The pathogenesis of experimental infections of Cryptosporidium muris (strain RN 66) in outbred nude mice

Three groups of six-week-old nude outbred mice were orally infected with 400, 20,000 and 1,000,000 oocysts of Cryptosporidium muris (strain RN 66) per mouse, respectively. Oocysts were detected in the faeces from 10-18 days post-infection (p.i.) and continued to be shed in large numbers in all groups until the termination of the trial on day 89 p.i. Clinical signs were not observed in any of the infected mice and there was no significant effect on weight gain compared to uninfected controls. Histological examination revealed the presence of parasites confined to the glandular stomach. Parasitised gastric glands were dilated, hypertrophied and filled with numerous parasites. The glands had lost their normal cellular architecture and were lined with many undifferentiated cells. In some mice receiving the largest innoculum, the glandular mucosa was congested and the lamina propria infiltrated with eosinophils, polymorphs and lymphocytes.

Cryptosporidium parvum induces apoptosis in biliary epithelia by a Fas/Fas ligand-dependent mechanism

Although the clinical features of sclerosing cholangitis from opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which associated pathogens, such as Cryptosporidium parvum, cause disease are obscure. Using an in vitro model of biliary cryptosporidiosis, we observed that C. parvum induces apoptosis in cultured human biliary epithelia. Both caspase protease inhibitors and neutralizing antibodies to either Fas receptor (Fas) and Fas ligand (FasL) inhibited this process; neutralizing antibodies to other apoptotic cytokines [interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta)] had no effect. C. parvum stimulated FasL membrane surface translocation, increased both FasL and Fas protein expression in infected biliary epithelia, and induced a marked increase of soluble FasL (but not IL-1beta, TNF-alpha, and TGF-beta) in supernatants from infected cells. When a coculture model is used in which infected and uninfected cell populations were physically separated by a semipermeable membrane, both uninfected biliary epithelia and uninfected Fas-sensitive Jurkat cells (but not a Fas-resistant Jurkat cell line) underwent apoptosis when cocultured with infected biliary epithelia. Moreover, both a neutralizing antibody to FasL and a metalloprotease inhibitor blocked the apoptosis in uninfected cocultured cells. Activation of caspase activity was also observed in uninfected cocultured biliary epithelia. The data suggest that C. parvum induces apoptosis in biliary epithelia by a Fas/FasL-dependent mechanism involving both autocrine and paracrine pathways. These observations may be relevant to both the pathogenesis and therapy of the cholangitis seen in AIDS patients with biliary cryptosporidiosis.

Experimental respiratory cryptosporidiosis in immunosuppressed rats: a light and electron microscopy study

Cryptosporidium parvum is a coccidian protozoon that causes diarrhoeal enteritis in immunocompetent and immunocompromised humans and other mammals. Sometimes, chiefly in HIV-infected subjects, anatomical sites other than gastro-intestinal tract, such as the biliary and respiratory tree, are involved. We performed an experimental respiratory infection in immunosuppressed albino rats with a C. parvum human-derived isolate, to confirm the possibility of a primary infection at this site and to evaluate the protozoan damages by light and also by transmission electron microscopy (TEM). The animals were infected intratracheally with 1 x 10(6) C. parvum oocysts/ml and, from the 7th day post-infection, biological specimens of trachea, bronchi, lung and ileum were zoopsied. A sole cryptosporidial colonization of the respiratory tract, from the trachea to the median bronchi, without lung parenchyma infection, was observed. Moreover 13/33 (39.4%) rats also developed intestinal infection. TEM study of the respiratory tree specimens demonstrated that cryptosporidia infect either ciliated or goblet cells, and confirmed the role of microvilli in the parasite cell adhesion. The most relevant alterations involved the ciliated cells, with loss of cilia and nuclear and cytoplasmic damages.

Liver and bile duct pathology following Cryptosporidium parvum infection of immunodeficient mice

Patients with acquired immune deficiency syndrome (AIDS) and boys with mutations of the CD154 gene (causing congenital X-linked immunodeficiency with hyper-IgM [XHIM]) are susceptible to chronic infections of the biliary tract with Cryptosporidium parvum (CP) that may lead to biliary sclerosis and ultimately to cholangiocarcinoma. To determine whether the CP infection and the consequent immune response contribute independently to this morbidity, we infected mice with severe combined immunodeficiency (SCID) or with disrupted genes for CD154, CD40, or interferon gamma (IFN-gamma) with CP. Even when CP infection persisted for 16 weeks, the SCID mice developed only mild triaditis, without apoptosis of biliary epithelial cells (BEC). Fifty percent of the CD154 knockout mice developed lobular hepatitis with acute and chronic triaditis. The CD40 knockout mice developed marked triaditis, and the IFN-gamma knockouts either succumbed to enteritis or survived to develop marked triaditis, portal fibrosis, biliary sclerosis, necrosis with dilation of duct-like structures within the porta hepatis, and dysplastic changes. CP-infected SCID mice reconstituted with T cells from IFN-gamma knockout donors either developed severe enteritis or survived to develop triaditis, cholangitis, lobular hepatitis with periductular sclerosis, and scarring. Mice with disruptions of both the CD40 and IFN-gamma genes remained infected by CP and developed bile duct and liver disease, but not enteritis. Our results suggest that T-cell cytokines are required for the inflammatory and sclerosing responses to CP infection in immunodeficient animals. The response of immunodeficient mice to CP infection may model at least the initial steps toward the development of sclerosing cholangitis or bile duct cancers in XHIM patients.

Cytomegalovirus and Cryptosporidium infections in AIDS: a necropsy study

A case of coinfection of cytomegalovirus (CMV) and Cryptosporidium in an AIDS patient is reported. Chronic diarrhea was the presenting symptom. Etiologic agents were diagnosed only at postmortem evaluation. CMV intranuclear inclusions were seen in the terminal ileum, colon and vermiform appendix. Cryptosporidium oocysts were also present in the intestinal brush border of the colon. Improvement of diagnostic procedures such as colonic biopsy and the use of appropriate staining procedure for AIDS patients with diarrhea can help identify the cause of illness.

Protection of kids against Cryptosporidium parvum infection after immunization of dams with CP15-DNA

In this study the effectiveness of a DNA vaccine to confer protection against cryptosporidiosis, an enteric infection of lifestock and humans, was evaluated. A vaccination protocol using a recombinant plasmid encoding the 15 kDa surface sporozoite protein of Cryptosporidium parvum was developed in adult pregnant goats. The present study reports that nasal immunization of pregnant goats with CP15-DNA led to a transfer of immunity to offspring conferring protection against C. parvum infection. Kids from CP15-DNA-vaccinated dams shed significantly fewer oocysts and over a shorter period than did kids from unvaccinated goats. The low level of parasite development in protected kids did not affect their growth whereas unprotected kids grew much slowly. There was still a significant difference in the weights of protected and unprotected kids after complete recovery. Anti-CP15 antibodies were present in serum and colostrum from vaccinated goats. Nevertheless, the precise immune mechanism of protection has still to be determined. This vaccine should reduce the economic losses due to cryptosporidiosis in ruminants, specially in small ruminants (calves, lambs, kids). It has also the potential to reduce environmental contamination by reducing oocyst shedding.

Gastric cryptosporidiosis: correlation between intensity of infection and histological alterations

AIMS

A retrospective study was carried out to determine the histopathological alterations of the gastric mucosa associated with the presence of Cryptosporidium parasites in the stomach.

METHODS AND RESULTS

Gastric biopsies from eight patients with AIDS and cryptosporidiosis were reviewed. Most individuals were males (7/8, mean age 34.7 years) intravenous drug users (6/8), with very low peripheral blood CD4 lymphocyte counts (< 150/mm3; mean 56/mm3). Endoscopic examination showed no significant mucosal abnormalities in half of the individuals; inflammation was observed in the other four individuals and was associated with erosions in two cases. The lesions observed (reactive changes, oedema, erosions, etc.) are not pathognomonic, since they are seen in most common acute and chronic gastrititis of various aetiologies (toxic, infectious, mechanical). The histological examination showed Cryptosporidium parasites in the antrum-pylorus of all examined persons, whereas only two of them had parasites in the corpus. Modifications of histological features consisted mostly of hyperplastic reactive changes of the gland epithelial and inflammation in the connective tissue of the lamina propria. No clear correlation was found between endoscopy and histological findings, whereas a close correlation between intensity of the infection and degree of histological alterations was observed.

CONCLUSION

These findings suggest that, in individuals with AIDS, cryptosporidiosis and severe immunodepression, upper endoscopy with random gastric biopsies should be performed, even in the absence of endoscopically appreciable lesions. The diagnosis of gastric cryptosporidiosis has to rely on histological findings, and pathologists must be aware of the fact that Cryptosporidium parasites are mainly found in areas showing reactive hyperplasia.

Cryptosporidiosis in a black bear in Virginia

Cryptosporidiosis has not been previously reported in black bears in North America, either free-roaming or captive. However, oocysts have been documented in two captive Malayan sun bears (Helarctos malayanus) located in zoological parks in Taiwan. Developmental stages of Cryptosporidium parvum were observed in tissue sections from the small intestine of a black bear cub found dead in Virginia (USA).

Pathogenesis of Cryptosporidium parvum infection

Cryptosporidium parvum can be regarded as a minimally invasive mucosal pathogen, since it invades surface epithelial cells that line the intestinal tract but does not invade deeper layers of the intestinal mucosa. Nonetheless, infection can be associated with diarrhea and marked mucosal inflammation. This article briefly reviews in vitro and in vivo models useful for studying the pathogenesis of C. parvum infection and explores the role of innate and acquired immune responses in host defense against this protozoan parasite.

A clinicopathologic analysis of AIDS-related cryptosporidiosis

OBJECTIVE

To characterize the histology of AIDS-associated cryptosporidiosis and identify features that explain the clinical variability.

DESIGN

A retrospective analysis of HIV-positive individuals with cryptosporidiosis who underwent endoscopy at the Johns Hopkins Hospital between 1985 and 1996.

METHODS

The histologic features (intensity of Cryptosporidium infection, inflammation, mucosal damage, copathogens) of gastrointestinal biopsies from 37 HIV-positive individuals with cryptosporidiosis were systematically graded. These histologic features were correlated with the severity of the diarrheal illness obtained from a patient chart review.

RESULTS

Histologic features associated with Cryptosporidium infection include a neutrophilic infiltrate in the stomach, villus blunting in the duodenum, cryptitis and epithelial apoptosis in the colon, and reactive epithelial changes in the stomach and duodenum. The nature and intensity of the inflammatory response varied widely; however, duodenal biopsies from a subset of patients (37%) revealed marked acute inflammation that was associated with concomitant cytomegalovirus infection. Although duodenal infection was common (93% of individuals), infection of other sites was variable (gastric cryptosporidiosis in 40% and colonic cryptosporidiosis in 74%). Widespread infection of the intestinal tract, which included both the large and small intestine, was associated with the most severe diarrheal illness.

CONCLUSIONS

Cryptosporidium infection produces histologic evidence of gastrointestinal mucosal injury. The inflammatory response to the infection is variable, and may be modified by copathogens such as cytomegalovirus. The clinical manifestations are influenced, in part, by the anatomic distribution of the infection, with extensive infections involving both small and large intestines producing the most severe illness.

Ultrastructural details of Cryptosporidium parvum development in calf intestine

Cryptosporidium parvum and C. muris appear to be different species found in calves, with different oocysts size and distribution on the gastrointestinal tract. This work presents new images of C. parvum ultrastructure in calf intestine, mainly its development in nonmicrovillous cells and the presence of microtubular structures in the membrane enveloping the macrogamonts and immature oocysts.

Variable distribution of Cryptosporidium parvum in the intestine of AIDS patients revealed by polymerase chain reaction

OBJECTIVE

Cryptosporidium parvum is associated with persistent diarrhoea and malnutrition in children, with large waterborne outbreaks and with the diarrhoea-wasting syndrome in AIDS. However, pathophysiology of infection remains to be defined and the reasons for the variability of clinical features are uncertain. The polymerase chain reaction (PCR) is valuable for the analysis of infections with non-culturable organisms because of its high sensitivity, so we compared PCR and microscopy as tools for the analysis of the distribution of infection.

DESIGN

PCR was compared with light microscopy (LM) and electron microscopy (EM) in duodenal biopsies from a well characterized series of 75 Zambian AIDS patients. PCR and LM were then used to define the distribution of infection in biopsies from duodenum, ileum, right colon and left colon in eight South African patients with persistent AIDS-related cryptosporidiosis.

RESULTS

PCR specifically detected 10 fg of genomic C. parvum DNA. When applied to duodenal biopsies from 75 Zambian AIDS patients, infection was detected in all seven cases of duodenal cryptosporidiosis that were identified by LM or EM and in six additional cases which appeared to be negative by microscopy. Distribution of infection was defined in six of eight South African AIDS patients. Two had pan-enteric infection, three had small bowel infection and one had purely ileo-colonic infection. In two cases infection could not be localized despite using PCR, suggesting that infection was confined to the inaccessible mid-small intestine.

CONCLUSIONS

PCR detection of C. parvum DNA demonstrated that infection is highly variable in distribution, which must be taken into account when designing and interpreting studies of pathophysiology.

Gastric cryptosporidiosis in a wild frilled lizard from Australia

An adult male frilled lizard (Chlamydosaurus kingi) was found dead in Northern Territory (Australia). On physical examination it was found to be severely emaciated. At necropsy the stomach was found to be firm with mild thickening of the gastric mucosa. Gastric rugae were prominent and the mucosa was red with a thin layer of dark red mucus on its surface. Light microscopic examination revealed a mild diffuse gastritis with infiltration of the lamina propria by lymphocytes, plasma cells, and heterophils. Large numbers of small, round amphophilic to basophilic (2 to 4 microns in diameter) organisms morphologically consistent with cryptosporidia were seen on the surface of the mucosal epithelium and free in the gastric lumen. The gastric lesions seen in this frilled lizard did not involve atrophy, as previously described in lizards with gastric cryptosporidiosis, and were similar to those described in snakes. The possibility that more than one species of Cryptosporidium parasitizes reptiles could explain the different lesions. This is the first report of cryptosporidiosis in a frilled lizard.

Cryptosporidiosis in patients with AIDS: correlates of disease and survival

Although 10%-15% of patients with AIDS in the United States may acquire cryptosporidium infection, little data exist on clinical or histological characteristics that differentiate clinical outcomes. A case-control study of 83 HIV-positive adult patients with cryptosporidiosis was conducted, as was a histopathologic review of data on gastrointestinal biopsy specimens from 30 patients. Four clinical syndromes were identified: chronic diarrhea (36% of patients), choleralike disease (33%), transient diarrhea (15%), and relapsing illness (15%). A multivariate analysis of data for cases and controls revealed that acquiring cryptosporidiosis was associated with the presence of candidal esophagitis (odds ratio [OR], 2.53; P < .002) and Caucasian race (OR, 6.71; P = .0001) but not with sexual orientation. Cases had a significantly shorter duration of survival from the time of diagnosis than did controls (240 vs. 666 days, respectively; P = .0004), which was independent of sex, race, or or injection drug use. Antiretroviral use was protective against disease (OR, 0.072; P = .0001). All four clinical syndromes were represented among the histological data. There was no statistically significant correlation between histological intensity of infection and clinical severity of illness.

Survey of Cryptosporidium oocysts from adult cattle in a slaughter house

Cryptosporidian oocysts were surveyed in rectal stools of adult cattle which were carried into slaughterhouse from April 1995 to July 1996. We morphologically and histologically investigated oocysts, and experimentally infected the isolated oocysts to mice and rats. Cryptosporidian oocysts were detected from 24 of 512 cattle (4.7%). They were spherical or ovoid, and the size was 7.0-7.9 x 5.3-6.1 microm. Mice and rats inoculated orally with 10(5)-10(7) oocysts became infected and discharged oocysts in the feces for a period of more than two months. Developing parasites were detected from the stomach of mice, and not detected from the other digestive tract. From these findings, present isolates from cattle were identified as Cryptosporidium muris.

Interaction of chicken anaemia virus and Cryptosporidium baileyi in experimentally infected chickens

The natural occurrence of concomitant chicken anaemia virus (CAV) and Cryptosporidium baileyi infection was described earlier. In this experiment, 1-day-old chickens were infected with CAV alone (anaemia virus infected, AI) or followed by inoculation with 8 x 10(5) C. baileyi oocysts orally at 1 wk of age (anaemia virus and Cryptosporidium infected, ACI). Another group of chickens received the same dose of C. baileyi oocysts without previous virus infection (Cryptosporidium infected, CI), and two groups of uninfected chickens served as controls. Except one group (uninfected control, UC), all groups -- including the other control group (challenged control, CC) -- were challenged with an oral inoculum of 8 x 10(5) C. baileyi oocysts at the age of 4 wk. Haematological, serological, immunohistochemical and pathological findings confirmed the effect of the virus agent. The individual C. baileyi oocyst shedding did not show significant difference between group CI and ACI, however, after challenge infection the AI chickens shed approximately three times more C. baileyi oocysts than those in group CC. Mortality and the percentage of birds that developed anaemia was significantly higher among ACI than AI chickens, while haematocrit values at 2 wk of age and relative bursal weights at 4 wk of age were moderately lower in the ACI group. The results presented here suggest that concurrent CAV infection increases the reproductive potential of C. baileyi in chickens, and both pathogens have synergistic effect on each other.

Fatal cryptosporidiosis in a juvenile captive African hedgehog (Ateletrix albiventris)

Fatal intestinal cryptosporidiosis of unknown source and unexplained epizootiology is reported in a neonatal captive African hedgehog (Ateletrinx albiventris) and for the first time in a hedgehog species. The infection, confined to ileum, jejunum, and colon, was extremely severe in the lower jejunum where over 75% of the epithelial cells harbored the pathogen. The ileum and the jejunum displayed moderate and severe villus atrophy and mucosal hyperplasia. Lamina propria and mucosa were infiltrated by eosinophils, lymphocytes, and macrophages. Developmental stages of Cryptosporidium sp. produced a positive reaction with immunofluorescent antibody for detection of the human pathogen, Cryptosporidium parvum. Personnel of captive centers with hedgehogs should be alerted and undertake appropriate precautions to prevent zoonotic transmission. Commercially offered hedgehog-pets may pose a risk for Cryptosporidium infection for human immunodeficiency virus-infected people.

[Cryptosporidiosis in adders (Pituiophis melanoleucus sayi)]

Infection of snakes with cryptosporidia is known to occur as hypertrophic gastritis associated with postprandial regurgitation. This is a report of a severe and fatal intestinal cryptosporidiosis in a group of snakes (Pituophis melanoleucus sayi) kept at a zoological garden. The clinical and pathological findings are described and discussed in this paper. Pathohistologically fibrinous, diphtheroid and necrotizing enteritides were diagnosed. Histological examination was completed by electron microscopy. Transmission electron microscopic examination revealed numerous cryptosporidia in close contact to the luminal surface of the intestinal epithelial cells. Different cryptosporidial stages developing in parasitophorous vacuoles occurred. By scanning electron microscopy the superficial localisation of the cryptosporidia in the damaged brush border of the intestinal epithelial cells was demonstrated. In addition, the ultrastructural examination of the small intestine of three animals revealed adenovirus-like particles.

Treatment of HIV-1-associated microsporidiosis and cryptosporidiosis with combination antiretroviral therapy

BACKGROUND

Enterocytozoon bieneusi and Cryptosporidium parvum cause chronic antimicrobial-resistant gastrointestinal infections in HIV-1-infected individuals. HIV-1 reverse transcriptase inhibitors delay the onset of opportunistic infections, but are not known to reverse established infections. HIV-1 protease inhibitors are more effective across a broader range of HIV-1-infected immune cells. Combination antiretroviral therapy that includes a protease inhibitor could improve immunity to E bieneusi and C parvum.

METHODS

HIV-1 infected patients with chronic microsporidiosis (five), cryptosporidiosis (three), or dual infection (one), were treated with combination therapy that included at least one HIV-1 protease inhibitor. Outcome measures were symptoms, weight, use of antidiarrhoeal and antimicrobial drugs, T-lymphocyte subsets, HIV-1 viraemia, stool microscopy, and biopsy by endoscopy.

FINDINGS

All patients had complete clinical responses, gained a median 15 kg in weight, and ceased all antidiarrhoeal and antimicrobial therapies. Biliary cryptosporidiosis responded in both affected patients. Neither pathogen was detected in follow-up stool microscopy (eight of eight patients) or in biopsy samples by endoscopy (five of five). Intestinal architecture returned to normal in three patients. There was a dense CD8 lymphocyte and macrophage infiltrate and staining of intraepithelial E bieneusi with interferon-gamma before and after treatment, but little staining for CD4 or B lymphocytes, interleukin 10, or HIV-1 gp41. Five patients remained symptom-free after a median 13 months follow-up. Four patients had recurrent diarrhoea at 7-13 months (one with positive stool microscopy), associated with declining CD4 counts.

INTERPRETATION

Combination antiretroviral therapy that includes a protease inhibitor can restore immunity to E bieneusi or C parvum in HIV-1 infected individuals, and result in complete clinical, microbiological, and histological responses. The persistent CD8 cell and macrophage infiltrate, and the rapid time to relapse in patients with declining CD4 lymphocyte counts, suggest that neither infection was eradicated.

Enteropathy in Zambians with HIV related diarrhoea: regression modelling of potential determinants of mucosal damage

BACKGROUND

AIDS is characterised by small intestinal mucosal damage, but its aetiopathogenesis is poorly understood. Enteric infections in Africa differ from those in northern countries, where protozoan infections have been associated with severe enteropathy in AIDS patients.

AIMS

To characterise enteropathy in Zambian AIDS patients compared with local controls, and to assess relative contributions of enteric infection, nutritional impairment, and immune dysfunction.

METHODS

Computer aided mucosal morphometry of small intestinal biopsy specimens from 56 HIV infected Zambians with persistent diarrhoea and 26 diarrhoea free controls, followed by regression modelling.

RESULTS

Patients with HIV related diarrhoea had reduced villous height and increased crypt depth compared with controls. There was no difference between HIV positive and negative controls. In regression models applied to AIDS mucosal measurements, villous height and crypt depth were related to nutritional parameters and to serum soluble tumour necrosis factor receptor p55 concentration. Crypt depth was also related to lamina propria plasma cell count. Intestinal infection was found in 79%, which consisted predominantly of microsporidia in 34%, Isospora belli in 24%, and Cryptosporidium parvum in 21%, but detection of these enteropathogens was not related to severity of enteropathy.

CONCLUSIONS

Nutritional and immune disturbances were associated with enteropathy, accounting for over one third of the variation in mucosal morphometric parameters.