Triterpenoids Manipulate a Broad Range of Virus-Host Fusion via Wrapping the HR2 Domain Prevalent in Viral Envelopes

Recent years have witnessed a breakthrough in identification of a trimer-of-hairpins motif within viral envelopes that triggers a broad range of virus-host fusion. Identifying a domain capable of controlling virus-host fusion remains a challenge due to sequence diversity, heavy glycan shielding and multiple conformations. Here, we report that HR2, a prevalent heptad repeat sequence comprising an alpha-helical coil anchored in viral membranes, is an accessible site to triterpenes, a class of widely distributed natural products. Triterpenes and their derivatives inhibit the entry of Ebola, HIV, and influenza A viruses with distinct structure-activity relationships. Specifically, triterpenoid probes, upon activation by ultraviolet light, capture the viral envelope via crosslinking the HR2 coil. Profiling the Ebola HR2 sequence using amino acid substitution, surface plasmon resonance (SPR) and nuclear magnetic resonance (NMR) spectroscopy disclosed six constitutive residues that are accessible to triterpenoids, leading to wrapping of the hydrophobic helix by triterpenoids and blocking of the HR1-HR2 interaction, which is critical in the trimer-of-hairpins formation. This finding was also observed in the envelopes of HIV and influenza A viruses and might potentially extend to a broader variety of viruses. Our findings might translate into a shared mechanism that host utilize natural product triterpenoids to antagonize membrane fusion of respective viruses, complementing the current repertoire of antiviral agents.

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Triterpenoids manipulate a broad range of virus-host fusion via wrapping the HR2 domain prevalent in viral envelopes

Science Advances ◽

10.1126/sciadv.aau8408 ◽

2018 ◽

Vol 4 (11) ◽

pp. eaau8408 ◽

Cited By ~ 18

Author(s):

Longlong Si ◽

Kun Meng ◽

Zhenyu Tian ◽

Jiaqi Sun ◽

Huiqiang Li ◽

...

Keyword(s):

Influenza A ◽

Viral Envelope ◽

Heptad Repeat ◽

Viral Fusion ◽

Influenza A Viruses ◽

Fusion Inhibitors ◽

Distinct Structure ◽

Viral Envelopes ◽

Hydrophobic Helix ◽

Insight Into

A trimer-of-hairpins motif has been identified in triggering virus-cell fusion within a variety of viral envelopes. Chemically manipulating such a motif represents current repertoire of viral fusion inhibitors. Here, we report that triterpenoids, a class of natural products, antagonize this trimer-of-hairpins via its constitutive heptad repeat-2 (HR2), a prevalent α-helical coil in class I viral fusion proteins. Triterpenoids inhibit the entry of Ebola, Marburg, HIV, and influenza A viruses with distinct structure-activity relationships. Specifically, triterpenoid probes capture the viral envelope via photocrosslinking HR2. Profiling the Ebola HR2-triterpenoid interactions using amino acid substitution, surface plasmon resonance, and nuclear magnetic resonance revealed six residues accessible to triterpenoids, leading to wrapping of the hydrophobic helix and blocking of the HR1-HR2 interaction critical in the trimer-of-hairpins formation. This finding was also observed in the envelopes of HIV and influenza A viruses and might potentially extend to a broader variety of viruses, providing a mechanistic insight into triterpenoid-mediated modulation of viral fusion.

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Obatoclax, Saliphenylhalamide, and Gemcitabine Inhibit Influenza A Virus Infection

Journal of Biological Chemistry ◽

10.1074/jbc.m112.392142 ◽

2012 ◽

Vol 287 (42) ◽

pp. 35324-35332 ◽

Cited By ~ 59

Author(s):

Oxana V. Denisova ◽

Laura Kakkola ◽

Lin Feng ◽

Jakob Stenman ◽

Ashwini Nagaraj ◽

...

Keyword(s):

Influenza A ◽

Treatment Options ◽

Antiviral Agents ◽

Cell Type ◽

Influenza A Viruses ◽

Novel Host ◽

Chemical Screen ◽

Species Specific ◽

Host Target ◽

Transcription And Replication

Influenza A viruses (IAVs) infect humans and cause significant morbidity and mortality. Different treatment options have been developed; however, these were insufficient during recent IAV outbreaks. Here, we conducted a targeted chemical screen in human nonmalignant cells to validate known and search for novel host-directed antivirals. The screen validated saliphenylhalamide (SaliPhe) and identified two novel anti-IAV agents, obatoclax and gemcitabine. Further experiments demonstrated that Mcl-1 (target of obatoclax) provides a novel host target for IAV treatment. Moreover, we showed that obatoclax and SaliPhe inhibited IAV uptake and gemcitabine suppressed viral RNA transcription and replication. These compounds possess broad spectrum antiviral activity, although their antiviral efficacies were virus-, cell type-, and species-specific. Altogether, our results suggest that phase II obatoclax, investigational SaliPhe, and FDA/EMEA-approved gemcitabine represent potent antiviral agents.

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Mutations flanking the carbohydrate binding site of surfactant protein D confer antiviral activity for pandemic influenza A viruses

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00035.2014 ◽

2014 ◽

Vol 306 (11) ◽

pp. L1036-L1044 ◽

Cited By ~ 13

Author(s):

Nikolaos M. Nikolaidis ◽

Mitchell R. White ◽

Kimberly Allen ◽

Shweta Tripathi ◽

Li Qi ◽

...

Keyword(s):

Antiviral Activity ◽

Host Defense ◽

Influenza A ◽

Surfactant Protein ◽

Viral Envelope ◽

Surfactant Protein D ◽

Carbohydrate Binding ◽

Influenza A Viruses ◽

Head Region ◽

Pandemic Strains

We recently reported that a trimeric neck and carbohydrate recognition domain (NCRD) fragment of human surfactant protein D (SP-D), a host defense lectin, with combinatorial substitutions at the 325 and 343 positions (D325A+R343V) exhibits markedly increased antiviral activity for seasonal strains of influenza A virus (IAV). The NCRD binds to glycan-rich viral envelope proteins including hemagglutinin (HA). We now show that replacement of D325 with serine to create D325S+R343V provided equal or increased neutralizing activity compared with D325A+R343V. The activity of the double mutants was significantly greater than that of either single mutant (D325A/S or R343V). D325A+R343V and D325S+R343V also strongly inhibited HA activity, and markedly aggregated, the 1968 pandemic H3N2 strain, Aichi68. D325S+R343V significantly reduced viral loads and mortality of mice infected with Aichi68, whereas wild-type SP-D NCRD did not. The pandemic H1N1 strains of 1918 and 2009 have only one N-linked glycan side on the head region of the HA and are fully resistant to inhibition by native SP-D. Importantly, we now show that D325A+R343V and D325S+R343V inhibited Cal09 H1N1 and related strains, and reduced uptake of Cal09 by epithelial cells. Inhibition of Cal09 was mediated by the lectin activity of the NCRDs. All known human pandemic strains have at least one glycan attachment on the top or side of the HA head, and our results indicate that they may be susceptible to inhibition by modified host defense lectins.

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A novel family of peptides with potent activity against influenza A viruses

Journal of General Virology ◽

10.1099/vir.0.038679-0 ◽

2012 ◽

Vol 93 (5) ◽

pp. 980-986 ◽

Cited By ~ 33

Author(s):

Marlynne Q. Nicol ◽

Yvonne Ligertwood ◽

Matthew N. Bacon ◽

Bernadette M. Dutia ◽

Anthony A. Nash

Keyword(s):

Influenza Virus ◽

Virus Infection ◽

Influenza A Virus ◽

Influenza A ◽

Antiviral Agents ◽

Influenza Virus Infection ◽

Influenza A Viruses ◽

Potent Inhibition ◽

Human Immunodeficiency Virus Entry ◽

Drug Resistant Strains

The emergence of drug-resistant strains of influenza virus has catalysed a search for new antiviral agents to supplement or replace existing drugs. Following the success of the human immunodeficiency virus entry blocker Enfuvirtide, there has been a resurgence of interest in peptide-based antivirals. In this paper, we report on the discovery of a novel family of peptides (FluPep, FP) that function as inhibitors of influenza A virus infection. The prototype peptide (FP1, also known as Tkip) interacts with haemagglutinin and inhibits the binding of the virus to cell membranes. Using a plaque-reduction assay, we have demonstrated that a variety of influenza A virus subtypes (including H1N1, H3N2 and H5N1) are inhibited by FluPep and its derivatives at nanomolar concentrations. By truncating FluPep we have identified a minimal sequence of 6 aa that binds to haemagglutinin and inhibits infection. Using a mouse model of intranasal influenza virus infection, we observed potent inhibition of virus infection when peptide is given at the time of virus administration. These data indicate that FluPep is a highly effective anti-influenza agent with the potential to translate to the clinic.

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Antiviral agents active against influenza A viruses

Nature Reviews Drug Discovery ◽

10.1038/nrd2175 ◽

2006 ◽

Vol 5 (12) ◽

pp. 1015-1025 ◽

Cited By ~ 453

Author(s):

Erik De Clercq

Keyword(s):

Influenza A ◽

Antiviral Agents ◽

Influenza A Viruses

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CMAS and ST3GAL4 Play an Important Role in the Adsorption of Influenza Virus by Affecting the Synthesis of Sialic Acid Receptors

International Journal of Molecular Sciences ◽

10.3390/ijms22116081 ◽

2021 ◽

Vol 22 (11) ◽

pp. 6081

Author(s):

Yaxin Zhao ◽

Jiahui Zou ◽

Qingxia Gao ◽

Shengsong Xie ◽

Jiyue Cao ◽

...

Keyword(s):

Influenza Virus ◽

Sialic Acid ◽

Cell Surface ◽

Influenza A ◽

Viral Envelope ◽

Host Gene ◽

Influenza A Viruses ◽

Strong Affinity ◽

Sialic Acid Receptors ◽

The Impact

Influenza A viruses (IAVs) initiate infection by attaching Hemagglutinin (HA) on the viral envelope to sialic acid (SA) receptors on the cell surface. Importantly, HA of human IAVs has a higher affinity for α-2,6-linked SA receptors, and avian strains prefer α-2,3-linked SA receptors, whereas swine strains have a strong affinity for both SA receptors. Host gene CMAS and ST3GAL4 were found to be essential for IAV attachment and entry. Loss of CMAS and ST3GAL4 hindered the synthesis of sialic acid receptors, which in turn prevented the adsorption of IAV. Further, the knockout of CMAS had an effect on the adsorption of swine, avian and human IAVs. However, ST3GAL4 knockout prevented the adsorption of swine and avian IAV and the impact on avian IAV was more distinct, whereas it had no effect on the adsorption of human IAV. Collectively, our findings demonstrate that knocking out CMAS and ST3GAL4 negatively regulated IAV replication by inhibiting the synthesis of SA receptors, which also provides new insights into the production of gene-edited animals in the future.

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