Hendra and Nipah viruses: pathogenesis, animal models and recent breakthroughs in vaccination

Hendra and Nipah viruses are two highly pathogenic zoonotic members of the genus Henipavirus , family Paramyxoviridae, requiring work under biosafety level 4 conditions due to a lack of effective therapy and human vaccines. Several vaccine candidates were protective in animal models: recombinant vaccinia virus expressing Nipah virus (NiV) F and G proteins in hamsters against NiV; recombinant ALVAC–NiV F and G in swine against NiV; recombinant Hendra virus (HeV) soluble G protein (sG HeV ) against HeV and NiV in cats, ferrets, horses, and African green monkeys (AGM); recombinant vesicular stomatitis virus-based vectors expressing NiV F or G against NiV in hamsters and ferrets; measles virus-based NiV G vaccine candidate in hamsters and AGMs against NiV; and adenoassociated virus expressing NiG protein, which protected hamsters against NiV. The sG HeV was licensed for use in horses (Equivac HeV ® ) in 2012. It is the first vaccine candidate licensed against a biosafety level 4 agent. With the development of suitable animal models (ferret, hamster and, importantly, AGM), progress can be made toward development of a human vaccine.