Potent broadly neutralizing antibody VIR-3434 controls hepatitis B and D virus infection and reduces HBsAg in humanized mice

BACKGROUND & AIMS

Chronic hepatitis B is a 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 treat chronic hepatitis B and chronic hepatitis D.

METHODS

HBsAg-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 3 weeks post HBV inoculation (spreading phase) or during stable HBV or HBV/HDV coinfection (chronic phase).

RESULTS

From a panel of human anti-HBs mAbs, VIR-3434 was selected and engineered for pre-clinical development. VIR-3434 targets a conserved, conformational epitope within the antigenic loop of HBsAg and neutralized HBV and HDV infection with 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 the increase in intrahepatic HBV RNA and covalently closed circular DNA. 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.

CONCLUSIONS

The potently neutralizing anti-HBs mAb VIR-3434 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.

IMPACT AND IMPLICATIONS

Chronic infection with hepatitis B virus and co-infection with hepatitis D virus place approximately 290 million individuals worldwide at risk of severe liver disease and cancer. 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.

Neutralization, effector function and immune imprinting of Omicron variants

Currently circulating SARS-CoV-2 variants have acquired convergent mutations at hot spots in the receptor-binding domain1 (RBD) of the spike protein. The effects of these mutations on viral infection and transmission and the efficacy of vaccines and therapies remains poorly understood. Here we demonstrate that recently emerged BQ.1.1 and XBB.1.5 variants bind host ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1, XBB.1 and BN.1 RBDs bound to the fragment antigen-binding region of the S309 antibody (the parent antibody for sotrovimab) and human ACE2 explain the preservation of antibody binding through conformational selection, altered ACE2 recognition and immune evasion. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1 and hamsters challenged with XBB.1.5. Vaccine-elicited human plasma antibodies cross-react with and trigger effector functions against current Omicron variants, despite a reduced neutralizing activity, suggesting a mechanism of protection against disease, exemplified by S309. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring the role of persistent immune imprinting.

Therapeutic and vaccine-induced cross-reactive antibodies with effector function against emerging Omicron variants

Currently circulating SARS-CoV-2 variants acquired convergent mutations at receptor-binding domain (RBD) hot spots. 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.

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages

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.

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages

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.

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages

SARS-CoV-2 Omicron sublineages carry distinct spike mutations and represent an antigenic shift resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters result in potent plasma neutralizing activity against Omicron BA.1 and BA.2 and that breakthrough infections, but not vaccination-only, induce neutralizing activity 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 and BA.2 receptor-binding domains whereas Omicron primary infections elicit B cells of narrow specificity. While most clinical antibodies have reduced neutralization of Omicron, we identified an ultrapotent pan-variant antibody, that is unaffected by any Omicron lineage spike mutations and is a strong candidate for clinical development.

ACE2-binding exposes the SARS-CoV-2 fusion peptide to broadly neutralizing coronavirus antibodies

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.

Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift

The recently emerged SARS-CoV-2 Omicron variant encodes 37 amino acid substitutions in the spike protein, 15 of which are in the receptor-binding domain (RBD), thereby raising concerns about the effectiveness of available vaccines and antibody-based therapeutics. Here we show that the Omicron RBD binds to human ACE2 with enhanced affinity, relative to the Wuhan-Hu-1 RBD, and binds to mouse ACE2. Marked reductions in neutralizing activity were observed against Omicron compared to the ancestral pseudovirus in plasma from convalescent individuals and from individuals who had been vaccinated against SARS-CoV-2, but this loss was less pronounced after a third dose of vaccine. Most monoclonal antibodies that are directed against the receptor-binding motif lost in vitro neutralizing activity against Omicron, with only 3 out of 29 monoclonal antibodies retaining unaltered potency, including the ACE2-mimicking S2K146 antibody¹. Furthermore, a fraction of broadly neutralizing sarbecovirus monoclonal antibodies neutralized Omicron through recognition of antigenic sites outside the receptor-binding motif, including sotrovimab², S2X259³ and S2H97⁴. The magnitude of Omicron-mediated immune evasion marks a major antigenic shift in SARS-CoV-2. Broadly neutralizing monoclonal antibodies that recognize RBD epitopes that are conserved among SARS-CoV-2 variants and other sarbecoviruses may prove key to controlling the ongoing pandemic and future zoonotic spillovers.

Antibody-mediated broad sarbecovirus neutralization through ACE2 molecular mimicry

Understanding broadly neutralizing sarbecovirus antibody responses is key to developing countermeasures against 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 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 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.

Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift

The 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 mAb ¹ , retaining unaltered potency. Furthermore, a fraction of broadly neutralizing sarbecovirus mAbs recognizing antigenic sites outside the RBM, including sotrovimab ² , S2X259 ³ and S2H97 ⁴ , 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.

Antibody-mediated broad sarbecovirus neutralization through ACE2 molecular mimicry

Understanding broadly neutralizing sarbecovirus antibody responses is key to developing countermeasures effective against SARS-CoV-2 variants and future spillovers of other sarbecoviruses. Here we describe the isolation and characterization of a human monoclonal antibody, designated S2K146, broadly neutralizing viruses belonging to all three sarbecovirus clades known to utilize ACE2 as entry receptor and protecting therapeutically against SARS-CoV-2 beta challenge in hamsters. Structural and functional studies show that most of the S2K146 epitope residues are shared with the ACE2 binding site and that the antibody inhibits receptor attachment competitively. Viral passaging experiments underscore an unusually high barrier for emergence of escape mutants making it an ideal candidate for clinical development. These findings unveil a key site of vulnerability for the development of a next generation of vaccines eliciting broad sarbecovirus immunity.

Broad betacoronavirus neutralization by a stem helix-specific human antibody

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.

Lectins enhance SARS-CoV-2 infection and influence neutralizing antibodies

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.

A SARS-CoV-2 protein interaction map reveals targets for drug repurposing

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 SARS-CoV-2 protein interaction map reveals targets for drug repurposing

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 disruption^1,2. 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 SARS-CoV-2-Human Protein-Protein Interaction Map Reveals Drug Targets and Potential Drug-Repurposing

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 disruption 1,2 . 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.

Ultrafast Relaxation Dynamics of the Antiferrodistortive Phase in Ca Doped SrTiO_{3}

The ultrafast dynamics of the octahedral rotation in Ca:SrTiO_{3} is studied by time-resolved x-ray diffraction after photoexcitation over the band gap. By monitoring the diffraction intensity of a superlattice reflection that is directly related to the structural order parameter of the soft-mode driven antiferrodistortive phase in Ca:SrTiO_{3}, we observe an ultrafast relaxation on a 0.2 ps timescale of the rotation of the oxygen octahedron, which is found to be independent of the initial temperature despite large changes in the corresponding soft-mode frequency. A further, much smaller reduction on a slower picosecond timescale is attributed to thermal effects. Time-dependent density-functional-theory calculations show that the fast response can be ascribed to an ultrafast displacive modification of the soft-mode potential towards the normal state induced by holes created in the oxygen 2p states.

Experimental Study and Modeling of the UV-Vis and Infrared Spectra of the [VO(O2)Hheida]- Complex Dissolved in Water

Combined theoretical and experimental studies of the [VO(O₂)Hheida]^- anion dissolved in water that may serve as a functional model for vanadium haloperoxidase enzymes have been performed. The geometrical structure and absorption and vibrational spectra of this system have been evaluated within the framework of density functional theory (DFT). The obtained theoretical results on the equilibrium structure and optical spectra are in quite good agreement with the experimental data. With the aid of the combination of UV-visible spectroscopy and electronic structure calculations, it has been revealed that, in the apparent absorption spectra of the [VO(O₂)Hheida]^- anion, the highest in energy band corresponds to a ligand to metal electron excitation, while the band with a maximum at 430 nm arises from the peroxo group. The calculations also reproduce quite well the positions, intensities and the grouping of frequencies in the near-infrared (NIR) spectra. The visualization of the calculated vibrations in the energy range of 400-1100 cm^-1 has been presented.

Consequences of temporary inhibition of the medial amygdala on social recognition memory performance in mice

Different lines of investigation suggest that the medial amygdala is causally involved in the processing of information linked to social behavior 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 behavior 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 behavior shown by the experimental subjects toward 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 odors as a major contributor to the olfactory signature for social recognition memory.

Optimisation of a sol–gel synthesis route for the preparation of MgF2 particles for a large scale coating process

Preparation of transparent and low viscous MgF₂ sols via sol–gel technique which can be applied for antireflective coatings on glass substrates is described.

A sphingosine kinase inhibitor combined with temozolomide induces glioblastoma cell death through accumulation of dihydrosphingosine and dihydroceramide, endoplasmic reticulum stress and autophagy

Glioblastomas (GBMs) are very aggressive tumors with low chemosensitivity. The DNA-alkylating agent temozolomide (TMZ) is currently the most efficient chemotoxic drug for GBM therapy; however, many patients develop resistance to TMZ. Combining TMZ with another agent could present an improved treatment option if it could overcome TMZ resistance and avoid side effects. Sphingosine kinase inhibitors (SKIs) have emerged as anticancer agents. Sphingosine kinases are often overexpressed in tumors where their activity of phosphorylating sphingosine (Sph) contributes to tumor growth and migration. They control the levels of the pro-apoptotic ceramide (Cer) and Sph and of the pro-survival sphingosine-1 phosphate. In the present work, TMZ was combined with a specific SKI, and the cytotoxic effect of each drug alone or in combination was tested on GBM cell lines. The combination of sublethal doses of both agents resulted in the cell death potentiation of GBM cell lines without affecting astrocyte viability. It triggered a caspase-3-dependent cell death that was preceded by accumulation of dihydrosphingosine (dhSph) and dihydroceramide (dhCer), oxidative stress, endoplasmic reticulum stress, and autophagy. Autophagy was identified as the crucial switch that facilitated induction of this cell death potentiation. The sublethal dose of the inhibitor induced these stress events, whereas that of TMZ induced the destructive autophagy switch. Remarkably, neither Cer nor Sph, but rather the Cer intermediates, dhSph and dhCer, was involved in the cytotoxicity from the combination. Cell lines sensitive to the combination expressed low levels of the antioxidant enzyme glutathione peroxidase-1, indicating this enzyme as a potential marker of sensitivity to such treatment. This work shows for the first time a strong interaction between a SKI and TMZ, leading to a tumor cell-specific death induction. It further demonstrates the biological relevance of dihydrosphingolipids in cell death mechanisms and emphasizes the potential of drugs that affect sphingolipid metabolism for cancer therapy.

Proteostasis: bad news and good news from the endoplasmic reticulum

The endoplasmic reticulum (ER) is an intracellular compartment dedicated to the synthesis and maturation of secretory and membrane proteins, totalling about 30% of the total eukaryotic cells proteome. The capacity to produce correctly folded polypeptides and to transport them to their correct intra- or extracellular destinations relies on proteostasis networks that regulate and balance the activity of protein folding, quality control, transport and degradation machineries. Nutrient and environmental changes, pathogen infection aging and, more relevant for the topics discussed in this review, mutations that impair attainment of the correct 3D structure of nascent polypeptide chains may compromise the activity of the proteostasis networks with devastating consequences on cells, organs and organisms' homeostasis. Here we present a review of mechanisms regulating folding and quality control of proteins expressed in the ER, and we describe the protein degradation and the ER stress pathways activated by the expression of misfolded proteins in the ER lumen. Finally, we highlight select examples of proteopathies (also known as conformational disorders or protein misfolding diseases) caused by protein misfolding in the ER and/or affecting cellular proteostasis and therapeutic interventions that might alleviate or cure the disease symptoms.

Non-Lipidated LC3 is Essential for Mouse Hepatitis Virus Infection

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.

Priming of CD8+ T cells against cytomegalovirus-encoded antigens is dominated by cross-presentation

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.

Changes in response properties of rostral ventromedial medulla neurons during prolonged inflammation: modulation by neurokinin-1 receptors

Activation of neurokinin-1 (NK-1) receptors in the rostral ventromedial medulla (RVM) can facilitate pain transmission in conditions such as inflammation, and thereby contribute to hyperalgesia. Since blockade of NK-1 receptors in the RVM can attenuate hyperalgesia produced by prolonged inflammation, we examined the role of NK-1 receptors in changes of response properties of RVM neurons following four days of hind paw inflammation with complete Freund's adjuvant. Recordings were made from functionally identified ON, OFF and NEUTRAL cells in the RVM. Spontaneous activity and responses evoked by a series of mechanical (10, 15, 26, 60, 100, and 180 g) and heat (34-50 °C) stimuli applied to the inflamed and non-inflamed hind paws were determined before and at 15 and 60 min after injection of the NK-1-antagonist L-733,060 or vehicle into the RVM. Prolonged inflammation did not alter the proportions of functionally-identified ON, OFF and NEUTRAL cells. ON cells exhibited enhanced responses to mechanical (60-100g) and heat (48-50 °C) stimuli applied to the inflamed paw, which were attenuated by L-733,060 but not by vehicle. Inhibitory responses of OFF cells evoked by mechanical stimuli applied to the inflamed paw were also inhibited by L-733,060, but responses evoked by stimulation of the contralateral paw were increased. Heat-evoked responses of OFF cells were not altered by L-733,060. Also, neither L-733,060 nor vehicle altered spontaneous ongoing discharge rate of RVM neurons. These data indicate that NK-1 receptors modulate excitability of ON cells which contribute to both mechanical and heat hyperalgesia, whereas NK-1 modulation of OFF cells contributes to mechanical hyperalgesia during prolonged inflammation.

Unconventional roles of nonlipidated LC3 in ERAD tuning and coronavirus infection

Secretory and membrane proteins attain their native structure in the endoplasmic reticulum (ER). Folding-defective polypeptides are selected for degradation by processes collectively defined as ER-associated degradation (ERAD). Enhanced ERAD activity may interfere with protein biogenesis by inappropriately targeting not-yet-native protein folding intermediates for disposal. The regulation of ERAD is therefore crucial to maintain cellular proteostasis. At steady-state, select ERAD regulators are constitutively removed from the ER in a series of processes collectively defined as ERAD tuning. This sets the ERAD activity at levels that do not interfere with completion of ongoing folding programs. Our latest work highlights a crucial, autophagy-independent role of nonlipidated LC3 (LC3-I) as part of a membrane-bound receptor that insures the vesicle-mediated clearance of at least two ERAD regulators from the ER, EDEM1 and OS9. This pathway is hijacked by coronaviruses (CoV), and silencing of LC3 substantially inhibits viral replication.

Testing declarative memory in laboratory rats and mice using the nonconditioned social discrimination procedure

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.

Expression of early growth response protein 1 in vasopressin neurones of the rat anterior olfactory nucleus following social odour exposure

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 importance of the volatile and non-volatile fractions of an olfactory signature for individual social recognition in rats versus mice and short-term versus long-term memory

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 intrinsic vasopressin system in the olfactory bulb is involved in social recognition

Many peptides, when released as chemical messengers within the brain, have powerful influences on complex behaviours. Most strikingly, vasopressin and oxytocin, once thought of as circulating hormones whose actions were confined to peripheral organs, are now known to be released in the brain where they play fundamentally important roles in social behaviours1. In humans, disruptions of these peptide systems have been linked to several neurobehavioural disorders, including Prader-Willi syndrome, affective disorders, and obsessive-compulsive disorder, and polymorphisms of the vasopressin V1a receptor have been linked to autism2,3. Here we report that the rat olfactory bulb contains a large population of interneurones which express vasopressin, that blocking the actions of vasopressin in the olfactory bulb impairs the social recognition abilities of rats, and that vasopressin agonists and antagonists can modulate the processing of information by olfactory bulb neurones. The findings indicate that social information is processed in part by a vasopressin system intrinsic to the olfactory system.

Introgression of genomic components from Chinese Brassica rapa contributes to widening the genetic diversity in rapeseed (B. napus L.), with emphasis on the evolution of Chinese rapeseed

In spite of its short history of being an oil crop in China, the Chinese semi-winter rapeseed (Brassica napus L., 2n = 38, AACC) has been improved rapidly by intentional introgression of genomic components from Chinese B. rapa (2n = 20, AA). As a result, the Chinese semi-winter rapeseed has diversified genetically from the spring and winter rapeseed grown in the other regions such as Europe and North America. The objectives of this study were to investigate the roles of the introgression of the genomic components from the Chinese B. rapa in widening the genetic diversity of rapeseed and to verify the role of this introgression in the evolution of the Chinese rapeseed. Ten lines of the new type of rapeseed, which were produced by introgression of Chinese B. rapa to Chinese normal rapeseed, were compared for genetic diversity using amplified fragment length polymorphism (AFLP) with three groups of 35 lines of the normal rapeseed, including 9 semi-winter rapeseed lines from China, 9 winter rapeseed lines from Europe and 17 spring rapeseed lines from Northern Europe, Canada and Australia. Analysis of 799 polymorphic fragments revealed that within the groups, the new type rapeseed had the highest genetic diversity, followed by the semi-winter normal rapeseed from China. Spring and winter rapeseed had the lowest genetic diversity. Among the groups, the new type rapeseed group had the largest average genetic distance to the other three groups. Principal component analysis and cluster analysis, however, could not separate the new type rapeseed group from Chinese normal rapeseed group. Our data suggested that the introgression of Chinese B. rapa could significantly diversify the genetic basis of the rapeseed and play an important role in the evolution of Chinese rapeseed. The use of new genetic variation for the exploitation of heterosis in Brassica hybrid breeding is discussed.

AMPA receptor-induced intracellular calcium response in the paraventricular nucleus is modulated by nitric oxide: calcium imaging in a hypothalamic organotypic cell culture model

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.

Three-dimensional topographic angiography in chorioretinal vascular disease

PURPOSE

To evaluate a new angiographic technique that offers three-dimensional imaging of chorioretinal vascular diseases.

METHODS

Fluorescein (FA) and indocyanine green angiography (ICGA) were performed using a confocal scanning laser ophthalmoscope. Tomographic series with 32 images per set were taken over a depth of 4 mm at an image frequency of 20 Hz. An axial analysis was performed for each x/y position to determine the fluorescence distribution along the z-axis. The location of the onset of fluorescence at a defined threshold intensity was identified and a depth profile was generated. The overall results of fluorescence topography were displayed in a gray scale-coded image and three-dimensional relief.

RESULTS

Topographic angiography delineated the choriocapillary surface covering the posterior pole with exposed larger retinal vessels. Superficial masking of fluorescence by hemorrhage or absorbing fluid did not preclude detection of underlying diseases. Choroidal neovascularization (CNV) appeared as a vascular formation with distinct configuration and prominence. Chorioretinal infiltrates exhibited perfusion defects with dye pooling. Retinal pigment epithelium detachments (PEDs) demonstrated dynamic filling mechanisms. Intraretinal extravasation in retinal vascular disease was detected within a well-demarcated area with prominent retinal thickening.

CONCLUSIONS

Confocal topographic angiography allows high-resolution three-dimensional imaging of chorioretinal vascular and exudative diseases. Structural vascular changes (e.g., proliferation) are detected in respect to location and size. Dynamic processes (e.g., perfusion defects, extravasation, and barrier dysfunction) are clearly identified and may be quantified. Topographic angiography is a promising technique in the diagnosis, therapeutic evaluation, and pathophysiological evaluation of macular disease.

Confocal laser scanning fluorescence topography: a new method for three-dimensional functional imaging of vascular structures

Three-dimensional topography of perfused vascular structures is possible via confocal laser scanning of intravascular fluorescence. The lateral resolution is given by the spot size of the scanning laser beam (optimally 10 microm at the retina). The axial resolution, however, depends on the accuracy of detection of the surface of the fluorescent structure, which is typically one order of magnitude higher (30 microm at the retina) than the confocal resolution. The vascular structure is stained with an appropriate fluorescent dye prior to the investigation using standard systemic dye injection. Confocal scanning of the fluorescence in planes of different depths within the vascular structure under investigation leads to a three-dimensional data set. Signal processing includes passive eye tracking, lateral averaging and axial determination of the surface of the fluorescent structure. The potential of this new technique is demonstrated by showing the topography of physiological vessel structures as well as of selected vascular diseases such as cone dystrophy, RPE detachment, choroidal haemangioma and retinal laser coagulation. Confocal laser angioscopic fluorescence topography (CLAFT) measures the three-dimensional surface structure of functional (perfused) vasculature and surrounding leakage. CLAFT may help to diagnose and quantify status and time course of vascular diseases.

The human gut bacteria Bacteroides thetaiotaomicron and Fusobacterium varium produce putrescine and spermidine in cecum of pectin-fed gnotobiotic rats

Pectin is a soluble indigestible polysaccharide that stimulates cecal polyamine formation in rats. Bacteroides and fusobacteria, two numerically dominant bacterial population groups in the large intestine, were found to synthesize in vitro high amounts of spermidine and putrescine. The purpose of this study was to elucidate the effect of pectin on the polyamine production by defined bacterial species in vivo. Germfree male Wistar rats (n = 18) were randomly assigned to one of three treatments: (i) monoassociation with Bacteroides thetaiotaomicron + fiber-free diet; (ii) diassociation with B. thetaiotaomicron + Fusobacterium varium + fiber-free diet or (iii) diassociation with B. thetaiotaomicron + F. varium + fiber-free diet + 10% pectin. The cecal contents of monoassociated rats fed fiber-free diet contained large amounts (1.51+/-0.21 micromol/dry total cecum content) of spermidine which was the major polyamine. The cecum of diassociated rats fed the fiber-free diet contained even higher concentrations of spermidine (2.53+/-0.21 micromol/dry total cecum content) and also putrescine, which was now the dominant polyamine (putrescine 0.32+/-0.28 vs. 3.01+/-0.28 micromol/dry total cecum content; monoassociation vs. diassociation). Pectin consumption by diassociated rats led to an additional increase in the cecal concentrations of all polyamines: putrescine, spermidine and spermine were 40, 37 and 100%, respectively, higher in the diassociated rats consuming the pectin diet than in those consuming the pectin-free diet. Since the microbial counts in the cecum did not differ in the diassociated treatment groups, the elevated concentrations of polyamines observed in the pectin group must have been due to stimulated bacterial polyamine synthesis. The decline of individual polyamines from cecum to feces detected at the end of the study in all treatment groups and the high microbial counts in the cecum and in feces suggest that bacterial polyamines are absorbed in cecum and colon. Pectin stimulates intestinal microbes to synthesize large amounts of polyamines which may be utilized by the host.

[Confocal indocyanine green angiography with 3-dimensional topography. Results in choroid neovascularization (CNV)]

BACKGROUND

Confocal indocyanin green angiography (ICGA) offers detailed two-dimensional imaging of choroidal pathologies. However, the spatial extension of lesions is not reproduced. We developed a novel method for three-dimensional documentation of choroidal vascular abnormalities.

METHODS

Focal series were performed using a laser scanning ophthalmoscope (Heidelberg Retina Angiograph). Thirty-two images within a distance of 4 mm were taken at a frequency of 20 Hz. Following correction of dislocation, a surface of normalized fluorescence intensity was determined and displayed topographically.

RESULTS

In physiological eyes three-dimensional ICGA demonstrates the homogeneous concavity of the choroid with prominent overlay of retinal vessels. Classic choroidal neovascularization (CNV) imposes as substantial elevation. Occult CNV are demarcated despite negative conventional ICGA due to reduction of blocking phenomena. Therapeutic interventions such as photocoagulation, photodynamic therapy and surgery induce a resolution of CNV with or without residual defects within the choroidal pattern.

CONCLUSION

Topographic ICGA allows for the first time in-vivo representation of prominence and depth of vascularized pathologies and provides a tool for improved diagnostic and therapeutic evaluation.

An algorithm for the fast registration of image sequences obtained with a scanning laser ophthalmoscope

There is a need to quantify images of retinal pathology so that the natural progression and response to various forms of treatment such as laser therapy can be reliably monitored. The images obtained with a scanning laser ophthalmoscope are better than those from a traditional fundus camera, and the method of data collection leads naturally to digitization and quantitative techniques. However, during any angiographic sequence, there will inevitably be eye movement and it is essential that this be corrected for prior to the application of quantitative analysis. This article presents an algorithm (the smart localized binary correlation algorithm) for the automatic registration of fluorescein or indocyanine green angiograms which is based on localized correlation of binary templates in binary thresholded gradient images. The use of this algorithm decreases the calculation time up to 180 times when compared with the fastest applicable algorithm found in the literature. The algorithm only detects translational movement of the images but proves to be robust against rotational movement for the small angles (< 4 degrees) encountered in ophthalmic imaging. Registration accuracy is estimated to be +/- 2 pixels.

Dietary guar gum and pectin stimulate intestinal microbial polyamine synthesis in rats

The effects of two highly fermentable dietary fibers (guar gum and pectin) on the type and concentrations of cecal polyamines as affected by the intestinal microflora were studied in groups of germ-free (n = 10/group) and conventional rats (n = 6/group). Both germ-free and conventional rats were randomly assigned to one of three treatments as follows: 1) fiber-free control diet, 2) control diet + 10% guar gum and 3) control diet + 10% pectin. In germ-free rats, guar gum and pectin had no effect on cecal polyamine concentrations. Putrescine was confirmed to be the major endogenous polyamine within the gut lumen. In cecal contents of conventional rats, both guar gum and pectin led to the appearance of cadaverine and to elevated putrescine concentrations in comparison with the fiber-free control diet (1.35 +/- 0.15 and 2.27 +/- 0.32, respectively, vs. 0.20 +/- 0.03 micromol/g dry weight, P < 0.05). The cecal cadaverine concentration was higher in pectin- than in guar-fed rats (8.20 +/- 0.89 vs. 1.92 +/- 0.27 micromol/g dry weight, P < 0.05). Counts of total bacteria, bacteroides, fusobacteria and enterobacteria were higher (P < 0.05) in rats fed guar gum and pectin. Bifidobacteria were found exclusively in guar-fed rats. In vitro studies on selected species representing the numerically dominant population groups of the human gut flora (bacteroides, fusobacteria, anaerobic cocci and bifidobacteria) were examined for their ability to synthesize intracellular polyamines. These experiments demonstrated the ability of bacteroides, fusobacteria and anaerobic cocci to synthesize high amounts of putrescine and spermidine. Calculations based on these results suggest that the intestinal microflora are a major source of polyamines in the contents of the large intestine.

Single-shot spatially resolved characterization of laser-induced shock waves in water

We have developed an optical method for single-shot spatially resolved shock-wave peak-pressure measurements. A schlieren technique and streak photography were used to follow the propagation of the shock wave. The shock position r as a function of time was extracted from the streak images by digital image-processing techniques. The resulting r(t) curves were differentiated with respect to time to yield shock-wave velocities that were converted to shock pressures with the aid of the equation of the state of the medium. Features and limitations of the technique are demonstrated and discussed on the basis of measurements of shock-wave amplitudes generated by laser-induced breakdown in water. For this purpose, laser pulses of 6-ns duration and pulse energies of 1 and 10 mJ were focused into a cuvette containing water. Complete p(t) curves were obtained with a temporal resolution in the subnanosecond range. The total acquisition and processing time for a single event is ~2 min. The shock-peak pressures at the source were found to be 8.4 ? 1.5 and 11.8 ? 1.6 GPa for pulse energies of 1 and 10 mJ, respectively. Within the first two source radii, the shock-wave pressure p(r) was found to decay on average in proportion to r(-1.3?0.2) for both pulse energies. Thereafter the pressure dropped in proportion to r(-2.2?0.1). In water the method can be used to measure shock-wave amplitudes exceeding 0.1 GPa. Because it is a single-shot technique, the method is especially suited for investigating events with large statistical variations.