Hendra and Nipah Viruses: Lethal Zoonotic Paramyxoviruses

An emerging or reemerging infectious disease is one which either has newly appeared in a population or, although previously recognized, has increased in incidence and/or expanded its known geographic range. Nipah virus (NiV) and Hendra virus (HeV) are novel, zoonotic paramyxoviruses, and are biosecurity level 4 (BSL-4) restricted. This chapter focuses on Henipavirus biology. The HeV and NiV membrane-anchored envelope glycoproteins are the mediators of virus attachment and infection of susceptible host cells and major determinants of host cell tropism. The pathology caused by both HeV and NiV in horses is of greater severity than that caused by NiV in pigs. During the initial NiV outbreak in Malaysia, some patients were treated with ribavirin, and there was some evidence that this therapy may have been clinically beneficial. For the henipaviruses, the development of vaccines or therapeutics has largely focused on targeting virus attachment and infection. A major advance in furthering the development of specific monoclonal antibodies (MAbs) has been through the implementation of the bacterial phage display platform with combinatorial antibody libraries. The development of potential livestock vaccines against henipaviruses may also be desirable, and recently, a recombinant canarypox-based vaccine candidate for swine has been examined. In light of the highly pathogenic natures of HeV and NiV, the development of recombinant subunit immunogens would also represent a viable approach for vaccine development because they are inherently safe and are administered without risk of infection.