and apoptosis-related pathways. Among the downregulated RNAs, the miRNAs has-miR-324-3p and hsa-miR-3127-5p appear to be crucial miRNAs which could negatively regulate circRNA, lncRNA and mRNA.

CONCLUSIONS

The whole transcriptome profiles of HCT-8 cells infected with C. parvum were obtained in this study. The results of the GO and KEGG pathway analyses suggest significant roles for these dif-RNAs during the course of C. parvum infection. A ceRNA regulation network containing miRNA at its center was constructed for the first time, with hsa-miR-324-3p and hsa-miR-3127-5p being the crucial miRNAs. These findings provide novel insights into the responses of human intestinal epithelial cells to C. parvum infection.

Clofazimine for Treatment of Cryptosporidiosis in Human Immunodeficiency Virus Infected Adults: An Experimental Medicine, Randomized, Double-blind, Placebo-controlled Phase 2a Trial

Background

We evaluated the efficacy, pharmacokinetics (PK), and safety of clofazimine (CFZ) in patients living with human immunodeficiency virus (HIV) with cryptosporidiosis.

Methods

We performed a randomized, double-blind, placebo-controlled study. Primary outcomes in part A were reduction in Cryptosporidium shedding, safety, and PK. Primary analysis was according to protocol (ATP). Part B of the study compared CFZ PK in matched individuals living with HIV without cryptosporidiosis.

Results

Twenty part A and 10 part B participants completed the study ATP. Almost all part A participants had high viral loads and low CD4 counts, consistent with failure of antiretroviral (ARV) therapy. At study entry, the part A CFZ group had higher Cryptosporidium shedding, total stool weight, and more diarrheal episodes compared with the placebo group. Over the inpatient period, compared with those who received placebo, the CFZ group Cryptosporidium shedding increased by 2.17 log2 Cryptosporidium per gram stool (95% upper confidence limit, 3.82), total stool weight decreased by 45.3 g (P = .37), and number of diarrheal episodes increased by 2.32 (P = .87). The most frequent solicited adverse effects were diarrhea, abdominal pain, and malaise. One placebo and 3 CFZ participants died during the study. Plasma levels of CFZ in participants with cryptosporidiosis were 2-fold lower than in part B controls.

Conclusions

Our findings do not support the efficacy of CFZ for the treatment of cryptosporidiosis in a severely immunocompromised HIV population. However, this trial demonstrates a pathway to assess the therapeutic potential of drugs for cryptosporidiosis treatment. Screening persons living with HIV for diarrhea, and especially Cryptosporidium infection, may identify those failing ARV therapy.

Clinical Trials Registration

NCT03341767.

The Mucosal Innate Immune Response to Cryptosporidium parvum, a Global One Health Issue

Cryptosporidium parvum is an apicomplexan parasite that infects the intestinal epithelium of humans and livestock animals worldwide. Cryptosporidiosis is a leading cause of diarrheal-related deaths in young children and a major cause of economic loss in cattle operations. The disease is especially dangerous to infants and immunocompromised individuals, for which there is no effective treatment or vaccination. As human-to-human, animal-to-animal and animal-to-human transmission play a role in cryptosporidiosis disease ecology, a holistic 'One Health' approach is required for disease control. Upon infection, the host's innate immune response restricts parasite growth and initiates the adaptive immune response, which is necessary for parasite clearance and recovery. The innate immune response involves a complex communicative interplay between epithelial and specialized innate immune cells. Traditional models have been used to study innate immune responses to C. parvum but cannot fully recapitulate natural host-pathogen interactions. Recent shifts to human and bovine organoid cultures are enabling deeper understanding of host-specific innate immunity response to infection. This review examines recent advances and highlights research gaps in our understanding of the host-specific innate immune response to C. parvum. Furthermore, we discuss evolving research models used in the field and potential developments on the horizon.

Minimal Lesions of the Small Intestinal Mucosa: More than Morphology

Minimal lesions of the small bowel are mucosal changes characterized by an increased number of intraepithelial lymphocytes (with or without crypt hyperplasia) and normal villous architecture. Such changes are associated with a wide spectrum of conditions, ranging from food intolerances to infections, and from drugs to immune diseases, with different clinical profiles and manifestations, which complicates the formulation of a differential diagnosis. Patient history, symptom evaluation, and histopathology are the diagnostic features needed to establish a correct diagnosis. Physicians should assist pathologists in formulating a precise morphological evaluation by taking well-oriented small intestinal biopsies and collecting informative clinical findings that inform histopathology. In this current clinical controversy, the authors provide the reader with an appraisal of the small intestine minimal lesions through a careful analysis of the major conditions (e.g., celiac disease and other non-celiac disorders) responsible for such changes and their differential diagnosis. Also, we acknowledge that some of the diseases detailed in this article may progress from an early minimal lesion to overt mucosal atrophy. Thus, the timing of the diagnosis is of paramount importance.

Targeting the TS dimer interface in bifunctional Cryptosporidium hominis TS-DHFR from parasitic protozoa: Virtual screening identifies novel TS allosteric inhibitors

Effective therapies are lacking to treat gastrointestinal infections caused by the genus Cryptosporidium, which can be fatal in the immunocompromised. One target of interest is Cryptosporidium hominis (C. hominis) thymidylate synthase-dihydrofolate reductase (ChTS-DHFR), a bifunctional enzyme necessary for DNA biosynthesis. Targeting the TS-TS dimer interface is a novel strategy previously used to identify inhibitors against the related bifunctional enzyme in Toxoplasma gondii. In the present study, we target the ChTS dimer interface through homology modeling and high-throughput virtual screening to identifying allosteric, ChTS-specific inhibitors. Our work led to the discovery of methylenedioxyphenyl-aminophenoxypropanol analogues which inhibit ChTS activity in a manner that is both dose-dependent and influenced by the conformation of the enzyme. Preliminary results presented here include an analysis of structure activity relationships and a ChTS-apo crystal structure of ChTS-DHFR supporting the continued development of inhibitors that stabilize a novel pocket formed in the open conformation of ChTS-TS.

NMR metabolomics reveals effects of Cryptosporidium infections on host cell metabolome

Background

Cryptosporidium is an important gut microbe whose contributions towards infant and immunocompromise patient mortality rates are steadily increasing. Over the last decade, we have seen the development of various tools and methods for studying Cryptosporidium infection and its interactions with their hosts. One area that is sorely overlooked is the effect infection has on host metabolic processes.

Results

Using a ¹H nuclear magnetic resonance approach to metabolomics, we have explored the nature of the mouse gut metabolome as well as providing the first insight into the metabolome of an infected cell line. Statistical analysis and predictive modelling demonstrated new understandings of the effects of a Cryptosporidium infection, while verifying the presence of known metabolic changes. Of note is the potential contribution of host derived taurine to the diarrhoeal aspects of the disease previously attributed to a solely parasite-based alteration of the gut environment, in addition to other metabolites involved with host cell catabolism.

Conclusion

This approach will spearhead our understanding of the Cryptosporidium-host metabolic exchange and provide novel targets for tackling this deadly parasite.

Subcutaneous Immunoglobulin Replacement Therapy with Hizentra® is Safe and Effective in Children Less Than 5 Years of Age

Background

Hizentra® (IGSC 20 %) is a 20 % liquid IgG product approved for subcutaneous administration in adults and children 2 years of age and older who have primary immunodeficiency disease (PIDD). There is limited information about the use of IGSC 20 % in very young children including those less than 5 years of age.

Methods

A retrospective chart review involved 88 PIDD infants and children less than 5 years of age who received Hizentra®.

Results

The mean age at the start of Hizentra® was 34 months (range 2 to 59 months). IGSC 20 % was administered weekly to 86 infants (two additional infants received twice weekly and three times weekly infusions, respectively) and included an average of 63 infusions (range 6–182) for an observation period up to 45.5 months. Infusion by manual delivery occurred in 15 patients. The mean dose was 674 mg/kg/4 weeks. The mean IgG level was 942 mg/dL while on IGSC 20 %, compared to a mean trough IgG level of 794 mg/dL (p < 0.0001) during intravenous or subcutaneous IgG administration prior to IGSC 20 %. Average infusion time was 47 (range 5–120) minutes, and the median number of infusion sites was 2 (range 1–4). Local reactions were mostly mild and observed in 36/88 (41 %) children. No serious adverse events were reported. A significant increase in weight percentile (7 % ± 19.2, p = 0.0012) among subjects was observed during IGSC 20 % administration. The rate of serious bacterial infections was 0.067 per patient-year while receiving IGSC 20 %, similar to previously reported efficacy studies.

Conclusions

Hizentra® is effective in preventing infections, and is well tolerated in children less than age 5 years.

Treatment of Cryptosporidium: What We Know, Gaps, and the Way Forward

Cryptosporidiosis is increasingly recognized as an important global health concern. While initially reported in immunocompromised such as AIDS patients, cryptosporidiosis has now been documented as a major cause of childhood diarrhea and an important factor in childhood malnutrition. Currently, nitazoxanide is the only proven anti-parasitic treatment for Cryptosporidium infections. However, it is not effective in severely immunocompromised patients and there is limited data in infants. Immune reconstitution or decreased immunosuppression is critical to therapy in AIDS and transplant patients. This limitation of treatment options presents a major public health challenge given the important burden of disease. Repurposing of drugs developed for other indications and development of inhibitors for novel targets offer hope for improved therapies, but none have advanced to clinical studies.

Correlation between diarrhea severity and oocyst count via quantitative PCR or fluorescence microscopy in experimental cryptosporidiosis in calves

Cryptosporidium is an important diarrhea-associated pathogen, however the correlation between parasite burden and diarrhea severity remains unclear. We studied this relationship in 10 experimentally infected calves using immunofluorescence microscopy and real-time polymerase chain reaction (qPCR) (N = 124 fecal samples). The qPCR data were corrected for extraction/amplification efficiency and gene copy number to generate parasite counts. The qPCR and microscopic oocyst quantities exhibited significant correlation (R(2) = 0.33, P < 0.05), however qPCR had increased sensitivity. Upon comparison with diarrhea severity scores (from 0 to 3), a PCR-based count of ≥ 2.6 × 10(5) parasites or an immunofluorescence microscopy count of ≥ 4.5 × 10(4) oocysts were discriminatory predictors of moderate-to-severe diarrhea (versus no-to-mild diarrhea), with accuracies and predictive values of 72-82%. In summary, a quantitative approach for Cryptosporidium can refine predictive power for diarrhea and appears useful for distinguishing clinical cryptosporidiosis versus subclinical infection.

A review of the global burden, novel diagnostics, therapeutics, and vaccine targets for cryptosporidium

Cryptosporidium spp are well recognised as causes of diarrhoeal disease during waterborne epidemics and in immunocompromised hosts. Studies have also drawn attention to an underestimated global burden and suggest major gaps in optimum diagnosis, treatment, and immunisation. Cryptosporidiosis is increasingly identified as an important cause of morbidity and mortality worldwide. Studies in low-resource settings and high-income countries have confirmed the importance of cryptosporidium as a cause of diarrhoea and childhood malnutrition. Diagnostic tests for cryptosporidium infection are suboptimum, necessitating specialised tests that are often insensitive. Antigen-detection and PCR improve sensitivity, and multiplexed antigen detection and molecular assays are underused. Therapy has some effect in healthy hosts and no proven efficacy in patients with AIDS. Use of cryptosporidium genomes has helped to identify promising therapeutic targets, and drugs are in development, but methods to assess the efficacy in vitro and in animals are not well standardised. Partial immunity after exposure suggests the potential for successful vaccines, and several are in development; however, surrogates of protection are not well defined. Improved methods for propagation and genetic manipulation of the organism would be significant advances.

Development of an untargeted metabolomics method for the analysis of human faecal samples using Cryptosporidium-infected samples

Faecal metabolite profiling, though in its infancy, allows for investigation of complex metabolic interactions between gastrointestinal infections or diseases and host health. In the present study, we describe a faecal metabolite extraction method for untargeted gas chromatography-mass spectrometry (GC-MS) analysis using Cryptosporidium positive and negative human faecal samples. The extraction method takes into account the varying faecal consistencies and quantities received for clinical diagnosis. Optimisation was carried out using different extraction solvents and on three different faecal quantities to determine the minimum amount of faecal sample required. The method was validated by untargeted GC-MS analysis on 8 Cryptosporidium positive and 8 Cryptosporidium negative human faecal samples, extracted using the optimised conditions. The method showed good extraction reproducibility with a relative standard deviation of 9.14%. Multivariate analysis of the GC-MS generated dataset showed distinct differences between profiles of Cryptosporidium positive and Cryptosporidium negative samples. The most notable differences included changes in amino acid, nitrogen and energy metabolism, demonstrating the association of infection with Cryptosporidium and altered permeability of the small intestine.

In vitro evaluation of the suppressive effect of chitosan/poly(vinyl alcohol) microspheres on attachment of C. parvum to enterocytic cells

We present a new strategy to suppress the attachment of Cryptosporidium parvum to the enterocytes cell surface by bioadhesive microspheres. An optimized microsphere system based on chitosan/poly(vinyl alcohol) was prepared by experimental design for the delivery of Diloxanide Furoate-cyclodextrin complex. Formulations were characterized in terms of size, surface charge, drug release, IR spectroscopy and morphology. Bioadhesion properties of chitosan/poly(vinyl alcohol) microspheres, evaluated in the human enterocytic HCT-8 model, were concentration and time dependent. In vitro efficacy of chitosan/poly(vinyl alcohol) microspheres against Cryptosporidium was tested in infected cultures and stages of parasite were assessed by immunofluorescence. The degree of adherence to cells and the inhibition of infectivity were directly related with the lowest level of cross-linking. The C. parvum attachment to cells surface was efficiently suppressed by a concentration of 100 μg/ml of microspheres. TEM observations showed no epithelial-cell damage when microspheres were co-incubated in infected cultures. These results were coincident with the lack of toxicity in cytocompatibility studies. Microspheres remained adhered after 72 h to the apical area of enterocytes. The results suggest that chitosan/poly(vinyl alcohol) with adequate size and appropriate surface characteristics suppress by impairment the attachment of sporozoites to enterocytes and may have a great potential in the oral chemotherapy of Cryptosporidium infections.

Cryptosporidiosis-an overview

Apicomplexan protozoan parasites of the genus Cryptosporidium infect the gastrointestinal tract and lungs of a wide variety of animals, including humans. The majority of human infections are due to either Cryptosporidium hominis (C. hominis) and/or Cryptosporidium parvum (C. parvum). The parasite has a complex life cycle that includes both asexual and sexual stages. While there are invasive free living stages, proliferation and differentiation take place within a unique parasitrophorous vacuole under the host cell brush border but outside the host cell cytoplasm. Infection is spread by environmentally resistant spores that primarily contaminate drinking water and occasionally food sources, which may cause significant outbreaks of diarrhea that generally lasts less than 2 w in immunocompetent individuals. In immunodeficient or immunosuppressed individuals, diarrhea may be copious and can result in significant morbidity and mortality, particularly in AIDS patients. Although diagnosis is relatively simple, effective drug treatment, particulary for infections in immunodeficient patients, has not been uniformly successful. This overview summarizes the species known to infect humans, aspects of the parasite life cycle, sources of infection, the pathophysiology of cryptosporidiosis, the immune response to infection, diagnosis, treatment and some aspects of cryptosporidiosis in China.

Will we ever model PSC? - "it's hard to be a PSC model!"

Cholangiopathies such as primary sclerosing cholangitis (PSC) represent an important group of liver diseases of the intra- and extrahepatic bile ducts frequently causing end-stage liver disease with significant morbidity and mortality due to limited treatment options. The relatively low incidence of PSC and the difficult accessibility of the human bile duct system for longitudinal studies may represent some of the critical reasons for the lack of profound knowledge in regard to PSC pathophysiology. Therefore, there is an urgent need for reliable, well-defined and easily reproducible animal models to learn more about the pathophysiology of PSC and to test novel treatment modalities. In an ideal world, immunogenetically predisposed animals would develop fibrous-obliterative cholangitis of the intra- and extrahepatic bile ducts in association with inflammation of the gut (especially colitis) in a highly reproducible manner allowing to test new drugs. To date, however, no such animal model is available. We aimed to provide a systematic overview of current available rodent models for sclerosing cholangitis and biliary fibrosis and therefore critically analyzed the characteristics of models for chemically-induced cholangitis, knock-out mouse models with cholangitis, cholangitis induced by infectious agents, models of experimental biliary obstruction, models involving enteric bacterial cell-wall components or colitis, and models of primary biliary epithelial and endothelial cell injury.

Serum immunoglobulin G, M and A response to Cryptosporidium parvum in Cryptosporidium-HIV co-infected patients

Background

Cryptosporidium parvum, the protozoan parasite, causes a significant enteric disease in immunocompromised hosts such as HIV patients. The present study was aimed to compare serum IgG, IgM and IgA responses to crude soluble antigen of C. parvum in HIV seropositive and seronegative patients co-infected with Cryptosporidium and to correlate the responses with symptomatology.

Methods

Cryptosporidium parvum specific serum antibody (IgG, IgM and IgA) responses were assessed by ELISA in 11 HIV seropositive Cryptosporidium positive (Group I), 20 HIV seropositive Cryptosporidium negative (Group II), 10 HIV seronegative Cryptosporidium positive (Group III), 20 HIV seronegative Cryptosporidium negative healthy individuals (Group IV) and 25 patients with other parasitic diseases (Group V).

Results

A positive IgG and IgA antibody response was observed in significantly higher number of Cryptosporidium infected individuals (Gp I and III) compared to Cryptosporidium un-infected individuals (Gp II, IV and V) irrespective of HIV/immune status. Sensitivity of IgG ELISA in our study was found to be higher as compared to IgM and IgA ELISA. The number of patients with positive IgG, IgM and IgA response was not significantly different in HIV seropositive Cryptosporidium positive patients with diarrhoea when compared to patients without diarrhoea and in patients with CD4 counts <200 when compared to patients with CD4 counts >200 cells/μl.

Conclusion

The study showed specific serum IgG and IgA production in patients infected with Cryptosporidium, both HIV seropositive and seronegative as compared to uninfected subjects suggesting induction of Cryptosporidium specific humoral immune response in infected subjects. However, there was no difference in number of patients with positive response in HIV seropositive or seronegative groups indicating that HIV status may not be playing significant role in modulation of Cryptosporidium specific antibody responses. The number of patients with positive IgG, IgM and IgA response was not significantly different in patients with or without history of diarrhoea thereby indicating that Cryptosporidium specific antibody responses may not be necessarily associated with protection from symptomatology.

Substance P receptor antagonism for treatment of cryptosporidiosis in immunosuppressed mice

Cryptosporidiosis, caused by the protozoan parasite Cryptosporidium parvum, causes self-limited diarrhea in normal hosts but can cause life-threatening diarrhea for immunosuppressed patients. There is an urgent need for new drugs to treat this chronic disease. Cryptosporidium parvum infection is associated with intestinal structural and pathophysiologic changes, including villi blunting and glucose malabsorption. Substance P (SP), a neuropeptide and pain transmitter, is associated with the gastrointestinal tract and is elevated in humans and macaques after experimental C. parvum challenge. To examine the relevance of SP in the pathogenesis of cryptosporidiosis, and to determine if SP receptor antagonism can be employed for treatment of cryptosporidiosis in immunosuppressed hosts, we used an immunosuppressed murine model (dexamethasone-immunosuppressed mice) that is frequently utilized for examining chemotherapeutic potential of drugs. Quantitative ELISA was used to measure intestinal SP levels in immunosuppressed mice with, and without, C. parvum infection. Intestinal physiological alterations, as studied by the Ussing chamber technique, plus weight change, fecal oocyst shedding, and villi measurements, were compared in infected mice with, and without, SP receptor antagonist (aprepitant) treatment. Immunosuppressed mice infected with C. parvum demonstrated increased SP levels as well as physiological alterations (glucose malabsorption), weight loss, fecal oocyst shedding, and structural alterations (increased intestinal villi blunting) compared to uninfected mice. Each of these defects was significantly inhibited by aprepitant treatment. These studies demonstrate the potential of SP receptor antagonism for treatment of pathogenesis of cryptosporidiosis in immunosuppressed hosts.

Lymphoproliferative and cytokine responses to Cryptosporidium parvum in patients coinfected with C. parvum and human immunodeficiency virus

We compared the lymphoproliferative and cytokine responses to Cryptosporidium parvum in human immunodeficiency virus (HIV)-seropositive and -seronegative patients. The lymphoproliferative and cytokine responses (interleukin-2 [IL-2], IL-4, IL-5, IL-10, gamma interferon, and tumor necrosis factor alpha) were assessed for 11 HIV-seropositive, Cryptosporidium-positive (group I) patients; 20 HIV-seropositive, Cryptosporidium-negative (group II) patients; 10 HIV-seronegative, Cryptosporidium-positive (group III) patients, including four post-renal transplant (group IIIa) and 6 presumably immunocompetent (group IIIb) patients; and 20 HIV-seronegative, Cryptosporidium-negative healthy individuals (group IV). No significant difference was observed in the number of patients showing positive lymphoproliferative responses in group I compared to group III (post-renal transplant [group IIIa] or immunocompetent [group IIIb]) patients, while a comparison of the median stimulation indices shows that responses were significantly lower in Cryptosporidium-infected, immunosuppressed (group I and IIIa) patients than in immunocompetent (group IIIb) patients. The number of patients showing positive responses and median stimulation indices was significantly higher for Cryptosporidium-infected (HIV-seropositive and -seronegative) individuals than for uninfected individuals, suggesting that Cryptosporidium induces significant in vitro lymphoproliferative responses in infected individuals. Cytokine levels, except for that of IL-5, were significantly higher in Cryptosporidium-infected (groups I and III) individuals than in uninfected (groups II and IV) individuals. There was no significant difference between the group I and III patients and between Cryptosporidium-infected immunosuppressed (group I or IIIa) and immunocompetent (group IIIb) patients.

Detection of epithelial-cell injury, and quantification of infection, in the HCT-8 organoid model of cryptosporidiosis

BACKGROUND

Intestinal cells grown in microgravity produce a three-dimensional tissue assembly, or "organoid," similar to the human intestinal mucosa, making it an ideal model for enteric infections such as cryptosporidiosis.

METHODS

HCT-8 cells were grown in a reduced-gravity, low-shear, rotating-wall vessel (RWV) and were infected with Cryptosporidium parvum oocysts. Routine and electron microscopy (EM), immunolabeling with fluorescein-labeled Vicia villosa lectin and phycoerythrin-labeled monoclonal antibody to a 15-kD surface-membrane protein, and quantitative polymerase chain reaction (qPCR) using probes for 18s rRNA of C. parvum and HCT-8 cells were performed.

RESULTS

The RWV allowed development of columnar epithelium-like structures. Higher magnification revealed well-developed brush borders at the apical side of the tissue. Incubation with C. parvum resulted in patchy disruption of the epithelium and, at the surface of several epithelial cells, in localized infection with the organism. EM revealed irregular stunting of microvilli, foci of indistinct tight junctions, and areas of loose paracellular spaces. qPCR showed a 1.85-log (i.e., 70-fold) progression of infection from 6 h to 48 h of incubation.

CONCLUSION

The HCT-8 organoid displayed morphologic changes indicative of successful and quantifiable infection with C. parvum. The HCT-8 organoid-culture system may have application in interventional in vitro studies of cryptosporidiosis.

A serological study of Cryptosporidium transmission in a periurban area of a Brazilian Northeastern city

OBJECTIVES

To study the prevalence of Cryptosporidium infection by measuring the levels of anti-Cryptosporidium IgG antibodies among people inhabiting three neighbourhoods of a periurban area of Salvador, Northeast of Brazil; and to investigate the effects of environmental sanitation measures, hygienic habits and household water supply, storage and handling on the frequency of these antibodies in sera of the studied population.

METHODS

Cryptosporidium inter-household transmission was studied by comparing the frequency of anti-Cryptosporidium IgG antibodies among people inhabiting areas with or without different environmental sanitation measures and intra-household transmission by comparing the presence of these antibodies in families with or without cases of diarrhoea, associated with the presence of Cryptosporidium oocysts in their stools. Children or family members with diarrhoeal episodes were evaluated parasitologically for Cryptosporidium infection by testing stool specimens with the Ritchie-modified formol-ether concentration and the acid-fast staining methods. All groups were serologically evaluated for parasite exposure by an indirect enzyme-linked immunosorbent assay.

RESULTS

A statistically significant difference was detected in the prevalence of Cryptosporidium infection between area 1 which had no environmental sanitation measures and area 3 which had improved environmental sanitation measures (P = 0.044). Most of the hygienic habits investigated did not correlate with the presence of anti-Cryptosporidium antibody in sera of the population studied. However, positive associations were found between both poor household water supply (OD = 0.17; 90% CI = 0.09-0.32; P = 0.0001) and drinking unboiled/unfiltered water (OD = 0.40; 90% CI = 0.24-0.67; P = 0.0002) with high levels of anti-Cryptosporidium antibodies in sera.

CONCLUSIONS

These data suggest that although uncorrected household water supply, storage and handling play an important role on Cryptosporidium transmission in periurban areas of developing country cities, like Salvador, Brazil, inadequate environmental conditions may also contribute to the spread of this parasite.

Substance P is responsible for physiological alterations such as increased chloride ion secretion and glucose malabsorption in cryptosporidiosis

Cryptosporidiosis, caused by the protozoan parasite Cryptosporidium, causes self-limited diarrhea in immunocompetent hosts and severe life-threatening diarrhea in AIDS patients. Highly active antiretroviral therapy has been used to effectively treat cryptosporiosis in some but not all AIDS patients. Therefore, there is an urgent need for innovative drugs to treat this disease. Cryptosporidium infection results in intestinal pathophysiological changes such as glucose malabsorption, increased chloride ion (Cl(-)) secretion, and epithelial barrier disruption, leading to disease pathogenesis. In order to develop tools to combat this opportunistic pathogen, it is vital to understand mediators involved in disease pathogenesis. Substance P (SP), a neuropeptide and pain transmitter, is located in the gastrointestinal tract. SP can cause Cl(-) secretion in human gastrointestinal explants. However, its role in cryptosporidiosis has not been fully studied. Jejunal samples from macaques before and after Cryptosporidium parvum infection were assayed for SP and SP receptor mRNA and protein levels by reverse transcription-PCR and by immunohistochemistry and enzyme-linked immunosorbent assay, respectively. The role of SP in pathophysiological alterations, such as Cl(-) secretion and glucose malabsorption, was studied using tissues derived from macaques infected with C. parvum by the Ussing chamber technique. SP and SP receptor mRNA and protein expression levels were increased in jejunal samples following C. parvum infection and were accompanied by increased basal ion secretion and glucose malabsorption. In vitro treatment of samples obtained from infected macaques with the SP receptor antagonist aprepitant (Emend; Merck, Whitehouse Station, NJ) completely reversed the increase in basal ion secretion and corrected the glucose malabsorption. Our findings raise the possibility of using SP receptor antagonists for the treatment of symptoms associated with cryptosporidiosis.

Neutrophils do not mediate the pathophysiological sequelae of Cryptosporidium parvum infection in neonatal piglets

Cryptosporidium parvum is a minimally invasive protozoal pathogen of intestinal epithelium that results in villus atrophy, mucosal lipid peroxidation, diarrhea, and diminished barrier function. Influx of neutrophils is a consistent feature of human and animal cryptosporidiosis, and yet their contribution to the pathological sequelae of infection has not been investigated. Accordingly, we used an established neonatal piglet model of C. parvum infection to examine the role of neutrophils in disease pathogenesis by inhibiting their recruitment and activation in vivo using a monoclonal anti-CD18 antibody. Infected piglets were treated daily with anti-CD18 or isotype control immunoglobulin G and euthanized at peak infection, at which time neutrophil infiltrates, lipid peroxidation, severity of infection, and intestinal barrier function were quantified. C. parvum infection resulted in a significant increase in mucosal neutrophil myeloperoxidase activity that was prevented by treatment of piglets with anti-CD18 antibody. Neutrophil recruitment was dependent on mucosal superoxide formation (prevented by treatment of infected piglets with superoxide dismutase). Neutrophils did not contribute to peroxynitrite formation or peroxidative injury of C. parvum-infected mucosa and had no impact on the severity of epithelial infection, villus atrophy, or diarrhea. The presence of neutrophils in C. parvum-infected mucosa was associated with enhanced barrier function that could not be attributed to mucosal elaboration of prostaglandins or stimulation of their synthesis. These studies are the first to demonstrate that neutrophilic inflammation arising in response to infection by a noninvasive epithelial pathogen results in physiologic rather than pathological effects in vivo.

High levels of CXCL10 are produced by intestinal epithelial cells in AIDS patients with active cryptosporidiosis but not after reconstitution of immunity

Chemokines play key roles in attracting immune cells to sites of infections. However, few data on chemokine expression in the gut during human infections are available. We examined expression of chemokines in intestinal tissues of AIDS patients during active Cryptosporidium infection and during resolution of such an infection. The chemokines and cytokines in cell lysates from jejunal biopsy tissues were assayed by a 22-multiplex bead immunoassay. CXCL10 (IP-10) and its receptor, CXCR3, in sections were studied by immunohistochemistry. In biopsies from AIDS patients with active cryptosporidiosis, four chemokines (CXCL10, CCL11 [eotaxin], CCL5 [RANTES], and CCL2 [monocyte chemoattractant protein 1]) and three cytokines (interleukin-1alpha [IL-1alpha], IL-10, and granulocyte colony-stimulating factor) were detected. The level of CXCL10 was significantly increased in AIDS patients with cryptosporidiosis compared to the level in AIDS patients without cryptosporidiosis or in normal volunteers (median in AIDS patients with cryptosporidiosis, 508 pg/mg protein, compared to 111 pg/mg and 72 pg/mg protein in AIDS patients without cryptosporidiosis and in normal volunteers, respectively [P < 0.05 and P < 0.005, respectively, as determined by a Mann-Whitney test]). The level of CXCL10 correlated with the parasite burden (as measured by the number of Cryptosporidium oocysts in the stools) and also with the IL-1alpha concentration (Pearson correlation values, 0.961 [P < 0.01] and 0.737 [P < 0.05]). As determined by immunohistochemistry, CXCL10 localized to epithelial cells at the site of infection. Following effective antiparasite and antiretroviral therapy, Cryptosporidium infections resolved, and the levels of CXCL10 decreased to normal levels. We hypothesized that CXCL10 plays an important role in the resolution of cryptosporidiosis by attracting immune effector cells to the site of infection. By contrast, in AIDS patients lacking effector cells, CXCL10 may contribute to the immunopathogenesis by recruiting inflammatory cells.

An updated review on Cryptosporidium and Giardia

Cryptosporidium and Giardia are two of the most commonly occurring enteric protozoans. They are responsible for diarrheal diseases that may lead to nutritional deficiencies and significant morbidity and mortality, especially among children in developing countries and patients who have immune defects. Both are difficult to diagnose with microscopic techniques. This article provides an updated review of the epidemiology, pathogenesis, clinical manifestations, and treatment of Cryptosporidium and Giardia.

Management of gastrointestinal disorders in children with HIV infection

A double scenario characterizes the epidemiology of HIV infection in children. In countries where highly active antiretroviral therapy (HAART) is available, the pattern of HIV infection is evolving into that of a chronic disease, for which control strictly depends on patients' adherence to treatment. In developing countries with no or limited access to HAART, AIDS is rapidly expanding and is loaded with a high fatality ratio, due to the combined effects of malnutrition and opportunistic infections. The digestive tract is a target of the disease in both settings. Opportunistic infections play a major role in children with severe immune impairment, with Cryptosporidium parvum being the leading agent of severe diarrhea. Several therapeutic approaches are effective in reducing fecal output, but the eradication of the parasite is rarely obtained. Other opportunistic infections may induce severe and protracted diarrhea, including atypical mycobacteria and cytomegalovirus. Diagnosis of diarrhea should be individually tailored based on presenting symptoms and risk factors. A stepwise approach is effective in limiting patient discomfort and minimizing the costs of investigations, starting with microbiologic investigation and proceeding with endoscopy and histology. Aggressive treatment of infectious diarrhea is required in severely immunocompromised children. However, antiretroviral therapy prevents the development of severe cryptosporidiosis. The liver and pancreas are also target organs in HIV infection, although functional failure is rare. The digestive-absorptive functions are impaired, with steatorrhea, nutrient malabsorption, and increased permeability occurring in 20-70% of children. Intestinal dysfunction contributes to growth failure and further immune derangement, leading to wasting, the terminal stage of AIDS. Nutritional management is crucial in HIV-infected children and is based on aggressive nutritional rehabilitation through enteral or parenteral routes and micronutrient supplementation.HIV may play a direct enteropathogenic role and is implicated in both diarrhea and intestinal dysfunction. This explains the efficacy of antiretroviral therapy in inducing remission of diarrhea and restoring intestinal function. Gastrointestinal side effects of antiretroviral drugs are increasingly observed; they are often mild and transient. Severe reactions are rare but require the withdrawal of drugs. In conclusion, severe enteric infections and intestinal dysfunction characterize the intestinal involvement of HIV infection. This is more common in, but not limited to, children who do not receive effective antiretroviral therapy. Diagnostic approaches include microbiologic and morphologic examinations and assessment of digestive processes, but immunologic and virologic data should be also carefully considered. Treatment is based upon specific anti-infectious drugs, antiretroviral therapy, and nutritional rehabilitation.

Nitric oxide synthase stimulates prostaglandin synthesis and barrier function in C. parvum-infected porcine ileum

Cell culture models implicate increased nitric oxide (NO) synthesis as a cause of mucosal hyperpermeability in intestinal epithelial infection. NO may also mediate a multitude of subepithelial events, including activation of cyclooxygenases. We examined whether NO promotes barrier function via prostaglandin synthesis using Cryptosporidium parvum-infected ileal epithelium in residence with an intact submucosa. Expression of NO synthase (NOS) isoforms was examined by real-time RT-PCR of ileal mucosa from control and C. parvum-infected piglets. The isoforms mediating and mechanism of NO action on barrier function were assessed by measuring transepithelial resistance (TER) and eicosanoid synthesis by ileal mucosa mounted in Ussing chambers in the presence of selective and nonselective NOS inhibitors and after rescue with exogenous prostaglandins. C. parvum infection results in induction of mucosal inducible NOS (iNOS), increased synthesis of NO and PGE2, and increased mucosal permeability. Nonselective inhibition of NOS (NG-nitro-L-arginine methyl ester) inhibited prostaglandin synthesis, resulting in further increases in paracellular permeability. Baseline permeability was restored in the absence of NO by exogenous PGE2. Selective inhibition of iNOS [L-N6-(1-iminoethyl)-L-lysine] accounted for approximately 50% of NOS-dependent PGE2 synthesis and TER. Using an entire intestinal mucosa, we have demonstrated for the first time that NO serves as a proximal mediator of PGE2 synthesis and barrier function in C. parvum infection. Expression of iNOS by infected mucosa was without detriment to overall barrier function and may serve to promote clearance of infected enterocytes.

Emerging Causes of Traveler's Diarrhea: Cryptosporidium, Cyclospora, Isospora, and Microsporidia

Travel is a risk factor for acquiring infection with a spore-forming protozoa: Cryptosopridium, Cyclospora, Microsporidia, and Isospora. Certain travel destinations have a high disease burden and intense exposure. Patients present with persistent diarrhea and a history of recent travel to a developing country in the tropics. Very mild infections may be underdiagnosed and may cause typical traveler's diarrhea. In a patient with a history of travel and persistent diarrhea unresponsive to the usual antibiotic and antidiarrhea treatment, stool studies for all four of these protozoa infections should be performed. If immune status is normal and the disease is mild, symptomatic therapy may suffice. Effective treatment is available for Cyclospora, Microsporidia, and Isospora.

Apoptosis of intestinal crypt epithelium after Cryptosporidium parvum infection

Using a neonatal mouse model of Cryptosporidium parvum infection, we investigated whether apoptosis of epithelial cells was induced in the small intestine. At the time when the number of C. parvum oocysts in the ileum was maximal, columnar goblet cells and absorptive cells showed a decrease in the ileal epithelium that was accompanied by a significant reduction in the height of the villi. A few apoptotic epithelial cells were also observed in the vicinity of the basal crypts where C. parvum was proliferating. Morphological changes of the villous structure and apoptotic epithelial cells associated with proliferation of the parasite were scarcely detected in the duodenum, cecum, and colon of the infected mice. These findings suggest that the loss of absorptive cells and goblet cells, and the apoptosis of intestinal epithelial cells, are common events in the ileum after C. parvum infection, and that epithelial apoptosis may have a significant role in the pathogenesis of cryptosporidiosis.

Absence of weight loss during Cryptosporidium infection in susceptible mice deficient in Fas-mediated apoptosis

Apoptosis plays a major role in the development of pathogenesis due to a number of microbial infections. Epithelial cells have been previously shown to die through apoptosis during in vitro infection by the Apicomplexan parasite Cryptosporidium parvum. We now test the possibility that Fas (APO-1/CD95)-dependent apoptosis of uninfected cells, due to enhanced expression of the Fas ligand (FasL) on infected cells, may contribute to the pathology of cryptosporidiosis. Expression of the FasL increased by a large amount on the surface of intestinal epithelial cells infected with C. parvum, and the increase was limited exclusively to infected cells. In addition, a significant increase in FasL expression was observed in epithelial cells from the small intestine of mice infected with C. parvum. Finally, whereas wild-type mice depleted of CD4(+) lymphocytes lost weight during C. parvum infection, CD4(+) cell-depleted lpr mice (deficient in Fas function) infected with C. parvum gained weight at the same rate as undepleted wild-type or lpr mice. These results suggest that bystander Fas-dependent apoptosis of uninfected epithelial cells may exacerbate the weight loss associated with cryptosporidiosis.

Cryptosporidiosis: epidemiology and impact

Cryptosporidium was first recognized in humans in 1976 and came to prominence in the 1980s and 1990s as a cause of severe diarrheal illness in patients with AIDS. Its hardy, chlorine-resistant oocysts, tiny size, low infectious dose, fully infectious development when shed and zoonotic potential make it a threat in drinking and recreational water, contaminated food, day care centers, hospitals, and in persons with exposure to animals or unsanitary conditions, with potentially huge, long-term impact in malnourished children, as reviewed herein.

Enteric pathogens, intestinal permeability and nitric oxide production in acute gastroenteritis

BACKGROUND

Aboriginal children hospitalized with diarrheal disease in northern Australia have high rates of acidosis, hypokalemia and osmotic diarrhea, as well as abnormal small bowel permeability and elevated nitric oxide (NO) production.

METHODS

In a study of 291 diarrheal admissions and 84 controls, we examined the relationship of diarrheal severity outcomes with specific enteric pathogens. NO production was measured by urine nitrate plus nitrite excretion on a low nitrate diet, small bowel permeability by the lactulose:rhamnose ratio on a timed blood specimen and stool pathogens by standard microbiologic investigations and PCR.

RESULTS

The addition of diagnostic tests for diarrheagenic Escherichia coli to standard stool microbiologic testing increased the rate of specific diagnoses from 53% to 75%, but with multiple pathogens isolated from 34%. The most frequently isolated pathogens from diarrheal patients were enteroaggregative E. coli (28.9%), rotavirus (26.5%), enteropathogenic E. coli (17.2%), Salmonella spp. (10.7%), Cryptosporidium parvum (7.2%) and Strongyloides stercoralis (7.2%). High geometric mean permeability ratios (95% confidence intervals) occurred with rotavirus (19.6; 15.3 to 25.1), enteroaggregative E. coli (21.2; 15.3 to 29.3) and Cryptosporidium (23.0; 15.1 to 35.1) compared with 9.4 (6.8 to 13.1) for no pathogens. NO production was highest for Cryptosporidium (3.7; 2.3 to 6.1) compared with 0.6 (0.4 to 1.1) for no pathogens. Multiple regression analysis revealed significant associations (P < 0.001) for rotavirus with acidosis and osmotic diarrhea, for Strongyloides with wasting and hypokalemia and for Cryptospoidium with severe and prolonged diarrhea.

CONCLUSIONS

Cryptosporidium, Strongyloides, rotavirus and enteroaggregative E. coli are important contributors to the severe manifestations of acute gastroenteritis in Australian Aboriginal children.

Magnitude and impact of diarrheal diseases

Among the increasingly unacceptable costs of the diseases of poverty are the largely unmeasured but potentially huge human and economic long-term costs of common tropical infectious diseases, especially those such as repeated dehydrating and malnourishing diarrheal diseases (and enteric infections, even without overt liquid stools) that are so prevalent in the developmentally critical first year or two of early childhood. We review here the high costs of diseases of poverty, increasing diarrhea morbidity (despite decreasing mortality), and new emerging evidence for long-term consequences of early childhood diarrhea on growth and on physical and cognitive development, effects that may translate into costly impairment of human potential and productivity.

Cryptosporidium virulence determinants--are we there yet?

Exposure to Cryptosporidium parvum in healthy individuals results in transient infection that may be asymptomatic or can result in self-limited diarrhoea. In contrast, acquired immune deficiency syndrome patients with cryptosporidiosis can experience severe manifestations of disease. Volunteer studies have demonstrated that as few as 10 oocysts can cause infection in otherwise healthy adults and that isolates from geographically diverse regions differ in infectivity and, perhaps, virulence. Variability in isolate pathogenicity and infectivity has also been seen in bovine and murine models, respectively. Furthermore, isolate specific differences in protein composition and in host immunoreactivity have been observed. The molecular basis for differences in pathogenicity is not understood. Determining which factors are responsible for host selectivity and for the initiation, establishment, and perpetuation of infection with Cryptosporidium is key to rational drug design and vaccine development. To date, no specific virulence factors have been unequivocally shown to individually cause direct or indirect damage to host tissues nor have mutant strains been produced that could prove that particular deletions result in less virulent strains. Nevertheless, a number of candidate molecules have been identified by immunological and molecular methods. Here, we review the salient characteristics of some of these putative virulence determinants, including molecules that are involved in adhesion, protein degradation and the modulation of the host responses.

Vitamin B12 and folic acid in children with intestinal parasitic infection

OBJECTIVE

To determine prospectively plasma levels of vitamin B12 and folic acid in children with intestinal parasitic infection before and three months after antiparasitic treatment.

METHODS

3036 stool samples were collected from 1959 children and 939 cello-tape anal swabs were taken from 688 children for intestinal parasite investigation. Of these, 155 children were identified as having a parasitic infection; however, only 86 were followed up during this study: 26 children with Giardia lamblia infection were treated with tinidazole and metronidazole, pyrantel pamoate was used in the treatment of 40 children with Enterobius vermicularis, and 20 patients infected with Cryptosporidium parvum received only symptomatic treatment. Vitamin B12 and folic acid levels were measured by radioimmunoassay, before and three months after the completion of treatment.

RESULTS

Vitamin B12 serum concentrations did not show any significant differences among the three groups. There was a significant increase in vitamin B12 serum concentrations after three months of anti-parasitic treatment (630.57+/-200.97 vs. 667.97+/-181.55 pg/dL, p = 0.002, n = 86). Paired analysis in each group showed only significant increases for vitamin B12 in the Giardia lamblia group and in the Enterobius vermicularis group. No statistically significant differences were found for folic acid serum concentrations before and three months after treatment.

CONCLUSIONS

Patients with symptomatic infection by Giardia lamblia and Enterobius vermicularis have lower vitamin B12 levels than asymptomatic patients. This could reflect a more affected intestinal mucous. These results could present the opportunity to treat these parasitic infections and to use vitamin B12 supplementation in symptomatic children with Giardia lamblia and Enterobius vermicularis infection.

Intact intestinal mRNAs and intestinal epithelial cell esterase, but not Cryptosporidium parvum, reach mesenteric lymph nodes of infected mice

Dendritic cells from the mesenteric lymph nodes (MLN) contain dense esterase-positive inclusions that may originate in effete intestinal epithelial cells and reach MLN without degradation. The MLN esterases have the electrophoretic mobilities of both intestinal and mononuclear cells. Cryptosporidium parvum (CP)-infected mice have CP Ag-positive cells in MLN and also increased numbers of dense esterase-positive cells, but the CP Ag-positive cells do not stain for esterase. To characterize the handling of epithelial cell products by dendritic cells, we analyzed mRNAs in the MLN of control and CP-infected recombination-activating gene(-/-)DO11.10 mice by oligoarrays. mRNAs for 115 proteins were increased in MLN after CP infection, of which the principal increases in trypsin and chymotrypsin approximated to 250-fold. Colipase, reg-1, C-reactive protein-ductin, and amyloid were also up-regulated >10-fold and all returned to baseline by 28 days after infection. mRNAs for the same proteins were detected in intestinal epithelial cells of infected mice by oligoarrays and RT-PCR after infection. mRNA for CP beta-tubulin was detectable in intestinal epithelial cells between 5 and 18 days after infection but was not detected in the MLN throughout the observation period. It appears that host response to CP infection includes expression of mRNA for some pancreatic enzymes by intestinal epithelial cells and their subsequent transport to the MLN. The esterase and trypsin, and mRNAs for chymotrypsin, colipase, and others that may derive from uninfected epithelial cells, appear to be transported to the MLN intact, while mRNA for CP beta-tubulin that is derived from infected cells is degraded.

[Intestinal absorption of D-xylose in children infected with the human immunodeficiency virus]

AIM

To evaluate the intestinal absorption in HIV-infected children children 14 months to 14 years and to investigate its relationship to diarrhea, nutritional status, immune dysfunction, classical enteric parasites and Cryptosporidium.

METHODS

Intestinal absorption was investigated by measuring serum D-xylose. Fecal samples were investigated for classical pathogens and Cryptosporidium. The sample size was calculated considering a 30% prevalence of altered D-xylose absorption in HIV-infected children with a 5% accuracy. Statistical procedures used were: descriptive measurements, multiple correspondence analysis and logistic regression.

RESULTS

D-xylose absorption was altered in only 8 out of 104 (7.7%) and Cryptosporidium was positive in 33 out of 104 (31.73%) HIV-infected children. The multiple correspondence analysis suggested an association between an altered D-xylose test and Cryptosporidium. D-xylose malabsorption was not associated with diarrhea, nutritional status, immune disfunction and classic enteric parasites.

CONCLUSIONS

Intestinal malabsorption evaluated through the D-xylose test was an uncommon finding in HIV-infected children. Intestinal dysfunction when present seems to be related to Cryptosporidium, but not to diarrhea, nutritional status, immune disfunction and classic enteric parasites.

Cytotoxic T cells in AIDS colonic cryptosporidiosis

BACKGROUND/AIMS

It is not known how enteric cryptosporidiosis induces severe intestinal impairment despite minimal invasion by the parasite. The aim of this study was to analyse the histological features and locally implicated immune cells in colonic biopsies of AIDS related cryptosporidiosis.

PATIENTS/METHODS

Colonic biopsies from patients with AIDS related cryptosporidiosis (n = 10, group I), patients with AIDS but without intestinal infection (n = 9, group II), and human seronegative controls (n = 9, group III) were studied. Using immunohistochemistry the infiltrating mononuclear cells were analysed in both the epithelium and lamina propria for the expression of CD3, CD8, TiA1, granzyme B, and CD68 and for glandular expression of human major histocompatibility complex DR antigen (HLA-DR).

RESULTS

Severe histological changes, resulting in abundant crypt epithelial apoptosis and inflammatory infiltrate in the lamina propria, were seen in all biopsies from group I. A significant increase of CD8+, TiA1+, and granzyme B+ T cells in the lamina propria and HLA-DR glandular expression was noted in group I compared with groups II and III. However, the number of intraepithelial lymphocytes, lamina propria CD3+ T cells, and macrophages was not significantly increased in cryptosporidiosis specimens compared with controls.

CONCLUSION

Epithelial apoptosis mediated by granzyme B+ cytotoxic host T cells might play a major role in the development of colonic lesions in AIDS related cryptosporidiosis.

Expression of tumor necrosis factor alpha and interleukin 1 beta in jejuna of volunteers after experimental challenge with Cryptosporidium parvum correlates with exposure but not with symptoms

Jejunal biopsies from volunteers challenged with Cryptosporidium parvum were examined for tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-1 beta mRNA. Postchallenge biopsies from 15 of 28 (54%) volunteers expressed TNF-alpha; 14% expressed IL-1 beta. Cytokine expression did not correlate with enteric symptoms, suggesting that TNF-alpha and IL-1 beta are not key mediators of diarrhea in human cryptosporidiosis.

Host cell-mediated responses to infection with Cryptosporidium

The coccidian Cryptosporidium infects epithelial cells of a variety of vertebrate hosts and is the causative agent of cryptosporidiosis. In mammals, including humans and domestic animals, C. parvum infects the gastrointestinal tract producing an acute watery diarrhoea and weight loss. CD4+ T-cell-deficient hosts have increased susceptibility to infection with the parasite and may develop severe life-threatening complications. The host responses which induce protective immunity and contribute to pathogenesis are poorly understood. In the immunological control of infection, recent studies with murine infection models suggest that IFN-gamma plays a key role in a partially protective innate immunity against infection identified in immunocompromised mice and also in the elimination of infection mediated by CD4+ T-cells. At the mucosal level, CD4+ intraepithelial lymphocytes are involved in the control of cryptosporidial infection, acting at least in part through production of IFN-gamma which has a direct inhibitory effect on parasite development in enterocytes. Primary infection of ruminants induces an intestinal inflammatory response in which increased numbers of various T-cell subpopulations appear in the villi. In addition, infection results in increased intestinal expression of pro-inflammatory cytokines such as IL-12, IFN-gamma and TNF-alpha. Because these cytokines appear to be important in the aetiology of inflammatory bowel disease, it is possible that they are involved in the mucosal pathogenesis of cryptosporidiosis.