| 51. |
- Omer, Abubakr A. M., 1982-, et al.
(författare)
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Plantaricin NC8 αβ rapidly and efficiently inhibits flaviviruses and SARS-CoV-2 by disrupting their envelopes
- 2022
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 17:11
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Tidskriftsartikel (refereegranskat)abstract
- Potent broad-spectrum antiviral agents are urgently needed to combat existing and emerging viral infections. This is particularly important considering that vaccine development is a costly and time consuming process and that viruses constantly mutate and render the vaccine ineffective. Antimicrobial peptides (AMP), such as bacteriocins, are attractive candidates as antiviral agents against enveloped viruses. One of these bacteriocins is PLNC8 αβ, which consists of amphipathic peptides with positive net charges that display high affinity for negatively charged pathogen membrane structures, including phosphatidylserine rich lipid membranes of viral envelopes. Due to the morphological and physiological differences between viral envelopes and host cell plasma membranes, PLNC8 αβ is thought to have high safety profile by specifically targeting viral envelopes without effecting host cell membranes. In this study, we have tested the antiviral effects of PLNC8 αβ against the flaviviruses Langat and Kunjin, coronavirus SARS-CoV-2, influenza A virus (IAV), and human immunodeficiency virus-1 (HIV-1). The concentration of PLNC8 αβ that is required to eliminate all the infective virus particles is in the range of nanomolar (nM) to micromolar (μM), which is surprisingly efficient considering the high content of cholesterol (8–35%) in their lipid envelopes. We found that viruses replicating in the endoplasmic reticulum (ER)/Golgi complex, e.g. SARS-CoV-2 and flaviviruses, are considerably more susceptible to PLNC8 αβ, compared to viruses that acquire their lipid envelope from the plasma membrane, such as IAV and HIV-1. Development of novel broad-spectrum antiviral agents can significantly benefit human health by rapidly and efficiently eliminating infectious virions and thereby limit virus dissemination and spreading between individuals. PLNC8 αβ can potentially be developed into an effective and safe antiviral agent that targets the lipid compartments of viral envelopes of extracellular virions, more or less independent of virus antigenic mutations, which faces many antiviral drugs and vaccines.
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| 52. |
- Skoog, Emma C, 1983, et al.
(författare)
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Human Gastric Mucins Differently Regulate Helicobacter pylori Proliferation, Gene Expression and Interactions with Host Cells. : Effects of gastric mucins on Helicobacter pylori
- 2012
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Ingår i: PLoS One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- Helicobacter pylori colonizes the mucus niche of the gastric mucosa and is a risk factor for gastritis, ulcers and cancer. The main components of the mucus layer are heavily glycosylated mucins, to which H. pylori can adhere. Mucin glycosylation differs between individuals and changes during disease. Here we have examined the H. pylori response to purified mucins from a range of tumor and normal human gastric tissue samples. Our results demonstrate that mucins from different individuals differ in how they modulate both proliferation and gene expression of H. pylori. The mucin effect on proliferation varied significantly between samples, and ranged from stimulatory to inhibitory, depending on the type of mucins and the ability of the mucins to bind to H. pylori. Tumor-derived mucins and mucins from the surface mucosa had potential to stimulate proliferation, while gland-derived mucins tended to inhibit proliferation and mucins from healthy uninfected individuals showed little effect. Artificial glycoconjugates containing H. pylori ligands also modulated H. pylori proliferation, albeit to a lesser degree than human mucins. Expression of genes important for the pathogenicity of H. pylori (babA, sabA, cagA, flaA and ureA) appeared co-regulated in response to mucins. The addition of mucins to co-cultures of H. pylori and gastric epithelial cells protected the viability of the cells and modulated the cytokine production in a manner that differed between individuals, was partially dependent of adhesion of H. pylori to the gastric cells, but also revealed that other mucin factors in addition to adhesion are important for H. pylori-induced host signaling. The combined data reveal host-specific effects on proliferation, gene expression and virulence of H. pylori due to the gastric mucin environment, demonstrating a dynamic interplay between the bacterium and its host.
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| 53. |
- Jönsson, Göran
(författare)
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Studies on hereditary C2 deficiency: Frequent occurrence of severe infections, atherosclerosis and rheumatological manifestations
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The complement system is a part of the innate immunity and is essential in the defence against microorganisms. Hereditary C2 deficiency (C2D) is one of the most common complement deficiency states with an estimated prevalence of 1:20,000 in persons of Western descent. In the present investigation, the identification of more than 40 C2D persons at a single centre combined with long observation periods provided a unique basis for assessment of C2D-associated manifestations and diseases. The predominant clinical manifestation was severe bacterial infections. The infections were mainly caused by Streptococcus pneumoniae. Repeated infections occurred primarily during infancy and childhood. On the other hand, about 25-30 % of the C2D persons remained healthy during the observation period. Immunological factors as IgG subclass levels, GM allotypes, complement proteins, and Fc receptors were assessed to explain this difference. Homozygosity for the G2M*n allele was strongly associated with protection against severe infections (p<0.001). This indicated that an efficient antibody response to polysaccharide antigens is of great importance in C2D. Mannan-binding lectin deficiency also contributed to the susceptibility to infection. The association between C2D and systemic lupus erythematosus (SLE) was confirmed, but notably the severity of SLE in patients with C2D was similar to that of other SLE patients. Another novel finding was a high occurrence of anti-cardiolipin antibodies (aCL) and antibodies to the collagen-like region of C1q. Both autoantibodies have a pro-atherosclerotic effect that might explain the high occurrence of cardiovascular disease found in the cohort. Interestingly, anti-phospholipid syndrome was not observed despite the high occurrence of aCL. Vaccination in 25 C2D persons resulted in antibody responses which show that C2D persons benefit from vaccination against infections caused by encapsulated bacteria such as pneumococci.
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| 54. |
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| 55. |
- Li, Yunlong, et al.
(författare)
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Yersinia Ysc-Yop type III secretion feedback inhibition is relieved through YscV-dependent recognition and secretion of LcrQ
- 2014
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 91:3, s. 494-507
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Tidskriftsartikel (refereegranskat)abstract
- Human pathogenic Yersinia species share a virulence plasmid encoding the Ysc-Yop type III secretion system (T3SS). A plasmid-encoded anti-activator, LcrQ, negatively regulates the expression of this secretion system. Under inducible conditions, LcrQ is secreted outside of bacterial cells and this activates the T3SS, but the mechanism of targeting LcrQ for type III secretion remains largely unknown. In this study, we characterized the regulatory role of the export apparatus component YscV. Depletion or overexpression of YscV compromised Yop synthesis and this primarily prevented secretion of LcrQ. It followed that a lcrQ deletion reversed the repressive effects of excessive YscV. Further characterization demonstrated that the YscV residues 493–511 located within the C-terminal soluble cytoplasmic domain directly bound with LcrQ. Critically, YscV-LcrQ complex formation was a requirement for LcrQ secretion, since YscVΔ493–511 failed to secrete LcrQ. This forced a cytoplasmic accumulation of LcrQ, which predictably caused the feedback inhibition of Yops synthesis. Based on these observations, we proposed a model for the YscV-dependent secretion of LcrQ and its role in regulating Yop synthesis in Yersinia.
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| 56. |
- Thulin Hedberg, Sara
(författare)
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Antibiotic susceptibility and resistance in Neisseria meningitidis : phenotypic and genotypic characteristics
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Neisseria meningitidis, also known as the meningococcus, is a globally spread obligate human bacterium causing meningitis and/or septicaemia. It is responsible for epidemics in both developed and developing countries. Untreated invasive meningococcal disease is often fatal, and despite modern intensive care units, the mortality is still remarkably high (approximately 10%). The continuously increasing antibiotic resistance in many bacterial pathogens is a serious public health threat worldwide and there have been numerous reports of emerging resistance in meningococci during the past decades. In paper I, the gene linked to reduced susceptibility to penicillins, the penA gene, was examined. The totally reported variation in all published penA genes was described. The penA gene was highly variable (in total 130 variants were identified). By examination of clinical meningococcal isolates, the association between penA gene sequences and penicillin susceptibility could be determined. Isolates with reduced susceptibility displayed mosaic structures in the penA gene. Two closely positioned nucleotide polymorphisms were identified in all isolates with reduced penicillin susceptibility and mosaic structured penA genes. These alterations were absent in all susceptible isolates and were successfully used to detect reduced penicillin susceptibility by real-time PCR and pyrosequencing in paper II. In papers III and IV, antibiotic susceptibility and characteristics of Swedish and African meningitis belt meningococcal isolates were comprehensively described. Although both populations were mainly susceptible to the antibiotics used for treatment and prophylaxis, the proportion of meningococci with reduced penicillin susceptibility was slightly higher in Sweden. A large proportion of the African isolates was resistant to tetracycline and erythromycin. In paper V, the gene linked to rifampicin resistance, the rpoB gene, was examined in meningococci from 12 mainly European countries. Alterations of three amino acids in the RpoB protein were found to always and directly lead to rifampicin resistance. A new breakpoint for rifampicin resistance in meningococci was suggested. The biological cost of the RpoB alterations was investigated in mice. The pathogenicity/virulence was significantly lower in rifampicin resistant mutants as compared with susceptible wild-type bacteria.
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| 57. |
- de Oliveira, Ana Henriques
(författare)
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RsbX and stress response in Listeria monocytogenes
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Listeria monocytogenes is a ubiquitous foodborne Gram-positive bacterium. Despite being mainly a soil bacterium, it can reach the food processing environment and contaminate food destined for human consumption, causing outbreaks. Because of its pathogenicity, it poses a danger for certain high-risk groups, including children, elderly, and immune-compromised people, as well as pregnant women, being capable of causing a life-threatening systemic infection known as listeriosis.All bacteria require an efficient transcriptional response and its fine-tuned modulation in order to survive the different stresses it encounters. This is especially true for L. monocytogenes, which presents an impressive range of stress adaptions that allows it survival in certain extreme conditions such as low temperature, low pH and high osmolarity. The alternative Sigma factor B, SigB, is responsible for the expression of the general stress response of this bacterium and plays a key role in the survival and adaption to new environments. The activation of SigB requires an intricate system of partner switching mechanisms, involving anti-sigma and anti-anti-sigma factors, triggered by a number of phosphorylation and dephosphorylation events that culminates with SigB being available to interact with RNA polymerase and lead the transcription of the general stress response regulon. At the top of this signal transduction pathway lies a large multi-protein complex, known as the stressosome. It is formed by RsbR (and its paralogs), RsbS and RsbT and is believed to function as a sensory hub for environmental stimuli. After signal detection, the stressosome proteins are phosphorylated and the complex goes through conformational changes that will ultimately allow for SigB activation. The reset of the stressosome to its pre-stress conformation, is hypothesized to be exerted by a putative phosphatase, RsbX, which most likely dephosphorylates the stressosome proteins post-stress.The role of RsbX in modulating the activity and conformation of the stressosome as well as in subsequent regulation of SigB activity was investigated. RsbX was shown to be required for maintaining SigB levels and activity low in non-stressed conditions as well as for proper SigB mediated stress adaptation. A ΔrsbX mutant strain was shown to have a very slight growth defect, but it also exhibited impaired motility, reduced biofilm formation, as well as a more acid resistant phenotype. The absence of RsbX was shown to alter the composition of the stressosome without drastically affecting its phosphorylation pattern. In general, RsbX was shown to play a crucial role in modulating the signal transduction pathways by preventing SigB activation under non-stressed conditions.Strains that acquire sigB operon mutations have been shown to have a growth advantage under certain mild stress conditions recurrent in a laboratory set. These strains were shown to outcompete the wild-type strain when grown in these conditions, demonstrating how a deficient SigB activity poses an advantage to the cell. On the other hand, and the ΔrsbX mutant strain was shown to have a growth disadvantage, since it was outcompeted by the wild-type strain when co-cultured. The data highlights the significant cost stress protection presents to this pathogen, since deploying the general stress response is a burden on cellular resources, and in its absence the cell can redirect energy for growth. In contrast, in the presence of a lethal stress (low pH) the strains with impaired SigB activity showed a reduced survival and an overall increased sensitivity to the stress. Hence demonstrating that in a more stressful condition the high cost of the general stress response regulon is outweighed by the protection benefits it confers to the cell. The importance of RsbX, which prevents unnecessary SigB activation, is even more evident. RsbX is not only critical to shut down the general stress response post-stress and subsequent recovery of homeostasis, but it also keeps SigB activity to low levels in non-stressed conditions, avoiding unwarranted gene expression and contributing to important energy saving. SigB also plays an important role in the transition of L. monocytogenes from a saprophytic to a pathogenic lifestyle. Even though most of the virulence factors are under the control of PrfA, the master regulator of virulence, SigB is fundamental in the survival of the bacteria inside the host’s gastro-intestinal tract (e.g., stomach high acidity and bile salt release in the duodenum), as well as in the early stages of infection, such as internalization into not phagocytic cells. Because of the importance of SigB for virulence, we speculated if RsbX, by controlling activity of SigB, would also impact the virulence of the bacteria. The data showed somewhat contradicting results, but in general it suggests that even though the expression of the virulence genes responsible for the uptake of the bacteria are increased in a strain lacking RsbX compared with the wild-type strain, the effect on the general infectivity of this strain was either minimal or not existent at all. A reason for this could be the suggested growth defect caused by the absence of RsbX, which could also jeopardize the bacteria’s ability to efficiently grow within infected cells or organisms.Overall, RsbX seems to play a crucial role for L. monocytogenes, since it is responsible to maintain a very important, but extremely costly, stress protection mechanism in an inactive mode in absence of stress. Its functions span from alteration of stressosome conformation and subsequent modulation of stress response, to homeostasis recovery, motility, biofilm formation, stress survival, and even to indirect impact in the bacteria’s infectivity. This shows the diversified, but impactful range of effects RsbX seems to have for the bacterial cell.
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| 58. |
- Wennergren, Göran, 1947, et al.
(författare)
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Relationship between respiratory syncytial virus bronchiolitis and future obstructive airway diseases.
- 2001
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Ingår i: The European respiratory journal. - 0903-1936. ; 18:6, s. 1044-58
-
Forskningsöversikt (refereegranskat)abstract
- Evidence from a large number of prospective case-control studies shows that respiratory syncytial virus (RSV) bronchiolitis in infancy is often associated with recurrent wheezing and asthma during subsequent years. However, wheezing tends to diminish and most studies show no significant increase in wheezing compared to controls by school age or adolescence. An unresolved question is whether severe RSV infection during infancy causes the respiratory sequelae or inherent abnormalities predispose an infant to develop severe respiratory infection and sequelae, i.e. RSV is associated with the development of pulmonary sequelae. Studies on long-term outcome of RSV bronchiolitis are reviewed from an evidence-based perspective. The majority of prospective placebo-controlled studies do not show any long-term beneficial effects of corticosteroid treatment, i.e. the risk of subsequent wheezing is not diminished by the treatment. The evidence for an increased risk of allergic sensitization after RSV bronchiolitis is not nearly as strong as the evidence for an increased risk of subsequent wheezing. In fact, most studies do not show any significant increase in atopy after RSV bronchiolitis. This suggests that the increased risk of wheezing after RSV is not linked to an increased risk of atopy. There are some indications that infants who develop severe RSV and subsequent wheezing may have aberrations that predate the RSV infection. To decide whether respiratory syncytial virus bronchiolitis causes, or is associated with the respiratory sequelae (or with subsequent allergy), it will be necessary to conduct prospective, randomized studies, where the cytokine profile prior to bronchiolitis onset is known. Such studies should preferably include some form of intervention against respiratory syncytial virus. A more complete understanding of the risk factors for severe respiratory syncytial virus infection and the role of respiratory syncytial virus infection in the initiation of asthma is needed as a basis for large-scale and cost-effective programmes to prevent respiratory syncytial virus-related morbidity.
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| 59. |
- Al-Adwani, S, et al.
(författare)
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Studies on citrullinated LL-37: detection in human airways, antibacterial effects and biophysical properties
- 2020
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1, s. 2376-
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Tidskriftsartikel (refereegranskat)abstract
- Arginine residues of the antimicrobial peptide LL-37 can be citrullinated by peptidyl arginine deiminases, which reduce the positive charge of the peptide. Notably, citrullinated LL-37 has not yet been detected in human samples. In addition, functional and biophysical properties of citrullinated LL-37 are not fully explored. The aim of this study was to detect citrullinated LL-37 in human bronchoalveolar lavage (BAL) fluid and to determine antibacterial and biophysical properties of citrullinated LL-37. BAL fluid was obtained from healthy human volunteers after intra-bronchial exposure to lipopolysaccharide. Synthetic peptides were used for bacterial killing assays, transmission electron microscopy, isothermal titration calorimetry, mass-spectrometry and circular dichroism. Using targeted proteomics, we were able to detect both native and citrullinated LL-37 in BAL fluid. The citrullinated peptide did not kill Escherichia coli nor lysed human red blood cells. Both peptides had similar α-helical secondary structures but citrullinated LL-37 was more stable at higher temperatures, as shown by circular dichroism. In conclusion, citrullinated LL-37 is present in the human airways and citrullination impaired bacterial killing, indicating that a net positive charge is important for antibacterial and membrane lysing effects. It is possible that citrullination serves as a homeostatic regulator of AMP-function by alteration of key functions.
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| 60. |
- Schröder, Björn, et al.
(författare)
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Intestinales Mikrobiom und Schleimhautbarriere
- 2021
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Ingår i: Intestinales Mikrobiom und Innere Medizin. - : UNI-MED Verlag AG. - 9783837416053 ; , s. 39-45
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Das intestinale Mikrobiom repräsentiert aktuell eines der Topthemen, die im Fokus der modernen Humanmedizin stehen. Doch erstaunlicherweise gab es bisher im deutschen Sprachraum keine handliche, aktuelle Übersicht zu diesem Thema. Daher werden in diesem Band zunächst Zusammensetzung und Dynamik des humanen intestinalen Mikrobioms erläutert, ehe in weiteren Kapiteln dann die wichtigsten Veränderungen und vor allem die Rolle des Mikrobioms bei zahlreichen Krankheiten wie chronisch entzündlichen Darmerkrankungen, Reizdarmsyndrom, Leber- und Gallenwegs- sowie Autoimmunerkrankungen diskutiert werden. Es folgen der Komplex Ernährung, Adipositas und Diabetes sowie Atherosklerose mit jeweils eigenen Kapiteln. Schließlich gibt es überraschende Beziehungen der Mikrobiota zur Malignomentstehung. Es folgt ein Abschnitt über Antibiotika und deren Rolle bei zum Teil dauerhaften Störungen der intestinalen Bakterien und Pilze. Am Ende des Buches wird am Beispiel von Mikrobiomtransfer (“Stuhltransplantation”) und Probiotika auf die therapeutischen Konsequenzen eingegangen. Alle Kapitel sind auch für sich lesbar und verständlich.
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