Henipaviruses are the newest genus of paramyxoviruses, and recent studies have shown that bats, on a global scale, are host to major genera of mammalian paramyxoviruses1. Paramyxoviruses are membrane enveloped, singled-stranded, negative-sense RNA viruses that include pathogens of global biomedical and agricultural import. Click
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Although henipavirus spillover events are currently limited to Southeast Asia and Australia, a recent global survey of almost 5,000 bat specimens revealed at least 23 distinct viral clades within the henipavirus genus, with the known Nipah and Hendra viruses representing only two of those clades1. The phylogenetic diversity of henipaviruses is thus vastly greater than what was thought previously. Henipaviruses also exhibit a much broader species tropism than other paramyxoviruses, largely due to the highly conserved protein receptors that these viruses use. In the various taxonomic schemes proposed for the transitional dynamics of zoonotic pathogens2,3 all these features justifiably place henipavirus at or close to the penultimate stage for sustained transmission in human outbreaks.
Our laboratory4, and others5, independently discovered EphrinB2 as the major receptor for Nipah and Hendra virus entry. We also identified EphrinB3 as an alternative receptor for henipavirus entry6. EphrinB2 and B3 belong to a class of highly conserved receptor tyrosine kinases (RTKs) that are involved in germ layer differentiation, tissue boundary formation, and other critical developmental processes such as angiogenesis, neurogenesis and axonal guidance7.
Paramyxovirus entry and fusion is a molecular choreography requiring cognate interactions between protein partners, the fusion (F) and attachment (HN/H/G) envelope glycoproteins, in which motion and form must both, be carefully regulated. Please see "Modes of paramyxovirus fusion: a Henipavirus perspective" for a recent review on paramyxovirus fusion from this lab8.
Our research on henipavirus entry have focused on:
- Elucidating the molecular determinants of attachment protein (G)-receptor specificity4,6,9-13
- Identifying the parameters that modulate fusion (F) protein activity14-16
- Dissecting the receptor binding triggered membrane fusion cascade16-20
- Developing quantitative and immunological tools to shed light on the kinetics and stoichiometry of the fusion process12,16,18,21
- Characterizing the prevalence of cross-reactive neutralizing antibodies from wild-life (mostly bats) and humans at high-risk for exposure in various locales (West Africa, South America) that have now reported the presence of henipavirus-related viruses
In the longer term, we are developing highly efficient reverse genetics rescue systems for single-stranded negative-sense RNA viruses (Mononegavirales) that are more robust (easy to optimize) and do not required the use of vaccinia-driven T7 polymerase (a standard method in the field). Protocols will be published on our lab's web-site, as and when they are published in the peer reviewed literature.
- Drexler, J. F. et al. Bats host major mammalian paramyxoviruses. Nature communications 3, 796, doi:10.1038/ncomms1796 (2012).
- Wolfe, N. D., Dunavan, C. P. & Diamond, J. Origins of major human infectious diseases. Nature 447, 279-283, doi:10.1038/nature05775 (2007).
- Lloyd-Smith, J. O. et al. Epidemic dynamics at the human-animal interface. Science 326, 1362-1367, doi:10.1126/science.1177345 (2009).
- Negrete, O. A. et al. EphrinB2 is the entry receptor for Nipah virus, an emergent deadly paramyxovirus. Nature 436, 401-405, doi:10.1038/nature03838 (2005).
- Bonaparte, M. I. et al. Ephrin-B2 ligand is a functional receptor for Hendra virus and Nipah virus. Proc Natl Acad Sci U S A 102, 10652-10657, doi:10.1073/pnas.0504887102 (2005).
- Negrete, O. A. et al. Two key residues in ephrinB3 are critical for its use as an alternative receptor for Nipah virus. PLoS Pathog 2, e7, doi:10.1371/journal.ppat.0020007 (2006).
- Pasquale, E. B. Eph-ephrin bidirectional signaling in physiology and disease. Cell 133, 38-5