The henipaviruses, Nipah virus (NiV), and Hendra virus (HeV) can cause fatal diseases in humans and animals, whereas Cedar virus is a nonpathogenic henipavirus. Here, using a recombinant Cedar virus (rCedV) reverse genetics platform, the fusion (F) and attachment (G) glycoprotein genes of rCedV were replaced with those of NiV-Bangladesh (NiV-B) or HeV, generating replication-competent chimeric viruses (rCedV-NiV-B and rCedV-HeV), both with and without green fluorescent protein (GFP) or luciferase protein genes. The rCedV chimeras induced a Type I interferon response and utilized only ephrin-B2 and ephrin-B3 as entry receptors compared to rCedV. The neutralizing potencies of well-characterized cross-reactive NiV/HeV F and G specific monoclonal antibodies against rCedV-NiV-B-GFP and rCedV-HeV-GFP highly correlated with measurements obtained using authentic NiV-B and HeV when tested in parallel by plaque reduction neutralization tests (PRNT). A rapid, high-throughput, and quantitative fluorescence reduction neutralization test (FRNT) using the GFP-encoding chimeras was established, and monoclonal antibody neutralization data derived by FRNT highly correlated with data derived by PRNT. The FRNT assay could also measure serum neutralization titers from henipavirus G glycoprotein immunized animals. These rCedV chimeras are an authentic henipavirus-based surrogate neutralization assay that is rapid, cost-effective, and can be utilized outside high containment.

Nipah Virus (NiV) and Hendra Virus (HeV), are the prototype species of the genus Henipavirus and are highly pathogenic agents capable of causing fatal diseases in both animals and humans. Both NiV and HeV are classified as biosafety level-4 (BSL-4) restricted pathogens and remain the only henipaviruses within the genus known to cause systemic, severe respiratory and encephalitic henipaviral disease, and represent substantial transboundary threats. There are no approved prophylactic or therapeutic treatments for human henipavirus infections, and the World Health Organization acknowledges them as priority pathogens needing urgent research. The discovery of Cedar virus (CedV), the only recognized non-pathogenic henipavirus, has provided a number of unique opportunities to study henipavirus and host interactions and also facilitate countermeasure development research at lower BSL-2 containment. This review will highlight the unique aspects of CedV biology and how it has been exploited as a model for developing therapeutic strategies against more virulent henipavirus species.

Cedar virus (CedV), related to the highly pathogenic bat-borne henipaviruses, Hendra virus (HeV) and Nipah virus (NiV), is non-pathogenic in small animal models, likely due to the inability to produce interferon-antagonist proteins. We evaluated the pathogenesis of recombinant CedV (rCedV) in the African green monkey (AGM) model and determined if prior infection conferred cross-protective immunity against a lethal challenge with NiV Bangladesh (NiV-B) or HeV. AGMs infected with rCedV remained asymptomatic, with no clinical signs of disease or detectable viremia. The rCedV infected animals developed homologous neutralizing antibody responses that failed to cross-neutralize NiV-B or HeV. At 42 days post-rCedV infection, AGMs were challenged with a lethal dose of NiV-B or HeV, and prior infection with rCedV failed to protect against NiV-B challenge, with all animals succumbing to NiV-B. Similarly, rCedV infection did not confer consistent protection against HeV, with 2/4 animals succumbing to lethal HeV. These findings confirm that CedV is non-pathogenic in the AGM model of NiV and HeV infection, justifying its classification as a BSL-2 agent. The findings also demonstrate that rCedV does not elicit a cross-protective immune response to prevent lethal disease from either NiV-B or HeV highlighting significant immunological differences between CedV and the pathogenic henipaviruses.

Nipah virus (NiV) is a zoonotic virus that causes severe encephalitis and respiratory disease with a mortality rate often exceeding 70%. Currently, there are no licensed vaccines or therapeutics for NiV disease. This study aimed to identify and experimentally evaluate small-molecule inhibitors targeting the NiV-G (attachment) glycoprotein using integrated in silico and in vitro approaches. A high-throughput virtual screening of >215,000 compounds was conducted against the NiV-G glycoprotein, using docking and molecular dynamics (MD) simulations. The next potential candidates were evaluated using an established, BSL-2-compatible recombinant Cedar virus (rCedV)-based green fluorescent protein (GFP) reporter virus expressing the NiV-F (fusion) and G glycoproteins (rCedV-NiV-B-GFP). During MD simulations, quercetin demonstrated the most stable binding, maintaining a consistent RMSD (3.25 ± 0.3 Å). In vitro testing showed dose-dependent inhibition of rCedV-NiV-B-GFP infection. Although quercetin alone was less potent (IC₅₀ = 24 µM; 95% CI: 7.6–93.6 µM) than a reference NiV-neutralizing monoclonal antibody mAb-7B7 (IC₅₀ = 0.027 μg/mL; approximately 0.00018 μM; 95% CI: 0.0108 to 0.0735), combination with ascorbic acid enhanced neutralization (IC₅₀ = 4.4 µM; 95% CI: 2.9–6.8 µM). Quercetin demonstrated a high Selectivity Index of >20.8. The study identifies quercetin as a promising small-molecule inhibitor of NiV cellular infection, potentially through a stable interaction with NiV-G at the ephrin-B2/B3 binding interface identified computationally. These findings highlight the importance of combining computational screening with BSL-2 cell-based bioassays to accelerate NiV countermeasure discovery.