Biology subjects

Leon, B.

Publications and source records attributed to Leon, B..

4 recordsLinked to original sources

bioRxiv2022

IL-6 prevents Th2 cell polarization by promoting SOCS3-dependent suppression of IL-2 signaling

Defective interleukin-6 (IL-6) signaling has been associated with Th2 bias and elevated IgE. However, the underlying mechanism by which IL-6 prevents the development of Th2-driven diseases remains unknown. Using a model of house-dust-mite (HDM)-induced Th2 differentiation and allergic airway inflammation, we show that IL-6 signaling in allergen-specific T cells was required to prevent Th2 development and subsequent IgE response and allergic inflammation. Th2 cell lineage commitment required strong sustained IL-2 signaling. Importantly, we found that IL-6 turned off IL-2 signaling during early T cell activation and thus inhibited Th2 priming. Mechanistically, we found that IL-6-driven inhibition of IL-2 signaling in responding T cells was mediated by upregulation of Suppressor Of Cytokine Signaling 3 (SOCS3). This mechanism could be mimicked by pharmacological Janus Kinase-1 (JAK1) inhibition. Collectively, our results identify an unrecognized mechanism that prevents the development of unwanted Th2 cell responses and associated diseases and outline potential preventive interventions.

immunology↗

bioRxiv2022

Profiling cell envelope-antibiotic interactions reveals vulnerabilities to β-lactams in a multidrug-resistant bacterium

The cell envelope of the Gram-negative Burkholderia cepacia complex (Bcc) presents unique restrictions to antibiotic penetration. As a consequence, Bcc species are notorious for causing recalcitrant multidrug-resistant infections in immunocompromised individuals, such as those living with cystic fibrosis. To systematically identify cell envelope-associated resistance and susceptibility determinants at the genome level, we constructed a high-density, randomly-barcoded transposon mutant library in the clinical isolate B. cenocepacia K56-2 and exposed it to a panel of more than twenty cell envelope-targeting antibiotics. By quantifying relative mutant fitness with BarSeq, followed by validation with CRISPR-interference, we profiled over a hundred new functional associations and identified novel mediators of antibiotic susceptibility in the Bcc cell envelope. We revealed new connections between {beta}-lactam susceptibility, peptidoglycan synthesis, and blockages in undecaprenyl phosphate metabolism, which highlight a vulnerability in sharing this lipid intermediate. We then show that the clinically relevant synergy of the {beta}-lactam/{beta}-lactamase inhibitor combination ceftazidime/avibactam is primarily mediated by inhibition of the PenB carbapenemase. Importantly, we found that avibactam more strongly potentiates the activity of aztreonam and meropenem than ceftazidime in a panel of Bcc clinical isolates. Finally, we characterize for first time in the Bcc the iron and receptor-dependent activity of the novel siderophore-cephalosporin antibiotic, cefiderocol. Overall, our work has implications for antibiotic target prioritization, and for using additional combinations of {beta}-lactam/{beta}-lactamase inhibitors that can extend the utility of our current clinical arsenal of antibacterial therapies. Author SummaryWhile the Gram-negative cell envelope is a major barrier to antibiotic action, we have an incomplete picture of how each component contributes to antibiotic resistance. To answer this question from a genome-wide perspective in a model of antibiotic-resistant bacteria, we constructed a library of randomly-barcoded transposon mutants in Burkholderia cenocepacia and exposed it to a panel of diverse cell envelope-targeting antibiotics. We identified individual genes and whole pathways associated with antibiotic resistance, including several novel players. Focusing on clinically relevant antibiotics, our strategy dissected how the synergy of the important {beta}-lactam/{beta}-lactamase inhibitor combination ceftazidime/avibactam primarily depends upon inhibition of a single {beta}-lactamase. Additionally, we are the first to characterise the molecular basis of the antibiotic mechanism of cefiderocol in Burkholderia, a new and very potent siderophore-cephalosporin conjugate drug. Encouragingly, we found that cefiderocol susceptibility was greatest at physiological iron concentrations. Overall, we highlight several avenues that can be taken to enhance or develop new therapeutic strategies against Burkholderia infection.

microbiology↗

bioRxiv2022

Chitinase-3-like 1 regulates TH2 cells, TFH cells and IgE following helminth infection

Data from patient cohorts and mouse models of atopic dermatitis, food allergy and asthma strongly support a role for the chitinase-like protein ChI3L1 in allergic disease. To address whether CHI3L1 also contributes to TH2 responses following nematode infection, we infected Chi3l1-/- mice with Heligmosomoides polygyrus (Hp) and analyzed T cell responses. Not surprisingly, we observed impaired TH2 responses in Hp-infected Chi3l1-/- mice. However, we also found that T cell intrinsic expression of Chi3l1 was required for ICOS upregulation following activation of naive CD4 T cells and was necessary for the development of the IL-4+ TFH subset, which supports germinal center (GC) B cell reactions and IgE responses. The requirement for Chi3l1 in TFH and IgE responses was also seen following alum-adjuvanted vaccination. While Chi3l1 was critical for IgE humoral responses it was not required for vaccine or infection induced IgG1 responses. These results suggest that Chi3l1 specifically modulates IgE responses that are highly dependent on help from IL-4-producing TFH cells.

immunology↗

bioRxiv2021

Passive epidemiological surveillance in wildlife in Costa Rica identifies pathogens of zoonotic and conservation importance

Epidemiological surveillance systems for pathogens in wild species have been proposed as a preventive measure for epidemic events. These systems can minimize the detrimental effects of an outbreak, but most importantly, passive surveillance systems are the best adapted to countries with limited resources. Therefore, the present study aims to evaluate the technical and infrastructural feasibility to establish this type of scheme in Costa Rica targeting thedetection of pathogens of zoonotic and conservation importance in wildlife. Between 2018 and 2020, 85 carcasses of free-ranging vertebrates were admitted for post mortem analysis and complementary laboratory analysis, representing a solid basis for the implementation of a passive surveillance system for wildlife diseases in the country. However, we encounter during this research significant constraints that affected the availability of carcasses for analysis, mainly related to the initial identification of cases, detection biases towards events in populated- or easily accessible-areas with nearby located wildlife management centers, further associated with financial disincentives, and limited local logistics capacity. Thus resulting in the exclusion of some geographic regions of the country. This epidemiological surveillance scheme allowed us to estimate the general state of health of the countrys wildlife, establishing the cause of death of the analyzed animals as follows: (i) 46 (54.1%) traumatic events, (ii) 23 (27.1%) infectious agents, (iii) two (2.4%) degenerative illness, (iv) three (3.5%) presumably poisoning, and (v) in 11 (12.9%)undetermined. It also allowed the detection of pathogens such as, canine distemper virus, Klebsiella pneumoniae, Toxoplasma gondii, Trypanosoma spp., Angiostrongylus spp., Dirofilaria spp., Baylisascaris spp., among others. As well as recognizing the circulation of these pathogens around national territory and also on those analyzed species. This strategy is crucial in geographical regions defined as critical for the appearance of diseases due to their great biodiversity and social conditions.

pathology↗