Nipah virus (NiV) outbreaks have occurred in Malaysia, India, and Bangladesh, and the virus continues to cause annual outbreaks of fatal human encephalitis in Bangladesh due to spillover from its bat host reservoir. Due to its high pathogenicity, its potential use for bio/agro-terrorism, and to the current lack of approved therapeutics, NiV is designated as an overlap select agent requiring biosafety level-4 containment. Although the development of therapeutic monoclonal antibodies and soluble protein subunit vaccines have shown great promise, the paucity of effective antiviral drugs against NiV merits further exploration of compound libraries using rapid quantitative antiviral assays. As a proof-of-concept study, we evaluated the use of fluorescent and luminescent reporter NiVs for antiviral screening. We constructed and rescued NiVs expressing either Renilla luciferase or green fluorescent protein, and characterized their reporter signal kinetics in different cell types as well as in the presence of several inhibitors. The 50% effective concentrations (EC50s) derived for inhibitors against both reporter viruses are within range of EC50s derived from virus yield-based dose-response assays against wild-type NiV (within 1Log10), thus demonstrating that both reporter NiVs can serve as robust antiviral screening tools. Utilizing these live NiV-based reporter assays requires modest instrumentation, and circumvents the time and labor-intensive steps associated with cytopathic effect or viral antigen-based assays. These reporter NiVs will not only facilitate antiviral screening, but also the study of host cell components that influence the virus life cycle.
Interferon (IFN) can activate Signal Transducer and Activator of Transcription (STAT) proteins to establish a cellular antiviral response and inhibit virus replication. Many viruses have evolved strategies to inhibit this antiviral mechanism, but paramyxoviruses are unique in their abilities to directly target the IFN-responsive STAT proteins. Hendra virus and Nipah virus (Henipaviruses) are recently emerged paramyxoviruses that are the causative agents of fatal disease outbreaks in Australia and peninsular Malaysia. Similar to other paramyxoviruses, Henipaviruses inhibit IFN signal transduction through a virus-encoded protein called V. Recent studies have shown that Henipavirus V proteins target STAT proteins by inducing the formation of cytoplasmically localized high molecular weight STAT-containing complexes. This sequestration of STAT1 and STAT2 prevents STAT activation and blocks antiviral IFN signaling. As the V proteins are important factors for host evasion, they represent logical targets for therapeutics directed against Henipavirus epidemics.
Hendra virus and Nipah virus are bat-borne paramyxoviruses that are the prototypic members of the genus Henipavirus. The henipaviruses emerged in the 1990s, spilling over from their natural bat hosts and causing serious disease outbreaks in humans and livestock. Hendra virus emerged in Australia and since 1994 there have been 7 human infections with 4 case fatalities. Nipah virus first appeared in Malaysia and subsequent outbreaks have occurred in Bangladesh and India. In total, there have been an estimated 582 human cases of Nipah virus and of these, 54% were fatal. Their broad species tropism and ability to cause fatal respiratory and/or neurologic disease in humans and animals make them important transboundary biological threats. Recent experimental findings in animals have demonstrated that a human monoclonal antibody targeting the viral G glycoprotein is an effective post-exposure treatment against Hendra and Nipah virus infection. In addition, a subunit vaccine based on the G glycoprotein of Hendra virus affords protection against Hendra and Nipah virus challenge. The vaccine has been developed for use in horses in Australia and is the first vaccine against a Biosafety Level-4 (BSL-4) agent to be licensed and commercially deployed. Together, these advances offer viable approaches to address Hendra and Nipah virus infection of livestock and people.
Nipah virus (NiV) infections are highly contagious and can cause severe febrile encephalitis. An outbreak of NiV infection has reported high mortality rates in Southeast Asian countries including Bangladesh, East Timor, Malaysia, Papua New Guinea, Vietnam, Cambodia, Indonesia, Madagascar, Philippines, Thailand and India. Considering the high risk for an epidemic outbreak, the World Health Organization (WHO) declared NiV as an emerging priority pathogen. However, there are no effective therapeutics or any FDA approved drugs available for the treatment of this infection. Among the known nine proteins of NiV, glycoprotein plays an important role in initiating the entry of viruses and attaching to the host cell receptors. Herein, three antiviral databases consisting of 79,892 chemical entities have been computationally screened against NiV glycoprotein (NiV-G). Particularly, multi-step molecular docking followed by extensive molecular binding interactions analyses, binding free energy estimation, in silico pharmacokinetics, synthetic accessibility and toxicity profile evaluations have been carried out for initial identification of potential NiV-G inhibitors. Further, molecular dynamics (MD) simulation has been performed to understand the dynamic properties of NiV-G protein-bound with proposed five inhibitors (G1-G5) and their interactions behavior, and any conformational changes in NiV-G protein during simulations. Moreover, Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) based binding free energies (∆G) has been calculated from all MD simulation trajectories to understand the energy contribution of each proposed compound in maintaining and stabilizing the complex binding interactions with NiV-G protein. Proposed compounds showed high negative ∆G values ranging from -166.246 to -226.652 kJ/mol indicating a strong affinity towards the NiV-G protein.