Bacterial sialoglycosidases in Virulence and Pathogenesis

Cross-feeding between beneficial and pathogenic bacteria to utilize eukaryotic host cell-derived sialic acids and bacteriophages shape the pathogen-host interface milieu

Under an inflamed-intestinal milieu, increased free sialic acids are associated with the overgrowth of some pathogenic bacterial strains. Recently, the protective immunomodulatory activity of gut bacteriophages (phages) has also been highlighted. However, the role of phages in triple reciprocal interactions between pathogenic bacteria, beneficial bacteria, and their host cell sialic acids has not been studied so far. We established a sialidase-explicit model in which beneficial and pathogenic bacteria interact through cross-feeding and competition for free sialic acid using a human triple co-culture cell model incorporating colonocytes (T84 cells), monocytes (THP-1 cells), and hepatocytes (Huh7 cells). Triple co-cultured cells were challenged with Gram-positive Bifidobacterium bifidum (B. bifidum) and Gram-negative Pseudomonas aeruginosa PAO1 (P. a PAO1) in the absence or presence of its KPP22 phage in two different cell culture mediums: 1) standard Dulbecco's Modified Eagle Medium (DMEM) and 2) DMEM with 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA). Changes in physiological, functional, and structural health markers of stimulated cocultured cells were evaluated. The concentrations of sialic acid and pro-inflammatory cytokines in the cell culture supernatants were quantified. P. a PAO1 triggered the release of interleukin 6 and 8 (IL-6 and IL-8), accompanied by increased levels of free sialic acid, reduced viability of co-cultured cells, and disrupted the integrity of the cellular monolayer. These disruptive effects were markedly attenuated by KPP22 phage and B. bifidum. In addition to well-documented differences in the structure and composition of the bacterial cell walls of Gram-negative pathogenic bacteria and bifidobacteria, two distinct factors seem to be pivotal in modulating the pathogen-host interface milieu: (i) the presence of phages and (ii) the utilization of free sialic acids secreted from host cells by bifidobacteria.

In vitro antiviral activity of NanB bacterial sialidase against avian influenza H9N2 virus in MDCK cells

The avian influenza virus is an infectious agent that may cause global health problems in poultry and is potentially zoonotic. In the recent decades, bacterial-derived sialidases have been extensively studied for their ability to inhibit avian influenza virus infections. In this study, the antiviral activity of NanB sialidase from Pasteurella multocida was investigated through in vitro analysis using Madin-Darby canine kidney (MDCK) cells. NanB sialidase was purified from P. multocida to test its toxicity and its ability to hydrolyse its sialic acid receptors on MDCK cells. The H9N2 challenge virus was propagated in MDCK cells until cytopathic effects appeared. Antiviral activity of NanB sialidase was tested using MDCK cells, and then observed based on cell morphology, viral copy number, and expression of apoptosis-mediating genes. NanB sialidase effectively hydrolysed Neu5Acα(2,6)-Gal sialic acid at a dose of 129 mU/ml, while at 258 mU/ml, it caused toxicity to MDCK cells. Antiviral activity of sialidase was evident based on the significant decrease in viral copy number at all doses administered. The increase of p53 and caspase-3 expression was observed in infected cells without sialidase. Our study demonstrates the ability of NanB sialidase to inhibit H9N2 virus replication based on observations of sialic acid hydrolysis, reduction in viral copy number, and expression of apoptosis-related genes. The future application of sialidase may be considered as an antiviral strategy against avian influenza H9N2 virus infections. RESEARCH HIGHLIGHTSNanB sialidase effectively hydrolyses Neu5Acα(2,6)-Gal at a dose of 129 mU/ml.NanB sialidase from Pasteurella multocida can inhibit the entry of H9N2 virus into cells.NanB sialidase of Pasteurella multocida prevents infection-induced cell apoptosis.NanB sialidase reduces the H9N2 viral copy number in MDCK cells.

Clostridium perfringens sialidase interaction with Neu5Ac α-Gal sialic acid receptors by in-silico observation and its impact on monolayers cellular behavior structure

Objective

This study aims to evaluate the effect of Clostridium perfringens sialidase treatment on monolayer cell behavior using computational screening and an in vitro approach to demonstrate interaction between enzyme-based drugs and ligands in host cells.

Materials and Methods

The in silico study was carried out by molecular docking analysis used to predict the interactions between atoms that occur, followed by genetic characterization of sialidase from a wild isolate. Sialidase, which has undergone further production and purification processes exposed to chicken embryonic fibroblast cell culture, and observations-based structural morphology of cells compared between treated cells and normal cells without treatment.

Results

Based on an in silico study, C. perfringens sialidase has an excellent binding affinity with Neu5Acα (2.3) Gal ligand receptor with Gibbs energy value (∆G)-7.35 kcal/mol and Ki value of 4.11 µM. Wild C. perfringens isolates in this study have 99.1%-100% similarity to the plc gene, NanH, and NanI genes, while NanJ shows 93.18% similarity compared to the reference isolate from GenBank. Sialidase at 750 and 150 mU may impact the viability, cell count, and cell behavior structure of fibroblast cells by significantly increasing the empty area and perimeter of chicken embryo fibroblast (CEF) cells, while at 30 mU sialidase shows no significant difference compared with mock control.

Conclusion

Sialidase-derived C. perfringens has the capacity to compete with viral molecules for attachment to host sialic acid based on in silico analysis. However, sialidase treatment has an impact on monolayer cell fibroblasts given exposure to high doses.

Discovery and Characterization of Chemical Compounds That Inhibit the Function of Bacterial Neuraminidase from Codonopsis ussuriensis

Codonopsis ussuriensis (Rupr. and Maxim.) Hemsl is a medicinal herb commonly found in Korea, Japan, and the Russian Far East. However, its chemical composition and bioactivity have not been extensively studied. Thus, in this study, we aimed to examine and characterize the major components of the plant’s roots. Liquid chromatography with high-resolution mass spectrometry (LC-HRMS) was used to identify the components of the crude extracts. The compounds that were identified were named ussurienoside I (1) and tangshenoside I (2). The identified compounds were tested in vitro for inhibitory action against bacterial neuraminidase, and the mechanisms of inhibition were revealed. Compound 1 significantly inhibited bacterial neuraminidase activity in a dose-dependent manner (IC50 = 56.0 μM). The neuraminidase inhibitor (compound 1) exhibited mixed type-I kinetic characteristics. The LC-HRMS data showed that the root extracts contained eight compounds. The findings of this study may aid in the development of bacterial neuraminidase inhibitors with medicinal potential.

Metagenomic Analysis Reveals A Possible Association Between Respiratory Infection and Periodontitis

Periodontitis is an inflammatory disease that is characterized by progressive destruction of the periodontium and causes tooth loss in adults. Periodontitis is known to be associated with dysbiosis of the oral microflora, which is often linked to various diseases. However, the complexity of plaque microbial communities of periodontitis, antibiotic resistance, and enhanced virulence make this disease difficult to treat. In this study, using metagenomic shotgun sequencing, we investigated the etiology, antibiotic resistance genes (ARGs), and virulence genes (VirGs) of periodontitis. We revealed a significant shift in the composition of oral microbiota as well as several functional pathways that were represented significantly more abundantly in periodontitis patients than in controls. In addition, we observed several positively selected ARGs and VirGs with the Ka/Ks ratio > 1 by analyzing our data and a previous periodontitis dataset, indicating that ARGs and VirGs in oral microbiota may be subjected to positive selection. Moreover, 5 of 12 positively selected ARGs and VirGs in periodontitis patients were found in the genomes of respiratory tract pathogens. Of note, 91.8% of the background VirGs with at least one non-synonymous single-nucleotide polymorphism for natural selection were also from respiratory tract pathogens. These observations suggest a potential association between periodontitis and respiratory infection at the gene level. Our study enriches the knowledge of pathogens and functional pathways as well as the positive selection of antibiotic resistance and pathogen virulence in periodontitis patients, and provides evidence at the gene level for an association between periodontitis and respiratory infection.

Comparative Reverse Vaccinology of Piscirickettsia salmonis, Aeromonas salmonicida, Yersinia ruckeri, Vibrio anguillarum and Moritella viscosa, Frequent Pathogens of Atlantic Salmon and Lumpfish Aquaculture

Marine finfish aquaculture is affected by diverse infectious diseases, and they commonly occur as co-infection. Some of the most frequent and prevalent Gram-negative bacterial pathogens of the finfish aquaculture include Piscirickettsia salmonis, Aeromonas salmonicida, Yersinia ruckeri, Vibrio anguillarum and Moritella viscosa. To prevent co-infections in aquaculture, polyvalent or universal vaccines would be ideal. Commercial polyvalent vaccines against some of these pathogens are based on whole inactivated microbes and their efficacy is controversial. Identification of common antigens can contribute to the development of effective universal or polyvalent vaccines. In this study, we identified common and unique antigens of P. salmonis, A. salmonicida, Y. ruckeri, V. anguillarum and M. viscosa based on a reverse vaccinology pipeline. We screened the proteome of several strains using complete available genomes and identified a total of 154 potential antigens, 74 of these identified antigens corresponded to secreted proteins, and 80 corresponded to exposed outer membrane proteins (OMPs). Further analysis revealed the outer membrane antigens TonB-dependent siderophore receptor, OMP assembly factor BamA, the LPS assembly protein LptD and secreted antigens flagellar hook assembly protein FlgD and flagellar basal body rod protein FlgG are present in all pathogens used in this study. Sequence and structural alignment of these antigens showed relatively low percentage sequence identity but good structural homology. Common domains harboring several B-cells and T-cell epitopes binding to major histocompatibility (MHC) class I and II were identified. Selected peptides were evaluated for docking with Atlantic salmon (Salmo salar) and Lumpfish MHC class II. Interaction of common peptide-MHC class II showed good in-silico binding affinities and dissociation constants between −10.3 to −6.5 kcal mol−1 and 5.10 × 10−9 to 9.4 × 10−6 M. This study provided the first list of antigens that can be used for the development of polyvalent or universal vaccines against these Gram-negative bacterial pathogens affecting finfish aquaculture.

Remodeling of host glycoproteins during bacterial infection

Protein glycosylation is a common post-translational modification found in all living organisms. This modification in bacterial pathogens plays a pivotal role in their infectious processes including pathogenicity, immune evasion, and host-pathogen interactions. Importantly, many key proteins of host immune systems are also glycosylated and bacterial pathogens can notably modulate glycosylation of these host proteins to facilitate pathogenesis through the induction of abnormal host protein activity and abundance. In recent years, interest in studying the regulation of host protein glycosylation caused by bacterial pathogens is increasing to fully understand bacterial pathogenesis. In this review, we focus on how bacterial pathogens regulate remodeling of host glycoproteins during infections to promote the pathogenesis.

Production and Composition of Group B Streptococcal Membrane Vesicles Vary Across Diverse Lineages

Although the neonatal and fetal pathogen Group B Streptococcus (GBS) asymptomatically colonizes the vaginal tract of ∼30% of pregnant women, only a fraction of their offspring develops invasive disease. We and others have postulated that these dimorphic clinical phenotypes are driven by strain variability; however, the bacterial factors that promote these divergent clinical phenotypes remain unclear. It was previously shown that GBS produces membrane vesicles (MVs) that contain active virulence factors capable of inducing adverse pregnancy outcomes. Because the relationship between strain variation and vesicle composition or production is unknown, we sought to quantify MV production and examine the protein composition, using label-free proteomics on MVs produced by diverse clinical GBS strains representing three phylogenetically distinct lineages. We found that MV production varied across strains, with certain strains displaying nearly twofold increases in production relative to others. Hierarchical clustering and principal component analysis of the proteomes revealed that MV composition is lineage-dependent but independent of clinical phenotype. Multiple proteins that contribute to virulence or immunomodulation, including hyaluronidase, C5a peptidase, and sialidases, were differentially abundant in MVs, and were partially responsible for this divergence. Together, these data indicate that production and composition of GBS MVs vary in a strain-dependent manner, suggesting that MVs have lineage-specific functions relating to virulence. Such differences may contribute to variation in clinical phenotypes observed among individuals infected with GBS strains representing distinct lineages.

Bioinformatics analysis of structures and ligand-bindings of predicted zymogen granule protein observed on Bali cattle (Bos javanicus) saliva

Objective

Previously, we have shown that predicted zymogen granule protein 16 homolog B (P-G3MZ19) existed in Bali cattle (Bos javanicus) saliva. It was suggested that P-G3MZ19 is a member of the mannose-binding lectin family that plays an essential role in innate immunity. In the present study, we aimed to analyze the structure and ligand-binding of P-3MZ19 in Bali cattle saliva.

Materials and Methods

Saliva of four adult healthy Bali cattle was collected, lyophilized, and subjected to two-dimensional (2-D) gel electrophoresis. The target spot of around 17 kDa related to P-G3MZ19 was excised for matrix-assisted laser desorption ionization time-of-flight mass spectrometer/time-of-flight mass spectrometer mass spectrometry analysis and sequencing. The structure and the ligand-binding of P-3MZ19 were analyzed using bioinformatics software programs published elsewhere.

Results

Based on Iterative Threading ASSEmbly Refinement the 3D model of P-G3MZ19 was suggested to have similarities to exo-alpha-sialidase (EC 3.2.1.18); while its ligand-binding sites consisted of seven residues, i.e., 25aa-26aa (Gly-Gly), 95aa (Phe), 138aa (Tyr), 140aa (Leu), 141aa (Gly), and 143aa (Thr).

Conclusion

The structure of P-G3MZ19 of Bali cattle saliva and its ligand-binding sites have been successfully determined by using bioinformatics techniques. The biological and immunological roles of the peptide are currently under investigation based on P-G3MZ19 synthetic peptides.

Sialic acid removal by trans-sialidase modulates MMP-2 activity during Trypanosoma cruzi infection

Matrix metalloproteinases (MMPs) not only play a relevant role in homeostatic processes but are also involved in several pathological mechanisms associated with infectious diseases. As their clinical relevance in Chagas disease has recently been highlighted, we studied the modulation of circulating MMPs by Trypanosoma cruzi infection. We found that virulent parasites from Discrete Typing Units (DTU) VI induced higher proMMP-2 and MMP-2 activity in blood, whereas both low (DTU I) and high virulence parasites induced a significant decrease in proMMP-9 plasma activity. Moreover, trans-sialidase, a relevant T. cruzi virulence factor, is involved in MMP-2 activity modulation both in vivo and in vitro. It removes α2,3-linked sialyl residues from cell surface glycoconjugates, which then triggers the PKC/MEK/ERK signaling pathway. Additionally, bacterial sialidases specific for this sialyl residue linkage displayed similar MMP modulation profiles and triggered the same signaling pathways. This novel pathogenic mechanism, dependent on sialic acid removal by the neuraminidase activity of trans-sialidase, can be exploited by different pathogens expressing sialidases with similar specificity. Thus, here we present a new pathogen strategy through the regulation of the MMP network.

Distribution of a novel enzyme of sialidase family among native filamentous fungi

Sialidases (neuraminidases, EC 3.2.1.18) are widely distributed in biological systems but there are only scarce data on its production by filamentous fungi. The aim of this study was to obtain information about sialidase distribution in filamentous fungi from non-clinical isolates, to determine availability of sialidase gene, and to select a perspective producer. A total of 113 fungal strains belonging to Ascomycota and Zygomycota compassing 21 genera and 51 species were screened. Among them, 77 strains (11 orders, 14 families and 16 genera) were able to synthesize sialidase. Present data showed a habitat-dependent variation of sialidase activity between species and within species, depending on location. Sialidase gene was identified in sialidase-positive and sialidase-negative strains. . Among three perspective strains, the best producer was chosen based on their sialidase production depending on type of cultivation, medium composition, and growth temperature. The selected P. griseofulvum Р29 was cultivated in 3L bioreactor at 20 °C on medium supplemented with 0.5% milk whey. The results demonstrated better growth and 2.3-fold higher maximum enzyme activity compared to the shaken flask cultures. Moreover, the early occurring maximum (48 h) is an important prerequisite for future up scaling of the process.

Immunoglobulin A Glycosylation and Its Role in Disease

Human IgA is comprised of two subclasses, IgA1 and IgA2. Monomeric IgA (mIgA), polymeric IgA (pIgA), and secretory IgA (SIgA) are the main molecular forms of IgA. The production of IgA rivals all other immunoglobulin isotypes. The large quantities of IgA reflect the fundamental roles it plays in immune defense, protecting vulnerable mucosal surfaces against invading pathogens. SIgA dominates mucosal surfaces, whereas IgA in circulation is predominately monomeric. All forms of IgA are glycosylated, and the glycans significantly influence its various roles, including antigen binding and the antibody effector functions, mediated by the Fab and Fc portions, respectively. In contrast to its protective role, the aberrant glycosylation of IgA1 has been implicated in the pathogenesis of autoimmune diseases, such as IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). Furthermore, detailed characterization of IgA glycosylation, including its diverse range of heterogeneity, is of emerging interest. We provide an overview of the glycosylation observed for each subclass and molecular form of IgA as well as the range of heterogeneity for each site of glycosylation. In many ways, the role of IgA glycosylation is in its early stages of being elucidated. This chapter provides an overview of the current knowledge and research directions.