The emergence and reemergence of pathogenic viruses represent continuous infectious disease threats to public health. Among these, the paramyxoviruses, which include many important human and animal pathogens, also include two excellent examples of emerged, zoonotic viral pathogens of importance: the henipaviruses; Nipah virus (NiV) and Hendra virus (HeV). NiV and HeV have a uniquely broad host tropism capable of infecting at least 18 animal species across 6 orders of mammals. NiV and HeV can also cause a systemic and often fatal respiratory and/or neurological disease in 11 mammalian species including humans. These henipaviruses remain significant biothreats to humans and economically important livestock in Australia and throughout South East Asia. In addition, there are no vaccines or therapeutics approved for human use. The henipaviruses are single-stranded, negative sense, enveloped RNA viruses and possess two membrane anchored glycoproteins involved in virus entry, one mediates host cell receptor attachment (G glycoprotein) and the other is a Class I fusion (F) glycoprotein which facilitates virion and host cell membrane fusion. The viral G and F glycoproteins are the major antigenic targets of neutralizing antibodies and are the main focus of active vaccine strategies. We have been characterizing the non-pathogenic species of henipavirus, Cedar virus (CedPV). Using recombinant viral glycoprotein mediated cell fusion assays, we have determined that CedPV- mediated fusion tropism is similar to NiV and HeV, however, the ephrin receptor tropism of CedPV is remarkably broad and fusion is triggered by ephrin-B1 and -B2 as well as the glycophosphatidylinositol- anchored A subtype ephrins-A1, -A2, and -A5. The fusion tropism activity by each of these ephrins is also correlated with CedPV G binding, and using a recently developed reverse genetics system for preparing recombinant CedPV (rCedPV) we have confirmed the fusion tropism findings with rCedPV infection studies. The rCedPV platform now offers a new virological system that can be used in a variety of applications to study henipaviruses safely under BSL-2 containment which will be broadly used by the CETR Research Projects and Cores. But of additional importance, it is an authentic henipavirus system that is attenuated in comparison to NiV and HeV, and can be genetically manipulated to serve as a live-attenuated universal henipavirus vaccine platform, and one likely capable of inducting a long-lasting and balanced immune response. Using this new system our objectives here will be to develop rCedPV chimeric viruses encoding the F and G glycoproteins of NiV or HeV and characterize and explore their potential a novel henipavirus vaccine. Specifically, we will: 1) Construct and rescue rCedPV-NiV/HeV viruses; 2) Characterize the chimeric viruses in cell-based infection and tropism studies; 3) Analyze the immune responses and outcomes in both immunocompetent and immunodeficient mice following infection with rCedPVs; 4) Test the protective abilities of rCedPVs by vaccination in animal subjects, in response to NiV and HeV challenge.
