Inhibition of Rift Valley Fever Virus Replication and Perturbation of Nucleocapsid-RNA Interactions by Suramin

Abstract

Rift Valley fever virus (RVFV) is an emerging infectious pathogen that causes severe disease in humans and livestock and has the potential for global spread. There are currently no proven safe and effective treatment options for RVFV infection. Inhibition of RNA binding to RVFV nucleocapsid protein (N) represents an attractive antiviral therapeutic strategy because several essential steps in the RVFV replication cycle involve N binding to viral RNA. In this study, we demonstrate the therapeutic potential of the drug suramin by showing that it functions well as an inhibitor of RVFV replication at multiple stages in human cell culture. Suramin has been used previously to treat trypanosomiasis in Africa. We characterize the dynamic and cooperative nature of N-RNA binding interactions and the dissociation of high-molecular-mass ribonucleoprotein complexes using suramin, which we previously identified as an N-RNA binding inhibitor in a high-throughput screen. Finally, we elucidate the molecular mechanism used by suramin in vitro to disrupt both specific and nonspecific binding events important for ribonucleoprotein formation. Rift Valley fever virus (RVFV) is a mosquito-transmitted bunyavirus (genus Phlebovirus) that causes severe disease in humans and ruminant livestock. In humans, disease symptoms can range from a mild flu-like illness to hemorrhagic fever, encephalitis, neurological disorders, and blindness (1). Pregnant livestock are at risk for miscarriage, and high mortality rates among newborn animals have been reported (2-4). RVFV can be transmitted by a diverse set of mosquito species, and outbreaks have been more severe outside the historically defined areas of endemicity of sub-Saharan Africa. The potential for RVFV to cause devastating epidemics worldwide is evidenced by its classification as a category A high-priority disease agent by the National Institute for Allergy and Infectious Diseases (NIAID) (5, 6). There are currently no proven safe and effective treatment options for RVFV-infected people or livestock. Increasing our understanding of the basic molecular virology of this important pathogen represents an essential step toward identification of new drug targets and the development of more efficacious antiviral therapeutic compounds.The single-stranded RNA genome of RVFV is composed of three segments (L, M, and S) that appear circular by electron microscopy due to complementarity between the 5=-and 3=-terminal regions (7). The L segment encodes the RNA-dependent RNA polymerase responsible for transcription and replication of the viral genome. The M segment encodes glycoproteins (Gn and Gc) involved in entry into the host cell and nonstructural proteins NSm and 78-kDa protein (8). The S segment utilizes an ambisense strategy to encode the nucleocapsid (N) and NSs proteins, while the genes of the M and L segments are in the negative sense (9). Among all viral gene products, the importance of N is underscored by its involvement during many stages of the RVFV replication cycle. N is an RNA binding prot...

Transcription and replication mechanisms of Bunyaviridae and Arenaviridae L proteins

“…The interference of viral protein − RNA interactions have been addressed also by small RNA molecules (aptamers) or compounds (Suramin) that can block RNA binding sites of the nucleoproteins with potential antiviral effect. This have been explored for RVFV NP and similar approaches could be undertaken now towards the L protein − vRNA specific binding sites based on the available structures for the in silico design of interfering compounds and aptamers and using the high-throughput fluorescence-based methods available for the study of L protein vRNA interactions (Ellenbecker et al, 2015(Ellenbecker et al, , 2014Gerlach et al, 2015).…”

Suramin inhibits chikungunya virus replication through multiple mechanisms

“…actually due to its inhibitory effect on the interaction between the viral gp120 and the CD4 receptor (Schols et al, 1990). Suramin has also been shown to block the binding or early steps of infection of several DNA and RNA viruses, like herpes simplex virus type-1 (Aguilar et al, 1999), cytomegalovirus (Baba et al, 1993), human hepatitis B virus (Schulze et al, 2007), hepatitis delta virus (Petcu et al, 1988), hepatitis C virus (Garson et al, 1999), dengue virus (Chen et al, 1997), several bunyaviruses (Crance et al, 1997;Ellenbecker et al, 2014;Iqbal et al, 2000;Jiao et al, 2013), norovirus-like particles (Tamura et al, 2004) and enterovirus 71 (Wang et al, 2014), for which the antiviral activity of suramin was also confirmed in an animal model (Ren et al, 2014). In recent in vitro studies suramin was identified as a hepatis C virus and dengue virus helicase inhibitor (Basavannacharya and Vasudevan, 2014;Mukherjee et al, 2012) and also as a norovirus RdRp inhibitor by virtual screening and biochemical assays with purified enzymes (Mastrangelo et al, 2012;Tarantino et al, 2014).…”

Computational prediction and biochemical characterization of novel RNA aptamers to Rift Valley fever virus nucleocapsid protein

“…These data suggest that the aptamer RNAs competitively bind to N in infected cells, and thereby interfere with N’s normal functions in viral replication. Nucleocapsid protein has been regarded as a potential antiviral target in many viruses [9–12], these results emphasize that perturbing N function is an effective way to inhibit viral replication.…”