Influenza B mutant viruses with truncated NS1 proteins grow efficiently in Vero cells and are immunogenic in mice Wressnigg, Nina and Shurygina, Anna Polina and Wolff, Thorsten and Redlberger-Fritz, Monika and Popow-Kraupp, Therese and Muster, Thomas and Egorov, Andrej and Kittel, Christian,, 90, 366-374 (2009), doi = https://doi.org/10.1099/vir.0.006122-0, publicationName = Microbiology Society, issn = 0022-1317, abstract= Contemporary influenza B virus strains were generated encoding C-terminally truncated NS1 proteins. Viable viruses containing the N-terminal 14, 38, 57 or 80 aa of the NS1 protein were rescued in Vero cells. The influenza B virus NS1-truncated mutants were impaired in their ability to counteract interferon (IFN) production, induce antiviral pro-inflammatory cytokines early after infection and show attenuated or restricted growth in IFN-competent hosts. In Vero cells, all of the mutant viruses replicated to high titres comparable to the wild-type influenza B virus. Mice that received a single, intranasal immunization of the NS1-truncated mutants elicited an antibody response and protection against wild-type virus challenge. Therefore, these NS1-truncated mutants should prove useful as potential candidates for live-attenuated influenza virus vaccines., language=, type=