The budding capacity of virus proteins as VLPs, the proteinprotein interactions that facilitate this process, and the central role of M protein in VLP assembly and release has been described for several paramyxoviruses such as Sendai virus (SeV), Newcastle disease virus (NDV), respiratory syncytial virus (RSV), paramyxovirus simian virus 5 (PIV-5) and human parainfluenza virus type 1 (hPIV1) [20, 43, 44, 45, 46, 47] : The efficiency of VLP formation in virtually all these studies was based on M protein release in the supernatant. NiV virus-like particles have also been described [48] ; the results of this study showed 1) that NiV G and F proteins individually retained some budding capacity although it was far less efficient than that of the M protein and 2) NiV N, M, F and Gcontaining VLPs resembled the virus in some respects but differed significantly from it with respect to ratio of VLP-incorporated F protein; most of it was present in precursor F 0 form. Recently, the vaccine potential of native VLPs of NDV [49] has been described: these particles, composed of HN, F, M and NP proteins, had several virus-like properties. However, since the F protein in this formulation was modified by design to ablate the cleavage site, it remained in its precursor form; consequently, the NDV VLPs were non-fusogenic, and therefore incapable of inducing syncytia formation.