China
Africa
Explore chapters and articles related to this topic
Helicobacter pylori infection
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Diane Bimczok, Anne Müller, Phillip D. Smith
VacA is a pore-forming toxin best known for its ability to cause vacuolation in host cells, which leads to cell death through programmed necrosis. In addition to inducing vacuolation, VacA specifically interferes with the induction of T-cell responses. Purified VacA inhibits processing and presentation of antigenic peptides to human CD4+ T cells and can specifically block antigen-dependent T-cell proliferation by interfering with IL-2-mediated signaling. H. pylori co-opts CD18 as a VacA receptor on human T cells. After entering the cell, VacA inhibits activation of the transcription factor nuclear factor of activated T cells (NFAT) and thus expression of NFAT target genes such as IL-2 and IL-2 receptor. Additionally, VacA can suppress IL-2-induced proliferation of primary T cells in an NFAT-independent manner. Thus, VacA can inhibit the clonal expansion of H. pylori-specific T cells, thereby promoting H. pylori evasion of the adaptive immune response and long-term persistence.
Where Cancer and Bacteria Meet
Published in Ananda M. Chakrabarty, Arsénio M. Fialho, Microbial Infections and Cancer Therapy, 2019
Alexandra Merlos, Ricardo Perez-Tomás, José López-López, Miguel Viñas
The Bacillus species isolated from different tobacco brands include B. amyloliquefaciens, B. cereus, B. subtilis, B. methylotrophicus, B. pumilus, Oceanobacillus chungangensis, and B. licheniformis, whereas B. subtilis, B. pumilus, B. methylotrophicus, and B. licheniformis have been identified in lung cancer biopsies. Tobacco flakes carrying bacteria and trapped within the cigarette filters provide the main entrance for the pathogen into the pulmonary airways [22]. The powerful colonization ability of the isolates has been demonstrated in adhesion assays, as has the secretion of pore-forming toxins with high cytotoxicity in cytotoxicity assays using planar lipid bilayers and cell cultures [23]. Molecular pathways involving mycobacteria in carcinogenesis have been identified as well [24].
Serratia
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Naheed S. Kanji, Umesh Narsinghani, Ritu A. Kumar
Infections by Serratia and related microbes secrete a pore-forming toxin hemolysin/cytolysin, which is responsible for its virulence. This hemolysin ShIA is cytotoxic that lyses erythrocytes, leukocytes, and macrophages precipitating a systemic inflammatory response. The S. marcescens hemolysin represents the prototype of a growing family of pore-forming toxins. This cytotoxin is believed to aid in tissue penetration and may be linked to a widespread host invasive pathogenic pathway involving bacterial swarming, quorum sensing, and biofilm production. The hemolysin is determined by two genes, ShlA and shlB, arranged in tandem. ShlA encodes the hemolysin, and ShlB encodes the outer membrane protein that secretes ShlA. Both have proteins with signal sequences for export across the cytoplasmic membrane by the Sec system. ShlB not only secretes ShlA but also activates ShlA. The hemolysin was the first characterized example of a large group of proteins secreted by the two partner secretion system (TPSS) or type V-secretion system.62,63
Alpha-synuclein in Parkinson's disease: a villain or tragic hero? A critical view of the formation of α-synuclein aggregates induced by dopamine metabolites and viral infection
Published in Expert Review of Neurotherapeutics, 2023
Phelippe Carmo-Gonçalves, Eduardo Coelho-Cerqueira, Vanderlei de Araujo Lima, Cristian Follmer
Several groups have proposed that the oligomers of aSyn, instead of the fibrils, are the putative toxic species generated during the aggregation of the protein. For instance, aSyn oligomers are capable of forming pores in lipid membranes in vitro, similarly to some pore-forming toxins, which could result in calcium efflux and destabilization of the membrane potential [25–27]. In addition, aSyn oligomers can affect intracellular membranes, such as vesicles containing neurotransmitters or mitochondrial membranes, causing synaptic dysfunction and impairment of autophagy-lysosome and ubiquitin-proteasome systems [28–32]. In vitro-produced aSyn oligomers are able to cross the cell membrane and, once internalized, promote the aggregation of the endogenous protein [33–35]. Regarding how PD mutations affect the aSyn oligomerization process, the results seem to be influenced by the cellular model or in vitro conditions used to evaluate the aggregation propensity of the protein. For instance, in cell assays indicate that among aSyn variants, A53T exhibits faster oligomerization and forms larger oligomers, whereas the smallest oligomers were found for A30P [36]. In another study, it was found that familial mutants (A30P, E46K, H50Q, G51D, and A53T) exhibited identical propensities to oligomerize in living cells, but they exhibit distinct propensity to form inclusions [37].
Healthy Intestinal Function Relies on Coordinated Enteric Nervous System, Immune System, and Epithelium Responses
Published in Gut Microbes, 2021
Fatima B. Saldana-Morales, Dasom V. Kim, Ming-Ting Tsai, Gretchen E. Diehl
There are many other bacterial toxins that damage host systems and modulate their responses. IECs can detect very low levels of bacterial pore-forming toxins (PFT), including pneumolysin, alpha-hemolysin, streptolysin O, and aerolysin.111 Bacterial PFTs damage the intestinal epithelium and disrupt barrier integrity.112,113 Subcytolytic concentrations of these toxins phosphorylate p38 MAPK in IECs resulting in proinflammatory responses early during infection.111 PFTs also contribute to pathogen spread by suppressing immune responses including inhibiting neutrophil migration or lysing immune cells.112,113 Activation of the nervous system by bacterial toxins has been shown in the skin, where Staphylococcus aureus directly activates sensory neurons in the mouse via the toxins N-formyl peptides and alpha-hemolysin. These toxins upregulate sensory neuron release of CGRP, galanin, and somatostatin and suppress S. aureus-induced innate immune activation by phagocytes, which have the highest neuropeptide receptor expression.25,114 It will be important to identify if similar systems function during intestinal infections.
Prevalence, clinical expression, invasiveness and outcome of Staphylococcus aureus containing Panton-Valentine leukocidin in children treated in a university hospital of Lithuania
Published in Infectious Diseases, 2020
Birute Petraitiene, Pablo Rojo Conejo, Lina Jankauskaite, Rimantas Kevalas, Giedre Trumpulyte, Ausra Snipaitiene, Astra Vitkauskiene, Vaidotas Gurskis
For many years PVL toxin has been known as pore-forming toxin that primarily affects polymorphonuclears and has no effect on red blood cells and lymphocytes [30]. SA-PVL(+) was not associated with leucopoenia or neutropenia in this study. No differences were found in CBC between SA-PVL(+) and SA-PVL(–) in invasive infections. Differences in CBC between SA-PVL(+) and SA-PVL(–) groups were best seen in non-invasive S. aureus infections. Normal lymphocytes and platelet counts were roughly twice as often found in SA-PVL(+) infection comparing to SA-PVL(–) infections. Lymphocytosis and thrombocytosis were 2.5 to 3 times less common in SA-PVL(+) than in SA-PVL(–). Although there is no evidence that PVL toxin affects lymphocytes, there are clearly different expression and pathogenesis of SA-PVL(+) and SA-PVL(–) strains. Boyle-Vavra et al. show the impact of PVL toxin on polymorphonuclear cells’, that can induce the release of interleukins and inflammatory mediators even without lysis, and by causing cells death, release reactive oxygen species and variety mediators, that affect a host-dependent inflammatory response [31]. Two studies revealed high inflammatory response in SA-PVL(+) invasive infections [32,33]. We have found that SA-PVL(+) infections were associated with higher CRP values among non-invasive and invasive infections comparing with SA-PVL(–) infections.