Evaluation on Elongation Factor 1 Alpha of Entamoeba histolytica Interaction with the Intermediate Subunit of the Gal/GalNAc Lectin and Actin in Phagocytosis

Analysis of gill and skin microbiota in Larimichthys crocea reveals bacteria associated with cryptocaryoniasis resistance potential

Cryptocaryoniasis, caused by the ciliate parasite Cryptocaryon irritans, poses a significant threat to the large yellow croaker (Larimichthys crocea) in intensive marine aquaculture. This study explores the interaction between skin and gill microbiota and C. irritans infection, focusing on the role of commensal microbes in disease resistance. Fish were challenged with 100 theronts per gram of body weight, leading to substantial microbial dysbiosis, characterized by decreased alpha diversity and disrupted co-occurrence networks, particularly on the skin. Post-infection, Vibrio abundance significantly increased in both gills and skin, suggesting potential for secondary infections. Conversely, lower Vibrio levels correlated with higher populations of Bdellovibrio-like organisms (BALOs), which may play a beneficial role in microbial balance. Fish showed varying susceptibility, with mildly infected individuals exhibiting less histopathological damage and a stronger immune response, indicated by elevated interleukin-1β (IL-1β) and interleukin-8 (IL-8) levels. Correlation analyses revealed significant relationships between relative infection intensity (RII) and microbial composition, with certain bacteria known for anti-eukaryotic microbial properties showing negative correlations with RII. Additionally, the abundance of nitrogen-metabolizing bacteria also correlated negatively with RII. Functional predictions indicated increased bacterial genes related to denitrification and vitamin biosynthesis post-infection. Notably, Candidatus Midichloria was identified as a potential biomarker for C. irritans infection and is thought to be an endosymbiont of C. irritans, with its presence validated through PCR analysis. These findings illuminate microbial dynamics during C. irritans infection and suggest probiotic candidates for managing cryptocaryoniasis.

Identification and characterization of a carbohydrate recognition domain-like region in Entamoeba histolytica Gal/GalNAc lectin intermediate subunit

Entamoeba histolytica is an enteric protozoan parasite that causes human amebic colitis and extraintestinal abscesses. As a prerequisite for parasite colonization and invasion, adherence of E. histolytica is predominantly mediated by galactose (Gal)- and N-acetyl-d-galactosamine (GalNAc)-inhibitable lectins. The intermediate subunit (Igl) of Gal-/GalNAc-inhibitable lectin is a cysteine-rich protein containing multiple CXXC motifs and is considered a key factor affecting trophozoite's pathogenicity. However, details of the function of Igl during parasite adherence remain unclear. Here, using segmentally expressed Igl proteins and a CHO cell model transfected with Igl fragments, we identified a carbohydrate-recognition domain (CRD)-like region between amino acids 989 and 1,088. Through single- and double-point mutations in the Igl segments, two core CXXC motifs responsible for carbohydrate recognition in the CRD-like region, which are highly conserved among several lectins, were confirmed. In addition to adhesion, the roles of CRD-like region and its core CXXC motifs in various pathogenic effects were further explored. To our knowledge, this is the first report showing an adhesion-related region in E. histolytica Igl. The identification and characterization of this CRD-like region provides further insights into molecular mechanisms underlying E. histolytica pathogenicity and also aids in the determination of a potential drug target in this parasite.

IMPORTANCE

Entamoeba histolytica adhesion mainly depends on galactose (Gal)-/N-acetyl-d-galactosamine (GalNAc)-inhibitable lectins, subsequently triggering a series of amebic reactions. Among the three subunits of Gal-/GalNAc-inhibitable lectin, heavy subunit and intermediate subunit (Igl) have exhibited lectin activity, but that of Igl remains poorly understood. In this study, we confirmed a carbohydrate-recognition domain (CRD)-like limiting region in E. histolytica Igl and further identified its two core CXXC motifs responsible for carbohydrate recognition. Moreover, the role of Igl's CRD-like region and its CXXC motifs in hemolysis and pathogenic effects was explored. This is the first study to determine an adhesion-related region in E. histolytica Igl protein, providing a new reference direction for subsequent research studies. Since the potential homogeneity of galectin-2 in several mammals and Igl CRD-like region, it could be meaningful to relate the corresponding pathogeneses and phenotypes of these two proteins. Except for adhesion, studies on the involvement of Igl CRD-like region in different parasite-host interactions are also promising.

Entamoeba moshkovskii as a potential model organism for Gal/GalNAc lectin intermediate subunit exhibition and functional identification

In humans, Entamoeba histolytica is the main pathogen causing various amoebiases, while E. moshkovskii falls between being a pathogen and non-pathogen. The two species have similar behavior patterns but differ significantly in pathogenicity, with previous studies and clinical data indicating that E. moshkovskii has a low level of pathogenicity. Meaningfully, the biological characteristics of E. moshkovskii make it a potential model organism and a protein display platform for studying the functions of important Entamoeba proteins. Here, an Amoeba-pcDNA3.1 vector capable of overexpressing E. histolytica-sourced Igl-C protein was constructed and successfully transfected into E. moshkovskii. High levels of expression of the Igl-C, EGFP, and NeoR genes were identified in Igl-C-transfected trophozoites using qRT-PCR, and they were subsequently confirmed using immunoblotting. Transfection of Igl-C protein improved the adherence and phagocytosis of E. moshkovskii, demonstrating that E. histolytica Igl mediated amoebic adhesion. Moreover, as a manifestation of protein virulence, the ability of post-transfected trophozoites to induce inflammation in host macrophages was also enhanced. In conclusion, this study utilizing the characteristics of E. moshkovskii confirmed its potential to serve as a model organism. E. moshkovskii could replace E. histolytica as the target of gene editing, allowing more efficient study of amoebic pathogenicity.

Combination of computational techniques and RNAi reveal targets in Anopheles gambiae for malaria vector control

Increasing reports of insecticide resistance continue to hamper the gains of vector control strategies in curbing malaria transmission. This makes identifying new insecticide targets or alternative vector control strategies necessary. CLassifier of Essentiality AcRoss EukaRyote (CLEARER), a leave-one-organism-out cross-validation machine learning classifier for essential genes, was used to predict essential genes in Anopheles gambiae and selected predicted genes experimentally validated. The CLEARER algorithm was trained on six model organisms: Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens, Mus musculus, Saccharomyces cerevisiae and Schizosaccharomyces pombe, and employed to identify essential genes in An. gambiae. Of the 10,426 genes in An. gambiae, 1,946 genes (18.7%) were predicted to be Cellular Essential Genes (CEGs), 1716 (16.5%) to be Organism Essential Genes (OEGs), and 852 genes (8.2%) to be essential as both OEGs and CEGs. RNA interference (RNAi) was used to validate the top three highly expressed non-ribosomal predictions as probable vector control targets, by determining the effect of these genes on the survival of An. gambiae G3 mosquitoes. In addition, the effect of knockdown of arginase (AGAP008783) on Plasmodium berghei infection in mosquitoes was evaluated, an enzyme we computationally inferred earlier to be essential based on chokepoint analysis. Arginase and the top three genes, AGAP007406 (Elongation factor 1-alpha, Elf1), AGAP002076 (Heat shock 70kDa protein 1/8, HSP), AGAP009441 (Elongation factor 2, Elf2), had knockdown efficiencies of 91%, 75%, 63%, and 61%, respectively. While knockdown of HSP or Elf2 significantly reduced longevity of the mosquitoes (p<0.0001) compared to control groups, Elf1 or arginase knockdown had no effect on survival. However, arginase knockdown significantly reduced P. berghei oocytes counts in the midgut of mosquitoes when compared to LacZ-injected controls. The study reveals HSP and Elf2 as important contributors to mosquito survival and arginase as important for parasite development, hence placing them as possible targets for vector control.

Immunogens in Balamuthia mandrillaris: a proteomic exploration

Balamuthia mandrillaris is the causative agent of granulomatous amoebic encephalitis, a rare and often fatal infection affecting the central nervous system. The amoeba is isolated from diverse environmental sources and can cause severe infections in both immunocompromised and immunocompetent individuals. Given the limited understanding of B. mandrillaris, our research aimed to explore its protein profile, identifying potential immunogens crucial for early granulomatous amoebic encephalitis diagnosis. Cultures of B. mandrillaris and other amoebas were grown under axenic conditions, and total amoebic extracts were obtained. Proteomic analyses, including two-dimensional electrophoresis and mass spectrometry, were performed. A 50-kDa band showed a robust recognition of antibodies from immunized BALB/c mice; peptides contained in this band were matched with elongation factor-1 alpha, which emerged as a putative key immunogen. Besides, lectin blotting revealed the presence of glycoproteins in B. mandrillaris, and confocal microscopy demonstrated the focal distribution of the 50-kDa band throughout trophozoites. Cumulatively, these observations suggest the participation of the 50-kDa band in adhesion and recognition mechanisms. Thus, these collective findings demonstrate some protein characteristics of B. mandrillaris, opening avenues for understanding its pathogenicity and developing diagnostic and therapeutic strategies.

Dynamic Association of ESCRT-II Proteins with ESCRT-I and ESCRT-III Complexes during Phagocytosis of Entamoeba histolytica

By their active movement and voraux phagocytosis, the trophozoites of Entamoeba histolytica constitute an excellent system to investigate the dynamics of the Endosomal Sorting Complex Required for Transport (ESCRT) protein interactions through phagocytosis. Here, we studied the proteins forming the E. histolytica ESCRT-II complex and their relationship with other phagocytosis-involved molecules. Bioinformatics analysis predicted that EhVps22, EhVps25, and EhVps36 are E. histolytica bona fide orthologues of the ESCRT-II protein families. Recombinant proteins and specific antibodies revealed that ESCRT-II proteins interact with each other, with other ESCRT proteins, and phagocytosis-involved molecules, such as the adhesin (EhADH). Laser confocal microscopy, pull-down assays, and mass spectrometry analysis disclosed that during phagocytosis, ESCRT-II accompanies the red blood cells (RBCs) from their attachment to the trophozoites until their arrival to multivesicular bodies (MVBs), changing their interactive patterns according to the time and place of the process. Knocked-down trophozoites in the Ehvps25 gene presented a 50% lower rate of phagocytosis than the controls and lower efficiency to adhere RBCs. In conclusion, ESCRT-II interacts with other molecules during prey contact and conduction throughout the phagocytic channel and trophozoites membranous system. ESCRT-II proteins are members of the protein chain during vesicle trafficking and are fundamental for the continuity and efficiency of phagocytosis.

Comparative transcriptome profiling of virulent and avirulent isolates of Neoparamoeba perurans

Neoparamoeba perurans, the aetiological agent of amoebic gill disease, remains a persistent threat to Atlantic salmon mariculture operations worldwide. Innovation in methods of AGD control is required yet constrained by a limited understanding of the mechanisms of amoebic gill disease pathogenesis. In the current study, a comparative transcriptome analysis of two N. perurans isolates of contrasting virulence phenotypes is presented using gill-associated, virulent (wild type) isolates, and in vitro cultured, avirulent (clonal) isolates. Differential gene expression analysis identified a total of 21,198 differentially expressed genes between the wild type and clonal isolates, with 5674 of these genes upregulated in wild type N. perurans. Gene set enrichment analysis predicted gene sets enriched in the wild type isolates including, although not limited to, cortical actin cytoskeleton, pseudopodia, phagocytosis, macropinocytic cup, and fatty acid beta-oxidation. Combined, the results from these analyses suggest that upregulated gene expression associated with lipid metabolism, oxidative stress response, protease activity, and cytoskeleton reorganisation is linked to pathogenicity in wild type N. perurans. These findings provide a foundation for future AGD research and the development of novel therapeutic and prophylactic AGD control measures for commercial aquaculture.

Quantitative Proteomics Reveals Metabolic Reprogramming in Host Cells Induced by Trophozoites and Intermediate Subunit of Gal/GalNAc Lectins from Entamoeba histolytica

Entamoeba histolytica is an intestinal protozoan parasite with remarkable ability to kill and phagocytose host cells, causing amoebic colitis and extraintestinal abscesses. The intermediate subunit (Igl) of galactose (Gal)- and N-acetyl-d-galactosamine (GalNAc)-specific lectins is considered an important surface antigen involved in the pathogenesis of E. histolytica. Here, we applied mass spectrometry-based quantitative proteomics technology to analyze the protein expression profile changes occurring in host Caco2 cells incubated with E. histolytica trophozoites or stimulated by purified native Igl protein. The expression levels of 1,490 and 489 proteins were significantly altered in the E. histolytica-treated and Igl-treated groups, respectively, among 6,875 proteins totally identified. Intriguingly, central carbon metabolism of host cells was suppressed in both E. histolytica-treated and Igl-treated groups, with evidence of decreased expression levels of several key enzymes, including pyruvate kinase muscle type 2, presenting a Warburg-like effect in host cells. Besides, Igl had potential physical interactions with central carbon metabolism enzymes and the proteolytic degradation family members proteasome subunit alpha and beta, which may be responsible for the degradation of key enzymes in carbon metabolism. These results provided a novel perspective on the pathogenic mechanism of E. histolytica and compelling evidence supporting the important role of Igl in the virulence of E. histolytica.

IMPORTANCE Metabolic reprogramming is considered a hallmark of some infectious diseases. However, in amoebiasis, a neglected tropical disease caused by protozoan parasite E. histolytica, metabolic changes in host cells have yet to be proven. In this study, advanced data-independent acquisition mass spectrometry-based quantitative proteomics was applied to investigate the overall host cellular metabolic changes as high-throughput proteomics could measure molecular changes in a cell or tissue with high efficiency. Enrichment analysis of differentially expressed proteins showed biological processes and cellular pathways related to amoeba infection and Igl cytotoxicity. Specifically, central carbon metabolism of host cells was dramatically suppressed in both E. histolytica-treated and Igl-treated groups, indicating the occurrence of a Warburg-like effect induced by trophozoites or Igl from E. histolytica. Distinct differences in ubiquitin-mediated proteolysis, rapamycin (mTOR) signaling pathway, autophagy, endocytosis, and tight junctions provided novel perspectives on the pathogenic mechanism of E. histolytica.