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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant exhibits high transmissibility with a strong immune escape ability and causes frequent large-scale global infections by producing predominant subvariants. Here, using human upper/lower airway and intestinal cells, we examined the previously dominant BA.1-BA.5 and BA.2.75 subvariants, together with the recently emerged XBB/BQ lineages, in comparison to the former Delta variant. We observed a tendency for each virus to demonstrate higher growth capability than the previously dominant subvariants. Unlike human bronchial and intestinal cells, nasal epithelial cells accommodated the efficient entry of certain Omicron subvariants, similar to the Delta variant. In contrast to the Delta's reliance on cell-surface transmembrane protease serine 2, all tested Omicron variants depended on endosomal cathepsin L. Moreover, S1/S2 cleavage of early Omicron spikes was less efficient, whereas recent viruses exhibit improved cleavage efficacy. Our results show that the Omicron variant progressively adapts to human cells through continuous endosome-mediated host cell entry.IMPORTANCESARS-CoV-2, the causative agent of coronavirus disease 2019, has evolved into a number of variants/subvariants, which have generated multiple global waves of infection. In order to monitor/predict virological features of emerging variants and determine appropriate strategies for anti-viral development, understanding conserved or altered features of evolving SARS-CoV-2 is important. In this study, we addressed previously or recently predominant Omicron subvariants and demonstrated the gradual adaptation to human cells. The host cell entry route, which was altered from the former Delta variant, was conserved among all tested Omicron subvariants. Collectively, this study revealed both changing and maintained features of SARS-CoV-2 during the Omicron variant evolution.
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Transmissibility and immune evasion of the recently emerged, highly mutated SARS-CoV-2 BA.2.87.1 are unknown. Here, we report that BA.2.87.1 efficiently enters human cells but is more sensitive to antibody-mediated neutralization than the currently dominating JN.1 variant. Acquisition of adaptive mutations might thus be needed for efficient spread in the population.
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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant of concern, first identified in November 2021, rapidly spread worldwide and diversified into several subvariants. The Omicron spike (S) protein accumulated an unprecedented number of sequence changes relative to previous variants. In this review, we discuss how Omicron S protein structural features modulate host cell receptor binding, virus entry, and immune evasion and highlight how these structural features differentiate Omicron from previous variants. We also examine how key structural properties track across the still-evolving Omicron subvariants and the importance of continuing surveillance of the S protein sequence evolution over time.
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COVID-19 , Humanos , SARS-CoV-2 , Evasión InmuneRESUMEN
The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses mediates host cell entry and is S-acylated on multiple phylogenetically conserved cysteine residues. Multiple protein acyltransferase enzymes have been reported to post-translationally modify spike proteins; however, strategies to exploit this modification are lacking. Using resin-assisted capture MS, we demonstrate that the spike protein is S-acylated in SARS-CoV-2-infected human and monkey epithelial cells. We further show that increased abundance of the acyltransferase ZDHHC5 associates with increased S-acylation of the spike protein, whereas ZDHHC5 knockout cells had a 40% reduction in the incorporation of an alkynyl-palmitate using click chemistry detection. We also found that the S-acylation of the spike protein is not limited to palmitate, as clickable versions of myristate and stearate were also labelled the protein. Yet, we observed that ZDHHC5 was only modified when incubated with alkyne-palmitate, suggesting it has specificity for this acyl-CoA, and that other ZDHHC enzymes may use additional fatty acids to modify the spike protein. Since multiple ZDHHC isoforms may modify the spike protein, we also examined the ability of the FASN inhibitor TVB-3166 to prevent S-acylation of the spike proteins of SARS-CoV-2 and human CoV-229E. We show that treating cells with TVB-3166 inhibited S-acylation of expressed spike proteins and attenuated the ability of SARS-CoV-2 and human CoV-229E to spread in vitro. Our findings further substantiate the necessity of CoV spike protein S-acylation and demonstrate that de novo fatty acid synthesis is critical for the proper S-acylation of the spike protein.
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COVID-19 , Glicoproteína de la Espiga del Coronavirus , Acilación , Aciltransferasas/metabolismo , Alquinos , Azetidinas , Coenzima A/metabolismo , Cisteína , Acido Graso Sintasa Tipo I/metabolismo , Humanos , Miristatos , Nitrilos , Palmitatos , Pirazoles , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus/metabolismo , EstearatosRESUMEN
Since the beginning of the COVID-19 pandemic, multiple SARS-CoV-2 variants have emerged. While some variants spread only locally, others, referred to as variants of concern, disseminated globally and became drivers of the pandemic. All SARS-CoV-2 variants harbor mutations relative to the virus circulating early in the pandemic, and mutations in the viral spike (S) protein are considered of particular relevance since the S protein mediates host cell entry and constitutes the key target of the neutralizing antibody response. As a consequence, mutations in the S protein may increase SARS-CoV-2 infectivity and enable its evasion of neutralizing antibodies. Furthermore, mutations in the S protein can modulate viral transmissibility and pathogenicity.
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Anticuerpos Neutralizantes/inmunología , Anticuerpos Antivirales/inmunología , COVID-19/inmunología , SARS-CoV-2/inmunología , Humanos , Mutación/inmunología , Pruebas de Neutralización/métodos , Glicoproteína de la Espiga del Coronavirus/inmunología , Internalización del VirusRESUMEN
The global spread of SARS-CoV-2/COVID-19 is devastating health systems and economies worldwide. Recombinant or vaccine-induced neutralizing antibodies are used to combat the COVID-19 pandemic. However, the recently emerged SARS-CoV-2 variants B.1.1.7 (UK), B.1.351 (South Africa), and P.1 (Brazil) harbor mutations in the viral spike (S) protein that may alter virus-host cell interactions and confer resistance to inhibitors and antibodies. Here, using pseudoparticles, we show that entry of all variants into human cells is susceptible to blockade by the entry inhibitors soluble ACE2, Camostat, EK-1, and EK-1-C4. In contrast, entry of the B.1.351 and P.1 variant was partially (Casirivimab) or fully (Bamlanivimab) resistant to antibodies used for COVID-19 treatment. Moreover, entry of these variants was less efficiently inhibited by plasma from convalescent COVID-19 patients and sera from BNT162b2-vaccinated individuals. These results suggest that SARS-CoV-2 may escape neutralizing antibody responses, which has important implications for efforts to contain the pandemic.
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Anticuerpos Neutralizantes/inmunología , Anticuerpos Antivirales/inmunología , SARS-CoV-2/inmunología , Animales , COVID-19/inmunología , COVID-19/terapia , COVID-19/virología , Línea Celular , Farmacorresistencia Viral , Humanos , Inmunización Pasiva , Cinética , Fusión de Membrana , Modelos Moleculares , Pruebas de Neutralización , Serina Endopeptidasas/metabolismo , Solubilidad , Glicoproteína de la Espiga del Coronavirus/inmunología , Vacunación , Internalización del Virus , Sueroterapia para COVID-19RESUMEN
Lysosomotropism is a biological characteristic of small molecules, independently present of their intrinsic pharmacological effects. Lysosomotropic compounds, in general, affect various targets, such as lipid second messengers originating from lysosomal enzymes promoting endothelial stress response in systemic inflammation; inflammatory messengers, such as IL-6; and cathepsin L-dependent viral entry into host cells. This heterogeneous group of drugs and active metabolites comprise various promising candidates with more favorable drug profiles than initially considered (hydroxy) chloroquine in prophylaxis and treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections/Coronavirus disease 2019 (COVID-19) and cytokine release syndrome (CRS) triggered by bacterial or viral infections. In this hypothesis, we discuss the possible relationships among lysosomotropism, enrichment in lysosomes of pulmonary tissue, SARS-CoV-2 infection, and transition to COVID-19. Moreover, we deduce further suitable approved drugs and active metabolites based with a more favorable drug profile on rational eligibility criteria, including readily available over-the-counter (OTC) drugs. Benefits to patients already receiving lysosomotropic drugs for other pre-existing conditions underline their vital clinical relevance in the current SARS-CoV2/COVID-19 pandemic.
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Antivirales/farmacología , Tratamiento Farmacológico de COVID-19 , Descubrimiento de Drogas , Lisosomas/efectos de los fármacos , SARS-CoV-2/efectos de los fármacos , Bibliotecas de Moléculas Pequeñas/farmacología , Antivirales/farmacocinética , Antivirales/uso terapéutico , COVID-19/inmunología , COVID-19/metabolismo , COVID-19/virología , Clorpromazina/farmacocinética , Clorpromazina/farmacología , Clorpromazina/uso terapéutico , Síndrome de Liberación de Citoquinas/tratamiento farmacológico , Descubrimiento de Drogas/métodos , Reposicionamiento de Medicamentos/métodos , Fluvoxamina/farmacocinética , Fluvoxamina/farmacología , Fluvoxamina/uso terapéutico , Humanos , Hidroxicloroquina/farmacocinética , Hidroxicloroquina/farmacología , Hidroxicloroquina/uso terapéutico , Interleucina-1/antagonistas & inhibidores , Interleucina-1/inmunología , Interleucina-6/antagonistas & inhibidores , Interleucina-6/inmunología , Pulmón/efectos de los fármacos , Pulmón/inmunología , Pulmón/metabolismo , Pulmón/virología , Lisosomas/inmunología , Lisosomas/metabolismo , Lisosomas/virología , SARS-CoV-2/inmunología , SARS-CoV-2/fisiología , Bibliotecas de Moléculas Pequeñas/farmacocinética , Bibliotecas de Moléculas Pequeñas/uso terapéutico , Replicación Viral/efectos de los fármacosRESUMEN
The heartland virus (HRTV) is a novel phlebovirus that causes severe infections in the USA and closely related to the severe fever thrombocytopenia syndrome virus (SFTSV), a causative agent for SFTS in Asia. The entry mechanisms of HRTV remain unclear. Here, we developed the pseudotyped vesicular stomatitis virus bearing the HRTV glycoprotein (GP) (HRTVpv), and the antigenicity and the entry mechanisms of HRTV were analyzed. HRTVpv was neutralized by anti-SFTSV Gc antibody, but not the anti-SFTSV Gn antibodies. Entry of HRTVpv to cells was inhibited by bafilomycin A1 and dynasore, and but it was enhanced in cells overexpressed with C-type lectins. Production of infectious HRTVpv and SFTSVpv was reduced by Nn-DNJ, α-glucosidase inhibitor. The entry of HRTV occurs via pH- and dynamin-dependent endocytosis. Furthermore, Nn-DNJ may be a possible therapeutic agent against HRTV and SFTSV.
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Infecciones por Bunyaviridae/virología , Phlebovirus/patogenicidad , Estomatitis Vesicular/virología , Vesiculovirus/patogenicidad , Proteínas del Envoltorio Viral/metabolismo , 1-Desoxinojirimicina/análogos & derivados , 1-Desoxinojirimicina/farmacología , Animales , Línea Celular , Cricetinae , Haplorrinos , Humanos , Ratones , Internalización del VirusRESUMEN
Many efforts to design and screen therapeutics for the current severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic have focused on inhibiting viral host cell entry by disrupting angiotensin-converting enzyme-2 (ACE2) binding with the SARS-CoV-2 spike protein. This work focuses on the potential to inhibit SARS-CoV-2 entry through a hypothesized α5ß1 integrin-based mechanism and indicates that inhibiting the spike protein interaction with α5ß1 integrin (+/- ACE2) and the interaction between α5ß1 integrin and ACE2 using a novel molecule (ATN-161) represents a promising approach to treat coronavirus disease-19.
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BACKGROUND: Currently, novel coronavirus disease (Covid-19) outbreak creates global panic across the continents, as people from almost all countries and territories have been affected by this highly contagious viral disease. The scenario is deteriorating due to lack of proper & specific target-oriented pharmacologically safe prophylactic agents or drugs, and or any effective vaccine. drug development is urgently required to back in the normalcy in the community and to combat this pandemic. PURPOSE: Thus, we have proposed two novel drug targets, Furin and TMPRSS2, as Covid-19 treatment strategy. We have highlighted this target-oriented novel drug delivery strategy, based on their pathophysiological implication on SARS-CoV-2 infection, as evident from earlier SARS-CoV-1, MERS, and influenza virus infection via host cell entry, priming, fusion, and endocytosis. STUDY DESIGN & METHODS: An earlier study suggested that Furin and TMPRSS2 knockout mice had reduced level of viral load and a lower degree of organ damage such as the lung. The present study thus highlights the promise of some selected novel and potential anti-viral Phytopharmaceutical that bind to Furin and TMPRSS2 as target. RESULT: Few of them had shown promising anti-viral response in both preclinical and clinical study with acceptable therapeutic safety-index. CONCLUSION: Hence, this strategy may limit life-threatening Covid-19 infection and its mortality rate through nano-suspension based intra-nasal or oral nebulizer spray, to treat mild to moderate SARS-COV-2 infection when Furin and TMPRSS2 receptor may initiate to express and activate for processing the virus to cause cellular infection by replication within the host cell and blocking of host-viral interaction.
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Tratamiento Farmacológico de COVID-19 , Furina/antagonistas & inhibidores , Fitoquímicos/farmacología , Receptores Virales/antagonistas & inhibidores , Serina Endopeptidasas/metabolismo , Inhibidores de Serina Proteinasa/farmacología , Enzima Convertidora de Angiotensina 2/antagonistas & inhibidores , Animales , Furina/metabolismo , Humanos , Ratones , Ratones Noqueados , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus/metabolismoRESUMEN
In line with SARS and MERS, the SARS-CoV-2/COVID-19 pandemic is one of the largest challenges in medicine and health care worldwide. SARS-CoV-2 infection/COVID-19 provides numerous therapeutic targets, each of them promising, but not leading to the success of therapy to date. Neither an antiviral nor an immunomodulatory therapy in patients with SARS-CoV-2 infection/COVID-19 or pre-exposure prophylaxis against SARS-CoV-2 has proved to be effective. In this review, we try to close the gap and point out the likely relationships among lysosomotropism, increasing lysosomal pH, SARS-CoV-2 infection, and disease process, and we deduce an approach for the treatment and prophylaxis of COVID-19, and cytokine release syndrome (CRS)/cytokine storm triggered by bacteria or viruses. Lysosomotropic compounds affect prominent inflammatory messengers (e.g., IL-1B, CCL4, CCL20, and IL-6), cathepsin-L-dependent viral entry of host cells, and products of lysosomal enzymes that promote endothelial stress response in systemic inflammation. As supported by recent clinical data, patients who have already taken lysosomotropic drugs for other pre-existing conditions likely benefit from this treatment in the COVID-19 pandemic. The early administration of a combination of antivirals such as remdesivir and lysosomotropic drugs, such as the antibiotics teicoplanin or dalbavancin, seems to be able to prevent SARS-CoV-2 infection and transition to COVID-19.
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Infecciones por Coronavirus/patología , Lisosomas/metabolismo , Neumonía Viral/patología , Enzima Convertidora de Angiotensina 2 , Animales , Antivirales/farmacología , Antivirales/uso terapéutico , Betacoronavirus/aislamiento & purificación , Betacoronavirus/fisiología , COVID-19 , Proteasas 3C de Coronavirus , Infecciones por Coronavirus/complicaciones , Infecciones por Coronavirus/tratamiento farmacológico , Infecciones por Coronavirus/virología , Síndrome de Liberación de Citoquinas/etiología , Síndrome de Liberación de Citoquinas/patología , Humanos , Pandemias , Peptidil-Dipeptidasa A/metabolismo , Neumonía Viral/complicaciones , Neumonía Viral/tratamiento farmacológico , Neumonía Viral/virología , SARS-CoV-2 , Proteínas no Estructurales Virales/antagonistas & inhibidores , Proteínas no Estructurales Virales/metabolismo , Internalización del Virus/efectos de los fármacosRESUMEN
BACKGROUND: Nipah virus (NiV) and Hendra virus (HeV) of genus Henipavirus are the deadliest zoonotic viruses, which cause severe respiratory ailments and fatal encephalitis in humans and other susceptible animals. The fatality rate for these infections had been alarmingly high with no approved treatment available to date. Viral attachment and fusion with host cell membrane is essential for viral entry and is the most essential event of viral infection. Viral attachment is mediated by interaction of Henipavirus attachment glycoprotein (G) with the host cell receptor: Ephrin B2/B3, while viral fusion and endocytosis are mediated by the combined action of both viral glycoprotein (G) and fusion protein (F). CONCLUSION: This review highlights the mechanism of viral attachment, fusion and also explains the basic mechanism and pathobiology of this infection in humans. The drugs and therapeutics used either experimentally or clinically against NiV and HeV infection have been documented and classified in detail. Some amino acid residues essential for the functionality of G and F proteins were also emphasized. Therapeutic designing to target and block these residues can serve as a promising approach in future drug development against NiV and HeV.
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Antivirales/farmacología , Diseño de Fármacos , Virus Hendra/efectos de los fármacos , Virus Nipah/efectos de los fármacos , Animales , Virus Hendra/genética , Infecciones por Henipavirus/fisiopatología , Humanos , Virus Nipah/genética , Internalización del Virus/efectos de los fármacosRESUMEN
Priming of the viral glycoprotein (GP) by the cellular proteases cathepsin B and L (CatB, CatL) is believed to be essential for cell entry of filoviruses. However, pseudotyping systems that predominantly produce non-filamentous particles have frequently been used to prove this concept. Here, we report that GP-mediated entry of retroviral-, rhabdoviral and filoviral particles depends on CatB/CatL activity and that this effect is cell line-independent. Moreover, we show that the human cell line Calu-3, which expresses low amounts of CatL, is largely resistant to entry driven by diverse filovirus GPs. Finally, we demonstrate that Calu-3â¯cell entry mediated by certain filovirus GPs can be rescued upon directed expression of CatL or DC-SIGN. Our results identify Calu-3â¯cells as largely resistant to filovirus GP-driven entry and demonstrate that entry is limited at the stage of virion attachment and GP priming.
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Catepsina L/genética , Moléculas de Adhesión Celular/genética , Ebolavirus/genética , Células Epiteliales/inmunología , Lectinas Tipo C/genética , Receptores de Superficie Celular/genética , Proteínas Virales/genética , Células A549 , Animales , Catepsina B/antagonistas & inhibidores , Catepsina B/genética , Catepsina B/inmunología , Catepsina B/metabolismo , Catepsina L/antagonistas & inhibidores , Catepsina L/inmunología , Catepsina L/metabolismo , Moléculas de Adhesión Celular/antagonistas & inhibidores , Moléculas de Adhesión Celular/inmunología , Moléculas de Adhesión Celular/metabolismo , Línea Celular Tumoral , Chlorocebus aethiops , Inhibidores de Cisteína Proteinasa/farmacología , Dipéptidos/farmacología , Ebolavirus/crecimiento & desarrollo , Ebolavirus/metabolismo , Células Epiteliales/metabolismo , Células Epiteliales/virología , Regulación de la Expresión Génica , Glicoproteínas/genética , Glicoproteínas/metabolismo , Células HEK293 , Interacciones Huésped-Patógeno/genética , Humanos , Lectinas Tipo C/antagonistas & inhibidores , Lectinas Tipo C/inmunología , Lectinas Tipo C/metabolismo , Leucina/análogos & derivados , Leucina/farmacología , Marburgvirus/genética , Marburgvirus/crecimiento & desarrollo , Marburgvirus/metabolismo , Receptores de Superficie Celular/antagonistas & inhibidores , Receptores de Superficie Celular/inmunología , Receptores de Superficie Celular/metabolismo , Transducción de Señal , Células Vero , Vesiculovirus/genética , Vesiculovirus/crecimiento & desarrollo , Vesiculovirus/metabolismo , Proteínas Virales/metabolismo , Virión/genética , Virión/crecimiento & desarrollo , Virión/metabolismo , Internalización del Virus/efectos de los fármacosRESUMEN
The emergence of Old and New World arenaviruses from rodent reservoirs persistently threatens human health. The GP1 subunit of the envelope-displayed arenaviral glycoprotein spike complex (GPC) mediates host cell recognition and is an important determinant of cross-species transmission. Previous structural analyses of Old World arenaviral GP1 glycoproteins, alone and in complex with a cognate GP2 subunit, have revealed that GP1 adopts two distinct conformational states distinguished by differences in the orientations of helical regions of the molecule. Here, through comparative study of the GP1 glycoprotein architectures of Old World Loei River virus and New World Whitewater Arroyo virus, we show that these rearrangements are restricted to Old World arenaviruses and are not induced solely by the pH change that is associated with virus endosomal trafficking. Our structure-based phylogenetic analysis of arenaviral GP1s provides a blueprint for understanding the discrete structural classes adopted by these therapeutically important targets.IMPORTANCE The genetically and geographically diverse group of viruses within the family Arenaviridae includes a number of zoonotic pathogens capable of causing fatal hemorrhagic fever. The multisubunit GPC glycoprotein spike complex displayed on the arenavirus envelope is a key determinant of species tropism and a primary target of the host humoral immune response. Here, we show that the receptor-binding GP1 subcomponent of the GPC spike from Old World but not New World arenaviruses adopts a distinct, pH-independent conformation in the absence of the cognate GP2. Our analysis provides a structure-based approach to understanding the discrete conformational classes sampled by these therapeutically important targets, informing strategies to develop arenaviral glycoprotein immunogens that resemble GPC as presented on the mature virion surface.
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Arenavirus del Nuevo Mundo/clasificación , Arenavirus del Viejo Mundo/clasificación , Proteínas del Envoltorio Viral/química , Arenavirus del Nuevo Mundo/química , Arenavirus del Nuevo Mundo/metabolismo , Arenavirus del Viejo Mundo/química , Arenavirus del Viejo Mundo/metabolismo , Endosomas/virología , Evolución Molecular , Concentración de Iones de Hidrógeno , Modelos Moleculares , Filogenia , Estructura Secundaria de ProteínaRESUMEN
The large scale of the Ebola virus disease (EVD) outbreak in West Africa in 2013-2016 raised the question whether the host cell interactions of the responsible Ebola virus (EBOV) strain differed from those of other ebolaviruses. We previously reported that the glycoprotein (GP) of the virus circulating in West Africa in 2014 (EBOV2014) exhibited reduced ability to mediate entry into two nonhuman primate (NHP)-derived cell lines relative to the GP of EBOV1976. Here, we investigated the molecular determinants underlying the differential entry efficiency. We found that EBOV2014-GP-driven entry into diverse NHP-derived cell lines, as well as human monocyte-derived macrophages and dendritic cells, was reduced compared to EBOV1976-GP, although entry into most human- and all bat-derived cell lines tested was comparable. Moreover, EBOV2014 replication in NHP but not human cells was diminished relative to EBOV1976, suggesting that reduced cell entry translated into reduced viral spread. Mutagenic analysis of EBOV2014-GP and EBOV1976-GP revealed that an amino acid polymorphism in the receptor-binding domain, A82V, modulated entry efficiency in a cell line-independent manner and did not account for the reduced EBOV2014-GP-driven entry into NHP cells. In contrast, polymorphism T544I, located in the internal fusion loop in the GP2 subunit, was found to be responsible for the entry phenotype. These results suggest that position 544 is an important determinant of EBOV infectivity for both NHP and certain human target cells.IMPORTANCE The Ebola virus disease outbreak in West Africa in 2013 entailed more than 10,000 deaths. The scale of the outbreak and its dramatic impact on human health raised the question whether the responsible virus was particularly adept at infecting human cells. Our study shows that an amino acid exchange, A82V, that was acquired during the epidemic and that was not observed in previously circulating viruses, increases viral entry into diverse target cells. In contrast, the epidemic virus showed a reduced ability to enter cells of nonhuman primates compared to the virus circulating in 1976, and a single amino acid exchange in the internal fusion loop of the viral glycoprotein was found to account for this phenotype.
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Sustitución de Aminoácidos/genética , Ebolavirus/patogenicidad , Proteínas del Envoltorio Viral/genética , Acoplamiento Viral , Internalización del Virus , Animales , Células COS , Línea Celular , Chlorocebus aethiops , Ebolavirus/genética , Células HEK293 , Fiebre Hemorrágica Ebola/virología , Humanos , Macaca mulatta , Polimorfismo de Nucleótido Simple/genética , Unión Proteica/genética , Estructura Terciaria de Proteína/genética , Células Vero , Replicación Viral/genéticaRESUMEN
The recent Ebola virus outbreak in western Africa highlights the need for novel therapeutics that target Ebola virus and other filoviruses. Filoviruses require processing by host cell-derived cysteine cathepsins for productive infection. Here we report the generation of a focused library of cysteine cathepsin inhibitors and subsequent screening to identify compounds with potent activity against viral entry and replication. Our top compounds show highly potent and broad-spectrum activity against cysteine cathepsins and were able to effectively block entry of Ebola and Marburg viruses. These agents are promising leads for development as antifilovirus therapeutics.
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The translocation of effector proteins into the host plant cells is essential for pathogens to suppress plant immune responses. The oomycete pathogen Phytophthora infestans secretes AVR3a, a crucial virulence effector protein with an N-terminal RXLR motif that is required for this translocation. It has been reported that the RXLR motif of P. sojae Avr1b, which is a close homolog of AVR3a, is required for binding to phosphatidylinositol monophosphates (PIPs). However, in our previous report, AVR3a as well as Avr1b bind to PIPs not via RXLR but via lysine residues forming a positively-charged area in the effector domain. In this report, we examined whether other RXLR effectors whose structures have been determined bind to PIPs. Both P. capsici AVR3a11 and Hyaloperonospora arabidopsidis ATR1 have an RXLR motif in their N-terminal regions but did not bind to any PIPs. These results suggest that the RXLR motif is not sufficient for PIP binding.