Association of Blastocystis ST6 with higher protease activity among symptomatic subjects

Profiling of the fecal microbiota and circulating microRNA-16 in IBS subjects with Blastocystis infection : a case-control study

Irritable bowel syndrome (IBS) is a prevalent gastrointestinal (GI) tract disorder. Although the main reason for IBS is not clear, the interaction between intestinal microorganisms and the gut barrier seems to play an important role in pathogenesis of IBS. The current study aimed to investigate the effect of Blastocystis on the gut microbiota profile and the circulation levels of microRNA (mir)-16 of IBS patients compared to healthy subjects. Stool and blood samples were collected from 80 participants including 40 samples from each IBS and healthy group. Upon DNA extraction from stool samples, barcoding region and quantitative real-time PCR were analyzed to investigate Blastocystis and the microbiota profile, respectively. RNA was extracted from serum samples of included subjects and the expression of mir-16 was evaluated using stem-loop protocol and qreal-time PCR. Significant changes between IBS patients and healthy controls was observed in Firmicutes, Actinobacteria, Faecalibacterium, and Alistipes. In IBS patients, the relative abundance of Bifidobacteria was directly correlated with the presence of Blastocystis, while Alistipes was decreased with Blastocystis. Lactobacillus was significantly increased in Blastocystis carriers. In healthy subjects, the relative abundance of Bifidobacteria was decreased, but Alistipes was increased in Blastocystis carriers. The changes in the Firmicutes/Bacteroidetes ratio was not significant in different groups. The relative expression of mir-16 in Blastocystis-negative IBS patients and healthy carriers was significantly overexpressed compared to control group. The presence of Blastocystis, decreased the relative expression of mir-16 in IBS patients compared to Blastocystis-negative IBS patients. The present study revealed that Blastocystis has the ability to change the abundance of some phyla/genera of bacteria in IBS and healthy subjects. Moreover, Blastocystis seems to  modulate the relative expression of microRNAs  to control the gut atmosphere, apply its pathogenicity, and provide a favor niche for its colonization.

Identification and validation of novel Blastocystis subtype ST41 in a Colombian patient undergoing colorectal cancer screening

Blastocystis sp. is among the most frequent intestinal protists identified in humans globally. However, characterization of Blastocystis subtype diversity in humans is ongoing. We report here the identification of novel Blastocystis subtype ST41 in a Colombian patient undergoing colorectal cancer screening involving colonoscopy and fecal testing (microscopy, culture, PCR). The full-length ssu rRNA gene sequence of the protist was generated using MinION long-read sequencing technology. The validity of the novel subtype was confirmed via phylogenetic and pairwise distance analyses of the full-length ST41 sequence and all other valid subtypes. The study provides reference material essential for conducting subsequent experimental studies.

Extracellular Cysteine Proteases of Key Intestinal Protozoan Pathogens-Factors Linked to Virulence and Pathogenicity

Intestinal diseases caused by protistan parasites of the genera Giardia (giardiasis), Entamoeba (amoebiasis), Cryptosporidium (cryptosporidiosis) and Blastocystis (blastocystosis) represent a major burden in human and animal populations worldwide due to the severity of diarrhea and/or inflammation in susceptible hosts. These pathogens interact with epithelial cells, promoting increased paracellular permeability and enterocyte cell death (mainly apoptosis), which precede physiological and immunological disorders. Some cell-surface-anchored and molecules secreted from these parasites function as virulence markers, of which peptide hydrolases, particularly cysteine proteases (CPs), are abundant and have versatile lytic activities. Upon secretion, CPs can affect host tissues and immune responses beyond the site of parasite colonization, thereby increasing the pathogens' virulence. The four intestinal protists considered here are known to secrete predominantly clan A (C1- and C2-type) CPs, some of which have been characterized. CPs of Giardia duodenalis (e.g., Giardipain-1) and Entamoeba histolytica (EhCPs 1-6 and EhCP112) degrade mucin and villin, cause damage to intercellular junction proteins, induce apoptosis in epithelial cells and degrade immunoglobulins, cytokines and defensins. In Cryptosporidium, five Cryptopains are encoded in its genome, but only Cryptopains 4 and 5 are likely secreted. In Blastocystis sp., a legumain-activated CP, called Blastopain-1, and legumain itself have been detected in the extracellular medium, and the former has similar adverse effects on epithelial integrity and enterocyte survival. Due to their different functions, these enzymes could represent novel drug targets. Indeed, some promising results with CP inhibitors, such as vinyl sulfones (K11777 and WRR605), the garlic derivative, allicin, and purified amoebic CPs have been obtained in experimental models, suggesting that these enzymes might be useful drug targets.

Higher amoebic and metronidazole resistant forms of Blastocystis sp. seen in schizophrenic patients

Background

Blastocystis sp. is one of the most common colonisers of the intestinal tract that demonstrate strong interaction with accompanying gut bacteria. Previously, the protozoan isolated from individuals with irritable bowel syndrome (IBS) showed altered phenotypic features suggesting that it can be triggered to become pathogenic. Previous studies reported altered gut microbiota and high prevalence of Blastocystis sp. in schizophrenia patients. However, the phenotypic characteristics of Blastocystis sp. isolated from individuals with SZ have yet to be described.

Methods

In this study, faecal samples from 50 patients with severe schizophrenia (SZ) and 100 non-schizophrenic (NS) individuals were screened for Blastocystis sp. infection. Positive isolates were subjected to genotypic and phenotypic characterization.

Results

We found that 12 out of 50 (24%) SZ and 5 out of 100 (5%) NS individuals were detected Blastocystis sp. positive using both in vitro culture and PCR method with no significant association to age and gender. Out of the 15 sequenced isolates, ST3 was the most prevalent subtype (66.7%) followed by ST1 (20%) and ST6 (13.3%). The isolates from SZ individuals demonstrated significant slower growth rate (34.9 ± 15.6 h) and larger range of cell diameter (3.3–140 µm). We detected higher amoebic forms and metronidazole resistance among SZ isolates with variation in cell surface glycoprotein where 98% of cells from SZ showed consistent medium to high binding affinity (+ 2 to + 3) to Concavalin A staining compared to NS isolates that demonstrated only 76% high lectin (+ 3) binding affinity. Cysteine and serine protease levels were predominantly found among SZ isolates. We also demonstrate the presence of metalloprotease in Blastocystis sp. especially among NS isolates. Introduction of solubilised antigens from SZ isolates increased the cell proliferation of HCT116 cells by two fold when compared to NS isolates.

Conclusion

Our findings demonstrated Blastocystis sp. isolated from SZ individuals showed variation in phenotype specifically in morphology and drug resistance. The findings indicate that the gut environment (SZ and NS) and treatment of SZ could have influenced the phenotype of Blastocystis sp.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05418-0.

Variations in active proteases of Blastocystis sp. obtained from water and animal isolates from the Philippines

Blastocystis sp. is a commonly encountered gut protozoan with unclear pathogenicity. The presence of proteases in this organism may be related to its potential pathogenicity or other physiological differences. This study aimed to identify the various proteases that may be present in different subtypes (STs) of Blastocystis sp. using azocasein assay and gelatin zymography. In this study, cysteine, serine, aspartic protease, metalloproteases, and unknown proteases were identified in Blastocystis sp. cultures obtained from animal and water samples belonging to ST1-ST5 and ST7. Azocasein assay and gelatin zymography were conducted on different batches of protease extracts, which showed varying results. Cysteine protease was the most commonly encountered. Protease activity in general is not associated with ST or source (animal or water). However, the presence of cysteine protease alone was associated with animal samples, whereas the presence of more than two protease types was associated with water samples. Azocasein assay and gelatin zymography were conducted on different batches of protease extracts, which showed varying results. Protease activity and the types present may change over time. Blastocystis sp. shows high protease diversity, including possible novel types.

Gut Microbiota Shifting in Irritable Bowel Syndrome: The Mysterious Role of Blastocystis sp

Irritable bowel syndrome (IBS) is a chronic disorder, which its causative agent is not completely clear; however, the interaction between microorganisms and gastrointestinal (GI) epithelial cells plays a critical role in the development of IBS and presenting symptoms. During recent decades, many studies have highlighted the high prevalence of Blastocystis sp. in patients with IBS and suggested a probable role for this protist in this disease. Recent studies have documented changes in the gut microbiota composition in patients with IBS regarding the presence of Blastocystis sp., but it is not clear that either disturbance of the gut during GI disorders is a favorable condition for Blastocystis sp. colonization or the presence of this protist may lead to alteration in the gut microbiota in IBS patients. In this review, we comprehensively gather and discuss scientific findings covering the role of Blastocystis sp. in IBS via gut microbiota shifting.

Modulation of microRNAs and claudin-7 in Caco-2 cell line treated with Blastocystis sp., subtype 3 soluble total antigen

Background

Blastocystis sp., is a eukaryote of the large intestine, which is reported from almost all countries. The pathogenesis of this protist is not clear. The current study aimed to analyze the effects of Blastocystis sp., ST3 soluble total antigen (B3STA) on the microRNAs (miRNAs) involved in the gut permeability and also pro-inflammatory cytokines, occludin, and claudin-7.

Methods

Blastocystis sp., ST3 isolated from stool sample was purified, and its soluble total antigen was extracted using freeze and thawing. The Caco-2 cell line was treated with B3STA for 24 h and the expression levels of mir-16, mir-21, mir-29a, mir-223, and mir-874 were analyzed. In addition, the expression levels of il-8, il-15, occludin, and claudin-7 genes were assessed.

Results

B3STA significantly upregulated the expression of mir-223, and mir-874, and downregulated mir-29a. The expression of mir-16 and mir-21 was not significant. In addition, the expression of il-8 and il-15 was not significant. B3STA significantly decreased the expression level of claudin-7 (P-value < 0.0001), but the expression of occludin was not significant. Our results showed significant correlation between all studied miRNAs, except mir-29a, with downregulation of claudin-7.

Conclusions

This is the first study investigating the effects of Blastocystis sp., ST3 isolated from symptomatic subjects on the expression levels of miRNAs involved in the gut permeability. Our results demonstrated that B3STA may change miRNA expression, which are involved in the gut barrier integrity, and downregulates claudin-7, which is known as sealing factor.