Generation of a Live Attenuated Influenza A Vaccine Using Chemical-Triggered Intein

Noticeablemorbidity and mortality can be caused by influenza Avirus in humans. Conventional live attenuated influenza vaccine (LAIV)is one of the main strategies to control the spread of influenza,but its protective efficacy is often limited by its suboptimal immunogenicityand safety. Therefore, a new type of LAIV that can overcome the shortageof existing vaccines is urgently needed. Here, we report a novel methodto construct the recombinant influenza A virus (IAV) regulated bysmall molecules. By inserting 4-hydroxytamoxifen (4-HT)-dependentintein into the polymerase acidic (PA) protein of IAV, a series of4-HT-dependent recombinant viruses were generated and screened. Amongthem, the S218 recombinant virus strain showed excellent 4-HT dependentreplication characteristics both in vitro and in vivo. Further immunologicalevaluation indicated that the 4-HT-dependent viruses were highly attenuatedin the host and could elicit robust humoral, mucosal, and cellularimmunity against the challenge of homologous viruses. The attenuatedstrategies presented here could also be broadly applied to the developmentof vaccines against other pathogens.