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Abstract The tropism of adenoviruses (Ads) is significantly influenced by the binding of various blood factors. To investigate differences in their binding, we conducted cryo-EM analysis on complexes of several human adenoviruses with human platelet factor-4 (PF4), coagulation factors FII (Prothrombin), and FX. While we observed EM densities for FII and FX bound to all the species-C adenoviruses examined, no densities were seen for PF4, even though PF4 can co-pellet with various Ads. Similar to FX, the γ-carboxyglutamic acid (Gla) domain of FII binds within the surface cavity of hexon trimers. While FII binds equally to species-C Ads: Ad5, Ad6, and Ad657, FX exhibits significantly better binding to Ad5 and Ad657 compared to Ad6. Although only the FX-Gla domain is observed at high-resolution (3.7 Å), the entire FX is visible at low-resolution bound to Ad5 in three equivalent binding modes consistent with the 3-fold symmetric hexon. Only the Gla and kringle-1 domains of FII are visible on all the species-C adenoviruses, where the rigid FII binds in an upright fashion, in contrast to the flexible and bent FX. These data suggest that differential binding of FII and FX may shield certain species-C adenoviruses differently against immune molecules, thereby modulating their tropism.

Abstract How intracellular bacteria subvert the major histocompatibility complex (MHC) class I pathway is poorly understood. Here, we show that the obligate intracellular bacterium Orientia tsutsugamushi uses its effector protein, Ank5, to inhibit nuclear translocation of the MHC class I gene transactivator, NLRC5, and orchestrate its proteasomal degradation. Ank5 uses a tyrosine in its fourth ankyrin repeat to bind the NLRC5 N-terminus while its F-box directs host SCF complex ubiquitination of NLRC5 in the leucine-rich repeat region that dictates susceptibility to Orientia- and Ank5-mediated degradation. The ability of O. tsutsugamushi strains to degrade NLRC5 correlates with ank5 genomic carriage. Ectopically expressed Ank5 that can bind but not degrade NLRC5 protects the transactivator during Orientia infection. Thus, Ank5 is an immunoevasin that uses its bipartite architecture to rid host cells of NLRC5 and reduce surface MHC class I molecules. This study offers insight into how intracellular pathogens can impair MHC class I expression.

Abstract Plasma RNAemia, delayed antibody responses and inflammation predict COVID-19 outcomes, but the mechanisms underlying these immunovirological patterns are poorly understood. We profile 782 longitudinal plasma samples from 318 hospitalized patients with COVID-19. Integrated analysis using k-means reveals four patient clusters in a discovery cohort: mechanically ventilated critically-ill cases are subdivided into good prognosis and high-fatality clusters (reproduced in a validation cohort), while non-critical survivors segregate into high and low early antibody responders. Only the high-fatality cluster is enriched for transcriptomic signatures associated with COVID-19 severity, and each cluster has distinct RBD-specific antibody elicitation kinetics. Both critical and non-critical clusters with delayed antibody responses exhibit sustained IFN signatures, which negatively correlate with contemporaneous RBD-specific IgG levels and absolute SARS-CoV-2-specific B and CD4+ T cell frequencies. These data suggest that the “Interferon paradox” previously described in murine LCMV models is operative in COVID-19, with excessive IFN signaling delaying development of adaptive virus-specific immunity.

Streptococcal siglec-like binding regions (SLBRs) selectively bind cell surface glycans, but the basis for this selectivity is not understood. Here, the authors identify selectivity-modulating SLBR regions and study how changes in SLBR glycan selectivity affect interactions with human glycoprotein receptors.

SWI/SNF chromatin remodelling complex is a major regulator of chromatin structure and of transcription. Here, using mouse embryonic fibroblasts and human rhabdoid tumour cells, the authors provide evidence that SWI/SNF functions as a regulator of enhancers.

Bacterial binding to host receptors underlies both commensalism and pathogenesis. Many streptococci adhere to protein-attached carbohydrates expressed on cell surfaces using Siglec-like binding regions (SLBRs). The precise glycan repertoire recognized may dictate whether the organism is a strict commensal versus a pathogen. However, it is currently not clear what drives receptor selectivity. Here, we use five representative SLBRs and identify regions of the receptor binding site that are hypervariable in sequence and structure. We show that these regions control the identity of the preferred carbohydrate ligand using chimeragenesis and single amino acid substitutions. We further evaluate how the identity of the preferred ligand affects the interaction with glycoprotein receptors in human saliva and plasma samples. As point mutations can change the preferred human receptor, these studies suggest how streptococci may adapt to changes in the environmental glycan repertoire.

The tropism of adenoviruses (Ads) is significantly influenced by the binding of various blood factors. To investigate differences in their binding, we conducted cryo-EM analysis on complexes of several human adenoviruses with human platelet factor-4 (PF4), coagulation factors FII (Prothrombin), and FX. While we observed EM densities for FII and FX bound to all the species-C adenoviruses examined, no densities were seen for PF4, even though PF4 can co-pellet with various Ads. Similar to FX, the γ-carboxyglutamic acid (Gla) domain of FII binds within the surface cavity of hexon trimers. While FII binds equally to species-C Ads: Ad5, Ad6, and Ad657, FX exhibits significantly better binding to Ad5 and Ad657 compared to Ad6. Although only the FX-Gla domain is observed at high-resolution (3.7 Å), the entire FX is visible at low-resolution bound to Ad5 in three equivalent binding modes consistent with the 3-fold symmetric hexon. Only the Gla and kringle-1 domains of FII are visible on all the species-C adenoviruses, where the rigid FII binds in an upright fashion, in contrast to the flexible and bent FX. These data suggest that differential binding of FII and FX may shield certain species-C adenoviruses differently against immune molecules, thereby modulating their tropism. The tropism of adenoviruses is influenced by the binding of host blood factors. Here, the authors show the N-terminal non-polar residues of γ-carboxyglutamic acid domains of vitamin K-dependent blood clotting factors interact with the hexon cavities on the surface of species-C adenoviruses. [ABSTRACT FROM AUTHOR]

Plasma RNAemia, delayed antibody responses and inflammation predict COVID-19 outcomes, but the mechanisms underlying these immunovirological patterns are poorly understood. We profile 782 longitudinal plasma samples from 318 hospitalized patients with COVID-19. Integrated analysis using k-means reveals four patient clusters in a discovery cohort: mechanically ventilated critically-ill cases are subdivided into good prognosis and high-fatality clusters (reproduced in a validation cohort), while non-critical survivors segregate into high and low early antibody responders. Only the high-fatality cluster is enriched for transcriptomic signatures associated with COVID-19 severity, and each cluster has distinct RBD-specific antibody elicitation kinetics. Both critical and non-critical clusters with delayed antibody responses exhibit sustained IFN signatures, which negatively correlate with contemporaneous RBD-specific IgG levels and absolute SARS-CoV-2-specific B and CD4+ T cell frequencies. These data suggest that the "Interferon paradox" previously described in murine LCMV models is operative in COVID-19, with excessive IFN signaling delaying development of adaptive virus-specific immunity. The role of IFN signaling in SARS-CoV-2 infection and outcome is still debated. Here, the authors longitudinally profiled plasma samples from hospitalized patients and show that a persistent inflammatory response is linked to delayed generation of adaptive immunity and increased risk of death when coupled with severe infection. [ABSTRACT FROM AUTHOR]

Abstract Genomic alterations that activate Fibroblast Growth Factor Receptor 2 (FGFR2) are common in intrahepatic cholangiocarcinoma (ICC) and confer sensitivity to FGFR inhibition. However, the depth and duration of response is often limited. Here, we conduct integrative transcriptomics, metabolomics, and phosphoproteomics analysis of patient-derived models to define pathways downstream of oncogenic FGFR2 signaling that fuel ICC growth and to uncover compensatory mechanisms associated with pathway inhibition. We find that FGFR2-mediated activation of Nuclear factor-κB (NF-κB) maintains a highly glycolytic phenotype. Conversely, FGFR inhibition blocks glucose uptake and glycolysis while inciting adaptive changes, including switching fuel source utilization favoring fatty acid oxidation and increasing mitochondrial fusion and autophagy. Accordingly, FGFR inhibitor efficacy is potentiated by combined mitochondrial targeting, an effect enhanced in xenograft models by intermittent fasting. Thus, we show that oncogenic FGFR2 signaling drives NF-κB-dependent glycolysis in ICC and that metabolic reprogramming in response to FGFR inhibition confers new targetable vulnerabilities.