Mice immunized with Recombinant-derived nucleoprotein (rNP) from S. typhimurium expressing the cloned NP gene from A/NT/60/68 (Jones & Brownlee, 1985) were protected against a lethal challenge with Influenza A/Puerto Rico/8/34 (A/PR8) virus but showed considerable morbidity before recovery (Tite et al., 1990).
Tite et al., 1990: Tite JP, Hughes-Jenkins C, O'Callaghan D, Dougan G, Russell SM, Gao XM, Liew FY. Anti-viral immunity induced by recombinant nucleoprotein of influenza A virus. II. Protection from influenza infection and mechanism of protection. Immunology. 1990; 71(2); 202-207. [PubMed: 2172156].