Microsporidia: emerging pathogenic protists

The global epidemiology of Microsporidia infection in birds: A systematic review and meta-analysis

This study aimed to assess the global status and genetic diversity of Microsporidia infection in different birds. An online search was conducted in international databases from 1 January 1990 to 30 June 2022. A total of 34 articles (including 37 datasets) were included for the final meta-analysis. The pooled global prevalence of Microsporidia infection in birds was 14.6% (95% CI: 11.6-18.1). The highest prevalence of Microsporidia was found in wild waterfowl which was 54.5% (28.1-78.6). In terms of detection methods, the pooled prevalence was estimated to be 21.2% (95% CI: 12.1-34.4) and 13.4% (95% CI: 10.3-17.3) for using microscopic and molecular detection methods, respectively. Enterocytozoon bieneusi was the most common pathogen (24/31; 77.42% of the studies) according to PCR-based methods, and genotype D was the highest reported genotype (nine studies). In conclusion, designing strategies for the control and prevention of Microsporidia infection in birds should be recommended.

E. hellem Ser/Thr protein phosphatase PP1 targets the DC MAPK pathway and impairs immune functions

Microsporidia are difficult to be completely eliminated once infected, and the persistence disrupts host cell functions. Here in this study, we aimed to elucidate the impairing effects and consequences of microsporidia on host DCs. Enterocytozoon hellem, one of the most commonly diagnosed zoonotic microsporidia species, was applied. In vivo models demonstrated that E. hellem-infected mice were more susceptible to further pathogenic challenges, and DCs were identified as the most affected groups of cells. In vitro assays revealed that E. hellem infection impaired DCs' immune functions, reflected by down-regulated cytokine expressions, lower extent of maturation, phagocytosis ability, and antigen presentations. E. hellem infection also detained DCs' potencies to prime and stimulate T cells; therefore, host immunities were disrupted. We found that E. hellem Ser/Thr protein phosphatase PP1 directly interacts with host p38α (MAPK14) to manipulate the p38α(MAPK14)/NFAT5 axis of the MAPK pathway. Our study is the first to elucidate the molecular mechanisms of the impairing effects of microsporidia on host DCs' immune functions. The emergence of microsporidiosis may be of great threat to public health.

Microsporidia persistence in host impairs epithelial barriers and increases chances of inflammatory bowel disease

Microsporidia are intracellular fungus-like pathogens and the infection symptoms include recurrent diarrhea and systematic inflammations. The major infection route of microsporidia is the digestive tract. Since microsporidia are hard to fully eliminate, the interactions and persistence of the pathogen within epithelium may modulate host susceptibility to digestive disorders. In this study, both in vitro and in vivo infection models were applied. The alterations of epithelial barrier integrity, permeability, and tight junction proteins after microsporidia infection were assessed on MDCK/Caco-2 monolayers. The fecal intestinal microbiota and tissue alterations after microsporidia infection were assessed on C57BL/6 mice. Moreover, the susceptibility to develop dextran sulfate sodium (DSS)-induced inflammatory bowel diseases (IBDs) was also analyzed by the murine infection model. The results demonstrated that microsporidia infection increased epithelium permeability, weakened wound healing capability, and destructed tight junction protein zonula occludens-1. Microsporidia infection also dysregulates intestinal microbiota. These impairing effects of microsporidia increased host vulnerability to develop enteritis as shown by the murine model of DSS-induced IBD. Our study is the first to elucidate molecular mechanisms of the damaging effects of microsporidia on host epithelium and pointed out the cryptic threats of latent microsporidia infection to public health as reflected by the increased chances of developing more severe diseases.IMPORTANCEMicrosporidia are widely present in nature and usually cause latent and persistent infections in hosts. Given the fact that the digestive tract is the major infection route, it is of great importance to explore the consequences of microsporidia infection on the intestinal epithelial barrier and the risks to the host. In this study, we demonstrated the destructing effects of microsporidium infection on epithelial barriers manifested as increased epithelial permeability, weakened wound healing ability, and disrupted tight junctions. Moreover, microsporidia made the host more susceptible to dextran sulfate sodium-induced inflammatory bowel disease. These findings provide new evidence for us to better understand and develop novel strategies for microsporidia prevention and disease control.

Ssn6 Interacts with Polar Tube Protein 2 and Transcriptional Repressor for RNA Polymerase II: Insight into Its Involvement in the Biological Process of Microsporidium Nosema bombycis

Nosema bombycis is a representative species of Microsporidia, and is the pathogen that causes pebrine disease in silkworms. In the process of infection, the polar tube of N. bombycis is injected into the host cells. During proliferation, N. bombycis recruits the mitochondria of host cells. The general transcriptional corepressor Ssn6 contains six tetratricopeptide repeats (TPR) and undertakes various important functions. In this study, we isolated and characterized Nbssn6 of the microsporidium N. bombycis. The Nbssn6 gene contains a complete ORF of 1182 bp in length that encodes a 393 amino acid polypeptide. Indirect immunofluorescence assay showed that the Ssn6 protein was mainly distributed in the cytoplasm and nucleus at the proliferative phase of N. bombycis. We revealed the interaction of Nbssn6 with polar tube protein 2 (Nbptp2) and the transcriptional repressor for RNA polymerase II (Nbtrrp2) by Co-IP and yeast two-hybrid assays. Results from RNA interference further confirmed that the transcriptional level of Nbptp2 and Nbtrrp2 was regulated by Nbssn6. These results suggest that Nbssn6 impacts the infection and proliferation of N. bombycis via interacting with the polar tube protein and transcriptional repressor for RNA polymerase II.

The microsporidian polar tube: origin, structure, composition, function, and application

Microsporidia are a class of obligate intracellular parasitic unicellular eukaryotes that infect a variety of hosts, even including humans. Although different species of microsporidia differ in host range and specificity, they all share a similar infection organelle, the polar tube, which is also defined as the polar filament in mature spores. In response to the appropriate environmental stimulation, the spore germinates with the polar filament everted, forming a hollow polar tube, and then the infectious cargo is transported into host cells via the polar tube. Hence, the polar tube plays a key role in microsporidian infection. Here, we review the origin, structure, composition, function, and application of the microsporidian polar tube, focusing on the origin of the polar filament, the structural differences between the polar filament and polar tube, and the characteristics of polar tube proteins. Comparing the three-dimensional structure of PTP6 homologous proteins provides new insight for the screening of additional novel polar tube proteins with low sequence similarity in microsporidia. In addition, the interaction of the polar tube with the spore wall and the host are summarized to better understand the infection mechanism of microsporidia. Due to the specificity of polar tube proteins, they are also used as the target in the diagnosis and prevention of microsporidiosis. With the present findings, we propose a future study on the polar tube of microsporidia.

Occurrence of microsporidia spp. infection in children with diarrhea in southern Iran

Microsporidia spp. are recognized emerging zoonotic microorganisms in immunocompromised and immunocompetent populations. Therefore, we conducted a study to investigate the occurrence, sociodemographic and risk factors of microsporidia spp. infection using microscopic and molecular techniques in children with diarrhea in Jahrom city (Fars province, southern Iran). Stool samples were gathered from 395 children aged ≤ 14 years between January 2017 and January 2018. Next, a questionnaire includes the age, sex, living area, immune system status, breast milk consumption, contact with animals, and type of water source was completed for all children. For microscopic assessment, modified acid-fast trichrome staining was applied for detection of microsporidia spores. Furthermore, DNA extraction and PCR were accomplished for all samples. A total of 15 (3.79%; 95% confidence interval [CI] 2.14-6.19) and 8 (2.02%; 95% CI 0.88-3.95) samples were positive for microsporidia infection by microscopic and molecular techniques, respectively. Although none of the sociodemographic and risk factors were significant (p value > 0.05), the prevalence of this infection was higher in some variables (e.g., rurality, contact with animals and well water consumption). Three random samples were sequenced that all isolates belonged to Enterocytozoon bieneusi. Cognizance of microsporidia occurrence, risk factors, and disease disorders for the health specialists, physicians, children's families are important for appropriately control the infection.

Characterizing the Proliferation Patterns of Representative Microsporidian Species Enlightens Future Studies of Infection Mechanisms

Background: Microsporidia are a group of pathogens that infect all kinds of animals, such as humans, silkworms, honeybees, and shrimp; they, therefore, pose a severe threat to public health and the economy. There are over 1500 species of microsporidia that have been reported, among which Encephalitozoon hellem and Nosema bombycis are the representative zoonotic and insect-infecting species, respectively. Investigating their cell infection patterns is of great significance for understanding their infection mechanisms. Methods: Specific probes were designed for the ribosomal RNA sequences of microsporidia. Fluorescence in situ hybridization (FISH) was used to trace the proliferation cycle of the pathogens in different cells. Results: Here, two rRNA large subunit gene (LSUrRNA) probes specifically labeling N. bombycis were obtained. The life cycle of N. bombycis in silkworm cells and E. hellem in three kinds of host cells was graphically drawn. N. bombycis meronts were first observed at 30 hours post-infection (hpi), and they began merogony. Sporonts were observed at 42 hpi, and the first entire proliferation cycle was completed at 48 hpi. The proliferation cycle of E. hellem in RK13 and HEK293 epithelial cells was almost the same, completing the first life cycle after 24 hpi, but it was significantly delayed to 32 hpi in RAW264.7. Conclusions: Specific FISH probes were established for labeling microsporidia in multiple host cells. The proliferation characteristics of representative zoonotic and insect-infecting microsporidian species were clarified. This study provides an experimental pattern for future analyses of microsporidian infection mechanisms.

Encephalitozoon hellem Infection Promotes Monocytes Extravasation

Background: Microsporidia are a group of obligated intracellular fungus pathogens. Monocytes and the derivative macrophages are among the most important players in host immunity. The invasion of microsporidia may significantly affect the monocytes maturation and extravasation processes. Methods: We utilized a previously established microsporidia infection murine model to investigate the influences of microsporidia Encephalitozoon hellem (E. hellem) infection on monocyte maturation, releasing into the circulation and extravasation to the inflammation site. Flow cytometry and qPCR analysis were used to compare the monocytes and derivative macrophages isolated from bone marrow, peripheral blood and tissues of E. hellem-infected and control mice. Results: The results showed that the pro-inflammatory group of CD11b⁺Ly-6C⁺ monocytes are promoted in E. hellem-infected mice. Interestingly, the percentage of Ly-6C⁺ monocytes from E. hellem-infected mice are significantly lower in peripheral blood while significantly higher in the inflamed small intestine, together with up-regulated ratio of F4/80 macrophage in small intestine as well. Conclusions: Our findings demonstrated that E. hellem infection leads to promoted monocytes maturation in bone marrow, up-regulation of extravasation from peripheral blood to inflammation site and maturation into macrophages. Our study is the first systematic analysis of monocytes maturation and trafficking during microsporidia infection, and will provide better understanding of the pathogen–host interactions.

Microsporidia Promote Host Mitochondrial Fragmentation by Modulating DRP1 Phosphorylation

Microsporidia are obligate intracellular parasites that infect a wide variety of hosts ranging from invertebrates to vertebrates. These parasites have evolved strategies to directly hijack host mitochondria for manipulating host metabolism and immunity. However, the mechanism of microsporidia interacting with host mitochondria is unclear. In the present study, we show that microsporidian Encephalitozoon greatly induce host mitochondrial fragmentation (HMF) in multiple cells. We then reveal that the parasites promote the phosphorylation of dynamin 1-like protein (DRP1) at the 616th serine (Ser616), and dephosphorylation of the 637th serine (Ser637) by highly activating mitochondrial phosphoglycerate mutase 5 (PGAM5). These phosphorylation modifications result in the translocation of DRP1 from cytosol to the mitochondrial outer membrane, and finally lead to HMF. Furthermore, treatment with mitochondrial division inhibitor 1 (Mdivi1) significantly reduced microsporidian proliferation, indicating that the HMF are crucial for microsporidian replication. In summary, our findings reveal the mechanism that microsporidia manipulate HMF and provide references for further understanding the interactions between these ubiquitous pathogens with host mitochondria.

A Systematic Review and Meta-analysis on the Global Molecular Epidemiology of Microsporidia Infection Among Rodents: A Serious Threat to Public Health

BACKGROUND

Microsporidiosis as a zoonotic disease has caused serious health problems in high-risk groups, including immunosuppressed individuals. Among the potential animal reservoirs of microsporidia, rodents play a key role due to close-contact with humans and their dispersion in different environments. Therefore, this systematic review and meta-analysis aimed to assess the global status and genetic diversity of microsporidia infection in different rodents.

METHODS

The standard protocol of preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed. Scopus, PubMed, Web of Science, and Google Scholar were searched from 1 January 2000 to 15 April 2021. All peer-reviewed original research articles describing the molecular prevalence of microsporidia infection in rodents were included. Inclusion and exclusion criteria were applied. The point estimates and 95% confidence intervals were calculated using a random-effects model. The variance between studies (heterogeneity) were quantified by I² index.

RESULTS

Of 1695 retrieved studies, 22 articles (including 34 datasets) were included for final meta-analysis. The pooled global molecular prevalence (95% CI) of microsporidia infection in rodents was 14.2% (95% CI 10.9-18.3%). The highest prevalence of microsporidia was found in Apodemus spp. 27.3% (95% CI 15-44.5%). Enterocytozoon bieneusi was the most common pathogen (26/34; 76.47% studies) according to PCR-based methods, and the genotype D as the highest reported genotype (15 studies).

CONCLUSIONS

The findings of the study showed a relatively high prevalence of microsporidia infection in rodents as a potential animal reservoir for infecting human. Given the relatively high incidence of microsporidiosis, designing strategies for control, and prevention of microsporidia infection in rodents should be recommended.

The global molecular epidemiology of microsporidia infection in sheep and goats with focus on Enterocytozoon bieneusi: a systematic review and meta-analysis

BACKGROUND

Microsporidia is a zoonotic pathogen with health consequences in immunocompromised patients. Small ruminants are a potential reservoir of microsporidia for humans in their vicinity. Hence, we aimed to evaluate the molecular prevalence of microsporidian infections with emphasis on Enterocytozoon bieneusi genotypes among sheep and goats at a global scale through systematic review and meta-analysis approach.

METHODS

The standard protocol of preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed. Eligible prevalence studies on small ruminant microsporidiosis, published from 1 January 2000 until 15 April 2021 were gathered using systematic literature search in PubMed, Scopus, Web of Science and Google Scholar databases. Inclusion and exclusion criteria were applied. The point estimates and 95% confidence intervals were calculated using a random-effects model. The variance between studies (heterogeneity) was quantified by I² index.

RESULTS

In total, 25 articles (including 34 datasets) were included for final meta-analysis. The pooled molecular prevalence of microsporidia in sheep and goats was estimated to be 17.4% (95% CI: 11.8-25%) and 16% (95% CI: 11.2-22.4%), respectively. Likewise, the overall prevalence of E. bieneusi was estimated to be 17.4% (95% CI: 11.8-25%) for sheep and 16.3% (95% CI: 11.3-22.8%) for goats. According to internal transcribed spacer (ITS) gene analysis, E. bieneusi with genotypes BEB6 (15 studies) and COS-1 (nine studies) in sheep, and CHG3 (six studies) and BEB6 (five studies) in goats were the highest reported genotypes.

CONCLUSION

The present results highlight the role of sheep and goats as reservoir hosts for human-infecting microsporidia. Therefore, this global estimate could be beneficial on preventive and control measures.

Encephalitozoon intestinalis: A new target for auranofin in a mice model

Despite the fact that many approaches have been developed over years to find efficient and well-tolerated therapeutic regimens for microsporidiosis, the effectiveness of current drugs remains doubtful, and effective drugs against specific targets are still scarce. The present study is the first that was designed to evaluate the potency of auranofin, an anti-rheumatoid FDA approved drug, against intestinal Encephalitozoon intestinalis. Evaluation of the drug was achieved through counting of fecal and intestinal spores, studying the intestinal histopathological changes, measuring of intestinal hydrogen peroxide level, and post therapy follow-up of mice for 2 weeks for detection of relapse. Results showed that auranofin has promising anti-microsporidia potential. It showed a promising efficacy in mice experimentally infected with E. intestinalis. It has revealed an obvious reduction in fecal spore shedding and intestinal tissue spore load, amelioration of intestinal tissue pathological changes, and improvement of the local inflammatory infiltration without significant changes in hydrogen peroxide level. Interestingly, auranofin prevented the relapse of infection. Thus, considering the results of the present work, auranofin could be considered a therapeutic alternative for the gold standard drug 'albendazole' against the intestinal E. intestinalis infection especially in relapsing cases.

Comparative Assessment of In-House Real-Time PCRs Targeting Enteric Disease-Associated Microsporidia in Human Stool Samples

Microsporidiosis is an infection predominantly occurring in immunosuppressed patients and infrequently also in travelers. This study was performed to comparatively evaluate the diagnostic accuracy of real-time PCR assays targeting microsporidia with etiological relevance in the stool of human patients in a latent class analysis-based test comparison without a reference standard with perfect accuracy. Thereby, two one-tube real-time PCR assays and two two-tube real-time PCR assays targeting Enterocytozoon bieneusi and Encephalocytozoon spp. were included in the assessment with reference stool material (20), stool samples from Ghanaian HIV-positive patients (903), and from travelers, migrants and Colombian indigenous people (416). Sensitivity of the assays ranged from 60.4% to 97.4% and specificity from 99.1% to 100% with substantial agreement according to Cohen’s kappa of 79.6%. Microsporidia DNA was detected in the reference material and the stool of the HIV patients but not in the stool of the travelers, migrants, and the Colombian indigenous people. Accuracy-adjusted prevalence was 5.8% (n = 78) for the study population as a whole. In conclusion, reliable detection of enteric disease-associated microsporidia in stool samples by real-time PCR could be demonstrated, but sensitivity between the compared microsporidia-specific real-time PCR assays varied.

Von Willebrand Factor Facilitates Intravascular Dissemination of Microsporidia Encephalitozoon hellem

Microsporidia are a group of spore-forming, fungus-related pathogens that can infect both invertebrates and vertebrates including humans. The primary infection site is usually digestive tract, but systemic infections occur as well and cause damages to organs such as lung, brain, and liver. The systemic spread of microsporidia may be intravascular, requiring attachment and colonization in the presence of shear stress. Von Willebrand Factor (VWF) is a large multimeric intravascular protein and the key attachment sites for platelets and coagulation factors. Here in this study, we investigated the interactions between VWF and microsporidia Encephalitozoon hellem (E. hellem), and the modulating effects on E. hellem after VWF binding. Microfluidic assays showed that E. hellem binds to ultra-large VWF strings under shear stress. In vitro germination assay and infection assay proved that E. hellem significantly increased the rates of germination and infection, and these effects would be reversed by VWF blocking antibody. Mass spectrometry analysis further revealed that VWF-incubation altered various aspects of E. hellem including metabolic activity, levels of structural molecules, and protein maturation. Our findings demonstrated that VWF can bind microsporidia in circulation, and modulate its pathogenicity, including promoting germination and infection rate. VWF facilitates microsporidia intravascular spreading and systemic infection.

Is Encephalitozoon cuniculi of Significance in Young Dogs With Neurological Signs?

Encephalitozoon cuniculi is a microsporidium belonging to the phylum Microspora. A few reports have described the clinical significance of E. cuniculi infection in young dogs. In American and Japanese household dog populations, the seroprevalence was found to be 21%, indicating its wide-spread existence. To evaluate the clinical significance of E. cuniculi in a cohort of young dogs with neurological signs, the presence of the organism and possible response to treatment were studied. Over a 1-year period, all young dogs (<3 years old) that were referred with neurological signs were examined for the presence of E. cuniculi. Dogs were selected if serology revealed a clearly elevated IgM titer (>100) and/or if an EDTA-blood sample and/or urine sample tested positive by polymerase chain reaction (PCR). Sixteen dogs with various neurological signs were included in this study. Additional work-up included magnetic resonance imaging and cerebrospinal fluid analysis, but these revealed no abnormalities or indication of infection. All dogs were treated with fenbendazole for 10–30 days. Neurological signs disappeared completely in five dogs, 11 dogs continued to show neurological signs, and five dogs deteriorated and were euthanized, after which necropsy was performed in three. At necropsy no evidence of an E. cuniculi infection was found. We concluded that, although IgM titers and PCR indicated an E. cuniculi infection, it is most likely of limited clinical significance in young dogs.

Microsporidia infection upregulates host energy metabolism but maintains ATP homeostasis

Microsporidia are a group of obligate intracellular parasites which lack mitochondria and have highly reduced genomes. Therefore, they are unable to produce ATP via the tricarboxylic acid (TCA) cycle and oxidative phosphorylation. Instead, they have evolved strategies to obtain and manipulate host metabolism to acquire nutrients. However, little is known about how microsporidia modulate host energy metabolisms. Here, we present the first targeted metabolomics study to investigate changes in host energy metabolism as a result of infection by a microsporidian. Metabolites of silkworm embryo cell (BmE) were measured 48 h post infection by Nosema bombycis. Thirty metabolites were detected, nine of which were upregulated and mainly involved in glycolysis (glucose 6-phosphate, fructose 1,6-bisphosphate) and the TCA cycle (succinate, α-ketoglutarate, cis-aconitate, isocitrate, citrate, fumarate). Pathway enrichment analysis suggested that the upregulated metabolites could promote the synthesization of nucleotides, fatty acids, and amino acids by the host. ATP concentration in host cells, however, was not significantly changed by the infection. This ATP homeostasis was also found in Encephalitozoon hellem infected mouse macrophage RAW264.7, human monocytic leukemia THP-1, human embryonic kidney 293, and human foreskin fibroblast cells. These findings suggest that microsporidia have evolved strategies to maintain levels of ATP in the host while stimulating metabolic pathways to provide additional nutrients for the parasite.

Prevalence of Nosema species infections in Apis cerana japonica and Apis mellifera honeybees in the Tohoku region of Japan

We investigated here, the prevalence of Nosema microsporidia infections in the honeybees, Apis cerana japonica and Apis mellifera, in the Tohoku region of Japan. We detected Nosema ceranae DNA in 14 (2.8%) of 509 A. cerana japonica and in 34 (21.9%) of 155 A. mellifera honeybees from Aomori, Iwate, Akita, Yamagata, and Fukushima prefectures. Nosema apis DNA was undetectable in A. cerana japonica and A. mellifera. The unidentifiable Nosema species that genetically differed from N. apis, N. ceranae, and N. neumanni in terms of small subunit (SSU) rDNA, large subunit rDNA, and internal transcribed spacer sequences was identified in 105 (20.6%) of 509 A. cerana japonica and in 1 (0.6%) of 155 A. mellifera honeybees, and from Iwate prefecture. A phylogenetic tree based on SSU rDNA sequences showed that the Nosema sp. belonged to the same clade as N. thomsoni detected in moth and solitary bees in North America and N. pieriae found in cabbage butterfly in Turkey, which have not hitherto been detected in honeybees. The morphological characteristics of the spores should be analyzed to enable species identification of the Nosema sp.

Integrated qPCR and Staining Methods for Detection and Quantification of Enterocytozoon hepatopenaei in Shrimp Litopenaeus vannamei

Enterocytozoon hepatopenaei (EHP) is an obligate, intracellular, spore-forming parasite, which mainly infects the gastrointestinal tract of shrimp. It significantly hinders the growth of shrimp, which causes substantial economic losses in farming. In this study, we established and optimized a SYBR Green I fluorescent quantitative PCR (qPCR) assay based on the polar tube protein 2 (PTP2) gene for the quantitative analysis of EHP-infected shrimp. The result showed that the optimum annealing temperature was 60 °C for the corresponding relation between the amplification quantitative (Cq) and the logarithmic of the initial template quantity (x), conformed to Cq = −3.2751x + 31.269 with a correlation coefficient R² = 0.993. The amplification efficiency was 102%. This qPCR method also showed high sensitivity, specificity, and repeatability. Moreover, a microscopy method was developed to observe and count EHP spores in hepatopancreas tissue of EHP-infected shrimp using Fluorescent Brightener 28 staining. By comparing the PTP2-qPCR and microscopy method, the microscopic examination was easier to operate whereas PTP2-qPCR was more sensitive for analysis. And we found that there was a correspondence between the results of these two methods. In summary, the PTP2-qPCR method integrated microscopy could serve for EHP detection during the whole period of shrimp farming and satisfy different requirements for detecting EHP in shrimp farming.

Intestinal microsporidia infection among cat owners and non-pet owners in Iran: a case-control study

Microsporidia is a group of spore-forming microorganisms with zoonotic potential. This study aimed to compare intestinal microsporidia infections in cat owners and non-pet owners. In total, 210 fecal samples were collected from indoor cats, cat owners, and non-pet owners. DNA extraction was performed and the small subunit ribosomal RNA (SSU rRNA) gene was amplified. To characterize the genotypes, the internal transcribed spacer (ITS) fragment was amplified and sequenced. The phylogenetic trees were drawn to evaluate the relationship among Enterocytozoon bieneusi isolates. Two (2.9%) and one (1.4%) fecal samples from cat owners and one (1.4%) and two (2.9%) fecal samples from non-pet owners were positive for E. bieneusi and Encephalitozoon intestinalis, respectively. E. bieneusi was detected in two cat samples (2.9%). Same infection was not seen between infected cats and their owners. There was no significant difference between the prevalence rate of microsporidia among the cat owners and non-pet owners. Indeed, the genotypes L and type IV were seen in cats, while the genotype D was only detected in human. In this study, E. bieneusi and E. intestinalis were more prevalent among the cat owners and non-pet owners, respectively. Indeed, the higher prevalence of E. bieneusi in cats and their owners might be resulted from the worldwide distribution of this species.

Molecular identification of microsporidian species in patients with epithelial keratitis

Introduction. Ocular microsporidiosis is a significant emerging infectious disease reported in immunocompromised patients and immunocompetent persons throughout the world.Aim. To identify the pathogens responsible for human keratitis, via corneal scrapings.Methodology. Thirty-three hospitalized patients with epithelial keratitis were examined using staining and DNA sequencing. DNA was extracted from corneal samples and the small-subunit ribosomal RNA gene was amplified by polymerase chain reaction (PCR) and sequenced.Results. Twenty-one samples were positive by staining while PCR generated amplicons in 18 cases. Of the 18 sequences, 16 were identical with, or very similar to, those of Vittaforma corneae (99-100 % similarity) and the remaining two sequences were similar to that of unidentified Microsporidium species deposited in the GenBank.Conclusion. This study has reconfirmed that V. corneae causes epithelial keratitis in humans and that a newly detected Microsporidium species is also involved in microsporidial keratitis as one of the emerging pathogens in Thailand. Ophthalomologists should be aware of microsporidial keratitis in people from Thailand and those from neighbouring countries.

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.

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.

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.

In vitro antimicrosporidial activity of gold nanoparticles against Heterosporis saurida

BACKGROUND

Worldwide, there is a need to expand the number of drugs available to treat parasitic infections in aquaculture. One of the new materials being tested is metal nanoparticles, which have unique chemical and physical characteristics owing to their extremely small size and high surface area to volume ratio. We examined the effectiveness of gold nanoparticles against the microsporidian parasite Heterosporis saurida, which causes severe economic losses in lizard fish, Saurida undosquamis aquaculture.

RESULTS

We synthesized gold nanoparticles by chemical reduction of tetrachloroauric acid as a metal precursor. We assessed the antimicrosporidial efficacy of the nanoparticles against H. saurida using an in vitro screening approach, which we had developed previously using the eel kidney cell line EK-1. The number of H. saurida spores produced in EK-1 cells was reduced in a proportional manner to the dosage of gold nanoparticles administered. A cell metabolic activity test (MTT) indicated that the gold nanoparticles did not appear to be toxic to the host cells.

CONCLUSIONS

Gold nanoparticles can act as an effective antimicrosporidial agent and hold promise to reduce disease in lizardfish aquaculture. Metal nanoparticles should be considered as an alternate choice for development of new antimicrosporidial drugs to combat disease problems in aquaculture.

In vitro antimicrosporidial activity of gold nanoparticles against Heterosporis saurida

Background

Worldwide, there is a need to expand the number of drugs available to treat parasitic infections in aquaculture. One of the new materials being tested is metal nanoparticles, which have unique chemical and physical characteristics owing to their extremely small size and high surface area to volume ratio. We examined the effectiveness of gold nanoparticles against the microsporidian parasite Heterosporis saurida, which causes severe economic losses in lizard fish, Saurida undosquamis aquaculture.

Results

We synthesized gold nanoparticles by chemical reduction of tetrachloroauric acid as a metal precursor. We assessed the antimicrosporidial efficacy of the nanoparticles against H. saurida using an in vitro screening approach, which we had developed previously using the eel kidney cell line EK-1. The number of H. saurida spores produced in EK-1 cells was reduced in a proportional manner to the dosage of gold nanoparticles administered. A cell metabolic activity test (MTT) indicated that the gold nanoparticles did not appear to be toxic to the host cells.

Conclusions

Gold nanoparticles can act as an effective antimicrosporidial agent and hold promise to reduce disease in lizardfish aquaculture. Metal nanoparticles should be considered as an alternate choice for development of new antimicrosporidial drugs to combat disease problems in aquaculture.

Inaccuracy of Labeling and Visual Inspection for Microsporidian Parasites in Anglerfish Lophius litulon (Jordan, 1902) Collected from Chinese Retail Markets in Sardinia, Italy

The aim of the present study was to evaluate the accuracy of labeling and the efficacy of visual inspection to detect the lesions by visible parasites in anglerfish Lophius litulon. One hundred samples were collected over a 2-year period (2011 to 2012) from Chinese retail markets in Sardinia, Italy. To assess the conformity of the items with the trade name, a preliminary visual inspection of the samples by a simple morphological analysis was performed. According to the Council Regulations (EC) 104/2000, 1224/2009, and 2074/2005, the Italian labels were examined to verify the appropriate indication of relevant information on traceability (trade name, scientific name, geographical area, and production method), and the samples of L. litulon were subjected to visual inspection to detect "visible parasites." Altogether, a high percentage of mismatching (70%) between the scientific name and trade name was pointed out. Moreover, 60% of the samples were visibly infected by Spraguea lophii, a microsporidian parasite of the nervous tissue that forms typical lesions (xenomas) in the fish flesh near the vertebral column. Although S. lophii is not pathogenic to humans, the presence of xenomas can decompose the fish flesh and render it unfit for human consumption. The high percentage of mislabeling, together with the inaccuracy in the visual inspection by Chinese food business operators highlighted the need to improve the European Union control system of fishery products imported from China and marketed in Europe.

Do microsporidia function as "biological weapon" for Harmonia axyridis under natural conditions?

Invasive alien species, such as the multicoloured Asian ladybird Harmonia axyridis, are often regarded as major drivers of biodiversity loss. Therefore understanding which characteristics or mechanisms contribute to their invasive success is important. Here the role of symbiotic microsporidia in the hemolymph of H. axyridis was investigated in the context of intraguild predation between wild-caught H. axyridis and the native ladybird species Coccinella septempunctata. The microsporidia were recently discussed to contribute to the unpalatability of Harmonia for other coccinellids during intraguild predation and to function as "biological weapons". In the present study, visual detection of microsporidia in hemolymph samples revealed that 73.5% of H. axyridis were infected. Intraguild predation experiments between larvae of the two species showed a significant competitive advantage for H. axyridis, even against larger larvae of C. septempunctata. Adult C. septempunctata always killed and fed on H. axyridis larvae. However only 11.4% (4 of 47) of C. septempunctata that fed on infected H. axyridis died within 4 months. In contrast to previous studies this suggests that microsporidia or harmonine, the chemical defense compound of H. axyridis, do not lead to death of C. septempunctata preying on larvae of H. axyridis. Instead our results support the idea that competitive advantage during intraguild predation greatly facilitates the success of H. axyridis and that this may help this highly invasive species to outcompete native species. The impact of microsporidia on Harmonia itself as well as on interspecific interactions require further studies.

Molecular detection of microsporidiosis in various samples of Iranian immunocompromised patients

Microsporidia infections occur in virtually all invertebrate and vertebrate hosts, including humans. The aim of this study is detection of microsporidiosis in various samples of Iranian immunosuppressed patients during 2011-2012 by molecular methods. The samples included stool samples from the healthy participants and samples from biological fluids of the patients according to consult of their physician and the site of infection. The sample size was determined as 258 for each group. Clinical and demographical data related to each participant was collected. DNA extraction and nested polymerase chain reaction were carried out on all the samples. In the control group, the rates of Encephalitozoon and Enterocytozoon infections were 5.3 and 4 % respectively higher in males and in the age range of 30-45, and all positive cases had gastrointestinal symptoms. In the patient group, most infection cases occurred in male patients and in the age range of 60 and above. Patients with microsporidiosis mostly had the symptoms of chronic diarrhea, vomiting, weight loss, dyspepsia, and malabsorption. In BAL samples from patients 2 % Encephalitozoon and 0.7 % Enterocytozoon, in the sampling bone marrow transplantation from patients 5.7 % Encephalitozoon, 1.43 % Enterocytozoon and from patients who underwent kidney transplantation 5.26 % Enterocytozoon were detected. The most cases of human microsporidiosis are associated with human immunodeficiency virus infection or other states of immunosuppression, particularly in organ transplant recipients; the result of this study confirms this claim.

Prevalence and diversity of Encephalitozoon spp. and Enterocytozoon bieneusi in wild boars (Sus scrofa) in Central Europe

From 2011 to 2012, the occurrence of Enterocytozoon bieneusi and Encephalitozoon spp. was surveyed at 29 randomly selected localities (both forest areas and enclosures) across four Central European countries: Austria, the Czech Republic, Poland, and the Slovak Republic. Isolates were genotyped by PCR amplification and characterization of the internal transcribed spacer (ITS) region using Enterocytozoon and Encephalitozoon-specific protocols. PCR revealed 16 mono-infections of Encephalitozoon cuniculi, 33 mono-infections of Enterocytozoon bieneusi and 5 concurrent infections of both Encephalitozoon cuniculi and Enterocytozoon bieneusi out of 460 faecal samples. Two genotypes (I and II) were revealed by sequence analysis of the ITS region of Encephalitozoon cuniculi. Eleven genotypes, five previously found in other hosts including domestic pigs (D, EbpA, EbpC, G and Henan-I) and six novel (WildBoar1-6), were identified in Enterocytozoon bieneusi. No other microsporidia infection was found in the examined faecal samples. Prevalence of microsporidia at the locality level ranged from 0 to 58.8 %; the prevalence was less than 25 % at more than 86 % of localities. Enterocytozoon bieneusi was detected as a predominant species infecting Eurasian wild boars (Sus scrofa). The present report is the most comprehensive survey of microsporidia infections in wild boars within the Czech Republic and selected Central European countries.

Treatment of microsporidial keratoconjunctivitis with repeated corneal swabbing

PURPOSE

To report the effect of repeated corneal swabbing in patients with microsporidial keratoconjunctivitis.

DESIGN

Retrospective noncomparative case series.

METHODS

Sixteen eyes of 14 healthy patients with microsporidial keratoconjunctivitis were diagnosed based on the detection of microsporidia in corneal scrapings using Gram stain, the modified Kinyoun acid-fast stain, or both. Polymerase chain reaction plus gene analysis of the microsporidian 16S ribosomal RNA had been performed in 10 patients who sought treatment between 2010 and 2011. Some of the lesions were scraped for procurement of specimens. The remaining lesions were wiped off gently by cotton swabs. Repeated swabbing was performed if infection persisted or new lesions were observed at follow-up. To prevent secondary bacterial infection, 0.3% norfloxacin or 0.25 % chloramphenicol were prescribed.

RESULTS

The mean age was 52.2 years. All patients had the characteristic disseminated, punctate, slightly elevated, white epithelial lesions. The denser white lesions could be removed easily after gentle swabbing, and most epithelium remained intact. The 10 cases with positive polymerase chain reaction results were all identified to be Vittaforma corneae. The mean number of corneal swabbing was 3.3, and the mean disease resolution time was 6.6 days. No patients had recurrence or loss of visual acuity at last follow-up.

CONCLUSIONS

Repeated swabbing effectively can eradicate corneal epithelial microsporidial lesions in approximately 1 week. It is easy to perform, less painful, and more acceptable for the patients.

Encephalitozoon and Enterocytozoon (Microsporidia) spores in stool from pigeons and exotic birds: microsporidia spores in birds

Microsporidia are considered to be a cause of emerging and opportunistic infections in humans, and the species that infect humans can also infect a wide range of animals, raising concerns for zoonotic transmission. To understand the role of birds in the transmission of diseases caused by microsporidia, we examined 196 fecal specimens from birds, including birds of the families Psittacidae, Emberizidae, Icteridae and Columbidae, using Gram-chromotrope stain and polymerase chain reaction (PCR). Of the 196 fecal samples surveyed, 48 (24.5%) tested positive for microsporidia. The prevalence of microsporidia infection was higher in pigeons (31.1%) than in other birds (18.8%). The species of microsporidia that were detected in the birds surveyed in this study included Encephalitozoon hellem (found in 16.3% of positive samples), Enterocytozoon bieneusi (5.6%), Encephalitozoon intestinalis (1.5%) and Encephalitozoon cuniculi (1%). All the internal transcribed spacer (ITS) sequence of the rRNA from the study samples matched (with 100% identity) their correlate reference genotypes in GenBank, which included E. hellem 1A (AF338367), E. hellem 3 (AF110328), E. cuniculi I (AF338410) and E. bieneusi EpbA (AF076040). No fecal sample contained more than one type of microsporidian species. This study implicates exotic birds and pigeons as potential sources of microsporidia infection for humans living in urban areas.

Molecular epidemiologic characterization of Enterocytozoon bieneusi in HIV-infected persons in Benin City, Nigeria

Molecular characterization of Enterocytozoon bieneusi has led to better understanding of microsporidiosis transmission in humans. This study aimed to detect and genotype E. bieneusi in human immunodeficiency virus (HIV)-infected persons. Stool specimens were collected from 463 HIV-infected patients and analyzed for E. bieneusi by polymerase chain reaction (PCR) and DNA sequence analysis of the internal transcribed spacer. E. bieneusi was detected in 77 HIV patients. CD4 cell counts < 200 cells/μL was associated with E. bieneusi infection (P = 0.09). E. bieneusi was significantly associated with weight loss (P < 0.0001), diarrhea (P = 0.006), fever (P < 0.0001), not being married (P < 0.0001), and flush type of toilet (P = 0.0007). Six known genotypes of D, A, IV, CAF2, EbpA, and Peru 8 in 31, 22, 14, 2, 1, and 1 patients, respectively, five novel genotypes of E. bieneusi, and one infection with mixed genotypes were observed in this study. Three of the novel genotypes were genetically distant to the genotypes commonly found in humans.

Identification of Encephalitozoon and Enterocytozoon (microsporidia) spores in stool and urine samples obtained from free-living South American Coatis (Nasua nasua)

This study emphasizes the importance of free-living coatis as a potential source of microsporidian infection for humans living in large cities. We found 19 (31.7%) positive results among 60 fecal samples analyzed by PCR-based analysis and the Gram-Chromotrope staining technique (11.7% were positive for Encephalitozoon cuniculi, 6.7% for E. intestinalis, 6.7% for E. hellem, and 6.7% for Enterocytozoon bieneusi). Only 5 (8.4%) urine samples tested positive for E. cuniculi as assessed by the two techniques.

T cell response and persistence of the microsporidia

The microsporidia are a diverse phylum of obligate intracellular parasites related to the fungi that cause significant and sometimes life-threatening disease in immune-compromised hosts, such as AIDS and organ transplant patients. More recently, their role in causing pathology in immune-competent populations has also been appreciated. Interestingly, in several instances, the microsporidia have been shown to persist in their hosts long term, causing at opposite ends of the spectrum either an intractable chronic diarrhea and wasting in patients with advanced-stage AIDS or asymptomatic shedding of spores in healthy populations. Much remains to be studied regarding the immune response to these pathogens, but it seems clear that CD8+ T cells are essential in clearing infection. However, in the infection models examined thus far, the role for CD4+ T cells is unclear at best. Here, we discuss the possible reasons and ramifications of what may be a weak primary CD4+ T cell response against Encephalitozoon cuniculi. Given the central role of the CD4+ T cell in other models of adaptive immunity, a better appreciation of its role in responding to microsporidia may provide insight into the survival strategies of these pathogens, which allow them to persist in hosts of varied immune status.

Microsporidial infections due toEncephalitozoon intestinalisin non-HIV-infected patients with chronic diarrhoea

We determined the prevalence of microsporidiaEnterocytozoon(Ent.)bieneusiandEncephalitozoon(E.)intestinalisinfection in patients with chronic diarrhoea and hepatocellular carcinoma (HCC). A total of 330 stool samples were examined from 171 (52%) patients with chronic diarrhoea, 18 (5%) with HCC while 141 (43%) were controls. Stool microscopy, polymerase chain reaction (PCR) with species-specific primers forEnt. bieneusiandE. intestinalisand sequencing were carried out. Microsporidia were found by trichrome staining in 11/330 (3%) andE. intestinalisby PCR in 13/330 (4%) whileEnt. bieneusiwas not detected. PCR forE. intestinaliswas positive in 8/171 (5%) stool samples from patients with chronic diarrhoea, 2/141 (1·4%) samples from healthy controls and in 3/18 (17%) samples from patients with HCC. In the chronic diarrhoea group,E. intestinaliswas positive in 4/171 (2·3%) (P=0·69) stool samples compared to 2/18 (11%) (P=0·06) in the HCC group and 2/141 (1·4%) from healthy controls.E. intestinalisinfection was significantly associated with chronic diarrhoea and HCC in these patients who were negative for HIV. Stool examination with trichrome or species-specific PCR for microsporidia may help establish the cause of chronic diarrhoea.

Clinical spectrum of microsporidial keratoconjunctivitis

The purpose of this paper was to analyse the causes, pathogenesis, diagnostic modalities and treatment outcomes of microsporidial keratoconjunctivitis (MKC). Microsporidia are increasingly recognized as opportunistic infectious pathogens in immunocompromized patients causing keratoconjunctivitis. In the recent years, there has been a surge in reports of MKC in immunocompetent individuals presenting with stromal keratitis. A detailed literature search was done using Medline, OVID, Cochrane Library, UptoDate and Google Scholar databases with the terms microsporidia, keratitis, conjunctivitis, immunocompromized and immunocompetent. The articles were reviewed to determine the spectrum of clinical presentation, disease course, investigations, treatment modalities and outcome. Thirty-six publications were reviewed, and 151 cases of MKC were included for this review. The main presenting features included pain, redness, photophobia, epiphora and blurring of vision. Duration of the symptoms lasted between 4 days and 18 months. Light microscopy with modified trichrome stain was most commonly used to diagnose MKC. Resolution of symptoms was most commonly achieved with oral albendazole and/or topical fumidil B. Topical fluoroquinolones are also effective as a monotherapy as suggested by recent studies. Clinical outcome was good (visual acuity ≤ 6/12) for the patients who presented earlier (≤1 month) (75% of cases with documented final best-corrected visual acuity). MKC occurs more commonly in immunocompetent individuals than expected and can be diagnosed in earlier stages. From our review, we conclude that the patients, who were diagnosed early and treated, had complete resolution of symptoms with a better clinical outcome.

Microsporidial keratitis in patients with hot springs exposure

This retrospective study included 10 eyes of 9 patients diagnosed with microsporidial keratitis. All of them were known to contract this disease after taking baths in hot springs. The disease was diagnosed based on detecting microsporidia in corneal scrapings using Gram stain and the modified Kinyoun's acid-fast stain. The specimens from the last six patients were subjected to PCR and then sequencing. All of them revealed that the microorganism identified has a high similarity to Vittaforma corneae. Repeated debridement of the epithelial lesions successfully eradicated the microsporidial infection in all nine patients.

Fish microsporidia: immune response, immunomodulation and vaccination

Immune response to fish microsporidia is still unknown and there are current research trying to elucidate the events involved in the immune response to this parasite. There is evidence suggesting the role of innate immune response and it is clear that adaptive immunity plays an essential part for eliminating and then mounting a solid resistance against subsequent microsporidian infections. This review article discusses the main mechanisms of resistance to fish microsporidia, which are considered under four main headings. 1) Innate immunity: the inflammatory tissue reaction associated with fish microsporidiosis has been studied at the ultrastructural level, providing identification of many of the inflammatory cells and molecules that are actively participating in the spore elimination, such as macrophages, neutrophils, eosinophilic granular cells, soluble factors and MHC molecules. 2) Adaptive immunity: the study of the humoral response is relatively new and controversial. In some cases, the antibody response is well established and it has a protective role, while in other situations, the immune response is not protective or it is depressed. Study of the cellular response against fish microsporidia is still in its infancy. Although the nature of the microsporidian infection suggests participation of cellular mechanisms, few studies have focused on the cellular immune response of infected fish. 3) Immunomodulation: glucans are compounds that can modulate the immune system and potentiate resistance to microorganisms. These compounds have been proposed that can interact with receptors on the surface of leukocytes that result in the stimulation on non-specific immune responses. 4) Vaccination: little is known about a biological product that could be used as a vaccine for preventing this infection in fish. In the Loma salmonae experience, one of the arguments that favor the production of a vaccine is the development in fish of resistance, associated to a cellular immune response. A recently proved spore-based vaccine to prevent microsporidial gill disease in salmon has recently shown its efficacy by considerably reducing the incidence of infection. This recent discovery would be first anti-microsporidian vaccine that is effective against this elusive parasite.

Branching network of proteinaceous filaments within the parasitophorous vacuole of Encephalitozoon cuniculi and Encephalitozoon hellem

The microsporidia are a diverse phylum of obligate intracellular parasites that infect all major animal groups and have been recognized as emerging human pathogens for which few chemotherapeutic options currently exist. These organisms infect every tissue and organ system, causing significant pathology, especially in immune-compromised populations. The microsporidian spore employs a unique infection strategy in which its contents are delivered into a host cell via the polar tube, an organelle that lies coiled within the resting spore but erupts with a force sufficient to pierce the plasma membrane of its host cell. Using biochemical and molecular approaches, we have previously identified components of the polar tube and spore wall of the Encephalitozoonidae. In this study, we employed a shotgun proteomic strategy to identify novel structural components of these organelles in Encephalitozoon cuniculi. As a result, a new component of the E. cuniculi developing spore wall was identified. Surprisingly, using the same approach, a heretofore undescribed filamentous network within the lumen of the parasitophorous vacuole was discovered. This network was also present in the parasitophorous vacuole of Encephalitozoon hellem. Thus, in addition to further elucidating the molecular composition of seminal organelles and revealing novel diagnostic and therapeutic targets, proteomic analysis-driven approaches exploring the spore may also uncover unknown facets of microsporidian biology.

The intriguing nature of microsporidian genomes

Microsporidia are a group of highly adapted unicellular fungi that are known to infect a wide range of animals, including humans and species of great economic importance. These organisms are best known for their very simple cellular and genomic features, an adaptive consequence of their obligate intracellular parasitism. In the last decade, the acquisition of a large amount of genomic and transcriptomic data from several microsporidian species has greatly improved our understanding of the consequences of a purely intracellular lifestyle. In particular, genome sequence data from these pathogens has revealed how obligate intracellular parasitism can result in radical changes in the composition and structure of nuclear genomes and how these changes can affect cellular and evolutionary mechanisms that are otherwise well conserved among eukaryotes. This article reviews our current understanding of the genome content and structure of microsporidia, discussing their evolutionary origin and cataloguing the mechanisms that have often been involved in their extreme reduction.

Importance of nonenteric protozoan infections in immunocompromised people

There are many neglected nonenteric protozoa able to cause serious morbidity and mortality in humans, particularly in the developing world. Diseases caused by certain protozoa are often more severe in the presence of HIV. While information regarding neglected tropical diseases caused by trypanosomatids and Plasmodium is abundant, these protozoa are often not a first consideration in Western countries where they are not endemic. As such, diagnostics may not be available in these regions. Due to global travel and immigration, this has become an increasing problem. Inversely, in certain parts of the world (particularly sub-Saharan Africa), the HIV problem is so severe that diseases like microsporidiosis and toxoplasmosis are common. In Western countries, due to the availability of highly active antiretroviral therapy (HAART), these diseases are infrequently encountered. While free-living amoebae are rarely encountered in a clinical setting, when infections do occur, they are often fatal. Rapid diagnosis and treatment are essential to the survival of patients infected with these organisms. This paper reviews information on the diagnosis and treatment of nonenteric protozoal diseases in immunocompromised people, with a focus on patients infected with HIV. The nonenteric microsporidia, some trypanosomatids, Toxoplasma spp., Neospora spp., some free-living amoebae, Plasmodium spp., and Babesia spp. are discussed.

The complete sequence of the smallest known nuclear genome from the microsporidian Encephalitozoon intestinalis

The genome of the microsporidia Encephalitozoon cuniculi is widely recognized as a model for extreme reduction and compaction. At only 2.9 Mbp, the genome encodes approximately 2,000 densely packed genes and little else. However, the nuclear genome of its sister, Encephalitozoon intestinalis, is even more reduced; at 2.3 Mbp, it represents a 20% reduction from an already severely compacted genome, raising the question, what else can be lost? In this paper, we describe the complete sequence of the E. intestinalis genome and its comparison with that of E. cuniculi. The two species share a conserved gene content, order and density over most of their genomes. The exceptions are the subtelomeric regions, where E. intestinalis chromosomes are missing large gene blocks of sequence found in E. cuniculi. In the remaining gene-dense chromosome 'cores', the diminutive intergenic sequences and introns are actually more highly conserved than the genes themselves, suggesting that they have reached the limits of reduction for a fully functional genome.

A comparison of related genomes provides valuable information about how they evolve. Here, the complete sequence of the smallest known nuclear genome from the microsporidia E. intestinalis is described and compared with its larger sister E. cuniculi, revealing what parts are indispensable in even the most reduced genomes.

Interactions of Encephalitozoon cuniculi polar tube proteins

Microsporidia are eukaryotic, obligate intracellular organisms defined by small spores that contain a single invasion organelle, the polar tube, which coils around the interior of the spore. When these parasites infect host cells, the polar tube is discharged from the anterior pole of the spore, pierces the cell, and transfers sporoplasm into the cytoplasm of the host. Three polar tube proteins (PTP1, PTP2, and PTP3) have been identified in this structure. The interactions of these proteins in the assembly and function of the polar tube are not known. This study was undertaken to examine the protein interactions of the Encephalitozoon cuniculi polar tube proteins (EcPTPs). Immunofluorescence and immunoelectron microscopy confirmed the colocalization of EcPTP1, EcPTP2, and EcPTP3 to the polar tube. Experiments using cross-linkers indicated that EcPTP1, EcPTP2, and EcPTP3 form a complex in the polar tube, which was confirmed by immunoprecipitation using EcPTP1 antiserum. Yeast two-hybrid analysis revealed that full-length EcPTP1, EcPTP2, and EcPTP3 interact with each other in vivo. Both the N and C termini of EcPTP1 were involved in these interactions, but the central region of this protein, which contains a repetitive motif, was not. Further studies of polar tube proteins and their structural interactions may help elucidate the formation of the polar tube during the invasion process.