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1.
PLoS Pathog ; 18(9): e1010809, 2022 09.
Article in English | MEDLINE | ID: covidwho-2009723

ABSTRACT

Acinetobacter baumannii is an opportunistic pathogen and an emerging global health threat. Within healthcare settings, major presentations of A. baumannii include bloodstream infections and ventilator-associated pneumonia. The increased prevalence of ventilated patients during the COVID-19 pandemic has led to a rise in secondary bacterial pneumonia caused by multidrug resistant (MDR) A. baumannii. Additionally, due to its MDR status and the lack of antimicrobial drugs in the development pipeline, the World Health Organization has designated carbapenem-resistant A. baumannii to be its priority critical pathogen for the development of novel therapeutics. To better inform the design of new treatment options, a comprehensive understanding of how the host contains A. baumannii infection is required. Here, we investigate the innate immune response to A. baumannii by assessing the impact of infection on host gene expression using NanoString technology. The transcriptional profile observed in the A. baumannii infected host is characteristic of Gram-negative bacteremia and reveals expression patterns consistent with the induction of nutritional immunity, a process by which the host exploits the availability of essential nutrient metals to curtail bacterial proliferation. The gene encoding for lipocalin-2 (Lcn2), a siderophore sequestering protein, was the most highly upregulated during A. baumannii bacteremia, of the targets assessed, and corresponds to robust LCN2 expression in tissues. Lcn2-/- mice exhibited distinct organ-specific gene expression changes including increased transcription of genes involved in metal sequestration, such as S100A8 and S100A9, suggesting a potential compensatory mechanism to perturbed metal homeostasis. In vitro, LCN2 inhibits the iron-dependent growth of A. baumannii and induces iron-regulated gene expression. To elucidate the role of LCN2 in infection, WT and Lcn2-/- mice were infected with A. baumannii using both bacteremia and pneumonia models. LCN2 was not required to control bacterial growth during bacteremia but was protective against mortality. In contrast, during pneumonia Lcn2-/- mice had increased bacterial burdens in all organs evaluated, suggesting that LCN2 plays an important role in inhibiting the survival and dissemination of A. baumannii. The control of A. baumannii infection by LCN2 is likely multifactorial, and our results suggest that impairment of iron acquisition by the pathogen is a contributing factor. Modulation of LCN2 expression or modifying the structure of LCN2 to expand upon its ability to sequester siderophores may thus represent feasible avenues for therapeutic development against this pathogen.


Subject(s)
Acinetobacter Infections , Acinetobacter baumannii , Bacteremia , COVID-19 , Pneumonia, Bacterial , Acinetobacter baumannii/genetics , Acinetobacter baumannii/metabolism , Animals , Carbapenems/pharmacology , Humans , Immunity, Innate , Iron/metabolism , Lipocalin-2/genetics , Lipocalin-2/metabolism , Mice , Pandemics , Siderophores/metabolism
2.
PLoS Pathog ; 17(4): e1009487, 2021 04.
Article in English | MEDLINE | ID: covidwho-1231264

ABSTRACT

Lipocalin 2 (LCN2) is a secreted glycoprotein with roles in multiple biological processes. It contributes to host defense by interference with bacterial iron uptake and exerts immunomodulatory functions in various diseases. Here, we aimed to characterize the function of LCN2 in lung macrophages and dendritic cells (DCs) using Lcn2-/- mice. Transcriptome analysis revealed strong LCN2-related effects in CD103+ DCs during homeostasis, with differential regulation of antigen processing and presentation and antiviral immunity pathways. We next validated the relevance of LCN2 in a mouse model of influenza infection, wherein LCN2 protected from excessive weight loss and improved survival. LCN2-deficiency was associated with enlarged mediastinal lymph nodes and increased lung T cell numbers, indicating a dysregulated immune response to influenza infection. Depletion of CD8+ T cells equalized weight loss between WT and Lcn2-/- mice, proving that LCN2 protects from excessive disease morbidity by dampening CD8+ T cell responses. In vivo T cell chimerism and in vitro T cell proliferation assays indicated that improved antigen processing by CD103+ DCs, rather than T cell intrinsic effects of LCN2, contribute to the exacerbated T cell response. Considering the antibacterial potential of LCN2 and that commensal microbes can modulate antiviral immune responses, we speculated that LCN2 might cause the observed influenza phenotype via the microbiome. Comparing the lung and gut microbiome of WT and Lcn2-/- mice by 16S rRNA gene sequencing, we observed profound effects of LCN2 on gut microbial composition. Interestingly, antibiotic treatment or co-housing of WT and Lcn2-/- mice prior to influenza infection equalized lung CD8+ T cell counts, suggesting that the LCN2-related effects are mediated by the microbiome. In summary, our results highlight a novel regulatory function of LCN2 in the modulation of antiviral immunity.


Subject(s)
Influenza, Human/immunology , Lipocalin-2/metabolism , Microbiota/immunology , Transcriptome , Animals , Antigen Presentation , CD8-Positive T-Lymphocytes/immunology , Dendritic Cells/immunology , Dendritic Cells/virology , Female , Gastrointestinal Microbiome , Homeostasis , Humans , Immunity , Influenza, Human/virology , Lipocalin-2/genetics , Lung/immunology , Lung/virology , Lymphocyte Activation , Macrophages/immunology , Male , Mice , Mice, Inbred C57BL , Specific Pathogen-Free Organisms
3.
JCI Insight ; 6(1)2021 01 11.
Article in English | MEDLINE | ID: covidwho-1027164

ABSTRACT

Immune and inflammatory responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contribute to disease severity of coronavirus disease 2019 (COVID-19). However, the utility of specific immune-based biomarkers to predict clinical outcome remains elusive. Here, we analyzed levels of 66 soluble biomarkers in 175 Italian patients with COVID-19 ranging from mild/moderate to critical severity and assessed type I IFN-, type II IFN-, and NF-κB-dependent whole-blood transcriptional signatures. A broad inflammatory signature was observed, implicating activation of various immune and nonhematopoietic cell subsets. Discordance between IFN-α2a protein and IFNA2 transcript levels in blood suggests that type I IFNs during COVID-19 may be primarily produced by tissue-resident cells. Multivariable analysis of patients' first samples revealed 12 biomarkers (CCL2, IL-15, soluble ST2 [sST2], NGAL, sTNFRSF1A, ferritin, IL-6, S100A9, MMP-9, IL-2, sVEGFR1, IL-10) that when increased were independently associated with mortality. Multivariate analyses of longitudinal biomarker trajectories identified 8 of the aforementioned biomarkers (IL-15, IL-2, NGAL, CCL2, MMP-9, sTNFRSF1A, sST2, IL-10) and 2 additional biomarkers (lactoferrin, CXCL9) that were substantially associated with mortality when increased, while IL-1α was associated with mortality when decreased. Among these, sST2, sTNFRSF1A, IL-10, and IL-15 were consistently higher throughout the hospitalization in patients who died versus those who recovered, suggesting that these biomarkers may provide an early warning of eventual disease outcome.


Subject(s)
COVID-19/immunology , COVID-19/mortality , Adrenal Cortex Hormones/therapeutic use , Adult , Aged , Anti-Bacterial Agents/therapeutic use , Antibodies, Monoclonal, Humanized/therapeutic use , Antiviral Agents/therapeutic use , Azithromycin/therapeutic use , Biomarkers , COVID-19/genetics , COVID-19/therapy , Calgranulin B/genetics , Calgranulin B/immunology , Case-Control Studies , Chemokine CCL2/genetics , Chemokine CCL2/immunology , Chemokine CXCL9/genetics , Chemokine CXCL9/immunology , Enzyme Inhibitors/therapeutic use , Female , Ferritins/genetics , Ferritins/immunology , Gene Expression Profiling , Humans , Hydroxychloroquine/therapeutic use , Immunologic Factors/therapeutic use , Interferon Type I/genetics , Interferon Type I/immunology , Interferon-gamma/genetics , Interferon-gamma/immunology , Interleukin-1 Receptor-Like 1 Protein/genetics , Interleukin-1 Receptor-Like 1 Protein/immunology , Interleukin-10/genetics , Interleukin-10/immunology , Interleukin-15/genetics , Interleukin-15/immunology , Interleukin-2/genetics , Interleukin-2/immunology , Interleukin-6/genetics , Interleukin-6/immunology , Lactoferrin/genetics , Lactoferrin/immunology , Lipocalin-2/genetics , Lipocalin-2/immunology , Male , Matrix Metalloproteinase 9/genetics , Matrix Metalloproteinase 9/immunology , Middle Aged , Multivariate Analysis , NF-kappa B/genetics , NF-kappa B/immunology
4.
Epigenomics ; 12(22): 1969-1981, 2020 11.
Article in English | MEDLINE | ID: covidwho-948022

ABSTRACT

Aim: To elucidate the transcriptional characteristics of COVID-19. Materials & methods: We utilized an integrative approach to comprehensively analyze the transcriptional features of both COVID-19 patients and SARS-CoV-2 infected cells. Results: Widespread infiltration of immune cells was observed. We identified 233 genes that were codifferentially expressed in both bronchoalveolar lavage fluid and lung samples of COVID-19 patients. Functional analysis suggested upregulated genes were related to immune response such as neutrophil activation and antivirus response, while downregulated genes were associated with cell adhesion. Finally, we identified LCN2, STAT1 and UBE2L6 as core genes during SARS-CoV-2 infection. Conclusion: The identification of core genes involved in COVID-19 can provide us with more insights into the molecular features of COVID-19.


Subject(s)
COVID-19/pathology , Lipocalin-2/genetics , SARS-CoV-2/immunology , STAT1 Transcription Factor/genetics , Ubiquitin-Conjugating Enzymes/genetics , A549 Cells , Bronchoalveolar Lavage Fluid/cytology , COVID-19/immunology , Cell Adhesion/genetics , Cell Adhesion/physiology , Cell Line, Tumor , Cytokines/blood , Humans , Lung/immunology , Neutrophil Activation/genetics , Neutrophil Activation/immunology , SARS-CoV-2/genetics , Transcription, Genetic/genetics
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