Declining CD4+ T-lymphocyte counts are associated with increased risk of enteric parasitosis and chronic diarrhea: results of a 3-year longitudinal study

Mode of action studies confirm on-target engagement of lysyl-tRNA synthetase inhibitor and lead to new selection marker for Cryptosporidium

Introduction

Cryptosporidiosis is a leading cause of diarrheal-associated morbidity and mortality, predominantly affecting children under 5 years old in low-and-middle-income countries. There is no effective treatment and no vaccine. New therapeutics are emerging from drug discovery efforts. It is critical that mode of action studies are performed alongside drug discovery to ensure the best clinical outcomes. Unfortunately, technology to identify and validate drug targets for Cryptosporidium is severely lacking.

Methods

We used C. parvum lysyl-tRNA synthetase (CpKRS) and DDD01510706 as a target-compound pair to develop both chemical and genetic tools for mode of action studies for Cryptosporidium. We adapted thermal proteome profiling (TPP) for Cryptosporidium, an unbiased approach for target identification.

Results

Using TPP we identified the molecular target of DDD01510706 and confirm that it is CpKRS. Genetic tools confirm that CpKRS is expressed throughout the life cycle and that this target is essential for parasite survival. Parasites genetically modified to over-express CpKRS or parasites with a mutation at the compound-binding site are resistant to treatment with DDD01510706. We leveraged these mutations to generate a second drug selection marker for genetic modification of Cryptosporidium, KRSR. This second selection marker is interchangeable with the original selection marker, NeoR, and expands the range of reverse genetic approaches available to study parasite biology. Due to the sexual nature of the Cryptosporidium life cycle, parental strains containing different drug selection markers can be crossed in vivo.

Discussion

Selection with both drug markers produces highly efficient genetic crosses (>99% hybrid progeny), paving the way for forward genetics approaches in Cryptosporidium.

Structure-Activity Relationship Studies of the Aryl Acetamide Triazolopyridazines against Cryptosporidium Reveals Remarkable Role of Fluorine

Our previous work identified compound 1 (SLU-2633) as a potent lead compound toward the identification of a novel treatment for cryptosporidiosis, caused by the parasite Cryptosporidium (EC50 = 0.17 μM). While this compound is potent and orally efficacious, the mechanism of action and biological target(s) of this series are currently unknown. In this study, we synthesized 70 compounds to develop phenotypic structure-activity relationships around the aryl "tail" group. In this process, we found that 2-substituted compounds are inactive, confirmed that electron withdrawing groups are preferred over electron donating groups, and that fluorine plays a remarkable role in the potency of these compounds. The most potent compound resulting from this work is SLU-10482 (52, EC50 = 0.07 μΜ), which was found to be orally efficacious with an ED90 < 5 mg/kg BID in a Cryptosporidium-infection mouse model, superior to SLU-2633.

Structure-Activity relationships of replacements for the triazolopyridazine of Anti-Cryptosporidium lead SLU-2633

Cryptosporidiosis is a diarrheal disease particularly harmful to children and immunocompromised people. Infection is caused by the parasite Cryptosporidium and leads to dehydration, malnutrition, and death in severe cases. Nitazoxanide is the only FDA approved drug but is only modestly effective in children and ineffective in immunocompromised patients. To address this unmet medical need, we previously identified triazolopyridazine SLU-2633 as potent against Cryptosporidium parvum, with an EC50 of 0.17 µM. In the present study, we develop structure-activity relationships (SAR) for the replacement of the triazolopyridazine head group by exploring different heteroaryl groups with the aim of maintaining potency while reducing affinity for the hERG channel. 64 new analogs of SLU-2633 were synthesized and assayed for potency versus C. parvum. The most potent compound, 7,8-dihydro-[1,2,4]triazolo[4,3-b]pyridazine 17a, was found to have a Cp EC50 of 1.2 µM, 7-fold less potent than SLU-2633 but has an improved lipophilic efficiency (LipE) score. 17a was found to decrease inhibition in an hERG patch-clamp assay by about two-fold relative to SLU-2633 at 10 µM despite having similar inhibition in a [3H]-dofetilide competitive binding assay. While most other heterocycles were significantly less potent than the lead, some analogs such as azabenzothiazole 31b, have promising potency in the low micromolar range, similar to the drug nitazoxanide, and represent potential new leads for optimization. Overall, this work highlights the important role of the terminal heterocyclic head group and represents a significant extension of the understanding of the SAR for this class of anti-Cryptosporidium compounds.

The influence of hospitalization and HIV severity on gastrointestinal PCR panel evaluation of HIV-related acute diarrhea in New York City: a retrospective, cross-sectional study

INTRODUCTION

Diarrhea is common in persons living with HIV (PLWH)/AIDS. With the increasing utilization of multiplex gastrointestinal PCR panel (GI panel) testing, we aimed to characterize the roles of CD4 count and hospitalization in GI panel assessments of PLWH with acute diarrhea.

METHODS

We performed a cross-sectional study of adult PLWH with acute diarrhea who underwent GI panel testing at two urban academic centers. Demographic, HIV disease, GI panel result, and hospitalization data were collected, and patients were cohorted by CD4 count (CD4 < 200, CD4 200-499, CD4 > = 500). The primary outcome was enteric infection as detected by GI panel, and hospitalization.

RESULTS

Of 298 PLWH, 119 (39.9%) had a CD4 count below 200, 195 (65.4%) were hospitalized, and 137 (46.0%) had enteric infection. Bacterial infection correlated with higher CD4 count (41.9% (CD4 > = 500) vs 31.2% (CD4 200-499) vs 25.2% (CD4 < 200), p = 0.041). Hospitalization correlated with poorly controlled HIV and fewer enteric infections (34.4% vs 68.0%, p < 0.001). After adjusting for HIV disease severity, a negative GI panel remained independently associated with hospitalization (adjusted odds ratio (aOR) 5.32, 95% confidence interval (CI) 2.72-10.9), even in patients tested within 72 hours of hospitalization. Despite better HIV control, men who have sex with men (MSM) had more frequent infectious diarrhea, including from E. coli, giardiasis, and multiple pathogens. MSM status independently predicted enteric infection (aOR 1.93, 95% CI: 1.02-3.67).

CONCLUSIONS

GI panel results vary by HIV disease severity and hospitalization in PLWH. Clinicians - especially in the inpatient setting - should carefully consider these factors when interpreting GI panel results. Further characterization of diarrheal etiology in PLWH with a negative GI panel is needed.

PLAIN LANGUAGE SUMMARY

PCR stool test results are affected by certain factors in HIV-related diarrhea Diarrhea is common in people living with HIV (PLWH) and has a variety of causes, including infections, medications, and HIV itself. Multiplex polymerase chain reaction (PCR) stool testing simultaneously evaluates for a variety of common viral, bacterial, and parasitic infections of the gastrointestinal tract, and is increasingly being used in patients with diarrhea. However, patients with HIV and diarrheal illness may have uncommon infections not typically present in those with normal immune function - and thus not routinely evaluated for in stool testing. It is not known what factors, if any, might affect the results of PCR testing in HIV-related diarrhea.In this study, we examined all PLWH who underwent stool PCR testing for diarrhea over a 4-year period. We separated the patients into groups based on HIV disease severity as measured by CD4 T-cell count, or the count of the immune cells affected by HIV. We examined whether there were differences among groups in infection rates as detected by PCR stool testing. Separately, we studied the role of hospitalization in stool PCR test results.Of 298 PLWH who underwent stool PCR testing for diarrhea, 119 had a CD4 count less than 200 (low CD4 count), 195 were hospitalized at time of testing, and 137 had a positive stool PCR test. Compared to those with a low CD4 count, subjects with less severe HIV disease were more likely to have a bacterial infection on stool PCR testing and less likely to be hospitalized. Hospitalized patients were more likely to have a negative PCR stool test, regardless of CD4 count. Many patients with a low CD4 count had diarrheal etiologies not evaluated by multiplex stool PCR. In PLWH who experience diarrhea, stool PCR testing results vary by CD4 count and hospitalization. Providers should be mindful of these factors when interpreting stool PCR test results.

Enterocyte-innate lymphoid cell crosstalk drives early IFN-γ-mediated control of Cryptosporidium

The intestinal parasite, Cryptosporidium, is a major contributor to global child mortality and causes opportunistic infection in immune deficient individuals. Innate resistance to Cryptosporidium, which specifically invades enterocytes, is dependent on the production of IFN-γ, yet whether enterocytes contribute to parasite control is poorly understood. In this study, utilizing a mouse-adapted strain of C. parvum, we show that epithelial-derived IL-18 synergized with IL-12 to stimulate innate lymphoid cell (ILC) production of IFN-γ required for early parasite control. The loss of IFN-γ-mediated STAT1 signaling in enterocytes, but not dendritic cells or macrophages, antagonized early parasite control. Transcriptional profiling of enterocytes from infected mice identified an IFN-γ signature and enrichment of the anti-microbial effectors IDO, GBP, and IRG. Deletion experiments identified a role for Irgm1/m3 in parasite control. Thus, enterocytes promote ILC production of IFN-γ that acts on enterocytes to restrict the growth of Cryptosporidium.

E-waste polycyclic aromatic hydrocarbon (PAH) exposure leads to child gut-mucosal inflammation and adaptive immune response

Polycyclic aromatic hydrocarbon (PAH) exposure alters immunological responses. Research concerning PAH exposure on intestinal immunity of children in electronic waste (e-waste) areas is scarce. The aim of this study was to evaluate the effects of polycyclic aromatic hydrocarbon (PAH) pollutants on intestinal mucosal immunity of children in e-waste areas. Results showed higher hydroxylated PAH (OH-PAH) concentrations in e-waste-exposed children, accompanied with higher sialyl Lewis A (SLA) level, absolute lymphocyte and monocyte counts, decreased of percentage of CD4⁺ T cells, and had a higher risk of diarrhea. OH-PAH concentrations were negative with child growth. 1-OHNap mediated through WBCs, along with 1-OHPyr, was correlated with an increase SLA concentration. 2-OHFlu, 1-OHPhe, 2-OHPhe, 1-OHPyr, and 6-OHChr were positively correlated with secretory immunoglobulin A (sIgA) concentration. Our results indicated that PAH pollutants caused inflammation, affected the intestinal epithelium, and led to transformation of microfold cell (M cell). M cells initiating mucosal immune responses and the subsequent increasing sIgA production might be an adaptive immune respond of children in the e-waste areas. To our knowledge, this is the first study of PAH exposure on children intestinal immunity in e-waste area, showing that PAH exposure plays a negative role in child growth and impairs the intestinal immune function.

Optimization of the Urea Linker of Triazolopyridazine MMV665917 Results in a New Anticryptosporidial Lead with Improved Potency and Predicted hERG Safety Margin

Cryptosporidiosis is caused by infection of the small intestine by Cryptosporidium parasites, resulting in severe diarrhea, dehydration, malabsorption, and potentially death. The only FDA-approved therapeutic is only partially effective in young children and ineffective for immunocompromised patients. Triazolopyridazine MMV665917 is a previously reported anti-Cryptosporidium screening hit with in vivo efficacy but suffers from modest inhibition of the hERG ion channel, which could portend cardiotoxicity. Herein, we describe our initial development of structure-activity relationships of this novel lead series with a particular focus on optimization of the piperazine-urea linker. We have discovered that piperazine-acetamide is a superior linker resulting in identification of SLU-2633, which has an EC₅₀ of 0.17 μM, an improved projected margin versus hERG, prolonged pharmacokinetic exposure in small intestine, and oral efficacy in vivo with minimal systemic exposure. SLU-2633 represents a significant advancement toward the identification of a new effective and safe treatment for cryptosporidiosis.

Boromycin Has Potent Anti-Toxoplasma and Anti-Cryptosporidium Activity

Toxoplasma gondii and Cryptosporidium parvum, members of the phylum Apicomplexa, are significant pathogens of both humans and animals worldwide for which new and effective therapeutics are needed. Here, we describe the activity of the antibiotic boromycin against Toxoplasma and Cryptosporidium Boromycin potently inhibited intracellular proliferation of both T. gondii and C. parvum at half-maximal effective concentrations (EC₅₀) of 2.27 nM and 4.99 nM, respectively. Treatment of extracellular T. gondii tachyzoites with 25 nM boromycin for 30 min suppressed 84% of parasite growth, but T. gondii tachyzoite invasion into host cells was not affected by boromycin. Immunofluorescence of boromycin-treated T. gondii showed loss of morphologically intact parasites with randomly distributed surface antigens inside the parasitophorous vacuoles. Boromycin exhibited a high selectivity for the parasites over their host cells. These results suggest that boromycin is a promising new drug candidate for treating toxoplasmosis and cryptosporidiosis.

Advancement in our understanding of immune response against Encephalitozoon infection

Microsporidia are a group of obligate, intracellular, spore-forming eukaryotic pathogens, which predominantly infects immunocompromised individuals worldwide. Encephalitozoon spp. is one of the most prevalent microsporidia known to infect humans. Host immune system plays a major role in combating pathogens including Encephalitozoon spp. infecting humans. Both innate and adaptive arms of host immune system work together in combating Encephalitozoon infection. Researchers are conducting studies to elucidate the role of both arms of immune system against Encephalitozoon infection. In addition to cell-mediated adaptive immunity, role of innate immunity is also being highlighted in clearance of Encephalitozoon spp. from host body. Therefore, the current review will give a clear and consolidated update on the role of innate as well as adaptive immunity in protection against Encephalitozoon spp.

High Frequency of Enterocytozoon bieneusi Genotype WL12 Occurrence among Immunocompromised Patients with Intestinal Microsporidiosis

Microsporidiosis is an emerging opportunistic infection causing severe digestive disorders in immunocompromised patients. The aim of this study was to investigate the prevalence of intestinal microsporidia carriage among immunocompromised patients hospitalized at a major hospital complex in the Tunis capital area, Tunisia (North Africa), and perform molecular epidemiology and population structure analyses of Enterocytozoon bieneusi, which is an emerging fungal pathogen. We screened 250 stool samples for the presence of intestinal microsporidia from 171 patients, including 81 organ transplant recipients, 73 Human Immunodeficiency Virus (HIV)-positive patients, and 17 patients with unspecified immunodeficiency. Using a nested PCR-based diagnostic approach for the detection of E. bieneusi and Encephalitozoon spp., we identified 18 microsporidia-positive patients out of 171 (10.5%), among which 17 were infected with E. bieneusi. Microsporidia-positive cases displayed chronic diarrhea (17 out of 18), which was associated more with HIV rather than with immunosuppression other than HIV (12 out of 73 versus 6 out of 98, respectively, p = 0.02) and correlated with extended hospital stays compared to microsporidia-negative cases (60 versus 19 days on average, respectively; p = 0.001). Strikingly, internal transcribed spacer (ITS)-based genotyping of E. bieneusi strains revealed high-frequency occurrence of ITS sequences that were identical (n = 10) or similar (with one single polymorphic site, n = 3) to rare genotype WL12. Minimum-spanning tree analyses segregated the 17 E. bieneusi infection cases into four distinct genotypic clusters and confirmed the high prevalence of genotype WL12 in our patient population. Phylogenetic analyses allowed the mapping of all 17 E. bieneusi strains to zoonotic group 1 (subgroups 1a and 1b/1c), indicating loose host specificity and raising public health concern. Our study suggests a probable common source of E. bieneusi genotype WL12 transmission and prompts the implementation of a wider epidemiological investigation.

Cryptosporidiosis in HIV-positive patients and related risk factors: A systematic review and meta-analysis

Cryptosporidium is one of the major causes of diarrhea in HIV-positive patients. The aim of this study is to systematically review and meta-analyze the prevalence of Cryptosporidium in these patients. PubMed, Science Direct, Google Scholar, Web of Science, Cochrane and Ovid databases were searched for relevant studies dating from the period of 1 January 2000 to 31 December 2017. Data extraction for the included studies was performed independently by two authors. The overall pooled prevalence was calculated and subgroup analysis was performed on diagnostic methods, geographical distribution and study population. Meta-regression was performed on the year of publication, proportion of patients with diarrhea, and proportion of patients with CD4 < 200 cells/mL. One hundred and sixty-one studies and 51,123 HIV-positive participants were included. The overall pooled prevalence of Cryptosporidium infection in HIV-positive patients was 11.2% (CI95%: 9.4%–13.0%). The pooled prevalence was estimated to be 10.0% (CI95%: 8.4%–11.8%) using staining methods, 13.5% (CI95%: 8.9%–19.8%) using molecular methods, and 26.3% (CI95%: 15.0%–42.0%) using antigen detection methods. The prevalence of Cryptosporidium in HIV patients was significantly associated with the country of study. Also, there were statistical differences between the diarrhea, CD4 < 200 cells/mL, and antiretroviral therapy risk factors with Cryptosporidiosis. Thus, Cryptosporidium is a common infection in HIV-positive patients, and safe water and hand-hygiene should be implemented to prevent cryptosporidiosis occurrence in these patients.

Identification of a potent benzoxaborole drug candidate for treating cryptosporidiosis

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children and causes chronic diarrhea in AIDS patients, but the only approved treatment is ineffective in malnourished children and immunocompromised people. We here use a drug repositioning strategy and identify a promising anticryptosporidial drug candidate. Screening a library of benzoxaboroles comprised of analogs to four antiprotozoal chemical scaffolds under pre-clinical development for neglected tropical diseases for Cryptosporidium growth inhibitors identifies the 6-carboxamide benzoxaborole AN7973. AN7973 blocks intracellular parasite development, appears to be parasiticidal, and potently inhibits the two Cryptosporidium species most relevant to human health, C. parvum and C. hominis. It is efficacious in murine models of both acute and established infection, and in a neonatal dairy calf model of cryptosporidiosis. AN7973 also possesses favorable safety, stability, and PK parameters, and therefore, is an exciting drug candidate for treating cryptosporidiosis.

A suite of phenotypic assays to ensure pipeline diversity when prioritizing drug-like Cryptosporidium growth inhibitors

Cryptosporidiosis is a leading cause of life-threatening diarrhea in children, and the only currently approved drug is ineffective in malnourished children and immunocompromised people. Large-scale phenotypic screens are ongoing to identify anticryptosporidial compounds, but optimal approaches to prioritize inhibitors and establish a mechanistically diverse drug development pipeline are unknown. Here, we present a panel of medium-throughput mode of action assays that enable testing of compounds in several stages of the Cryptosporidium life cycle. Phenotypic profiles are given for thirty-nine anticryptosporidials. Using a clustering algorithm, the compounds sort by phenotypic profile into distinct groups of inhibitors that are either chemical analogs (i.e. same molecular mechanism of action (MMOA)) or known to have similar MMOA. Furthermore, compounds belonging to multiple phenotypic clusters are efficacious in a chronic mouse model of cryptosporidiosis. This suite of phenotypic assays should ensure a drug development pipeline with diverse MMOA without the need to identify underlying mechanisms.

Molecular Diagnosis of Microsporidia among Immunocompromised Patients in Kuala Lumpur, Malaysia

Microsporidia are obligate intracellular parasitic fungi causing chronic diarrhea, particularly among immunocompromised patients. The current method used for diagnosis is based on conventional microscopy, which does not differentiate parasites at the species level. The present study was carried out to identify microsporidian species in immunocompromised patients. From March 2016 to March 2017, a total of 289 archived stool samples were examined microscopically for microsporidian spores using Gram-chromotrope Kinyoun (GCK) stain. Positive stool samples by microscopy were subjected to polymerase chain reaction and sequencing for species identification. Based on microscopy examination, the overall prevalence of microsporidian infections was 32.2% (93/289; 95% CI = 27.1-37.8). Of these stool samples, 45 samples were successfully amplified and confirmed as Enterocytozoon bieneusi. No Encephalitozoon intestinalis was detected. Accurate identification of species might help clinicians to decide appropriate management strategies as dissemination risks and treatment response vary for different species, hence improving the management of microsporidian infections.

A Novel Piperazine-Based Drug Lead for Cryptosporidiosis from the Medicines for Malaria Venture Open-Access Malaria Box

Cryptosporidiosis causes life-threatening diarrhea in children under the age of 5 years and prolonged diarrhea in immunodeficient people, especially AIDS patients. The standard of care, nitazoxanide, is modestly effective in children and ineffective in immunocompromised individuals. In addition to the need for new drugs, better knowledge of drug properties that drive in vivo efficacy is needed to facilitate drug development. We report the identification of a piperazine-based lead compound for Cryptosporidium drug development, MMV665917, and a new pharmacodynamic method used for its characterization. The identification of MMV665917 from the Medicines for Malaria Venture Malaria Box was followed by dose-response studies, in vitro toxicity studies, and structure-activity relationship studies using commercial analogues. The potency of this compound against Cryptosporidium parvum Iowa and field isolates was comparable to that against Cryptosporidium hominis Furthermore, unlike nitazoxanide, clofazimine, and paromomycin, MMV665917 appeared to be curative in a NOD SCID gamma mouse model of chronic cryptosporidiosis. MMV665917 was also efficacious in a gamma interferon knockout mouse model of acute cryptosporidiosis. To determine if efficacy in this mouse model of chronic infection might relate to whether compounds are parasiticidal or parasitistatic for C. parvum, we developed a novel in vitro parasite persistence assay. This assay suggested that MMV665917 was parasiticidal, unlike nitazoxanide, clofazimine, and paromomycin. The assay also enabled determination of the concentration of the compound required to maximize the rate of parasite elimination. This time-kill assay can be used to prioritize early-stage Cryptosporidium drug leads and may aid in planning in vivo efficacy experiments. Collectively, these results identify MMV665917 as a promising lead and establish a new method for characterizing potential anticryptosporidial agents.

Clinical and microbiologic efficacy of the piperazine-based drug lead MMV665917 in the dairy calf cryptosporidiosis model

Cryptosporidiosis causes life-threatening diarrhea in infants, but the best available treatment is only modestly efficacious. Rodents infected with relevant Cryptosporidium species do not develop diarrhea, which complicates drug development. Cryptosporidium parvum infection of dairy calves, however, causes an illness like that seen in infants. Here, the clinical and microbiologic anti-Cryptosporidium efficacy of the piperazine-based compound MMV665917 was demonstrated in neonatal calves. Oral administration of MMV665917 (22 mg/kg once daily) was begun two days after the onset of severe diarrhea and continued for seven days. Treatment resulted in prompt resolution of diarrhea, and reduced total fecal oocyst shedding by ~94%. MMV665917 was useful for treatment, rather than just prophylaxis, since it was safe and effective when administered well after the onset of diarrhea. Furthermore, even though all animals received intensive supportive care, there was a strong trend towards improved secondary health outcomes, including general health, appetite, and dehydration measures amongst treated animals. These data establish MMV665917 as an outstanding lead compound for Cryptosporidium drug development.

Susceptibility Testing of Medically Important Parasites

In the last 2 decades, renewed attention to neglected tropical diseases (NTDs) has spurred the development of antiparasitic agents, especially in light of emerging drug resistance. The need for new drugs has required in vitro screening methods using parasite culture. Furthermore, clinical laboratories sought to correlate in vitro susceptibility methods with treatment outcomes, most notably with malaria. Parasites with their various life cycles present greater complexity than bacteria, for which standardized susceptibility methods exist. This review catalogs the state-of-the-art methodologies used to evaluate the effects of drugs on key human parasites from the point of view of drug discovery as well as the need for laboratory methods that correlate with clinical outcomes.

Efficacy of a potential DNA vaccine encoding Cryptosporidium baileyi rhomboid protein against homologous challenge in chickens

The parasite Cryptosporidium baileyi can infect the larynx, trachea, bursa and cloaca of poultry, causing high mortality during severe infection and leading to substantial economic losses of the poultry industry. The rhomboid protein is very important in Cryptosporidium infection. In this study, a nucleic acid based vaccine candidate pEGFP-CbROM was constructed. After orally challenging with C. baileyi oocysts, the corresponding immune responses induced were analyzed and the immunoprotective effect evaluated in chickens. Obtained results revealed that this nucleic acid based vaccine could induce antibody responses and peripheral blood T lymphocytes proliferation significantly (P<0.05), while the peripheral blood B lymphocyte proliferation increased significantly (P<0.05) only at a high dose of 100μg of pEGFP-CbROM, compared with the PBS control group. After C. baileyi infection, the duration of oocysts shedding was shortened by 2days in the 100μg pEGFP-CbROM group, and the rate of reduction could reach to around 71.3%. While no significant difference in body weight gain was observed among the immunized groups (P>0.05), the differences between the immunized and the non-immunized groups were found to be significant (P<0.05). Our data provides a useful basis for further work in cryptosporidiosis prevention and treatment.

Identification and genotyping of Enterocytozoon bieneusi among human immunodeficiency virus infected patients

Microsporidia cause diarrhea among human immunodeficiency virus (HIV) infected patients worldwide. Enterocytozoon bieneusi and Encephalitozoon intestinalis are the most common species infecting HIV patients. Various genotypes of E. bieneusi are transmitted from human to human (anthroponotic route) or from animal to human (zoonotic route). However, there is no study from India on genotypes of E. bieneusi among infected hosts. Therefore, we aimed to (a) study the prevalence, clinical symptoms, and species identification of microsporidia among HIV infected patients and (b) perform a genotypic analysis of E. bieneusi and a phylogenetic interpretation of the transmission of different genotypes among infected hosts. Two hundred and twenty-two HIV-infected patients and 220 healthy controls (HC) were tested for the presence of microsporidia using modified trichrome (MT) staining and PCR. Demographic, clinical and laboratory parameters were studied. Species identification was performed using PCR-RFLP. All E. bieneusi isolates were subjected to genotypic and phylogenetic analysis. Patients with HIV [n=222, age 37.4±10.4y, 169 (76%) male] were more commonly infected with microsporidia than the HC [n=220, age 34.5±6.5y, 156 (71%) male], using MT stain and PCR [4/222, 1.8% vs. 0/220, p=0.04]. Patients infected with microsporidia more commonly presented with diarrhea than those not infected with microsporidia [4, 100% vs. 98/218, 45%; p=0.04]. E. bieneusi was detected in all patients with microsporidia. Four novel genotypes (Ind1 to Ind4) were identified. Ind1 showed 95% similarity with genotype L (AF267142.1) reported in cats (Germany). Genotypes Ind2 to Ind4 showed 94-96% similarity to host-specific genotype A (AF101197.1) reported in humans. Phylogenetic analysis mainly showed an anthroponotic route of transmission (3/4), while the zoonotic route (1/4) was also observed. The prevalence of microsporidia among HIV-infected patients was 1.8%. Patients with microsporidia commonly present with diarrhea. E. bieneusi is the most common species infecting the study population. Four novel genotypes of E. bieneusi were identified, suggesting presumptive transmission mainly through the anthropological route.

Infections by Intestinal Coccidia and Giardia duodenalis

The coccidians Cryptosporidium spp, Cyclospora cayetanensis, and Cystoisospora belli and the flagellate Giardia duodenalis are pathogenic protozoa associated with gastrointestinal manifestations. Diagnosis relies heavily on microscopy, and although ova-and-parasite examinations can detect Giardia and Cystoisospora, Cryptosporidium and Cyclospora often require specific diagnostic requests. Approved non-microscopy methods are available for Giardia and Cryptosporidium, although negative results are frequently followed by microscopic assays. Polymerase chain reaction-based methods are not frequently used for diagnosis of Giardia and Cryptosporidium and have been used primarily for epidemiologic or outbreak investigations of Giardia and Cryptosporidium.

Evaluation of different modifications of acid-fast staining techniques and stool enzyme-linked immunosorbent assay in detecting fecal Cryptosporidium in diarrheic HIV seropositive and seronegative patients

Rational:

The role of Cryptosporidium as an agent of human diarrhea has been redefined over the past decade following recognition of the strong association between cases of cryptosporidiosis and immune deficient individuals (such as those with AIDS).

Purpose:

The purpose of this study is to determine the prevalence of enteric parasites and to compare the diagnostic utility of stool enzyme-linked immunosorbent assay (ELISA) with various modifications of acid-fast (AF) staining in detection of Cryptosporidium in stool samples of diarrheic patients.

Materials and Methods:

Stool samples from 186 cases comprising of 93 HIV seropositive and 93 seronegative patients were included. These were subjected to routine and microscopic examination as well as various modifications of AF staining for detection of coccidian parasites and ELISA for the detection of Cryptosporidium.

Results:

The prevalence of enteric parasites was 54.8% and of Cryptosporidium was 17.2% in HIV seropositive patients while it was 29.0% and 5.4%, respectively in seronegative patients. Of the 186 cases, 33 cases (17.7%) were positive for Cryptosporidium by stool ELISA as compared to 21 (11.3%) by modified AF staining (gold standard) showing sensitivity and specificity of 100% and 92.7%, respectively. The maximum cases of Cryptosporidium (21; 11.3%) were detected by AF staining using 3% acid alcohol.

Conclusion:

ELISA is a simple, useful, and rapid tool for detection of Cryptosporidium in stool, especially for large scale population studies. However, the role of modified AF staining in detection of Cryptosporidium and other coccidian parasites is important. Based on the results of various modifications of AF staining, the present study recommends the use of 3% acid alcohol along with 10% H₂SO₄.

Cryptosporidiosis and Isosporiasis among HIV-positive individuals in south Ethiopia: a cross sectional study

BACKGROUND

Cryptosporidium spp and I. belli are intestinal opportunistic infections associated with HIV/AIDS. A decline in the incidence of these opportunistic infections due to HAART was reported. We aim to investigate these parasites among HAART naïve and experienced HIV patients in south Ethiopia.

METHODS

A cross sectional study was carried out among 268 HIV- positive patients between January and September, 2007. Interview with questionnaires and document reviews were used to collect data. Stool samples were obtained from each patient and parasites were examined by direct, formol-ether and modified Ziehl-Neelsen stain for Cryptosporidium spp and I. belli. Univariate and multivariate analysis were carried out. Level of significance was set at p-value of 0.05.

RESULTS

A total of 268 patients participated in the study. The mean age was 34.0 (±1 SD of 8.34) years. Females constituted 53.4% (143) of the study participants. Half of the study participants were on HAART; majorities (85.8%) of such patients were within the first year of treatment. The prevalence of Cryptosporidium spp was 34.3% (92/268) and I. belli was 1.5% (4/268). Dual infection was detected in two patients (0.75%). The crude analysis revealed significant reduction in the odds of Cryptosporidium spp infection among patients who have started HAART (crude OR = 0.59, 95% CI 0.35, 0.98). The adjusted analysis remained in the same direction but has lost significance (Adj OR 0.65, 95%CI 0.35, 1.24). No differences in the risk of developing infection with Cryptosporidium spp were observed between groups based on most recent CD4 counts, sex, duration on HAART and age (p > 0.05 for all variables). Patients with Cryptosporidium spp were more likely to report vomiting [Adj OR 2.34 (95% CI 1.22, 5.41)], weight loss [Adj OR 2.10 (95% CI 1.15, 3.81)] and chronic diarrhea [Adj OR 3.35 (95%CI 1.05, 10.63)].

CONCLUSION

There is high burden of infection with Cryptosporidium spp among HIV infected individuals in southern Ethiopia but that of I. belli is low. We recommend considering infection with Cryptosporidium spp in HIV infected people with chronic diarrhea, weight loss and vomiting for HAART naïve patients and/or for patients who are within the first year of starting HAART.

Management of protozoa-related diarrhea in HIV infection

Protozoa infections are an important cause of chronic diarrhea in patients infected with HIV. The introduction of highly active antiretroviral treatment to the management of HIV in the mid 1990s has led to a dramatic reduction in the incidence of these opportunistic infections in Europe and America. In contrast, in the developing world where such treatments are not readily affordable, protozoa-related diarrhea remains a major cause of morbidity and mortality in HIV-infected individuals. In this review, the optimum investigations required to diagnose these pathogens in HIV-related diarrhea, as well as current treatment options, will be discussed.

Cryptosporidium enteritis in solid organ transplant recipients: multicenter retrospective evaluation of 10 cases reveals an association with elevated tacrolimus concentrations

BACKGROUND

Cryptosporidial enteritis, a diarrheal infection of the small intestine caused by the apicomplexan protozoa Cryptosporidium, is infrequently recognized in transplant recipients from developed countries.

METHODS

A retrospective review of all cases of cryptosporidiosis in solid organ transplant (SOT) recipients at 2 centers from January 2001 to October 2010 was performed and compared with transplant recipients with community-onset Clostridium difficile infection (CDI). A literature search was performed with regard to reported cases of cryptosporidiosis in SOT recipients.

RESULTS

Eight renal, 1 liver, and 1 lung transplant recipient were diagnosed with cryptosporidiosis at median 46.0 months (interquartile range [IQR] 25.2-62.8) following SOT. Symptoms existed for a median 14 days (IQR 10.5-14.8) before diagnosis. For the 9 patients receiving tacrolimus (TAC), mean TAC levels increased from 6.3 ± 1.1 to 21.3 ± 9.2 ng/mL (P = 0.0007) and median serum creatinine increased temporarily from 1.3 (IQR 1.1-1.7) to 2.4 (IQR 2.0-4.6) mg/dL (P = 0.008). By comparison, 8 SOT recipients (6 kidney, 2 liver) hospitalized with community-onset CDI had a mean TAC level of 10.8 ± 2.8 ng/dL during disease compared with 9.2 ± 2.3 ng/mL at baseline (P = 0.07) and had no change in median creatinine. All patients recovered from Cryptosporidium enteritis after receiving various chemotherapeutic regimens.

CONCLUSIONS

Cryptosporidiosis should be recognized as an important cause of diarrhea after SOT and is associated with elevated TAC levels and acute kidney injury. Increased TAC levels may reflect altered drug metabolism in the small intestine.

High diversity of Cryptosporidium subgenotypes identified in Malaysian HIV/AIDS individuals targeting gp60 gene

Background

Currently, there is a lack of vital information in the genetic makeup of Cryptosporidium especially in developing countries. The present study aimed at determining the genotypes and subgenotypes of Cryptosporidium in hospitalized Malaysian human immunodeficiency virus (HIV) positive patients.

Methodology/Principal Findings

In this study, 346 faecal samples collected from Malaysian HIV positive patients were genetically analysed via PCR targeting the 60 kDa glycoprotein (gp60) gene. Eighteen (5.2% of 346) isolates were determined as Cryptosporidium positive with 72.2% (of 18) identified as Cryptosporidium parvum whilst 27.7% as Cryptosporidium hominis. Further gp60 analysis revealed C. parvum belonging to subgenotypes IIaA13G1R1 (2 isolates), IIaA13G2R1 (2 isolates), IIaA14G2R1 (3 isolates), IIaA15G2R1 (5 isolates) and IIdA15G1R1 (1 isolate). C. hominis was represented by subgenotypes IaA14R1 (2 isolates), IaA18R1 (1 isolate) and IbA10G2R2 (2 isolates).

Conclusions/Significance

These findings highlighted the presence of high diversity of Cryptosporidium subgenotypes among Malaysian HIV infected individuals. The predominance of the C. parvum subgenotypes signified the possibility of zoonotic as well as anthroponotic transmissions of cryptosporidiosis in HIV infected individuals.

Microsporidia as emerging pathogens and the implication for public health: a 10-year study on HIV-positive and -negative patients

Despite recent advances in the understanding and diagnosis of emerging microsporidian pathogens, more research is necessary to elucidate their complex epidemiology. In fact, studies that reflect true human-infecting microsporidian prevalence are still inadequate. The present 10-year study was undertaken to examine the occurrence of Microsporidia in 1989 stools, 69 urine and 200 pulmonary specimens from HIV-positive and HIV-negative patients using PCR and DNA sequencing. In stools, 12.0% were Microsporidia-positive. Prevalences of 13.9% and 8.5% were observed for HIV+ and HIV- samples, respectively. The percentage of children that were Microsporidia-positive (18.8%) was significantly higher than that of adults (10.2%). In stools, Enterocytozoon bieneusi (6.3%) and Vittaforma-like parasites (6.8%) were identified. Based on the internal transcribed spacer (ITS) region of E. bieneusi, Type IV (37.5%), Peru 6 (29.2%), D (12.5%), A (8.3%), C (6.3%) and PtEb II (6.3%) genotypes were identified. Microsporidia were detected in 1.5% and 1.0% of urine and pulmonary specimens, respectively. Encephalitozoonintestinalis was detected in urine. In pulmonary specimens, Encephalitozoon cuniculi and Vittaforma-like parasites were identified. An immunosuppressive condition and youth (children) appear to be risk factors for microsporidian infection. Microsporidia seems to have an important impact on public health in Portugal, highlighting the need to implement routine diagnosis.

First genetic classification of Cryptosporidium and Giardia from HIV/AIDS patients in Malaysia

Given the HIV epidemic in Malaysia, genetic information on opportunistic pathogens, such as Cryptosporidium and Giardia, in HIV/AIDS patients is pivotal to enhance our understanding of epidemiology, patient care, management and disease surveillance. In the present study, 122 faecal samples from HIV/AIDS patients were examined for the presence of Cryptosporidium oocysts and Giardia cysts using a conventional coproscopic approach. Such oocysts and cysts were detected in 22.1% and 5.7% of the 122 faecal samples, respectively. Genomic DNAs from selected samples were tested in a nested-PCR, targeting regions of the small subunit (SSU) of nuclear ribosomal RNA and the 60kDa glycoprotein (gp60) genes (for Cryptosporidium), and the triose-phosphate isomerase (tpi) gene (for Giardia), followed by direct sequencing. The sequencing of amplicons derived from SSU revealed that Cryptosporidium parvum was the most frequently detected species (64% of 25 samples tested), followed by C. hominis (24%), C. meleagridis (8%) and C. felis (4%). Sequencing of a region of gp60 identified C. parvum subgenotype IIdA15G2R1 and C. hominis subgenotypes IaA14R1, IbA10G2R2, IdA15R2, IeA11G2T3R1 and IfA11G1R2. Sequencing of amplicons derived from tpi revealed G. duodenalis assemblage A, which is of zoonotic importance. This is the first report of C. hominis, C. meleagridis and C. felis from Malaysian HIV/AIDS patients. Future work should focus on an extensive analysis of Cryptosporidium and Giardia in such patients as well as in domestic and wild animals, in order to improve the understanding of transmission patterns and dynamics in Malaysia. It would also be particularly interesting to establish the relationship among clinical manifestation, CD4 cell counts and genotypes/subgenotypes of Cryptosporidium and Giardia in HIV/AIDS patients. Such insights would assist in a better management of clinical disease in immuno-deficient patients as well as improved preventive and control strategies.

Putative cis-regulatory elements associated with heat shock genes activated during excystation of Cryptosporidium parvum

Background

Cryptosporidiosis is a ubiquitous infectious disease, caused by the protozoan parasites Cryptosporidium hominis and C. parvum, leading to acute, persistent and chronic diarrhea worldwide. Although the complications of this disease can be serious, even fatal, in immunocompromised patients of any age, they have also been found to lead to long term effects, including growth inhibition and impaired cognitive development, in infected immunocompetent children. The Cryptosporidium life cycle alternates between a dormant stage, the oocyst, and a highly replicative phase that includes both asexual vegetative stages as well as sexual stages, implying fine genetic regulatory mechanisms. The parasite is extremely difficult to study because it cannot be cultured in vitro and animal models are equally challenging. The recent publication of the genome sequence of C. hominis and C. parvum has, however, significantly advanced our understanding of the biology and pathogenesis of this parasite.

Methodology/Principal Findings

Herein, our goal was to identify cis-regulatory elements associated with heat shock response in Cryptosporidium using a combination of in silico and real time RT-PCR strategies. Analysis with Gibbs-Sampling algorithms of upstream non-translated regions of twelve genes annotated as heat shock proteins in the Cryptosporidium genome identified a highly conserved over-represented sequence motif in eleven of them. RT-PCR analyses, described herein and also by others, show that these eleven genes bearing the putative element are induced concurrent with excystation of parasite oocysts via heat shock.

Conclusions/Significance

Our analyses suggest that occurrences of a motif identified in the upstream regions of the Cryptosporidium heat shock genes represent parts of the transcriptional apparatus and function as stress response elements that activate expression of these genes during excystation, and possibly at other stages in the life cycle of the parasite. Since heat shock and excystation represent a critical step in the development of the infectious sporozoite form of Cryptosporidium, these results provide important insight into the pathogenicity of the parasite.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Limited genetic diversity among genotypes of Enterocytozoon bieneusi strains isolated from HIV-infected patients from Sydney, Australia

Microsporidia are intracellular parasites, with over 1200 species belonging to 143 genera described to date. They are opportunistic pathogens in humans and can cause chronic diarrhoea in immunosuppressed patients. Both Enterocytozoon bieneusi and Encephalitozoon intestinalis cause intestinal disease, with Enterocytozoon bieneusi more commonly identified in patients with human immunodeficiency virus (HIV) infection. In this study, intestinal microsporidial clinical isolates from patients in Sydney, Australia, were genotyped. All specimens were from HIV-infected men with low CD4(+) T-cell counts (<100 cells mm(-3)). Genotyping of the internal transcribed spacer regions of the rRNA gene showed the presence of only one genotype, the anthroponotic Enterocytozoon bieneusi genotype B strain. This study thus highlighted the limited genetic diversity among Australian Enterocytozoon bieneusi isolates, and it is hypothesized that, due to the reduced incidence of microsporidia and the subsequent reduction in the human reservoir of the anthroponotic genotype B, locally acquired intestinal microsporidiosis will rarely be seen in HIV-infected persons undergoing highly active antiretroviral therapy in the future in Australia.

Minireview: clinical cryptosporidiosis

Cryptosporidium has emerged as an important cause of diarrhoeal illness worldwide, especially amongst young children and patients with immune deficiencies. Usually presenting as a gastro-enteritis-like syndrome, disease ranges in seriousness from mild to severe and signs and symptoms depend on the site of infection, nutritional and immune status of the host, and parasite-related factors. Sources and routes of transmission are multiple, involving both zoonotic and anthroponotic spread, and facilitated by the resistance of the parasite to many commonly used disinfectants. Prevention and control measures are important for the protection of vulnerable groups since treatment options are limited. This review covers the life cycle, pathogenesis, clinical presentations, diagnosis, prevention and management of cryptosporidiosis in humans.

Cryptosporidium in commercially produced turkeys on-farm and postslaughter

AIMS

To determine the presence of Cryptosporidium species in commercially produced turkey flocks on farm and postslaughter.

METHODS AND RESULTS

Three separate turkey flocks were sampled at a single farm and again postslaughter at a commercial processing facility. DNA was extracted and purified from faecal (farm) or caecal (postslaughter) samples and a fragment of 18S rDNA was amplified using a nested PCR approach. Amplified fragments were sequenced, aligned and a neighbour joining tree was constructed. Cryptosporidium meleagridis was not identified in any of the flocks tested. However, all flocks tested positive for Cryptosporidium parvum species. One of the flocks tested positive at the farm and postslaughter.

CONCLUSIONS

While C. parvum was present in birds at the farm and postslaughter, turkeys at this facility are not likely to be a significant reservoir for this species.

SIGNIFICANCE AND IMPACT OF THE STUDY

Cryptosporidium meleagridis infects avian and human hosts and is increasingly being recognized as a significant human pathogen. However, this study found no evidence of C. meleagridis in commercially produced turkeys at a single location.

Methylprednisolone acetate immune suppression produces differing effects on Cryptosporidium muris oocyst production depending on when administered

At different times after inoculation with Cryptosporidium muris, infected CF-1 female mice were immunosuppressed with a single subcutaneous dose of methylprednisolone acetate (MPA; 600 mg/kg). MPA immunosuppression decreases circulating CD3, CD4 and CD8 T-lymphocytes and B-lymphocytes by greater than 90% for approximately 14 days with numbers not returning to pre-suppression levels until after 41 days post-suppression. Immunosuppression was initiated at selected times before, during, and after oocyst production. Immunosuppression initiated prior to oocyst production delayed the start of production by 4-5 days and extended oocyst shedding by 16 days. Initiation of immunosuppression during oocyst production both extended oocyst shedding and greatly increased the number of oocysts shed per day over most of the extended shedding period. Immunosuppression during the decline of oocyst production resulted in only a moderate extension of shedding and a moderate increase in oocyst numbers. Immunosuppression initiated soon after oocyst shedding had ceased resulted in the re-initiation of limited oocyst production for only a few days. Suppression initiated on days 40 and 46 post-infection, 11 and 17 days after oocysts could no longer be detected in the feces, did not result in a resumption of oocyst production. In all cases, where oocyst production was extended or reinitiated, the shedding of oocysts halted between days 45 and 53 post-oocyst inoculation. These studies demonstrate that the effect of MPA immunosuppression depends on the immunologic conditions existing in the host at the time immunosuppression was initiated. Immunosuppression initiated during oocyst production allows an overwhelming parasitism to exist, implying that T- and B-lymphocytes play an important role in moving the host immune process along during this period of the infection. Conversely, severe suppression of T- and B-lymphocytes initiated as oocyst production is decreasing does not result in a complete relapse of the disease suggesting that T- and B-lymphocytes are not critical to the continuation of the immune process after this point. These studies also show that the C. muris infection persists beyond the end of the detection of oocysts in the feces.

Characterization of a Cryptosporidium muris infection and reinfection in CF-1 mice

To establish control values for circulating cells and immune associated organs over the course of a self-limiting Cryptosporidium muris infection and rechallenge infection, mice were sacrificed at intervals starting before oral inoculation and ending after oocyst shedding had ceased. These values were used in other experiments to evaluate changes in these parameters induced by a single dose glucocorticoid immunosuppression model and in other immunosuppression studies. Flow cytometry counts of circulating T-lymphocytes and neutrophils, differential leukocyte counts, leukocyte morphology, spleen and thymus changes, and oocyst shedding were evaluated. Immediately after C. muris oocyst inoculation and up to the start of oocyst production (day 0 to day 7), the circulating blood profile showed a 50% drop in all leukocytes, including both large and small lymphocytes and CD3, CD4 and CD8 T-lymphocytes. There was an initial slight rise in circulating mature neutrophils after oocyst inoculation but numbers promptly dropped below normal and remaineded below normal. In the differential cell counts, monocytes with a fat, oval morphology increased by 60% at 24 h and remained high through oocyst shedding and beyond (day 8 through day 36). During oocyst shedding and continuing past the end of shedding, T-lymphocytes increased 100%. Monocytes with a flat, angular morphology increased in a similar manner. Immediately after oocyst inoculation the spleen contracted by 29%, but became 92% larger than its pre-inoculation size by day 14 when heavy oocyst shedding began. It remained enlarged through the end of oocyst shedding (day 29) and beyond (day 36). Spleen volume decreased and increased similar to changes in T-cell numbers. Throughout the C. muris infection the thymus remained largely unchanged. The transit of an oocyst bolus was followed from the stomach through the gut to the colon. No oocysts could be found in the stomach, caecum or feces of mice one half hour after oocyst inoculation. Likewise, an oral bolus of India ink passed from the stomach entirely into the colon after 3 h; therefore, no oocysts from the inoculum passed completely through the intestine and out into the feces. Recovered mice rechallenged with C. muris showed increased B-lymphocyte numbers; however, T-lymphocyte numbers remained level. The large lymphocytes increased after rechallenge, peaking on day 3, then decreased through day 10. B-cell numbers followed a pattern similar to the large lymphocytes. On day 10 of infection monocytes with a fat oval morphology rose sharply while B-cells fell in number. In both the initial infection and the rechallenge there was no unique blood profile which could definitely indicate a protozoal disease or identify a specific point during the course of the disease. There was no increase in the number of either small or large lymphocytes prior to increases in fat or flat monocytes.

Prevalence of Intestinal Infection due to Cryptosporidium Species Among Taiwanese Patients with Human Immunodeficiency Virus Infection

BACKGROUND/PURPOSE

Cryptosporidiosis causes significant morbidity and mortality in human immunodeficiency virus (HIV)-infected patients who do not receive highly active antiretroviral therapy. Related data on cryptosporidiosis in Taiwanese HIV-infected patients are very limited. This study assessed the prevalence of intestinal infection due to Cryptosporidium spp. among Taiwanese patients with HIV infection.

METHODS

This retrospective review included 1044 patients with HIV infection treated between June 1994 and June 2004. Intestinal colonization due to Cryptosporidium spp. was identified by polymerase chain reaction and restriction fragment length polymorphism of stool specimens collected from 332 of the HIV-infected patients without gastrointestinal symptoms, 90% of whom were receiving highly active antiretroviral therapy.

RESULTS

Five out of 1044 (0.5%) HIV-infected patients had a diagnosis of intestinal cryptosporidiosis by endoscopic biopsy or examinations of stool specimens. Intestinal colonization due to Cryptosporidium spp. was found in four of 332 (1.2%) asymptomatic HIV-infected patients between 2001 and 2003; two were due to C. hominis, and one each were due to C. felis and C. meleagridis.

CONCLUSION

Our findings indicate that the prevalence of intestinal colonization due to Cryptosporidium is low among HIV-infected patients in Taiwan.

Evidence supporting zoonotic transmission of Cryptosporidium spp. in Wisconsin

Cryptosporidium hominis and Cryptosporidium parvum are the primary species of Cryptosporidium that infect humans. C. hominis has an anthroponotic transmission cycle, while C. parvum is zoonotic, infecting cattle and other ruminants, in addition to humans. Most cryptosporidiosis outbreaks in the United States have been caused by C. hominis, and this species is often reported as the primary cause of cryptosporidiosis in this country. However, outbreaks account for only 10% of the overall cryptosporidiosis cases, and there are few data on the species that cause sporadic cases. The present study identified the species/genotypes and subgenotypes of Cryptosporidium in 49 cases of sporadic cryptosporidiosis in Wisconsin during the period from 2003 to 2005. The species/genotype of isolates was determined by PCR restriction fragment length polymorphism analysis of the 18S rRNA and Cryptosporidium oocyst wall protein genes. The C. parvum and C. hominis isolates were subgenotyped by sequence analysis of the GP60 gene. Forty-four of 49 isolates were identified as C. parvum, and 1 was identified as C. hominis. Of the remaining isolates, one was identified as being of the cervine genotype, one was identified as being a cervine genotype variant, and two were identified as being of a novel human genotype, previously reported as W17. Nine different subgenotypes were identified within the C. parvum species, and two of these were responsible for 60% of the cases. In this study we found that most sporadic cases of cryptosporidiosis in Wisconsin are caused by zoonotic Cryptosporidium species, indicating that zoonotic transmission could be more frequently associated with sporadic cases in the United States.

Characterization of a single dose methylprednisolone acetate immune suppression model using Cryptosporidium muris and Cryptosporidium parvum

An immunosuppressive dose of methylprednisolone acetate (MPA) was compared with a non-immunosuppressive dose using Cryptosporidium oocyst production as an indicator of immunosuppression. To be classified as immunosuppressive, the dose had to satisfy five criteria. First, the dose had to abrogate normal immune defenses allowing the propagation of an organism to which the host is normally resistant, i.e. Cryptosporidium parvum in adult mice. Second, the dose had to decrease overall circulating CD4 T-lymphocyte numbers by greater than 80%. Third, the immunosuppressive dose had to prolong the infection beyond the normal infection length, and fourth, increase the severity of an active infection. Lastly, after complete recovery from a C. muris infection, immunosuppression must suppress the naturally acquired post infection immunity and allow reinfection. In mice immunosuppression with 600 mgMPA/kg lasted approximately 14 days and satisfied all five criteria. Fecal oocyst production could be perpetuated by dosing at 10-day intervals. A 200 mgMPA/kg dose transiently lowered CD4 counts by over 80%, but failed to override the naturally acquired post infection immunity or allow infection with C. parvum. The immunosuppressed blood profile consisted of an immediate sharp rise of mature segmented neutrophils combined with a severe decrease in circulating T-lymphocyte numbers. The rise and fall of neutrophils proved to be a good indicator of the severity and duration of immunosuppression. The thymus and spleen likewise contracted and then expanded in accordance with the steroid effect. The metabolism of MPA resulted in the eventual recovery of immune function signified by the cessation of C. parvum oocyst production. The recovery blood profile was associated with circulating CD8 counts near control levels, continuing 80% depression of CD4 counts and a dropping total neutrophil count. This study shows that the 600 mg/kg MPA dose is a good model for immunosuppression, which satisfies all five criteria for immunosuppression with low morbidity and low mortality.

Diarrhea, CD4 counts and enteric infections in a hospital - based cohort of HIV-infected patients around Varanasi, India

BACKGROUND

As most of the studies in HIV patients with diarrhea were cross sectional, focusing on the etiological agents, we are reporting data on the rate of diarrhea, associations between diarrhea and CD4 counts and variation in frequency of identifying a pathogen with consistency of diarrhea and duration in a prospective hospital based study.

METHODS

Stool specimens were obtained between Jan 2001 and April 2003 from HIV infected adults with diarrhea presenting to Infectious Disease clinic, Banaras Hindu University, Varanasi. In all patients with diarrhea, specimens were examined by microscopy and cultures to identify pathogens.

RESULTS

During the study, 630 person years of observations with diarrhea were analyzed. 140 stool samples were collected representing 43% of episodes of reported diarrhea. Positivity of finding a pathogen from watery stools and formed stools were 40%&24% respectively (p < 0.01) probably due to associated inflammation is more in watery diarrhea. Patients having chronic diarrhea are 2.25 (95%CI 1.52-2.81) times at more risk of developing other opportunistic infections compared to those who don't have. However this is not true with the acute diarrhea where risk of harboring the opportunistic infections remain same.

CONCLUSION

Diarrhea was most strongly associated with low CD4 counts. Over two-thirds of diarrheal episodes were undiagnosed, suggesting that unidentified agents or primary HIV enteropathy are important causes of diarrhea in this population. There is a strong negative association between duration of diarrhea and CD4 levels.

The efficacy and safety of probiotic Lactobacillus rhamnosus GG on prolonged, noninfectious diarrhea in HIV Patients on antiretroviral therapy: a randomized, placebo-controlled, crossover study

PURPOSE

The aim of this placebo-controlled, crossover study was to evaluate the efficacy and safety of probiotic Lactobacillus rhamnosus GG (LGG) in ameliorating gastrointestinal symptoms in HIV-infected patients on antiretroviral therapy.

METHOD

Infectious causes for diarrhea (bacteria, ova, parasites, and viruses including cryptosporidium, microsporidia, and cyclospora) were excluded with fecal samples before the study. HIV-infected patients with diarrhea for more than 1 month received in randomized order probiotic LGG preparation (containing viable LGG 1-5 x 1010 cfu/dose) and placebo twice a day for 2 weeks. Gastrointestinal symptoms were assessed daily and included the daily number of bowel movements, classification of stool consistency (watery, semi-watery, loose, firm, or foaming), and Visual Analog Scale (VAS) of gastrointestinal symptoms (flatulence, stomach pain, bloating disorders, general well-being).

RESULTS

Seventeen HIV-infected patients completed the study. There were no significant differences between the treatment groups in the frequency or the consistency of diarrhea. In the VAS assessments of gastrointestinal symptoms, no difference between LGG and placebo could be detected. No adverse events were reported. The number of HIV RNA copies in the blood and CD4 cell counts remained stable during the study.

CONCLUSION

Probiotic LGG preparation was well-tolerated in HIV infected patients. No significant differences in noninfectious diarrhea or gastrointestinal symptoms compared to placebo could be observed in this crossover study.

Complete development of Cryptosporidium parvum in host cell-free culture

The present study describes the complete in vitro development of Cryptosporidium parvum (cattle genotype) in RPMI-1640 maintenance medium devoid of host cells. This represents the first report in which Cryptosporidium is shown to multiply, develop and complete its life cycle without the need for host cells. Furthermore, cultivation of Cryptosporidium in diphasic medium consisting of a coagulated new born calf serum base overlaid with maintenance medium greatly increased the total number of Cryptosporidium stages. Type I and II meronts were detected giving rise to two morphologically different merozoites. Type I meronts, which appear as grape-like clusters as early as 48 h post culture inoculation, release merozoites, which are actively motile, and circular to oval in shape. Type II meronts group in a rosette-like pattern and could not be detected until day 3 of culturing. Most of the merozoites released from type II meronts are generally spindle-shaped with pointed ends, while others are rounded or pleomorphic. In contrast to type I, merozoites from type II meronts are less active and larger in size. Sexual stages (micro and macrogamonts) were observed within 6-7 days of culturing. Microgamonts were darker than macrogamonts, with developing microgametes, which could be seen accumulating at the periphery. Macrogamonts have a characteristic peripheral nucleus and smooth outer surface. Oocysts at different levels of sporulation were seen 8 days post culture inoculation. Cultures were terminated after 4 months when the C. parvum life cycle was still being perpetuated with the presence of large numbers of excysting and intact oocysts. Culture-derived oocysts obtained after 46 days p.i. were infective to 7- to 8-day-old ARC/Swiss mice. The impact of C. parvum developing in cell-free culture is very significant and will facilitate many aspects of Cryptosporidium research.

Cryptosporidium taxonomy: recent advances and implications for public health

There has been an explosion of descriptions of new species of Cryptosporidium during the last two decades. This has been accompanied by confusion regarding the criteria for species designation, largely because of the lack of distinct morphologic differences and strict host specificity among Cryptosporidium spp. A review of the biologic species concept, the International Code of Zoological Nomenclature (ICZN), and current practices for Cryptosporidium species designation calls for the establishment of guidelines for naming Cryptosporidium species. All reports of new Cryptosporidium species should include at least four basic components: oocyst morphology, natural host specificity, genetic characterizations, and compliance with the ICZN. Altogether, 13 Cryptosporidium spp. are currently recognized: C. muris, C. andersoni, C. parvum, C. hominis, C. wrairi, C. felis, and C. cannis in mammals; C. baïleyi, C. meleagridis, and C. galli in birds; C. serpentis and C. saurophilum in reptiles; and C. molnari in fish. With the establishment of a framework for naming Cryptosporidium species and the availability of new taxonomic tools, there should be less confusion associated with the taxonomy of the genus Cryptosporidium. The clarification of Cryptosporidium taxonomy is also useful for understanding the biology of Cryptosporidium spp., assessing the public health significance of Cryptosporidium spp. in animals and the environment, characterizing transmission dynamics, and tracking infection and contamination sources.

Rapid displacement of Cryptosporidium parvum type 1 by type 2 in mixed infections in piglets

Genotypes 1 and 2 of Cryptosporidium parvum are the primary types associated with infections in humans, with type 1 being by far the predominant genotype. The frequency of mixed infection with both genotypes in humans is relatively rare, while type 1, which experimentally infects other mammals, has been found to naturally infect almost exclusively humans. One possible explanation for the absence of type 1 in other mammals and the low frequency of mixed infections in humans is the inability of type 1 to compete with type 2 in nature when both occur simultaneously. To investigate this, we challenged gnotobiotic piglets with equal number of oocysts of type 1 and type 2, given either simultaneously or with type 2 given 24 or 48 h after type 1. The genotype of the oocysts excreted in feces and the relative distribution of each of the genotypes throughout the gut at necropsy were determined. Regardless of the time interval between challenges with the two genotypes, type 2 invariably displaced type 1. The rate of displacement was rapid when both genotypes were given simultaneously, after which no traces of type 1 were detected in the feces or in gut sections by PCR. Infection with type 1 24 or 48 h before challenge with type 2, while permitting type 1 to become established, was still rapidly eliminated within 3 days after challenge with type 2. These observations have major implications regarding the relative perpetuation and survival of these two genotypes in mammals.

[Extraintestinal finding of Isospora belli unizoic cysts in a patient with AIDS: case report]

This report describes the presence of Isospora belli unizoic cysts in mesenteric lymph nodes and of gametocytes in the gallbladder epitelium of a 26 year-old Brazilian male patient with Acquired Immune Deficiency Syndrome. This patient had received treatment for several times with sulfamethoxazole-trimethoprim. It is discussed the significance of I. belli tissue cysts as possible foci of resistance of the parasite and their association with the infection relapse even post-treatment with anticoccidian medication.

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.