Cryptosporidiosis in patients with AIDS: correlates of disease and survival

Intestinal cDC1s provide cues required for CD4+ T cell-mediated resistance to Cryptosporidium

Cryptosporidium is an enteric pathogen and a prominent cause of diarrheal disease worldwide. Control of Cryptosporidium requires CD4+ T cells, but how protective CD4+ T cell responses are generated is poorly understood. Here, Cryptosporidium parasites that express MHCII-restricted model antigens were generated to understand the basis for CD4+ T cell priming and effector function. These studies revealed that parasite-specific CD4+ T cells are primed in the draining mesenteric lymph node but differentiate into Th1 cells in the gut to provide local parasite control. Although type 1 conventional dendritic cells (cDC1s) were dispensable for CD4+ T cell priming, they were required for CD4+ T cell gut homing and were a source of IL-12 at the site of infection that promoted local production of IFN-γ. Thus, cDC1s have distinct roles in shaping CD4+ T cell responses to an enteric infection: first, to promote gut homing from the mesLN, and second, to drive effector responses in the intestine.

Factors associated with Cryptosporidium in men who have sex with men: A systematic review

BACKGROUND

Cryptosporidium parasites are an important cause of diarrhoea globally and sexual transmission may occur in men who have sex with men (MSM). We aimed to systematically review the literature to explore any factors associated with transmission of Cryptosporidium in MSM to provide insight for future guidelines and public health strategies.

METHODS

We searched MEDLINE, Embase, CINAHL and Web of Science for manuscripts published up to July 2023. A primary author conducted an initial screen of abstracts and full text eligibility, and risk of bias was assessed independently by two authors using the Joanna Briggs Institute critical appraisal tools. We used the nine-point synthesis without meta-analysis method to synthesise narrative data. The review was registered on PROSPERO (CRD42023374279).

RESULTS

Six manuscripts were included in the final review from the USA (n = 3), Europe (n = 1) and Australia (n = 2) and were case series (n = 2), cross sectional (n = 2) and case control studies (n = 2) published between 1984 and 2021 and overall there were 1582 cases of Cryptosporidium in MSM. We identified demographic factors (living with HIV, younger age [<30 years old], geographical areas [Southern Europe v Northern Europe], previous Treponema pallidum, previous Entamoeba histolytica) and behavioural factors (recreational drug use, higher number of sexual partners and MSM attending sex on premises venues with spa/sauna) associated with Cryptosporidium in MSM.

CONCLUSIONS

Despite a small number of manuscripts in this review, we identified demographic and behavioural factors associated with Cryptosporidium in MSM. These data will provide insight for public health interventions for future outbreaks of Cryptosporidium in MSM.

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.

Dietary environmental factors shape the immune defense against Cryptosporidium infection

Cryptosporidium is a leading cause of diarrheal-related deaths in children, especially in resource-poor settings. It also targets the immunocompromised, chronically infecting people living with HIV and primary immunodeficiencies. There is no vaccine or effective treatment. Although it is known from human cases and animal models that CD4+ T cells play a role in curbing Cryptosporidium, the role of CD8+ T cells remains to be defined. Using a Cryptosporidium tyzzeri mouse model, we show that gut-resident CD8+ intraepithelial lymphocytes (IELs) confer resistance to parasite growth. CD8+ IELs express and depend on the ligand-dependent transcription factor aryl hydrocarbon receptor (AHR). AHR deficiency reduces CD8+ IELs, decreases their cytotoxicity, and worsens infection. Transfer of CD8+ IELs rescues severely immunodeficient mice from death following Cryptosporidium challenge. Finally, dietary supplementation of the AHR pro-ligand indole-3-carbinol in newborn mice promotes resistance to infection. Therefore, common dietary metabolites augment the host immune response to cryptosporidiosis, protecting against disease.

Intestinal cDC1s provide IL-12 dependent and independent functions required for CD4 + T cell-mediated resistance to Cryptosporidium

Cryptosporidium is an enteric pathogen that is a prominent cause of diarrheal disease. Control of this infection requires CD4 + T cells, though the processes that lead to T cell-mediated resistance have been difficult to assess. Here, Cryptosporidium parasites that express MHCII-restricted model antigens were generated to dissect the early events that influence CD4 + T cell priming and effector function. These studies highlight that parasite-specific CD4 + T cells are primed in the draining mesenteric lymph node (mesLN) and differentiate into Th1 cells in the gut, where they mediate IFN-γ-dependent control of the infection. Although type 1 conventional dendritic cells (cDC1s) were not required for initial priming of CD4 + T cells, cDC1s were required for CD4 + T cell expansion and gut homing. cDC1s were also a major source of IL-12 that was not required for priming but promoted full differentiation of CD4 + T cells and local production of IFN-γ. Together, these studies reveal distinct roles for cDC1s in shaping CD4 + T cell responses to enteric infection: first to drive early expansion in the mesLN and second to drive effector responses in the gut.

Summary

Cryptosporidium parasites that express model antigens were generated to dissect how parasite-specific CD4 + T cells are primed and mediate effector functions required to control this enteric pathogen. cDC1s produced IL-12p40 and were required for early expansion and gut homing of CD4 + T cells. However, IL-12p40 was only required for the development of Th1 CD4 + T cell effector function in the gut.

Clofazimine-Loaded Mucoadhesive Nanoparticles Prepared by Flash Nanoprecipitation for Strategic Intestinal Delivery

PURPOSE

This study was undertaken to develop novel mucoadhesive formulations of clofazimine (CFZ), a drug candidate for the treatment of cryptosporidiosis, with the aim of strategic delivery to the small intestine, the main site of the disease parasites.

METHODS

CFZ-loaded nanoparticles (nCFZ) coated with non-biodegradable anionic polymer (nCFZ/A) and biodegradable anionic protein complex (nCFZ/dA) were prepared by Flash NanoPrecipitation (FNP) and evaluated for their physicochemical and biopharmaceutical properties.

RESULTS

The mean diameters of nCFZ/A and nCFZ/dA were ca. 90 and 240 nm, respectively, and they showed narrow size distributions and negative ζ-potentials. Both formulations showed higher solubility of CFZ in aqueous solution than crystalline CFZ. Despite their improved dispersion behaviors, both formulations exhibited significantly lower diffusiveness than crystalline CFZ in a diffusion test using artificial mucus (AM). Quartz crystal microbalance analysis showed that both formulations clearly interacted with mucin, which appeared to be responsible for their reduced diffusiveness in AM. These results suggest the potent mucoadhesion of nCFZ/A and nCFZ/dA. After the oral administration of CFZ samples (10 mg-CFZ/kg) to rats, nCFZ/dA and nCFZ/A exhibited a prolongation in T_max by 2 and >9 h, respectively, compared with crystalline CFZ. At 24 h after oral doses of nCFZ/A and nCFZ/dA with mucoadhesion, there were marked increases in the intestinal CFZ concentration (4-7 fold) compared with Lamprene^®, a commercial CFZ product, indicating enhanced CFZ exposure in the small intestine.

CONCLUSION

The use of FNP may produce mucoadhesive CFZ formulations with improved intestinal exposure, possibly offering enhanced anti-cryptosporidium therapy.

Comparative proteomics reveals Cryptosporidium parvum manipulation of the host cell molecular expression and immune response

Cryptosporidium is a life-threating protozoan parasite belonging to the phylum Apicomplexa, which mainly causes gastroenteritis in a variety of vertebrate hosts. Currently, there is a re-emergence of Cryptosporidium infection; however, no fully effective drug or vaccine is available to treat Cryptosporidiosis. In the present study, to better understand the detailed interaction between the host and Cryptosporidium parvum, a large-scale label-free proteomics study was conducted to characterize the changes to the proteome induced by C. parvum infection. Among 4406 proteins identified, 121 proteins were identified as differentially abundant (> 1.5-fold cutoff, P < 0.05) in C. parvum infected HCT-8 cells compared with uninfected cells. Among them, 67 proteins were upregulated, and 54 proteins were downregulated at 36 h post infection. Analysis of the differentially abundant proteins revealed an interferon-centered immune response of the host cells against C. parvum infection and extensive inhibition of metabolism-related enzymes in the host cells caused by infection. Several proteins were further verified using quantitative real-time reverse transcription polymerase chain reaction and western blotting. This systematic analysis of the proteomics of C. parvum-infected HCT-8 cells identified a wide range of functional proteins that participate in host anti-parasite immunity or act as potential targets during infection, providing new insights into the molecular mechanism of C. parvum infection.

Cryptosporidium parvum is an emerging zoonotic pathogen transmitted via the fecal–oral route, and is considered a leading cause of moderate-to-severe diarrheal disease in young children in resource limited areas. After infection, C. parvum parasitizes intestinal epithelial cells and evokes an inflammatory immune response, leading to severe damage of the intestinal mucosa. The infection can be lethal to immunosuppressed individuals. However, no fully effective drug or vaccine is available for cryptosporidiosis, and the pathogenesis and immune mechanisms during C. parvum infection are obscure. Thus, an in-depth understanding of host-parasite interaction is needed. Hence, we established a C. parvum-infected HCT-8 cell model and performed comparative quantitative proteomic analyses to profile global host-parasite interactions and determine the molecular mechanisms that are activated during infection, aiming to offer new insights into the treatment of Cryptosporidium.

CRYPTOSPORIDIUM SPP. IN PET DWARF WINTER WHITE RUSSIAN HAMSTERS (PHODOPUS SUNGORIS SUNGORIS) IN CHINA

Cryptosporidium spp. have been identified in a wide range of hosts, such as humans and domestic and wild animals, while less information about the prevalence of Cryptosporidium spp. in pet hamsters is documented. A total of 351 dwarf winter white Russian hamsters' fecal specimens were collected from 6 pet markets from the cities of Luzhou and Ziyang in Sichuan province in the southwestern part of China. The prevalence of Cryptosporidium spp. determined with nested-PCR amplification of the partial small-subunit (SSU) rRNA gene was 39.32% (138/351). The highest prevalence of Cryptosporidium spp. was in pet market 5 (79.49%, 62/78), followed by pet market 6 (38.64%, 17/44). The lowest prevalence of Cryptosporidium spp. was observed in pet market 3 (14.89%, 7/47). Statistically significant differences in the prevalence of Cryptosporidium spp. were observed among different pet markets (χ2 = 76.386, df = 5, P < 0.05), and a further post hoc test revealed that only pet market 5 was significantly different from other pet markets. Molecular analysis showed that 4 different Cryptosporidium species or genotypes were identified: Cryptosporidium parvum (n = 127), Cryptosporidium chipmunk genotype III (n = 6), Cryptosporidium andersoni (n = 4), and Cryptosporidium wrairi (n = 1). The identification of Cryptosporidium spp. was further tested with the 60-kDa glycoprotein (GP60) gene, and the positive rate was 29.7% (41/138). This is the first molecular report on Cryptosporidium spp. infection in dwarf winter white Russian hamsters in China. With C. parvum and C. andersoni being identified in both humans and pet hamsters, these findings suggest that pet hamsters may be potential reservoirs of zoonotic Cryptosporidium species and subtypes.

A Genetically Tractable, Natural Mouse Model of Cryptosporidiosis Offers Insights into Host Protective Immunity

Cryptosporidium is a leading cause of diarrheal disease and an important contributor to early childhood mortality, malnutrition, and growth faltering. Older children in high endemicity regions appear resistant to infection, while previously unexposed adults remain susceptible. Experimental studies in humans and animals support the development of disease resistance, but we do not understand the mechanisms that underlie protective immunity to Cryptosporidium. Here, we derive an in vivo model of Cryptosporidium infection in immunocompetent C57BL/6 mice by isolating parasites from naturally infected wild mice. Similar to human cryptosporidiosis, this infection causes intestinal pathology, and interferon-γ controls early infection while T cells are critical for clearance. Importantly, mice that controlled a live infection were resistant to secondary challenge and vaccination with attenuated parasites provided protection equal to live infection. Both parasite and host are genetically tractable and this in vivo model will facilitate mechanistic investigation and rational vaccine design.

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We isolated and sequenced Cryptosporidium tyzzeri, a natural mouse pathogen

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C. tyzzeri can be genetically manipulated using CRISPR-driven homologous repair

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C. tyzzeri models human cryptosporidiosis with T cell- and IFN-γ-dependent resolution

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Mice develop protective immunity following both live infection and vaccination

Induction of Inflammatory Responses in Splenocytes by Exosomes Released from Intestinal Epithelial Cells following Cryptosporidium parvum Infection

Cryptosporidium, a protozoan parasite that infects the gastrointestinal epithelium and other mucosal surfaces in humans and animals, is an important opportunistic pathogen in AIDS patients and one of the most common enteric pathogens affecting young children in developing regions. This parasite is referred to as a "minimally invasive" mucosal pathogen, and epithelial cells play a central role in activating and orchestrating host immune responses. We previously demonstrated that Cryptosporidium parvum infection stimulates host epithelial cells to release exosomes, and these released exosomes shuttle several antimicrobial peptides to carry out anti-C. parvum activity. In this study, we detected the upregulation of inflammatory genes in the liver and spleen following C. parvum intestinal infection in neonatal mice. Interestingly, exosomes released from intestinal epithelial cells following C. parvum infection could activate the nuclear factor kappa B signaling pathway and trigger inflammatory gene transcription in isolated primary splenocytes. Several epithelial cell-derived proteins and a subset of parasite RNAs were detected in the exosomes released from C. parvum-infected intestinal epithelial cells. Shuttling of these effector molecules, including the high mobility group box 1 protein, was involved in the induction of inflammatory responses in splenocytes induced by the exosomes released from infected cells. Our data indicate that exosomes released from intestinal epithelial cells upon C. parvum infection can activate immune cells by shuttling various effector molecules, a process that may be relevant to host systemic responses to Cryptosporidium infection.

Involvement of Cryptosporidium parvum Cdg7_FLc_1000 RNA in the Attenuation of Intestinal Epithelial Cell Migration via Trans-Suppression of Host Cell SMPD3

Intestinal infection by Cryptosporidium parvum causes inhibition of epithelial turnover, but underlying mechanisms are unclear. Previous studies demonstrate that a panel of parasite RNA transcripts of low protein-coding potential are delivered into infected epithelial cells. Using in vitro and in vivo models of intestinal cryptosporidiosis, we report here that host delivery of parasite Cdg7_FLc_1000 RNA results in inhibition of epithelial cell migration through suppression of the gene encoding sphingomyelinase 3 (SMPD3). Delivery of Cdg7_FLc_1000 into infected cells promotes the histone methyltransferase G9a-mediated H3K9 methylation in the SMPD3 locus. The DNA-binding transcriptional repressor, PR domain zinc finger protein 1, is required for the assembly of Cdg7_FLc_1000 into the G9a complex and associated with the enrichment of H3K9 methylation at the gene locus. Pathologically, nuclear transfer of Cryptosporidium parvum Cdg7_FLc_1000 RNA is involved in the attenuation of intestinal epithelial cell migration via trans-suppression of host cell SMPD3.

Generating and Maintaining Transgenic Cryptosporidium parvum Parasites

The apicomplexan parasite Cryptosporidium is a leading cause of diarrheal disease and an important contributor to overall global child mortality. We currently lack effective treatment and immune prophylaxis. Recent advances now permit genetic modification of this important pathogen. We expect this to produce rapid advances in fundamental as well as translational research on cryptosporidiosis. Here we outline genetic engineering for Cryptosporidium in sufficient detail to establish transfection in any laboratory that requires access to this key technology. This chapter details the conceptual design consideration, as well as the experimental steps required to transfect, select, and isolate transgenic parasites. We also provide detail on key in vitro and in vivo assays to detect, validate, and quantify genetically modified Cryptosporidium parasites. © 2017 by John Wiley & Sons, Inc.

Cryptosporidium and cryptosporidiosis: The Asian perspective

This review discusses findings of Cryptosporidium and cryptosporidiosis research in Asia and highlights the current situation of Cryptosporidium epidemiology, genetic diversity and distribution, and transmission throughout Asia taking into account all the available papers published for Cryptosporidium research in Asian countries since 2000. This effort will facilitate future research approaches and further developments in the understanding of Cryptosporidium epidemiology in Asia. The intent is to contribute to improvement in protection measures for mitigating the burden associated with this illness in the future.

Therapeutic effects of acetylspiramycin and garlicin on cryptosporidiosis among drug users

Cryptosporidiosis affects humans of all ages, particularly malnourished children and those with compromised immune systems such as HIV/AIDS. This study investigated the therapeutic effects of acetylspiramycin and garlicin on Cryptosporidium infection in institutionalized male drug users receiving rehabilitative treatment. Examination of stool specimens from 903 drug users via modified acid-fast bacilli staining resulted in 172 positive cases. Among them 151 subjects consented to participate in a randomized trial of acetylspiramycin and garlicin in four groups: acetylspiramycin plus garlicin, acetylspiramycin only, garlicin only, and placebo control. The cryptosporidiosis rate was higher in younger subjects with longer drug use history than subjects who are older with shorter history of drug use. After two segments of treatments, 76.2% of the cases achieved negative test results, with the four groups achieving the rates of 92.1%, 76.7%, 72.2%, and 61.8%, respectively (χ(2) = 9.517, P = 0.023). These results indicate clinical potential of garlicin in conjunction with acetylspiramycin in treating cryptosporidiosis.

Rapid microfluidic immunoassay for surveillance and diagnosis of Cryptosporidium infection in human immunodeficiency virus-infected patients

Cryptosporidiosis has been reported to be associated with HIV/acquired immune deficiency syndrome, which greatly reduces the quality of life and shortens the life expectancy of HIV-infected patients. In order to properly treat the infected patients, accurate and automatic diagnostic tools need to be developed. In this study, a novel microfluidic immunochip system was presented for the surveillance and the rapid detection of Cryptosporidium infection in 190 HIV-infected patients from Guangxi, China, using the P23 antigen of Cryptosporidium. The procedure of detection can be completed within 10 min with 2 μl sample consumption. The system also was evaluated using the standard ELISA method. Among 190 HIV-infected individuals, the rate of P23 positivity was 13.7%. Seropositivity in HIV-infected individuals was higher in female patients. The seropositivity to P23 was higher in HIV-infected individuals with high viral load, although the difference was statistically insignificant. Significantly higher Cryptosporidium seropositivity was observed in HIV-infected individuals with a CD4(+) T-cell count of <200 cells/μl than in those with ≥200 cells/μl. Our results also demonstrate that a lower CD4(+) T-cell count may reflect an increased accumulated risk for cryptosporidiosis. The detection system was further validated using the standard ELISA method and good correlation between the two methods was found (r = 0.80). Under the same sensitivity, this new microfluidic chip device had a specificity of 98.2%. This developed system may provide a powerful platform for the fast screening of Cryptospordium infection in HIV-infected patients.

Oxidative stress control by apicomplexan parasites

Apicomplexan parasites cause infectious diseases that are either a severe public health problem or an economic burden. In this paper we will shed light on how oxidative stress can influence the host-pathogen relationship by focusing on three major diseases: babesiosis, coccidiosis, and toxoplasmosis.

Cryptosporidiosis causing severe persistent diarrhea in a patient with multiple myeloma: A Case report and brief review of literature

Cryptosporidiosis is a protozoal infection that leads to self-limited diarrheal disease in immunocompetent individuals and a more severe illness in immunocompromised patients especially those infected with the human immunodeficiency virus. Although patients with hematolymphoid malignancies can develop this infection, it is an uncommon cause of diarrhea in these patients. The patient was a 64-year-old woman, a known case of multiple myeloma for 17 years, who had been treated with multiple lines of chemotherapy earlier. She was being treated with lenalidomide plus dexamethasone for active myeloma at the time of this episode. She presented with profuse watery diarrhea of 15 days duration that was proven to be due to Cryptosporidium parvum on stool examination. The diarrheal illness resolved after treatment with nitazoxanide. Although uncommon, cryptosporidial infection should be suspected in patients with hematological malignancies who have persistent diarrhea. Stool examination with the modified acid-fast Kenyoun stain establishes the diagnosis in the majority of cases. Antiparasitic treatment is effective in controlling the infection.

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.

High anti-Cryptosporidium parvum IgG seroprevalence in HIV-infected adults in Limpopo, South Africa

A seroepidemiological study was performed to determine the seroprevalence of Cryptosporidium in human immunodeficiency virus (HIV)-infected adults and local university students in the Limpopo Province, South Africa. Using a custom anti-C. parvum immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA), the seroprevalence of Cryptosporidium was found to be significantly higher (75.3%; 146 of 193) in HIV-infected individuals compared with student volunteers (32.8%; 19 of 58) (P < 0.001). A more recent diagnosis of HIV was associated with anti-C. parvum IgG seropositivity, as was lower weight among HIV-infected women. This is the first seroepidemiologic study of Cryptosporidium in rural South Africa, and it shows high endemicity among the HIV-infected population. In addition to raising the possibility of significant Cryptosporidium-related morbidities, this finding reveals that in Limpopo and perhaps in other low-income, rural populations, interrupting waterborne pathogen transmission will require strategies effective against environmentally hardy parasites such as Cryptosporidium.

Cryptosporidiosis: An under-recognized public health problem

Cryptosporidium spp. is under recognized as an important pathogen causing diarrhea in children and HIV-infected individuals with associated high morbidity and mortality. In endemic areas, most symptomatic infections are in childhood and in immunocompromised adults. The immune status of the host plays a critical role in determining the severity of cryptosporidiosis. Infection is self-limited in immunocompetent hosts, but can be severe and persistent in the immunocompromised such as AIDS patients or malnourished children. Cryptosporidiosis in developing countries is a major cause of acute and persistent diarrhea in children and is associated with subsequent impairment in growth, physical fitness, and cognitive function. Despite recognition of the importance of immune status, the correlates of protective immunity in cryptosporidiosis in humans are poorly understood, and treatment modalities are limited.

Cryptosporidium pathogenicity and virulence

Cryptosporidium is a protozoan parasite of medical and veterinary importance that causes gastroenteritis in a variety of vertebrate hosts. Several studies have reported different degrees of pathogenicity and virulence among Cryptosporidium species and isolates of the same species as well as evidence of variation in host susceptibility to infection. The identification and validation of Cryptosporidium virulence factors have been hindered by the renowned difficulties pertaining to the in vitro culture and genetic manipulation of this parasite. Nevertheless, substantial progress has been made in identifying putative virulence factors for Cryptosporidium. This progress has been accelerated since the publication of the Cryptosporidium parvum and C. hominis genomes, with the characterization of over 25 putative virulence factors identified by using a variety of immunological and molecular techniques and which are proposed to be involved in aspects of host-pathogen interactions from adhesion and locomotion to invasion and proliferation. Progress has also been made in the contribution of host factors that are associated with variations in both the severity and risk of infection. Here we provide a review comprised of the current state of knowledge on Cryptosporidium infectivity, pathogenesis, and transmissibility in light of our contemporary understanding of microbial virulence.

Human immunodeficiency virus-related gastrointestinal pathology: a southern Africa perspective with review of the literature (part 1: infections)

CONTEXT

Human immunodeficiency virus infection is rife in sub-Saharan Africa and in southern Africa in particular. Despite the increasing availability of antiretroviral therapy in this region, opportunistic infections remain common and frequently involve the gastrointestinal tract.

OBJECTIVE

To review the histopathologic findings and distinguishing features of human immunodeficiency virus-associated gastrointestinal infections in southern Africa and relate those findings to the documented international literature.

DATA SOURCES

The available literature on this topic was reviewed and supplemented with personal experience in a private histopathology practice in South Africa.

CONCLUSIONS

In southern Africa, the range of gastrointestinal, opportunistic infectious pathology in human immunodeficiency virus afflicted patients is diverse and includes viral, bacterial, fungal, and parasitic infections. This infectious pathology is sometimes a manifestation of systemic disease. In profoundly immunocompromised patients, unusual histologic features, involvement of uncommon gastrointestinal tract sites, and more than one pathogen may be seen.

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.

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.

Challenges in understanding the immunopathogenesis of Cryptosporidium infections in humans

Water and foodborne enteric cryptosporidiosis is a globally emerging public health issue. Although the clinical manifestations of enteric cryptosporidiosis are generally limited to intestinal infection and subsequent diarrhoea, extra-intestinal invasion has also been diagnosed in immunocompromised individuals, particularly in those infected with human immunodeficiency virus (HIV) or AIDS. Due to an inadequate understanding of Cryptosporidium immunopathogenesis in humans, the development of vaccines or therapeutic agents and their application in diseases management is difficult. Current therapeutic measures are not fully effective in the treatment of the disease. Therefore, the implementation of strategies designed to control the chain of cryptosporidiosis transmission (environment ↔ human ↔ food/water ↔ animal) is a critical but challenging issue to public health authorities across the world. Several excellent studies have been done on innate, acquired and mucosal immunity against Cryptosporidium infections using animal models, in vitro human cell lines and human volunteers. However, there are still multiple challenges in understanding the intestinal immune response (immunopathogenesis) to Cryptosporidium infection in humans. This paper reviews recent updates on immunopathogenesis and immune responses to Cryptosporidium infection in humans, while also discussing the current limitations that exist regarding a precise understanding of the immunopathological mechanisms.

A screening pipeline for antiparasitic agents targeting cryptosporidium inosine monophosphate dehydrogenase

Background

The protozoan parasite Cryptosporidium parvum is responsible for significant disease burden among children in developing countries. In addition Cryptosporidiosis can result in chronic and life-threatening enteritis in AIDS patients, and the currently available drugs lack efficacy in treating these severe conditions. The discovery and development of novel anti-cryptosporidial therapeutics has been hampered by the poor experimental tractability of this pathogen. While the genome sequencing effort has identified several intriguing new targets including a unique inosine monophosphate dehydrogenase (IMPDH), pursuing these targets and testing inhibitors has been frustratingly difficult.

Methodology and Principal Findings

Here we have developed a pipeline of tools to accelerate the in vivo screening of inhibitors of C. parvum IMPDH. We have genetically engineered the related parasite Toxoplasma gondii to serve as a model of C. parvum infection as the first screen. This assay provides crucial target validation and a large signal window that is currently not possible in assays involving C. parvum. To further develop compounds that pass this first filter, we established a fluorescence-based assay of host cell proliferation, and a C. parvum growth assay that utilizes automated high-content imaging analysis for enhanced throughput.

Conclusions and Significance

We have used these assays to evaluate C. parvum IMPDH inhibitors emerging from our ongoing medicinal chemistry effort and have identified a subset of 1,2,3-triazole ethers that exhibit excellent in vivo selectivity in the T. gondii model and improved anti-cryptosporidial activity.

Persistent diarrhea is a leading cause of illness and death among impoverished children, and a growing share of this disease burden can be attributed to the parasite Cryptosporidium. There are no vaccines to prevent Cryptosporidium infection, and the treatment options are limited and unreliable. Critically, no effective treatment exists for children or adults suffering from AIDS. Cryptosporidium presents many technical obstacles for drug discovery; perhaps the most important roadblock is the difficulty of monitoring drug action. Here we have developed a set of methods to accelerate the drug discovery process for cryptosporidiosis. We exploit the opportunities for experimental manipulation in the related parasite Toxoplasma to genetically engineer a Cryptosporidium model. This new model parasite mirrors the metabolism of Cryptosporidium for a particularly promising drug target that supplies the building blocks for DNA and RNA. Drug effectiveness can be assayed through simple fluorescence measurements for many candidates. Using this assay as an initial filter, and adapting other assays to a high throughput format, we identify several novel chemical compounds that exhibit markedly improved anti-cryptosporidial activity and excellent selectivity.

Human CD8(+) T cells clear Cryptosporidium parvum from infected intestinal epithelial cells

Intracellular protozoans of the genus Cryptosporidium are a major cause of diarrheal illness worldwide, especially in immunocompromised individuals. CD4(+) T cells and interferon-gamma are key factors in the control of cryptosporidiosis in human and murine models. Previous studies led us to hypothesize that CD8(+) T cells contribute to clearance of intestinal epithelial Cryptosporidium infection in humans. We report here that antigen expanded sensitized CD8(+) T cells reduce the parasite load in infected intestinal epithelial cell cultures and lyse infected intestinal epithelial cells. These effects are most likely mediated by the release of cytotoxic granules. Elimination of parasites seems to require antigen presentation through both human leukocyte antigen (HLA)-A and HLA-B. These data suggest that cytotoxic CD8(+) T cells play a role in clearing Cryptosporidium from the intestine, a previously unrecognized feature of the human immune response against this parasite.

Charting the proteome of Cryptosporidium parvum sporozoites using sequence similarity-based BLAST searching

Cryptosporidium (C.) spp. are important zoonotic parasites causing widespread diarrhoeal disease in man and animals. The recent release of the complete genome sequences for C. parvum and C. hominis has facilitated the comprehensive global proteome analysis of these opportunistic pathogens. The well-known approach for mass spectrometry (MS) based data analysis using the BLAST tool (MS BLAST) is a database search protocol for identifying unknown proteins by sequence similarity to homologous proteins using peptide sequences produced by mass spectrometry. We have used several complementary approaches to explore the global sporozoite proteome of C. parvum with available proteomic tools. To optimize the output of the MS data, a sequence similarity-based MS BLAST strategy was employed for bioinformatic analysis. Most significantly, almost all the constituents of glycolysis and several mitochondrion-related proteins were identified. In addition, many hypothetical Cryptosporidium proteins were validated by the identification of their constituent peptides. The MS BLAST approach was found to be useful during the study and could provide valuable information towards a complete understanding of the unique biology of Cryptosporidium.

Echinococcus, Giardia and Cryptosporidium: observational studies challenging accepted dogma

The development of in vitro culture systems that allow the maintenance, and support the development of Echinococcus, Giardia and Cryptosporidium in the laboratory have had a significant impact on their biology and taxonomy and the epidemiology of infections they cause. This short retrospective review demonstrates how radical shifts in our understanding have occurred as a result of being able to grow these organisms in culture, and how molecular tools have helped in the interpretation of such research that often reflects the observations of earlier workers.

HIV-1 Tat protein suppresses cholangiocyte toll-like receptor 4 expression and defense against Cryptosporidium parvum

Biliary cryptosporidiosis is associated with acquired immunodeficiency syndrome (AIDS) cholangiopathy and occurs almost exclusively in adult patients with AIDS. Infection of biliary epithelial cells (cholangiocytes) with Cryptosporidium parvum induces Toll-like receptor (TLR) 4 expression and stimulates a TLR-dependent response against infection. Here, we tested whether human immunodeficiency virus type 1 (HIV-1) Tat affects TLR expression and, hence, anti-C. parvum defense responses. Using an in vitro model of human biliary cryptosporidiosis, we found that recombinant Tat protein increased TLR4 mRNA expression in both uninfected and C. parvum-infected cholangiocytes. Conversely, Tat decreased TLR4 protein levels and suppressed C. parvum-induced TLR4 protein expression. Using actinomycin to inhibit transcription, we found that Tat increased the half-life of TLR4 mRNA from approximately 25 to 60 min, and RNA gel-shift assays demonstrated direct binding of Tat to TLR4 mRNA. In vitro transcription/translation studies suggested that Tat does not affect transcription but does decrease TLR4 translation. Importantly, more parasites were found in Tat-treated cells than in control cells 48 h after infection. These findings suggest that Tat inhibits cholangiocyte TLR4 protein expression through translational inhibition. These events appear to diminish the ability of cholangiocytes to initiate an innate immune response to C. parvum. We suggest that these findings may contribute to the unusual susceptibility of HIV-infected individuals to biliary cryptosporidiosis.

Risks of recreational exposure to waterborne pathogens among persons with HIV/AIDS in Baltimore, Maryland

OBJECTIVES

We assessed the prevalence of recreational activities in the waterways of Baltimore, MD, and the risk of exposure to Cryptosporidium among persons with HIV/AIDS.

METHODS

We studied patients at the Johns Hopkins Moore Outpatient AIDS Clinic. We conducted oral interviews with a convenience sample of 157 HIV/AIDS patients to ascertain the sites used for recreational water contact within Baltimore waters and assess risk behaviors.

RESULTS

Approximately 48% of respondents reported participating in recreational water activities (fishing, crabbing, boating, and swimming). Men and women were almost equally likely to engage in recreational water activities (53.3% versus 51.3%). Approximately 67% (105 of 157) ate their own catch or that of friends or family members, and a majority (61%, or 46 of 75) of respondents who reported recreational water contact reported consumption of their own catch.

CONCLUSIONS

Baltimoreans with HIV/AIDS are engaging in recreational water activities in urban waters that may expose them to waterborne pathogens and recreational water illnesses. Susceptible persons, such as patients with HIV/AIDS, should be cautioned regarding potential microbial risks from recreational water contact with surface waters.

Polymorphic mucin antigens CpMuc4 and CpMuc5 are integral to Cryptosporidium parvum infection in vitro

Cryptosporidium, a waterborne enteric parasite, is a frequent cause of diarrheal disease outbreaks worldwide. Thus far, the few antigens shown to be important for attachment to and invasion of the host cell by Cryptosporidium are all mucin-like glycoproteins. In order to investigate other antigens that could be important for Cryptosporidium host-parasite interactions, the Cryptosporidium genome databases were mined for other mucin-like genes. A single locus of seven small mucin sequences was identified on chromosome 2 (CpMuc1 to -7). Reverse transcriptase PCR analysis demonstrated that all seven CpMucs were expressed throughout intracellular development. CpMuc4 and CpMuc5 were selected for further investigation because of the significant sequence divergence between Cryptosporidium parvum and C. hominis alleles. Rabbit anti-CpMuc5 and -CpMuc4 antibodies identified several polypeptides in C. parvum lysates, suggestive of proteolytic processing of the mucins. All polypeptides were larger than the predicted molecular weight, which is suggestive of posttranslational processing, most likely O-glycosylation. In immunofluorescence assays, both anti-CpMuc4 and -CpMuc5 antibodies reacted with the apical region of sporozoites and revealed surface-exposed epitopes. The antigens were not shed during excystation but did partition into the aqueous phase of Triton X-114 extractions. Consistent with a role in attachment and invasion, CpMuc4 and CpMuc5 could be detected binding to fixed Caco-2A cells, and anti-CpMuc4 peptide antibodies inhibited Cryptosporidium infection in vitro. Sequencing of CpMuc4 and CpMuc5 from C. hominis clinical isolates identified several polymorphic alleles. The data suggest that these antigens are integral for Cryptosporidium infection in vitro and may be potential vaccine candidates.

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.

High-yield amplification of Cryptosporidium parvum in interferon gamma receptor knockout mice

To date, large-scale production of Cryptosporidium parvum oocysts has only been achieved by amplification in neonatal calves and sheep. Many laboratories currently depend on supplies from external sources and store oocysts for prolonged periods which results in progressive loss of viability. Six to 8-week-old interferon gamma receptor knockout (IFN gamma R-KO) mice on a C57BL/6 background were inoculated by gavage (2000 oocysts/animal). Fecal pellets were collected daily from 7 days post-infection (p.i.) up to 2 weeks p.i. Intestinal oocyst yield was assessed at days 11, 12 and 14 p.i. by homogenization of intestinal tissues. Ether extraction and one or more NaCl flotations were used to purify oocysts. Total recoveries averaged 2.6 x 10(6) oocysts/mouse from fecal material and 3.8 x 10(7) oocysts/mouse from intestinal tissues. Overall, 2.3 x 10(9) purified oocysts were obtained from 60 mice. Recovered oocysts were capable of sporulation and were shown to be infectious both in vitro and in vivo. Oocyst amplification was achieved in only 11-14 days with minimal expense. The simplicity of this method presents a practical alternative for the routine passage, maintenance and storage of C. parvum in biomedical laboratories.

Cryptosporidium parvum-associated sclerosing cholangitis in a liver transplant patient

Cryptosporidium parvum causes severe long-standing diarrhea in immunocompromised patients. Sclerosing cholangitis caused by C. parvum is a rare complication in transplant recipients. We report herein the presentation of Cryptosporidium-associated cholangitis in an adult liver transplant patient diagnosed by liver biopsy. The patient improved on treatment with azithromycin and paromomycin.

Severe cryptosporidiosis in a seven-year-old renal transplant recipient: case report and review of the literature

Cryptosporidium is an intracellular protozoa that can cause gastroenteritis in humans. In immunocompromised hosts, infection can be severe, leading to life-threatening persistent diarrhea. There is limited experience in treating this infection in solid organ transplants. Although newer drugs active against Cryptosporidium exist, they are only licensed in the USA for treatment of immunocompetent hosts. Here we describe a seven-year-old renal transplant recipient with severe cryptosporidiosis. He had a protracted course of diarrhea of up to 2 L/day. He was successfully managed with combination antimicrobial therapy including nitazoxanide, paromomycin, and azithromycin. In conjunction with this regimen, he had a reduction in immunosuppression and complete bowel rest. His stool pattern normalized in four weeks and he has had no recurrence after six months of follow up.

[Cryptosporidium hominis diarrhea outbreak and transmission linked to diaper infant use]

BACKGROUND AND OBJECTIVE

On the basis of several cases of cryptosporidiosis detected in a child day-care center, we stablished the extent of the outbreak and investigated causes of parasite transmission.

PATIENTS AND METHOD

A retrospective cohort study was designed on all children attending day-care center and care givers to determine their infection status and identify risk factors associated to the outbreak.

RESULTS

24 cases of cryptosporidiosis were detected, with an attack rate of 0.46 (24/52); 12 of them were parasitologycally confirmed. All care givers were negative for Cryptosporidium and none of them reported symptoms of acute gastroenteritis. Transmission pattern was compatible with person to person modes. Among the factors investigated, two were associated with the risk of disease: diaper wear (relative risk = 2.06; p = 0.059); and diarrhea in relatives (relative risk = 2.05; p = 0.01). In all confirmed cases, Cryptosporidium hominis (previously known as C. parvum, genotype 1), was identified.

CONCLUSIONS

Cryptosporidiosis should be considered as a possible cause of outbreaks of gastroenteritis at day-care centers. Increasing care on diaper changing practices, specially over children with diarrhea, may be the key factor to prevent transmission of Cryptosporidium.

The human immunodeficiency virus type 1 tat protein enhances Cryptosporidium parvum-induced apoptosis in cholangiocytes via a Fas ligand-dependent mechanism

While Cryptosporidium parvum infection of the intestine has been reported in both immunocompetent and immunocompromised individuals, biliary infection is seen primarily in adult AIDS patients and is associated with development of AIDS cholangiopathy. However, the mechanisms of pathogen-induced AIDS cholangiopathy remain unclear. Since we previously demonstrated that the Fas/Fas ligand (FasL) system is involved in paracrine-mediated C. parvum cytopathicity in cholangiocytes, we also tested the potential synergistic effects of human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat)-mediated FasL regulation on C. parvum-induced apoptosis in cholangiocytes by semiquantitative reverse transcription-PCR, immunoblotting, immunofluorescence analysis, and immunogold electron microscopy. H69 cells do not express CXCR4 and CCR5, which are receptors required for direct HIV-1 viral infection. However, recombinant biologically active HIV-1-associated Tat protein increased FasL expression in the cytoplasm of cholangiocytes without a significant increase in apoptosis. We found that C. parvum-induced apoptosis was associated with translocation of intracellular FasL to the cell membrane surface and release of full-length FasL from infected H69 cells. Tat significantly (P < 0.05) increased C. parvum-induced apoptosis in bystander cells in a dose-dependent manner. Moreover, Tat enhanced both C. parvum-induced FasL membrane translocation and release of full-length FasL. In addition, the FasL neutralizing antibody NOK-1 and the caspase-8 inhibitor Z-IETD-fmk both blocked C. parvum-induced apoptosis in cholangiocytes. The data demonstrated that HIV-1 Tat enhances C. parvum-induced cholangiocyte apoptosis via a paracrine-mediated, FasL-dependent mechanism. Our results suggest that concurrent active HIV replication, with associated production of Tat protein, and C. parvum infection synergistically increase cholangiocyte apoptosis and thus jointly contribute to AIDS-related cholangiopathies.

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.

What is Cryptosporidium? Reappraising its biology and phylogenetic affinities

In raising the question "What is Cryptosporidium?", we aim to emphasize a growing need to re-evaluate the affinities of Cryptosporidium species within the phylum Apicomplexa so as to better understand the biology and ecology of these parasites. Here, we have compiled evidence from a variety of molecular and biological studies to build a convincing case for distancing Cryptosporidium species from the coccidia conceptually, biologically and taxonomically. We suggest that Cryptosporidium species must no longer be considered unusual or unique coccidia but rather seen for what they are--a distantly related lineage of apicomplexan parasites that are not in fact coccidia but that do occupy many of the same ecological niches. Looking at Cryptosporidium species without traditional coccidian blinders is likely to reveal new avenues of investigation into pathogenesis, epidemiology, treatment and control of these ubiquitous pathogens.

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.