Microsporidia: Obligate Intracellular Pathogens Within the Fungal Kingdom

Innate and Adaptive Immune Responses Against Microsporidia Infection in Mammals

Microsporidia are obligate intracellular and eukaryotic pathogens that can infect immunocompromised and immunocompetent mammals, including humans. Both innate and adaptive immune systems play important roles against microsporidian infection. The innate immune system can partially eliminate the infection by immune cells, such as gamma delta T cell, natural killer cells (NKs), macrophages and dendritic cells (DCs), and present the pathogens to lymphocytes. The innate immune cells can also prime and enhance the adaptive immune response via surface molecules and secreted cytokines. The adaptive immune system is critical to eliminate microsporidian infection by activating cytotoxic T lymphocyte (CTL) and humoral immune responses, and feedback regulation of the innate immune mechanism. In this review, we will discuss the cellular and molecular responses and functions of innate and adaptive immune systems against microsporidian infection.

Microscopic and PCR-based detection of microsporidia spores in human stool samples

Microsporidia are obligate intracellular fungi with a remarkable ability to infect a wide range of invertebrate and vertebrate hosts. Namely, Enterocytozoon bieneusi is the most frequently microsporidia reported worldwide, and mainly associated with chronic diarrhea and wasting syndrome in AIDS patients. Microscopy and PCR-based detection techniques are effective for diagnosis and identification of species and genotypes; however, these methods should be standardized in each laboratory. In this study, we performed microscopy and nested PCR techniques with PCR product sequencing to detect E. bieneusi in human stool samples. These techniques, if applied together, might prove useful for diagnosis and future epidemiological studies of intestinal microsporidiosis in Argentina.

A microsporidian impairs Plasmodium falciparum transmission in Anopheles arabiensis mosquitoes

A possible malaria control approach involves the dissemination in mosquitoes of inherited symbiotic microbes to block Plasmodium transmission. However, in the Anopheles gambiae complex, the primary African vectors of malaria, there are limited reports of inherited symbionts that impair transmission. We show that a vertically transmitted microsporidian symbiont (Microsporidia MB) in the An. gambiae complex can impair Plasmodium transmission. Microsporidia MB is present at moderate prevalence in geographically dispersed populations of An. arabiensis in Kenya, localized to the mosquito midgut and ovaries, and is not associated with significant reductions in adult host fecundity or survival. Field-collected Microsporidia MB infected An. arabiensis tested negative for P. falciparum gametocytes and, on experimental infection with P. falciparum, sporozoites aren't detected in Microsporidia MB infected mosquitoes. As a microbe that impairs Plasmodium transmission that is non-virulent and vertically transmitted, Microsporidia MB could be investigated as a strategy to limit malaria transmission.

Expression of Nosema bombycis polar tube protein 1 in lepidopteran Sf9 cells and its effect on microsporidian proliferation

Nosema bombycis, the first identified microsporidium, causes heavy losses to the sericulture industry in China. During infection, microsporidia discharge a long and hollow polar tube, which delivers the sporoplasm into host cells. Polar tube protein 1 was the major component on the polar tube. Previously, we expressed the polar tube protein 1 from Nosema bombycis (NbPTP1) intercellularly in Drosophila S2 cells. Here, the microsporidian protein was expressed in Lepidopteran Sf9 cells. During heterologous expression, NbPTP1 protein was secreted and glycosylated. Microsporidian proliferation decreased in NbPTP1-expressing Sf9 cells. This confirms that NbPTP1 protein can interact with the host cell membrane receptor protein to facilitate microsporidian invasion.

Evolutionary Diversity in the Intracellular Microsporidian Parasite Nosema sp. Infecting Wild Silkworm Revealed by IGS Nucleotide Sequence Diversity

Intracellular microsporidian Nosema mylitta infects Indian wild silkworm Antheraea mylitta causing pebrine disease. Genetic structure and phylogeny of N. mylitta are analysed using nucleotide variability in 5S ribosomal DNA and intergenic spacer (IGS) sequence from 20 isolates collected from Southern, Northern and Central regions of Jharkhand State. Nucleotide diversity (π) and genetic differentiation Gst were highest in the Central isolates whereas lowest in the North. Among the isolates, absence of nucleotides, transitions and transversions were observed. Haplotyping showed nucleotide variability at 83 positions in IGS and 13 positions in 5S rDNA. Haplotype-based genetic differentiation was 0.96 to 0.97 whereas nucleotide sequence-based genetic differentiation was higher (Ks = 22.29) between Southern and Central isolates. Bottleneck analysis showed negative value for Tajima's D and other summary statistics revealing induction of loss of rare alleles and population explosion. From IGS, 17 ancestral sequences were inferred by Network algorithm. Core of nine closely related nodes having ancient nucleotides and peripheral nodes with highly divergent nucleotides were derived. Most diverged peripheral haplotype was Bero (H11) from the Central region whereas Deoghar (H3) of the Northern region diverged early. Phylogeny of N. mylitta grouped Southern and Northern isolates together revealed weak phylogenetic signal for these locations. Phylogeny of N. mylitta with Nosema sp. infecting other lepidopterans clustered N. mylitta isolates with N. antheraea and N. philosamiae of China indicating genetic similarity whereas other species were dissimilar showing diversity irrespective of country of origin.

Encephalitozoon cuniculi infection in farmed rabbits in Egypt

BACKGROUND

Encephalitozoon cuniculi is an important microsporidian parasite with zoonotic potential. The present study highlights the impact of encephalitozoonosis on rabbit health in Egypt. Three rabbit farms in Giza, with a total of 16,400 rabbits were investigated due to occurrence of rabbits displaying clinical signs consistent with encephalitozoonosis.

RESULTS

Clinical signs observed during a 4 months observation period in 2018 included vestibular disease, paresis, limb paralysis, cataracts, phacoclastic uveitis, frequent urination, marked decrease in body weight and in some pregnant females, also repeated abortions. The total morbidity rates in adult and young rabbits were 76.7% and 81.5%, respectively. The highest mortality rate was recorded in offspring (12.3%), followed by dams (5.6%), and the lowest recorded mortality rate was in males (0.04%). Post-mortem findings included enteritis, pale enlarged kidneys, congested leptomeninges, focal brain necrosis, and endometrial congestion. Histopathological examination revealed nonsuppurative meningoencephalitis and glial nodules with central necrosis in the brain, vacuolation and necrosis of renal tubular epithelium, and corneal ulceration and ruptured lens capsule with fragmentation of lenticular fibres. E. cuniculi were observed in the brain, retinal ganglion cells, kidneys, and liver. Transmission electron microscopy examination revealed the presence of different developmental stages of E. cuniculi in the brain and kidney. Presence of E. cuniculi was confirmed by conventional polymerase chain reaction using a universal 16S gene for Encephalitozoon spp. followed by sequencing and sequence analysis.

CONCLUSIONS

The presence of E. cuniculi in rabbits was confirmed at three farms in Egypt. Nervous signs and ocular lesions were the most predominant findings in these farms.

Cell invasion by intracellular parasites - the many roads to infection

Intracellular parasites from the genera Toxoplasma, Plasmodium, Trypanosoma, Leishmania and from the phylum Microsporidia are, respectively, the causative agents of toxoplasmosis, malaria, Chagas disease, leishmaniasis and microsporidiosis, illnesses that kill millions of people around the globe. Crossing the host cell plasma membrane (PM) is an obstacle these parasites must overcome to establish themselves intracellularly and so cause diseases. The mechanisms of cell invasion are quite diverse and include (1) formation of moving junctions that drive parasites into host cells, as for the protozoans Toxoplasma gondii and Plasmodium spp., (2) subversion of endocytic pathways used by the host cell to repair PM, as for Trypanosoma cruzi and Leishmania, (3) induction of phagocytosis as for Leishmania or (4) endocytosis of parasites induced by specialized structures, such as the polar tubes present in microsporidian species. Understanding the early steps of cell entry is essential for the development of vaccines and drugs for the prevention or treatment of these diseases, and thus enormous research efforts have been made to unveil their underlying biological mechanisms. This Review will focus on these mechanisms and the factors involved, with an emphasis on the recent insights into the cell biology of invasion by these pathogens.

Invasion of Host Cells by Microsporidia

Microsporidia are found worldwide and both vertebrates and invertebrates can serve as hosts for these organisms. While microsporidiosis in humans can occur in both immune competent and immune compromised hosts, it has most often been seen in the immune suppressed population, e.g., patients with advanced HIV infection, patients who have had organ transplantation, those undergoing chemotherapy, or patients using other immune suppressive agents. Infection can be associated with either focal infection in a specific organ (e.g., keratoconjunctivitis, cerebritis, or hepatitis) or with disseminated disease. The most common presentation of microsporidiosis being gastrointestinal infection with chronic diarrhea and wasting syndrome. In the setting of advanced HIV infection or other cases of profound immune deficiency microsporidiosis can be extremely debilitating and carries a significant mortality risk. Microsporidia are transmitted as spores which invade host cells by a specialized invasion apparatus the polar tube (PT). This review summarizes recent studies that have provided information on the composition of the spore wall and PT, as well as insights into the mechanism of invasion and interaction of the PT and spore wall with host cells during infection.

Morphology and Transcriptome Analysis of Nosema bombycis Sporoplasm and Insights into the Initial Infection of Microsporidia

Once awoken from dormancy, the cellular matter of microsporidia is delivered directly into the host cell cytoplasm through the polar tube. This means that the microsporidia are difficult to study biologically in their active state without a contaminating signal from the host cell. Sporoplasm is a cell type of microsporidia in vitro, but relatively little attention has been paid to the sporoplasm in the past 150 years due to a lack of an effective separation method. Nosema bombycis, the first reported microsporidium, is a type of obligate intracellular parasite that infects silkworms and can be induced to germinate in alkaline solution in vitro. We successfully separated the N. bombycis sporoplasm in vitro, and the morphological and structural characteristics were investigated. These results provide important insight into the biology and pathogenesis of microsporidia and potentially provide a possible strategy for genetic manipulation of microsporidia targeting the sporoplasm.

Microsporidia are obligate intracellular parasites that infect a wide variety of host organisms, including humans. The sporoplasm is the initial stage of microsporidian infection and proliferation, but its morphological and molecular characteristics are poorly understood. In this study, the sporoplasm of Nosema bombycis was successfully isolated and characterized after the induction of spore germination in vitro. The sporoplasm was spherical, 3.64 ± 0.41 μm in diameter, had the typical two nuclei, and was nonrefractive. Scanning and transmission electron microscopy analyses revealed that the sporoplasm was surrounded by a single membrane, and the cytoplasm was usually filled with relatively homogeneous granules, possibly ribosomes, and contained a vesicular structure comprising a concentric ring and coiled tubules. Propidium iodide staining revealed that the sporoplasm membrane showed stronger membrane permeability than did the cell plasma membrane. Transmission electron microscopy (TEM) revealed that the sporoplasm can gain entry to the host cell by phagocytosis. Transcriptome analysis of mature spores and sporoplasms showed that 541 significantly differentially expressed genes were screened (adjusted P value [P_adj] < 0.05), of which 302 genes were upregulated and 239 genes were downregulated in the sporoplasm. The majority of the genes involved in trehalose synthesis metabolism, glycolysis, and the pentose phosphate pathway were downregulated, whereas 10 transporter genes were upregulated, suggesting that the sporoplasm may inhibit its own carbon metabolic activity and obtain the substances required for proliferation through transporter proteins. This study represents the first comprehensive and in-depth investigation of the sporoplasm at the morphological and molecular levels and provides novel insights into the biology of microsporidia and their infection mechanism.

IMPORTANCE Once awoken from dormancy, the cellular matter of microsporidia is delivered directly into the host cell cytoplasm through the polar tube. This means that the microsporidia are difficult to study biologically in their active state without a contaminating signal from the host cell. Sporoplasm is a cell type of microsporidia in vitro, but relatively little attention has been paid to the sporoplasm in the past 150 years due to a lack of an effective separation method. Nosema bombycis, the first reported microsporidium, is a type of obligate intracellular parasite that infects silkworms and can be induced to germinate in alkaline solution in vitro. We successfully separated the N. bombycis sporoplasm in vitro, and the morphological and structural characteristics were investigated. These results provide important insight into the biology and pathogenesis of microsporidia and potentially provide a possible strategy for genetic manipulation of microsporidia targeting the sporoplasm.

Molecular epidemiology of Enterocytozoon bieneusi and Encephalitozoon sp., among immunocompromised and immunocompetent subjects in Iran

Intestinal microsporidiosis is known as an opportunistic infection in immunocompromised patients. The current study aimed to investigate intestinal microsporidia infection in human subjects with/without immunodeficiency. Totally, 600 stool samples were collected from immunocompromised (254) and immunocompetent (346) subjects. DNA extraction was performed and the SSU rRNA and the ITS genes were amplified to detect and characterize microsporidia and the relevant genotypes. Phylogenetic trees were drawn using MEGA7 software to illustrate the correlation between isolates. From 600 enrolled subjects, 283 and 317 were male and female, respectively. The average age ± SD of all tested subjects was 28.85 ± 26.92. The results of PCR demonstrated the presence of E. bieneusi and Encephalitozoon sp., among 10/600 (1.67%) and 26/600 (4.33%) of samples, respectively. Accordingly, E. bieneusi was seen among 4/346 (1.15%), 1/53 (1.88%), 3/124 (2.42%), and 2/63 (3.17%), and Encephalitozoon sp., was detected from 17/346 (4.91%), 3/53 (5.36%), 4/124 (3.22%) and 2/63 (3.17%) of healthy subjects, RA patients, cancer patients, and transplantation recipients, respectively. Statistical significant correlation was not seen between the presence of microsporidia and age, gender, stool appearance, and geographical region. Molecular analysis showed that all E. bieneusi were the genotype D. Phylogenetic tree demonstrated no classification according to the presence/absence of immunodeficiency, geographical locations and presence of diarrhea. The high prevalence of Encephalitozoon sp., in comparison to E. bieneusi in this study suggested the importance of this genus alongside with E. bieneusi in Iran. In addition, predominance of the genotype D highlighted the wide distribution of this genotype in Iran.

Microsporidia Nosema spp. - obligate bee parasites are transmitted by air

Microsporidia Nosema are transferred among bees via the faecal-oral route. Nosema spp. spores have been detected on flowers and transferred to hives along with the bee pollen. The aim of the present study was to determine whether Nosema microsporidia are transferred by air in an apiary, in a control area (without the presence of bee colonies), and/or in a laboratory during cage experiments with artificially infected bees. The novel way of transmission by air was investigated by the volumetric method using a Hirst-type aerobiological sampler located on the ground in the apiary, in the Botanical Garden and on the laboratory floor. Concurrently, the mean rate of Nosema infections in the foragers in the apiary was estimated with the Bürker haemocytometer method. Spore-trapping tapes were imaged by means of light microscopy, Nomarski interference contrast microscopy and scanning electron microscopy. The highest concentration of Nosema spores per 1m3 of air (4.65) was recorded in August, while the lowest concentration (2.89) was noted in July. This was confirmed by a Real-Time PCR analysis. The presence of N. apis as well as N. ceranae was detected in each of the tested tapes from the apiary. The average copy number of N. apis was estimated at 14.4 × 104 copies per 1 cm2 of the tape; whereas the number of N. ceranae was 2.24 × 104 copies per tape per 1 cm2. The results indicate that Nosema microsporidia were transferred by the wind in the apiary, but not in the Botanical Garden and laboratory by air. This was confirmed by genetic analyses. DNA from immobilised biological material was isolated and subjected to a PCR to detect the Nosema species. A fragment of the 16S rRNA gene, characteristic of Nosema apis and N. ceranae, was detected. Our research adds knowledge about the transfer of Nosema spp. microsporidia in the natural environment and indicates the season associated with the greatest risk of a bee colony infection with Nosema spp.

Cyclophosphamide Treatment Mimics Sub-Lethal Infections With Encephalitozoon intestinalis in Immunocompromised Individuals

Microsporidia, including Encephalitozoon intestinalis, are emerging pathogens which cause opportunistic infections in immunocompromised patients, such as those with AIDS, cancer, the elderly and people on immunosuppressive drugs. Intestinal mucosa (IM) is crucial for developing an efficient adaptive immune response against pathogenic micro-organisms, thereby preventing their colonization and subsequent infection. As immunosuppressive drugs affect the intestinal immune response is little known. In the present study, we investigated the immune response to E. intestinalis infection in the IM and gut-associated lymphoid tissue (GALT) in cyclophosphamide (Cy) immunosuppressed mice, to mimic an immunocompromised condition. Histopathology revealed lymphoplasmacytic enteritis at 7 and 14 days-post-infection (dpi) in all infected groups, however, inflammation diminished at 21 and 28 dpi. Cy treatment also led to a higher number of E. intestinalis spores and lesions, which reduced at 28 dpi. In addition, flow cytometry analysis demonstrated CD4⁺ and CD8⁺ T cells to be predominant immune cells, with up-regulation in both Th1 and Th2 cytokines at 7 and 14 dpi, as demonstrated by histopathology. In conclusion, Cy treatment reduced GALT (Peyer’s plaques and mesenteric lymph nodes) and peritoneum populations but increased the T-cell population in the intestinal mucosa and the production of pro-and anti-inflammatory cytokines, which were able to eliminate this opportunistic fungus and reduced the E. intestinalis infection.

Microsporidial myositis in adult-onset immunodeficiency: case-based review

Polymyositis is a diagnosis of exclusion. In patients with odd features, it can be of infective etiology. A high index of suspicion is required for diagnosis. A 55-year-old gentleman presented with gradual-onset proximal muscle weakness. Examination revealed mild distal weakness but no rash. Muscle enzymes were raised and tests for autoantibodies were negative. Biopsy revealed microsporidiosis. In view of this unusual infection, immunodeficiency was considered and he was found to have lymphopenia which antedated his illness. Later, he developed cranial nerve palsies due to multiple lesions in the pons. In addition, he had Cytomegalovirus viremia. Literature was reviewed to identify 20 cases of microsporidial myositis, its presentation, underlying immunodeficient state, and clinical course. Infective polymyositis should be considered in a patient with paucity of clinical and serological autoimmune features. Lymphopenia can point to underlying immunodeficiency. CMV infection could be the contributor to or bystander-effect of idiopathic lymphopenia.

A new scope for orlistat: Effect of approved anti-obesity drug against experimental microsporidiosis

As the current therapies for intestinal microsporidiosis are either inconsistent in their efficacies or hampered by several adverse effects, alternative antimicrosporidial agents are being sought. The present study is the first that was designed to evaluate the potency of orlistat, an approved anti-obesity drug, against intestinal microsporidiosis caused by both Enterocytozoon bieneusi and Encephalitozoon intestinalis. Results were assessed through studying fecal and intestinal spore load, intestinal histopathological changes, viability, and infectivity of spores from treated animals. Results showed that orlistat has promising antimicrosporidia potential, with better results in E. intestinalis than E. bieneusi. The animals that received orlistat showed statistically significant decrease in the fecal and intestinal spore load, when compared to the corresponding control infected nontreated mice. The results were insignificant compared to fumagillin and albendazole. Light microscopic examination of stained intestinal sections revealed amelioration of the pathological changes and decreased inflammatory cells detected in the control infected nontreated mice. Spores encountered from stool of orlistat-treated E. bieneusi and E. intestinalis mice showed low viability and significant reduction of infectivity versus their control. Thus, considering the results of the present work, orlistat proved its effectiveness against the intestinal microsporidial infection.

Putative group I introns in the eukaryote nuclear internal transcribed spacers

Group I introns are mobile genetic elements that interrupt genes encoding proteins and RNAs. In the rRNA operon, introns can insert in the small subunit (SSU) and large subunit (LSU) of a wide variety of protists and various prokaryotes, but they were never found in the ITS region. In this study, unusually long ITS regions of fungi and closely related unicellular organisms (Polychytrium aggregatum, Mitosporidium daphniae, Amoeboaphelidium occidentale and Nuclearia simplex) were analysed. While the insertion of repeats is responsible for long ITS in other eukaryotes, the increased size of the sequences analysed herein seems rather due to the presence of introns in ITS-1 or ITS-2. The identified insertions can be folded in secondary structures according to group I intron models, and they cluster within introns in conserved core-based phylogeny. In addition, for Mitosporidium, Amoeboaphelidium and Nuclearia, more conventional ITS-2 structures can be deduced once spacer introns are removed. Sequences of five shark species were also analysed for their structure and included in phylogeny because of unpublished work reporting introns in their ITS, obtaining congruent results. Overall, the data presented herein indicate that spacer regions may contain introns.

Microsporidia Interact with Host Cell Mitochondria via Voltage-Dependent Anion Channels Using Sporoplasm Surface Protein 1

Microsporidia are opportunistic intracellular pathogens that can infect a wide variety of hosts ranging from invertebrates to vertebrates. During invasion, the microsporidian polar tube pushes into the host cell, creating a protective microenvironment, the invasion synapse, into which the sporoplasm extrudes. Within the synapse, the sporoplasm then invades the host cell, forming a parasitophorous vacuole (PV). Using a proteomic approach, we identified Encephalitozoon hellem sporoplasm surface protein 1 (EhSSP1), which localized to the surface of extruded sporoplasms. EhSSP1 was also found to interact with polar tube protein 4 (PTP4). Recombinant EhSSP1 (rEhSSP1) bound to human foreskin fibroblasts, and both anti-EhSSP1 and rEhSSP1 caused decreased levels of host cell invasion, suggesting that interaction of SSP1 with the host cell was involved in invasion. Coimmunoprecipitation (Co-IP) followed by proteomic analysis identified host cell voltage-dependent anion channels (VDACs) as EhSSP1 interacting proteins. Yeast two-hybrid assays demonstrated that EhSSP1 was able to interact with VDAC1, VDAC2, and VDAC3. rEhSSP1 colocalized with the host mitochondria which were associated with microsporidian PVs in infected cells. Transmission electron microscopy revealed that the outer mitochondrial membrane interacted with meronts and the PV membrane, mitochondria clustered around meronts, and the VDACs were concentrated at the interface of mitochondria and parasite. Knockdown of VDAC1, VDAC2, and VDAC3 in host cells resulted in significant decreases in the number and size of the PVs and a decrease in mitochondrial PV association. The interaction of EhSSP1 with VDAC probably plays an important part in energy acquisition by microsporidia via its role in the association of mitochondria with the PV.IMPORTANCE Microsporidia are important opportunistic human pathogens in immune-suppressed individuals, such as those with HIV/AIDS and recipients of organ transplants. The sporoplasm is critical for establishing microsporidian infection. Despite the biological importance of this structure for transmission, there is limited information about its structure and composition that could be targeted for therapeutic intervention. Here, we identified a novel E. hellem sporoplasm surface protein, EhSSP1, and demonstrated that it can bind to host cell mitochondria via host VDAC. Our data strongly suggest that the interaction between SSP1 and VDAC is important for the association of mitochondria with the parasitophorous vacuole during microsporidian infection. In addition, binding of SSP1 to the host cell is associated with the final steps of invasion in the invasion synapse.

First insight into Encephalitozoon cuniculi infection in laboratory and pet rabbits in Iran

Encephalitozoon cuniculi infects a wide variety of domestic and wild mammalian species including humans. Although the infection status has been studied in laboratory and pet rabbits worldwide, there is shortage of information regarding the disease in Iran. In the present study, the occurrence of infection in brains of 117 asymptomatic rabbits from six breeding and experimental units with highest population of rabbit colonies in the country (n = 60) as well as pet rabbits of pet stores in two cities (n = 57) were examined by nested-PCR. Histological sections of brains and kidneys were also studied by light microscopy. PCR results revealed that 3.3% of laboratory rabbits (2/60) and 59.6% of pet rabbits (34/57) harboured E. cuniculi in their brains. Histopathology on the other hand showed spores of the parasite in kidney and brain of one and kidney of another pet rabbit. As encephalitozoonosis may interfere with results of experiments performed on laboratory rabbits, routine screenings for identification and culling of infected animals is recommended. Furthermore, infected companion rabbits can transmit E. cuniculi to people in close contact with them, therefore, improving public knowledge of this zoonotic infection is suggested.

An optimized assay for detecting Encephalitozoon intestinalis and Enterocytozoon bieneusi in dairy calf feces using polymerase chain reaction technology

The purpose of this study was to optimize primary and nested polymerase chain reaction (PCR) assays for detecting the microsporidia Encephalitozoon intestinalis and Enterocytozoon bieneusi in fecal samples from dairy calves. PCR for these microsporidia were compared to immunofluorescence assays (IFA) based on commercially available monoclonal antibodies specific for outer wall proteins of Enc. intestinalis or Ent. bieneusi. Fecal samples were collected from 15 dairy calves and processed by molecular sieving followed by salt floatation to recover Enc. intestinalis and Ent. bieneusi spores. An aliquot of the final supernatant was applied to glass slides for IFA testing; another aliquot was extracted for total DNA using a QIAamp Stool Mini-Kit for primary and nested Enc. intestinalis- and Ent. bieneusi-specific PCR analysis. Internal standards were generated for both Enc. intestinalis and Ent. bieneusi PCR assays to control for false negative reactions due to the presence of inhibitors commonly found in fecal samples. Using the commercial MicrosporIFA (Waterborne, Inc.) as the gold standard, the optimized Enc. intestinalis PCR method provided 85.7% sensitivity and 100% specificity with a kappa value = 0.865. Likewise, using the commercial BienusiGlo IFA (Waterborne, Inc.) as the gold standard, the optimized Ent. bieneusi PCR method provided 83.3% sensitivity and 100% specificity with a kappa value = 0.857. Sequencing of amplicons from both PCR assays confirmed the presence of Enc. intestinalis or Ent. bieneusi. In conclusion, our optimized assays for recovering and detecting Enc. intestinalis or Ent. bieneusi in feces from dairy calves provides a valuable alternative to traditional IFA methods that require expertise to identify extremely small microsporidia spores (~ 2.0 µm). Our assays also improve upon existing molecular detection techniques for these microsporidia by incorporating an internal standard to control for false negative reactions.

Single-cell analysis reveals the effects of glutaraldehyde and formaldehyde on individual Nosema bombycis spores

Single-cell analysis based on optical techniques offers new understanding of the action underlying the use of aldehyde disinfectants against microsporidia spores.

Encephalitozoon: Tissue Culture, Cryopreservation, and Murine Infection

Microsporidia are eukaryotic unicellular parasites that have been studied for more than 150 years. They are found throughout the world and are capable of infecting various invertebrate and vertebrate hosts. They can cause disease in both immune-compromised and immune-competent humans. In immune-compromised individuals, infections can be severe and often fatal. Microsporidia possess a unique, highly specialized invasion mechanism that involves a structure known as the polar tube as well as the spore wall. During spore germination, the polar tube rapidly discharges from the spore and deliver the sporoplasm into the host cell. Spores are the only stage of microsporidia that can survive outside of host cells. Since the first attempt to culture microsporidia in vitro in 1930s, their cultivation has served a critical role in the study and diagnosis of these parasites. In this chapter, we include methods on the cultivation, isolation, and cryopreservation of Encephalitozoon cuniculi, which can infect humans and provides a useful model for other microsporidia. These methods can also be utilized for the culture of Encephalitozoon hellem or Encephalitozoon intestinalis. © 2018 by John Wiley & Sons, Inc.

Therapeutic targets for the treatment of microsporidiosis in humans

INTRODUCTION

Microsporidia have been increasingly reported to infect humans. The most common presentation of microsporidiosis is chronic diarrhea, a significant mortality risk in immune-compromised patients. Albendazole, which inhibits tubulin, and fumagillin, which inhibits methionine aminopeptidase type 2 (MetAP2), are the two main therapeutic agents used for treatment of microsporidiosis. In addition, to their role as emerging pathogens in humans, microsporidia are important pathogens in insects, aquaculture, and veterinary medicine. New therapeutic targets and therapies have become a recent focus of attention for medicine, veterinary, and agricultural use. Areas covered: Herein, we discuss the detection and symptoms of microsporidiosis in humans and the therapeutic targets that have been utilized for the design of new drugs for the treatment of this infection, including triosephosphate isomerase, tubulin, MetAP2, topoisomerase IV, chitin synthases, and polyamines. Expert opinion: Enterocytozoon bieneusi is the most common microsporidia in human infection. Fumagillin has a broader anti-microsporidian activity than albendazole and is active against both Ent. bieneusi and Encephaliozoonidae. Microsporidia lack methionine aminopeptidase type 1 and are, therefore, dependent on MetAP2, while mammalian cells have both enzymes. Thus, MetAP2 is an essential enzyme in microsporidia and new inhibitors of this pathway have significant promise as therapeutic agents.

Single-cell Raman spectroscopy reveals microsporidia spore heterogeneity in various insect hosts

Single-cell Raman spectroscopy was used to analyze the spore heterogeneity of 16 microsporidia strains from various insect hosts in order to better understand the basic biology of microsporidia. The Raman spectrum of a single spore revealed basic spore composition, and microsporidia spores in various hosts were found to be rich in trehalose. Principal component analysis and Raman intensity showed obvious heterogeneity in the trehalose, nucleic acid, and protein content of various spores; however, there was no correlation between various spore groups and host type. Trehalose content correlated with spore infectivity on Bombyx mori. Raman spectroscopy is an excellent tool for label-free investigation of intercellular molecular constituents, providing insight into the heterogeneity of microsporidia spores.

The genome of an intranuclear parasite, Paramicrosporidium saccamoebae, reveals alternative adaptations to obligate intracellular parasitism

Intracellular parasitism often results in gene loss, genome reduction, and dependence upon the host for cellular functioning. Rozellomycota is a clade comprising many such parasites and is related to the diverse, highly reduced, animal parasites, Microsporidia. We sequenced the nuclear and mitochondrial genomes of Paramicrosporidium saccamoebae [Rozellomycota], an intranuclear parasite of amoebae. A canonical fungal mitochondrial genome was recovered from P. saccamoebae that encodes genes necessary for the complete oxidative phosphorylation pathway including Complex I, differentiating it from most endoparasites including its sequenced relatives in Rozellomycota and Microsporidia. Comparative analysis revealed that P. saccamoebae shares more gene content with distantly related Fungi than with its closest relatives, suggesting that genome evolution in Rozellomycota and Microsporidia has been affected by repeated and independent gene losses, possibly as a result of variation in parasitic strategies (e.g. host and subcellular localization) or due to multiple transitions to parasitism.