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The coronavirus spike glycoprotein attaches to host receptors and mediates viral fusion. Using a broad screening approach, we isolated seven monoclonal antibodies (mAbs) that bind to all human-infecting coronavirus spike proteins from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immune donors. These mAbs recognize the fusion peptide and acquire affinity and breadth through somatic mutations. Despite targeting a conserved motif, only some mAbs show broad neutralizing activity in vitro against alpha- and betacoronaviruses, including animal coronaviruses WIV-1 and PDF-2180. Two selected mAbs also neutralize Omicron BA.1 and BA.2 authentic viruses and reduce viral burden and pathology in vivo. Structural and functional analyses showed that the fusion peptide-specific mAbs bound with different modalities to a cryptic epitope hidden in prefusion stabilized spike, which became exposed upon binding of angiotensin-converting enzyme 2 (ACE2) or ACE2-mimicking mAbs. ispartof: SCIENCE vol:377 issue:6607 pages:735-741 ispartof: location:United States status: published

Currently circulating SARS-CoV-2 variants acquired convergent mutations at receptor-binding domain (RBD) hot spots1. Their impact on viral infection, transmission, and efficacy of vaccines and therapeutics remains poorly understood. Here, we demonstrate that recently emerged BQ.1.1. and XBB.1 variants bind ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1 and XBB.1 RBDs bound to human ACE2 and S309 Fab (sotrovimab parent) explain the altered ACE2 recognition and preserved antibody binding through conformational selection. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1, the variant displaying the greatest loss of neutralization. Moreover, in several donors vaccine-elicited plasma antibodies cross-react with and trigger effector functions against Omicron variants despite reduced neutralizing activity. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring persistent immune imprinting. Our findings suggest that this previously overlooked class of cross-reactive antibodies, exemplified by S309, may contribute to protection against disease caused by emerging variants through elicitation of effector functions.

SARS-CoV-2 infection—which involves both cell attachment and membrane fusion—relies on the angiotensin-converting enzyme 2 (ACE2) receptor, which is paradoxically found at low levels in the respiratory tract1–3, suggesting that there may be additional mechanisms facilitating infection. Here we show that C-type lectin receptors, DC-SIGN, L-SIGN and the sialic acid–binding immunoglobulin-like lectin 1 (SIGLEC1) function as attachment receptors by enhancing ACE2-mediated infection and modulating the neutralizing activity of different classes of spike-specific antibodies. Antibodies to the amino-terminal domain or to the conserved site at the base of the receptor-binding domain, while poorly neutralizing infection of ACE2-overexpressing cells, effectively block lectin-facilitated infection. Conversely, antibodies to the receptor binding motif, while potently neutralizing infection of ACE2-overexpressing cells, poorly neutralize infection of cells expressing DC-SIGN or L-SIGN and trigger fusogenic rearrangement of the spike, promoting cell-to-cell fusion. Collectively, these findings identify a lectin-dependent pathway that enhances ACE2-dependent infection by SARS-CoV-2 and reveal distinct mechanisms of neutralization by different classes of spike-specific antibodies. C-type lectins and SIGLEC1 function as attachment receptors for SARS-CoV-2 and enhance ACE2-mediated infection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron sublineages carry distinct spike mutations resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters elicit plasma-neutralizing antibodies against Omicron BA.1, BA.2, BA.2.12.1, and BA.4/5, and that breakthrough infections, but not vaccination alone, induce neutralizing antibodies in the nasal mucosa. Consistent with immunological imprinting, most antibodies derived from memory B cells or plasma cells of Omicron breakthrough cases cross-react with the Wuhan-Hu-1, BA.1, BA.2, and BA.4/5 receptor-binding domains, whereas Omicron primary infections elicit B cells of narrow specificity up to 6 months after infection. Although most clinical antibodies have reduced neutralization of Omicron, we identified an ultrapotent pan-variant-neutralizing antibody that is a strong candidate for clinical development. ispartof: SCIENCE vol:378 issue:6620 pages:619-+ ispartof: location:United States status: published

Background & AimsChronic hepatitis B is a major global public health problem, and coinfection with hepatitis delta virus (HDV) worsens disease outcome. Here, we describe a hepatitis B virus (HBV) surface antigen (HBsAg)-targeting monoclonal antibody (mAb) with the potential to promote functional cure of chronic hepatitis B and D to address this unmet medical need.MethodsHBsAg-specific mAbs were isolated from memory B cells of HBV vaccinated individuals. In vitro neutralization was determined against HBV and HDV enveloped with HBsAg representing eight HBV genotypes. Human liver-chimeric mice were treated twice weekly with a candidate mAb starting three weeks post HBV inoculation (spreading phase) or during stable HBV or HBV/HDV coinfection (chronic phase).ResultsFrom a panel of human anti-HBs mAbs, VIR-3434 was selected and engineered for pre-clinical development. VIR-3434 targets a putative conserved, conformational epitope within the antigenic loop of HBsAg and neutralized HBV and HDV infection with >12,000-fold higher potency than Hepatitis B Immunoglobulins in vitro. Neutralization was pan-genotypic against strains representative of HBV genotypes A-H. In the spreading phase of HBV infection in human liver-chimeric mice, a parental mAb of VIR-3434 (HBC34) prevented HBV dissemination and intrahepatic HBV RNA and cccDNA increase. In the chronic phase of HBV infection or co-infection with HDV, HBC34 treatment decreased circulating HBsAg by >1 log and HDV RNA by >2 logs.ConclusionsThis in vitro and in vivo characterization identified the potent anti-HBs mAb VIR-3434, which reduces circulating HBsAg and HBV/HDV viremia in human liver-chimeric mice. VIR-3434 is currently in clinical development for treatment of patients with chronic hepatitis B or D.Lay summaryChronic infection with hepatitis B virus places approximately 290 million individuals worldwide at risk for severe liver disease and cancer. Currently available treatments result in low rates of functional cure or require lifelong therapy that does not eliminate the risk of liver disease. We isolated and characterized a potent, human antibody that neutralizes hepatitis B and D viruses and reduces infection in a mouse model. This antibody could provide a new treatment for patients with chronic hepatitis B and D.HighlightsIdentification of a human mAb VIR-3434 that potently neutralizes HBV and HDVVIR-3434 targets a conserved, conformational epitope of the HBsAg antigenic loopVIR-3434 treatment blocks intrahepatic HBV spread in human liver-chimeric miceVIR-3434 treatment reduces circulating HBsAg and HDV RNA in co-infected miceData have enabled clinical development of VIR-3434 against chronic hepatitis B/D

Coronaviruses use diverse Spike (S) glycoproteins to attach to host receptors and fuse with target cells. Using a broad screening approach, we isolated from SARS-CoV-2 immune donors seven monoclonal antibodies (mAbs) that bind to all human alpha and beta coronavirus S proteins. These mAbs recognize the fusion peptide and acquire high affinity and breadth through somatic mutations. Despite targeting a conserved motif, only some mAbs show broad neutralizing activity in vitro against alpha and beta coronaviruses, including Omicron BA.1 variant and bat WIV-1, and reduce viral titers and pathology in vivo. Structural and functional analyses show that the fusion peptide-specific mAbs bind with different modalities to a cryptic epitope which is concealed by prefusion-stabilizing ‘2P’ mutations and becomes exposed upon binding of ACE2 or ACE2-mimicking mAbs. This study identifies a new class of pan-coronavirus neutralizing mAbs and reveals a receptor-induced conformational change in the S protein that exposes the fusion peptide region.

Intracellular pathogens have evolved multiple ways to manipulate their host cells in order to survive and replicate in a hostile environment. They often exploit membrane trafficking pathways at multiple steps of their infection cycle: entry, establishment of a replicative niche, avoid degradation and immune response, acquire nutrients and lastly, egress. Recent studies on membrane trafficking exploitation by intracellular pathogens have led to the discovery of novel and fascinating cell biology, including a non-canonical mechanism of ubiquitination and a novel mitophagy receptor. Thus, studying how pathogens target host cell membrane trafficking pathways is not only important for the development of new therapeutics, but also helps understanding fundamental mechanisms of cell biology.

Understanding broadly neutralizing sarbecovirus antibody responses is key to developing countermeasures against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and future zoonotic sarbecoviruses. We describe the isolation and characterization of a human monoclonal antibody, designated S2K146, that broadly neutralizes viruses belonging to SARS-CoV– and SARS-CoV-2–related sarbecovirus clades, which use angiotensin-converting enzyme 2 (ACE2) as an entry receptor. Structural and functional studies show that most of the virus residues that directly bind S2K146 are also involved in binding to ACE2. This allows the antibody to potently inhibit receptor attachment. S2K146 protects against SARS-CoV-2 Beta variant challenge in hamsters, and viral passaging experiments reveal a high barrier for emergence of escape mutants, making it a good candidate for clinical development. The conserved ACE2-binding residues present a site of vulnerability that might be leveraged for developing vaccines eliciting broad sarbecovirus immunity.

SUMMARYThe recently emerged SARS-CoV-2 Omicron variant harbors 37 amino acid substitutions in the spike (S) protein, 15 of which are in the receptor-binding domain (RBD), thereby raising concerns about the effectiveness of available vaccines and antibody therapeutics. Here, we show that the Omicron RBD binds to human ACE2 with enhanced affinity relative to the Wuhan-Hu-1 RBD and acquires binding to mouse ACE2. Severe reductions of plasma neutralizing activity were observed against Omicron compared to the ancestral pseudovirus for vaccinated and convalescent individuals. Most (26 out of 29) receptor-binding motif (RBM)-directed monoclonal antibodies (mAbs) lost in vitro neutralizing activity against Omicron, with only three mAbs, including the ACE2-mimicking S2K146 mAb1, retaining unaltered potency. Furthermore, a fraction of broadly neutralizing sarbecovirus mAbs recognizing antigenic sites outside the RBM, including sotrovimab2, S2X2593 and S2H974, neutralized Omicron. The magnitude of Omicron-mediated immune evasion and the acquisition of binding to mouse ACE2 mark a major SARS-CoV-2 mutational shift. Broadly neutralizing sarbecovirus mAbs recognizing epitopes conserved among SARS-CoV-2 variants and other sarbecoviruses may prove key to controlling the ongoing pandemic and future zoonotic spillovers.

The spillovers of betacoronaviruses in humans and the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants highlight the need for broad coronavirus countermeasures. We describe five monoclonal antibodies (mAbs) cross-reacting with the stem helix of multiple betacoronavirus spike glycoproteins isolated from COVID-19 convalescent individuals. Using structural and functional studies, we show that the mAb with the greatest breadth (S2P6) neutralizes pseudotyped viruses from three different subgenera through the inhibition of membrane fusion, and we delineate the molecular basis for its cross-reactivity. S2P6 reduces viral burden in hamsters challenged with SARS-CoV-2 through viral neutralization and Fc-mediated effector functions. Stem helix antibodies are rare, oftentimes of narrow specificity, and can acquire neutralization breadth through somatic mutations. These data provide a framework for structure-guided design of pan-betacoronavirus vaccines eliciting broad protection. ispartof: SCIENCE vol:373 issue:6559 pages:1109-1115 ispartof: location:United States status: published

The repeated spillovers of {beta}-coronaviruses in humans along with the rapid emergence of SARS-CoV-2 escape variants highlight the need to develop broad coronavirus therapeutics and vaccines. Five monoclonal antibodies (mAbs) were isolated from COVID-19 convalescent individuals and found to cross-react with multiple {beta}-coronavirus spike (S) glycoproteins by targeting the stem helix. One of these mAbs, S2P6, cross-reacts with more than twenty human and animal {beta}-coronavirus S glycoproteins and broadly neutralizes SARS-CoV-2 and pseudotyped viruses from the sarbecovirus, merbecovirus and embecovirus subgenera. Structural and functional studies delineate the molecular basis of S2P6 cross-reactivity and broad neutralization and indicate that this mAb blocks viral entry by inhibiting membrane fusion. S2P6 protects hamsters challenged with SARS-CoV-2 (including the B.1.351 variant of concern) through direct viral neutralization and Fc-mediated effector functions. Serological and B cell repertoire analyses indicate that antibodies targeting the stem helix are found in some convalescent donors and vaccinees but are predominantly of narrow specificity. Germline reversion of the identified cross-reactive mAbs revealed that their unmutated ancestors are specific for the endemic OC43 or HKU1 viruses and acquired enhanced affinity and breadth through somatic mutations. These data demonstrate that conserved epitopes in the coronavirus fusion machinery can be targeted by protective antibodies and provide a framework for structure-guided design of pan-{beta}-coronavirus vaccines eliciting broad protection.

Investigating the mechanisms of SARS-CoV-2 cellular infection is key to better understand COVID-19 immunity and pathogenesis. Infection, which involves both cell attachment and membrane fusion, relies on the ACE2 receptor that is paradoxically found at low levels in the respiratory tract, suggesting that additional mechanisms facilitating infection may exist. Here we show that C-type lectin receptors, DC-SIGN, L-SIGN and the sialic acid-binding Ig-like lectin 1 (SIGLEC1) function as auxiliary receptors by enhancing ACE2-mediated infection and modulating the neutralizing activity of different classes of spike-specific antibodies. Antibodies to the N-terminal domain (NTD) or to the conserved proteoglycan site at the base of the Receptor Binding Domain (RBD), while poorly neutralizing infection of ACE2 over-expressing cells, effectively block lectin-facilitated infection. Conversely, antibodies to the Receptor Binding Motif (RBM), while potently neutralizing infection of ACE2 over-expressing cells, poorly neutralize infection of cells expressing DC-SIGN or L-SIGN and trigger fusogenic rearrangement of the spike promoting cell-to-cell fusion. Collectively, these findings identify a lectin-dependent pathway that enhances ACE2-dependent infection by SARS-CoV-2 and reveal distinct mechanisms of neutralization by different classes of spike-specific antibodies.

VIR-7831 and VIR-7832 are dual action monoclonal antibodies (mAbs) targeting the spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). VIR-7831 and VIR-7832 were derived from a parent antibody (S309) isolated from memory B cells of a 2003 severe acute respiratory syndrome coronavirus (SARS-CoV) survivor. Both mAbs contain an “LS” mutation in the Fc region to prolong serum half-life and potentially enhance distribution to the respiratory mucosa. In addition, VIR-7832 encodes an Fc GAALIE mutation that has been shown previously to evoke CD8+ T-cells in the context of an in vivo viral respiratory infection. VIR-7831 and VIR-7832 potently neutralize wild-type and variant authentic virus in vitro as well as variant pseudotyped viruses. In addition, they retain activity against monoclonal antibody resistance mutations conferring reduced susceptibility to currently authorized mAbs. The VIR-7831/VIR-7832 epitope does not overlap with mutational sites in current variants of concern and continues to be highly conserved among circulating sequences consistent with the high barrier to resistance observed in vitro. Furthermore, both mAbs can recruit effector mechanisms in vitro that may contribute to clinical efficacy via elimination of infected host cells. In vitro studies with these mAbs demonstrated no enhancement of infection. In a Syrian Golden hamster proof-of concept wildtype SARS-CoV-2 infection model, animals treated with VIR-7831 had less weight loss, and significantly decreased total viral load and infectious virus levels in the lung compared to a control mAb. Taken together, these data indicate that VIR-7831 and VIR-7832 are promising new agents in the fight against COVID-19.

SARS-CoV-2 infection-which involves both cell attachment and membrane fusion-relies on the angiotensin-converting enzyme 2 (ACE2) receptor, which is paradoxically found at low levels in the respiratory tract(1-3), suggesting that there may be additional mechanisms facilitating infection. Here we show that C-type lectin receptors, DC-SIGN, L-SIGN and the sialic acid-binding immunoglobulin-like lectin 1 (SIGLEC1) function as attachment receptors by enhancing ACE2-mediated infection and modulating the neutralizing activity of different classes of spike-specific antibodies. Antibodies to the amino-terminal domain or to the conserved site at the base of the receptor-binding domain, while poorly neutralizing infection of ACE2-overexpressing cells, effectively block lectin-facilitated infection. Conversely, antibodies to the receptor binding motif, while potently neutralizing infection of ACE2-overexpressing cells, poorly neutralize infection of cells expressing DC-SIGN or L-SIGN and trigger fusogenic rearrangement of the spike, promoting cell-to-cell fusion. Collectively, these findings identify a lectin-dependent pathway that enhances ACE2-dependent infection by SARS-CoV-2 and reveal distinct mechanisms of neutralization by different classes of spike-specific antibodies.

SUMMARYThe human pathogenLegionella pneumophila (L.p.)secretes ~330 bacterial effector proteins into the host cell which interfere with numerous cellular pathways and often regulate host cell proteins through post-translational modifications. However, the cellular targets and functions of mostL.p.effectors are not known. In order to obtain a global overview of potential targets of these effectors, we analyzed the host cell proteome, ubiquitinome, and phosphoproteome duringL.p.infection. Our analysis reveals dramatic spatiotemporal changes in the host cell proteome that are dependent on the secretion of bacterial effectors. Strikingly, we show thatL.p.substantially reshapes the mitochondrial proteome and modulates mitochondrial stress response pathways such as the mitochondrial unfolded protein response (UPRmt). To our knowledge, this is the first evidence of manipulation of the UPRmtby a bacterial pathogen in mammalian cells. In addition, we have identified a previously uncharacterizedL.p.effector that is targeted to host cell mitochondria and protects mitochondrial network integrity during mitochondrial stress.

A newly described coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of coronavirus disease 2019 (COVID-19), has infected over 2.3 million people, led to the death of more than 160,000 individuals and caused worldwide social and economic disruption1,2. There are no antiviral drugs with proven clinical efficacy for the treatment of COVID-19, nor are there any vaccines that prevent infection with SARS-CoV-2, and efforts to develop drugs and vaccines are hampered by the limited knowledge of the molecular details of how SARS-CoV-2 infects cells. Here we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins that physically associated with each of the SARS-CoV-2 proteins using affinity-purification mass spectrometry, identifying 332 high-confidence protein–protein interactions between SARS-CoV-2 and human proteins. Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (of which, 29 drugs are approved by the US Food and Drug Administration, 12 are in clinical trials and 28 are preclinical compounds). We screened a subset of these in multiple viral assays and found two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the sigma-1 and sigma-2 receptors. Further studies of these host-factor-targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19. A human–SARS-CoV-2 protein interaction map highlights cellular processes that are hijacked by the virus and that can be targeted by existing drugs, including inhibitors of mRNA translation and predicted regulators of the sigma receptors.

Author(s): Gordon, David E; Jang, Gwendolyn M; Bouhaddou, Mehdi; Xu, Jiewei; Obernier, Kirsten; O'Meara, Matthew J; Guo, Jeffrey Z; Swaney, Danielle L; Tummino, Tia A; Huttenhain, Ruth; Kaake, Robyn M; Richards, Alicia L; Tutuncuoglu, Beril; Foussard, Helene; Batra, Jyoti; Haas, Kelsey; Modak, Maya; Kim, Minkyu; Haas, Paige; Polacco, Benjamin J; Braberg, Hannes; Fabius, Jacqueline M; Eckhardt, Manon; Soucheray, Margaret; Bennett, Melanie J; Cakir, Merve; McGregor, Michael J; Li, Qiongyu; Naing, Zun Zar Chi; Zhou, Yuan; Peng, Shiming; Kirby, Ilsa T; Melnyk, James E; Chorba, John S; Lou, Kevin; Dai, Shizhong A; Shen, Wenqi; Shi, Ying; Zhang, Ziyang; Barrio-Hernandez, Inigo; Memon, Danish; Hernandez-Armenta, Claudia; Mathy, Christopher JP; Perica, Tina; Pilla, Kala B; Ganesan, Sai J; Saltzberg, Daniel J; Ramachandran, Rakesh; Liu, Xi; Rosenthal, Sara B; Calviello, Lorenzo; Venkataramanan, Srivats; Lin, Yizhu; Wankowicz, Stephanie A; Bohn, Markus; Trenker, Raphael; Young, Janet M; Cavero, Devin; Hiatt, Joe; Roth, Theo; Rathore, Ujjwal; Subramanian, Advait; Noack, Julia; Hubert, Mathieu; Roesch, Ferdinand; Vallet, Thomas; Meyer, Bjorn; White, Kris M; Miorin, Lisa; Agard, David; Emerman, Michael; Ruggero, Davide; Garcia-Sastre, Adolfo; Jura, Natalia; von Zastrow, Mark; Taunton, Jack; Schwartz, Olivier; Vignuzzi, Marco; d'Enfert, Christophe; Mukherjee, Shaeri; Jacobson, Matt; Malik, Harmit S; Fujimori, Danica G; Ideker, Trey; Craik, Charles S | Abstract: An outbreak of the novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 290,000 people since the end of 2019, killed over 12,000, and caused worldwide social and economic disruption1,2. There are currently no antiviral drugs with proven efficacy nor are there vaccines for its prevention. Unfortunately, the scientific community has little knowledge of the molecular details of SARS-CoV-2 infection. To illuminate this, we cloned, tagged and expressed 26 of the 29 viral proteins in human cells and identified the human proteins physically associated with each using affinity- purification mass spectrometry (AP-MS), which identified 332 high confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 existing FDA-approved drugs, drugs in clinical trials and/or preclinical compounds, that we are currently evaluating for efficacy in live SARS-CoV-2 infection assays. The identification of host dependency factors mediating virus infection may provide key insights into effective molecular targets for developing broadly acting antiviral therapeutics against SARS-CoV-2 and other deadly coronavirus strains.

The human pathogen Legionella pneumophila (L.p.) secretes ~330 bacterial effector proteins into the host cell which interfere with numerous cellular pathways and often regulate host cell proteins through post-translational modifications. However, the cellular targets and functions of most L.p. effectors are not known. In order to obtain a global overview of potential targets of these effectors, we analyzed the host cell proteome, ubiquitinome, and phosphoproteome during L.p. infection. Our analysis reveals dramatic spatiotemporal changes in the host cell proteome that are dependent on the secretion of bacterial effectors. Strikingly, we show that L.p. substantially reshapes the mitochondrial proteome and modulates mitochondrial stress response pathways such as the mitochondrial unfolded protein response (UPRmt). To our knowledge, this is the first evidence of manipulation of the UPRmt by a bacterial pathogen in mammalian cells. In addition, we have identified a previously uncharacterized L.p. effector that is targeted to host cell mitochondria and protects mitochondrial network integrity during mitochondrial stress.

The portfolio is often described as an approach effective for the fostering of self-regulated learning in different educational areas. The processes of planning, documenting, and reflecting on individual learning activities are core issues of the portfolio approach. Two aims of the use of portfolios in education are discussed in this contribution. First, the enhancement of self-regulated learning and learning competencies is an important topic. Second, aspects of evaluation and assessment through the use of portfolios are discussed. In this context, the application of portfolios may be seen as an example of a shift from teacher-based instruction to student-centered learning. However, up to now, there has been a lack of empirical evidence regarding these assumptions. In this contribution, three studies are presented that focus on portfolio implementation for the fostering of self-regulated learning in schools, teacher education, and higher education. Central theoretical aspects of the portfolio concept and empirical designs of the studies are described.

The endoplasmic reticulum (ER) is a site of protein biogenesis in eukaryotic cells. Perturbing ER homeostasis activates stress programs collectively called the unfolded protein response (UPR). The UPR enhances production of ER-resident chaperones and enzymes to reduce the burden of misfolded proteins. On resolution of ER stress, ill-defined, selective autophagic programs remove excess ER components. Here we identify Sec62, a constituent of the translocon complex regulating protein import in the mammalian ER, as an ER-resident autophagy receptor. Sec62 intervenes during recovery from ER stress to selectively deliver ER components to the autolysosomal system for clearance in a series of events that we name recovER-phagy. Sec62 contains a conserved LC3-interacting region in the C-terminal cytosolic domain that is required for its function in recovER-phagy, but is dispensable for its function in the protein translocation machinery. Our results identify Sec62 as a critical molecular component in maintenance and recovery of ER homeostasis.

An essential step during the intracellular life cycle of many positive-strand RNA viruses is the rearrangement of host cell membranes to generate membrane-bound replication platforms. For example, Nidovirales and Flaviviridae subvert the membrane of the endoplasmic reticulum (ER) for their replication. However, the absence of conventional ER and secretory pathway markers in virus-induced ER-derived membranes has for a long time hampered a thorough understanding of their biogenesis. Recent reports highlight the analogies between mouse hepatitis virus-, equine arteritis virus-, and Japanese encephalitis virus-induced replication platforms and ER-associated degradation (ERAD) tuning vesicles (or EDEMosomes) that display nonlipidated LC3 at their cytosolic face and segregate the ERAD factors EDEM1, OS-9, and SEL1L from the ER lumen. In this Gem, we briefly summarize the current knowledge on ERAD tuning pathways and how they might be hijacked for viral genome replication. As ERAD tuning components, such as SEL1L and nonlipidated LC3, appear to contribute to viral infection, these cellular pathways represent novel candidate drug targets to combat positive-strand RNA viruses.

Testing declarative memory in laboratory rodents can provide insights into the fundamental mechanisms underlying this type of learning and memory processing, and these insights are likely to be applicable to humans. Here we provide a detailed description of the social discrimination procedure used to investigate recognition memory in rats and mice, as established during the last 20 years in our laboratory. The test is based on the use of olfactory signals for social communication in rodents; this involves a direct encounter between conspecifics, during which the investigatory behavior of the experimental subject serves as an index for learning and memory performance. The procedure is inexpensive, fast and very reliable, but it requires well-trained human observers. We include recent modifications to the procedure that allow memory extinction to be investigated by retroactive and proactive interference, and that enable the dissociated analysis of the central nervous processing of the volatile fraction of an individual's olfactory signature. Depending on the memory retention interval under study (short-term memory, intermediate-term memory, long-term memory or long-lasting memory), the protocol takes ~10 min or up to several days to complete.

The anterior olfactory nucleus (AON), a component of the main olfactory system, is a cortical region that processes olfactory information and acts as a relay between the main olfactory bulbs and higher brain regions such as the piriform cortex. Utilizing a transgenic rat in which an enhanced green fluorescent protein reporter gene is expressed in vasopressin neurones (eGFP-vasopressin), we have discovered a population of vasopressin neurones in the AON. These vasopressin neurones co-express vasopressin V1 receptors. They also co-express GABA and calbinin-D28k indicating that they are neurochemically different from the newly described vasopressin neurons in the main olfactory bulb. We utilized the immediate early gene product, early growth response protein 1 (Egr-1), to examine the functional role of these vasopressin neurons in processing social and non-social odours in the AON. Exposure of adult rats to a conspecific juvenile or a heterospecific predator odour leads to increases in Egr-1 expression in the AON in a subregion specific manner. However, only exposure to a juvenile increases Egr-1 expression in AON vasopressin neurons. These data suggest that vasopressin neurones in the AON may be selectively involved in the coding of social odour information.

Different lines of investigation suggest that the medial amygdala is causally involved in the processing of information linked to social behaviour in rodents. Here we investigated the consequences of temporary inhibition of the medial amygdala by bilateral injections of lidocaine on long-term social recognition memory as tested in the social discrimination task. Lidocaine or control NaCl solution was infused immediately before learning or before retrieval. Our data show that lidocaine infusion immediately before learning did not affect long-term memory retrieval. However, intra-amygdalar lidocaine infusions immediately before choice interfered with correct memory retrieval. Analysis of the aggressive behaviour measured simultaneously during all sessions in the social recognition memory task support the impression that the lidocaine dosage used here was effective as it – at least partially – reduced the aggressive behaviour shown by the experimental subjects towards the juveniles. Surprisingly, also infusions of NaCl solution blocked recognition memory at both injection time points. The results are interpreted in the context of the importance of the medial amygdala for the processing of non-volatile odours as a major contributor to the olfactory signature for social recognition memory.

An essential step during the intracellular life cycle of many positive-strand RNA viruses is the rearrangement of host cell membranes to generate membrane-bound replication platforms. For example, Nidovirales and Flaviviridae subvert the membrane of the endoplasmic reticulum (ER) for their replication. However, the absence of conventional ER and secretory pathway markers in virus-induced ER-derived membranes has for a long time hampered a thorough understanding of their biogenesis. Recent reports highlight the analogies between mouse hepatitis virus-, equine arteritis virus-, and Japanese encephalitis virus-induced replication platforms and ER-associated degradation (ERAD) tuning vesicles (or EDEMosomes) that display nonlipidated LC3 at their cytosolic face and segregate the ERAD factors EDEM1, OS-9, and SEL1L from the ER lumen. In this Gem, we briefly summarize the current knowledge on ERAD tuning pathways and how they might be hijacked for viral genome replication. As ERAD tuning components, such as SEL1L and nonlipidated LC3, appear to contribute to viral infection, these cellular pathways represent novel candidate drug targets to combat positive-strand RNA viruses.

(Molecular Cell 46, 809–819; June 29, 2012)This article has been retracted at the request of the authors. The study reported that expression of misfolded proteins in the ER affects the composition of complexes containing EDEM1, SEL1L, and LC3-I, thereby modulating ERAD activity in the absence of UPR induction. During efforts to extend this work, we have been unable to replicate some of the results obtained by the first author of the paper. The authors have now found that Western blot data shown in Figures 1B, 3A, and 4A were inappropriately processed by the first author of the paper, such that they do not accurately report the original data. This could call into question some of our conclusions on how the presence of misfolded proteins might affect assembly and function of the ERAD machinery. The authors therefore wish to immediately retract the paper. The authors’ lab continues working on the regulation of the ERAD machinery aiming to publish verified data in the near future. The authors sincerely apologize for any difficulties that may have been experienced by the scientific community. The first author, R.B., declined to sign the Retraction Notice.

Nature Cell Biology 18, 1173–1184 (2016); published online 17 October 2016; corrected after print 18 November 2016. In the version of this Article originally published, the name of co-author Eduardo Cebollero Presmanes was coded wrongly resulting in it being incorrect when exported to citation databases.

CMV can infect dendritic cells (DCs), and direct Ag presentation could, therefore, lead to the priming of CMV-specific CD8+ T cells. However, CMV-encoded immune evasins severely impair Ag presentation in the MHC class I pathway; thus, it is widely assumed that cross-presentation drives the priming of antiviral T cells. We assessed the contribution of direct versus cross priming in mouse CMV (MCMV) infection using recombinant viruses. DCs infected with an MCMV strain encoding the gB498 epitope from HSV-1 were unable to stimulate in vitro naive gB498-specific CD8+ T cells from TCR transgenic mice. Infection of C57BL/6 mice with this recombinant virus led, however, to the generation of abundant numbers of gB498-specific T cells in vivo. Of the DC subsets isolated from infected mice, only CD8α+ DCs were able to stimulate naive T cells, suggesting that this DC subset cross-presents MCMV-encoded Ag in vivo. Upon infection of mice with MCMV mutants encoding Ag that can either be well or hardly cross-presented, mainly CD8+ T cells specific for cross-presented epitopes were generated. Moreover, even in the absence of immune evasion genes interfering with MHC class I–mediated Ag presentation, priming of T cells to Ag that can only be presented directly was not observed. We conclude that the host uses mainly DCs capable of cross-presentation to induce the CMV-specific CD8+ T cell response during primary, acute infection and discuss the implications for the development of a CMV vaccine.

Coronaviruses (CoVs) are enveloped viruses responsible for severe respiratory diseases in birds and mammals. In infected cells they induce double membrane vesicles (DMVs) and convoluted membranes (CMs) which are thought to be the site of virus replication. Until recently both the origin of the CoV induced vesicles and the exact localization of CoV replication remained unknown. It was assumed that the vesicles derive from the endoplasmic reticulum (ER). Nevertheless no conventional protein markers of the ER ER to Golgi intermediate compartment (ERGIC) Golgi or coatomer proteins could be detected in these structures.Recent data from our laboratory and others shed light on this mystery. It appears that the Mouse Hepatitis Virus (MHV) a prototype CoV co opts ERAD tuning vesicles as replication platforms. These vesicles are released from the ER but do not contain conventional ER markers or coatomer proteins. Rather they contain ERAD factors such as SEL1L EDEM1 and OS 9 that are constitutively cleared from the folding compartment by so called ERAD tuning programs and display non lipidated LC3 (LC3 I) periferically associated at their limiting membrane. In MHV infected cells the ERAD tuning vesicle markers co localize with viral non structural proteins and double stranded RNA which are DMV markers. The unconventional role of LC3 I in the MHV infection cycle is further supported by the fact that Atg5 and Atg7 both essential proteins for LC3 I to LC3 II conversion and macroautophagy are dispensable for CoV replication and DMV formation. These new insights into CoV replication might lead to new therapies to treat CoV infections. They also reveal a novel role for LC3 in its non lipidated form in both maintenance of cellular proteostasis and viral infection the latter function supported by recent findings showing involvement of LC3 I in equine arteritis virus replication. © 2014 Elsevier Inc. All rights reserved.

Several regulators of endoplasmic reticulum (ER)-associated degradation (ERAD) have a shorter half-life compared to conventional ER chaperones. At steady state, they are selectively removed from the ER by poorly defined events collectively referred to as ERAD tuning. Here we identify the complex comprising the type-I transmembrane protein SEL1L and the cytosolic protein LC3-I as an ERAD tuning receptor regulating the COPII-independent, vesicle-mediated removal of the lumenal ERAD regulators EDEM1 and OS-9 from the ER. Expression of folding-defective polypeptides enhances the lumenal content of EDEM1 and OS-9 by inhibiting their SEL1L:LC3-I-mediated segregation. This raises ERAD activity in the absence of UPR-induction. The mouse hepatitis virus (MHV) subverts ERAD tuning for replication. Consistently, SEL1L or LC3 silencing impair the MHV life cycle. Collectively, our data provide new molecular information about the ERAD tuning mechanisms that regulate ERAD in mammalian cells at the post translational level and how these mechanisms are hijacked by a pathogen.

A recent study reveals a new cellular pathway that clears the endoplasmic reticulum of misfolded, GPI-anchored proteins at the onset of endoplasmic reticulum (ER) stress. This mechanism, termed rapid ER stress–induced export, represents a nontranscriptional response to mitigate acute ER stress.

The anterior olfactory nucleus (AON), a component of the main olfactory system, is a cortical region that processes olfactory information and acts as a relay between the main olfactory bulbs and higher brain regions such as the piriform cortex. Utilizing a transgenic rat in which an enhanced green fluorescent protein reporter gene is expressed in vasopressin neurones (eGFP-vasopressin), we have discovered a population of vasopressin neurones in the AON. These vasopressin neurones co-express vasopressin V1 receptors. They also co-express GABA and calbinin-D28k indicating that they are neurochemically different from the newly described vasopressin neurons in the main olfactory bulb. We utilized the immediate early gene product, early growth response protein 1 (Egr-1), to examine the functional role of these vasopressin neurons in processing social and non-social odours in the AON. Exposure of adult rats to a conspecific juvenile or a heterospecific predator odour leads to increases in Egr-1 expression in the AON in a subregion specific manner. However, only exposure to a juvenile increases Egr-1 expression in AON vasopressin neurons. These data suggest that vasopressin neurones in the AON may be selectively involved in the coding of social odour information.

When tested in the olfactory cued social recognition/discrimination test, rats and mice differ in their retention of a recognition memory for a previously encountered conspecific juvenile: Rats are able to recognize a given juvenile for approximately 45 min only whereas mice show not only short-term, but also long-term recognition memory (≥ 24 h). Here we modified the social recognition/social discrimination procedure to investigate the neurobiological mechanism(s) underlying the species differences. We presented a conspecific juvenile repeatedly to the experimental subjects and monitored the investigation duration as a measure for recognition. Presentation of only the volatile fraction of the juvenile olfactory signature was sufficient for both short- and long-term recognition in mice but not rats. Applying additional volatile, mono-molecular odours to the "to be recognized" juveniles failed to affect short-term memory in both species, but interfered with long-term recognition in mice. Finally immunocytochemical analysis of c-Fos as a marker for cellular activation, revealed that juvenile exposure stimulated areas involved in the processing of olfactory signals in both the main and the accessory olfactory bulb in mice. In rats, we measured an increased c-Fos synthesis almost exclusively in cells of the accessory olfactory bulb. Our data suggest that the species difference in the retention of social recognition memory is based on differences in the processing of the volatile versus non-volatile fraction of the individuals' olfactory signature. The non-volatile fraction is sufficient for retaining a short-term social memory only. Long-term social memory - as observed in mice - requires a processing of both the volatile and non-volatile fractions of the olfactory signature.

An organotypic cell culture (OCC) model of the rat hypothalamic paraventricular nucleus (PVN) was established to monitor intracellular calcium levels ([Ca(2+)](i)) of magnocellular neurons in response to glutamate and nitric oxide (NO). The histoarchitectural organization of these cultures was characterized either by immunohistochemical labeling of vasopressin, neuronal nitric oxide synthase (nNOS) and the neuronal marker NeuN or by the enzyme histochemical NADPH-diaphorase staining. A distinct NeuN positive cell population in 14-days old OCC's was confirmed as being the PVN by its vasopressin- and nNOS-immunostained neurons as well as by its NADPH-diaphorase labeling. Life cell imaging was performed using the [Ca(2+)](i) sensor Fluo-4 to measure [Ca(2+)](i) transients in response to bath applications of glutamate, high potassium (60 mM), and ATP. The glutamate-induced [Ca(2+)](i) response was mimicked by AMPA but not NMDA in the PVN. NMDA, however, elicited a [Ca(2+)](i) transient in a different area of the OCC that corresponds to the suprachiasmatic nucleus indicating the potential effectiveness of the stimulus. The AMPA-receptor blocker NBQX abolished the glutamate-induced response in the PVN. An inhibition of endogenous NO production by the NOS inhibitor L-NAME decreased the amplitude of AMPA- and glutamate-induced [Ca(2+)](i) rises. Taken together, these data suggest that AMPA mediates the glutamate-induced [Ca(2+)](i) rises within the PVN, where endogenous NO is able to modulate such glutamate signaling in OCC.

Toll-like receptor 9 (TLR9) triggering is a promising novel strategy to combat cancer as it induces innate and adaptive immunity responses. B-cell lymphoma is unique in this context as tumor cells express TLR9 and may harbor latent Epstein-Barr virus (EBV), a gamma-herpesvirus with remarkable oncogenic potential when latent. Latent EBV may be promoted by TLR9 triggering via suppression of lytic EBV. Here, we elaborated an initial assessment of the impact of TLR9 triggering on EBV-positive and EBV-negative B-cell lymphoma using Burkitt's lymphoma (BL) cell lines as an in vitro model. We show that, independent of the presence of EBV, the TLR9 ligand oligodeoxynucleotide (ODN) CpG-2006 may or may not induce caspase-dependent cell death in BL cells. Moreover, ODN CpG-2006-induced cell death responses of BL cells were associated with TLR9 single-nucleotide polymorphisms (SNPs) rs5743836 or rs352140, which we detected in primary BL tumors and in peripheral blood from healthy individuals at similar frequencies. Thus, our findings suggest that the effect of TLR9 agonists on BL cells should be tested in vitro before installment of therapy and TLR9 SNPs in BL patients should be determined as potential biological markers for the therapeutic response to treatment targeting innate immunity.