Clearance Of Microbial Pathogens Research Articles

Oropharyngeal Candidiasis, Candida Albicans Infections, and Oral Immune Mediators Associated with Oral Human Immunodeficiency Virus: A Literature Review

Introduction: While Candida albicans are usually commensal and present in low density in the oral cavity of healthy individuals, an immunocompromised immune system can lead to the overgrowth of this fungal species, leading to oral microbiome “dysbiosis” and activation of immune responses. In severe cases, C. albicans overgrowth can lead to an oral infection called oropharyngeal candidiasis (OPC), which is associated with inflammation, lesions, and sores of the oral cavity. While human immunodeficiency virus (HIV) infection has been linked to an increased risk of OPC, few studies have associated OPC and C. albicans infection with subsequent risk for oral HIV acquisition. Evidence on the oral microbiome and how it can alter HIV risk is also lacking. Methods: A literature search was performed on PubMed, Google Scholar, and the University of Alberta Library Database from inception to November 2023. Results and Discussion: The risk of oral HIV transmission is low. OPC and C. albicans fungal infection can increase HIV susceptibility by activating immune responses associated with the clearance of microbial pathogens, inducing inflammation and elevations in cytokines related to HIV risk including IL-17, IL-6 and IL-1ß. Persistent C. albicans infections also promote the recruitment of T-helper 17 cells, which is a common HIV target cell, and neutrophils, which releases neutrophil proteases upon inflammation and mediates the cleavage of tight junction proteins, ultimately disrupting the oral microbiome. Conclusion: Increased immune cell recruitment to the mucosa and increased epithelial breakdown may facilitate the diffusion and access of HIV virions across the epithelium to immune target cells, suggesting that OPC and C.albicans infections has the potential to increase risk for oral HIV acquisition. Limited evidence of the relationship between C. albicans density, OPC, and oral HIV risk, warrants high-quality cross-sectional studies in the future.

C-reactive Protein: An Inflammatory Biomarker and a Predictor of Neurodegenerative Disease in Patients With Inflammatory Bowel Disease?

Inflammatory bowel disease (IBD) refers to two chronic conditions of the digestive tract: ulcerative colitis (UC) and Crohn's disease (CD), representing a progressive inflammatory process that mainly occurs in the gut, with frequent extra-intestinal manifestations. Even if remission is periodically obtained for some patients, the histological activity and digestive symptoms may continue, maintaining a persistent systemic inflammation that could induce further extra-intestinal complications and contribute to the development of neurodegenerative disease. C-reactive protein (CRP) is an acute-phase reactant that is widely accepted as a dominant serum biomarker in IBD. CRP consequently activates the complement cascade, supports the release of pro-inflammatory cytokines, and the clearance of microbial pathogens. All these processes facilitate further processes, including atherosclerosis and hypercoagulability, alteration of the intestinal microbiota, and the increased permeability of the intestinal barrier for neurotoxic substances produced by gut microorganisms, due to the presence of a high level of lipopolysaccharides. For IBD, the connection between intestinal inflammation and central nervous system inflammation could be explained through the activity of the vagus nerve, a carrier of cytokines, CRP, and toxic materials to the brain, potentially inducing vascular lesions and damage of the glial vascular unit, with further risk for degeneration within the central nervous system. CRP is a key marker for IBD pathogenesis and is able to dissociate into its monomeric form, mCRP, on contact with activated cell and tissue components via the systemic circulation. We hypothesize that the chronic inflammatory process within IBD could initiate neuroinflammation and neurodegeneration, and therefore, further investigation of the significance of chronically raised plasma of CRP and mCRP in patients with IBD is warranted, as it may represent a critical predictive factor associated with a later neurodegenerative risk. Any future initiative aimed at pharmacologic modulation of CRP (e.g., blocking CRP-mCRP dissociation), could represent a new therapeutic approach protecting against intestinal inflammation and concomitantly reducing the risk of neuroinflammation, neurodegeneration, and cognitive decline.

Mast cells are at the interface between the external environment and the inner organism.

Mast cells localized at the level of the mucosal barrier in the skin, lung, and gastrointestinal tract, intervene in the modulation of the function of the epithelial cells and are involved in innate and adaptive defensive responses. In this context, mast cells intervene in the recognition and clearance of microbial pathogens. This mini-review article discusses the role of mast cells in these barrier systems.

Periodontal disease as a model to study chronic inflammation in aging.

Periodontal disease is a chronic inflammatory condition that results in the destruction of the teeth supporting tissues, eventually leading to the loss of teeth and reduced quality of life. In severe cases, periodontal disease can limit proper nutritional intake, cause acute pain and infection, and cause a withdrawal from social situations due to esthetic and phonetic concerns. Similar to other chronic inflammatory conditions, periodontal disease increases in prevalence with age. Research into what drives periodontal disease pathogenesis in older adults is contributing to our general understanding of age-related chronic inflammation. This review will present periodontal disease as an age-related chronic inflammatory disease and as an effective geroscience model to study mechanisms of age-related inflammatory dysregulation. The current understanding of the cellular and molecular mechanisms that drive inflammatory dysregulation as a function of age will be discussed with a focus on the major pathogenic immune cells in periodontal disease, which include neutrophils, macrophages, and T cells. Research in the aging biology field has shown that the age-related changes in these immune cells result in the cells becoming less effective in the clearance of microbial pathogens, expansion of pathogenic subpopulations, or an increase in pro-inflammatory cytokine secretions. Such changes can be pathogenic and contribute to inflammatory dysregulation that is associated with a myriad of age-related disease including periodontal disease. An improved understanding is needed to develop better interventions that target the molecules or pathways that are perturbed with age in order to improve treatment of chronic inflammatory conditions, including periodontal disease, in older adult populations.

F-type lectin from serum of the Antarctic teleost fish Trematomus bernacchii (Boulenger, 1902): Purification, structural characterization, and bacterial agglutinating activity.

The increasing availability of sequenced genomes has enabled a deeper understanding of the complexity of fish lectin repertoires involved in early development and immune recognition. The teleost fucose-type lectin (FTL) family includes proteins that preferentially bind fucose and display tandemly arrayed carbohydrate-recognition domains (CRDs) or are found in mosaic combinations with other domains. They function as opsonins, promoting phagocytosis and the clearance of microbial pathogens. The Antarctic fish Trematomus bernacchii is a Perciforme living at extremely low temperatures (-1.68°C) which is considered a model for studying adaptability to the variability of environmental waters. Here, we isolated a Ca++-independent fucose-binding protein from the serum of T. bernacchii by affinity chromatography with apparent molecular weights of 32 and 30kDa under reducing and non-reducing conditions, respectively. We have characterized its carbohydrate binding properties, thermal stability and potential ability to recognize bacterial pathogens. In western blot analysis, the protein showed intense cross-reactivity with antibodies specific for a sea bass (Dicentrarchus labrax) fucose-binding lectin. In addition, its molecular and structural aspects, showing that it contains two CRD-FTLs confirmed that T. bernacchii FTL (TbFTL) is a bona fide member of the FTL family, with binding activity at low temperatures and the ability to agglutinate bacteria, thereby suggesting it participates in host-pathogen interactions in low temperature environments.

Mannose-Binding Lectin Possesses Agglutination Activity and Promotes Opsonophagocytosis of Macrophages with Calreticulin Interaction in an Early Vertebrate.

The innate immune system is an ancient defense system in the process of biological evolution, which can quickly and efficiently resist pathogen infection. In mammals, mannose-binding lectin (MBL) is a key molecule in the innate immune and plays an essential role in the first line of host defense against pathogenic bacteria. However, the evolutionary origins and ancient roles of immune defense of MBL and its mechanism in clearance of microbial pathogens are still unclear, especially in early vertebrates. In this study, Oreochromis niloticus MBL (OnMBL) was successfully isolated and purified from the serum of Nile tilapia (O. niloticus). The OnMBL was able to bind and agglutinate with two important pathogens of tilapia, Streptococcus agalactiae and Aeromonas hydrophila Interestingly, the OnMBL was able to significantly inhibit the proliferation of pathogenic bacteria and reduce the inflammatory response. Upon bacterial challenge, the downregulation of OnMBL expression by RNA interference could lead to rapid proliferation of the pathogenic bacteria, ultimately resulting in tilapia death. However, the phenotype was rescued by reinjection of the OnMBL, which restored the healthy status of the knockdown tilapia. Moreover, a mechanistic analysis revealed that the OnMBL could clear pathogenic bacteria by collaborating with cell-surface calreticulin to facilitate phagocytosis in a complement activation-independent manner. To our knowledge, these results provide the first evidence on the antibacterial response mechanism of MBL performing evolutionary conserved function to promote opsonophagocytosis of macrophages in early vertebrates and reveals new insights into the understanding of the evolutionary origins and ancient roles basis of the C-type lectins in the innate immune defense.

Oral Pathogen Porphyromonas gingivalis Can Escape Phagocytosis of Mammalian Macrophages.

Macrophages are phagocytic cells that play a key role in host immune response and clearance of microbial pathogens. Porphyromonas gingivalis is an oral pathogen associated with the development of periodontitis. Escape from macrophage phagocytosis was tested by infecting THP-1-derived human macrophages and RAW 264.7 mouse macrophages with strains of P. gingivalis W83 and 33277 as well as Streptococcus gordonii DL1 and Escherichia coli OP50 at MOI = 100. CFU counts for all intracellular bacteria were determined. Then, infected macrophages were cultured in media without antibiotics to allow for escape and escaping bacteria were quantified by CFU counting. P. gingivalis W83 displayed over 60% of the bacterial escape from the total amount of intracellular CFUs, significantly higher compared to all other bacteria strains. In addition, bacterial escape and re-entry were also tested and P. gingivalis W83, once again, showed the highest numbers of CFUs able to exit and re-enter macrophages. Lastly, the function of the PG0717 gene of P. gingivalis W83 was tested on escape but found not related to this activity. Altogether, our results suggest that P. gingivalis W83 is able to significantly avoid macrophage phagocytosis. We propose this ability is likely linked to the chronic nature of periodontitis.

T cell dynamics and response of the microbiota after gene therapy to treat X-linked severe combined immunodeficiency

BackgroundMutation of the IL2RG gene results in a form of severe combined immune deficiency (SCID-X1), which has been treated successfully with hematopoietic stem cell gene therapy. SCID-X1 gene therapy results in reconstitution of the previously lacking T cell compartment, allowing analysis of the roles of T cell immunity in humans by comparing before and after gene correction.MethodsHere we interrogate T cell reconstitution using four forms of high throughput analysis. (1) Estimation of the numbers of transduced progenitor cells by monitoring unique positions of integration of the therapeutic gene transfer vector. (2) Estimation of T cell population structure by sequencing of the recombined T cell receptor (TCR) beta locus. (3) Metagenomic analysis of microbial populations in oropharyngeal, nasopharyngeal, and gut samples. (4) Metagenomic analysis of viral populations in gut samples.ResultsComparison of progenitor and mature T cell populations allowed estimation of a minimum number of cell divisions needed to generate the observed populations. Analysis of microbial populations showed the effects of immune reconstitution, including normalization of gut microbiota and clearance of viral infections. Metagenomic analysis revealed enrichment of genes for antibiotic resistance in gene-corrected subjects relative to healthy controls, likely a result of higher healthcare exposure.ConclusionsThis multi-omic approach enables the characterization of multiple effects of SCID-X1 gene therapy, including T cell repertoire reconstitution, estimation of numbers of cell divisions between progenitors and daughter T cells, normalization of the microbiome, clearance of microbial pathogens, and modulations in antibiotic resistance gene levels. Together, these results quantify several aspects of the long-term efficacy of gene therapy for SCID-X1. This study includes data from ClinicalTrials.gov numbers NCT01410019, NCT01175239, and NCT01129544.

Innate and adaptive lymphocytes sequentially shape the gut microbiota and lipid metabolism.

The mammalian gut is colonized by numerous microorganisms collectively termed the microbiota, which have a mutually beneficial relationship with their host. Normally, the gut microbiota matures during ontogeny to a state of balanced commensalism marked by the absence of adverse inflammation. Subsets of innate lymphoid cells (ILCs) and conventional T cells are considered to have redundant functions in containment and clearance of microbial pathogens, but how these two major lymphoid-cell populations each contribute to shaping the mature commensal microbiome and help to maintain tissue homeostasis has not been determined. Here we identify, using advanced multiplex quantitative imaging methods, an extensive and persistent phosphorylated-STAT3 signature in group 3 ILCs and intestinal epithelial cells that is induced by interleukin (IL)-23 and IL-22 in mice that lack CD4+ T cells. By contrast, in immune-competent mice, phosphorylated-STAT3 activation is induced only transiently by microbial colonization at weaning. This early signature is extinguished as CD4+ T cell immunity develops in response to the expanding commensal burden. Physiologically, the persistent IL-22 production from group 3 ILCs that occurs in the absence of adaptive CD4+ T-cell activity results in impaired host lipid metabolism by decreasing lipid transporter expression in the small bowel. These findings provide new insights into how innate and adaptive lymphocytes operate sequentially and in distinct ways during normal development to establish steady-state commensalism and tissue metabolic homeostasis.

Sequential activity of innate and adaptive lymphocytes supports non-inflammatory gut microbial commensalism

Abstract The mammalian gut is colonized by trillions of microorganisms termed the “microbiota”, which have a mutually beneficial relationship with their host. In normal individuals, the gut microbiota matures after birth to a state of balanced commensalism that is marked by the absence of adverse inflammation. Both innate lymphoid cells (ILCs) and antigen-specific conventional T cells contribute to containment and clearance of microbial pathogens. But how these two major lymphoid cell populations help shape the mature commensal (non-pathogenic) microbiome and maintain tissue homeostasis has not been determined. Using advanced multiplex quantitative imaging methods, here we show that in the absence of adaptive lymphocytes, IL-23 induced by specific commensal bacteria such as Segmented Filamentous Bacteria (SFB) persistently activates RORgt+ group 3 innate lymphoid cells (ILC3s) in the ileum to produce IL-22, which induces STAT3 activation in virtually all epithelial cells, contributing to production of molecules such as anti-microbial peptides that protect the tissue from microbial damage. The distinct roles of ILCs in handling gut microbes play out in normal mice during development. The pSTAT3 signature is absent after birth, which is followed by microbial colonization and strong ILC3 activation and an extensive epithelial pSTAT3 signature upon weaning. This innate immune activity is subsequently extinguished as adaptive CD4+ T cell immunity develops in response to the expanding commensal burden. Our findings provide new insights into how innate and adaptive lymphocytes sequentially operate during normal development to establish steady state commensalism.

P-161 YI Atg16l1 Deficiency in Macrophages Leads to Worsened Murine Colitis

Genetic studies identified several autophagy genes including ATG16L1 and IRGM to be associated with IBD. Autophagy describes a biological process that involves trafficking and handling of macro-molecules including bacteria. Studies show that autophagy plays an important role in the clearance of microbial pathogens. Alterations in the autophagic machinery such as in ATG16L1 and IRGM may result in the ineffective elimination of pathogens and the persistent activation of the inflammatory cascade in the intestine, which may contribute to the pathogenesis of IBD. This study examines the role of autophagy in the function of macrophages in vitro and in vivo. Bone marrow-derived macrophages (BMMs) were isolated. Autophagy function was assessed with LC3, P62 and P40 immunoblotting. Uptake of Salmonella enterica serovar Typhimurium was assessed by confocal microscopy, flow cytometry and electron microscopy. Reactive oxygen (ROS) production and intracellular S. typhimurium killing in macrophages were assessed. Chronic DSS induced colitis and S. typhimurium infection were used to assess the in vivo role of macrophage specific Atg16l1 deficiency in murine colitis. Atg16l1f/f x LysM-cre mice exhibit defective autophagy in macrophages and led to mildly worsened colitis but not ileitis in both chronic DSS and S. typhimurium murine colitis models. Atg16l1 deficiency in macrophages also led to increased recovery of S. typhimurium in the colon, MLN, liver and the spleen. Increased TNFα production in Atg16l1 deficient macrophages with S. typhimurium infection was observed. In vitro experiments using BMMs were performed to assess the possible cellular and molecular mechanisms of Atg16l1 function in macrophages. No differences in S. typhimurium uptake in Atg16l1f/f x LysM-cre macrophages when compared to control Atg16l1f/f counterparts. Higher ROS production in response to S. typhimurium infection is observed in Atg16l1 deficient macrophages as compared to WT macrophages. Consistently, the expression of p40phox, a component of the NADPH oxidase, is also increased in Atg16l1 deficient macrophages as compared to WT macrophages. Interestingly, although there was higher ROS production with Atg16l1 deficiency, we observe reduced S. typhimurium killing with Atg16l1 deficiency. Confocal and electron microscopy showed that there was altered intracellular trafficking of S. typhimurium and increased salmonella number within phagosomes. Our data show that Atg16l1 is an essential component of the autophagic machinery, involves in the trafficking of intracellular pathogen and plays a role in the clearance of microbial organisms. Reduced bacterial clearance due to altered intracellular trafficking in macrophages may be a potential mechanism for the increased colitis seen in macrophage specific Atg16l1 deficient mice.

Pathogen induced upregulation of the lysosomal maturation protein, Melanoregulin (MREG) in macrophages

In professional phagocytic cells such as the retinal Pigment epithelial (RPE) cells, the product of the Mregdsu gene, melanoregulin (Mreg) plays a critical role in lysosome‐dependent phagosome maturation and degradation of phagocytosed photoreceptor debris. MREG null mice demonstrate defects in lysosomal maturation, alkalanization of lysosomal pH, incorrect processing of key degradative enzymes such as cathepsin‐D resulting in the accumulation of the engulfed cargo. We hypothesize that in macrophages Mreg plays a similar in the phagolysosmal dependent clearance of engulfed microbial pathogens. Treatment of macrophage cells, J774 with purified lipopolysaccharide (LPS) from E. coli and the periodontal pathogen, P. gingivalis resulted in the transcriptional up regulation of Mreg mRNA and protein. Treatment of J774 cells with the PI‐3‐kinase inhibitors, LY29004 and Wortmanin inhibited LPS induced expression of Mreg. Analysis of Mreg promoter indicated conservation in sequence and transcription factor binding sites such as SP1 and AP1. Mreg induction in macrophages challenged with bacterial endotoxins and its proposed role in lysosomal maturation suggests that Mreg may have a pivotal role to play in the clearance of microbial pathogens.

Influence of body mass index on the innate immune response during human endotoxemia

Accumulating data suggest a protective effect of obesity in the case of severe infections. Higher baseline levels of the proinflammatory cytokine TNFα as well as more pronounced TNFα release following whole blood stimulation with endotoxin are reported in patients with a higher body mass index (BMI). This more pronounced proinflammatory response in obese patients may enable a rapid and more effective clearance of microbial pathogens. The effect of the body mass index on the innate immune response in vivo has not been assessed.

Phagocytosis and antigen presentation: a partnership initiated by Toll-like receptors

Professional phagocytes play an important role in the clearance of microbial pathogens and apoptotic cells. Many receptors are involved in this process, some with signalling capabilities, some without. Increasing evidence...

Sequence Diversity of theTrypanosoma cruziComplement Regulatory Protein Family

As a central component of innate immunity, complement activation is a critical mechanism of containment and clearance of microbial pathogens in advance of the development of acquired immunity. Several pathogens restrict complement activation through the acquisition of host proteins that regulate complement activation or through the production of their own complement regulatory molecules (M. K. Liszewski, M. K. Leung, R. Hauhart, R. M. Buller, P. Bertram, X. Wang, A. M. Rosengard, G. J. Kotwal, and J. P. Atkinson, J. Immunol. 176:3725-3734, 2006; J. Lubinski, L. Wang, D. Mastellos, A. Sahu, J. D. Lambris, and H. M. Friedman, J. Exp. Med. 190:1637-1646, 1999). The infectious stage of the protozoan parasite Trypanosoma cruzi produces a surface-anchored complement regulatory protein (CRP) that functions to inhibit alternative and classical pathway complement activation (K. A. Norris, B. Bradt, N. R. Cooper, and M. So, J. Immunol. 147:2240-2247, 1991). This study addresses the genomic complexity of the T. cruzi CRP and its relationship to the T. cruzi supergene family comprising active trans-sialidase (TS) and TS-like proteins. The TS superfamily consists of several functionally distinct subfamilies that share a characteristic sialidase domain at their amino termini. These TS families include active TS, adhesions, CRPs, and proteins of unknown functions (G. A. Cross and G. B. Takle, Annu. Rev. Microbiol. 47:385-411, 1993). A sequence comparison search of GenBank using BLASTP revealed several full-length paralogs of CRP. These proteins share significant homology at their amino termini and a strong spatial conservation of cysteine residues. Alternative pathway complement regulation was confirmed for CRP paralogs with 58% (low) and 83% (high) identity to AAB49414. CRPs are functionally similar to the microbial and mammalian proteins that regulate complement activation. Sequence alignment of mammalian complement control proteins to CRP showed that these sequences are distinct, supporting a convergent evolutionary pathway. Finally, we show that a clonal line of T. cruzi expresses multiple unique copies of CRP that are differentially recognized by patient sera.