Elimination Of Microbial Pathogens Research Articles

The role of surfactant proteins SP-A and SP-D in viral infection: a focus on COVID-19

An immune response to invasion of viral pathogens is an integral part of maintaining the physiological functioning of the bronchopulmonary system and effective gas exchange. Collagen-containing C-type lectins (lung collectins) are some of the key proteins in the identification of viral particles. They have image-recognizing receptors that identify pathogen-associated molecular patterns, particularly viral glycoproteins. The surfactant proteins SP-A and SP-D, which are composed of trimerized units, belong to pulmonary collectins and oligomerize into higher-order structures. These proteins play an essential role in recognition and elimination of microbial pathogens (viruses, bacteria, fungi, parasites, nanoparticles, allergens) through a variety of mechanisms. Taking into account the burden of the novel coronavirus infection caused by the SARS-CoV-2 virus, it is important to consider the role of the surfactant proteins SP-A and SP-D in the pathogenesis of the immune response to viral invasion. Currently, there are data on the direct relationship between surfactant proteins and viruses belonging to the Coronaviridae family. The SP-A and SP-D proteins modulate inflammatory responses and cytokine synthesis, but prevent an excessive inflammatory response (cytokine storm). There is also an assumption that SARSCoV-2 directly suppresses and alters the production of surfactant proteins. Thus, the key pathogenetic role of the surfactant proteins SP-A and SP-D in the response to the viral pathogen SARS-CoV-2 is evident. Today, this is a promising area of translational medicine, which will contribute to a profound understanding of the pathogenesis of coronavirus infection for assessing the diagnostic and prognostic potentials of the surfactant proteins SP-A and SP-D in COVID-19. Additionally, it will help evaluate the therapeutic potential of recombinant fragments of human SP-A and SP-D.

Bacillus licheniformis and Bacillus subtilis, Probiotics That Induce the Formation of Macrophage Extracellular Traps.

Probiotics are considered living microorganisms that help preserve the health of the host who uses them. Bacillus are a genus of Gram-positive bacteria used as probiotics for animal and human consumption. They are currently distributed in various commercial forms. Two of the species used as probiotics are B. licheniformis and B. subtilis. Macrophages are central cells in the immune response, being fundamental in the elimination of microbial pathogens, for which they use various mechanisms, including the formation of extracellular traps (METs). There have been very few studies carried out on the participation of macrophages in response to the interaction of probiotics of the genus Bacillus with the host. In this work, we used macrophages from the J774A mouse cell line.1, and we found that they are susceptible to infection by the two Bacillus species. However, both species were eliminated as the infection progressed. Using confocal microscopy, we identified the formation of METs from the first hours of infection, which were characterized by the presence of myeloperoxidase (MPO) and citrullinated histone (Hit3Cit). Quantitative data on extracellular DNA release were also obtained; release was observed starting in the first hour of infection. The induction of METs by B. licheniformis caused a significant decrease in the colony-forming units (CFU) of Staphylococcus aureus. The induction of METS by bacteria of the Bacillus genus is a mechanism that participates in controlling the probiotic and potentially pathogenic bacteria such as S. aureus. The induction of METs to control pathogens may be a novel mechanism that could explain the beneficial effects of probiotics of the genus Bacillus.

The Multiple Roles of Trogocytosis in Immunity, the Nervous System, and Development

Trogocytosis is a general biological process that involves one cell physically taking small parts of the membrane and other components from another cell. In trogocytosis, one cell seems to take little “bites” from another cell resulting in multiple outcomes from these cell-cell interactions. Trogocytosis was first described in protozoan parasites, which by taking pieces of host cells, kill them and cause tissue damage. Now, it is known that this process is also performed by cells of the immune system with important consequences such as cell communication and activation, elimination of microbial pathogens, and even control of cancer cells. More recently, trogocytosis has also been reported to occur in cells of the central nervous system and in various cells during development. Some of the molecules involved in phagocytosis also participate in trogocytosis. However, the molecular mechanisms that regulate trogocytosis are still a mystery. Elucidating these mechanisms is becoming a research area of much interest. For example, why neutrophils can engage trogocytosis to kill Trichomonas vaginalis parasites, but neutrophils use phagocytosis to eliminate already death parasites? Thus, trogocytosis is a significant process in normal physiology that multiple cells from different organisms use in various scenarios of health and disease. In this review, we present the basic principles known on the process of trogocytosis and discuss the importance in this process to host-pathogen interactions and to normal functions in the immune and nervous systems.

Graphene oxide‐based noble‐metal nanoparticles composites for environmental application

Noble metal nanoparticles (NPs)-based materials have been widely applied in various environmental applications, including the catalytic reduction of organic pollutants and elimination of the microbial pathogens in wastewater due to its unique physicochemical properties. However, the stability and catalytic activity of NPs-based materials are limited due to their severe aggregation in aqueous environments. Recently, graphene oxide (GO), a 2D material with large specific surface area, has been used as a platform to load NPs as a NPs@GO nanocomposite with enhanced catalytic performance and stability. In this review, we focus on the discussion about the recent progress in the synthesis methods and properties of NPs@GO nanocomposites, recyclability of NPs@GO nanocomposites, and applications of the NPs@GO nanocomposites in catalytic reduction of organic pollutants and elimination of microbial pathogens in wastewater as well as the corresponding catalytic and antibacterial mechanisms. Finally, we conclude with perspectives on the remaining challenges as well as the recommendations for future development in this field.

Effects of NOD1 and NOD2 agonists polymuramyl as well as NOD2 agonist glucosaminylmuramyldipeptide on phenotype of neutrophile granulocyte CD64-CD16+CD32+CD11b+, CD16+CD62L+CD63-, CD16+CD62L+CD63+ subsets

Antimicrobial activity of neutrophilic granulocytes (NG) is based on effective recognition and elimination of microbial pathogens, as well as on complex intracellular signal transduction pathways interconnecting these processes. NG dysfunction leads to emergence of atypical infectious and inflammatory diseases recalcitrant to standard interventions, which requires new vector platforms aimed at restoring normal NG functioning and overcoming antibiotic resistance. Moreover, we emphasize about special interest paid to the NOD1 and NOD2 agonist polymuramyl and NOD2 agonist glucosaminylmuramyldipeptide. Objective of the study was to compare effects triggered by NOD1 and NOD2 agonist polymuramyl and NOD2 agonist glucosaminylmuramyldipeptide on phenotype of neutrophilic granulocyte subsets CD64- CD16+CD32+CD11b+, CD16+CD62L+CD63-, CD16+CD62L+CD63+ in the in vitro system. 64 samples of peripheral blood (PC) collected from 8 apparently healthy children (4 boys and 4 girls) aged 3 to 9 years were examined by flow cytometry (FC 500, Beckman Coulter, USA) assessing NG surface receptors CD64, CD16, CD32, CD11b, CD62L, CD63 with MonAb (Beckman Coulter International S. A., France) by analyzing NG number (%) expressing receptors examined, density of receptor expression measured as mean fluorescence intensity (MFI). For this, there were assessed intact peripheral blood NG from apparently healthy children (comparison group) as well as those exposed to polymuramyl (PM) (at concentration of 10-6 g/l) or glucosaminylmuramyl-dipeptide (GMDP) (at concentration of 10-6 g/l) for 60 minutes at 37 °С temperature. Comparative analysis of surface receptor expression was performed on CD64-CD16+CD32+CD11b+, CD16+CD62L+CD63- and CD16+CD62L+CD63+ NG subsets that suggested about positive transformation of activation parameters in circulating NG exposed to NOD1 and NOD2 agonist polymuramyl as well as NOD2 agonist glucosaminylmuramyldipeptide. At the same time, similar effects of varying intensity were revealed manifested as increased count of NG subsets CD16+CD62L+CD63+ bearing increased level of CD16 and reduced CD62L expression, as well as differences uncovered as significantly increased expression of surface membrane molecules CD16 and CD11b in CD64-CD16+CD32+CD11b+ NG subset from apparently healthy children exposed to polymuramyl as well as increased surface CD32 expression after incubation with GMDP.

Expansion of natural killer cells with optimal killing activity for cancer immunotherapy

Abstract Natural killer (NK) cells play a key role in the elimination of microbial pathogens and cancer cells. NK cells rapidly respond to stressed cells that are infected or bear tumorigenic mutations that reduce “self” markers of MHC class 1 and/or display increased presentation of activating ligands. These signals prompt NK cells to form an immunological synapse with an infected or tumor cell and discharge lytic granules containing cytotoxic proteins such as IFNγ, perforin and granzyme B leading to target cell destruction. Because of their natural ability to recognize and kill cancer cells, a plethora of preclinical studies and clinical trials have shown that NK cell therapies offer a potentially powerful weapon to fight both advanced-stage blood cancers and solid tumors. Given the great potential of NK cell therapies, we developed clinically relevant serum- and xeno-free methods for human NK cell expansion. Using optimized media and cytokines, either with anti-NKp46 coated tissue culture dishes or Cloudz™ CD2/NKp46 microspheres we have greatly expanded highly purified NK cells from human peripheral blood mononuclear cells (PBMCs) that are capable of potent cytolytic activity, as indicated with a novel flow cytometry-based NK cytotoxicity assay. Using this NK expansion methodology, we performed high-throughput screening methods to identify novel agents that enhance NK cell killing activity as assessed by IFNγ and Granzyme B quantikine ELISA assays which were then confirmed with NK cytotoxicity assays. The methods established here provide a novel workflow for generating highly purified NK cells that are applicable to clinical translation. Furthermore, the agents identified in this work provide insight for augmenting NK killing potential.

Transcription of Tnfaip3 Is Regulated by NF-κB and p38 via C/EBPβ in Activated Macrophages

Macrophages play a pivotal role in the immune system through recognition and elimination of microbial pathogens. Toll-like receptors (TLRs) on macrophages interact with microbial substances and initiate signal transduction through intracellular adapters. TLR4, which recognizes the lipopolysaccharides (LPS) on Gram-positive and Gram-negative bacteria, triggers downstream signaling mediators and eventually activates IκB kinase (IKK) complex and mitogen-activated protein kinases (MAPKs) such as p38. Previous reports revealed that, in addition to NF-κB, a core transcription factor of the innate immune response, the induction of some LPS-induced genes in macrophages required another transcription factor whose activity depends on p38. However, these additional transcription factors remain to be identified. In order to identify p38-activated transcription factors that cooperate with NF-κB in response to LPS stimulation, microarrays were used to identify genes regulated by both NF-κB and p38 using wild-type, IKK-depleted, and p38 inhibitor-treated mouse bone marrow-derived macrophages (BMDMs). In silico analysis of transcription factor binding sites was used to predict the potential synergistic transcription factors from the co-expressed genes. Among these genes, NF-κB and C/EBPβ, a p38 downstream transcription factor, were predicted to co-regulate genes in LPS-stimulated BMDMs. Based on the subsequent results of a chromatin immunoprecipitation assay and TNFAIP3 expression in C/EBPβ-ablated macrophages, we demonstrated that Tnfaip3 is regulated by both NF-κB and p38-dependent C/EBPβ. These results identify a novel regulatory mechanism in TLR4-mediated innate immunity.

The protein kinase PKR is required for macrophage apoptosis after activation of Toll-like receptor 4.

Macrophages are pivotal constituents of the innate immune system, vital for recognition and elimination of microbial pathogens. Macrophages use Toll-like receptors (TLRs) to detect pathogen-associated molecular patterns--including bacterial cell wall components, such as lipopolysaccharide or lipoteichoic acid, and viral nucleic acids, such as double-stranded (ds)RNA--and in turn activate effector functions, including anti-apoptotic signalling pathways. Certain pathogens, however, such as Salmonella spp., Shigellae spp. and Yersiniae spp., use specialized virulence factors to overcome these protective responses and induce macrophage apoptosis. We found that the anthrax bacterium, Bacillus anthracis, selectively induces apoptosis of activated macrophages through its lethal toxin, which prevents activation of the anti-apoptotic p38 mitogen-activated protein kinase. We now demonstrate that macrophage apoptosis by three different bacterial pathogens depends on activation of TLR4. Dissection of anti- and pro-apoptotic signalling events triggered by TLR4 identified the dsRNA responsive protein kinase PKR as a critical mediator of pathogen-induced macrophage apoptosis. The pro-apoptotic actions of PKR are mediated both through inhibition of protein synthesis and activation of interferon response factor 3.