Encephalitozoon-like organisms in patients with alveolar hydatid disease: cell culture, ultrastructure, histoimmunochemical localization and seroprevalence

In vitro cultivation of microsporidia of clinical importance

Although attempts to develop methods for the in vitro cultivation of microsporidia began as early as 1937, the interest in the culture of these organisms was confined mostly to microsporidia that infect insects. The successful cultivation in 1969 of Encephalitozoon cuniculi, a microsporidium of mammalian origin, and the subsequent identification of these organisms as agents of human disease heightened interest in the cultivation of microsporidia. I describe the methodology as well as the cell lines, the culture media, and culture conditions used in the in vitro culture of microsporidia such as Brachiola (Nosema) algerae, Encephalitozoon cuniculi, E. hellem, E. intestinalis, Enterocytozoon bieneusi, Trachipleistophora hominis, and Vittaforma corneae that cause human disease.

Mouse antibody response to a microsporidian parasite following inoculation with a gene coding for parasite ribosomal RNA

This study found that a plasmid construct encoding the small-subunit ribosomal RNA (SSUrRNA) of the microsporidian Microgemma caulleryi generates a humoral response upon intramuscular inoculation in mice. The plasmid used was pCMV, following preliminary trials indicating efficient beta-galactosidase gene expression in mouse muscle cells transfected with pCMV/beta-Gal. The antibodies produced after inoculation with pCMV/SSUDNA recognized parasite spore antigens and reached maximum levels at 30 days postinoculation, subsequently remaining stable for at least 120 days. Due to the highly conserved sequence of the SSUrDNA in different microsporidian species, these results open up interesting prospects for broad-spectrum vaccination.

Respiratory burst responses of rat macrophages to microsporidian spores

This study investigated the respiratory burst responses of rat resident peritoneal macrophages and of peritoneal macrophages stimulated 5 days previously with viable spores of the fish infecting microsporidian Microgemma caulleryi. Nitric oxide production by resident macrophages and prestimulated macrophages in response to viable microsporidian spores was significantly lower than in response to Escherichia coli lipopolysaccharide (LPS) (nitrite concentration in medium 57 +/- 1 microM for resident macrophages stimulated with LPS versus 31 +/- 1 microM for resident macrophages stimulated with microsporidian spores and 36 +/- 4 microM for M. caulleryi prestimulated macrophages; P < 0.05). Extracellular release of reactive oxygen species (ROS) by resident macrophages in response to microsporidian spores was similar to that in response to Kluyveromyces lactis yeast cells and to that in response to phorbol myristate (a stimulator of protein C kinase). Intracellular ROS production by resident macrophages in response to microsporidian spores was similar to that produced in response to yeast cells. Both extracellular ROS production and intracellular ROS production (in response to all stimuli) were significantly lower after in vivo prestimulation of macrophages with microsporidian spores. These results demonstrate that microsporidian spores of species other than those that habitually infect mammals are capable of modulating the respiratory burst of rat peritoneal macrophages. Such modulation may contribute to avoidance by the microsporidian of cytotoxic responses associated with the respiratory burst.

Isolation of Encephalitozoon cuniculi using primary tissue culture techniques from a rabbit in a colony showing encephalitozoonosis

Encephalitozoon spores were isolated in a primary tissue culture of the kidneys from an encephalitozoonosis-suspected rabbit in a municipal zoo in Hokkaido. The isolated spores were morphologically characteristic of microsporidial ones in chromotrope stain, and proven to be E. cuniculi by a polymerase chain reaction (PCR) with a species-specific primer set and by direct DNA sequencing of the PCR products.

Detection of microsporidia spore-specific antigens by monoclonal antibodies

Microsporidia (phylum Microspora) are unicellular parasites commonly found in invertebrates, fish, and laboratory animals; however, microsporidiosis is an emerging problem in patients with the acquired immunodeficiency syndrome (AIDS). The infective stage of these parasites is the spore, which possesses a rigid cell wall that protects the parasite outside its host. Little is known about their antigenic composition. Sensitive, reliable, and easily performed methods for identification and speciation are generally not available. Here, we report the production of 21 MAbs specific to spore antigens of several species of Microsporidia. MAbs were generated to purified spores of Encephalitozoon intestinalis and Encephalitozoon hellem, and their reactivities were tested against spores and intracellular developing forms of E. intestinalis, E. hellem, Encephalitozoon cuniculi, and Vittaforma corneae. Both species-specific and broad-reactivity MAbs were produced. Five MAbs reacted against the spores of all four species tested: 7 with 3 species, 6 with 2 species, 1 with E. intestinalis, and 4 with the polar tube of all species. Immunoelectron microscopy confirmed the reactivity of specific MAbs to the spore wall or the polar tube. These MAbs reacted to a few antigens as determined by Western blot, and none of the epitopes were periodate-sensitive. These MAbs may be useful in the diagnosis and speciation of Microsporidia as well in the purification, cloning, and detection of these antigens.

Nucleotide sequences of DNA fragments of Encephalitozoon cuniculi amplified by polymerase chain reaction with primers regarded as specific for Echinococcus

Encephalitozoon-like spores were separated from a human echinococcal liver lesion, which was caused by Echinococcus multilocularis. They were found to fall into the species Encephalitozoon cuniculi, which was shown to have En. cuniculi-specific DNA by way of polymerase chain reaction (PCR). We also used PCR to genetically discriminate between the En. cuniculi spores and the Ec. multilocularis larvae. Two primer sets, known to be specific for Echinococcus, were examined. These primers were expected to work normally when the two quite different DNA preparations were tested as templates, i.e. only Echinococcus DNA could give a positive signal in the PCR tests. However, it was found that the two Echinococcus-specific primer sets could amplify not only Ec. multilocularis DNA, but also En. cuniculi spore DNA. We then tried to determine the order of nucleotides in the Echinococcus-specific primers-amplified En. cuniculi PCR products and compared the determined sequences with those of Ec. multilocularis. The results clearly indicated that sequencing made little difference between En. cuniculi and Ec. multilocularis.