Potential IFNγ Modulation of Inflammasome Pathway in Chlamydia trachomatis Infected Synovial Cells

Following a Chlamydia trachomatis infection, the host immune response is characterized by its recognition via Toll-like and Nod-like Receptors, and the subsequent activation of interferon (IFN)-γ-mediated signaling pathways. Recently, the inflammasome-mediated host cell response has emerged to play a role in the physiopathology of C. trachomatis infection. Here we investigated, for the first time, the interaction of IFN-γ and inflammasome in an in vitro model of C. trachomatis-infected primary human synovial cells. Chlamydial replication as well as the expression of caspase-1, IL-1β, as well as IL-18 and IL-6, were assayed. Our results demonstrated the inhibitory activity of IFN-γ by interfering with the inflammasome network through the downregulation of caspase-1 mRNA expression. In addition, the ability of C. trachomatis to hinder the inflammasome pathway favoring its intracellular survival within synovial cells, was observed. Overall, our data suggest a potential mechanism of immune evasion by C. trachomatis in synovial cells, that may be contested by IFN-γ.

Staphylococcus aureus Decreases SUMOylation Host Response to Promote Intramacrophage Survival

Staphylococcus aureus is a commensal bacterium that causes severe infections in soft tissue and the bloodstream. During infection, S. aureus manipulates host cell response to facilitate its own replication and dissemination. Here, we show that S. aureus significantly decreases the level of SUMOylation, an essential post-translational modification, in infected macrophages 24 h post-phagocytosis. The reduced level of SUMOylation correlates with a decrease in the SUMO-conjugating enzyme Ubc9. The over-expression of SUMO proteins in macrophages impaired bacterial intracellular proliferation and the inhibition of SUMOylation with ML-792 increased it. Together, these findings demonstrated for the first time the role of host SUMOylation response toward S. aureus infection.

Time course profiling of host cell response to herpesvirus infection using nanopore and synthetic long-read transcriptome sequencing

Third-generation sequencing is able to read full-length transcripts and thus to efficiently identify RNA molecules and transcript isoforms, including transcript length and splice isoforms. In this study, we report the time-course profiling of the effect of bovine alphaherpesvirus type 1 on the gene expression of bovine epithelial cells using direct cDNA sequencing carried out on MinION device of Oxford Nanopore Technologies. These investigations revealed a substantial up- and down-regulatory effect of the virus on several gene networks of the host cells, including those that are associated with antiviral response, as well as with viral transcription and translation. Additionally, we report a large number of novel bovine transcript isoforms identified by nanopore and synthetic long-read sequencing. This study demonstrates that viral infection causes differential expression of host transcript isoforms. We could not detect an increased rate of transcriptional readthroughs as described in another alphaherpesvirus. According to our knowledge, this is the first report on the use of LoopSeq for the analysis of eukaryotic transcriptomes. This is also the first report on the application of nanopore sequencing for the kinetic characterization of cellular transcriptomes. This study also demonstrates the utility of nanopore sequencing for the characterization of dynamic transcriptomes in any organisms.

Time-course transcriptome analysis of host cell response to poxvirus infection using a dual long-read sequencing approach

Objective In this study, we applied two long-read sequencing (LRS) approaches, including single-molecule real-time and nanopore-based sequencing methods to investigate the time-lapse transcriptome patterns of host gene expression as a response to Vaccinia virus infection. Transcriptomes determined using short-read sequencing approaches are incomplete because these platforms are inefficient or fail to distinguish between polycistronic RNAs, transcript isoforms, transcriptional start sites, as well as transcriptional readthroughs and overlaps. Long-read sequencing is able to read full-length nucleic acids and can therefore be used to assemble complete transcriptome atlases. Results In this work, we identified a number of novel transcripts and transcript isoforms of Chlorocebus sabaeus. Additionally, analysis of the most abundant 768 host transcripts revealed a significant overrepresentation of the class of genes in the “regulation of signaling receptor activity” Gene Ontology annotation as a result of viral infection.

Systematic Analysis of Lysine Succinylation in Vero cells infected with Small Ruminant Morbillivirus

Small ruminant morbillivirus (SRMV), formerly named Peste-des-petits ruminants virus (PPRV), belongs to the genus Morbillivirus in the family Paramyxoviridae and causes a highly contagious disease in small ruminants, especially goats and sheep. Lysine succinylation is a newly identified and conserved modification and plays an important role in host cell response to pathogen infection. Here, we present a global analysis of the succinylome of SRMV-infected Vero cell using succinylation specific antibody-based enrichment and dimethylation labeling-based quantitative proteomics. As a result, 2633 succinylation sites derived from 823 cellular proteins were quantified. Comparative analysis revealed that 228 down-regulated succinylation sites on 139 proteins and 44 up-regulated succinylation sites on 38 proteins were significantly modified in response to SRMV infection, seven lysine succinylation motifs were identified. Bioinformatics analysis showed that the succinylated proteins mainly participated in cellular respiration and biosynthetic process. Protein-protein interaction networks of the identified proteins provided further evidence that a variety of ATP synthase subunits and carbon metabolism were modulated by succinylation while the overlapped proteins between succinylation and acetylation are involved in glyoxylate and dicarboxylate metabolism. Taken together, these findings provide the first report of succinylome in SRMV infection, lysine acetylation may have a more important effect than succinylation in SRMV infection. These findings provide a novel view on investigating the pathogenic mechanism of SRMV.

Analysis of the Neurotropic and Anti-inflammatory Effects of Neuroelectrode Functionalization with a Heparan Sulphate Mimetic

Further in the search for biomimicry of the properties analogous to neural tissues, and with an ultimate goal of mitigating electrode deterioration via reactive host cell response and glial scar formation, the bio-functionalisation of PEDOT:PTS neural coating is here presented using a heparan mimetic termed (HM) F6. A sulphated mimetic polyanion, with a potential role in neuromodulation in neurodegenerative diseases, and used here for the first time as neural coating. This work acts as a first step towards the use of HM biological dopants, to enhance neuroelectrode functionality, to promote neural outgrowth and to maintain minimal glial scar formation in vitro at the neural-interface. Further, this study opens new possibilities for the evaluation of glycan mimetics in neuroelectrode functionalisation.

Hiding in Plain Sight: Formation and Function of Stress Granules During Microbial Infection of Mammalian Cells

Stress granule (SG) formation is a host cell response to stress-induced translational repression. SGs assemble with RNA-binding proteins and translationally silent mRNA. SGs have been demonstrated to be both inhibitory to viruses, as well as being subverted for viral roles. In contrast, the function of SGs during non-viral microbial infections remains largely unexplored. A handful of microbial infections have been shown to result in host SG assembly. Nevertheless, a large body of evidence suggests SG formation in hosts is a widespread response to microbial infection. Diverse stresses caused by microbes and their products can activate the integrated stress response in order to inhibit translation initiation through phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). This translational response in other contexts results in SG assembly, suggesting that SG assembly can be a general phenomenon during microbial infection. This review explores evidence for host SG formation in response to bacterial, fungal, and protozoan infection and potential functions of SGs in the host and for adaptations of the pathogen.

Systematic analysis of SARS-CoV-2 infection of an ACE2-negative human airway cell

Established in vitro models for SARS-CoV-2 infection are limited and include cell lines of non-human origin and those engineered to overexpress ACE2, the cognate host cell receptor. We identified human H522 lung adenocarcinoma cells as naturally permissive to SARS-CoV-2 infection despite complete absence of ACE2. Infection of H522 cells required the SARS-CoV-2 spike protein, though in contrast to ACE2-dependent models, spike alone was not sufficient for H522 infection. Temporally resolved transcriptomic and proteomic profiling revealed alterations in cell cycle and the antiviral host cell response, including MDA5-dependent activation of type-I interferon signaling. Focused chemical screens point to important roles for clathrin-mediated endocytosis and endosomal cathepsins in SARS-CoV-2 infection of H522 cells. These findings imply the utilization of an alternative SARS-CoV-2 host cell receptor which may impact tropism of SARS-CoV-2 and consequently human disease pathogenesis.

A Mycobacterium tuberculosis effector targets mitochondrion, controls energy metabolism and limits cytochrome c exit

Host metabolism reprogramming is a key feature of Mycobacterium tuberculosis (Mtb) infection that enables the survival of this pathogen within phagocytic cells and modulates the immune response facilitating the spread of the tuberculosis disease. Here, we demonstrate that a previously uncharacterized secreted protein from Mtb, Rv1813c manipulates the host metabolism by targeting mitochondria. When expressed in eukaryotic cells, the protein is delivered to the mitochondrial intermembrane space and enhances host ATP production by boosting the oxidative phosphorylation metabolic pathway. Furthermore, Rv1813c appears to differentially modulate the host cell response to oxidative stress. Expression of Rv1813 in host cells inhibits the release of cytochrome c from mitochondria, an early apoptotic event, in response to short-term oxidative stress. However, Rv1813c expressing cells showed increased sensitivity to prolonged stress. This study reveals a novel class of mitochondria targeting effectors from Mtb and opens new research directions on host metabolic reprogramming and apoptosis control.