A Recombinant Chimeric Cedar Virus-Based Surrogate Neutralization Assay Platform for Pathogenic Henipaviruses

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.

Automated summary

Using a recombinant Cedar virus (rCedV) reverse genetics platform, chimeric viruses (rCedV-NiV-B and rCedV-HeV) were generated with the fusion (F) and attachment (G) glycoprotein genes of Nipah virus (NiV-Bangladesh) or Hendra virus in place of those of rCedV. These chimeras induced an interferon response and utilized specific entry receptors compared to rCedV. Neutralization tests with monoclonal antibodies showed a high correlation between the chimeras and authentic NiV-B and HeV. A high-throughput fluorescence reduction neutralization test (FRNT) using the chimeras was established and showed highly correlated results with plaque reduction neutralization tests (PRNT). The FRNT assay also measured serum neutralization titers from henipavirus G glycoprotein immunized animals. These rCedV chimeras provide a rapid and cost-effective henipavirus-based surrogate neutralization assay.