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At least 199 records · Page 11Linked to original sources
PubMed1996

Prevalence of microsporidiosis due to Enterocytozoon bieneusi and Encephalitozoon (Septata) intestinalis among patients with AIDS-related diarrhea: determination by polymerase chain reaction to the microsporidian small-subunit rRNA gene.

Microsporidia are emerging as opportunistic pathogens in patients with AIDS. Enterocytozoon bieneusi and Encephalitozoon (Septata) intestinalis have been implicated in enteric infections in AIDS patients with chronic diarrhea, a wasting syndrome, and malabsorption. We used the polymerase chain reaction (PCR) and primers that amplify the conserved regions of the small-subunit rRNA (SSU-rRNA) gene of E. bieneusi and E. intestinalis in tissue specimens from HIV-infected patients with and without diarrhea to examine the association between microsporidia and diarrhea in patients with AIDS. Tissue specimens were obtained from 68 patients with AIDS and diarrhea (mean CD4 lymphocyte count, 21/mm3) and 43 AIDS patients without diarrhea (mean CD4 lymphocyte count, 60/mm3). By means of PCR with use of the SSU-rRNA primers specific for E. bieneusi and E. intestinalis, we found that 44% of patients with diarrhea were infected with microsporidia, whereas only 2.3% of the patients without diarrhea were infected with microsporidia (P < .001). There was a clear association between the presence of microsporidia and diarrhea. In addition, the SSU-rRNA primers proved to be sensitive and specific when used in this clinical setting.

AIDS-Related Opportunistic Infections↗
PubMed1981

Susceptibility of selected inbred strains of mice to Encephalitozoon cuniculi.

Selected inbred strains of mice were examined for susceptibility to peritoneal infections with Encephalitozoon cuniculi. Marked differences in susceptibility and resistance among mouse strains were not controlled by loci within the mouse major histocompatibility (H-2) complex, but resistance in BALB/c mice was influenced by a dominant gene(s) outside the H-2 complex. The lethality of peritoneal infections in hypothymic nude mice suggested that resistance to encephalitozoonosis is dependent on thymus-derived lymphocytes. Peritoneal infection with E. cuniculi was associated with slightly enhanced proliferative spleen cell responses to mitogens in BALB/c mice and significantly depressed responses in C57Bl/6 mice. Infection in BALB/c mice was accompanied by normal antibody responses to sheep erythrocyte immunogens, but C57Bl/6 mice had depressed antibody responses. The results indicate that the immune system plays a major role in determining the course of peritoneal infections with E. cuniculi and that encephalitozoonosis can modulate the host's immune system.

Animals↗
PubMed1995

Polymerase chain reaction and culture confirmation of disseminated Encephalitozoon cuniculi in a patient with AIDS: successful therapy with albendazole.

Infections due to microsporidia are being recognized increasingly, especially in AIDS patients. A patient with disseminated microsporidiosis with advanced renal failure due to Encephalitozoon cuniculi (confirmed by culture and polymerase chain reaction [PCR]) is described. The organism from urine and sputum was characterized by culture, Weber's chromotrope-based staining, transmission electron microscopy, and indirect immunofluorescence (IIF) tests. PCR was done on DNA extracted from the infected cell cultures. Treatment with albendazole resulted in improvement in serum creatinine levels, complete disappearance of spores from sputum, a negative urine culture, and a 3-log decline in the number of spores in the urine, as evidenced by chromotrope-based staining. IIF and PCR were used to confirm E. cuniculi as the etiologic agent. Our findings indicate that disseminated microsporidiosis with renal failure in AIDS is treatable.

AIDS-Related Opportunistic Infections↗
PubMed1998

Encephalitozoon-like microsporidia in the ticks Amblyomma cajennense and Anocentor nitens (Acari: Ixodidae).

A Encephalitozoon-like microsporidia was found in epithelial cells of the midgut and the salivary glands of Amblyomma cajennense (F.) and Anocentor nitens (Neumann) that had fed on rabbits. Ultrastructural studies demonstrated that all stages of the life cycle of the parasite occur in parasitophorous vacuoles and contain only 1 nucleus. The sporonts detach from the limiting membrane of the vacuole and divide by binary fission to produce the sporoblasts, each presenting a thickened electron-dense wall, and a primordium of a polar filament. Each spore contained a single nucleus, an electron-dense and rough exospore, an electron-lucent and thick endospore, and 5 coils of the polar tubule.

Animals↗
PubMed2000

Encephalitozoon cuniculi (Microspora) genome: physical map and evidence for telomere-associated rDNA units on all chromosomes.

A restriction map of the 2.8-Mb genome of the unicellular eukaryote Encephalitozoon cuniculi (phylum Microspora), a mammal-infecting intracellular parasite, has been constructed using two restriction enzymes with 6 bp recognition sites (Bss HII and Mlu I). The fragments resulting from either single digestions of the whole molecular karyotype or double digestions of 11 individual chromosomes have been separated by two-dimensional pulsed field gel electrophoresis (2D-PFGE) procedures. The average distance between successive restriction sites is approximately 19 kb. The terminal regions of the chromosomes show a common pattern covering approximately 15 kb and including one 16S-23S rDNA unit. Results of hybridisation and molecular combing experiments indicate a palindromic-like orientation of the two subtelomeric rDNA copies on each chromosome. We have also located 67 DNA markers (clones from a partial E. cuniculi genomic library) by hybridisation to restriction fragments. Partial or complete sequencing has revealed homologies with known protein-coding genes for 32 of these clones. Evidence for two homologous chromosomes III, with a size difference (3 kb) related to a subtelomeric deletion/insertion event, argues for diploidy of E.cuniculi. The physical map should be useful for both the whole genome sequencing project and studies on genome plasticity of this widespread parasite.

Animals↗
PubMed2004

Polyamine metabolism in a member of the phylum Microspora (Encephalitozoon cuniculi): effects of polyamine analogues.

The uptake, biosynthesis and catabolism of polyamines in the microsporidian parasite Encephalitozoon cuniculi are detailed with reference to the effects of oligoamine and arylamine analogues of polyamines. Enc. cuniculi, an intracellular parasite of mammalian cells, has both biosynthetic and catabolic enzymes of polyamine metabolism, as demonstrated in cell-free extracts of mature spores. The uptake of polyamines was measured in immature, pre-emergent spores isolated from host cells by Percoll gradient. Spermine was rapidly taken up and metabolized to spermidine and an unknown, possibly acetamidopropanal, by spermidine/spermine N(1)-acetyltransferase (SSAT) and polyamine oxidase (PAO). Most of the spermidine and the unknown product were found in the cell incubation medium, indicating they were released from the cell. bis(Ethyl) oligoamine analogues of polyamines, such as SL-11144 and SL-11158, as well as arylamine analogues [BW-1, a bis(phenylbenzyl) 3-7-3 analogue] blocked uptake and interconversion of spermine at micromolar levels and, in the case of BW-1, acted as substrate for PAO. The Enc. cuniculi PAO activity differed from that found in mammalian cells with respect to pH optimum, substrate specificity and sensitivity to known PAO inhibitors. SL-11158 inhibited SSAT activity with a mixed type of inhibition in which the analogue had a 70-fold higher affinity for the enzyme than the natural substrate, spermine. The interest in Enc. cuniculi polyamine metabolism and the biochemical effects of these polyamine analogues is warranted since they cure model infections of Enc. cuniculi in mice and are potential candidates for human clinical trials.

Acetyltransferases↗
PubMed2001

Sequence and analysis of chromosome I of the amitochondriate intracellular parasite Encephalitozoon cuniculi (Microspora).

A DNA sequencing program was applied to the small (<3 Mb) genome of the microsporidian Encephalitozoon cuniculi, an amitochondriate eukaryotic parasite of mammals, and the sequence of the smallest chromosome was determined. The approximately 224-kb E. cuniculi chromosome I exhibits a dyad symmetry characterized by two identical 37-kb subtelomeric regions which are divergently oriented and extend just downstream of the inverted copies of an 8-kb duplicated cluster of six genes. Each subtelomeric region comprises a single 16S-23S rDNA transcription unit, flanked by various tandemly repeated sequences, and ends with approximately 1 kb of heterogeneous telomeric repeats. The central (or core) region of the chromosome harbors a highly compact arrangement of 132 potential protein-coding genes plus two tRNA genes (one gene per 1.14 kb). Most genes occur as single copies with no identified introns. Of these putative genes, only 53 could be assigned to known functions. A number of genes from the transcription and translation machineries as well as from other cellular processes display characteristic eukaryotic signatures or are clearly eukaryote-specific.

Animals↗
PubMed1995

Reactive nitrogen intermediates implicated in the inhibition of Encephalitozoon cuniculi (phylum microspora) replication in murine peritoneal macrophages.

Encephalitozoon cuniculi (phylum microspora) is a protozoan parasite that can replicate within parasitophorous vacuoles in macrophages. Thioglycollate-elicited BALB/c peritoneal macrophages treated with murine recombinant interferon-gamma (rIFN-gamma; 100 7/ml) in combination with lipopolysaccharide (LPS; 10 ng/ml) for 24 h killed E. cuniculi as determined by significant reductions in the number of parasites and percent of infected macrophages 48 h later compared with cultures treated with medium only. Treatment of the elicited macrophages with murine rIFN-gamma (10 u/ml or 100 u/ml) only, resulted in microbistatic activity. Significantly higher levels of nitrite (NO2) were detected in supernatants from macrophage cultures treated with rIFN-gamma (10 u/ml or 100 u/ml) which induced microbistatic macrophage activity as well as from macrophage cultures treated with LPS + rIFN- when compared with levels of nitrite detected in supernatants of infected macrophages treated with medium only. Addition of the L-arginine analogue, N3 monomethyl-L-arginine (NMMA) at concentrations of 50, 100 or 250 uM significantly inhibited nitrite synthesis and prevented microsporidia killing. Addition of exogenous L-arginine at concentrations of 5 mM or 10 mM reversed the NMMA-induced inhibition of parasite killing. These results indicate that reactive nitrogen intermediates contribute to the killing of E. cuniculi by LPS + rIFN-gamma-activated murine peritoneal macrophages in vitro.

Animals↗
PubMed2006

Antibodies enhance the protective effect of CD4+ T lymphocytes in SCID mice perorally infected with Encephalitozoon cuniculi.

The role of antibodies in the immune response to microsporidiosis was studied using a novel anti-exospore monoclonal antibody (MAb) P5/H1, which recognizes surface antigens of Encephalitozoon cuniculi. The effect of the MAb on microsporidial infection in vivo was to prolong the survival of previously CD4+ reconstituted, perorally infected and intraperitoneally MAb-treated SCID mice. The MAb decreased the numbers of E. cuniculi spores in peritoneal smears obtained post mortem. These results suggest a possible role for antibodies in protection against perorally acquired E. cuniculi infection.

Animals↗
PubMedDate not supplied

Encephalitozoon hellem infection as the cause of a unilateral chronic keratoconjunctivitis in an umbrella cockatoo (Cacatua alba).

An umbrella cockatoo (Cacatua alba) was presented with a keratoconjunctivitis of 9 months' duration that was refractory to antibacterial and antifungal treatments. Microsporidian-type spores were observed in calcofluor M2R-stained cytological preparations of debrided corneal epithelium. Hematoxylin and eosin-stained sections of a conjunctival biopsy also showed a small number of intracellular parasites. Microsporidial DNA was detected by polymerase chain reaction in DNA extracted from the remaining biopsy material. Sequence analysis of the small subunit ribosomal RNA gene identified the microsporidium as Encephalitozoon hellem. The cockatoo was treated with oral albendazole for 3 months with resolution of the signs, and then again for 4 months when the signs returned. Since then, the bird has remained healthy for 2 years. This is the second report of a microsporidial keratoconjunctivitis in a bird, and the first report of an E. hellem infection in a cockatoo. Ophthalmologists should consider E. hellem as a possible cause of a keratoconjunctivitis in parrots that is refractory to treatment with traditional antimicrobials.

Administration, Oral↗
PubMed1988

Encephalitozoon cuniculi: quantitation of parasites and evaluation of viability.

Two methods (manual and automated) for quantitation of viable versus dead Encephalitozoon cuniculi are reported. The manual method uses ethidium bromide and acridine orange to stain dead and viable organisms, respectively. The stained organisms are visually differentiated with the aid of a fluorescence microscope. The automated method uses propidium iodide to stain dead parasites, which are differentiated from viable unstained parasites with the aid of a flow cytometer. An automated cell counter (Coulter Counter) was used to count rapidly large numbers of samples and to improve the sensitivity of counting low concentrations of parasites. These methods will enhance investigators' abilities to conduct quantitative experiments on host defense mechanisms against E. cuniculi.

Acridine Orange↗
PubMedDate not supplied

Inhibition of the spore polar filament extrusion of the microsporidium, Encephalitozoon hellem, isolated from an AIDS patient.

Spores of the microsporidian parasitic protozoan Encephalitozoon hellem were purified and incubated at 37 degrees C in a solution with an electrolyte composition similar to that of mammalian extracellular fluid, and in solution in which the calcium had been replaced with 0.2 mM EGTA. Polar filament extrusion (germination) was monitored by both scanning electron microscopy and light microscopy. Germination was pH-dependent, with optima at pH 7.4 and 9.5, and was significantly greater in the presence of medium calcium. Hydrogen peroxide caused a concentration-dependent increase in germination that was also reduced in a calcium-free medium. Four agents were found to inhibit spontaneous and H2O2-stimulated polar filament extrusion: the microfilament disrupter, cytochalasin D; the microtubule disrupter, demecolcine; the calcium channel blocker, nifedipine; and the antifungal agent, itraconazole. These results are consistent with the existence of a calcium-channel-mediated step, and requirements for an F-actin- and for a tubulin-containing element in the germination process of the spore of this parasite. Nifedipine, cytochalasin D and itraconazole all have different sites of action and were therefore able to potentiate one another when used in paired combination to inhibit germination.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Microsporidian spore wall: ultrastructural findings on Encephalitozoon hellem exospore.

A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze-fracture, and deep-etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30-35 nm electron-lucent endospore and an outer 25-30 nm electron-dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron-lucent intermediate lamina and an inner fibrous layer. Freeze-fracture and deep-etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4-nm thick fibrils. In thin sections the endospore reveals a scattered electron-dense material that appears in the form of trabecular structures when analyzed in deep-etched samples. The presence of chitin in the exospore is discussed.

Animals↗
PubMedDate not supplied

Ultrastructural features of spindle microtubule organization during the nuclear division of Encephalitozoon hellem.

Ultrastructural studies were carried out to describe the nuclear division cycle of a strain of Encephalitozoon hellem isolated from an Italian AIDS patient. The nuclear division occurs during the proliferative vegetative phase and it is characterized by the intranuclear mitosis and by the lack of centrioles. The spindle termini are electron dense spindle plaques (ESPs), resembling to the spindle pole bodies (SPBs) of Saccharomycetes. The ESPs are bifacial organella forming microtubules on both nucleoplasic and cytoplasmic faces. In the outer layer of the spindle plaque are present vesicular elements lined by a double membrane of unknown function. The peculiar morphological features of E. hellem ESPs indicate that both intranuclear spindle and cytoplasmic microtubules are involved in the nuclear division.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Mechanisms of microsporidial cell division: ultrastructural study on Encephalitozoon hellem.

The mitotic process in microsporidian Encephalitozoon hellem, a known human pathogen, has been studied with the aim of elucidating some ultrastructural aspects of its nuclear division. The presence of a nuclear spindle, of "electrondense spindle plaques" associated with the nuclear envelope and of cytoplasmic double walled vesicles are reported. We suggest that these "electrondense spindle plaques" serve as foci for intranuclear and cytoplasmic microtubule arrangements, similar to the microtubule organizing centers within the centrosomes of animal cells. The extent to which the microsporidial division process is comparable with that of more familiar eukaryotes such as yeast cells is discussed.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Encephalitozoon hellem in two eclectus parrots (Eclectus roratus): identification from archival tissues.

Members of the phylum Microspora are obligate, intracellular, single-celled parasites identified in a wide range of vertebrate and invertebrate hosts. Only a few cases of microsporidial infections have been documented in psittacine birds including peach-faced, masked, and Fischer's lovebirds (Agapornis roseicollis, A. personata, and A. fischeri, respectively), budgerigars (Melopsittacus undulatus), and a double yellow-headed Amazon parrot (Amazona ochrocephala). Parasite identification has typically been limited to phylum or genus, and no avian species of microsporidia has clearly been described. In this report, microsporidia were identified in the kidney and intestine of a new host, the eclectus parrot (Eclectus roratus). Parasites were identified as Encephalitozoon hellem using morphologic, ultrastructural, and small subunit ribosomal RNA gene sequence data obtained from archived tissues. This parasite species was first identified in immunocompromised humans and may be a potential zoonotic pathogen. The epidemiology and prevalence of this parasite in humans and birds should be further explored.

Animals↗
PubMedDate not supplied

Identification of proteins in Encephalitozoon intestinalis, a microsporidian pathogen of immunocompromised humans: an immunoblotting and immunocytochemical study.

Microsporidia are unicellular and obligate intracellular spore-forming parasites. The spore inoculates the host cell with its non-motile infectious content, the sporoplasm, by way of the polar tube--the typical invasive apparatus of the microsporidian spore. Molecules involved in host cell invasion were investigated in Encephalitozoon intestinalis. Mouse polyclonal and monoclonal antibodies were raised against spore proteins and their reactivity was tested by Western-blotting and immunolocalization techniques, including electron and confocal microscopy. The antibodies thus generated could be divided into two major groups. One group reacted to the surface of the parasite at different developmental stages, mostly presporous stages and mature spores, whereas the other group recognized the polar tube. Of the antibodies reacting to the spore wall, one identified an exospore protein at 125 kDa while all others recognized a major doublet at 55-60 kDa, and minor proteins present at the surface of sporogonic stages and in the endospore. All antibodies recognizing spore wall proteins reacted also to the material forming septa in the parasitophorous vacuole. A major polar tube protein at 60 kDa was identified by another group of antibodies.

Animals↗
PubMedDate not supplied

Genetic diversity in the microsporidian Encephalitozoon hellem demonstrated by pulsed-field gel electrophoresis.

Encephalitozoon hellem is a microsporidian species responsible for opportunistic infections in AIDS patients. Use of a novel chitinase-based method allowed unsheared chromosomal DNA to be recovered from eleven E. hellem isolates derived from three geographic regions. All isolates were typed by 18S rDNA sequencing, which showed that they belonged to intemal transcribed spacer type 1. After ethidium bromide staining, pulsed-field gel electrophoresis (PFGE) analysis discriminated two new karyotypes comprising 7 and 8 chromosomal bands respectively, ranging in size from 205- to 272-kb pairs. Genomic size was estimated to be 2.39 Mb. Our data indicate PFGE is useful for typing E. hellem and confirms genetic diversity among E. hellem genotypes.

Animals↗