Project description:Evolutionarily successful poxviruses presented effective and diverse strategies to circumvent or overcome host defense mechanisms. Poxviruses encode many immunoregulatory proteins to evade host immunity for a productive infection and unique means of inhibiting DNA-sensing dependent type 1 interferon (IFN-I) responses is anticipated due to the biology of its dsDNA genome in nature and an exclusive cytoplasmic life cycle. We found the key DNA sensing inhibition by poxvirus infection was dominant during the early stage of poxvirus infection independent from DNA replication. In an effort of identifying poxvirus novel means to subdue antiviral proinflammatory responses e.g., IFN-I response, we focused on the function of one early gene that is the known host range determinant from the highly conserved poxvirus host range C7L superfamily, myxoma virus (MYXV) M062. Host range factors are unique features of poxviruses that determine the species and cell type tropism. Almost all sequenced mammalian poxviruses retain at least one homologue of the poxvirus host range C7L superfamily. In MYXV, a rabbit specific poxvirus, the dominant and broad-spectrum host range determinant of the C7L superfamily is the M062R gene. M062R gene product is essential for MYXV infection in almost all cells tested from different mammalian species and specifically inhibits the function of host Sterile α Motif Domain-containing 9 (SAMD9), as M062R-null (ΔM062R) MYXV causes abortive infection in a SAMD9-dependend manner. In this study we investigated the immunostimulatory property of the ΔM062R. We found that the replication-defective ΔM062R infection activated host DNA sensing pathway in the cGAS dependent fashion and knocking down SAMD9 expression attenuated proinflammatory responses. Moreover, transcriptomic analyses showed a unique feature of host gene expression landscape that is different from dsDNA stimulated inflammatory state. This study built a link between the anti-neoplastic SAMD9 and the regulation of the innate immune responses.
Project description:Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, a chronic granulomatous disease. Mtb is mostly restricted to humans and seldom causes disease in animals. M. bovis (Mbv) on the other hand causes tuberculosis in cows (bovine tuberculosis) and several wild animals. Each of these pathogens therefore has unique host adaptations and the host- and pathogen-specific factors driving this differential tropism still remain largely unknown. Here we profiled the secretomes of Mtb- and Mbv-infected bovine macrophages to characterise host-specific responses to each pathogen.
Project description:Highly pathogenic Zaire ebolavirus (EBOV) infection is associated with a dysregulated immune response and high levels of cytokines and chemokines are observed in fatal human cases. . In stark contrast Reston ebolavirus (RESTV) might be non-pathogenic for humans yet the underlying mechanisms determining pathogenicity for different Ebola viruses are not understood. In this study we investigate antiviral immune responses in EBOV- and RESTV- infected primary human monocyte-derived macrophages (MDM). We provide evidence that increased pathogenicity of the highly pathogenic EBOV is associated with a strong activation of host responses from infected MDM. The observed cytokine response after EBOV infection is strikingly similar to LPS-mediated immune signatures however EBOV caused significant induction of the interferon response in addition. In contrast we show that the low pathogenic RESTV fails to elicit significant immune responses in infected MDM. These results demonstrate a correlation of pathogenicity and excessive MDM activation for different Ebola virus species. Interaction of the viral glycoprotein (GP) with Toll-like receptor 4 (TLR4) leading to activation of NF_B signaling is responsible for this effect rather than differences in replication or blocking of immune signaling. We demonstrate that inhibition of TLR4 is able to abolish EBOV-GP mediated NF_B activation which might offer the possibility to develop targeted treatments for EBOV limiting the extreme immune response that seems to be detrimental to the host.
Project description:We used the microarray data to analyse the host cell responses on mouse macrophages infected with the three Influenza A viruses The global expression analysis showed increased expression changes in H5N3 infected mouse macrophages compared to H5N2/F118 and H1N1/WSN
Project description:The human facilitates chromatin transcription (FACT) complex is a chromatin remodeller composed of human suppressor of Ty 16 homologue (hSpt16) and structure-specific recognition protein-1 subunits that regulates cellular gene expression. Whether FACT regulates host responses to infection remained unclear. We identify a FACT-mediated, interferon-independent, antiviral pathway that restricts poxvirus replication. Cell culture and bioinformatics approaches suggest that early viral gene expression triggers nuclear accumulation of SUMOylated hSpt16 subunits required for the expression of E26 transformation-specific sequence-1 (ETS-1)-a transcription factor that activates virus restriction programs. However, biochemical studies show that poxvirus-encoded A51R proteins block ETS-1 expression by outcompeting structure-specific recognition protein-1 binding to SUMOylated hSpt16 and by tethering SUMOylated hSpt16 to microtubules. Furthermore, A51R antagonism of FACT enhances poxvirus replication in human cells and virulence in mice. Finally, we show that FACT also restricts rhabdoviruses, flaviviruses and orthomyxoviruses, suggesting broad roles for FACT in antiviral immunity. Our study reveals the FACT-ETS-1 antiviral response (FEAR) pathway to be critical for eukaryotic antiviral immunity and describes a unique mechanism of viral immune evasion.
Project description:Toxoplasma gondii is a ubiquitous protozoan pathogen able to infect both mammalian and avian hosts. Surprisingly, just three strains appear to account for the majority of isolates from Europe and N. America. To test the hypothesis that strain divergence might be driven by differences between mammalian and avian response to infection, we examine in vitro strain-dependent host responses in a representative avian host, the chicken. Chicken embryonic fibroblasts were cultivated in vitro and infected with different strains of Toxoplasma gondii; host transcriptional responses were then analyzed at 24 hours post-infection.
Project description:Background: Mycobacterium avium is an opportunistic pathogen that requires complex multidrug treatment. Macrolides, like clarithromycin, are the cornerstone of treatment, but even macrolide-based treatment regimens have suboptimal outcomes. Combining transcriptomic profiling of macrophages and mycobacteria in an in vitro infection model may increase our understanding of the host-pathogen interaction and the effect of antibiotic treatment. Methods: To investigate the molecular interplay between pathogen and host, we developed an optimized protocol for dual RNA-sequencing of human monocyte-derived macrophages infected with M. avium. Results: Upon phagocytosis, host defense processes including immune activation and pathogen recognition were upregulated, while M. avium upregulated expression of PE/PPE genes, which are important for immune recognition. Clarithromycin did not affect gene regulation of the host; the effect of clarithromycin on M. avium gene expression was very different in RPMI compared to intracellular mycobacteria, likely due to the influence of the host environment on expression of the important regulatory WhiB genes. Conclusions These data identify the distinct stress responses of M. avium upon infection and clarithromycin treatment and underline the importance of taking the intracellular localization and interaction with the host into account when studying antibiotics against intracellular pathogens.