The Role of the Hendra Virus and Nipah Virus Attachment Glycoproteins in Receptor Binding and Antibody Neutralization
Uniformed Services University Of The Health Sciences Bethesda United States
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Recently identified as members of the family Paramyxoviridae, Hendra virus HeV and Nipah virus NiV are newly emerged agents capable of causing severe respiratory and encephalitic illness with high mortality in both animals and humans. Both viruses infect cells using a highly conserved attachment glycoprotein G that engages host cellular receptors ephrin-B2 or ephrin-B3 and a fusion glycoprotein F that mediates membrane merger. Passive immunization with the henipavirus G glycoprotein-specific human monoclonal antibody m102.4 has been shown to neutralize HeV and NiV infection. Recent findings have revealed that both receptors and m102.4 bind the same ectodomain of G. In order to improve the efficacy of m102.4 we constructed variants of m102.4 in which the binding residues were replaced with the corresponding residues of ephrin-B2B3. Using soluble, tetrameric forms of HeVNiV-G wt-G and m102.4 escape mutants of G esc-G, which were generated in vitro, m102.4 variants were tested for their ability to bind G, block Greceptor interaction and inhibit cell-cell fusion. Variants with a single mutation bound G, inhibited G-receptor interactions and decreased cell-cell fusion better than multiple mutation variants, but none of the variants were able to bind or inhibit interactions and fusion at the level of m102.4, indicating that manipulation of m102.4 to resemble receptors decreases the potency of m102.4 neutralization. Additionally m102.4 and m102.4 variants were able to bind G escape variants esc-G but had little effect on inhibiting fusion mediated by these esc-Gs,suggesting that m102.4 neutralization does not solely rely on blocking G-receptor binding. New escape variants of HeVNiV were generated using m102.4 variants and resulted in the same or similar mutations as were seen previously. The HeV and NiVesc-Gs were also used to further characterize m102.4-G interactions in order to determine the mechanism of m102.4 neutralization.