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Journal articleFarne H, Glanville N, Johnson N, et al., 2022,
Effect of CRTH2 antagonism on the response to experimental rhinovirus infection in asthma: a pilot randomized controlled trial, Thorax, Vol: 77, Pages: 950-959, ISSN: 0040-6376
Background and aimsThe CRTH2 antagonist timapiprant improved lung function and asthma control in a phase 2 study, with evidence suggesting reduced exacerbations. We aimed to assess whether timapiprant attenuated or prevented asthma exacerbations induced by experimental rhinovirus (RV) infection. We furthermore hypothesized that timapiprant would dampen RV-induced type 2 inflammation and consequently improve antiviral immune responses.MethodsAtopic patients with partially controlled asthma on maintenance inhaled corticosteroids were randomized to timapiprant (n=22) or placebo (n=22) and challenged with RV-A16 three weeks later. The primary endpoint was the cumulative lower respiratory symptom score over the 14 days post-infection. Upper respiratory symptoms, spirometry, airway hyperresponsiveness, exhaled nitric oxide, RV-A16 virus load and soluble mediators in upper and lower airways samples, and CRTH2 staining in bronchial biopsies were additionally assessed before and during RV-A16 infection.ResultsSix subjects discontinued the study and eight were not infected; outcomes were assessed in 16 timapiprant- and 14 placebo-treated, successfully infected subjects. There were no differences between treatment groups in clinical exacerbation severity including cumulative lower respiratory symptom score day 0-14 (difference 3.0 (95% CI -29.0 to 17.0), P=0.78), virus load, antiviral immune responses, or RV-A16-induced airway inflammation other than in the bronchial biopsies, where CRTH2 staining was increased during RV-A16 infection in the placebo- but not the timapiprant-treated group. Timapiprant had a favourable safety profile, with no deaths, serious adverse events, or drug-related withdrawals.ConclusionTimapiprant treatment had little impact on the clinicopathological changes induced by RV-A16 infection in partially controlled asthma.
Journal articleWong J, David S, Sanchez Garrido J, et al., 2022,
Recurrent emergence of Klebsiella pneumoniae carbapenem resistance mediated by an inhibitory ompK36 mRNA secondary structure, Proceedings of the National Academy of Sciences of USA, Vol: 119, Pages: 1-12, ISSN: 0027-8424
Outer membrane porins in Gram-negative bacteria facilitate antibiotic influx. In Klebsiella pneumoniae (KP), modifications in the porin OmpK36 are implicated in increasing resistance to carbapenems. Analysis of large KP genome collections, encompassing major healthcare-associated clones, revealed the recurrent emergence of a synonymous cytosine to thymine transition at position 25 (25c>t) in ompK36. We show that the 25c>t transition increases carbapenem resistance through depletion of OmpK36 from the outer membrane. The mutation attenuates KP in a murine pneumonia model, which accounts for its limited clonal expansion observed by phylogenetic analysis. However, in the context of carbapenem treatment, the 25c>t transition tips the balance towards treatment failure, thus accounting for its recurrent emergence. Mechanistically, the 25c>t transition mediates an intramolecular mRNA interaction between a uracil encoded by 25t and the first adenine within the Shine-Dalgarno sequence. This specific interaction leads to the formation of an RNA stem structure, which obscures the ribosomal binding site thus disrupting translation. While mutations reducing OmpK36 expression via transcriptional silencing are known, we uniquely demonstrate the repeated selection of a synonymous ompK36 mutation mediating translational suppression in response to antibiotic pressure.
Journal articleAsai M, Li Y, Spiropoulos J, et al., 2022,
Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a leading cause of infectious disease mortality. Animal infection models have contributed substantially to our understanding of TB, yet their biological and non-biological limitations are a research bottleneck. There is a need for more ethically acceptable, economical, and reproducible TB infection models capable of mimicking key aspects of disease. Here we demonstrate and present a basic description of how Galleria mellonella (the greater wax moth, Gm) larvae can be used as a low cost, rapid and ethically more acceptable model for TB research. This is the first study to infect Gm with the fully virulent MTB H37Rv, the most widely used strain in research. Infection of Gm with MTB resulted in a symptomatic lethal infection, the virulence of which differed from both attenuated Mycobacterium bovis BCG and auxotrophic MTB strains. The Gm-MTB model can also be used for anti-TB drug screening, although CFU enumeration from Gm is necessary for confirmation of mycobacterial load reducing activity of the tested compound. Furthermore, comparative virulence of MTB isogenic mutants can be determined in Gm. However, comparison of mutant phenotypes in Gm against conventional models must consider the limitations of innate immunity. Our findings indicate that Gm will be a practical, valuable and advantageous additional model to be used alongside existing models to advance tuberculosis research.
Journal articleWeng Y, Shepherd D, Liu Y, et al., 2022,
Inhibition of the Niemann-Pick C1 protein is a conserved feature of multiple strains of pathogenic mycobacteria, Nature Communications, Vol: 13, Pages: 1-16, ISSN: 2041-1723
Mycobacterium tuberculosis (Mtb) survives and replicates within host macrophages (MΦ) and subverts multiple antimicrobial defense mechanisms. Previously, we reported that lipids shed by pathogenic mycobacteria inhibit NPC1, the lysosomal membrane protein deficient in the lysosomal storage disorder Niemann-Pick disease type C (NPC). Inhibition of NPC1 leads to a drop in lysosomal calcium levels, blocking phagosome-lysosome fusion leading to mycobacterial survival. We speculated that the production of specific cell wall lipid(s) that inhibit NPC1 could have been a critical step in the evolution of pathogenicity. We therefore investigated whether lipid extracts from clinical Mtb strains from multiple Mtb lineages, Mtb complex (MTBC) members and non-tubercular mycobacteria (NTM) inhibit the NPC pathway. We report that inhibition of the NPC pathway was present in all clinical isolates from Mtb lineages 1, 2, 3 and 4, Mycobacterium bovis and the NTM, Mycobacterium abscessus and Mycobacterium avium. However, lipid extract from Mycobacterium canettii, which is considered to resemble the common ancestor of the MTBC did not inhibit the NPC1 pathway. We conclude that the evolution of NPC1 inhibitory mycobacterial cell wall lipids evolved early and post divergence from Mycobacterium canettii-related mycobacteria and that this activity contributes significantly to the promotion of disease.
Journal articleAlqurainy N, Miguel-Romero L, Moura de Sousa J, et al., 2022,
A widespread family of phage-inducible chromosomal islands only steals bacteriophage tails to spread in nature
<jats:title>Abstract</jats:title><jats:p>Phage satellites interfere with helper phage packaging through the production of small-capsids, where only satellites can be packaged. So far, in all the analysed systems, the satellite-sized capsids are composed of phage proteins. Here we report the first demonstration that a family of phage-inducible chromosomal island (PICIs), a type of satellites, encodes all the proteins required for both the production of the small-sized capsids and the exclusive packaging of the PICIs into these capsids. Therefore, this new family, that we have named cf-PICIs (<jats:underline>c</jats:underline>apsid forming PICIs), only requires phage tails to generate infective PICI particles. Remarkably, the representative cf-PICI reproduces without cost for their helper phages, suggesting that the relationship between these elements is not parasitic but commensalistic. Finally, our phylogenomic studies indicate that cf-PICIs are present both in Gram-positive and Gram-negative bacteria and have evolved at least three times independently to spread widely into the satellite universe.</jats:p>
Journal articleLedger EVK, Lau K, Tate EW, et al., 2022,
XerC is required for the repair of antibiotic- and immune-mediated DNA damage in <i>Staphylococcus aureus</i>
<jats:title>Abstract</jats:title><jats:p>To survive in the host environment, pathogenic bacteria need to be able repair DNA damage caused by both antibiotics and the immune system. The SOS response is a key bacterial pathway to repair DNA double strand breaks and may therefore be a good target for novel therapeutics to sensitise bacteria to antibiotics and the immune response. However, the genes required for the SOS response in <jats:italic>Staphylococcus aureus</jats:italic> have not been fully established. Therefore, we carried out a screen of mutants involved in various DNA repair pathways to understand which were required for induction of the SOS response. This led to the identification of 16 genes that may play a role in SOS response induction, and of these, 3 that affected susceptibility of <jats:italic>S. aureus</jats:italic> to ciprofloxacin. Further characterisation revealed that, in addition to ciprofloxacin, loss of the tyrosine recombinase XerC increased the susceptibility of <jats:italic>S. aureus</jats:italic> to various classes of antibiotics, as well as to host immune defences. Therefore, the inhibition of XerC may be a viable therapeutic approach to sensitise <jats:italic>S. aureus</jats:italic> to both antibiotics and the immune response.</jats:p>
Journal articleNolan AC, Zeden MS, Campbell C, et al., 2022,
Purine nucleosides interfere with c-di-AMP levels and act as adjuvants to re-sensitise MRSA to β-lactam antibiotics
<jats:title>Abstract</jats:title><jats:p>Elucidating the complex mechanisms controlling <jats:italic>mecA</jats:italic>/PBP2a-mediated β-lactam resistance in methicillin resistant <jats:italic>Staphylococcus aureus</jats:italic> (MRSA) has the potential to identify new drug targets with therapeutic potential. Here, we report that mutations that interfere with <jats:italic>de novo</jats:italic> purine synthesis (<jats:italic>pur</jats:italic> operon), purine transport (NupG, PbuG and PbuX) and the nucleotide salvage pathway (DeoD2, Hpt) increased β-lactam resistance in MRSA strain JE2. Extrapolating from these findings, exogenous guanosine and xanthosine, which are fluxed through the GTP branch of purine biosynthesis were shown to significantly reduce MRSA β-lactam resistance. In contrast adenosine, which is fluxed to ATP, significantly increased oxacillin resistance, whereas inosine, which can be fluxed to ATP and GTP via hypoxanthine, only marginally reduced the oxacillin MIC. Increased oxacillin resistance of the <jats:italic>nupG</jats:italic> mutant was not significantly reversed by guanosine, indicating that NupG is required for guanosine transport, which in turn is required to reduce β-lactam resistance. Suppressor mutants resistant to oxacillin/guanosine combinations contained several purine salvage pathway mutations, including <jats:italic>nupG</jats:italic> and <jats:italic>hpt</jats:italic>. Microscopic analysis revealed that guanosine significantly increased cell size, a phenotype also associated with reduced levels of c-di-AMP. Consistent with this, guanosine significantly reduced levels of c-di-AMP, and inactivation of GdpP, the c-di-AMP phosphodiesterase negated the impact of guanosine on β-lactam susceptibility. PBP2a expression was unaffected in <jats:italic>nupG</jats:italic> or <jats:italic>deoD2</jats:
Journal articleVincent CM, Beckwith EJ, Simoes da Silva CJ, et al., 2022,
Infection increases activity via Toll dependent and independent mechanisms in Drosophila melanogaster., PLoS Pathog, Vol: 18
Host behavioural changes are among the most apparent effects of infection. 'Sickness behaviour' can involve a variety of symptoms, including anorexia, depression, and changed activity levels. Here, using a real-time tracking and behavioural profiling platform, we show that in Drosophila melanogaster, several systemic bacterial infections cause significant increases in physical activity, and that the extent of this activity increase is a predictor of survival time in some lethal infections. Using multiple bacteria and D. melanogaster immune and activity mutants, we show that increased activity is driven by at least two different mechanisms. Increased activity after infection with Micrococcus luteus, a Gram-positive bacterium rapidly cleared by the immune response, strictly requires the Toll ligand spätzle. In contrast, increased activity after infection with Francisella novicida, a Gram-negative bacterium that cannot be cleared by the immune response, is entirely independent of both Toll and the parallel IMD pathway. The existence of multiple signalling mechanisms by which bacterial infections drive increases in physical activity implies that this effect may be an important aspect of the host response.
Journal articleBoeck L, Burbaud S, Skwark M, et al., 2022,
Journal articleWang G, Brunel J-M, Preusse M, et al., 2022,
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