Mode of antiviral action of silver nanoparticles against HIV-1

<p>Abstract</p> <p>Background</p> <p>Silver nanoparticles have proven to exert antiviral activity against HIV-1 at non-cytotoxic concentrations, but the mechanism underlying their HIV-inhibitory activity has not been not fully elucidated. In this study, silver nanoparticles are evaluated to elucidate their mode of antiviral action against HIV-1 using a panel of different <it>in vitro </it>assays.</p> <p>Results</p> <p>Our data suggest that silver nanoparticles exert anti-HIV activity at an early stage of viral replication, most likely as a virucidal agent or as an inhibitor of viral entry. Silver nanoparticles bind to gp120 in a manner that prevents CD4-dependent virion binding, fusion, and infectivity, acting as an effective virucidal agent against cell-free virus (laboratory strains, clinical isolates, T and M tropic strains, and resistant strains) and cell-associated virus. Besides, silver nanoparticles inhibit post-entry stages of the HIV-1 life cycle.</p> <p>Conclusions</p> <p>These properties make them a broad-spectrum agent not prone to inducing resistance that could be used preventively against a wide variety of circulating HIV-1 strains.</p

Antibody-dependent enhancement of dengue virus infection is inhibited by SA-17, a doxorubicin derivative

Antibody-dependent enhancement (ADE) is thought to play a critical role in the exacerbation of dengue virus (DENV)-induced disease during a heterologous re-infection. Despite ADE's clinical impact, only a few antiviral compounds have been assessed for their anti-ADE activity. We reported earlier that SA-17, a doxorubicin derivative, efficiently inhibits the in vitro infection of DENV and yellow fever virus. Here we explored SA-17's mechanism of inhibition and investigated if the compound is active against ADE of DENV infection. Since enhanced infectivity stimulated by antibodies has been observed with standard and immature DENV, both types of virions were included in the study. We observed that SA-17 (i) inhibits DENV infection by preventing binding/entry to the cell and (ii) interferes with antibody-mediated infection of both standard and immature DENV2. SA-17 markedly reduced the infectivity of DENV2 in ADE conditions, with IC50s ranging from 0.26 to 2.89μM. The compound exerted its activity when added before, during, and after antibody-opsonization of standard and immature virus. Thus, molecules with the characteristics of SA-17 may be attractive antiviral agents since they can be used both to block DENV2 entry during primary and secondary infection and to inhibit ADE of standard and immature virus.publisher: Elsevier articletitle: Antibody-dependent enhancement of dengue virus infection is inhibited by SA-17, a doxorubicin derivative journaltitle: Antiviral Research articlelink: http://dx.doi.org/10.1016/j.antiviral.2013.08.013 content_type: article copyright: Copyright © 2013 Elsevier B.V. All rights reserved.status: publishe

Dynamics of Chikungunya Virus Cell Entry Unraveled by Single-Virus Tracking in Living Cells

Chikungunya virus (CHIKV) is a rapidly emerging mosquito-borne human pathogen causing major outbreaks in Africa, Asia and the Americas. The cell entry pathway hijacked by CHIKV to infect a cell has been studied before using inhibitory compounds. There has been some debate on the mechanism by which CHIKV enters the cell, as several studies suggest that it enters via clathrin-mediated endocytosis, while some other studies show that CHIKV enters cells independently of clathrin. Here, we applied live-cell microscopy and monitored the cell entry behaviour of single CHIKV particles in living cells transfected with fluorescent marker proteins. This approach allowed us to obtain a detailed insight in the dynamic events that occur during CHIKV entry. We observed that almost all particles fused within 20 minutes post-addition to the cells. The vast majority of particles that fused first colocalized with clathrin. The time from initial colocalization with clathrin till the moment of membrane fusion was on average 1.7 minutes, highlighting the fast nature of the cell entry process of CHIKV. Furthermore, these results also show that the virus spends a profound time searching for a receptor. Membrane fusion was predominantly observed from within Rab5-positive endosomes and often occurred within 40 seconds post-delivery to endosomes. Furthermore, we confirmed that a valine at position E1-226 enhances the cholesterol-dependent membrane fusion properties of CHIKV. To conclude, our work confirms that CHIKV cell entry occurs via clathrin-mediated endocytosis and shows that fusion occurs from within acidic early endosomes. IMPORTANCE: Since its re-emergence in 2004 chikungunya (CHIKV) has rapidly spread around the world, leading to millions of infections. CHIKV often causes chikungunya fever, a self-limiting febrile illness with severe arthralgia. Currently, there is no vaccine or specific antiviral treatment available against CHIKV. A potential antiviral strategy is to interfere with the cell entry process of the virus. However, contradicting results were published with regard to the cell entry pathway used by CHIKV. Here, we applied a novel technology to visualize the entry behaviour of single CHIKV particles in living cells. Our results show that CHIKV cell entry is extremely rapid and occurs via clathrin-mediated endocytosis. Membrane fusion is seen from within acidic early endosomes. Furthermore, the membrane fusion capacity of CHIKV is strongly promoted by cholesterol in the target membrane. Taken together, this study provides an exquisite insight in the cell entry process of CHIKV