Molecular characterization of a third malic enzyme-like AP65 adhesin gene of Trichomonas vaginalis

Adherence to the vaginal epithelium by the sexually transmitted parasite Trichomonas vaginalis is mediated by four trichomonad surface proteins (AP65, AP51, AP33 and AP23). We recently showed that the 65-kDa adhesin is a member of a multigene family comprised of two similar but distinct proteins, AP65-1 and AP65-2, encoded by the genes ap65-1 and ap65-2, respectively. An additional immuno-crossreactive clone, the 1.2 kb F11.1 cDNA, was isolated from a phagemid expression library and encoded a fusion protein of approximately 46,000 daltons (46 kDa) that bound to HeLa cell surfaces. A significant portion of the 5' end was missing which, using the 5'-RACE method, was obtained and combined with the F11.1 clone to give a full-length cDNA. The ap65-3 gene encoded for a protein of 567 amino acids with a molecular mass of 63.1 kDa. The gene showed 88% and 96% identity at the DNA level with ap65-1 and ap65-2, respectively. Restriction mapping confirmed that the three AP65 genes are different. Southern analysis revealed that the ap65-3 gene is present in the T. vaginalis genome in multiple copies. Experiments with agar clones of trichomonads showed that each gene of the multigene family is present in all parasites, and Northern analysis showed that ap65-3 is expressed and transcriptionally regulated by iron. The ap65-3 gene had a leader sequence and, as with ap65-1 and ap65-2, showed significant homology to malic enzyme. Finally, analysis of the 3'-untranslated regions revealed that the transcript of ap65-3 had a long poly (A) tail in comparison to ap65-1 and ap65-2. Even more intriguing, sequences were found that may relate to differential degradation of select AP65 transcripts, such as the sequence motifs AUUUA for ap65-1 mRNA and UUAUUUAU for the ap65-2 mRNA, which were not found for ap65-3.

Microsporidial keratoconjunctivitis caused by Septata intestinalis in a patient with acquired immunodeficiency syndrome

PURPOSE

To examine and treat a patient with acquired immunodeficiency syndrome (AIDS) who had mildly hyperemic conjunctiva and epithelial keratopathy in both eyes.

METHODS

The patient underwent conjunctival biopsy. The specimen was examined by transmission electron microscopy.

RESULTS

Septata intestinalis was demonstrated to be the cause of keratoconjunctivitis in the patient. The keratoconjunctivitis resolved after three weeks of therapy with topical fumagillin. No organisms were seen on repeat conjunctival biopsy.

CONCLUSIONS

Microsporidial keratoconjunctivitis in patients with AIDS can be caused by S. intestinalis. This condition appears to respond to topical fumagillin.

Confocal microscopy findings of Acanthamoeba keratitis

PURPOSE

Tandem scanning confocal microscopy was performed on two patients with Acanthamoeba keratitis to provide images detailing characteristic findings of the disease. Although tandem scanning confocal microscopy of Acanthamoeba has been described in previous reports, Acanthamoeba keratitis has not been fully characterized with this instrument. In vivo confocal micrographs showed the double-walled structure of the Acanthamoeba cyst and associated radial keratoneuritis (perineuritis).

METHODS

We reviewed the records of two patients with a clinical diagnosis of Acanthamoeba keratitis, one with culture-proven Acanthamoeba and the other with a suspected Acanthamoeba infection. Slit-lamp biomicroscopy and in vivo tandem scanning confocal microscopy were performed. The images obtained were compared with images from patients without corneal disease.

RESULTS

High-contrast round bodies suggestive of Acanthamoeba cysts, as previously described, and irregular forms suggestive of Acanthamoeba trophozoites were found by tandem scanning confocal microscopy. Additionally, we showed conclusively that under certain circumstances (that is, corneal scarring) tandem scanning confocal microscopy can resolve the double-walled structure of the Acanthamoeba ectocyst surrounding the endocyst. Furthermore, radial keratoneuritis was demonstrated, consisting of an irregularly swollen nerve fiber with probable amoebic infiltration.

CONCLUSIONS

Confocal microscopy can be a useful, noninvasive imaging technique helpful in the study, diagnosis, and treatment of Acanthamoeba keratitis.

Complete development of Cryptosporidium parvum in bovine fallopian tube epithelial cells

Cryptosporidium parvum is a coccidian parasite responsible for causing protracted and life-threatening diarrheal illness in immunocompromised humans, especially patients with AIDS. The lack of medications effective in treating people suffering from cryptosporidiosis has prompted the development of in vivo and in vitro models for this disease. This study is the first to demonstrate that C. parvum can complete its entire life cycle (from sporozoite to infective oocyst) in a primary culture of bovine fallopian tube epithelial (BFTE) cells. Scanning and transmission electron photomicrographs were used to detail the ultrastructure of individual parasitic stages. Successful infections were produced by inoculating cell cultures with either oocysts or purified sporozoites. Infection of BFTE cells with C. parvum close paralleled in vivo infections with regard to host cell location and chronology of parasite development. Infecting BFTE cells with sporulated oocysts provided a reproducible and quantitative cultivation system with significantly (P < or = 0.001) higher infection rates than in Madin-Darby canine kidney cells. Oocysts produced in BFTE cells were infective for immunosuppressed adult C57BL/6N mice. Cultivation of C. parvum in BFTE cells will facilitate the study of interactions between parasites and host cells as well as provide a reliable system for evaluating anticryptosporidial compound efficacy.

Papillary apocrine change of the breast: associations with atypical hyperplasia and risk of breast cancer

Micropapillary patterns of apocrine change in human female breasts are common histological findings. They have been identified as cancer associated and implicated as an indicator of cancer risk in a predictive manner. This study has stratified papillary apocrine change (PAC) into categories of increasing complexity using a combination of cytological and histological pattern rules. Cases (2,876) were identified in a review of 10,357 benign breast biopsies. Of 5966 women, 1613 and PAC and were followed for a median of 20 years after biopsy for the development of invasive carcinoma of the breast. There was a slight association with cancer risk elevation, but most of this disappeared when women with concurrent, specifically identified patterns of atypical hyperplasia (AH) were excluded from the groups with PAC. The resultant relative risk was only 1.2 after women with AH were excluded. Only 1% of the reviewed biopsies demonstrated highly complex patterns of PAC, and 20% of these had coexistent lesions of AH. Women with highly complex patterns of PAC without AH did experience a relative risk of 2.4 (95% confidence interval = 0.77-7.04) but without statistical significance. More than one-half of all PAC patterns occurred without concurrent foci of lesions of proliferative disease that are associated with a slight elevation of breast cancer risk (at least 1.5 times); when present without proliferative disease, there was no suggestion of later breast cancer risk for PAC.

Diagnosis of microsporidial keratitis by confocal microscopy and the chromatrope stain

PURPOSE

To illustrate the value of confocal microscopy and chromatrope stain in the diagnosis of microsporidial keratitis.

METHODS

In vivo confocal microscopy was performed on a man with the human immunodeficiency virus who had severe bilateral epithelial keratitis refractory to topical antibacterial medications. The results were compared to conjunctival scrapings stained with the chromatrope-based Weber stain.

RESULTS

Confocal microscopy demonstrated many small, intraepithelial opacities of the corneal epithelium, which were suggestive of Microsporidia. Results of the chromatrope stain of conjunctival scrapings confirmed the diagnosis of microsporidial keratitis.

CONCLUSIONS

Rapid diagnosis allowed prompt initiation of topical fumagillin, which permitted rapid, long-term control of the symptoms of microsporidial keratitis.

Remarks on the morphology, site of infection and validity of some coccidian species from fish

The morphological identification of carpelli-type oocysts of Goussia species parasitizing the gut of different cyprinids is unreliable. Species similar in shape and size can be differentiated only by cross-infection experiments. Goussia scardinii (Pellérdy et Molnár, 1968), developing in the renal tubules of cyprinids, is a synonym of Goussia leucisci (Shulman et Zaika, 1964). The morphology and location hitherto assumed to be species characteristics of G. scardinii can be explained by the aging of oocysts and the type of host reaction. Eimeria rutili Dogiel et Bychowsky, 1938 is a coccidian parasite occurring in various organs of the roach. Its oocysts can be found in the blood vessels and, thus, also in the gill capillaries. Eimeria branchiphila Dyková, Lom et Grupcheva, 1983, described from blood vessels of the gills of the same fish species, should be regarded as a synonym of E. rutili. The Octosporella species described from fish are based on erroneous identification and should be considered nomina nuda. Similarly, the Eimeria and Isospora species described from fish by Davronov in 1987 should also be regarded as nomina nuda, as they appear to be avian or mammalian coccidia that entered the intestinal tract of fish with food. The sporocyst residua of fish coccidia cannot be used as characters suitable for species identification, as they tend to change with oocyst aging.

Trichomonas vaginalis: ultrastructural bases of the cytopathic effect

The in vitro cytopathic effect of Trichomonas vaginalis on epithelial cells was explored through the interaction of trophozoites of the virulent strain GT-10 with MDCK monolayers. The interaction was analyzed through electrophysiology, video microscopy, and transmission and scanning electron microscopy. Electrical measurements revealed that living parasites produced severe damage to the cell monolayers within 30 min, manifested as a rapid decrease in transepithelial resistance. Microscopic observations demonstrated that when placed in contact with epithelial cells, trichomonas formed clumps through interdigitations and transient plasma membrane junctions between adjacent parasites. Also, attached trophozoites adopted an ameboid shape. The in vitro cytopathic action of T. vaginalis on MDCK cells was initially evident by modifications of the plasma membrane, resulting in opening of tight junctions, membrane blebbing, and monolayer disruption. After 15 min of interaction the damage was focal, concentrating at sites where parasite clumps adhered to the monolayer. At 30 min practically all MDCK cells were dead, whether or not trichomonas were attached to them. These events were followed by detachment of lysed cells and complete disruption of the monolayer at 60 min. Electron microscopy demonstrated a peculiar form of adhesion that appears to be specific for trichomonas, in which the basal surface of T. vaginalis formed slender channels through which microvilli and cytoplasmic fragments of epithelial cells were internalized. The same sequence of lytic events was found with the less virulent GT-3 strain. However, the time course of cytolysis with GT-3 parasites was much slower, and lysis was limited to areas of attachment of T. vaginalis.

Eimeria tenella: sporozoites rarely enter leukocytes in the cecal epithelium of the chicken (Gallus domesticus)

In this study, the intraepithelial leukocytes supposedly involved in the transportation of Eimeria tenella sporozoites through the cecal lamina propria were phenotypically characterized. The ceca of naive and immune chickens were examined at various times after inoculation by light microscopy and immunocytochemical techniques. The distribution of sporozoites within the villus differed markedly between both groups. From 16 hr postinoculation, significantly fewer sporozoites had reached the crypts in immune chickens, and schizont formation was inhibited. In the villus epithelium of both naive and immune chickens, few sporozoites were found within a leukocyte. Using anti-sporozoite and anti-CD45 monoclonals, we showed that even when intraepithelial leukocytes are abundantly present, only a few sporozoites were inside them. In the lamina propria of immune chickens significantly more sporozoites were found within leukocytes than in the lamina propria of naive chickens. The phenotype of the few leukocytes that harbored sporozoites was similar in naive and immune chickens. A few sporozoites were detected in B cells, 10% in macrophages, and 50% in T cells, especially CD8+ cells. These results show that E. tenella sporozoites rarely enter intraepithelial leukocytes and therefore their putative role in transporting sporozoites through the lamina propria is doubtful.

Donkey klossiellosis in Kenya

Out of eight donkeys examined, two had gametogonic and sporogonic stages of Klossiella equi in their kidneys. Gametogonic stages included microgametocytes and macrogametocytes, some of them in syzygy. They were found in enlarged parasitophorous vacuoles situated in epithelial cells of the renal tubules. Sporonts were seen in the epithelial cells protruding into the tubular lumen while sporoblasts, sporocysts and sporozoites were found freely in the tubular lumen. Entire sporocysts were rarely encountered but sporozoites liberated from the ruptured sporocysts could be seen. No inflammatory reaction could be attributed to the presence of these parasites.

Trypanosome invasion of mammalian cells requires activation of the TGF beta signaling pathway

Trypanosoma cruzi invades most nucleated mammalian cells by as yet unknown mechanisms. We report here that while T. cruzi attaches to epithelial cells lacking signaling transforming growth factor beta (TGF beta) receptor I or II, the adherent parasites cannot penetrate and replicate inside the mutant cells, as they do in parental cells. Invasion of the mutants is restored by transfection with the TGF beta receptor genes, as are biological responses to TGF beta. Similar rescue of both TGF beta antiproliferative response and T. cruzi invasion was demonstrated in a hybrid of TGF beta-resistant bladder and colon carcinoma cells. In addition, T. cruzi did not efficiently invade epithelial cells with dysfunction of the intracellular signaling cascade caused by the constitutive expression of the cyclin-dependent kinase cdk4 or of the oncogene H-ras. Treatment with TGF beta, but not with other antiproliferative agents of non-phagocytic cells, greatly enhances T. cruzi invasion. Moreover, infective, but not noninfective, trypanosomes strongly induce a TGF beta-responsive reporter gene in TGF beta-sensitive, but not in TGF beta-insensitive, cell lines. Thus, T. cruzi itself may directly trigger activation of the TGF beta signaling pathway required for parasite entry into the mammalian cells.

Localization of parasite antigens in Cryptosporidium parvum-infected epithelial cells using monoclonal antibodies

An immunogold ultrastructural study was made of Cryptosporidium parvum-infected intestinal cells from SCID mice to locate parasite antigens recognized by monoclonal antibodies raised against sporozoite or oocyst wall antigens. The results suggested that these antigens were present in more than one life-cycle stage and demonstrated that the intracellular parasite modified the parasitophorous vacuole membrane and villous membrane surrounding the parasite. In an immunofluorescence antibody test monoclonal antibody (MAb) 1B5 reacted with the oocyst wall, MAb 2C3 with the whole sporozoite and MAb 2B2 with the sporozoite surface. Western and dot-blot studies demonstrated that different carbohydrate epitopes were recognized by the respective sporozoite-reactive antibodies. In the ultrastructural examination MAb 1B5 reacted with macro- and microgametocytes as well as the oocyst wall. In the macrogametocyte MAb 1B5 recognized the large electron-dense bodies characteristic of this stage and, in some parasites, the parasitophorous vacuole and the parasite pellicle. The sporozoite-reactive MAbs were able to bind to all developmental stages. These antibodies recognized the parasite cytoplasm and, additionally, MAb 2B2 produced substantial labelling of the parasite membrane. Significantly, both these antibodies also detected antigen in the parasitophorous vacuole membrane and, to a lesser extent, the villous membrane surrounding the parasite.

Intestinal function and injury in acquired immunodeficiency syndrome-related cryptosporidiosis

BACKGROUND/AIMS

The pathogenesis of the diarrhea in acquired immunodeficiency syndrome (AIDS)-related cryptosporidiosis is not known. The hypothesis of this study was that the intestinal dysfunction and injury are related to the number of organisms infecting the intestinal mucosa. The aim of this study was to study the influence of intensity of infection on intestinal function and injury in AIDS-related cryptosporidiosis.

METHODS

In 16 patients with AIDS with intestinal Cryptosporidium infection, the intensity of infection was quantified by counting the total number of fecal oocysts excreted in 24 hours and by determining the percent of duodenal epithelium covered by organisms. Intestinal function was assessed by vitamin B12 absorption and serum D-xylose test. Intestinal injury was assessed by morphology of duodenal mucosa, differential urinary excretion of lactulose and mannitol, and fecal alpha 1-antitrypsin clearance. Measurements were repeated after treatment with paromomycin.

RESULTS

Vitamin B12 and D-xylose absorption negatively correlated with intensity of infection. Villus atrophy occurred only in patients with oocyst excretion of > 10(8) oocyst/24 hours. Lactulose/mannitol urinary excretion ratio showed a positive correlation with intensity of infection. Intestinal function and injury improved in patients whose oocyst counts were reduced by treatment with paromomycin.

CONCLUSIONS

Cryptosporidium infection in patients with AIDS causes malabsorption and intestinal injury in proportion to the number of organisms infecting the intestine.

Interaction of filarial proteins on growth regulation of normal lung epithelial cells in vitro

An in vitro model to examine the effects of filarial proteins on lung epithelial cells has been developed. Several of these proteins appear in circulation of infected individuals. A close association between tropical pulmonary eosinophilia (TPE) and filariasis has been reported by several workers. [3H]-thymidine studies do indicate that when optimum concentration of these filarial proteins were added to lung cultures in proliferating and basal/maintenance media a further increase in growth stimulation was observed early in culture. However, on longer exposures and at higher concentrations an inhibitory effect with distinct morphological changes were noted. The dual role of these proteins on lung epithelial cells in vitro may highlight the possibility of a direct interaction of these proteins with lung cells during disease also contributing to tissue damage.

Respiratory tract cryptosporidiosis in immunosuppressed rat is associated with an epithelial metaplasia

Cryptosporidium parvum is an opportunistic protozoa that chronically infects the digestive tract of immunocompromised hosts. Respiratory cryptosporidiosis, which was reported in AIDS patients, is an uncommon feature of mammalian cryptosporidiosis models. In this study, we document the respiratory lesion; observed in an immunosuppressed rat model of cryptosporidiosis. Twenty rats were immunosuppressed with corticosteroids and low protein diet. They were challenged intratracheally with 10(6) C. parvum sporozoites. Lungs and ileums were examined on D3, D6, D10, D14. On D10 and D14, C. parvum were present in the respiratory tract of all animals in association with the progressive appearance of an immature malpighian metaplasia. On D14, an intestinal infection was also detected in 2/4 animals. The respiratory tract appears to be a fully permissive area for the protozoa in immunosuppressed rats. Introduction of parasites on the respiratory mucosa seems a requisite to induce respiratory cryptosporidiosis. This experimental protocol yields a low mortality rate, and so modelizes late and/or chronic stages of respiratory cryptosporidiosis.

Giardia lamblia: in vitro cytopathic effect of human isolates

The variable clinical course of human giardiasis may be due in part to differences in the virulence of various strains of Giardia lamblia. To address this issue, the in vitro cytopathic effect of isolates obtained from human symptomatic or asymptomatic infections was assessed by ultrastructural and electrophysiological methods. Axenic trophozoites of 10 strains of G. lamblia isolated from children with infections in Mexico City were cultured for 12 to 24 hr on live MDCK epithelial cells. No decrease in transepithelial resistance of MDCK monolayers mounted in Ussing chambers was detected with any of the isolates analyzed. On the contrary, trophozoites or media in which the isolates grew produced up to a twofold increase in transepithelial resistance. Transmission and scanning electron microscopy revealed that all isolates of G. lamblia, irrespective of their origin, gave rise to focal regions of microvilli depletion. These modifications were induced by the close attachment of the ventrolateral flange of the parasite adhesive disk to the apical surface of MDCK cells. The circular imprints evolved progressively to larger areas devoid of microvilli. In conclusion, under in vitro conditions, isolates of G. lamblia trophozoites derived from symptomatic or asymptomatic human infections damage epithelial cultured cells mainly by depleting their microvilli. None of the isolates showed evidence of an invasive effect.

Enteritis in turkeys associated with an unusual flagellated protozoan (Cochlosoma anatis)

Outbreaks of enteritis associated with an unusual flagellated protozoan occurred in six California turkey flocks during the summer of 1992. Certain morphological and ultrastructural details of the parasite, which resembles Cochlosoma anatis, are illustrated with scanning and transmission electron micrographs. The flagellate attached to the intestinal mucosa by means of a sucker-like apparatus, and circular impressions of the sucker were created on the surface epithelium. Histological lesions were characterized by blunting and fusion of villi; cellular infiltration of the lamina propria with lymphocytes, plasma cells, histiocytes, and heterophils; and increased numbers of mitotic figures in crypt epithelium.

A giant merogonial stage (Apicomplexa, Coccidia) in the intestine of Blicca bjoerkna (L.) (Cyprinidae)

A giant meront containing thousands of merozoites has been found in the intestinal epithelium of an adult specimen of white bream (Blicca bjoerkna). The taxonomic position of this unusual coccidian stage is discussed.

Entamoeba histolytica interactions with polarized human intestinal Caco-2 epithelial cells

To model the initial pathogenic effects of Entamoeba histolytica trophozoites on intestinal epithelial cells, the interactions of E. histolytica HM1-IMSS trophozoites with polarized human intestinal Caco-2 cell monolayers grown on permeabilized filters were examined. Trophozoites, when incubated with the apical surface of the monolayers at 37 degrees C, induced a rapid decrease in transepithelial resistance over 15 to 60 min. The transmonolayer resistance response was not associated with changes in short-circuit current but was associated with an increase in mannitol flux, suggesting that the drop in resistance reflected a nonselective increase in epithelial permeability rather than stimulation of electrogenic ion transport. This response preceded the earliest detection of morphologic disruption of monolayer integrity by light or electron microscopy. Apical injury to the monolayer was detected by ultrastructural studies which revealed a loss of brush border in regions of contact between epithelial cells and amebas and by chromium release assays where a small increase in the apical release of 51Cr from the monolayer (6% over background) was observed. The transmonolayer resistance response was inhibited when the temperature was reduced to 4 degrees C and by addition of cytochalasin D (1 microgram/ml) to the medium at concentrations that did not directly affect transmonolayer resistance. Application of amebic lysates or medium conditioned by coincubation of amebas with Caco-2 monolayers failed to lower transmonolayer resistance, suggesting that this effect was not mediated by soluble amebic cytotoxins. Polarized Caco-2 monolayers grown on permeable filters provide a useful model for studying the initial interactions of E. histolytica trophozoites with intestinal epithelial cells.

Explanatum explanatum (Creplin, 1847) Fukui, 1929, in buffaloes in the Ahwaz area, southwest Iran

Explanatum explanatum (Creplin, 1847) Fukui 1929, was found in three indigenous buffaloes in the west Ahwaz area, southwest Iran for the first time. The presence of this amphistome in bile ducts caused remarkable fibrosis of submucosa ad hyperplasia of the endothelial layer, such that villus-like structures and protuberances were formed in large bile ducts of the infected livers.

Role of surface components in the process of interaction of Giardia duodenalis with epithelial cells in vitro

Monosaccharides, lectins, periodate, trypsin and neuraminidase were used to analyse the process of adhesion of Giardia duodenalis trophozoites to IEC cells, an intestinal epithelial cell line. Addition of N-acetyl-glucosamine, N-acetyl-galactosamine, galactose and fucose to the interaction medium inhibited attachment of the parasites to the epithelial cells. Experiments in which the parasites or epithelial cells were treated before interaction showed that these monosaccharides interfered with both cell surfaces. Trypsin-sensitive, but not neuraminidase-sensitive, groups exposed on the cell surface are important for the parasite-epithelial cell association. Fluorescein isothiocyanate (FITC)- or colloidal gold-labeled lectins were used to analyse the distribution of carbohydrates on the surface of G. duodenalis and epithelial cells. It is important to stress here the presence of fucose on the parasite surface. Treatment of the cells with lectins was also used to analyse the role of carbohydrate-containing macromolecules in the parasite-cell interaction.

Cryptosporidium parvum infection of intestinal epithelium: morphologic and functional studies in an in vitro model

A monolayer of mature polarized colonic epithelial cells (T84) able to generate and maintain a barrier to macromolecular flow was used to study pathophysiologic events that occur on microvillus cell exposure to Cryptosporidium parvum. By 24-48 h, several life cycle forms were seen in parasitophorous vacuoles near the apical cell surface, along with a time- and oocyst dose-dependent reduction in epithelial barrier function. As few as 10(5) organisms constituted a successful infecting dose, and heat inactivation of organisms markedly reduced the monolayer barrier alteration. Horseradish peroxidase flux studies demonstrated a substantial increase in macromolecular permeability of the monolayer, and lactate dehydrogenase determinations indicated modest injury of the T84 epithelial cells on exposure to oocysts. Thus, disruption of the epithelial cell barrier, not just opening of transcellular channels for ion flow as reported previously, is responsible for the effects of C. parvum oocysts on intestinal epithelium.

The invasion of the rabbit intestinal tract by Eimeria intestinalis sporozoites

To follow the route of migration of Eimeria intestinalis sporozoites from the excystation stage to their development in the epithelial cells of the ileum, we inoculated sporocysts into the duodenum of coccidia-free rabbits and euthanized the animals at 10 min to 12 h post-inoculation. Excystation occurred at less than 10 min after the experimental infection. The sporozoites penetrated into the epithelium of the duodenum at as early as 10 min post-inoculation; 6 h later, the number of sporozoites had dramatically decreased in the duodenal mucosa, with a corresponding increase being noted in the ileal mucosa. These findings suggest that sporozoites invade the duodenal epithelium and migrate to the ileum by an as yet unknown nonlumenal tissue route.

[Naturally-acquired microsporidia (Encephalitozoon cuniculi) infections in hens]

During a short period of time, four approximately ten months old chickens from an egg production (group A) unit developed symptoms of apathy, lameness, mild diarrhoea and loss of weight. The layers were killed and submitted for necropsy. For the first time, microsporidia infection, probably Encephalitozoon cuniculi (E.c.) was diagnosed in chickens. The diagnosis was mainly based on immunohistochemical methods. E.c. was found particularly in the cells of the cutaneous mucous membrane of the crop and in epithelial cells, the cells of the propria mucosae and the smooth muscle cells of the small intestine. E.c. also frequently occurred in the fibres of the skeletal muscle. Intracellularly, E.c. and its development stages were located primarily in the cytoplasm and less frequently in the nucleus of cells. Retrospective investigations on tissue samples from a domestic cock and 9 hens by immunohistochemical methods also revealed occurrence of this microsporidian. The results showed that in chickens E.c. infections can cause multi-symptomatic illness but may also be clinically inapparent.

Relationships of Trichomonas gallinae to the palatal-esophageal junction of ring doves (Streptopelia risoria) as revealed by scanning electron microscopy

Ring doves (Streptopelia risoria) were experimentally infected with pathogenic (virulent) Trichomonas gallinae so that trichomonad activities in the upper alimentary tract, prior to canker formation, could be examined with scanning electron microscopy. Between 6 and 15 hr postinoculation low numbers of ameboid T. gallinae were attached to apical microfolds and cell borders of the palatal-esophageal junction squamous epithelium. Initial parasite activities at tightly attached cell borders and apical microfolds suggest that some parasite-secreted factor or factors initiated squamous cell damage, separation, and removal. As squamous cell borders separated, trichomonads invaded areas beneath them and ultimately aided in their complete removal. Accelerated parasite-mediated desquamation, the invasion of increased mucosal surface area by trichomonads, and the eruption and expansion of cankers were the primary changes to the palatal-esophageal junction and other upper alimentary tract tissues that occurred between 19 and 240 hr postinoculation.

Ultrastructural observations of host-cell invasion by sporozoites of Eimeria papillata in vivo

Scanning and transmission electron microscopy were used to study the invasion of mouse small-intestinal epithelium by sporozoites of Eimeria papillata. Some mice received oocysts by gavage and others received either sporocysts or sporozoites by direct injection into the small intestine. The highest concentration of invaded cells were found in ligated intestinal tissues studied at 5-45 min after the inoculation of sporozoites. Sporozoites actively invaded anterior end first, which resulted in extensive damage to the host cell. Such cells showed disrupted microvilli; protuberances of cytoplasm into the lumen, apparently the result of a disrupted plasma membrane; vacuolization of the cytoplasm; and damage to the mitochondria. These damaged cells were rapidly vacated as the sporozoite moved laterally into one or more adjacent intact host cells without entering the lumen. It is suggested that the host cell initially entered from the lumen becomes so severely traumatized that the parasite of necessity enters an adjacent cell as a prelude to further development. Various aspects of host-cell invasion by coccidia and malarial parasites are reviewed.

[Study by the immunofluorescence reaction of antibodies directed against antigens of the gut epithelium of Schistosoma mansoni. V. Modulation of granulomatous reaction around the egg under the influence of an IgM monoclonal antibody]

The periovular granulomatous reaction has been reduced in vivo by an IgM monoclonal antibody. The granulomatous reaction has been obtained either in unsensitized, or sensitized as well as immunized mouse. The granulomatous reduction could be explained by a decrease in egg viability, owing to the fact that the monoclonal antibody is lethal against an in vitro miracidium suspension.

Characterization and pathogenic potential of a soil isolate and an ocular isolate of Acanthamoeba castellanii in relation to Acanthamoeba keratitis

Acanthamoeba castellanii, one isolate from the eye and one from the soil, were compared on the basis of: (a) pathogenic potential; (b) plasminogen activator activity; (c) chemotactic activity; (d) cytopathic effects; (e) collagenolytic activity; (f) binding ability to contact lenses; and (g) and binding ability to corneal buttons. The ocular isolate of A. castellanii was found to be pathogenic based on its ability to produce corneal infections in Chinese hamsters. By contrast, the soil isolate produced only mild lesions in a single Chinese hamster. Amoebae from the ocular isolate bound to corneal epithelium in greater numbers than the soil isolate counterparts. Moreover, ocular isolate organisms displayed plasminogen activator activity that was not detected in cultures from soil isolates of A. castellanii. Although neither the soil isolate nor the ocular isolate amoebae responded chemotactically to epithelial or stromal components, the ocular isolate displayed a curious and reproducible positive chemotactic response to endothelial extracts. Both A. castellanii isolates produced cytopathic effects on pig corneal epithelium, however the cytotoxicity from the ocular isolate was significantly greater than that of the soil isolate. The results indicate that the pathogenic potential of A. castellanii is correlated with the parasite's capacity to bind to corneal epithelium, respond chemotactically to corneal endothelial extracts, elaborate plasminogen activators, and produce cytopathic effects on corneal epithelium.

Verminous bronchitis and bronchiolitis in potoroid marsupials associated with a new Capillaria sp

We describe verminous bronchitis and bronchiolitis in potoroid marsupials associated with a new species of Capillaria resident in the epithelial lining of bronchi and bronchioles. The parasites was associated with alveolar oedema and emphysema, and a mixed inflammatory cell exudate within and surrounding the airways.

Identification of a lectin activity in Pneumocystis carinii

Pneumocystitis carinii is known to adhere to pulmonary alveolar epithelial cells in vivo and to epithelial cell lines in vitro by a mechanism unknown at the molecular level. P. carinii is now found to adhere to rabbit and human red blood cells leading to rosette formation and hemagglutination. P. carinii erythrocyte-adherence was best inhibited by bovine submaxillary mucin and by a polysaccharide from the wall of group A Streptococcus, and to a lesser extent by Streptococcus group C polysaccharide, asialofetuin and fetuin. Among the mono- and oligosaccharides tested, only lactose inhibited hemagglutination. Other glycoconjugates and oligosaccharides tested were inactive. P. carinii also bound to purified glycoproteins coupled to Sepharose or adsorbed to plastic, and the binding was inhibited by soluble bovine submaxillary mucin. These results indicate that P. carinii has a novel surface lectin that may be important in adherence to lung alveolar epithelial cells.

Acanthamoebae bind to glycolipids of rabbit corneal epithelium

By use of a thin-layer chromatogram (TLC) overlay procedure, 35S-labeled acanthamoebae were shown to bind to seven glycolipids of rabbit corneal epithelium. Corneal epithelial cells were grown in culture and were subjected to Folch extraction to isolate a chloroform-rich lower phase containing neutral glycosphingolipids (NGSL) and an aqueous upper phase containing gangliosides, i.e., sialic acid-containing glycolipids. Thin-layer chromatography of the upper phase revealed the presence of 10 ganglioside components. Acanthamoebae were shown to bind to four of these components, referred to as 2, 3, 6, and 7. On TLC plates, ganglioside components 2 and 3 migrated slightly ahead of the glycolipid standard GD1a, component 7 comigrated with standard GM3, and component 6 migrated a little more slowly than GM3. Likewise, of the 10 NGSL known to be present in the lower phase, acanthamoebae bound to components 1, 5, and 6. NGSL components 1, 5, and 6 migrated on TLC plates with relative mobilities similar to those of standards asialo GM1, asialo GM2, and ceramidetrihexoside, respectively. We propose that one or more of the Acanthamoeba-reactive glycolipids of corneal epithelium identified in this study may play a role in the pathogenesis of Acanthamoeba keratitis by mediating the adherence of the parasites to the cornea.

Scanning and transmission electron microscopy of host cell pathology associated with penetration by Eimeria papillata sporozoites

Scanning and electron microscopy was used to study the pathogenesis that occurred in mouse epithelial cells that had been penetrated by Eimeria papillata sporozoites. Optimal penetration of parasites injected into nonligated and ligated mouse intestine was found to occur at 4-15 min post-inoculation. During initial penetration, the parasite caused disruption of the microvilli of the intestinal cells, which led to detachment of the microvilli from the plasma membrane of the penetrated cell. Host cells penetrated by the parasite showed extensive destruction of the internal cellular organization together with blebbing of host-cell cytoplasm and release of internal organelles such as mitochondria. Ultimately, the penetrated cells completely broke down, leaving vacuolated areas next to ultrastructurally normal epithelial cells.

Toxoplasma gondii-like schizonts in the tracheal epithelium of a cat

Toxoplasma gondii-like schizonts were found in tracheal epithelium of an 8-yr-old male cat. The parasites were located in parasitophorous vacuoles within the host cell cytoplasm, divided by schizogony, contained periodic acid-Schiff-positive granules, and reacted with anti-T. gondii serum but not with anti-Neospora caninum serum. Mature schizonts were 7.0 x 5.9 microns (5-10 x 4-10 microns; n = 22) and contained 4-16 merozoites. The merozoites were approximately 5 x 1 microns.

Cytopathogenicity of Entamoeba histolytica to human intestinal epithelial cells: inhibition by monoclonal antibodies and sera from amoebic patients

Interactions of pathogenic Entamoeba histolytica (HM 1) with human intestinal epithelial cells (Henle-407) were investigated. The E. histolytica trophozoites adhered and cytolysed 87% of cultured epithelial cell monolayers. A significant (P less than 0.001) inhibition of cytopathic effect of amoebic trophozoites pretreated with monoclonal antibodies to a 29 kDa surface associated protein suggested utilization of the 29 kDa surface protein in recognition and cytolysis of epithelial target cells. The polyclonal sera from treated patients of amoebic liver abscess and anti-amoebic hyperimmune serum inhibited cytopathogenicity to a greater degree (P less than 0.001) than did the monoclonal antibodies. The data thus suggest involvement of several amoebic molecules in exercising cytopathogenicity to epithelial cells.

In vitro penetration of human corneal epithelium by Acanthamoeba castellanii: a scanning and transmission electron microscopy study

Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35 degrees C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis. It is likely that the secretion of one or more enzymes constitutes the initial step in preparing the host tissue for endocytosis or that the secretory mechanism is used by the amebas to move through the outer squamous layer to the basement epithelium where phagocytosis occurs. Based on this study and a previous study, it appears that entry into the cornea is a two-step process involving adherence and penetration by trophozoites.

In vitro intercellular adherence of Acanthamoeba castellanii: a scanning and transmission electron microscopy study

Human corneal buttons were exposed to trophozoites and cysts of Acanthamoeba castellanii for 12 hours. Examination of the buttons by scanning electron microscopy showed numerous trophozoites on the surface of the epithelium. Trophozoites examined by transmission electron microscopy had limited regions of attachment to the epithelium but extensive regions of attachment to each other. Attachment regions were characterized as plaque-like maculae of an incomplete desmosome junction. Firm attachment mechanisms may explain how penetration of the human cornea occurs.

Eimeria tenella: localization of the sporozoites in the caecum of the domestic fowl

When sporozoites of Eimeria tenella were inoculated into an isolated horn of the bicornuate caecum of the domestic fowl, replicating infections, culminating in the production of oocysts, were found, almost exclusively, in the inoculated horn. In contrast, sporozoites of E. tenella introduced into the bloodstream via a superficial vein induced infections of equivalent intensity in both horns of the caecum. These findings are discussed with reference to (1) the detection (by tissue transfer) of infective sporozoites in samples of cardiac blood and vascular tissues taken within 3 to 18 h of the oral inoculation of oocysts, and (2) the (previously published) observation that the sporozoites of E. tenella are transported from the superficial epithelium of the caecum (site of invasion) to the crypts (site of initial development) within host intra-epithelial lymphocytes. We suggest that a local inflammatory response to the invasion of sporozoites may be responsible for their re-location in proximity to the site of entry. This could act by directing the homing (or retention) of the parasite-bearing lymphocytes, and/or by providing a stimulus for the sporozoite to leave its transporting cell.

Corneal microsporidiosis in a patient with AIDS

Microsporidia are obligate intracellular protozoan parasites that are becoming increasingly recognized as opportunistic pathogens in patients with AIDS. They have been associated with enteritis, hepatitis, and peritonitis and recently keratoconjunctivitis. Gram stain demonstrates the presence of these organisms on light microscopic sections. The specific diagnostic features that distinguish microsporidia from other small nonspore-forming organisms are best demonstrated by electron microscopy, which is also used to characterize the members of Microsporea. In this study, salient histopathologic features of microsporidia in corneal epithelium obtained from an HIV-seropositive individual who developed AIDS are illustrated and discussed.

Gamma interferon-mediated inhibition of Eimeria vermiformis growth in cultured fibroblasts and epithelial cells

The growth of Eimeria vermiformis within cultured murine fibroblastlike (L-929) or rat epithelial-like (RATEC) cells was inhibited by treatment of the cells with the appropriate recombinant gamma interferon. The effect was apparent as a reduction in both the initial numbers of intracellular sporozoites and, to a much greater extent, the numbers of subsequent developmental stages. Pretreatment of the host cells was more effective than treatment in the early postinvasive period, and recombinant gamma interferon had no effect on the development of the parasite if added 24 h or later after the inoculation of sporozoites. Incubation of sporozoites in medium containing recombinant gamma interferon in no way affected their ability to invade or to grow within host cells. These findings indicate that the inhibitory effects of recombinant gamma interferon on the growth of E. vermiformis are mediated via the host cell and are directed mainly against the transforming sporozoite, although the ability of the sporozoite to invade the host cell was also reduced to some extent. The later developmental stages were refractory to the effects of this lymphokine.

Ultrastructural studies of the effects of the ionophore lasalocid on Eimeria tenella in chickens

The ultrastructural development of Eimeria tenella was studied in experimentally infected chicks fed 90 ppm lasalocid, an ionophorous anticoccidial antibiotic. Drug treatment was timed to target-specific endogenous stages. At 6 h after infection, many sporozoites within the epithelium showed degradation as a result of drug action. Only a few intact sporozoites were seen. The drug caused outer-membrane blistering, large surface swellings and enlarged mitochondria in both first- and second-generation merozoites. No effect on the gamonts was discerned.

Tight junctional inhibition of entry of Toxoplasma gondii into MDCK cells

Various conditions of cultures were performed to investigate the role of tight junctions formed between adjacent MDCK cells on the entry of Toxoplasma. When MDCK cells were cocultured with excess number of Toxoplasma at the seeding density of 1 x 10(5), 3 x 10(5), and 5 x 10(5) cells/ml for 4 days, the number of intracellular parasites decreased rapidly as the host cells reached saturation density, i.e., the formation of tight junctions. When the concentration of calcium in the media (1.8 mM in general) was shifted to 5 microM that resulted in the elimination of tight junction, the penetration of Toxoplasma increased about 2-fold (p less than 0.05) in the saturated culture, while that of non-saturated culture decreased by half. Trypsin-EDTA which was treated to conquer the tight junctions of saturated culture favored the entry of Toxoplasma about 2.5-fold (p less than 0.05) compared to the non-treated, while that of non-saturated culture decreased to about one fifth. It was suggested that the tight junctions of epithelial cells play a role as a barrier for the entry of Toxoplasma and Toxoplasma penetrate into host cells through membrane structure-specific, i.e., certain kind of receptors present on the basolateral rather than apical surface of MDCK cells.

Inhibition of Trichomonas vaginalis motility by monoclonal antibodies is associated with reduced adherence to HeLa cell monolayers

Adherence of trichomonads to host epithelial cells appears to be a critical step in the pathogenesis of trichomoniasis. We evaluated the effect of a panel of 10 monoclonal antibodies on attachment of [35S]methionine-radiolabeled Trichomonas vaginalis strains to HeLa cell monolayers. Of 10 monoclonal antibodies, 3 totally eliminated motility of PHS2J strain trichomonads and reduced their adherence to 48 to 60% of control values (P less than 0.001). However, none of the monoclonal antibodies affected motility or adherence of STD13 strain trichomonads. Although the antibodies all reacted with PHS2J trichomonads by immunofluorescence, there was no correlation between inhibition of adherence and findings on either immunofluorescence or radioimmunoprecipitation. Direct microscopic observations showed that incubation with the monoclonal antibodies did not cause cytolysis of T. vaginalis. In quantitative cultures there was no difference in the number of colonies produced by parasites that had been incubated with antibodies that inhibited or had no effect on adherence. We conclude that our monoclonal antibodies reduced adherence not by cytotoxic effects or by competing for specific sites mediating adherence of the protozoa, but by inhibiting motility of T. vaginalis.

Trichomonas vaginalis surface proteinase activity is necessary for parasite adherence to epithelial cells

The role of cysteine proteinases in adherence of Trichomonas vaginalis NYH 286 to HeLa and human vaginal epithelial cells was evaluated. Only pretreatment of trichomonads, but not epithelial cells, with N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK), an inhibitor of trichomonad cysteine proteinases, greatly diminished the ability of T. vaginalis to recognize and bind to epithelial cells. Leupeptin and L-1-tosylamide-2-phenylethyl chloromethyl ketone, other cysteine proteinase inhibitors, also decreased T. vaginalis cytadherence. Parasites incubated with TLCK and washed extensively still did not adhere to cells at levels equal to those seen for control trichomonads treated with phosphate-buffered saline or culture medium alone. Exposure of TLCK-treated organisms with other cysteine proteinases restored cytadherence levels, indicating that proteinase action on the parasite surface is prerequisite for host cell attachment. Concentrations of TLCK which inhibited cytadherence did not alter the metabolism of T. vaginalis, as determined by metabolic labeling of trichomonad proteins; the protein patterns of T. vaginalis in the presence and absence of TLCK were identical. Kinetics of TLCK-mediated inhibition of cytadherence of other T. vaginalis isolates with different levels of epithelial-cell parasitism were similar to the concentration-dependent inhibition seen for isolate NYH 286. Incubation of TLCK-treated, washed organisms in growth medium resulted in regeneration of adherence. Finally, treatment of T. vaginalis organisms with proteinase inhibitors for abrogation of cytadherence effectively rendered the trichomonads unable to kill host cells, which is consistent with the contact-dependent nature of host cytotoxicity. These data show for the first time the involvement of T. vaginalis cysteine proteinases in parasite attachment to human epithelial cells. These results have implications for future pharmacologic intervention at a key step in infection.

Studies on the thymus in Chagas' disease. I. Changes in the thymic microenvironment in mice acutely infected with Trypanosoma cruzi

Previous observations demonstrated severe thymocyte depletion in mice undergoing acute Chagas' disease. These data led us to investigate the status of the thymic microenvironment in these animals. Young adult C57BL/6 and C3H/HeJ mice were infected i.p. with 10(5) blood-derived trypomastigote forms of Trypanosoma cruzi (CL strain) and killed 7-14 days after infection. Sera were then analyzed for thymic hormone (thymulin) levels, and frozen thymus sections were studied by immunohistochemistry for the expression of functional antigens (thymulin and Ia), the distribution of distinct thymic epithelial cell subsets and extracellular matrix components. Infected mice exhibited a transient decrease in thymulin production and those with severe thymic atrophy showed a denser Ia-bearing cellular network. In addition, an abnormal localization of the TR5 and CK18 antigens restricted to the medullary and cortical TEC subsets, respectively, was observed. Furthermore, an increase in the basement membrane proteins was detected within thymic lobules. We suggest that the thymic microenvironment is also affected during T. cruzi infection, extending the concept that the thymus should be regarded as a target in Chagas' disease.

Adherence of Tritrichomonas foetus to bovine vaginal epithelial cells

Adherence of Tritrichomonas foetus to bovine vaginal epithelial cells (VECs) in vitro was investigated with fresh washed bovine VECs and log-phase cultures of T. foetus. Observation under phase-contrast microscopy showed that T. foetus usually adhered first by the posterior flagellum and later by the body. Significantly more keratinized squamous epithelial cells were detected with attached parasites than nonkeratinized round epithelial cells. The optimal pH range for attachment was 6.0 to 7.5, with peak attachment at pH 6.5 for squamous VECs. Surface-reactive bovine antiserum to T. foetus prevented adherence to bovine squamous VECs. Inhibition of adherence occurred at nonagglutinating, nonimmobilizing serum dilutions. Antiserum fractions enriched for immunoglobulin G1 inhibited adherence, but fractions enriched for immunoglobulin G2 did not. The inhibitory antiserum was specific for several medium- to high-molecular-weight membrane antigens as detected in Western blots (immunoblots). The ability of surface-reactive antibodies to prevent adherence and to agglutinate and immobilize T. foetus indicates that they may be protective.