Influenza viruses pose a global health threat, particularly to infants and the elderly. The viruses constantly change. As a consequence, vaccines have to be constantly adapted and therapeutics may cease to be effective. Therefore, we seek to develop novel influenza therapies. One focus of our work is on the host cell protease TMPRSS2 since we obtained evidence that TMPRSS2 depend on the protease for acquisition of infectivity and spread in the host. Moreover, we are investigating how defective interfering particles (DIPs) can be generated in the absence of infectious virus and how DIPs inhibit influenza virus infection.
Emerging viruses that are transmitted from animals to humans may cause severe disease. Outbreaks frequently occur abroad but the responsible viruses might be imported into Germany due to infected travelers. We are investigating how emerging viruses interact with host cells and cause disease. A recently started project focuses on lymphocytic choriomeningitis virus (LCMV). LCMV is related to the highly pathogenic Lassa virus, circulates globally and is responsible for outbreaks of lethal hepatitis in marmoset colonies. Moreover, LCMV may cause severe disease in immunosuppressed patients and can constitute a threat to pregnant woman and their unborn children. In addition to LCMV and Ebola virus we are also investigating MERS coronavirus. The aim of our research is to develop cell culture systems that allow predicting transmissibility and thus pandemic potential of novel MERS coronavirus variants.
Another focus of our research is on primate herpesviruses. The transmission of herpes B virus from macaques to humans as well as transmission of related viruses among non-human primates can cause serve disease. We are investigating which viral and host factors determine whether infection will result in severe disease. Moreover, we are developing diagnostics for herpesvirus infections of non-human primates. Finally, we are offering diagnostics for many other viral infections of non-human primates, including a chip-based antibody detection system useful for screening of non-human primate colonies.
Recent publications summarized in three sentences
Defective interfering particles (DIP) for influenza therapy
This study from the laboratory of Prof. Reichl, Max-Planck-Institute Magdeburg, shows that genetically homogenous influenza A virus defective interfering particles (DIPs) produced in cell culture can inhibit influenza A virus infection in a rodent model. These encouraging results indicate that DIPs could be developed as novel influenza therapy.
Hein et al, Cell culture-based production and in vivo characterization of purely clonal defective interfering influenza virus particles. BMC Biol. 2021 May 3;19(1):91.
SARS-CoV-2 can evade neutralizing antibodies
This study of the DPZ Infection Biology Unit shows that SARS-CoV-2 variants Beta (B.1.351) and Gamma (P.1) can partially evade neutralizing antibodies, while the antibody evasion of the Alpha variant (B.1.1.7) is inefficient. This study is among the first to show that SARS-CoV-2 can acquire mutations that allow immune evasion and may promote viral spread in populations with a high percentage of convalescent individuals.
Hoffmann et al, SARS-CoV-2 variants B.1.351 and P.1 escape from neutralizing antibodies. Cell. 2021 Apr 29;184(9):2384-2393.e12.
SARS-CoV-2 is well adapted to proteases and temperature in human airways
This study from the laboratory of Prof. Naesens, KU Leuven, Belgium, shows which airway proteases apart from TMPRSS2 are used by SARS-CoV-2 spike for activation and which amino acids in spike determine activation efficiency. Further, the study shows that the spike-protein is robustly expressed at the temperature in human airways.
Laporte et al, The SARS-CoV-2 and other human coronavirus spike proteins are fine-tuned towards temperature and proteases of the human airways. PLoS Pathog. 2021 Apr 22;17(4):e1009500.
SARS-CoV-2 acquires mutations in mink that reduce antibody-mediated neutralization
SARS-CoV-2 has been transmitted from humans to mink and acquired mutations during spread in mink. Subsequently, the mutated viruses were transmitted back to humans. The Infection Biology Unit shows in this manuscript that mutations acquired in mink can reduce antibody-mediated neutralization.
Hoffmann et al, SARS-CoV-2 mutations acquired in mink reduce antibody-mediated neutralization. Cell Rep. 2021 Apr 20;35(3):109017.
Protease inhibitor produced in the human body blocks SARS-CoV-2 infection
Studies of the Infection Biology Unit revealed that SARS-CoV-2 uses the cellular protease for activation of its spike protein. The present manuscript from the laboratory of Prof. Münch, University Medical Center, Ulm, demonstrates that alpha 1 antitrypsin, a protease inhibitor produced in the human body during inflammation, blocks TMPRSS2 and SARS-CoV-2 infection.
Wettstein et al, Alpha-1 antitrypsin inhibits TMPRSS2 protease activity and SARS-CoV-2 infection. Nat Commun. 2021 Mar 19;12(1):1726.
Methods for analysis of SARS-CoV-2 entry into cells and its inhibition
This manuscript from the laboratory of Prof. Gulbins, University Hospital Essen, reports methods for the analysis of SARS-CoV-2 entry into epithelial cells and its inhibition by antiviral compounds.
Becker et al, Ex vivo assay to evaluate the efficacy of drugs targeting sphingolipids in preventing SARS-CoV-2 infection of nasal epithelial cells. STAR Protoc. 2021 Mar 19;2(1):100356. doi: 10.1016/j.xpro.2021.100356.
A novel strategy to inhibit Ebola virus
This study from the laboratory of Prof. Pfeilschifter, University Frankfurt am Main, shows that activating an enzyme that modifies sphingosine, a component of the membrans, blocks Ebola virus infection of target cells.
Imre et al, The sphingosine kinase 1 activator, K6PC-5, attenuates Ebola virus infection. iScience. 2021 Mar 5;24(4):102266.
Dalbavancin: novel candidate for COVID-19 treatment
Markus Hoffmann, Yeonhwa Jin and Stefan Pöhlmann highlight a study showing that the antibiotic Dalbavancin blocks binding of the SARS-CoV-2 spike protein to its receptor ACE2 and interferes with SARS-CoV-2 spread and pathogenesis in animal models.
Hoffmann et al, Dalbavancin: novel candidate for COVID-19 treatment. Cell Res. 2021 in press
Cystatin C fragments block HIV and SIV entry
This study, led by the laboratory of Prof. Frank Kirchhoff, University Ulm, shows that fragments of the cellular protein Cystatin C block HIV and SIV usage of GPR15 as coreceptor for host cell entry. Blockade of GPR15 does not interfere with GPR15 activation by its natural ligand GPR15L. Cystatin C fragments are generated by proteases involved in inflammatory processes.
Hayn et al, Natural cystatin C fragments inhibit GPR15-mediated HIV and SIV infection without interfering with GPR15L signaling. Proc Natl Acad Sci U S A. 2021 118(3):e2023776118
First evidence that Camostat may be suitable for treatment of COVID-19
The Infection Biology Unit identified the cellular protease TMPRSS2 as SARS-CoV-2 activator and showed that the clinically-proven TMPRSS2 inhibitor Camostat blocks viral entry into lung cells. This study, which was conducted in close collaboration with Dr. Martin Sebastian Winkler, Universitätsklinikum Göttingen, provided first evidence that Camostat may be suitable for treatment of severe COVID-19. Thus, Camostat-treated patients developed organ failure less frequently than hydroxychloroquine treated patients and had lower levels of proinflammatory cytokines.
Hofmann-Winkler et al, Camostat Mesylate May Reduce Severity of Coronavirus Disease 2019 Sepsis: A First Observation Crit Care Explor. 2020 2(11):e0284.
Mechanism of TMPRSS2 inhibition by Camostat and Nafamostat
This study, led by the laboratory of Prof. Frank Noe, Freie Universitaet Berlin, shows that Camostat and Nafamostat block the activity of recombinant TMPRSS2. Moreover, evidence is provided that both Camostat and Nafamostot bind covalently to TMPRSS2. The interaction of Nafamostat with TMPRSS2 is more efficient as compared to Camostat, in keeping with the higher antiviral activity of Nafamostat.
Hempel et al, Molecular mechanism of inhibiting the SARS-CoV-2 cell entry facilitator TMPRSS2 with camostat and nafamostat. Chemical Science, 2020
COVID-19 patients generate neutralising antibodies
The study led by the laboratory of Prof. Reinhold Förster shows that most COVID-19 patients with mild disease and all patients with severe disease generate neutralizing antibodies. The neutralizing antibodies block binding of the viral spike protein to the cellular receptor ACE2 and neutralizing antibody levels correlate with severity and duration of clinical symptoms but not with patient age.
Bošnjak et al, Low serum neutralizing anti-SARS-CoV-2 S antibody levels in mildly affected COVID-19 convalescent patients revealed by two different detection methods. Cell Mol Immunol. 2020 Nov 2;1-9.
Acid sphingomyelinase as target for COVID-19 therapy
This study from the laboratory of Dr. Erich Gulbins provides evidence that the cellular protein acid sphingomyelinase promotes SARS-CoV-2 entry into cells and constitute a potential target for antiviral intervention. Blockade of acid sphingomyelinase by the drug amitriptyline, which has been approved for human use, blocks viral entry into cell lines and primary cells. Moreover, nasal epithelial cells from amitriptyline treated patients were resistant to SARS-CoV-2 spike protein-driven cell entry.
Carpinteiro et al, Pharmacological Inhibition of Acid Sphingomyelinase Prevents Uptake of SARS-CoV-2 by Epithelial Cells. Cell Rep Med. 2020 1(8):100142.
Gold nanoparticles with glycan coat block host cell entry of Ebola virus
This study led by the laboratory of Dr. Yuan Guo and Prof. Dejian Zhou, university Leeds, England, shows that gold nanoparticles coated with glycans can be used to analyze multivalent glycan-lectin interactions. The nanoparticles allow to determine the affinity of glycan-lectin interactions and to uncover mechanisms of affinity augmentation. Moreover, the nanoparticles allow blockade of DC-SIGN-mediated augmentation of Ebola virus glycoprotein-driven entry.
Budhadev et al, Glycan-Gold Nanoparticles as Multifunctional Probes for Multivalent Lectin-Carbohydrate Binding: Implications for Blocking Virus Infection and Nanoparticle Assembly. J Am Chem Soc. 2020 142(42):18022-18034.
Sphingosine blocks SARS-CoV-2 entry into cells
This study from the laboratory of Dr. Erich Gulbins shows that Sphingosine, a central component of membrane lipids, blocks SARS-CoV-2 spike protein-driven entry into cells when added to target cells before virus. Inhibition of entry is due to Sphingosine binding to the cellular protein ACE2. ACE2 is used by SARS-CoV-2 as receptor for host cell entry and Sphingosin binding to ACE2 blocks subsequent interactions of ACE2 with the viral spike protein.
Edwards et al, Sphingosine prevents binding of SARS-CoV-2 spike to its cellular receptor ACE2. J Biol Chem. 2020 295(45):15174-15182.
LY6E inhibits coronavirus infection
This study from the laboratory of Prof. Volker Thiel shows that the cellular protein lymphocyte antigen 6 complex, locus E (LY6E) plays an important role in the immune defenses against coronavirus infection. Expression of LY6E is interferon-induced and the protein blocks fusion of the virus with the target cell. Loss of LY6E results in exacerabated disease in an rodent model of coronavirus infection.
Pfänder et al, LY6E impairs coronavirus fusion and confers immune control of viral disease. Nat Microbiol. 2020 5(11):1330-1339.
Chloroquine does not inhibit SARS-CoV-2
Chloroquine blocks SARS-CoV-2 infection of the kidney cell line Vero and it thus used for COVID-19 therapy. Hoffmann and coworkers now show that chloroquine does not block SARS-CoV-2 infection of the lung cell line Calu-3 and that lack of inhibition is associated with SARS-CoV-2 activation by the cellular protease TMPRSS2. These results indicate that chloroquine and the closely related drug hydroxychloroquine should not be used for COVID-19 therapy.
Hoffmann et al, Chloroquine does not inhibit infection of human lung cells with SARS-CoV-2. Nature. 2020, In press
Llama antibody blocks SARS-CoV-2 entry
Recombinant antibodies that neutralized SARS-CoV-2 could be used for COVID-19 therapy and prevention. Wrapp and colleagues report the identification of a llama single domain antibody that inhibits SARS-CoV-1 and SARS-CoV-2 entry into cells. This antibody or related ones could be developed to combat COVID-19.
Wrapp et al, Structural Basis for Potent Neutralization of Betacoronaviruses by Single-Domain Camelid Antibodies, Cell. 2020 May 28;181(5):1004-1015.e15.
Two-step activation of SARS-CoV-2
Cleavage of the SARS-CoV-2 surface protein spike by host cell proteases is required for viral infectivity. Hoffmann and colleagues demonstrate that spike protein cleavage by furin is required for viral infectivity. This finding and our previously published results demonstrate that spike protein cleavage by furin in infected cells is required for subsequent spike protein cleavage and activation by TMPRSS2, which occurs during viral entry and is essential for infection of lung cells.
Hoffmann et al, A Multibasic Cleavage Site in the Spike Protein of SARS-CoV-2 Is Essential for Infection of Human Lung Cells. Mol Cell. 2020 May 21;78(4):779-784.e5.
H2 influenza A viruses depend on TMPRSS2 for spread and pathogenesis
The cellular serine protease TMPRSS2 was shown to activate several influenza A viruses and coronaviruses. Lambertz and colleagues demonstrate that also H2 influenza A viruses depend on TMPRSS2 for spread and pathogenesis.
Lambertz et al, H2 influenza A virus is not pathogenic in Tmprss2 knock-out mice. Virol J. 2020 Apr 22;17(1):56.
Nafamostat mesylate inhibits SARS-CoV-2
Host cell entry of the novel coronavirus SARS-CoV-2 depends on activation of the viral spike protein by the cellular serine protease TMPRSS2. Hoffmann and colleagues show that Nafamostat mesylate, a serine protease inhibitors approved for treatment of pancreatitis in Japan, inhibits SARS-CoV-2 infection of lung cells.
Hoffmann et al, Nafamostat mesylate blocks activation of SARS-CoV-2: New treatment option for COVID-19. Antimicrob Agents Chemother. 2020 Apr 20. pii: AAC.00754-20.
Drug blocks SARS-CoV-2 infection of lung cells
Hoffmann and colleagues show that SARS-CoV-2 like SARS-CoV-1 uses the host cell proteins ACE2 and TMPRSS2 for entry into lung cells. TMPRSS2 is a serine protease that cleaves and thereby activates that viral spike protein – process that is disrupted by the clinically proven protease inhibitor camostat mesylate. Moreover, evidence is provided that sera from convalsecent SARS patients inhibit SARS-CoV-2 infection, although with low efficiency.
Hoffmann et al, SARS-CoV-2 Cell Entry Depends on ACE2 and TMPRSS2 and Is Blocked by a Clinically Proven Protease Inhibitor. Cell 2020 181(2):271-28
Polymorphisms in DPP4 gene might impact MERS-CoV infection
MERS-coronavirus uses the host cell protein DPP4/CD26 for entry into target cells. Kleine-Weber and colleagues show that polymorphisms in the DPP4 gene can reduce DPP4 binding and viral entry. It will thus be interesting to determine whether such polymorphisms are present in the Saudia Arabian population and whether they impact the course of MERS-coronavirus infection.
Kleine-Weber et al, Polymorphisms in dipeptidyl peptidase 4 reduce host cell entry of Middle East respiratory syndrome coronavirus. Emerg Microbes Infect. 2020 Dec;9(1):155-168