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Together, they devise a variety of imaging techniques to study virus–host interactions, such as single-molecule super-resolution imaging, quantitative live cell microscopy, super-resolution microscopy, volume scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron tomography, imaging techniques for whole organs, labeling methods for proteins and nucleic acids, including immunogold, labeling with nucleotide analogs, in situ hybridization and EM autoradiography, and strategies to fluorescently label viral and cellular components. The figure contains images from live-cell microscopy, correlative light and electron microscopy (CLEM), two- and three-dimensional TEM, super-resolution microscopy methods such as STED (Stimulated Emission Depletion) and STORM (Stochastic Optical Reconstruction Microscopy), and techniques for molecular mapping in TEM, such as immunogold and metal-tagging TEM (METTEM). With high throughput widefield microscopy, spinning disc confocal microscopy, and spatiotemporal analysis of live cell microscopy, in this article the authors study viral replication in live cells and inside subnuclear domains, characterizing the temporal dynamics of viral replication centers (VRC) formation and expansion over the course of infection. The authors describe macroscopic techniques such as tissue-printing hybridization and microscopy techniques including light microscopy, confocal laser scanning microscopy, and scanning and transmission electron microscopies and their contributions to plant virology.

Mammalian orthoreoviruses (reoviruses) are nonenveloped, double-stranded RNA viruses that assemble progeny particles in cytoplasmic viral factories (VFs) and exit some types of cells using a nonlytic release mechanism. In human brain microvascular endothelial cells (HBMECs), progeny reovirus virions are selectively sorted from VFs into sorting organelles (SOs), which are derived from lysosomes. Smaller membranous carriers (MCs) bud from SOs and transport progeny virions to the plasma membrane where they are released nonlytically by fusion of MCs with the plasma membrane. To discover cellular factors required for lysosomal modification and nonlytic egress, we used mass spectrometry to identify proteins associated with lysosomes purified from uninfected and reovirus-infected HBMECs as well as virions purified from HBMECs and L929 cells, which differ in the pathways used by reovirus for egress. Network analysis of the proteomic results from HBMECs yielded an enrichment of cytoskeletal proteins centered on myosin-9. Using siRNA gene-silencing of myosin-9, pharmacological inhibition of myosin-9, super-resolution light microscopy, electron microscopy, and three-dimensional electron tomography, we found that myosin-9 acts at late stages of reovirus replication to promote viral egress. Myosin-9 associates with actin filaments attached to mature virions and mediates nonlytic egress of viral progeny from HBMECs. Our findings provide insights into the role of myosin-9 in the intracellular lysosome-mediated reovirus egress pathway and illuminate a new potential therapeutic target for viruses that use this nonlytic egress pathway.

Assembling of the membrane-bound viral replicase complexes (VRCs) consisting of viral- and host-encoded proteins is a key step during the replication of positive-stranded RNA viruses in the infected cells. Previous genome-wide screens with Tomato bushy stunt tombusvirus (TBSV) in a yeast model host have revealed the involvement of eleven cellular ESCRT (endosomal sorting complexes required for transport) proteins in viral replication. The ESCRT proteins are involved in endosomal sorting of cellular membrane proteins by forming multiprotein complexes, deforming membranes away from the cytosol and, ultimately, pinching off vesicles into the lumen of the endosomes. In this paper, we show an unexpected key role for the conserved Vps4p AAA+ ATPase, whose canonical function is to disassemble the ESCRT complexes and recycle them from the membranes back to the cytosol. We find that the tombusvirus p33 replication protein interacts with Vps4p and three ESCRT-III proteins. Interestingly, Vps4p is recruited to become a permanent component of the VRCs as shown by co-purification assays and immuno-EM. Vps4p is co-localized with the viral dsRNA and contacts the viral (+)RNA in the intracellular membrane. Deletion of Vps4p in yeast leads to the formation of crescent-like membrane structures instead of the characteristic spherule and vesicle-like structures. The in vitro assembled tombusvirus replicase based on cell-free extracts (CFE) from vps4Δ yeast is highly nuclease sensitive, in contrast with the nuclease insensitive replicase in wt CFE. These data suggest that the role of Vps4p and the ESCRT machinery is to aid building the membrane-bound VRCs, which become nuclease-insensitive to avoid the recognition by the host antiviral surveillance system and the destruction of the viral RNA. Other (+)RNA viruses of plants and animals might also subvert Vps4p and the ESCRT machinery for formation of VRCs, which require membrane deformation and spherule formation.

Transport of neo-synthesized influenza A virus (IAV) viral ribonucleoproteins (vRNPs) from the nucleus to the plasma membrane involves Rab 11 but the precise mechanism remains poorly understood. We used metal-tagging and immunolabeling to visualize viral proteins and cellular endomembrane markers by electron microscopy of IAV-infected cells. Unexpectedly, we provide evidence that the vRNP components and the Rab11 protein are present at the membrane of a modified, tubulated endoplasmic reticulum (ER) that extends all throughout the cell, and on irregularly coated vesicles (ICVs). Some ICVs are found very close to the ER and to the plasma membrane. ICV formation is observed only in infected cells and requires an active Rab11 GTPase. Against the currently accepted model in which vRNPs are carried onto Rab11-positive recycling endosomes across the cytoplasm, our findings reveal that the endomembrane organelle that is primarily involved in the transport of vRNPs is the ER.

Hfq is a bacterial protein involved in several aspects of nucleic acid transactions, but one of its best-characterized functions is to affect the post-transcriptional regulation of mRNA by virtue of its interactions with stress-related small regulatory (sRNA). By using cellular imaging based on the metallothionein clonable tag for electron microscopy, we demonstrate here that in addition to its localization in the cytoplasm and in the nucleoid, a significant amount of Hfq protein is located at the cell periphery. Simultaneous immunogold detection of specific markers strongly suggests that peripheral Hfq is close to the bacterial membrane. Because sRNAs regulate the synthesis of several membrane proteins, our result implies that the sRNA- and Hfq-dependent translational regulation of these proteins takes place in the cytoplasmic region underlying the membrane. This finding supports the proposal that RNA processing and translational machineries dedicated to membrane protein translation may often be located in close proximity to the membrane of the bacterial cell.

OBJECTIVES/GOALS: Our overarching aim is to examine, in an African American population, cognitive, affective, and neurophysiological processes, as well as risk-taking behavior, in response to racial stigma cues. While accounting for individual differences, we aim to see how these processes and drug-cue reactivity are impacted or altered by exposure to racial cues. METHODS/STUDY POPULATION: Participants will be African Americans between 18 and 25 years of age, equally distributed across genders. We will recruit 75 participants in order to have adequate power to conduct our intended analyses—particularly pertaining to individual differences in risk behavior outcomes. Participants will be asked to complete demographic and self-report questionnaires. Participants will also be asked to complete computerized tasks while their physiological responses (heart rate, skin conductance, and electroencephalographic (EEG) data) are recorded. The tasks are as follow: resting, gambling, go/no-go, picture viewing (positive, negative, and neutral images), and a drug cue image set. These tasks will be repeated after the participant views a racial stigma image set to evaluate the impact of discrimination. RESULTS/ANTICIPATED RESULTS: Data from 18 participants has been collected. Data will be periodically preprocessed and validated (e.g., 1 participant was removed due to data recording errors, so the current valid Nis 17). Generally, we anticipate that behaviors and neural activity will be modulated across all tasks after viewing the racial stigma image set. Specifically, (a) cognitive and affective processing of singular events of racial stigma may indicate a stress response, (b) modulation from chronic experiences of racial stigma render neural systems increasingly sensitive to stigma cues, and thereby less equipped to regulate stress response, (c) the impact of these processes on altering risk behavior (may increase such behaviors), and (d) the impact of these modulations on altering drug-cue reactivity (may amplify reactivity). DISCUSSION/SIGNIFICANCE: The study will identify factors that contribute to stress and risk behavior among African Americans. A substantial gap continues to exist regarding the nature of risk behavior among African Americans, despite the fact that African Americans represent a health disparity population with unique vulnerabilities to health-relevant risk behavior.

Objectives/Goals: Mood and anxiety disorders are a risk factor (Ozer et al., 2003) for posttraumatic stress disorder (PTSD) following trauma exposure. As such, a latent internalizing dimension may also be a risk factor. We examine how the shared variance between mood and anxiety symptoms (as in HiTOP; Kotov et al., 2021) impacts development of posttraumatic stress (PTS) symptoms, and symptom clusters. Methods/Study Population: Using data from a prior study of individuals who arrived at emergency rooms and were assessed at later time points (AURORA study; McLean et al., 2020), our sample included 1866 participants (1208 females, Mage  =  38.49 years) with available data for the proposed analyses. A latent factor (INTtotal) was operationalized as the shared variance between mood and anxiety symptoms (PROMIS Anxiety and Depression; Cella et al., 2010) as well as PTS symptoms (PCL-5, Weathers et al., 2013). We computed a second internalizing factor excluding PTS symptoms (INTma) to isolate the contribution of baseline affect and anxiety from PTS at baseline. We examined how baseline PTS symptoms, INTtotal, and INTma compare as prospective predictors for PTS symptoms at later time points and how these variables predict individual PTS symptoms. Results/Anticipated Results: Baseline INTma, INTtotal, and PTS symptoms were significant prospective predictors of PTS symptoms across all time points (all with t > 10, p < .005). When focusing on INTma relative to DSM-5 PTSD criterion (American Psychiatric Association, 2013), INTma significantly predicted later symptoms at six months posttrauma pertaining to Criterion D (t  =  18.88, p < .005), negative alterations in cognition and mood, Criterion E (t  =  15.44, p < .005) arousal and reactivity, and Criterion B, intrusion (t  =  15.44, p < .005). INTma significantly predicted symptoms in Criterion C, avoidance, though to a lesser degree (t  =  12.87, p Discussion/Significance of Impact: These findings bolster the utility of examining PTSD risk factors through a transdiagnostic lens. INTma was predictive of later PTS symptoms, independent of baseline PTS. Our analyses reveal clinical implications for the assessment of PTSD, and the tailoring of treatment for patients high in internalizing following trauma exposure.

Like most viruses that replicate in the cytoplasm, mammalian reoviruses assemble membranous neo-organelles called inclusions that serve as sites of viral genome replication and particle morphogenesis. Viral inclusion formation is essential for viral infection, but how these organelles form is not well understood. We investigated the biogenesis of reovirus inclusions. Correlative light and electron microscopy showed that endoplasmic reticulum (ER) membranes are in contact with nascent inclusions, which form by collections of membranous tubules and vesicles as revealed by electron tomography. ER markers and newly synthesized viral RNA are detected in inclusion internal membranes. Live-cell imaging showed that early in infection, the ER is transformed into thin cisternae that fragment into small tubules and vesicles. We discovered that ER tubulation and vesiculation are mediated by the reovirus σNS and μNS proteins, respectively. Our results enhance an understanding of how viruses remodel cellular compartments to build functional replication organelles. IMPORTANCE Viruses modify cellular structures to build replication organelles. These organelles serve as sites of viral genome replication and particle morphogenesis and are essential for viral infection. However, how these organelles are constructed is not well understood. We found that the replication organelles of mammalian reoviruses are formed by collections of membranous tubules and vesicles derived from extensive remodeling of the peripheral endoplasmic reticulum (ER). We also observed that ER tubulation and vesiculation are triggered by the reovirus σNS and μNS proteins, respectively. Our results enhance an understanding of how viruses remodel cellular compartments to build functional replication organelles and provide functions for two enigmatic reovirus replication proteins. Most importantly, this research uncovers a new mechanism by which viruses form factories for particle assembly. Viruses modify cellular structures to build replication organelles. These organelles serve as sites of viral genome replication and particle morphogenesis and are essential for viral infection. However, how these organelles are constructed is not well understood. We found that the replication organelles of mammalian reoviruses are formed by collections of membranous tubules and vesicles derived from extensive remodeling of the peripheral endoplasmic reticulum (ER). We also observed that ER tubulation and vesiculation are triggered by the reovirus σNS and μNS proteins, respectively. Our results enhance an understanding of how viruses remodel cellular compartments to build functional replication organelles and provide functions for two enigmatic reovirus replication proteins. Most importantly, this research uncovers a new mechanism by which viruses form factories for particle assembly.

Most viruses that replicate in the cytoplasm of host cells form neoorganelles that serve as sites of viral genome replication and particle assembly. These highly specialized structures concentrate viral proteins and nucleic acids, prevent the activation of cell-intrinsic defenses, and coordinate the release of progeny particles. Reoviruses are common pathogens of mammals that have been linked to celiac disease and show promise for oncolytic applications. These viruses form nonenveloped, double-shelled virions that contain ten segments of double-stranded RNA. Replication organelles in reovirus-infected cells are nucleated by viral nonstructural proteins µNS and σNS. Both proteins partition the endoplasmic reticulum to form the matrix of these structures. The resultant membranous webs likely serve to anchor viral RNA–protein complexes for the replication of the reovirus genome and the assembly of progeny virions. Ongoing studies of reovirus replication organelles will advance our knowledge about the strategies used by viruses to commandeer host biosynthetic pathways and may expose new targets for therapeutic intervention against diverse families of pathogenic viruses.

RNA viruses exploit host cells by co-opting host factors and lipids and escaping host antiviral responses. Previous genome-wide screens with Tomato bushy stunt virus (TBSV) in the model host yeast have identified 18 cellular genes that are part of the actin network. In this paper, we show that the p33 viral replication factor interacts with the cellular cofilin (Cof1p), which is an actin depolymerization factor. Using temperature-sensitive (ts) Cof1p or actin (Act1p) mutants at a semi-permissive temperature, we find an increased level of TBSV RNA accumulation in yeast cells and elevated in vitro activity of the tombusvirus replicase. We show that the large p33 containing replication organelle-like structures are located in the close vicinity of actin patches in yeast cells or around actin cable hubs in infected plant cells. Therefore, the actin filaments could be involved in VRC assembly and the formation of large viral replication compartments containing many individual VRCs. Moreover, we show that the actin network affects the recruitment of viral and cellular components, including oxysterol binding proteins and VAP proteins to form membrane contact sites for efficient transfer of sterols to the sites of replication. Altogether, the emerging picture is that TBSV, via direct interaction between the p33 replication protein and Cof1p, controls cofilin activities to obstruct the dynamic actin network that leads to efficient subversion of cellular factors for pro-viral functions. In summary, the discovery that TBSV interacts with cellular cofilin and blocks the severing of existing filaments and the formation of new actin filaments in infected cells opens a new window to unravel the way by which viruses could subvert/co-opt cellular proteins and lipids. By regulating the functions of cofilin and the actin network, which are central nodes in cellular pathways, viruses could gain supremacy in subversion of cellular factors for pro-viral functions.