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Sialoglycan-binding enveloped viruses often possess receptor-destroying activity to avoid being immobilized by non-functional decoy receptors. Sialic acid (Sia)-binding paramyxoviruses contain a hemagglutinin-neuraminidase (HN) protein that possesses both Sia-binding and -cleavage activities. The multivalent, dynamic receptor interactions of paramyxovirus particles provide virion motility and are a key determinant of host tropism. However, such multivalent interactions have not been exhaustively analyzed, because such studies are complicated by the low affinity of the individual interactions and the requirement of high titer virus stocks. Moreover, the dynamics of multivalent particle-receptor interactions are difficult to predict from Michalis-Menten enzyme kinetics. Therefore, we here developed Ni-NTA nanoparticles that multivalently display recombinant soluble HN tetramers via their His tags (HN-NPs). Applying this HN-NP platform to Newcastle disease virus (NDV), we investigated using biolayer interferometry (BLI) the role of important HN residues in receptor-interactions and analyzed long-range effects between the catalytic site and the second Sia binding site (2SBS). The HN-NP system was also applicable to other paramyxoviruses. Comparative analysis of HN-NPs revealed and confirmed differences in dynamic receptor-interactions between type 1 human and murine parainfluenza viruses as well as of lab-adapted and clinical isolates of human parainfluenza virus type 3, which are likely to contribute to differences in tropism of these viruses. We propose this novel platform to be applicable to elucidate the dynamics of multivalent-receptor interactions important for host tropism and pathogenesis, particularly for difficult to grow sialoglycan-binding (paramyxo)viruses. Author summary: Multivalent dynamic interactions of sialoglycan-binding viruses, including several paramyxoviruses, are a key determinant of host tropism and pathogenesis as they allow virion motility and escape from decoy receptors to find the functional receptors at the cell surface. To facilitate analysis of these interactions by biolayer interferometry, we developed system nanoparticles that multivalently present paramyxovirus hemagglutinin-neuraminidase (HN) proteins (referred to HN-NPs), thereby omitting the need of growing high titer virus stocks. Using the HN-NP system, we performed a detailed analysis of the importance of residues in the catalytic site and the second sialic acid-binding site (2SBS) of Newcastle disease virus (NDV) for multivalent dynamic receptor interactions. Our results show that the observed phenotypes are difficult to predict from Michalis-Menten enzyme kinetics. In addition, we analyzed long-range effects between the two sites. Finally, we applied this system to compare the dynamic receptor-interactions of various parainfluenza viruses, collectively resulting in novel insights into the dynamics of multivalent-receptor interactions of paramyxoviruses. [ABSTRACT FROM AUTHOR]