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1.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327167

ABSTRACT

The continuous emergence of new SARS-CoV-2 variants urges better understanding of the functional motifs in the spike (S) protein and their tolerance towards mutations. We here focus on the S2′ motif which, during virus entry, requires cleavage by a cell surface protease to release the fusion peptide. Though belonging to an immunogenic region, the SARS-CoV-2 S2′ motif (811-KPSKR-815) has shown hardly any variation, with its three basic (K/R) residues being >99.99% conserved thus far. By creating a series of mutant S-pseudotyped viruses, we show that K 814 , which precedes the scissile R 815 residue, is dispensable for SARS-CoV-2 spike activation by TMPRSS2 but not TMPRSS13. The latter protease lost its activity towards SARS-CoV-2 S when the S2′ motif was swapped with that of the low pathogenic 229E coronavirus (685-RVAGR-689) and also the reverse effect was seen. This swap had no impact on TMPRSS2 activation. Also in the MERS-CoV spike, introducing a dibasic scissile motif was fully accepted by TMPRSS13 but less so by TMPRSS2. Our findings are the first to demonstrate which S2′ residues are important for SARS-CoV-2 spike activation by these two airway proteases, with TMPRSS13 exhibiting higher preference for K/R rich motifs than TMPRSS2. This preemptive insight can help to estimate the impact of S2′ motif changes as they may appear in new SARS-CoV-2 variants.

2.
J Fungi (Basel) ; 8(1)2021 Dec 21.
Article in English | MEDLINE | ID: covidwho-1637486

ABSTRACT

Influenza-associated pulmonary aspergillosis (IAPA) is a global recognized superinfection in critically ill influenza patients. Baloxavir marboxil, a cap-dependent endonuclease inhibitor, is a newly approved anti-influenza therapeutic. Although the benefits as a treatment for influenza are clear, its efficacy against an influenza-A. fumigatus co-infection has yet to be determined. We investigated the therapeutic effect of baloxavir marboxil in a murine model for IAPA. Immunocompetent mice received intranasal instillation of influenza A followed by orotracheal inoculation with Aspergillus fumigatus 4 days later. Administration of baloxavir marboxil or sham was started at day 0, day 2 or day 4. Mice were monitored daily for overall health status, lung pathology with micro-computed tomography (µCT) and fungal burden with bioluminescence imaging (BLI). In vivo imaging was supplemented with virological, mycological and biochemical endpoint investigations. We observed an improved body weight, survival and viral clearance in baloxavir marboxil treated mice. µCT showed less pulmonary lesions and bronchial dilation after influenza and after Aspergillus co-infection in a treatment-dependent pattern. Furthermore, baloxavir marboxil was associated with effective inhibition of fungal invasion. Hence, our results provide evidence that baloxavir marboxil mitigates severe influenza thereby decreasing the susceptibility to a lethal invasive Aspergillus superinfection.

3.
Bioorg Chem ; 114: 105153, 2021 09.
Article in English | MEDLINE | ID: covidwho-1324044

ABSTRACT

A series of novel substituted phenyl 1, 3-thiazolidin-4-one sulfonyl derivatives 5 (a-t) were synthesized and screened for their in-vitro anti-microbial and anti-viral activity. The result of the anti-microbial assay demonstrated compounds 5d, 5f, 5g, 5h, 5i, 5j showed prominent inhibitory activity against all the tested Gram-positive and Gram-negative bacterial strains, while compounds 5g, 5j, 5o, 5p, 5q showed significant activity against the entire set of fungal strains as compared to standard drug Ampicillin and Clotrimazole, respectively. The antimicrobial study revealed that compounds having electron-withdrawing groups showed significant antimicrobial potency. The most active antibacterial compound 5j showed potent inhibition of S. aureus DNA Gyrase enzyme as a possible mechanism of action for antimicrobial activity. Moreover, the antiviral testing of selected compounds showed considerable activity against Herpes simplex virus-1(KOS), Herpes simplex virus-2 (G), Herpes simplex virus-1(TK- KOS ACVr), Vaccinia virus, Human Coronavirus (229E), Reovirus-1, Sindbis virus, Coxsackie virus B4, Yellow Fever virus and Influenza A, B virus. Compounds 5h exhibited low anti-viral activity against HIV-1(strain IIIB) and HIV-2 (strain ROD). The study clearly outlined that synthesized compounds endowed with good antimicrobial property together with considerable antiviral activity.


Subject(s)
Phenols/chemical synthesis , Sulfonamides/chemical synthesis , Toluene/analogs & derivatives , Animals , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Antiviral Agents/chemical synthesis , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Bacteria/classification , Bacteria/drug effects , Cell Line , Chlorocebus aethiops , Humans , Phenols/chemistry , Phenols/pharmacology , Sulfonamides/chemistry , Sulfonamides/pharmacology , Toluene/chemical synthesis , Toluene/chemistry , Toluene/pharmacology , Vero Cells , Viruses/classification , Viruses/drug effects
4.
Microorganisms ; 9(5)2021 Apr 27.
Article in English | MEDLINE | ID: covidwho-1244074

ABSTRACT

Favipiravir (T-705) is a broad-spectrum antiviral drug that inhibits RNA viruses after intracellular conversion into its active form, T-705 ribofuranosyl 5'-triphosphate. We previously showed that T-705 is able to significantly inhibit the replication of chikungunya virus (CHIKV), an arbovirus transmitted by Aedes mosquitoes, in mammalian cells and in mouse models. In contrast, the effect of T-705 on CHIKV infection and replication in the mosquito vector is unknown. Since the antiviral activity of T-705 has been shown to be cell line-dependent, we studied here its antiviral efficacy in Aedes-derived mosquito cells and in Aedes aegypti mosquitoes. Interestingly, T-705 was devoid of anti-CHIKV activity in mosquito cells, despite being effective against CHIKV in Vero cells. By investigating the metabolic activation profile, we showed that, unlike Vero cells, mosquito cells were not able to convert T-705 into its active form. To explore whether alternative metabolization pathways might exist in vivo, Aedes aegypti mosquitoes were infected with CHIKV and administered T-705 via an artificial blood meal. Virus titrations of whole mosquitoes showed that T-705 was not able to reduce CHIKV infection in mosquitoes. Combined, these in vitro and in vivo data indicate that T-705 lacks antiviral activity in mosquitoes due to inadequate metabolic activation in this animal species.

5.
PLoS Pathog ; 17(4): e1009500, 2021 04.
Article in English | MEDLINE | ID: covidwho-1197396

ABSTRACT

The high transmissibility of SARS-CoV-2 is related to abundant replication in the upper airways, which is not observed for the other highly pathogenic coronaviruses SARS-CoV and MERS-CoV. We here reveal features of the coronavirus spike (S) protein, which optimize the virus towards the human respiratory tract. First, the S proteins exhibit an intrinsic temperature preference, corresponding with the temperature of the upper or lower airways. Pseudoviruses bearing the SARS-CoV-2 spike (SARS-2-S) were more infectious when produced at 33°C instead of 37°C, a property shared with the S protein of HCoV-229E, a common cold coronavirus. In contrast, the S proteins of SARS-CoV and MERS-CoV favored 37°C, in accordance with virus preference for the lower airways. Next, SARS-2-S-driven entry was efficiently activated by not only TMPRSS2, but also the TMPRSS13 protease, thus broadening the cell tropism of SARS-CoV-2. Both proteases proved relevant in the context of authentic virus replication. TMPRSS13 appeared an effective spike activator for the virulent coronaviruses but not the low pathogenic HCoV-229E virus. Activation of SARS-2-S by these surface proteases requires processing of the S1/S2 cleavage loop, in which both the furin recognition motif and extended loop length proved critical. Conversely, entry of loop deletion mutants is significantly increased in cathepsin-rich cells. Finally, we demonstrate that the D614G mutation increases SARS-CoV-2 stability, particularly at 37°C, and, enhances its use of the cathepsin L pathway. This indicates a link between S protein stability and usage of this alternative route for virus entry. Since these spike properties may promote virus spread, they potentially explain why the spike-G614 variant has replaced the early D614 variant to become globally predominant. Collectively, our findings reveal adaptive mechanisms whereby the coronavirus spike protein is adjusted to match the temperature and protease conditions of the airways, to enhance virus transmission and pathology.


Subject(s)
COVID-19/metabolism , Respiratory System/metabolism , Respiratory System/virology , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , COVID-19/transmission , Coronavirus 229E, Human/metabolism , Furin/metabolism , Humans , Membrane Proteins/metabolism , Middle East Respiratory Syndrome Coronavirus/metabolism , Peptide Hydrolases/metabolism , Serine Endopeptidases/metabolism , Spike Glycoprotein, Coronavirus/genetics , Temperature , Virus Internalization , Virus Replication/physiology
6.
J Med Chem ; 64(9): 5632-5644, 2021 05 13.
Article in English | MEDLINE | ID: covidwho-1193564

ABSTRACT

To develop antiviral therapeutics against human coronavirus (HCoV) infections, suitable coronavirus drug targets and corresponding lead molecules must be urgently identified. Here, we describe the discovery of a class of HCoV inhibitors acting on nsp15, a hexameric protein component of the viral replication-transcription complexes, endowed with immune evasion-associated endoribonuclease activity. Structure-activity relationship exploration of these 1,2,3-triazolo-fused betulonic acid derivatives yielded lead molecule 5h as a strong inhibitor (antiviral EC50: 0.6 µM) of HCoV-229E replication. An nsp15 endoribonuclease active site mutant virus was markedly less sensitive to 5h, and selected resistance to the compound mapped to mutations in the N-terminal part of HCoV-229E nsp15, at an interface between two nsp15 monomers. The biological findings were substantiated by the nsp15 binding mode for 5h, predicted by docking. Hence, besides delivering a distinct class of inhibitors, our study revealed a druggable pocket in the nsp15 hexamer with relevance for anti-coronavirus drug development.


Subject(s)
Antiviral Agents/pharmacology , Coronavirus 229E, Human/drug effects , Coronavirus 229E, Human/enzymology , Endoribonucleases/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , Oleanolic Acid/analogs & derivatives , Viral Nonstructural Proteins/antagonists & inhibitors , Virus Replication/drug effects , Antiviral Agents/chemical synthesis , Antiviral Agents/chemistry , Cell Line , Dose-Response Relationship, Drug , Endoribonucleases/metabolism , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Humans , Microbial Sensitivity Tests , Models, Molecular , Oleanolic Acid/chemical synthesis , Oleanolic Acid/chemistry , Oleanolic Acid/pharmacology , Viral Nonstructural Proteins/metabolism
7.
Bioorg Chem ; 104: 104320, 2020 11.
Article in English | MEDLINE | ID: covidwho-848890

ABSTRACT

In the present study, we intend to synthesize a series of novel substituted phenyl azetidine-2-one sulphonyl derivatives. The entire set of derivatives 5 (a-t) were screened for in-vitro antibacterial, and antifungal activity, and among them eleven compounds were further screened for the antiviral activity to predict their efficacy against pathogenic viruses. Interestingly, compound 5d, 5e, 5f, 5h, 5i, and 5j showed similar or better antibacterial activity as compared to ampicillin (standard). Moreover, compounds 5h, 5i, 5j, and 5q showed good inhibitory activity against fungal strains whereas other derivatives had mild or diminished activity in comparison with standard drug clotrimazole. The antimicrobial study indicated that compounds having electron-withdrawing groups showed the highest activity. Interestingly, these tested compounds showed weak antiviral activity against Vaccinia virus, Human Coronavirus (229E), Reovirus-1, Herpes simplex virus, Sindbis virus, Coxsackievirus B4, Yellow Fever virus, and Influenza B virus in HEL cell, Vero cell, and MDCK cell cultures. The findings of the present study might open new avenues to target human disease-causing deadly microbes and viruses.


Subject(s)
Anti-Bacterial Agents/pharmacology , Antifungal Agents/pharmacology , Antiviral Agents/pharmacology , Azetidines/pharmacology , Sulfonamides/pharmacology , Animals , Anti-Bacterial Agents/chemical synthesis , Antifungal Agents/chemical synthesis , Antiviral Agents/chemical synthesis , Aspergillus fumigatus/drug effects , Aspergillus niger/drug effects , Azetidines/chemical synthesis , Candida albicans/drug effects , Cell Line, Tumor , Chlorocebus aethiops , Dogs , Escherichia coli/drug effects , Humans , Madin Darby Canine Kidney Cells , Microbial Sensitivity Tests , Molecular Structure , Pseudomonas aeruginosa/drug effects , Staphylococcus aureus/drug effects , Structure-Activity Relationship , Sulfonamides/chemical synthesis , Vero Cells , Viruses/drug effects
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