 Thus, a SeV infection in a form of genetic material in partially assembled virions can spread without any exposure to host neutralizing antibodies (see the section "Directed cells fusion (syncytium formation) for details and references).Sendai virus, as all other envelope viruses, uses host cellular membrane lipid bilayer for viral capsid membrane formation.Binding to a host cell membrane of viral proteins (M, HN and F) promotes their interaction with RNP complex, which is composed of the viral genomic RNA bound to SeV proteins (NP, P and L).