Cells were analyzed by flow cytometry and gated for AF647+ cells. by blocking viral attachment to the host cell receptors ephrin-B2 and ephrin-B3, with a second class being enhanced by receptor binding. mAbs from both classes display synergistic activity and enhanced therapeutic efficacy when delivered as a cocktail. INTRODUCTION Hendra computer virus (HeV) (Guirakhoo et al., 2002) and Nipah computer virus (NiV), the prototypic henipaviruses, are emerging zoonotic paramyxoviruses known to cause severe disease in humans and diverse other mammalian orders. Multiple species of pteropid bats (flying foxes) act as reservoir hosts for these negative-sense, single-stranded RNA viruses in the Paramyxoviridae family with which they are comprehended to have co-evolved (Chua et al., 2002; Halpin et al., 2011; Halpin et al., 2000; Vidgen et al., 2015). HeV is usually transmitted from flying foxes to horses and from horses to in-contact humans, causing severe respiratory and/or encephalitic disease mediated by endothelial vasculitis in both (Escaffre Protopanaxdiol et al., 2013; Field, 2016; Murray et al., 1995a). HeV was identified in 1994, having caused the death of 14 of 21 infected horses and 1 of 2 infected humans in Queensland, Australia (Murray et al., 1995b; Selvey et al., 1995). Spillover has occurred sporadically with some seasonal and climatic trends since then, causing disease in 105 horses and 7 humans, with high case fatality rates (Queensland Government, 2020). NiV, which was discovered 4 years after HeV when hundreds of pig handlers fell ill with encephalitic disease (Chua et al., 1999), has continued to cause sporadic outbreaks in Bangladesh and India (Arunkumar et al., 2019; Soman Pillai et al., 2020). More direct routes of contamination, including human-to-human transmission, and mortality rates approaching 100% have been observed during recent NiV outbreaks (Chadha et al., 2006; Clayton et al., 2012; Gurley et al., 2007). Anthropogenic and climatic influences on flying foxes are affecting their roosting, feeding, and migration habits as well as their susceptibility to heat-stress, disease, and injury (Kessler et al., 2018; Plowright et al., 2015). These factors together with their resultant increase in intermediate host contact (humans and domestic animals) are associated with increasing geographic range and frequency of henipavirus disease spillover (Martin et al., 2018; Walsh et al., 2017). While HeV and NiV outbreaks historically have been confined geographically to Australia and Southeast Asia, respectively, the risk of pandemic spread of these highly pathogenic agents related to regional and global populace densities and the difficulty of avoiding international transmission via infected travelers have been highlighted by recent experience with SARS-CoV-2 (Morens and Fauci, Protopanaxdiol 2020). Such concern prompted the World Health Business (WHO) to designate henipavirus infections as priority diseases requiring extensive and immediate Protopanaxdiol research and development (Sweileh, 2017). The risk of a global health crisis associated with henipaviruses is usually exacerbated by the lack of licensed antiviral drugs or vaccines for (HNV) and a dearth of knowledge of the human immune response to these viruses (Escaffre et al., 2013; Gmez Romn et al., 2020). Rabbit Polyclonal to TLE4 Passive immune transfer studies in both hamsters and ferrets have provided evidence that neutralizing antibodies are a correlate of immunoprotection from henipaviruses (Bossart et al., 2009; Guillaume et al., 2004, 2006). These data have been corroborated in multiple studies by investigators using murine, rabbit, or human antibody discovery technologies to isolate potently neutralizing antibodies to HeV and/or NiV (Aguilar et al., 2009; Mire et al., 2020; Zhu et al., 2006). One of these studies used phage display technology to isolate a human monoclonal antibody (hmAb), designated m102.4 (Zhu et al., 2008). This mAb potently neutralizes both HeV and NiV and protects against contamination and disease in experimental henipavirus challenge models using Protopanaxdiol ferrets or non-human primates (Bossart et al., 2011; Geisbert et al., 2014; Mire et al., 2016). More recently, two human mAbs, HENV-26 and HENV-32, were shown to neutralize HeV and NiV by distinct mechanisms and protect from NiV Bangladesh (NiVB) strain challenge in a ferret model (Dong et al., 2020). While these studies have laid a foundation for our understanding of how to target henipaviruses therapeutically, many questions remain regarding the antigenicity of the attachment glycoprotein, and whether escape mutations from these mAbs can develop by distinct molecular mechanisms and provided protection when used as monotherapy against lethal challenge in hamsters with the highly virulent NiVB strain. Antibodies recognizing these sites cooperate for binding to the henipavirus receptor-binding protein (RBP) glycoprotein that mediates attachment (formerly designated the G or glycosylated attachment protein, but recently renamed by the International Committee on Taxonomy of Viruses) (Rima et al., 2019). These mAbs also synergize for neutralization of both vesicular stomatitis computer virus (VSV)-NiVB, as well as two Cedar viruses chimerized to display the HeV or NiVB RBP and F surface.